1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
3 @c 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
4 @c 2010, 2011 Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
26 @c readline appendices use @vindex, @findex and @ftable,
27 @c annotate.texi and gdbmi use @findex.
31 @c !!set GDB manual's edition---not the same as GDB version!
32 @c This is updated by GNU Press.
35 @c !!set GDB edit command default editor
38 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
40 @c This is a dir.info fragment to support semi-automated addition of
41 @c manuals to an info tree.
42 @dircategory Software development
44 * Gdb: (gdb). The GNU debugger.
48 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
49 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
50 Free Software Foundation, Inc.
52 Permission is granted to copy, distribute and/or modify this document
53 under the terms of the GNU Free Documentation License, Version 1.3 or
54 any later version published by the Free Software Foundation; with the
55 Invariant Sections being ``Free Software'' and ``Free Software Needs
56 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
57 and with the Back-Cover Texts as in (a) below.
59 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
60 this GNU Manual. Buying copies from GNU Press supports the FSF in
61 developing GNU and promoting software freedom.''
65 This file documents the @sc{gnu} debugger @value{GDBN}.
67 This is the @value{EDITION} Edition, of @cite{Debugging with
68 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
69 @ifset VERSION_PACKAGE
70 @value{VERSION_PACKAGE}
72 Version @value{GDBVN}.
78 @title Debugging with @value{GDBN}
79 @subtitle The @sc{gnu} Source-Level Debugger
81 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
82 @ifset VERSION_PACKAGE
84 @subtitle @value{VERSION_PACKAGE}
86 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
90 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
91 \hfill {\it Debugging with @value{GDBN}}\par
92 \hfill \TeX{}info \texinfoversion\par
96 @vskip 0pt plus 1filll
97 Published by the Free Software Foundation @*
98 51 Franklin Street, Fifth Floor,
99 Boston, MA 02110-1301, USA@*
100 ISBN 1-882114-77-9 @*
104 This edition of the GDB manual is dedicated to the memory of Fred
105 Fish. Fred was a long-standing contributor to GDB and to Free
106 software in general. We will miss him.
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2010 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
164 * GDB Bugs:: Reporting bugs in @value{GDBN}
166 @ifset SYSTEM_READLINE
167 * Command Line Editing: (rluserman). Command Line Editing
168 * Using History Interactively: (history). Using History Interactively
170 @ifclear SYSTEM_READLINE
171 * Command Line Editing:: Command Line Editing
172 * Using History Interactively:: Using History Interactively
174 * Formatting Documentation:: How to format and print @value{GDBN} documentation
175 * Installing GDB:: Installing GDB
176 * Maintenance Commands:: Maintenance Commands
177 * Remote Protocol:: GDB Remote Serial Protocol
178 * Agent Expressions:: The GDB Agent Expression Mechanism
179 * Target Descriptions:: How targets can describe themselves to
181 * Operating System Information:: Getting additional information from
183 * Trace File Format:: GDB trace file format
184 * Index Section Format:: .gdb_index section format
185 * Copying:: GNU General Public License says
186 how you can copy and share GDB
187 * GNU Free Documentation License:: The license for this documentation
196 @unnumbered Summary of @value{GDBN}
198 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
199 going on ``inside'' another program while it executes---or what another
200 program was doing at the moment it crashed.
202 @value{GDBN} can do four main kinds of things (plus other things in support of
203 these) to help you catch bugs in the act:
207 Start your program, specifying anything that might affect its behavior.
210 Make your program stop on specified conditions.
213 Examine what has happened, when your program has stopped.
216 Change things in your program, so you can experiment with correcting the
217 effects of one bug and go on to learn about another.
220 You can use @value{GDBN} to debug programs written in C and C@t{++}.
221 For more information, see @ref{Supported Languages,,Supported Languages}.
222 For more information, see @ref{C,,C and C++}.
224 Support for D is partial. For information on D, see
228 Support for Modula-2 is partial. For information on Modula-2, see
229 @ref{Modula-2,,Modula-2}.
231 Support for OpenCL C is partial. For information on OpenCL C, see
232 @ref{OpenCL C,,OpenCL C}.
235 Debugging Pascal programs which use sets, subranges, file variables, or
236 nested functions does not currently work. @value{GDBN} does not support
237 entering expressions, printing values, or similar features using Pascal
241 @value{GDBN} can be used to debug programs written in Fortran, although
242 it may be necessary to refer to some variables with a trailing
245 @value{GDBN} can be used to debug programs written in Objective-C,
246 using either the Apple/NeXT or the GNU Objective-C runtime.
249 * Free Software:: Freely redistributable software
250 * Contributors:: Contributors to GDB
254 @unnumberedsec Free Software
256 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
257 General Public License
258 (GPL). The GPL gives you the freedom to copy or adapt a licensed
259 program---but every person getting a copy also gets with it the
260 freedom to modify that copy (which means that they must get access to
261 the source code), and the freedom to distribute further copies.
262 Typical software companies use copyrights to limit your freedoms; the
263 Free Software Foundation uses the GPL to preserve these freedoms.
265 Fundamentally, the General Public License is a license which says that
266 you have these freedoms and that you cannot take these freedoms away
269 @unnumberedsec Free Software Needs Free Documentation
271 The biggest deficiency in the free software community today is not in
272 the software---it is the lack of good free documentation that we can
273 include with the free software. Many of our most important
274 programs do not come with free reference manuals and free introductory
275 texts. Documentation is an essential part of any software package;
276 when an important free software package does not come with a free
277 manual and a free tutorial, that is a major gap. We have many such
280 Consider Perl, for instance. The tutorial manuals that people
281 normally use are non-free. How did this come about? Because the
282 authors of those manuals published them with restrictive terms---no
283 copying, no modification, source files not available---which exclude
284 them from the free software world.
286 That wasn't the first time this sort of thing happened, and it was far
287 from the last. Many times we have heard a GNU user eagerly describe a
288 manual that he is writing, his intended contribution to the community,
289 only to learn that he had ruined everything by signing a publication
290 contract to make it non-free.
292 Free documentation, like free software, is a matter of freedom, not
293 price. The problem with the non-free manual is not that publishers
294 charge a price for printed copies---that in itself is fine. (The Free
295 Software Foundation sells printed copies of manuals, too.) The
296 problem is the restrictions on the use of the manual. Free manuals
297 are available in source code form, and give you permission to copy and
298 modify. Non-free manuals do not allow this.
300 The criteria of freedom for a free manual are roughly the same as for
301 free software. Redistribution (including the normal kinds of
302 commercial redistribution) must be permitted, so that the manual can
303 accompany every copy of the program, both on-line and on paper.
305 Permission for modification of the technical content is crucial too.
306 When people modify the software, adding or changing features, if they
307 are conscientious they will change the manual too---so they can
308 provide accurate and clear documentation for the modified program. A
309 manual that leaves you no choice but to write a new manual to document
310 a changed version of the program is not really available to our
313 Some kinds of limits on the way modification is handled are
314 acceptable. For example, requirements to preserve the original
315 author's copyright notice, the distribution terms, or the list of
316 authors, are ok. It is also no problem to require modified versions
317 to include notice that they were modified. Even entire sections that
318 may not be deleted or changed are acceptable, as long as they deal
319 with nontechnical topics (like this one). These kinds of restrictions
320 are acceptable because they don't obstruct the community's normal use
323 However, it must be possible to modify all the @emph{technical}
324 content of the manual, and then distribute the result in all the usual
325 media, through all the usual channels. Otherwise, the restrictions
326 obstruct the use of the manual, it is not free, and we need another
327 manual to replace it.
329 Please spread the word about this issue. Our community continues to
330 lose manuals to proprietary publishing. If we spread the word that
331 free software needs free reference manuals and free tutorials, perhaps
332 the next person who wants to contribute by writing documentation will
333 realize, before it is too late, that only free manuals contribute to
334 the free software community.
336 If you are writing documentation, please insist on publishing it under
337 the GNU Free Documentation License or another free documentation
338 license. Remember that this decision requires your approval---you
339 don't have to let the publisher decide. Some commercial publishers
340 will use a free license if you insist, but they will not propose the
341 option; it is up to you to raise the issue and say firmly that this is
342 what you want. If the publisher you are dealing with refuses, please
343 try other publishers. If you're not sure whether a proposed license
344 is free, write to @email{licensing@@gnu.org}.
346 You can encourage commercial publishers to sell more free, copylefted
347 manuals and tutorials by buying them, and particularly by buying
348 copies from the publishers that paid for their writing or for major
349 improvements. Meanwhile, try to avoid buying non-free documentation
350 at all. Check the distribution terms of a manual before you buy it,
351 and insist that whoever seeks your business must respect your freedom.
352 Check the history of the book, and try to reward the publishers that
353 have paid or pay the authors to work on it.
355 The Free Software Foundation maintains a list of free documentation
356 published by other publishers, at
357 @url{http://www.fsf.org/doc/other-free-books.html}.
360 @unnumberedsec Contributors to @value{GDBN}
362 Richard Stallman was the original author of @value{GDBN}, and of many
363 other @sc{gnu} programs. Many others have contributed to its
364 development. This section attempts to credit major contributors. One
365 of the virtues of free software is that everyone is free to contribute
366 to it; with regret, we cannot actually acknowledge everyone here. The
367 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
368 blow-by-blow account.
370 Changes much prior to version 2.0 are lost in the mists of time.
373 @emph{Plea:} Additions to this section are particularly welcome. If you
374 or your friends (or enemies, to be evenhanded) have been unfairly
375 omitted from this list, we would like to add your names!
378 So that they may not regard their many labors as thankless, we
379 particularly thank those who shepherded @value{GDBN} through major
381 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
382 Jim Blandy (release 4.18);
383 Jason Molenda (release 4.17);
384 Stan Shebs (release 4.14);
385 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
386 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
387 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
388 Jim Kingdon (releases 3.5, 3.4, and 3.3);
389 and Randy Smith (releases 3.2, 3.1, and 3.0).
391 Richard Stallman, assisted at various times by Peter TerMaat, Chris
392 Hanson, and Richard Mlynarik, handled releases through 2.8.
394 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
395 in @value{GDBN}, with significant additional contributions from Per
396 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
397 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
398 much general update work leading to release 3.0).
400 @value{GDBN} uses the BFD subroutine library to examine multiple
401 object-file formats; BFD was a joint project of David V.
402 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
404 David Johnson wrote the original COFF support; Pace Willison did
405 the original support for encapsulated COFF.
407 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
409 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
410 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
412 Jean-Daniel Fekete contributed Sun 386i support.
413 Chris Hanson improved the HP9000 support.
414 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
415 David Johnson contributed Encore Umax support.
416 Jyrki Kuoppala contributed Altos 3068 support.
417 Jeff Law contributed HP PA and SOM support.
418 Keith Packard contributed NS32K support.
419 Doug Rabson contributed Acorn Risc Machine support.
420 Bob Rusk contributed Harris Nighthawk CX-UX support.
421 Chris Smith contributed Convex support (and Fortran debugging).
422 Jonathan Stone contributed Pyramid support.
423 Michael Tiemann contributed SPARC support.
424 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
425 Pace Willison contributed Intel 386 support.
426 Jay Vosburgh contributed Symmetry support.
427 Marko Mlinar contributed OpenRISC 1000 support.
429 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
431 Rich Schaefer and Peter Schauer helped with support of SunOS shared
434 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
435 about several machine instruction sets.
437 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
438 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
439 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
440 and RDI targets, respectively.
442 Brian Fox is the author of the readline libraries providing
443 command-line editing and command history.
445 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
446 Modula-2 support, and contributed the Languages chapter of this manual.
448 Fred Fish wrote most of the support for Unix System Vr4.
449 He also enhanced the command-completion support to cover C@t{++} overloaded
452 Hitachi America (now Renesas America), Ltd. sponsored the support for
453 H8/300, H8/500, and Super-H processors.
455 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
457 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
460 Toshiba sponsored the support for the TX39 Mips processor.
462 Matsushita sponsored the support for the MN10200 and MN10300 processors.
464 Fujitsu sponsored the support for SPARClite and FR30 processors.
466 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
469 Michael Snyder added support for tracepoints.
471 Stu Grossman wrote gdbserver.
473 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
474 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
476 The following people at the Hewlett-Packard Company contributed
477 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
478 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
479 compiler, and the Text User Interface (nee Terminal User Interface):
480 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
481 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
482 provided HP-specific information in this manual.
484 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
485 Robert Hoehne made significant contributions to the DJGPP port.
487 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
488 development since 1991. Cygnus engineers who have worked on @value{GDBN}
489 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
490 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
491 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
492 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
493 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
494 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
495 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
496 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
497 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
498 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
499 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
500 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
501 Zuhn have made contributions both large and small.
503 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
504 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
506 Jim Blandy added support for preprocessor macros, while working for Red
509 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
510 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
511 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
512 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
513 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
514 with the migration of old architectures to this new framework.
516 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
517 unwinder framework, this consisting of a fresh new design featuring
518 frame IDs, independent frame sniffers, and the sentinel frame. Mark
519 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
520 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
521 trad unwinders. The architecture-specific changes, each involving a
522 complete rewrite of the architecture's frame code, were carried out by
523 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
524 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
525 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
526 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
529 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
530 Tensilica, Inc.@: contributed support for Xtensa processors. Others
531 who have worked on the Xtensa port of @value{GDBN} in the past include
532 Steve Tjiang, John Newlin, and Scott Foehner.
534 Michael Eager and staff of Xilinx, Inc., contributed support for the
535 Xilinx MicroBlaze architecture.
538 @chapter A Sample @value{GDBN} Session
540 You can use this manual at your leisure to read all about @value{GDBN}.
541 However, a handful of commands are enough to get started using the
542 debugger. This chapter illustrates those commands.
545 In this sample session, we emphasize user input like this: @b{input},
546 to make it easier to pick out from the surrounding output.
549 @c FIXME: this example may not be appropriate for some configs, where
550 @c FIXME...primary interest is in remote use.
552 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
553 processor) exhibits the following bug: sometimes, when we change its
554 quote strings from the default, the commands used to capture one macro
555 definition within another stop working. In the following short @code{m4}
556 session, we define a macro @code{foo} which expands to @code{0000}; we
557 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
558 same thing. However, when we change the open quote string to
559 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
560 procedure fails to define a new synonym @code{baz}:
569 @b{define(bar,defn(`foo'))}
573 @b{changequote(<QUOTE>,<UNQUOTE>)}
575 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
578 m4: End of input: 0: fatal error: EOF in string
582 Let us use @value{GDBN} to try to see what is going on.
585 $ @b{@value{GDBP} m4}
586 @c FIXME: this falsifies the exact text played out, to permit smallbook
587 @c FIXME... format to come out better.
588 @value{GDBN} is free software and you are welcome to distribute copies
589 of it under certain conditions; type "show copying" to see
591 There is absolutely no warranty for @value{GDBN}; type "show warranty"
594 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
599 @value{GDBN} reads only enough symbol data to know where to find the
600 rest when needed; as a result, the first prompt comes up very quickly.
601 We now tell @value{GDBN} to use a narrower display width than usual, so
602 that examples fit in this manual.
605 (@value{GDBP}) @b{set width 70}
609 We need to see how the @code{m4} built-in @code{changequote} works.
610 Having looked at the source, we know the relevant subroutine is
611 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
612 @code{break} command.
615 (@value{GDBP}) @b{break m4_changequote}
616 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
620 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
621 control; as long as control does not reach the @code{m4_changequote}
622 subroutine, the program runs as usual:
625 (@value{GDBP}) @b{run}
626 Starting program: /work/Editorial/gdb/gnu/m4/m4
634 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
635 suspends execution of @code{m4}, displaying information about the
636 context where it stops.
639 @b{changequote(<QUOTE>,<UNQUOTE>)}
641 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
643 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
647 Now we use the command @code{n} (@code{next}) to advance execution to
648 the next line of the current function.
652 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
657 @code{set_quotes} looks like a promising subroutine. We can go into it
658 by using the command @code{s} (@code{step}) instead of @code{next}.
659 @code{step} goes to the next line to be executed in @emph{any}
660 subroutine, so it steps into @code{set_quotes}.
664 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
666 530 if (lquote != def_lquote)
670 The display that shows the subroutine where @code{m4} is now
671 suspended (and its arguments) is called a stack frame display. It
672 shows a summary of the stack. We can use the @code{backtrace}
673 command (which can also be spelled @code{bt}), to see where we are
674 in the stack as a whole: the @code{backtrace} command displays a
675 stack frame for each active subroutine.
678 (@value{GDBP}) @b{bt}
679 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
681 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
683 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
684 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
686 #4 0x79dc in expand_input () at macro.c:40
687 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
691 We step through a few more lines to see what happens. The first two
692 times, we can use @samp{s}; the next two times we use @code{n} to avoid
693 falling into the @code{xstrdup} subroutine.
697 0x3b5c 532 if (rquote != def_rquote)
699 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
700 def_lquote : xstrdup(lq);
702 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
705 538 len_lquote = strlen(rquote);
709 The last line displayed looks a little odd; we can examine the variables
710 @code{lquote} and @code{rquote} to see if they are in fact the new left
711 and right quotes we specified. We use the command @code{p}
712 (@code{print}) to see their values.
715 (@value{GDBP}) @b{p lquote}
716 $1 = 0x35d40 "<QUOTE>"
717 (@value{GDBP}) @b{p rquote}
718 $2 = 0x35d50 "<UNQUOTE>"
722 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
723 To look at some context, we can display ten lines of source
724 surrounding the current line with the @code{l} (@code{list}) command.
730 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
732 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
735 538 len_lquote = strlen(rquote);
736 539 len_rquote = strlen(lquote);
743 Let us step past the two lines that set @code{len_lquote} and
744 @code{len_rquote}, and then examine the values of those variables.
748 539 len_rquote = strlen(lquote);
751 (@value{GDBP}) @b{p len_lquote}
753 (@value{GDBP}) @b{p len_rquote}
758 That certainly looks wrong, assuming @code{len_lquote} and
759 @code{len_rquote} are meant to be the lengths of @code{lquote} and
760 @code{rquote} respectively. We can set them to better values using
761 the @code{p} command, since it can print the value of
762 any expression---and that expression can include subroutine calls and
766 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
768 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
773 Is that enough to fix the problem of using the new quotes with the
774 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
775 executing with the @code{c} (@code{continue}) command, and then try the
776 example that caused trouble initially:
782 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
789 Success! The new quotes now work just as well as the default ones. The
790 problem seems to have been just the two typos defining the wrong
791 lengths. We allow @code{m4} exit by giving it an EOF as input:
795 Program exited normally.
799 The message @samp{Program exited normally.} is from @value{GDBN}; it
800 indicates @code{m4} has finished executing. We can end our @value{GDBN}
801 session with the @value{GDBN} @code{quit} command.
804 (@value{GDBP}) @b{quit}
808 @chapter Getting In and Out of @value{GDBN}
810 This chapter discusses how to start @value{GDBN}, and how to get out of it.
814 type @samp{@value{GDBP}} to start @value{GDBN}.
816 type @kbd{quit} or @kbd{Ctrl-d} to exit.
820 * Invoking GDB:: How to start @value{GDBN}
821 * Quitting GDB:: How to quit @value{GDBN}
822 * Shell Commands:: How to use shell commands inside @value{GDBN}
823 * Logging Output:: How to log @value{GDBN}'s output to a file
827 @section Invoking @value{GDBN}
829 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
830 @value{GDBN} reads commands from the terminal until you tell it to exit.
832 You can also run @code{@value{GDBP}} with a variety of arguments and options,
833 to specify more of your debugging environment at the outset.
835 The command-line options described here are designed
836 to cover a variety of situations; in some environments, some of these
837 options may effectively be unavailable.
839 The most usual way to start @value{GDBN} is with one argument,
840 specifying an executable program:
843 @value{GDBP} @var{program}
847 You can also start with both an executable program and a core file
851 @value{GDBP} @var{program} @var{core}
854 You can, instead, specify a process ID as a second argument, if you want
855 to debug a running process:
858 @value{GDBP} @var{program} 1234
862 would attach @value{GDBN} to process @code{1234} (unless you also have a file
863 named @file{1234}; @value{GDBN} does check for a core file first).
865 Taking advantage of the second command-line argument requires a fairly
866 complete operating system; when you use @value{GDBN} as a remote
867 debugger attached to a bare board, there may not be any notion of
868 ``process'', and there is often no way to get a core dump. @value{GDBN}
869 will warn you if it is unable to attach or to read core dumps.
871 You can optionally have @code{@value{GDBP}} pass any arguments after the
872 executable file to the inferior using @code{--args}. This option stops
875 @value{GDBP} --args gcc -O2 -c foo.c
877 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
878 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
880 You can run @code{@value{GDBP}} without printing the front material, which describes
881 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
888 You can further control how @value{GDBN} starts up by using command-line
889 options. @value{GDBN} itself can remind you of the options available.
899 to display all available options and briefly describe their use
900 (@samp{@value{GDBP} -h} is a shorter equivalent).
902 All options and command line arguments you give are processed
903 in sequential order. The order makes a difference when the
904 @samp{-x} option is used.
908 * File Options:: Choosing files
909 * Mode Options:: Choosing modes
910 * Startup:: What @value{GDBN} does during startup
914 @subsection Choosing Files
916 When @value{GDBN} starts, it reads any arguments other than options as
917 specifying an executable file and core file (or process ID). This is
918 the same as if the arguments were specified by the @samp{-se} and
919 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
920 first argument that does not have an associated option flag as
921 equivalent to the @samp{-se} option followed by that argument; and the
922 second argument that does not have an associated option flag, if any, as
923 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
924 If the second argument begins with a decimal digit, @value{GDBN} will
925 first attempt to attach to it as a process, and if that fails, attempt
926 to open it as a corefile. If you have a corefile whose name begins with
927 a digit, you can prevent @value{GDBN} from treating it as a pid by
928 prefixing it with @file{./}, e.g.@: @file{./12345}.
930 If @value{GDBN} has not been configured to included core file support,
931 such as for most embedded targets, then it will complain about a second
932 argument and ignore it.
934 Many options have both long and short forms; both are shown in the
935 following list. @value{GDBN} also recognizes the long forms if you truncate
936 them, so long as enough of the option is present to be unambiguous.
937 (If you prefer, you can flag option arguments with @samp{--} rather
938 than @samp{-}, though we illustrate the more usual convention.)
940 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
941 @c way, both those who look for -foo and --foo in the index, will find
945 @item -symbols @var{file}
947 @cindex @code{--symbols}
949 Read symbol table from file @var{file}.
951 @item -exec @var{file}
953 @cindex @code{--exec}
955 Use file @var{file} as the executable file to execute when appropriate,
956 and for examining pure data in conjunction with a core dump.
960 Read symbol table from file @var{file} and use it as the executable
963 @item -core @var{file}
965 @cindex @code{--core}
967 Use file @var{file} as a core dump to examine.
969 @item -pid @var{number}
970 @itemx -p @var{number}
973 Connect to process ID @var{number}, as with the @code{attach} command.
975 @item -command @var{file}
977 @cindex @code{--command}
979 Execute commands from file @var{file}. The contents of this file is
980 evaluated exactly as the @code{source} command would.
981 @xref{Command Files,, Command files}.
983 @item -eval-command @var{command}
984 @itemx -ex @var{command}
985 @cindex @code{--eval-command}
987 Execute a single @value{GDBN} command.
989 This option may be used multiple times to call multiple commands. It may
990 also be interleaved with @samp{-command} as required.
993 @value{GDBP} -ex 'target sim' -ex 'load' \
994 -x setbreakpoints -ex 'run' a.out
997 @item -directory @var{directory}
998 @itemx -d @var{directory}
999 @cindex @code{--directory}
1001 Add @var{directory} to the path to search for source and script files.
1005 @cindex @code{--readnow}
1007 Read each symbol file's entire symbol table immediately, rather than
1008 the default, which is to read it incrementally as it is needed.
1009 This makes startup slower, but makes future operations faster.
1014 @subsection Choosing Modes
1016 You can run @value{GDBN} in various alternative modes---for example, in
1017 batch mode or quiet mode.
1024 Do not execute commands found in any initialization files. Normally,
1025 @value{GDBN} executes the commands in these files after all the command
1026 options and arguments have been processed. @xref{Command Files,,Command
1032 @cindex @code{--quiet}
1033 @cindex @code{--silent}
1035 ``Quiet''. Do not print the introductory and copyright messages. These
1036 messages are also suppressed in batch mode.
1039 @cindex @code{--batch}
1040 Run in batch mode. Exit with status @code{0} after processing all the
1041 command files specified with @samp{-x} (and all commands from
1042 initialization files, if not inhibited with @samp{-n}). Exit with
1043 nonzero status if an error occurs in executing the @value{GDBN} commands
1044 in the command files. Batch mode also disables pagination, sets unlimited
1045 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1046 off} were in effect (@pxref{Messages/Warnings}).
1048 Batch mode may be useful for running @value{GDBN} as a filter, for
1049 example to download and run a program on another computer; in order to
1050 make this more useful, the message
1053 Program exited normally.
1057 (which is ordinarily issued whenever a program running under
1058 @value{GDBN} control terminates) is not issued when running in batch
1062 @cindex @code{--batch-silent}
1063 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1064 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1065 unaffected). This is much quieter than @samp{-silent} and would be useless
1066 for an interactive session.
1068 This is particularly useful when using targets that give @samp{Loading section}
1069 messages, for example.
1071 Note that targets that give their output via @value{GDBN}, as opposed to
1072 writing directly to @code{stdout}, will also be made silent.
1074 @item -return-child-result
1075 @cindex @code{--return-child-result}
1076 The return code from @value{GDBN} will be the return code from the child
1077 process (the process being debugged), with the following exceptions:
1081 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1082 internal error. In this case the exit code is the same as it would have been
1083 without @samp{-return-child-result}.
1085 The user quits with an explicit value. E.g., @samp{quit 1}.
1087 The child process never runs, or is not allowed to terminate, in which case
1088 the exit code will be -1.
1091 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1092 when @value{GDBN} is being used as a remote program loader or simulator
1097 @cindex @code{--nowindows}
1099 ``No windows''. If @value{GDBN} comes with a graphical user interface
1100 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1101 interface. If no GUI is available, this option has no effect.
1105 @cindex @code{--windows}
1107 If @value{GDBN} includes a GUI, then this option requires it to be
1110 @item -cd @var{directory}
1112 Run @value{GDBN} using @var{directory} as its working directory,
1113 instead of the current directory.
1115 @item -data-directory @var{directory}
1116 @cindex @code{--data-directory}
1117 Run @value{GDBN} using @var{directory} as its data directory.
1118 The data directory is where @value{GDBN} searches for its
1119 auxiliary files. @xref{Data Files}.
1123 @cindex @code{--fullname}
1125 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1126 subprocess. It tells @value{GDBN} to output the full file name and line
1127 number in a standard, recognizable fashion each time a stack frame is
1128 displayed (which includes each time your program stops). This
1129 recognizable format looks like two @samp{\032} characters, followed by
1130 the file name, line number and character position separated by colons,
1131 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1132 @samp{\032} characters as a signal to display the source code for the
1136 @cindex @code{--epoch}
1137 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1138 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1139 routines so as to allow Epoch to display values of expressions in a
1142 @item -annotate @var{level}
1143 @cindex @code{--annotate}
1144 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1145 effect is identical to using @samp{set annotate @var{level}}
1146 (@pxref{Annotations}). The annotation @var{level} controls how much
1147 information @value{GDBN} prints together with its prompt, values of
1148 expressions, source lines, and other types of output. Level 0 is the
1149 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1150 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1151 that control @value{GDBN}, and level 2 has been deprecated.
1153 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1157 @cindex @code{--args}
1158 Change interpretation of command line so that arguments following the
1159 executable file are passed as command line arguments to the inferior.
1160 This option stops option processing.
1162 @item -baud @var{bps}
1164 @cindex @code{--baud}
1166 Set the line speed (baud rate or bits per second) of any serial
1167 interface used by @value{GDBN} for remote debugging.
1169 @item -l @var{timeout}
1171 Set the timeout (in seconds) of any communication used by @value{GDBN}
1172 for remote debugging.
1174 @item -tty @var{device}
1175 @itemx -t @var{device}
1176 @cindex @code{--tty}
1178 Run using @var{device} for your program's standard input and output.
1179 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1181 @c resolve the situation of these eventually
1183 @cindex @code{--tui}
1184 Activate the @dfn{Text User Interface} when starting. The Text User
1185 Interface manages several text windows on the terminal, showing
1186 source, assembly, registers and @value{GDBN} command outputs
1187 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1188 Text User Interface can be enabled by invoking the program
1189 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1190 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1193 @c @cindex @code{--xdb}
1194 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1195 @c For information, see the file @file{xdb_trans.html}, which is usually
1196 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1199 @item -interpreter @var{interp}
1200 @cindex @code{--interpreter}
1201 Use the interpreter @var{interp} for interface with the controlling
1202 program or device. This option is meant to be set by programs which
1203 communicate with @value{GDBN} using it as a back end.
1204 @xref{Interpreters, , Command Interpreters}.
1206 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1207 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1208 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1209 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1210 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1211 @sc{gdb/mi} interfaces are no longer supported.
1214 @cindex @code{--write}
1215 Open the executable and core files for both reading and writing. This
1216 is equivalent to the @samp{set write on} command inside @value{GDBN}
1220 @cindex @code{--statistics}
1221 This option causes @value{GDBN} to print statistics about time and
1222 memory usage after it completes each command and returns to the prompt.
1225 @cindex @code{--version}
1226 This option causes @value{GDBN} to print its version number and
1227 no-warranty blurb, and exit.
1232 @subsection What @value{GDBN} Does During Startup
1233 @cindex @value{GDBN} startup
1235 Here's the description of what @value{GDBN} does during session startup:
1239 Sets up the command interpreter as specified by the command line
1240 (@pxref{Mode Options, interpreter}).
1244 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1245 used when building @value{GDBN}; @pxref{System-wide configuration,
1246 ,System-wide configuration and settings}) and executes all the commands in
1250 Reads the init file (if any) in your home directory@footnote{On
1251 DOS/Windows systems, the home directory is the one pointed to by the
1252 @code{HOME} environment variable.} and executes all the commands in
1256 Processes command line options and operands.
1259 Reads and executes the commands from init file (if any) in the current
1260 working directory. This is only done if the current directory is
1261 different from your home directory. Thus, you can have more than one
1262 init file, one generic in your home directory, and another, specific
1263 to the program you are debugging, in the directory where you invoke
1267 If the command line specified a program to debug, or a process to
1268 attach to, or a core file, @value{GDBN} loads any auto-loaded
1269 scripts provided for the program or for its loaded shared libraries.
1270 @xref{Auto-loading}.
1272 If you wish to disable the auto-loading during startup,
1273 you must do something like the following:
1276 $ gdb -ex "set auto-load-scripts off" -ex "file myprogram"
1279 The following does not work because the auto-loading is turned off too late:
1282 $ gdb -ex "set auto-load-scripts off" myprogram
1286 Reads command files specified by the @samp{-x} option. @xref{Command
1287 Files}, for more details about @value{GDBN} command files.
1290 Reads the command history recorded in the @dfn{history file}.
1291 @xref{Command History}, for more details about the command history and the
1292 files where @value{GDBN} records it.
1295 Init files use the same syntax as @dfn{command files} (@pxref{Command
1296 Files}) and are processed by @value{GDBN} in the same way. The init
1297 file in your home directory can set options (such as @samp{set
1298 complaints}) that affect subsequent processing of command line options
1299 and operands. Init files are not executed if you use the @samp{-nx}
1300 option (@pxref{Mode Options, ,Choosing Modes}).
1302 To display the list of init files loaded by gdb at startup, you
1303 can use @kbd{gdb --help}.
1305 @cindex init file name
1306 @cindex @file{.gdbinit}
1307 @cindex @file{gdb.ini}
1308 The @value{GDBN} init files are normally called @file{.gdbinit}.
1309 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1310 the limitations of file names imposed by DOS filesystems. The Windows
1311 ports of @value{GDBN} use the standard name, but if they find a
1312 @file{gdb.ini} file, they warn you about that and suggest to rename
1313 the file to the standard name.
1317 @section Quitting @value{GDBN}
1318 @cindex exiting @value{GDBN}
1319 @cindex leaving @value{GDBN}
1322 @kindex quit @r{[}@var{expression}@r{]}
1323 @kindex q @r{(@code{quit})}
1324 @item quit @r{[}@var{expression}@r{]}
1326 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1327 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1328 do not supply @var{expression}, @value{GDBN} will terminate normally;
1329 otherwise it will terminate using the result of @var{expression} as the
1334 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1335 terminates the action of any @value{GDBN} command that is in progress and
1336 returns to @value{GDBN} command level. It is safe to type the interrupt
1337 character at any time because @value{GDBN} does not allow it to take effect
1338 until a time when it is safe.
1340 If you have been using @value{GDBN} to control an attached process or
1341 device, you can release it with the @code{detach} command
1342 (@pxref{Attach, ,Debugging an Already-running Process}).
1344 @node Shell Commands
1345 @section Shell Commands
1347 If you need to execute occasional shell commands during your
1348 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1349 just use the @code{shell} command.
1353 @cindex shell escape
1354 @item shell @var{command string}
1355 Invoke a standard shell to execute @var{command string}.
1356 If it exists, the environment variable @code{SHELL} determines which
1357 shell to run. Otherwise @value{GDBN} uses the default shell
1358 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1361 The utility @code{make} is often needed in development environments.
1362 You do not have to use the @code{shell} command for this purpose in
1367 @cindex calling make
1368 @item make @var{make-args}
1369 Execute the @code{make} program with the specified
1370 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1373 @node Logging Output
1374 @section Logging Output
1375 @cindex logging @value{GDBN} output
1376 @cindex save @value{GDBN} output to a file
1378 You may want to save the output of @value{GDBN} commands to a file.
1379 There are several commands to control @value{GDBN}'s logging.
1383 @item set logging on
1385 @item set logging off
1387 @cindex logging file name
1388 @item set logging file @var{file}
1389 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1390 @item set logging overwrite [on|off]
1391 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1392 you want @code{set logging on} to overwrite the logfile instead.
1393 @item set logging redirect [on|off]
1394 By default, @value{GDBN} output will go to both the terminal and the logfile.
1395 Set @code{redirect} if you want output to go only to the log file.
1396 @kindex show logging
1398 Show the current values of the logging settings.
1402 @chapter @value{GDBN} Commands
1404 You can abbreviate a @value{GDBN} command to the first few letters of the command
1405 name, if that abbreviation is unambiguous; and you can repeat certain
1406 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1407 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1408 show you the alternatives available, if there is more than one possibility).
1411 * Command Syntax:: How to give commands to @value{GDBN}
1412 * Completion:: Command completion
1413 * Help:: How to ask @value{GDBN} for help
1416 @node Command Syntax
1417 @section Command Syntax
1419 A @value{GDBN} command is a single line of input. There is no limit on
1420 how long it can be. It starts with a command name, which is followed by
1421 arguments whose meaning depends on the command name. For example, the
1422 command @code{step} accepts an argument which is the number of times to
1423 step, as in @samp{step 5}. You can also use the @code{step} command
1424 with no arguments. Some commands do not allow any arguments.
1426 @cindex abbreviation
1427 @value{GDBN} command names may always be truncated if that abbreviation is
1428 unambiguous. Other possible command abbreviations are listed in the
1429 documentation for individual commands. In some cases, even ambiguous
1430 abbreviations are allowed; for example, @code{s} is specially defined as
1431 equivalent to @code{step} even though there are other commands whose
1432 names start with @code{s}. You can test abbreviations by using them as
1433 arguments to the @code{help} command.
1435 @cindex repeating commands
1436 @kindex RET @r{(repeat last command)}
1437 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1438 repeat the previous command. Certain commands (for example, @code{run})
1439 will not repeat this way; these are commands whose unintentional
1440 repetition might cause trouble and which you are unlikely to want to
1441 repeat. User-defined commands can disable this feature; see
1442 @ref{Define, dont-repeat}.
1444 The @code{list} and @code{x} commands, when you repeat them with
1445 @key{RET}, construct new arguments rather than repeating
1446 exactly as typed. This permits easy scanning of source or memory.
1448 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1449 output, in a way similar to the common utility @code{more}
1450 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1451 @key{RET} too many in this situation, @value{GDBN} disables command
1452 repetition after any command that generates this sort of display.
1454 @kindex # @r{(a comment)}
1456 Any text from a @kbd{#} to the end of the line is a comment; it does
1457 nothing. This is useful mainly in command files (@pxref{Command
1458 Files,,Command Files}).
1460 @cindex repeating command sequences
1461 @kindex Ctrl-o @r{(operate-and-get-next)}
1462 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1463 commands. This command accepts the current line, like @key{RET}, and
1464 then fetches the next line relative to the current line from the history
1468 @section Command Completion
1471 @cindex word completion
1472 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1473 only one possibility; it can also show you what the valid possibilities
1474 are for the next word in a command, at any time. This works for @value{GDBN}
1475 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1477 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1478 of a word. If there is only one possibility, @value{GDBN} fills in the
1479 word, and waits for you to finish the command (or press @key{RET} to
1480 enter it). For example, if you type
1482 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1483 @c complete accuracy in these examples; space introduced for clarity.
1484 @c If texinfo enhancements make it unnecessary, it would be nice to
1485 @c replace " @key" by "@key" in the following...
1487 (@value{GDBP}) info bre @key{TAB}
1491 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1492 the only @code{info} subcommand beginning with @samp{bre}:
1495 (@value{GDBP}) info breakpoints
1499 You can either press @key{RET} at this point, to run the @code{info
1500 breakpoints} command, or backspace and enter something else, if
1501 @samp{breakpoints} does not look like the command you expected. (If you
1502 were sure you wanted @code{info breakpoints} in the first place, you
1503 might as well just type @key{RET} immediately after @samp{info bre},
1504 to exploit command abbreviations rather than command completion).
1506 If there is more than one possibility for the next word when you press
1507 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1508 characters and try again, or just press @key{TAB} a second time;
1509 @value{GDBN} displays all the possible completions for that word. For
1510 example, you might want to set a breakpoint on a subroutine whose name
1511 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1512 just sounds the bell. Typing @key{TAB} again displays all the
1513 function names in your program that begin with those characters, for
1517 (@value{GDBP}) b make_ @key{TAB}
1518 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1519 make_a_section_from_file make_environ
1520 make_abs_section make_function_type
1521 make_blockvector make_pointer_type
1522 make_cleanup make_reference_type
1523 make_command make_symbol_completion_list
1524 (@value{GDBP}) b make_
1528 After displaying the available possibilities, @value{GDBN} copies your
1529 partial input (@samp{b make_} in the example) so you can finish the
1532 If you just want to see the list of alternatives in the first place, you
1533 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1534 means @kbd{@key{META} ?}. You can type this either by holding down a
1535 key designated as the @key{META} shift on your keyboard (if there is
1536 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1538 @cindex quotes in commands
1539 @cindex completion of quoted strings
1540 Sometimes the string you need, while logically a ``word'', may contain
1541 parentheses or other characters that @value{GDBN} normally excludes from
1542 its notion of a word. To permit word completion to work in this
1543 situation, you may enclose words in @code{'} (single quote marks) in
1544 @value{GDBN} commands.
1546 The most likely situation where you might need this is in typing the
1547 name of a C@t{++} function. This is because C@t{++} allows function
1548 overloading (multiple definitions of the same function, distinguished
1549 by argument type). For example, when you want to set a breakpoint you
1550 may need to distinguish whether you mean the version of @code{name}
1551 that takes an @code{int} parameter, @code{name(int)}, or the version
1552 that takes a @code{float} parameter, @code{name(float)}. To use the
1553 word-completion facilities in this situation, type a single quote
1554 @code{'} at the beginning of the function name. This alerts
1555 @value{GDBN} that it may need to consider more information than usual
1556 when you press @key{TAB} or @kbd{M-?} to request word completion:
1559 (@value{GDBP}) b 'bubble( @kbd{M-?}
1560 bubble(double,double) bubble(int,int)
1561 (@value{GDBP}) b 'bubble(
1564 In some cases, @value{GDBN} can tell that completing a name requires using
1565 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1566 completing as much as it can) if you do not type the quote in the first
1570 (@value{GDBP}) b bub @key{TAB}
1571 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1572 (@value{GDBP}) b 'bubble(
1576 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1577 you have not yet started typing the argument list when you ask for
1578 completion on an overloaded symbol.
1580 For more information about overloaded functions, see @ref{C Plus Plus
1581 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1582 overload-resolution off} to disable overload resolution;
1583 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1585 @cindex completion of structure field names
1586 @cindex structure field name completion
1587 @cindex completion of union field names
1588 @cindex union field name completion
1589 When completing in an expression which looks up a field in a
1590 structure, @value{GDBN} also tries@footnote{The completer can be
1591 confused by certain kinds of invalid expressions. Also, it only
1592 examines the static type of the expression, not the dynamic type.} to
1593 limit completions to the field names available in the type of the
1597 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1598 magic to_delete to_fputs to_put to_rewind
1599 to_data to_flush to_isatty to_read to_write
1603 This is because the @code{gdb_stdout} is a variable of the type
1604 @code{struct ui_file} that is defined in @value{GDBN} sources as
1611 ui_file_flush_ftype *to_flush;
1612 ui_file_write_ftype *to_write;
1613 ui_file_fputs_ftype *to_fputs;
1614 ui_file_read_ftype *to_read;
1615 ui_file_delete_ftype *to_delete;
1616 ui_file_isatty_ftype *to_isatty;
1617 ui_file_rewind_ftype *to_rewind;
1618 ui_file_put_ftype *to_put;
1625 @section Getting Help
1626 @cindex online documentation
1629 You can always ask @value{GDBN} itself for information on its commands,
1630 using the command @code{help}.
1633 @kindex h @r{(@code{help})}
1636 You can use @code{help} (abbreviated @code{h}) with no arguments to
1637 display a short list of named classes of commands:
1641 List of classes of commands:
1643 aliases -- Aliases of other commands
1644 breakpoints -- Making program stop at certain points
1645 data -- Examining data
1646 files -- Specifying and examining files
1647 internals -- Maintenance commands
1648 obscure -- Obscure features
1649 running -- Running the program
1650 stack -- Examining the stack
1651 status -- Status inquiries
1652 support -- Support facilities
1653 tracepoints -- Tracing of program execution without
1654 stopping the program
1655 user-defined -- User-defined commands
1657 Type "help" followed by a class name for a list of
1658 commands in that class.
1659 Type "help" followed by command name for full
1661 Command name abbreviations are allowed if unambiguous.
1664 @c the above line break eliminates huge line overfull...
1666 @item help @var{class}
1667 Using one of the general help classes as an argument, you can get a
1668 list of the individual commands in that class. For example, here is the
1669 help display for the class @code{status}:
1672 (@value{GDBP}) help status
1677 @c Line break in "show" line falsifies real output, but needed
1678 @c to fit in smallbook page size.
1679 info -- Generic command for showing things
1680 about the program being debugged
1681 show -- Generic command for showing things
1684 Type "help" followed by command name for full
1686 Command name abbreviations are allowed if unambiguous.
1690 @item help @var{command}
1691 With a command name as @code{help} argument, @value{GDBN} displays a
1692 short paragraph on how to use that command.
1695 @item apropos @var{args}
1696 The @code{apropos} command searches through all of the @value{GDBN}
1697 commands, and their documentation, for the regular expression specified in
1698 @var{args}. It prints out all matches found. For example:
1709 set symbol-reloading -- Set dynamic symbol table reloading
1710 multiple times in one run
1711 show symbol-reloading -- Show dynamic symbol table reloading
1712 multiple times in one run
1717 @item complete @var{args}
1718 The @code{complete @var{args}} command lists all the possible completions
1719 for the beginning of a command. Use @var{args} to specify the beginning of the
1720 command you want completed. For example:
1726 @noindent results in:
1737 @noindent This is intended for use by @sc{gnu} Emacs.
1740 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1741 and @code{show} to inquire about the state of your program, or the state
1742 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1743 manual introduces each of them in the appropriate context. The listings
1744 under @code{info} and under @code{show} in the Index point to
1745 all the sub-commands. @xref{Index}.
1750 @kindex i @r{(@code{info})}
1752 This command (abbreviated @code{i}) is for describing the state of your
1753 program. For example, you can show the arguments passed to a function
1754 with @code{info args}, list the registers currently in use with @code{info
1755 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1756 You can get a complete list of the @code{info} sub-commands with
1757 @w{@code{help info}}.
1761 You can assign the result of an expression to an environment variable with
1762 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1763 @code{set prompt $}.
1767 In contrast to @code{info}, @code{show} is for describing the state of
1768 @value{GDBN} itself.
1769 You can change most of the things you can @code{show}, by using the
1770 related command @code{set}; for example, you can control what number
1771 system is used for displays with @code{set radix}, or simply inquire
1772 which is currently in use with @code{show radix}.
1775 To display all the settable parameters and their current
1776 values, you can use @code{show} with no arguments; you may also use
1777 @code{info set}. Both commands produce the same display.
1778 @c FIXME: "info set" violates the rule that "info" is for state of
1779 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1780 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1784 Here are three miscellaneous @code{show} subcommands, all of which are
1785 exceptional in lacking corresponding @code{set} commands:
1788 @kindex show version
1789 @cindex @value{GDBN} version number
1791 Show what version of @value{GDBN} is running. You should include this
1792 information in @value{GDBN} bug-reports. If multiple versions of
1793 @value{GDBN} are in use at your site, you may need to determine which
1794 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1795 commands are introduced, and old ones may wither away. Also, many
1796 system vendors ship variant versions of @value{GDBN}, and there are
1797 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1798 The version number is the same as the one announced when you start
1801 @kindex show copying
1802 @kindex info copying
1803 @cindex display @value{GDBN} copyright
1806 Display information about permission for copying @value{GDBN}.
1808 @kindex show warranty
1809 @kindex info warranty
1811 @itemx info warranty
1812 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1813 if your version of @value{GDBN} comes with one.
1818 @chapter Running Programs Under @value{GDBN}
1820 When you run a program under @value{GDBN}, you must first generate
1821 debugging information when you compile it.
1823 You may start @value{GDBN} with its arguments, if any, in an environment
1824 of your choice. If you are doing native debugging, you may redirect
1825 your program's input and output, debug an already running process, or
1826 kill a child process.
1829 * Compilation:: Compiling for debugging
1830 * Starting:: Starting your program
1831 * Arguments:: Your program's arguments
1832 * Environment:: Your program's environment
1834 * Working Directory:: Your program's working directory
1835 * Input/Output:: Your program's input and output
1836 * Attach:: Debugging an already-running process
1837 * Kill Process:: Killing the child process
1839 * Inferiors and Programs:: Debugging multiple inferiors and programs
1840 * Threads:: Debugging programs with multiple threads
1841 * Forks:: Debugging forks
1842 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1846 @section Compiling for Debugging
1848 In order to debug a program effectively, you need to generate
1849 debugging information when you compile it. This debugging information
1850 is stored in the object file; it describes the data type of each
1851 variable or function and the correspondence between source line numbers
1852 and addresses in the executable code.
1854 To request debugging information, specify the @samp{-g} option when you run
1857 Programs that are to be shipped to your customers are compiled with
1858 optimizations, using the @samp{-O} compiler option. However, some
1859 compilers are unable to handle the @samp{-g} and @samp{-O} options
1860 together. Using those compilers, you cannot generate optimized
1861 executables containing debugging information.
1863 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1864 without @samp{-O}, making it possible to debug optimized code. We
1865 recommend that you @emph{always} use @samp{-g} whenever you compile a
1866 program. You may think your program is correct, but there is no sense
1867 in pushing your luck. For more information, see @ref{Optimized Code}.
1869 Older versions of the @sc{gnu} C compiler permitted a variant option
1870 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1871 format; if your @sc{gnu} C compiler has this option, do not use it.
1873 @value{GDBN} knows about preprocessor macros and can show you their
1874 expansion (@pxref{Macros}). Most compilers do not include information
1875 about preprocessor macros in the debugging information if you specify
1876 the @option{-g} flag alone, because this information is rather large.
1877 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1878 provides macro information if you specify the options
1879 @option{-gdwarf-2} and @option{-g3}; the former option requests
1880 debugging information in the Dwarf 2 format, and the latter requests
1881 ``extra information''. In the future, we hope to find more compact
1882 ways to represent macro information, so that it can be included with
1887 @section Starting your Program
1893 @kindex r @r{(@code{run})}
1896 Use the @code{run} command to start your program under @value{GDBN}.
1897 You must first specify the program name (except on VxWorks) with an
1898 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1899 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1900 (@pxref{Files, ,Commands to Specify Files}).
1904 If you are running your program in an execution environment that
1905 supports processes, @code{run} creates an inferior process and makes
1906 that process run your program. In some environments without processes,
1907 @code{run} jumps to the start of your program. Other targets,
1908 like @samp{remote}, are always running. If you get an error
1909 message like this one:
1912 The "remote" target does not support "run".
1913 Try "help target" or "continue".
1917 then use @code{continue} to run your program. You may need @code{load}
1918 first (@pxref{load}).
1920 The execution of a program is affected by certain information it
1921 receives from its superior. @value{GDBN} provides ways to specify this
1922 information, which you must do @emph{before} starting your program. (You
1923 can change it after starting your program, but such changes only affect
1924 your program the next time you start it.) This information may be
1925 divided into four categories:
1928 @item The @emph{arguments.}
1929 Specify the arguments to give your program as the arguments of the
1930 @code{run} command. If a shell is available on your target, the shell
1931 is used to pass the arguments, so that you may use normal conventions
1932 (such as wildcard expansion or variable substitution) in describing
1934 In Unix systems, you can control which shell is used with the
1935 @code{SHELL} environment variable.
1936 @xref{Arguments, ,Your Program's Arguments}.
1938 @item The @emph{environment.}
1939 Your program normally inherits its environment from @value{GDBN}, but you can
1940 use the @value{GDBN} commands @code{set environment} and @code{unset
1941 environment} to change parts of the environment that affect
1942 your program. @xref{Environment, ,Your Program's Environment}.
1944 @item The @emph{working directory.}
1945 Your program inherits its working directory from @value{GDBN}. You can set
1946 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1947 @xref{Working Directory, ,Your Program's Working Directory}.
1949 @item The @emph{standard input and output.}
1950 Your program normally uses the same device for standard input and
1951 standard output as @value{GDBN} is using. You can redirect input and output
1952 in the @code{run} command line, or you can use the @code{tty} command to
1953 set a different device for your program.
1954 @xref{Input/Output, ,Your Program's Input and Output}.
1957 @emph{Warning:} While input and output redirection work, you cannot use
1958 pipes to pass the output of the program you are debugging to another
1959 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1963 When you issue the @code{run} command, your program begins to execute
1964 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1965 of how to arrange for your program to stop. Once your program has
1966 stopped, you may call functions in your program, using the @code{print}
1967 or @code{call} commands. @xref{Data, ,Examining Data}.
1969 If the modification time of your symbol file has changed since the last
1970 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1971 table, and reads it again. When it does this, @value{GDBN} tries to retain
1972 your current breakpoints.
1977 @cindex run to main procedure
1978 The name of the main procedure can vary from language to language.
1979 With C or C@t{++}, the main procedure name is always @code{main}, but
1980 other languages such as Ada do not require a specific name for their
1981 main procedure. The debugger provides a convenient way to start the
1982 execution of the program and to stop at the beginning of the main
1983 procedure, depending on the language used.
1985 The @samp{start} command does the equivalent of setting a temporary
1986 breakpoint at the beginning of the main procedure and then invoking
1987 the @samp{run} command.
1989 @cindex elaboration phase
1990 Some programs contain an @dfn{elaboration} phase where some startup code is
1991 executed before the main procedure is called. This depends on the
1992 languages used to write your program. In C@t{++}, for instance,
1993 constructors for static and global objects are executed before
1994 @code{main} is called. It is therefore possible that the debugger stops
1995 before reaching the main procedure. However, the temporary breakpoint
1996 will remain to halt execution.
1998 Specify the arguments to give to your program as arguments to the
1999 @samp{start} command. These arguments will be given verbatim to the
2000 underlying @samp{run} command. Note that the same arguments will be
2001 reused if no argument is provided during subsequent calls to
2002 @samp{start} or @samp{run}.
2004 It is sometimes necessary to debug the program during elaboration. In
2005 these cases, using the @code{start} command would stop the execution of
2006 your program too late, as the program would have already completed the
2007 elaboration phase. Under these circumstances, insert breakpoints in your
2008 elaboration code before running your program.
2010 @kindex set exec-wrapper
2011 @item set exec-wrapper @var{wrapper}
2012 @itemx show exec-wrapper
2013 @itemx unset exec-wrapper
2014 When @samp{exec-wrapper} is set, the specified wrapper is used to
2015 launch programs for debugging. @value{GDBN} starts your program
2016 with a shell command of the form @kbd{exec @var{wrapper}
2017 @var{program}}. Quoting is added to @var{program} and its
2018 arguments, but not to @var{wrapper}, so you should add quotes if
2019 appropriate for your shell. The wrapper runs until it executes
2020 your program, and then @value{GDBN} takes control.
2022 You can use any program that eventually calls @code{execve} with
2023 its arguments as a wrapper. Several standard Unix utilities do
2024 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2025 with @code{exec "$@@"} will also work.
2027 For example, you can use @code{env} to pass an environment variable to
2028 the debugged program, without setting the variable in your shell's
2032 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2036 This command is available when debugging locally on most targets, excluding
2037 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2039 @kindex set disable-randomization
2040 @item set disable-randomization
2041 @itemx set disable-randomization on
2042 This option (enabled by default in @value{GDBN}) will turn off the native
2043 randomization of the virtual address space of the started program. This option
2044 is useful for multiple debugging sessions to make the execution better
2045 reproducible and memory addresses reusable across debugging sessions.
2047 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2051 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2054 @item set disable-randomization off
2055 Leave the behavior of the started executable unchanged. Some bugs rear their
2056 ugly heads only when the program is loaded at certain addresses. If your bug
2057 disappears when you run the program under @value{GDBN}, that might be because
2058 @value{GDBN} by default disables the address randomization on platforms, such
2059 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2060 disable-randomization off} to try to reproduce such elusive bugs.
2062 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2063 It protects the programs against some kinds of security attacks. In these
2064 cases the attacker needs to know the exact location of a concrete executable
2065 code. Randomizing its location makes it impossible to inject jumps misusing
2066 a code at its expected addresses.
2068 Prelinking shared libraries provides a startup performance advantage but it
2069 makes addresses in these libraries predictable for privileged processes by
2070 having just unprivileged access at the target system. Reading the shared
2071 library binary gives enough information for assembling the malicious code
2072 misusing it. Still even a prelinked shared library can get loaded at a new
2073 random address just requiring the regular relocation process during the
2074 startup. Shared libraries not already prelinked are always loaded at
2075 a randomly chosen address.
2077 Position independent executables (PIE) contain position independent code
2078 similar to the shared libraries and therefore such executables get loaded at
2079 a randomly chosen address upon startup. PIE executables always load even
2080 already prelinked shared libraries at a random address. You can build such
2081 executable using @command{gcc -fPIE -pie}.
2083 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2084 (as long as the randomization is enabled).
2086 @item show disable-randomization
2087 Show the current setting of the explicit disable of the native randomization of
2088 the virtual address space of the started program.
2093 @section Your Program's Arguments
2095 @cindex arguments (to your program)
2096 The arguments to your program can be specified by the arguments of the
2098 They are passed to a shell, which expands wildcard characters and
2099 performs redirection of I/O, and thence to your program. Your
2100 @code{SHELL} environment variable (if it exists) specifies what shell
2101 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2102 the default shell (@file{/bin/sh} on Unix).
2104 On non-Unix systems, the program is usually invoked directly by
2105 @value{GDBN}, which emulates I/O redirection via the appropriate system
2106 calls, and the wildcard characters are expanded by the startup code of
2107 the program, not by the shell.
2109 @code{run} with no arguments uses the same arguments used by the previous
2110 @code{run}, or those set by the @code{set args} command.
2115 Specify the arguments to be used the next time your program is run. If
2116 @code{set args} has no arguments, @code{run} executes your program
2117 with no arguments. Once you have run your program with arguments,
2118 using @code{set args} before the next @code{run} is the only way to run
2119 it again without arguments.
2123 Show the arguments to give your program when it is started.
2127 @section Your Program's Environment
2129 @cindex environment (of your program)
2130 The @dfn{environment} consists of a set of environment variables and
2131 their values. Environment variables conventionally record such things as
2132 your user name, your home directory, your terminal type, and your search
2133 path for programs to run. Usually you set up environment variables with
2134 the shell and they are inherited by all the other programs you run. When
2135 debugging, it can be useful to try running your program with a modified
2136 environment without having to start @value{GDBN} over again.
2140 @item path @var{directory}
2141 Add @var{directory} to the front of the @code{PATH} environment variable
2142 (the search path for executables) that will be passed to your program.
2143 The value of @code{PATH} used by @value{GDBN} does not change.
2144 You may specify several directory names, separated by whitespace or by a
2145 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2146 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2147 is moved to the front, so it is searched sooner.
2149 You can use the string @samp{$cwd} to refer to whatever is the current
2150 working directory at the time @value{GDBN} searches the path. If you
2151 use @samp{.} instead, it refers to the directory where you executed the
2152 @code{path} command. @value{GDBN} replaces @samp{.} in the
2153 @var{directory} argument (with the current path) before adding
2154 @var{directory} to the search path.
2155 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2156 @c document that, since repeating it would be a no-op.
2160 Display the list of search paths for executables (the @code{PATH}
2161 environment variable).
2163 @kindex show environment
2164 @item show environment @r{[}@var{varname}@r{]}
2165 Print the value of environment variable @var{varname} to be given to
2166 your program when it starts. If you do not supply @var{varname},
2167 print the names and values of all environment variables to be given to
2168 your program. You can abbreviate @code{environment} as @code{env}.
2170 @kindex set environment
2171 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2172 Set environment variable @var{varname} to @var{value}. The value
2173 changes for your program only, not for @value{GDBN} itself. @var{value} may
2174 be any string; the values of environment variables are just strings, and
2175 any interpretation is supplied by your program itself. The @var{value}
2176 parameter is optional; if it is eliminated, the variable is set to a
2178 @c "any string" here does not include leading, trailing
2179 @c blanks. Gnu asks: does anyone care?
2181 For example, this command:
2188 tells the debugged program, when subsequently run, that its user is named
2189 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2190 are not actually required.)
2192 @kindex unset environment
2193 @item unset environment @var{varname}
2194 Remove variable @var{varname} from the environment to be passed to your
2195 program. This is different from @samp{set env @var{varname} =};
2196 @code{unset environment} removes the variable from the environment,
2197 rather than assigning it an empty value.
2200 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2202 by your @code{SHELL} environment variable if it exists (or
2203 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2204 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2205 @file{.bashrc} for BASH---any variables you set in that file affect
2206 your program. You may wish to move setting of environment variables to
2207 files that are only run when you sign on, such as @file{.login} or
2210 @node Working Directory
2211 @section Your Program's Working Directory
2213 @cindex working directory (of your program)
2214 Each time you start your program with @code{run}, it inherits its
2215 working directory from the current working directory of @value{GDBN}.
2216 The @value{GDBN} working directory is initially whatever it inherited
2217 from its parent process (typically the shell), but you can specify a new
2218 working directory in @value{GDBN} with the @code{cd} command.
2220 The @value{GDBN} working directory also serves as a default for the commands
2221 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2226 @cindex change working directory
2227 @item cd @var{directory}
2228 Set the @value{GDBN} working directory to @var{directory}.
2232 Print the @value{GDBN} working directory.
2235 It is generally impossible to find the current working directory of
2236 the process being debugged (since a program can change its directory
2237 during its run). If you work on a system where @value{GDBN} is
2238 configured with the @file{/proc} support, you can use the @code{info
2239 proc} command (@pxref{SVR4 Process Information}) to find out the
2240 current working directory of the debuggee.
2243 @section Your Program's Input and Output
2248 By default, the program you run under @value{GDBN} does input and output to
2249 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2250 to its own terminal modes to interact with you, but it records the terminal
2251 modes your program was using and switches back to them when you continue
2252 running your program.
2255 @kindex info terminal
2257 Displays information recorded by @value{GDBN} about the terminal modes your
2261 You can redirect your program's input and/or output using shell
2262 redirection with the @code{run} command. For example,
2269 starts your program, diverting its output to the file @file{outfile}.
2272 @cindex controlling terminal
2273 Another way to specify where your program should do input and output is
2274 with the @code{tty} command. This command accepts a file name as
2275 argument, and causes this file to be the default for future @code{run}
2276 commands. It also resets the controlling terminal for the child
2277 process, for future @code{run} commands. For example,
2284 directs that processes started with subsequent @code{run} commands
2285 default to do input and output on the terminal @file{/dev/ttyb} and have
2286 that as their controlling terminal.
2288 An explicit redirection in @code{run} overrides the @code{tty} command's
2289 effect on the input/output device, but not its effect on the controlling
2292 When you use the @code{tty} command or redirect input in the @code{run}
2293 command, only the input @emph{for your program} is affected. The input
2294 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2295 for @code{set inferior-tty}.
2297 @cindex inferior tty
2298 @cindex set inferior controlling terminal
2299 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2300 display the name of the terminal that will be used for future runs of your
2304 @item set inferior-tty /dev/ttyb
2305 @kindex set inferior-tty
2306 Set the tty for the program being debugged to /dev/ttyb.
2308 @item show inferior-tty
2309 @kindex show inferior-tty
2310 Show the current tty for the program being debugged.
2314 @section Debugging an Already-running Process
2319 @item attach @var{process-id}
2320 This command attaches to a running process---one that was started
2321 outside @value{GDBN}. (@code{info files} shows your active
2322 targets.) The command takes as argument a process ID. The usual way to
2323 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2324 or with the @samp{jobs -l} shell command.
2326 @code{attach} does not repeat if you press @key{RET} a second time after
2327 executing the command.
2330 To use @code{attach}, your program must be running in an environment
2331 which supports processes; for example, @code{attach} does not work for
2332 programs on bare-board targets that lack an operating system. You must
2333 also have permission to send the process a signal.
2335 When you use @code{attach}, the debugger finds the program running in
2336 the process first by looking in the current working directory, then (if
2337 the program is not found) by using the source file search path
2338 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2339 the @code{file} command to load the program. @xref{Files, ,Commands to
2342 The first thing @value{GDBN} does after arranging to debug the specified
2343 process is to stop it. You can examine and modify an attached process
2344 with all the @value{GDBN} commands that are ordinarily available when
2345 you start processes with @code{run}. You can insert breakpoints; you
2346 can step and continue; you can modify storage. If you would rather the
2347 process continue running, you may use the @code{continue} command after
2348 attaching @value{GDBN} to the process.
2353 When you have finished debugging the attached process, you can use the
2354 @code{detach} command to release it from @value{GDBN} control. Detaching
2355 the process continues its execution. After the @code{detach} command,
2356 that process and @value{GDBN} become completely independent once more, and you
2357 are ready to @code{attach} another process or start one with @code{run}.
2358 @code{detach} does not repeat if you press @key{RET} again after
2359 executing the command.
2362 If you exit @value{GDBN} while you have an attached process, you detach
2363 that process. If you use the @code{run} command, you kill that process.
2364 By default, @value{GDBN} asks for confirmation if you try to do either of these
2365 things; you can control whether or not you need to confirm by using the
2366 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2370 @section Killing the Child Process
2375 Kill the child process in which your program is running under @value{GDBN}.
2378 This command is useful if you wish to debug a core dump instead of a
2379 running process. @value{GDBN} ignores any core dump file while your program
2382 On some operating systems, a program cannot be executed outside @value{GDBN}
2383 while you have breakpoints set on it inside @value{GDBN}. You can use the
2384 @code{kill} command in this situation to permit running your program
2385 outside the debugger.
2387 The @code{kill} command is also useful if you wish to recompile and
2388 relink your program, since on many systems it is impossible to modify an
2389 executable file while it is running in a process. In this case, when you
2390 next type @code{run}, @value{GDBN} notices that the file has changed, and
2391 reads the symbol table again (while trying to preserve your current
2392 breakpoint settings).
2394 @node Inferiors and Programs
2395 @section Debugging Multiple Inferiors and Programs
2397 @value{GDBN} lets you run and debug multiple programs in a single
2398 session. In addition, @value{GDBN} on some systems may let you run
2399 several programs simultaneously (otherwise you have to exit from one
2400 before starting another). In the most general case, you can have
2401 multiple threads of execution in each of multiple processes, launched
2402 from multiple executables.
2405 @value{GDBN} represents the state of each program execution with an
2406 object called an @dfn{inferior}. An inferior typically corresponds to
2407 a process, but is more general and applies also to targets that do not
2408 have processes. Inferiors may be created before a process runs, and
2409 may be retained after a process exits. Inferiors have unique
2410 identifiers that are different from process ids. Usually each
2411 inferior will also have its own distinct address space, although some
2412 embedded targets may have several inferiors running in different parts
2413 of a single address space. Each inferior may in turn have multiple
2414 threads running in it.
2416 To find out what inferiors exist at any moment, use @w{@code{info
2420 @kindex info inferiors
2421 @item info inferiors
2422 Print a list of all inferiors currently being managed by @value{GDBN}.
2424 @value{GDBN} displays for each inferior (in this order):
2428 the inferior number assigned by @value{GDBN}
2431 the target system's inferior identifier
2434 the name of the executable the inferior is running.
2439 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2440 indicates the current inferior.
2444 @c end table here to get a little more width for example
2447 (@value{GDBP}) info inferiors
2448 Num Description Executable
2449 2 process 2307 hello
2450 * 1 process 3401 goodbye
2453 To switch focus between inferiors, use the @code{inferior} command:
2456 @kindex inferior @var{infno}
2457 @item inferior @var{infno}
2458 Make inferior number @var{infno} the current inferior. The argument
2459 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2460 in the first field of the @samp{info inferiors} display.
2464 You can get multiple executables into a debugging session via the
2465 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2466 systems @value{GDBN} can add inferiors to the debug session
2467 automatically by following calls to @code{fork} and @code{exec}. To
2468 remove inferiors from the debugging session use the
2469 @w{@code{remove-inferiors}} command.
2472 @kindex add-inferior
2473 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2474 Adds @var{n} inferiors to be run using @var{executable} as the
2475 executable. @var{n} defaults to 1. If no executable is specified,
2476 the inferiors begins empty, with no program. You can still assign or
2477 change the program assigned to the inferior at any time by using the
2478 @code{file} command with the executable name as its argument.
2480 @kindex clone-inferior
2481 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2482 Adds @var{n} inferiors ready to execute the same program as inferior
2483 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2484 number of the current inferior. This is a convenient command when you
2485 want to run another instance of the inferior you are debugging.
2488 (@value{GDBP}) info inferiors
2489 Num Description Executable
2490 * 1 process 29964 helloworld
2491 (@value{GDBP}) clone-inferior
2494 (@value{GDBP}) info inferiors
2495 Num Description Executable
2497 * 1 process 29964 helloworld
2500 You can now simply switch focus to inferior 2 and run it.
2502 @kindex remove-inferiors
2503 @item remove-inferiors @var{infno}@dots{}
2504 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2505 possible to remove an inferior that is running with this command. For
2506 those, use the @code{kill} or @code{detach} command first.
2510 To quit debugging one of the running inferiors that is not the current
2511 inferior, you can either detach from it by using the @w{@code{detach
2512 inferior}} command (allowing it to run independently), or kill it
2513 using the @w{@code{kill inferiors}} command:
2516 @kindex detach inferiors @var{infno}@dots{}
2517 @item detach inferior @var{infno}@dots{}
2518 Detach from the inferior or inferiors identified by @value{GDBN}
2519 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2520 still stays on the list of inferiors shown by @code{info inferiors},
2521 but its Description will show @samp{<null>}.
2523 @kindex kill inferiors @var{infno}@dots{}
2524 @item kill inferiors @var{infno}@dots{}
2525 Kill the inferior or inferiors identified by @value{GDBN} inferior
2526 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2527 stays on the list of inferiors shown by @code{info inferiors}, but its
2528 Description will show @samp{<null>}.
2531 After the successful completion of a command such as @code{detach},
2532 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2533 a normal process exit, the inferior is still valid and listed with
2534 @code{info inferiors}, ready to be restarted.
2537 To be notified when inferiors are started or exit under @value{GDBN}'s
2538 control use @w{@code{set print inferior-events}}:
2541 @kindex set print inferior-events
2542 @cindex print messages on inferior start and exit
2543 @item set print inferior-events
2544 @itemx set print inferior-events on
2545 @itemx set print inferior-events off
2546 The @code{set print inferior-events} command allows you to enable or
2547 disable printing of messages when @value{GDBN} notices that new
2548 inferiors have started or that inferiors have exited or have been
2549 detached. By default, these messages will not be printed.
2551 @kindex show print inferior-events
2552 @item show print inferior-events
2553 Show whether messages will be printed when @value{GDBN} detects that
2554 inferiors have started, exited or have been detached.
2557 Many commands will work the same with multiple programs as with a
2558 single program: e.g., @code{print myglobal} will simply display the
2559 value of @code{myglobal} in the current inferior.
2562 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2563 get more info about the relationship of inferiors, programs, address
2564 spaces in a debug session. You can do that with the @w{@code{maint
2565 info program-spaces}} command.
2568 @kindex maint info program-spaces
2569 @item maint info program-spaces
2570 Print a list of all program spaces currently being managed by
2573 @value{GDBN} displays for each program space (in this order):
2577 the program space number assigned by @value{GDBN}
2580 the name of the executable loaded into the program space, with e.g.,
2581 the @code{file} command.
2586 An asterisk @samp{*} preceding the @value{GDBN} program space number
2587 indicates the current program space.
2589 In addition, below each program space line, @value{GDBN} prints extra
2590 information that isn't suitable to display in tabular form. For
2591 example, the list of inferiors bound to the program space.
2594 (@value{GDBP}) maint info program-spaces
2597 Bound inferiors: ID 1 (process 21561)
2601 Here we can see that no inferior is running the program @code{hello},
2602 while @code{process 21561} is running the program @code{goodbye}. On
2603 some targets, it is possible that multiple inferiors are bound to the
2604 same program space. The most common example is that of debugging both
2605 the parent and child processes of a @code{vfork} call. For example,
2608 (@value{GDBP}) maint info program-spaces
2611 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2614 Here, both inferior 2 and inferior 1 are running in the same program
2615 space as a result of inferior 1 having executed a @code{vfork} call.
2619 @section Debugging Programs with Multiple Threads
2621 @cindex threads of execution
2622 @cindex multiple threads
2623 @cindex switching threads
2624 In some operating systems, such as HP-UX and Solaris, a single program
2625 may have more than one @dfn{thread} of execution. The precise semantics
2626 of threads differ from one operating system to another, but in general
2627 the threads of a single program are akin to multiple processes---except
2628 that they share one address space (that is, they can all examine and
2629 modify the same variables). On the other hand, each thread has its own
2630 registers and execution stack, and perhaps private memory.
2632 @value{GDBN} provides these facilities for debugging multi-thread
2636 @item automatic notification of new threads
2637 @item @samp{thread @var{threadno}}, a command to switch among threads
2638 @item @samp{info threads}, a command to inquire about existing threads
2639 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2640 a command to apply a command to a list of threads
2641 @item thread-specific breakpoints
2642 @item @samp{set print thread-events}, which controls printing of
2643 messages on thread start and exit.
2644 @item @samp{set libthread-db-search-path @var{path}}, which lets
2645 the user specify which @code{libthread_db} to use if the default choice
2646 isn't compatible with the program.
2650 @emph{Warning:} These facilities are not yet available on every
2651 @value{GDBN} configuration where the operating system supports threads.
2652 If your @value{GDBN} does not support threads, these commands have no
2653 effect. For example, a system without thread support shows no output
2654 from @samp{info threads}, and always rejects the @code{thread} command,
2658 (@value{GDBP}) info threads
2659 (@value{GDBP}) thread 1
2660 Thread ID 1 not known. Use the "info threads" command to
2661 see the IDs of currently known threads.
2663 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2664 @c doesn't support threads"?
2667 @cindex focus of debugging
2668 @cindex current thread
2669 The @value{GDBN} thread debugging facility allows you to observe all
2670 threads while your program runs---but whenever @value{GDBN} takes
2671 control, one thread in particular is always the focus of debugging.
2672 This thread is called the @dfn{current thread}. Debugging commands show
2673 program information from the perspective of the current thread.
2675 @cindex @code{New} @var{systag} message
2676 @cindex thread identifier (system)
2677 @c FIXME-implementors!! It would be more helpful if the [New...] message
2678 @c included GDB's numeric thread handle, so you could just go to that
2679 @c thread without first checking `info threads'.
2680 Whenever @value{GDBN} detects a new thread in your program, it displays
2681 the target system's identification for the thread with a message in the
2682 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2683 whose form varies depending on the particular system. For example, on
2684 @sc{gnu}/Linux, you might see
2687 [New Thread 0x41e02940 (LWP 25582)]
2691 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2692 the @var{systag} is simply something like @samp{process 368}, with no
2695 @c FIXME!! (1) Does the [New...] message appear even for the very first
2696 @c thread of a program, or does it only appear for the
2697 @c second---i.e.@: when it becomes obvious we have a multithread
2699 @c (2) *Is* there necessarily a first thread always? Or do some
2700 @c multithread systems permit starting a program with multiple
2701 @c threads ab initio?
2703 @cindex thread number
2704 @cindex thread identifier (GDB)
2705 For debugging purposes, @value{GDBN} associates its own thread
2706 number---always a single integer---with each thread in your program.
2709 @kindex info threads
2710 @item info threads @r{[}@var{id}@dots{}@r{]}
2711 Display a summary of all threads currently in your program. Optional
2712 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2713 means to print information only about the specified thread or threads.
2714 @value{GDBN} displays for each thread (in this order):
2718 the thread number assigned by @value{GDBN}
2721 the target system's thread identifier (@var{systag})
2724 the thread's name, if one is known. A thread can either be named by
2725 the user (see @code{thread name}, below), or, in some cases, by the
2729 the current stack frame summary for that thread
2733 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2734 indicates the current thread.
2738 @c end table here to get a little more width for example
2741 (@value{GDBP}) info threads
2743 3 process 35 thread 27 0x34e5 in sigpause ()
2744 2 process 35 thread 23 0x34e5 in sigpause ()
2745 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2749 On Solaris, you can display more information about user threads with a
2750 Solaris-specific command:
2753 @item maint info sol-threads
2754 @kindex maint info sol-threads
2755 @cindex thread info (Solaris)
2756 Display info on Solaris user threads.
2760 @kindex thread @var{threadno}
2761 @item thread @var{threadno}
2762 Make thread number @var{threadno} the current thread. The command
2763 argument @var{threadno} is the internal @value{GDBN} thread number, as
2764 shown in the first field of the @samp{info threads} display.
2765 @value{GDBN} responds by displaying the system identifier of the thread
2766 you selected, and its current stack frame summary:
2769 (@value{GDBP}) thread 2
2770 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2771 #0 some_function (ignore=0x0) at example.c:8
2772 8 printf ("hello\n");
2776 As with the @samp{[New @dots{}]} message, the form of the text after
2777 @samp{Switching to} depends on your system's conventions for identifying
2780 @vindex $_thread@r{, convenience variable}
2781 The debugger convenience variable @samp{$_thread} contains the number
2782 of the current thread. You may find this useful in writing breakpoint
2783 conditional expressions, command scripts, and so forth. See
2784 @xref{Convenience Vars,, Convenience Variables}, for general
2785 information on convenience variables.
2787 @kindex thread apply
2788 @cindex apply command to several threads
2789 @item thread apply [@var{threadno} | all] @var{command}
2790 The @code{thread apply} command allows you to apply the named
2791 @var{command} to one or more threads. Specify the numbers of the
2792 threads that you want affected with the command argument
2793 @var{threadno}. It can be a single thread number, one of the numbers
2794 shown in the first field of the @samp{info threads} display; or it
2795 could be a range of thread numbers, as in @code{2-4}. To apply a
2796 command to all threads, type @kbd{thread apply all @var{command}}.
2799 @cindex name a thread
2800 @item thread name [@var{name}]
2801 This command assigns a name to the current thread. If no argument is
2802 given, any existing user-specified name is removed. The thread name
2803 appears in the @samp{info threads} display.
2805 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2806 determine the name of the thread as given by the OS. On these
2807 systems, a name specified with @samp{thread name} will override the
2808 system-give name, and removing the user-specified name will cause
2809 @value{GDBN} to once again display the system-specified name.
2812 @cindex search for a thread
2813 @item thread find [@var{regexp}]
2814 Search for and display thread ids whose name or @var{systag}
2815 matches the supplied regular expression.
2817 As well as being the complement to the @samp{thread name} command,
2818 this command also allows you to identify a thread by its target
2819 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2823 (@value{GDBN}) thread find 26688
2824 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2825 (@value{GDBN}) info thread 4
2827 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2830 @kindex set print thread-events
2831 @cindex print messages on thread start and exit
2832 @item set print thread-events
2833 @itemx set print thread-events on
2834 @itemx set print thread-events off
2835 The @code{set print thread-events} command allows you to enable or
2836 disable printing of messages when @value{GDBN} notices that new threads have
2837 started or that threads have exited. By default, these messages will
2838 be printed if detection of these events is supported by the target.
2839 Note that these messages cannot be disabled on all targets.
2841 @kindex show print thread-events
2842 @item show print thread-events
2843 Show whether messages will be printed when @value{GDBN} detects that threads
2844 have started and exited.
2847 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2848 more information about how @value{GDBN} behaves when you stop and start
2849 programs with multiple threads.
2851 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2852 watchpoints in programs with multiple threads.
2855 @kindex set libthread-db-search-path
2856 @cindex search path for @code{libthread_db}
2857 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2858 If this variable is set, @var{path} is a colon-separated list of
2859 directories @value{GDBN} will use to search for @code{libthread_db}.
2860 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2863 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2864 @code{libthread_db} library to obtain information about threads in the
2865 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2866 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2867 with default system shared library directories, and finally the directory
2868 from which @code{libpthread} was loaded in the inferior process.
2870 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2871 @value{GDBN} attempts to initialize it with the current inferior process.
2872 If this initialization fails (which could happen because of a version
2873 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2874 will unload @code{libthread_db}, and continue with the next directory.
2875 If none of @code{libthread_db} libraries initialize successfully,
2876 @value{GDBN} will issue a warning and thread debugging will be disabled.
2878 Setting @code{libthread-db-search-path} is currently implemented
2879 only on some platforms.
2881 @kindex show libthread-db-search-path
2882 @item show libthread-db-search-path
2883 Display current libthread_db search path.
2885 @kindex set debug libthread-db
2886 @kindex show debug libthread-db
2887 @cindex debugging @code{libthread_db}
2888 @item set debug libthread-db
2889 @itemx show debug libthread-db
2890 Turns on or off display of @code{libthread_db}-related events.
2891 Use @code{1} to enable, @code{0} to disable.
2895 @section Debugging Forks
2897 @cindex fork, debugging programs which call
2898 @cindex multiple processes
2899 @cindex processes, multiple
2900 On most systems, @value{GDBN} has no special support for debugging
2901 programs which create additional processes using the @code{fork}
2902 function. When a program forks, @value{GDBN} will continue to debug the
2903 parent process and the child process will run unimpeded. If you have
2904 set a breakpoint in any code which the child then executes, the child
2905 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2906 will cause it to terminate.
2908 However, if you want to debug the child process there is a workaround
2909 which isn't too painful. Put a call to @code{sleep} in the code which
2910 the child process executes after the fork. It may be useful to sleep
2911 only if a certain environment variable is set, or a certain file exists,
2912 so that the delay need not occur when you don't want to run @value{GDBN}
2913 on the child. While the child is sleeping, use the @code{ps} program to
2914 get its process ID. Then tell @value{GDBN} (a new invocation of
2915 @value{GDBN} if you are also debugging the parent process) to attach to
2916 the child process (@pxref{Attach}). From that point on you can debug
2917 the child process just like any other process which you attached to.
2919 On some systems, @value{GDBN} provides support for debugging programs that
2920 create additional processes using the @code{fork} or @code{vfork} functions.
2921 Currently, the only platforms with this feature are HP-UX (11.x and later
2922 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2924 By default, when a program forks, @value{GDBN} will continue to debug
2925 the parent process and the child process will run unimpeded.
2927 If you want to follow the child process instead of the parent process,
2928 use the command @w{@code{set follow-fork-mode}}.
2931 @kindex set follow-fork-mode
2932 @item set follow-fork-mode @var{mode}
2933 Set the debugger response to a program call of @code{fork} or
2934 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2935 process. The @var{mode} argument can be:
2939 The original process is debugged after a fork. The child process runs
2940 unimpeded. This is the default.
2943 The new process is debugged after a fork. The parent process runs
2948 @kindex show follow-fork-mode
2949 @item show follow-fork-mode
2950 Display the current debugger response to a @code{fork} or @code{vfork} call.
2953 @cindex debugging multiple processes
2954 On Linux, if you want to debug both the parent and child processes, use the
2955 command @w{@code{set detach-on-fork}}.
2958 @kindex set detach-on-fork
2959 @item set detach-on-fork @var{mode}
2960 Tells gdb whether to detach one of the processes after a fork, or
2961 retain debugger control over them both.
2965 The child process (or parent process, depending on the value of
2966 @code{follow-fork-mode}) will be detached and allowed to run
2967 independently. This is the default.
2970 Both processes will be held under the control of @value{GDBN}.
2971 One process (child or parent, depending on the value of
2972 @code{follow-fork-mode}) is debugged as usual, while the other
2977 @kindex show detach-on-fork
2978 @item show detach-on-fork
2979 Show whether detach-on-fork mode is on/off.
2982 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2983 will retain control of all forked processes (including nested forks).
2984 You can list the forked processes under the control of @value{GDBN} by
2985 using the @w{@code{info inferiors}} command, and switch from one fork
2986 to another by using the @code{inferior} command (@pxref{Inferiors and
2987 Programs, ,Debugging Multiple Inferiors and Programs}).
2989 To quit debugging one of the forked processes, you can either detach
2990 from it by using the @w{@code{detach inferiors}} command (allowing it
2991 to run independently), or kill it using the @w{@code{kill inferiors}}
2992 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
2995 If you ask to debug a child process and a @code{vfork} is followed by an
2996 @code{exec}, @value{GDBN} executes the new target up to the first
2997 breakpoint in the new target. If you have a breakpoint set on
2998 @code{main} in your original program, the breakpoint will also be set on
2999 the child process's @code{main}.
3001 On some systems, when a child process is spawned by @code{vfork}, you
3002 cannot debug the child or parent until an @code{exec} call completes.
3004 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3005 call executes, the new target restarts. To restart the parent
3006 process, use the @code{file} command with the parent executable name
3007 as its argument. By default, after an @code{exec} call executes,
3008 @value{GDBN} discards the symbols of the previous executable image.
3009 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3013 @kindex set follow-exec-mode
3014 @item set follow-exec-mode @var{mode}
3016 Set debugger response to a program call of @code{exec}. An
3017 @code{exec} call replaces the program image of a process.
3019 @code{follow-exec-mode} can be:
3023 @value{GDBN} creates a new inferior and rebinds the process to this
3024 new inferior. The program the process was running before the
3025 @code{exec} call can be restarted afterwards by restarting the
3031 (@value{GDBP}) info inferiors
3033 Id Description Executable
3036 process 12020 is executing new program: prog2
3037 Program exited normally.
3038 (@value{GDBP}) info inferiors
3039 Id Description Executable
3045 @value{GDBN} keeps the process bound to the same inferior. The new
3046 executable image replaces the previous executable loaded in the
3047 inferior. Restarting the inferior after the @code{exec} call, with
3048 e.g., the @code{run} command, restarts the executable the process was
3049 running after the @code{exec} call. This is the default mode.
3054 (@value{GDBP}) info inferiors
3055 Id Description Executable
3058 process 12020 is executing new program: prog2
3059 Program exited normally.
3060 (@value{GDBP}) info inferiors
3061 Id Description Executable
3068 You can use the @code{catch} command to make @value{GDBN} stop whenever
3069 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3070 Catchpoints, ,Setting Catchpoints}.
3072 @node Checkpoint/Restart
3073 @section Setting a @emph{Bookmark} to Return to Later
3078 @cindex snapshot of a process
3079 @cindex rewind program state
3081 On certain operating systems@footnote{Currently, only
3082 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3083 program's state, called a @dfn{checkpoint}, and come back to it
3086 Returning to a checkpoint effectively undoes everything that has
3087 happened in the program since the @code{checkpoint} was saved. This
3088 includes changes in memory, registers, and even (within some limits)
3089 system state. Effectively, it is like going back in time to the
3090 moment when the checkpoint was saved.
3092 Thus, if you're stepping thru a program and you think you're
3093 getting close to the point where things go wrong, you can save
3094 a checkpoint. Then, if you accidentally go too far and miss
3095 the critical statement, instead of having to restart your program
3096 from the beginning, you can just go back to the checkpoint and
3097 start again from there.
3099 This can be especially useful if it takes a lot of time or
3100 steps to reach the point where you think the bug occurs.
3102 To use the @code{checkpoint}/@code{restart} method of debugging:
3107 Save a snapshot of the debugged program's current execution state.
3108 The @code{checkpoint} command takes no arguments, but each checkpoint
3109 is assigned a small integer id, similar to a breakpoint id.
3111 @kindex info checkpoints
3112 @item info checkpoints
3113 List the checkpoints that have been saved in the current debugging
3114 session. For each checkpoint, the following information will be
3121 @item Source line, or label
3124 @kindex restart @var{checkpoint-id}
3125 @item restart @var{checkpoint-id}
3126 Restore the program state that was saved as checkpoint number
3127 @var{checkpoint-id}. All program variables, registers, stack frames
3128 etc.@: will be returned to the values that they had when the checkpoint
3129 was saved. In essence, gdb will ``wind back the clock'' to the point
3130 in time when the checkpoint was saved.
3132 Note that breakpoints, @value{GDBN} variables, command history etc.
3133 are not affected by restoring a checkpoint. In general, a checkpoint
3134 only restores things that reside in the program being debugged, not in
3137 @kindex delete checkpoint @var{checkpoint-id}
3138 @item delete checkpoint @var{checkpoint-id}
3139 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3143 Returning to a previously saved checkpoint will restore the user state
3144 of the program being debugged, plus a significant subset of the system
3145 (OS) state, including file pointers. It won't ``un-write'' data from
3146 a file, but it will rewind the file pointer to the previous location,
3147 so that the previously written data can be overwritten. For files
3148 opened in read mode, the pointer will also be restored so that the
3149 previously read data can be read again.
3151 Of course, characters that have been sent to a printer (or other
3152 external device) cannot be ``snatched back'', and characters received
3153 from eg.@: a serial device can be removed from internal program buffers,
3154 but they cannot be ``pushed back'' into the serial pipeline, ready to
3155 be received again. Similarly, the actual contents of files that have
3156 been changed cannot be restored (at this time).
3158 However, within those constraints, you actually can ``rewind'' your
3159 program to a previously saved point in time, and begin debugging it
3160 again --- and you can change the course of events so as to debug a
3161 different execution path this time.
3163 @cindex checkpoints and process id
3164 Finally, there is one bit of internal program state that will be
3165 different when you return to a checkpoint --- the program's process
3166 id. Each checkpoint will have a unique process id (or @var{pid}),
3167 and each will be different from the program's original @var{pid}.
3168 If your program has saved a local copy of its process id, this could
3169 potentially pose a problem.
3171 @subsection A Non-obvious Benefit of Using Checkpoints
3173 On some systems such as @sc{gnu}/Linux, address space randomization
3174 is performed on new processes for security reasons. This makes it
3175 difficult or impossible to set a breakpoint, or watchpoint, on an
3176 absolute address if you have to restart the program, since the
3177 absolute location of a symbol will change from one execution to the
3180 A checkpoint, however, is an @emph{identical} copy of a process.
3181 Therefore if you create a checkpoint at (eg.@:) the start of main,
3182 and simply return to that checkpoint instead of restarting the
3183 process, you can avoid the effects of address randomization and
3184 your symbols will all stay in the same place.
3187 @chapter Stopping and Continuing
3189 The principal purposes of using a debugger are so that you can stop your
3190 program before it terminates; or so that, if your program runs into
3191 trouble, you can investigate and find out why.
3193 Inside @value{GDBN}, your program may stop for any of several reasons,
3194 such as a signal, a breakpoint, or reaching a new line after a
3195 @value{GDBN} command such as @code{step}. You may then examine and
3196 change variables, set new breakpoints or remove old ones, and then
3197 continue execution. Usually, the messages shown by @value{GDBN} provide
3198 ample explanation of the status of your program---but you can also
3199 explicitly request this information at any time.
3202 @kindex info program
3204 Display information about the status of your program: whether it is
3205 running or not, what process it is, and why it stopped.
3209 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3210 * Continuing and Stepping:: Resuming execution
3212 * Thread Stops:: Stopping and starting multi-thread programs
3216 @section Breakpoints, Watchpoints, and Catchpoints
3219 A @dfn{breakpoint} makes your program stop whenever a certain point in
3220 the program is reached. For each breakpoint, you can add conditions to
3221 control in finer detail whether your program stops. You can set
3222 breakpoints with the @code{break} command and its variants (@pxref{Set
3223 Breaks, ,Setting Breakpoints}), to specify the place where your program
3224 should stop by line number, function name or exact address in the
3227 On some systems, you can set breakpoints in shared libraries before
3228 the executable is run. There is a minor limitation on HP-UX systems:
3229 you must wait until the executable is run in order to set breakpoints
3230 in shared library routines that are not called directly by the program
3231 (for example, routines that are arguments in a @code{pthread_create}
3235 @cindex data breakpoints
3236 @cindex memory tracing
3237 @cindex breakpoint on memory address
3238 @cindex breakpoint on variable modification
3239 A @dfn{watchpoint} is a special breakpoint that stops your program
3240 when the value of an expression changes. The expression may be a value
3241 of a variable, or it could involve values of one or more variables
3242 combined by operators, such as @samp{a + b}. This is sometimes called
3243 @dfn{data breakpoints}. You must use a different command to set
3244 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3245 from that, you can manage a watchpoint like any other breakpoint: you
3246 enable, disable, and delete both breakpoints and watchpoints using the
3249 You can arrange to have values from your program displayed automatically
3250 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3254 @cindex breakpoint on events
3255 A @dfn{catchpoint} is another special breakpoint that stops your program
3256 when a certain kind of event occurs, such as the throwing of a C@t{++}
3257 exception or the loading of a library. As with watchpoints, you use a
3258 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3259 Catchpoints}), but aside from that, you can manage a catchpoint like any
3260 other breakpoint. (To stop when your program receives a signal, use the
3261 @code{handle} command; see @ref{Signals, ,Signals}.)
3263 @cindex breakpoint numbers
3264 @cindex numbers for breakpoints
3265 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3266 catchpoint when you create it; these numbers are successive integers
3267 starting with one. In many of the commands for controlling various
3268 features of breakpoints you use the breakpoint number to say which
3269 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3270 @dfn{disabled}; if disabled, it has no effect on your program until you
3273 @cindex breakpoint ranges
3274 @cindex ranges of breakpoints
3275 Some @value{GDBN} commands accept a range of breakpoints on which to
3276 operate. A breakpoint range is either a single breakpoint number, like
3277 @samp{5}, or two such numbers, in increasing order, separated by a
3278 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3279 all breakpoints in that range are operated on.
3282 * Set Breaks:: Setting breakpoints
3283 * Set Watchpoints:: Setting watchpoints
3284 * Set Catchpoints:: Setting catchpoints
3285 * Delete Breaks:: Deleting breakpoints
3286 * Disabling:: Disabling breakpoints
3287 * Conditions:: Break conditions
3288 * Break Commands:: Breakpoint command lists
3289 * Save Breakpoints:: How to save breakpoints in a file
3290 * Error in Breakpoints:: ``Cannot insert breakpoints''
3291 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3295 @subsection Setting Breakpoints
3297 @c FIXME LMB what does GDB do if no code on line of breakpt?
3298 @c consider in particular declaration with/without initialization.
3300 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3303 @kindex b @r{(@code{break})}
3304 @vindex $bpnum@r{, convenience variable}
3305 @cindex latest breakpoint
3306 Breakpoints are set with the @code{break} command (abbreviated
3307 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3308 number of the breakpoint you've set most recently; see @ref{Convenience
3309 Vars,, Convenience Variables}, for a discussion of what you can do with
3310 convenience variables.
3313 @item break @var{location}
3314 Set a breakpoint at the given @var{location}, which can specify a
3315 function name, a line number, or an address of an instruction.
3316 (@xref{Specify Location}, for a list of all the possible ways to
3317 specify a @var{location}.) The breakpoint will stop your program just
3318 before it executes any of the code in the specified @var{location}.
3320 When using source languages that permit overloading of symbols, such as
3321 C@t{++}, a function name may refer to more than one possible place to break.
3322 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3325 It is also possible to insert a breakpoint that will stop the program
3326 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3327 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3330 When called without any arguments, @code{break} sets a breakpoint at
3331 the next instruction to be executed in the selected stack frame
3332 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3333 innermost, this makes your program stop as soon as control
3334 returns to that frame. This is similar to the effect of a
3335 @code{finish} command in the frame inside the selected frame---except
3336 that @code{finish} does not leave an active breakpoint. If you use
3337 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3338 the next time it reaches the current location; this may be useful
3341 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3342 least one instruction has been executed. If it did not do this, you
3343 would be unable to proceed past a breakpoint without first disabling the
3344 breakpoint. This rule applies whether or not the breakpoint already
3345 existed when your program stopped.
3347 @item break @dots{} if @var{cond}
3348 Set a breakpoint with condition @var{cond}; evaluate the expression
3349 @var{cond} each time the breakpoint is reached, and stop only if the
3350 value is nonzero---that is, if @var{cond} evaluates as true.
3351 @samp{@dots{}} stands for one of the possible arguments described
3352 above (or no argument) specifying where to break. @xref{Conditions,
3353 ,Break Conditions}, for more information on breakpoint conditions.
3356 @item tbreak @var{args}
3357 Set a breakpoint enabled only for one stop. @var{args} are the
3358 same as for the @code{break} command, and the breakpoint is set in the same
3359 way, but the breakpoint is automatically deleted after the first time your
3360 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3363 @cindex hardware breakpoints
3364 @item hbreak @var{args}
3365 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3366 @code{break} command and the breakpoint is set in the same way, but the
3367 breakpoint requires hardware support and some target hardware may not
3368 have this support. The main purpose of this is EPROM/ROM code
3369 debugging, so you can set a breakpoint at an instruction without
3370 changing the instruction. This can be used with the new trap-generation
3371 provided by SPARClite DSU and most x86-based targets. These targets
3372 will generate traps when a program accesses some data or instruction
3373 address that is assigned to the debug registers. However the hardware
3374 breakpoint registers can take a limited number of breakpoints. For
3375 example, on the DSU, only two data breakpoints can be set at a time, and
3376 @value{GDBN} will reject this command if more than two are used. Delete
3377 or disable unused hardware breakpoints before setting new ones
3378 (@pxref{Disabling, ,Disabling Breakpoints}).
3379 @xref{Conditions, ,Break Conditions}.
3380 For remote targets, you can restrict the number of hardware
3381 breakpoints @value{GDBN} will use, see @ref{set remote
3382 hardware-breakpoint-limit}.
3385 @item thbreak @var{args}
3386 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3387 are the same as for the @code{hbreak} command and the breakpoint is set in
3388 the same way. However, like the @code{tbreak} command,
3389 the breakpoint is automatically deleted after the
3390 first time your program stops there. Also, like the @code{hbreak}
3391 command, the breakpoint requires hardware support and some target hardware
3392 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3393 See also @ref{Conditions, ,Break Conditions}.
3396 @cindex regular expression
3397 @cindex breakpoints at functions matching a regexp
3398 @cindex set breakpoints in many functions
3399 @item rbreak @var{regex}
3400 Set breakpoints on all functions matching the regular expression
3401 @var{regex}. This command sets an unconditional breakpoint on all
3402 matches, printing a list of all breakpoints it set. Once these
3403 breakpoints are set, they are treated just like the breakpoints set with
3404 the @code{break} command. You can delete them, disable them, or make
3405 them conditional the same way as any other breakpoint.
3407 The syntax of the regular expression is the standard one used with tools
3408 like @file{grep}. Note that this is different from the syntax used by
3409 shells, so for instance @code{foo*} matches all functions that include
3410 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3411 @code{.*} leading and trailing the regular expression you supply, so to
3412 match only functions that begin with @code{foo}, use @code{^foo}.
3414 @cindex non-member C@t{++} functions, set breakpoint in
3415 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3416 breakpoints on overloaded functions that are not members of any special
3419 @cindex set breakpoints on all functions
3420 The @code{rbreak} command can be used to set breakpoints in
3421 @strong{all} the functions in a program, like this:
3424 (@value{GDBP}) rbreak .
3427 @item rbreak @var{file}:@var{regex}
3428 If @code{rbreak} is called with a filename qualification, it limits
3429 the search for functions matching the given regular expression to the
3430 specified @var{file}. This can be used, for example, to set breakpoints on
3431 every function in a given file:
3434 (@value{GDBP}) rbreak file.c:.
3437 The colon separating the filename qualifier from the regex may
3438 optionally be surrounded by spaces.
3440 @kindex info breakpoints
3441 @cindex @code{$_} and @code{info breakpoints}
3442 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3443 @itemx info break @r{[}@var{n}@dots{}@r{]}
3444 Print a table of all breakpoints, watchpoints, and catchpoints set and
3445 not deleted. Optional argument @var{n} means print information only
3446 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3447 For each breakpoint, following columns are printed:
3450 @item Breakpoint Numbers
3452 Breakpoint, watchpoint, or catchpoint.
3454 Whether the breakpoint is marked to be disabled or deleted when hit.
3455 @item Enabled or Disabled
3456 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3457 that are not enabled.
3459 Where the breakpoint is in your program, as a memory address. For a
3460 pending breakpoint whose address is not yet known, this field will
3461 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3462 library that has the symbol or line referred by breakpoint is loaded.
3463 See below for details. A breakpoint with several locations will
3464 have @samp{<MULTIPLE>} in this field---see below for details.
3466 Where the breakpoint is in the source for your program, as a file and
3467 line number. For a pending breakpoint, the original string passed to
3468 the breakpoint command will be listed as it cannot be resolved until
3469 the appropriate shared library is loaded in the future.
3473 If a breakpoint is conditional, @code{info break} shows the condition on
3474 the line following the affected breakpoint; breakpoint commands, if any,
3475 are listed after that. A pending breakpoint is allowed to have a condition
3476 specified for it. The condition is not parsed for validity until a shared
3477 library is loaded that allows the pending breakpoint to resolve to a
3481 @code{info break} with a breakpoint
3482 number @var{n} as argument lists only that breakpoint. The
3483 convenience variable @code{$_} and the default examining-address for
3484 the @code{x} command are set to the address of the last breakpoint
3485 listed (@pxref{Memory, ,Examining Memory}).
3488 @code{info break} displays a count of the number of times the breakpoint
3489 has been hit. This is especially useful in conjunction with the
3490 @code{ignore} command. You can ignore a large number of breakpoint
3491 hits, look at the breakpoint info to see how many times the breakpoint
3492 was hit, and then run again, ignoring one less than that number. This
3493 will get you quickly to the last hit of that breakpoint.
3496 @value{GDBN} allows you to set any number of breakpoints at the same place in
3497 your program. There is nothing silly or meaningless about this. When
3498 the breakpoints are conditional, this is even useful
3499 (@pxref{Conditions, ,Break Conditions}).
3501 @cindex multiple locations, breakpoints
3502 @cindex breakpoints, multiple locations
3503 It is possible that a breakpoint corresponds to several locations
3504 in your program. Examples of this situation are:
3508 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3509 instances of the function body, used in different cases.
3512 For a C@t{++} template function, a given line in the function can
3513 correspond to any number of instantiations.
3516 For an inlined function, a given source line can correspond to
3517 several places where that function is inlined.
3520 In all those cases, @value{GDBN} will insert a breakpoint at all
3521 the relevant locations@footnote{
3522 As of this writing, multiple-location breakpoints work only if there's
3523 line number information for all the locations. This means that they
3524 will generally not work in system libraries, unless you have debug
3525 info with line numbers for them.}.
3527 A breakpoint with multiple locations is displayed in the breakpoint
3528 table using several rows---one header row, followed by one row for
3529 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3530 address column. The rows for individual locations contain the actual
3531 addresses for locations, and show the functions to which those
3532 locations belong. The number column for a location is of the form
3533 @var{breakpoint-number}.@var{location-number}.
3538 Num Type Disp Enb Address What
3539 1 breakpoint keep y <MULTIPLE>
3541 breakpoint already hit 1 time
3542 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3543 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3546 Each location can be individually enabled or disabled by passing
3547 @var{breakpoint-number}.@var{location-number} as argument to the
3548 @code{enable} and @code{disable} commands. Note that you cannot
3549 delete the individual locations from the list, you can only delete the
3550 entire list of locations that belong to their parent breakpoint (with
3551 the @kbd{delete @var{num}} command, where @var{num} is the number of
3552 the parent breakpoint, 1 in the above example). Disabling or enabling
3553 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3554 that belong to that breakpoint.
3556 @cindex pending breakpoints
3557 It's quite common to have a breakpoint inside a shared library.
3558 Shared libraries can be loaded and unloaded explicitly,
3559 and possibly repeatedly, as the program is executed. To support
3560 this use case, @value{GDBN} updates breakpoint locations whenever
3561 any shared library is loaded or unloaded. Typically, you would
3562 set a breakpoint in a shared library at the beginning of your
3563 debugging session, when the library is not loaded, and when the
3564 symbols from the library are not available. When you try to set
3565 breakpoint, @value{GDBN} will ask you if you want to set
3566 a so called @dfn{pending breakpoint}---breakpoint whose address
3567 is not yet resolved.
3569 After the program is run, whenever a new shared library is loaded,
3570 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3571 shared library contains the symbol or line referred to by some
3572 pending breakpoint, that breakpoint is resolved and becomes an
3573 ordinary breakpoint. When a library is unloaded, all breakpoints
3574 that refer to its symbols or source lines become pending again.
3576 This logic works for breakpoints with multiple locations, too. For
3577 example, if you have a breakpoint in a C@t{++} template function, and
3578 a newly loaded shared library has an instantiation of that template,
3579 a new location is added to the list of locations for the breakpoint.
3581 Except for having unresolved address, pending breakpoints do not
3582 differ from regular breakpoints. You can set conditions or commands,
3583 enable and disable them and perform other breakpoint operations.
3585 @value{GDBN} provides some additional commands for controlling what
3586 happens when the @samp{break} command cannot resolve breakpoint
3587 address specification to an address:
3589 @kindex set breakpoint pending
3590 @kindex show breakpoint pending
3592 @item set breakpoint pending auto
3593 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3594 location, it queries you whether a pending breakpoint should be created.
3596 @item set breakpoint pending on
3597 This indicates that an unrecognized breakpoint location should automatically
3598 result in a pending breakpoint being created.
3600 @item set breakpoint pending off
3601 This indicates that pending breakpoints are not to be created. Any
3602 unrecognized breakpoint location results in an error. This setting does
3603 not affect any pending breakpoints previously created.
3605 @item show breakpoint pending
3606 Show the current behavior setting for creating pending breakpoints.
3609 The settings above only affect the @code{break} command and its
3610 variants. Once breakpoint is set, it will be automatically updated
3611 as shared libraries are loaded and unloaded.
3613 @cindex automatic hardware breakpoints
3614 For some targets, @value{GDBN} can automatically decide if hardware or
3615 software breakpoints should be used, depending on whether the
3616 breakpoint address is read-only or read-write. This applies to
3617 breakpoints set with the @code{break} command as well as to internal
3618 breakpoints set by commands like @code{next} and @code{finish}. For
3619 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3622 You can control this automatic behaviour with the following commands::
3624 @kindex set breakpoint auto-hw
3625 @kindex show breakpoint auto-hw
3627 @item set breakpoint auto-hw on
3628 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3629 will try to use the target memory map to decide if software or hardware
3630 breakpoint must be used.
3632 @item set breakpoint auto-hw off
3633 This indicates @value{GDBN} should not automatically select breakpoint
3634 type. If the target provides a memory map, @value{GDBN} will warn when
3635 trying to set software breakpoint at a read-only address.
3638 @value{GDBN} normally implements breakpoints by replacing the program code
3639 at the breakpoint address with a special instruction, which, when
3640 executed, given control to the debugger. By default, the program
3641 code is so modified only when the program is resumed. As soon as
3642 the program stops, @value{GDBN} restores the original instructions. This
3643 behaviour guards against leaving breakpoints inserted in the
3644 target should gdb abrubptly disconnect. However, with slow remote
3645 targets, inserting and removing breakpoint can reduce the performance.
3646 This behavior can be controlled with the following commands::
3648 @kindex set breakpoint always-inserted
3649 @kindex show breakpoint always-inserted
3651 @item set breakpoint always-inserted off
3652 All breakpoints, including newly added by the user, are inserted in
3653 the target only when the target is resumed. All breakpoints are
3654 removed from the target when it stops.
3656 @item set breakpoint always-inserted on
3657 Causes all breakpoints to be inserted in the target at all times. If
3658 the user adds a new breakpoint, or changes an existing breakpoint, the
3659 breakpoints in the target are updated immediately. A breakpoint is
3660 removed from the target only when breakpoint itself is removed.
3662 @cindex non-stop mode, and @code{breakpoint always-inserted}
3663 @item set breakpoint always-inserted auto
3664 This is the default mode. If @value{GDBN} is controlling the inferior
3665 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3666 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3667 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3668 @code{breakpoint always-inserted} mode is off.
3671 @cindex negative breakpoint numbers
3672 @cindex internal @value{GDBN} breakpoints
3673 @value{GDBN} itself sometimes sets breakpoints in your program for
3674 special purposes, such as proper handling of @code{longjmp} (in C
3675 programs). These internal breakpoints are assigned negative numbers,
3676 starting with @code{-1}; @samp{info breakpoints} does not display them.
3677 You can see these breakpoints with the @value{GDBN} maintenance command
3678 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3681 @node Set Watchpoints
3682 @subsection Setting Watchpoints
3684 @cindex setting watchpoints
3685 You can use a watchpoint to stop execution whenever the value of an
3686 expression changes, without having to predict a particular place where
3687 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3688 The expression may be as simple as the value of a single variable, or
3689 as complex as many variables combined by operators. Examples include:
3693 A reference to the value of a single variable.
3696 An address cast to an appropriate data type. For example,
3697 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3698 address (assuming an @code{int} occupies 4 bytes).
3701 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3702 expression can use any operators valid in the program's native
3703 language (@pxref{Languages}).
3706 You can set a watchpoint on an expression even if the expression can
3707 not be evaluated yet. For instance, you can set a watchpoint on
3708 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3709 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3710 the expression produces a valid value. If the expression becomes
3711 valid in some other way than changing a variable (e.g.@: if the memory
3712 pointed to by @samp{*global_ptr} becomes readable as the result of a
3713 @code{malloc} call), @value{GDBN} may not stop until the next time
3714 the expression changes.
3716 @cindex software watchpoints
3717 @cindex hardware watchpoints
3718 Depending on your system, watchpoints may be implemented in software or
3719 hardware. @value{GDBN} does software watchpointing by single-stepping your
3720 program and testing the variable's value each time, which is hundreds of
3721 times slower than normal execution. (But this may still be worth it, to
3722 catch errors where you have no clue what part of your program is the
3725 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3726 x86-based targets, @value{GDBN} includes support for hardware
3727 watchpoints, which do not slow down the running of your program.
3731 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3732 Set a watchpoint for an expression. @value{GDBN} will break when the
3733 expression @var{expr} is written into by the program and its value
3734 changes. The simplest (and the most popular) use of this command is
3735 to watch the value of a single variable:
3738 (@value{GDBP}) watch foo
3741 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3742 clause, @value{GDBN} breaks only when the thread identified by
3743 @var{threadnum} changes the value of @var{expr}. If any other threads
3744 change the value of @var{expr}, @value{GDBN} will not break. Note
3745 that watchpoints restricted to a single thread in this way only work
3746 with Hardware Watchpoints.
3748 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3749 (see below). The @code{-location} argument tells @value{GDBN} to
3750 instead watch the memory referred to by @var{expr}. In this case,
3751 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3752 and watch the memory at that address. The type of the result is used
3753 to determine the size of the watched memory. If the expression's
3754 result does not have an address, then @value{GDBN} will print an
3758 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3759 Set a watchpoint that will break when the value of @var{expr} is read
3763 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3764 Set a watchpoint that will break when @var{expr} is either read from
3765 or written into by the program.
3767 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3768 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3769 This command prints a list of watchpoints, using the same format as
3770 @code{info break} (@pxref{Set Breaks}).
3773 If you watch for a change in a numerically entered address you need to
3774 dereference it, as the address itself is just a constant number which will
3775 never change. @value{GDBN} refuses to create a watchpoint that watches
3776 a never-changing value:
3779 (@value{GDBP}) watch 0x600850
3780 Cannot watch constant value 0x600850.
3781 (@value{GDBP}) watch *(int *) 0x600850
3782 Watchpoint 1: *(int *) 6293584
3785 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3786 watchpoints execute very quickly, and the debugger reports a change in
3787 value at the exact instruction where the change occurs. If @value{GDBN}
3788 cannot set a hardware watchpoint, it sets a software watchpoint, which
3789 executes more slowly and reports the change in value at the next
3790 @emph{statement}, not the instruction, after the change occurs.
3792 @cindex use only software watchpoints
3793 You can force @value{GDBN} to use only software watchpoints with the
3794 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3795 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3796 the underlying system supports them. (Note that hardware-assisted
3797 watchpoints that were set @emph{before} setting
3798 @code{can-use-hw-watchpoints} to zero will still use the hardware
3799 mechanism of watching expression values.)
3802 @item set can-use-hw-watchpoints
3803 @kindex set can-use-hw-watchpoints
3804 Set whether or not to use hardware watchpoints.
3806 @item show can-use-hw-watchpoints
3807 @kindex show can-use-hw-watchpoints
3808 Show the current mode of using hardware watchpoints.
3811 For remote targets, you can restrict the number of hardware
3812 watchpoints @value{GDBN} will use, see @ref{set remote
3813 hardware-breakpoint-limit}.
3815 When you issue the @code{watch} command, @value{GDBN} reports
3818 Hardware watchpoint @var{num}: @var{expr}
3822 if it was able to set a hardware watchpoint.
3824 Currently, the @code{awatch} and @code{rwatch} commands can only set
3825 hardware watchpoints, because accesses to data that don't change the
3826 value of the watched expression cannot be detected without examining
3827 every instruction as it is being executed, and @value{GDBN} does not do
3828 that currently. If @value{GDBN} finds that it is unable to set a
3829 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3830 will print a message like this:
3833 Expression cannot be implemented with read/access watchpoint.
3836 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3837 data type of the watched expression is wider than what a hardware
3838 watchpoint on the target machine can handle. For example, some systems
3839 can only watch regions that are up to 4 bytes wide; on such systems you
3840 cannot set hardware watchpoints for an expression that yields a
3841 double-precision floating-point number (which is typically 8 bytes
3842 wide). As a work-around, it might be possible to break the large region
3843 into a series of smaller ones and watch them with separate watchpoints.
3845 If you set too many hardware watchpoints, @value{GDBN} might be unable
3846 to insert all of them when you resume the execution of your program.
3847 Since the precise number of active watchpoints is unknown until such
3848 time as the program is about to be resumed, @value{GDBN} might not be
3849 able to warn you about this when you set the watchpoints, and the
3850 warning will be printed only when the program is resumed:
3853 Hardware watchpoint @var{num}: Could not insert watchpoint
3857 If this happens, delete or disable some of the watchpoints.
3859 Watching complex expressions that reference many variables can also
3860 exhaust the resources available for hardware-assisted watchpoints.
3861 That's because @value{GDBN} needs to watch every variable in the
3862 expression with separately allocated resources.
3864 If you call a function interactively using @code{print} or @code{call},
3865 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3866 kind of breakpoint or the call completes.
3868 @value{GDBN} automatically deletes watchpoints that watch local
3869 (automatic) variables, or expressions that involve such variables, when
3870 they go out of scope, that is, when the execution leaves the block in
3871 which these variables were defined. In particular, when the program
3872 being debugged terminates, @emph{all} local variables go out of scope,
3873 and so only watchpoints that watch global variables remain set. If you
3874 rerun the program, you will need to set all such watchpoints again. One
3875 way of doing that would be to set a code breakpoint at the entry to the
3876 @code{main} function and when it breaks, set all the watchpoints.
3878 @cindex watchpoints and threads
3879 @cindex threads and watchpoints
3880 In multi-threaded programs, watchpoints will detect changes to the
3881 watched expression from every thread.
3884 @emph{Warning:} In multi-threaded programs, software watchpoints
3885 have only limited usefulness. If @value{GDBN} creates a software
3886 watchpoint, it can only watch the value of an expression @emph{in a
3887 single thread}. If you are confident that the expression can only
3888 change due to the current thread's activity (and if you are also
3889 confident that no other thread can become current), then you can use
3890 software watchpoints as usual. However, @value{GDBN} may not notice
3891 when a non-current thread's activity changes the expression. (Hardware
3892 watchpoints, in contrast, watch an expression in all threads.)
3895 @xref{set remote hardware-watchpoint-limit}.
3897 @node Set Catchpoints
3898 @subsection Setting Catchpoints
3899 @cindex catchpoints, setting
3900 @cindex exception handlers
3901 @cindex event handling
3903 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3904 kinds of program events, such as C@t{++} exceptions or the loading of a
3905 shared library. Use the @code{catch} command to set a catchpoint.
3909 @item catch @var{event}
3910 Stop when @var{event} occurs. @var{event} can be any of the following:
3913 @cindex stop on C@t{++} exceptions
3914 The throwing of a C@t{++} exception.
3917 The catching of a C@t{++} exception.
3920 @cindex Ada exception catching
3921 @cindex catch Ada exceptions
3922 An Ada exception being raised. If an exception name is specified
3923 at the end of the command (eg @code{catch exception Program_Error}),
3924 the debugger will stop only when this specific exception is raised.
3925 Otherwise, the debugger stops execution when any Ada exception is raised.
3927 When inserting an exception catchpoint on a user-defined exception whose
3928 name is identical to one of the exceptions defined by the language, the
3929 fully qualified name must be used as the exception name. Otherwise,
3930 @value{GDBN} will assume that it should stop on the pre-defined exception
3931 rather than the user-defined one. For instance, assuming an exception
3932 called @code{Constraint_Error} is defined in package @code{Pck}, then
3933 the command to use to catch such exceptions is @kbd{catch exception
3934 Pck.Constraint_Error}.
3936 @item exception unhandled
3937 An exception that was raised but is not handled by the program.
3940 A failed Ada assertion.
3943 @cindex break on fork/exec
3944 A call to @code{exec}. This is currently only available for HP-UX
3948 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3949 @cindex break on a system call.
3950 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3951 syscall is a mechanism for application programs to request a service
3952 from the operating system (OS) or one of the OS system services.
3953 @value{GDBN} can catch some or all of the syscalls issued by the
3954 debuggee, and show the related information for each syscall. If no
3955 argument is specified, calls to and returns from all system calls
3958 @var{name} can be any system call name that is valid for the
3959 underlying OS. Just what syscalls are valid depends on the OS. On
3960 GNU and Unix systems, you can find the full list of valid syscall
3961 names on @file{/usr/include/asm/unistd.h}.
3963 @c For MS-Windows, the syscall names and the corresponding numbers
3964 @c can be found, e.g., on this URL:
3965 @c http://www.metasploit.com/users/opcode/syscalls.html
3966 @c but we don't support Windows syscalls yet.
3968 Normally, @value{GDBN} knows in advance which syscalls are valid for
3969 each OS, so you can use the @value{GDBN} command-line completion
3970 facilities (@pxref{Completion,, command completion}) to list the
3973 You may also specify the system call numerically. A syscall's
3974 number is the value passed to the OS's syscall dispatcher to
3975 identify the requested service. When you specify the syscall by its
3976 name, @value{GDBN} uses its database of syscalls to convert the name
3977 into the corresponding numeric code, but using the number directly
3978 may be useful if @value{GDBN}'s database does not have the complete
3979 list of syscalls on your system (e.g., because @value{GDBN} lags
3980 behind the OS upgrades).
3982 The example below illustrates how this command works if you don't provide
3986 (@value{GDBP}) catch syscall
3987 Catchpoint 1 (syscall)
3989 Starting program: /tmp/catch-syscall
3991 Catchpoint 1 (call to syscall 'close'), \
3992 0xffffe424 in __kernel_vsyscall ()
3996 Catchpoint 1 (returned from syscall 'close'), \
3997 0xffffe424 in __kernel_vsyscall ()
4001 Here is an example of catching a system call by name:
4004 (@value{GDBP}) catch syscall chroot
4005 Catchpoint 1 (syscall 'chroot' [61])
4007 Starting program: /tmp/catch-syscall
4009 Catchpoint 1 (call to syscall 'chroot'), \
4010 0xffffe424 in __kernel_vsyscall ()
4014 Catchpoint 1 (returned from syscall 'chroot'), \
4015 0xffffe424 in __kernel_vsyscall ()
4019 An example of specifying a system call numerically. In the case
4020 below, the syscall number has a corresponding entry in the XML
4021 file, so @value{GDBN} finds its name and prints it:
4024 (@value{GDBP}) catch syscall 252
4025 Catchpoint 1 (syscall(s) 'exit_group')
4027 Starting program: /tmp/catch-syscall
4029 Catchpoint 1 (call to syscall 'exit_group'), \
4030 0xffffe424 in __kernel_vsyscall ()
4034 Program exited normally.
4038 However, there can be situations when there is no corresponding name
4039 in XML file for that syscall number. In this case, @value{GDBN} prints
4040 a warning message saying that it was not able to find the syscall name,
4041 but the catchpoint will be set anyway. See the example below:
4044 (@value{GDBP}) catch syscall 764
4045 warning: The number '764' does not represent a known syscall.
4046 Catchpoint 2 (syscall 764)
4050 If you configure @value{GDBN} using the @samp{--without-expat} option,
4051 it will not be able to display syscall names. Also, if your
4052 architecture does not have an XML file describing its system calls,
4053 you will not be able to see the syscall names. It is important to
4054 notice that these two features are used for accessing the syscall
4055 name database. In either case, you will see a warning like this:
4058 (@value{GDBP}) catch syscall
4059 warning: Could not open "syscalls/i386-linux.xml"
4060 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4061 GDB will not be able to display syscall names.
4062 Catchpoint 1 (syscall)
4066 Of course, the file name will change depending on your architecture and system.
4068 Still using the example above, you can also try to catch a syscall by its
4069 number. In this case, you would see something like:
4072 (@value{GDBP}) catch syscall 252
4073 Catchpoint 1 (syscall(s) 252)
4076 Again, in this case @value{GDBN} would not be able to display syscall's names.
4079 A call to @code{fork}. This is currently only available for HP-UX
4083 A call to @code{vfork}. This is currently only available for HP-UX
4088 @item tcatch @var{event}
4089 Set a catchpoint that is enabled only for one stop. The catchpoint is
4090 automatically deleted after the first time the event is caught.
4094 Use the @code{info break} command to list the current catchpoints.
4096 There are currently some limitations to C@t{++} exception handling
4097 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4101 If you call a function interactively, @value{GDBN} normally returns
4102 control to you when the function has finished executing. If the call
4103 raises an exception, however, the call may bypass the mechanism that
4104 returns control to you and cause your program either to abort or to
4105 simply continue running until it hits a breakpoint, catches a signal
4106 that @value{GDBN} is listening for, or exits. This is the case even if
4107 you set a catchpoint for the exception; catchpoints on exceptions are
4108 disabled within interactive calls.
4111 You cannot raise an exception interactively.
4114 You cannot install an exception handler interactively.
4117 @cindex raise exceptions
4118 Sometimes @code{catch} is not the best way to debug exception handling:
4119 if you need to know exactly where an exception is raised, it is better to
4120 stop @emph{before} the exception handler is called, since that way you
4121 can see the stack before any unwinding takes place. If you set a
4122 breakpoint in an exception handler instead, it may not be easy to find
4123 out where the exception was raised.
4125 To stop just before an exception handler is called, you need some
4126 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4127 raised by calling a library function named @code{__raise_exception}
4128 which has the following ANSI C interface:
4131 /* @var{addr} is where the exception identifier is stored.
4132 @var{id} is the exception identifier. */
4133 void __raise_exception (void **addr, void *id);
4137 To make the debugger catch all exceptions before any stack
4138 unwinding takes place, set a breakpoint on @code{__raise_exception}
4139 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4141 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4142 that depends on the value of @var{id}, you can stop your program when
4143 a specific exception is raised. You can use multiple conditional
4144 breakpoints to stop your program when any of a number of exceptions are
4149 @subsection Deleting Breakpoints
4151 @cindex clearing breakpoints, watchpoints, catchpoints
4152 @cindex deleting breakpoints, watchpoints, catchpoints
4153 It is often necessary to eliminate a breakpoint, watchpoint, or
4154 catchpoint once it has done its job and you no longer want your program
4155 to stop there. This is called @dfn{deleting} the breakpoint. A
4156 breakpoint that has been deleted no longer exists; it is forgotten.
4158 With the @code{clear} command you can delete breakpoints according to
4159 where they are in your program. With the @code{delete} command you can
4160 delete individual breakpoints, watchpoints, or catchpoints by specifying
4161 their breakpoint numbers.
4163 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4164 automatically ignores breakpoints on the first instruction to be executed
4165 when you continue execution without changing the execution address.
4170 Delete any breakpoints at the next instruction to be executed in the
4171 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4172 the innermost frame is selected, this is a good way to delete a
4173 breakpoint where your program just stopped.
4175 @item clear @var{location}
4176 Delete any breakpoints set at the specified @var{location}.
4177 @xref{Specify Location}, for the various forms of @var{location}; the
4178 most useful ones are listed below:
4181 @item clear @var{function}
4182 @itemx clear @var{filename}:@var{function}
4183 Delete any breakpoints set at entry to the named @var{function}.
4185 @item clear @var{linenum}
4186 @itemx clear @var{filename}:@var{linenum}
4187 Delete any breakpoints set at or within the code of the specified
4188 @var{linenum} of the specified @var{filename}.
4191 @cindex delete breakpoints
4193 @kindex d @r{(@code{delete})}
4194 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4195 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4196 ranges specified as arguments. If no argument is specified, delete all
4197 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4198 confirm off}). You can abbreviate this command as @code{d}.
4202 @subsection Disabling Breakpoints
4204 @cindex enable/disable a breakpoint
4205 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4206 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4207 it had been deleted, but remembers the information on the breakpoint so
4208 that you can @dfn{enable} it again later.
4210 You disable and enable breakpoints, watchpoints, and catchpoints with
4211 the @code{enable} and @code{disable} commands, optionally specifying
4212 one or more breakpoint numbers as arguments. Use @code{info break} to
4213 print a list of all breakpoints, watchpoints, and catchpoints if you
4214 do not know which numbers to use.
4216 Disabling and enabling a breakpoint that has multiple locations
4217 affects all of its locations.
4219 A breakpoint, watchpoint, or catchpoint can have any of four different
4220 states of enablement:
4224 Enabled. The breakpoint stops your program. A breakpoint set
4225 with the @code{break} command starts out in this state.
4227 Disabled. The breakpoint has no effect on your program.
4229 Enabled once. The breakpoint stops your program, but then becomes
4232 Enabled for deletion. The breakpoint stops your program, but
4233 immediately after it does so it is deleted permanently. A breakpoint
4234 set with the @code{tbreak} command starts out in this state.
4237 You can use the following commands to enable or disable breakpoints,
4238 watchpoints, and catchpoints:
4242 @kindex dis @r{(@code{disable})}
4243 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4244 Disable the specified breakpoints---or all breakpoints, if none are
4245 listed. A disabled breakpoint has no effect but is not forgotten. All
4246 options such as ignore-counts, conditions and commands are remembered in
4247 case the breakpoint is enabled again later. You may abbreviate
4248 @code{disable} as @code{dis}.
4251 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4252 Enable the specified breakpoints (or all defined breakpoints). They
4253 become effective once again in stopping your program.
4255 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4256 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4257 of these breakpoints immediately after stopping your program.
4259 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4260 Enable the specified breakpoints to work once, then die. @value{GDBN}
4261 deletes any of these breakpoints as soon as your program stops there.
4262 Breakpoints set by the @code{tbreak} command start out in this state.
4265 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4266 @c confusing: tbreak is also initially enabled.
4267 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4268 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4269 subsequently, they become disabled or enabled only when you use one of
4270 the commands above. (The command @code{until} can set and delete a
4271 breakpoint of its own, but it does not change the state of your other
4272 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4276 @subsection Break Conditions
4277 @cindex conditional breakpoints
4278 @cindex breakpoint conditions
4280 @c FIXME what is scope of break condition expr? Context where wanted?
4281 @c in particular for a watchpoint?
4282 The simplest sort of breakpoint breaks every time your program reaches a
4283 specified place. You can also specify a @dfn{condition} for a
4284 breakpoint. A condition is just a Boolean expression in your
4285 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4286 a condition evaluates the expression each time your program reaches it,
4287 and your program stops only if the condition is @emph{true}.
4289 This is the converse of using assertions for program validation; in that
4290 situation, you want to stop when the assertion is violated---that is,
4291 when the condition is false. In C, if you want to test an assertion expressed
4292 by the condition @var{assert}, you should set the condition
4293 @samp{! @var{assert}} on the appropriate breakpoint.
4295 Conditions are also accepted for watchpoints; you may not need them,
4296 since a watchpoint is inspecting the value of an expression anyhow---but
4297 it might be simpler, say, to just set a watchpoint on a variable name,
4298 and specify a condition that tests whether the new value is an interesting
4301 Break conditions can have side effects, and may even call functions in
4302 your program. This can be useful, for example, to activate functions
4303 that log program progress, or to use your own print functions to
4304 format special data structures. The effects are completely predictable
4305 unless there is another enabled breakpoint at the same address. (In
4306 that case, @value{GDBN} might see the other breakpoint first and stop your
4307 program without checking the condition of this one.) Note that
4308 breakpoint commands are usually more convenient and flexible than break
4310 purpose of performing side effects when a breakpoint is reached
4311 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4313 Break conditions can be specified when a breakpoint is set, by using
4314 @samp{if} in the arguments to the @code{break} command. @xref{Set
4315 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4316 with the @code{condition} command.
4318 You can also use the @code{if} keyword with the @code{watch} command.
4319 The @code{catch} command does not recognize the @code{if} keyword;
4320 @code{condition} is the only way to impose a further condition on a
4325 @item condition @var{bnum} @var{expression}
4326 Specify @var{expression} as the break condition for breakpoint,
4327 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4328 breakpoint @var{bnum} stops your program only if the value of
4329 @var{expression} is true (nonzero, in C). When you use
4330 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4331 syntactic correctness, and to determine whether symbols in it have
4332 referents in the context of your breakpoint. If @var{expression} uses
4333 symbols not referenced in the context of the breakpoint, @value{GDBN}
4334 prints an error message:
4337 No symbol "foo" in current context.
4342 not actually evaluate @var{expression} at the time the @code{condition}
4343 command (or a command that sets a breakpoint with a condition, like
4344 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4346 @item condition @var{bnum}
4347 Remove the condition from breakpoint number @var{bnum}. It becomes
4348 an ordinary unconditional breakpoint.
4351 @cindex ignore count (of breakpoint)
4352 A special case of a breakpoint condition is to stop only when the
4353 breakpoint has been reached a certain number of times. This is so
4354 useful that there is a special way to do it, using the @dfn{ignore
4355 count} of the breakpoint. Every breakpoint has an ignore count, which
4356 is an integer. Most of the time, the ignore count is zero, and
4357 therefore has no effect. But if your program reaches a breakpoint whose
4358 ignore count is positive, then instead of stopping, it just decrements
4359 the ignore count by one and continues. As a result, if the ignore count
4360 value is @var{n}, the breakpoint does not stop the next @var{n} times
4361 your program reaches it.
4365 @item ignore @var{bnum} @var{count}
4366 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4367 The next @var{count} times the breakpoint is reached, your program's
4368 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4371 To make the breakpoint stop the next time it is reached, specify
4374 When you use @code{continue} to resume execution of your program from a
4375 breakpoint, you can specify an ignore count directly as an argument to
4376 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4377 Stepping,,Continuing and Stepping}.
4379 If a breakpoint has a positive ignore count and a condition, the
4380 condition is not checked. Once the ignore count reaches zero,
4381 @value{GDBN} resumes checking the condition.
4383 You could achieve the effect of the ignore count with a condition such
4384 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4385 is decremented each time. @xref{Convenience Vars, ,Convenience
4389 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4392 @node Break Commands
4393 @subsection Breakpoint Command Lists
4395 @cindex breakpoint commands
4396 You can give any breakpoint (or watchpoint or catchpoint) a series of
4397 commands to execute when your program stops due to that breakpoint. For
4398 example, you might want to print the values of certain expressions, or
4399 enable other breakpoints.
4403 @kindex end@r{ (breakpoint commands)}
4404 @item commands @r{[}@var{range}@dots{}@r{]}
4405 @itemx @dots{} @var{command-list} @dots{}
4407 Specify a list of commands for the given breakpoints. The commands
4408 themselves appear on the following lines. Type a line containing just
4409 @code{end} to terminate the commands.
4411 To remove all commands from a breakpoint, type @code{commands} and
4412 follow it immediately with @code{end}; that is, give no commands.
4414 With no argument, @code{commands} refers to the last breakpoint,
4415 watchpoint, or catchpoint set (not to the breakpoint most recently
4416 encountered). If the most recent breakpoints were set with a single
4417 command, then the @code{commands} will apply to all the breakpoints
4418 set by that command. This applies to breakpoints set by
4419 @code{rbreak}, and also applies when a single @code{break} command
4420 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4424 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4425 disabled within a @var{command-list}.
4427 You can use breakpoint commands to start your program up again. Simply
4428 use the @code{continue} command, or @code{step}, or any other command
4429 that resumes execution.
4431 Any other commands in the command list, after a command that resumes
4432 execution, are ignored. This is because any time you resume execution
4433 (even with a simple @code{next} or @code{step}), you may encounter
4434 another breakpoint---which could have its own command list, leading to
4435 ambiguities about which list to execute.
4438 If the first command you specify in a command list is @code{silent}, the
4439 usual message about stopping at a breakpoint is not printed. This may
4440 be desirable for breakpoints that are to print a specific message and
4441 then continue. If none of the remaining commands print anything, you
4442 see no sign that the breakpoint was reached. @code{silent} is
4443 meaningful only at the beginning of a breakpoint command list.
4445 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4446 print precisely controlled output, and are often useful in silent
4447 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4449 For example, here is how you could use breakpoint commands to print the
4450 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4456 printf "x is %d\n",x
4461 One application for breakpoint commands is to compensate for one bug so
4462 you can test for another. Put a breakpoint just after the erroneous line
4463 of code, give it a condition to detect the case in which something
4464 erroneous has been done, and give it commands to assign correct values
4465 to any variables that need them. End with the @code{continue} command
4466 so that your program does not stop, and start with the @code{silent}
4467 command so that no output is produced. Here is an example:
4478 @node Save Breakpoints
4479 @subsection How to save breakpoints to a file
4481 To save breakpoint definitions to a file use the @w{@code{save
4482 breakpoints}} command.
4485 @kindex save breakpoints
4486 @cindex save breakpoints to a file for future sessions
4487 @item save breakpoints [@var{filename}]
4488 This command saves all current breakpoint definitions together with
4489 their commands and ignore counts, into a file @file{@var{filename}}
4490 suitable for use in a later debugging session. This includes all
4491 types of breakpoints (breakpoints, watchpoints, catchpoints,
4492 tracepoints). To read the saved breakpoint definitions, use the
4493 @code{source} command (@pxref{Command Files}). Note that watchpoints
4494 with expressions involving local variables may fail to be recreated
4495 because it may not be possible to access the context where the
4496 watchpoint is valid anymore. Because the saved breakpoint definitions
4497 are simply a sequence of @value{GDBN} commands that recreate the
4498 breakpoints, you can edit the file in your favorite editing program,
4499 and remove the breakpoint definitions you're not interested in, or
4500 that can no longer be recreated.
4503 @c @ifclear BARETARGET
4504 @node Error in Breakpoints
4505 @subsection ``Cannot insert breakpoints''
4507 If you request too many active hardware-assisted breakpoints and
4508 watchpoints, you will see this error message:
4510 @c FIXME: the precise wording of this message may change; the relevant
4511 @c source change is not committed yet (Sep 3, 1999).
4513 Stopped; cannot insert breakpoints.
4514 You may have requested too many hardware breakpoints and watchpoints.
4518 This message is printed when you attempt to resume the program, since
4519 only then @value{GDBN} knows exactly how many hardware breakpoints and
4520 watchpoints it needs to insert.
4522 When this message is printed, you need to disable or remove some of the
4523 hardware-assisted breakpoints and watchpoints, and then continue.
4525 @node Breakpoint-related Warnings
4526 @subsection ``Breakpoint address adjusted...''
4527 @cindex breakpoint address adjusted
4529 Some processor architectures place constraints on the addresses at
4530 which breakpoints may be placed. For architectures thus constrained,
4531 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4532 with the constraints dictated by the architecture.
4534 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4535 a VLIW architecture in which a number of RISC-like instructions may be
4536 bundled together for parallel execution. The FR-V architecture
4537 constrains the location of a breakpoint instruction within such a
4538 bundle to the instruction with the lowest address. @value{GDBN}
4539 honors this constraint by adjusting a breakpoint's address to the
4540 first in the bundle.
4542 It is not uncommon for optimized code to have bundles which contain
4543 instructions from different source statements, thus it may happen that
4544 a breakpoint's address will be adjusted from one source statement to
4545 another. Since this adjustment may significantly alter @value{GDBN}'s
4546 breakpoint related behavior from what the user expects, a warning is
4547 printed when the breakpoint is first set and also when the breakpoint
4550 A warning like the one below is printed when setting a breakpoint
4551 that's been subject to address adjustment:
4554 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4557 Such warnings are printed both for user settable and @value{GDBN}'s
4558 internal breakpoints. If you see one of these warnings, you should
4559 verify that a breakpoint set at the adjusted address will have the
4560 desired affect. If not, the breakpoint in question may be removed and
4561 other breakpoints may be set which will have the desired behavior.
4562 E.g., it may be sufficient to place the breakpoint at a later
4563 instruction. A conditional breakpoint may also be useful in some
4564 cases to prevent the breakpoint from triggering too often.
4566 @value{GDBN} will also issue a warning when stopping at one of these
4567 adjusted breakpoints:
4570 warning: Breakpoint 1 address previously adjusted from 0x00010414
4574 When this warning is encountered, it may be too late to take remedial
4575 action except in cases where the breakpoint is hit earlier or more
4576 frequently than expected.
4578 @node Continuing and Stepping
4579 @section Continuing and Stepping
4583 @cindex resuming execution
4584 @dfn{Continuing} means resuming program execution until your program
4585 completes normally. In contrast, @dfn{stepping} means executing just
4586 one more ``step'' of your program, where ``step'' may mean either one
4587 line of source code, or one machine instruction (depending on what
4588 particular command you use). Either when continuing or when stepping,
4589 your program may stop even sooner, due to a breakpoint or a signal. (If
4590 it stops due to a signal, you may want to use @code{handle}, or use
4591 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4595 @kindex c @r{(@code{continue})}
4596 @kindex fg @r{(resume foreground execution)}
4597 @item continue @r{[}@var{ignore-count}@r{]}
4598 @itemx c @r{[}@var{ignore-count}@r{]}
4599 @itemx fg @r{[}@var{ignore-count}@r{]}
4600 Resume program execution, at the address where your program last stopped;
4601 any breakpoints set at that address are bypassed. The optional argument
4602 @var{ignore-count} allows you to specify a further number of times to
4603 ignore a breakpoint at this location; its effect is like that of
4604 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4606 The argument @var{ignore-count} is meaningful only when your program
4607 stopped due to a breakpoint. At other times, the argument to
4608 @code{continue} is ignored.
4610 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4611 debugged program is deemed to be the foreground program) are provided
4612 purely for convenience, and have exactly the same behavior as
4616 To resume execution at a different place, you can use @code{return}
4617 (@pxref{Returning, ,Returning from a Function}) to go back to the
4618 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4619 Different Address}) to go to an arbitrary location in your program.
4621 A typical technique for using stepping is to set a breakpoint
4622 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4623 beginning of the function or the section of your program where a problem
4624 is believed to lie, run your program until it stops at that breakpoint,
4625 and then step through the suspect area, examining the variables that are
4626 interesting, until you see the problem happen.
4630 @kindex s @r{(@code{step})}
4632 Continue running your program until control reaches a different source
4633 line, then stop it and return control to @value{GDBN}. This command is
4634 abbreviated @code{s}.
4637 @c "without debugging information" is imprecise; actually "without line
4638 @c numbers in the debugging information". (gcc -g1 has debugging info but
4639 @c not line numbers). But it seems complex to try to make that
4640 @c distinction here.
4641 @emph{Warning:} If you use the @code{step} command while control is
4642 within a function that was compiled without debugging information,
4643 execution proceeds until control reaches a function that does have
4644 debugging information. Likewise, it will not step into a function which
4645 is compiled without debugging information. To step through functions
4646 without debugging information, use the @code{stepi} command, described
4650 The @code{step} command only stops at the first instruction of a source
4651 line. This prevents the multiple stops that could otherwise occur in
4652 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4653 to stop if a function that has debugging information is called within
4654 the line. In other words, @code{step} @emph{steps inside} any functions
4655 called within the line.
4657 Also, the @code{step} command only enters a function if there is line
4658 number information for the function. Otherwise it acts like the
4659 @code{next} command. This avoids problems when using @code{cc -gl}
4660 on MIPS machines. Previously, @code{step} entered subroutines if there
4661 was any debugging information about the routine.
4663 @item step @var{count}
4664 Continue running as in @code{step}, but do so @var{count} times. If a
4665 breakpoint is reached, or a signal not related to stepping occurs before
4666 @var{count} steps, stepping stops right away.
4669 @kindex n @r{(@code{next})}
4670 @item next @r{[}@var{count}@r{]}
4671 Continue to the next source line in the current (innermost) stack frame.
4672 This is similar to @code{step}, but function calls that appear within
4673 the line of code are executed without stopping. Execution stops when
4674 control reaches a different line of code at the original stack level
4675 that was executing when you gave the @code{next} command. This command
4676 is abbreviated @code{n}.
4678 An argument @var{count} is a repeat count, as for @code{step}.
4681 @c FIX ME!! Do we delete this, or is there a way it fits in with
4682 @c the following paragraph? --- Vctoria
4684 @c @code{next} within a function that lacks debugging information acts like
4685 @c @code{step}, but any function calls appearing within the code of the
4686 @c function are executed without stopping.
4688 The @code{next} command only stops at the first instruction of a
4689 source line. This prevents multiple stops that could otherwise occur in
4690 @code{switch} statements, @code{for} loops, etc.
4692 @kindex set step-mode
4694 @cindex functions without line info, and stepping
4695 @cindex stepping into functions with no line info
4696 @itemx set step-mode on
4697 The @code{set step-mode on} command causes the @code{step} command to
4698 stop at the first instruction of a function which contains no debug line
4699 information rather than stepping over it.
4701 This is useful in cases where you may be interested in inspecting the
4702 machine instructions of a function which has no symbolic info and do not
4703 want @value{GDBN} to automatically skip over this function.
4705 @item set step-mode off
4706 Causes the @code{step} command to step over any functions which contains no
4707 debug information. This is the default.
4709 @item show step-mode
4710 Show whether @value{GDBN} will stop in or step over functions without
4711 source line debug information.
4714 @kindex fin @r{(@code{finish})}
4716 Continue running until just after function in the selected stack frame
4717 returns. Print the returned value (if any). This command can be
4718 abbreviated as @code{fin}.
4720 Contrast this with the @code{return} command (@pxref{Returning,
4721 ,Returning from a Function}).
4724 @kindex u @r{(@code{until})}
4725 @cindex run until specified location
4728 Continue running until a source line past the current line, in the
4729 current stack frame, is reached. This command is used to avoid single
4730 stepping through a loop more than once. It is like the @code{next}
4731 command, except that when @code{until} encounters a jump, it
4732 automatically continues execution until the program counter is greater
4733 than the address of the jump.
4735 This means that when you reach the end of a loop after single stepping
4736 though it, @code{until} makes your program continue execution until it
4737 exits the loop. In contrast, a @code{next} command at the end of a loop
4738 simply steps back to the beginning of the loop, which forces you to step
4739 through the next iteration.
4741 @code{until} always stops your program if it attempts to exit the current
4744 @code{until} may produce somewhat counterintuitive results if the order
4745 of machine code does not match the order of the source lines. For
4746 example, in the following excerpt from a debugging session, the @code{f}
4747 (@code{frame}) command shows that execution is stopped at line
4748 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4752 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4754 (@value{GDBP}) until
4755 195 for ( ; argc > 0; NEXTARG) @{
4758 This happened because, for execution efficiency, the compiler had
4759 generated code for the loop closure test at the end, rather than the
4760 start, of the loop---even though the test in a C @code{for}-loop is
4761 written before the body of the loop. The @code{until} command appeared
4762 to step back to the beginning of the loop when it advanced to this
4763 expression; however, it has not really gone to an earlier
4764 statement---not in terms of the actual machine code.
4766 @code{until} with no argument works by means of single
4767 instruction stepping, and hence is slower than @code{until} with an
4770 @item until @var{location}
4771 @itemx u @var{location}
4772 Continue running your program until either the specified location is
4773 reached, or the current stack frame returns. @var{location} is any of
4774 the forms described in @ref{Specify Location}.
4775 This form of the command uses temporary breakpoints, and
4776 hence is quicker than @code{until} without an argument. The specified
4777 location is actually reached only if it is in the current frame. This
4778 implies that @code{until} can be used to skip over recursive function
4779 invocations. For instance in the code below, if the current location is
4780 line @code{96}, issuing @code{until 99} will execute the program up to
4781 line @code{99} in the same invocation of factorial, i.e., after the inner
4782 invocations have returned.
4785 94 int factorial (int value)
4787 96 if (value > 1) @{
4788 97 value *= factorial (value - 1);
4795 @kindex advance @var{location}
4796 @itemx advance @var{location}
4797 Continue running the program up to the given @var{location}. An argument is
4798 required, which should be of one of the forms described in
4799 @ref{Specify Location}.
4800 Execution will also stop upon exit from the current stack
4801 frame. This command is similar to @code{until}, but @code{advance} will
4802 not skip over recursive function calls, and the target location doesn't
4803 have to be in the same frame as the current one.
4807 @kindex si @r{(@code{stepi})}
4809 @itemx stepi @var{arg}
4811 Execute one machine instruction, then stop and return to the debugger.
4813 It is often useful to do @samp{display/i $pc} when stepping by machine
4814 instructions. This makes @value{GDBN} automatically display the next
4815 instruction to be executed, each time your program stops. @xref{Auto
4816 Display,, Automatic Display}.
4818 An argument is a repeat count, as in @code{step}.
4822 @kindex ni @r{(@code{nexti})}
4824 @itemx nexti @var{arg}
4826 Execute one machine instruction, but if it is a function call,
4827 proceed until the function returns.
4829 An argument is a repeat count, as in @code{next}.
4836 A signal is an asynchronous event that can happen in a program. The
4837 operating system defines the possible kinds of signals, and gives each
4838 kind a name and a number. For example, in Unix @code{SIGINT} is the
4839 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4840 @code{SIGSEGV} is the signal a program gets from referencing a place in
4841 memory far away from all the areas in use; @code{SIGALRM} occurs when
4842 the alarm clock timer goes off (which happens only if your program has
4843 requested an alarm).
4845 @cindex fatal signals
4846 Some signals, including @code{SIGALRM}, are a normal part of the
4847 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4848 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4849 program has not specified in advance some other way to handle the signal.
4850 @code{SIGINT} does not indicate an error in your program, but it is normally
4851 fatal so it can carry out the purpose of the interrupt: to kill the program.
4853 @value{GDBN} has the ability to detect any occurrence of a signal in your
4854 program. You can tell @value{GDBN} in advance what to do for each kind of
4857 @cindex handling signals
4858 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4859 @code{SIGALRM} be silently passed to your program
4860 (so as not to interfere with their role in the program's functioning)
4861 but to stop your program immediately whenever an error signal happens.
4862 You can change these settings with the @code{handle} command.
4865 @kindex info signals
4869 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4870 handle each one. You can use this to see the signal numbers of all
4871 the defined types of signals.
4873 @item info signals @var{sig}
4874 Similar, but print information only about the specified signal number.
4876 @code{info handle} is an alias for @code{info signals}.
4879 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4880 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4881 can be the number of a signal or its name (with or without the
4882 @samp{SIG} at the beginning); a list of signal numbers of the form
4883 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4884 known signals. Optional arguments @var{keywords}, described below,
4885 say what change to make.
4889 The keywords allowed by the @code{handle} command can be abbreviated.
4890 Their full names are:
4894 @value{GDBN} should not stop your program when this signal happens. It may
4895 still print a message telling you that the signal has come in.
4898 @value{GDBN} should stop your program when this signal happens. This implies
4899 the @code{print} keyword as well.
4902 @value{GDBN} should print a message when this signal happens.
4905 @value{GDBN} should not mention the occurrence of the signal at all. This
4906 implies the @code{nostop} keyword as well.
4910 @value{GDBN} should allow your program to see this signal; your program
4911 can handle the signal, or else it may terminate if the signal is fatal
4912 and not handled. @code{pass} and @code{noignore} are synonyms.
4916 @value{GDBN} should not allow your program to see this signal.
4917 @code{nopass} and @code{ignore} are synonyms.
4921 When a signal stops your program, the signal is not visible to the
4923 continue. Your program sees the signal then, if @code{pass} is in
4924 effect for the signal in question @emph{at that time}. In other words,
4925 after @value{GDBN} reports a signal, you can use the @code{handle}
4926 command with @code{pass} or @code{nopass} to control whether your
4927 program sees that signal when you continue.
4929 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4930 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4931 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4934 You can also use the @code{signal} command to prevent your program from
4935 seeing a signal, or cause it to see a signal it normally would not see,
4936 or to give it any signal at any time. For example, if your program stopped
4937 due to some sort of memory reference error, you might store correct
4938 values into the erroneous variables and continue, hoping to see more
4939 execution; but your program would probably terminate immediately as
4940 a result of the fatal signal once it saw the signal. To prevent this,
4941 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4944 @cindex extra signal information
4945 @anchor{extra signal information}
4947 On some targets, @value{GDBN} can inspect extra signal information
4948 associated with the intercepted signal, before it is actually
4949 delivered to the program being debugged. This information is exported
4950 by the convenience variable @code{$_siginfo}, and consists of data
4951 that is passed by the kernel to the signal handler at the time of the
4952 receipt of a signal. The data type of the information itself is
4953 target dependent. You can see the data type using the @code{ptype
4954 $_siginfo} command. On Unix systems, it typically corresponds to the
4955 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4958 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4959 referenced address that raised a segmentation fault.
4963 (@value{GDBP}) continue
4964 Program received signal SIGSEGV, Segmentation fault.
4965 0x0000000000400766 in main ()
4967 (@value{GDBP}) ptype $_siginfo
4974 struct @{...@} _kill;
4975 struct @{...@} _timer;
4977 struct @{...@} _sigchld;
4978 struct @{...@} _sigfault;
4979 struct @{...@} _sigpoll;
4982 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4986 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4987 $1 = (void *) 0x7ffff7ff7000
4991 Depending on target support, @code{$_siginfo} may also be writable.
4994 @section Stopping and Starting Multi-thread Programs
4996 @cindex stopped threads
4997 @cindex threads, stopped
4999 @cindex continuing threads
5000 @cindex threads, continuing
5002 @value{GDBN} supports debugging programs with multiple threads
5003 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5004 are two modes of controlling execution of your program within the
5005 debugger. In the default mode, referred to as @dfn{all-stop mode},
5006 when any thread in your program stops (for example, at a breakpoint
5007 or while being stepped), all other threads in the program are also stopped by
5008 @value{GDBN}. On some targets, @value{GDBN} also supports
5009 @dfn{non-stop mode}, in which other threads can continue to run freely while
5010 you examine the stopped thread in the debugger.
5013 * All-Stop Mode:: All threads stop when GDB takes control
5014 * Non-Stop Mode:: Other threads continue to execute
5015 * Background Execution:: Running your program asynchronously
5016 * Thread-Specific Breakpoints:: Controlling breakpoints
5017 * Interrupted System Calls:: GDB may interfere with system calls
5018 * Observer Mode:: GDB does not alter program behavior
5022 @subsection All-Stop Mode
5024 @cindex all-stop mode
5026 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5027 @emph{all} threads of execution stop, not just the current thread. This
5028 allows you to examine the overall state of the program, including
5029 switching between threads, without worrying that things may change
5032 Conversely, whenever you restart the program, @emph{all} threads start
5033 executing. @emph{This is true even when single-stepping} with commands
5034 like @code{step} or @code{next}.
5036 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5037 Since thread scheduling is up to your debugging target's operating
5038 system (not controlled by @value{GDBN}), other threads may
5039 execute more than one statement while the current thread completes a
5040 single step. Moreover, in general other threads stop in the middle of a
5041 statement, rather than at a clean statement boundary, when the program
5044 You might even find your program stopped in another thread after
5045 continuing or even single-stepping. This happens whenever some other
5046 thread runs into a breakpoint, a signal, or an exception before the
5047 first thread completes whatever you requested.
5049 @cindex automatic thread selection
5050 @cindex switching threads automatically
5051 @cindex threads, automatic switching
5052 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5053 signal, it automatically selects the thread where that breakpoint or
5054 signal happened. @value{GDBN} alerts you to the context switch with a
5055 message such as @samp{[Switching to Thread @var{n}]} to identify the
5058 On some OSes, you can modify @value{GDBN}'s default behavior by
5059 locking the OS scheduler to allow only a single thread to run.
5062 @item set scheduler-locking @var{mode}
5063 @cindex scheduler locking mode
5064 @cindex lock scheduler
5065 Set the scheduler locking mode. If it is @code{off}, then there is no
5066 locking and any thread may run at any time. If @code{on}, then only the
5067 current thread may run when the inferior is resumed. The @code{step}
5068 mode optimizes for single-stepping; it prevents other threads
5069 from preempting the current thread while you are stepping, so that
5070 the focus of debugging does not change unexpectedly.
5071 Other threads only rarely (or never) get a chance to run
5072 when you step. They are more likely to run when you @samp{next} over a
5073 function call, and they are completely free to run when you use commands
5074 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5075 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5076 the current thread away from the thread that you are debugging.
5078 @item show scheduler-locking
5079 Display the current scheduler locking mode.
5082 @cindex resume threads of multiple processes simultaneously
5083 By default, when you issue one of the execution commands such as
5084 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5085 threads of the current inferior to run. For example, if @value{GDBN}
5086 is attached to two inferiors, each with two threads, the
5087 @code{continue} command resumes only the two threads of the current
5088 inferior. This is useful, for example, when you debug a program that
5089 forks and you want to hold the parent stopped (so that, for instance,
5090 it doesn't run to exit), while you debug the child. In other
5091 situations, you may not be interested in inspecting the current state
5092 of any of the processes @value{GDBN} is attached to, and you may want
5093 to resume them all until some breakpoint is hit. In the latter case,
5094 you can instruct @value{GDBN} to allow all threads of all the
5095 inferiors to run with the @w{@code{set schedule-multiple}} command.
5098 @kindex set schedule-multiple
5099 @item set schedule-multiple
5100 Set the mode for allowing threads of multiple processes to be resumed
5101 when an execution command is issued. When @code{on}, all threads of
5102 all processes are allowed to run. When @code{off}, only the threads
5103 of the current process are resumed. The default is @code{off}. The
5104 @code{scheduler-locking} mode takes precedence when set to @code{on},
5105 or while you are stepping and set to @code{step}.
5107 @item show schedule-multiple
5108 Display the current mode for resuming the execution of threads of
5113 @subsection Non-Stop Mode
5115 @cindex non-stop mode
5117 @c This section is really only a place-holder, and needs to be expanded
5118 @c with more details.
5120 For some multi-threaded targets, @value{GDBN} supports an optional
5121 mode of operation in which you can examine stopped program threads in
5122 the debugger while other threads continue to execute freely. This
5123 minimizes intrusion when debugging live systems, such as programs
5124 where some threads have real-time constraints or must continue to
5125 respond to external events. This is referred to as @dfn{non-stop} mode.
5127 In non-stop mode, when a thread stops to report a debugging event,
5128 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5129 threads as well, in contrast to the all-stop mode behavior. Additionally,
5130 execution commands such as @code{continue} and @code{step} apply by default
5131 only to the current thread in non-stop mode, rather than all threads as
5132 in all-stop mode. This allows you to control threads explicitly in
5133 ways that are not possible in all-stop mode --- for example, stepping
5134 one thread while allowing others to run freely, stepping
5135 one thread while holding all others stopped, or stepping several threads
5136 independently and simultaneously.
5138 To enter non-stop mode, use this sequence of commands before you run
5139 or attach to your program:
5142 # Enable the async interface.
5145 # If using the CLI, pagination breaks non-stop.
5148 # Finally, turn it on!
5152 You can use these commands to manipulate the non-stop mode setting:
5155 @kindex set non-stop
5156 @item set non-stop on
5157 Enable selection of non-stop mode.
5158 @item set non-stop off
5159 Disable selection of non-stop mode.
5160 @kindex show non-stop
5162 Show the current non-stop enablement setting.
5165 Note these commands only reflect whether non-stop mode is enabled,
5166 not whether the currently-executing program is being run in non-stop mode.
5167 In particular, the @code{set non-stop} preference is only consulted when
5168 @value{GDBN} starts or connects to the target program, and it is generally
5169 not possible to switch modes once debugging has started. Furthermore,
5170 since not all targets support non-stop mode, even when you have enabled
5171 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5174 In non-stop mode, all execution commands apply only to the current thread
5175 by default. That is, @code{continue} only continues one thread.
5176 To continue all threads, issue @code{continue -a} or @code{c -a}.
5178 You can use @value{GDBN}'s background execution commands
5179 (@pxref{Background Execution}) to run some threads in the background
5180 while you continue to examine or step others from @value{GDBN}.
5181 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5182 always executed asynchronously in non-stop mode.
5184 Suspending execution is done with the @code{interrupt} command when
5185 running in the background, or @kbd{Ctrl-c} during foreground execution.
5186 In all-stop mode, this stops the whole process;
5187 but in non-stop mode the interrupt applies only to the current thread.
5188 To stop the whole program, use @code{interrupt -a}.
5190 Other execution commands do not currently support the @code{-a} option.
5192 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5193 that thread current, as it does in all-stop mode. This is because the
5194 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5195 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5196 changed to a different thread just as you entered a command to operate on the
5197 previously current thread.
5199 @node Background Execution
5200 @subsection Background Execution
5202 @cindex foreground execution
5203 @cindex background execution
5204 @cindex asynchronous execution
5205 @cindex execution, foreground, background and asynchronous
5207 @value{GDBN}'s execution commands have two variants: the normal
5208 foreground (synchronous) behavior, and a background
5209 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5210 the program to report that some thread has stopped before prompting for
5211 another command. In background execution, @value{GDBN} immediately gives
5212 a command prompt so that you can issue other commands while your program runs.
5214 You need to explicitly enable asynchronous mode before you can use
5215 background execution commands. You can use these commands to
5216 manipulate the asynchronous mode setting:
5219 @kindex set target-async
5220 @item set target-async on
5221 Enable asynchronous mode.
5222 @item set target-async off
5223 Disable asynchronous mode.
5224 @kindex show target-async
5225 @item show target-async
5226 Show the current target-async setting.
5229 If the target doesn't support async mode, @value{GDBN} issues an error
5230 message if you attempt to use the background execution commands.
5232 To specify background execution, add a @code{&} to the command. For example,
5233 the background form of the @code{continue} command is @code{continue&}, or
5234 just @code{c&}. The execution commands that accept background execution
5240 @xref{Starting, , Starting your Program}.
5244 @xref{Attach, , Debugging an Already-running Process}.
5248 @xref{Continuing and Stepping, step}.
5252 @xref{Continuing and Stepping, stepi}.
5256 @xref{Continuing and Stepping, next}.
5260 @xref{Continuing and Stepping, nexti}.
5264 @xref{Continuing and Stepping, continue}.
5268 @xref{Continuing and Stepping, finish}.
5272 @xref{Continuing and Stepping, until}.
5276 Background execution is especially useful in conjunction with non-stop
5277 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5278 However, you can also use these commands in the normal all-stop mode with
5279 the restriction that you cannot issue another execution command until the
5280 previous one finishes. Examples of commands that are valid in all-stop
5281 mode while the program is running include @code{help} and @code{info break}.
5283 You can interrupt your program while it is running in the background by
5284 using the @code{interrupt} command.
5291 Suspend execution of the running program. In all-stop mode,
5292 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5293 only the current thread. To stop the whole program in non-stop mode,
5294 use @code{interrupt -a}.
5297 @node Thread-Specific Breakpoints
5298 @subsection Thread-Specific Breakpoints
5300 When your program has multiple threads (@pxref{Threads,, Debugging
5301 Programs with Multiple Threads}), you can choose whether to set
5302 breakpoints on all threads, or on a particular thread.
5305 @cindex breakpoints and threads
5306 @cindex thread breakpoints
5307 @kindex break @dots{} thread @var{threadno}
5308 @item break @var{linespec} thread @var{threadno}
5309 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5310 @var{linespec} specifies source lines; there are several ways of
5311 writing them (@pxref{Specify Location}), but the effect is always to
5312 specify some source line.
5314 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5315 to specify that you only want @value{GDBN} to stop the program when a
5316 particular thread reaches this breakpoint. @var{threadno} is one of the
5317 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5318 column of the @samp{info threads} display.
5320 If you do not specify @samp{thread @var{threadno}} when you set a
5321 breakpoint, the breakpoint applies to @emph{all} threads of your
5324 You can use the @code{thread} qualifier on conditional breakpoints as
5325 well; in this case, place @samp{thread @var{threadno}} before or
5326 after the breakpoint condition, like this:
5329 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5334 @node Interrupted System Calls
5335 @subsection Interrupted System Calls
5337 @cindex thread breakpoints and system calls
5338 @cindex system calls and thread breakpoints
5339 @cindex premature return from system calls
5340 There is an unfortunate side effect when using @value{GDBN} to debug
5341 multi-threaded programs. If one thread stops for a
5342 breakpoint, or for some other reason, and another thread is blocked in a
5343 system call, then the system call may return prematurely. This is a
5344 consequence of the interaction between multiple threads and the signals
5345 that @value{GDBN} uses to implement breakpoints and other events that
5348 To handle this problem, your program should check the return value of
5349 each system call and react appropriately. This is good programming
5352 For example, do not write code like this:
5358 The call to @code{sleep} will return early if a different thread stops
5359 at a breakpoint or for some other reason.
5361 Instead, write this:
5366 unslept = sleep (unslept);
5369 A system call is allowed to return early, so the system is still
5370 conforming to its specification. But @value{GDBN} does cause your
5371 multi-threaded program to behave differently than it would without
5374 Also, @value{GDBN} uses internal breakpoints in the thread library to
5375 monitor certain events such as thread creation and thread destruction.
5376 When such an event happens, a system call in another thread may return
5377 prematurely, even though your program does not appear to stop.
5380 @subsection Observer Mode
5382 If you want to build on non-stop mode and observe program behavior
5383 without any chance of disruption by @value{GDBN}, you can set
5384 variables to disable all of the debugger's attempts to modify state,
5385 whether by writing memory, inserting breakpoints, etc. These operate
5386 at a low level, intercepting operations from all commands.
5388 When all of these are set to @code{off}, then @value{GDBN} is said to
5389 be @dfn{observer mode}. As a convenience, the variable
5390 @code{observer} can be set to disable these, plus enable non-stop
5393 Note that @value{GDBN} will not prevent you from making nonsensical
5394 combinations of these settings. For instance, if you have enabled
5395 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5396 then breakpoints that work by writing trap instructions into the code
5397 stream will still not be able to be placed.
5402 @item set observer on
5403 @itemx set observer off
5404 When set to @code{on}, this disables all the permission variables
5405 below (except for @code{insert-fast-tracepoints}), plus enables
5406 non-stop debugging. Setting this to @code{off} switches back to
5407 normal debugging, though remaining in non-stop mode.
5410 Show whether observer mode is on or off.
5412 @kindex may-write-registers
5413 @item set may-write-registers on
5414 @itemx set may-write-registers off
5415 This controls whether @value{GDBN} will attempt to alter the values of
5416 registers, such as with assignment expressions in @code{print}, or the
5417 @code{jump} command. It defaults to @code{on}.
5419 @item show may-write-registers
5420 Show the current permission to write registers.
5422 @kindex may-write-memory
5423 @item set may-write-memory on
5424 @itemx set may-write-memory off
5425 This controls whether @value{GDBN} will attempt to alter the contents
5426 of memory, such as with assignment expressions in @code{print}. It
5427 defaults to @code{on}.
5429 @item show may-write-memory
5430 Show the current permission to write memory.
5432 @kindex may-insert-breakpoints
5433 @item set may-insert-breakpoints on
5434 @itemx set may-insert-breakpoints off
5435 This controls whether @value{GDBN} will attempt to insert breakpoints.
5436 This affects all breakpoints, including internal breakpoints defined
5437 by @value{GDBN}. It defaults to @code{on}.
5439 @item show may-insert-breakpoints
5440 Show the current permission to insert breakpoints.
5442 @kindex may-insert-tracepoints
5443 @item set may-insert-tracepoints on
5444 @itemx set may-insert-tracepoints off
5445 This controls whether @value{GDBN} will attempt to insert (regular)
5446 tracepoints at the beginning of a tracing experiment. It affects only
5447 non-fast tracepoints, fast tracepoints being under the control of
5448 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5450 @item show may-insert-tracepoints
5451 Show the current permission to insert tracepoints.
5453 @kindex may-insert-fast-tracepoints
5454 @item set may-insert-fast-tracepoints on
5455 @itemx set may-insert-fast-tracepoints off
5456 This controls whether @value{GDBN} will attempt to insert fast
5457 tracepoints at the beginning of a tracing experiment. It affects only
5458 fast tracepoints, regular (non-fast) tracepoints being under the
5459 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5461 @item show may-insert-fast-tracepoints
5462 Show the current permission to insert fast tracepoints.
5464 @kindex may-interrupt
5465 @item set may-interrupt on
5466 @itemx set may-interrupt off
5467 This controls whether @value{GDBN} will attempt to interrupt or stop
5468 program execution. When this variable is @code{off}, the
5469 @code{interrupt} command will have no effect, nor will
5470 @kbd{Ctrl-c}. It defaults to @code{on}.
5472 @item show may-interrupt
5473 Show the current permission to interrupt or stop the program.
5477 @node Reverse Execution
5478 @chapter Running programs backward
5479 @cindex reverse execution
5480 @cindex running programs backward
5482 When you are debugging a program, it is not unusual to realize that
5483 you have gone too far, and some event of interest has already happened.
5484 If the target environment supports it, @value{GDBN} can allow you to
5485 ``rewind'' the program by running it backward.
5487 A target environment that supports reverse execution should be able
5488 to ``undo'' the changes in machine state that have taken place as the
5489 program was executing normally. Variables, registers etc.@: should
5490 revert to their previous values. Obviously this requires a great
5491 deal of sophistication on the part of the target environment; not
5492 all target environments can support reverse execution.
5494 When a program is executed in reverse, the instructions that
5495 have most recently been executed are ``un-executed'', in reverse
5496 order. The program counter runs backward, following the previous
5497 thread of execution in reverse. As each instruction is ``un-executed'',
5498 the values of memory and/or registers that were changed by that
5499 instruction are reverted to their previous states. After executing
5500 a piece of source code in reverse, all side effects of that code
5501 should be ``undone'', and all variables should be returned to their
5502 prior values@footnote{
5503 Note that some side effects are easier to undo than others. For instance,
5504 memory and registers are relatively easy, but device I/O is hard. Some
5505 targets may be able undo things like device I/O, and some may not.
5507 The contract between @value{GDBN} and the reverse executing target
5508 requires only that the target do something reasonable when
5509 @value{GDBN} tells it to execute backwards, and then report the
5510 results back to @value{GDBN}. Whatever the target reports back to
5511 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5512 assumes that the memory and registers that the target reports are in a
5513 consistant state, but @value{GDBN} accepts whatever it is given.
5516 If you are debugging in a target environment that supports
5517 reverse execution, @value{GDBN} provides the following commands.
5520 @kindex reverse-continue
5521 @kindex rc @r{(@code{reverse-continue})}
5522 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5523 @itemx rc @r{[}@var{ignore-count}@r{]}
5524 Beginning at the point where your program last stopped, start executing
5525 in reverse. Reverse execution will stop for breakpoints and synchronous
5526 exceptions (signals), just like normal execution. Behavior of
5527 asynchronous signals depends on the target environment.
5529 @kindex reverse-step
5530 @kindex rs @r{(@code{step})}
5531 @item reverse-step @r{[}@var{count}@r{]}
5532 Run the program backward until control reaches the start of a
5533 different source line; then stop it, and return control to @value{GDBN}.
5535 Like the @code{step} command, @code{reverse-step} will only stop
5536 at the beginning of a source line. It ``un-executes'' the previously
5537 executed source line. If the previous source line included calls to
5538 debuggable functions, @code{reverse-step} will step (backward) into
5539 the called function, stopping at the beginning of the @emph{last}
5540 statement in the called function (typically a return statement).
5542 Also, as with the @code{step} command, if non-debuggable functions are
5543 called, @code{reverse-step} will run thru them backward without stopping.
5545 @kindex reverse-stepi
5546 @kindex rsi @r{(@code{reverse-stepi})}
5547 @item reverse-stepi @r{[}@var{count}@r{]}
5548 Reverse-execute one machine instruction. Note that the instruction
5549 to be reverse-executed is @emph{not} the one pointed to by the program
5550 counter, but the instruction executed prior to that one. For instance,
5551 if the last instruction was a jump, @code{reverse-stepi} will take you
5552 back from the destination of the jump to the jump instruction itself.
5554 @kindex reverse-next
5555 @kindex rn @r{(@code{reverse-next})}
5556 @item reverse-next @r{[}@var{count}@r{]}
5557 Run backward to the beginning of the previous line executed in
5558 the current (innermost) stack frame. If the line contains function
5559 calls, they will be ``un-executed'' without stopping. Starting from
5560 the first line of a function, @code{reverse-next} will take you back
5561 to the caller of that function, @emph{before} the function was called,
5562 just as the normal @code{next} command would take you from the last
5563 line of a function back to its return to its caller
5564 @footnote{Unless the code is too heavily optimized.}.
5566 @kindex reverse-nexti
5567 @kindex rni @r{(@code{reverse-nexti})}
5568 @item reverse-nexti @r{[}@var{count}@r{]}
5569 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5570 in reverse, except that called functions are ``un-executed'' atomically.
5571 That is, if the previously executed instruction was a return from
5572 another function, @code{reverse-nexti} will continue to execute
5573 in reverse until the call to that function (from the current stack
5576 @kindex reverse-finish
5577 @item reverse-finish
5578 Just as the @code{finish} command takes you to the point where the
5579 current function returns, @code{reverse-finish} takes you to the point
5580 where it was called. Instead of ending up at the end of the current
5581 function invocation, you end up at the beginning.
5583 @kindex set exec-direction
5584 @item set exec-direction
5585 Set the direction of target execution.
5586 @itemx set exec-direction reverse
5587 @cindex execute forward or backward in time
5588 @value{GDBN} will perform all execution commands in reverse, until the
5589 exec-direction mode is changed to ``forward''. Affected commands include
5590 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5591 command cannot be used in reverse mode.
5592 @item set exec-direction forward
5593 @value{GDBN} will perform all execution commands in the normal fashion.
5594 This is the default.
5598 @node Process Record and Replay
5599 @chapter Recording Inferior's Execution and Replaying It
5600 @cindex process record and replay
5601 @cindex recording inferior's execution and replaying it
5603 On some platforms, @value{GDBN} provides a special @dfn{process record
5604 and replay} target that can record a log of the process execution, and
5605 replay it later with both forward and reverse execution commands.
5608 When this target is in use, if the execution log includes the record
5609 for the next instruction, @value{GDBN} will debug in @dfn{replay
5610 mode}. In the replay mode, the inferior does not really execute code
5611 instructions. Instead, all the events that normally happen during
5612 code execution are taken from the execution log. While code is not
5613 really executed in replay mode, the values of registers (including the
5614 program counter register) and the memory of the inferior are still
5615 changed as they normally would. Their contents are taken from the
5619 If the record for the next instruction is not in the execution log,
5620 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5621 inferior executes normally, and @value{GDBN} records the execution log
5624 The process record and replay target supports reverse execution
5625 (@pxref{Reverse Execution}), even if the platform on which the
5626 inferior runs does not. However, the reverse execution is limited in
5627 this case by the range of the instructions recorded in the execution
5628 log. In other words, reverse execution on platforms that don't
5629 support it directly can only be done in the replay mode.
5631 When debugging in the reverse direction, @value{GDBN} will work in
5632 replay mode as long as the execution log includes the record for the
5633 previous instruction; otherwise, it will work in record mode, if the
5634 platform supports reverse execution, or stop if not.
5636 For architecture environments that support process record and replay,
5637 @value{GDBN} provides the following commands:
5640 @kindex target record
5644 This command starts the process record and replay target. The process
5645 record and replay target can only debug a process that is already
5646 running. Therefore, you need first to start the process with the
5647 @kbd{run} or @kbd{start} commands, and then start the recording with
5648 the @kbd{target record} command.
5650 Both @code{record} and @code{rec} are aliases of @code{target record}.
5652 @cindex displaced stepping, and process record and replay
5653 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5654 will be automatically disabled when process record and replay target
5655 is started. That's because the process record and replay target
5656 doesn't support displaced stepping.
5658 @cindex non-stop mode, and process record and replay
5659 @cindex asynchronous execution, and process record and replay
5660 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5661 the asynchronous execution mode (@pxref{Background Execution}), the
5662 process record and replay target cannot be started because it doesn't
5663 support these two modes.
5668 Stop the process record and replay target. When process record and
5669 replay target stops, the entire execution log will be deleted and the
5670 inferior will either be terminated, or will remain in its final state.
5672 When you stop the process record and replay target in record mode (at
5673 the end of the execution log), the inferior will be stopped at the
5674 next instruction that would have been recorded. In other words, if
5675 you record for a while and then stop recording, the inferior process
5676 will be left in the same state as if the recording never happened.
5678 On the other hand, if the process record and replay target is stopped
5679 while in replay mode (that is, not at the end of the execution log,
5680 but at some earlier point), the inferior process will become ``live''
5681 at that earlier state, and it will then be possible to continue the
5682 usual ``live'' debugging of the process from that state.
5684 When the inferior process exits, or @value{GDBN} detaches from it,
5685 process record and replay target will automatically stop itself.
5688 @item record save @var{filename}
5689 Save the execution log to a file @file{@var{filename}}.
5690 Default filename is @file{gdb_record.@var{process_id}}, where
5691 @var{process_id} is the process ID of the inferior.
5693 @kindex record restore
5694 @item record restore @var{filename}
5695 Restore the execution log from a file @file{@var{filename}}.
5696 File must have been created with @code{record save}.
5698 @kindex set record insn-number-max
5699 @item set record insn-number-max @var{limit}
5700 Set the limit of instructions to be recorded. Default value is 200000.
5702 If @var{limit} is a positive number, then @value{GDBN} will start
5703 deleting instructions from the log once the number of the record
5704 instructions becomes greater than @var{limit}. For every new recorded
5705 instruction, @value{GDBN} will delete the earliest recorded
5706 instruction to keep the number of recorded instructions at the limit.
5707 (Since deleting recorded instructions loses information, @value{GDBN}
5708 lets you control what happens when the limit is reached, by means of
5709 the @code{stop-at-limit} option, described below.)
5711 If @var{limit} is zero, @value{GDBN} will never delete recorded
5712 instructions from the execution log. The number of recorded
5713 instructions is unlimited in this case.
5715 @kindex show record insn-number-max
5716 @item show record insn-number-max
5717 Show the limit of instructions to be recorded.
5719 @kindex set record stop-at-limit
5720 @item set record stop-at-limit
5721 Control the behavior when the number of recorded instructions reaches
5722 the limit. If ON (the default), @value{GDBN} will stop when the limit
5723 is reached for the first time and ask you whether you want to stop the
5724 inferior or continue running it and recording the execution log. If
5725 you decide to continue recording, each new recorded instruction will
5726 cause the oldest one to be deleted.
5728 If this option is OFF, @value{GDBN} will automatically delete the
5729 oldest record to make room for each new one, without asking.
5731 @kindex show record stop-at-limit
5732 @item show record stop-at-limit
5733 Show the current setting of @code{stop-at-limit}.
5735 @kindex set record memory-query
5736 @item set record memory-query
5737 Control the behavior when @value{GDBN} is unable to record memory
5738 changes caused by an instruction. If ON, @value{GDBN} will query
5739 whether to stop the inferior in that case.
5741 If this option is OFF (the default), @value{GDBN} will automatically
5742 ignore the effect of such instructions on memory. Later, when
5743 @value{GDBN} replays this execution log, it will mark the log of this
5744 instruction as not accessible, and it will not affect the replay
5747 @kindex show record memory-query
5748 @item show record memory-query
5749 Show the current setting of @code{memory-query}.
5753 Show various statistics about the state of process record and its
5754 in-memory execution log buffer, including:
5758 Whether in record mode or replay mode.
5760 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5762 Highest recorded instruction number.
5764 Current instruction about to be replayed (if in replay mode).
5766 Number of instructions contained in the execution log.
5768 Maximum number of instructions that may be contained in the execution log.
5771 @kindex record delete
5774 When record target runs in replay mode (``in the past''), delete the
5775 subsequent execution log and begin to record a new execution log starting
5776 from the current address. This means you will abandon the previously
5777 recorded ``future'' and begin recording a new ``future''.
5782 @chapter Examining the Stack
5784 When your program has stopped, the first thing you need to know is where it
5785 stopped and how it got there.
5788 Each time your program performs a function call, information about the call
5790 That information includes the location of the call in your program,
5791 the arguments of the call,
5792 and the local variables of the function being called.
5793 The information is saved in a block of data called a @dfn{stack frame}.
5794 The stack frames are allocated in a region of memory called the @dfn{call
5797 When your program stops, the @value{GDBN} commands for examining the
5798 stack allow you to see all of this information.
5800 @cindex selected frame
5801 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5802 @value{GDBN} commands refer implicitly to the selected frame. In
5803 particular, whenever you ask @value{GDBN} for the value of a variable in
5804 your program, the value is found in the selected frame. There are
5805 special @value{GDBN} commands to select whichever frame you are
5806 interested in. @xref{Selection, ,Selecting a Frame}.
5808 When your program stops, @value{GDBN} automatically selects the
5809 currently executing frame and describes it briefly, similar to the
5810 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5813 * Frames:: Stack frames
5814 * Backtrace:: Backtraces
5815 * Selection:: Selecting a frame
5816 * Frame Info:: Information on a frame
5821 @section Stack Frames
5823 @cindex frame, definition
5825 The call stack is divided up into contiguous pieces called @dfn{stack
5826 frames}, or @dfn{frames} for short; each frame is the data associated
5827 with one call to one function. The frame contains the arguments given
5828 to the function, the function's local variables, and the address at
5829 which the function is executing.
5831 @cindex initial frame
5832 @cindex outermost frame
5833 @cindex innermost frame
5834 When your program is started, the stack has only one frame, that of the
5835 function @code{main}. This is called the @dfn{initial} frame or the
5836 @dfn{outermost} frame. Each time a function is called, a new frame is
5837 made. Each time a function returns, the frame for that function invocation
5838 is eliminated. If a function is recursive, there can be many frames for
5839 the same function. The frame for the function in which execution is
5840 actually occurring is called the @dfn{innermost} frame. This is the most
5841 recently created of all the stack frames that still exist.
5843 @cindex frame pointer
5844 Inside your program, stack frames are identified by their addresses. A
5845 stack frame consists of many bytes, each of which has its own address; each
5846 kind of computer has a convention for choosing one byte whose
5847 address serves as the address of the frame. Usually this address is kept
5848 in a register called the @dfn{frame pointer register}
5849 (@pxref{Registers, $fp}) while execution is going on in that frame.
5851 @cindex frame number
5852 @value{GDBN} assigns numbers to all existing stack frames, starting with
5853 zero for the innermost frame, one for the frame that called it,
5854 and so on upward. These numbers do not really exist in your program;
5855 they are assigned by @value{GDBN} to give you a way of designating stack
5856 frames in @value{GDBN} commands.
5858 @c The -fomit-frame-pointer below perennially causes hbox overflow
5859 @c underflow problems.
5860 @cindex frameless execution
5861 Some compilers provide a way to compile functions so that they operate
5862 without stack frames. (For example, the @value{NGCC} option
5864 @samp{-fomit-frame-pointer}
5866 generates functions without a frame.)
5867 This is occasionally done with heavily used library functions to save
5868 the frame setup time. @value{GDBN} has limited facilities for dealing
5869 with these function invocations. If the innermost function invocation
5870 has no stack frame, @value{GDBN} nevertheless regards it as though
5871 it had a separate frame, which is numbered zero as usual, allowing
5872 correct tracing of the function call chain. However, @value{GDBN} has
5873 no provision for frameless functions elsewhere in the stack.
5876 @kindex frame@r{, command}
5877 @cindex current stack frame
5878 @item frame @var{args}
5879 The @code{frame} command allows you to move from one stack frame to another,
5880 and to print the stack frame you select. @var{args} may be either the
5881 address of the frame or the stack frame number. Without an argument,
5882 @code{frame} prints the current stack frame.
5884 @kindex select-frame
5885 @cindex selecting frame silently
5887 The @code{select-frame} command allows you to move from one stack frame
5888 to another without printing the frame. This is the silent version of
5896 @cindex call stack traces
5897 A backtrace is a summary of how your program got where it is. It shows one
5898 line per frame, for many frames, starting with the currently executing
5899 frame (frame zero), followed by its caller (frame one), and on up the
5904 @kindex bt @r{(@code{backtrace})}
5907 Print a backtrace of the entire stack: one line per frame for all
5908 frames in the stack.
5910 You can stop the backtrace at any time by typing the system interrupt
5911 character, normally @kbd{Ctrl-c}.
5913 @item backtrace @var{n}
5915 Similar, but print only the innermost @var{n} frames.
5917 @item backtrace -@var{n}
5919 Similar, but print only the outermost @var{n} frames.
5921 @item backtrace full
5923 @itemx bt full @var{n}
5924 @itemx bt full -@var{n}
5925 Print the values of the local variables also. @var{n} specifies the
5926 number of frames to print, as described above.
5931 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5932 are additional aliases for @code{backtrace}.
5934 @cindex multiple threads, backtrace
5935 In a multi-threaded program, @value{GDBN} by default shows the
5936 backtrace only for the current thread. To display the backtrace for
5937 several or all of the threads, use the command @code{thread apply}
5938 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5939 apply all backtrace}, @value{GDBN} will display the backtrace for all
5940 the threads; this is handy when you debug a core dump of a
5941 multi-threaded program.
5943 Each line in the backtrace shows the frame number and the function name.
5944 The program counter value is also shown---unless you use @code{set
5945 print address off}. The backtrace also shows the source file name and
5946 line number, as well as the arguments to the function. The program
5947 counter value is omitted if it is at the beginning of the code for that
5950 Here is an example of a backtrace. It was made with the command
5951 @samp{bt 3}, so it shows the innermost three frames.
5955 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5957 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5958 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5960 (More stack frames follow...)
5965 The display for frame zero does not begin with a program counter
5966 value, indicating that your program has stopped at the beginning of the
5967 code for line @code{993} of @code{builtin.c}.
5970 The value of parameter @code{data} in frame 1 has been replaced by
5971 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5972 only if it is a scalar (integer, pointer, enumeration, etc). See command
5973 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5974 on how to configure the way function parameter values are printed.
5976 @cindex optimized out, in backtrace
5977 @cindex function call arguments, optimized out
5978 If your program was compiled with optimizations, some compilers will
5979 optimize away arguments passed to functions if those arguments are
5980 never used after the call. Such optimizations generate code that
5981 passes arguments through registers, but doesn't store those arguments
5982 in the stack frame. @value{GDBN} has no way of displaying such
5983 arguments in stack frames other than the innermost one. Here's what
5984 such a backtrace might look like:
5988 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5990 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
5991 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
5993 (More stack frames follow...)
5998 The values of arguments that were not saved in their stack frames are
5999 shown as @samp{<optimized out>}.
6001 If you need to display the values of such optimized-out arguments,
6002 either deduce that from other variables whose values depend on the one
6003 you are interested in, or recompile without optimizations.
6005 @cindex backtrace beyond @code{main} function
6006 @cindex program entry point
6007 @cindex startup code, and backtrace
6008 Most programs have a standard user entry point---a place where system
6009 libraries and startup code transition into user code. For C this is
6010 @code{main}@footnote{
6011 Note that embedded programs (the so-called ``free-standing''
6012 environment) are not required to have a @code{main} function as the
6013 entry point. They could even have multiple entry points.}.
6014 When @value{GDBN} finds the entry function in a backtrace
6015 it will terminate the backtrace, to avoid tracing into highly
6016 system-specific (and generally uninteresting) code.
6018 If you need to examine the startup code, or limit the number of levels
6019 in a backtrace, you can change this behavior:
6022 @item set backtrace past-main
6023 @itemx set backtrace past-main on
6024 @kindex set backtrace
6025 Backtraces will continue past the user entry point.
6027 @item set backtrace past-main off
6028 Backtraces will stop when they encounter the user entry point. This is the
6031 @item show backtrace past-main
6032 @kindex show backtrace
6033 Display the current user entry point backtrace policy.
6035 @item set backtrace past-entry
6036 @itemx set backtrace past-entry on
6037 Backtraces will continue past the internal entry point of an application.
6038 This entry point is encoded by the linker when the application is built,
6039 and is likely before the user entry point @code{main} (or equivalent) is called.
6041 @item set backtrace past-entry off
6042 Backtraces will stop when they encounter the internal entry point of an
6043 application. This is the default.
6045 @item show backtrace past-entry
6046 Display the current internal entry point backtrace policy.
6048 @item set backtrace limit @var{n}
6049 @itemx set backtrace limit 0
6050 @cindex backtrace limit
6051 Limit the backtrace to @var{n} levels. A value of zero means
6054 @item show backtrace limit
6055 Display the current limit on backtrace levels.
6059 @section Selecting a Frame
6061 Most commands for examining the stack and other data in your program work on
6062 whichever stack frame is selected at the moment. Here are the commands for
6063 selecting a stack frame; all of them finish by printing a brief description
6064 of the stack frame just selected.
6067 @kindex frame@r{, selecting}
6068 @kindex f @r{(@code{frame})}
6071 Select frame number @var{n}. Recall that frame zero is the innermost
6072 (currently executing) frame, frame one is the frame that called the
6073 innermost one, and so on. The highest-numbered frame is the one for
6076 @item frame @var{addr}
6078 Select the frame at address @var{addr}. This is useful mainly if the
6079 chaining of stack frames has been damaged by a bug, making it
6080 impossible for @value{GDBN} to assign numbers properly to all frames. In
6081 addition, this can be useful when your program has multiple stacks and
6082 switches between them.
6084 On the SPARC architecture, @code{frame} needs two addresses to
6085 select an arbitrary frame: a frame pointer and a stack pointer.
6087 On the MIPS and Alpha architecture, it needs two addresses: a stack
6088 pointer and a program counter.
6090 On the 29k architecture, it needs three addresses: a register stack
6091 pointer, a program counter, and a memory stack pointer.
6095 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6096 advances toward the outermost frame, to higher frame numbers, to frames
6097 that have existed longer. @var{n} defaults to one.
6100 @kindex do @r{(@code{down})}
6102 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6103 advances toward the innermost frame, to lower frame numbers, to frames
6104 that were created more recently. @var{n} defaults to one. You may
6105 abbreviate @code{down} as @code{do}.
6108 All of these commands end by printing two lines of output describing the
6109 frame. The first line shows the frame number, the function name, the
6110 arguments, and the source file and line number of execution in that
6111 frame. The second line shows the text of that source line.
6119 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6121 10 read_input_file (argv[i]);
6125 After such a printout, the @code{list} command with no arguments
6126 prints ten lines centered on the point of execution in the frame.
6127 You can also edit the program at the point of execution with your favorite
6128 editing program by typing @code{edit}.
6129 @xref{List, ,Printing Source Lines},
6133 @kindex down-silently
6135 @item up-silently @var{n}
6136 @itemx down-silently @var{n}
6137 These two commands are variants of @code{up} and @code{down},
6138 respectively; they differ in that they do their work silently, without
6139 causing display of the new frame. They are intended primarily for use
6140 in @value{GDBN} command scripts, where the output might be unnecessary and
6145 @section Information About a Frame
6147 There are several other commands to print information about the selected
6153 When used without any argument, this command does not change which
6154 frame is selected, but prints a brief description of the currently
6155 selected stack frame. It can be abbreviated @code{f}. With an
6156 argument, this command is used to select a stack frame.
6157 @xref{Selection, ,Selecting a Frame}.
6160 @kindex info f @r{(@code{info frame})}
6163 This command prints a verbose description of the selected stack frame,
6168 the address of the frame
6170 the address of the next frame down (called by this frame)
6172 the address of the next frame up (caller of this frame)
6174 the language in which the source code corresponding to this frame is written
6176 the address of the frame's arguments
6178 the address of the frame's local variables
6180 the program counter saved in it (the address of execution in the caller frame)
6182 which registers were saved in the frame
6185 @noindent The verbose description is useful when
6186 something has gone wrong that has made the stack format fail to fit
6187 the usual conventions.
6189 @item info frame @var{addr}
6190 @itemx info f @var{addr}
6191 Print a verbose description of the frame at address @var{addr}, without
6192 selecting that frame. The selected frame remains unchanged by this
6193 command. This requires the same kind of address (more than one for some
6194 architectures) that you specify in the @code{frame} command.
6195 @xref{Selection, ,Selecting a Frame}.
6199 Print the arguments of the selected frame, each on a separate line.
6203 Print the local variables of the selected frame, each on a separate
6204 line. These are all variables (declared either static or automatic)
6205 accessible at the point of execution of the selected frame.
6208 @cindex catch exceptions, list active handlers
6209 @cindex exception handlers, how to list
6211 Print a list of all the exception handlers that are active in the
6212 current stack frame at the current point of execution. To see other
6213 exception handlers, visit the associated frame (using the @code{up},
6214 @code{down}, or @code{frame} commands); then type @code{info catch}.
6215 @xref{Set Catchpoints, , Setting Catchpoints}.
6221 @chapter Examining Source Files
6223 @value{GDBN} can print parts of your program's source, since the debugging
6224 information recorded in the program tells @value{GDBN} what source files were
6225 used to build it. When your program stops, @value{GDBN} spontaneously prints
6226 the line where it stopped. Likewise, when you select a stack frame
6227 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6228 execution in that frame has stopped. You can print other portions of
6229 source files by explicit command.
6231 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6232 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6233 @value{GDBN} under @sc{gnu} Emacs}.
6236 * List:: Printing source lines
6237 * Specify Location:: How to specify code locations
6238 * Edit:: Editing source files
6239 * Search:: Searching source files
6240 * Source Path:: Specifying source directories
6241 * Machine Code:: Source and machine code
6245 @section Printing Source Lines
6248 @kindex l @r{(@code{list})}
6249 To print lines from a source file, use the @code{list} command
6250 (abbreviated @code{l}). By default, ten lines are printed.
6251 There are several ways to specify what part of the file you want to
6252 print; see @ref{Specify Location}, for the full list.
6254 Here are the forms of the @code{list} command most commonly used:
6257 @item list @var{linenum}
6258 Print lines centered around line number @var{linenum} in the
6259 current source file.
6261 @item list @var{function}
6262 Print lines centered around the beginning of function
6266 Print more lines. If the last lines printed were printed with a
6267 @code{list} command, this prints lines following the last lines
6268 printed; however, if the last line printed was a solitary line printed
6269 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6270 Stack}), this prints lines centered around that line.
6273 Print lines just before the lines last printed.
6276 @cindex @code{list}, how many lines to display
6277 By default, @value{GDBN} prints ten source lines with any of these forms of
6278 the @code{list} command. You can change this using @code{set listsize}:
6281 @kindex set listsize
6282 @item set listsize @var{count}
6283 Make the @code{list} command display @var{count} source lines (unless
6284 the @code{list} argument explicitly specifies some other number).
6286 @kindex show listsize
6288 Display the number of lines that @code{list} prints.
6291 Repeating a @code{list} command with @key{RET} discards the argument,
6292 so it is equivalent to typing just @code{list}. This is more useful
6293 than listing the same lines again. An exception is made for an
6294 argument of @samp{-}; that argument is preserved in repetition so that
6295 each repetition moves up in the source file.
6297 In general, the @code{list} command expects you to supply zero, one or two
6298 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6299 of writing them (@pxref{Specify Location}), but the effect is always
6300 to specify some source line.
6302 Here is a complete description of the possible arguments for @code{list}:
6305 @item list @var{linespec}
6306 Print lines centered around the line specified by @var{linespec}.
6308 @item list @var{first},@var{last}
6309 Print lines from @var{first} to @var{last}. Both arguments are
6310 linespecs. When a @code{list} command has two linespecs, and the
6311 source file of the second linespec is omitted, this refers to
6312 the same source file as the first linespec.
6314 @item list ,@var{last}
6315 Print lines ending with @var{last}.
6317 @item list @var{first},
6318 Print lines starting with @var{first}.
6321 Print lines just after the lines last printed.
6324 Print lines just before the lines last printed.
6327 As described in the preceding table.
6330 @node Specify Location
6331 @section Specifying a Location
6332 @cindex specifying location
6335 Several @value{GDBN} commands accept arguments that specify a location
6336 of your program's code. Since @value{GDBN} is a source-level
6337 debugger, a location usually specifies some line in the source code;
6338 for that reason, locations are also known as @dfn{linespecs}.
6340 Here are all the different ways of specifying a code location that
6341 @value{GDBN} understands:
6345 Specifies the line number @var{linenum} of the current source file.
6348 @itemx +@var{offset}
6349 Specifies the line @var{offset} lines before or after the @dfn{current
6350 line}. For the @code{list} command, the current line is the last one
6351 printed; for the breakpoint commands, this is the line at which
6352 execution stopped in the currently selected @dfn{stack frame}
6353 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6354 used as the second of the two linespecs in a @code{list} command,
6355 this specifies the line @var{offset} lines up or down from the first
6358 @item @var{filename}:@var{linenum}
6359 Specifies the line @var{linenum} in the source file @var{filename}.
6361 @item @var{function}
6362 Specifies the line that begins the body of the function @var{function}.
6363 For example, in C, this is the line with the open brace.
6365 @item @var{function}:@var{label}
6366 Specifies the line where @var{label} appears in @var{function}.
6368 @item @var{filename}:@var{function}
6369 Specifies the line that begins the body of the function @var{function}
6370 in the file @var{filename}. You only need the file name with a
6371 function name to avoid ambiguity when there are identically named
6372 functions in different source files.
6375 Specifies the line at which the label named @var{label} appears.
6376 @value{GDBN} searches for the label in the function corresponding to
6377 the currently selected stack frame. If there is no current selected
6378 stack frame (for instance, if the inferior is not running), then
6379 @value{GDBN} will not search for a label.
6381 @item *@var{address}
6382 Specifies the program address @var{address}. For line-oriented
6383 commands, such as @code{list} and @code{edit}, this specifies a source
6384 line that contains @var{address}. For @code{break} and other
6385 breakpoint oriented commands, this can be used to set breakpoints in
6386 parts of your program which do not have debugging information or
6389 Here @var{address} may be any expression valid in the current working
6390 language (@pxref{Languages, working language}) that specifies a code
6391 address. In addition, as a convenience, @value{GDBN} extends the
6392 semantics of expressions used in locations to cover the situations
6393 that frequently happen during debugging. Here are the various forms
6397 @item @var{expression}
6398 Any expression valid in the current working language.
6400 @item @var{funcaddr}
6401 An address of a function or procedure derived from its name. In C,
6402 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6403 simply the function's name @var{function} (and actually a special case
6404 of a valid expression). In Pascal and Modula-2, this is
6405 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6406 (although the Pascal form also works).
6408 This form specifies the address of the function's first instruction,
6409 before the stack frame and arguments have been set up.
6411 @item '@var{filename}'::@var{funcaddr}
6412 Like @var{funcaddr} above, but also specifies the name of the source
6413 file explicitly. This is useful if the name of the function does not
6414 specify the function unambiguously, e.g., if there are several
6415 functions with identical names in different source files.
6422 @section Editing Source Files
6423 @cindex editing source files
6426 @kindex e @r{(@code{edit})}
6427 To edit the lines in a source file, use the @code{edit} command.
6428 The editing program of your choice
6429 is invoked with the current line set to
6430 the active line in the program.
6431 Alternatively, there are several ways to specify what part of the file you
6432 want to print if you want to see other parts of the program:
6435 @item edit @var{location}
6436 Edit the source file specified by @code{location}. Editing starts at
6437 that @var{location}, e.g., at the specified source line of the
6438 specified file. @xref{Specify Location}, for all the possible forms
6439 of the @var{location} argument; here are the forms of the @code{edit}
6440 command most commonly used:
6443 @item edit @var{number}
6444 Edit the current source file with @var{number} as the active line number.
6446 @item edit @var{function}
6447 Edit the file containing @var{function} at the beginning of its definition.
6452 @subsection Choosing your Editor
6453 You can customize @value{GDBN} to use any editor you want
6455 The only restriction is that your editor (say @code{ex}), recognizes the
6456 following command-line syntax:
6458 ex +@var{number} file
6460 The optional numeric value +@var{number} specifies the number of the line in
6461 the file where to start editing.}.
6462 By default, it is @file{@value{EDITOR}}, but you can change this
6463 by setting the environment variable @code{EDITOR} before using
6464 @value{GDBN}. For example, to configure @value{GDBN} to use the
6465 @code{vi} editor, you could use these commands with the @code{sh} shell:
6471 or in the @code{csh} shell,
6473 setenv EDITOR /usr/bin/vi
6478 @section Searching Source Files
6479 @cindex searching source files
6481 There are two commands for searching through the current source file for a
6486 @kindex forward-search
6487 @item forward-search @var{regexp}
6488 @itemx search @var{regexp}
6489 The command @samp{forward-search @var{regexp}} checks each line,
6490 starting with the one following the last line listed, for a match for
6491 @var{regexp}. It lists the line that is found. You can use the
6492 synonym @samp{search @var{regexp}} or abbreviate the command name as
6495 @kindex reverse-search
6496 @item reverse-search @var{regexp}
6497 The command @samp{reverse-search @var{regexp}} checks each line, starting
6498 with the one before the last line listed and going backward, for a match
6499 for @var{regexp}. It lists the line that is found. You can abbreviate
6500 this command as @code{rev}.
6504 @section Specifying Source Directories
6507 @cindex directories for source files
6508 Executable programs sometimes do not record the directories of the source
6509 files from which they were compiled, just the names. Even when they do,
6510 the directories could be moved between the compilation and your debugging
6511 session. @value{GDBN} has a list of directories to search for source files;
6512 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6513 it tries all the directories in the list, in the order they are present
6514 in the list, until it finds a file with the desired name.
6516 For example, suppose an executable references the file
6517 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6518 @file{/mnt/cross}. The file is first looked up literally; if this
6519 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6520 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6521 message is printed. @value{GDBN} does not look up the parts of the
6522 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6523 Likewise, the subdirectories of the source path are not searched: if
6524 the source path is @file{/mnt/cross}, and the binary refers to
6525 @file{foo.c}, @value{GDBN} would not find it under
6526 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6528 Plain file names, relative file names with leading directories, file
6529 names containing dots, etc.@: are all treated as described above; for
6530 instance, if the source path is @file{/mnt/cross}, and the source file
6531 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6532 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6533 that---@file{/mnt/cross/foo.c}.
6535 Note that the executable search path is @emph{not} used to locate the
6538 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6539 any information it has cached about where source files are found and where
6540 each line is in the file.
6544 When you start @value{GDBN}, its source path includes only @samp{cdir}
6545 and @samp{cwd}, in that order.
6546 To add other directories, use the @code{directory} command.
6548 The search path is used to find both program source files and @value{GDBN}
6549 script files (read using the @samp{-command} option and @samp{source} command).
6551 In addition to the source path, @value{GDBN} provides a set of commands
6552 that manage a list of source path substitution rules. A @dfn{substitution
6553 rule} specifies how to rewrite source directories stored in the program's
6554 debug information in case the sources were moved to a different
6555 directory between compilation and debugging. A rule is made of
6556 two strings, the first specifying what needs to be rewritten in
6557 the path, and the second specifying how it should be rewritten.
6558 In @ref{set substitute-path}, we name these two parts @var{from} and
6559 @var{to} respectively. @value{GDBN} does a simple string replacement
6560 of @var{from} with @var{to} at the start of the directory part of the
6561 source file name, and uses that result instead of the original file
6562 name to look up the sources.
6564 Using the previous example, suppose the @file{foo-1.0} tree has been
6565 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6566 @value{GDBN} to replace @file{/usr/src} in all source path names with
6567 @file{/mnt/cross}. The first lookup will then be
6568 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6569 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6570 substitution rule, use the @code{set substitute-path} command
6571 (@pxref{set substitute-path}).
6573 To avoid unexpected substitution results, a rule is applied only if the
6574 @var{from} part of the directory name ends at a directory separator.
6575 For instance, a rule substituting @file{/usr/source} into
6576 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6577 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6578 is applied only at the beginning of the directory name, this rule will
6579 not be applied to @file{/root/usr/source/baz.c} either.
6581 In many cases, you can achieve the same result using the @code{directory}
6582 command. However, @code{set substitute-path} can be more efficient in
6583 the case where the sources are organized in a complex tree with multiple
6584 subdirectories. With the @code{directory} command, you need to add each
6585 subdirectory of your project. If you moved the entire tree while
6586 preserving its internal organization, then @code{set substitute-path}
6587 allows you to direct the debugger to all the sources with one single
6590 @code{set substitute-path} is also more than just a shortcut command.
6591 The source path is only used if the file at the original location no
6592 longer exists. On the other hand, @code{set substitute-path} modifies
6593 the debugger behavior to look at the rewritten location instead. So, if
6594 for any reason a source file that is not relevant to your executable is
6595 located at the original location, a substitution rule is the only
6596 method available to point @value{GDBN} at the new location.
6598 @cindex @samp{--with-relocated-sources}
6599 @cindex default source path substitution
6600 You can configure a default source path substitution rule by
6601 configuring @value{GDBN} with the
6602 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6603 should be the name of a directory under @value{GDBN}'s configured
6604 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6605 directory names in debug information under @var{dir} will be adjusted
6606 automatically if the installed @value{GDBN} is moved to a new
6607 location. This is useful if @value{GDBN}, libraries or executables
6608 with debug information and corresponding source code are being moved
6612 @item directory @var{dirname} @dots{}
6613 @item dir @var{dirname} @dots{}
6614 Add directory @var{dirname} to the front of the source path. Several
6615 directory names may be given to this command, separated by @samp{:}
6616 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6617 part of absolute file names) or
6618 whitespace. You may specify a directory that is already in the source
6619 path; this moves it forward, so @value{GDBN} searches it sooner.
6623 @vindex $cdir@r{, convenience variable}
6624 @vindex $cwd@r{, convenience variable}
6625 @cindex compilation directory
6626 @cindex current directory
6627 @cindex working directory
6628 @cindex directory, current
6629 @cindex directory, compilation
6630 You can use the string @samp{$cdir} to refer to the compilation
6631 directory (if one is recorded), and @samp{$cwd} to refer to the current
6632 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6633 tracks the current working directory as it changes during your @value{GDBN}
6634 session, while the latter is immediately expanded to the current
6635 directory at the time you add an entry to the source path.
6638 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6640 @c RET-repeat for @code{directory} is explicitly disabled, but since
6641 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6643 @item set directories @var{path-list}
6644 @kindex set directories
6645 Set the source path to @var{path-list}.
6646 @samp{$cdir:$cwd} are added if missing.
6648 @item show directories
6649 @kindex show directories
6650 Print the source path: show which directories it contains.
6652 @anchor{set substitute-path}
6653 @item set substitute-path @var{from} @var{to}
6654 @kindex set substitute-path
6655 Define a source path substitution rule, and add it at the end of the
6656 current list of existing substitution rules. If a rule with the same
6657 @var{from} was already defined, then the old rule is also deleted.
6659 For example, if the file @file{/foo/bar/baz.c} was moved to
6660 @file{/mnt/cross/baz.c}, then the command
6663 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6667 will tell @value{GDBN} to replace @samp{/usr/src} with
6668 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6669 @file{baz.c} even though it was moved.
6671 In the case when more than one substitution rule have been defined,
6672 the rules are evaluated one by one in the order where they have been
6673 defined. The first one matching, if any, is selected to perform
6676 For instance, if we had entered the following commands:
6679 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6680 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6684 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6685 @file{/mnt/include/defs.h} by using the first rule. However, it would
6686 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6687 @file{/mnt/src/lib/foo.c}.
6690 @item unset substitute-path [path]
6691 @kindex unset substitute-path
6692 If a path is specified, search the current list of substitution rules
6693 for a rule that would rewrite that path. Delete that rule if found.
6694 A warning is emitted by the debugger if no rule could be found.
6696 If no path is specified, then all substitution rules are deleted.
6698 @item show substitute-path [path]
6699 @kindex show substitute-path
6700 If a path is specified, then print the source path substitution rule
6701 which would rewrite that path, if any.
6703 If no path is specified, then print all existing source path substitution
6708 If your source path is cluttered with directories that are no longer of
6709 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6710 versions of source. You can correct the situation as follows:
6714 Use @code{directory} with no argument to reset the source path to its default value.
6717 Use @code{directory} with suitable arguments to reinstall the
6718 directories you want in the source path. You can add all the
6719 directories in one command.
6723 @section Source and Machine Code
6724 @cindex source line and its code address
6726 You can use the command @code{info line} to map source lines to program
6727 addresses (and vice versa), and the command @code{disassemble} to display
6728 a range of addresses as machine instructions. You can use the command
6729 @code{set disassemble-next-line} to set whether to disassemble next
6730 source line when execution stops. When run under @sc{gnu} Emacs
6731 mode, the @code{info line} command causes the arrow to point to the
6732 line specified. Also, @code{info line} prints addresses in symbolic form as
6737 @item info line @var{linespec}
6738 Print the starting and ending addresses of the compiled code for
6739 source line @var{linespec}. You can specify source lines in any of
6740 the ways documented in @ref{Specify Location}.
6743 For example, we can use @code{info line} to discover the location of
6744 the object code for the first line of function
6745 @code{m4_changequote}:
6747 @c FIXME: I think this example should also show the addresses in
6748 @c symbolic form, as they usually would be displayed.
6750 (@value{GDBP}) info line m4_changequote
6751 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6755 @cindex code address and its source line
6756 We can also inquire (using @code{*@var{addr}} as the form for
6757 @var{linespec}) what source line covers a particular address:
6759 (@value{GDBP}) info line *0x63ff
6760 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6763 @cindex @code{$_} and @code{info line}
6764 @cindex @code{x} command, default address
6765 @kindex x@r{(examine), and} info line
6766 After @code{info line}, the default address for the @code{x} command
6767 is changed to the starting address of the line, so that @samp{x/i} is
6768 sufficient to begin examining the machine code (@pxref{Memory,
6769 ,Examining Memory}). Also, this address is saved as the value of the
6770 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6775 @cindex assembly instructions
6776 @cindex instructions, assembly
6777 @cindex machine instructions
6778 @cindex listing machine instructions
6780 @itemx disassemble /m
6781 @itemx disassemble /r
6782 This specialized command dumps a range of memory as machine
6783 instructions. It can also print mixed source+disassembly by specifying
6784 the @code{/m} modifier and print the raw instructions in hex as well as
6785 in symbolic form by specifying the @code{/r}.
6786 The default memory range is the function surrounding the
6787 program counter of the selected frame. A single argument to this
6788 command is a program counter value; @value{GDBN} dumps the function
6789 surrounding this value. When two arguments are given, they should
6790 be separated by a comma, possibly surrounded by whitespace. The
6791 arguments specify a range of addresses to dump, in one of two forms:
6794 @item @var{start},@var{end}
6795 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6796 @item @var{start},+@var{length}
6797 the addresses from @var{start} (inclusive) to
6798 @code{@var{start}+@var{length}} (exclusive).
6802 When 2 arguments are specified, the name of the function is also
6803 printed (since there could be several functions in the given range).
6805 The argument(s) can be any expression yielding a numeric value, such as
6806 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6808 If the range of memory being disassembled contains current program counter,
6809 the instruction at that location is shown with a @code{=>} marker.
6812 The following example shows the disassembly of a range of addresses of
6813 HP PA-RISC 2.0 code:
6816 (@value{GDBP}) disas 0x32c4, 0x32e4
6817 Dump of assembler code from 0x32c4 to 0x32e4:
6818 0x32c4 <main+204>: addil 0,dp
6819 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6820 0x32cc <main+212>: ldil 0x3000,r31
6821 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6822 0x32d4 <main+220>: ldo 0(r31),rp
6823 0x32d8 <main+224>: addil -0x800,dp
6824 0x32dc <main+228>: ldo 0x588(r1),r26
6825 0x32e0 <main+232>: ldil 0x3000,r31
6826 End of assembler dump.
6829 Here is an example showing mixed source+assembly for Intel x86, when the
6830 program is stopped just after function prologue:
6833 (@value{GDBP}) disas /m main
6834 Dump of assembler code for function main:
6836 0x08048330 <+0>: push %ebp
6837 0x08048331 <+1>: mov %esp,%ebp
6838 0x08048333 <+3>: sub $0x8,%esp
6839 0x08048336 <+6>: and $0xfffffff0,%esp
6840 0x08048339 <+9>: sub $0x10,%esp
6842 6 printf ("Hello.\n");
6843 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6844 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6848 0x08048348 <+24>: mov $0x0,%eax
6849 0x0804834d <+29>: leave
6850 0x0804834e <+30>: ret
6852 End of assembler dump.
6855 Here is another example showing raw instructions in hex for AMD x86-64,
6858 (gdb) disas /r 0x400281,+10
6859 Dump of assembler code from 0x400281 to 0x40028b:
6860 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6861 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6862 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
6863 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
6864 End of assembler dump.
6867 Some architectures have more than one commonly-used set of instruction
6868 mnemonics or other syntax.
6870 For programs that were dynamically linked and use shared libraries,
6871 instructions that call functions or branch to locations in the shared
6872 libraries might show a seemingly bogus location---it's actually a
6873 location of the relocation table. On some architectures, @value{GDBN}
6874 might be able to resolve these to actual function names.
6877 @kindex set disassembly-flavor
6878 @cindex Intel disassembly flavor
6879 @cindex AT&T disassembly flavor
6880 @item set disassembly-flavor @var{instruction-set}
6881 Select the instruction set to use when disassembling the
6882 program via the @code{disassemble} or @code{x/i} commands.
6884 Currently this command is only defined for the Intel x86 family. You
6885 can set @var{instruction-set} to either @code{intel} or @code{att}.
6886 The default is @code{att}, the AT&T flavor used by default by Unix
6887 assemblers for x86-based targets.
6889 @kindex show disassembly-flavor
6890 @item show disassembly-flavor
6891 Show the current setting of the disassembly flavor.
6895 @kindex set disassemble-next-line
6896 @kindex show disassemble-next-line
6897 @item set disassemble-next-line
6898 @itemx show disassemble-next-line
6899 Control whether or not @value{GDBN} will disassemble the next source
6900 line or instruction when execution stops. If ON, @value{GDBN} will
6901 display disassembly of the next source line when execution of the
6902 program being debugged stops. This is @emph{in addition} to
6903 displaying the source line itself, which @value{GDBN} always does if
6904 possible. If the next source line cannot be displayed for some reason
6905 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6906 info in the debug info), @value{GDBN} will display disassembly of the
6907 next @emph{instruction} instead of showing the next source line. If
6908 AUTO, @value{GDBN} will display disassembly of next instruction only
6909 if the source line cannot be displayed. This setting causes
6910 @value{GDBN} to display some feedback when you step through a function
6911 with no line info or whose source file is unavailable. The default is
6912 OFF, which means never display the disassembly of the next line or
6918 @chapter Examining Data
6920 @cindex printing data
6921 @cindex examining data
6924 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6925 @c document because it is nonstandard... Under Epoch it displays in a
6926 @c different window or something like that.
6927 The usual way to examine data in your program is with the @code{print}
6928 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6929 evaluates and prints the value of an expression of the language your
6930 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6931 Different Languages}). It may also print the expression using a
6932 Python-based pretty-printer (@pxref{Pretty Printing}).
6935 @item print @var{expr}
6936 @itemx print /@var{f} @var{expr}
6937 @var{expr} is an expression (in the source language). By default the
6938 value of @var{expr} is printed in a format appropriate to its data type;
6939 you can choose a different format by specifying @samp{/@var{f}}, where
6940 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6944 @itemx print /@var{f}
6945 @cindex reprint the last value
6946 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6947 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6948 conveniently inspect the same value in an alternative format.
6951 A more low-level way of examining data is with the @code{x} command.
6952 It examines data in memory at a specified address and prints it in a
6953 specified format. @xref{Memory, ,Examining Memory}.
6955 If you are interested in information about types, or about how the
6956 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6957 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6961 * Expressions:: Expressions
6962 * Ambiguous Expressions:: Ambiguous Expressions
6963 * Variables:: Program variables
6964 * Arrays:: Artificial arrays
6965 * Output Formats:: Output formats
6966 * Memory:: Examining memory
6967 * Auto Display:: Automatic display
6968 * Print Settings:: Print settings
6969 * Pretty Printing:: Python pretty printing
6970 * Value History:: Value history
6971 * Convenience Vars:: Convenience variables
6972 * Registers:: Registers
6973 * Floating Point Hardware:: Floating point hardware
6974 * Vector Unit:: Vector Unit
6975 * OS Information:: Auxiliary data provided by operating system
6976 * Memory Region Attributes:: Memory region attributes
6977 * Dump/Restore Files:: Copy between memory and a file
6978 * Core File Generation:: Cause a program dump its core
6979 * Character Sets:: Debugging programs that use a different
6980 character set than GDB does
6981 * Caching Remote Data:: Data caching for remote targets
6982 * Searching Memory:: Searching memory for a sequence of bytes
6986 @section Expressions
6989 @code{print} and many other @value{GDBN} commands accept an expression and
6990 compute its value. Any kind of constant, variable or operator defined
6991 by the programming language you are using is valid in an expression in
6992 @value{GDBN}. This includes conditional expressions, function calls,
6993 casts, and string constants. It also includes preprocessor macros, if
6994 you compiled your program to include this information; see
6997 @cindex arrays in expressions
6998 @value{GDBN} supports array constants in expressions input by
6999 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7000 you can use the command @code{print @{1, 2, 3@}} to create an array
7001 of three integers. If you pass an array to a function or assign it
7002 to a program variable, @value{GDBN} copies the array to memory that
7003 is @code{malloc}ed in the target program.
7005 Because C is so widespread, most of the expressions shown in examples in
7006 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7007 Languages}, for information on how to use expressions in other
7010 In this section, we discuss operators that you can use in @value{GDBN}
7011 expressions regardless of your programming language.
7013 @cindex casts, in expressions
7014 Casts are supported in all languages, not just in C, because it is so
7015 useful to cast a number into a pointer in order to examine a structure
7016 at that address in memory.
7017 @c FIXME: casts supported---Mod2 true?
7019 @value{GDBN} supports these operators, in addition to those common
7020 to programming languages:
7024 @samp{@@} is a binary operator for treating parts of memory as arrays.
7025 @xref{Arrays, ,Artificial Arrays}, for more information.
7028 @samp{::} allows you to specify a variable in terms of the file or
7029 function where it is defined. @xref{Variables, ,Program Variables}.
7031 @cindex @{@var{type}@}
7032 @cindex type casting memory
7033 @cindex memory, viewing as typed object
7034 @cindex casts, to view memory
7035 @item @{@var{type}@} @var{addr}
7036 Refers to an object of type @var{type} stored at address @var{addr} in
7037 memory. @var{addr} may be any expression whose value is an integer or
7038 pointer (but parentheses are required around binary operators, just as in
7039 a cast). This construct is allowed regardless of what kind of data is
7040 normally supposed to reside at @var{addr}.
7043 @node Ambiguous Expressions
7044 @section Ambiguous Expressions
7045 @cindex ambiguous expressions
7047 Expressions can sometimes contain some ambiguous elements. For instance,
7048 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7049 a single function name to be defined several times, for application in
7050 different contexts. This is called @dfn{overloading}. Another example
7051 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7052 templates and is typically instantiated several times, resulting in
7053 the same function name being defined in different contexts.
7055 In some cases and depending on the language, it is possible to adjust
7056 the expression to remove the ambiguity. For instance in C@t{++}, you
7057 can specify the signature of the function you want to break on, as in
7058 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7059 qualified name of your function often makes the expression unambiguous
7062 When an ambiguity that needs to be resolved is detected, the debugger
7063 has the capability to display a menu of numbered choices for each
7064 possibility, and then waits for the selection with the prompt @samp{>}.
7065 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7066 aborts the current command. If the command in which the expression was
7067 used allows more than one choice to be selected, the next option in the
7068 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7071 For example, the following session excerpt shows an attempt to set a
7072 breakpoint at the overloaded symbol @code{String::after}.
7073 We choose three particular definitions of that function name:
7075 @c FIXME! This is likely to change to show arg type lists, at least
7078 (@value{GDBP}) b String::after
7081 [2] file:String.cc; line number:867
7082 [3] file:String.cc; line number:860
7083 [4] file:String.cc; line number:875
7084 [5] file:String.cc; line number:853
7085 [6] file:String.cc; line number:846
7086 [7] file:String.cc; line number:735
7088 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7089 Breakpoint 2 at 0xb344: file String.cc, line 875.
7090 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7091 Multiple breakpoints were set.
7092 Use the "delete" command to delete unwanted
7099 @kindex set multiple-symbols
7100 @item set multiple-symbols @var{mode}
7101 @cindex multiple-symbols menu
7103 This option allows you to adjust the debugger behavior when an expression
7106 By default, @var{mode} is set to @code{all}. If the command with which
7107 the expression is used allows more than one choice, then @value{GDBN}
7108 automatically selects all possible choices. For instance, inserting
7109 a breakpoint on a function using an ambiguous name results in a breakpoint
7110 inserted on each possible match. However, if a unique choice must be made,
7111 then @value{GDBN} uses the menu to help you disambiguate the expression.
7112 For instance, printing the address of an overloaded function will result
7113 in the use of the menu.
7115 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7116 when an ambiguity is detected.
7118 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7119 an error due to the ambiguity and the command is aborted.
7121 @kindex show multiple-symbols
7122 @item show multiple-symbols
7123 Show the current value of the @code{multiple-symbols} setting.
7127 @section Program Variables
7129 The most common kind of expression to use is the name of a variable
7132 Variables in expressions are understood in the selected stack frame
7133 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7137 global (or file-static)
7144 visible according to the scope rules of the
7145 programming language from the point of execution in that frame
7148 @noindent This means that in the function
7163 you can examine and use the variable @code{a} whenever your program is
7164 executing within the function @code{foo}, but you can only use or
7165 examine the variable @code{b} while your program is executing inside
7166 the block where @code{b} is declared.
7168 @cindex variable name conflict
7169 There is an exception: you can refer to a variable or function whose
7170 scope is a single source file even if the current execution point is not
7171 in this file. But it is possible to have more than one such variable or
7172 function with the same name (in different source files). If that
7173 happens, referring to that name has unpredictable effects. If you wish,
7174 you can specify a static variable in a particular function or file,
7175 using the colon-colon (@code{::}) notation:
7177 @cindex colon-colon, context for variables/functions
7179 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7180 @cindex @code{::}, context for variables/functions
7183 @var{file}::@var{variable}
7184 @var{function}::@var{variable}
7188 Here @var{file} or @var{function} is the name of the context for the
7189 static @var{variable}. In the case of file names, you can use quotes to
7190 make sure @value{GDBN} parses the file name as a single word---for example,
7191 to print a global value of @code{x} defined in @file{f2.c}:
7194 (@value{GDBP}) p 'f2.c'::x
7197 @cindex C@t{++} scope resolution
7198 This use of @samp{::} is very rarely in conflict with the very similar
7199 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7200 scope resolution operator in @value{GDBN} expressions.
7201 @c FIXME: Um, so what happens in one of those rare cases where it's in
7204 @cindex wrong values
7205 @cindex variable values, wrong
7206 @cindex function entry/exit, wrong values of variables
7207 @cindex optimized code, wrong values of variables
7209 @emph{Warning:} Occasionally, a local variable may appear to have the
7210 wrong value at certain points in a function---just after entry to a new
7211 scope, and just before exit.
7213 You may see this problem when you are stepping by machine instructions.
7214 This is because, on most machines, it takes more than one instruction to
7215 set up a stack frame (including local variable definitions); if you are
7216 stepping by machine instructions, variables may appear to have the wrong
7217 values until the stack frame is completely built. On exit, it usually
7218 also takes more than one machine instruction to destroy a stack frame;
7219 after you begin stepping through that group of instructions, local
7220 variable definitions may be gone.
7222 This may also happen when the compiler does significant optimizations.
7223 To be sure of always seeing accurate values, turn off all optimization
7226 @cindex ``No symbol "foo" in current context''
7227 Another possible effect of compiler optimizations is to optimize
7228 unused variables out of existence, or assign variables to registers (as
7229 opposed to memory addresses). Depending on the support for such cases
7230 offered by the debug info format used by the compiler, @value{GDBN}
7231 might not be able to display values for such local variables. If that
7232 happens, @value{GDBN} will print a message like this:
7235 No symbol "foo" in current context.
7238 To solve such problems, either recompile without optimizations, or use a
7239 different debug info format, if the compiler supports several such
7240 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7241 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7242 produces debug info in a format that is superior to formats such as
7243 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7244 an effective form for debug info. @xref{Debugging Options,,Options
7245 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7246 Compiler Collection (GCC)}.
7247 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7248 that are best suited to C@t{++} programs.
7250 If you ask to print an object whose contents are unknown to
7251 @value{GDBN}, e.g., because its data type is not completely specified
7252 by the debug information, @value{GDBN} will say @samp{<incomplete
7253 type>}. @xref{Symbols, incomplete type}, for more about this.
7255 Strings are identified as arrays of @code{char} values without specified
7256 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7257 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7258 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7259 defines literal string type @code{"char"} as @code{char} without a sign.
7264 signed char var1[] = "A";
7267 You get during debugging
7272 $2 = @{65 'A', 0 '\0'@}
7276 @section Artificial Arrays
7278 @cindex artificial array
7280 @kindex @@@r{, referencing memory as an array}
7281 It is often useful to print out several successive objects of the
7282 same type in memory; a section of an array, or an array of
7283 dynamically determined size for which only a pointer exists in the
7286 You can do this by referring to a contiguous span of memory as an
7287 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7288 operand of @samp{@@} should be the first element of the desired array
7289 and be an individual object. The right operand should be the desired length
7290 of the array. The result is an array value whose elements are all of
7291 the type of the left argument. The first element is actually the left
7292 argument; the second element comes from bytes of memory immediately
7293 following those that hold the first element, and so on. Here is an
7294 example. If a program says
7297 int *array = (int *) malloc (len * sizeof (int));
7301 you can print the contents of @code{array} with
7307 The left operand of @samp{@@} must reside in memory. Array values made
7308 with @samp{@@} in this way behave just like other arrays in terms of
7309 subscripting, and are coerced to pointers when used in expressions.
7310 Artificial arrays most often appear in expressions via the value history
7311 (@pxref{Value History, ,Value History}), after printing one out.
7313 Another way to create an artificial array is to use a cast.
7314 This re-interprets a value as if it were an array.
7315 The value need not be in memory:
7317 (@value{GDBP}) p/x (short[2])0x12345678
7318 $1 = @{0x1234, 0x5678@}
7321 As a convenience, if you leave the array length out (as in
7322 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7323 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7325 (@value{GDBP}) p/x (short[])0x12345678
7326 $2 = @{0x1234, 0x5678@}
7329 Sometimes the artificial array mechanism is not quite enough; in
7330 moderately complex data structures, the elements of interest may not
7331 actually be adjacent---for example, if you are interested in the values
7332 of pointers in an array. One useful work-around in this situation is
7333 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7334 Variables}) as a counter in an expression that prints the first
7335 interesting value, and then repeat that expression via @key{RET}. For
7336 instance, suppose you have an array @code{dtab} of pointers to
7337 structures, and you are interested in the values of a field @code{fv}
7338 in each structure. Here is an example of what you might type:
7348 @node Output Formats
7349 @section Output Formats
7351 @cindex formatted output
7352 @cindex output formats
7353 By default, @value{GDBN} prints a value according to its data type. Sometimes
7354 this is not what you want. For example, you might want to print a number
7355 in hex, or a pointer in decimal. Or you might want to view data in memory
7356 at a certain address as a character string or as an instruction. To do
7357 these things, specify an @dfn{output format} when you print a value.
7359 The simplest use of output formats is to say how to print a value
7360 already computed. This is done by starting the arguments of the
7361 @code{print} command with a slash and a format letter. The format
7362 letters supported are:
7366 Regard the bits of the value as an integer, and print the integer in
7370 Print as integer in signed decimal.
7373 Print as integer in unsigned decimal.
7376 Print as integer in octal.
7379 Print as integer in binary. The letter @samp{t} stands for ``two''.
7380 @footnote{@samp{b} cannot be used because these format letters are also
7381 used with the @code{x} command, where @samp{b} stands for ``byte'';
7382 see @ref{Memory,,Examining Memory}.}
7385 @cindex unknown address, locating
7386 @cindex locate address
7387 Print as an address, both absolute in hexadecimal and as an offset from
7388 the nearest preceding symbol. You can use this format used to discover
7389 where (in what function) an unknown address is located:
7392 (@value{GDBP}) p/a 0x54320
7393 $3 = 0x54320 <_initialize_vx+396>
7397 The command @code{info symbol 0x54320} yields similar results.
7398 @xref{Symbols, info symbol}.
7401 Regard as an integer and print it as a character constant. This
7402 prints both the numerical value and its character representation. The
7403 character representation is replaced with the octal escape @samp{\nnn}
7404 for characters outside the 7-bit @sc{ascii} range.
7406 Without this format, @value{GDBN} displays @code{char},
7407 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7408 constants. Single-byte members of vectors are displayed as integer
7412 Regard the bits of the value as a floating point number and print
7413 using typical floating point syntax.
7416 @cindex printing strings
7417 @cindex printing byte arrays
7418 Regard as a string, if possible. With this format, pointers to single-byte
7419 data are displayed as null-terminated strings and arrays of single-byte data
7420 are displayed as fixed-length strings. Other values are displayed in their
7423 Without this format, @value{GDBN} displays pointers to and arrays of
7424 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7425 strings. Single-byte members of a vector are displayed as an integer
7429 @cindex raw printing
7430 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7431 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7432 Printing}). This typically results in a higher-level display of the
7433 value's contents. The @samp{r} format bypasses any Python
7434 pretty-printer which might exist.
7437 For example, to print the program counter in hex (@pxref{Registers}), type
7444 Note that no space is required before the slash; this is because command
7445 names in @value{GDBN} cannot contain a slash.
7447 To reprint the last value in the value history with a different format,
7448 you can use the @code{print} command with just a format and no
7449 expression. For example, @samp{p/x} reprints the last value in hex.
7452 @section Examining Memory
7454 You can use the command @code{x} (for ``examine'') to examine memory in
7455 any of several formats, independently of your program's data types.
7457 @cindex examining memory
7459 @kindex x @r{(examine memory)}
7460 @item x/@var{nfu} @var{addr}
7463 Use the @code{x} command to examine memory.
7466 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7467 much memory to display and how to format it; @var{addr} is an
7468 expression giving the address where you want to start displaying memory.
7469 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7470 Several commands set convenient defaults for @var{addr}.
7473 @item @var{n}, the repeat count
7474 The repeat count is a decimal integer; the default is 1. It specifies
7475 how much memory (counting by units @var{u}) to display.
7476 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7479 @item @var{f}, the display format
7480 The display format is one of the formats used by @code{print}
7481 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7482 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7483 The default is @samp{x} (hexadecimal) initially. The default changes
7484 each time you use either @code{x} or @code{print}.
7486 @item @var{u}, the unit size
7487 The unit size is any of
7493 Halfwords (two bytes).
7495 Words (four bytes). This is the initial default.
7497 Giant words (eight bytes).
7500 Each time you specify a unit size with @code{x}, that size becomes the
7501 default unit the next time you use @code{x}. For the @samp{i} format,
7502 the unit size is ignored and is normally not written. For the @samp{s} format,
7503 the unit size defaults to @samp{b}, unless it is explicitly given.
7504 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7505 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7506 Note that the results depend on the programming language of the
7507 current compilation unit. If the language is C, the @samp{s}
7508 modifier will use the UTF-16 encoding while @samp{w} will use
7509 UTF-32. The encoding is set by the programming language and cannot
7512 @item @var{addr}, starting display address
7513 @var{addr} is the address where you want @value{GDBN} to begin displaying
7514 memory. The expression need not have a pointer value (though it may);
7515 it is always interpreted as an integer address of a byte of memory.
7516 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7517 @var{addr} is usually just after the last address examined---but several
7518 other commands also set the default address: @code{info breakpoints} (to
7519 the address of the last breakpoint listed), @code{info line} (to the
7520 starting address of a line), and @code{print} (if you use it to display
7521 a value from memory).
7524 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7525 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7526 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7527 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7528 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7530 Since the letters indicating unit sizes are all distinct from the
7531 letters specifying output formats, you do not have to remember whether
7532 unit size or format comes first; either order works. The output
7533 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7534 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7536 Even though the unit size @var{u} is ignored for the formats @samp{s}
7537 and @samp{i}, you might still want to use a count @var{n}; for example,
7538 @samp{3i} specifies that you want to see three machine instructions,
7539 including any operands. For convenience, especially when used with
7540 the @code{display} command, the @samp{i} format also prints branch delay
7541 slot instructions, if any, beyond the count specified, which immediately
7542 follow the last instruction that is within the count. The command
7543 @code{disassemble} gives an alternative way of inspecting machine
7544 instructions; see @ref{Machine Code,,Source and Machine Code}.
7546 All the defaults for the arguments to @code{x} are designed to make it
7547 easy to continue scanning memory with minimal specifications each time
7548 you use @code{x}. For example, after you have inspected three machine
7549 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7550 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7551 the repeat count @var{n} is used again; the other arguments default as
7552 for successive uses of @code{x}.
7554 When examining machine instructions, the instruction at current program
7555 counter is shown with a @code{=>} marker. For example:
7558 (@value{GDBP}) x/5i $pc-6
7559 0x804837f <main+11>: mov %esp,%ebp
7560 0x8048381 <main+13>: push %ecx
7561 0x8048382 <main+14>: sub $0x4,%esp
7562 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7563 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7566 @cindex @code{$_}, @code{$__}, and value history
7567 The addresses and contents printed by the @code{x} command are not saved
7568 in the value history because there is often too much of them and they
7569 would get in the way. Instead, @value{GDBN} makes these values available for
7570 subsequent use in expressions as values of the convenience variables
7571 @code{$_} and @code{$__}. After an @code{x} command, the last address
7572 examined is available for use in expressions in the convenience variable
7573 @code{$_}. The contents of that address, as examined, are available in
7574 the convenience variable @code{$__}.
7576 If the @code{x} command has a repeat count, the address and contents saved
7577 are from the last memory unit printed; this is not the same as the last
7578 address printed if several units were printed on the last line of output.
7580 @cindex remote memory comparison
7581 @cindex verify remote memory image
7582 When you are debugging a program running on a remote target machine
7583 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7584 remote machine's memory against the executable file you downloaded to
7585 the target. The @code{compare-sections} command is provided for such
7589 @kindex compare-sections
7590 @item compare-sections @r{[}@var{section-name}@r{]}
7591 Compare the data of a loadable section @var{section-name} in the
7592 executable file of the program being debugged with the same section in
7593 the remote machine's memory, and report any mismatches. With no
7594 arguments, compares all loadable sections. This command's
7595 availability depends on the target's support for the @code{"qCRC"}
7600 @section Automatic Display
7601 @cindex automatic display
7602 @cindex display of expressions
7604 If you find that you want to print the value of an expression frequently
7605 (to see how it changes), you might want to add it to the @dfn{automatic
7606 display list} so that @value{GDBN} prints its value each time your program stops.
7607 Each expression added to the list is given a number to identify it;
7608 to remove an expression from the list, you specify that number.
7609 The automatic display looks like this:
7613 3: bar[5] = (struct hack *) 0x3804
7617 This display shows item numbers, expressions and their current values. As with
7618 displays you request manually using @code{x} or @code{print}, you can
7619 specify the output format you prefer; in fact, @code{display} decides
7620 whether to use @code{print} or @code{x} depending your format
7621 specification---it uses @code{x} if you specify either the @samp{i}
7622 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7626 @item display @var{expr}
7627 Add the expression @var{expr} to the list of expressions to display
7628 each time your program stops. @xref{Expressions, ,Expressions}.
7630 @code{display} does not repeat if you press @key{RET} again after using it.
7632 @item display/@var{fmt} @var{expr}
7633 For @var{fmt} specifying only a display format and not a size or
7634 count, add the expression @var{expr} to the auto-display list but
7635 arrange to display it each time in the specified format @var{fmt}.
7636 @xref{Output Formats,,Output Formats}.
7638 @item display/@var{fmt} @var{addr}
7639 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7640 number of units, add the expression @var{addr} as a memory address to
7641 be examined each time your program stops. Examining means in effect
7642 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7645 For example, @samp{display/i $pc} can be helpful, to see the machine
7646 instruction about to be executed each time execution stops (@samp{$pc}
7647 is a common name for the program counter; @pxref{Registers, ,Registers}).
7650 @kindex delete display
7652 @item undisplay @var{dnums}@dots{}
7653 @itemx delete display @var{dnums}@dots{}
7654 Remove items from the list of expressions to display. Specify the
7655 numbers of the displays that you want affected with the command
7656 argument @var{dnums}. It can be a single display number, one of the
7657 numbers shown in the first field of the @samp{info display} display;
7658 or it could be a range of display numbers, as in @code{2-4}.
7660 @code{undisplay} does not repeat if you press @key{RET} after using it.
7661 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7663 @kindex disable display
7664 @item disable display @var{dnums}@dots{}
7665 Disable the display of item numbers @var{dnums}. A disabled display
7666 item is not printed automatically, but is not forgotten. It may be
7667 enabled again later. Specify the numbers of the displays that you
7668 want affected with the command argument @var{dnums}. It can be a
7669 single display number, one of the numbers shown in the first field of
7670 the @samp{info display} display; or it could be a range of display
7671 numbers, as in @code{2-4}.
7673 @kindex enable display
7674 @item enable display @var{dnums}@dots{}
7675 Enable display of item numbers @var{dnums}. It becomes effective once
7676 again in auto display of its expression, until you specify otherwise.
7677 Specify the numbers of the displays that you want affected with the
7678 command argument @var{dnums}. It can be a single display number, one
7679 of the numbers shown in the first field of the @samp{info display}
7680 display; or it could be a range of display numbers, as in @code{2-4}.
7683 Display the current values of the expressions on the list, just as is
7684 done when your program stops.
7686 @kindex info display
7688 Print the list of expressions previously set up to display
7689 automatically, each one with its item number, but without showing the
7690 values. This includes disabled expressions, which are marked as such.
7691 It also includes expressions which would not be displayed right now
7692 because they refer to automatic variables not currently available.
7695 @cindex display disabled out of scope
7696 If a display expression refers to local variables, then it does not make
7697 sense outside the lexical context for which it was set up. Such an
7698 expression is disabled when execution enters a context where one of its
7699 variables is not defined. For example, if you give the command
7700 @code{display last_char} while inside a function with an argument
7701 @code{last_char}, @value{GDBN} displays this argument while your program
7702 continues to stop inside that function. When it stops elsewhere---where
7703 there is no variable @code{last_char}---the display is disabled
7704 automatically. The next time your program stops where @code{last_char}
7705 is meaningful, you can enable the display expression once again.
7707 @node Print Settings
7708 @section Print Settings
7710 @cindex format options
7711 @cindex print settings
7712 @value{GDBN} provides the following ways to control how arrays, structures,
7713 and symbols are printed.
7716 These settings are useful for debugging programs in any language:
7720 @item set print address
7721 @itemx set print address on
7722 @cindex print/don't print memory addresses
7723 @value{GDBN} prints memory addresses showing the location of stack
7724 traces, structure values, pointer values, breakpoints, and so forth,
7725 even when it also displays the contents of those addresses. The default
7726 is @code{on}. For example, this is what a stack frame display looks like with
7727 @code{set print address on}:
7732 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7734 530 if (lquote != def_lquote)
7738 @item set print address off
7739 Do not print addresses when displaying their contents. For example,
7740 this is the same stack frame displayed with @code{set print address off}:
7744 (@value{GDBP}) set print addr off
7746 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7747 530 if (lquote != def_lquote)
7751 You can use @samp{set print address off} to eliminate all machine
7752 dependent displays from the @value{GDBN} interface. For example, with
7753 @code{print address off}, you should get the same text for backtraces on
7754 all machines---whether or not they involve pointer arguments.
7757 @item show print address
7758 Show whether or not addresses are to be printed.
7761 When @value{GDBN} prints a symbolic address, it normally prints the
7762 closest earlier symbol plus an offset. If that symbol does not uniquely
7763 identify the address (for example, it is a name whose scope is a single
7764 source file), you may need to clarify. One way to do this is with
7765 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7766 you can set @value{GDBN} to print the source file and line number when
7767 it prints a symbolic address:
7770 @item set print symbol-filename on
7771 @cindex source file and line of a symbol
7772 @cindex symbol, source file and line
7773 Tell @value{GDBN} to print the source file name and line number of a
7774 symbol in the symbolic form of an address.
7776 @item set print symbol-filename off
7777 Do not print source file name and line number of a symbol. This is the
7780 @item show print symbol-filename
7781 Show whether or not @value{GDBN} will print the source file name and
7782 line number of a symbol in the symbolic form of an address.
7785 Another situation where it is helpful to show symbol filenames and line
7786 numbers is when disassembling code; @value{GDBN} shows you the line
7787 number and source file that corresponds to each instruction.
7789 Also, you may wish to see the symbolic form only if the address being
7790 printed is reasonably close to the closest earlier symbol:
7793 @item set print max-symbolic-offset @var{max-offset}
7794 @cindex maximum value for offset of closest symbol
7795 Tell @value{GDBN} to only display the symbolic form of an address if the
7796 offset between the closest earlier symbol and the address is less than
7797 @var{max-offset}. The default is 0, which tells @value{GDBN}
7798 to always print the symbolic form of an address if any symbol precedes it.
7800 @item show print max-symbolic-offset
7801 Ask how large the maximum offset is that @value{GDBN} prints in a
7805 @cindex wild pointer, interpreting
7806 @cindex pointer, finding referent
7807 If you have a pointer and you are not sure where it points, try
7808 @samp{set print symbol-filename on}. Then you can determine the name
7809 and source file location of the variable where it points, using
7810 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7811 For example, here @value{GDBN} shows that a variable @code{ptt} points
7812 at another variable @code{t}, defined in @file{hi2.c}:
7815 (@value{GDBP}) set print symbol-filename on
7816 (@value{GDBP}) p/a ptt
7817 $4 = 0xe008 <t in hi2.c>
7821 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7822 does not show the symbol name and filename of the referent, even with
7823 the appropriate @code{set print} options turned on.
7826 Other settings control how different kinds of objects are printed:
7829 @item set print array
7830 @itemx set print array on
7831 @cindex pretty print arrays
7832 Pretty print arrays. This format is more convenient to read,
7833 but uses more space. The default is off.
7835 @item set print array off
7836 Return to compressed format for arrays.
7838 @item show print array
7839 Show whether compressed or pretty format is selected for displaying
7842 @cindex print array indexes
7843 @item set print array-indexes
7844 @itemx set print array-indexes on
7845 Print the index of each element when displaying arrays. May be more
7846 convenient to locate a given element in the array or quickly find the
7847 index of a given element in that printed array. The default is off.
7849 @item set print array-indexes off
7850 Stop printing element indexes when displaying arrays.
7852 @item show print array-indexes
7853 Show whether the index of each element is printed when displaying
7856 @item set print elements @var{number-of-elements}
7857 @cindex number of array elements to print
7858 @cindex limit on number of printed array elements
7859 Set a limit on how many elements of an array @value{GDBN} will print.
7860 If @value{GDBN} is printing a large array, it stops printing after it has
7861 printed the number of elements set by the @code{set print elements} command.
7862 This limit also applies to the display of strings.
7863 When @value{GDBN} starts, this limit is set to 200.
7864 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7866 @item show print elements
7867 Display the number of elements of a large array that @value{GDBN} will print.
7868 If the number is 0, then the printing is unlimited.
7870 @item set print frame-arguments @var{value}
7871 @kindex set print frame-arguments
7872 @cindex printing frame argument values
7873 @cindex print all frame argument values
7874 @cindex print frame argument values for scalars only
7875 @cindex do not print frame argument values
7876 This command allows to control how the values of arguments are printed
7877 when the debugger prints a frame (@pxref{Frames}). The possible
7882 The values of all arguments are printed.
7885 Print the value of an argument only if it is a scalar. The value of more
7886 complex arguments such as arrays, structures, unions, etc, is replaced
7887 by @code{@dots{}}. This is the default. Here is an example where
7888 only scalar arguments are shown:
7891 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7896 None of the argument values are printed. Instead, the value of each argument
7897 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7900 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7905 By default, only scalar arguments are printed. This command can be used
7906 to configure the debugger to print the value of all arguments, regardless
7907 of their type. However, it is often advantageous to not print the value
7908 of more complex parameters. For instance, it reduces the amount of
7909 information printed in each frame, making the backtrace more readable.
7910 Also, it improves performance when displaying Ada frames, because
7911 the computation of large arguments can sometimes be CPU-intensive,
7912 especially in large applications. Setting @code{print frame-arguments}
7913 to @code{scalars} (the default) or @code{none} avoids this computation,
7914 thus speeding up the display of each Ada frame.
7916 @item show print frame-arguments
7917 Show how the value of arguments should be displayed when printing a frame.
7919 @item set print repeats
7920 @cindex repeated array elements
7921 Set the threshold for suppressing display of repeated array
7922 elements. When the number of consecutive identical elements of an
7923 array exceeds the threshold, @value{GDBN} prints the string
7924 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7925 identical repetitions, instead of displaying the identical elements
7926 themselves. Setting the threshold to zero will cause all elements to
7927 be individually printed. The default threshold is 10.
7929 @item show print repeats
7930 Display the current threshold for printing repeated identical
7933 @item set print null-stop
7934 @cindex @sc{null} elements in arrays
7935 Cause @value{GDBN} to stop printing the characters of an array when the first
7936 @sc{null} is encountered. This is useful when large arrays actually
7937 contain only short strings.
7940 @item show print null-stop
7941 Show whether @value{GDBN} stops printing an array on the first
7942 @sc{null} character.
7944 @item set print pretty on
7945 @cindex print structures in indented form
7946 @cindex indentation in structure display
7947 Cause @value{GDBN} to print structures in an indented format with one member
7948 per line, like this:
7963 @item set print pretty off
7964 Cause @value{GDBN} to print structures in a compact format, like this:
7968 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7969 meat = 0x54 "Pork"@}
7974 This is the default format.
7976 @item show print pretty
7977 Show which format @value{GDBN} is using to print structures.
7979 @item set print sevenbit-strings on
7980 @cindex eight-bit characters in strings
7981 @cindex octal escapes in strings
7982 Print using only seven-bit characters; if this option is set,
7983 @value{GDBN} displays any eight-bit characters (in strings or
7984 character values) using the notation @code{\}@var{nnn}. This setting is
7985 best if you are working in English (@sc{ascii}) and you use the
7986 high-order bit of characters as a marker or ``meta'' bit.
7988 @item set print sevenbit-strings off
7989 Print full eight-bit characters. This allows the use of more
7990 international character sets, and is the default.
7992 @item show print sevenbit-strings
7993 Show whether or not @value{GDBN} is printing only seven-bit characters.
7995 @item set print union on
7996 @cindex unions in structures, printing
7997 Tell @value{GDBN} to print unions which are contained in structures
7998 and other unions. This is the default setting.
8000 @item set print union off
8001 Tell @value{GDBN} not to print unions which are contained in
8002 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8005 @item show print union
8006 Ask @value{GDBN} whether or not it will print unions which are contained in
8007 structures and other unions.
8009 For example, given the declarations
8012 typedef enum @{Tree, Bug@} Species;
8013 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8014 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8025 struct thing foo = @{Tree, @{Acorn@}@};
8029 with @code{set print union on} in effect @samp{p foo} would print
8032 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8036 and with @code{set print union off} in effect it would print
8039 $1 = @{it = Tree, form = @{...@}@}
8043 @code{set print union} affects programs written in C-like languages
8049 These settings are of interest when debugging C@t{++} programs:
8052 @cindex demangling C@t{++} names
8053 @item set print demangle
8054 @itemx set print demangle on
8055 Print C@t{++} names in their source form rather than in the encoded
8056 (``mangled'') form passed to the assembler and linker for type-safe
8057 linkage. The default is on.
8059 @item show print demangle
8060 Show whether C@t{++} names are printed in mangled or demangled form.
8062 @item set print asm-demangle
8063 @itemx set print asm-demangle on
8064 Print C@t{++} names in their source form rather than their mangled form, even
8065 in assembler code printouts such as instruction disassemblies.
8068 @item show print asm-demangle
8069 Show whether C@t{++} names in assembly listings are printed in mangled
8072 @cindex C@t{++} symbol decoding style
8073 @cindex symbol decoding style, C@t{++}
8074 @kindex set demangle-style
8075 @item set demangle-style @var{style}
8076 Choose among several encoding schemes used by different compilers to
8077 represent C@t{++} names. The choices for @var{style} are currently:
8081 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8084 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8085 This is the default.
8088 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8091 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8094 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8095 @strong{Warning:} this setting alone is not sufficient to allow
8096 debugging @code{cfront}-generated executables. @value{GDBN} would
8097 require further enhancement to permit that.
8100 If you omit @var{style}, you will see a list of possible formats.
8102 @item show demangle-style
8103 Display the encoding style currently in use for decoding C@t{++} symbols.
8105 @item set print object
8106 @itemx set print object on
8107 @cindex derived type of an object, printing
8108 @cindex display derived types
8109 When displaying a pointer to an object, identify the @emph{actual}
8110 (derived) type of the object rather than the @emph{declared} type, using
8111 the virtual function table.
8113 @item set print object off
8114 Display only the declared type of objects, without reference to the
8115 virtual function table. This is the default setting.
8117 @item show print object
8118 Show whether actual, or declared, object types are displayed.
8120 @item set print static-members
8121 @itemx set print static-members on
8122 @cindex static members of C@t{++} objects
8123 Print static members when displaying a C@t{++} object. The default is on.
8125 @item set print static-members off
8126 Do not print static members when displaying a C@t{++} object.
8128 @item show print static-members
8129 Show whether C@t{++} static members are printed or not.
8131 @item set print pascal_static-members
8132 @itemx set print pascal_static-members on
8133 @cindex static members of Pascal objects
8134 @cindex Pascal objects, static members display
8135 Print static members when displaying a Pascal object. The default is on.
8137 @item set print pascal_static-members off
8138 Do not print static members when displaying a Pascal object.
8140 @item show print pascal_static-members
8141 Show whether Pascal static members are printed or not.
8143 @c These don't work with HP ANSI C++ yet.
8144 @item set print vtbl
8145 @itemx set print vtbl on
8146 @cindex pretty print C@t{++} virtual function tables
8147 @cindex virtual functions (C@t{++}) display
8148 @cindex VTBL display
8149 Pretty print C@t{++} virtual function tables. The default is off.
8150 (The @code{vtbl} commands do not work on programs compiled with the HP
8151 ANSI C@t{++} compiler (@code{aCC}).)
8153 @item set print vtbl off
8154 Do not pretty print C@t{++} virtual function tables.
8156 @item show print vtbl
8157 Show whether C@t{++} virtual function tables are pretty printed, or not.
8160 @node Pretty Printing
8161 @section Pretty Printing
8163 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8164 Python code. It greatly simplifies the display of complex objects. This
8165 mechanism works for both MI and the CLI.
8168 * Pretty-Printer Introduction:: Introduction to pretty-printers
8169 * Pretty-Printer Example:: An example pretty-printer
8170 * Pretty-Printer Commands:: Pretty-printer commands
8173 @node Pretty-Printer Introduction
8174 @subsection Pretty-Printer Introduction
8176 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8177 registered for the value. If there is then @value{GDBN} invokes the
8178 pretty-printer to print the value. Otherwise the value is printed normally.
8180 Pretty-printers are normally named. This makes them easy to manage.
8181 The @samp{info pretty-printer} command will list all the installed
8182 pretty-printers with their names.
8183 If a pretty-printer can handle multiple data types, then its
8184 @dfn{subprinters} are the printers for the individual data types.
8185 Each such subprinter has its own name.
8186 The format of the name is @var{printer-name};@var{subprinter-name}.
8188 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8189 Typically they are automatically loaded and registered when the corresponding
8190 debug information is loaded, thus making them available without having to
8191 do anything special.
8193 There are three places where a pretty-printer can be registered.
8197 Pretty-printers registered globally are available when debugging
8201 Pretty-printers registered with a program space are available only
8202 when debugging that program.
8203 @xref{Progspaces In Python}, for more details on program spaces in Python.
8206 Pretty-printers registered with an objfile are loaded and unloaded
8207 with the corresponding objfile (e.g., shared library).
8208 @xref{Objfiles In Python}, for more details on objfiles in Python.
8211 @xref{Selecting Pretty-Printers}, for further information on how
8212 pretty-printers are selected,
8214 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8217 @node Pretty-Printer Example
8218 @subsection Pretty-Printer Example
8220 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8223 (@value{GDBP}) print s
8225 static npos = 4294967295,
8227 <std::allocator<char>> = @{
8228 <__gnu_cxx::new_allocator<char>> = @{
8229 <No data fields>@}, <No data fields>
8231 members of std::basic_string<char, std::char_traits<char>,
8232 std::allocator<char> >::_Alloc_hider:
8233 _M_p = 0x804a014 "abcd"
8238 With a pretty-printer for @code{std::string} only the contents are printed:
8241 (@value{GDBP}) print s
8245 @node Pretty-Printer Commands
8246 @subsection Pretty-Printer Commands
8247 @cindex pretty-printer commands
8250 @kindex info pretty-printer
8251 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8252 Print the list of installed pretty-printers.
8253 This includes disabled pretty-printers, which are marked as such.
8255 @var{object-regexp} is a regular expression matching the objects
8256 whose pretty-printers to list.
8257 Objects can be @code{global}, the program space's file
8258 (@pxref{Progspaces In Python}),
8259 and the object files within that program space (@pxref{Objfiles In Python}).
8260 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8261 looks up a printer from these three objects.
8263 @var{name-regexp} is a regular expression matching the name of the printers
8266 @kindex disable pretty-printer
8267 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8268 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8269 A disabled pretty-printer is not forgotten, it may be enabled again later.
8271 @kindex enable pretty-printer
8272 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8273 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8278 Suppose we have three pretty-printers installed: one from library1.so
8279 named @code{foo} that prints objects of type @code{foo}, and
8280 another from library2.so named @code{bar} that prints two types of objects,
8281 @code{bar1} and @code{bar2}.
8284 (gdb) info pretty-printer
8291 (gdb) info pretty-printer library2
8296 (gdb) disable pretty-printer library1
8298 2 of 3 printers enabled
8299 (gdb) info pretty-printer
8306 (gdb) disable pretty-printer library2 bar:bar1
8308 1 of 3 printers enabled
8309 (gdb) info pretty-printer library2
8316 (gdb) disable pretty-printer library2 bar
8318 0 of 3 printers enabled
8319 (gdb) info pretty-printer library2
8328 Note that for @code{bar} the entire printer can be disabled,
8329 as can each individual subprinter.
8332 @section Value History
8334 @cindex value history
8335 @cindex history of values printed by @value{GDBN}
8336 Values printed by the @code{print} command are saved in the @value{GDBN}
8337 @dfn{value history}. This allows you to refer to them in other expressions.
8338 Values are kept until the symbol table is re-read or discarded
8339 (for example with the @code{file} or @code{symbol-file} commands).
8340 When the symbol table changes, the value history is discarded,
8341 since the values may contain pointers back to the types defined in the
8346 @cindex history number
8347 The values printed are given @dfn{history numbers} by which you can
8348 refer to them. These are successive integers starting with one.
8349 @code{print} shows you the history number assigned to a value by
8350 printing @samp{$@var{num} = } before the value; here @var{num} is the
8353 To refer to any previous value, use @samp{$} followed by the value's
8354 history number. The way @code{print} labels its output is designed to
8355 remind you of this. Just @code{$} refers to the most recent value in
8356 the history, and @code{$$} refers to the value before that.
8357 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8358 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8359 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8361 For example, suppose you have just printed a pointer to a structure and
8362 want to see the contents of the structure. It suffices to type
8368 If you have a chain of structures where the component @code{next} points
8369 to the next one, you can print the contents of the next one with this:
8376 You can print successive links in the chain by repeating this
8377 command---which you can do by just typing @key{RET}.
8379 Note that the history records values, not expressions. If the value of
8380 @code{x} is 4 and you type these commands:
8388 then the value recorded in the value history by the @code{print} command
8389 remains 4 even though the value of @code{x} has changed.
8394 Print the last ten values in the value history, with their item numbers.
8395 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8396 values} does not change the history.
8398 @item show values @var{n}
8399 Print ten history values centered on history item number @var{n}.
8402 Print ten history values just after the values last printed. If no more
8403 values are available, @code{show values +} produces no display.
8406 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8407 same effect as @samp{show values +}.
8409 @node Convenience Vars
8410 @section Convenience Variables
8412 @cindex convenience variables
8413 @cindex user-defined variables
8414 @value{GDBN} provides @dfn{convenience variables} that you can use within
8415 @value{GDBN} to hold on to a value and refer to it later. These variables
8416 exist entirely within @value{GDBN}; they are not part of your program, and
8417 setting a convenience variable has no direct effect on further execution
8418 of your program. That is why you can use them freely.
8420 Convenience variables are prefixed with @samp{$}. Any name preceded by
8421 @samp{$} can be used for a convenience variable, unless it is one of
8422 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8423 (Value history references, in contrast, are @emph{numbers} preceded
8424 by @samp{$}. @xref{Value History, ,Value History}.)
8426 You can save a value in a convenience variable with an assignment
8427 expression, just as you would set a variable in your program.
8431 set $foo = *object_ptr
8435 would save in @code{$foo} the value contained in the object pointed to by
8438 Using a convenience variable for the first time creates it, but its
8439 value is @code{void} until you assign a new value. You can alter the
8440 value with another assignment at any time.
8442 Convenience variables have no fixed types. You can assign a convenience
8443 variable any type of value, including structures and arrays, even if
8444 that variable already has a value of a different type. The convenience
8445 variable, when used as an expression, has the type of its current value.
8448 @kindex show convenience
8449 @cindex show all user variables
8450 @item show convenience
8451 Print a list of convenience variables used so far, and their values.
8452 Abbreviated @code{show conv}.
8454 @kindex init-if-undefined
8455 @cindex convenience variables, initializing
8456 @item init-if-undefined $@var{variable} = @var{expression}
8457 Set a convenience variable if it has not already been set. This is useful
8458 for user-defined commands that keep some state. It is similar, in concept,
8459 to using local static variables with initializers in C (except that
8460 convenience variables are global). It can also be used to allow users to
8461 override default values used in a command script.
8463 If the variable is already defined then the expression is not evaluated so
8464 any side-effects do not occur.
8467 One of the ways to use a convenience variable is as a counter to be
8468 incremented or a pointer to be advanced. For example, to print
8469 a field from successive elements of an array of structures:
8473 print bar[$i++]->contents
8477 Repeat that command by typing @key{RET}.
8479 Some convenience variables are created automatically by @value{GDBN} and given
8480 values likely to be useful.
8483 @vindex $_@r{, convenience variable}
8485 The variable @code{$_} is automatically set by the @code{x} command to
8486 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8487 commands which provide a default address for @code{x} to examine also
8488 set @code{$_} to that address; these commands include @code{info line}
8489 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8490 except when set by the @code{x} command, in which case it is a pointer
8491 to the type of @code{$__}.
8493 @vindex $__@r{, convenience variable}
8495 The variable @code{$__} is automatically set by the @code{x} command
8496 to the value found in the last address examined. Its type is chosen
8497 to match the format in which the data was printed.
8500 @vindex $_exitcode@r{, convenience variable}
8501 The variable @code{$_exitcode} is automatically set to the exit code when
8502 the program being debugged terminates.
8505 @vindex $_sdata@r{, inspect, convenience variable}
8506 The variable @code{$_sdata} contains extra collected static tracepoint
8507 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8508 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8509 if extra static tracepoint data has not been collected.
8512 @vindex $_siginfo@r{, convenience variable}
8513 The variable @code{$_siginfo} contains extra signal information
8514 (@pxref{extra signal information}). Note that @code{$_siginfo}
8515 could be empty, if the application has not yet received any signals.
8516 For example, it will be empty before you execute the @code{run} command.
8519 @vindex $_tlb@r{, convenience variable}
8520 The variable @code{$_tlb} is automatically set when debugging
8521 applications running on MS-Windows in native mode or connected to
8522 gdbserver that supports the @code{qGetTIBAddr} request.
8523 @xref{General Query Packets}.
8524 This variable contains the address of the thread information block.
8528 On HP-UX systems, if you refer to a function or variable name that
8529 begins with a dollar sign, @value{GDBN} searches for a user or system
8530 name first, before it searches for a convenience variable.
8532 @cindex convenience functions
8533 @value{GDBN} also supplies some @dfn{convenience functions}. These
8534 have a syntax similar to convenience variables. A convenience
8535 function can be used in an expression just like an ordinary function;
8536 however, a convenience function is implemented internally to
8541 @kindex help function
8542 @cindex show all convenience functions
8543 Print a list of all convenience functions.
8550 You can refer to machine register contents, in expressions, as variables
8551 with names starting with @samp{$}. The names of registers are different
8552 for each machine; use @code{info registers} to see the names used on
8556 @kindex info registers
8557 @item info registers
8558 Print the names and values of all registers except floating-point
8559 and vector registers (in the selected stack frame).
8561 @kindex info all-registers
8562 @cindex floating point registers
8563 @item info all-registers
8564 Print the names and values of all registers, including floating-point
8565 and vector registers (in the selected stack frame).
8567 @item info registers @var{regname} @dots{}
8568 Print the @dfn{relativized} value of each specified register @var{regname}.
8569 As discussed in detail below, register values are normally relative to
8570 the selected stack frame. @var{regname} may be any register name valid on
8571 the machine you are using, with or without the initial @samp{$}.
8574 @cindex stack pointer register
8575 @cindex program counter register
8576 @cindex process status register
8577 @cindex frame pointer register
8578 @cindex standard registers
8579 @value{GDBN} has four ``standard'' register names that are available (in
8580 expressions) on most machines---whenever they do not conflict with an
8581 architecture's canonical mnemonics for registers. The register names
8582 @code{$pc} and @code{$sp} are used for the program counter register and
8583 the stack pointer. @code{$fp} is used for a register that contains a
8584 pointer to the current stack frame, and @code{$ps} is used for a
8585 register that contains the processor status. For example,
8586 you could print the program counter in hex with
8593 or print the instruction to be executed next with
8600 or add four to the stack pointer@footnote{This is a way of removing
8601 one word from the stack, on machines where stacks grow downward in
8602 memory (most machines, nowadays). This assumes that the innermost
8603 stack frame is selected; setting @code{$sp} is not allowed when other
8604 stack frames are selected. To pop entire frames off the stack,
8605 regardless of machine architecture, use @code{return};
8606 see @ref{Returning, ,Returning from a Function}.} with
8612 Whenever possible, these four standard register names are available on
8613 your machine even though the machine has different canonical mnemonics,
8614 so long as there is no conflict. The @code{info registers} command
8615 shows the canonical names. For example, on the SPARC, @code{info
8616 registers} displays the processor status register as @code{$psr} but you
8617 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8618 is an alias for the @sc{eflags} register.
8620 @value{GDBN} always considers the contents of an ordinary register as an
8621 integer when the register is examined in this way. Some machines have
8622 special registers which can hold nothing but floating point; these
8623 registers are considered to have floating point values. There is no way
8624 to refer to the contents of an ordinary register as floating point value
8625 (although you can @emph{print} it as a floating point value with
8626 @samp{print/f $@var{regname}}).
8628 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8629 means that the data format in which the register contents are saved by
8630 the operating system is not the same one that your program normally
8631 sees. For example, the registers of the 68881 floating point
8632 coprocessor are always saved in ``extended'' (raw) format, but all C
8633 programs expect to work with ``double'' (virtual) format. In such
8634 cases, @value{GDBN} normally works with the virtual format only (the format
8635 that makes sense for your program), but the @code{info registers} command
8636 prints the data in both formats.
8638 @cindex SSE registers (x86)
8639 @cindex MMX registers (x86)
8640 Some machines have special registers whose contents can be interpreted
8641 in several different ways. For example, modern x86-based machines
8642 have SSE and MMX registers that can hold several values packed
8643 together in several different formats. @value{GDBN} refers to such
8644 registers in @code{struct} notation:
8647 (@value{GDBP}) print $xmm1
8649 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8650 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8651 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8652 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8653 v4_int32 = @{0, 20657912, 11, 13@},
8654 v2_int64 = @{88725056443645952, 55834574859@},
8655 uint128 = 0x0000000d0000000b013b36f800000000
8660 To set values of such registers, you need to tell @value{GDBN} which
8661 view of the register you wish to change, as if you were assigning
8662 value to a @code{struct} member:
8665 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8668 Normally, register values are relative to the selected stack frame
8669 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8670 value that the register would contain if all stack frames farther in
8671 were exited and their saved registers restored. In order to see the
8672 true contents of hardware registers, you must select the innermost
8673 frame (with @samp{frame 0}).
8675 However, @value{GDBN} must deduce where registers are saved, from the machine
8676 code generated by your compiler. If some registers are not saved, or if
8677 @value{GDBN} is unable to locate the saved registers, the selected stack
8678 frame makes no difference.
8680 @node Floating Point Hardware
8681 @section Floating Point Hardware
8682 @cindex floating point
8684 Depending on the configuration, @value{GDBN} may be able to give
8685 you more information about the status of the floating point hardware.
8690 Display hardware-dependent information about the floating
8691 point unit. The exact contents and layout vary depending on the
8692 floating point chip. Currently, @samp{info float} is supported on
8693 the ARM and x86 machines.
8697 @section Vector Unit
8700 Depending on the configuration, @value{GDBN} may be able to give you
8701 more information about the status of the vector unit.
8706 Display information about the vector unit. The exact contents and
8707 layout vary depending on the hardware.
8710 @node OS Information
8711 @section Operating System Auxiliary Information
8712 @cindex OS information
8714 @value{GDBN} provides interfaces to useful OS facilities that can help
8715 you debug your program.
8717 @cindex @code{ptrace} system call
8718 @cindex @code{struct user} contents
8719 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8720 machines), it interfaces with the inferior via the @code{ptrace}
8721 system call. The operating system creates a special sata structure,
8722 called @code{struct user}, for this interface. You can use the
8723 command @code{info udot} to display the contents of this data
8729 Display the contents of the @code{struct user} maintained by the OS
8730 kernel for the program being debugged. @value{GDBN} displays the
8731 contents of @code{struct user} as a list of hex numbers, similar to
8732 the @code{examine} command.
8735 @cindex auxiliary vector
8736 @cindex vector, auxiliary
8737 Some operating systems supply an @dfn{auxiliary vector} to programs at
8738 startup. This is akin to the arguments and environment that you
8739 specify for a program, but contains a system-dependent variety of
8740 binary values that tell system libraries important details about the
8741 hardware, operating system, and process. Each value's purpose is
8742 identified by an integer tag; the meanings are well-known but system-specific.
8743 Depending on the configuration and operating system facilities,
8744 @value{GDBN} may be able to show you this information. For remote
8745 targets, this functionality may further depend on the remote stub's
8746 support of the @samp{qXfer:auxv:read} packet, see
8747 @ref{qXfer auxiliary vector read}.
8752 Display the auxiliary vector of the inferior, which can be either a
8753 live process or a core dump file. @value{GDBN} prints each tag value
8754 numerically, and also shows names and text descriptions for recognized
8755 tags. Some values in the vector are numbers, some bit masks, and some
8756 pointers to strings or other data. @value{GDBN} displays each value in the
8757 most appropriate form for a recognized tag, and in hexadecimal for
8758 an unrecognized tag.
8761 On some targets, @value{GDBN} can access operating-system-specific information
8762 and display it to user, without interpretation. For remote targets,
8763 this functionality depends on the remote stub's support of the
8764 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8769 List the types of OS information available for the target. If the
8770 target does not return a list of possible types, this command will
8773 @kindex info os processes
8774 @item info os processes
8775 Display the list of processes on the target. For each process,
8776 @value{GDBN} prints the process identifier, the name of the user, and
8777 the command corresponding to the process.
8780 @node Memory Region Attributes
8781 @section Memory Region Attributes
8782 @cindex memory region attributes
8784 @dfn{Memory region attributes} allow you to describe special handling
8785 required by regions of your target's memory. @value{GDBN} uses
8786 attributes to determine whether to allow certain types of memory
8787 accesses; whether to use specific width accesses; and whether to cache
8788 target memory. By default the description of memory regions is
8789 fetched from the target (if the current target supports this), but the
8790 user can override the fetched regions.
8792 Defined memory regions can be individually enabled and disabled. When a
8793 memory region is disabled, @value{GDBN} uses the default attributes when
8794 accessing memory in that region. Similarly, if no memory regions have
8795 been defined, @value{GDBN} uses the default attributes when accessing
8798 When a memory region is defined, it is given a number to identify it;
8799 to enable, disable, or remove a memory region, you specify that number.
8803 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8804 Define a memory region bounded by @var{lower} and @var{upper} with
8805 attributes @var{attributes}@dots{}, and add it to the list of regions
8806 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8807 case: it is treated as the target's maximum memory address.
8808 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8811 Discard any user changes to the memory regions and use target-supplied
8812 regions, if available, or no regions if the target does not support.
8815 @item delete mem @var{nums}@dots{}
8816 Remove memory regions @var{nums}@dots{} from the list of regions
8817 monitored by @value{GDBN}.
8820 @item disable mem @var{nums}@dots{}
8821 Disable monitoring of memory regions @var{nums}@dots{}.
8822 A disabled memory region is not forgotten.
8823 It may be enabled again later.
8826 @item enable mem @var{nums}@dots{}
8827 Enable monitoring of memory regions @var{nums}@dots{}.
8831 Print a table of all defined memory regions, with the following columns
8835 @item Memory Region Number
8836 @item Enabled or Disabled.
8837 Enabled memory regions are marked with @samp{y}.
8838 Disabled memory regions are marked with @samp{n}.
8841 The address defining the inclusive lower bound of the memory region.
8844 The address defining the exclusive upper bound of the memory region.
8847 The list of attributes set for this memory region.
8852 @subsection Attributes
8854 @subsubsection Memory Access Mode
8855 The access mode attributes set whether @value{GDBN} may make read or
8856 write accesses to a memory region.
8858 While these attributes prevent @value{GDBN} from performing invalid
8859 memory accesses, they do nothing to prevent the target system, I/O DMA,
8860 etc.@: from accessing memory.
8864 Memory is read only.
8866 Memory is write only.
8868 Memory is read/write. This is the default.
8871 @subsubsection Memory Access Size
8872 The access size attribute tells @value{GDBN} to use specific sized
8873 accesses in the memory region. Often memory mapped device registers
8874 require specific sized accesses. If no access size attribute is
8875 specified, @value{GDBN} may use accesses of any size.
8879 Use 8 bit memory accesses.
8881 Use 16 bit memory accesses.
8883 Use 32 bit memory accesses.
8885 Use 64 bit memory accesses.
8888 @c @subsubsection Hardware/Software Breakpoints
8889 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8890 @c will use hardware or software breakpoints for the internal breakpoints
8891 @c used by the step, next, finish, until, etc. commands.
8895 @c Always use hardware breakpoints
8896 @c @item swbreak (default)
8899 @subsubsection Data Cache
8900 The data cache attributes set whether @value{GDBN} will cache target
8901 memory. While this generally improves performance by reducing debug
8902 protocol overhead, it can lead to incorrect results because @value{GDBN}
8903 does not know about volatile variables or memory mapped device
8908 Enable @value{GDBN} to cache target memory.
8910 Disable @value{GDBN} from caching target memory. This is the default.
8913 @subsection Memory Access Checking
8914 @value{GDBN} can be instructed to refuse accesses to memory that is
8915 not explicitly described. This can be useful if accessing such
8916 regions has undesired effects for a specific target, or to provide
8917 better error checking. The following commands control this behaviour.
8920 @kindex set mem inaccessible-by-default
8921 @item set mem inaccessible-by-default [on|off]
8922 If @code{on} is specified, make @value{GDBN} treat memory not
8923 explicitly described by the memory ranges as non-existent and refuse accesses
8924 to such memory. The checks are only performed if there's at least one
8925 memory range defined. If @code{off} is specified, make @value{GDBN}
8926 treat the memory not explicitly described by the memory ranges as RAM.
8927 The default value is @code{on}.
8928 @kindex show mem inaccessible-by-default
8929 @item show mem inaccessible-by-default
8930 Show the current handling of accesses to unknown memory.
8934 @c @subsubsection Memory Write Verification
8935 @c The memory write verification attributes set whether @value{GDBN}
8936 @c will re-reads data after each write to verify the write was successful.
8940 @c @item noverify (default)
8943 @node Dump/Restore Files
8944 @section Copy Between Memory and a File
8945 @cindex dump/restore files
8946 @cindex append data to a file
8947 @cindex dump data to a file
8948 @cindex restore data from a file
8950 You can use the commands @code{dump}, @code{append}, and
8951 @code{restore} to copy data between target memory and a file. The
8952 @code{dump} and @code{append} commands write data to a file, and the
8953 @code{restore} command reads data from a file back into the inferior's
8954 memory. Files may be in binary, Motorola S-record, Intel hex, or
8955 Tektronix Hex format; however, @value{GDBN} can only append to binary
8961 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8962 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8963 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8964 or the value of @var{expr}, to @var{filename} in the given format.
8966 The @var{format} parameter may be any one of:
8973 Motorola S-record format.
8975 Tektronix Hex format.
8978 @value{GDBN} uses the same definitions of these formats as the
8979 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8980 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8984 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8985 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8986 Append the contents of memory from @var{start_addr} to @var{end_addr},
8987 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8988 (@value{GDBN} can only append data to files in raw binary form.)
8991 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8992 Restore the contents of file @var{filename} into memory. The
8993 @code{restore} command can automatically recognize any known @sc{bfd}
8994 file format, except for raw binary. To restore a raw binary file you
8995 must specify the optional keyword @code{binary} after the filename.
8997 If @var{bias} is non-zero, its value will be added to the addresses
8998 contained in the file. Binary files always start at address zero, so
8999 they will be restored at address @var{bias}. Other bfd files have
9000 a built-in location; they will be restored at offset @var{bias}
9003 If @var{start} and/or @var{end} are non-zero, then only data between
9004 file offset @var{start} and file offset @var{end} will be restored.
9005 These offsets are relative to the addresses in the file, before
9006 the @var{bias} argument is applied.
9010 @node Core File Generation
9011 @section How to Produce a Core File from Your Program
9012 @cindex dump core from inferior
9014 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9015 image of a running process and its process status (register values
9016 etc.). Its primary use is post-mortem debugging of a program that
9017 crashed while it ran outside a debugger. A program that crashes
9018 automatically produces a core file, unless this feature is disabled by
9019 the user. @xref{Files}, for information on invoking @value{GDBN} in
9020 the post-mortem debugging mode.
9022 Occasionally, you may wish to produce a core file of the program you
9023 are debugging in order to preserve a snapshot of its state.
9024 @value{GDBN} has a special command for that.
9028 @kindex generate-core-file
9029 @item generate-core-file [@var{file}]
9030 @itemx gcore [@var{file}]
9031 Produce a core dump of the inferior process. The optional argument
9032 @var{file} specifies the file name where to put the core dump. If not
9033 specified, the file name defaults to @file{core.@var{pid}}, where
9034 @var{pid} is the inferior process ID.
9036 Note that this command is implemented only for some systems (as of
9037 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9040 @node Character Sets
9041 @section Character Sets
9042 @cindex character sets
9044 @cindex translating between character sets
9045 @cindex host character set
9046 @cindex target character set
9048 If the program you are debugging uses a different character set to
9049 represent characters and strings than the one @value{GDBN} uses itself,
9050 @value{GDBN} can automatically translate between the character sets for
9051 you. The character set @value{GDBN} uses we call the @dfn{host
9052 character set}; the one the inferior program uses we call the
9053 @dfn{target character set}.
9055 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9056 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9057 remote protocol (@pxref{Remote Debugging}) to debug a program
9058 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9059 then the host character set is Latin-1, and the target character set is
9060 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9061 target-charset EBCDIC-US}, then @value{GDBN} translates between
9062 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9063 character and string literals in expressions.
9065 @value{GDBN} has no way to automatically recognize which character set
9066 the inferior program uses; you must tell it, using the @code{set
9067 target-charset} command, described below.
9069 Here are the commands for controlling @value{GDBN}'s character set
9073 @item set target-charset @var{charset}
9074 @kindex set target-charset
9075 Set the current target character set to @var{charset}. To display the
9076 list of supported target character sets, type
9077 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9079 @item set host-charset @var{charset}
9080 @kindex set host-charset
9081 Set the current host character set to @var{charset}.
9083 By default, @value{GDBN} uses a host character set appropriate to the
9084 system it is running on; you can override that default using the
9085 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9086 automatically determine the appropriate host character set. In this
9087 case, @value{GDBN} uses @samp{UTF-8}.
9089 @value{GDBN} can only use certain character sets as its host character
9090 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9091 @value{GDBN} will list the host character sets it supports.
9093 @item set charset @var{charset}
9095 Set the current host and target character sets to @var{charset}. As
9096 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9097 @value{GDBN} will list the names of the character sets that can be used
9098 for both host and target.
9101 @kindex show charset
9102 Show the names of the current host and target character sets.
9104 @item show host-charset
9105 @kindex show host-charset
9106 Show the name of the current host character set.
9108 @item show target-charset
9109 @kindex show target-charset
9110 Show the name of the current target character set.
9112 @item set target-wide-charset @var{charset}
9113 @kindex set target-wide-charset
9114 Set the current target's wide character set to @var{charset}. This is
9115 the character set used by the target's @code{wchar_t} type. To
9116 display the list of supported wide character sets, type
9117 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9119 @item show target-wide-charset
9120 @kindex show target-wide-charset
9121 Show the name of the current target's wide character set.
9124 Here is an example of @value{GDBN}'s character set support in action.
9125 Assume that the following source code has been placed in the file
9126 @file{charset-test.c}:
9132 = @{72, 101, 108, 108, 111, 44, 32, 119,
9133 111, 114, 108, 100, 33, 10, 0@};
9134 char ibm1047_hello[]
9135 = @{200, 133, 147, 147, 150, 107, 64, 166,
9136 150, 153, 147, 132, 90, 37, 0@};
9140 printf ("Hello, world!\n");
9144 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9145 containing the string @samp{Hello, world!} followed by a newline,
9146 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9148 We compile the program, and invoke the debugger on it:
9151 $ gcc -g charset-test.c -o charset-test
9152 $ gdb -nw charset-test
9153 GNU gdb 2001-12-19-cvs
9154 Copyright 2001 Free Software Foundation, Inc.
9159 We can use the @code{show charset} command to see what character sets
9160 @value{GDBN} is currently using to interpret and display characters and
9164 (@value{GDBP}) show charset
9165 The current host and target character set is `ISO-8859-1'.
9169 For the sake of printing this manual, let's use @sc{ascii} as our
9170 initial character set:
9172 (@value{GDBP}) set charset ASCII
9173 (@value{GDBP}) show charset
9174 The current host and target character set is `ASCII'.
9178 Let's assume that @sc{ascii} is indeed the correct character set for our
9179 host system --- in other words, let's assume that if @value{GDBN} prints
9180 characters using the @sc{ascii} character set, our terminal will display
9181 them properly. Since our current target character set is also
9182 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9185 (@value{GDBP}) print ascii_hello
9186 $1 = 0x401698 "Hello, world!\n"
9187 (@value{GDBP}) print ascii_hello[0]
9192 @value{GDBN} uses the target character set for character and string
9193 literals you use in expressions:
9196 (@value{GDBP}) print '+'
9201 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9204 @value{GDBN} relies on the user to tell it which character set the
9205 target program uses. If we print @code{ibm1047_hello} while our target
9206 character set is still @sc{ascii}, we get jibberish:
9209 (@value{GDBP}) print ibm1047_hello
9210 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9211 (@value{GDBP}) print ibm1047_hello[0]
9216 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9217 @value{GDBN} tells us the character sets it supports:
9220 (@value{GDBP}) set target-charset
9221 ASCII EBCDIC-US IBM1047 ISO-8859-1
9222 (@value{GDBP}) set target-charset
9225 We can select @sc{ibm1047} as our target character set, and examine the
9226 program's strings again. Now the @sc{ascii} string is wrong, but
9227 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9228 target character set, @sc{ibm1047}, to the host character set,
9229 @sc{ascii}, and they display correctly:
9232 (@value{GDBP}) set target-charset IBM1047
9233 (@value{GDBP}) show charset
9234 The current host character set is `ASCII'.
9235 The current target character set is `IBM1047'.
9236 (@value{GDBP}) print ascii_hello
9237 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9238 (@value{GDBP}) print ascii_hello[0]
9240 (@value{GDBP}) print ibm1047_hello
9241 $8 = 0x4016a8 "Hello, world!\n"
9242 (@value{GDBP}) print ibm1047_hello[0]
9247 As above, @value{GDBN} uses the target character set for character and
9248 string literals you use in expressions:
9251 (@value{GDBP}) print '+'
9256 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9259 @node Caching Remote Data
9260 @section Caching Data of Remote Targets
9261 @cindex caching data of remote targets
9263 @value{GDBN} caches data exchanged between the debugger and a
9264 remote target (@pxref{Remote Debugging}). Such caching generally improves
9265 performance, because it reduces the overhead of the remote protocol by
9266 bundling memory reads and writes into large chunks. Unfortunately, simply
9267 caching everything would lead to incorrect results, since @value{GDBN}
9268 does not necessarily know anything about volatile values, memory-mapped I/O
9269 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9270 memory can be changed @emph{while} a gdb command is executing.
9271 Therefore, by default, @value{GDBN} only caches data
9272 known to be on the stack@footnote{In non-stop mode, it is moderately
9273 rare for a running thread to modify the stack of a stopped thread
9274 in a way that would interfere with a backtrace, and caching of
9275 stack reads provides a significant speed up of remote backtraces.}.
9276 Other regions of memory can be explicitly marked as
9277 cacheable; see @pxref{Memory Region Attributes}.
9280 @kindex set remotecache
9281 @item set remotecache on
9282 @itemx set remotecache off
9283 This option no longer does anything; it exists for compatibility
9286 @kindex show remotecache
9287 @item show remotecache
9288 Show the current state of the obsolete remotecache flag.
9290 @kindex set stack-cache
9291 @item set stack-cache on
9292 @itemx set stack-cache off
9293 Enable or disable caching of stack accesses. When @code{ON}, use
9294 caching. By default, this option is @code{ON}.
9296 @kindex show stack-cache
9297 @item show stack-cache
9298 Show the current state of data caching for memory accesses.
9301 @item info dcache @r{[}line@r{]}
9302 Print the information about the data cache performance. The
9303 information displayed includes the dcache width and depth, and for
9304 each cache line, its number, address, and how many times it was
9305 referenced. This command is useful for debugging the data cache
9308 If a line number is specified, the contents of that line will be
9312 @node Searching Memory
9313 @section Search Memory
9314 @cindex searching memory
9316 Memory can be searched for a particular sequence of bytes with the
9317 @code{find} command.
9321 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9322 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9323 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9324 etc. The search begins at address @var{start_addr} and continues for either
9325 @var{len} bytes or through to @var{end_addr} inclusive.
9328 @var{s} and @var{n} are optional parameters.
9329 They may be specified in either order, apart or together.
9332 @item @var{s}, search query size
9333 The size of each search query value.
9339 halfwords (two bytes)
9343 giant words (eight bytes)
9346 All values are interpreted in the current language.
9347 This means, for example, that if the current source language is C/C@t{++}
9348 then searching for the string ``hello'' includes the trailing '\0'.
9350 If the value size is not specified, it is taken from the
9351 value's type in the current language.
9352 This is useful when one wants to specify the search
9353 pattern as a mixture of types.
9354 Note that this means, for example, that in the case of C-like languages
9355 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9356 which is typically four bytes.
9358 @item @var{n}, maximum number of finds
9359 The maximum number of matches to print. The default is to print all finds.
9362 You can use strings as search values. Quote them with double-quotes
9364 The string value is copied into the search pattern byte by byte,
9365 regardless of the endianness of the target and the size specification.
9367 The address of each match found is printed as well as a count of the
9368 number of matches found.
9370 The address of the last value found is stored in convenience variable
9372 A count of the number of matches is stored in @samp{$numfound}.
9374 For example, if stopped at the @code{printf} in this function:
9380 static char hello[] = "hello-hello";
9381 static struct @{ char c; short s; int i; @}
9382 __attribute__ ((packed)) mixed
9383 = @{ 'c', 0x1234, 0x87654321 @};
9384 printf ("%s\n", hello);
9389 you get during debugging:
9392 (gdb) find &hello[0], +sizeof(hello), "hello"
9393 0x804956d <hello.1620+6>
9395 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9396 0x8049567 <hello.1620>
9397 0x804956d <hello.1620+6>
9399 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9400 0x8049567 <hello.1620>
9402 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9403 0x8049560 <mixed.1625>
9405 (gdb) print $numfound
9408 $2 = (void *) 0x8049560
9411 @node Optimized Code
9412 @chapter Debugging Optimized Code
9413 @cindex optimized code, debugging
9414 @cindex debugging optimized code
9416 Almost all compilers support optimization. With optimization
9417 disabled, the compiler generates assembly code that corresponds
9418 directly to your source code, in a simplistic way. As the compiler
9419 applies more powerful optimizations, the generated assembly code
9420 diverges from your original source code. With help from debugging
9421 information generated by the compiler, @value{GDBN} can map from
9422 the running program back to constructs from your original source.
9424 @value{GDBN} is more accurate with optimization disabled. If you
9425 can recompile without optimization, it is easier to follow the
9426 progress of your program during debugging. But, there are many cases
9427 where you may need to debug an optimized version.
9429 When you debug a program compiled with @samp{-g -O}, remember that the
9430 optimizer has rearranged your code; the debugger shows you what is
9431 really there. Do not be too surprised when the execution path does not
9432 exactly match your source file! An extreme example: if you define a
9433 variable, but never use it, @value{GDBN} never sees that
9434 variable---because the compiler optimizes it out of existence.
9436 Some things do not work as well with @samp{-g -O} as with just
9437 @samp{-g}, particularly on machines with instruction scheduling. If in
9438 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9439 please report it to us as a bug (including a test case!).
9440 @xref{Variables}, for more information about debugging optimized code.
9443 * Inline Functions:: How @value{GDBN} presents inlining
9446 @node Inline Functions
9447 @section Inline Functions
9448 @cindex inline functions, debugging
9450 @dfn{Inlining} is an optimization that inserts a copy of the function
9451 body directly at each call site, instead of jumping to a shared
9452 routine. @value{GDBN} displays inlined functions just like
9453 non-inlined functions. They appear in backtraces. You can view their
9454 arguments and local variables, step into them with @code{step}, skip
9455 them with @code{next}, and escape from them with @code{finish}.
9456 You can check whether a function was inlined by using the
9457 @code{info frame} command.
9459 For @value{GDBN} to support inlined functions, the compiler must
9460 record information about inlining in the debug information ---
9461 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9462 other compilers do also. @value{GDBN} only supports inlined functions
9463 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9464 do not emit two required attributes (@samp{DW_AT_call_file} and
9465 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9466 function calls with earlier versions of @value{NGCC}. It instead
9467 displays the arguments and local variables of inlined functions as
9468 local variables in the caller.
9470 The body of an inlined function is directly included at its call site;
9471 unlike a non-inlined function, there are no instructions devoted to
9472 the call. @value{GDBN} still pretends that the call site and the
9473 start of the inlined function are different instructions. Stepping to
9474 the call site shows the call site, and then stepping again shows
9475 the first line of the inlined function, even though no additional
9476 instructions are executed.
9478 This makes source-level debugging much clearer; you can see both the
9479 context of the call and then the effect of the call. Only stepping by
9480 a single instruction using @code{stepi} or @code{nexti} does not do
9481 this; single instruction steps always show the inlined body.
9483 There are some ways that @value{GDBN} does not pretend that inlined
9484 function calls are the same as normal calls:
9488 You cannot set breakpoints on inlined functions. @value{GDBN}
9489 either reports that there is no symbol with that name, or else sets the
9490 breakpoint only on non-inlined copies of the function. This limitation
9491 will be removed in a future version of @value{GDBN}; until then,
9492 set a breakpoint by line number on the first line of the inlined
9496 Setting breakpoints at the call site of an inlined function may not
9497 work, because the call site does not contain any code. @value{GDBN}
9498 may incorrectly move the breakpoint to the next line of the enclosing
9499 function, after the call. This limitation will be removed in a future
9500 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9501 or inside the inlined function instead.
9504 @value{GDBN} cannot locate the return value of inlined calls after
9505 using the @code{finish} command. This is a limitation of compiler-generated
9506 debugging information; after @code{finish}, you can step to the next line
9507 and print a variable where your program stored the return value.
9513 @chapter C Preprocessor Macros
9515 Some languages, such as C and C@t{++}, provide a way to define and invoke
9516 ``preprocessor macros'' which expand into strings of tokens.
9517 @value{GDBN} can evaluate expressions containing macro invocations, show
9518 the result of macro expansion, and show a macro's definition, including
9519 where it was defined.
9521 You may need to compile your program specially to provide @value{GDBN}
9522 with information about preprocessor macros. Most compilers do not
9523 include macros in their debugging information, even when you compile
9524 with the @option{-g} flag. @xref{Compilation}.
9526 A program may define a macro at one point, remove that definition later,
9527 and then provide a different definition after that. Thus, at different
9528 points in the program, a macro may have different definitions, or have
9529 no definition at all. If there is a current stack frame, @value{GDBN}
9530 uses the macros in scope at that frame's source code line. Otherwise,
9531 @value{GDBN} uses the macros in scope at the current listing location;
9534 Whenever @value{GDBN} evaluates an expression, it always expands any
9535 macro invocations present in the expression. @value{GDBN} also provides
9536 the following commands for working with macros explicitly.
9540 @kindex macro expand
9541 @cindex macro expansion, showing the results of preprocessor
9542 @cindex preprocessor macro expansion, showing the results of
9543 @cindex expanding preprocessor macros
9544 @item macro expand @var{expression}
9545 @itemx macro exp @var{expression}
9546 Show the results of expanding all preprocessor macro invocations in
9547 @var{expression}. Since @value{GDBN} simply expands macros, but does
9548 not parse the result, @var{expression} need not be a valid expression;
9549 it can be any string of tokens.
9552 @item macro expand-once @var{expression}
9553 @itemx macro exp1 @var{expression}
9554 @cindex expand macro once
9555 @i{(This command is not yet implemented.)} Show the results of
9556 expanding those preprocessor macro invocations that appear explicitly in
9557 @var{expression}. Macro invocations appearing in that expansion are
9558 left unchanged. This command allows you to see the effect of a
9559 particular macro more clearly, without being confused by further
9560 expansions. Since @value{GDBN} simply expands macros, but does not
9561 parse the result, @var{expression} need not be a valid expression; it
9562 can be any string of tokens.
9565 @cindex macro definition, showing
9566 @cindex definition, showing a macro's
9567 @item info macro @var{macro}
9568 Show the definition of the macro named @var{macro}, and describe the
9569 source location or compiler command-line where that definition was established.
9571 @kindex macro define
9572 @cindex user-defined macros
9573 @cindex defining macros interactively
9574 @cindex macros, user-defined
9575 @item macro define @var{macro} @var{replacement-list}
9576 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9577 Introduce a definition for a preprocessor macro named @var{macro},
9578 invocations of which are replaced by the tokens given in
9579 @var{replacement-list}. The first form of this command defines an
9580 ``object-like'' macro, which takes no arguments; the second form
9581 defines a ``function-like'' macro, which takes the arguments given in
9584 A definition introduced by this command is in scope in every
9585 expression evaluated in @value{GDBN}, until it is removed with the
9586 @code{macro undef} command, described below. The definition overrides
9587 all definitions for @var{macro} present in the program being debugged,
9588 as well as any previous user-supplied definition.
9591 @item macro undef @var{macro}
9592 Remove any user-supplied definition for the macro named @var{macro}.
9593 This command only affects definitions provided with the @code{macro
9594 define} command, described above; it cannot remove definitions present
9595 in the program being debugged.
9599 List all the macros defined using the @code{macro define} command.
9602 @cindex macros, example of debugging with
9603 Here is a transcript showing the above commands in action. First, we
9604 show our source files:
9612 #define ADD(x) (M + x)
9617 printf ("Hello, world!\n");
9619 printf ("We're so creative.\n");
9621 printf ("Goodbye, world!\n");
9628 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9629 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9630 compiler includes information about preprocessor macros in the debugging
9634 $ gcc -gdwarf-2 -g3 sample.c -o sample
9638 Now, we start @value{GDBN} on our sample program:
9642 GNU gdb 2002-05-06-cvs
9643 Copyright 2002 Free Software Foundation, Inc.
9644 GDB is free software, @dots{}
9648 We can expand macros and examine their definitions, even when the
9649 program is not running. @value{GDBN} uses the current listing position
9650 to decide which macro definitions are in scope:
9653 (@value{GDBP}) list main
9656 5 #define ADD(x) (M + x)
9661 10 printf ("Hello, world!\n");
9663 12 printf ("We're so creative.\n");
9664 (@value{GDBP}) info macro ADD
9665 Defined at /home/jimb/gdb/macros/play/sample.c:5
9666 #define ADD(x) (M + x)
9667 (@value{GDBP}) info macro Q
9668 Defined at /home/jimb/gdb/macros/play/sample.h:1
9669 included at /home/jimb/gdb/macros/play/sample.c:2
9671 (@value{GDBP}) macro expand ADD(1)
9672 expands to: (42 + 1)
9673 (@value{GDBP}) macro expand-once ADD(1)
9674 expands to: once (M + 1)
9678 In the example above, note that @code{macro expand-once} expands only
9679 the macro invocation explicit in the original text --- the invocation of
9680 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9681 which was introduced by @code{ADD}.
9683 Once the program is running, @value{GDBN} uses the macro definitions in
9684 force at the source line of the current stack frame:
9687 (@value{GDBP}) break main
9688 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9690 Starting program: /home/jimb/gdb/macros/play/sample
9692 Breakpoint 1, main () at sample.c:10
9693 10 printf ("Hello, world!\n");
9697 At line 10, the definition of the macro @code{N} at line 9 is in force:
9700 (@value{GDBP}) info macro N
9701 Defined at /home/jimb/gdb/macros/play/sample.c:9
9703 (@value{GDBP}) macro expand N Q M
9705 (@value{GDBP}) print N Q M
9710 As we step over directives that remove @code{N}'s definition, and then
9711 give it a new definition, @value{GDBN} finds the definition (or lack
9712 thereof) in force at each point:
9717 12 printf ("We're so creative.\n");
9718 (@value{GDBP}) info macro N
9719 The symbol `N' has no definition as a C/C++ preprocessor macro
9720 at /home/jimb/gdb/macros/play/sample.c:12
9723 14 printf ("Goodbye, world!\n");
9724 (@value{GDBP}) info macro N
9725 Defined at /home/jimb/gdb/macros/play/sample.c:13
9727 (@value{GDBP}) macro expand N Q M
9728 expands to: 1729 < 42
9729 (@value{GDBP}) print N Q M
9734 In addition to source files, macros can be defined on the compilation command
9735 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9736 such a way, @value{GDBN} displays the location of their definition as line zero
9737 of the source file submitted to the compiler.
9740 (@value{GDBP}) info macro __STDC__
9741 Defined at /home/jimb/gdb/macros/play/sample.c:0
9748 @chapter Tracepoints
9749 @c This chapter is based on the documentation written by Michael
9750 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9753 In some applications, it is not feasible for the debugger to interrupt
9754 the program's execution long enough for the developer to learn
9755 anything helpful about its behavior. If the program's correctness
9756 depends on its real-time behavior, delays introduced by a debugger
9757 might cause the program to change its behavior drastically, or perhaps
9758 fail, even when the code itself is correct. It is useful to be able
9759 to observe the program's behavior without interrupting it.
9761 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9762 specify locations in the program, called @dfn{tracepoints}, and
9763 arbitrary expressions to evaluate when those tracepoints are reached.
9764 Later, using the @code{tfind} command, you can examine the values
9765 those expressions had when the program hit the tracepoints. The
9766 expressions may also denote objects in memory---structures or arrays,
9767 for example---whose values @value{GDBN} should record; while visiting
9768 a particular tracepoint, you may inspect those objects as if they were
9769 in memory at that moment. However, because @value{GDBN} records these
9770 values without interacting with you, it can do so quickly and
9771 unobtrusively, hopefully not disturbing the program's behavior.
9773 The tracepoint facility is currently available only for remote
9774 targets. @xref{Targets}. In addition, your remote target must know
9775 how to collect trace data. This functionality is implemented in the
9776 remote stub; however, none of the stubs distributed with @value{GDBN}
9777 support tracepoints as of this writing. The format of the remote
9778 packets used to implement tracepoints are described in @ref{Tracepoint
9781 It is also possible to get trace data from a file, in a manner reminiscent
9782 of corefiles; you specify the filename, and use @code{tfind} to search
9783 through the file. @xref{Trace Files}, for more details.
9785 This chapter describes the tracepoint commands and features.
9789 * Analyze Collected Data::
9790 * Tracepoint Variables::
9794 @node Set Tracepoints
9795 @section Commands to Set Tracepoints
9797 Before running such a @dfn{trace experiment}, an arbitrary number of
9798 tracepoints can be set. A tracepoint is actually a special type of
9799 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9800 standard breakpoint commands. For instance, as with breakpoints,
9801 tracepoint numbers are successive integers starting from one, and many
9802 of the commands associated with tracepoints take the tracepoint number
9803 as their argument, to identify which tracepoint to work on.
9805 For each tracepoint, you can specify, in advance, some arbitrary set
9806 of data that you want the target to collect in the trace buffer when
9807 it hits that tracepoint. The collected data can include registers,
9808 local variables, or global data. Later, you can use @value{GDBN}
9809 commands to examine the values these data had at the time the
9812 Tracepoints do not support every breakpoint feature. Ignore counts on
9813 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9814 commands when they are hit. Tracepoints may not be thread-specific
9817 @cindex fast tracepoints
9818 Some targets may support @dfn{fast tracepoints}, which are inserted in
9819 a different way (such as with a jump instead of a trap), that is
9820 faster but possibly restricted in where they may be installed.
9822 @cindex static tracepoints
9823 @cindex markers, static tracepoints
9824 @cindex probing markers, static tracepoints
9825 Regular and fast tracepoints are dynamic tracing facilities, meaning
9826 that they can be used to insert tracepoints at (almost) any location
9827 in the target. Some targets may also support controlling @dfn{static
9828 tracepoints} from @value{GDBN}. With static tracing, a set of
9829 instrumentation points, also known as @dfn{markers}, are embedded in
9830 the target program, and can be activated or deactivated by name or
9831 address. These are usually placed at locations which facilitate
9832 investigating what the target is actually doing. @value{GDBN}'s
9833 support for static tracing includes being able to list instrumentation
9834 points, and attach them with @value{GDBN} defined high level
9835 tracepoints that expose the whole range of convenience of
9836 @value{GDBN}'s tracepoints support. Namely, support for collecting
9837 registers values and values of global or local (to the instrumentation
9838 point) variables; tracepoint conditions and trace state variables.
9839 The act of installing a @value{GDBN} static tracepoint on an
9840 instrumentation point, or marker, is referred to as @dfn{probing} a
9841 static tracepoint marker.
9843 @code{gdbserver} supports tracepoints on some target systems.
9844 @xref{Server,,Tracepoints support in @code{gdbserver}}.
9846 This section describes commands to set tracepoints and associated
9847 conditions and actions.
9850 * Create and Delete Tracepoints::
9851 * Enable and Disable Tracepoints::
9852 * Tracepoint Passcounts::
9853 * Tracepoint Conditions::
9854 * Trace State Variables::
9855 * Tracepoint Actions::
9856 * Listing Tracepoints::
9857 * Listing Static Tracepoint Markers::
9858 * Starting and Stopping Trace Experiments::
9859 * Tracepoint Restrictions::
9862 @node Create and Delete Tracepoints
9863 @subsection Create and Delete Tracepoints
9866 @cindex set tracepoint
9868 @item trace @var{location}
9869 The @code{trace} command is very similar to the @code{break} command.
9870 Its argument @var{location} can be a source line, a function name, or
9871 an address in the target program. @xref{Specify Location}. The
9872 @code{trace} command defines a tracepoint, which is a point in the
9873 target program where the debugger will briefly stop, collect some
9874 data, and then allow the program to continue. Setting a tracepoint or
9875 changing its actions doesn't take effect until the next @code{tstart}
9876 command, and once a trace experiment is running, further changes will
9877 not have any effect until the next trace experiment starts.
9879 Here are some examples of using the @code{trace} command:
9882 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9884 (@value{GDBP}) @b{trace +2} // 2 lines forward
9886 (@value{GDBP}) @b{trace my_function} // first source line of function
9888 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9890 (@value{GDBP}) @b{trace *0x2117c4} // an address
9894 You can abbreviate @code{trace} as @code{tr}.
9896 @item trace @var{location} if @var{cond}
9897 Set a tracepoint with condition @var{cond}; evaluate the expression
9898 @var{cond} each time the tracepoint is reached, and collect data only
9899 if the value is nonzero---that is, if @var{cond} evaluates as true.
9900 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9901 information on tracepoint conditions.
9903 @item ftrace @var{location} [ if @var{cond} ]
9904 @cindex set fast tracepoint
9905 @cindex fast tracepoints, setting
9907 The @code{ftrace} command sets a fast tracepoint. For targets that
9908 support them, fast tracepoints will use a more efficient but possibly
9909 less general technique to trigger data collection, such as a jump
9910 instruction instead of a trap, or some sort of hardware support. It
9911 may not be possible to create a fast tracepoint at the desired
9912 location, in which case the command will exit with an explanatory
9915 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9918 @item strace @var{location} [ if @var{cond} ]
9919 @cindex set static tracepoint
9920 @cindex static tracepoints, setting
9921 @cindex probe static tracepoint marker
9923 The @code{strace} command sets a static tracepoint. For targets that
9924 support it, setting a static tracepoint probes a static
9925 instrumentation point, or marker, found at @var{location}. It may not
9926 be possible to set a static tracepoint at the desired location, in
9927 which case the command will exit with an explanatory message.
9929 @value{GDBN} handles arguments to @code{strace} exactly as for
9930 @code{trace}, with the addition that the user can also specify
9931 @code{-m @var{marker}} as @var{location}. This probes the marker
9932 identified by the @var{marker} string identifier. This identifier
9933 depends on the static tracepoint backend library your program is
9934 using. You can find all the marker identifiers in the @samp{ID} field
9935 of the @code{info static-tracepoint-markers} command output.
9936 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
9937 Markers}. For example, in the following small program using the UST
9943 trace_mark(ust, bar33, "str %s", "FOOBAZ");
9948 the marker id is composed of joining the first two arguments to the
9949 @code{trace_mark} call with a slash, which translates to:
9952 (@value{GDBP}) info static-tracepoint-markers
9953 Cnt Enb ID Address What
9954 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
9960 so you may probe the marker above with:
9963 (@value{GDBP}) strace -m ust/bar33
9966 Static tracepoints accept an extra collect action --- @code{collect
9967 $_sdata}. This collects arbitrary user data passed in the probe point
9968 call to the tracing library. In the UST example above, you'll see
9969 that the third argument to @code{trace_mark} is a printf-like format
9970 string. The user data is then the result of running that formating
9971 string against the following arguments. Note that @code{info
9972 static-tracepoint-markers} command output lists that format string in
9973 the @samp{Data:} field.
9975 You can inspect this data when analyzing the trace buffer, by printing
9976 the $_sdata variable like any other variable available to
9977 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
9980 @cindex last tracepoint number
9981 @cindex recent tracepoint number
9982 @cindex tracepoint number
9983 The convenience variable @code{$tpnum} records the tracepoint number
9984 of the most recently set tracepoint.
9986 @kindex delete tracepoint
9987 @cindex tracepoint deletion
9988 @item delete tracepoint @r{[}@var{num}@r{]}
9989 Permanently delete one or more tracepoints. With no argument, the
9990 default is to delete all tracepoints. Note that the regular
9991 @code{delete} command can remove tracepoints also.
9996 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9998 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10002 You can abbreviate this command as @code{del tr}.
10005 @node Enable and Disable Tracepoints
10006 @subsection Enable and Disable Tracepoints
10008 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10011 @kindex disable tracepoint
10012 @item disable tracepoint @r{[}@var{num}@r{]}
10013 Disable tracepoint @var{num}, or all tracepoints if no argument
10014 @var{num} is given. A disabled tracepoint will have no effect during
10015 the next trace experiment, but it is not forgotten. You can re-enable
10016 a disabled tracepoint using the @code{enable tracepoint} command.
10018 @kindex enable tracepoint
10019 @item enable tracepoint @r{[}@var{num}@r{]}
10020 Enable tracepoint @var{num}, or all tracepoints. The enabled
10021 tracepoints will become effective the next time a trace experiment is
10025 @node Tracepoint Passcounts
10026 @subsection Tracepoint Passcounts
10030 @cindex tracepoint pass count
10031 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10032 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10033 automatically stop a trace experiment. If a tracepoint's passcount is
10034 @var{n}, then the trace experiment will be automatically stopped on
10035 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10036 @var{num} is not specified, the @code{passcount} command sets the
10037 passcount of the most recently defined tracepoint. If no passcount is
10038 given, the trace experiment will run until stopped explicitly by the
10044 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10045 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10047 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10048 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10049 (@value{GDBP}) @b{trace foo}
10050 (@value{GDBP}) @b{pass 3}
10051 (@value{GDBP}) @b{trace bar}
10052 (@value{GDBP}) @b{pass 2}
10053 (@value{GDBP}) @b{trace baz}
10054 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10055 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10056 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10057 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10061 @node Tracepoint Conditions
10062 @subsection Tracepoint Conditions
10063 @cindex conditional tracepoints
10064 @cindex tracepoint conditions
10066 The simplest sort of tracepoint collects data every time your program
10067 reaches a specified place. You can also specify a @dfn{condition} for
10068 a tracepoint. A condition is just a Boolean expression in your
10069 programming language (@pxref{Expressions, ,Expressions}). A
10070 tracepoint with a condition evaluates the expression each time your
10071 program reaches it, and data collection happens only if the condition
10074 Tracepoint conditions can be specified when a tracepoint is set, by
10075 using @samp{if} in the arguments to the @code{trace} command.
10076 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10077 also be set or changed at any time with the @code{condition} command,
10078 just as with breakpoints.
10080 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10081 the conditional expression itself. Instead, @value{GDBN} encodes the
10082 expression into an agent expression (@pxref{Agent Expressions})
10083 suitable for execution on the target, independently of @value{GDBN}.
10084 Global variables become raw memory locations, locals become stack
10085 accesses, and so forth.
10087 For instance, suppose you have a function that is usually called
10088 frequently, but should not be called after an error has occurred. You
10089 could use the following tracepoint command to collect data about calls
10090 of that function that happen while the error code is propagating
10091 through the program; an unconditional tracepoint could end up
10092 collecting thousands of useless trace frames that you would have to
10096 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10099 @node Trace State Variables
10100 @subsection Trace State Variables
10101 @cindex trace state variables
10103 A @dfn{trace state variable} is a special type of variable that is
10104 created and managed by target-side code. The syntax is the same as
10105 that for GDB's convenience variables (a string prefixed with ``$''),
10106 but they are stored on the target. They must be created explicitly,
10107 using a @code{tvariable} command. They are always 64-bit signed
10110 Trace state variables are remembered by @value{GDBN}, and downloaded
10111 to the target along with tracepoint information when the trace
10112 experiment starts. There are no intrinsic limits on the number of
10113 trace state variables, beyond memory limitations of the target.
10115 @cindex convenience variables, and trace state variables
10116 Although trace state variables are managed by the target, you can use
10117 them in print commands and expressions as if they were convenience
10118 variables; @value{GDBN} will get the current value from the target
10119 while the trace experiment is running. Trace state variables share
10120 the same namespace as other ``$'' variables, which means that you
10121 cannot have trace state variables with names like @code{$23} or
10122 @code{$pc}, nor can you have a trace state variable and a convenience
10123 variable with the same name.
10127 @item tvariable $@var{name} [ = @var{expression} ]
10129 The @code{tvariable} command creates a new trace state variable named
10130 @code{$@var{name}}, and optionally gives it an initial value of
10131 @var{expression}. @var{expression} is evaluated when this command is
10132 entered; the result will be converted to an integer if possible,
10133 otherwise @value{GDBN} will report an error. A subsequent
10134 @code{tvariable} command specifying the same name does not create a
10135 variable, but instead assigns the supplied initial value to the
10136 existing variable of that name, overwriting any previous initial
10137 value. The default initial value is 0.
10139 @item info tvariables
10140 @kindex info tvariables
10141 List all the trace state variables along with their initial values.
10142 Their current values may also be displayed, if the trace experiment is
10145 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10146 @kindex delete tvariable
10147 Delete the given trace state variables, or all of them if no arguments
10152 @node Tracepoint Actions
10153 @subsection Tracepoint Action Lists
10157 @cindex tracepoint actions
10158 @item actions @r{[}@var{num}@r{]}
10159 This command will prompt for a list of actions to be taken when the
10160 tracepoint is hit. If the tracepoint number @var{num} is not
10161 specified, this command sets the actions for the one that was most
10162 recently defined (so that you can define a tracepoint and then say
10163 @code{actions} without bothering about its number). You specify the
10164 actions themselves on the following lines, one action at a time, and
10165 terminate the actions list with a line containing just @code{end}. So
10166 far, the only defined actions are @code{collect}, @code{teval}, and
10167 @code{while-stepping}.
10169 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10170 Commands, ,Breakpoint Command Lists}), except that only the defined
10171 actions are allowed; any other @value{GDBN} command is rejected.
10173 @cindex remove actions from a tracepoint
10174 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10175 and follow it immediately with @samp{end}.
10178 (@value{GDBP}) @b{collect @var{data}} // collect some data
10180 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10182 (@value{GDBP}) @b{end} // signals the end of actions.
10185 In the following example, the action list begins with @code{collect}
10186 commands indicating the things to be collected when the tracepoint is
10187 hit. Then, in order to single-step and collect additional data
10188 following the tracepoint, a @code{while-stepping} command is used,
10189 followed by the list of things to be collected after each step in a
10190 sequence of single steps. The @code{while-stepping} command is
10191 terminated by its own separate @code{end} command. Lastly, the action
10192 list is terminated by an @code{end} command.
10195 (@value{GDBP}) @b{trace foo}
10196 (@value{GDBP}) @b{actions}
10197 Enter actions for tracepoint 1, one per line:
10200 > while-stepping 12
10201 > collect $pc, arr[i]
10206 @kindex collect @r{(tracepoints)}
10207 @item collect @var{expr1}, @var{expr2}, @dots{}
10208 Collect values of the given expressions when the tracepoint is hit.
10209 This command accepts a comma-separated list of any valid expressions.
10210 In addition to global, static, or local variables, the following
10211 special arguments are supported:
10215 Collect all registers.
10218 Collect all function arguments.
10221 Collect all local variables.
10224 @vindex $_sdata@r{, collect}
10225 Collect static tracepoint marker specific data. Only available for
10226 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10227 Lists}. On the UST static tracepoints library backend, an
10228 instrumentation point resembles a @code{printf} function call. The
10229 tracing library is able to collect user specified data formatted to a
10230 character string using the format provided by the programmer that
10231 instrumented the program. Other backends have similar mechanisms.
10232 Here's an example of a UST marker call:
10235 const char master_name[] = "$your_name";
10236 trace_mark(channel1, marker1, "hello %s", master_name)
10239 In this case, collecting @code{$_sdata} collects the string
10240 @samp{hello $yourname}. When analyzing the trace buffer, you can
10241 inspect @samp{$_sdata} like any other variable available to
10245 You can give several consecutive @code{collect} commands, each one
10246 with a single argument, or one @code{collect} command with several
10247 arguments separated by commas; the effect is the same.
10249 The command @code{info scope} (@pxref{Symbols, info scope}) is
10250 particularly useful for figuring out what data to collect.
10252 @kindex teval @r{(tracepoints)}
10253 @item teval @var{expr1}, @var{expr2}, @dots{}
10254 Evaluate the given expressions when the tracepoint is hit. This
10255 command accepts a comma-separated list of expressions. The results
10256 are discarded, so this is mainly useful for assigning values to trace
10257 state variables (@pxref{Trace State Variables}) without adding those
10258 values to the trace buffer, as would be the case if the @code{collect}
10261 @kindex while-stepping @r{(tracepoints)}
10262 @item while-stepping @var{n}
10263 Perform @var{n} single-step instruction traces after the tracepoint,
10264 collecting new data after each step. The @code{while-stepping}
10265 command is followed by the list of what to collect while stepping
10266 (followed by its own @code{end} command):
10269 > while-stepping 12
10270 > collect $regs, myglobal
10276 Note that @code{$pc} is not automatically collected by
10277 @code{while-stepping}; you need to explicitly collect that register if
10278 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10281 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10282 @kindex set default-collect
10283 @cindex default collection action
10284 This variable is a list of expressions to collect at each tracepoint
10285 hit. It is effectively an additional @code{collect} action prepended
10286 to every tracepoint action list. The expressions are parsed
10287 individually for each tracepoint, so for instance a variable named
10288 @code{xyz} may be interpreted as a global for one tracepoint, and a
10289 local for another, as appropriate to the tracepoint's location.
10291 @item show default-collect
10292 @kindex show default-collect
10293 Show the list of expressions that are collected by default at each
10298 @node Listing Tracepoints
10299 @subsection Listing Tracepoints
10302 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
10303 @kindex info tp @r{[}@var{n}@dots{}@r{]}
10304 @cindex information about tracepoints
10305 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
10306 Display information about the tracepoint @var{num}. If you don't
10307 specify a tracepoint number, displays information about all the
10308 tracepoints defined so far. The format is similar to that used for
10309 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10310 command, simply restricting itself to tracepoints.
10312 A tracepoint's listing may include additional information specific to
10317 its passcount as given by the @code{passcount @var{n}} command
10321 (@value{GDBP}) @b{info trace}
10322 Num Type Disp Enb Address What
10323 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10325 collect globfoo, $regs
10334 This command can be abbreviated @code{info tp}.
10337 @node Listing Static Tracepoint Markers
10338 @subsection Listing Static Tracepoint Markers
10341 @kindex info static-tracepoint-markers
10342 @cindex information about static tracepoint markers
10343 @item info static-tracepoint-markers
10344 Display information about all static tracepoint markers defined in the
10347 For each marker, the following columns are printed:
10351 An incrementing counter, output to help readability. This is not a
10354 The marker ID, as reported by the target.
10355 @item Enabled or Disabled
10356 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10357 that are not enabled.
10359 Where the marker is in your program, as a memory address.
10361 Where the marker is in the source for your program, as a file and line
10362 number. If the debug information included in the program does not
10363 allow @value{GDBN} to locate the source of the marker, this column
10364 will be left blank.
10368 In addition, the following information may be printed for each marker:
10372 User data passed to the tracing library by the marker call. In the
10373 UST backend, this is the format string passed as argument to the
10375 @item Static tracepoints probing the marker
10376 The list of static tracepoints attached to the marker.
10380 (@value{GDBP}) info static-tracepoint-markers
10381 Cnt ID Enb Address What
10382 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10383 Data: number1 %d number2 %d
10384 Probed by static tracepoints: #2
10385 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10391 @node Starting and Stopping Trace Experiments
10392 @subsection Starting and Stopping Trace Experiments
10396 @cindex start a new trace experiment
10397 @cindex collected data discarded
10399 This command takes no arguments. It starts the trace experiment, and
10400 begins collecting data. This has the side effect of discarding all
10401 the data collected in the trace buffer during the previous trace
10405 @cindex stop a running trace experiment
10407 This command takes no arguments. It ends the trace experiment, and
10408 stops collecting data.
10410 @strong{Note}: a trace experiment and data collection may stop
10411 automatically if any tracepoint's passcount is reached
10412 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10415 @cindex status of trace data collection
10416 @cindex trace experiment, status of
10418 This command displays the status of the current trace data
10422 Here is an example of the commands we described so far:
10425 (@value{GDBP}) @b{trace gdb_c_test}
10426 (@value{GDBP}) @b{actions}
10427 Enter actions for tracepoint #1, one per line.
10428 > collect $regs,$locals,$args
10429 > while-stepping 11
10433 (@value{GDBP}) @b{tstart}
10434 [time passes @dots{}]
10435 (@value{GDBP}) @b{tstop}
10438 @cindex disconnected tracing
10439 You can choose to continue running the trace experiment even if
10440 @value{GDBN} disconnects from the target, voluntarily or
10441 involuntarily. For commands such as @code{detach}, the debugger will
10442 ask what you want to do with the trace. But for unexpected
10443 terminations (@value{GDBN} crash, network outage), it would be
10444 unfortunate to lose hard-won trace data, so the variable
10445 @code{disconnected-tracing} lets you decide whether the trace should
10446 continue running without @value{GDBN}.
10449 @item set disconnected-tracing on
10450 @itemx set disconnected-tracing off
10451 @kindex set disconnected-tracing
10452 Choose whether a tracing run should continue to run if @value{GDBN}
10453 has disconnected from the target. Note that @code{detach} or
10454 @code{quit} will ask you directly what to do about a running trace no
10455 matter what this variable's setting, so the variable is mainly useful
10456 for handling unexpected situations, such as loss of the network.
10458 @item show disconnected-tracing
10459 @kindex show disconnected-tracing
10460 Show the current choice for disconnected tracing.
10464 When you reconnect to the target, the trace experiment may or may not
10465 still be running; it might have filled the trace buffer in the
10466 meantime, or stopped for one of the other reasons. If it is running,
10467 it will continue after reconnection.
10469 Upon reconnection, the target will upload information about the
10470 tracepoints in effect. @value{GDBN} will then compare that
10471 information to the set of tracepoints currently defined, and attempt
10472 to match them up, allowing for the possibility that the numbers may
10473 have changed due to creation and deletion in the meantime. If one of
10474 the target's tracepoints does not match any in @value{GDBN}, the
10475 debugger will create a new tracepoint, so that you have a number with
10476 which to specify that tracepoint. This matching-up process is
10477 necessarily heuristic, and it may result in useless tracepoints being
10478 created; you may simply delete them if they are of no use.
10480 @cindex circular trace buffer
10481 If your target agent supports a @dfn{circular trace buffer}, then you
10482 can run a trace experiment indefinitely without filling the trace
10483 buffer; when space runs out, the agent deletes already-collected trace
10484 frames, oldest first, until there is enough room to continue
10485 collecting. This is especially useful if your tracepoints are being
10486 hit too often, and your trace gets terminated prematurely because the
10487 buffer is full. To ask for a circular trace buffer, simply set
10488 @samp{circular-trace-buffer} to on. You can set this at any time,
10489 including during tracing; if the agent can do it, it will change
10490 buffer handling on the fly, otherwise it will not take effect until
10494 @item set circular-trace-buffer on
10495 @itemx set circular-trace-buffer off
10496 @kindex set circular-trace-buffer
10497 Choose whether a tracing run should use a linear or circular buffer
10498 for trace data. A linear buffer will not lose any trace data, but may
10499 fill up prematurely, while a circular buffer will discard old trace
10500 data, but it will have always room for the latest tracepoint hits.
10502 @item show circular-trace-buffer
10503 @kindex show circular-trace-buffer
10504 Show the current choice for the trace buffer. Note that this may not
10505 match the agent's current buffer handling, nor is it guaranteed to
10506 match the setting that might have been in effect during a past run,
10507 for instance if you are looking at frames from a trace file.
10511 @node Tracepoint Restrictions
10512 @subsection Tracepoint Restrictions
10514 @cindex tracepoint restrictions
10515 There are a number of restrictions on the use of tracepoints. As
10516 described above, tracepoint data gathering occurs on the target
10517 without interaction from @value{GDBN}. Thus the full capabilities of
10518 the debugger are not available during data gathering, and then at data
10519 examination time, you will be limited by only having what was
10520 collected. The following items describe some common problems, but it
10521 is not exhaustive, and you may run into additional difficulties not
10527 Tracepoint expressions are intended to gather objects (lvalues). Thus
10528 the full flexibility of GDB's expression evaluator is not available.
10529 You cannot call functions, cast objects to aggregate types, access
10530 convenience variables or modify values (except by assignment to trace
10531 state variables). Some language features may implicitly call
10532 functions (for instance Objective-C fields with accessors), and therefore
10533 cannot be collected either.
10536 Collection of local variables, either individually or in bulk with
10537 @code{$locals} or @code{$args}, during @code{while-stepping} may
10538 behave erratically. The stepping action may enter a new scope (for
10539 instance by stepping into a function), or the location of the variable
10540 may change (for instance it is loaded into a register). The
10541 tracepoint data recorded uses the location information for the
10542 variables that is correct for the tracepoint location. When the
10543 tracepoint is created, it is not possible, in general, to determine
10544 where the steps of a @code{while-stepping} sequence will advance the
10545 program---particularly if a conditional branch is stepped.
10548 Collection of an incompletely-initialized or partially-destroyed object
10549 may result in something that @value{GDBN} cannot display, or displays
10550 in a misleading way.
10553 When @value{GDBN} displays a pointer to character it automatically
10554 dereferences the pointer to also display characters of the string
10555 being pointed to. However, collecting the pointer during tracing does
10556 not automatically collect the string. You need to explicitly
10557 dereference the pointer and provide size information if you want to
10558 collect not only the pointer, but the memory pointed to. For example,
10559 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10563 It is not possible to collect a complete stack backtrace at a
10564 tracepoint. Instead, you may collect the registers and a few hundred
10565 bytes from the stack pointer with something like @code{*$esp@@300}
10566 (adjust to use the name of the actual stack pointer register on your
10567 target architecture, and the amount of stack you wish to capture).
10568 Then the @code{backtrace} command will show a partial backtrace when
10569 using a trace frame. The number of stack frames that can be examined
10570 depends on the sizes of the frames in the collected stack. Note that
10571 if you ask for a block so large that it goes past the bottom of the
10572 stack, the target agent may report an error trying to read from an
10576 If you do not collect registers at a tracepoint, @value{GDBN} can
10577 infer that the value of @code{$pc} must be the same as the address of
10578 the tracepoint and use that when you are looking at a trace frame
10579 for that tracepoint. However, this cannot work if the tracepoint has
10580 multiple locations (for instance if it was set in a function that was
10581 inlined), or if it has a @code{while-stepping} loop. In those cases
10582 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10587 @node Analyze Collected Data
10588 @section Using the Collected Data
10590 After the tracepoint experiment ends, you use @value{GDBN} commands
10591 for examining the trace data. The basic idea is that each tracepoint
10592 collects a trace @dfn{snapshot} every time it is hit and another
10593 snapshot every time it single-steps. All these snapshots are
10594 consecutively numbered from zero and go into a buffer, and you can
10595 examine them later. The way you examine them is to @dfn{focus} on a
10596 specific trace snapshot. When the remote stub is focused on a trace
10597 snapshot, it will respond to all @value{GDBN} requests for memory and
10598 registers by reading from the buffer which belongs to that snapshot,
10599 rather than from @emph{real} memory or registers of the program being
10600 debugged. This means that @strong{all} @value{GDBN} commands
10601 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10602 behave as if we were currently debugging the program state as it was
10603 when the tracepoint occurred. Any requests for data that are not in
10604 the buffer will fail.
10607 * tfind:: How to select a trace snapshot
10608 * tdump:: How to display all data for a snapshot
10609 * save tracepoints:: How to save tracepoints for a future run
10613 @subsection @code{tfind @var{n}}
10616 @cindex select trace snapshot
10617 @cindex find trace snapshot
10618 The basic command for selecting a trace snapshot from the buffer is
10619 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10620 counting from zero. If no argument @var{n} is given, the next
10621 snapshot is selected.
10623 Here are the various forms of using the @code{tfind} command.
10627 Find the first snapshot in the buffer. This is a synonym for
10628 @code{tfind 0} (since 0 is the number of the first snapshot).
10631 Stop debugging trace snapshots, resume @emph{live} debugging.
10634 Same as @samp{tfind none}.
10637 No argument means find the next trace snapshot.
10640 Find the previous trace snapshot before the current one. This permits
10641 retracing earlier steps.
10643 @item tfind tracepoint @var{num}
10644 Find the next snapshot associated with tracepoint @var{num}. Search
10645 proceeds forward from the last examined trace snapshot. If no
10646 argument @var{num} is given, it means find the next snapshot collected
10647 for the same tracepoint as the current snapshot.
10649 @item tfind pc @var{addr}
10650 Find the next snapshot associated with the value @var{addr} of the
10651 program counter. Search proceeds forward from the last examined trace
10652 snapshot. If no argument @var{addr} is given, it means find the next
10653 snapshot with the same value of PC as the current snapshot.
10655 @item tfind outside @var{addr1}, @var{addr2}
10656 Find the next snapshot whose PC is outside the given range of
10657 addresses (exclusive).
10659 @item tfind range @var{addr1}, @var{addr2}
10660 Find the next snapshot whose PC is between @var{addr1} and
10661 @var{addr2} (inclusive).
10663 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10664 Find the next snapshot associated with the source line @var{n}. If
10665 the optional argument @var{file} is given, refer to line @var{n} in
10666 that source file. Search proceeds forward from the last examined
10667 trace snapshot. If no argument @var{n} is given, it means find the
10668 next line other than the one currently being examined; thus saying
10669 @code{tfind line} repeatedly can appear to have the same effect as
10670 stepping from line to line in a @emph{live} debugging session.
10673 The default arguments for the @code{tfind} commands are specifically
10674 designed to make it easy to scan through the trace buffer. For
10675 instance, @code{tfind} with no argument selects the next trace
10676 snapshot, and @code{tfind -} with no argument selects the previous
10677 trace snapshot. So, by giving one @code{tfind} command, and then
10678 simply hitting @key{RET} repeatedly you can examine all the trace
10679 snapshots in order. Or, by saying @code{tfind -} and then hitting
10680 @key{RET} repeatedly you can examine the snapshots in reverse order.
10681 The @code{tfind line} command with no argument selects the snapshot
10682 for the next source line executed. The @code{tfind pc} command with
10683 no argument selects the next snapshot with the same program counter
10684 (PC) as the current frame. The @code{tfind tracepoint} command with
10685 no argument selects the next trace snapshot collected by the same
10686 tracepoint as the current one.
10688 In addition to letting you scan through the trace buffer manually,
10689 these commands make it easy to construct @value{GDBN} scripts that
10690 scan through the trace buffer and print out whatever collected data
10691 you are interested in. Thus, if we want to examine the PC, FP, and SP
10692 registers from each trace frame in the buffer, we can say this:
10695 (@value{GDBP}) @b{tfind start}
10696 (@value{GDBP}) @b{while ($trace_frame != -1)}
10697 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10698 $trace_frame, $pc, $sp, $fp
10702 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10703 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10704 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10705 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10706 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10707 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10708 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10709 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10710 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10711 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10712 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10715 Or, if we want to examine the variable @code{X} at each source line in
10719 (@value{GDBP}) @b{tfind start}
10720 (@value{GDBP}) @b{while ($trace_frame != -1)}
10721 > printf "Frame %d, X == %d\n", $trace_frame, X
10731 @subsection @code{tdump}
10733 @cindex dump all data collected at tracepoint
10734 @cindex tracepoint data, display
10736 This command takes no arguments. It prints all the data collected at
10737 the current trace snapshot.
10740 (@value{GDBP}) @b{trace 444}
10741 (@value{GDBP}) @b{actions}
10742 Enter actions for tracepoint #2, one per line:
10743 > collect $regs, $locals, $args, gdb_long_test
10746 (@value{GDBP}) @b{tstart}
10748 (@value{GDBP}) @b{tfind line 444}
10749 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10751 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10753 (@value{GDBP}) @b{tdump}
10754 Data collected at tracepoint 2, trace frame 1:
10755 d0 0xc4aa0085 -995491707
10759 d4 0x71aea3d 119204413
10762 d7 0x380035 3670069
10763 a0 0x19e24a 1696330
10764 a1 0x3000668 50333288
10766 a3 0x322000 3284992
10767 a4 0x3000698 50333336
10768 a5 0x1ad3cc 1758156
10769 fp 0x30bf3c 0x30bf3c
10770 sp 0x30bf34 0x30bf34
10772 pc 0x20b2c8 0x20b2c8
10776 p = 0x20e5b4 "gdb-test"
10783 gdb_long_test = 17 '\021'
10788 @code{tdump} works by scanning the tracepoint's current collection
10789 actions and printing the value of each expression listed. So
10790 @code{tdump} can fail, if after a run, you change the tracepoint's
10791 actions to mention variables that were not collected during the run.
10793 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10794 uses the collected value of @code{$pc} to distinguish between trace
10795 frames that were collected at the tracepoint hit, and frames that were
10796 collected while stepping. This allows it to correctly choose whether
10797 to display the basic list of collections, or the collections from the
10798 body of the while-stepping loop. However, if @code{$pc} was not collected,
10799 then @code{tdump} will always attempt to dump using the basic collection
10800 list, and may fail if a while-stepping frame does not include all the
10801 same data that is collected at the tracepoint hit.
10802 @c This is getting pretty arcane, example would be good.
10804 @node save tracepoints
10805 @subsection @code{save tracepoints @var{filename}}
10806 @kindex save tracepoints
10807 @kindex save-tracepoints
10808 @cindex save tracepoints for future sessions
10810 This command saves all current tracepoint definitions together with
10811 their actions and passcounts, into a file @file{@var{filename}}
10812 suitable for use in a later debugging session. To read the saved
10813 tracepoint definitions, use the @code{source} command (@pxref{Command
10814 Files}). The @w{@code{save-tracepoints}} command is a deprecated
10815 alias for @w{@code{save tracepoints}}
10817 @node Tracepoint Variables
10818 @section Convenience Variables for Tracepoints
10819 @cindex tracepoint variables
10820 @cindex convenience variables for tracepoints
10823 @vindex $trace_frame
10824 @item (int) $trace_frame
10825 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10826 snapshot is selected.
10828 @vindex $tracepoint
10829 @item (int) $tracepoint
10830 The tracepoint for the current trace snapshot.
10832 @vindex $trace_line
10833 @item (int) $trace_line
10834 The line number for the current trace snapshot.
10836 @vindex $trace_file
10837 @item (char []) $trace_file
10838 The source file for the current trace snapshot.
10840 @vindex $trace_func
10841 @item (char []) $trace_func
10842 The name of the function containing @code{$tracepoint}.
10845 Note: @code{$trace_file} is not suitable for use in @code{printf},
10846 use @code{output} instead.
10848 Here's a simple example of using these convenience variables for
10849 stepping through all the trace snapshots and printing some of their
10850 data. Note that these are not the same as trace state variables,
10851 which are managed by the target.
10854 (@value{GDBP}) @b{tfind start}
10856 (@value{GDBP}) @b{while $trace_frame != -1}
10857 > output $trace_file
10858 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10864 @section Using Trace Files
10865 @cindex trace files
10867 In some situations, the target running a trace experiment may no
10868 longer be available; perhaps it crashed, or the hardware was needed
10869 for a different activity. To handle these cases, you can arrange to
10870 dump the trace data into a file, and later use that file as a source
10871 of trace data, via the @code{target tfile} command.
10876 @item tsave [ -r ] @var{filename}
10877 Save the trace data to @var{filename}. By default, this command
10878 assumes that @var{filename} refers to the host filesystem, so if
10879 necessary @value{GDBN} will copy raw trace data up from the target and
10880 then save it. If the target supports it, you can also supply the
10881 optional argument @code{-r} (``remote'') to direct the target to save
10882 the data directly into @var{filename} in its own filesystem, which may be
10883 more efficient if the trace buffer is very large. (Note, however, that
10884 @code{target tfile} can only read from files accessible to the host.)
10886 @kindex target tfile
10888 @item target tfile @var{filename}
10889 Use the file named @var{filename} as a source of trace data. Commands
10890 that examine data work as they do with a live target, but it is not
10891 possible to run any new trace experiments. @code{tstatus} will report
10892 the state of the trace run at the moment the data was saved, as well
10893 as the current trace frame you are examining. @var{filename} must be
10894 on a filesystem accessible to the host.
10899 @chapter Debugging Programs That Use Overlays
10902 If your program is too large to fit completely in your target system's
10903 memory, you can sometimes use @dfn{overlays} to work around this
10904 problem. @value{GDBN} provides some support for debugging programs that
10908 * How Overlays Work:: A general explanation of overlays.
10909 * Overlay Commands:: Managing overlays in @value{GDBN}.
10910 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10911 mapped by asking the inferior.
10912 * Overlay Sample Program:: A sample program using overlays.
10915 @node How Overlays Work
10916 @section How Overlays Work
10917 @cindex mapped overlays
10918 @cindex unmapped overlays
10919 @cindex load address, overlay's
10920 @cindex mapped address
10921 @cindex overlay area
10923 Suppose you have a computer whose instruction address space is only 64
10924 kilobytes long, but which has much more memory which can be accessed by
10925 other means: special instructions, segment registers, or memory
10926 management hardware, for example. Suppose further that you want to
10927 adapt a program which is larger than 64 kilobytes to run on this system.
10929 One solution is to identify modules of your program which are relatively
10930 independent, and need not call each other directly; call these modules
10931 @dfn{overlays}. Separate the overlays from the main program, and place
10932 their machine code in the larger memory. Place your main program in
10933 instruction memory, but leave at least enough space there to hold the
10934 largest overlay as well.
10936 Now, to call a function located in an overlay, you must first copy that
10937 overlay's machine code from the large memory into the space set aside
10938 for it in the instruction memory, and then jump to its entry point
10941 @c NB: In the below the mapped area's size is greater or equal to the
10942 @c size of all overlays. This is intentional to remind the developer
10943 @c that overlays don't necessarily need to be the same size.
10947 Data Instruction Larger
10948 Address Space Address Space Address Space
10949 +-----------+ +-----------+ +-----------+
10951 +-----------+ +-----------+ +-----------+<-- overlay 1
10952 | program | | main | .----| overlay 1 | load address
10953 | variables | | program | | +-----------+
10954 | and heap | | | | | |
10955 +-----------+ | | | +-----------+<-- overlay 2
10956 | | +-----------+ | | | load address
10957 +-----------+ | | | .-| overlay 2 |
10959 mapped --->+-----------+ | | +-----------+
10960 address | | | | | |
10961 | overlay | <-' | | |
10962 | area | <---' +-----------+<-- overlay 3
10963 | | <---. | | load address
10964 +-----------+ `--| overlay 3 |
10971 @anchor{A code overlay}A code overlay
10975 The diagram (@pxref{A code overlay}) shows a system with separate data
10976 and instruction address spaces. To map an overlay, the program copies
10977 its code from the larger address space to the instruction address space.
10978 Since the overlays shown here all use the same mapped address, only one
10979 may be mapped at a time. For a system with a single address space for
10980 data and instructions, the diagram would be similar, except that the
10981 program variables and heap would share an address space with the main
10982 program and the overlay area.
10984 An overlay loaded into instruction memory and ready for use is called a
10985 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10986 instruction memory. An overlay not present (or only partially present)
10987 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10988 is its address in the larger memory. The mapped address is also called
10989 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10990 called the @dfn{load memory address}, or @dfn{LMA}.
10992 Unfortunately, overlays are not a completely transparent way to adapt a
10993 program to limited instruction memory. They introduce a new set of
10994 global constraints you must keep in mind as you design your program:
10999 Before calling or returning to a function in an overlay, your program
11000 must make sure that overlay is actually mapped. Otherwise, the call or
11001 return will transfer control to the right address, but in the wrong
11002 overlay, and your program will probably crash.
11005 If the process of mapping an overlay is expensive on your system, you
11006 will need to choose your overlays carefully to minimize their effect on
11007 your program's performance.
11010 The executable file you load onto your system must contain each
11011 overlay's instructions, appearing at the overlay's load address, not its
11012 mapped address. However, each overlay's instructions must be relocated
11013 and its symbols defined as if the overlay were at its mapped address.
11014 You can use GNU linker scripts to specify different load and relocation
11015 addresses for pieces of your program; see @ref{Overlay Description,,,
11016 ld.info, Using ld: the GNU linker}.
11019 The procedure for loading executable files onto your system must be able
11020 to load their contents into the larger address space as well as the
11021 instruction and data spaces.
11025 The overlay system described above is rather simple, and could be
11026 improved in many ways:
11031 If your system has suitable bank switch registers or memory management
11032 hardware, you could use those facilities to make an overlay's load area
11033 contents simply appear at their mapped address in instruction space.
11034 This would probably be faster than copying the overlay to its mapped
11035 area in the usual way.
11038 If your overlays are small enough, you could set aside more than one
11039 overlay area, and have more than one overlay mapped at a time.
11042 You can use overlays to manage data, as well as instructions. In
11043 general, data overlays are even less transparent to your design than
11044 code overlays: whereas code overlays only require care when you call or
11045 return to functions, data overlays require care every time you access
11046 the data. Also, if you change the contents of a data overlay, you
11047 must copy its contents back out to its load address before you can copy a
11048 different data overlay into the same mapped area.
11053 @node Overlay Commands
11054 @section Overlay Commands
11056 To use @value{GDBN}'s overlay support, each overlay in your program must
11057 correspond to a separate section of the executable file. The section's
11058 virtual memory address and load memory address must be the overlay's
11059 mapped and load addresses. Identifying overlays with sections allows
11060 @value{GDBN} to determine the appropriate address of a function or
11061 variable, depending on whether the overlay is mapped or not.
11063 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11064 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11069 Disable @value{GDBN}'s overlay support. When overlay support is
11070 disabled, @value{GDBN} assumes that all functions and variables are
11071 always present at their mapped addresses. By default, @value{GDBN}'s
11072 overlay support is disabled.
11074 @item overlay manual
11075 @cindex manual overlay debugging
11076 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11077 relies on you to tell it which overlays are mapped, and which are not,
11078 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11079 commands described below.
11081 @item overlay map-overlay @var{overlay}
11082 @itemx overlay map @var{overlay}
11083 @cindex map an overlay
11084 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11085 be the name of the object file section containing the overlay. When an
11086 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11087 functions and variables at their mapped addresses. @value{GDBN} assumes
11088 that any other overlays whose mapped ranges overlap that of
11089 @var{overlay} are now unmapped.
11091 @item overlay unmap-overlay @var{overlay}
11092 @itemx overlay unmap @var{overlay}
11093 @cindex unmap an overlay
11094 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11095 must be the name of the object file section containing the overlay.
11096 When an overlay is unmapped, @value{GDBN} assumes it can find the
11097 overlay's functions and variables at their load addresses.
11100 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11101 consults a data structure the overlay manager maintains in the inferior
11102 to see which overlays are mapped. For details, see @ref{Automatic
11103 Overlay Debugging}.
11105 @item overlay load-target
11106 @itemx overlay load
11107 @cindex reloading the overlay table
11108 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11109 re-reads the table @value{GDBN} automatically each time the inferior
11110 stops, so this command should only be necessary if you have changed the
11111 overlay mapping yourself using @value{GDBN}. This command is only
11112 useful when using automatic overlay debugging.
11114 @item overlay list-overlays
11115 @itemx overlay list
11116 @cindex listing mapped overlays
11117 Display a list of the overlays currently mapped, along with their mapped
11118 addresses, load addresses, and sizes.
11122 Normally, when @value{GDBN} prints a code address, it includes the name
11123 of the function the address falls in:
11126 (@value{GDBP}) print main
11127 $3 = @{int ()@} 0x11a0 <main>
11130 When overlay debugging is enabled, @value{GDBN} recognizes code in
11131 unmapped overlays, and prints the names of unmapped functions with
11132 asterisks around them. For example, if @code{foo} is a function in an
11133 unmapped overlay, @value{GDBN} prints it this way:
11136 (@value{GDBP}) overlay list
11137 No sections are mapped.
11138 (@value{GDBP}) print foo
11139 $5 = @{int (int)@} 0x100000 <*foo*>
11142 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11146 (@value{GDBP}) overlay list
11147 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11148 mapped at 0x1016 - 0x104a
11149 (@value{GDBP}) print foo
11150 $6 = @{int (int)@} 0x1016 <foo>
11153 When overlay debugging is enabled, @value{GDBN} can find the correct
11154 address for functions and variables in an overlay, whether or not the
11155 overlay is mapped. This allows most @value{GDBN} commands, like
11156 @code{break} and @code{disassemble}, to work normally, even on unmapped
11157 code. However, @value{GDBN}'s breakpoint support has some limitations:
11161 @cindex breakpoints in overlays
11162 @cindex overlays, setting breakpoints in
11163 You can set breakpoints in functions in unmapped overlays, as long as
11164 @value{GDBN} can write to the overlay at its load address.
11166 @value{GDBN} can not set hardware or simulator-based breakpoints in
11167 unmapped overlays. However, if you set a breakpoint at the end of your
11168 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11169 you are using manual overlay management), @value{GDBN} will re-set its
11170 breakpoints properly.
11174 @node Automatic Overlay Debugging
11175 @section Automatic Overlay Debugging
11176 @cindex automatic overlay debugging
11178 @value{GDBN} can automatically track which overlays are mapped and which
11179 are not, given some simple co-operation from the overlay manager in the
11180 inferior. If you enable automatic overlay debugging with the
11181 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11182 looks in the inferior's memory for certain variables describing the
11183 current state of the overlays.
11185 Here are the variables your overlay manager must define to support
11186 @value{GDBN}'s automatic overlay debugging:
11190 @item @code{_ovly_table}:
11191 This variable must be an array of the following structures:
11196 /* The overlay's mapped address. */
11199 /* The size of the overlay, in bytes. */
11200 unsigned long size;
11202 /* The overlay's load address. */
11205 /* Non-zero if the overlay is currently mapped;
11207 unsigned long mapped;
11211 @item @code{_novlys}:
11212 This variable must be a four-byte signed integer, holding the total
11213 number of elements in @code{_ovly_table}.
11217 To decide whether a particular overlay is mapped or not, @value{GDBN}
11218 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11219 @code{lma} members equal the VMA and LMA of the overlay's section in the
11220 executable file. When @value{GDBN} finds a matching entry, it consults
11221 the entry's @code{mapped} member to determine whether the overlay is
11224 In addition, your overlay manager may define a function called
11225 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11226 will silently set a breakpoint there. If the overlay manager then
11227 calls this function whenever it has changed the overlay table, this
11228 will enable @value{GDBN} to accurately keep track of which overlays
11229 are in program memory, and update any breakpoints that may be set
11230 in overlays. This will allow breakpoints to work even if the
11231 overlays are kept in ROM or other non-writable memory while they
11232 are not being executed.
11234 @node Overlay Sample Program
11235 @section Overlay Sample Program
11236 @cindex overlay example program
11238 When linking a program which uses overlays, you must place the overlays
11239 at their load addresses, while relocating them to run at their mapped
11240 addresses. To do this, you must write a linker script (@pxref{Overlay
11241 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11242 since linker scripts are specific to a particular host system, target
11243 architecture, and target memory layout, this manual cannot provide
11244 portable sample code demonstrating @value{GDBN}'s overlay support.
11246 However, the @value{GDBN} source distribution does contain an overlaid
11247 program, with linker scripts for a few systems, as part of its test
11248 suite. The program consists of the following files from
11249 @file{gdb/testsuite/gdb.base}:
11253 The main program file.
11255 A simple overlay manager, used by @file{overlays.c}.
11260 Overlay modules, loaded and used by @file{overlays.c}.
11263 Linker scripts for linking the test program on the @code{d10v-elf}
11264 and @code{m32r-elf} targets.
11267 You can build the test program using the @code{d10v-elf} GCC
11268 cross-compiler like this:
11271 $ d10v-elf-gcc -g -c overlays.c
11272 $ d10v-elf-gcc -g -c ovlymgr.c
11273 $ d10v-elf-gcc -g -c foo.c
11274 $ d10v-elf-gcc -g -c bar.c
11275 $ d10v-elf-gcc -g -c baz.c
11276 $ d10v-elf-gcc -g -c grbx.c
11277 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11278 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11281 The build process is identical for any other architecture, except that
11282 you must substitute the appropriate compiler and linker script for the
11283 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11287 @chapter Using @value{GDBN} with Different Languages
11290 Although programming languages generally have common aspects, they are
11291 rarely expressed in the same manner. For instance, in ANSI C,
11292 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11293 Modula-2, it is accomplished by @code{p^}. Values can also be
11294 represented (and displayed) differently. Hex numbers in C appear as
11295 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11297 @cindex working language
11298 Language-specific information is built into @value{GDBN} for some languages,
11299 allowing you to express operations like the above in your program's
11300 native language, and allowing @value{GDBN} to output values in a manner
11301 consistent with the syntax of your program's native language. The
11302 language you use to build expressions is called the @dfn{working
11306 * Setting:: Switching between source languages
11307 * Show:: Displaying the language
11308 * Checks:: Type and range checks
11309 * Supported Languages:: Supported languages
11310 * Unsupported Languages:: Unsupported languages
11314 @section Switching Between Source Languages
11316 There are two ways to control the working language---either have @value{GDBN}
11317 set it automatically, or select it manually yourself. You can use the
11318 @code{set language} command for either purpose. On startup, @value{GDBN}
11319 defaults to setting the language automatically. The working language is
11320 used to determine how expressions you type are interpreted, how values
11323 In addition to the working language, every source file that
11324 @value{GDBN} knows about has its own working language. For some object
11325 file formats, the compiler might indicate which language a particular
11326 source file is in. However, most of the time @value{GDBN} infers the
11327 language from the name of the file. The language of a source file
11328 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11329 show each frame appropriately for its own language. There is no way to
11330 set the language of a source file from within @value{GDBN}, but you can
11331 set the language associated with a filename extension. @xref{Show, ,
11332 Displaying the Language}.
11334 This is most commonly a problem when you use a program, such
11335 as @code{cfront} or @code{f2c}, that generates C but is written in
11336 another language. In that case, make the
11337 program use @code{#line} directives in its C output; that way
11338 @value{GDBN} will know the correct language of the source code of the original
11339 program, and will display that source code, not the generated C code.
11342 * Filenames:: Filename extensions and languages.
11343 * Manually:: Setting the working language manually
11344 * Automatically:: Having @value{GDBN} infer the source language
11348 @subsection List of Filename Extensions and Languages
11350 If a source file name ends in one of the following extensions, then
11351 @value{GDBN} infers that its language is the one indicated.
11369 C@t{++} source file
11375 Objective-C source file
11379 Fortran source file
11382 Modula-2 source file
11386 Assembler source file. This actually behaves almost like C, but
11387 @value{GDBN} does not skip over function prologues when stepping.
11390 In addition, you may set the language associated with a filename
11391 extension. @xref{Show, , Displaying the Language}.
11394 @subsection Setting the Working Language
11396 If you allow @value{GDBN} to set the language automatically,
11397 expressions are interpreted the same way in your debugging session and
11400 @kindex set language
11401 If you wish, you may set the language manually. To do this, issue the
11402 command @samp{set language @var{lang}}, where @var{lang} is the name of
11403 a language, such as
11404 @code{c} or @code{modula-2}.
11405 For a list of the supported languages, type @samp{set language}.
11407 Setting the language manually prevents @value{GDBN} from updating the working
11408 language automatically. This can lead to confusion if you try
11409 to debug a program when the working language is not the same as the
11410 source language, when an expression is acceptable to both
11411 languages---but means different things. For instance, if the current
11412 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11420 might not have the effect you intended. In C, this means to add
11421 @code{b} and @code{c} and place the result in @code{a}. The result
11422 printed would be the value of @code{a}. In Modula-2, this means to compare
11423 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11425 @node Automatically
11426 @subsection Having @value{GDBN} Infer the Source Language
11428 To have @value{GDBN} set the working language automatically, use
11429 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11430 then infers the working language. That is, when your program stops in a
11431 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11432 working language to the language recorded for the function in that
11433 frame. If the language for a frame is unknown (that is, if the function
11434 or block corresponding to the frame was defined in a source file that
11435 does not have a recognized extension), the current working language is
11436 not changed, and @value{GDBN} issues a warning.
11438 This may not seem necessary for most programs, which are written
11439 entirely in one source language. However, program modules and libraries
11440 written in one source language can be used by a main program written in
11441 a different source language. Using @samp{set language auto} in this
11442 case frees you from having to set the working language manually.
11445 @section Displaying the Language
11447 The following commands help you find out which language is the
11448 working language, and also what language source files were written in.
11451 @item show language
11452 @kindex show language
11453 Display the current working language. This is the
11454 language you can use with commands such as @code{print} to
11455 build and compute expressions that may involve variables in your program.
11458 @kindex info frame@r{, show the source language}
11459 Display the source language for this frame. This language becomes the
11460 working language if you use an identifier from this frame.
11461 @xref{Frame Info, ,Information about a Frame}, to identify the other
11462 information listed here.
11465 @kindex info source@r{, show the source language}
11466 Display the source language of this source file.
11467 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11468 information listed here.
11471 In unusual circumstances, you may have source files with extensions
11472 not in the standard list. You can then set the extension associated
11473 with a language explicitly:
11476 @item set extension-language @var{ext} @var{language}
11477 @kindex set extension-language
11478 Tell @value{GDBN} that source files with extension @var{ext} are to be
11479 assumed as written in the source language @var{language}.
11481 @item info extensions
11482 @kindex info extensions
11483 List all the filename extensions and the associated languages.
11487 @section Type and Range Checking
11490 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11491 checking are included, but they do not yet have any effect. This
11492 section documents the intended facilities.
11494 @c FIXME remove warning when type/range code added
11496 Some languages are designed to guard you against making seemingly common
11497 errors through a series of compile- and run-time checks. These include
11498 checking the type of arguments to functions and operators, and making
11499 sure mathematical overflows are caught at run time. Checks such as
11500 these help to ensure a program's correctness once it has been compiled
11501 by eliminating type mismatches, and providing active checks for range
11502 errors when your program is running.
11504 @value{GDBN} can check for conditions like the above if you wish.
11505 Although @value{GDBN} does not check the statements in your program,
11506 it can check expressions entered directly into @value{GDBN} for
11507 evaluation via the @code{print} command, for example. As with the
11508 working language, @value{GDBN} can also decide whether or not to check
11509 automatically based on your program's source language.
11510 @xref{Supported Languages, ,Supported Languages}, for the default
11511 settings of supported languages.
11514 * Type Checking:: An overview of type checking
11515 * Range Checking:: An overview of range checking
11518 @cindex type checking
11519 @cindex checks, type
11520 @node Type Checking
11521 @subsection An Overview of Type Checking
11523 Some languages, such as Modula-2, are strongly typed, meaning that the
11524 arguments to operators and functions have to be of the correct type,
11525 otherwise an error occurs. These checks prevent type mismatch
11526 errors from ever causing any run-time problems. For example,
11534 The second example fails because the @code{CARDINAL} 1 is not
11535 type-compatible with the @code{REAL} 2.3.
11537 For the expressions you use in @value{GDBN} commands, you can tell the
11538 @value{GDBN} type checker to skip checking;
11539 to treat any mismatches as errors and abandon the expression;
11540 or to only issue warnings when type mismatches occur,
11541 but evaluate the expression anyway. When you choose the last of
11542 these, @value{GDBN} evaluates expressions like the second example above, but
11543 also issues a warning.
11545 Even if you turn type checking off, there may be other reasons
11546 related to type that prevent @value{GDBN} from evaluating an expression.
11547 For instance, @value{GDBN} does not know how to add an @code{int} and
11548 a @code{struct foo}. These particular type errors have nothing to do
11549 with the language in use, and usually arise from expressions, such as
11550 the one described above, which make little sense to evaluate anyway.
11552 Each language defines to what degree it is strict about type. For
11553 instance, both Modula-2 and C require the arguments to arithmetical
11554 operators to be numbers. In C, enumerated types and pointers can be
11555 represented as numbers, so that they are valid arguments to mathematical
11556 operators. @xref{Supported Languages, ,Supported Languages}, for further
11557 details on specific languages.
11559 @value{GDBN} provides some additional commands for controlling the type checker:
11561 @kindex set check type
11562 @kindex show check type
11564 @item set check type auto
11565 Set type checking on or off based on the current working language.
11566 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11569 @item set check type on
11570 @itemx set check type off
11571 Set type checking on or off, overriding the default setting for the
11572 current working language. Issue a warning if the setting does not
11573 match the language default. If any type mismatches occur in
11574 evaluating an expression while type checking is on, @value{GDBN} prints a
11575 message and aborts evaluation of the expression.
11577 @item set check type warn
11578 Cause the type checker to issue warnings, but to always attempt to
11579 evaluate the expression. Evaluating the expression may still
11580 be impossible for other reasons. For example, @value{GDBN} cannot add
11581 numbers and structures.
11584 Show the current setting of the type checker, and whether or not @value{GDBN}
11585 is setting it automatically.
11588 @cindex range checking
11589 @cindex checks, range
11590 @node Range Checking
11591 @subsection An Overview of Range Checking
11593 In some languages (such as Modula-2), it is an error to exceed the
11594 bounds of a type; this is enforced with run-time checks. Such range
11595 checking is meant to ensure program correctness by making sure
11596 computations do not overflow, or indices on an array element access do
11597 not exceed the bounds of the array.
11599 For expressions you use in @value{GDBN} commands, you can tell
11600 @value{GDBN} to treat range errors in one of three ways: ignore them,
11601 always treat them as errors and abandon the expression, or issue
11602 warnings but evaluate the expression anyway.
11604 A range error can result from numerical overflow, from exceeding an
11605 array index bound, or when you type a constant that is not a member
11606 of any type. Some languages, however, do not treat overflows as an
11607 error. In many implementations of C, mathematical overflow causes the
11608 result to ``wrap around'' to lower values---for example, if @var{m} is
11609 the largest integer value, and @var{s} is the smallest, then
11612 @var{m} + 1 @result{} @var{s}
11615 This, too, is specific to individual languages, and in some cases
11616 specific to individual compilers or machines. @xref{Supported Languages, ,
11617 Supported Languages}, for further details on specific languages.
11619 @value{GDBN} provides some additional commands for controlling the range checker:
11621 @kindex set check range
11622 @kindex show check range
11624 @item set check range auto
11625 Set range checking on or off based on the current working language.
11626 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11629 @item set check range on
11630 @itemx set check range off
11631 Set range checking on or off, overriding the default setting for the
11632 current working language. A warning is issued if the setting does not
11633 match the language default. If a range error occurs and range checking is on,
11634 then a message is printed and evaluation of the expression is aborted.
11636 @item set check range warn
11637 Output messages when the @value{GDBN} range checker detects a range error,
11638 but attempt to evaluate the expression anyway. Evaluating the
11639 expression may still be impossible for other reasons, such as accessing
11640 memory that the process does not own (a typical example from many Unix
11644 Show the current setting of the range checker, and whether or not it is
11645 being set automatically by @value{GDBN}.
11648 @node Supported Languages
11649 @section Supported Languages
11651 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
11652 assembly, Modula-2, and Ada.
11653 @c This is false ...
11654 Some @value{GDBN} features may be used in expressions regardless of the
11655 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11656 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11657 ,Expressions}) can be used with the constructs of any supported
11660 The following sections detail to what degree each source language is
11661 supported by @value{GDBN}. These sections are not meant to be language
11662 tutorials or references, but serve only as a reference guide to what the
11663 @value{GDBN} expression parser accepts, and what input and output
11664 formats should look like for different languages. There are many good
11665 books written on each of these languages; please look to these for a
11666 language reference or tutorial.
11669 * C:: C and C@t{++}
11671 * Objective-C:: Objective-C
11672 * OpenCL C:: OpenCL C
11673 * Fortran:: Fortran
11675 * Modula-2:: Modula-2
11680 @subsection C and C@t{++}
11682 @cindex C and C@t{++}
11683 @cindex expressions in C or C@t{++}
11685 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11686 to both languages. Whenever this is the case, we discuss those languages
11690 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11691 @cindex @sc{gnu} C@t{++}
11692 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11693 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11694 effectively, you must compile your C@t{++} programs with a supported
11695 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11696 compiler (@code{aCC}).
11698 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11699 format; if it doesn't work on your system, try the stabs+ debugging
11700 format. You can select those formats explicitly with the @code{g++}
11701 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11702 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11703 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11706 * C Operators:: C and C@t{++} operators
11707 * C Constants:: C and C@t{++} constants
11708 * C Plus Plus Expressions:: C@t{++} expressions
11709 * C Defaults:: Default settings for C and C@t{++}
11710 * C Checks:: C and C@t{++} type and range checks
11711 * Debugging C:: @value{GDBN} and C
11712 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11713 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11717 @subsubsection C and C@t{++} Operators
11719 @cindex C and C@t{++} operators
11721 Operators must be defined on values of specific types. For instance,
11722 @code{+} is defined on numbers, but not on structures. Operators are
11723 often defined on groups of types.
11725 For the purposes of C and C@t{++}, the following definitions hold:
11730 @emph{Integral types} include @code{int} with any of its storage-class
11731 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11734 @emph{Floating-point types} include @code{float}, @code{double}, and
11735 @code{long double} (if supported by the target platform).
11738 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11741 @emph{Scalar types} include all of the above.
11746 The following operators are supported. They are listed here
11747 in order of increasing precedence:
11751 The comma or sequencing operator. Expressions in a comma-separated list
11752 are evaluated from left to right, with the result of the entire
11753 expression being the last expression evaluated.
11756 Assignment. The value of an assignment expression is the value
11757 assigned. Defined on scalar types.
11760 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11761 and translated to @w{@code{@var{a} = @var{a op b}}}.
11762 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11763 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11764 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11767 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11768 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11772 Logical @sc{or}. Defined on integral types.
11775 Logical @sc{and}. Defined on integral types.
11778 Bitwise @sc{or}. Defined on integral types.
11781 Bitwise exclusive-@sc{or}. Defined on integral types.
11784 Bitwise @sc{and}. Defined on integral types.
11787 Equality and inequality. Defined on scalar types. The value of these
11788 expressions is 0 for false and non-zero for true.
11790 @item <@r{, }>@r{, }<=@r{, }>=
11791 Less than, greater than, less than or equal, greater than or equal.
11792 Defined on scalar types. The value of these expressions is 0 for false
11793 and non-zero for true.
11796 left shift, and right shift. Defined on integral types.
11799 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11802 Addition and subtraction. Defined on integral types, floating-point types and
11805 @item *@r{, }/@r{, }%
11806 Multiplication, division, and modulus. Multiplication and division are
11807 defined on integral and floating-point types. Modulus is defined on
11811 Increment and decrement. When appearing before a variable, the
11812 operation is performed before the variable is used in an expression;
11813 when appearing after it, the variable's value is used before the
11814 operation takes place.
11817 Pointer dereferencing. Defined on pointer types. Same precedence as
11821 Address operator. Defined on variables. Same precedence as @code{++}.
11823 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11824 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11825 to examine the address
11826 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11830 Negative. Defined on integral and floating-point types. Same
11831 precedence as @code{++}.
11834 Logical negation. Defined on integral types. Same precedence as
11838 Bitwise complement operator. Defined on integral types. Same precedence as
11843 Structure member, and pointer-to-structure member. For convenience,
11844 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11845 pointer based on the stored type information.
11846 Defined on @code{struct} and @code{union} data.
11849 Dereferences of pointers to members.
11852 Array indexing. @code{@var{a}[@var{i}]} is defined as
11853 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11856 Function parameter list. Same precedence as @code{->}.
11859 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11860 and @code{class} types.
11863 Doubled colons also represent the @value{GDBN} scope operator
11864 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11868 If an operator is redefined in the user code, @value{GDBN} usually
11869 attempts to invoke the redefined version instead of using the operator's
11870 predefined meaning.
11873 @subsubsection C and C@t{++} Constants
11875 @cindex C and C@t{++} constants
11877 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11882 Integer constants are a sequence of digits. Octal constants are
11883 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11884 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11885 @samp{l}, specifying that the constant should be treated as a
11889 Floating point constants are a sequence of digits, followed by a decimal
11890 point, followed by a sequence of digits, and optionally followed by an
11891 exponent. An exponent is of the form:
11892 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11893 sequence of digits. The @samp{+} is optional for positive exponents.
11894 A floating-point constant may also end with a letter @samp{f} or
11895 @samp{F}, specifying that the constant should be treated as being of
11896 the @code{float} (as opposed to the default @code{double}) type; or with
11897 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11901 Enumerated constants consist of enumerated identifiers, or their
11902 integral equivalents.
11905 Character constants are a single character surrounded by single quotes
11906 (@code{'}), or a number---the ordinal value of the corresponding character
11907 (usually its @sc{ascii} value). Within quotes, the single character may
11908 be represented by a letter or by @dfn{escape sequences}, which are of
11909 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11910 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11911 @samp{@var{x}} is a predefined special character---for example,
11912 @samp{\n} for newline.
11915 String constants are a sequence of character constants surrounded by
11916 double quotes (@code{"}). Any valid character constant (as described
11917 above) may appear. Double quotes within the string must be preceded by
11918 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11922 Pointer constants are an integral value. You can also write pointers
11923 to constants using the C operator @samp{&}.
11926 Array constants are comma-separated lists surrounded by braces @samp{@{}
11927 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11928 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11929 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11932 @node C Plus Plus Expressions
11933 @subsubsection C@t{++} Expressions
11935 @cindex expressions in C@t{++}
11936 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11938 @cindex debugging C@t{++} programs
11939 @cindex C@t{++} compilers
11940 @cindex debug formats and C@t{++}
11941 @cindex @value{NGCC} and C@t{++}
11943 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11944 proper compiler and the proper debug format. Currently, @value{GDBN}
11945 works best when debugging C@t{++} code that is compiled with
11946 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11947 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11948 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11949 stabs+ as their default debug format, so you usually don't need to
11950 specify a debug format explicitly. Other compilers and/or debug formats
11951 are likely to work badly or not at all when using @value{GDBN} to debug
11957 @cindex member functions
11959 Member function calls are allowed; you can use expressions like
11962 count = aml->GetOriginal(x, y)
11965 @vindex this@r{, inside C@t{++} member functions}
11966 @cindex namespace in C@t{++}
11968 While a member function is active (in the selected stack frame), your
11969 expressions have the same namespace available as the member function;
11970 that is, @value{GDBN} allows implicit references to the class instance
11971 pointer @code{this} following the same rules as C@t{++}.
11973 @cindex call overloaded functions
11974 @cindex overloaded functions, calling
11975 @cindex type conversions in C@t{++}
11977 You can call overloaded functions; @value{GDBN} resolves the function
11978 call to the right definition, with some restrictions. @value{GDBN} does not
11979 perform overload resolution involving user-defined type conversions,
11980 calls to constructors, or instantiations of templates that do not exist
11981 in the program. It also cannot handle ellipsis argument lists or
11984 It does perform integral conversions and promotions, floating-point
11985 promotions, arithmetic conversions, pointer conversions, conversions of
11986 class objects to base classes, and standard conversions such as those of
11987 functions or arrays to pointers; it requires an exact match on the
11988 number of function arguments.
11990 Overload resolution is always performed, unless you have specified
11991 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11992 ,@value{GDBN} Features for C@t{++}}.
11994 You must specify @code{set overload-resolution off} in order to use an
11995 explicit function signature to call an overloaded function, as in
11997 p 'foo(char,int)'('x', 13)
12000 The @value{GDBN} command-completion facility can simplify this;
12001 see @ref{Completion, ,Command Completion}.
12003 @cindex reference declarations
12005 @value{GDBN} understands variables declared as C@t{++} references; you can use
12006 them in expressions just as you do in C@t{++} source---they are automatically
12009 In the parameter list shown when @value{GDBN} displays a frame, the values of
12010 reference variables are not displayed (unlike other variables); this
12011 avoids clutter, since references are often used for large structures.
12012 The @emph{address} of a reference variable is always shown, unless
12013 you have specified @samp{set print address off}.
12016 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12017 expressions can use it just as expressions in your program do. Since
12018 one scope may be defined in another, you can use @code{::} repeatedly if
12019 necessary, for example in an expression like
12020 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12021 resolving name scope by reference to source files, in both C and C@t{++}
12022 debugging (@pxref{Variables, ,Program Variables}).
12025 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
12026 calling virtual functions correctly, printing out virtual bases of
12027 objects, calling functions in a base subobject, casting objects, and
12028 invoking user-defined operators.
12031 @subsubsection C and C@t{++} Defaults
12033 @cindex C and C@t{++} defaults
12035 If you allow @value{GDBN} to set type and range checking automatically, they
12036 both default to @code{off} whenever the working language changes to
12037 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12038 selects the working language.
12040 If you allow @value{GDBN} to set the language automatically, it
12041 recognizes source files whose names end with @file{.c}, @file{.C}, or
12042 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12043 these files, it sets the working language to C or C@t{++}.
12044 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12045 for further details.
12047 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12048 @c unimplemented. If (b) changes, it might make sense to let this node
12049 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12052 @subsubsection C and C@t{++} Type and Range Checks
12054 @cindex C and C@t{++} checks
12056 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12057 is not used. However, if you turn type checking on, @value{GDBN}
12058 considers two variables type equivalent if:
12062 The two variables are structured and have the same structure, union, or
12066 The two variables have the same type name, or types that have been
12067 declared equivalent through @code{typedef}.
12070 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12073 The two @code{struct}, @code{union}, or @code{enum} variables are
12074 declared in the same declaration. (Note: this may not be true for all C
12079 Range checking, if turned on, is done on mathematical operations. Array
12080 indices are not checked, since they are often used to index a pointer
12081 that is not itself an array.
12084 @subsubsection @value{GDBN} and C
12086 The @code{set print union} and @code{show print union} commands apply to
12087 the @code{union} type. When set to @samp{on}, any @code{union} that is
12088 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12089 appears as @samp{@{...@}}.
12091 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12092 with pointers and a memory allocation function. @xref{Expressions,
12095 @node Debugging C Plus Plus
12096 @subsubsection @value{GDBN} Features for C@t{++}
12098 @cindex commands for C@t{++}
12100 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12101 designed specifically for use with C@t{++}. Here is a summary:
12104 @cindex break in overloaded functions
12105 @item @r{breakpoint menus}
12106 When you want a breakpoint in a function whose name is overloaded,
12107 @value{GDBN} has the capability to display a menu of possible breakpoint
12108 locations to help you specify which function definition you want.
12109 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12111 @cindex overloading in C@t{++}
12112 @item rbreak @var{regex}
12113 Setting breakpoints using regular expressions is helpful for setting
12114 breakpoints on overloaded functions that are not members of any special
12116 @xref{Set Breaks, ,Setting Breakpoints}.
12118 @cindex C@t{++} exception handling
12121 Debug C@t{++} exception handling using these commands. @xref{Set
12122 Catchpoints, , Setting Catchpoints}.
12124 @cindex inheritance
12125 @item ptype @var{typename}
12126 Print inheritance relationships as well as other information for type
12128 @xref{Symbols, ,Examining the Symbol Table}.
12130 @cindex C@t{++} symbol display
12131 @item set print demangle
12132 @itemx show print demangle
12133 @itemx set print asm-demangle
12134 @itemx show print asm-demangle
12135 Control whether C@t{++} symbols display in their source form, both when
12136 displaying code as C@t{++} source and when displaying disassemblies.
12137 @xref{Print Settings, ,Print Settings}.
12139 @item set print object
12140 @itemx show print object
12141 Choose whether to print derived (actual) or declared types of objects.
12142 @xref{Print Settings, ,Print Settings}.
12144 @item set print vtbl
12145 @itemx show print vtbl
12146 Control the format for printing virtual function tables.
12147 @xref{Print Settings, ,Print Settings}.
12148 (The @code{vtbl} commands do not work on programs compiled with the HP
12149 ANSI C@t{++} compiler (@code{aCC}).)
12151 @kindex set overload-resolution
12152 @cindex overloaded functions, overload resolution
12153 @item set overload-resolution on
12154 Enable overload resolution for C@t{++} expression evaluation. The default
12155 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12156 and searches for a function whose signature matches the argument types,
12157 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12158 Expressions, ,C@t{++} Expressions}, for details).
12159 If it cannot find a match, it emits a message.
12161 @item set overload-resolution off
12162 Disable overload resolution for C@t{++} expression evaluation. For
12163 overloaded functions that are not class member functions, @value{GDBN}
12164 chooses the first function of the specified name that it finds in the
12165 symbol table, whether or not its arguments are of the correct type. For
12166 overloaded functions that are class member functions, @value{GDBN}
12167 searches for a function whose signature @emph{exactly} matches the
12170 @kindex show overload-resolution
12171 @item show overload-resolution
12172 Show the current setting of overload resolution.
12174 @item @r{Overloaded symbol names}
12175 You can specify a particular definition of an overloaded symbol, using
12176 the same notation that is used to declare such symbols in C@t{++}: type
12177 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12178 also use the @value{GDBN} command-line word completion facilities to list the
12179 available choices, or to finish the type list for you.
12180 @xref{Completion,, Command Completion}, for details on how to do this.
12183 @node Decimal Floating Point
12184 @subsubsection Decimal Floating Point format
12185 @cindex decimal floating point format
12187 @value{GDBN} can examine, set and perform computations with numbers in
12188 decimal floating point format, which in the C language correspond to the
12189 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12190 specified by the extension to support decimal floating-point arithmetic.
12192 There are two encodings in use, depending on the architecture: BID (Binary
12193 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12194 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12197 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12198 to manipulate decimal floating point numbers, it is not possible to convert
12199 (using a cast, for example) integers wider than 32-bit to decimal float.
12201 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12202 point computations, error checking in decimal float operations ignores
12203 underflow, overflow and divide by zero exceptions.
12205 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12206 to inspect @code{_Decimal128} values stored in floating point registers.
12207 See @ref{PowerPC,,PowerPC} for more details.
12213 @value{GDBN} can be used to debug programs written in D and compiled with
12214 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12215 specific feature --- dynamic arrays.
12218 @subsection Objective-C
12220 @cindex Objective-C
12221 This section provides information about some commands and command
12222 options that are useful for debugging Objective-C code. See also
12223 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12224 few more commands specific to Objective-C support.
12227 * Method Names in Commands::
12228 * The Print Command with Objective-C::
12231 @node Method Names in Commands
12232 @subsubsection Method Names in Commands
12234 The following commands have been extended to accept Objective-C method
12235 names as line specifications:
12237 @kindex clear@r{, and Objective-C}
12238 @kindex break@r{, and Objective-C}
12239 @kindex info line@r{, and Objective-C}
12240 @kindex jump@r{, and Objective-C}
12241 @kindex list@r{, and Objective-C}
12245 @item @code{info line}
12250 A fully qualified Objective-C method name is specified as
12253 -[@var{Class} @var{methodName}]
12256 where the minus sign is used to indicate an instance method and a
12257 plus sign (not shown) is used to indicate a class method. The class
12258 name @var{Class} and method name @var{methodName} are enclosed in
12259 brackets, similar to the way messages are specified in Objective-C
12260 source code. For example, to set a breakpoint at the @code{create}
12261 instance method of class @code{Fruit} in the program currently being
12265 break -[Fruit create]
12268 To list ten program lines around the @code{initialize} class method,
12272 list +[NSText initialize]
12275 In the current version of @value{GDBN}, the plus or minus sign is
12276 required. In future versions of @value{GDBN}, the plus or minus
12277 sign will be optional, but you can use it to narrow the search. It
12278 is also possible to specify just a method name:
12284 You must specify the complete method name, including any colons. If
12285 your program's source files contain more than one @code{create} method,
12286 you'll be presented with a numbered list of classes that implement that
12287 method. Indicate your choice by number, or type @samp{0} to exit if
12290 As another example, to clear a breakpoint established at the
12291 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12294 clear -[NSWindow makeKeyAndOrderFront:]
12297 @node The Print Command with Objective-C
12298 @subsubsection The Print Command With Objective-C
12299 @cindex Objective-C, print objects
12300 @kindex print-object
12301 @kindex po @r{(@code{print-object})}
12303 The print command has also been extended to accept methods. For example:
12306 print -[@var{object} hash]
12309 @cindex print an Objective-C object description
12310 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12312 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12313 and print the result. Also, an additional command has been added,
12314 @code{print-object} or @code{po} for short, which is meant to print
12315 the description of an object. However, this command may only work
12316 with certain Objective-C libraries that have a particular hook
12317 function, @code{_NSPrintForDebugger}, defined.
12320 @subsection OpenCL C
12323 This section provides information about @value{GDBN}s OpenCL C support.
12326 * OpenCL C Datatypes::
12327 * OpenCL C Expressions::
12328 * OpenCL C Operators::
12331 @node OpenCL C Datatypes
12332 @subsubsection OpenCL C Datatypes
12334 @cindex OpenCL C Datatypes
12335 @value{GDBN} supports the builtin scalar and vector datatypes specified
12336 by OpenCL 1.1. In addition the half- and double-precision floating point
12337 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12338 extensions are also known to @value{GDBN}.
12340 @node OpenCL C Expressions
12341 @subsubsection OpenCL C Expressions
12343 @cindex OpenCL C Expressions
12344 @value{GDBN} supports accesses to vector components including the access as
12345 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12346 supported by @value{GDBN} can be used as well.
12348 @node OpenCL C Operators
12349 @subsubsection OpenCL C Operators
12351 @cindex OpenCL C Operators
12352 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12356 @subsection Fortran
12357 @cindex Fortran-specific support in @value{GDBN}
12359 @value{GDBN} can be used to debug programs written in Fortran, but it
12360 currently supports only the features of Fortran 77 language.
12362 @cindex trailing underscore, in Fortran symbols
12363 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12364 among them) append an underscore to the names of variables and
12365 functions. When you debug programs compiled by those compilers, you
12366 will need to refer to variables and functions with a trailing
12370 * Fortran Operators:: Fortran operators and expressions
12371 * Fortran Defaults:: Default settings for Fortran
12372 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12375 @node Fortran Operators
12376 @subsubsection Fortran Operators and Expressions
12378 @cindex Fortran operators and expressions
12380 Operators must be defined on values of specific types. For instance,
12381 @code{+} is defined on numbers, but not on characters or other non-
12382 arithmetic types. Operators are often defined on groups of types.
12386 The exponentiation operator. It raises the first operand to the power
12390 The range operator. Normally used in the form of array(low:high) to
12391 represent a section of array.
12394 The access component operator. Normally used to access elements in derived
12395 types. Also suitable for unions. As unions aren't part of regular Fortran,
12396 this can only happen when accessing a register that uses a gdbarch-defined
12400 @node Fortran Defaults
12401 @subsubsection Fortran Defaults
12403 @cindex Fortran Defaults
12405 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12406 default uses case-insensitive matches for Fortran symbols. You can
12407 change that with the @samp{set case-insensitive} command, see
12408 @ref{Symbols}, for the details.
12410 @node Special Fortran Commands
12411 @subsubsection Special Fortran Commands
12413 @cindex Special Fortran commands
12415 @value{GDBN} has some commands to support Fortran-specific features,
12416 such as displaying common blocks.
12419 @cindex @code{COMMON} blocks, Fortran
12420 @kindex info common
12421 @item info common @r{[}@var{common-name}@r{]}
12422 This command prints the values contained in the Fortran @code{COMMON}
12423 block whose name is @var{common-name}. With no argument, the names of
12424 all @code{COMMON} blocks visible at the current program location are
12431 @cindex Pascal support in @value{GDBN}, limitations
12432 Debugging Pascal programs which use sets, subranges, file variables, or
12433 nested functions does not currently work. @value{GDBN} does not support
12434 entering expressions, printing values, or similar features using Pascal
12437 The Pascal-specific command @code{set print pascal_static-members}
12438 controls whether static members of Pascal objects are displayed.
12439 @xref{Print Settings, pascal_static-members}.
12442 @subsection Modula-2
12444 @cindex Modula-2, @value{GDBN} support
12446 The extensions made to @value{GDBN} to support Modula-2 only support
12447 output from the @sc{gnu} Modula-2 compiler (which is currently being
12448 developed). Other Modula-2 compilers are not currently supported, and
12449 attempting to debug executables produced by them is most likely
12450 to give an error as @value{GDBN} reads in the executable's symbol
12453 @cindex expressions in Modula-2
12455 * M2 Operators:: Built-in operators
12456 * Built-In Func/Proc:: Built-in functions and procedures
12457 * M2 Constants:: Modula-2 constants
12458 * M2 Types:: Modula-2 types
12459 * M2 Defaults:: Default settings for Modula-2
12460 * Deviations:: Deviations from standard Modula-2
12461 * M2 Checks:: Modula-2 type and range checks
12462 * M2 Scope:: The scope operators @code{::} and @code{.}
12463 * GDB/M2:: @value{GDBN} and Modula-2
12467 @subsubsection Operators
12468 @cindex Modula-2 operators
12470 Operators must be defined on values of specific types. For instance,
12471 @code{+} is defined on numbers, but not on structures. Operators are
12472 often defined on groups of types. For the purposes of Modula-2, the
12473 following definitions hold:
12478 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12482 @emph{Character types} consist of @code{CHAR} and its subranges.
12485 @emph{Floating-point types} consist of @code{REAL}.
12488 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12492 @emph{Scalar types} consist of all of the above.
12495 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12498 @emph{Boolean types} consist of @code{BOOLEAN}.
12502 The following operators are supported, and appear in order of
12503 increasing precedence:
12507 Function argument or array index separator.
12510 Assignment. The value of @var{var} @code{:=} @var{value} is
12514 Less than, greater than on integral, floating-point, or enumerated
12518 Less than or equal to, greater than or equal to
12519 on integral, floating-point and enumerated types, or set inclusion on
12520 set types. Same precedence as @code{<}.
12522 @item =@r{, }<>@r{, }#
12523 Equality and two ways of expressing inequality, valid on scalar types.
12524 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
12525 available for inequality, since @code{#} conflicts with the script
12529 Set membership. Defined on set types and the types of their members.
12530 Same precedence as @code{<}.
12533 Boolean disjunction. Defined on boolean types.
12536 Boolean conjunction. Defined on boolean types.
12539 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12542 Addition and subtraction on integral and floating-point types, or union
12543 and difference on set types.
12546 Multiplication on integral and floating-point types, or set intersection
12550 Division on floating-point types, or symmetric set difference on set
12551 types. Same precedence as @code{*}.
12554 Integer division and remainder. Defined on integral types. Same
12555 precedence as @code{*}.
12558 Negative. Defined on @code{INTEGER} and @code{REAL} data.
12561 Pointer dereferencing. Defined on pointer types.
12564 Boolean negation. Defined on boolean types. Same precedence as
12568 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
12569 precedence as @code{^}.
12572 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
12575 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
12579 @value{GDBN} and Modula-2 scope operators.
12583 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
12584 treats the use of the operator @code{IN}, or the use of operators
12585 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
12586 @code{<=}, and @code{>=} on sets as an error.
12590 @node Built-In Func/Proc
12591 @subsubsection Built-in Functions and Procedures
12592 @cindex Modula-2 built-ins
12594 Modula-2 also makes available several built-in procedures and functions.
12595 In describing these, the following metavariables are used:
12600 represents an @code{ARRAY} variable.
12603 represents a @code{CHAR} constant or variable.
12606 represents a variable or constant of integral type.
12609 represents an identifier that belongs to a set. Generally used in the
12610 same function with the metavariable @var{s}. The type of @var{s} should
12611 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12614 represents a variable or constant of integral or floating-point type.
12617 represents a variable or constant of floating-point type.
12623 represents a variable.
12626 represents a variable or constant of one of many types. See the
12627 explanation of the function for details.
12630 All Modula-2 built-in procedures also return a result, described below.
12634 Returns the absolute value of @var{n}.
12637 If @var{c} is a lower case letter, it returns its upper case
12638 equivalent, otherwise it returns its argument.
12641 Returns the character whose ordinal value is @var{i}.
12644 Decrements the value in the variable @var{v} by one. Returns the new value.
12646 @item DEC(@var{v},@var{i})
12647 Decrements the value in the variable @var{v} by @var{i}. Returns the
12650 @item EXCL(@var{m},@var{s})
12651 Removes the element @var{m} from the set @var{s}. Returns the new
12654 @item FLOAT(@var{i})
12655 Returns the floating point equivalent of the integer @var{i}.
12657 @item HIGH(@var{a})
12658 Returns the index of the last member of @var{a}.
12661 Increments the value in the variable @var{v} by one. Returns the new value.
12663 @item INC(@var{v},@var{i})
12664 Increments the value in the variable @var{v} by @var{i}. Returns the
12667 @item INCL(@var{m},@var{s})
12668 Adds the element @var{m} to the set @var{s} if it is not already
12669 there. Returns the new set.
12672 Returns the maximum value of the type @var{t}.
12675 Returns the minimum value of the type @var{t}.
12678 Returns boolean TRUE if @var{i} is an odd number.
12681 Returns the ordinal value of its argument. For example, the ordinal
12682 value of a character is its @sc{ascii} value (on machines supporting the
12683 @sc{ascii} character set). @var{x} must be of an ordered type, which include
12684 integral, character and enumerated types.
12686 @item SIZE(@var{x})
12687 Returns the size of its argument. @var{x} can be a variable or a type.
12689 @item TRUNC(@var{r})
12690 Returns the integral part of @var{r}.
12692 @item TSIZE(@var{x})
12693 Returns the size of its argument. @var{x} can be a variable or a type.
12695 @item VAL(@var{t},@var{i})
12696 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12700 @emph{Warning:} Sets and their operations are not yet supported, so
12701 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12705 @cindex Modula-2 constants
12707 @subsubsection Constants
12709 @value{GDBN} allows you to express the constants of Modula-2 in the following
12715 Integer constants are simply a sequence of digits. When used in an
12716 expression, a constant is interpreted to be type-compatible with the
12717 rest of the expression. Hexadecimal integers are specified by a
12718 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12721 Floating point constants appear as a sequence of digits, followed by a
12722 decimal point and another sequence of digits. An optional exponent can
12723 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12724 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12725 digits of the floating point constant must be valid decimal (base 10)
12729 Character constants consist of a single character enclosed by a pair of
12730 like quotes, either single (@code{'}) or double (@code{"}). They may
12731 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12732 followed by a @samp{C}.
12735 String constants consist of a sequence of characters enclosed by a
12736 pair of like quotes, either single (@code{'}) or double (@code{"}).
12737 Escape sequences in the style of C are also allowed. @xref{C
12738 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12742 Enumerated constants consist of an enumerated identifier.
12745 Boolean constants consist of the identifiers @code{TRUE} and
12749 Pointer constants consist of integral values only.
12752 Set constants are not yet supported.
12756 @subsubsection Modula-2 Types
12757 @cindex Modula-2 types
12759 Currently @value{GDBN} can print the following data types in Modula-2
12760 syntax: array types, record types, set types, pointer types, procedure
12761 types, enumerated types, subrange types and base types. You can also
12762 print the contents of variables declared using these type.
12763 This section gives a number of simple source code examples together with
12764 sample @value{GDBN} sessions.
12766 The first example contains the following section of code:
12775 and you can request @value{GDBN} to interrogate the type and value of
12776 @code{r} and @code{s}.
12779 (@value{GDBP}) print s
12781 (@value{GDBP}) ptype s
12783 (@value{GDBP}) print r
12785 (@value{GDBP}) ptype r
12790 Likewise if your source code declares @code{s} as:
12794 s: SET ['A'..'Z'] ;
12798 then you may query the type of @code{s} by:
12801 (@value{GDBP}) ptype s
12802 type = SET ['A'..'Z']
12806 Note that at present you cannot interactively manipulate set
12807 expressions using the debugger.
12809 The following example shows how you might declare an array in Modula-2
12810 and how you can interact with @value{GDBN} to print its type and contents:
12814 s: ARRAY [-10..10] OF CHAR ;
12818 (@value{GDBP}) ptype s
12819 ARRAY [-10..10] OF CHAR
12822 Note that the array handling is not yet complete and although the type
12823 is printed correctly, expression handling still assumes that all
12824 arrays have a lower bound of zero and not @code{-10} as in the example
12827 Here are some more type related Modula-2 examples:
12831 colour = (blue, red, yellow, green) ;
12832 t = [blue..yellow] ;
12840 The @value{GDBN} interaction shows how you can query the data type
12841 and value of a variable.
12844 (@value{GDBP}) print s
12846 (@value{GDBP}) ptype t
12847 type = [blue..yellow]
12851 In this example a Modula-2 array is declared and its contents
12852 displayed. Observe that the contents are written in the same way as
12853 their @code{C} counterparts.
12857 s: ARRAY [1..5] OF CARDINAL ;
12863 (@value{GDBP}) print s
12864 $1 = @{1, 0, 0, 0, 0@}
12865 (@value{GDBP}) ptype s
12866 type = ARRAY [1..5] OF CARDINAL
12869 The Modula-2 language interface to @value{GDBN} also understands
12870 pointer types as shown in this example:
12874 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12881 and you can request that @value{GDBN} describes the type of @code{s}.
12884 (@value{GDBP}) ptype s
12885 type = POINTER TO ARRAY [1..5] OF CARDINAL
12888 @value{GDBN} handles compound types as we can see in this example.
12889 Here we combine array types, record types, pointer types and subrange
12900 myarray = ARRAY myrange OF CARDINAL ;
12901 myrange = [-2..2] ;
12903 s: POINTER TO ARRAY myrange OF foo ;
12907 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12911 (@value{GDBP}) ptype s
12912 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12915 f3 : ARRAY [-2..2] OF CARDINAL;
12920 @subsubsection Modula-2 Defaults
12921 @cindex Modula-2 defaults
12923 If type and range checking are set automatically by @value{GDBN}, they
12924 both default to @code{on} whenever the working language changes to
12925 Modula-2. This happens regardless of whether you or @value{GDBN}
12926 selected the working language.
12928 If you allow @value{GDBN} to set the language automatically, then entering
12929 code compiled from a file whose name ends with @file{.mod} sets the
12930 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12931 Infer the Source Language}, for further details.
12934 @subsubsection Deviations from Standard Modula-2
12935 @cindex Modula-2, deviations from
12937 A few changes have been made to make Modula-2 programs easier to debug.
12938 This is done primarily via loosening its type strictness:
12942 Unlike in standard Modula-2, pointer constants can be formed by
12943 integers. This allows you to modify pointer variables during
12944 debugging. (In standard Modula-2, the actual address contained in a
12945 pointer variable is hidden from you; it can only be modified
12946 through direct assignment to another pointer variable or expression that
12947 returned a pointer.)
12950 C escape sequences can be used in strings and characters to represent
12951 non-printable characters. @value{GDBN} prints out strings with these
12952 escape sequences embedded. Single non-printable characters are
12953 printed using the @samp{CHR(@var{nnn})} format.
12956 The assignment operator (@code{:=}) returns the value of its right-hand
12960 All built-in procedures both modify @emph{and} return their argument.
12964 @subsubsection Modula-2 Type and Range Checks
12965 @cindex Modula-2 checks
12968 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12971 @c FIXME remove warning when type/range checks added
12973 @value{GDBN} considers two Modula-2 variables type equivalent if:
12977 They are of types that have been declared equivalent via a @code{TYPE
12978 @var{t1} = @var{t2}} statement
12981 They have been declared on the same line. (Note: This is true of the
12982 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
12985 As long as type checking is enabled, any attempt to combine variables
12986 whose types are not equivalent is an error.
12988 Range checking is done on all mathematical operations, assignment, array
12989 index bounds, and all built-in functions and procedures.
12992 @subsubsection The Scope Operators @code{::} and @code{.}
12994 @cindex @code{.}, Modula-2 scope operator
12995 @cindex colon, doubled as scope operator
12997 @vindex colon-colon@r{, in Modula-2}
12998 @c Info cannot handle :: but TeX can.
13001 @vindex ::@r{, in Modula-2}
13004 There are a few subtle differences between the Modula-2 scope operator
13005 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13010 @var{module} . @var{id}
13011 @var{scope} :: @var{id}
13015 where @var{scope} is the name of a module or a procedure,
13016 @var{module} the name of a module, and @var{id} is any declared
13017 identifier within your program, except another module.
13019 Using the @code{::} operator makes @value{GDBN} search the scope
13020 specified by @var{scope} for the identifier @var{id}. If it is not
13021 found in the specified scope, then @value{GDBN} searches all scopes
13022 enclosing the one specified by @var{scope}.
13024 Using the @code{.} operator makes @value{GDBN} search the current scope for
13025 the identifier specified by @var{id} that was imported from the
13026 definition module specified by @var{module}. With this operator, it is
13027 an error if the identifier @var{id} was not imported from definition
13028 module @var{module}, or if @var{id} is not an identifier in
13032 @subsubsection @value{GDBN} and Modula-2
13034 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13035 Five subcommands of @code{set print} and @code{show print} apply
13036 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13037 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13038 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13039 analogue in Modula-2.
13041 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13042 with any language, is not useful with Modula-2. Its
13043 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13044 created in Modula-2 as they can in C or C@t{++}. However, because an
13045 address can be specified by an integral constant, the construct
13046 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13048 @cindex @code{#} in Modula-2
13049 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13050 interpreted as the beginning of a comment. Use @code{<>} instead.
13056 The extensions made to @value{GDBN} for Ada only support
13057 output from the @sc{gnu} Ada (GNAT) compiler.
13058 Other Ada compilers are not currently supported, and
13059 attempting to debug executables produced by them is most likely
13063 @cindex expressions in Ada
13065 * Ada Mode Intro:: General remarks on the Ada syntax
13066 and semantics supported by Ada mode
13068 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13069 * Additions to Ada:: Extensions of the Ada expression syntax.
13070 * Stopping Before Main Program:: Debugging the program during elaboration.
13071 * Ada Tasks:: Listing and setting breakpoints in tasks.
13072 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13073 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13075 * Ada Glitches:: Known peculiarities of Ada mode.
13078 @node Ada Mode Intro
13079 @subsubsection Introduction
13080 @cindex Ada mode, general
13082 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13083 syntax, with some extensions.
13084 The philosophy behind the design of this subset is
13088 That @value{GDBN} should provide basic literals and access to operations for
13089 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13090 leaving more sophisticated computations to subprograms written into the
13091 program (which therefore may be called from @value{GDBN}).
13094 That type safety and strict adherence to Ada language restrictions
13095 are not particularly important to the @value{GDBN} user.
13098 That brevity is important to the @value{GDBN} user.
13101 Thus, for brevity, the debugger acts as if all names declared in
13102 user-written packages are directly visible, even if they are not visible
13103 according to Ada rules, thus making it unnecessary to fully qualify most
13104 names with their packages, regardless of context. Where this causes
13105 ambiguity, @value{GDBN} asks the user's intent.
13107 The debugger will start in Ada mode if it detects an Ada main program.
13108 As for other languages, it will enter Ada mode when stopped in a program that
13109 was translated from an Ada source file.
13111 While in Ada mode, you may use `@t{--}' for comments. This is useful
13112 mostly for documenting command files. The standard @value{GDBN} comment
13113 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13114 middle (to allow based literals).
13116 The debugger supports limited overloading. Given a subprogram call in which
13117 the function symbol has multiple definitions, it will use the number of
13118 actual parameters and some information about their types to attempt to narrow
13119 the set of definitions. It also makes very limited use of context, preferring
13120 procedures to functions in the context of the @code{call} command, and
13121 functions to procedures elsewhere.
13123 @node Omissions from Ada
13124 @subsubsection Omissions from Ada
13125 @cindex Ada, omissions from
13127 Here are the notable omissions from the subset:
13131 Only a subset of the attributes are supported:
13135 @t{'First}, @t{'Last}, and @t{'Length}
13136 on array objects (not on types and subtypes).
13139 @t{'Min} and @t{'Max}.
13142 @t{'Pos} and @t{'Val}.
13148 @t{'Range} on array objects (not subtypes), but only as the right
13149 operand of the membership (@code{in}) operator.
13152 @t{'Access}, @t{'Unchecked_Access}, and
13153 @t{'Unrestricted_Access} (a GNAT extension).
13161 @code{Characters.Latin_1} are not available and
13162 concatenation is not implemented. Thus, escape characters in strings are
13163 not currently available.
13166 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13167 equality of representations. They will generally work correctly
13168 for strings and arrays whose elements have integer or enumeration types.
13169 They may not work correctly for arrays whose element
13170 types have user-defined equality, for arrays of real values
13171 (in particular, IEEE-conformant floating point, because of negative
13172 zeroes and NaNs), and for arrays whose elements contain unused bits with
13173 indeterminate values.
13176 The other component-by-component array operations (@code{and}, @code{or},
13177 @code{xor}, @code{not}, and relational tests other than equality)
13178 are not implemented.
13181 @cindex array aggregates (Ada)
13182 @cindex record aggregates (Ada)
13183 @cindex aggregates (Ada)
13184 There is limited support for array and record aggregates. They are
13185 permitted only on the right sides of assignments, as in these examples:
13188 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13189 (@value{GDBP}) set An_Array := (1, others => 0)
13190 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13191 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13192 (@value{GDBP}) set A_Record := (1, "Peter", True);
13193 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13197 discriminant's value by assigning an aggregate has an
13198 undefined effect if that discriminant is used within the record.
13199 However, you can first modify discriminants by directly assigning to
13200 them (which normally would not be allowed in Ada), and then performing an
13201 aggregate assignment. For example, given a variable @code{A_Rec}
13202 declared to have a type such as:
13205 type Rec (Len : Small_Integer := 0) is record
13207 Vals : IntArray (1 .. Len);
13211 you can assign a value with a different size of @code{Vals} with two
13215 (@value{GDBP}) set A_Rec.Len := 4
13216 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13219 As this example also illustrates, @value{GDBN} is very loose about the usual
13220 rules concerning aggregates. You may leave out some of the
13221 components of an array or record aggregate (such as the @code{Len}
13222 component in the assignment to @code{A_Rec} above); they will retain their
13223 original values upon assignment. You may freely use dynamic values as
13224 indices in component associations. You may even use overlapping or
13225 redundant component associations, although which component values are
13226 assigned in such cases is not defined.
13229 Calls to dispatching subprograms are not implemented.
13232 The overloading algorithm is much more limited (i.e., less selective)
13233 than that of real Ada. It makes only limited use of the context in
13234 which a subexpression appears to resolve its meaning, and it is much
13235 looser in its rules for allowing type matches. As a result, some
13236 function calls will be ambiguous, and the user will be asked to choose
13237 the proper resolution.
13240 The @code{new} operator is not implemented.
13243 Entry calls are not implemented.
13246 Aside from printing, arithmetic operations on the native VAX floating-point
13247 formats are not supported.
13250 It is not possible to slice a packed array.
13253 The names @code{True} and @code{False}, when not part of a qualified name,
13254 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13256 Should your program
13257 redefine these names in a package or procedure (at best a dubious practice),
13258 you will have to use fully qualified names to access their new definitions.
13261 @node Additions to Ada
13262 @subsubsection Additions to Ada
13263 @cindex Ada, deviations from
13265 As it does for other languages, @value{GDBN} makes certain generic
13266 extensions to Ada (@pxref{Expressions}):
13270 If the expression @var{E} is a variable residing in memory (typically
13271 a local variable or array element) and @var{N} is a positive integer,
13272 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13273 @var{N}-1 adjacent variables following it in memory as an array. In
13274 Ada, this operator is generally not necessary, since its prime use is
13275 in displaying parts of an array, and slicing will usually do this in
13276 Ada. However, there are occasional uses when debugging programs in
13277 which certain debugging information has been optimized away.
13280 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13281 appears in function or file @var{B}.'' When @var{B} is a file name,
13282 you must typically surround it in single quotes.
13285 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13286 @var{type} that appears at address @var{addr}.''
13289 A name starting with @samp{$} is a convenience variable
13290 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13293 In addition, @value{GDBN} provides a few other shortcuts and outright
13294 additions specific to Ada:
13298 The assignment statement is allowed as an expression, returning
13299 its right-hand operand as its value. Thus, you may enter
13302 (@value{GDBP}) set x := y + 3
13303 (@value{GDBP}) print A(tmp := y + 1)
13307 The semicolon is allowed as an ``operator,'' returning as its value
13308 the value of its right-hand operand.
13309 This allows, for example,
13310 complex conditional breaks:
13313 (@value{GDBP}) break f
13314 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13318 Rather than use catenation and symbolic character names to introduce special
13319 characters into strings, one may instead use a special bracket notation,
13320 which is also used to print strings. A sequence of characters of the form
13321 @samp{["@var{XX}"]} within a string or character literal denotes the
13322 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13323 sequence of characters @samp{["""]} also denotes a single quotation mark
13324 in strings. For example,
13326 "One line.["0a"]Next line.["0a"]"
13329 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13333 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13334 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13338 (@value{GDBP}) print 'max(x, y)
13342 When printing arrays, @value{GDBN} uses positional notation when the
13343 array has a lower bound of 1, and uses a modified named notation otherwise.
13344 For example, a one-dimensional array of three integers with a lower bound
13345 of 3 might print as
13352 That is, in contrast to valid Ada, only the first component has a @code{=>}
13356 You may abbreviate attributes in expressions with any unique,
13357 multi-character subsequence of
13358 their names (an exact match gets preference).
13359 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13360 in place of @t{a'length}.
13363 @cindex quoting Ada internal identifiers
13364 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13365 to lower case. The GNAT compiler uses upper-case characters for
13366 some of its internal identifiers, which are normally of no interest to users.
13367 For the rare occasions when you actually have to look at them,
13368 enclose them in angle brackets to avoid the lower-case mapping.
13371 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13375 Printing an object of class-wide type or dereferencing an
13376 access-to-class-wide value will display all the components of the object's
13377 specific type (as indicated by its run-time tag). Likewise, component
13378 selection on such a value will operate on the specific type of the
13383 @node Stopping Before Main Program
13384 @subsubsection Stopping at the Very Beginning
13386 @cindex breakpointing Ada elaboration code
13387 It is sometimes necessary to debug the program during elaboration, and
13388 before reaching the main procedure.
13389 As defined in the Ada Reference
13390 Manual, the elaboration code is invoked from a procedure called
13391 @code{adainit}. To run your program up to the beginning of
13392 elaboration, simply use the following two commands:
13393 @code{tbreak adainit} and @code{run}.
13396 @subsubsection Extensions for Ada Tasks
13397 @cindex Ada, tasking
13399 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13400 @value{GDBN} provides the following task-related commands:
13405 This command shows a list of current Ada tasks, as in the following example:
13412 (@value{GDBP}) info tasks
13413 ID TID P-ID Pri State Name
13414 1 8088000 0 15 Child Activation Wait main_task
13415 2 80a4000 1 15 Accept Statement b
13416 3 809a800 1 15 Child Activation Wait a
13417 * 4 80ae800 3 15 Runnable c
13422 In this listing, the asterisk before the last task indicates it to be the
13423 task currently being inspected.
13427 Represents @value{GDBN}'s internal task number.
13433 The parent's task ID (@value{GDBN}'s internal task number).
13436 The base priority of the task.
13439 Current state of the task.
13443 The task has been created but has not been activated. It cannot be
13447 The task is not blocked for any reason known to Ada. (It may be waiting
13448 for a mutex, though.) It is conceptually "executing" in normal mode.
13451 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13452 that were waiting on terminate alternatives have been awakened and have
13453 terminated themselves.
13455 @item Child Activation Wait
13456 The task is waiting for created tasks to complete activation.
13458 @item Accept Statement
13459 The task is waiting on an accept or selective wait statement.
13461 @item Waiting on entry call
13462 The task is waiting on an entry call.
13464 @item Async Select Wait
13465 The task is waiting to start the abortable part of an asynchronous
13469 The task is waiting on a select statement with only a delay
13472 @item Child Termination Wait
13473 The task is sleeping having completed a master within itself, and is
13474 waiting for the tasks dependent on that master to become terminated or
13475 waiting on a terminate Phase.
13477 @item Wait Child in Term Alt
13478 The task is sleeping waiting for tasks on terminate alternatives to
13479 finish terminating.
13481 @item Accepting RV with @var{taskno}
13482 The task is accepting a rendez-vous with the task @var{taskno}.
13486 Name of the task in the program.
13490 @kindex info task @var{taskno}
13491 @item info task @var{taskno}
13492 This command shows detailled informations on the specified task, as in
13493 the following example:
13498 (@value{GDBP}) info tasks
13499 ID TID P-ID Pri State Name
13500 1 8077880 0 15 Child Activation Wait main_task
13501 * 2 807c468 1 15 Runnable task_1
13502 (@value{GDBP}) info task 2
13503 Ada Task: 0x807c468
13506 Parent: 1 (main_task)
13512 @kindex task@r{ (Ada)}
13513 @cindex current Ada task ID
13514 This command prints the ID of the current task.
13520 (@value{GDBP}) info tasks
13521 ID TID P-ID Pri State Name
13522 1 8077870 0 15 Child Activation Wait main_task
13523 * 2 807c458 1 15 Runnable t
13524 (@value{GDBP}) task
13525 [Current task is 2]
13528 @item task @var{taskno}
13529 @cindex Ada task switching
13530 This command is like the @code{thread @var{threadno}}
13531 command (@pxref{Threads}). It switches the context of debugging
13532 from the current task to the given task.
13538 (@value{GDBP}) info tasks
13539 ID TID P-ID Pri State Name
13540 1 8077870 0 15 Child Activation Wait main_task
13541 * 2 807c458 1 15 Runnable t
13542 (@value{GDBP}) task 1
13543 [Switching to task 1]
13544 #0 0x8067726 in pthread_cond_wait ()
13546 #0 0x8067726 in pthread_cond_wait ()
13547 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
13548 #2 0x805cb63 in system.task_primitives.operations.sleep ()
13549 #3 0x806153e in system.tasking.stages.activate_tasks ()
13550 #4 0x804aacc in un () at un.adb:5
13553 @item break @var{linespec} task @var{taskno}
13554 @itemx break @var{linespec} task @var{taskno} if @dots{}
13555 @cindex breakpoints and tasks, in Ada
13556 @cindex task breakpoints, in Ada
13557 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
13558 These commands are like the @code{break @dots{} thread @dots{}}
13559 command (@pxref{Thread Stops}).
13560 @var{linespec} specifies source lines, as described
13561 in @ref{Specify Location}.
13563 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
13564 to specify that you only want @value{GDBN} to stop the program when a
13565 particular Ada task reaches this breakpoint. @var{taskno} is one of the
13566 numeric task identifiers assigned by @value{GDBN}, shown in the first
13567 column of the @samp{info tasks} display.
13569 If you do not specify @samp{task @var{taskno}} when you set a
13570 breakpoint, the breakpoint applies to @emph{all} tasks of your
13573 You can use the @code{task} qualifier on conditional breakpoints as
13574 well; in this case, place @samp{task @var{taskno}} before the
13575 breakpoint condition (before the @code{if}).
13583 (@value{GDBP}) info tasks
13584 ID TID P-ID Pri State Name
13585 1 140022020 0 15 Child Activation Wait main_task
13586 2 140045060 1 15 Accept/Select Wait t2
13587 3 140044840 1 15 Runnable t1
13588 * 4 140056040 1 15 Runnable t3
13589 (@value{GDBP}) b 15 task 2
13590 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
13591 (@value{GDBP}) cont
13596 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13598 (@value{GDBP}) info tasks
13599 ID TID P-ID Pri State Name
13600 1 140022020 0 15 Child Activation Wait main_task
13601 * 2 140045060 1 15 Runnable t2
13602 3 140044840 1 15 Runnable t1
13603 4 140056040 1 15 Delay Sleep t3
13607 @node Ada Tasks and Core Files
13608 @subsubsection Tasking Support when Debugging Core Files
13609 @cindex Ada tasking and core file debugging
13611 When inspecting a core file, as opposed to debugging a live program,
13612 tasking support may be limited or even unavailable, depending on
13613 the platform being used.
13614 For instance, on x86-linux, the list of tasks is available, but task
13615 switching is not supported. On Tru64, however, task switching will work
13618 On certain platforms, including Tru64, the debugger needs to perform some
13619 memory writes in order to provide Ada tasking support. When inspecting
13620 a core file, this means that the core file must be opened with read-write
13621 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13622 Under these circumstances, you should make a backup copy of the core
13623 file before inspecting it with @value{GDBN}.
13625 @node Ravenscar Profile
13626 @subsubsection Tasking Support when using the Ravenscar Profile
13627 @cindex Ravenscar Profile
13629 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
13630 specifically designed for systems with safety-critical real-time
13634 @kindex set ravenscar task-switching on
13635 @cindex task switching with program using Ravenscar Profile
13636 @item set ravenscar task-switching on
13637 Allows task switching when debugging a program that uses the Ravenscar
13638 Profile. This is the default.
13640 @kindex set ravenscar task-switching off
13641 @item set ravenscar task-switching off
13642 Turn off task switching when debugging a program that uses the Ravenscar
13643 Profile. This is mostly intended to disable the code that adds support
13644 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
13645 the Ravenscar runtime is preventing @value{GDBN} from working properly.
13646 To be effective, this command should be run before the program is started.
13648 @kindex show ravenscar task-switching
13649 @item show ravenscar task-switching
13650 Show whether it is possible to switch from task to task in a program
13651 using the Ravenscar Profile.
13656 @subsubsection Known Peculiarities of Ada Mode
13657 @cindex Ada, problems
13659 Besides the omissions listed previously (@pxref{Omissions from Ada}),
13660 we know of several problems with and limitations of Ada mode in
13662 some of which will be fixed with planned future releases of the debugger
13663 and the GNU Ada compiler.
13667 Static constants that the compiler chooses not to materialize as objects in
13668 storage are invisible to the debugger.
13671 Named parameter associations in function argument lists are ignored (the
13672 argument lists are treated as positional).
13675 Many useful library packages are currently invisible to the debugger.
13678 Fixed-point arithmetic, conversions, input, and output is carried out using
13679 floating-point arithmetic, and may give results that only approximate those on
13683 The GNAT compiler never generates the prefix @code{Standard} for any of
13684 the standard symbols defined by the Ada language. @value{GDBN} knows about
13685 this: it will strip the prefix from names when you use it, and will never
13686 look for a name you have so qualified among local symbols, nor match against
13687 symbols in other packages or subprograms. If you have
13688 defined entities anywhere in your program other than parameters and
13689 local variables whose simple names match names in @code{Standard},
13690 GNAT's lack of qualification here can cause confusion. When this happens,
13691 you can usually resolve the confusion
13692 by qualifying the problematic names with package
13693 @code{Standard} explicitly.
13696 Older versions of the compiler sometimes generate erroneous debugging
13697 information, resulting in the debugger incorrectly printing the value
13698 of affected entities. In some cases, the debugger is able to work
13699 around an issue automatically. In other cases, the debugger is able
13700 to work around the issue, but the work-around has to be specifically
13703 @kindex set ada trust-PAD-over-XVS
13704 @kindex show ada trust-PAD-over-XVS
13707 @item set ada trust-PAD-over-XVS on
13708 Configure GDB to strictly follow the GNAT encoding when computing the
13709 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
13710 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
13711 a complete description of the encoding used by the GNAT compiler).
13712 This is the default.
13714 @item set ada trust-PAD-over-XVS off
13715 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
13716 sometimes prints the wrong value for certain entities, changing @code{ada
13717 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
13718 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
13719 @code{off}, but this incurs a slight performance penalty, so it is
13720 recommended to leave this setting to @code{on} unless necessary.
13724 @node Unsupported Languages
13725 @section Unsupported Languages
13727 @cindex unsupported languages
13728 @cindex minimal language
13729 In addition to the other fully-supported programming languages,
13730 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
13731 It does not represent a real programming language, but provides a set
13732 of capabilities close to what the C or assembly languages provide.
13733 This should allow most simple operations to be performed while debugging
13734 an application that uses a language currently not supported by @value{GDBN}.
13736 If the language is set to @code{auto}, @value{GDBN} will automatically
13737 select this language if the current frame corresponds to an unsupported
13741 @chapter Examining the Symbol Table
13743 The commands described in this chapter allow you to inquire about the
13744 symbols (names of variables, functions and types) defined in your
13745 program. This information is inherent in the text of your program and
13746 does not change as your program executes. @value{GDBN} finds it in your
13747 program's symbol table, in the file indicated when you started @value{GDBN}
13748 (@pxref{File Options, ,Choosing Files}), or by one of the
13749 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13751 @cindex symbol names
13752 @cindex names of symbols
13753 @cindex quoting names
13754 Occasionally, you may need to refer to symbols that contain unusual
13755 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13756 most frequent case is in referring to static variables in other
13757 source files (@pxref{Variables,,Program Variables}). File names
13758 are recorded in object files as debugging symbols, but @value{GDBN} would
13759 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13760 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13761 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13768 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13771 @cindex case-insensitive symbol names
13772 @cindex case sensitivity in symbol names
13773 @kindex set case-sensitive
13774 @item set case-sensitive on
13775 @itemx set case-sensitive off
13776 @itemx set case-sensitive auto
13777 Normally, when @value{GDBN} looks up symbols, it matches their names
13778 with case sensitivity determined by the current source language.
13779 Occasionally, you may wish to control that. The command @code{set
13780 case-sensitive} lets you do that by specifying @code{on} for
13781 case-sensitive matches or @code{off} for case-insensitive ones. If
13782 you specify @code{auto}, case sensitivity is reset to the default
13783 suitable for the source language. The default is case-sensitive
13784 matches for all languages except for Fortran, for which the default is
13785 case-insensitive matches.
13787 @kindex show case-sensitive
13788 @item show case-sensitive
13789 This command shows the current setting of case sensitivity for symbols
13792 @kindex info address
13793 @cindex address of a symbol
13794 @item info address @var{symbol}
13795 Describe where the data for @var{symbol} is stored. For a register
13796 variable, this says which register it is kept in. For a non-register
13797 local variable, this prints the stack-frame offset at which the variable
13800 Note the contrast with @samp{print &@var{symbol}}, which does not work
13801 at all for a register variable, and for a stack local variable prints
13802 the exact address of the current instantiation of the variable.
13804 @kindex info symbol
13805 @cindex symbol from address
13806 @cindex closest symbol and offset for an address
13807 @item info symbol @var{addr}
13808 Print the name of a symbol which is stored at the address @var{addr}.
13809 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13810 nearest symbol and an offset from it:
13813 (@value{GDBP}) info symbol 0x54320
13814 _initialize_vx + 396 in section .text
13818 This is the opposite of the @code{info address} command. You can use
13819 it to find out the name of a variable or a function given its address.
13821 For dynamically linked executables, the name of executable or shared
13822 library containing the symbol is also printed:
13825 (@value{GDBP}) info symbol 0x400225
13826 _start + 5 in section .text of /tmp/a.out
13827 (@value{GDBP}) info symbol 0x2aaaac2811cf
13828 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13832 @item whatis [@var{arg}]
13833 Print the data type of @var{arg}, which can be either an expression or
13834 a data type. With no argument, print the data type of @code{$}, the
13835 last value in the value history. If @var{arg} is an expression, it is
13836 not actually evaluated, and any side-effecting operations (such as
13837 assignments or function calls) inside it do not take place. If
13838 @var{arg} is a type name, it may be the name of a type or typedef, or
13839 for C code it may have the form @samp{class @var{class-name}},
13840 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13841 @samp{enum @var{enum-tag}}.
13842 @xref{Expressions, ,Expressions}.
13845 @item ptype [@var{arg}]
13846 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13847 detailed description of the type, instead of just the name of the type.
13848 @xref{Expressions, ,Expressions}.
13850 For example, for this variable declaration:
13853 struct complex @{double real; double imag;@} v;
13857 the two commands give this output:
13861 (@value{GDBP}) whatis v
13862 type = struct complex
13863 (@value{GDBP}) ptype v
13864 type = struct complex @{
13872 As with @code{whatis}, using @code{ptype} without an argument refers to
13873 the type of @code{$}, the last value in the value history.
13875 @cindex incomplete type
13876 Sometimes, programs use opaque data types or incomplete specifications
13877 of complex data structure. If the debug information included in the
13878 program does not allow @value{GDBN} to display a full declaration of
13879 the data type, it will say @samp{<incomplete type>}. For example,
13880 given these declarations:
13884 struct foo *fooptr;
13888 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13891 (@value{GDBP}) ptype foo
13892 $1 = <incomplete type>
13896 ``Incomplete type'' is C terminology for data types that are not
13897 completely specified.
13900 @item info types @var{regexp}
13902 Print a brief description of all types whose names match the regular
13903 expression @var{regexp} (or all types in your program, if you supply
13904 no argument). Each complete typename is matched as though it were a
13905 complete line; thus, @samp{i type value} gives information on all
13906 types in your program whose names include the string @code{value}, but
13907 @samp{i type ^value$} gives information only on types whose complete
13908 name is @code{value}.
13910 This command differs from @code{ptype} in two ways: first, like
13911 @code{whatis}, it does not print a detailed description; second, it
13912 lists all source files where a type is defined.
13915 @cindex local variables
13916 @item info scope @var{location}
13917 List all the variables local to a particular scope. This command
13918 accepts a @var{location} argument---a function name, a source line, or
13919 an address preceded by a @samp{*}, and prints all the variables local
13920 to the scope defined by that location. (@xref{Specify Location}, for
13921 details about supported forms of @var{location}.) For example:
13924 (@value{GDBP}) @b{info scope command_line_handler}
13925 Scope for command_line_handler:
13926 Symbol rl is an argument at stack/frame offset 8, length 4.
13927 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13928 Symbol linelength is in static storage at address 0x150a1c, length 4.
13929 Symbol p is a local variable in register $esi, length 4.
13930 Symbol p1 is a local variable in register $ebx, length 4.
13931 Symbol nline is a local variable in register $edx, length 4.
13932 Symbol repeat is a local variable at frame offset -8, length 4.
13936 This command is especially useful for determining what data to collect
13937 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13940 @kindex info source
13942 Show information about the current source file---that is, the source file for
13943 the function containing the current point of execution:
13946 the name of the source file, and the directory containing it,
13948 the directory it was compiled in,
13950 its length, in lines,
13952 which programming language it is written in,
13954 whether the executable includes debugging information for that file, and
13955 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13957 whether the debugging information includes information about
13958 preprocessor macros.
13962 @kindex info sources
13964 Print the names of all source files in your program for which there is
13965 debugging information, organized into two lists: files whose symbols
13966 have already been read, and files whose symbols will be read when needed.
13968 @kindex info functions
13969 @item info functions
13970 Print the names and data types of all defined functions.
13972 @item info functions @var{regexp}
13973 Print the names and data types of all defined functions
13974 whose names contain a match for regular expression @var{regexp}.
13975 Thus, @samp{info fun step} finds all functions whose names
13976 include @code{step}; @samp{info fun ^step} finds those whose names
13977 start with @code{step}. If a function name contains characters
13978 that conflict with the regular expression language (e.g.@:
13979 @samp{operator*()}), they may be quoted with a backslash.
13981 @kindex info variables
13982 @item info variables
13983 Print the names and data types of all variables that are defined
13984 outside of functions (i.e.@: excluding local variables).
13986 @item info variables @var{regexp}
13987 Print the names and data types of all variables (except for local
13988 variables) whose names contain a match for regular expression
13991 @kindex info classes
13992 @cindex Objective-C, classes and selectors
13994 @itemx info classes @var{regexp}
13995 Display all Objective-C classes in your program, or
13996 (with the @var{regexp} argument) all those matching a particular regular
13999 @kindex info selectors
14000 @item info selectors
14001 @itemx info selectors @var{regexp}
14002 Display all Objective-C selectors in your program, or
14003 (with the @var{regexp} argument) all those matching a particular regular
14007 This was never implemented.
14008 @kindex info methods
14010 @itemx info methods @var{regexp}
14011 The @code{info methods} command permits the user to examine all defined
14012 methods within C@t{++} program, or (with the @var{regexp} argument) a
14013 specific set of methods found in the various C@t{++} classes. Many
14014 C@t{++} classes provide a large number of methods. Thus, the output
14015 from the @code{ptype} command can be overwhelming and hard to use. The
14016 @code{info-methods} command filters the methods, printing only those
14017 which match the regular-expression @var{regexp}.
14020 @cindex reloading symbols
14021 Some systems allow individual object files that make up your program to
14022 be replaced without stopping and restarting your program. For example,
14023 in VxWorks you can simply recompile a defective object file and keep on
14024 running. If you are running on one of these systems, you can allow
14025 @value{GDBN} to reload the symbols for automatically relinked modules:
14028 @kindex set symbol-reloading
14029 @item set symbol-reloading on
14030 Replace symbol definitions for the corresponding source file when an
14031 object file with a particular name is seen again.
14033 @item set symbol-reloading off
14034 Do not replace symbol definitions when encountering object files of the
14035 same name more than once. This is the default state; if you are not
14036 running on a system that permits automatic relinking of modules, you
14037 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14038 may discard symbols when linking large programs, that may contain
14039 several modules (from different directories or libraries) with the same
14042 @kindex show symbol-reloading
14043 @item show symbol-reloading
14044 Show the current @code{on} or @code{off} setting.
14047 @cindex opaque data types
14048 @kindex set opaque-type-resolution
14049 @item set opaque-type-resolution on
14050 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14051 declared as a pointer to a @code{struct}, @code{class}, or
14052 @code{union}---for example, @code{struct MyType *}---that is used in one
14053 source file although the full declaration of @code{struct MyType} is in
14054 another source file. The default is on.
14056 A change in the setting of this subcommand will not take effect until
14057 the next time symbols for a file are loaded.
14059 @item set opaque-type-resolution off
14060 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14061 is printed as follows:
14063 @{<no data fields>@}
14066 @kindex show opaque-type-resolution
14067 @item show opaque-type-resolution
14068 Show whether opaque types are resolved or not.
14070 @kindex maint print symbols
14071 @cindex symbol dump
14072 @kindex maint print psymbols
14073 @cindex partial symbol dump
14074 @item maint print symbols @var{filename}
14075 @itemx maint print psymbols @var{filename}
14076 @itemx maint print msymbols @var{filename}
14077 Write a dump of debugging symbol data into the file @var{filename}.
14078 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14079 symbols with debugging data are included. If you use @samp{maint print
14080 symbols}, @value{GDBN} includes all the symbols for which it has already
14081 collected full details: that is, @var{filename} reflects symbols for
14082 only those files whose symbols @value{GDBN} has read. You can use the
14083 command @code{info sources} to find out which files these are. If you
14084 use @samp{maint print psymbols} instead, the dump shows information about
14085 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14086 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14087 @samp{maint print msymbols} dumps just the minimal symbol information
14088 required for each object file from which @value{GDBN} has read some symbols.
14089 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14090 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14092 @kindex maint info symtabs
14093 @kindex maint info psymtabs
14094 @cindex listing @value{GDBN}'s internal symbol tables
14095 @cindex symbol tables, listing @value{GDBN}'s internal
14096 @cindex full symbol tables, listing @value{GDBN}'s internal
14097 @cindex partial symbol tables, listing @value{GDBN}'s internal
14098 @item maint info symtabs @r{[} @var{regexp} @r{]}
14099 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14101 List the @code{struct symtab} or @code{struct partial_symtab}
14102 structures whose names match @var{regexp}. If @var{regexp} is not
14103 given, list them all. The output includes expressions which you can
14104 copy into a @value{GDBN} debugging this one to examine a particular
14105 structure in more detail. For example:
14108 (@value{GDBP}) maint info psymtabs dwarf2read
14109 @{ objfile /home/gnu/build/gdb/gdb
14110 ((struct objfile *) 0x82e69d0)
14111 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14112 ((struct partial_symtab *) 0x8474b10)
14115 text addresses 0x814d3c8 -- 0x8158074
14116 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14117 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14118 dependencies (none)
14121 (@value{GDBP}) maint info symtabs
14125 We see that there is one partial symbol table whose filename contains
14126 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14127 and we see that @value{GDBN} has not read in any symtabs yet at all.
14128 If we set a breakpoint on a function, that will cause @value{GDBN} to
14129 read the symtab for the compilation unit containing that function:
14132 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14133 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14135 (@value{GDBP}) maint info symtabs
14136 @{ objfile /home/gnu/build/gdb/gdb
14137 ((struct objfile *) 0x82e69d0)
14138 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14139 ((struct symtab *) 0x86c1f38)
14142 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14143 linetable ((struct linetable *) 0x8370fa0)
14144 debugformat DWARF 2
14153 @chapter Altering Execution
14155 Once you think you have found an error in your program, you might want to
14156 find out for certain whether correcting the apparent error would lead to
14157 correct results in the rest of the run. You can find the answer by
14158 experiment, using the @value{GDBN} features for altering execution of the
14161 For example, you can store new values into variables or memory
14162 locations, give your program a signal, restart it at a different
14163 address, or even return prematurely from a function.
14166 * Assignment:: Assignment to variables
14167 * Jumping:: Continuing at a different address
14168 * Signaling:: Giving your program a signal
14169 * Returning:: Returning from a function
14170 * Calling:: Calling your program's functions
14171 * Patching:: Patching your program
14175 @section Assignment to Variables
14178 @cindex setting variables
14179 To alter the value of a variable, evaluate an assignment expression.
14180 @xref{Expressions, ,Expressions}. For example,
14187 stores the value 4 into the variable @code{x}, and then prints the
14188 value of the assignment expression (which is 4).
14189 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14190 information on operators in supported languages.
14192 @kindex set variable
14193 @cindex variables, setting
14194 If you are not interested in seeing the value of the assignment, use the
14195 @code{set} command instead of the @code{print} command. @code{set} is
14196 really the same as @code{print} except that the expression's value is
14197 not printed and is not put in the value history (@pxref{Value History,
14198 ,Value History}). The expression is evaluated only for its effects.
14200 If the beginning of the argument string of the @code{set} command
14201 appears identical to a @code{set} subcommand, use the @code{set
14202 variable} command instead of just @code{set}. This command is identical
14203 to @code{set} except for its lack of subcommands. For example, if your
14204 program has a variable @code{width}, you get an error if you try to set
14205 a new value with just @samp{set width=13}, because @value{GDBN} has the
14206 command @code{set width}:
14209 (@value{GDBP}) whatis width
14211 (@value{GDBP}) p width
14213 (@value{GDBP}) set width=47
14214 Invalid syntax in expression.
14218 The invalid expression, of course, is @samp{=47}. In
14219 order to actually set the program's variable @code{width}, use
14222 (@value{GDBP}) set var width=47
14225 Because the @code{set} command has many subcommands that can conflict
14226 with the names of program variables, it is a good idea to use the
14227 @code{set variable} command instead of just @code{set}. For example, if
14228 your program has a variable @code{g}, you run into problems if you try
14229 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14230 the command @code{set gnutarget}, abbreviated @code{set g}:
14234 (@value{GDBP}) whatis g
14238 (@value{GDBP}) set g=4
14242 The program being debugged has been started already.
14243 Start it from the beginning? (y or n) y
14244 Starting program: /home/smith/cc_progs/a.out
14245 "/home/smith/cc_progs/a.out": can't open to read symbols:
14246 Invalid bfd target.
14247 (@value{GDBP}) show g
14248 The current BFD target is "=4".
14253 The program variable @code{g} did not change, and you silently set the
14254 @code{gnutarget} to an invalid value. In order to set the variable
14258 (@value{GDBP}) set var g=4
14261 @value{GDBN} allows more implicit conversions in assignments than C; you can
14262 freely store an integer value into a pointer variable or vice versa,
14263 and you can convert any structure to any other structure that is the
14264 same length or shorter.
14265 @comment FIXME: how do structs align/pad in these conversions?
14266 @comment /doc@cygnus.com 18dec1990
14268 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14269 construct to generate a value of specified type at a specified address
14270 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14271 to memory location @code{0x83040} as an integer (which implies a certain size
14272 and representation in memory), and
14275 set @{int@}0x83040 = 4
14279 stores the value 4 into that memory location.
14282 @section Continuing at a Different Address
14284 Ordinarily, when you continue your program, you do so at the place where
14285 it stopped, with the @code{continue} command. You can instead continue at
14286 an address of your own choosing, with the following commands:
14290 @item jump @var{linespec}
14291 @itemx jump @var{location}
14292 Resume execution at line @var{linespec} or at address given by
14293 @var{location}. Execution stops again immediately if there is a
14294 breakpoint there. @xref{Specify Location}, for a description of the
14295 different forms of @var{linespec} and @var{location}. It is common
14296 practice to use the @code{tbreak} command in conjunction with
14297 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14299 The @code{jump} command does not change the current stack frame, or
14300 the stack pointer, or the contents of any memory location or any
14301 register other than the program counter. If line @var{linespec} is in
14302 a different function from the one currently executing, the results may
14303 be bizarre if the two functions expect different patterns of arguments or
14304 of local variables. For this reason, the @code{jump} command requests
14305 confirmation if the specified line is not in the function currently
14306 executing. However, even bizarre results are predictable if you are
14307 well acquainted with the machine-language code of your program.
14310 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14311 On many systems, you can get much the same effect as the @code{jump}
14312 command by storing a new value into the register @code{$pc}. The
14313 difference is that this does not start your program running; it only
14314 changes the address of where it @emph{will} run when you continue. For
14322 makes the next @code{continue} command or stepping command execute at
14323 address @code{0x485}, rather than at the address where your program stopped.
14324 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14326 The most common occasion to use the @code{jump} command is to back
14327 up---perhaps with more breakpoints set---over a portion of a program
14328 that has already executed, in order to examine its execution in more
14333 @section Giving your Program a Signal
14334 @cindex deliver a signal to a program
14338 @item signal @var{signal}
14339 Resume execution where your program stopped, but immediately give it the
14340 signal @var{signal}. @var{signal} can be the name or the number of a
14341 signal. For example, on many systems @code{signal 2} and @code{signal
14342 SIGINT} are both ways of sending an interrupt signal.
14344 Alternatively, if @var{signal} is zero, continue execution without
14345 giving a signal. This is useful when your program stopped on account of
14346 a signal and would ordinary see the signal when resumed with the
14347 @code{continue} command; @samp{signal 0} causes it to resume without a
14350 @code{signal} does not repeat when you press @key{RET} a second time
14351 after executing the command.
14355 Invoking the @code{signal} command is not the same as invoking the
14356 @code{kill} utility from the shell. Sending a signal with @code{kill}
14357 causes @value{GDBN} to decide what to do with the signal depending on
14358 the signal handling tables (@pxref{Signals}). The @code{signal} command
14359 passes the signal directly to your program.
14363 @section Returning from a Function
14366 @cindex returning from a function
14369 @itemx return @var{expression}
14370 You can cancel execution of a function call with the @code{return}
14371 command. If you give an
14372 @var{expression} argument, its value is used as the function's return
14376 When you use @code{return}, @value{GDBN} discards the selected stack frame
14377 (and all frames within it). You can think of this as making the
14378 discarded frame return prematurely. If you wish to specify a value to
14379 be returned, give that value as the argument to @code{return}.
14381 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14382 Frame}), and any other frames inside of it, leaving its caller as the
14383 innermost remaining frame. That frame becomes selected. The
14384 specified value is stored in the registers used for returning values
14387 The @code{return} command does not resume execution; it leaves the
14388 program stopped in the state that would exist if the function had just
14389 returned. In contrast, the @code{finish} command (@pxref{Continuing
14390 and Stepping, ,Continuing and Stepping}) resumes execution until the
14391 selected stack frame returns naturally.
14393 @value{GDBN} needs to know how the @var{expression} argument should be set for
14394 the inferior. The concrete registers assignment depends on the OS ABI and the
14395 type being returned by the selected stack frame. For example it is common for
14396 OS ABI to return floating point values in FPU registers while integer values in
14397 CPU registers. Still some ABIs return even floating point values in CPU
14398 registers. Larger integer widths (such as @code{long long int}) also have
14399 specific placement rules. @value{GDBN} already knows the OS ABI from its
14400 current target so it needs to find out also the type being returned to make the
14401 assignment into the right register(s).
14403 Normally, the selected stack frame has debug info. @value{GDBN} will always
14404 use the debug info instead of the implicit type of @var{expression} when the
14405 debug info is available. For example, if you type @kbd{return -1}, and the
14406 function in the current stack frame is declared to return a @code{long long
14407 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14408 into a @code{long long int}:
14411 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14413 (@value{GDBP}) return -1
14414 Make func return now? (y or n) y
14415 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
14416 43 printf ("result=%lld\n", func ());
14420 However, if the selected stack frame does not have a debug info, e.g., if the
14421 function was compiled without debug info, @value{GDBN} has to find out the type
14422 to return from user. Specifying a different type by mistake may set the value
14423 in different inferior registers than the caller code expects. For example,
14424 typing @kbd{return -1} with its implicit type @code{int} would set only a part
14425 of a @code{long long int} result for a debug info less function (on 32-bit
14426 architectures). Therefore the user is required to specify the return type by
14427 an appropriate cast explicitly:
14430 Breakpoint 2, 0x0040050b in func ()
14431 (@value{GDBP}) return -1
14432 Return value type not available for selected stack frame.
14433 Please use an explicit cast of the value to return.
14434 (@value{GDBP}) return (long long int) -1
14435 Make selected stack frame return now? (y or n) y
14436 #0 0x00400526 in main ()
14441 @section Calling Program Functions
14444 @cindex calling functions
14445 @cindex inferior functions, calling
14446 @item print @var{expr}
14447 Evaluate the expression @var{expr} and display the resulting value.
14448 @var{expr} may include calls to functions in the program being
14452 @item call @var{expr}
14453 Evaluate the expression @var{expr} without displaying @code{void}
14456 You can use this variant of the @code{print} command if you want to
14457 execute a function from your program that does not return anything
14458 (a.k.a.@: @dfn{a void function}), but without cluttering the output
14459 with @code{void} returned values that @value{GDBN} will otherwise
14460 print. If the result is not void, it is printed and saved in the
14464 It is possible for the function you call via the @code{print} or
14465 @code{call} command to generate a signal (e.g., if there's a bug in
14466 the function, or if you passed it incorrect arguments). What happens
14467 in that case is controlled by the @code{set unwindonsignal} command.
14469 Similarly, with a C@t{++} program it is possible for the function you
14470 call via the @code{print} or @code{call} command to generate an
14471 exception that is not handled due to the constraints of the dummy
14472 frame. In this case, any exception that is raised in the frame, but has
14473 an out-of-frame exception handler will not be found. GDB builds a
14474 dummy-frame for the inferior function call, and the unwinder cannot
14475 seek for exception handlers outside of this dummy-frame. What happens
14476 in that case is controlled by the
14477 @code{set unwind-on-terminating-exception} command.
14480 @item set unwindonsignal
14481 @kindex set unwindonsignal
14482 @cindex unwind stack in called functions
14483 @cindex call dummy stack unwinding
14484 Set unwinding of the stack if a signal is received while in a function
14485 that @value{GDBN} called in the program being debugged. If set to on,
14486 @value{GDBN} unwinds the stack it created for the call and restores
14487 the context to what it was before the call. If set to off (the
14488 default), @value{GDBN} stops in the frame where the signal was
14491 @item show unwindonsignal
14492 @kindex show unwindonsignal
14493 Show the current setting of stack unwinding in the functions called by
14496 @item set unwind-on-terminating-exception
14497 @kindex set unwind-on-terminating-exception
14498 @cindex unwind stack in called functions with unhandled exceptions
14499 @cindex call dummy stack unwinding on unhandled exception.
14500 Set unwinding of the stack if a C@t{++} exception is raised, but left
14501 unhandled while in a function that @value{GDBN} called in the program being
14502 debugged. If set to on (the default), @value{GDBN} unwinds the stack
14503 it created for the call and restores the context to what it was before
14504 the call. If set to off, @value{GDBN} the exception is delivered to
14505 the default C@t{++} exception handler and the inferior terminated.
14507 @item show unwind-on-terminating-exception
14508 @kindex show unwind-on-terminating-exception
14509 Show the current setting of stack unwinding in the functions called by
14514 @cindex weak alias functions
14515 Sometimes, a function you wish to call is actually a @dfn{weak alias}
14516 for another function. In such case, @value{GDBN} might not pick up
14517 the type information, including the types of the function arguments,
14518 which causes @value{GDBN} to call the inferior function incorrectly.
14519 As a result, the called function will function erroneously and may
14520 even crash. A solution to that is to use the name of the aliased
14524 @section Patching Programs
14526 @cindex patching binaries
14527 @cindex writing into executables
14528 @cindex writing into corefiles
14530 By default, @value{GDBN} opens the file containing your program's
14531 executable code (or the corefile) read-only. This prevents accidental
14532 alterations to machine code; but it also prevents you from intentionally
14533 patching your program's binary.
14535 If you'd like to be able to patch the binary, you can specify that
14536 explicitly with the @code{set write} command. For example, you might
14537 want to turn on internal debugging flags, or even to make emergency
14543 @itemx set write off
14544 If you specify @samp{set write on}, @value{GDBN} opens executable and
14545 core files for both reading and writing; if you specify @kbd{set write
14546 off} (the default), @value{GDBN} opens them read-only.
14548 If you have already loaded a file, you must load it again (using the
14549 @code{exec-file} or @code{core-file} command) after changing @code{set
14550 write}, for your new setting to take effect.
14554 Display whether executable files and core files are opened for writing
14555 as well as reading.
14559 @chapter @value{GDBN} Files
14561 @value{GDBN} needs to know the file name of the program to be debugged,
14562 both in order to read its symbol table and in order to start your
14563 program. To debug a core dump of a previous run, you must also tell
14564 @value{GDBN} the name of the core dump file.
14567 * Files:: Commands to specify files
14568 * Separate Debug Files:: Debugging information in separate files
14569 * Index Files:: Index files speed up GDB
14570 * Symbol Errors:: Errors reading symbol files
14571 * Data Files:: GDB data files
14575 @section Commands to Specify Files
14577 @cindex symbol table
14578 @cindex core dump file
14580 You may want to specify executable and core dump file names. The usual
14581 way to do this is at start-up time, using the arguments to
14582 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
14583 Out of @value{GDBN}}).
14585 Occasionally it is necessary to change to a different file during a
14586 @value{GDBN} session. Or you may run @value{GDBN} and forget to
14587 specify a file you want to use. Or you are debugging a remote target
14588 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
14589 Program}). In these situations the @value{GDBN} commands to specify
14590 new files are useful.
14593 @cindex executable file
14595 @item file @var{filename}
14596 Use @var{filename} as the program to be debugged. It is read for its
14597 symbols and for the contents of pure memory. It is also the program
14598 executed when you use the @code{run} command. If you do not specify a
14599 directory and the file is not found in the @value{GDBN} working directory,
14600 @value{GDBN} uses the environment variable @code{PATH} as a list of
14601 directories to search, just as the shell does when looking for a program
14602 to run. You can change the value of this variable, for both @value{GDBN}
14603 and your program, using the @code{path} command.
14605 @cindex unlinked object files
14606 @cindex patching object files
14607 You can load unlinked object @file{.o} files into @value{GDBN} using
14608 the @code{file} command. You will not be able to ``run'' an object
14609 file, but you can disassemble functions and inspect variables. Also,
14610 if the underlying BFD functionality supports it, you could use
14611 @kbd{gdb -write} to patch object files using this technique. Note
14612 that @value{GDBN} can neither interpret nor modify relocations in this
14613 case, so branches and some initialized variables will appear to go to
14614 the wrong place. But this feature is still handy from time to time.
14617 @code{file} with no argument makes @value{GDBN} discard any information it
14618 has on both executable file and the symbol table.
14621 @item exec-file @r{[} @var{filename} @r{]}
14622 Specify that the program to be run (but not the symbol table) is found
14623 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
14624 if necessary to locate your program. Omitting @var{filename} means to
14625 discard information on the executable file.
14627 @kindex symbol-file
14628 @item symbol-file @r{[} @var{filename} @r{]}
14629 Read symbol table information from file @var{filename}. @code{PATH} is
14630 searched when necessary. Use the @code{file} command to get both symbol
14631 table and program to run from the same file.
14633 @code{symbol-file} with no argument clears out @value{GDBN} information on your
14634 program's symbol table.
14636 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
14637 some breakpoints and auto-display expressions. This is because they may
14638 contain pointers to the internal data recording symbols and data types,
14639 which are part of the old symbol table data being discarded inside
14642 @code{symbol-file} does not repeat if you press @key{RET} again after
14645 When @value{GDBN} is configured for a particular environment, it
14646 understands debugging information in whatever format is the standard
14647 generated for that environment; you may use either a @sc{gnu} compiler, or
14648 other compilers that adhere to the local conventions.
14649 Best results are usually obtained from @sc{gnu} compilers; for example,
14650 using @code{@value{NGCC}} you can generate debugging information for
14653 For most kinds of object files, with the exception of old SVR3 systems
14654 using COFF, the @code{symbol-file} command does not normally read the
14655 symbol table in full right away. Instead, it scans the symbol table
14656 quickly to find which source files and which symbols are present. The
14657 details are read later, one source file at a time, as they are needed.
14659 The purpose of this two-stage reading strategy is to make @value{GDBN}
14660 start up faster. For the most part, it is invisible except for
14661 occasional pauses while the symbol table details for a particular source
14662 file are being read. (The @code{set verbose} command can turn these
14663 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
14664 Warnings and Messages}.)
14666 We have not implemented the two-stage strategy for COFF yet. When the
14667 symbol table is stored in COFF format, @code{symbol-file} reads the
14668 symbol table data in full right away. Note that ``stabs-in-COFF''
14669 still does the two-stage strategy, since the debug info is actually
14673 @cindex reading symbols immediately
14674 @cindex symbols, reading immediately
14675 @item symbol-file @r{[} -readnow @r{]} @var{filename}
14676 @itemx file @r{[} -readnow @r{]} @var{filename}
14677 You can override the @value{GDBN} two-stage strategy for reading symbol
14678 tables by using the @samp{-readnow} option with any of the commands that
14679 load symbol table information, if you want to be sure @value{GDBN} has the
14680 entire symbol table available.
14682 @c FIXME: for now no mention of directories, since this seems to be in
14683 @c flux. 13mar1992 status is that in theory GDB would look either in
14684 @c current dir or in same dir as myprog; but issues like competing
14685 @c GDB's, or clutter in system dirs, mean that in practice right now
14686 @c only current dir is used. FFish says maybe a special GDB hierarchy
14687 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
14691 @item core-file @r{[}@var{filename}@r{]}
14693 Specify the whereabouts of a core dump file to be used as the ``contents
14694 of memory''. Traditionally, core files contain only some parts of the
14695 address space of the process that generated them; @value{GDBN} can access the
14696 executable file itself for other parts.
14698 @code{core-file} with no argument specifies that no core file is
14701 Note that the core file is ignored when your program is actually running
14702 under @value{GDBN}. So, if you have been running your program and you
14703 wish to debug a core file instead, you must kill the subprocess in which
14704 the program is running. To do this, use the @code{kill} command
14705 (@pxref{Kill Process, ,Killing the Child Process}).
14707 @kindex add-symbol-file
14708 @cindex dynamic linking
14709 @item add-symbol-file @var{filename} @var{address}
14710 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
14711 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
14712 The @code{add-symbol-file} command reads additional symbol table
14713 information from the file @var{filename}. You would use this command
14714 when @var{filename} has been dynamically loaded (by some other means)
14715 into the program that is running. @var{address} should be the memory
14716 address at which the file has been loaded; @value{GDBN} cannot figure
14717 this out for itself. You can additionally specify an arbitrary number
14718 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
14719 section name and base address for that section. You can specify any
14720 @var{address} as an expression.
14722 The symbol table of the file @var{filename} is added to the symbol table
14723 originally read with the @code{symbol-file} command. You can use the
14724 @code{add-symbol-file} command any number of times; the new symbol data
14725 thus read keeps adding to the old. To discard all old symbol data
14726 instead, use the @code{symbol-file} command without any arguments.
14728 @cindex relocatable object files, reading symbols from
14729 @cindex object files, relocatable, reading symbols from
14730 @cindex reading symbols from relocatable object files
14731 @cindex symbols, reading from relocatable object files
14732 @cindex @file{.o} files, reading symbols from
14733 Although @var{filename} is typically a shared library file, an
14734 executable file, or some other object file which has been fully
14735 relocated for loading into a process, you can also load symbolic
14736 information from relocatable @file{.o} files, as long as:
14740 the file's symbolic information refers only to linker symbols defined in
14741 that file, not to symbols defined by other object files,
14743 every section the file's symbolic information refers to has actually
14744 been loaded into the inferior, as it appears in the file, and
14746 you can determine the address at which every section was loaded, and
14747 provide these to the @code{add-symbol-file} command.
14751 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14752 relocatable files into an already running program; such systems
14753 typically make the requirements above easy to meet. However, it's
14754 important to recognize that many native systems use complex link
14755 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14756 assembly, for example) that make the requirements difficult to meet. In
14757 general, one cannot assume that using @code{add-symbol-file} to read a
14758 relocatable object file's symbolic information will have the same effect
14759 as linking the relocatable object file into the program in the normal
14762 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14764 @kindex add-symbol-file-from-memory
14765 @cindex @code{syscall DSO}
14766 @cindex load symbols from memory
14767 @item add-symbol-file-from-memory @var{address}
14768 Load symbols from the given @var{address} in a dynamically loaded
14769 object file whose image is mapped directly into the inferior's memory.
14770 For example, the Linux kernel maps a @code{syscall DSO} into each
14771 process's address space; this DSO provides kernel-specific code for
14772 some system calls. The argument can be any expression whose
14773 evaluation yields the address of the file's shared object file header.
14774 For this command to work, you must have used @code{symbol-file} or
14775 @code{exec-file} commands in advance.
14777 @kindex add-shared-symbol-files
14779 @item add-shared-symbol-files @var{library-file}
14780 @itemx assf @var{library-file}
14781 The @code{add-shared-symbol-files} command can currently be used only
14782 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14783 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14784 @value{GDBN} automatically looks for shared libraries, however if
14785 @value{GDBN} does not find yours, you can invoke
14786 @code{add-shared-symbol-files}. It takes one argument: the shared
14787 library's file name. @code{assf} is a shorthand alias for
14788 @code{add-shared-symbol-files}.
14791 @item section @var{section} @var{addr}
14792 The @code{section} command changes the base address of the named
14793 @var{section} of the exec file to @var{addr}. This can be used if the
14794 exec file does not contain section addresses, (such as in the
14795 @code{a.out} format), or when the addresses specified in the file
14796 itself are wrong. Each section must be changed separately. The
14797 @code{info files} command, described below, lists all the sections and
14801 @kindex info target
14804 @code{info files} and @code{info target} are synonymous; both print the
14805 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14806 including the names of the executable and core dump files currently in
14807 use by @value{GDBN}, and the files from which symbols were loaded. The
14808 command @code{help target} lists all possible targets rather than
14811 @kindex maint info sections
14812 @item maint info sections
14813 Another command that can give you extra information about program sections
14814 is @code{maint info sections}. In addition to the section information
14815 displayed by @code{info files}, this command displays the flags and file
14816 offset of each section in the executable and core dump files. In addition,
14817 @code{maint info sections} provides the following command options (which
14818 may be arbitrarily combined):
14822 Display sections for all loaded object files, including shared libraries.
14823 @item @var{sections}
14824 Display info only for named @var{sections}.
14825 @item @var{section-flags}
14826 Display info only for sections for which @var{section-flags} are true.
14827 The section flags that @value{GDBN} currently knows about are:
14830 Section will have space allocated in the process when loaded.
14831 Set for all sections except those containing debug information.
14833 Section will be loaded from the file into the child process memory.
14834 Set for pre-initialized code and data, clear for @code{.bss} sections.
14836 Section needs to be relocated before loading.
14838 Section cannot be modified by the child process.
14840 Section contains executable code only.
14842 Section contains data only (no executable code).
14844 Section will reside in ROM.
14846 Section contains data for constructor/destructor lists.
14848 Section is not empty.
14850 An instruction to the linker to not output the section.
14851 @item COFF_SHARED_LIBRARY
14852 A notification to the linker that the section contains
14853 COFF shared library information.
14855 Section contains common symbols.
14858 @kindex set trust-readonly-sections
14859 @cindex read-only sections
14860 @item set trust-readonly-sections on
14861 Tell @value{GDBN} that readonly sections in your object file
14862 really are read-only (i.e.@: that their contents will not change).
14863 In that case, @value{GDBN} can fetch values from these sections
14864 out of the object file, rather than from the target program.
14865 For some targets (notably embedded ones), this can be a significant
14866 enhancement to debugging performance.
14868 The default is off.
14870 @item set trust-readonly-sections off
14871 Tell @value{GDBN} not to trust readonly sections. This means that
14872 the contents of the section might change while the program is running,
14873 and must therefore be fetched from the target when needed.
14875 @item show trust-readonly-sections
14876 Show the current setting of trusting readonly sections.
14879 All file-specifying commands allow both absolute and relative file names
14880 as arguments. @value{GDBN} always converts the file name to an absolute file
14881 name and remembers it that way.
14883 @cindex shared libraries
14884 @anchor{Shared Libraries}
14885 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14886 and IBM RS/6000 AIX shared libraries.
14888 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14889 shared libraries. @xref{Expat}.
14891 @value{GDBN} automatically loads symbol definitions from shared libraries
14892 when you use the @code{run} command, or when you examine a core file.
14893 (Before you issue the @code{run} command, @value{GDBN} does not understand
14894 references to a function in a shared library, however---unless you are
14895 debugging a core file).
14897 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14898 automatically loads the symbols at the time of the @code{shl_load} call.
14900 @c FIXME: some @value{GDBN} release may permit some refs to undef
14901 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14902 @c FIXME...lib; check this from time to time when updating manual
14904 There are times, however, when you may wish to not automatically load
14905 symbol definitions from shared libraries, such as when they are
14906 particularly large or there are many of them.
14908 To control the automatic loading of shared library symbols, use the
14912 @kindex set auto-solib-add
14913 @item set auto-solib-add @var{mode}
14914 If @var{mode} is @code{on}, symbols from all shared object libraries
14915 will be loaded automatically when the inferior begins execution, you
14916 attach to an independently started inferior, or when the dynamic linker
14917 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14918 is @code{off}, symbols must be loaded manually, using the
14919 @code{sharedlibrary} command. The default value is @code{on}.
14921 @cindex memory used for symbol tables
14922 If your program uses lots of shared libraries with debug info that
14923 takes large amounts of memory, you can decrease the @value{GDBN}
14924 memory footprint by preventing it from automatically loading the
14925 symbols from shared libraries. To that end, type @kbd{set
14926 auto-solib-add off} before running the inferior, then load each
14927 library whose debug symbols you do need with @kbd{sharedlibrary
14928 @var{regexp}}, where @var{regexp} is a regular expression that matches
14929 the libraries whose symbols you want to be loaded.
14931 @kindex show auto-solib-add
14932 @item show auto-solib-add
14933 Display the current autoloading mode.
14936 @cindex load shared library
14937 To explicitly load shared library symbols, use the @code{sharedlibrary}
14941 @kindex info sharedlibrary
14943 @item info share @var{regex}
14944 @itemx info sharedlibrary @var{regex}
14945 Print the names of the shared libraries which are currently loaded
14946 that match @var{regex}. If @var{regex} is omitted then print
14947 all shared libraries that are loaded.
14949 @kindex sharedlibrary
14951 @item sharedlibrary @var{regex}
14952 @itemx share @var{regex}
14953 Load shared object library symbols for files matching a
14954 Unix regular expression.
14955 As with files loaded automatically, it only loads shared libraries
14956 required by your program for a core file or after typing @code{run}. If
14957 @var{regex} is omitted all shared libraries required by your program are
14960 @item nosharedlibrary
14961 @kindex nosharedlibrary
14962 @cindex unload symbols from shared libraries
14963 Unload all shared object library symbols. This discards all symbols
14964 that have been loaded from all shared libraries. Symbols from shared
14965 libraries that were loaded by explicit user requests are not
14969 Sometimes you may wish that @value{GDBN} stops and gives you control
14970 when any of shared library events happen. Use the @code{set
14971 stop-on-solib-events} command for this:
14974 @item set stop-on-solib-events
14975 @kindex set stop-on-solib-events
14976 This command controls whether @value{GDBN} should give you control
14977 when the dynamic linker notifies it about some shared library event.
14978 The most common event of interest is loading or unloading of a new
14981 @item show stop-on-solib-events
14982 @kindex show stop-on-solib-events
14983 Show whether @value{GDBN} stops and gives you control when shared
14984 library events happen.
14987 Shared libraries are also supported in many cross or remote debugging
14988 configurations. @value{GDBN} needs to have access to the target's libraries;
14989 this can be accomplished either by providing copies of the libraries
14990 on the host system, or by asking @value{GDBN} to automatically retrieve the
14991 libraries from the target. If copies of the target libraries are
14992 provided, they need to be the same as the target libraries, although the
14993 copies on the target can be stripped as long as the copies on the host are
14996 @cindex where to look for shared libraries
14997 For remote debugging, you need to tell @value{GDBN} where the target
14998 libraries are, so that it can load the correct copies---otherwise, it
14999 may try to load the host's libraries. @value{GDBN} has two variables
15000 to specify the search directories for target libraries.
15003 @cindex prefix for shared library file names
15004 @cindex system root, alternate
15005 @kindex set solib-absolute-prefix
15006 @kindex set sysroot
15007 @item set sysroot @var{path}
15008 Use @var{path} as the system root for the program being debugged. Any
15009 absolute shared library paths will be prefixed with @var{path}; many
15010 runtime loaders store the absolute paths to the shared library in the
15011 target program's memory. If you use @code{set sysroot} to find shared
15012 libraries, they need to be laid out in the same way that they are on
15013 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15016 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15017 retrieve the target libraries from the remote system. This is only
15018 supported when using a remote target that supports the @code{remote get}
15019 command (@pxref{File Transfer,,Sending files to a remote system}).
15020 The part of @var{path} following the initial @file{remote:}
15021 (if present) is used as system root prefix on the remote file system.
15022 @footnote{If you want to specify a local system root using a directory
15023 that happens to be named @file{remote:}, you need to use some equivalent
15024 variant of the name like @file{./remote:}.}
15026 For targets with an MS-DOS based filesystem, such as MS-Windows and
15027 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15028 absolute file name with @var{path}. But first, on Unix hosts,
15029 @value{GDBN} converts all backslash directory separators into forward
15030 slashes, because the backslash is not a directory separator on Unix:
15033 c:\foo\bar.dll @result{} c:/foo/bar.dll
15036 Then, @value{GDBN} attempts prefixing the target file name with
15037 @var{path}, and looks for the resulting file name in the host file
15041 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15044 If that does not find the shared library, @value{GDBN} tries removing
15045 the @samp{:} character from the drive spec, both for convenience, and,
15046 for the case of the host file system not supporting file names with
15050 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15053 This makes it possible to have a system root that mirrors a target
15054 with more than one drive. E.g., you may want to setup your local
15055 copies of the target system shared libraries like so (note @samp{c} vs
15059 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15060 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15061 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15065 and point the system root at @file{/path/to/sysroot}, so that
15066 @value{GDBN} can find the correct copies of both
15067 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15069 If that still does not find the shared library, @value{GDBN} tries
15070 removing the whole drive spec from the target file name:
15073 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15076 This last lookup makes it possible to not care about the drive name,
15077 if you don't want or need to.
15079 The @code{set solib-absolute-prefix} command is an alias for @code{set
15082 @cindex default system root
15083 @cindex @samp{--with-sysroot}
15084 You can set the default system root by using the configure-time
15085 @samp{--with-sysroot} option. If the system root is inside
15086 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15087 @samp{--exec-prefix}), then the default system root will be updated
15088 automatically if the installed @value{GDBN} is moved to a new
15091 @kindex show sysroot
15093 Display the current shared library prefix.
15095 @kindex set solib-search-path
15096 @item set solib-search-path @var{path}
15097 If this variable is set, @var{path} is a colon-separated list of
15098 directories to search for shared libraries. @samp{solib-search-path}
15099 is used after @samp{sysroot} fails to locate the library, or if the
15100 path to the library is relative instead of absolute. If you want to
15101 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15102 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15103 finding your host's libraries. @samp{sysroot} is preferred; setting
15104 it to a nonexistent directory may interfere with automatic loading
15105 of shared library symbols.
15107 @kindex show solib-search-path
15108 @item show solib-search-path
15109 Display the current shared library search path.
15111 @cindex DOS file-name semantics of file names.
15112 @kindex set target-file-system-kind (unix|dos-based|auto)
15113 @kindex show target-file-system-kind
15114 @item set target-file-system-kind @var{kind}
15115 Set assumed file system kind for target reported file names.
15117 Shared library file names as reported by the target system may not
15118 make sense as is on the system @value{GDBN} is running on. For
15119 example, when remote debugging a target that has MS-DOS based file
15120 system semantics, from a Unix host, the target may be reporting to
15121 @value{GDBN} a list of loaded shared libraries with file names such as
15122 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15123 drive letters, so the @samp{c:\} prefix is not normally understood as
15124 indicating an absolute file name, and neither is the backslash
15125 normally considered a directory separator character. In that case,
15126 the native file system would interpret this whole absolute file name
15127 as a relative file name with no directory components. This would make
15128 it impossible to point @value{GDBN} at a copy of the remote target's
15129 shared libraries on the host using @code{set sysroot}, and impractical
15130 with @code{set solib-search-path}. Setting
15131 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15132 to interpret such file names similarly to how the target would, and to
15133 map them to file names valid on @value{GDBN}'s native file system
15134 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15135 to one of the supported file system kinds. In that case, @value{GDBN}
15136 tries to determine the appropriate file system variant based on the
15137 current target's operating system (@pxref{ABI, ,Configuring the
15138 Current ABI}). The supported file system settings are:
15142 Instruct @value{GDBN} to assume the target file system is of Unix
15143 kind. Only file names starting the forward slash (@samp{/}) character
15144 are considered absolute, and the directory separator character is also
15148 Instruct @value{GDBN} to assume the target file system is DOS based.
15149 File names starting with either a forward slash, or a drive letter
15150 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15151 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15152 considered directory separators.
15155 Instruct @value{GDBN} to use the file system kind associated with the
15156 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15157 This is the default.
15162 @node Separate Debug Files
15163 @section Debugging Information in Separate Files
15164 @cindex separate debugging information files
15165 @cindex debugging information in separate files
15166 @cindex @file{.debug} subdirectories
15167 @cindex debugging information directory, global
15168 @cindex global debugging information directory
15169 @cindex build ID, and separate debugging files
15170 @cindex @file{.build-id} directory
15172 @value{GDBN} allows you to put a program's debugging information in a
15173 file separate from the executable itself, in a way that allows
15174 @value{GDBN} to find and load the debugging information automatically.
15175 Since debugging information can be very large---sometimes larger
15176 than the executable code itself---some systems distribute debugging
15177 information for their executables in separate files, which users can
15178 install only when they need to debug a problem.
15180 @value{GDBN} supports two ways of specifying the separate debug info
15185 The executable contains a @dfn{debug link} that specifies the name of
15186 the separate debug info file. The separate debug file's name is
15187 usually @file{@var{executable}.debug}, where @var{executable} is the
15188 name of the corresponding executable file without leading directories
15189 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15190 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15191 checksum for the debug file, which @value{GDBN} uses to validate that
15192 the executable and the debug file came from the same build.
15195 The executable contains a @dfn{build ID}, a unique bit string that is
15196 also present in the corresponding debug info file. (This is supported
15197 only on some operating systems, notably those which use the ELF format
15198 for binary files and the @sc{gnu} Binutils.) For more details about
15199 this feature, see the description of the @option{--build-id}
15200 command-line option in @ref{Options, , Command Line Options, ld.info,
15201 The GNU Linker}. The debug info file's name is not specified
15202 explicitly by the build ID, but can be computed from the build ID, see
15206 Depending on the way the debug info file is specified, @value{GDBN}
15207 uses two different methods of looking for the debug file:
15211 For the ``debug link'' method, @value{GDBN} looks up the named file in
15212 the directory of the executable file, then in a subdirectory of that
15213 directory named @file{.debug}, and finally under the global debug
15214 directory, in a subdirectory whose name is identical to the leading
15215 directories of the executable's absolute file name.
15218 For the ``build ID'' method, @value{GDBN} looks in the
15219 @file{.build-id} subdirectory of the global debug directory for a file
15220 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15221 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15222 are the rest of the bit string. (Real build ID strings are 32 or more
15223 hex characters, not 10.)
15226 So, for example, suppose you ask @value{GDBN} to debug
15227 @file{/usr/bin/ls}, which has a debug link that specifies the
15228 file @file{ls.debug}, and a build ID whose value in hex is
15229 @code{abcdef1234}. If the global debug directory is
15230 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15231 debug information files, in the indicated order:
15235 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15237 @file{/usr/bin/ls.debug}
15239 @file{/usr/bin/.debug/ls.debug}
15241 @file{/usr/lib/debug/usr/bin/ls.debug}.
15244 You can set the global debugging info directory's name, and view the
15245 name @value{GDBN} is currently using.
15249 @kindex set debug-file-directory
15250 @item set debug-file-directory @var{directories}
15251 Set the directories which @value{GDBN} searches for separate debugging
15252 information files to @var{directory}. Multiple directory components can be set
15253 concatenating them by a directory separator.
15255 @kindex show debug-file-directory
15256 @item show debug-file-directory
15257 Show the directories @value{GDBN} searches for separate debugging
15262 @cindex @code{.gnu_debuglink} sections
15263 @cindex debug link sections
15264 A debug link is a special section of the executable file named
15265 @code{.gnu_debuglink}. The section must contain:
15269 A filename, with any leading directory components removed, followed by
15272 zero to three bytes of padding, as needed to reach the next four-byte
15273 boundary within the section, and
15275 a four-byte CRC checksum, stored in the same endianness used for the
15276 executable file itself. The checksum is computed on the debugging
15277 information file's full contents by the function given below, passing
15278 zero as the @var{crc} argument.
15281 Any executable file format can carry a debug link, as long as it can
15282 contain a section named @code{.gnu_debuglink} with the contents
15285 @cindex @code{.note.gnu.build-id} sections
15286 @cindex build ID sections
15287 The build ID is a special section in the executable file (and in other
15288 ELF binary files that @value{GDBN} may consider). This section is
15289 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15290 It contains unique identification for the built files---the ID remains
15291 the same across multiple builds of the same build tree. The default
15292 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15293 content for the build ID string. The same section with an identical
15294 value is present in the original built binary with symbols, in its
15295 stripped variant, and in the separate debugging information file.
15297 The debugging information file itself should be an ordinary
15298 executable, containing a full set of linker symbols, sections, and
15299 debugging information. The sections of the debugging information file
15300 should have the same names, addresses, and sizes as the original file,
15301 but they need not contain any data---much like a @code{.bss} section
15302 in an ordinary executable.
15304 The @sc{gnu} binary utilities (Binutils) package includes the
15305 @samp{objcopy} utility that can produce
15306 the separated executable / debugging information file pairs using the
15307 following commands:
15310 @kbd{objcopy --only-keep-debug foo foo.debug}
15315 These commands remove the debugging
15316 information from the executable file @file{foo} and place it in the file
15317 @file{foo.debug}. You can use the first, second or both methods to link the
15322 The debug link method needs the following additional command to also leave
15323 behind a debug link in @file{foo}:
15326 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15329 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15330 a version of the @code{strip} command such that the command @kbd{strip foo -f
15331 foo.debug} has the same functionality as the two @code{objcopy} commands and
15332 the @code{ln -s} command above, together.
15335 Build ID gets embedded into the main executable using @code{ld --build-id} or
15336 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15337 compatibility fixes for debug files separation are present in @sc{gnu} binary
15338 utilities (Binutils) package since version 2.18.
15343 @cindex CRC algorithm definition
15344 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15345 IEEE 802.3 using the polynomial:
15347 @c TexInfo requires naked braces for multi-digit exponents for Tex
15348 @c output, but this causes HTML output to barf. HTML has to be set using
15349 @c raw commands. So we end up having to specify this equation in 2
15354 <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>
15355 + <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
15361 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15362 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15366 The function is computed byte at a time, taking the least
15367 significant bit of each byte first. The initial pattern
15368 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15369 the final result is inverted to ensure trailing zeros also affect the
15372 @emph{Note:} This is the same CRC polynomial as used in handling the
15373 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15374 , @value{GDBN} Remote Serial Protocol}). However in the
15375 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15376 significant bit first, and the result is not inverted, so trailing
15377 zeros have no effect on the CRC value.
15379 To complete the description, we show below the code of the function
15380 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15381 initially supplied @code{crc} argument means that an initial call to
15382 this function passing in zero will start computing the CRC using
15385 @kindex gnu_debuglink_crc32
15388 gnu_debuglink_crc32 (unsigned long crc,
15389 unsigned char *buf, size_t len)
15391 static const unsigned long crc32_table[256] =
15393 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
15394 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
15395 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
15396 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
15397 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
15398 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15399 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15400 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
15401 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
15402 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
15403 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
15404 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
15405 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
15406 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
15407 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
15408 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
15409 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
15410 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
15411 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
15412 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
15413 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
15414 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
15415 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
15416 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
15417 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
15418 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
15419 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
15420 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
15421 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
15422 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
15423 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
15424 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
15425 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
15426 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
15427 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
15428 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
15429 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
15430 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
15431 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
15432 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
15433 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
15434 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
15435 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
15436 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
15437 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
15438 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
15439 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
15440 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
15441 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
15442 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
15443 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
15446 unsigned char *end;
15448 crc = ~crc & 0xffffffff;
15449 for (end = buf + len; buf < end; ++buf)
15450 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15451 return ~crc & 0xffffffff;
15456 This computation does not apply to the ``build ID'' method.
15460 @section Index Files Speed Up @value{GDBN}
15461 @cindex index files
15462 @cindex @samp{.gdb_index} section
15464 When @value{GDBN} finds a symbol file, it scans the symbols in the
15465 file in order to construct an internal symbol table. This lets most
15466 @value{GDBN} operations work quickly---at the cost of a delay early
15467 on. For large programs, this delay can be quite lengthy, so
15468 @value{GDBN} provides a way to build an index, which speeds up
15471 The index is stored as a section in the symbol file. @value{GDBN} can
15472 write the index to a file, then you can put it into the symbol file
15473 using @command{objcopy}.
15475 To create an index file, use the @code{save gdb-index} command:
15478 @item save gdb-index @var{directory}
15479 @kindex save gdb-index
15480 Create an index file for each symbol file currently known by
15481 @value{GDBN}. Each file is named after its corresponding symbol file,
15482 with @samp{.gdb-index} appended, and is written into the given
15486 Once you have created an index file you can merge it into your symbol
15487 file, here named @file{symfile}, using @command{objcopy}:
15490 $ objcopy --add-section .gdb_index=symfile.gdb-index \
15491 --set-section-flags .gdb_index=readonly symfile symfile
15494 There are currently some limitation on indices. They only work when
15495 for DWARF debugging information, not stabs. And, they do not
15496 currently work for programs using Ada.
15498 @node Symbol Errors
15499 @section Errors Reading Symbol Files
15501 While reading a symbol file, @value{GDBN} occasionally encounters problems,
15502 such as symbol types it does not recognize, or known bugs in compiler
15503 output. By default, @value{GDBN} does not notify you of such problems, since
15504 they are relatively common and primarily of interest to people
15505 debugging compilers. If you are interested in seeing information
15506 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
15507 only one message about each such type of problem, no matter how many
15508 times the problem occurs; or you can ask @value{GDBN} to print more messages,
15509 to see how many times the problems occur, with the @code{set
15510 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
15513 The messages currently printed, and their meanings, include:
15516 @item inner block not inside outer block in @var{symbol}
15518 The symbol information shows where symbol scopes begin and end
15519 (such as at the start of a function or a block of statements). This
15520 error indicates that an inner scope block is not fully contained
15521 in its outer scope blocks.
15523 @value{GDBN} circumvents the problem by treating the inner block as if it had
15524 the same scope as the outer block. In the error message, @var{symbol}
15525 may be shown as ``@code{(don't know)}'' if the outer block is not a
15528 @item block at @var{address} out of order
15530 The symbol information for symbol scope blocks should occur in
15531 order of increasing addresses. This error indicates that it does not
15534 @value{GDBN} does not circumvent this problem, and has trouble
15535 locating symbols in the source file whose symbols it is reading. (You
15536 can often determine what source file is affected by specifying
15537 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
15540 @item bad block start address patched
15542 The symbol information for a symbol scope block has a start address
15543 smaller than the address of the preceding source line. This is known
15544 to occur in the SunOS 4.1.1 (and earlier) C compiler.
15546 @value{GDBN} circumvents the problem by treating the symbol scope block as
15547 starting on the previous source line.
15549 @item bad string table offset in symbol @var{n}
15552 Symbol number @var{n} contains a pointer into the string table which is
15553 larger than the size of the string table.
15555 @value{GDBN} circumvents the problem by considering the symbol to have the
15556 name @code{foo}, which may cause other problems if many symbols end up
15559 @item unknown symbol type @code{0x@var{nn}}
15561 The symbol information contains new data types that @value{GDBN} does
15562 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
15563 uncomprehended information, in hexadecimal.
15565 @value{GDBN} circumvents the error by ignoring this symbol information.
15566 This usually allows you to debug your program, though certain symbols
15567 are not accessible. If you encounter such a problem and feel like
15568 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
15569 on @code{complain}, then go up to the function @code{read_dbx_symtab}
15570 and examine @code{*bufp} to see the symbol.
15572 @item stub type has NULL name
15574 @value{GDBN} could not find the full definition for a struct or class.
15576 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
15577 The symbol information for a C@t{++} member function is missing some
15578 information that recent versions of the compiler should have output for
15581 @item info mismatch between compiler and debugger
15583 @value{GDBN} could not parse a type specification output by the compiler.
15588 @section GDB Data Files
15590 @cindex prefix for data files
15591 @value{GDBN} will sometimes read an auxiliary data file. These files
15592 are kept in a directory known as the @dfn{data directory}.
15594 You can set the data directory's name, and view the name @value{GDBN}
15595 is currently using.
15598 @kindex set data-directory
15599 @item set data-directory @var{directory}
15600 Set the directory which @value{GDBN} searches for auxiliary data files
15601 to @var{directory}.
15603 @kindex show data-directory
15604 @item show data-directory
15605 Show the directory @value{GDBN} searches for auxiliary data files.
15608 @cindex default data directory
15609 @cindex @samp{--with-gdb-datadir}
15610 You can set the default data directory by using the configure-time
15611 @samp{--with-gdb-datadir} option. If the data directory is inside
15612 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15613 @samp{--exec-prefix}), then the default data directory will be updated
15614 automatically if the installed @value{GDBN} is moved to a new
15617 The data directory may also be specified with the
15618 @code{--data-directory} command line option.
15619 @xref{Mode Options}.
15622 @chapter Specifying a Debugging Target
15624 @cindex debugging target
15625 A @dfn{target} is the execution environment occupied by your program.
15627 Often, @value{GDBN} runs in the same host environment as your program;
15628 in that case, the debugging target is specified as a side effect when
15629 you use the @code{file} or @code{core} commands. When you need more
15630 flexibility---for example, running @value{GDBN} on a physically separate
15631 host, or controlling a standalone system over a serial port or a
15632 realtime system over a TCP/IP connection---you can use the @code{target}
15633 command to specify one of the target types configured for @value{GDBN}
15634 (@pxref{Target Commands, ,Commands for Managing Targets}).
15636 @cindex target architecture
15637 It is possible to build @value{GDBN} for several different @dfn{target
15638 architectures}. When @value{GDBN} is built like that, you can choose
15639 one of the available architectures with the @kbd{set architecture}
15643 @kindex set architecture
15644 @kindex show architecture
15645 @item set architecture @var{arch}
15646 This command sets the current target architecture to @var{arch}. The
15647 value of @var{arch} can be @code{"auto"}, in addition to one of the
15648 supported architectures.
15650 @item show architecture
15651 Show the current target architecture.
15653 @item set processor
15655 @kindex set processor
15656 @kindex show processor
15657 These are alias commands for, respectively, @code{set architecture}
15658 and @code{show architecture}.
15662 * Active Targets:: Active targets
15663 * Target Commands:: Commands for managing targets
15664 * Byte Order:: Choosing target byte order
15667 @node Active Targets
15668 @section Active Targets
15670 @cindex stacking targets
15671 @cindex active targets
15672 @cindex multiple targets
15674 There are multiple classes of targets such as: processes, executable files or
15675 recording sessions. Core files belong to the process class, making core file
15676 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
15677 on multiple active targets, one in each class. This allows you to (for
15678 example) start a process and inspect its activity, while still having access to
15679 the executable file after the process finishes. Or if you start process
15680 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
15681 presented a virtual layer of the recording target, while the process target
15682 remains stopped at the chronologically last point of the process execution.
15684 Use the @code{core-file} and @code{exec-file} commands to select a new core
15685 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
15686 specify as a target a process that is already running, use the @code{attach}
15687 command (@pxref{Attach, ,Debugging an Already-running Process}).
15689 @node Target Commands
15690 @section Commands for Managing Targets
15693 @item target @var{type} @var{parameters}
15694 Connects the @value{GDBN} host environment to a target machine or
15695 process. A target is typically a protocol for talking to debugging
15696 facilities. You use the argument @var{type} to specify the type or
15697 protocol of the target machine.
15699 Further @var{parameters} are interpreted by the target protocol, but
15700 typically include things like device names or host names to connect
15701 with, process numbers, and baud rates.
15703 The @code{target} command does not repeat if you press @key{RET} again
15704 after executing the command.
15706 @kindex help target
15708 Displays the names of all targets available. To display targets
15709 currently selected, use either @code{info target} or @code{info files}
15710 (@pxref{Files, ,Commands to Specify Files}).
15712 @item help target @var{name}
15713 Describe a particular target, including any parameters necessary to
15716 @kindex set gnutarget
15717 @item set gnutarget @var{args}
15718 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
15719 knows whether it is reading an @dfn{executable},
15720 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
15721 with the @code{set gnutarget} command. Unlike most @code{target} commands,
15722 with @code{gnutarget} the @code{target} refers to a program, not a machine.
15725 @emph{Warning:} To specify a file format with @code{set gnutarget},
15726 you must know the actual BFD name.
15730 @xref{Files, , Commands to Specify Files}.
15732 @kindex show gnutarget
15733 @item show gnutarget
15734 Use the @code{show gnutarget} command to display what file format
15735 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
15736 @value{GDBN} will determine the file format for each file automatically,
15737 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
15740 @cindex common targets
15741 Here are some common targets (available, or not, depending on the GDB
15746 @item target exec @var{program}
15747 @cindex executable file target
15748 An executable file. @samp{target exec @var{program}} is the same as
15749 @samp{exec-file @var{program}}.
15751 @item target core @var{filename}
15752 @cindex core dump file target
15753 A core dump file. @samp{target core @var{filename}} is the same as
15754 @samp{core-file @var{filename}}.
15756 @item target remote @var{medium}
15757 @cindex remote target
15758 A remote system connected to @value{GDBN} via a serial line or network
15759 connection. This command tells @value{GDBN} to use its own remote
15760 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
15762 For example, if you have a board connected to @file{/dev/ttya} on the
15763 machine running @value{GDBN}, you could say:
15766 target remote /dev/ttya
15769 @code{target remote} supports the @code{load} command. This is only
15770 useful if you have some other way of getting the stub to the target
15771 system, and you can put it somewhere in memory where it won't get
15772 clobbered by the download.
15774 @item target sim @r{[}@var{simargs}@r{]} @dots{}
15775 @cindex built-in simulator target
15776 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
15784 works; however, you cannot assume that a specific memory map, device
15785 drivers, or even basic I/O is available, although some simulators do
15786 provide these. For info about any processor-specific simulator details,
15787 see the appropriate section in @ref{Embedded Processors, ,Embedded
15792 Some configurations may include these targets as well:
15796 @item target nrom @var{dev}
15797 @cindex NetROM ROM emulator target
15798 NetROM ROM emulator. This target only supports downloading.
15802 Different targets are available on different configurations of @value{GDBN};
15803 your configuration may have more or fewer targets.
15805 Many remote targets require you to download the executable's code once
15806 you've successfully established a connection. You may wish to control
15807 various aspects of this process.
15812 @kindex set hash@r{, for remote monitors}
15813 @cindex hash mark while downloading
15814 This command controls whether a hash mark @samp{#} is displayed while
15815 downloading a file to the remote monitor. If on, a hash mark is
15816 displayed after each S-record is successfully downloaded to the
15820 @kindex show hash@r{, for remote monitors}
15821 Show the current status of displaying the hash mark.
15823 @item set debug monitor
15824 @kindex set debug monitor
15825 @cindex display remote monitor communications
15826 Enable or disable display of communications messages between
15827 @value{GDBN} and the remote monitor.
15829 @item show debug monitor
15830 @kindex show debug monitor
15831 Show the current status of displaying communications between
15832 @value{GDBN} and the remote monitor.
15837 @kindex load @var{filename}
15838 @item load @var{filename}
15840 Depending on what remote debugging facilities are configured into
15841 @value{GDBN}, the @code{load} command may be available. Where it exists, it
15842 is meant to make @var{filename} (an executable) available for debugging
15843 on the remote system---by downloading, or dynamic linking, for example.
15844 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15845 the @code{add-symbol-file} command.
15847 If your @value{GDBN} does not have a @code{load} command, attempting to
15848 execute it gets the error message ``@code{You can't do that when your
15849 target is @dots{}}''
15851 The file is loaded at whatever address is specified in the executable.
15852 For some object file formats, you can specify the load address when you
15853 link the program; for other formats, like a.out, the object file format
15854 specifies a fixed address.
15855 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15857 Depending on the remote side capabilities, @value{GDBN} may be able to
15858 load programs into flash memory.
15860 @code{load} does not repeat if you press @key{RET} again after using it.
15864 @section Choosing Target Byte Order
15866 @cindex choosing target byte order
15867 @cindex target byte order
15869 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15870 offer the ability to run either big-endian or little-endian byte
15871 orders. Usually the executable or symbol will include a bit to
15872 designate the endian-ness, and you will not need to worry about
15873 which to use. However, you may still find it useful to adjust
15874 @value{GDBN}'s idea of processor endian-ness manually.
15878 @item set endian big
15879 Instruct @value{GDBN} to assume the target is big-endian.
15881 @item set endian little
15882 Instruct @value{GDBN} to assume the target is little-endian.
15884 @item set endian auto
15885 Instruct @value{GDBN} to use the byte order associated with the
15889 Display @value{GDBN}'s current idea of the target byte order.
15893 Note that these commands merely adjust interpretation of symbolic
15894 data on the host, and that they have absolutely no effect on the
15898 @node Remote Debugging
15899 @chapter Debugging Remote Programs
15900 @cindex remote debugging
15902 If you are trying to debug a program running on a machine that cannot run
15903 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15904 For example, you might use remote debugging on an operating system kernel,
15905 or on a small system which does not have a general purpose operating system
15906 powerful enough to run a full-featured debugger.
15908 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15909 to make this work with particular debugging targets. In addition,
15910 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15911 but not specific to any particular target system) which you can use if you
15912 write the remote stubs---the code that runs on the remote system to
15913 communicate with @value{GDBN}.
15915 Other remote targets may be available in your
15916 configuration of @value{GDBN}; use @code{help target} to list them.
15919 * Connecting:: Connecting to a remote target
15920 * File Transfer:: Sending files to a remote system
15921 * Server:: Using the gdbserver program
15922 * Remote Configuration:: Remote configuration
15923 * Remote Stub:: Implementing a remote stub
15927 @section Connecting to a Remote Target
15929 On the @value{GDBN} host machine, you will need an unstripped copy of
15930 your program, since @value{GDBN} needs symbol and debugging information.
15931 Start up @value{GDBN} as usual, using the name of the local copy of your
15932 program as the first argument.
15934 @cindex @code{target remote}
15935 @value{GDBN} can communicate with the target over a serial line, or
15936 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15937 each case, @value{GDBN} uses the same protocol for debugging your
15938 program; only the medium carrying the debugging packets varies. The
15939 @code{target remote} command establishes a connection to the target.
15940 Its arguments indicate which medium to use:
15944 @item target remote @var{serial-device}
15945 @cindex serial line, @code{target remote}
15946 Use @var{serial-device} to communicate with the target. For example,
15947 to use a serial line connected to the device named @file{/dev/ttyb}:
15950 target remote /dev/ttyb
15953 If you're using a serial line, you may want to give @value{GDBN} the
15954 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15955 (@pxref{Remote Configuration, set remotebaud}) before the
15956 @code{target} command.
15958 @item target remote @code{@var{host}:@var{port}}
15959 @itemx target remote @code{tcp:@var{host}:@var{port}}
15960 @cindex @acronym{TCP} port, @code{target remote}
15961 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15962 The @var{host} may be either a host name or a numeric @acronym{IP}
15963 address; @var{port} must be a decimal number. The @var{host} could be
15964 the target machine itself, if it is directly connected to the net, or
15965 it might be a terminal server which in turn has a serial line to the
15968 For example, to connect to port 2828 on a terminal server named
15972 target remote manyfarms:2828
15975 If your remote target is actually running on the same machine as your
15976 debugger session (e.g.@: a simulator for your target running on the
15977 same host), you can omit the hostname. For example, to connect to
15978 port 1234 on your local machine:
15981 target remote :1234
15985 Note that the colon is still required here.
15987 @item target remote @code{udp:@var{host}:@var{port}}
15988 @cindex @acronym{UDP} port, @code{target remote}
15989 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
15990 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
15993 target remote udp:manyfarms:2828
15996 When using a @acronym{UDP} connection for remote debugging, you should
15997 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
15998 can silently drop packets on busy or unreliable networks, which will
15999 cause havoc with your debugging session.
16001 @item target remote | @var{command}
16002 @cindex pipe, @code{target remote} to
16003 Run @var{command} in the background and communicate with it using a
16004 pipe. The @var{command} is a shell command, to be parsed and expanded
16005 by the system's command shell, @code{/bin/sh}; it should expect remote
16006 protocol packets on its standard input, and send replies on its
16007 standard output. You could use this to run a stand-alone simulator
16008 that speaks the remote debugging protocol, to make net connections
16009 using programs like @code{ssh}, or for other similar tricks.
16011 If @var{command} closes its standard output (perhaps by exiting),
16012 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16013 program has already exited, this will have no effect.)
16017 Once the connection has been established, you can use all the usual
16018 commands to examine and change data. The remote program is already
16019 running; you can use @kbd{step} and @kbd{continue}, and you do not
16020 need to use @kbd{run}.
16022 @cindex interrupting remote programs
16023 @cindex remote programs, interrupting
16024 Whenever @value{GDBN} is waiting for the remote program, if you type the
16025 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16026 program. This may or may not succeed, depending in part on the hardware
16027 and the serial drivers the remote system uses. If you type the
16028 interrupt character once again, @value{GDBN} displays this prompt:
16031 Interrupted while waiting for the program.
16032 Give up (and stop debugging it)? (y or n)
16035 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16036 (If you decide you want to try again later, you can use @samp{target
16037 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16038 goes back to waiting.
16041 @kindex detach (remote)
16043 When you have finished debugging the remote program, you can use the
16044 @code{detach} command to release it from @value{GDBN} control.
16045 Detaching from the target normally resumes its execution, but the results
16046 will depend on your particular remote stub. After the @code{detach}
16047 command, @value{GDBN} is free to connect to another target.
16051 The @code{disconnect} command behaves like @code{detach}, except that
16052 the target is generally not resumed. It will wait for @value{GDBN}
16053 (this instance or another one) to connect and continue debugging. After
16054 the @code{disconnect} command, @value{GDBN} is again free to connect to
16057 @cindex send command to remote monitor
16058 @cindex extend @value{GDBN} for remote targets
16059 @cindex add new commands for external monitor
16061 @item monitor @var{cmd}
16062 This command allows you to send arbitrary commands directly to the
16063 remote monitor. Since @value{GDBN} doesn't care about the commands it
16064 sends like this, this command is the way to extend @value{GDBN}---you
16065 can add new commands that only the external monitor will understand
16069 @node File Transfer
16070 @section Sending files to a remote system
16071 @cindex remote target, file transfer
16072 @cindex file transfer
16073 @cindex sending files to remote systems
16075 Some remote targets offer the ability to transfer files over the same
16076 connection used to communicate with @value{GDBN}. This is convenient
16077 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16078 running @code{gdbserver} over a network interface. For other targets,
16079 e.g.@: embedded devices with only a single serial port, this may be
16080 the only way to upload or download files.
16082 Not all remote targets support these commands.
16086 @item remote put @var{hostfile} @var{targetfile}
16087 Copy file @var{hostfile} from the host system (the machine running
16088 @value{GDBN}) to @var{targetfile} on the target system.
16091 @item remote get @var{targetfile} @var{hostfile}
16092 Copy file @var{targetfile} from the target system to @var{hostfile}
16093 on the host system.
16095 @kindex remote delete
16096 @item remote delete @var{targetfile}
16097 Delete @var{targetfile} from the target system.
16102 @section Using the @code{gdbserver} Program
16105 @cindex remote connection without stubs
16106 @code{gdbserver} is a control program for Unix-like systems, which
16107 allows you to connect your program with a remote @value{GDBN} via
16108 @code{target remote}---but without linking in the usual debugging stub.
16110 @code{gdbserver} is not a complete replacement for the debugging stubs,
16111 because it requires essentially the same operating-system facilities
16112 that @value{GDBN} itself does. In fact, a system that can run
16113 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16114 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16115 because it is a much smaller program than @value{GDBN} itself. It is
16116 also easier to port than all of @value{GDBN}, so you may be able to get
16117 started more quickly on a new system by using @code{gdbserver}.
16118 Finally, if you develop code for real-time systems, you may find that
16119 the tradeoffs involved in real-time operation make it more convenient to
16120 do as much development work as possible on another system, for example
16121 by cross-compiling. You can use @code{gdbserver} to make a similar
16122 choice for debugging.
16124 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16125 or a TCP connection, using the standard @value{GDBN} remote serial
16129 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16130 Do not run @code{gdbserver} connected to any public network; a
16131 @value{GDBN} connection to @code{gdbserver} provides access to the
16132 target system with the same privileges as the user running
16136 @subsection Running @code{gdbserver}
16137 @cindex arguments, to @code{gdbserver}
16138 @cindex @code{gdbserver}, command-line arguments
16140 Run @code{gdbserver} on the target system. You need a copy of the
16141 program you want to debug, including any libraries it requires.
16142 @code{gdbserver} does not need your program's symbol table, so you can
16143 strip the program if necessary to save space. @value{GDBN} on the host
16144 system does all the symbol handling.
16146 To use the server, you must tell it how to communicate with @value{GDBN};
16147 the name of your program; and the arguments for your program. The usual
16151 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16154 @var{comm} is either a device name (to use a serial line) or a TCP
16155 hostname and portnumber. For example, to debug Emacs with the argument
16156 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16160 target> gdbserver /dev/com1 emacs foo.txt
16163 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16166 To use a TCP connection instead of a serial line:
16169 target> gdbserver host:2345 emacs foo.txt
16172 The only difference from the previous example is the first argument,
16173 specifying that you are communicating with the host @value{GDBN} via
16174 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16175 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16176 (Currently, the @samp{host} part is ignored.) You can choose any number
16177 you want for the port number as long as it does not conflict with any
16178 TCP ports already in use on the target system (for example, @code{23} is
16179 reserved for @code{telnet}).@footnote{If you choose a port number that
16180 conflicts with another service, @code{gdbserver} prints an error message
16181 and exits.} You must use the same port number with the host @value{GDBN}
16182 @code{target remote} command.
16184 @subsubsection Attaching to a Running Program
16185 @cindex attach to a program, @code{gdbserver}
16186 @cindex @option{--attach}, @code{gdbserver} option
16188 On some targets, @code{gdbserver} can also attach to running programs.
16189 This is accomplished via the @code{--attach} argument. The syntax is:
16192 target> gdbserver --attach @var{comm} @var{pid}
16195 @var{pid} is the process ID of a currently running process. It isn't necessary
16196 to point @code{gdbserver} at a binary for the running process.
16199 You can debug processes by name instead of process ID if your target has the
16200 @code{pidof} utility:
16203 target> gdbserver --attach @var{comm} `pidof @var{program}`
16206 In case more than one copy of @var{program} is running, or @var{program}
16207 has multiple threads, most versions of @code{pidof} support the
16208 @code{-s} option to only return the first process ID.
16210 @subsubsection Multi-Process Mode for @code{gdbserver}
16211 @cindex @code{gdbserver}, multiple processes
16212 @cindex multiple processes with @code{gdbserver}
16214 When you connect to @code{gdbserver} using @code{target remote},
16215 @code{gdbserver} debugs the specified program only once. When the
16216 program exits, or you detach from it, @value{GDBN} closes the connection
16217 and @code{gdbserver} exits.
16219 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16220 enters multi-process mode. When the debugged program exits, or you
16221 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16222 though no program is running. The @code{run} and @code{attach}
16223 commands instruct @code{gdbserver} to run or attach to a new program.
16224 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16225 remote exec-file}) to select the program to run. Command line
16226 arguments are supported, except for wildcard expansion and I/O
16227 redirection (@pxref{Arguments}).
16229 @cindex @option{--multi}, @code{gdbserver} option
16230 To start @code{gdbserver} without supplying an initial command to run
16231 or process ID to attach, use the @option{--multi} command line option.
16232 Then you can connect using @kbd{target extended-remote} and start
16233 the program you want to debug.
16235 @code{gdbserver} does not automatically exit in multi-process mode.
16236 You can terminate it by using @code{monitor exit}
16237 (@pxref{Monitor Commands for gdbserver}).
16239 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16241 @cindex @option{--debug}, @code{gdbserver} option
16242 The @option{--debug} option tells @code{gdbserver} to display extra
16243 status information about the debugging process.
16244 @cindex @option{--remote-debug}, @code{gdbserver} option
16245 The @option{--remote-debug} option tells @code{gdbserver} to display
16246 remote protocol debug output. These options are intended for
16247 @code{gdbserver} development and for bug reports to the developers.
16249 @cindex @option{--wrapper}, @code{gdbserver} option
16250 The @option{--wrapper} option specifies a wrapper to launch programs
16251 for debugging. The option should be followed by the name of the
16252 wrapper, then any command-line arguments to pass to the wrapper, then
16253 @kbd{--} indicating the end of the wrapper arguments.
16255 @code{gdbserver} runs the specified wrapper program with a combined
16256 command line including the wrapper arguments, then the name of the
16257 program to debug, then any arguments to the program. The wrapper
16258 runs until it executes your program, and then @value{GDBN} gains control.
16260 You can use any program that eventually calls @code{execve} with
16261 its arguments as a wrapper. Several standard Unix utilities do
16262 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16263 with @code{exec "$@@"} will also work.
16265 For example, you can use @code{env} to pass an environment variable to
16266 the debugged program, without setting the variable in @code{gdbserver}'s
16270 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16273 @subsection Connecting to @code{gdbserver}
16275 Run @value{GDBN} on the host system.
16277 First make sure you have the necessary symbol files. Load symbols for
16278 your application using the @code{file} command before you connect. Use
16279 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16280 was compiled with the correct sysroot using @code{--with-sysroot}).
16282 The symbol file and target libraries must exactly match the executable
16283 and libraries on the target, with one exception: the files on the host
16284 system should not be stripped, even if the files on the target system
16285 are. Mismatched or missing files will lead to confusing results
16286 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16287 files may also prevent @code{gdbserver} from debugging multi-threaded
16290 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16291 For TCP connections, you must start up @code{gdbserver} prior to using
16292 the @code{target remote} command. Otherwise you may get an error whose
16293 text depends on the host system, but which usually looks something like
16294 @samp{Connection refused}. Don't use the @code{load}
16295 command in @value{GDBN} when using @code{gdbserver}, since the program is
16296 already on the target.
16298 @subsection Monitor Commands for @code{gdbserver}
16299 @cindex monitor commands, for @code{gdbserver}
16300 @anchor{Monitor Commands for gdbserver}
16302 During a @value{GDBN} session using @code{gdbserver}, you can use the
16303 @code{monitor} command to send special requests to @code{gdbserver}.
16304 Here are the available commands.
16308 List the available monitor commands.
16310 @item monitor set debug 0
16311 @itemx monitor set debug 1
16312 Disable or enable general debugging messages.
16314 @item monitor set remote-debug 0
16315 @itemx monitor set remote-debug 1
16316 Disable or enable specific debugging messages associated with the remote
16317 protocol (@pxref{Remote Protocol}).
16319 @item monitor set libthread-db-search-path [PATH]
16320 @cindex gdbserver, search path for @code{libthread_db}
16321 When this command is issued, @var{path} is a colon-separated list of
16322 directories to search for @code{libthread_db} (@pxref{Threads,,set
16323 libthread-db-search-path}). If you omit @var{path},
16324 @samp{libthread-db-search-path} will be reset to an empty list.
16327 Tell gdbserver to exit immediately. This command should be followed by
16328 @code{disconnect} to close the debugging session. @code{gdbserver} will
16329 detach from any attached processes and kill any processes it created.
16330 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16331 of a multi-process mode debug session.
16335 @subsection Tracepoints support in @code{gdbserver}
16336 @cindex tracepoints support in @code{gdbserver}
16338 On some targets, @code{gdbserver} supports tracepoints, fast
16339 tracepoints and static tracepoints.
16341 For fast or static tracepoints to work, a special library called the
16342 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16343 This library is built and distributed as an integral part of
16344 @code{gdbserver}. In addition, support for static tracepoints
16345 requires building the in-process agent library with static tracepoints
16346 support. At present, the UST (LTTng Userspace Tracer,
16347 @url{http://lttng.org/ust}) tracing engine is supported. This support
16348 is automatically available if UST development headers are found in the
16349 standard include path when @code{gdbserver} is built, or if
16350 @code{gdbserver} was explicitly configured using @option{--with-ust}
16351 to point at such headers. You can explicitly disable the support
16352 using @option{--with-ust=no}.
16354 There are several ways to load the in-process agent in your program:
16357 @item Specifying it as dependency at link time
16359 You can link your program dynamically with the in-process agent
16360 library. On most systems, this is accomplished by adding
16361 @code{-linproctrace} to the link command.
16363 @item Using the system's preloading mechanisms
16365 You can force loading the in-process agent at startup time by using
16366 your system's support for preloading shared libraries. Many Unixes
16367 support the concept of preloading user defined libraries. In most
16368 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16369 in the environment. See also the description of @code{gdbserver}'s
16370 @option{--wrapper} command line option.
16372 @item Using @value{GDBN} to force loading the agent at run time
16374 On some systems, you can force the inferior to load a shared library,
16375 by calling a dynamic loader function in the inferior that takes care
16376 of dynamically looking up and loading a shared library. On most Unix
16377 systems, the function is @code{dlopen}. You'll use the @code{call}
16378 command for that. For example:
16381 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16384 Note that on most Unix systems, for the @code{dlopen} function to be
16385 available, the program needs to be linked with @code{-ldl}.
16388 On systems that have a userspace dynamic loader, like most Unix
16389 systems, when you connect to @code{gdbserver} using @code{target
16390 remote}, you'll find that the program is stopped at the dynamic
16391 loader's entry point, and no shared library has been loaded in the
16392 program's address space yet, including the in-process agent. In that
16393 case, before being able to use any of the fast or static tracepoints
16394 features, you need to let the loader run and load the shared
16395 libraries. The simplest way to do that is to run the program to the
16396 main procedure. E.g., if debugging a C or C@t{++} program, start
16397 @code{gdbserver} like so:
16400 $ gdbserver :9999 myprogram
16403 Start GDB and connect to @code{gdbserver} like so, and run to main:
16407 (@value{GDBP}) target remote myhost:9999
16408 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16409 (@value{GDBP}) b main
16410 (@value{GDBP}) continue
16413 The in-process tracing agent library should now be loaded into the
16414 process; you can confirm it with the @code{info sharedlibrary}
16415 command, which will list @file{libinproctrace.so} as loaded in the
16416 process. You are now ready to install fast tracepoints, list static
16417 tracepoint markers, probe static tracepoints markers, and start
16420 @node Remote Configuration
16421 @section Remote Configuration
16424 @kindex show remote
16425 This section documents the configuration options available when
16426 debugging remote programs. For the options related to the File I/O
16427 extensions of the remote protocol, see @ref{system,
16428 system-call-allowed}.
16431 @item set remoteaddresssize @var{bits}
16432 @cindex address size for remote targets
16433 @cindex bits in remote address
16434 Set the maximum size of address in a memory packet to the specified
16435 number of bits. @value{GDBN} will mask off the address bits above
16436 that number, when it passes addresses to the remote target. The
16437 default value is the number of bits in the target's address.
16439 @item show remoteaddresssize
16440 Show the current value of remote address size in bits.
16442 @item set remotebaud @var{n}
16443 @cindex baud rate for remote targets
16444 Set the baud rate for the remote serial I/O to @var{n} baud. The
16445 value is used to set the speed of the serial port used for debugging
16448 @item show remotebaud
16449 Show the current speed of the remote connection.
16451 @item set remotebreak
16452 @cindex interrupt remote programs
16453 @cindex BREAK signal instead of Ctrl-C
16454 @anchor{set remotebreak}
16455 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
16456 when you type @kbd{Ctrl-c} to interrupt the program running
16457 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
16458 character instead. The default is off, since most remote systems
16459 expect to see @samp{Ctrl-C} as the interrupt signal.
16461 @item show remotebreak
16462 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
16463 interrupt the remote program.
16465 @item set remoteflow on
16466 @itemx set remoteflow off
16467 @kindex set remoteflow
16468 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
16469 on the serial port used to communicate to the remote target.
16471 @item show remoteflow
16472 @kindex show remoteflow
16473 Show the current setting of hardware flow control.
16475 @item set remotelogbase @var{base}
16476 Set the base (a.k.a.@: radix) of logging serial protocol
16477 communications to @var{base}. Supported values of @var{base} are:
16478 @code{ascii}, @code{octal}, and @code{hex}. The default is
16481 @item show remotelogbase
16482 Show the current setting of the radix for logging remote serial
16485 @item set remotelogfile @var{file}
16486 @cindex record serial communications on file
16487 Record remote serial communications on the named @var{file}. The
16488 default is not to record at all.
16490 @item show remotelogfile.
16491 Show the current setting of the file name on which to record the
16492 serial communications.
16494 @item set remotetimeout @var{num}
16495 @cindex timeout for serial communications
16496 @cindex remote timeout
16497 Set the timeout limit to wait for the remote target to respond to
16498 @var{num} seconds. The default is 2 seconds.
16500 @item show remotetimeout
16501 Show the current number of seconds to wait for the remote target
16504 @cindex limit hardware breakpoints and watchpoints
16505 @cindex remote target, limit break- and watchpoints
16506 @anchor{set remote hardware-watchpoint-limit}
16507 @anchor{set remote hardware-breakpoint-limit}
16508 @item set remote hardware-watchpoint-limit @var{limit}
16509 @itemx set remote hardware-breakpoint-limit @var{limit}
16510 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
16511 watchpoints. A limit of -1, the default, is treated as unlimited.
16513 @item set remote exec-file @var{filename}
16514 @itemx show remote exec-file
16515 @anchor{set remote exec-file}
16516 @cindex executable file, for remote target
16517 Select the file used for @code{run} with @code{target
16518 extended-remote}. This should be set to a filename valid on the
16519 target system. If it is not set, the target will use a default
16520 filename (e.g.@: the last program run).
16522 @item set remote interrupt-sequence
16523 @cindex interrupt remote programs
16524 @cindex select Ctrl-C, BREAK or BREAK-g
16525 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
16526 @samp{BREAK-g} as the
16527 sequence to the remote target in order to interrupt the execution.
16528 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
16529 is high level of serial line for some certain time.
16530 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
16531 It is @code{BREAK} signal followed by character @code{g}.
16533 @item show interrupt-sequence
16534 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
16535 is sent by @value{GDBN} to interrupt the remote program.
16536 @code{BREAK-g} is BREAK signal followed by @code{g} and
16537 also known as Magic SysRq g.
16539 @item set remote interrupt-on-connect
16540 @cindex send interrupt-sequence on start
16541 Specify whether interrupt-sequence is sent to remote target when
16542 @value{GDBN} connects to it. This is mostly needed when you debug
16543 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
16544 which is known as Magic SysRq g in order to connect @value{GDBN}.
16546 @item show interrupt-on-connect
16547 Show whether interrupt-sequence is sent
16548 to remote target when @value{GDBN} connects to it.
16552 @item set tcp auto-retry on
16553 @cindex auto-retry, for remote TCP target
16554 Enable auto-retry for remote TCP connections. This is useful if the remote
16555 debugging agent is launched in parallel with @value{GDBN}; there is a race
16556 condition because the agent may not become ready to accept the connection
16557 before @value{GDBN} attempts to connect. When auto-retry is
16558 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
16559 to establish the connection using the timeout specified by
16560 @code{set tcp connect-timeout}.
16562 @item set tcp auto-retry off
16563 Do not auto-retry failed TCP connections.
16565 @item show tcp auto-retry
16566 Show the current auto-retry setting.
16568 @item set tcp connect-timeout @var{seconds}
16569 @cindex connection timeout, for remote TCP target
16570 @cindex timeout, for remote target connection
16571 Set the timeout for establishing a TCP connection to the remote target to
16572 @var{seconds}. The timeout affects both polling to retry failed connections
16573 (enabled by @code{set tcp auto-retry on}) and waiting for connections
16574 that are merely slow to complete, and represents an approximate cumulative
16577 @item show tcp connect-timeout
16578 Show the current connection timeout setting.
16581 @cindex remote packets, enabling and disabling
16582 The @value{GDBN} remote protocol autodetects the packets supported by
16583 your debugging stub. If you need to override the autodetection, you
16584 can use these commands to enable or disable individual packets. Each
16585 packet can be set to @samp{on} (the remote target supports this
16586 packet), @samp{off} (the remote target does not support this packet),
16587 or @samp{auto} (detect remote target support for this packet). They
16588 all default to @samp{auto}. For more information about each packet,
16589 see @ref{Remote Protocol}.
16591 During normal use, you should not have to use any of these commands.
16592 If you do, that may be a bug in your remote debugging stub, or a bug
16593 in @value{GDBN}. You may want to report the problem to the
16594 @value{GDBN} developers.
16596 For each packet @var{name}, the command to enable or disable the
16597 packet is @code{set remote @var{name}-packet}. The available settings
16600 @multitable @columnfractions 0.28 0.32 0.25
16603 @tab Related Features
16605 @item @code{fetch-register}
16607 @tab @code{info registers}
16609 @item @code{set-register}
16613 @item @code{binary-download}
16615 @tab @code{load}, @code{set}
16617 @item @code{read-aux-vector}
16618 @tab @code{qXfer:auxv:read}
16619 @tab @code{info auxv}
16621 @item @code{symbol-lookup}
16622 @tab @code{qSymbol}
16623 @tab Detecting multiple threads
16625 @item @code{attach}
16626 @tab @code{vAttach}
16629 @item @code{verbose-resume}
16631 @tab Stepping or resuming multiple threads
16637 @item @code{software-breakpoint}
16641 @item @code{hardware-breakpoint}
16645 @item @code{write-watchpoint}
16649 @item @code{read-watchpoint}
16653 @item @code{access-watchpoint}
16657 @item @code{target-features}
16658 @tab @code{qXfer:features:read}
16659 @tab @code{set architecture}
16661 @item @code{library-info}
16662 @tab @code{qXfer:libraries:read}
16663 @tab @code{info sharedlibrary}
16665 @item @code{memory-map}
16666 @tab @code{qXfer:memory-map:read}
16667 @tab @code{info mem}
16669 @item @code{read-sdata-object}
16670 @tab @code{qXfer:sdata:read}
16671 @tab @code{print $_sdata}
16673 @item @code{read-spu-object}
16674 @tab @code{qXfer:spu:read}
16675 @tab @code{info spu}
16677 @item @code{write-spu-object}
16678 @tab @code{qXfer:spu:write}
16679 @tab @code{info spu}
16681 @item @code{read-siginfo-object}
16682 @tab @code{qXfer:siginfo:read}
16683 @tab @code{print $_siginfo}
16685 @item @code{write-siginfo-object}
16686 @tab @code{qXfer:siginfo:write}
16687 @tab @code{set $_siginfo}
16689 @item @code{threads}
16690 @tab @code{qXfer:threads:read}
16691 @tab @code{info threads}
16693 @item @code{get-thread-local-@*storage-address}
16694 @tab @code{qGetTLSAddr}
16695 @tab Displaying @code{__thread} variables
16697 @item @code{get-thread-information-block-address}
16698 @tab @code{qGetTIBAddr}
16699 @tab Display MS-Windows Thread Information Block.
16701 @item @code{search-memory}
16702 @tab @code{qSearch:memory}
16705 @item @code{supported-packets}
16706 @tab @code{qSupported}
16707 @tab Remote communications parameters
16709 @item @code{pass-signals}
16710 @tab @code{QPassSignals}
16711 @tab @code{handle @var{signal}}
16713 @item @code{hostio-close-packet}
16714 @tab @code{vFile:close}
16715 @tab @code{remote get}, @code{remote put}
16717 @item @code{hostio-open-packet}
16718 @tab @code{vFile:open}
16719 @tab @code{remote get}, @code{remote put}
16721 @item @code{hostio-pread-packet}
16722 @tab @code{vFile:pread}
16723 @tab @code{remote get}, @code{remote put}
16725 @item @code{hostio-pwrite-packet}
16726 @tab @code{vFile:pwrite}
16727 @tab @code{remote get}, @code{remote put}
16729 @item @code{hostio-unlink-packet}
16730 @tab @code{vFile:unlink}
16731 @tab @code{remote delete}
16733 @item @code{noack-packet}
16734 @tab @code{QStartNoAckMode}
16735 @tab Packet acknowledgment
16737 @item @code{osdata}
16738 @tab @code{qXfer:osdata:read}
16739 @tab @code{info os}
16741 @item @code{query-attached}
16742 @tab @code{qAttached}
16743 @tab Querying remote process attach state.
16745 @item @code{traceframe-info}
16746 @tab @code{qXfer:traceframe-info:read}
16747 @tab Traceframe info
16751 @section Implementing a Remote Stub
16753 @cindex debugging stub, example
16754 @cindex remote stub, example
16755 @cindex stub example, remote debugging
16756 The stub files provided with @value{GDBN} implement the target side of the
16757 communication protocol, and the @value{GDBN} side is implemented in the
16758 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
16759 these subroutines to communicate, and ignore the details. (If you're
16760 implementing your own stub file, you can still ignore the details: start
16761 with one of the existing stub files. @file{sparc-stub.c} is the best
16762 organized, and therefore the easiest to read.)
16764 @cindex remote serial debugging, overview
16765 To debug a program running on another machine (the debugging
16766 @dfn{target} machine), you must first arrange for all the usual
16767 prerequisites for the program to run by itself. For example, for a C
16772 A startup routine to set up the C runtime environment; these usually
16773 have a name like @file{crt0}. The startup routine may be supplied by
16774 your hardware supplier, or you may have to write your own.
16777 A C subroutine library to support your program's
16778 subroutine calls, notably managing input and output.
16781 A way of getting your program to the other machine---for example, a
16782 download program. These are often supplied by the hardware
16783 manufacturer, but you may have to write your own from hardware
16787 The next step is to arrange for your program to use a serial port to
16788 communicate with the machine where @value{GDBN} is running (the @dfn{host}
16789 machine). In general terms, the scheme looks like this:
16793 @value{GDBN} already understands how to use this protocol; when everything
16794 else is set up, you can simply use the @samp{target remote} command
16795 (@pxref{Targets,,Specifying a Debugging Target}).
16797 @item On the target,
16798 you must link with your program a few special-purpose subroutines that
16799 implement the @value{GDBN} remote serial protocol. The file containing these
16800 subroutines is called a @dfn{debugging stub}.
16802 On certain remote targets, you can use an auxiliary program
16803 @code{gdbserver} instead of linking a stub into your program.
16804 @xref{Server,,Using the @code{gdbserver} Program}, for details.
16807 The debugging stub is specific to the architecture of the remote
16808 machine; for example, use @file{sparc-stub.c} to debug programs on
16811 @cindex remote serial stub list
16812 These working remote stubs are distributed with @value{GDBN}:
16817 @cindex @file{i386-stub.c}
16820 For Intel 386 and compatible architectures.
16823 @cindex @file{m68k-stub.c}
16824 @cindex Motorola 680x0
16826 For Motorola 680x0 architectures.
16829 @cindex @file{sh-stub.c}
16832 For Renesas SH architectures.
16835 @cindex @file{sparc-stub.c}
16837 For @sc{sparc} architectures.
16839 @item sparcl-stub.c
16840 @cindex @file{sparcl-stub.c}
16843 For Fujitsu @sc{sparclite} architectures.
16847 The @file{README} file in the @value{GDBN} distribution may list other
16848 recently added stubs.
16851 * Stub Contents:: What the stub can do for you
16852 * Bootstrapping:: What you must do for the stub
16853 * Debug Session:: Putting it all together
16856 @node Stub Contents
16857 @subsection What the Stub Can Do for You
16859 @cindex remote serial stub
16860 The debugging stub for your architecture supplies these three
16864 @item set_debug_traps
16865 @findex set_debug_traps
16866 @cindex remote serial stub, initialization
16867 This routine arranges for @code{handle_exception} to run when your
16868 program stops. You must call this subroutine explicitly near the
16869 beginning of your program.
16871 @item handle_exception
16872 @findex handle_exception
16873 @cindex remote serial stub, main routine
16874 This is the central workhorse, but your program never calls it
16875 explicitly---the setup code arranges for @code{handle_exception} to
16876 run when a trap is triggered.
16878 @code{handle_exception} takes control when your program stops during
16879 execution (for example, on a breakpoint), and mediates communications
16880 with @value{GDBN} on the host machine. This is where the communications
16881 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
16882 representative on the target machine. It begins by sending summary
16883 information on the state of your program, then continues to execute,
16884 retrieving and transmitting any information @value{GDBN} needs, until you
16885 execute a @value{GDBN} command that makes your program resume; at that point,
16886 @code{handle_exception} returns control to your own code on the target
16890 @cindex @code{breakpoint} subroutine, remote
16891 Use this auxiliary subroutine to make your program contain a
16892 breakpoint. Depending on the particular situation, this may be the only
16893 way for @value{GDBN} to get control. For instance, if your target
16894 machine has some sort of interrupt button, you won't need to call this;
16895 pressing the interrupt button transfers control to
16896 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
16897 simply receiving characters on the serial port may also trigger a trap;
16898 again, in that situation, you don't need to call @code{breakpoint} from
16899 your own program---simply running @samp{target remote} from the host
16900 @value{GDBN} session gets control.
16902 Call @code{breakpoint} if none of these is true, or if you simply want
16903 to make certain your program stops at a predetermined point for the
16904 start of your debugging session.
16907 @node Bootstrapping
16908 @subsection What You Must Do for the Stub
16910 @cindex remote stub, support routines
16911 The debugging stubs that come with @value{GDBN} are set up for a particular
16912 chip architecture, but they have no information about the rest of your
16913 debugging target machine.
16915 First of all you need to tell the stub how to communicate with the
16919 @item int getDebugChar()
16920 @findex getDebugChar
16921 Write this subroutine to read a single character from the serial port.
16922 It may be identical to @code{getchar} for your target system; a
16923 different name is used to allow you to distinguish the two if you wish.
16925 @item void putDebugChar(int)
16926 @findex putDebugChar
16927 Write this subroutine to write a single character to the serial port.
16928 It may be identical to @code{putchar} for your target system; a
16929 different name is used to allow you to distinguish the two if you wish.
16932 @cindex control C, and remote debugging
16933 @cindex interrupting remote targets
16934 If you want @value{GDBN} to be able to stop your program while it is
16935 running, you need to use an interrupt-driven serial driver, and arrange
16936 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
16937 character). That is the character which @value{GDBN} uses to tell the
16938 remote system to stop.
16940 Getting the debugging target to return the proper status to @value{GDBN}
16941 probably requires changes to the standard stub; one quick and dirty way
16942 is to just execute a breakpoint instruction (the ``dirty'' part is that
16943 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
16945 Other routines you need to supply are:
16948 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
16949 @findex exceptionHandler
16950 Write this function to install @var{exception_address} in the exception
16951 handling tables. You need to do this because the stub does not have any
16952 way of knowing what the exception handling tables on your target system
16953 are like (for example, the processor's table might be in @sc{rom},
16954 containing entries which point to a table in @sc{ram}).
16955 @var{exception_number} is the exception number which should be changed;
16956 its meaning is architecture-dependent (for example, different numbers
16957 might represent divide by zero, misaligned access, etc). When this
16958 exception occurs, control should be transferred directly to
16959 @var{exception_address}, and the processor state (stack, registers,
16960 and so on) should be just as it is when a processor exception occurs. So if
16961 you want to use a jump instruction to reach @var{exception_address}, it
16962 should be a simple jump, not a jump to subroutine.
16964 For the 386, @var{exception_address} should be installed as an interrupt
16965 gate so that interrupts are masked while the handler runs. The gate
16966 should be at privilege level 0 (the most privileged level). The
16967 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
16968 help from @code{exceptionHandler}.
16970 @item void flush_i_cache()
16971 @findex flush_i_cache
16972 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
16973 instruction cache, if any, on your target machine. If there is no
16974 instruction cache, this subroutine may be a no-op.
16976 On target machines that have instruction caches, @value{GDBN} requires this
16977 function to make certain that the state of your program is stable.
16981 You must also make sure this library routine is available:
16984 @item void *memset(void *, int, int)
16986 This is the standard library function @code{memset} that sets an area of
16987 memory to a known value. If you have one of the free versions of
16988 @code{libc.a}, @code{memset} can be found there; otherwise, you must
16989 either obtain it from your hardware manufacturer, or write your own.
16992 If you do not use the GNU C compiler, you may need other standard
16993 library subroutines as well; this varies from one stub to another,
16994 but in general the stubs are likely to use any of the common library
16995 subroutines which @code{@value{NGCC}} generates as inline code.
16998 @node Debug Session
16999 @subsection Putting it All Together
17001 @cindex remote serial debugging summary
17002 In summary, when your program is ready to debug, you must follow these
17007 Make sure you have defined the supporting low-level routines
17008 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17010 @code{getDebugChar}, @code{putDebugChar},
17011 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17015 Insert these lines near the top of your program:
17023 For the 680x0 stub only, you need to provide a variable called
17024 @code{exceptionHook}. Normally you just use:
17027 void (*exceptionHook)() = 0;
17031 but if before calling @code{set_debug_traps}, you set it to point to a
17032 function in your program, that function is called when
17033 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17034 error). The function indicated by @code{exceptionHook} is called with
17035 one parameter: an @code{int} which is the exception number.
17038 Compile and link together: your program, the @value{GDBN} debugging stub for
17039 your target architecture, and the supporting subroutines.
17042 Make sure you have a serial connection between your target machine and
17043 the @value{GDBN} host, and identify the serial port on the host.
17046 @c The "remote" target now provides a `load' command, so we should
17047 @c document that. FIXME.
17048 Download your program to your target machine (or get it there by
17049 whatever means the manufacturer provides), and start it.
17052 Start @value{GDBN} on the host, and connect to the target
17053 (@pxref{Connecting,,Connecting to a Remote Target}).
17057 @node Configurations
17058 @chapter Configuration-Specific Information
17060 While nearly all @value{GDBN} commands are available for all native and
17061 cross versions of the debugger, there are some exceptions. This chapter
17062 describes things that are only available in certain configurations.
17064 There are three major categories of configurations: native
17065 configurations, where the host and target are the same, embedded
17066 operating system configurations, which are usually the same for several
17067 different processor architectures, and bare embedded processors, which
17068 are quite different from each other.
17073 * Embedded Processors::
17080 This section describes details specific to particular native
17085 * BSD libkvm Interface:: Debugging BSD kernel memory images
17086 * SVR4 Process Information:: SVR4 process information
17087 * DJGPP Native:: Features specific to the DJGPP port
17088 * Cygwin Native:: Features specific to the Cygwin port
17089 * Hurd Native:: Features specific to @sc{gnu} Hurd
17090 * Neutrino:: Features specific to QNX Neutrino
17091 * Darwin:: Features specific to Darwin
17097 On HP-UX systems, if you refer to a function or variable name that
17098 begins with a dollar sign, @value{GDBN} searches for a user or system
17099 name first, before it searches for a convenience variable.
17102 @node BSD libkvm Interface
17103 @subsection BSD libkvm Interface
17106 @cindex kernel memory image
17107 @cindex kernel crash dump
17109 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17110 interface that provides a uniform interface for accessing kernel virtual
17111 memory images, including live systems and crash dumps. @value{GDBN}
17112 uses this interface to allow you to debug live kernels and kernel crash
17113 dumps on many native BSD configurations. This is implemented as a
17114 special @code{kvm} debugging target. For debugging a live system, load
17115 the currently running kernel into @value{GDBN} and connect to the
17119 (@value{GDBP}) @b{target kvm}
17122 For debugging crash dumps, provide the file name of the crash dump as an
17126 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17129 Once connected to the @code{kvm} target, the following commands are
17135 Set current context from the @dfn{Process Control Block} (PCB) address.
17138 Set current context from proc address. This command isn't available on
17139 modern FreeBSD systems.
17142 @node SVR4 Process Information
17143 @subsection SVR4 Process Information
17145 @cindex examine process image
17146 @cindex process info via @file{/proc}
17148 Many versions of SVR4 and compatible systems provide a facility called
17149 @samp{/proc} that can be used to examine the image of a running
17150 process using file-system subroutines. If @value{GDBN} is configured
17151 for an operating system with this facility, the command @code{info
17152 proc} is available to report information about the process running
17153 your program, or about any process running on your system. @code{info
17154 proc} works only on SVR4 systems that include the @code{procfs} code.
17155 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17156 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17162 @itemx info proc @var{process-id}
17163 Summarize available information about any running process. If a
17164 process ID is specified by @var{process-id}, display information about
17165 that process; otherwise display information about the program being
17166 debugged. The summary includes the debugged process ID, the command
17167 line used to invoke it, its current working directory, and its
17168 executable file's absolute file name.
17170 On some systems, @var{process-id} can be of the form
17171 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17172 within a process. If the optional @var{pid} part is missing, it means
17173 a thread from the process being debugged (the leading @samp{/} still
17174 needs to be present, or else @value{GDBN} will interpret the number as
17175 a process ID rather than a thread ID).
17177 @item info proc mappings
17178 @cindex memory address space mappings
17179 Report the memory address space ranges accessible in the program, with
17180 information on whether the process has read, write, or execute access
17181 rights to each range. On @sc{gnu}/Linux systems, each memory range
17182 includes the object file which is mapped to that range, instead of the
17183 memory access rights to that range.
17185 @item info proc stat
17186 @itemx info proc status
17187 @cindex process detailed status information
17188 These subcommands are specific to @sc{gnu}/Linux systems. They show
17189 the process-related information, including the user ID and group ID;
17190 how many threads are there in the process; its virtual memory usage;
17191 the signals that are pending, blocked, and ignored; its TTY; its
17192 consumption of system and user time; its stack size; its @samp{nice}
17193 value; etc. For more information, see the @samp{proc} man page
17194 (type @kbd{man 5 proc} from your shell prompt).
17196 @item info proc all
17197 Show all the information about the process described under all of the
17198 above @code{info proc} subcommands.
17201 @comment These sub-options of 'info proc' were not included when
17202 @comment procfs.c was re-written. Keep their descriptions around
17203 @comment against the day when someone finds the time to put them back in.
17204 @kindex info proc times
17205 @item info proc times
17206 Starting time, user CPU time, and system CPU time for your program and
17209 @kindex info proc id
17211 Report on the process IDs related to your program: its own process ID,
17212 the ID of its parent, the process group ID, and the session ID.
17215 @item set procfs-trace
17216 @kindex set procfs-trace
17217 @cindex @code{procfs} API calls
17218 This command enables and disables tracing of @code{procfs} API calls.
17220 @item show procfs-trace
17221 @kindex show procfs-trace
17222 Show the current state of @code{procfs} API call tracing.
17224 @item set procfs-file @var{file}
17225 @kindex set procfs-file
17226 Tell @value{GDBN} to write @code{procfs} API trace to the named
17227 @var{file}. @value{GDBN} appends the trace info to the previous
17228 contents of the file. The default is to display the trace on the
17231 @item show procfs-file
17232 @kindex show procfs-file
17233 Show the file to which @code{procfs} API trace is written.
17235 @item proc-trace-entry
17236 @itemx proc-trace-exit
17237 @itemx proc-untrace-entry
17238 @itemx proc-untrace-exit
17239 @kindex proc-trace-entry
17240 @kindex proc-trace-exit
17241 @kindex proc-untrace-entry
17242 @kindex proc-untrace-exit
17243 These commands enable and disable tracing of entries into and exits
17244 from the @code{syscall} interface.
17247 @kindex info pidlist
17248 @cindex process list, QNX Neutrino
17249 For QNX Neutrino only, this command displays the list of all the
17250 processes and all the threads within each process.
17253 @kindex info meminfo
17254 @cindex mapinfo list, QNX Neutrino
17255 For QNX Neutrino only, this command displays the list of all mapinfos.
17259 @subsection Features for Debugging @sc{djgpp} Programs
17260 @cindex @sc{djgpp} debugging
17261 @cindex native @sc{djgpp} debugging
17262 @cindex MS-DOS-specific commands
17265 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17266 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17267 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17268 top of real-mode DOS systems and their emulations.
17270 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17271 defines a few commands specific to the @sc{djgpp} port. This
17272 subsection describes those commands.
17277 This is a prefix of @sc{djgpp}-specific commands which print
17278 information about the target system and important OS structures.
17281 @cindex MS-DOS system info
17282 @cindex free memory information (MS-DOS)
17283 @item info dos sysinfo
17284 This command displays assorted information about the underlying
17285 platform: the CPU type and features, the OS version and flavor, the
17286 DPMI version, and the available conventional and DPMI memory.
17291 @cindex segment descriptor tables
17292 @cindex descriptor tables display
17294 @itemx info dos ldt
17295 @itemx info dos idt
17296 These 3 commands display entries from, respectively, Global, Local,
17297 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17298 tables are data structures which store a descriptor for each segment
17299 that is currently in use. The segment's selector is an index into a
17300 descriptor table; the table entry for that index holds the
17301 descriptor's base address and limit, and its attributes and access
17304 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17305 segment (used for both data and the stack), and a DOS segment (which
17306 allows access to DOS/BIOS data structures and absolute addresses in
17307 conventional memory). However, the DPMI host will usually define
17308 additional segments in order to support the DPMI environment.
17310 @cindex garbled pointers
17311 These commands allow to display entries from the descriptor tables.
17312 Without an argument, all entries from the specified table are
17313 displayed. An argument, which should be an integer expression, means
17314 display a single entry whose index is given by the argument. For
17315 example, here's a convenient way to display information about the
17316 debugged program's data segment:
17319 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17320 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17324 This comes in handy when you want to see whether a pointer is outside
17325 the data segment's limit (i.e.@: @dfn{garbled}).
17327 @cindex page tables display (MS-DOS)
17329 @itemx info dos pte
17330 These two commands display entries from, respectively, the Page
17331 Directory and the Page Tables. Page Directories and Page Tables are
17332 data structures which control how virtual memory addresses are mapped
17333 into physical addresses. A Page Table includes an entry for every
17334 page of memory that is mapped into the program's address space; there
17335 may be several Page Tables, each one holding up to 4096 entries. A
17336 Page Directory has up to 4096 entries, one each for every Page Table
17337 that is currently in use.
17339 Without an argument, @kbd{info dos pde} displays the entire Page
17340 Directory, and @kbd{info dos pte} displays all the entries in all of
17341 the Page Tables. An argument, an integer expression, given to the
17342 @kbd{info dos pde} command means display only that entry from the Page
17343 Directory table. An argument given to the @kbd{info dos pte} command
17344 means display entries from a single Page Table, the one pointed to by
17345 the specified entry in the Page Directory.
17347 @cindex direct memory access (DMA) on MS-DOS
17348 These commands are useful when your program uses @dfn{DMA} (Direct
17349 Memory Access), which needs physical addresses to program the DMA
17352 These commands are supported only with some DPMI servers.
17354 @cindex physical address from linear address
17355 @item info dos address-pte @var{addr}
17356 This command displays the Page Table entry for a specified linear
17357 address. The argument @var{addr} is a linear address which should
17358 already have the appropriate segment's base address added to it,
17359 because this command accepts addresses which may belong to @emph{any}
17360 segment. For example, here's how to display the Page Table entry for
17361 the page where a variable @code{i} is stored:
17364 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17365 @exdent @code{Page Table entry for address 0x11a00d30:}
17366 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17370 This says that @code{i} is stored at offset @code{0xd30} from the page
17371 whose physical base address is @code{0x02698000}, and shows all the
17372 attributes of that page.
17374 Note that you must cast the addresses of variables to a @code{char *},
17375 since otherwise the value of @code{__djgpp_base_address}, the base
17376 address of all variables and functions in a @sc{djgpp} program, will
17377 be added using the rules of C pointer arithmetics: if @code{i} is
17378 declared an @code{int}, @value{GDBN} will add 4 times the value of
17379 @code{__djgpp_base_address} to the address of @code{i}.
17381 Here's another example, it displays the Page Table entry for the
17385 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17386 @exdent @code{Page Table entry for address 0x29110:}
17387 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17391 (The @code{+ 3} offset is because the transfer buffer's address is the
17392 3rd member of the @code{_go32_info_block} structure.) The output
17393 clearly shows that this DPMI server maps the addresses in conventional
17394 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17395 linear (@code{0x29110}) addresses are identical.
17397 This command is supported only with some DPMI servers.
17400 @cindex DOS serial data link, remote debugging
17401 In addition to native debugging, the DJGPP port supports remote
17402 debugging via a serial data link. The following commands are specific
17403 to remote serial debugging in the DJGPP port of @value{GDBN}.
17406 @kindex set com1base
17407 @kindex set com1irq
17408 @kindex set com2base
17409 @kindex set com2irq
17410 @kindex set com3base
17411 @kindex set com3irq
17412 @kindex set com4base
17413 @kindex set com4irq
17414 @item set com1base @var{addr}
17415 This command sets the base I/O port address of the @file{COM1} serial
17418 @item set com1irq @var{irq}
17419 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
17420 for the @file{COM1} serial port.
17422 There are similar commands @samp{set com2base}, @samp{set com3irq},
17423 etc.@: for setting the port address and the @code{IRQ} lines for the
17426 @kindex show com1base
17427 @kindex show com1irq
17428 @kindex show com2base
17429 @kindex show com2irq
17430 @kindex show com3base
17431 @kindex show com3irq
17432 @kindex show com4base
17433 @kindex show com4irq
17434 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
17435 display the current settings of the base address and the @code{IRQ}
17436 lines used by the COM ports.
17439 @kindex info serial
17440 @cindex DOS serial port status
17441 This command prints the status of the 4 DOS serial ports. For each
17442 port, it prints whether it's active or not, its I/O base address and
17443 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
17444 counts of various errors encountered so far.
17448 @node Cygwin Native
17449 @subsection Features for Debugging MS Windows PE Executables
17450 @cindex MS Windows debugging
17451 @cindex native Cygwin debugging
17452 @cindex Cygwin-specific commands
17454 @value{GDBN} supports native debugging of MS Windows programs, including
17455 DLLs with and without symbolic debugging information.
17457 @cindex Ctrl-BREAK, MS-Windows
17458 @cindex interrupt debuggee on MS-Windows
17459 MS-Windows programs that call @code{SetConsoleMode} to switch off the
17460 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
17461 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
17462 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
17463 sequence, which can be used to interrupt the debuggee even if it
17466 There are various additional Cygwin-specific commands, described in
17467 this section. Working with DLLs that have no debugging symbols is
17468 described in @ref{Non-debug DLL Symbols}.
17473 This is a prefix of MS Windows-specific commands which print
17474 information about the target system and important OS structures.
17476 @item info w32 selector
17477 This command displays information returned by
17478 the Win32 API @code{GetThreadSelectorEntry} function.
17479 It takes an optional argument that is evaluated to
17480 a long value to give the information about this given selector.
17481 Without argument, this command displays information
17482 about the six segment registers.
17484 @item info w32 thread-information-block
17485 This command displays thread specific information stored in the
17486 Thread Information Block (readable on the X86 CPU family using @code{$fs}
17487 selector for 32-bit programs and @code{$gs} for 64-bit programs).
17491 This is a Cygwin-specific alias of @code{info shared}.
17493 @kindex dll-symbols
17495 This command loads symbols from a dll similarly to
17496 add-sym command but without the need to specify a base address.
17498 @kindex set cygwin-exceptions
17499 @cindex debugging the Cygwin DLL
17500 @cindex Cygwin DLL, debugging
17501 @item set cygwin-exceptions @var{mode}
17502 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
17503 happen inside the Cygwin DLL. If @var{mode} is @code{off},
17504 @value{GDBN} will delay recognition of exceptions, and may ignore some
17505 exceptions which seem to be caused by internal Cygwin DLL
17506 ``bookkeeping''. This option is meant primarily for debugging the
17507 Cygwin DLL itself; the default value is @code{off} to avoid annoying
17508 @value{GDBN} users with false @code{SIGSEGV} signals.
17510 @kindex show cygwin-exceptions
17511 @item show cygwin-exceptions
17512 Displays whether @value{GDBN} will break on exceptions that happen
17513 inside the Cygwin DLL itself.
17515 @kindex set new-console
17516 @item set new-console @var{mode}
17517 If @var{mode} is @code{on} the debuggee will
17518 be started in a new console on next start.
17519 If @var{mode} is @code{off}, the debuggee will
17520 be started in the same console as the debugger.
17522 @kindex show new-console
17523 @item show new-console
17524 Displays whether a new console is used
17525 when the debuggee is started.
17527 @kindex set new-group
17528 @item set new-group @var{mode}
17529 This boolean value controls whether the debuggee should
17530 start a new group or stay in the same group as the debugger.
17531 This affects the way the Windows OS handles
17534 @kindex show new-group
17535 @item show new-group
17536 Displays current value of new-group boolean.
17538 @kindex set debugevents
17539 @item set debugevents
17540 This boolean value adds debug output concerning kernel events related
17541 to the debuggee seen by the debugger. This includes events that
17542 signal thread and process creation and exit, DLL loading and
17543 unloading, console interrupts, and debugging messages produced by the
17544 Windows @code{OutputDebugString} API call.
17546 @kindex set debugexec
17547 @item set debugexec
17548 This boolean value adds debug output concerning execute events
17549 (such as resume thread) seen by the debugger.
17551 @kindex set debugexceptions
17552 @item set debugexceptions
17553 This boolean value adds debug output concerning exceptions in the
17554 debuggee seen by the debugger.
17556 @kindex set debugmemory
17557 @item set debugmemory
17558 This boolean value adds debug output concerning debuggee memory reads
17559 and writes by the debugger.
17563 This boolean values specifies whether the debuggee is called
17564 via a shell or directly (default value is on).
17568 Displays if the debuggee will be started with a shell.
17573 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
17576 @node Non-debug DLL Symbols
17577 @subsubsection Support for DLLs without Debugging Symbols
17578 @cindex DLLs with no debugging symbols
17579 @cindex Minimal symbols and DLLs
17581 Very often on windows, some of the DLLs that your program relies on do
17582 not include symbolic debugging information (for example,
17583 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
17584 symbols in a DLL, it relies on the minimal amount of symbolic
17585 information contained in the DLL's export table. This section
17586 describes working with such symbols, known internally to @value{GDBN} as
17587 ``minimal symbols''.
17589 Note that before the debugged program has started execution, no DLLs
17590 will have been loaded. The easiest way around this problem is simply to
17591 start the program --- either by setting a breakpoint or letting the
17592 program run once to completion. It is also possible to force
17593 @value{GDBN} to load a particular DLL before starting the executable ---
17594 see the shared library information in @ref{Files}, or the
17595 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
17596 explicitly loading symbols from a DLL with no debugging information will
17597 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
17598 which may adversely affect symbol lookup performance.
17600 @subsubsection DLL Name Prefixes
17602 In keeping with the naming conventions used by the Microsoft debugging
17603 tools, DLL export symbols are made available with a prefix based on the
17604 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
17605 also entered into the symbol table, so @code{CreateFileA} is often
17606 sufficient. In some cases there will be name clashes within a program
17607 (particularly if the executable itself includes full debugging symbols)
17608 necessitating the use of the fully qualified name when referring to the
17609 contents of the DLL. Use single-quotes around the name to avoid the
17610 exclamation mark (``!'') being interpreted as a language operator.
17612 Note that the internal name of the DLL may be all upper-case, even
17613 though the file name of the DLL is lower-case, or vice-versa. Since
17614 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
17615 some confusion. If in doubt, try the @code{info functions} and
17616 @code{info variables} commands or even @code{maint print msymbols}
17617 (@pxref{Symbols}). Here's an example:
17620 (@value{GDBP}) info function CreateFileA
17621 All functions matching regular expression "CreateFileA":
17623 Non-debugging symbols:
17624 0x77e885f4 CreateFileA
17625 0x77e885f4 KERNEL32!CreateFileA
17629 (@value{GDBP}) info function !
17630 All functions matching regular expression "!":
17632 Non-debugging symbols:
17633 0x6100114c cygwin1!__assert
17634 0x61004034 cygwin1!_dll_crt0@@0
17635 0x61004240 cygwin1!dll_crt0(per_process *)
17639 @subsubsection Working with Minimal Symbols
17641 Symbols extracted from a DLL's export table do not contain very much
17642 type information. All that @value{GDBN} can do is guess whether a symbol
17643 refers to a function or variable depending on the linker section that
17644 contains the symbol. Also note that the actual contents of the memory
17645 contained in a DLL are not available unless the program is running. This
17646 means that you cannot examine the contents of a variable or disassemble
17647 a function within a DLL without a running program.
17649 Variables are generally treated as pointers and dereferenced
17650 automatically. For this reason, it is often necessary to prefix a
17651 variable name with the address-of operator (``&'') and provide explicit
17652 type information in the command. Here's an example of the type of
17656 (@value{GDBP}) print 'cygwin1!__argv'
17661 (@value{GDBP}) x 'cygwin1!__argv'
17662 0x10021610: "\230y\""
17665 And two possible solutions:
17668 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
17669 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
17673 (@value{GDBP}) x/2x &'cygwin1!__argv'
17674 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
17675 (@value{GDBP}) x/x 0x10021608
17676 0x10021608: 0x0022fd98
17677 (@value{GDBP}) x/s 0x0022fd98
17678 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
17681 Setting a break point within a DLL is possible even before the program
17682 starts execution. However, under these circumstances, @value{GDBN} can't
17683 examine the initial instructions of the function in order to skip the
17684 function's frame set-up code. You can work around this by using ``*&''
17685 to set the breakpoint at a raw memory address:
17688 (@value{GDBP}) break *&'python22!PyOS_Readline'
17689 Breakpoint 1 at 0x1e04eff0
17692 The author of these extensions is not entirely convinced that setting a
17693 break point within a shared DLL like @file{kernel32.dll} is completely
17697 @subsection Commands Specific to @sc{gnu} Hurd Systems
17698 @cindex @sc{gnu} Hurd debugging
17700 This subsection describes @value{GDBN} commands specific to the
17701 @sc{gnu} Hurd native debugging.
17706 @kindex set signals@r{, Hurd command}
17707 @kindex set sigs@r{, Hurd command}
17708 This command toggles the state of inferior signal interception by
17709 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
17710 affected by this command. @code{sigs} is a shorthand alias for
17715 @kindex show signals@r{, Hurd command}
17716 @kindex show sigs@r{, Hurd command}
17717 Show the current state of intercepting inferior's signals.
17719 @item set signal-thread
17720 @itemx set sigthread
17721 @kindex set signal-thread
17722 @kindex set sigthread
17723 This command tells @value{GDBN} which thread is the @code{libc} signal
17724 thread. That thread is run when a signal is delivered to a running
17725 process. @code{set sigthread} is the shorthand alias of @code{set
17728 @item show signal-thread
17729 @itemx show sigthread
17730 @kindex show signal-thread
17731 @kindex show sigthread
17732 These two commands show which thread will run when the inferior is
17733 delivered a signal.
17736 @kindex set stopped@r{, Hurd command}
17737 This commands tells @value{GDBN} that the inferior process is stopped,
17738 as with the @code{SIGSTOP} signal. The stopped process can be
17739 continued by delivering a signal to it.
17742 @kindex show stopped@r{, Hurd command}
17743 This command shows whether @value{GDBN} thinks the debuggee is
17746 @item set exceptions
17747 @kindex set exceptions@r{, Hurd command}
17748 Use this command to turn off trapping of exceptions in the inferior.
17749 When exception trapping is off, neither breakpoints nor
17750 single-stepping will work. To restore the default, set exception
17753 @item show exceptions
17754 @kindex show exceptions@r{, Hurd command}
17755 Show the current state of trapping exceptions in the inferior.
17757 @item set task pause
17758 @kindex set task@r{, Hurd commands}
17759 @cindex task attributes (@sc{gnu} Hurd)
17760 @cindex pause current task (@sc{gnu} Hurd)
17761 This command toggles task suspension when @value{GDBN} has control.
17762 Setting it to on takes effect immediately, and the task is suspended
17763 whenever @value{GDBN} gets control. Setting it to off will take
17764 effect the next time the inferior is continued. If this option is set
17765 to off, you can use @code{set thread default pause on} or @code{set
17766 thread pause on} (see below) to pause individual threads.
17768 @item show task pause
17769 @kindex show task@r{, Hurd commands}
17770 Show the current state of task suspension.
17772 @item set task detach-suspend-count
17773 @cindex task suspend count
17774 @cindex detach from task, @sc{gnu} Hurd
17775 This command sets the suspend count the task will be left with when
17776 @value{GDBN} detaches from it.
17778 @item show task detach-suspend-count
17779 Show the suspend count the task will be left with when detaching.
17781 @item set task exception-port
17782 @itemx set task excp
17783 @cindex task exception port, @sc{gnu} Hurd
17784 This command sets the task exception port to which @value{GDBN} will
17785 forward exceptions. The argument should be the value of the @dfn{send
17786 rights} of the task. @code{set task excp} is a shorthand alias.
17788 @item set noninvasive
17789 @cindex noninvasive task options
17790 This command switches @value{GDBN} to a mode that is the least
17791 invasive as far as interfering with the inferior is concerned. This
17792 is the same as using @code{set task pause}, @code{set exceptions}, and
17793 @code{set signals} to values opposite to the defaults.
17795 @item info send-rights
17796 @itemx info receive-rights
17797 @itemx info port-rights
17798 @itemx info port-sets
17799 @itemx info dead-names
17802 @cindex send rights, @sc{gnu} Hurd
17803 @cindex receive rights, @sc{gnu} Hurd
17804 @cindex port rights, @sc{gnu} Hurd
17805 @cindex port sets, @sc{gnu} Hurd
17806 @cindex dead names, @sc{gnu} Hurd
17807 These commands display information about, respectively, send rights,
17808 receive rights, port rights, port sets, and dead names of a task.
17809 There are also shorthand aliases: @code{info ports} for @code{info
17810 port-rights} and @code{info psets} for @code{info port-sets}.
17812 @item set thread pause
17813 @kindex set thread@r{, Hurd command}
17814 @cindex thread properties, @sc{gnu} Hurd
17815 @cindex pause current thread (@sc{gnu} Hurd)
17816 This command toggles current thread suspension when @value{GDBN} has
17817 control. Setting it to on takes effect immediately, and the current
17818 thread is suspended whenever @value{GDBN} gets control. Setting it to
17819 off will take effect the next time the inferior is continued.
17820 Normally, this command has no effect, since when @value{GDBN} has
17821 control, the whole task is suspended. However, if you used @code{set
17822 task pause off} (see above), this command comes in handy to suspend
17823 only the current thread.
17825 @item show thread pause
17826 @kindex show thread@r{, Hurd command}
17827 This command shows the state of current thread suspension.
17829 @item set thread run
17830 This command sets whether the current thread is allowed to run.
17832 @item show thread run
17833 Show whether the current thread is allowed to run.
17835 @item set thread detach-suspend-count
17836 @cindex thread suspend count, @sc{gnu} Hurd
17837 @cindex detach from thread, @sc{gnu} Hurd
17838 This command sets the suspend count @value{GDBN} will leave on a
17839 thread when detaching. This number is relative to the suspend count
17840 found by @value{GDBN} when it notices the thread; use @code{set thread
17841 takeover-suspend-count} to force it to an absolute value.
17843 @item show thread detach-suspend-count
17844 Show the suspend count @value{GDBN} will leave on the thread when
17847 @item set thread exception-port
17848 @itemx set thread excp
17849 Set the thread exception port to which to forward exceptions. This
17850 overrides the port set by @code{set task exception-port} (see above).
17851 @code{set thread excp} is the shorthand alias.
17853 @item set thread takeover-suspend-count
17854 Normally, @value{GDBN}'s thread suspend counts are relative to the
17855 value @value{GDBN} finds when it notices each thread. This command
17856 changes the suspend counts to be absolute instead.
17858 @item set thread default
17859 @itemx show thread default
17860 @cindex thread default settings, @sc{gnu} Hurd
17861 Each of the above @code{set thread} commands has a @code{set thread
17862 default} counterpart (e.g., @code{set thread default pause}, @code{set
17863 thread default exception-port}, etc.). The @code{thread default}
17864 variety of commands sets the default thread properties for all
17865 threads; you can then change the properties of individual threads with
17866 the non-default commands.
17871 @subsection QNX Neutrino
17872 @cindex QNX Neutrino
17874 @value{GDBN} provides the following commands specific to the QNX
17878 @item set debug nto-debug
17879 @kindex set debug nto-debug
17880 When set to on, enables debugging messages specific to the QNX
17883 @item show debug nto-debug
17884 @kindex show debug nto-debug
17885 Show the current state of QNX Neutrino messages.
17892 @value{GDBN} provides the following commands specific to the Darwin target:
17895 @item set debug darwin @var{num}
17896 @kindex set debug darwin
17897 When set to a non zero value, enables debugging messages specific to
17898 the Darwin support. Higher values produce more verbose output.
17900 @item show debug darwin
17901 @kindex show debug darwin
17902 Show the current state of Darwin messages.
17904 @item set debug mach-o @var{num}
17905 @kindex set debug mach-o
17906 When set to a non zero value, enables debugging messages while
17907 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
17908 file format used on Darwin for object and executable files.) Higher
17909 values produce more verbose output. This is a command to diagnose
17910 problems internal to @value{GDBN} and should not be needed in normal
17913 @item show debug mach-o
17914 @kindex show debug mach-o
17915 Show the current state of Mach-O file messages.
17917 @item set mach-exceptions on
17918 @itemx set mach-exceptions off
17919 @kindex set mach-exceptions
17920 On Darwin, faults are first reported as a Mach exception and are then
17921 mapped to a Posix signal. Use this command to turn on trapping of
17922 Mach exceptions in the inferior. This might be sometimes useful to
17923 better understand the cause of a fault. The default is off.
17925 @item show mach-exceptions
17926 @kindex show mach-exceptions
17927 Show the current state of exceptions trapping.
17932 @section Embedded Operating Systems
17934 This section describes configurations involving the debugging of
17935 embedded operating systems that are available for several different
17939 * VxWorks:: Using @value{GDBN} with VxWorks
17942 @value{GDBN} includes the ability to debug programs running on
17943 various real-time operating systems.
17946 @subsection Using @value{GDBN} with VxWorks
17952 @kindex target vxworks
17953 @item target vxworks @var{machinename}
17954 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
17955 is the target system's machine name or IP address.
17959 On VxWorks, @code{load} links @var{filename} dynamically on the
17960 current target system as well as adding its symbols in @value{GDBN}.
17962 @value{GDBN} enables developers to spawn and debug tasks running on networked
17963 VxWorks targets from a Unix host. Already-running tasks spawned from
17964 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
17965 both the Unix host and on the VxWorks target. The program
17966 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
17967 installed with the name @code{vxgdb}, to distinguish it from a
17968 @value{GDBN} for debugging programs on the host itself.)
17971 @item VxWorks-timeout @var{args}
17972 @kindex vxworks-timeout
17973 All VxWorks-based targets now support the option @code{vxworks-timeout}.
17974 This option is set by the user, and @var{args} represents the number of
17975 seconds @value{GDBN} waits for responses to rpc's. You might use this if
17976 your VxWorks target is a slow software simulator or is on the far side
17977 of a thin network line.
17980 The following information on connecting to VxWorks was current when
17981 this manual was produced; newer releases of VxWorks may use revised
17984 @findex INCLUDE_RDB
17985 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
17986 to include the remote debugging interface routines in the VxWorks
17987 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
17988 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
17989 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
17990 source debugging task @code{tRdbTask} when VxWorks is booted. For more
17991 information on configuring and remaking VxWorks, see the manufacturer's
17993 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
17995 Once you have included @file{rdb.a} in your VxWorks system image and set
17996 your Unix execution search path to find @value{GDBN}, you are ready to
17997 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
17998 @code{vxgdb}, depending on your installation).
18000 @value{GDBN} comes up showing the prompt:
18007 * VxWorks Connection:: Connecting to VxWorks
18008 * VxWorks Download:: VxWorks download
18009 * VxWorks Attach:: Running tasks
18012 @node VxWorks Connection
18013 @subsubsection Connecting to VxWorks
18015 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18016 network. To connect to a target whose host name is ``@code{tt}'', type:
18019 (vxgdb) target vxworks tt
18023 @value{GDBN} displays messages like these:
18026 Attaching remote machine across net...
18031 @value{GDBN} then attempts to read the symbol tables of any object modules
18032 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18033 these files by searching the directories listed in the command search
18034 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18035 to find an object file, it displays a message such as:
18038 prog.o: No such file or directory.
18041 When this happens, add the appropriate directory to the search path with
18042 the @value{GDBN} command @code{path}, and execute the @code{target}
18045 @node VxWorks Download
18046 @subsubsection VxWorks Download
18048 @cindex download to VxWorks
18049 If you have connected to the VxWorks target and you want to debug an
18050 object that has not yet been loaded, you can use the @value{GDBN}
18051 @code{load} command to download a file from Unix to VxWorks
18052 incrementally. The object file given as an argument to the @code{load}
18053 command is actually opened twice: first by the VxWorks target in order
18054 to download the code, then by @value{GDBN} in order to read the symbol
18055 table. This can lead to problems if the current working directories on
18056 the two systems differ. If both systems have NFS mounted the same
18057 filesystems, you can avoid these problems by using absolute paths.
18058 Otherwise, it is simplest to set the working directory on both systems
18059 to the directory in which the object file resides, and then to reference
18060 the file by its name, without any path. For instance, a program
18061 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18062 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18063 program, type this on VxWorks:
18066 -> cd "@var{vxpath}/vw/demo/rdb"
18070 Then, in @value{GDBN}, type:
18073 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18074 (vxgdb) load prog.o
18077 @value{GDBN} displays a response similar to this:
18080 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18083 You can also use the @code{load} command to reload an object module
18084 after editing and recompiling the corresponding source file. Note that
18085 this makes @value{GDBN} delete all currently-defined breakpoints,
18086 auto-displays, and convenience variables, and to clear the value
18087 history. (This is necessary in order to preserve the integrity of
18088 debugger's data structures that reference the target system's symbol
18091 @node VxWorks Attach
18092 @subsubsection Running Tasks
18094 @cindex running VxWorks tasks
18095 You can also attach to an existing task using the @code{attach} command as
18099 (vxgdb) attach @var{task}
18103 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18104 or suspended when you attach to it. Running tasks are suspended at
18105 the time of attachment.
18107 @node Embedded Processors
18108 @section Embedded Processors
18110 This section goes into details specific to particular embedded
18113 @cindex send command to simulator
18114 Whenever a specific embedded processor has a simulator, @value{GDBN}
18115 allows to send an arbitrary command to the simulator.
18118 @item sim @var{command}
18119 @kindex sim@r{, a command}
18120 Send an arbitrary @var{command} string to the simulator. Consult the
18121 documentation for the specific simulator in use for information about
18122 acceptable commands.
18128 * M32R/D:: Renesas M32R/D
18129 * M68K:: Motorola M68K
18130 * MicroBlaze:: Xilinx MicroBlaze
18131 * MIPS Embedded:: MIPS Embedded
18132 * OpenRISC 1000:: OpenRisc 1000
18133 * PA:: HP PA Embedded
18134 * PowerPC Embedded:: PowerPC Embedded
18135 * Sparclet:: Tsqware Sparclet
18136 * Sparclite:: Fujitsu Sparclite
18137 * Z8000:: Zilog Z8000
18140 * Super-H:: Renesas Super-H
18149 @item target rdi @var{dev}
18150 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18151 use this target to communicate with both boards running the Angel
18152 monitor, or with the EmbeddedICE JTAG debug device.
18155 @item target rdp @var{dev}
18160 @value{GDBN} provides the following ARM-specific commands:
18163 @item set arm disassembler
18165 This commands selects from a list of disassembly styles. The
18166 @code{"std"} style is the standard style.
18168 @item show arm disassembler
18170 Show the current disassembly style.
18172 @item set arm apcs32
18173 @cindex ARM 32-bit mode
18174 This command toggles ARM operation mode between 32-bit and 26-bit.
18176 @item show arm apcs32
18177 Display the current usage of the ARM 32-bit mode.
18179 @item set arm fpu @var{fputype}
18180 This command sets the ARM floating-point unit (FPU) type. The
18181 argument @var{fputype} can be one of these:
18185 Determine the FPU type by querying the OS ABI.
18187 Software FPU, with mixed-endian doubles on little-endian ARM
18190 GCC-compiled FPA co-processor.
18192 Software FPU with pure-endian doubles.
18198 Show the current type of the FPU.
18201 This command forces @value{GDBN} to use the specified ABI.
18204 Show the currently used ABI.
18206 @item set arm fallback-mode (arm|thumb|auto)
18207 @value{GDBN} uses the symbol table, when available, to determine
18208 whether instructions are ARM or Thumb. This command controls
18209 @value{GDBN}'s default behavior when the symbol table is not
18210 available. The default is @samp{auto}, which causes @value{GDBN} to
18211 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18214 @item show arm fallback-mode
18215 Show the current fallback instruction mode.
18217 @item set arm force-mode (arm|thumb|auto)
18218 This command overrides use of the symbol table to determine whether
18219 instructions are ARM or Thumb. The default is @samp{auto}, which
18220 causes @value{GDBN} to use the symbol table and then the setting
18221 of @samp{set arm fallback-mode}.
18223 @item show arm force-mode
18224 Show the current forced instruction mode.
18226 @item set debug arm
18227 Toggle whether to display ARM-specific debugging messages from the ARM
18228 target support subsystem.
18230 @item show debug arm
18231 Show whether ARM-specific debugging messages are enabled.
18234 The following commands are available when an ARM target is debugged
18235 using the RDI interface:
18238 @item rdilogfile @r{[}@var{file}@r{]}
18240 @cindex ADP (Angel Debugger Protocol) logging
18241 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18242 With an argument, sets the log file to the specified @var{file}. With
18243 no argument, show the current log file name. The default log file is
18246 @item rdilogenable @r{[}@var{arg}@r{]}
18247 @kindex rdilogenable
18248 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18249 enables logging, with an argument 0 or @code{"no"} disables it. With
18250 no arguments displays the current setting. When logging is enabled,
18251 ADP packets exchanged between @value{GDBN} and the RDI target device
18252 are logged to a file.
18254 @item set rdiromatzero
18255 @kindex set rdiromatzero
18256 @cindex ROM at zero address, RDI
18257 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18258 vector catching is disabled, so that zero address can be used. If off
18259 (the default), vector catching is enabled. For this command to take
18260 effect, it needs to be invoked prior to the @code{target rdi} command.
18262 @item show rdiromatzero
18263 @kindex show rdiromatzero
18264 Show the current setting of ROM at zero address.
18266 @item set rdiheartbeat
18267 @kindex set rdiheartbeat
18268 @cindex RDI heartbeat
18269 Enable or disable RDI heartbeat packets. It is not recommended to
18270 turn on this option, since it confuses ARM and EPI JTAG interface, as
18271 well as the Angel monitor.
18273 @item show rdiheartbeat
18274 @kindex show rdiheartbeat
18275 Show the setting of RDI heartbeat packets.
18279 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18280 The @value{GDBN} ARM simulator accepts the following optional arguments.
18283 @item --swi-support=@var{type}
18284 Tell the simulator which SWI interfaces to support.
18285 @var{type} may be a comma separated list of the following values.
18286 The default value is @code{all}.
18299 @subsection Renesas M32R/D and M32R/SDI
18302 @kindex target m32r
18303 @item target m32r @var{dev}
18304 Renesas M32R/D ROM monitor.
18306 @kindex target m32rsdi
18307 @item target m32rsdi @var{dev}
18308 Renesas M32R SDI server, connected via parallel port to the board.
18311 The following @value{GDBN} commands are specific to the M32R monitor:
18314 @item set download-path @var{path}
18315 @kindex set download-path
18316 @cindex find downloadable @sc{srec} files (M32R)
18317 Set the default path for finding downloadable @sc{srec} files.
18319 @item show download-path
18320 @kindex show download-path
18321 Show the default path for downloadable @sc{srec} files.
18323 @item set board-address @var{addr}
18324 @kindex set board-address
18325 @cindex M32-EVA target board address
18326 Set the IP address for the M32R-EVA target board.
18328 @item show board-address
18329 @kindex show board-address
18330 Show the current IP address of the target board.
18332 @item set server-address @var{addr}
18333 @kindex set server-address
18334 @cindex download server address (M32R)
18335 Set the IP address for the download server, which is the @value{GDBN}'s
18338 @item show server-address
18339 @kindex show server-address
18340 Display the IP address of the download server.
18342 @item upload @r{[}@var{file}@r{]}
18343 @kindex upload@r{, M32R}
18344 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18345 upload capability. If no @var{file} argument is given, the current
18346 executable file is uploaded.
18348 @item tload @r{[}@var{file}@r{]}
18349 @kindex tload@r{, M32R}
18350 Test the @code{upload} command.
18353 The following commands are available for M32R/SDI:
18358 @cindex reset SDI connection, M32R
18359 This command resets the SDI connection.
18363 This command shows the SDI connection status.
18366 @kindex debug_chaos
18367 @cindex M32R/Chaos debugging
18368 Instructs the remote that M32R/Chaos debugging is to be used.
18370 @item use_debug_dma
18371 @kindex use_debug_dma
18372 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18375 @kindex use_mon_code
18376 Instructs the remote to use the MON_CODE method of accessing memory.
18379 @kindex use_ib_break
18380 Instructs the remote to set breakpoints by IB break.
18382 @item use_dbt_break
18383 @kindex use_dbt_break
18384 Instructs the remote to set breakpoints by DBT.
18390 The Motorola m68k configuration includes ColdFire support, and a
18391 target command for the following ROM monitor.
18395 @kindex target dbug
18396 @item target dbug @var{dev}
18397 dBUG ROM monitor for Motorola ColdFire.
18402 @subsection MicroBlaze
18403 @cindex Xilinx MicroBlaze
18404 @cindex XMD, Xilinx Microprocessor Debugger
18406 The MicroBlaze is a soft-core processor supported on various Xilinx
18407 FPGAs, such as Spartan or Virtex series. Boards with these processors
18408 usually have JTAG ports which connect to a host system running the Xilinx
18409 Embedded Development Kit (EDK) or Software Development Kit (SDK).
18410 This host system is used to download the configuration bitstream to
18411 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
18412 communicates with the target board using the JTAG interface and
18413 presents a @code{gdbserver} interface to the board. By default
18414 @code{xmd} uses port @code{1234}. (While it is possible to change
18415 this default port, it requires the use of undocumented @code{xmd}
18416 commands. Contact Xilinx support if you need to do this.)
18418 Use these GDB commands to connect to the MicroBlaze target processor.
18421 @item target remote :1234
18422 Use this command to connect to the target if you are running @value{GDBN}
18423 on the same system as @code{xmd}.
18425 @item target remote @var{xmd-host}:1234
18426 Use this command to connect to the target if it is connected to @code{xmd}
18427 running on a different system named @var{xmd-host}.
18430 Use this command to download a program to the MicroBlaze target.
18432 @item set debug microblaze @var{n}
18433 Enable MicroBlaze-specific debugging messages if non-zero.
18435 @item show debug microblaze @var{n}
18436 Show MicroBlaze-specific debugging level.
18439 @node MIPS Embedded
18440 @subsection MIPS Embedded
18442 @cindex MIPS boards
18443 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
18444 MIPS board attached to a serial line. This is available when
18445 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
18448 Use these @value{GDBN} commands to specify the connection to your target board:
18451 @item target mips @var{port}
18452 @kindex target mips @var{port}
18453 To run a program on the board, start up @code{@value{GDBP}} with the
18454 name of your program as the argument. To connect to the board, use the
18455 command @samp{target mips @var{port}}, where @var{port} is the name of
18456 the serial port connected to the board. If the program has not already
18457 been downloaded to the board, you may use the @code{load} command to
18458 download it. You can then use all the usual @value{GDBN} commands.
18460 For example, this sequence connects to the target board through a serial
18461 port, and loads and runs a program called @var{prog} through the
18465 host$ @value{GDBP} @var{prog}
18466 @value{GDBN} is free software and @dots{}
18467 (@value{GDBP}) target mips /dev/ttyb
18468 (@value{GDBP}) load @var{prog}
18472 @item target mips @var{hostname}:@var{portnumber}
18473 On some @value{GDBN} host configurations, you can specify a TCP
18474 connection (for instance, to a serial line managed by a terminal
18475 concentrator) instead of a serial port, using the syntax
18476 @samp{@var{hostname}:@var{portnumber}}.
18478 @item target pmon @var{port}
18479 @kindex target pmon @var{port}
18482 @item target ddb @var{port}
18483 @kindex target ddb @var{port}
18484 NEC's DDB variant of PMON for Vr4300.
18486 @item target lsi @var{port}
18487 @kindex target lsi @var{port}
18488 LSI variant of PMON.
18490 @kindex target r3900
18491 @item target r3900 @var{dev}
18492 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
18494 @kindex target array
18495 @item target array @var{dev}
18496 Array Tech LSI33K RAID controller board.
18502 @value{GDBN} also supports these special commands for MIPS targets:
18505 @item set mipsfpu double
18506 @itemx set mipsfpu single
18507 @itemx set mipsfpu none
18508 @itemx set mipsfpu auto
18509 @itemx show mipsfpu
18510 @kindex set mipsfpu
18511 @kindex show mipsfpu
18512 @cindex MIPS remote floating point
18513 @cindex floating point, MIPS remote
18514 If your target board does not support the MIPS floating point
18515 coprocessor, you should use the command @samp{set mipsfpu none} (if you
18516 need this, you may wish to put the command in your @value{GDBN} init
18517 file). This tells @value{GDBN} how to find the return value of
18518 functions which return floating point values. It also allows
18519 @value{GDBN} to avoid saving the floating point registers when calling
18520 functions on the board. If you are using a floating point coprocessor
18521 with only single precision floating point support, as on the @sc{r4650}
18522 processor, use the command @samp{set mipsfpu single}. The default
18523 double precision floating point coprocessor may be selected using
18524 @samp{set mipsfpu double}.
18526 In previous versions the only choices were double precision or no
18527 floating point, so @samp{set mipsfpu on} will select double precision
18528 and @samp{set mipsfpu off} will select no floating point.
18530 As usual, you can inquire about the @code{mipsfpu} variable with
18531 @samp{show mipsfpu}.
18533 @item set timeout @var{seconds}
18534 @itemx set retransmit-timeout @var{seconds}
18535 @itemx show timeout
18536 @itemx show retransmit-timeout
18537 @cindex @code{timeout}, MIPS protocol
18538 @cindex @code{retransmit-timeout}, MIPS protocol
18539 @kindex set timeout
18540 @kindex show timeout
18541 @kindex set retransmit-timeout
18542 @kindex show retransmit-timeout
18543 You can control the timeout used while waiting for a packet, in the MIPS
18544 remote protocol, with the @code{set timeout @var{seconds}} command. The
18545 default is 5 seconds. Similarly, you can control the timeout used while
18546 waiting for an acknowledgment of a packet with the @code{set
18547 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
18548 You can inspect both values with @code{show timeout} and @code{show
18549 retransmit-timeout}. (These commands are @emph{only} available when
18550 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
18552 The timeout set by @code{set timeout} does not apply when @value{GDBN}
18553 is waiting for your program to stop. In that case, @value{GDBN} waits
18554 forever because it has no way of knowing how long the program is going
18555 to run before stopping.
18557 @item set syn-garbage-limit @var{num}
18558 @kindex set syn-garbage-limit@r{, MIPS remote}
18559 @cindex synchronize with remote MIPS target
18560 Limit the maximum number of characters @value{GDBN} should ignore when
18561 it tries to synchronize with the remote target. The default is 10
18562 characters. Setting the limit to -1 means there's no limit.
18564 @item show syn-garbage-limit
18565 @kindex show syn-garbage-limit@r{, MIPS remote}
18566 Show the current limit on the number of characters to ignore when
18567 trying to synchronize with the remote system.
18569 @item set monitor-prompt @var{prompt}
18570 @kindex set monitor-prompt@r{, MIPS remote}
18571 @cindex remote monitor prompt
18572 Tell @value{GDBN} to expect the specified @var{prompt} string from the
18573 remote monitor. The default depends on the target:
18583 @item show monitor-prompt
18584 @kindex show monitor-prompt@r{, MIPS remote}
18585 Show the current strings @value{GDBN} expects as the prompt from the
18588 @item set monitor-warnings
18589 @kindex set monitor-warnings@r{, MIPS remote}
18590 Enable or disable monitor warnings about hardware breakpoints. This
18591 has effect only for the @code{lsi} target. When on, @value{GDBN} will
18592 display warning messages whose codes are returned by the @code{lsi}
18593 PMON monitor for breakpoint commands.
18595 @item show monitor-warnings
18596 @kindex show monitor-warnings@r{, MIPS remote}
18597 Show the current setting of printing monitor warnings.
18599 @item pmon @var{command}
18600 @kindex pmon@r{, MIPS remote}
18601 @cindex send PMON command
18602 This command allows sending an arbitrary @var{command} string to the
18603 monitor. The monitor must be in debug mode for this to work.
18606 @node OpenRISC 1000
18607 @subsection OpenRISC 1000
18608 @cindex OpenRISC 1000
18610 @cindex or1k boards
18611 See OR1k Architecture document (@uref{www.opencores.org}) for more information
18612 about platform and commands.
18616 @kindex target jtag
18617 @item target jtag jtag://@var{host}:@var{port}
18619 Connects to remote JTAG server.
18620 JTAG remote server can be either an or1ksim or JTAG server,
18621 connected via parallel port to the board.
18623 Example: @code{target jtag jtag://localhost:9999}
18626 @item or1ksim @var{command}
18627 If connected to @code{or1ksim} OpenRISC 1000 Architectural
18628 Simulator, proprietary commands can be executed.
18630 @kindex info or1k spr
18631 @item info or1k spr
18632 Displays spr groups.
18634 @item info or1k spr @var{group}
18635 @itemx info or1k spr @var{groupno}
18636 Displays register names in selected group.
18638 @item info or1k spr @var{group} @var{register}
18639 @itemx info or1k spr @var{register}
18640 @itemx info or1k spr @var{groupno} @var{registerno}
18641 @itemx info or1k spr @var{registerno}
18642 Shows information about specified spr register.
18645 @item spr @var{group} @var{register} @var{value}
18646 @itemx spr @var{register @var{value}}
18647 @itemx spr @var{groupno} @var{registerno @var{value}}
18648 @itemx spr @var{registerno @var{value}}
18649 Writes @var{value} to specified spr register.
18652 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
18653 It is very similar to @value{GDBN} trace, except it does not interfere with normal
18654 program execution and is thus much faster. Hardware breakpoints/watchpoint
18655 triggers can be set using:
18658 Load effective address/data
18660 Store effective address/data
18662 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
18667 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
18668 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
18670 @code{htrace} commands:
18671 @cindex OpenRISC 1000 htrace
18674 @item hwatch @var{conditional}
18675 Set hardware watchpoint on combination of Load/Store Effective Address(es)
18676 or Data. For example:
18678 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18680 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18684 Display information about current HW trace configuration.
18686 @item htrace trigger @var{conditional}
18687 Set starting criteria for HW trace.
18689 @item htrace qualifier @var{conditional}
18690 Set acquisition qualifier for HW trace.
18692 @item htrace stop @var{conditional}
18693 Set HW trace stopping criteria.
18695 @item htrace record [@var{data}]*
18696 Selects the data to be recorded, when qualifier is met and HW trace was
18699 @item htrace enable
18700 @itemx htrace disable
18701 Enables/disables the HW trace.
18703 @item htrace rewind [@var{filename}]
18704 Clears currently recorded trace data.
18706 If filename is specified, new trace file is made and any newly collected data
18707 will be written there.
18709 @item htrace print [@var{start} [@var{len}]]
18710 Prints trace buffer, using current record configuration.
18712 @item htrace mode continuous
18713 Set continuous trace mode.
18715 @item htrace mode suspend
18716 Set suspend trace mode.
18720 @node PowerPC Embedded
18721 @subsection PowerPC Embedded
18723 @cindex DVC register
18724 @value{GDBN} supports using the DVC (Data Value Compare) register to
18725 implement in hardware simple hardware watchpoint conditions of the form:
18728 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
18729 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
18732 The DVC register will be automatically used when @value{GDBN} detects
18733 such pattern in a condition expression, and the created watchpoint uses one
18734 debug register (either the @code{exact-watchpoints} option is on and the
18735 variable is scalar, or the variable has a length of one byte). This feature
18736 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
18739 When running on PowerPC embedded processors, @value{GDBN} automatically uses
18740 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
18741 in which case watchpoints using only one debug register are created when
18742 watching variables of scalar types.
18744 You can create an artificial array to watch an arbitrary memory
18745 region using one of the following commands (@pxref{Expressions}):
18748 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
18749 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
18752 @cindex ranged breakpoint
18753 PowerPC embedded processors support hardware accelerated
18754 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
18755 the inferior whenever it executes an instruction at any address within
18756 the range it specifies. To set a ranged breakpoint in @value{GDBN},
18757 use the @code{break-range} command.
18759 @value{GDBN} provides the following PowerPC-specific commands:
18762 @kindex break-range
18763 @item break-range @var{start-location}, @var{end-location}
18764 Set a breakpoint for an address range.
18765 @var{start-location} and @var{end-location} can specify a function name,
18766 a line number, an offset of lines from the current line or from the start
18767 location, or an address of an instruction (see @ref{Specify Location},
18768 for a list of all the possible ways to specify a @var{location}.)
18769 The breakpoint will stop execution of the inferior whenever it
18770 executes an instruction at any address within the specified range,
18771 (including @var{start-location} and @var{end-location}.)
18773 @kindex set powerpc
18774 @item set powerpc soft-float
18775 @itemx show powerpc soft-float
18776 Force @value{GDBN} to use (or not use) a software floating point calling
18777 convention. By default, @value{GDBN} selects the calling convention based
18778 on the selected architecture and the provided executable file.
18780 @item set powerpc vector-abi
18781 @itemx show powerpc vector-abi
18782 Force @value{GDBN} to use the specified calling convention for vector
18783 arguments and return values. The valid options are @samp{auto};
18784 @samp{generic}, to avoid vector registers even if they are present;
18785 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
18786 registers. By default, @value{GDBN} selects the calling convention
18787 based on the selected architecture and the provided executable file.
18789 @item set powerpc exact-watchpoints
18790 @itemx show powerpc exact-watchpoints
18791 Allow @value{GDBN} to use only one debug register when watching a variable
18792 of scalar type, thus assuming that the variable is accessed through the
18793 address of its first byte.
18795 @kindex target dink32
18796 @item target dink32 @var{dev}
18797 DINK32 ROM monitor.
18799 @kindex target ppcbug
18800 @item target ppcbug @var{dev}
18801 @kindex target ppcbug1
18802 @item target ppcbug1 @var{dev}
18803 PPCBUG ROM monitor for PowerPC.
18806 @item target sds @var{dev}
18807 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
18810 @cindex SDS protocol
18811 The following commands specific to the SDS protocol are supported
18815 @item set sdstimeout @var{nsec}
18816 @kindex set sdstimeout
18817 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
18818 default is 2 seconds.
18820 @item show sdstimeout
18821 @kindex show sdstimeout
18822 Show the current value of the SDS timeout.
18824 @item sds @var{command}
18825 @kindex sds@r{, a command}
18826 Send the specified @var{command} string to the SDS monitor.
18831 @subsection HP PA Embedded
18835 @kindex target op50n
18836 @item target op50n @var{dev}
18837 OP50N monitor, running on an OKI HPPA board.
18839 @kindex target w89k
18840 @item target w89k @var{dev}
18841 W89K monitor, running on a Winbond HPPA board.
18846 @subsection Tsqware Sparclet
18850 @value{GDBN} enables developers to debug tasks running on
18851 Sparclet targets from a Unix host.
18852 @value{GDBN} uses code that runs on
18853 both the Unix host and on the Sparclet target. The program
18854 @code{@value{GDBP}} is installed and executed on the Unix host.
18857 @item remotetimeout @var{args}
18858 @kindex remotetimeout
18859 @value{GDBN} supports the option @code{remotetimeout}.
18860 This option is set by the user, and @var{args} represents the number of
18861 seconds @value{GDBN} waits for responses.
18864 @cindex compiling, on Sparclet
18865 When compiling for debugging, include the options @samp{-g} to get debug
18866 information and @samp{-Ttext} to relocate the program to where you wish to
18867 load it on the target. You may also want to add the options @samp{-n} or
18868 @samp{-N} in order to reduce the size of the sections. Example:
18871 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
18874 You can use @code{objdump} to verify that the addresses are what you intended:
18877 sparclet-aout-objdump --headers --syms prog
18880 @cindex running, on Sparclet
18882 your Unix execution search path to find @value{GDBN}, you are ready to
18883 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
18884 (or @code{sparclet-aout-gdb}, depending on your installation).
18886 @value{GDBN} comes up showing the prompt:
18893 * Sparclet File:: Setting the file to debug
18894 * Sparclet Connection:: Connecting to Sparclet
18895 * Sparclet Download:: Sparclet download
18896 * Sparclet Execution:: Running and debugging
18899 @node Sparclet File
18900 @subsubsection Setting File to Debug
18902 The @value{GDBN} command @code{file} lets you choose with program to debug.
18905 (gdbslet) file prog
18909 @value{GDBN} then attempts to read the symbol table of @file{prog}.
18910 @value{GDBN} locates
18911 the file by searching the directories listed in the command search
18913 If the file was compiled with debug information (option @samp{-g}), source
18914 files will be searched as well.
18915 @value{GDBN} locates
18916 the source files by searching the directories listed in the directory search
18917 path (@pxref{Environment, ,Your Program's Environment}).
18919 to find a file, it displays a message such as:
18922 prog: No such file or directory.
18925 When this happens, add the appropriate directories to the search paths with
18926 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
18927 @code{target} command again.
18929 @node Sparclet Connection
18930 @subsubsection Connecting to Sparclet
18932 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
18933 To connect to a target on serial port ``@code{ttya}'', type:
18936 (gdbslet) target sparclet /dev/ttya
18937 Remote target sparclet connected to /dev/ttya
18938 main () at ../prog.c:3
18942 @value{GDBN} displays messages like these:
18948 @node Sparclet Download
18949 @subsubsection Sparclet Download
18951 @cindex download to Sparclet
18952 Once connected to the Sparclet target,
18953 you can use the @value{GDBN}
18954 @code{load} command to download the file from the host to the target.
18955 The file name and load offset should be given as arguments to the @code{load}
18957 Since the file format is aout, the program must be loaded to the starting
18958 address. You can use @code{objdump} to find out what this value is. The load
18959 offset is an offset which is added to the VMA (virtual memory address)
18960 of each of the file's sections.
18961 For instance, if the program
18962 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
18963 and bss at 0x12010170, in @value{GDBN}, type:
18966 (gdbslet) load prog 0x12010000
18967 Loading section .text, size 0xdb0 vma 0x12010000
18970 If the code is loaded at a different address then what the program was linked
18971 to, you may need to use the @code{section} and @code{add-symbol-file} commands
18972 to tell @value{GDBN} where to map the symbol table.
18974 @node Sparclet Execution
18975 @subsubsection Running and Debugging
18977 @cindex running and debugging Sparclet programs
18978 You can now begin debugging the task using @value{GDBN}'s execution control
18979 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
18980 manual for the list of commands.
18984 Breakpoint 1 at 0x12010000: file prog.c, line 3.
18986 Starting program: prog
18987 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
18988 3 char *symarg = 0;
18990 4 char *execarg = "hello!";
18995 @subsection Fujitsu Sparclite
18999 @kindex target sparclite
19000 @item target sparclite @var{dev}
19001 Fujitsu sparclite boards, used only for the purpose of loading.
19002 You must use an additional command to debug the program.
19003 For example: target remote @var{dev} using @value{GDBN} standard
19009 @subsection Zilog Z8000
19012 @cindex simulator, Z8000
19013 @cindex Zilog Z8000 simulator
19015 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19018 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19019 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19020 segmented variant). The simulator recognizes which architecture is
19021 appropriate by inspecting the object code.
19024 @item target sim @var{args}
19026 @kindex target sim@r{, with Z8000}
19027 Debug programs on a simulated CPU. If the simulator supports setup
19028 options, specify them via @var{args}.
19032 After specifying this target, you can debug programs for the simulated
19033 CPU in the same style as programs for your host computer; use the
19034 @code{file} command to load a new program image, the @code{run} command
19035 to run your program, and so on.
19037 As well as making available all the usual machine registers
19038 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19039 additional items of information as specially named registers:
19044 Counts clock-ticks in the simulator.
19047 Counts instructions run in the simulator.
19050 Execution time in 60ths of a second.
19054 You can refer to these values in @value{GDBN} expressions with the usual
19055 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19056 conditional breakpoint that suspends only after at least 5000
19057 simulated clock ticks.
19060 @subsection Atmel AVR
19063 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19064 following AVR-specific commands:
19067 @item info io_registers
19068 @kindex info io_registers@r{, AVR}
19069 @cindex I/O registers (Atmel AVR)
19070 This command displays information about the AVR I/O registers. For
19071 each register, @value{GDBN} prints its number and value.
19078 When configured for debugging CRIS, @value{GDBN} provides the
19079 following CRIS-specific commands:
19082 @item set cris-version @var{ver}
19083 @cindex CRIS version
19084 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19085 The CRIS version affects register names and sizes. This command is useful in
19086 case autodetection of the CRIS version fails.
19088 @item show cris-version
19089 Show the current CRIS version.
19091 @item set cris-dwarf2-cfi
19092 @cindex DWARF-2 CFI and CRIS
19093 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19094 Change to @samp{off} when using @code{gcc-cris} whose version is below
19097 @item show cris-dwarf2-cfi
19098 Show the current state of using DWARF-2 CFI.
19100 @item set cris-mode @var{mode}
19102 Set the current CRIS mode to @var{mode}. It should only be changed when
19103 debugging in guru mode, in which case it should be set to
19104 @samp{guru} (the default is @samp{normal}).
19106 @item show cris-mode
19107 Show the current CRIS mode.
19111 @subsection Renesas Super-H
19114 For the Renesas Super-H processor, @value{GDBN} provides these
19119 @kindex regs@r{, Super-H}
19120 Show the values of all Super-H registers.
19122 @item set sh calling-convention @var{convention}
19123 @kindex set sh calling-convention
19124 Set the calling-convention used when calling functions from @value{GDBN}.
19125 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19126 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19127 convention. If the DWARF-2 information of the called function specifies
19128 that the function follows the Renesas calling convention, the function
19129 is called using the Renesas calling convention. If the calling convention
19130 is set to @samp{renesas}, the Renesas calling convention is always used,
19131 regardless of the DWARF-2 information. This can be used to override the
19132 default of @samp{gcc} if debug information is missing, or the compiler
19133 does not emit the DWARF-2 calling convention entry for a function.
19135 @item show sh calling-convention
19136 @kindex show sh calling-convention
19137 Show the current calling convention setting.
19142 @node Architectures
19143 @section Architectures
19145 This section describes characteristics of architectures that affect
19146 all uses of @value{GDBN} with the architecture, both native and cross.
19153 * HPPA:: HP PA architecture
19154 * SPU:: Cell Broadband Engine SPU architecture
19159 @subsection x86 Architecture-specific Issues
19162 @item set struct-convention @var{mode}
19163 @kindex set struct-convention
19164 @cindex struct return convention
19165 @cindex struct/union returned in registers
19166 Set the convention used by the inferior to return @code{struct}s and
19167 @code{union}s from functions to @var{mode}. Possible values of
19168 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19169 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19170 are returned on the stack, while @code{"reg"} means that a
19171 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19172 be returned in a register.
19174 @item show struct-convention
19175 @kindex show struct-convention
19176 Show the current setting of the convention to return @code{struct}s
19185 @kindex set rstack_high_address
19186 @cindex AMD 29K register stack
19187 @cindex register stack, AMD29K
19188 @item set rstack_high_address @var{address}
19189 On AMD 29000 family processors, registers are saved in a separate
19190 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19191 extent of this stack. Normally, @value{GDBN} just assumes that the
19192 stack is ``large enough''. This may result in @value{GDBN} referencing
19193 memory locations that do not exist. If necessary, you can get around
19194 this problem by specifying the ending address of the register stack with
19195 the @code{set rstack_high_address} command. The argument should be an
19196 address, which you probably want to precede with @samp{0x} to specify in
19199 @kindex show rstack_high_address
19200 @item show rstack_high_address
19201 Display the current limit of the register stack, on AMD 29000 family
19209 See the following section.
19214 @cindex stack on Alpha
19215 @cindex stack on MIPS
19216 @cindex Alpha stack
19218 Alpha- and MIPS-based computers use an unusual stack frame, which
19219 sometimes requires @value{GDBN} to search backward in the object code to
19220 find the beginning of a function.
19222 @cindex response time, MIPS debugging
19223 To improve response time (especially for embedded applications, where
19224 @value{GDBN} may be restricted to a slow serial line for this search)
19225 you may want to limit the size of this search, using one of these
19229 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19230 @item set heuristic-fence-post @var{limit}
19231 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19232 search for the beginning of a function. A value of @var{0} (the
19233 default) means there is no limit. However, except for @var{0}, the
19234 larger the limit the more bytes @code{heuristic-fence-post} must search
19235 and therefore the longer it takes to run. You should only need to use
19236 this command when debugging a stripped executable.
19238 @item show heuristic-fence-post
19239 Display the current limit.
19243 These commands are available @emph{only} when @value{GDBN} is configured
19244 for debugging programs on Alpha or MIPS processors.
19246 Several MIPS-specific commands are available when debugging MIPS
19250 @item set mips abi @var{arg}
19251 @kindex set mips abi
19252 @cindex set ABI for MIPS
19253 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
19254 values of @var{arg} are:
19258 The default ABI associated with the current binary (this is the
19269 @item show mips abi
19270 @kindex show mips abi
19271 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
19274 @itemx show mipsfpu
19275 @xref{MIPS Embedded, set mipsfpu}.
19277 @item set mips mask-address @var{arg}
19278 @kindex set mips mask-address
19279 @cindex MIPS addresses, masking
19280 This command determines whether the most-significant 32 bits of 64-bit
19281 MIPS addresses are masked off. The argument @var{arg} can be
19282 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
19283 setting, which lets @value{GDBN} determine the correct value.
19285 @item show mips mask-address
19286 @kindex show mips mask-address
19287 Show whether the upper 32 bits of MIPS addresses are masked off or
19290 @item set remote-mips64-transfers-32bit-regs
19291 @kindex set remote-mips64-transfers-32bit-regs
19292 This command controls compatibility with 64-bit MIPS targets that
19293 transfer data in 32-bit quantities. If you have an old MIPS 64 target
19294 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
19295 and 64 bits for other registers, set this option to @samp{on}.
19297 @item show remote-mips64-transfers-32bit-regs
19298 @kindex show remote-mips64-transfers-32bit-regs
19299 Show the current setting of compatibility with older MIPS 64 targets.
19301 @item set debug mips
19302 @kindex set debug mips
19303 This command turns on and off debugging messages for the MIPS-specific
19304 target code in @value{GDBN}.
19306 @item show debug mips
19307 @kindex show debug mips
19308 Show the current setting of MIPS debugging messages.
19314 @cindex HPPA support
19316 When @value{GDBN} is debugging the HP PA architecture, it provides the
19317 following special commands:
19320 @item set debug hppa
19321 @kindex set debug hppa
19322 This command determines whether HPPA architecture-specific debugging
19323 messages are to be displayed.
19325 @item show debug hppa
19326 Show whether HPPA debugging messages are displayed.
19328 @item maint print unwind @var{address}
19329 @kindex maint print unwind@r{, HPPA}
19330 This command displays the contents of the unwind table entry at the
19331 given @var{address}.
19337 @subsection Cell Broadband Engine SPU architecture
19338 @cindex Cell Broadband Engine
19341 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
19342 it provides the following special commands:
19345 @item info spu event
19347 Display SPU event facility status. Shows current event mask
19348 and pending event status.
19350 @item info spu signal
19351 Display SPU signal notification facility status. Shows pending
19352 signal-control word and signal notification mode of both signal
19353 notification channels.
19355 @item info spu mailbox
19356 Display SPU mailbox facility status. Shows all pending entries,
19357 in order of processing, in each of the SPU Write Outbound,
19358 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
19361 Display MFC DMA status. Shows all pending commands in the MFC
19362 DMA queue. For each entry, opcode, tag, class IDs, effective
19363 and local store addresses and transfer size are shown.
19365 @item info spu proxydma
19366 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
19367 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
19368 and local store addresses and transfer size are shown.
19372 When @value{GDBN} is debugging a combined PowerPC/SPU application
19373 on the Cell Broadband Engine, it provides in addition the following
19377 @item set spu stop-on-load @var{arg}
19379 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
19380 will give control to the user when a new SPE thread enters its @code{main}
19381 function. The default is @code{off}.
19383 @item show spu stop-on-load
19385 Show whether to stop for new SPE threads.
19387 @item set spu auto-flush-cache @var{arg}
19388 Set whether to automatically flush the software-managed cache. When set to
19389 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19390 cache to be flushed whenever SPE execution stops. This provides a consistent
19391 view of PowerPC memory that is accessed via the cache. If an application
19392 does not use the software-managed cache, this option has no effect.
19394 @item show spu auto-flush-cache
19395 Show whether to automatically flush the software-managed cache.
19400 @subsection PowerPC
19401 @cindex PowerPC architecture
19403 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
19404 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
19405 numbers stored in the floating point registers. These values must be stored
19406 in two consecutive registers, always starting at an even register like
19407 @code{f0} or @code{f2}.
19409 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
19410 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
19411 @code{f2} and @code{f3} for @code{$dl1} and so on.
19413 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
19414 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
19417 @node Controlling GDB
19418 @chapter Controlling @value{GDBN}
19420 You can alter the way @value{GDBN} interacts with you by using the
19421 @code{set} command. For commands controlling how @value{GDBN} displays
19422 data, see @ref{Print Settings, ,Print Settings}. Other settings are
19427 * Editing:: Command editing
19428 * Command History:: Command history
19429 * Screen Size:: Screen size
19430 * Numbers:: Numbers
19431 * ABI:: Configuring the current ABI
19432 * Messages/Warnings:: Optional warnings and messages
19433 * Debugging Output:: Optional messages about internal happenings
19434 * Other Misc Settings:: Other Miscellaneous Settings
19442 @value{GDBN} indicates its readiness to read a command by printing a string
19443 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
19444 can change the prompt string with the @code{set prompt} command. For
19445 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
19446 the prompt in one of the @value{GDBN} sessions so that you can always tell
19447 which one you are talking to.
19449 @emph{Note:} @code{set prompt} does not add a space for you after the
19450 prompt you set. This allows you to set a prompt which ends in a space
19451 or a prompt that does not.
19455 @item set prompt @var{newprompt}
19456 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
19458 @kindex show prompt
19460 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
19464 @section Command Editing
19466 @cindex command line editing
19468 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
19469 @sc{gnu} library provides consistent behavior for programs which provide a
19470 command line interface to the user. Advantages are @sc{gnu} Emacs-style
19471 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
19472 substitution, and a storage and recall of command history across
19473 debugging sessions.
19475 You may control the behavior of command line editing in @value{GDBN} with the
19476 command @code{set}.
19479 @kindex set editing
19482 @itemx set editing on
19483 Enable command line editing (enabled by default).
19485 @item set editing off
19486 Disable command line editing.
19488 @kindex show editing
19490 Show whether command line editing is enabled.
19493 @ifset SYSTEM_READLINE
19494 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
19496 @ifclear SYSTEM_READLINE
19497 @xref{Command Line Editing},
19499 for more details about the Readline
19500 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
19501 encouraged to read that chapter.
19503 @node Command History
19504 @section Command History
19505 @cindex command history
19507 @value{GDBN} can keep track of the commands you type during your
19508 debugging sessions, so that you can be certain of precisely what
19509 happened. Use these commands to manage the @value{GDBN} command
19512 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
19513 package, to provide the history facility.
19514 @ifset SYSTEM_READLINE
19515 @xref{Using History Interactively, , , history, GNU History Library},
19517 @ifclear SYSTEM_READLINE
19518 @xref{Using History Interactively},
19520 for the detailed description of the History library.
19522 To issue a command to @value{GDBN} without affecting certain aspects of
19523 the state which is seen by users, prefix it with @samp{server }
19524 (@pxref{Server Prefix}). This
19525 means that this command will not affect the command history, nor will it
19526 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
19527 pressed on a line by itself.
19529 @cindex @code{server}, command prefix
19530 The server prefix does not affect the recording of values into the value
19531 history; to print a value without recording it into the value history,
19532 use the @code{output} command instead of the @code{print} command.
19534 Here is the description of @value{GDBN} commands related to command
19538 @cindex history substitution
19539 @cindex history file
19540 @kindex set history filename
19541 @cindex @env{GDBHISTFILE}, environment variable
19542 @item set history filename @var{fname}
19543 Set the name of the @value{GDBN} command history file to @var{fname}.
19544 This is the file where @value{GDBN} reads an initial command history
19545 list, and where it writes the command history from this session when it
19546 exits. You can access this list through history expansion or through
19547 the history command editing characters listed below. This file defaults
19548 to the value of the environment variable @code{GDBHISTFILE}, or to
19549 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
19552 @cindex save command history
19553 @kindex set history save
19554 @item set history save
19555 @itemx set history save on
19556 Record command history in a file, whose name may be specified with the
19557 @code{set history filename} command. By default, this option is disabled.
19559 @item set history save off
19560 Stop recording command history in a file.
19562 @cindex history size
19563 @kindex set history size
19564 @cindex @env{HISTSIZE}, environment variable
19565 @item set history size @var{size}
19566 Set the number of commands which @value{GDBN} keeps in its history list.
19567 This defaults to the value of the environment variable
19568 @code{HISTSIZE}, or to 256 if this variable is not set.
19571 History expansion assigns special meaning to the character @kbd{!}.
19572 @ifset SYSTEM_READLINE
19573 @xref{Event Designators, , , history, GNU History Library},
19575 @ifclear SYSTEM_READLINE
19576 @xref{Event Designators},
19580 @cindex history expansion, turn on/off
19581 Since @kbd{!} is also the logical not operator in C, history expansion
19582 is off by default. If you decide to enable history expansion with the
19583 @code{set history expansion on} command, you may sometimes need to
19584 follow @kbd{!} (when it is used as logical not, in an expression) with
19585 a space or a tab to prevent it from being expanded. The readline
19586 history facilities do not attempt substitution on the strings
19587 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
19589 The commands to control history expansion are:
19592 @item set history expansion on
19593 @itemx set history expansion
19594 @kindex set history expansion
19595 Enable history expansion. History expansion is off by default.
19597 @item set history expansion off
19598 Disable history expansion.
19601 @kindex show history
19603 @itemx show history filename
19604 @itemx show history save
19605 @itemx show history size
19606 @itemx show history expansion
19607 These commands display the state of the @value{GDBN} history parameters.
19608 @code{show history} by itself displays all four states.
19613 @kindex show commands
19614 @cindex show last commands
19615 @cindex display command history
19616 @item show commands
19617 Display the last ten commands in the command history.
19619 @item show commands @var{n}
19620 Print ten commands centered on command number @var{n}.
19622 @item show commands +
19623 Print ten commands just after the commands last printed.
19627 @section Screen Size
19628 @cindex size of screen
19629 @cindex pauses in output
19631 Certain commands to @value{GDBN} may produce large amounts of
19632 information output to the screen. To help you read all of it,
19633 @value{GDBN} pauses and asks you for input at the end of each page of
19634 output. Type @key{RET} when you want to continue the output, or @kbd{q}
19635 to discard the remaining output. Also, the screen width setting
19636 determines when to wrap lines of output. Depending on what is being
19637 printed, @value{GDBN} tries to break the line at a readable place,
19638 rather than simply letting it overflow onto the following line.
19640 Normally @value{GDBN} knows the size of the screen from the terminal
19641 driver software. For example, on Unix @value{GDBN} uses the termcap data base
19642 together with the value of the @code{TERM} environment variable and the
19643 @code{stty rows} and @code{stty cols} settings. If this is not correct,
19644 you can override it with the @code{set height} and @code{set
19651 @kindex show height
19652 @item set height @var{lpp}
19654 @itemx set width @var{cpl}
19656 These @code{set} commands specify a screen height of @var{lpp} lines and
19657 a screen width of @var{cpl} characters. The associated @code{show}
19658 commands display the current settings.
19660 If you specify a height of zero lines, @value{GDBN} does not pause during
19661 output no matter how long the output is. This is useful if output is to a
19662 file or to an editor buffer.
19664 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
19665 from wrapping its output.
19667 @item set pagination on
19668 @itemx set pagination off
19669 @kindex set pagination
19670 Turn the output pagination on or off; the default is on. Turning
19671 pagination off is the alternative to @code{set height 0}. Note that
19672 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
19673 Options, -batch}) also automatically disables pagination.
19675 @item show pagination
19676 @kindex show pagination
19677 Show the current pagination mode.
19682 @cindex number representation
19683 @cindex entering numbers
19685 You can always enter numbers in octal, decimal, or hexadecimal in
19686 @value{GDBN} by the usual conventions: octal numbers begin with
19687 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
19688 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
19689 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
19690 10; likewise, the default display for numbers---when no particular
19691 format is specified---is base 10. You can change the default base for
19692 both input and output with the commands described below.
19695 @kindex set input-radix
19696 @item set input-radix @var{base}
19697 Set the default base for numeric input. Supported choices
19698 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19699 specified either unambiguously or using the current input radix; for
19703 set input-radix 012
19704 set input-radix 10.
19705 set input-radix 0xa
19709 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
19710 leaves the input radix unchanged, no matter what it was, since
19711 @samp{10}, being without any leading or trailing signs of its base, is
19712 interpreted in the current radix. Thus, if the current radix is 16,
19713 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
19716 @kindex set output-radix
19717 @item set output-radix @var{base}
19718 Set the default base for numeric display. Supported choices
19719 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19720 specified either unambiguously or using the current input radix.
19722 @kindex show input-radix
19723 @item show input-radix
19724 Display the current default base for numeric input.
19726 @kindex show output-radix
19727 @item show output-radix
19728 Display the current default base for numeric display.
19730 @item set radix @r{[}@var{base}@r{]}
19734 These commands set and show the default base for both input and output
19735 of numbers. @code{set radix} sets the radix of input and output to
19736 the same base; without an argument, it resets the radix back to its
19737 default value of 10.
19742 @section Configuring the Current ABI
19744 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
19745 application automatically. However, sometimes you need to override its
19746 conclusions. Use these commands to manage @value{GDBN}'s view of the
19753 One @value{GDBN} configuration can debug binaries for multiple operating
19754 system targets, either via remote debugging or native emulation.
19755 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
19756 but you can override its conclusion using the @code{set osabi} command.
19757 One example where this is useful is in debugging of binaries which use
19758 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
19759 not have the same identifying marks that the standard C library for your
19764 Show the OS ABI currently in use.
19767 With no argument, show the list of registered available OS ABI's.
19769 @item set osabi @var{abi}
19770 Set the current OS ABI to @var{abi}.
19773 @cindex float promotion
19775 Generally, the way that an argument of type @code{float} is passed to a
19776 function depends on whether the function is prototyped. For a prototyped
19777 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
19778 according to the architecture's convention for @code{float}. For unprototyped
19779 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
19780 @code{double} and then passed.
19782 Unfortunately, some forms of debug information do not reliably indicate whether
19783 a function is prototyped. If @value{GDBN} calls a function that is not marked
19784 as prototyped, it consults @kbd{set coerce-float-to-double}.
19787 @kindex set coerce-float-to-double
19788 @item set coerce-float-to-double
19789 @itemx set coerce-float-to-double on
19790 Arguments of type @code{float} will be promoted to @code{double} when passed
19791 to an unprototyped function. This is the default setting.
19793 @item set coerce-float-to-double off
19794 Arguments of type @code{float} will be passed directly to unprototyped
19797 @kindex show coerce-float-to-double
19798 @item show coerce-float-to-double
19799 Show the current setting of promoting @code{float} to @code{double}.
19803 @kindex show cp-abi
19804 @value{GDBN} needs to know the ABI used for your program's C@t{++}
19805 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
19806 used to build your application. @value{GDBN} only fully supports
19807 programs with a single C@t{++} ABI; if your program contains code using
19808 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
19809 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
19810 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
19811 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
19812 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
19813 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
19818 Show the C@t{++} ABI currently in use.
19821 With no argument, show the list of supported C@t{++} ABI's.
19823 @item set cp-abi @var{abi}
19824 @itemx set cp-abi auto
19825 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
19828 @node Messages/Warnings
19829 @section Optional Warnings and Messages
19831 @cindex verbose operation
19832 @cindex optional warnings
19833 By default, @value{GDBN} is silent about its inner workings. If you are
19834 running on a slow machine, you may want to use the @code{set verbose}
19835 command. This makes @value{GDBN} tell you when it does a lengthy
19836 internal operation, so you will not think it has crashed.
19838 Currently, the messages controlled by @code{set verbose} are those
19839 which announce that the symbol table for a source file is being read;
19840 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
19843 @kindex set verbose
19844 @item set verbose on
19845 Enables @value{GDBN} output of certain informational messages.
19847 @item set verbose off
19848 Disables @value{GDBN} output of certain informational messages.
19850 @kindex show verbose
19852 Displays whether @code{set verbose} is on or off.
19855 By default, if @value{GDBN} encounters bugs in the symbol table of an
19856 object file, it is silent; but if you are debugging a compiler, you may
19857 find this information useful (@pxref{Symbol Errors, ,Errors Reading
19862 @kindex set complaints
19863 @item set complaints @var{limit}
19864 Permits @value{GDBN} to output @var{limit} complaints about each type of
19865 unusual symbols before becoming silent about the problem. Set
19866 @var{limit} to zero to suppress all complaints; set it to a large number
19867 to prevent complaints from being suppressed.
19869 @kindex show complaints
19870 @item show complaints
19871 Displays how many symbol complaints @value{GDBN} is permitted to produce.
19875 @anchor{confirmation requests}
19876 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
19877 lot of stupid questions to confirm certain commands. For example, if
19878 you try to run a program which is already running:
19882 The program being debugged has been started already.
19883 Start it from the beginning? (y or n)
19886 If you are willing to unflinchingly face the consequences of your own
19887 commands, you can disable this ``feature'':
19891 @kindex set confirm
19893 @cindex confirmation
19894 @cindex stupid questions
19895 @item set confirm off
19896 Disables confirmation requests. Note that running @value{GDBN} with
19897 the @option{--batch} option (@pxref{Mode Options, -batch}) also
19898 automatically disables confirmation requests.
19900 @item set confirm on
19901 Enables confirmation requests (the default).
19903 @kindex show confirm
19905 Displays state of confirmation requests.
19909 @cindex command tracing
19910 If you need to debug user-defined commands or sourced files you may find it
19911 useful to enable @dfn{command tracing}. In this mode each command will be
19912 printed as it is executed, prefixed with one or more @samp{+} symbols, the
19913 quantity denoting the call depth of each command.
19916 @kindex set trace-commands
19917 @cindex command scripts, debugging
19918 @item set trace-commands on
19919 Enable command tracing.
19920 @item set trace-commands off
19921 Disable command tracing.
19922 @item show trace-commands
19923 Display the current state of command tracing.
19926 @node Debugging Output
19927 @section Optional Messages about Internal Happenings
19928 @cindex optional debugging messages
19930 @value{GDBN} has commands that enable optional debugging messages from
19931 various @value{GDBN} subsystems; normally these commands are of
19932 interest to @value{GDBN} maintainers, or when reporting a bug. This
19933 section documents those commands.
19936 @kindex set exec-done-display
19937 @item set exec-done-display
19938 Turns on or off the notification of asynchronous commands'
19939 completion. When on, @value{GDBN} will print a message when an
19940 asynchronous command finishes its execution. The default is off.
19941 @kindex show exec-done-display
19942 @item show exec-done-display
19943 Displays the current setting of asynchronous command completion
19946 @cindex gdbarch debugging info
19947 @cindex architecture debugging info
19948 @item set debug arch
19949 Turns on or off display of gdbarch debugging info. The default is off
19951 @item show debug arch
19952 Displays the current state of displaying gdbarch debugging info.
19953 @item set debug aix-thread
19954 @cindex AIX threads
19955 Display debugging messages about inner workings of the AIX thread
19957 @item show debug aix-thread
19958 Show the current state of AIX thread debugging info display.
19959 @item set debug dwarf2-die
19960 @cindex DWARF2 DIEs
19961 Dump DWARF2 DIEs after they are read in.
19962 The value is the number of nesting levels to print.
19963 A value of zero turns off the display.
19964 @item show debug dwarf2-die
19965 Show the current state of DWARF2 DIE debugging.
19966 @item set debug displaced
19967 @cindex displaced stepping debugging info
19968 Turns on or off display of @value{GDBN} debugging info for the
19969 displaced stepping support. The default is off.
19970 @item show debug displaced
19971 Displays the current state of displaying @value{GDBN} debugging info
19972 related to displaced stepping.
19973 @item set debug event
19974 @cindex event debugging info
19975 Turns on or off display of @value{GDBN} event debugging info. The
19977 @item show debug event
19978 Displays the current state of displaying @value{GDBN} event debugging
19980 @item set debug expression
19981 @cindex expression debugging info
19982 Turns on or off display of debugging info about @value{GDBN}
19983 expression parsing. The default is off.
19984 @item show debug expression
19985 Displays the current state of displaying debugging info about
19986 @value{GDBN} expression parsing.
19987 @item set debug frame
19988 @cindex frame debugging info
19989 Turns on or off display of @value{GDBN} frame debugging info. The
19991 @item show debug frame
19992 Displays the current state of displaying @value{GDBN} frame debugging
19994 @item set debug gnu-nat
19995 @cindex @sc{gnu}/Hurd debug messages
19996 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
19997 @item show debug gnu-nat
19998 Show the current state of @sc{gnu}/Hurd debugging messages.
19999 @item set debug infrun
20000 @cindex inferior debugging info
20001 Turns on or off display of @value{GDBN} debugging info for running the inferior.
20002 The default is off. @file{infrun.c} contains GDB's runtime state machine used
20003 for implementing operations such as single-stepping the inferior.
20004 @item show debug infrun
20005 Displays the current state of @value{GDBN} inferior debugging.
20006 @item set debug jit
20007 @cindex just-in-time compilation, debugging messages
20008 Turns on or off debugging messages from JIT debug support.
20009 @item show debug jit
20010 Displays the current state of @value{GDBN} JIT debugging.
20011 @item set debug lin-lwp
20012 @cindex @sc{gnu}/Linux LWP debug messages
20013 @cindex Linux lightweight processes
20014 Turns on or off debugging messages from the Linux LWP debug support.
20015 @item show debug lin-lwp
20016 Show the current state of Linux LWP debugging messages.
20017 @item set debug lin-lwp-async
20018 @cindex @sc{gnu}/Linux LWP async debug messages
20019 @cindex Linux lightweight processes
20020 Turns on or off debugging messages from the Linux LWP async debug support.
20021 @item show debug lin-lwp-async
20022 Show the current state of Linux LWP async debugging messages.
20023 @item set debug observer
20024 @cindex observer debugging info
20025 Turns on or off display of @value{GDBN} observer debugging. This
20026 includes info such as the notification of observable events.
20027 @item show debug observer
20028 Displays the current state of observer debugging.
20029 @item set debug overload
20030 @cindex C@t{++} overload debugging info
20031 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20032 info. This includes info such as ranking of functions, etc. The default
20034 @item show debug overload
20035 Displays the current state of displaying @value{GDBN} C@t{++} overload
20037 @cindex expression parser, debugging info
20038 @cindex debug expression parser
20039 @item set debug parser
20040 Turns on or off the display of expression parser debugging output.
20041 Internally, this sets the @code{yydebug} variable in the expression
20042 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20043 details. The default is off.
20044 @item show debug parser
20045 Show the current state of expression parser debugging.
20046 @cindex packets, reporting on stdout
20047 @cindex serial connections, debugging
20048 @cindex debug remote protocol
20049 @cindex remote protocol debugging
20050 @cindex display remote packets
20051 @item set debug remote
20052 Turns on or off display of reports on all packets sent back and forth across
20053 the serial line to the remote machine. The info is printed on the
20054 @value{GDBN} standard output stream. The default is off.
20055 @item show debug remote
20056 Displays the state of display of remote packets.
20057 @item set debug serial
20058 Turns on or off display of @value{GDBN} serial debugging info. The
20060 @item show debug serial
20061 Displays the current state of displaying @value{GDBN} serial debugging
20063 @item set debug solib-frv
20064 @cindex FR-V shared-library debugging
20065 Turns on or off debugging messages for FR-V shared-library code.
20066 @item show debug solib-frv
20067 Display the current state of FR-V shared-library code debugging
20069 @item set debug target
20070 @cindex target debugging info
20071 Turns on or off display of @value{GDBN} target debugging info. This info
20072 includes what is going on at the target level of GDB, as it happens. The
20073 default is 0. Set it to 1 to track events, and to 2 to also track the
20074 value of large memory transfers. Changes to this flag do not take effect
20075 until the next time you connect to a target or use the @code{run} command.
20076 @item show debug target
20077 Displays the current state of displaying @value{GDBN} target debugging
20079 @item set debug timestamp
20080 @cindex timestampping debugging info
20081 Turns on or off display of timestamps with @value{GDBN} debugging info.
20082 When enabled, seconds and microseconds are displayed before each debugging
20084 @item show debug timestamp
20085 Displays the current state of displaying timestamps with @value{GDBN}
20087 @item set debugvarobj
20088 @cindex variable object debugging info
20089 Turns on or off display of @value{GDBN} variable object debugging
20090 info. The default is off.
20091 @item show debugvarobj
20092 Displays the current state of displaying @value{GDBN} variable object
20094 @item set debug xml
20095 @cindex XML parser debugging
20096 Turns on or off debugging messages for built-in XML parsers.
20097 @item show debug xml
20098 Displays the current state of XML debugging messages.
20101 @node Other Misc Settings
20102 @section Other Miscellaneous Settings
20103 @cindex miscellaneous settings
20106 @kindex set interactive-mode
20107 @item set interactive-mode
20108 If @code{on}, forces @value{GDBN} to assume that GDB was started
20109 in a terminal. In practice, this means that @value{GDBN} should wait
20110 for the user to answer queries generated by commands entered at
20111 the command prompt. If @code{off}, forces @value{GDBN} to operate
20112 in the opposite mode, and it uses the default answers to all queries.
20113 If @code{auto} (the default), @value{GDBN} tries to determine whether
20114 its standard input is a terminal, and works in interactive-mode if it
20115 is, non-interactively otherwise.
20117 In the vast majority of cases, the debugger should be able to guess
20118 correctly which mode should be used. But this setting can be useful
20119 in certain specific cases, such as running a MinGW @value{GDBN}
20120 inside a cygwin window.
20122 @kindex show interactive-mode
20123 @item show interactive-mode
20124 Displays whether the debugger is operating in interactive mode or not.
20127 @node Extending GDB
20128 @chapter Extending @value{GDBN}
20129 @cindex extending GDB
20131 @value{GDBN} provides two mechanisms for extension. The first is based
20132 on composition of @value{GDBN} commands, and the second is based on the
20133 Python scripting language.
20135 To facilitate the use of these extensions, @value{GDBN} is capable
20136 of evaluating the contents of a file. When doing so, @value{GDBN}
20137 can recognize which scripting language is being used by looking at
20138 the filename extension. Files with an unrecognized filename extension
20139 are always treated as a @value{GDBN} Command Files.
20140 @xref{Command Files,, Command files}.
20142 You can control how @value{GDBN} evaluates these files with the following
20146 @kindex set script-extension
20147 @kindex show script-extension
20148 @item set script-extension off
20149 All scripts are always evaluated as @value{GDBN} Command Files.
20151 @item set script-extension soft
20152 The debugger determines the scripting language based on filename
20153 extension. If this scripting language is supported, @value{GDBN}
20154 evaluates the script using that language. Otherwise, it evaluates
20155 the file as a @value{GDBN} Command File.
20157 @item set script-extension strict
20158 The debugger determines the scripting language based on filename
20159 extension, and evaluates the script using that language. If the
20160 language is not supported, then the evaluation fails.
20162 @item show script-extension
20163 Display the current value of the @code{script-extension} option.
20168 * Sequences:: Canned Sequences of Commands
20169 * Python:: Scripting @value{GDBN} using Python
20173 @section Canned Sequences of Commands
20175 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20176 Command Lists}), @value{GDBN} provides two ways to store sequences of
20177 commands for execution as a unit: user-defined commands and command
20181 * Define:: How to define your own commands
20182 * Hooks:: Hooks for user-defined commands
20183 * Command Files:: How to write scripts of commands to be stored in a file
20184 * Output:: Commands for controlled output
20188 @subsection User-defined Commands
20190 @cindex user-defined command
20191 @cindex arguments, to user-defined commands
20192 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20193 which you assign a new name as a command. This is done with the
20194 @code{define} command. User commands may accept up to 10 arguments
20195 separated by whitespace. Arguments are accessed within the user command
20196 via @code{$arg0@dots{}$arg9}. A trivial example:
20200 print $arg0 + $arg1 + $arg2
20205 To execute the command use:
20212 This defines the command @code{adder}, which prints the sum of
20213 its three arguments. Note the arguments are text substitutions, so they may
20214 reference variables, use complex expressions, or even perform inferior
20217 @cindex argument count in user-defined commands
20218 @cindex how many arguments (user-defined commands)
20219 In addition, @code{$argc} may be used to find out how many arguments have
20220 been passed. This expands to a number in the range 0@dots{}10.
20225 print $arg0 + $arg1
20228 print $arg0 + $arg1 + $arg2
20236 @item define @var{commandname}
20237 Define a command named @var{commandname}. If there is already a command
20238 by that name, you are asked to confirm that you want to redefine it.
20239 @var{commandname} may be a bare command name consisting of letters,
20240 numbers, dashes, and underscores. It may also start with any predefined
20241 prefix command. For example, @samp{define target my-target} creates
20242 a user-defined @samp{target my-target} command.
20244 The definition of the command is made up of other @value{GDBN} command lines,
20245 which are given following the @code{define} command. The end of these
20246 commands is marked by a line containing @code{end}.
20249 @kindex end@r{ (user-defined commands)}
20250 @item document @var{commandname}
20251 Document the user-defined command @var{commandname}, so that it can be
20252 accessed by @code{help}. The command @var{commandname} must already be
20253 defined. This command reads lines of documentation just as @code{define}
20254 reads the lines of the command definition, ending with @code{end}.
20255 After the @code{document} command is finished, @code{help} on command
20256 @var{commandname} displays the documentation you have written.
20258 You may use the @code{document} command again to change the
20259 documentation of a command. Redefining the command with @code{define}
20260 does not change the documentation.
20262 @kindex dont-repeat
20263 @cindex don't repeat command
20265 Used inside a user-defined command, this tells @value{GDBN} that this
20266 command should not be repeated when the user hits @key{RET}
20267 (@pxref{Command Syntax, repeat last command}).
20269 @kindex help user-defined
20270 @item help user-defined
20271 List all user-defined commands, with the first line of the documentation
20276 @itemx show user @var{commandname}
20277 Display the @value{GDBN} commands used to define @var{commandname} (but
20278 not its documentation). If no @var{commandname} is given, display the
20279 definitions for all user-defined commands.
20281 @cindex infinite recursion in user-defined commands
20282 @kindex show max-user-call-depth
20283 @kindex set max-user-call-depth
20284 @item show max-user-call-depth
20285 @itemx set max-user-call-depth
20286 The value of @code{max-user-call-depth} controls how many recursion
20287 levels are allowed in user-defined commands before @value{GDBN} suspects an
20288 infinite recursion and aborts the command.
20291 In addition to the above commands, user-defined commands frequently
20292 use control flow commands, described in @ref{Command Files}.
20294 When user-defined commands are executed, the
20295 commands of the definition are not printed. An error in any command
20296 stops execution of the user-defined command.
20298 If used interactively, commands that would ask for confirmation proceed
20299 without asking when used inside a user-defined command. Many @value{GDBN}
20300 commands that normally print messages to say what they are doing omit the
20301 messages when used in a user-defined command.
20304 @subsection User-defined Command Hooks
20305 @cindex command hooks
20306 @cindex hooks, for commands
20307 @cindex hooks, pre-command
20310 You may define @dfn{hooks}, which are a special kind of user-defined
20311 command. Whenever you run the command @samp{foo}, if the user-defined
20312 command @samp{hook-foo} exists, it is executed (with no arguments)
20313 before that command.
20315 @cindex hooks, post-command
20317 A hook may also be defined which is run after the command you executed.
20318 Whenever you run the command @samp{foo}, if the user-defined command
20319 @samp{hookpost-foo} exists, it is executed (with no arguments) after
20320 that command. Post-execution hooks may exist simultaneously with
20321 pre-execution hooks, for the same command.
20323 It is valid for a hook to call the command which it hooks. If this
20324 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
20326 @c It would be nice if hookpost could be passed a parameter indicating
20327 @c if the command it hooks executed properly or not. FIXME!
20329 @kindex stop@r{, a pseudo-command}
20330 In addition, a pseudo-command, @samp{stop} exists. Defining
20331 (@samp{hook-stop}) makes the associated commands execute every time
20332 execution stops in your program: before breakpoint commands are run,
20333 displays are printed, or the stack frame is printed.
20335 For example, to ignore @code{SIGALRM} signals while
20336 single-stepping, but treat them normally during normal execution,
20341 handle SIGALRM nopass
20345 handle SIGALRM pass
20348 define hook-continue
20349 handle SIGALRM pass
20353 As a further example, to hook at the beginning and end of the @code{echo}
20354 command, and to add extra text to the beginning and end of the message,
20362 define hookpost-echo
20366 (@value{GDBP}) echo Hello World
20367 <<<---Hello World--->>>
20372 You can define a hook for any single-word command in @value{GDBN}, but
20373 not for command aliases; you should define a hook for the basic command
20374 name, e.g.@: @code{backtrace} rather than @code{bt}.
20375 @c FIXME! So how does Joe User discover whether a command is an alias
20377 You can hook a multi-word command by adding @code{hook-} or
20378 @code{hookpost-} to the last word of the command, e.g.@:
20379 @samp{define target hook-remote} to add a hook to @samp{target remote}.
20381 If an error occurs during the execution of your hook, execution of
20382 @value{GDBN} commands stops and @value{GDBN} issues a prompt
20383 (before the command that you actually typed had a chance to run).
20385 If you try to define a hook which does not match any known command, you
20386 get a warning from the @code{define} command.
20388 @node Command Files
20389 @subsection Command Files
20391 @cindex command files
20392 @cindex scripting commands
20393 A command file for @value{GDBN} is a text file made of lines that are
20394 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
20395 also be included. An empty line in a command file does nothing; it
20396 does not mean to repeat the last command, as it would from the
20399 You can request the execution of a command file with the @code{source}
20400 command. Note that the @code{source} command is also used to evaluate
20401 scripts that are not Command Files. The exact behavior can be configured
20402 using the @code{script-extension} setting.
20403 @xref{Extending GDB,, Extending GDB}.
20407 @cindex execute commands from a file
20408 @item source [-s] [-v] @var{filename}
20409 Execute the command file @var{filename}.
20412 The lines in a command file are generally executed sequentially,
20413 unless the order of execution is changed by one of the
20414 @emph{flow-control commands} described below. The commands are not
20415 printed as they are executed. An error in any command terminates
20416 execution of the command file and control is returned to the console.
20418 @value{GDBN} first searches for @var{filename} in the current directory.
20419 If the file is not found there, and @var{filename} does not specify a
20420 directory, then @value{GDBN} also looks for the file on the source search path
20421 (specified with the @samp{directory} command);
20422 except that @file{$cdir} is not searched because the compilation directory
20423 is not relevant to scripts.
20425 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
20426 on the search path even if @var{filename} specifies a directory.
20427 The search is done by appending @var{filename} to each element of the
20428 search path. So, for example, if @var{filename} is @file{mylib/myscript}
20429 and the search path contains @file{/home/user} then @value{GDBN} will
20430 look for the script @file{/home/user/mylib/myscript}.
20431 The search is also done if @var{filename} is an absolute path.
20432 For example, if @var{filename} is @file{/tmp/myscript} and
20433 the search path contains @file{/home/user} then @value{GDBN} will
20434 look for the script @file{/home/user/tmp/myscript}.
20435 For DOS-like systems, if @var{filename} contains a drive specification,
20436 it is stripped before concatenation. For example, if @var{filename} is
20437 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
20438 will look for the script @file{c:/tmp/myscript}.
20440 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
20441 each command as it is executed. The option must be given before
20442 @var{filename}, and is interpreted as part of the filename anywhere else.
20444 Commands that would ask for confirmation if used interactively proceed
20445 without asking when used in a command file. Many @value{GDBN} commands that
20446 normally print messages to say what they are doing omit the messages
20447 when called from command files.
20449 @value{GDBN} also accepts command input from standard input. In this
20450 mode, normal output goes to standard output and error output goes to
20451 standard error. Errors in a command file supplied on standard input do
20452 not terminate execution of the command file---execution continues with
20456 gdb < cmds > log 2>&1
20459 (The syntax above will vary depending on the shell used.) This example
20460 will execute commands from the file @file{cmds}. All output and errors
20461 would be directed to @file{log}.
20463 Since commands stored on command files tend to be more general than
20464 commands typed interactively, they frequently need to deal with
20465 complicated situations, such as different or unexpected values of
20466 variables and symbols, changes in how the program being debugged is
20467 built, etc. @value{GDBN} provides a set of flow-control commands to
20468 deal with these complexities. Using these commands, you can write
20469 complex scripts that loop over data structures, execute commands
20470 conditionally, etc.
20477 This command allows to include in your script conditionally executed
20478 commands. The @code{if} command takes a single argument, which is an
20479 expression to evaluate. It is followed by a series of commands that
20480 are executed only if the expression is true (its value is nonzero).
20481 There can then optionally be an @code{else} line, followed by a series
20482 of commands that are only executed if the expression was false. The
20483 end of the list is marked by a line containing @code{end}.
20487 This command allows to write loops. Its syntax is similar to
20488 @code{if}: the command takes a single argument, which is an expression
20489 to evaluate, and must be followed by the commands to execute, one per
20490 line, terminated by an @code{end}. These commands are called the
20491 @dfn{body} of the loop. The commands in the body of @code{while} are
20492 executed repeatedly as long as the expression evaluates to true.
20496 This command exits the @code{while} loop in whose body it is included.
20497 Execution of the script continues after that @code{while}s @code{end}
20500 @kindex loop_continue
20501 @item loop_continue
20502 This command skips the execution of the rest of the body of commands
20503 in the @code{while} loop in whose body it is included. Execution
20504 branches to the beginning of the @code{while} loop, where it evaluates
20505 the controlling expression.
20507 @kindex end@r{ (if/else/while commands)}
20509 Terminate the block of commands that are the body of @code{if},
20510 @code{else}, or @code{while} flow-control commands.
20515 @subsection Commands for Controlled Output
20517 During the execution of a command file or a user-defined command, normal
20518 @value{GDBN} output is suppressed; the only output that appears is what is
20519 explicitly printed by the commands in the definition. This section
20520 describes three commands useful for generating exactly the output you
20525 @item echo @var{text}
20526 @c I do not consider backslash-space a standard C escape sequence
20527 @c because it is not in ANSI.
20528 Print @var{text}. Nonprinting characters can be included in
20529 @var{text} using C escape sequences, such as @samp{\n} to print a
20530 newline. @strong{No newline is printed unless you specify one.}
20531 In addition to the standard C escape sequences, a backslash followed
20532 by a space stands for a space. This is useful for displaying a
20533 string with spaces at the beginning or the end, since leading and
20534 trailing spaces are otherwise trimmed from all arguments.
20535 To print @samp{@w{ }and foo =@w{ }}, use the command
20536 @samp{echo \@w{ }and foo = \@w{ }}.
20538 A backslash at the end of @var{text} can be used, as in C, to continue
20539 the command onto subsequent lines. For example,
20542 echo This is some text\n\
20543 which is continued\n\
20544 onto several lines.\n
20547 produces the same output as
20550 echo This is some text\n
20551 echo which is continued\n
20552 echo onto several lines.\n
20556 @item output @var{expression}
20557 Print the value of @var{expression} and nothing but that value: no
20558 newlines, no @samp{$@var{nn} = }. The value is not entered in the
20559 value history either. @xref{Expressions, ,Expressions}, for more information
20562 @item output/@var{fmt} @var{expression}
20563 Print the value of @var{expression} in format @var{fmt}. You can use
20564 the same formats as for @code{print}. @xref{Output Formats,,Output
20565 Formats}, for more information.
20568 @item printf @var{template}, @var{expressions}@dots{}
20569 Print the values of one or more @var{expressions} under the control of
20570 the string @var{template}. To print several values, make
20571 @var{expressions} be a comma-separated list of individual expressions,
20572 which may be either numbers or pointers. Their values are printed as
20573 specified by @var{template}, exactly as a C program would do by
20574 executing the code below:
20577 printf (@var{template}, @var{expressions}@dots{});
20580 As in @code{C} @code{printf}, ordinary characters in @var{template}
20581 are printed verbatim, while @dfn{conversion specification} introduced
20582 by the @samp{%} character cause subsequent @var{expressions} to be
20583 evaluated, their values converted and formatted according to type and
20584 style information encoded in the conversion specifications, and then
20587 For example, you can print two values in hex like this:
20590 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
20593 @code{printf} supports all the standard @code{C} conversion
20594 specifications, including the flags and modifiers between the @samp{%}
20595 character and the conversion letter, with the following exceptions:
20599 The argument-ordering modifiers, such as @samp{2$}, are not supported.
20602 The modifier @samp{*} is not supported for specifying precision or
20606 The @samp{'} flag (for separation of digits into groups according to
20607 @code{LC_NUMERIC'}) is not supported.
20610 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
20614 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
20617 The conversion letters @samp{a} and @samp{A} are not supported.
20621 Note that the @samp{ll} type modifier is supported only if the
20622 underlying @code{C} implementation used to build @value{GDBN} supports
20623 the @code{long long int} type, and the @samp{L} type modifier is
20624 supported only if @code{long double} type is available.
20626 As in @code{C}, @code{printf} supports simple backslash-escape
20627 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
20628 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
20629 single character. Octal and hexadecimal escape sequences are not
20632 Additionally, @code{printf} supports conversion specifications for DFP
20633 (@dfn{Decimal Floating Point}) types using the following length modifiers
20634 together with a floating point specifier.
20639 @samp{H} for printing @code{Decimal32} types.
20642 @samp{D} for printing @code{Decimal64} types.
20645 @samp{DD} for printing @code{Decimal128} types.
20648 If the underlying @code{C} implementation used to build @value{GDBN} has
20649 support for the three length modifiers for DFP types, other modifiers
20650 such as width and precision will also be available for @value{GDBN} to use.
20652 In case there is no such @code{C} support, no additional modifiers will be
20653 available and the value will be printed in the standard way.
20655 Here's an example of printing DFP types using the above conversion letters:
20657 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
20661 @item eval @var{template}, @var{expressions}@dots{}
20662 Convert the values of one or more @var{expressions} under the control of
20663 the string @var{template} to a command line, and call it.
20668 @section Scripting @value{GDBN} using Python
20669 @cindex python scripting
20670 @cindex scripting with python
20672 You can script @value{GDBN} using the @uref{http://www.python.org/,
20673 Python programming language}. This feature is available only if
20674 @value{GDBN} was configured using @option{--with-python}.
20676 @cindex python directory
20677 Python scripts used by @value{GDBN} should be installed in
20678 @file{@var{data-directory}/python}, where @var{data-directory} is
20679 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
20680 This directory, known as the @dfn{python directory},
20681 is automatically added to the Python Search Path in order to allow
20682 the Python interpreter to locate all scripts installed at this location.
20685 * Python Commands:: Accessing Python from @value{GDBN}.
20686 * Python API:: Accessing @value{GDBN} from Python.
20687 * Auto-loading:: Automatically loading Python code.
20688 * Python modules:: Python modules provided by @value{GDBN}.
20691 @node Python Commands
20692 @subsection Python Commands
20693 @cindex python commands
20694 @cindex commands to access python
20696 @value{GDBN} provides one command for accessing the Python interpreter,
20697 and one related setting:
20701 @item python @r{[}@var{code}@r{]}
20702 The @code{python} command can be used to evaluate Python code.
20704 If given an argument, the @code{python} command will evaluate the
20705 argument as a Python command. For example:
20708 (@value{GDBP}) python print 23
20712 If you do not provide an argument to @code{python}, it will act as a
20713 multi-line command, like @code{define}. In this case, the Python
20714 script is made up of subsequent command lines, given after the
20715 @code{python} command. This command list is terminated using a line
20716 containing @code{end}. For example:
20719 (@value{GDBP}) python
20721 End with a line saying just "end".
20727 @kindex maint set python print-stack
20728 @item maint set python print-stack
20729 By default, @value{GDBN} will print a stack trace when an error occurs
20730 in a Python script. This can be controlled using @code{maint set
20731 python print-stack}: if @code{on}, the default, then Python stack
20732 printing is enabled; if @code{off}, then Python stack printing is
20736 It is also possible to execute a Python script from the @value{GDBN}
20740 @item source @file{script-name}
20741 The script name must end with @samp{.py} and @value{GDBN} must be configured
20742 to recognize the script language based on filename extension using
20743 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
20745 @item python execfile ("script-name")
20746 This method is based on the @code{execfile} Python built-in function,
20747 and thus is always available.
20751 @subsection Python API
20753 @cindex programming in python
20755 @cindex python stdout
20756 @cindex python pagination
20757 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
20758 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
20759 A Python program which outputs to one of these streams may have its
20760 output interrupted by the user (@pxref{Screen Size}). In this
20761 situation, a Python @code{KeyboardInterrupt} exception is thrown.
20764 * Basic Python:: Basic Python Functions.
20765 * Exception Handling:: How Python exceptions are translated.
20766 * Values From Inferior:: Python representation of values.
20767 * Types In Python:: Python representation of types.
20768 * Pretty Printing API:: Pretty-printing values.
20769 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
20770 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
20771 * Inferiors In Python:: Python representation of inferiors (processes)
20772 * Events In Python:: Listening for events from @value{GDBN}.
20773 * Threads In Python:: Accessing inferior threads from Python.
20774 * Commands In Python:: Implementing new commands in Python.
20775 * Parameters In Python:: Adding new @value{GDBN} parameters.
20776 * Functions In Python:: Writing new convenience functions.
20777 * Progspaces In Python:: Program spaces.
20778 * Objfiles In Python:: Object files.
20779 * Frames In Python:: Accessing inferior stack frames from Python.
20780 * Blocks In Python:: Accessing frame blocks from Python.
20781 * Symbols In Python:: Python representation of symbols.
20782 * Symbol Tables In Python:: Python representation of symbol tables.
20783 * Lazy Strings In Python:: Python representation of lazy strings.
20784 * Breakpoints In Python:: Manipulating breakpoints using Python.
20788 @subsubsection Basic Python
20790 @cindex python functions
20791 @cindex python module
20793 @value{GDBN} introduces a new Python module, named @code{gdb}. All
20794 methods and classes added by @value{GDBN} are placed in this module.
20795 @value{GDBN} automatically @code{import}s the @code{gdb} module for
20796 use in all scripts evaluated by the @code{python} command.
20798 @findex gdb.PYTHONDIR
20800 A string containing the python directory (@pxref{Python}).
20803 @findex gdb.execute
20804 @defun execute command [from_tty] [to_string]
20805 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
20806 If a GDB exception happens while @var{command} runs, it is
20807 translated as described in @ref{Exception Handling,,Exception Handling}.
20809 @var{from_tty} specifies whether @value{GDBN} ought to consider this
20810 command as having originated from the user invoking it interactively.
20811 It must be a boolean value. If omitted, it defaults to @code{False}.
20813 By default, any output produced by @var{command} is sent to
20814 @value{GDBN}'s standard output. If the @var{to_string} parameter is
20815 @code{True}, then output will be collected by @code{gdb.execute} and
20816 returned as a string. The default is @code{False}, in which case the
20817 return value is @code{None}. If @var{to_string} is @code{True}, the
20818 @value{GDBN} virtual terminal will be temporarily set to unlimited width
20819 and height, and its pagination will be disabled; @pxref{Screen Size}.
20822 @findex gdb.breakpoints
20824 Return a sequence holding all of @value{GDBN}'s breakpoints.
20825 @xref{Breakpoints In Python}, for more information.
20828 @findex gdb.parameter
20829 @defun parameter parameter
20830 Return the value of a @value{GDBN} parameter. @var{parameter} is a
20831 string naming the parameter to look up; @var{parameter} may contain
20832 spaces if the parameter has a multi-part name. For example,
20833 @samp{print object} is a valid parameter name.
20835 If the named parameter does not exist, this function throws a
20836 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
20837 parameter's value is converted to a Python value of the appropriate
20838 type, and returned.
20841 @findex gdb.history
20842 @defun history number
20843 Return a value from @value{GDBN}'s value history (@pxref{Value
20844 History}). @var{number} indicates which history element to return.
20845 If @var{number} is negative, then @value{GDBN} will take its absolute value
20846 and count backward from the last element (i.e., the most recent element) to
20847 find the value to return. If @var{number} is zero, then @value{GDBN} will
20848 return the most recent element. If the element specified by @var{number}
20849 doesn't exist in the value history, a @code{gdb.error} exception will be
20852 If no exception is raised, the return value is always an instance of
20853 @code{gdb.Value} (@pxref{Values From Inferior}).
20856 @findex gdb.parse_and_eval
20857 @defun parse_and_eval expression
20858 Parse @var{expression} as an expression in the current language,
20859 evaluate it, and return the result as a @code{gdb.Value}.
20860 @var{expression} must be a string.
20862 This function can be useful when implementing a new command
20863 (@pxref{Commands In Python}), as it provides a way to parse the
20864 command's argument as an expression. It is also useful simply to
20865 compute values, for example, it is the only way to get the value of a
20866 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
20869 @findex gdb.post_event
20870 @defun post_event event
20871 Put @var{event}, a callable object taking no arguments, into
20872 @value{GDBN}'s internal event queue. This callable will be invoked at
20873 some later point, during @value{GDBN}'s event processing. Events
20874 posted using @code{post_event} will be run in the order in which they
20875 were posted; however, there is no way to know when they will be
20876 processed relative to other events inside @value{GDBN}.
20878 @value{GDBN} is not thread-safe. If your Python program uses multiple
20879 threads, you must be careful to only call @value{GDBN}-specific
20880 functions in the main @value{GDBN} thread. @code{post_event} ensures
20884 (@value{GDBP}) python
20888 > def __init__(self, message):
20889 > self.message = message;
20890 > def __call__(self):
20891 > gdb.write(self.message)
20893 >class MyThread1 (threading.Thread):
20895 > gdb.post_event(Writer("Hello "))
20897 >class MyThread2 (threading.Thread):
20899 > gdb.post_event(Writer("World\n"))
20901 >MyThread1().start()
20902 >MyThread2().start()
20904 (@value{GDBP}) Hello World
20909 @defun write string @r{[}stream{]}
20910 Print a string to @value{GDBN}'s paginated output stream. The
20911 optional @var{stream} determines the stream to print to. The default
20912 stream is @value{GDBN}'s standard output stream. Possible stream
20919 @value{GDBN}'s standard output stream.
20924 @value{GDBN}'s standard error stream.
20929 @value{GDBN}'s log stream (@pxref{Logging Output}).
20932 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
20933 call this function and will automatically direct the output to the
20939 Flush the buffer of a @value{GDBN} paginated stream so that the
20940 contents are displayed immediately. @value{GDBN} will flush the
20941 contents of a stream automatically when it encounters a newline in the
20942 buffer. The optional @var{stream} determines the stream to flush. The
20943 default stream is @value{GDBN}'s standard output stream. Possible
20950 @value{GDBN}'s standard output stream.
20955 @value{GDBN}'s standard error stream.
20960 @value{GDBN}'s log stream (@pxref{Logging Output}).
20964 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
20965 call this function for the relevant stream.
20968 @findex gdb.target_charset
20969 @defun target_charset
20970 Return the name of the current target character set (@pxref{Character
20971 Sets}). This differs from @code{gdb.parameter('target-charset')} in
20972 that @samp{auto} is never returned.
20975 @findex gdb.target_wide_charset
20976 @defun target_wide_charset
20977 Return the name of the current target wide character set
20978 (@pxref{Character Sets}). This differs from
20979 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
20983 @findex gdb.solib_name
20984 @defun solib_name address
20985 Return the name of the shared library holding the given @var{address}
20986 as a string, or @code{None}.
20989 @findex gdb.decode_line
20990 @defun decode_line @r{[}expression@r{]}
20991 Return locations of the line specified by @var{expression}, or of the
20992 current line if no argument was given. This function returns a Python
20993 tuple containing two elements. The first element contains a string
20994 holding any unparsed section of @var{expression} (or @code{None} if
20995 the expression has been fully parsed). The second element contains
20996 either @code{None} or another tuple that contains all the locations
20997 that match the expression represented as @code{gdb.Symtab_and_line}
20998 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
20999 provided, it is decoded the way that @value{GDBN}'s inbuilt
21000 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
21003 @node Exception Handling
21004 @subsubsection Exception Handling
21005 @cindex python exceptions
21006 @cindex exceptions, python
21008 When executing the @code{python} command, Python exceptions
21009 uncaught within the Python code are translated to calls to
21010 @value{GDBN} error-reporting mechanism. If the command that called
21011 @code{python} does not handle the error, @value{GDBN} will
21012 terminate it and print an error message containing the Python
21013 exception name, the associated value, and the Python call stack
21014 backtrace at the point where the exception was raised. Example:
21017 (@value{GDBP}) python print foo
21018 Traceback (most recent call last):
21019 File "<string>", line 1, in <module>
21020 NameError: name 'foo' is not defined
21023 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21024 Python code are converted to Python exceptions. The type of the
21025 Python exception depends on the error.
21029 This is the base class for most exceptions generated by @value{GDBN}.
21030 It is derived from @code{RuntimeError}, for compatibility with earlier
21031 versions of @value{GDBN}.
21033 If an error occurring in @value{GDBN} does not fit into some more
21034 specific category, then the generated exception will have this type.
21036 @item gdb.MemoryError
21037 This is a subclass of @code{gdb.error} which is thrown when an
21038 operation tried to access invalid memory in the inferior.
21040 @item KeyboardInterrupt
21041 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21042 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21045 In all cases, your exception handler will see the @value{GDBN} error
21046 message as its value and the Python call stack backtrace at the Python
21047 statement closest to where the @value{GDBN} error occured as the
21050 @findex gdb.GdbError
21051 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21052 it is useful to be able to throw an exception that doesn't cause a
21053 traceback to be printed. For example, the user may have invoked the
21054 command incorrectly. Use the @code{gdb.GdbError} exception
21055 to handle this case. Example:
21059 >class HelloWorld (gdb.Command):
21060 > """Greet the whole world."""
21061 > def __init__ (self):
21062 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21063 > def invoke (self, args, from_tty):
21064 > argv = gdb.string_to_argv (args)
21065 > if len (argv) != 0:
21066 > raise gdb.GdbError ("hello-world takes no arguments")
21067 > print "Hello, World!"
21070 (gdb) hello-world 42
21071 hello-world takes no arguments
21074 @node Values From Inferior
21075 @subsubsection Values From Inferior
21076 @cindex values from inferior, with Python
21077 @cindex python, working with values from inferior
21079 @cindex @code{gdb.Value}
21080 @value{GDBN} provides values it obtains from the inferior program in
21081 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21082 for its internal bookkeeping of the inferior's values, and for
21083 fetching values when necessary.
21085 Inferior values that are simple scalars can be used directly in
21086 Python expressions that are valid for the value's data type. Here's
21087 an example for an integer or floating-point value @code{some_val}:
21094 As result of this, @code{bar} will also be a @code{gdb.Value} object
21095 whose values are of the same type as those of @code{some_val}.
21097 Inferior values that are structures or instances of some class can
21098 be accessed using the Python @dfn{dictionary syntax}. For example, if
21099 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21100 can access its @code{foo} element with:
21103 bar = some_val['foo']
21106 Again, @code{bar} will also be a @code{gdb.Value} object.
21108 A @code{gdb.Value} that represents a function can be executed via
21109 inferior function call. Any arguments provided to the call must match
21110 the function's prototype, and must be provided in the order specified
21113 For example, @code{some_val} is a @code{gdb.Value} instance
21114 representing a function that takes two integers as arguments. To
21115 execute this function, call it like so:
21118 result = some_val (10,20)
21121 Any values returned from a function call will be stored as a
21124 The following attributes are provided:
21127 @defivar Value address
21128 If this object is addressable, this read-only attribute holds a
21129 @code{gdb.Value} object representing the address. Otherwise,
21130 this attribute holds @code{None}.
21133 @cindex optimized out value in Python
21134 @defivar Value is_optimized_out
21135 This read-only boolean attribute is true if the compiler optimized out
21136 this value, thus it is not available for fetching from the inferior.
21139 @defivar Value type
21140 The type of this @code{gdb.Value}. The value of this attribute is a
21141 @code{gdb.Type} object (@pxref{Types In Python}).
21144 @defivar Value dynamic_type
21145 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21146 type information (@acronym{RTTI}) to determine the dynamic type of the
21147 value. If this value is of class type, it will return the class in
21148 which the value is embedded, if any. If this value is of pointer or
21149 reference to a class type, it will compute the dynamic type of the
21150 referenced object, and return a pointer or reference to that type,
21151 respectively. In all other cases, it will return the value's static
21154 Note that this feature will only work when debugging a C@t{++} program
21155 that includes @acronym{RTTI} for the object in question. Otherwise,
21156 it will just return the static type of the value as in @kbd{ptype foo}
21157 (@pxref{Symbols, ptype}).
21161 The following methods are provided:
21164 @defmethod Value __init__ @var{val}
21165 Many Python values can be converted directly to a @code{gdb.Value} via
21166 this object initializer. Specifically:
21169 @item Python boolean
21170 A Python boolean is converted to the boolean type from the current
21173 @item Python integer
21174 A Python integer is converted to the C @code{long} type for the
21175 current architecture.
21178 A Python long is converted to the C @code{long long} type for the
21179 current architecture.
21182 A Python float is converted to the C @code{double} type for the
21183 current architecture.
21185 @item Python string
21186 A Python string is converted to a target string, using the current
21189 @item @code{gdb.Value}
21190 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
21192 @item @code{gdb.LazyString}
21193 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
21194 Python}), then the lazy string's @code{value} method is called, and
21195 its result is used.
21199 @defmethod Value cast type
21200 Return a new instance of @code{gdb.Value} that is the result of
21201 casting this instance to the type described by @var{type}, which must
21202 be a @code{gdb.Type} object. If the cast cannot be performed for some
21203 reason, this method throws an exception.
21206 @defmethod Value dereference
21207 For pointer data types, this method returns a new @code{gdb.Value} object
21208 whose contents is the object pointed to by the pointer. For example, if
21209 @code{foo} is a C pointer to an @code{int}, declared in your C program as
21216 then you can use the corresponding @code{gdb.Value} to access what
21217 @code{foo} points to like this:
21220 bar = foo.dereference ()
21223 The result @code{bar} will be a @code{gdb.Value} object holding the
21224 value pointed to by @code{foo}.
21227 @defmethod Value dynamic_cast type
21228 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
21229 operator were used. Consult a C@t{++} reference for details.
21232 @defmethod Value reinterpret_cast type
21233 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
21234 operator were used. Consult a C@t{++} reference for details.
21237 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
21238 If this @code{gdb.Value} represents a string, then this method
21239 converts the contents to a Python string. Otherwise, this method will
21240 throw an exception.
21242 Strings are recognized in a language-specific way; whether a given
21243 @code{gdb.Value} represents a string is determined by the current
21246 For C-like languages, a value is a string if it is a pointer to or an
21247 array of characters or ints. The string is assumed to be terminated
21248 by a zero of the appropriate width. However if the optional length
21249 argument is given, the string will be converted to that given length,
21250 ignoring any embedded zeros that the string may contain.
21252 If the optional @var{encoding} argument is given, it must be a string
21253 naming the encoding of the string in the @code{gdb.Value}, such as
21254 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
21255 the same encodings as the corresponding argument to Python's
21256 @code{string.decode} method, and the Python codec machinery will be used
21257 to convert the string. If @var{encoding} is not given, or if
21258 @var{encoding} is the empty string, then either the @code{target-charset}
21259 (@pxref{Character Sets}) will be used, or a language-specific encoding
21260 will be used, if the current language is able to supply one.
21262 The optional @var{errors} argument is the same as the corresponding
21263 argument to Python's @code{string.decode} method.
21265 If the optional @var{length} argument is given, the string will be
21266 fetched and converted to the given length.
21269 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
21270 If this @code{gdb.Value} represents a string, then this method
21271 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
21272 In Python}). Otherwise, this method will throw an exception.
21274 If the optional @var{encoding} argument is given, it must be a string
21275 naming the encoding of the @code{gdb.LazyString}. Some examples are:
21276 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
21277 @var{encoding} argument is an encoding that @value{GDBN} does
21278 recognize, @value{GDBN} will raise an error.
21280 When a lazy string is printed, the @value{GDBN} encoding machinery is
21281 used to convert the string during printing. If the optional
21282 @var{encoding} argument is not provided, or is an empty string,
21283 @value{GDBN} will automatically select the encoding most suitable for
21284 the string type. For further information on encoding in @value{GDBN}
21285 please see @ref{Character Sets}.
21287 If the optional @var{length} argument is given, the string will be
21288 fetched and encoded to the length of characters specified. If
21289 the @var{length} argument is not provided, the string will be fetched
21290 and encoded until a null of appropriate width is found.
21294 @node Types In Python
21295 @subsubsection Types In Python
21296 @cindex types in Python
21297 @cindex Python, working with types
21300 @value{GDBN} represents types from the inferior using the class
21303 The following type-related functions are available in the @code{gdb}
21306 @findex gdb.lookup_type
21307 @defun lookup_type name [block]
21308 This function looks up a type by name. @var{name} is the name of the
21309 type to look up. It must be a string.
21311 If @var{block} is given, then @var{name} is looked up in that scope.
21312 Otherwise, it is searched for globally.
21314 Ordinarily, this function will return an instance of @code{gdb.Type}.
21315 If the named type cannot be found, it will throw an exception.
21318 An instance of @code{Type} has the following attributes:
21322 The type code for this type. The type code will be one of the
21323 @code{TYPE_CODE_} constants defined below.
21326 @defivar Type sizeof
21327 The size of this type, in target @code{char} units. Usually, a
21328 target's @code{char} type will be an 8-bit byte. However, on some
21329 unusual platforms, this type may have a different size.
21333 The tag name for this type. The tag name is the name after
21334 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
21335 languages have this concept. If this type has no tag name, then
21336 @code{None} is returned.
21340 The following methods are provided:
21343 @defmethod Type fields
21344 For structure and union types, this method returns the fields. Range
21345 types have two fields, the minimum and maximum values. Enum types
21346 have one field per enum constant. Function and method types have one
21347 field per parameter. The base types of C@t{++} classes are also
21348 represented as fields. If the type has no fields, or does not fit
21349 into one of these categories, an empty sequence will be returned.
21351 Each field is an object, with some pre-defined attributes:
21354 This attribute is not available for @code{static} fields (as in
21355 C@t{++} or Java). For non-@code{static} fields, the value is the bit
21356 position of the field.
21359 The name of the field, or @code{None} for anonymous fields.
21362 This is @code{True} if the field is artificial, usually meaning that
21363 it was provided by the compiler and not the user. This attribute is
21364 always provided, and is @code{False} if the field is not artificial.
21366 @item is_base_class
21367 This is @code{True} if the field represents a base class of a C@t{++}
21368 structure. This attribute is always provided, and is @code{False}
21369 if the field is not a base class of the type that is the argument of
21370 @code{fields}, or if that type was not a C@t{++} class.
21373 If the field is packed, or is a bitfield, then this will have a
21374 non-zero value, which is the size of the field in bits. Otherwise,
21375 this will be zero; in this case the field's size is given by its type.
21378 The type of the field. This is usually an instance of @code{Type},
21379 but it can be @code{None} in some situations.
21383 @defmethod Type array @var{n1} @r{[}@var{n2}@r{]}
21384 Return a new @code{gdb.Type} object which represents an array of this
21385 type. If one argument is given, it is the inclusive upper bound of
21386 the array; in this case the lower bound is zero. If two arguments are
21387 given, the first argument is the lower bound of the array, and the
21388 second argument is the upper bound of the array. An array's length
21389 must not be negative, but the bounds can be.
21392 @defmethod Type const
21393 Return a new @code{gdb.Type} object which represents a
21394 @code{const}-qualified variant of this type.
21397 @defmethod Type volatile
21398 Return a new @code{gdb.Type} object which represents a
21399 @code{volatile}-qualified variant of this type.
21402 @defmethod Type unqualified
21403 Return a new @code{gdb.Type} object which represents an unqualified
21404 variant of this type. That is, the result is neither @code{const} nor
21408 @defmethod Type range
21409 Return a Python @code{Tuple} object that contains two elements: the
21410 low bound of the argument type and the high bound of that type. If
21411 the type does not have a range, @value{GDBN} will raise a
21412 @code{gdb.error} exception (@pxref{Exception Handling}).
21415 @defmethod Type reference
21416 Return a new @code{gdb.Type} object which represents a reference to this
21420 @defmethod Type pointer
21421 Return a new @code{gdb.Type} object which represents a pointer to this
21425 @defmethod Type strip_typedefs
21426 Return a new @code{gdb.Type} that represents the real type,
21427 after removing all layers of typedefs.
21430 @defmethod Type target
21431 Return a new @code{gdb.Type} object which represents the target type
21434 For a pointer type, the target type is the type of the pointed-to
21435 object. For an array type (meaning C-like arrays), the target type is
21436 the type of the elements of the array. For a function or method type,
21437 the target type is the type of the return value. For a complex type,
21438 the target type is the type of the elements. For a typedef, the
21439 target type is the aliased type.
21441 If the type does not have a target, this method will throw an
21445 @defmethod Type template_argument n [block]
21446 If this @code{gdb.Type} is an instantiation of a template, this will
21447 return a new @code{gdb.Type} which represents the type of the
21448 @var{n}th template argument.
21450 If this @code{gdb.Type} is not a template type, this will throw an
21451 exception. Ordinarily, only C@t{++} code will have template types.
21453 If @var{block} is given, then @var{name} is looked up in that scope.
21454 Otherwise, it is searched for globally.
21459 Each type has a code, which indicates what category this type falls
21460 into. The available type categories are represented by constants
21461 defined in the @code{gdb} module:
21464 @findex TYPE_CODE_PTR
21465 @findex gdb.TYPE_CODE_PTR
21466 @item TYPE_CODE_PTR
21467 The type is a pointer.
21469 @findex TYPE_CODE_ARRAY
21470 @findex gdb.TYPE_CODE_ARRAY
21471 @item TYPE_CODE_ARRAY
21472 The type is an array.
21474 @findex TYPE_CODE_STRUCT
21475 @findex gdb.TYPE_CODE_STRUCT
21476 @item TYPE_CODE_STRUCT
21477 The type is a structure.
21479 @findex TYPE_CODE_UNION
21480 @findex gdb.TYPE_CODE_UNION
21481 @item TYPE_CODE_UNION
21482 The type is a union.
21484 @findex TYPE_CODE_ENUM
21485 @findex gdb.TYPE_CODE_ENUM
21486 @item TYPE_CODE_ENUM
21487 The type is an enum.
21489 @findex TYPE_CODE_FLAGS
21490 @findex gdb.TYPE_CODE_FLAGS
21491 @item TYPE_CODE_FLAGS
21492 A bit flags type, used for things such as status registers.
21494 @findex TYPE_CODE_FUNC
21495 @findex gdb.TYPE_CODE_FUNC
21496 @item TYPE_CODE_FUNC
21497 The type is a function.
21499 @findex TYPE_CODE_INT
21500 @findex gdb.TYPE_CODE_INT
21501 @item TYPE_CODE_INT
21502 The type is an integer type.
21504 @findex TYPE_CODE_FLT
21505 @findex gdb.TYPE_CODE_FLT
21506 @item TYPE_CODE_FLT
21507 A floating point type.
21509 @findex TYPE_CODE_VOID
21510 @findex gdb.TYPE_CODE_VOID
21511 @item TYPE_CODE_VOID
21512 The special type @code{void}.
21514 @findex TYPE_CODE_SET
21515 @findex gdb.TYPE_CODE_SET
21516 @item TYPE_CODE_SET
21519 @findex TYPE_CODE_RANGE
21520 @findex gdb.TYPE_CODE_RANGE
21521 @item TYPE_CODE_RANGE
21522 A range type, that is, an integer type with bounds.
21524 @findex TYPE_CODE_STRING
21525 @findex gdb.TYPE_CODE_STRING
21526 @item TYPE_CODE_STRING
21527 A string type. Note that this is only used for certain languages with
21528 language-defined string types; C strings are not represented this way.
21530 @findex TYPE_CODE_BITSTRING
21531 @findex gdb.TYPE_CODE_BITSTRING
21532 @item TYPE_CODE_BITSTRING
21535 @findex TYPE_CODE_ERROR
21536 @findex gdb.TYPE_CODE_ERROR
21537 @item TYPE_CODE_ERROR
21538 An unknown or erroneous type.
21540 @findex TYPE_CODE_METHOD
21541 @findex gdb.TYPE_CODE_METHOD
21542 @item TYPE_CODE_METHOD
21543 A method type, as found in C@t{++} or Java.
21545 @findex TYPE_CODE_METHODPTR
21546 @findex gdb.TYPE_CODE_METHODPTR
21547 @item TYPE_CODE_METHODPTR
21548 A pointer-to-member-function.
21550 @findex TYPE_CODE_MEMBERPTR
21551 @findex gdb.TYPE_CODE_MEMBERPTR
21552 @item TYPE_CODE_MEMBERPTR
21553 A pointer-to-member.
21555 @findex TYPE_CODE_REF
21556 @findex gdb.TYPE_CODE_REF
21557 @item TYPE_CODE_REF
21560 @findex TYPE_CODE_CHAR
21561 @findex gdb.TYPE_CODE_CHAR
21562 @item TYPE_CODE_CHAR
21565 @findex TYPE_CODE_BOOL
21566 @findex gdb.TYPE_CODE_BOOL
21567 @item TYPE_CODE_BOOL
21570 @findex TYPE_CODE_COMPLEX
21571 @findex gdb.TYPE_CODE_COMPLEX
21572 @item TYPE_CODE_COMPLEX
21573 A complex float type.
21575 @findex TYPE_CODE_TYPEDEF
21576 @findex gdb.TYPE_CODE_TYPEDEF
21577 @item TYPE_CODE_TYPEDEF
21578 A typedef to some other type.
21580 @findex TYPE_CODE_NAMESPACE
21581 @findex gdb.TYPE_CODE_NAMESPACE
21582 @item TYPE_CODE_NAMESPACE
21583 A C@t{++} namespace.
21585 @findex TYPE_CODE_DECFLOAT
21586 @findex gdb.TYPE_CODE_DECFLOAT
21587 @item TYPE_CODE_DECFLOAT
21588 A decimal floating point type.
21590 @findex TYPE_CODE_INTERNAL_FUNCTION
21591 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
21592 @item TYPE_CODE_INTERNAL_FUNCTION
21593 A function internal to @value{GDBN}. This is the type used to represent
21594 convenience functions.
21597 Further support for types is provided in the @code{gdb.types}
21598 Python module (@pxref{gdb.types}).
21600 @node Pretty Printing API
21601 @subsubsection Pretty Printing API
21603 An example output is provided (@pxref{Pretty Printing}).
21605 A pretty-printer is just an object that holds a value and implements a
21606 specific interface, defined here.
21608 @defop Operation {pretty printer} children (self)
21609 @value{GDBN} will call this method on a pretty-printer to compute the
21610 children of the pretty-printer's value.
21612 This method must return an object conforming to the Python iterator
21613 protocol. Each item returned by the iterator must be a tuple holding
21614 two elements. The first element is the ``name'' of the child; the
21615 second element is the child's value. The value can be any Python
21616 object which is convertible to a @value{GDBN} value.
21618 This method is optional. If it does not exist, @value{GDBN} will act
21619 as though the value has no children.
21622 @defop Operation {pretty printer} display_hint (self)
21623 The CLI may call this method and use its result to change the
21624 formatting of a value. The result will also be supplied to an MI
21625 consumer as a @samp{displayhint} attribute of the variable being
21628 This method is optional. If it does exist, this method must return a
21631 Some display hints are predefined by @value{GDBN}:
21635 Indicate that the object being printed is ``array-like''. The CLI
21636 uses this to respect parameters such as @code{set print elements} and
21637 @code{set print array}.
21640 Indicate that the object being printed is ``map-like'', and that the
21641 children of this value can be assumed to alternate between keys and
21645 Indicate that the object being printed is ``string-like''. If the
21646 printer's @code{to_string} method returns a Python string of some
21647 kind, then @value{GDBN} will call its internal language-specific
21648 string-printing function to format the string. For the CLI this means
21649 adding quotation marks, possibly escaping some characters, respecting
21650 @code{set print elements}, and the like.
21654 @defop Operation {pretty printer} to_string (self)
21655 @value{GDBN} will call this method to display the string
21656 representation of the value passed to the object's constructor.
21658 When printing from the CLI, if the @code{to_string} method exists,
21659 then @value{GDBN} will prepend its result to the values returned by
21660 @code{children}. Exactly how this formatting is done is dependent on
21661 the display hint, and may change as more hints are added. Also,
21662 depending on the print settings (@pxref{Print Settings}), the CLI may
21663 print just the result of @code{to_string} in a stack trace, omitting
21664 the result of @code{children}.
21666 If this method returns a string, it is printed verbatim.
21668 Otherwise, if this method returns an instance of @code{gdb.Value},
21669 then @value{GDBN} prints this value. This may result in a call to
21670 another pretty-printer.
21672 If instead the method returns a Python value which is convertible to a
21673 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
21674 the resulting value. Again, this may result in a call to another
21675 pretty-printer. Python scalars (integers, floats, and booleans) and
21676 strings are convertible to @code{gdb.Value}; other types are not.
21678 Finally, if this method returns @code{None} then no further operations
21679 are peformed in this method and nothing is printed.
21681 If the result is not one of these types, an exception is raised.
21684 @value{GDBN} provides a function which can be used to look up the
21685 default pretty-printer for a @code{gdb.Value}:
21687 @findex gdb.default_visualizer
21688 @defun default_visualizer value
21689 This function takes a @code{gdb.Value} object as an argument. If a
21690 pretty-printer for this value exists, then it is returned. If no such
21691 printer exists, then this returns @code{None}.
21694 @node Selecting Pretty-Printers
21695 @subsubsection Selecting Pretty-Printers
21697 The Python list @code{gdb.pretty_printers} contains an array of
21698 functions or callable objects that have been registered via addition
21699 as a pretty-printer. Printers in this list are called @code{global}
21700 printers, they're available when debugging all inferiors.
21701 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
21702 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
21705 Each function on these lists is passed a single @code{gdb.Value}
21706 argument and should return a pretty-printer object conforming to the
21707 interface definition above (@pxref{Pretty Printing API}). If a function
21708 cannot create a pretty-printer for the value, it should return
21711 @value{GDBN} first checks the @code{pretty_printers} attribute of each
21712 @code{gdb.Objfile} in the current program space and iteratively calls
21713 each enabled lookup routine in the list for that @code{gdb.Objfile}
21714 until it receives a pretty-printer object.
21715 If no pretty-printer is found in the objfile lists, @value{GDBN} then
21716 searches the pretty-printer list of the current program space,
21717 calling each enabled function until an object is returned.
21718 After these lists have been exhausted, it tries the global
21719 @code{gdb.pretty_printers} list, again calling each enabled function until an
21720 object is returned.
21722 The order in which the objfiles are searched is not specified. For a
21723 given list, functions are always invoked from the head of the list,
21724 and iterated over sequentially until the end of the list, or a printer
21725 object is returned.
21727 For various reasons a pretty-printer may not work.
21728 For example, the underlying data structure may have changed and
21729 the pretty-printer is out of date.
21731 The consequences of a broken pretty-printer are severe enough that
21732 @value{GDBN} provides support for enabling and disabling individual
21733 printers. For example, if @code{print frame-arguments} is on,
21734 a backtrace can become highly illegible if any argument is printed
21735 with a broken printer.
21737 Pretty-printers are enabled and disabled by attaching an @code{enabled}
21738 attribute to the registered function or callable object. If this attribute
21739 is present and its value is @code{False}, the printer is disabled, otherwise
21740 the printer is enabled.
21742 @node Writing a Pretty-Printer
21743 @subsubsection Writing a Pretty-Printer
21744 @cindex writing a pretty-printer
21746 A pretty-printer consists of two parts: a lookup function to detect
21747 if the type is supported, and the printer itself.
21749 Here is an example showing how a @code{std::string} printer might be
21750 written. @xref{Pretty Printing API}, for details on the API this class
21754 class StdStringPrinter(object):
21755 "Print a std::string"
21757 def __init__(self, val):
21760 def to_string(self):
21761 return self.val['_M_dataplus']['_M_p']
21763 def display_hint(self):
21767 And here is an example showing how a lookup function for the printer
21768 example above might be written.
21771 def str_lookup_function(val):
21772 lookup_tag = val.type.tag
21773 if lookup_tag == None:
21775 regex = re.compile("^std::basic_string<char,.*>$")
21776 if regex.match(lookup_tag):
21777 return StdStringPrinter(val)
21781 The example lookup function extracts the value's type, and attempts to
21782 match it to a type that it can pretty-print. If it is a type the
21783 printer can pretty-print, it will return a printer object. If not, it
21784 returns @code{None}.
21786 We recommend that you put your core pretty-printers into a Python
21787 package. If your pretty-printers are for use with a library, we
21788 further recommend embedding a version number into the package name.
21789 This practice will enable @value{GDBN} to load multiple versions of
21790 your pretty-printers at the same time, because they will have
21793 You should write auto-loaded code (@pxref{Auto-loading}) such that it
21794 can be evaluated multiple times without changing its meaning. An
21795 ideal auto-load file will consist solely of @code{import}s of your
21796 printer modules, followed by a call to a register pretty-printers with
21797 the current objfile.
21799 Taken as a whole, this approach will scale nicely to multiple
21800 inferiors, each potentially using a different library version.
21801 Embedding a version number in the Python package name will ensure that
21802 @value{GDBN} is able to load both sets of printers simultaneously.
21803 Then, because the search for pretty-printers is done by objfile, and
21804 because your auto-loaded code took care to register your library's
21805 printers with a specific objfile, @value{GDBN} will find the correct
21806 printers for the specific version of the library used by each
21809 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
21810 this code might appear in @code{gdb.libstdcxx.v6}:
21813 def register_printers(objfile):
21814 objfile.pretty_printers.add(str_lookup_function)
21818 And then the corresponding contents of the auto-load file would be:
21821 import gdb.libstdcxx.v6
21822 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
21825 The previous example illustrates a basic pretty-printer.
21826 There are a few things that can be improved on.
21827 The printer doesn't have a name, making it hard to identify in a
21828 list of installed printers. The lookup function has a name, but
21829 lookup functions can have arbitrary, even identical, names.
21831 Second, the printer only handles one type, whereas a library typically has
21832 several types. One could install a lookup function for each desired type
21833 in the library, but one could also have a single lookup function recognize
21834 several types. The latter is the conventional way this is handled.
21835 If a pretty-printer can handle multiple data types, then its
21836 @dfn{subprinters} are the printers for the individual data types.
21838 The @code{gdb.printing} module provides a formal way of solving these
21839 problems (@pxref{gdb.printing}).
21840 Here is another example that handles multiple types.
21842 These are the types we are going to pretty-print:
21845 struct foo @{ int a, b; @};
21846 struct bar @{ struct foo x, y; @};
21849 Here are the printers:
21853 """Print a foo object."""
21855 def __init__(self, val):
21858 def to_string(self):
21859 return ("a=<" + str(self.val["a"]) +
21860 "> b=<" + str(self.val["b"]) + ">")
21863 """Print a bar object."""
21865 def __init__(self, val):
21868 def to_string(self):
21869 return ("x=<" + str(self.val["x"]) +
21870 "> y=<" + str(self.val["y"]) + ">")
21873 This example doesn't need a lookup function, that is handled by the
21874 @code{gdb.printing} module. Instead a function is provided to build up
21875 the object that handles the lookup.
21878 import gdb.printing
21880 def build_pretty_printer():
21881 pp = gdb.printing.RegexpCollectionPrettyPrinter(
21883 pp.add_printer('foo', '^foo$', fooPrinter)
21884 pp.add_printer('bar', '^bar$', barPrinter)
21888 And here is the autoload support:
21891 import gdb.printing
21893 gdb.printing.register_pretty_printer(
21894 gdb.current_objfile(),
21895 my_library.build_pretty_printer())
21898 Finally, when this printer is loaded into @value{GDBN}, here is the
21899 corresponding output of @samp{info pretty-printer}:
21902 (gdb) info pretty-printer
21909 @node Inferiors In Python
21910 @subsubsection Inferiors In Python
21911 @cindex inferiors in Python
21913 @findex gdb.Inferior
21914 Programs which are being run under @value{GDBN} are called inferiors
21915 (@pxref{Inferiors and Programs}). Python scripts can access
21916 information about and manipulate inferiors controlled by @value{GDBN}
21917 via objects of the @code{gdb.Inferior} class.
21919 The following inferior-related functions are available in the @code{gdb}
21923 Return a tuple containing all inferior objects.
21926 A @code{gdb.Inferior} object has the following attributes:
21929 @defivar Inferior num
21930 ID of inferior, as assigned by GDB.
21933 @defivar Inferior pid
21934 Process ID of the inferior, as assigned by the underlying operating
21938 @defivar Inferior was_attached
21939 Boolean signaling whether the inferior was created using `attach', or
21940 started by @value{GDBN} itself.
21944 A @code{gdb.Inferior} object has the following methods:
21947 @defmethod Inferior is_valid
21948 Returns @code{True} if the @code{gdb.Inferior} object is valid,
21949 @code{False} if not. A @code{gdb.Inferior} object will become invalid
21950 if the inferior no longer exists within @value{GDBN}. All other
21951 @code{gdb.Inferior} methods will throw an exception if it is invalid
21952 at the time the method is called.
21955 @defmethod Inferior threads
21956 This method returns a tuple holding all the threads which are valid
21957 when it is called. If there are no valid threads, the method will
21958 return an empty tuple.
21961 @findex gdb.read_memory
21962 @defmethod Inferior read_memory address length
21963 Read @var{length} bytes of memory from the inferior, starting at
21964 @var{address}. Returns a buffer object, which behaves much like an array
21965 or a string. It can be modified and given to the @code{gdb.write_memory}
21969 @findex gdb.write_memory
21970 @defmethod Inferior write_memory address buffer @r{[}length@r{]}
21971 Write the contents of @var{buffer} to the inferior, starting at
21972 @var{address}. The @var{buffer} parameter must be a Python object
21973 which supports the buffer protocol, i.e., a string, an array or the
21974 object returned from @code{gdb.read_memory}. If given, @var{length}
21975 determines the number of bytes from @var{buffer} to be written.
21978 @findex gdb.search_memory
21979 @defmethod Inferior search_memory address length pattern
21980 Search a region of the inferior memory starting at @var{address} with
21981 the given @var{length} using the search pattern supplied in
21982 @var{pattern}. The @var{pattern} parameter must be a Python object
21983 which supports the buffer protocol, i.e., a string, an array or the
21984 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
21985 containing the address where the pattern was found, or @code{None} if
21986 the pattern could not be found.
21990 @node Events In Python
21991 @subsubsection Events In Python
21992 @cindex inferior events in Python
21994 @value{GDBN} provides a general event facility so that Python code can be
21995 notified of various state changes, particularly changes that occur in
21998 An @dfn{event} is just an object that describes some state change. The
21999 type of the object and its attributes will vary depending on the details
22000 of the change. All the existing events are described below.
22002 In order to be notified of an event, you must register an event handler
22003 with an @dfn{event registry}. An event registry is an object in the
22004 @code{gdb.events} module which dispatches particular events. A registry
22005 provides methods to register and unregister event handlers:
22008 @defmethod EventRegistry connect object
22009 Add the given callable @var{object} to the registry. This object will be
22010 called when an event corresponding to this registry occurs.
22013 @defmethod EventRegistry disconnect object
22014 Remove the given @var{object} from the registry. Once removed, the object
22015 will no longer receive notifications of events.
22019 Here is an example:
22022 def exit_handler (event):
22023 print "event type: exit"
22024 print "exit code: %d" % (event.exit_code)
22026 gdb.events.exited.connect (exit_handler)
22029 In the above example we connect our handler @code{exit_handler} to the
22030 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22031 called when the inferior exits. The argument @dfn{event} in this example is
22032 of type @code{gdb.ExitedEvent}. As you can see in the example the
22033 @code{ExitedEvent} object has an attribute which indicates the exit code of
22036 The following is a listing of the event registries that are available and
22037 details of the events they emit:
22042 Emits @code{gdb.ThreadEvent}.
22044 Some events can be thread specific when @value{GDBN} is running in non-stop
22045 mode. When represented in Python, these events all extend
22046 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22047 events which are emitted by this or other modules might extend this event.
22048 Examples of these events are @code{gdb.BreakpointEvent} and
22049 @code{gdb.ContinueEvent}.
22052 @defivar ThreadEvent inferior_thread
22053 In non-stop mode this attribute will be set to the specific thread which was
22054 involved in the emitted event. Otherwise, it will be set to @code{None}.
22058 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
22060 This event indicates that the inferior has been continued after a stop. For
22061 inherited attribute refer to @code{gdb.ThreadEvent} above.
22063 @item events.exited
22064 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
22065 @code{events.ExitedEvent} has one attribute:
22067 @defivar ExitedEvent exit_code
22068 An integer representing the exit code which the inferior has returned.
22073 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
22075 Indicates that the inferior has stopped. All events emitted by this registry
22076 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
22077 will indicate the stopped thread when @value{GDBN} is running in non-stop
22078 mode. Refer to @code{gdb.ThreadEvent} above for more details.
22080 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
22082 This event indicates that the inferior or one of its threads has received as
22083 signal. @code{gdb.SignalEvent} has the following attributes:
22086 @defivar SignalEvent stop_signal
22087 A string representing the signal received by the inferior. A list of possible
22088 signal values can be obtained by running the command @code{info signals} in
22089 the @value{GDBN} command prompt.
22093 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
22095 @code{gdb.BreakpointEvent} event indicates that a breakpoint has been hit, and
22096 has the following attributes:
22099 @defivar BreakpointEvent breakpoint
22100 A reference to the breakpoint that was hit of type @code{gdb.Breakpoint}.
22101 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
22107 @node Threads In Python
22108 @subsubsection Threads In Python
22109 @cindex threads in python
22111 @findex gdb.InferiorThread
22112 Python scripts can access information about, and manipulate inferior threads
22113 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
22115 The following thread-related functions are available in the @code{gdb}
22118 @findex gdb.selected_thread
22119 @defun selected_thread
22120 This function returns the thread object for the selected thread. If there
22121 is no selected thread, this will return @code{None}.
22124 A @code{gdb.InferiorThread} object has the following attributes:
22127 @defivar InferiorThread name
22128 The name of the thread. If the user specified a name using
22129 @code{thread name}, then this returns that name. Otherwise, if an
22130 OS-supplied name is available, then it is returned. Otherwise, this
22131 returns @code{None}.
22133 This attribute can be assigned to. The new value must be a string
22134 object, which sets the new name, or @code{None}, which removes any
22135 user-specified thread name.
22138 @defivar InferiorThread num
22139 ID of the thread, as assigned by GDB.
22142 @defivar InferiorThread ptid
22143 ID of the thread, as assigned by the operating system. This attribute is a
22144 tuple containing three integers. The first is the Process ID (PID); the second
22145 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
22146 Either the LWPID or TID may be 0, which indicates that the operating system
22147 does not use that identifier.
22151 A @code{gdb.InferiorThread} object has the following methods:
22154 @defmethod InferiorThread is_valid
22155 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
22156 @code{False} if not. A @code{gdb.InferiorThread} object will become
22157 invalid if the thread exits, or the inferior that the thread belongs
22158 is deleted. All other @code{gdb.InferiorThread} methods will throw an
22159 exception if it is invalid at the time the method is called.
22162 @defmethod InferiorThread switch
22163 This changes @value{GDBN}'s currently selected thread to the one represented
22167 @defmethod InferiorThread is_stopped
22168 Return a Boolean indicating whether the thread is stopped.
22171 @defmethod InferiorThread is_running
22172 Return a Boolean indicating whether the thread is running.
22175 @defmethod InferiorThread is_exited
22176 Return a Boolean indicating whether the thread is exited.
22180 @node Commands In Python
22181 @subsubsection Commands In Python
22183 @cindex commands in python
22184 @cindex python commands
22185 You can implement new @value{GDBN} CLI commands in Python. A CLI
22186 command is implemented using an instance of the @code{gdb.Command}
22187 class, most commonly using a subclass.
22189 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
22190 The object initializer for @code{Command} registers the new command
22191 with @value{GDBN}. This initializer is normally invoked from the
22192 subclass' own @code{__init__} method.
22194 @var{name} is the name of the command. If @var{name} consists of
22195 multiple words, then the initial words are looked for as prefix
22196 commands. In this case, if one of the prefix commands does not exist,
22197 an exception is raised.
22199 There is no support for multi-line commands.
22201 @var{command_class} should be one of the @samp{COMMAND_} constants
22202 defined below. This argument tells @value{GDBN} how to categorize the
22203 new command in the help system.
22205 @var{completer_class} is an optional argument. If given, it should be
22206 one of the @samp{COMPLETE_} constants defined below. This argument
22207 tells @value{GDBN} how to perform completion for this command. If not
22208 given, @value{GDBN} will attempt to complete using the object's
22209 @code{complete} method (see below); if no such method is found, an
22210 error will occur when completion is attempted.
22212 @var{prefix} is an optional argument. If @code{True}, then the new
22213 command is a prefix command; sub-commands of this command may be
22216 The help text for the new command is taken from the Python
22217 documentation string for the command's class, if there is one. If no
22218 documentation string is provided, the default value ``This command is
22219 not documented.'' is used.
22222 @cindex don't repeat Python command
22223 @defmethod Command dont_repeat
22224 By default, a @value{GDBN} command is repeated when the user enters a
22225 blank line at the command prompt. A command can suppress this
22226 behavior by invoking the @code{dont_repeat} method. This is similar
22227 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
22230 @defmethod Command invoke argument from_tty
22231 This method is called by @value{GDBN} when this command is invoked.
22233 @var{argument} is a string. It is the argument to the command, after
22234 leading and trailing whitespace has been stripped.
22236 @var{from_tty} is a boolean argument. When true, this means that the
22237 command was entered by the user at the terminal; when false it means
22238 that the command came from elsewhere.
22240 If this method throws an exception, it is turned into a @value{GDBN}
22241 @code{error} call. Otherwise, the return value is ignored.
22243 @findex gdb.string_to_argv
22244 To break @var{argument} up into an argv-like string use
22245 @code{gdb.string_to_argv}. This function behaves identically to
22246 @value{GDBN}'s internal argument lexer @code{buildargv}.
22247 It is recommended to use this for consistency.
22248 Arguments are separated by spaces and may be quoted.
22252 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
22253 ['1', '2 "3', '4 "5', "6 '7"]
22258 @cindex completion of Python commands
22259 @defmethod Command complete text word
22260 This method is called by @value{GDBN} when the user attempts
22261 completion on this command. All forms of completion are handled by
22262 this method, that is, the @key{TAB} and @key{M-?} key bindings
22263 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
22266 The arguments @var{text} and @var{word} are both strings. @var{text}
22267 holds the complete command line up to the cursor's location.
22268 @var{word} holds the last word of the command line; this is computed
22269 using a word-breaking heuristic.
22271 The @code{complete} method can return several values:
22274 If the return value is a sequence, the contents of the sequence are
22275 used as the completions. It is up to @code{complete} to ensure that the
22276 contents actually do complete the word. A zero-length sequence is
22277 allowed, it means that there were no completions available. Only
22278 string elements of the sequence are used; other elements in the
22279 sequence are ignored.
22282 If the return value is one of the @samp{COMPLETE_} constants defined
22283 below, then the corresponding @value{GDBN}-internal completion
22284 function is invoked, and its result is used.
22287 All other results are treated as though there were no available
22292 When a new command is registered, it must be declared as a member of
22293 some general class of commands. This is used to classify top-level
22294 commands in the on-line help system; note that prefix commands are not
22295 listed under their own category but rather that of their top-level
22296 command. The available classifications are represented by constants
22297 defined in the @code{gdb} module:
22300 @findex COMMAND_NONE
22301 @findex gdb.COMMAND_NONE
22303 The command does not belong to any particular class. A command in
22304 this category will not be displayed in any of the help categories.
22306 @findex COMMAND_RUNNING
22307 @findex gdb.COMMAND_RUNNING
22308 @item COMMAND_RUNNING
22309 The command is related to running the inferior. For example,
22310 @code{start}, @code{step}, and @code{continue} are in this category.
22311 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
22312 commands in this category.
22314 @findex COMMAND_DATA
22315 @findex gdb.COMMAND_DATA
22317 The command is related to data or variables. For example,
22318 @code{call}, @code{find}, and @code{print} are in this category. Type
22319 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
22322 @findex COMMAND_STACK
22323 @findex gdb.COMMAND_STACK
22324 @item COMMAND_STACK
22325 The command has to do with manipulation of the stack. For example,
22326 @code{backtrace}, @code{frame}, and @code{return} are in this
22327 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
22328 list of commands in this category.
22330 @findex COMMAND_FILES
22331 @findex gdb.COMMAND_FILES
22332 @item COMMAND_FILES
22333 This class is used for file-related commands. For example,
22334 @code{file}, @code{list} and @code{section} are in this category.
22335 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
22336 commands in this category.
22338 @findex COMMAND_SUPPORT
22339 @findex gdb.COMMAND_SUPPORT
22340 @item COMMAND_SUPPORT
22341 This should be used for ``support facilities'', generally meaning
22342 things that are useful to the user when interacting with @value{GDBN},
22343 but not related to the state of the inferior. For example,
22344 @code{help}, @code{make}, and @code{shell} are in this category. Type
22345 @kbd{help support} at the @value{GDBN} prompt to see a list of
22346 commands in this category.
22348 @findex COMMAND_STATUS
22349 @findex gdb.COMMAND_STATUS
22350 @item COMMAND_STATUS
22351 The command is an @samp{info}-related command, that is, related to the
22352 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
22353 and @code{show} are in this category. Type @kbd{help status} at the
22354 @value{GDBN} prompt to see a list of commands in this category.
22356 @findex COMMAND_BREAKPOINTS
22357 @findex gdb.COMMAND_BREAKPOINTS
22358 @item COMMAND_BREAKPOINTS
22359 The command has to do with breakpoints. For example, @code{break},
22360 @code{clear}, and @code{delete} are in this category. Type @kbd{help
22361 breakpoints} at the @value{GDBN} prompt to see a list of commands in
22364 @findex COMMAND_TRACEPOINTS
22365 @findex gdb.COMMAND_TRACEPOINTS
22366 @item COMMAND_TRACEPOINTS
22367 The command has to do with tracepoints. For example, @code{trace},
22368 @code{actions}, and @code{tfind} are in this category. Type
22369 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
22370 commands in this category.
22372 @findex COMMAND_OBSCURE
22373 @findex gdb.COMMAND_OBSCURE
22374 @item COMMAND_OBSCURE
22375 The command is only used in unusual circumstances, or is not of
22376 general interest to users. For example, @code{checkpoint},
22377 @code{fork}, and @code{stop} are in this category. Type @kbd{help
22378 obscure} at the @value{GDBN} prompt to see a list of commands in this
22381 @findex COMMAND_MAINTENANCE
22382 @findex gdb.COMMAND_MAINTENANCE
22383 @item COMMAND_MAINTENANCE
22384 The command is only useful to @value{GDBN} maintainers. The
22385 @code{maintenance} and @code{flushregs} commands are in this category.
22386 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
22387 commands in this category.
22390 A new command can use a predefined completion function, either by
22391 specifying it via an argument at initialization, or by returning it
22392 from the @code{complete} method. These predefined completion
22393 constants are all defined in the @code{gdb} module:
22396 @findex COMPLETE_NONE
22397 @findex gdb.COMPLETE_NONE
22398 @item COMPLETE_NONE
22399 This constant means that no completion should be done.
22401 @findex COMPLETE_FILENAME
22402 @findex gdb.COMPLETE_FILENAME
22403 @item COMPLETE_FILENAME
22404 This constant means that filename completion should be performed.
22406 @findex COMPLETE_LOCATION
22407 @findex gdb.COMPLETE_LOCATION
22408 @item COMPLETE_LOCATION
22409 This constant means that location completion should be done.
22410 @xref{Specify Location}.
22412 @findex COMPLETE_COMMAND
22413 @findex gdb.COMPLETE_COMMAND
22414 @item COMPLETE_COMMAND
22415 This constant means that completion should examine @value{GDBN}
22418 @findex COMPLETE_SYMBOL
22419 @findex gdb.COMPLETE_SYMBOL
22420 @item COMPLETE_SYMBOL
22421 This constant means that completion should be done using symbol names
22425 The following code snippet shows how a trivial CLI command can be
22426 implemented in Python:
22429 class HelloWorld (gdb.Command):
22430 """Greet the whole world."""
22432 def __init__ (self):
22433 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
22435 def invoke (self, arg, from_tty):
22436 print "Hello, World!"
22441 The last line instantiates the class, and is necessary to trigger the
22442 registration of the command with @value{GDBN}. Depending on how the
22443 Python code is read into @value{GDBN}, you may need to import the
22444 @code{gdb} module explicitly.
22446 @node Parameters In Python
22447 @subsubsection Parameters In Python
22449 @cindex parameters in python
22450 @cindex python parameters
22451 @tindex gdb.Parameter
22453 You can implement new @value{GDBN} parameters using Python. A new
22454 parameter is implemented as an instance of the @code{gdb.Parameter}
22457 Parameters are exposed to the user via the @code{set} and
22458 @code{show} commands. @xref{Help}.
22460 There are many parameters that already exist and can be set in
22461 @value{GDBN}. Two examples are: @code{set follow fork} and
22462 @code{set charset}. Setting these parameters influences certain
22463 behavior in @value{GDBN}. Similarly, you can define parameters that
22464 can be used to influence behavior in custom Python scripts and commands.
22466 @defmethod Parameter __init__ name @var{command-class} @var{parameter-class} @r{[}@var{enum-sequence}@r{]}
22467 The object initializer for @code{Parameter} registers the new
22468 parameter with @value{GDBN}. This initializer is normally invoked
22469 from the subclass' own @code{__init__} method.
22471 @var{name} is the name of the new parameter. If @var{name} consists
22472 of multiple words, then the initial words are looked for as prefix
22473 parameters. An example of this can be illustrated with the
22474 @code{set print} set of parameters. If @var{name} is
22475 @code{print foo}, then @code{print} will be searched as the prefix
22476 parameter. In this case the parameter can subsequently be accessed in
22477 @value{GDBN} as @code{set print foo}.
22479 If @var{name} consists of multiple words, and no prefix parameter group
22480 can be found, an exception is raised.
22482 @var{command-class} should be one of the @samp{COMMAND_} constants
22483 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
22484 categorize the new parameter in the help system.
22486 @var{parameter-class} should be one of the @samp{PARAM_} constants
22487 defined below. This argument tells @value{GDBN} the type of the new
22488 parameter; this information is used for input validation and
22491 If @var{parameter-class} is @code{PARAM_ENUM}, then
22492 @var{enum-sequence} must be a sequence of strings. These strings
22493 represent the possible values for the parameter.
22495 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
22496 of a fourth argument will cause an exception to be thrown.
22498 The help text for the new parameter is taken from the Python
22499 documentation string for the parameter's class, if there is one. If
22500 there is no documentation string, a default value is used.
22503 @defivar Parameter set_doc
22504 If this attribute exists, and is a string, then its value is used as
22505 the help text for this parameter's @code{set} command. The value is
22506 examined when @code{Parameter.__init__} is invoked; subsequent changes
22510 @defivar Parameter show_doc
22511 If this attribute exists, and is a string, then its value is used as
22512 the help text for this parameter's @code{show} command. The value is
22513 examined when @code{Parameter.__init__} is invoked; subsequent changes
22517 @defivar Parameter value
22518 The @code{value} attribute holds the underlying value of the
22519 parameter. It can be read and assigned to just as any other
22520 attribute. @value{GDBN} does validation when assignments are made.
22523 There are two methods that should be implemented in any
22524 @code{Parameter} class. These are:
22526 @defop Operation {parameter} get_set_string self
22527 @value{GDBN} will call this method when a @var{parameter}'s value has
22528 been changed via the @code{set} API (for example, @kbd{set foo off}).
22529 The @code{value} attribute has already been populated with the new
22530 value and may be used in output. This method must return a string.
22533 @defop Operation {parameter} get_show_string self svalue
22534 @value{GDBN} will call this method when a @var{parameter}'s
22535 @code{show} API has been invoked (for example, @kbd{show foo}). The
22536 argument @code{svalue} receives the string representation of the
22537 current value. This method must return a string.
22540 When a new parameter is defined, its type must be specified. The
22541 available types are represented by constants defined in the @code{gdb}
22545 @findex PARAM_BOOLEAN
22546 @findex gdb.PARAM_BOOLEAN
22547 @item PARAM_BOOLEAN
22548 The value is a plain boolean. The Python boolean values, @code{True}
22549 and @code{False} are the only valid values.
22551 @findex PARAM_AUTO_BOOLEAN
22552 @findex gdb.PARAM_AUTO_BOOLEAN
22553 @item PARAM_AUTO_BOOLEAN
22554 The value has three possible states: true, false, and @samp{auto}. In
22555 Python, true and false are represented using boolean constants, and
22556 @samp{auto} is represented using @code{None}.
22558 @findex PARAM_UINTEGER
22559 @findex gdb.PARAM_UINTEGER
22560 @item PARAM_UINTEGER
22561 The value is an unsigned integer. The value of 0 should be
22562 interpreted to mean ``unlimited''.
22564 @findex PARAM_INTEGER
22565 @findex gdb.PARAM_INTEGER
22566 @item PARAM_INTEGER
22567 The value is a signed integer. The value of 0 should be interpreted
22568 to mean ``unlimited''.
22570 @findex PARAM_STRING
22571 @findex gdb.PARAM_STRING
22573 The value is a string. When the user modifies the string, any escape
22574 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
22575 translated into corresponding characters and encoded into the current
22578 @findex PARAM_STRING_NOESCAPE
22579 @findex gdb.PARAM_STRING_NOESCAPE
22580 @item PARAM_STRING_NOESCAPE
22581 The value is a string. When the user modifies the string, escapes are
22582 passed through untranslated.
22584 @findex PARAM_OPTIONAL_FILENAME
22585 @findex gdb.PARAM_OPTIONAL_FILENAME
22586 @item PARAM_OPTIONAL_FILENAME
22587 The value is a either a filename (a string), or @code{None}.
22589 @findex PARAM_FILENAME
22590 @findex gdb.PARAM_FILENAME
22591 @item PARAM_FILENAME
22592 The value is a filename. This is just like
22593 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
22595 @findex PARAM_ZINTEGER
22596 @findex gdb.PARAM_ZINTEGER
22597 @item PARAM_ZINTEGER
22598 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
22599 is interpreted as itself.
22602 @findex gdb.PARAM_ENUM
22604 The value is a string, which must be one of a collection string
22605 constants provided when the parameter is created.
22608 @node Functions In Python
22609 @subsubsection Writing new convenience functions
22611 @cindex writing convenience functions
22612 @cindex convenience functions in python
22613 @cindex python convenience functions
22614 @tindex gdb.Function
22616 You can implement new convenience functions (@pxref{Convenience Vars})
22617 in Python. A convenience function is an instance of a subclass of the
22618 class @code{gdb.Function}.
22620 @defmethod Function __init__ name
22621 The initializer for @code{Function} registers the new function with
22622 @value{GDBN}. The argument @var{name} is the name of the function,
22623 a string. The function will be visible to the user as a convenience
22624 variable of type @code{internal function}, whose name is the same as
22625 the given @var{name}.
22627 The documentation for the new function is taken from the documentation
22628 string for the new class.
22631 @defmethod Function invoke @var{*args}
22632 When a convenience function is evaluated, its arguments are converted
22633 to instances of @code{gdb.Value}, and then the function's
22634 @code{invoke} method is called. Note that @value{GDBN} does not
22635 predetermine the arity of convenience functions. Instead, all
22636 available arguments are passed to @code{invoke}, following the
22637 standard Python calling convention. In particular, a convenience
22638 function can have default values for parameters without ill effect.
22640 The return value of this method is used as its value in the enclosing
22641 expression. If an ordinary Python value is returned, it is converted
22642 to a @code{gdb.Value} following the usual rules.
22645 The following code snippet shows how a trivial convenience function can
22646 be implemented in Python:
22649 class Greet (gdb.Function):
22650 """Return string to greet someone.
22651 Takes a name as argument."""
22653 def __init__ (self):
22654 super (Greet, self).__init__ ("greet")
22656 def invoke (self, name):
22657 return "Hello, %s!" % name.string ()
22662 The last line instantiates the class, and is necessary to trigger the
22663 registration of the function with @value{GDBN}. Depending on how the
22664 Python code is read into @value{GDBN}, you may need to import the
22665 @code{gdb} module explicitly.
22667 @node Progspaces In Python
22668 @subsubsection Program Spaces In Python
22670 @cindex progspaces in python
22671 @tindex gdb.Progspace
22673 A program space, or @dfn{progspace}, represents a symbolic view
22674 of an address space.
22675 It consists of all of the objfiles of the program.
22676 @xref{Objfiles In Python}.
22677 @xref{Inferiors and Programs, program spaces}, for more details
22678 about program spaces.
22680 The following progspace-related functions are available in the
22683 @findex gdb.current_progspace
22684 @defun current_progspace
22685 This function returns the program space of the currently selected inferior.
22686 @xref{Inferiors and Programs}.
22689 @findex gdb.progspaces
22691 Return a sequence of all the progspaces currently known to @value{GDBN}.
22694 Each progspace is represented by an instance of the @code{gdb.Progspace}
22697 @defivar Progspace filename
22698 The file name of the progspace as a string.
22701 @defivar Progspace pretty_printers
22702 The @code{pretty_printers} attribute is a list of functions. It is
22703 used to look up pretty-printers. A @code{Value} is passed to each
22704 function in order; if the function returns @code{None}, then the
22705 search continues. Otherwise, the return value should be an object
22706 which is used to format the value. @xref{Pretty Printing API}, for more
22710 @node Objfiles In Python
22711 @subsubsection Objfiles In Python
22713 @cindex objfiles in python
22714 @tindex gdb.Objfile
22716 @value{GDBN} loads symbols for an inferior from various
22717 symbol-containing files (@pxref{Files}). These include the primary
22718 executable file, any shared libraries used by the inferior, and any
22719 separate debug info files (@pxref{Separate Debug Files}).
22720 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
22722 The following objfile-related functions are available in the
22725 @findex gdb.current_objfile
22726 @defun current_objfile
22727 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
22728 sets the ``current objfile'' to the corresponding objfile. This
22729 function returns the current objfile. If there is no current objfile,
22730 this function returns @code{None}.
22733 @findex gdb.objfiles
22735 Return a sequence of all the objfiles current known to @value{GDBN}.
22736 @xref{Objfiles In Python}.
22739 Each objfile is represented by an instance of the @code{gdb.Objfile}
22742 @defivar Objfile filename
22743 The file name of the objfile as a string.
22746 @defivar Objfile pretty_printers
22747 The @code{pretty_printers} attribute is a list of functions. It is
22748 used to look up pretty-printers. A @code{Value} is passed to each
22749 function in order; if the function returns @code{None}, then the
22750 search continues. Otherwise, the return value should be an object
22751 which is used to format the value. @xref{Pretty Printing API}, for more
22755 A @code{gdb.Objfile} object has the following methods:
22757 @defmethod Objfile is_valid
22758 Returns @code{True} if the @code{gdb.Objfile} object is valid,
22759 @code{False} if not. A @code{gdb.Objfile} object can become invalid
22760 if the object file it refers to is not loaded in @value{GDBN} any
22761 longer. All other @code{gdb.Objfile} methods will throw an exception
22762 if it is invalid at the time the method is called.
22765 @node Frames In Python
22766 @subsubsection Accessing inferior stack frames from Python.
22768 @cindex frames in python
22769 When the debugged program stops, @value{GDBN} is able to analyze its call
22770 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
22771 represents a frame in the stack. A @code{gdb.Frame} object is only valid
22772 while its corresponding frame exists in the inferior's stack. If you try
22773 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
22774 exception (@pxref{Exception Handling}).
22776 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
22780 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
22784 The following frame-related functions are available in the @code{gdb} module:
22786 @findex gdb.selected_frame
22787 @defun selected_frame
22788 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
22791 @findex gdb.newest_frame
22792 @defun newest_frame
22793 Return the newest frame object for the selected thread.
22796 @defun frame_stop_reason_string reason
22797 Return a string explaining the reason why @value{GDBN} stopped unwinding
22798 frames, as expressed by the given @var{reason} code (an integer, see the
22799 @code{unwind_stop_reason} method further down in this section).
22802 A @code{gdb.Frame} object has the following methods:
22805 @defmethod Frame is_valid
22806 Returns true if the @code{gdb.Frame} object is valid, false if not.
22807 A frame object can become invalid if the frame it refers to doesn't
22808 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
22809 an exception if it is invalid at the time the method is called.
22812 @defmethod Frame name
22813 Returns the function name of the frame, or @code{None} if it can't be
22817 @defmethod Frame type
22818 Returns the type of the frame. The value can be one of:
22820 @item gdb.NORMAL_FRAME
22821 An ordinary stack frame.
22823 @item gdb.DUMMY_FRAME
22824 A fake stack frame that was created by @value{GDBN} when performing an
22825 inferior function call.
22827 @item gdb.INLINE_FRAME
22828 A frame representing an inlined function. The function was inlined
22829 into a @code{gdb.NORMAL_FRAME} that is older than this one.
22831 @item gdb.SIGTRAMP_FRAME
22832 A signal trampoline frame. This is the frame created by the OS when
22833 it calls into a signal handler.
22835 @item gdb.ARCH_FRAME
22836 A fake stack frame representing a cross-architecture call.
22838 @item gdb.SENTINEL_FRAME
22839 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
22844 @defmethod Frame unwind_stop_reason
22845 Return an integer representing the reason why it's not possible to find
22846 more frames toward the outermost frame. Use
22847 @code{gdb.frame_stop_reason_string} to convert the value returned by this
22848 function to a string.
22851 @defmethod Frame pc
22852 Returns the frame's resume address.
22855 @defmethod Frame block
22856 Return the frame's code block. @xref{Blocks In Python}.
22859 @defmethod Frame function
22860 Return the symbol for the function corresponding to this frame.
22861 @xref{Symbols In Python}.
22864 @defmethod Frame older
22865 Return the frame that called this frame.
22868 @defmethod Frame newer
22869 Return the frame called by this frame.
22872 @defmethod Frame find_sal
22873 Return the frame's symtab and line object.
22874 @xref{Symbol Tables In Python}.
22877 @defmethod Frame read_var variable @r{[}block@r{]}
22878 Return the value of @var{variable} in this frame. If the optional
22879 argument @var{block} is provided, search for the variable from that
22880 block; otherwise start at the frame's current block (which is
22881 determined by the frame's current program counter). @var{variable}
22882 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
22883 @code{gdb.Block} object.
22886 @defmethod Frame select
22887 Set this frame to be the selected frame. @xref{Stack, ,Examining the
22892 @node Blocks In Python
22893 @subsubsection Accessing frame blocks from Python.
22895 @cindex blocks in python
22898 Within each frame, @value{GDBN} maintains information on each block
22899 stored in that frame. These blocks are organized hierarchically, and
22900 are represented individually in Python as a @code{gdb.Block}.
22901 Please see @ref{Frames In Python}, for a more in-depth discussion on
22902 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
22903 detailed technical information on @value{GDBN}'s book-keeping of the
22906 The following block-related functions are available in the @code{gdb}
22909 @findex gdb.block_for_pc
22910 @defun block_for_pc pc
22911 Return the @code{gdb.Block} containing the given @var{pc} value. If the
22912 block cannot be found for the @var{pc} value specified, the function
22913 will return @code{None}.
22916 A @code{gdb.Block} object has the following methods:
22919 @defmethod Block is_valid
22920 Returns @code{True} if the @code{gdb.Block} object is valid,
22921 @code{False} if not. A block object can become invalid if the block it
22922 refers to doesn't exist anymore in the inferior. All other
22923 @code{gdb.Block} methods will throw an exception if it is invalid at
22924 the time the method is called. This method is also made available to
22925 the Python iterator object that @code{gdb.Block} provides in an iteration
22926 context and via the Python @code{iter} built-in function.
22930 A @code{gdb.Block} object has the following attributes:
22933 @defivar Block start
22934 The start address of the block. This attribute is not writable.
22938 The end address of the block. This attribute is not writable.
22941 @defivar Block function
22942 The name of the block represented as a @code{gdb.Symbol}. If the
22943 block is not named, then this attribute holds @code{None}. This
22944 attribute is not writable.
22947 @defivar Block superblock
22948 The block containing this block. If this parent block does not exist,
22949 this attribute holds @code{None}. This attribute is not writable.
22953 @node Symbols In Python
22954 @subsubsection Python representation of Symbols.
22956 @cindex symbols in python
22959 @value{GDBN} represents every variable, function and type as an
22960 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
22961 Similarly, Python represents these symbols in @value{GDBN} with the
22962 @code{gdb.Symbol} object.
22964 The following symbol-related functions are available in the @code{gdb}
22967 @findex gdb.lookup_symbol
22968 @defun lookup_symbol name @r{[}block@r{]} @r{[}domain@r{]}
22969 This function searches for a symbol by name. The search scope can be
22970 restricted to the parameters defined in the optional domain and block
22973 @var{name} is the name of the symbol. It must be a string. The
22974 optional @var{block} argument restricts the search to symbols visible
22975 in that @var{block}. The @var{block} argument must be a
22976 @code{gdb.Block} object. If omitted, the block for the current frame
22977 is used. The optional @var{domain} argument restricts
22978 the search to the domain type. The @var{domain} argument must be a
22979 domain constant defined in the @code{gdb} module and described later
22982 The result is a tuple of two elements.
22983 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
22985 If the symbol is found, the second element is @code{True} if the symbol
22986 is a field of a method's object (e.g., @code{this} in C@t{++}),
22987 otherwise it is @code{False}.
22988 If the symbol is not found, the second element is @code{False}.
22991 @findex gdb.lookup_global_symbol
22992 @defun lookup_global_symbol name @r{[}domain@r{]}
22993 This function searches for a global symbol by name.
22994 The search scope can be restricted to by the domain argument.
22996 @var{name} is the name of the symbol. It must be a string.
22997 The optional @var{domain} argument restricts the search to the domain type.
22998 The @var{domain} argument must be a domain constant defined in the @code{gdb}
22999 module and described later in this chapter.
23001 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
23005 A @code{gdb.Symbol} object has the following attributes:
23008 @defivar Symbol symtab
23009 The symbol table in which the symbol appears. This attribute is
23010 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
23011 Python}. This attribute is not writable.
23014 @defivar Symbol name
23015 The name of the symbol as a string. This attribute is not writable.
23018 @defivar Symbol linkage_name
23019 The name of the symbol, as used by the linker (i.e., may be mangled).
23020 This attribute is not writable.
23023 @defivar Symbol print_name
23024 The name of the symbol in a form suitable for output. This is either
23025 @code{name} or @code{linkage_name}, depending on whether the user
23026 asked @value{GDBN} to display demangled or mangled names.
23029 @defivar Symbol addr_class
23030 The address class of the symbol. This classifies how to find the value
23031 of a symbol. Each address class is a constant defined in the
23032 @code{gdb} module and described later in this chapter.
23035 @defivar Symbol is_argument
23036 @code{True} if the symbol is an argument of a function.
23039 @defivar Symbol is_constant
23040 @code{True} if the symbol is a constant.
23043 @defivar Symbol is_function
23044 @code{True} if the symbol is a function or a method.
23047 @defivar Symbol is_variable
23048 @code{True} if the symbol is a variable.
23052 A @code{gdb.Symbol} object has the following methods:
23055 @defmethod Symbol is_valid
23056 Returns @code{True} if the @code{gdb.Symbol} object is valid,
23057 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
23058 the symbol it refers to does not exist in @value{GDBN} any longer.
23059 All other @code{gdb.Symbol} methods will throw an exception if it is
23060 invalid at the time the method is called.
23064 The available domain categories in @code{gdb.Symbol} are represented
23065 as constants in the @code{gdb} module:
23068 @findex SYMBOL_UNDEF_DOMAIN
23069 @findex gdb.SYMBOL_UNDEF_DOMAIN
23070 @item SYMBOL_UNDEF_DOMAIN
23071 This is used when a domain has not been discovered or none of the
23072 following domains apply. This usually indicates an error either
23073 in the symbol information or in @value{GDBN}'s handling of symbols.
23074 @findex SYMBOL_VAR_DOMAIN
23075 @findex gdb.SYMBOL_VAR_DOMAIN
23076 @item SYMBOL_VAR_DOMAIN
23077 This domain contains variables, function names, typedef names and enum
23079 @findex SYMBOL_STRUCT_DOMAIN
23080 @findex gdb.SYMBOL_STRUCT_DOMAIN
23081 @item SYMBOL_STRUCT_DOMAIN
23082 This domain holds struct, union and enum type names.
23083 @findex SYMBOL_LABEL_DOMAIN
23084 @findex gdb.SYMBOL_LABEL_DOMAIN
23085 @item SYMBOL_LABEL_DOMAIN
23086 This domain contains names of labels (for gotos).
23087 @findex SYMBOL_VARIABLES_DOMAIN
23088 @findex gdb.SYMBOL_VARIABLES_DOMAIN
23089 @item SYMBOL_VARIABLES_DOMAIN
23090 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
23091 contains everything minus functions and types.
23092 @findex SYMBOL_FUNCTIONS_DOMAIN
23093 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
23094 @item SYMBOL_FUNCTION_DOMAIN
23095 This domain contains all functions.
23096 @findex SYMBOL_TYPES_DOMAIN
23097 @findex gdb.SYMBOL_TYPES_DOMAIN
23098 @item SYMBOL_TYPES_DOMAIN
23099 This domain contains all types.
23102 The available address class categories in @code{gdb.Symbol} are represented
23103 as constants in the @code{gdb} module:
23106 @findex SYMBOL_LOC_UNDEF
23107 @findex gdb.SYMBOL_LOC_UNDEF
23108 @item SYMBOL_LOC_UNDEF
23109 If this is returned by address class, it indicates an error either in
23110 the symbol information or in @value{GDBN}'s handling of symbols.
23111 @findex SYMBOL_LOC_CONST
23112 @findex gdb.SYMBOL_LOC_CONST
23113 @item SYMBOL_LOC_CONST
23114 Value is constant int.
23115 @findex SYMBOL_LOC_STATIC
23116 @findex gdb.SYMBOL_LOC_STATIC
23117 @item SYMBOL_LOC_STATIC
23118 Value is at a fixed address.
23119 @findex SYMBOL_LOC_REGISTER
23120 @findex gdb.SYMBOL_LOC_REGISTER
23121 @item SYMBOL_LOC_REGISTER
23122 Value is in a register.
23123 @findex SYMBOL_LOC_ARG
23124 @findex gdb.SYMBOL_LOC_ARG
23125 @item SYMBOL_LOC_ARG
23126 Value is an argument. This value is at the offset stored within the
23127 symbol inside the frame's argument list.
23128 @findex SYMBOL_LOC_REF_ARG
23129 @findex gdb.SYMBOL_LOC_REF_ARG
23130 @item SYMBOL_LOC_REF_ARG
23131 Value address is stored in the frame's argument list. Just like
23132 @code{LOC_ARG} except that the value's address is stored at the
23133 offset, not the value itself.
23134 @findex SYMBOL_LOC_REGPARM_ADDR
23135 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
23136 @item SYMBOL_LOC_REGPARM_ADDR
23137 Value is a specified register. Just like @code{LOC_REGISTER} except
23138 the register holds the address of the argument instead of the argument
23140 @findex SYMBOL_LOC_LOCAL
23141 @findex gdb.SYMBOL_LOC_LOCAL
23142 @item SYMBOL_LOC_LOCAL
23143 Value is a local variable.
23144 @findex SYMBOL_LOC_TYPEDEF
23145 @findex gdb.SYMBOL_LOC_TYPEDEF
23146 @item SYMBOL_LOC_TYPEDEF
23147 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
23149 @findex SYMBOL_LOC_BLOCK
23150 @findex gdb.SYMBOL_LOC_BLOCK
23151 @item SYMBOL_LOC_BLOCK
23153 @findex SYMBOL_LOC_CONST_BYTES
23154 @findex gdb.SYMBOL_LOC_CONST_BYTES
23155 @item SYMBOL_LOC_CONST_BYTES
23156 Value is a byte-sequence.
23157 @findex SYMBOL_LOC_UNRESOLVED
23158 @findex gdb.SYMBOL_LOC_UNRESOLVED
23159 @item SYMBOL_LOC_UNRESOLVED
23160 Value is at a fixed address, but the address of the variable has to be
23161 determined from the minimal symbol table whenever the variable is
23163 @findex SYMBOL_LOC_OPTIMIZED_OUT
23164 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
23165 @item SYMBOL_LOC_OPTIMIZED_OUT
23166 The value does not actually exist in the program.
23167 @findex SYMBOL_LOC_COMPUTED
23168 @findex gdb.SYMBOL_LOC_COMPUTED
23169 @item SYMBOL_LOC_COMPUTED
23170 The value's address is a computed location.
23173 @node Symbol Tables In Python
23174 @subsubsection Symbol table representation in Python.
23176 @cindex symbol tables in python
23178 @tindex gdb.Symtab_and_line
23180 Access to symbol table data maintained by @value{GDBN} on the inferior
23181 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
23182 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
23183 from the @code{find_sal} method in @code{gdb.Frame} object.
23184 @xref{Frames In Python}.
23186 For more information on @value{GDBN}'s symbol table management, see
23187 @ref{Symbols, ,Examining the Symbol Table}, for more information.
23189 A @code{gdb.Symtab_and_line} object has the following attributes:
23192 @defivar Symtab_and_line symtab
23193 The symbol table object (@code{gdb.Symtab}) for this frame.
23194 This attribute is not writable.
23197 @defivar Symtab_and_line pc
23198 Indicates the current program counter address. This attribute is not
23202 @defivar Symtab_and_line line
23203 Indicates the current line number for this object. This
23204 attribute is not writable.
23208 A @code{gdb.Symtab_and_line} object has the following methods:
23211 @defmethod Symtab_and_line is_valid
23212 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
23213 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
23214 invalid if the Symbol table and line object it refers to does not
23215 exist in @value{GDBN} any longer. All other
23216 @code{gdb.Symtab_and_line} methods will throw an exception if it is
23217 invalid at the time the method is called.
23221 A @code{gdb.Symtab} object has the following attributes:
23224 @defivar Symtab filename
23225 The symbol table's source filename. This attribute is not writable.
23228 @defivar Symtab objfile
23229 The symbol table's backing object file. @xref{Objfiles In Python}.
23230 This attribute is not writable.
23234 A @code{gdb.Symtab} object has the following methods:
23237 @defmethod Symtab is_valid
23238 Returns @code{True} if the @code{gdb.Symtab} object is valid,
23239 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
23240 the symbol table it refers to does not exist in @value{GDBN} any
23241 longer. All other @code{gdb.Symtab} methods will throw an exception
23242 if it is invalid at the time the method is called.
23245 @defmethod Symtab fullname
23246 Return the symbol table's source absolute file name.
23250 @node Breakpoints In Python
23251 @subsubsection Manipulating breakpoints using Python
23253 @cindex breakpoints in python
23254 @tindex gdb.Breakpoint
23256 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
23259 @defmethod Breakpoint __init__ spec @r{[}type@r{]} @r{[}wp_class@r{]} @r{[}internal@r{]}
23260 Create a new breakpoint. @var{spec} is a string naming the
23261 location of the breakpoint, or an expression that defines a
23262 watchpoint. The contents can be any location recognized by the
23263 @code{break} command, or in the case of a watchpoint, by the @code{watch}
23264 command. The optional @var{type} denotes the breakpoint to create
23265 from the types defined later in this chapter. This argument can be
23266 either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}. @var{type}
23267 defaults to @code{BP_BREAKPOINT}. The optional @var{internal} argument
23268 allows the breakpoint to become invisible to the user. The breakpoint
23269 will neither be reported when created, nor will it be listed in the
23270 output from @code{info breakpoints} (but will be listed with the
23271 @code{maint info breakpoints} command). The optional @var{wp_class}
23272 argument defines the class of watchpoint to create, if @var{type} is
23273 @code{BP_WATCHPOINT}. If a watchpoint class is not provided, it is
23274 assumed to be a @var{WP_WRITE} class.
23277 @defop Operation {gdb.Breakpoint} stop (self)
23278 The @code{gdb.Breakpoint} class can be sub-classed and, in
23279 particular, you may choose to implement the @code{stop} method.
23280 If this method is defined as a sub-class of @code{gdb.Breakpoint},
23281 it will be called when the inferior reaches any location of a
23282 breakpoint which instantiates that sub-class. If the method returns
23283 @code{True}, the inferior will be stopped at the location of the
23284 breakpoint, otherwise the inferior will continue.
23286 If there are multiple breakpoints at the same location with a
23287 @code{stop} method, each one will be called regardless of the
23288 return status of the previous. This ensures that all @code{stop}
23289 methods have a chance to execute at that location. In this scenario
23290 if one of the methods returns @code{True} but the others return
23291 @code{False}, the inferior will still be stopped.
23293 Example @code{stop} implementation:
23296 class MyBreakpoint (gdb.Breakpoint):
23298 inf_val = gdb.parse_and_eval("foo")
23305 The available watchpoint types represented by constants are defined in the
23310 @findex gdb.WP_READ
23312 Read only watchpoint.
23315 @findex gdb.WP_WRITE
23317 Write only watchpoint.
23320 @findex gdb.WP_ACCESS
23322 Read/Write watchpoint.
23325 @defmethod Breakpoint is_valid
23326 Return @code{True} if this @code{Breakpoint} object is valid,
23327 @code{False} otherwise. A @code{Breakpoint} object can become invalid
23328 if the user deletes the breakpoint. In this case, the object still
23329 exists, but the underlying breakpoint does not. In the cases of
23330 watchpoint scope, the watchpoint remains valid even if execution of the
23331 inferior leaves the scope of that watchpoint.
23334 @defmethod Breakpoint delete
23335 Permanently deletes the @value{GDBN} breakpoint. This also
23336 invalidates the Python @code{Breakpoint} object. Any further access
23337 to this object's attributes or methods will raise an error.
23340 @defivar Breakpoint enabled
23341 This attribute is @code{True} if the breakpoint is enabled, and
23342 @code{False} otherwise. This attribute is writable.
23345 @defivar Breakpoint silent
23346 This attribute is @code{True} if the breakpoint is silent, and
23347 @code{False} otherwise. This attribute is writable.
23349 Note that a breakpoint can also be silent if it has commands and the
23350 first command is @code{silent}. This is not reported by the
23351 @code{silent} attribute.
23354 @defivar Breakpoint thread
23355 If the breakpoint is thread-specific, this attribute holds the thread
23356 id. If the breakpoint is not thread-specific, this attribute is
23357 @code{None}. This attribute is writable.
23360 @defivar Breakpoint task
23361 If the breakpoint is Ada task-specific, this attribute holds the Ada task
23362 id. If the breakpoint is not task-specific (or the underlying
23363 language is not Ada), this attribute is @code{None}. This attribute
23367 @defivar Breakpoint ignore_count
23368 This attribute holds the ignore count for the breakpoint, an integer.
23369 This attribute is writable.
23372 @defivar Breakpoint number
23373 This attribute holds the breakpoint's number --- the identifier used by
23374 the user to manipulate the breakpoint. This attribute is not writable.
23377 @defivar Breakpoint type
23378 This attribute holds the breakpoint's type --- the identifier used to
23379 determine the actual breakpoint type or use-case. This attribute is not
23383 @defivar Breakpoint visible
23384 This attribute tells whether the breakpoint is visible to the user
23385 when set, or when the @samp{info breakpoints} command is run. This
23386 attribute is not writable.
23389 The available types are represented by constants defined in the @code{gdb}
23393 @findex BP_BREAKPOINT
23394 @findex gdb.BP_BREAKPOINT
23395 @item BP_BREAKPOINT
23396 Normal code breakpoint.
23398 @findex BP_WATCHPOINT
23399 @findex gdb.BP_WATCHPOINT
23400 @item BP_WATCHPOINT
23401 Watchpoint breakpoint.
23403 @findex BP_HARDWARE_WATCHPOINT
23404 @findex gdb.BP_HARDWARE_WATCHPOINT
23405 @item BP_HARDWARE_WATCHPOINT
23406 Hardware assisted watchpoint.
23408 @findex BP_READ_WATCHPOINT
23409 @findex gdb.BP_READ_WATCHPOINT
23410 @item BP_READ_WATCHPOINT
23411 Hardware assisted read watchpoint.
23413 @findex BP_ACCESS_WATCHPOINT
23414 @findex gdb.BP_ACCESS_WATCHPOINT
23415 @item BP_ACCESS_WATCHPOINT
23416 Hardware assisted access watchpoint.
23419 @defivar Breakpoint hit_count
23420 This attribute holds the hit count for the breakpoint, an integer.
23421 This attribute is writable, but currently it can only be set to zero.
23424 @defivar Breakpoint location
23425 This attribute holds the location of the breakpoint, as specified by
23426 the user. It is a string. If the breakpoint does not have a location
23427 (that is, it is a watchpoint) the attribute's value is @code{None}. This
23428 attribute is not writable.
23431 @defivar Breakpoint expression
23432 This attribute holds a breakpoint expression, as specified by
23433 the user. It is a string. If the breakpoint does not have an
23434 expression (the breakpoint is not a watchpoint) the attribute's value
23435 is @code{None}. This attribute is not writable.
23438 @defivar Breakpoint condition
23439 This attribute holds the condition of the breakpoint, as specified by
23440 the user. It is a string. If there is no condition, this attribute's
23441 value is @code{None}. This attribute is writable.
23444 @defivar Breakpoint commands
23445 This attribute holds the commands attached to the breakpoint. If
23446 there are commands, this attribute's value is a string holding all the
23447 commands, separated by newlines. If there are no commands, this
23448 attribute is @code{None}. This attribute is not writable.
23451 @node Lazy Strings In Python
23452 @subsubsection Python representation of lazy strings.
23454 @cindex lazy strings in python
23455 @tindex gdb.LazyString
23457 A @dfn{lazy string} is a string whose contents is not retrieved or
23458 encoded until it is needed.
23460 A @code{gdb.LazyString} is represented in @value{GDBN} as an
23461 @code{address} that points to a region of memory, an @code{encoding}
23462 that will be used to encode that region of memory, and a @code{length}
23463 to delimit the region of memory that represents the string. The
23464 difference between a @code{gdb.LazyString} and a string wrapped within
23465 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
23466 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
23467 retrieved and encoded during printing, while a @code{gdb.Value}
23468 wrapping a string is immediately retrieved and encoded on creation.
23470 A @code{gdb.LazyString} object has the following functions:
23472 @defmethod LazyString value
23473 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
23474 will point to the string in memory, but will lose all the delayed
23475 retrieval, encoding and handling that @value{GDBN} applies to a
23476 @code{gdb.LazyString}.
23479 @defivar LazyString address
23480 This attribute holds the address of the string. This attribute is not
23484 @defivar LazyString length
23485 This attribute holds the length of the string in characters. If the
23486 length is -1, then the string will be fetched and encoded up to the
23487 first null of appropriate width. This attribute is not writable.
23490 @defivar LazyString encoding
23491 This attribute holds the encoding that will be applied to the string
23492 when the string is printed by @value{GDBN}. If the encoding is not
23493 set, or contains an empty string, then @value{GDBN} will select the
23494 most appropriate encoding when the string is printed. This attribute
23498 @defivar LazyString type
23499 This attribute holds the type that is represented by the lazy string's
23500 type. For a lazy string this will always be a pointer type. To
23501 resolve this to the lazy string's character type, use the type's
23502 @code{target} method. @xref{Types In Python}. This attribute is not
23507 @subsection Auto-loading
23508 @cindex auto-loading, Python
23510 When a new object file is read (for example, due to the @code{file}
23511 command, or because the inferior has loaded a shared library),
23512 @value{GDBN} will look for Python support scripts in several ways:
23513 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
23516 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
23517 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
23518 * Which flavor to choose?::
23521 The auto-loading feature is useful for supplying application-specific
23522 debugging commands and scripts.
23524 Auto-loading can be enabled or disabled.
23527 @kindex set auto-load-scripts
23528 @item set auto-load-scripts [yes|no]
23529 Enable or disable the auto-loading of Python scripts.
23531 @kindex show auto-load-scripts
23532 @item show auto-load-scripts
23533 Show whether auto-loading of Python scripts is enabled or disabled.
23536 When reading an auto-loaded file, @value{GDBN} sets the
23537 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
23538 function (@pxref{Objfiles In Python}). This can be useful for
23539 registering objfile-specific pretty-printers.
23541 @node objfile-gdb.py file
23542 @subsubsection The @file{@var{objfile}-gdb.py} file
23543 @cindex @file{@var{objfile}-gdb.py}
23545 When a new object file is read, @value{GDBN} looks for
23546 a file named @file{@var{objfile}-gdb.py},
23547 where @var{objfile} is the object file's real name, formed by ensuring
23548 that the file name is absolute, following all symlinks, and resolving
23549 @code{.} and @code{..} components. If this file exists and is
23550 readable, @value{GDBN} will evaluate it as a Python script.
23552 If this file does not exist, and if the parameter
23553 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
23554 then @value{GDBN} will look for @var{real-name} in all of the
23555 directories mentioned in the value of @code{debug-file-directory}.
23557 Finally, if this file does not exist, then @value{GDBN} will look for
23558 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
23559 @var{data-directory} is @value{GDBN}'s data directory (available via
23560 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
23561 is the object file's real name, as described above.
23563 @value{GDBN} does not track which files it has already auto-loaded this way.
23564 @value{GDBN} will load the associated script every time the corresponding
23565 @var{objfile} is opened.
23566 So your @file{-gdb.py} file should be careful to avoid errors if it
23567 is evaluated more than once.
23569 @node .debug_gdb_scripts section
23570 @subsubsection The @code{.debug_gdb_scripts} section
23571 @cindex @code{.debug_gdb_scripts} section
23573 For systems using file formats like ELF and COFF,
23574 when @value{GDBN} loads a new object file
23575 it will look for a special section named @samp{.debug_gdb_scripts}.
23576 If this section exists, its contents is a list of names of scripts to load.
23578 @value{GDBN} will look for each specified script file first in the
23579 current directory and then along the source search path
23580 (@pxref{Source Path, ,Specifying Source Directories}),
23581 except that @file{$cdir} is not searched, since the compilation
23582 directory is not relevant to scripts.
23584 Entries can be placed in section @code{.debug_gdb_scripts} with,
23585 for example, this GCC macro:
23588 /* Note: The "MS" section flags are to remove duplicates. */
23589 #define DEFINE_GDB_SCRIPT(script_name) \
23591 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
23593 .asciz \"" script_name "\"\n\
23599 Then one can reference the macro in a header or source file like this:
23602 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
23605 The script name may include directories if desired.
23607 If the macro is put in a header, any application or library
23608 using this header will get a reference to the specified script.
23610 @node Which flavor to choose?
23611 @subsubsection Which flavor to choose?
23613 Given the multiple ways of auto-loading Python scripts, it might not always
23614 be clear which one to choose. This section provides some guidance.
23616 Benefits of the @file{-gdb.py} way:
23620 Can be used with file formats that don't support multiple sections.
23623 Ease of finding scripts for public libraries.
23625 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
23626 in the source search path.
23627 For publicly installed libraries, e.g., @file{libstdc++}, there typically
23628 isn't a source directory in which to find the script.
23631 Doesn't require source code additions.
23634 Benefits of the @code{.debug_gdb_scripts} way:
23638 Works with static linking.
23640 Scripts for libraries done the @file{-gdb.py} way require an objfile to
23641 trigger their loading. When an application is statically linked the only
23642 objfile available is the executable, and it is cumbersome to attach all the
23643 scripts from all the input libraries to the executable's @file{-gdb.py} script.
23646 Works with classes that are entirely inlined.
23648 Some classes can be entirely inlined, and thus there may not be an associated
23649 shared library to attach a @file{-gdb.py} script to.
23652 Scripts needn't be copied out of the source tree.
23654 In some circumstances, apps can be built out of large collections of internal
23655 libraries, and the build infrastructure necessary to install the
23656 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
23657 cumbersome. It may be easier to specify the scripts in the
23658 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
23659 top of the source tree to the source search path.
23662 @node Python modules
23663 @subsection Python modules
23664 @cindex python modules
23666 @value{GDBN} comes with a module to assist writing Python code.
23669 * gdb.printing:: Building and registering pretty-printers.
23670 * gdb.types:: Utilities for working with types.
23674 @subsubsection gdb.printing
23675 @cindex gdb.printing
23677 This module provides a collection of utilities for working with
23681 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
23682 This class specifies the API that makes @samp{info pretty-printer},
23683 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
23684 Pretty-printers should generally inherit from this class.
23686 @item SubPrettyPrinter (@var{name})
23687 For printers that handle multiple types, this class specifies the
23688 corresponding API for the subprinters.
23690 @item RegexpCollectionPrettyPrinter (@var{name})
23691 Utility class for handling multiple printers, all recognized via
23692 regular expressions.
23693 @xref{Writing a Pretty-Printer}, for an example.
23695 @item register_pretty_printer (@var{obj}, @var{printer})
23696 Register @var{printer} with the pretty-printer list of @var{obj}.
23700 @subsubsection gdb.types
23703 This module provides a collection of utilities for working with
23704 @code{gdb.Types} objects.
23707 @item get_basic_type (@var{type})
23708 Return @var{type} with const and volatile qualifiers stripped,
23709 and with typedefs and C@t{++} references converted to the underlying type.
23714 typedef const int const_int;
23716 const_int& foo_ref (foo);
23717 int main () @{ return 0; @}
23724 (gdb) python import gdb.types
23725 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
23726 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
23730 @item has_field (@var{type}, @var{field})
23731 Return @code{True} if @var{type}, assumed to be a type with fields
23732 (e.g., a structure or union), has field @var{field}.
23734 @item make_enum_dict (@var{enum_type})
23735 Return a Python @code{dictionary} type produced from @var{enum_type}.
23739 @chapter Command Interpreters
23740 @cindex command interpreters
23742 @value{GDBN} supports multiple command interpreters, and some command
23743 infrastructure to allow users or user interface writers to switch
23744 between interpreters or run commands in other interpreters.
23746 @value{GDBN} currently supports two command interpreters, the console
23747 interpreter (sometimes called the command-line interpreter or @sc{cli})
23748 and the machine interface interpreter (or @sc{gdb/mi}). This manual
23749 describes both of these interfaces in great detail.
23751 By default, @value{GDBN} will start with the console interpreter.
23752 However, the user may choose to start @value{GDBN} with another
23753 interpreter by specifying the @option{-i} or @option{--interpreter}
23754 startup options. Defined interpreters include:
23758 @cindex console interpreter
23759 The traditional console or command-line interpreter. This is the most often
23760 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
23761 @value{GDBN} will use this interpreter.
23764 @cindex mi interpreter
23765 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
23766 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
23767 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
23771 @cindex mi2 interpreter
23772 The current @sc{gdb/mi} interface.
23775 @cindex mi1 interpreter
23776 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
23780 @cindex invoke another interpreter
23781 The interpreter being used by @value{GDBN} may not be dynamically
23782 switched at runtime. Although possible, this could lead to a very
23783 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
23784 enters the command "interpreter-set console" in a console view,
23785 @value{GDBN} would switch to using the console interpreter, rendering
23786 the IDE inoperable!
23788 @kindex interpreter-exec
23789 Although you may only choose a single interpreter at startup, you may execute
23790 commands in any interpreter from the current interpreter using the appropriate
23791 command. If you are running the console interpreter, simply use the
23792 @code{interpreter-exec} command:
23795 interpreter-exec mi "-data-list-register-names"
23798 @sc{gdb/mi} has a similar command, although it is only available in versions of
23799 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
23802 @chapter @value{GDBN} Text User Interface
23804 @cindex Text User Interface
23807 * TUI Overview:: TUI overview
23808 * TUI Keys:: TUI key bindings
23809 * TUI Single Key Mode:: TUI single key mode
23810 * TUI Commands:: TUI-specific commands
23811 * TUI Configuration:: TUI configuration variables
23814 The @value{GDBN} Text User Interface (TUI) is a terminal
23815 interface which uses the @code{curses} library to show the source
23816 file, the assembly output, the program registers and @value{GDBN}
23817 commands in separate text windows. The TUI mode is supported only
23818 on platforms where a suitable version of the @code{curses} library
23821 @pindex @value{GDBTUI}
23822 The TUI mode is enabled by default when you invoke @value{GDBN} as
23823 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
23824 You can also switch in and out of TUI mode while @value{GDBN} runs by
23825 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
23826 @xref{TUI Keys, ,TUI Key Bindings}.
23829 @section TUI Overview
23831 In TUI mode, @value{GDBN} can display several text windows:
23835 This window is the @value{GDBN} command window with the @value{GDBN}
23836 prompt and the @value{GDBN} output. The @value{GDBN} input is still
23837 managed using readline.
23840 The source window shows the source file of the program. The current
23841 line and active breakpoints are displayed in this window.
23844 The assembly window shows the disassembly output of the program.
23847 This window shows the processor registers. Registers are highlighted
23848 when their values change.
23851 The source and assembly windows show the current program position
23852 by highlighting the current line and marking it with a @samp{>} marker.
23853 Breakpoints are indicated with two markers. The first marker
23854 indicates the breakpoint type:
23858 Breakpoint which was hit at least once.
23861 Breakpoint which was never hit.
23864 Hardware breakpoint which was hit at least once.
23867 Hardware breakpoint which was never hit.
23870 The second marker indicates whether the breakpoint is enabled or not:
23874 Breakpoint is enabled.
23877 Breakpoint is disabled.
23880 The source, assembly and register windows are updated when the current
23881 thread changes, when the frame changes, or when the program counter
23884 These windows are not all visible at the same time. The command
23885 window is always visible. The others can be arranged in several
23896 source and assembly,
23899 source and registers, or
23902 assembly and registers.
23905 A status line above the command window shows the following information:
23909 Indicates the current @value{GDBN} target.
23910 (@pxref{Targets, ,Specifying a Debugging Target}).
23913 Gives the current process or thread number.
23914 When no process is being debugged, this field is set to @code{No process}.
23917 Gives the current function name for the selected frame.
23918 The name is demangled if demangling is turned on (@pxref{Print Settings}).
23919 When there is no symbol corresponding to the current program counter,
23920 the string @code{??} is displayed.
23923 Indicates the current line number for the selected frame.
23924 When the current line number is not known, the string @code{??} is displayed.
23927 Indicates the current program counter address.
23931 @section TUI Key Bindings
23932 @cindex TUI key bindings
23934 The TUI installs several key bindings in the readline keymaps
23935 @ifset SYSTEM_READLINE
23936 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
23938 @ifclear SYSTEM_READLINE
23939 (@pxref{Command Line Editing}).
23941 The following key bindings are installed for both TUI mode and the
23942 @value{GDBN} standard mode.
23951 Enter or leave the TUI mode. When leaving the TUI mode,
23952 the curses window management stops and @value{GDBN} operates using
23953 its standard mode, writing on the terminal directly. When reentering
23954 the TUI mode, control is given back to the curses windows.
23955 The screen is then refreshed.
23959 Use a TUI layout with only one window. The layout will
23960 either be @samp{source} or @samp{assembly}. When the TUI mode
23961 is not active, it will switch to the TUI mode.
23963 Think of this key binding as the Emacs @kbd{C-x 1} binding.
23967 Use a TUI layout with at least two windows. When the current
23968 layout already has two windows, the next layout with two windows is used.
23969 When a new layout is chosen, one window will always be common to the
23970 previous layout and the new one.
23972 Think of it as the Emacs @kbd{C-x 2} binding.
23976 Change the active window. The TUI associates several key bindings
23977 (like scrolling and arrow keys) with the active window. This command
23978 gives the focus to the next TUI window.
23980 Think of it as the Emacs @kbd{C-x o} binding.
23984 Switch in and out of the TUI SingleKey mode that binds single
23985 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
23988 The following key bindings only work in the TUI mode:
23993 Scroll the active window one page up.
23997 Scroll the active window one page down.
24001 Scroll the active window one line up.
24005 Scroll the active window one line down.
24009 Scroll the active window one column left.
24013 Scroll the active window one column right.
24017 Refresh the screen.
24020 Because the arrow keys scroll the active window in the TUI mode, they
24021 are not available for their normal use by readline unless the command
24022 window has the focus. When another window is active, you must use
24023 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24024 and @kbd{C-f} to control the command window.
24026 @node TUI Single Key Mode
24027 @section TUI Single Key Mode
24028 @cindex TUI single key mode
24030 The TUI also provides a @dfn{SingleKey} mode, which binds several
24031 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24032 switch into this mode, where the following key bindings are used:
24035 @kindex c @r{(SingleKey TUI key)}
24039 @kindex d @r{(SingleKey TUI key)}
24043 @kindex f @r{(SingleKey TUI key)}
24047 @kindex n @r{(SingleKey TUI key)}
24051 @kindex q @r{(SingleKey TUI key)}
24053 exit the SingleKey mode.
24055 @kindex r @r{(SingleKey TUI key)}
24059 @kindex s @r{(SingleKey TUI key)}
24063 @kindex u @r{(SingleKey TUI key)}
24067 @kindex v @r{(SingleKey TUI key)}
24071 @kindex w @r{(SingleKey TUI key)}
24076 Other keys temporarily switch to the @value{GDBN} command prompt.
24077 The key that was pressed is inserted in the editing buffer so that
24078 it is possible to type most @value{GDBN} commands without interaction
24079 with the TUI SingleKey mode. Once the command is entered the TUI
24080 SingleKey mode is restored. The only way to permanently leave
24081 this mode is by typing @kbd{q} or @kbd{C-x s}.
24085 @section TUI-specific Commands
24086 @cindex TUI commands
24088 The TUI has specific commands to control the text windows.
24089 These commands are always available, even when @value{GDBN} is not in
24090 the TUI mode. When @value{GDBN} is in the standard mode, most
24091 of these commands will automatically switch to the TUI mode.
24093 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24094 terminal, or @value{GDBN} has been started with the machine interface
24095 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24096 these commands will fail with an error, because it would not be
24097 possible or desirable to enable curses window management.
24102 List and give the size of all displayed windows.
24106 Display the next layout.
24109 Display the previous layout.
24112 Display the source window only.
24115 Display the assembly window only.
24118 Display the source and assembly window.
24121 Display the register window together with the source or assembly window.
24125 Make the next window active for scrolling.
24128 Make the previous window active for scrolling.
24131 Make the source window active for scrolling.
24134 Make the assembly window active for scrolling.
24137 Make the register window active for scrolling.
24140 Make the command window active for scrolling.
24144 Refresh the screen. This is similar to typing @kbd{C-L}.
24146 @item tui reg float
24148 Show the floating point registers in the register window.
24150 @item tui reg general
24151 Show the general registers in the register window.
24154 Show the next register group. The list of register groups as well as
24155 their order is target specific. The predefined register groups are the
24156 following: @code{general}, @code{float}, @code{system}, @code{vector},
24157 @code{all}, @code{save}, @code{restore}.
24159 @item tui reg system
24160 Show the system registers in the register window.
24164 Update the source window and the current execution point.
24166 @item winheight @var{name} +@var{count}
24167 @itemx winheight @var{name} -@var{count}
24169 Change the height of the window @var{name} by @var{count}
24170 lines. Positive counts increase the height, while negative counts
24173 @item tabset @var{nchars}
24175 Set the width of tab stops to be @var{nchars} characters.
24178 @node TUI Configuration
24179 @section TUI Configuration Variables
24180 @cindex TUI configuration variables
24182 Several configuration variables control the appearance of TUI windows.
24185 @item set tui border-kind @var{kind}
24186 @kindex set tui border-kind
24187 Select the border appearance for the source, assembly and register windows.
24188 The possible values are the following:
24191 Use a space character to draw the border.
24194 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
24197 Use the Alternate Character Set to draw the border. The border is
24198 drawn using character line graphics if the terminal supports them.
24201 @item set tui border-mode @var{mode}
24202 @kindex set tui border-mode
24203 @itemx set tui active-border-mode @var{mode}
24204 @kindex set tui active-border-mode
24205 Select the display attributes for the borders of the inactive windows
24206 or the active window. The @var{mode} can be one of the following:
24209 Use normal attributes to display the border.
24215 Use reverse video mode.
24218 Use half bright mode.
24220 @item half-standout
24221 Use half bright and standout mode.
24224 Use extra bright or bold mode.
24226 @item bold-standout
24227 Use extra bright or bold and standout mode.
24232 @chapter Using @value{GDBN} under @sc{gnu} Emacs
24235 @cindex @sc{gnu} Emacs
24236 A special interface allows you to use @sc{gnu} Emacs to view (and
24237 edit) the source files for the program you are debugging with
24240 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
24241 executable file you want to debug as an argument. This command starts
24242 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
24243 created Emacs buffer.
24244 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
24246 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
24251 All ``terminal'' input and output goes through an Emacs buffer, called
24254 This applies both to @value{GDBN} commands and their output, and to the input
24255 and output done by the program you are debugging.
24257 This is useful because it means that you can copy the text of previous
24258 commands and input them again; you can even use parts of the output
24261 All the facilities of Emacs' Shell mode are available for interacting
24262 with your program. In particular, you can send signals the usual
24263 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
24267 @value{GDBN} displays source code through Emacs.
24269 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
24270 source file for that frame and puts an arrow (@samp{=>}) at the
24271 left margin of the current line. Emacs uses a separate buffer for
24272 source display, and splits the screen to show both your @value{GDBN} session
24275 Explicit @value{GDBN} @code{list} or search commands still produce output as
24276 usual, but you probably have no reason to use them from Emacs.
24279 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
24280 a graphical mode, enabled by default, which provides further buffers
24281 that can control the execution and describe the state of your program.
24282 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
24284 If you specify an absolute file name when prompted for the @kbd{M-x
24285 gdb} argument, then Emacs sets your current working directory to where
24286 your program resides. If you only specify the file name, then Emacs
24287 sets your current working directory to the directory associated
24288 with the previous buffer. In this case, @value{GDBN} may find your
24289 program by searching your environment's @code{PATH} variable, but on
24290 some operating systems it might not find the source. So, although the
24291 @value{GDBN} input and output session proceeds normally, the auxiliary
24292 buffer does not display the current source and line of execution.
24294 The initial working directory of @value{GDBN} is printed on the top
24295 line of the GUD buffer and this serves as a default for the commands
24296 that specify files for @value{GDBN} to operate on. @xref{Files,
24297 ,Commands to Specify Files}.
24299 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
24300 need to call @value{GDBN} by a different name (for example, if you
24301 keep several configurations around, with different names) you can
24302 customize the Emacs variable @code{gud-gdb-command-name} to run the
24305 In the GUD buffer, you can use these special Emacs commands in
24306 addition to the standard Shell mode commands:
24310 Describe the features of Emacs' GUD Mode.
24313 Execute to another source line, like the @value{GDBN} @code{step} command; also
24314 update the display window to show the current file and location.
24317 Execute to next source line in this function, skipping all function
24318 calls, like the @value{GDBN} @code{next} command. Then update the display window
24319 to show the current file and location.
24322 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
24323 display window accordingly.
24326 Execute until exit from the selected stack frame, like the @value{GDBN}
24327 @code{finish} command.
24330 Continue execution of your program, like the @value{GDBN} @code{continue}
24334 Go up the number of frames indicated by the numeric argument
24335 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
24336 like the @value{GDBN} @code{up} command.
24339 Go down the number of frames indicated by the numeric argument, like the
24340 @value{GDBN} @code{down} command.
24343 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
24344 tells @value{GDBN} to set a breakpoint on the source line point is on.
24346 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
24347 separate frame which shows a backtrace when the GUD buffer is current.
24348 Move point to any frame in the stack and type @key{RET} to make it
24349 become the current frame and display the associated source in the
24350 source buffer. Alternatively, click @kbd{Mouse-2} to make the
24351 selected frame become the current one. In graphical mode, the
24352 speedbar displays watch expressions.
24354 If you accidentally delete the source-display buffer, an easy way to get
24355 it back is to type the command @code{f} in the @value{GDBN} buffer, to
24356 request a frame display; when you run under Emacs, this recreates
24357 the source buffer if necessary to show you the context of the current
24360 The source files displayed in Emacs are in ordinary Emacs buffers
24361 which are visiting the source files in the usual way. You can edit
24362 the files with these buffers if you wish; but keep in mind that @value{GDBN}
24363 communicates with Emacs in terms of line numbers. If you add or
24364 delete lines from the text, the line numbers that @value{GDBN} knows cease
24365 to correspond properly with the code.
24367 A more detailed description of Emacs' interaction with @value{GDBN} is
24368 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
24371 @c The following dropped because Epoch is nonstandard. Reactivate
24372 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
24374 @kindex Emacs Epoch environment
24378 Version 18 of @sc{gnu} Emacs has a built-in window system
24379 called the @code{epoch}
24380 environment. Users of this environment can use a new command,
24381 @code{inspect} which performs identically to @code{print} except that
24382 each value is printed in its own window.
24387 @chapter The @sc{gdb/mi} Interface
24389 @unnumberedsec Function and Purpose
24391 @cindex @sc{gdb/mi}, its purpose
24392 @sc{gdb/mi} is a line based machine oriented text interface to
24393 @value{GDBN} and is activated by specifying using the
24394 @option{--interpreter} command line option (@pxref{Mode Options}). It
24395 is specifically intended to support the development of systems which
24396 use the debugger as just one small component of a larger system.
24398 This chapter is a specification of the @sc{gdb/mi} interface. It is written
24399 in the form of a reference manual.
24401 Note that @sc{gdb/mi} is still under construction, so some of the
24402 features described below are incomplete and subject to change
24403 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
24405 @unnumberedsec Notation and Terminology
24407 @cindex notational conventions, for @sc{gdb/mi}
24408 This chapter uses the following notation:
24412 @code{|} separates two alternatives.
24415 @code{[ @var{something} ]} indicates that @var{something} is optional:
24416 it may or may not be given.
24419 @code{( @var{group} )*} means that @var{group} inside the parentheses
24420 may repeat zero or more times.
24423 @code{( @var{group} )+} means that @var{group} inside the parentheses
24424 may repeat one or more times.
24427 @code{"@var{string}"} means a literal @var{string}.
24431 @heading Dependencies
24435 * GDB/MI General Design::
24436 * GDB/MI Command Syntax::
24437 * GDB/MI Compatibility with CLI::
24438 * GDB/MI Development and Front Ends::
24439 * GDB/MI Output Records::
24440 * GDB/MI Simple Examples::
24441 * GDB/MI Command Description Format::
24442 * GDB/MI Breakpoint Commands::
24443 * GDB/MI Program Context::
24444 * GDB/MI Thread Commands::
24445 * GDB/MI Program Execution::
24446 * GDB/MI Stack Manipulation::
24447 * GDB/MI Variable Objects::
24448 * GDB/MI Data Manipulation::
24449 * GDB/MI Tracepoint Commands::
24450 * GDB/MI Symbol Query::
24451 * GDB/MI File Commands::
24453 * GDB/MI Kod Commands::
24454 * GDB/MI Memory Overlay Commands::
24455 * GDB/MI Signal Handling Commands::
24457 * GDB/MI Target Manipulation::
24458 * GDB/MI File Transfer Commands::
24459 * GDB/MI Miscellaneous Commands::
24462 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24463 @node GDB/MI General Design
24464 @section @sc{gdb/mi} General Design
24465 @cindex GDB/MI General Design
24467 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
24468 parts---commands sent to @value{GDBN}, responses to those commands
24469 and notifications. Each command results in exactly one response,
24470 indicating either successful completion of the command, or an error.
24471 For the commands that do not resume the target, the response contains the
24472 requested information. For the commands that resume the target, the
24473 response only indicates whether the target was successfully resumed.
24474 Notifications is the mechanism for reporting changes in the state of the
24475 target, or in @value{GDBN} state, that cannot conveniently be associated with
24476 a command and reported as part of that command response.
24478 The important examples of notifications are:
24482 Exec notifications. These are used to report changes in
24483 target state---when a target is resumed, or stopped. It would not
24484 be feasible to include this information in response of resuming
24485 commands, because one resume commands can result in multiple events in
24486 different threads. Also, quite some time may pass before any event
24487 happens in the target, while a frontend needs to know whether the resuming
24488 command itself was successfully executed.
24491 Console output, and status notifications. Console output
24492 notifications are used to report output of CLI commands, as well as
24493 diagnostics for other commands. Status notifications are used to
24494 report the progress of a long-running operation. Naturally, including
24495 this information in command response would mean no output is produced
24496 until the command is finished, which is undesirable.
24499 General notifications. Commands may have various side effects on
24500 the @value{GDBN} or target state beyond their official purpose. For example,
24501 a command may change the selected thread. Although such changes can
24502 be included in command response, using notification allows for more
24503 orthogonal frontend design.
24507 There's no guarantee that whenever an MI command reports an error,
24508 @value{GDBN} or the target are in any specific state, and especially,
24509 the state is not reverted to the state before the MI command was
24510 processed. Therefore, whenever an MI command results in an error,
24511 we recommend that the frontend refreshes all the information shown in
24512 the user interface.
24516 * Context management::
24517 * Asynchronous and non-stop modes::
24521 @node Context management
24522 @subsection Context management
24524 In most cases when @value{GDBN} accesses the target, this access is
24525 done in context of a specific thread and frame (@pxref{Frames}).
24526 Often, even when accessing global data, the target requires that a thread
24527 be specified. The CLI interface maintains the selected thread and frame,
24528 and supplies them to target on each command. This is convenient,
24529 because a command line user would not want to specify that information
24530 explicitly on each command, and because user interacts with
24531 @value{GDBN} via a single terminal, so no confusion is possible as
24532 to what thread and frame are the current ones.
24534 In the case of MI, the concept of selected thread and frame is less
24535 useful. First, a frontend can easily remember this information
24536 itself. Second, a graphical frontend can have more than one window,
24537 each one used for debugging a different thread, and the frontend might
24538 want to access additional threads for internal purposes. This
24539 increases the risk that by relying on implicitly selected thread, the
24540 frontend may be operating on a wrong one. Therefore, each MI command
24541 should explicitly specify which thread and frame to operate on. To
24542 make it possible, each MI command accepts the @samp{--thread} and
24543 @samp{--frame} options, the value to each is @value{GDBN} identifier
24544 for thread and frame to operate on.
24546 Usually, each top-level window in a frontend allows the user to select
24547 a thread and a frame, and remembers the user selection for further
24548 operations. However, in some cases @value{GDBN} may suggest that the
24549 current thread be changed. For example, when stopping on a breakpoint
24550 it is reasonable to switch to the thread where breakpoint is hit. For
24551 another example, if the user issues the CLI @samp{thread} command via
24552 the frontend, it is desirable to change the frontend's selected thread to the
24553 one specified by user. @value{GDBN} communicates the suggestion to
24554 change current thread using the @samp{=thread-selected} notification.
24555 No such notification is available for the selected frame at the moment.
24557 Note that historically, MI shares the selected thread with CLI, so
24558 frontends used the @code{-thread-select} to execute commands in the
24559 right context. However, getting this to work right is cumbersome. The
24560 simplest way is for frontend to emit @code{-thread-select} command
24561 before every command. This doubles the number of commands that need
24562 to be sent. The alternative approach is to suppress @code{-thread-select}
24563 if the selected thread in @value{GDBN} is supposed to be identical to the
24564 thread the frontend wants to operate on. However, getting this
24565 optimization right can be tricky. In particular, if the frontend
24566 sends several commands to @value{GDBN}, and one of the commands changes the
24567 selected thread, then the behaviour of subsequent commands will
24568 change. So, a frontend should either wait for response from such
24569 problematic commands, or explicitly add @code{-thread-select} for
24570 all subsequent commands. No frontend is known to do this exactly
24571 right, so it is suggested to just always pass the @samp{--thread} and
24572 @samp{--frame} options.
24574 @node Asynchronous and non-stop modes
24575 @subsection Asynchronous command execution and non-stop mode
24577 On some targets, @value{GDBN} is capable of processing MI commands
24578 even while the target is running. This is called @dfn{asynchronous
24579 command execution} (@pxref{Background Execution}). The frontend may
24580 specify a preferrence for asynchronous execution using the
24581 @code{-gdb-set target-async 1} command, which should be emitted before
24582 either running the executable or attaching to the target. After the
24583 frontend has started the executable or attached to the target, it can
24584 find if asynchronous execution is enabled using the
24585 @code{-list-target-features} command.
24587 Even if @value{GDBN} can accept a command while target is running,
24588 many commands that access the target do not work when the target is
24589 running. Therefore, asynchronous command execution is most useful
24590 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
24591 it is possible to examine the state of one thread, while other threads
24594 When a given thread is running, MI commands that try to access the
24595 target in the context of that thread may not work, or may work only on
24596 some targets. In particular, commands that try to operate on thread's
24597 stack will not work, on any target. Commands that read memory, or
24598 modify breakpoints, may work or not work, depending on the target. Note
24599 that even commands that operate on global state, such as @code{print},
24600 @code{set}, and breakpoint commands, still access the target in the
24601 context of a specific thread, so frontend should try to find a
24602 stopped thread and perform the operation on that thread (using the
24603 @samp{--thread} option).
24605 Which commands will work in the context of a running thread is
24606 highly target dependent. However, the two commands
24607 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
24608 to find the state of a thread, will always work.
24610 @node Thread groups
24611 @subsection Thread groups
24612 @value{GDBN} may be used to debug several processes at the same time.
24613 On some platfroms, @value{GDBN} may support debugging of several
24614 hardware systems, each one having several cores with several different
24615 processes running on each core. This section describes the MI
24616 mechanism to support such debugging scenarios.
24618 The key observation is that regardless of the structure of the
24619 target, MI can have a global list of threads, because most commands that
24620 accept the @samp{--thread} option do not need to know what process that
24621 thread belongs to. Therefore, it is not necessary to introduce
24622 neither additional @samp{--process} option, nor an notion of the
24623 current process in the MI interface. The only strictly new feature
24624 that is required is the ability to find how the threads are grouped
24627 To allow the user to discover such grouping, and to support arbitrary
24628 hierarchy of machines/cores/processes, MI introduces the concept of a
24629 @dfn{thread group}. Thread group is a collection of threads and other
24630 thread groups. A thread group always has a string identifier, a type,
24631 and may have additional attributes specific to the type. A new
24632 command, @code{-list-thread-groups}, returns the list of top-level
24633 thread groups, which correspond to processes that @value{GDBN} is
24634 debugging at the moment. By passing an identifier of a thread group
24635 to the @code{-list-thread-groups} command, it is possible to obtain
24636 the members of specific thread group.
24638 To allow the user to easily discover processes, and other objects, he
24639 wishes to debug, a concept of @dfn{available thread group} is
24640 introduced. Available thread group is an thread group that
24641 @value{GDBN} is not debugging, but that can be attached to, using the
24642 @code{-target-attach} command. The list of available top-level thread
24643 groups can be obtained using @samp{-list-thread-groups --available}.
24644 In general, the content of a thread group may be only retrieved only
24645 after attaching to that thread group.
24647 Thread groups are related to inferiors (@pxref{Inferiors and
24648 Programs}). Each inferior corresponds to a thread group of a special
24649 type @samp{process}, and some additional operations are permitted on
24650 such thread groups.
24652 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24653 @node GDB/MI Command Syntax
24654 @section @sc{gdb/mi} Command Syntax
24657 * GDB/MI Input Syntax::
24658 * GDB/MI Output Syntax::
24661 @node GDB/MI Input Syntax
24662 @subsection @sc{gdb/mi} Input Syntax
24664 @cindex input syntax for @sc{gdb/mi}
24665 @cindex @sc{gdb/mi}, input syntax
24667 @item @var{command} @expansion{}
24668 @code{@var{cli-command} | @var{mi-command}}
24670 @item @var{cli-command} @expansion{}
24671 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
24672 @var{cli-command} is any existing @value{GDBN} CLI command.
24674 @item @var{mi-command} @expansion{}
24675 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
24676 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
24678 @item @var{token} @expansion{}
24679 "any sequence of digits"
24681 @item @var{option} @expansion{}
24682 @code{"-" @var{parameter} [ " " @var{parameter} ]}
24684 @item @var{parameter} @expansion{}
24685 @code{@var{non-blank-sequence} | @var{c-string}}
24687 @item @var{operation} @expansion{}
24688 @emph{any of the operations described in this chapter}
24690 @item @var{non-blank-sequence} @expansion{}
24691 @emph{anything, provided it doesn't contain special characters such as
24692 "-", @var{nl}, """ and of course " "}
24694 @item @var{c-string} @expansion{}
24695 @code{""" @var{seven-bit-iso-c-string-content} """}
24697 @item @var{nl} @expansion{}
24706 The CLI commands are still handled by the @sc{mi} interpreter; their
24707 output is described below.
24710 The @code{@var{token}}, when present, is passed back when the command
24714 Some @sc{mi} commands accept optional arguments as part of the parameter
24715 list. Each option is identified by a leading @samp{-} (dash) and may be
24716 followed by an optional argument parameter. Options occur first in the
24717 parameter list and can be delimited from normal parameters using
24718 @samp{--} (this is useful when some parameters begin with a dash).
24725 We want easy access to the existing CLI syntax (for debugging).
24728 We want it to be easy to spot a @sc{mi} operation.
24731 @node GDB/MI Output Syntax
24732 @subsection @sc{gdb/mi} Output Syntax
24734 @cindex output syntax of @sc{gdb/mi}
24735 @cindex @sc{gdb/mi}, output syntax
24736 The output from @sc{gdb/mi} consists of zero or more out-of-band records
24737 followed, optionally, by a single result record. This result record
24738 is for the most recent command. The sequence of output records is
24739 terminated by @samp{(gdb)}.
24741 If an input command was prefixed with a @code{@var{token}} then the
24742 corresponding output for that command will also be prefixed by that same
24746 @item @var{output} @expansion{}
24747 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
24749 @item @var{result-record} @expansion{}
24750 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
24752 @item @var{out-of-band-record} @expansion{}
24753 @code{@var{async-record} | @var{stream-record}}
24755 @item @var{async-record} @expansion{}
24756 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
24758 @item @var{exec-async-output} @expansion{}
24759 @code{[ @var{token} ] "*" @var{async-output}}
24761 @item @var{status-async-output} @expansion{}
24762 @code{[ @var{token} ] "+" @var{async-output}}
24764 @item @var{notify-async-output} @expansion{}
24765 @code{[ @var{token} ] "=" @var{async-output}}
24767 @item @var{async-output} @expansion{}
24768 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
24770 @item @var{result-class} @expansion{}
24771 @code{"done" | "running" | "connected" | "error" | "exit"}
24773 @item @var{async-class} @expansion{}
24774 @code{"stopped" | @var{others}} (where @var{others} will be added
24775 depending on the needs---this is still in development).
24777 @item @var{result} @expansion{}
24778 @code{ @var{variable} "=" @var{value}}
24780 @item @var{variable} @expansion{}
24781 @code{ @var{string} }
24783 @item @var{value} @expansion{}
24784 @code{ @var{const} | @var{tuple} | @var{list} }
24786 @item @var{const} @expansion{}
24787 @code{@var{c-string}}
24789 @item @var{tuple} @expansion{}
24790 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
24792 @item @var{list} @expansion{}
24793 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
24794 @var{result} ( "," @var{result} )* "]" }
24796 @item @var{stream-record} @expansion{}
24797 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
24799 @item @var{console-stream-output} @expansion{}
24800 @code{"~" @var{c-string}}
24802 @item @var{target-stream-output} @expansion{}
24803 @code{"@@" @var{c-string}}
24805 @item @var{log-stream-output} @expansion{}
24806 @code{"&" @var{c-string}}
24808 @item @var{nl} @expansion{}
24811 @item @var{token} @expansion{}
24812 @emph{any sequence of digits}.
24820 All output sequences end in a single line containing a period.
24823 The @code{@var{token}} is from the corresponding request. Note that
24824 for all async output, while the token is allowed by the grammar and
24825 may be output by future versions of @value{GDBN} for select async
24826 output messages, it is generally omitted. Frontends should treat
24827 all async output as reporting general changes in the state of the
24828 target and there should be no need to associate async output to any
24832 @cindex status output in @sc{gdb/mi}
24833 @var{status-async-output} contains on-going status information about the
24834 progress of a slow operation. It can be discarded. All status output is
24835 prefixed by @samp{+}.
24838 @cindex async output in @sc{gdb/mi}
24839 @var{exec-async-output} contains asynchronous state change on the target
24840 (stopped, started, disappeared). All async output is prefixed by
24844 @cindex notify output in @sc{gdb/mi}
24845 @var{notify-async-output} contains supplementary information that the
24846 client should handle (e.g., a new breakpoint information). All notify
24847 output is prefixed by @samp{=}.
24850 @cindex console output in @sc{gdb/mi}
24851 @var{console-stream-output} is output that should be displayed as is in the
24852 console. It is the textual response to a CLI command. All the console
24853 output is prefixed by @samp{~}.
24856 @cindex target output in @sc{gdb/mi}
24857 @var{target-stream-output} is the output produced by the target program.
24858 All the target output is prefixed by @samp{@@}.
24861 @cindex log output in @sc{gdb/mi}
24862 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
24863 instance messages that should be displayed as part of an error log. All
24864 the log output is prefixed by @samp{&}.
24867 @cindex list output in @sc{gdb/mi}
24868 New @sc{gdb/mi} commands should only output @var{lists} containing
24874 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
24875 details about the various output records.
24877 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24878 @node GDB/MI Compatibility with CLI
24879 @section @sc{gdb/mi} Compatibility with CLI
24881 @cindex compatibility, @sc{gdb/mi} and CLI
24882 @cindex @sc{gdb/mi}, compatibility with CLI
24884 For the developers convenience CLI commands can be entered directly,
24885 but there may be some unexpected behaviour. For example, commands
24886 that query the user will behave as if the user replied yes, breakpoint
24887 command lists are not executed and some CLI commands, such as
24888 @code{if}, @code{when} and @code{define}, prompt for further input with
24889 @samp{>}, which is not valid MI output.
24891 This feature may be removed at some stage in the future and it is
24892 recommended that front ends use the @code{-interpreter-exec} command
24893 (@pxref{-interpreter-exec}).
24895 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24896 @node GDB/MI Development and Front Ends
24897 @section @sc{gdb/mi} Development and Front Ends
24898 @cindex @sc{gdb/mi} development
24900 The application which takes the MI output and presents the state of the
24901 program being debugged to the user is called a @dfn{front end}.
24903 Although @sc{gdb/mi} is still incomplete, it is currently being used
24904 by a variety of front ends to @value{GDBN}. This makes it difficult
24905 to introduce new functionality without breaking existing usage. This
24906 section tries to minimize the problems by describing how the protocol
24909 Some changes in MI need not break a carefully designed front end, and
24910 for these the MI version will remain unchanged. The following is a
24911 list of changes that may occur within one level, so front ends should
24912 parse MI output in a way that can handle them:
24916 New MI commands may be added.
24919 New fields may be added to the output of any MI command.
24922 The range of values for fields with specified values, e.g.,
24923 @code{in_scope} (@pxref{-var-update}) may be extended.
24925 @c The format of field's content e.g type prefix, may change so parse it
24926 @c at your own risk. Yes, in general?
24928 @c The order of fields may change? Shouldn't really matter but it might
24929 @c resolve inconsistencies.
24932 If the changes are likely to break front ends, the MI version level
24933 will be increased by one. This will allow the front end to parse the
24934 output according to the MI version. Apart from mi0, new versions of
24935 @value{GDBN} will not support old versions of MI and it will be the
24936 responsibility of the front end to work with the new one.
24938 @c Starting with mi3, add a new command -mi-version that prints the MI
24941 The best way to avoid unexpected changes in MI that might break your front
24942 end is to make your project known to @value{GDBN} developers and
24943 follow development on @email{gdb@@sourceware.org} and
24944 @email{gdb-patches@@sourceware.org}.
24945 @cindex mailing lists
24947 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24948 @node GDB/MI Output Records
24949 @section @sc{gdb/mi} Output Records
24952 * GDB/MI Result Records::
24953 * GDB/MI Stream Records::
24954 * GDB/MI Async Records::
24955 * GDB/MI Frame Information::
24956 * GDB/MI Thread Information::
24957 * GDB/MI Ada Exception Information::
24960 @node GDB/MI Result Records
24961 @subsection @sc{gdb/mi} Result Records
24963 @cindex result records in @sc{gdb/mi}
24964 @cindex @sc{gdb/mi}, result records
24965 In addition to a number of out-of-band notifications, the response to a
24966 @sc{gdb/mi} command includes one of the following result indications:
24970 @item "^done" [ "," @var{results} ]
24971 The synchronous operation was successful, @code{@var{results}} are the return
24976 This result record is equivalent to @samp{^done}. Historically, it
24977 was output instead of @samp{^done} if the command has resumed the
24978 target. This behaviour is maintained for backward compatibility, but
24979 all frontends should treat @samp{^done} and @samp{^running}
24980 identically and rely on the @samp{*running} output record to determine
24981 which threads are resumed.
24985 @value{GDBN} has connected to a remote target.
24987 @item "^error" "," @var{c-string}
24989 The operation failed. The @code{@var{c-string}} contains the corresponding
24994 @value{GDBN} has terminated.
24998 @node GDB/MI Stream Records
24999 @subsection @sc{gdb/mi} Stream Records
25001 @cindex @sc{gdb/mi}, stream records
25002 @cindex stream records in @sc{gdb/mi}
25003 @value{GDBN} internally maintains a number of output streams: the console, the
25004 target, and the log. The output intended for each of these streams is
25005 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25007 Each stream record begins with a unique @dfn{prefix character} which
25008 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25009 Syntax}). In addition to the prefix, each stream record contains a
25010 @code{@var{string-output}}. This is either raw text (with an implicit new
25011 line) or a quoted C string (which does not contain an implicit newline).
25014 @item "~" @var{string-output}
25015 The console output stream contains text that should be displayed in the
25016 CLI console window. It contains the textual responses to CLI commands.
25018 @item "@@" @var{string-output}
25019 The target output stream contains any textual output from the running
25020 target. This is only present when GDB's event loop is truly
25021 asynchronous, which is currently only the case for remote targets.
25023 @item "&" @var{string-output}
25024 The log stream contains debugging messages being produced by @value{GDBN}'s
25028 @node GDB/MI Async Records
25029 @subsection @sc{gdb/mi} Async Records
25031 @cindex async records in @sc{gdb/mi}
25032 @cindex @sc{gdb/mi}, async records
25033 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25034 additional changes that have occurred. Those changes can either be a
25035 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25036 target activity (e.g., target stopped).
25038 The following is the list of possible async records:
25042 @item *running,thread-id="@var{thread}"
25043 The target is now running. The @var{thread} field tells which
25044 specific thread is now running, and can be @samp{all} if all threads
25045 are running. The frontend should assume that no interaction with a
25046 running thread is possible after this notification is produced.
25047 The frontend should not assume that this notification is output
25048 only once for any command. @value{GDBN} may emit this notification
25049 several times, either for different threads, because it cannot resume
25050 all threads together, or even for a single thread, if the thread must
25051 be stepped though some code before letting it run freely.
25053 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25054 The target has stopped. The @var{reason} field can have one of the
25058 @item breakpoint-hit
25059 A breakpoint was reached.
25060 @item watchpoint-trigger
25061 A watchpoint was triggered.
25062 @item read-watchpoint-trigger
25063 A read watchpoint was triggered.
25064 @item access-watchpoint-trigger
25065 An access watchpoint was triggered.
25066 @item function-finished
25067 An -exec-finish or similar CLI command was accomplished.
25068 @item location-reached
25069 An -exec-until or similar CLI command was accomplished.
25070 @item watchpoint-scope
25071 A watchpoint has gone out of scope.
25072 @item end-stepping-range
25073 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25074 similar CLI command was accomplished.
25075 @item exited-signalled
25076 The inferior exited because of a signal.
25078 The inferior exited.
25079 @item exited-normally
25080 The inferior exited normally.
25081 @item signal-received
25082 A signal was received by the inferior.
25085 The @var{id} field identifies the thread that directly caused the stop
25086 -- for example by hitting a breakpoint. Depending on whether all-stop
25087 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25088 stop all threads, or only the thread that directly triggered the stop.
25089 If all threads are stopped, the @var{stopped} field will have the
25090 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25091 field will be a list of thread identifiers. Presently, this list will
25092 always include a single thread, but frontend should be prepared to see
25093 several threads in the list. The @var{core} field reports the
25094 processor core on which the stop event has happened. This field may be absent
25095 if such information is not available.
25097 @item =thread-group-added,id="@var{id}"
25098 @itemx =thread-group-removed,id="@var{id}"
25099 A thread group was either added or removed. The @var{id} field
25100 contains the @value{GDBN} identifier of the thread group. When a thread
25101 group is added, it generally might not be associated with a running
25102 process. When a thread group is removed, its id becomes invalid and
25103 cannot be used in any way.
25105 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
25106 A thread group became associated with a running program,
25107 either because the program was just started or the thread group
25108 was attached to a program. The @var{id} field contains the
25109 @value{GDBN} identifier of the thread group. The @var{pid} field
25110 contains process identifier, specific to the operating system.
25112 @itemx =thread-group-exited,id="@var{id}"
25113 A thread group is no longer associated with a running program,
25114 either because the program has exited, or because it was detached
25115 from. The @var{id} field contains the @value{GDBN} identifier of the
25118 @item =thread-created,id="@var{id}",group-id="@var{gid}"
25119 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
25120 A thread either was created, or has exited. The @var{id} field
25121 contains the @value{GDBN} identifier of the thread. The @var{gid}
25122 field identifies the thread group this thread belongs to.
25124 @item =thread-selected,id="@var{id}"
25125 Informs that the selected thread was changed as result of the last
25126 command. This notification is not emitted as result of @code{-thread-select}
25127 command but is emitted whenever an MI command that is not documented
25128 to change the selected thread actually changes it. In particular,
25129 invoking, directly or indirectly (via user-defined command), the CLI
25130 @code{thread} command, will generate this notification.
25132 We suggest that in response to this notification, front ends
25133 highlight the selected thread and cause subsequent commands to apply to
25136 @item =library-loaded,...
25137 Reports that a new library file was loaded by the program. This
25138 notification has 4 fields---@var{id}, @var{target-name},
25139 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
25140 opaque identifier of the library. For remote debugging case,
25141 @var{target-name} and @var{host-name} fields give the name of the
25142 library file on the target, and on the host respectively. For native
25143 debugging, both those fields have the same value. The
25144 @var{symbols-loaded} field is emitted only for backward compatibility
25145 and should not be relied on to convey any useful information. The
25146 @var{thread-group} field, if present, specifies the id of the thread
25147 group in whose context the library was loaded. If the field is
25148 absent, it means the library was loaded in the context of all present
25151 @item =library-unloaded,...
25152 Reports that a library was unloaded by the program. This notification
25153 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
25154 the same meaning as for the @code{=library-loaded} notification.
25155 The @var{thread-group} field, if present, specifies the id of the
25156 thread group in whose context the library was unloaded. If the field is
25157 absent, it means the library was unloaded in the context of all present
25162 @node GDB/MI Frame Information
25163 @subsection @sc{gdb/mi} Frame Information
25165 Response from many MI commands includes an information about stack
25166 frame. This information is a tuple that may have the following
25171 The level of the stack frame. The innermost frame has the level of
25172 zero. This field is always present.
25175 The name of the function corresponding to the frame. This field may
25176 be absent if @value{GDBN} is unable to determine the function name.
25179 The code address for the frame. This field is always present.
25182 The name of the source files that correspond to the frame's code
25183 address. This field may be absent.
25186 The source line corresponding to the frames' code address. This field
25190 The name of the binary file (either executable or shared library) the
25191 corresponds to the frame's code address. This field may be absent.
25195 @node GDB/MI Thread Information
25196 @subsection @sc{gdb/mi} Thread Information
25198 Whenever @value{GDBN} has to report an information about a thread, it
25199 uses a tuple with the following fields:
25203 The numeric id assigned to the thread by @value{GDBN}. This field is
25207 Target-specific string identifying the thread. This field is always present.
25210 Additional information about the thread provided by the target.
25211 It is supposed to be human-readable and not interpreted by the
25212 frontend. This field is optional.
25215 Either @samp{stopped} or @samp{running}, depending on whether the
25216 thread is presently running. This field is always present.
25219 The value of this field is an integer number of the processor core the
25220 thread was last seen on. This field is optional.
25223 @node GDB/MI Ada Exception Information
25224 @subsection @sc{gdb/mi} Ada Exception Information
25226 Whenever a @code{*stopped} record is emitted because the program
25227 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
25228 @value{GDBN} provides the name of the exception that was raised via
25229 the @code{exception-name} field.
25231 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25232 @node GDB/MI Simple Examples
25233 @section Simple Examples of @sc{gdb/mi} Interaction
25234 @cindex @sc{gdb/mi}, simple examples
25236 This subsection presents several simple examples of interaction using
25237 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
25238 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
25239 the output received from @sc{gdb/mi}.
25241 Note the line breaks shown in the examples are here only for
25242 readability, they don't appear in the real output.
25244 @subheading Setting a Breakpoint
25246 Setting a breakpoint generates synchronous output which contains detailed
25247 information of the breakpoint.
25250 -> -break-insert main
25251 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25252 enabled="y",addr="0x08048564",func="main",file="myprog.c",
25253 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
25257 @subheading Program Execution
25259 Program execution generates asynchronous records and MI gives the
25260 reason that execution stopped.
25266 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
25267 frame=@{addr="0x08048564",func="main",
25268 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
25269 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
25274 <- *stopped,reason="exited-normally"
25278 @subheading Quitting @value{GDBN}
25280 Quitting @value{GDBN} just prints the result class @samp{^exit}.
25288 Please note that @samp{^exit} is printed immediately, but it might
25289 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
25290 performs necessary cleanups, including killing programs being debugged
25291 or disconnecting from debug hardware, so the frontend should wait till
25292 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
25293 fails to exit in reasonable time.
25295 @subheading A Bad Command
25297 Here's what happens if you pass a non-existent command:
25301 <- ^error,msg="Undefined MI command: rubbish"
25306 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25307 @node GDB/MI Command Description Format
25308 @section @sc{gdb/mi} Command Description Format
25310 The remaining sections describe blocks of commands. Each block of
25311 commands is laid out in a fashion similar to this section.
25313 @subheading Motivation
25315 The motivation for this collection of commands.
25317 @subheading Introduction
25319 A brief introduction to this collection of commands as a whole.
25321 @subheading Commands
25323 For each command in the block, the following is described:
25325 @subsubheading Synopsis
25328 -command @var{args}@dots{}
25331 @subsubheading Result
25333 @subsubheading @value{GDBN} Command
25335 The corresponding @value{GDBN} CLI command(s), if any.
25337 @subsubheading Example
25339 Example(s) formatted for readability. Some of the described commands have
25340 not been implemented yet and these are labeled N.A.@: (not available).
25343 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25344 @node GDB/MI Breakpoint Commands
25345 @section @sc{gdb/mi} Breakpoint Commands
25347 @cindex breakpoint commands for @sc{gdb/mi}
25348 @cindex @sc{gdb/mi}, breakpoint commands
25349 This section documents @sc{gdb/mi} commands for manipulating
25352 @subheading The @code{-break-after} Command
25353 @findex -break-after
25355 @subsubheading Synopsis
25358 -break-after @var{number} @var{count}
25361 The breakpoint number @var{number} is not in effect until it has been
25362 hit @var{count} times. To see how this is reflected in the output of
25363 the @samp{-break-list} command, see the description of the
25364 @samp{-break-list} command below.
25366 @subsubheading @value{GDBN} Command
25368 The corresponding @value{GDBN} command is @samp{ignore}.
25370 @subsubheading Example
25375 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25376 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25377 fullname="/home/foo/hello.c",line="5",times="0"@}
25384 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25385 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25386 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25387 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25388 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25389 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25390 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25391 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25392 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25393 line="5",times="0",ignore="3"@}]@}
25398 @subheading The @code{-break-catch} Command
25399 @findex -break-catch
25402 @subheading The @code{-break-commands} Command
25403 @findex -break-commands
25405 @subsubheading Synopsis
25408 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
25411 Specifies the CLI commands that should be executed when breakpoint
25412 @var{number} is hit. The parameters @var{command1} to @var{commandN}
25413 are the commands. If no command is specified, any previously-set
25414 commands are cleared. @xref{Break Commands}. Typical use of this
25415 functionality is tracing a program, that is, printing of values of
25416 some variables whenever breakpoint is hit and then continuing.
25418 @subsubheading @value{GDBN} Command
25420 The corresponding @value{GDBN} command is @samp{commands}.
25422 @subsubheading Example
25427 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25428 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25429 fullname="/home/foo/hello.c",line="5",times="0"@}
25431 -break-commands 1 "print v" "continue"
25436 @subheading The @code{-break-condition} Command
25437 @findex -break-condition
25439 @subsubheading Synopsis
25442 -break-condition @var{number} @var{expr}
25445 Breakpoint @var{number} will stop the program only if the condition in
25446 @var{expr} is true. The condition becomes part of the
25447 @samp{-break-list} output (see the description of the @samp{-break-list}
25450 @subsubheading @value{GDBN} Command
25452 The corresponding @value{GDBN} command is @samp{condition}.
25454 @subsubheading Example
25458 -break-condition 1 1
25462 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25463 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25464 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25465 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25466 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25467 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25468 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25469 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25470 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25471 line="5",cond="1",times="0",ignore="3"@}]@}
25475 @subheading The @code{-break-delete} Command
25476 @findex -break-delete
25478 @subsubheading Synopsis
25481 -break-delete ( @var{breakpoint} )+
25484 Delete the breakpoint(s) whose number(s) are specified in the argument
25485 list. This is obviously reflected in the breakpoint list.
25487 @subsubheading @value{GDBN} Command
25489 The corresponding @value{GDBN} command is @samp{delete}.
25491 @subsubheading Example
25499 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
25500 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25501 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25502 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25503 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25504 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25505 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25510 @subheading The @code{-break-disable} Command
25511 @findex -break-disable
25513 @subsubheading Synopsis
25516 -break-disable ( @var{breakpoint} )+
25519 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
25520 break list is now set to @samp{n} for the named @var{breakpoint}(s).
25522 @subsubheading @value{GDBN} Command
25524 The corresponding @value{GDBN} command is @samp{disable}.
25526 @subsubheading Example
25534 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25535 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25536 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25537 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25538 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25539 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25540 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25541 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
25542 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25543 line="5",times="0"@}]@}
25547 @subheading The @code{-break-enable} Command
25548 @findex -break-enable
25550 @subsubheading Synopsis
25553 -break-enable ( @var{breakpoint} )+
25556 Enable (previously disabled) @var{breakpoint}(s).
25558 @subsubheading @value{GDBN} Command
25560 The corresponding @value{GDBN} command is @samp{enable}.
25562 @subsubheading Example
25570 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25571 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25572 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25573 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25574 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25575 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25576 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25577 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
25578 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25579 line="5",times="0"@}]@}
25583 @subheading The @code{-break-info} Command
25584 @findex -break-info
25586 @subsubheading Synopsis
25589 -break-info @var{breakpoint}
25593 Get information about a single breakpoint.
25595 @subsubheading @value{GDBN} Command
25597 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
25599 @subsubheading Example
25602 @subheading The @code{-break-insert} Command
25603 @findex -break-insert
25605 @subsubheading Synopsis
25608 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
25609 [ -c @var{condition} ] [ -i @var{ignore-count} ]
25610 [ -p @var{thread} ] [ @var{location} ]
25614 If specified, @var{location}, can be one of:
25621 @item filename:linenum
25622 @item filename:function
25626 The possible optional parameters of this command are:
25630 Insert a temporary breakpoint.
25632 Insert a hardware breakpoint.
25633 @item -c @var{condition}
25634 Make the breakpoint conditional on @var{condition}.
25635 @item -i @var{ignore-count}
25636 Initialize the @var{ignore-count}.
25638 If @var{location} cannot be parsed (for example if it
25639 refers to unknown files or functions), create a pending
25640 breakpoint. Without this flag, @value{GDBN} will report
25641 an error, and won't create a breakpoint, if @var{location}
25644 Create a disabled breakpoint.
25646 Create a tracepoint. @xref{Tracepoints}. When this parameter
25647 is used together with @samp{-h}, a fast tracepoint is created.
25650 @subsubheading Result
25652 The result is in the form:
25655 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
25656 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
25657 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
25658 times="@var{times}"@}
25662 where @var{number} is the @value{GDBN} number for this breakpoint,
25663 @var{funcname} is the name of the function where the breakpoint was
25664 inserted, @var{filename} is the name of the source file which contains
25665 this function, @var{lineno} is the source line number within that file
25666 and @var{times} the number of times that the breakpoint has been hit
25667 (always 0 for -break-insert but may be greater for -break-info or -break-list
25668 which use the same output).
25670 Note: this format is open to change.
25671 @c An out-of-band breakpoint instead of part of the result?
25673 @subsubheading @value{GDBN} Command
25675 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
25676 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
25678 @subsubheading Example
25683 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
25684 fullname="/home/foo/recursive2.c,line="4",times="0"@}
25686 -break-insert -t foo
25687 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
25688 fullname="/home/foo/recursive2.c,line="11",times="0"@}
25691 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25692 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25693 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25694 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25695 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25696 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25697 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25698 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25699 addr="0x0001072c", func="main",file="recursive2.c",
25700 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
25701 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
25702 addr="0x00010774",func="foo",file="recursive2.c",
25703 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
25705 -break-insert -r foo.*
25706 ~int foo(int, int);
25707 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
25708 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
25712 @subheading The @code{-break-list} Command
25713 @findex -break-list
25715 @subsubheading Synopsis
25721 Displays the list of inserted breakpoints, showing the following fields:
25725 number of the breakpoint
25727 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
25729 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
25732 is the breakpoint enabled or no: @samp{y} or @samp{n}
25734 memory location at which the breakpoint is set
25736 logical location of the breakpoint, expressed by function name, file
25739 number of times the breakpoint has been hit
25742 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
25743 @code{body} field is an empty list.
25745 @subsubheading @value{GDBN} Command
25747 The corresponding @value{GDBN} command is @samp{info break}.
25749 @subsubheading Example
25754 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25755 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25756 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25757 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25758 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25759 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25760 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25761 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25762 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
25763 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
25764 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
25765 line="13",times="0"@}]@}
25769 Here's an example of the result when there are no breakpoints:
25774 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
25775 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25776 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25777 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25778 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25779 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25780 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25785 @subheading The @code{-break-passcount} Command
25786 @findex -break-passcount
25788 @subsubheading Synopsis
25791 -break-passcount @var{tracepoint-number} @var{passcount}
25794 Set the passcount for tracepoint @var{tracepoint-number} to
25795 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
25796 is not a tracepoint, error is emitted. This corresponds to CLI
25797 command @samp{passcount}.
25799 @subheading The @code{-break-watch} Command
25800 @findex -break-watch
25802 @subsubheading Synopsis
25805 -break-watch [ -a | -r ]
25808 Create a watchpoint. With the @samp{-a} option it will create an
25809 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
25810 read from or on a write to the memory location. With the @samp{-r}
25811 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
25812 trigger only when the memory location is accessed for reading. Without
25813 either of the options, the watchpoint created is a regular watchpoint,
25814 i.e., it will trigger when the memory location is accessed for writing.
25815 @xref{Set Watchpoints, , Setting Watchpoints}.
25817 Note that @samp{-break-list} will report a single list of watchpoints and
25818 breakpoints inserted.
25820 @subsubheading @value{GDBN} Command
25822 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
25825 @subsubheading Example
25827 Setting a watchpoint on a variable in the @code{main} function:
25832 ^done,wpt=@{number="2",exp="x"@}
25837 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
25838 value=@{old="-268439212",new="55"@},
25839 frame=@{func="main",args=[],file="recursive2.c",
25840 fullname="/home/foo/bar/recursive2.c",line="5"@}
25844 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
25845 the program execution twice: first for the variable changing value, then
25846 for the watchpoint going out of scope.
25851 ^done,wpt=@{number="5",exp="C"@}
25856 *stopped,reason="watchpoint-trigger",
25857 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
25858 frame=@{func="callee4",args=[],
25859 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25860 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
25865 *stopped,reason="watchpoint-scope",wpnum="5",
25866 frame=@{func="callee3",args=[@{name="strarg",
25867 value="0x11940 \"A string argument.\""@}],
25868 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25869 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25873 Listing breakpoints and watchpoints, at different points in the program
25874 execution. Note that once the watchpoint goes out of scope, it is
25880 ^done,wpt=@{number="2",exp="C"@}
25883 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25884 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25885 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25886 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25887 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25888 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25889 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25890 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25891 addr="0x00010734",func="callee4",
25892 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25893 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
25894 bkpt=@{number="2",type="watchpoint",disp="keep",
25895 enabled="y",addr="",what="C",times="0"@}]@}
25900 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
25901 value=@{old="-276895068",new="3"@},
25902 frame=@{func="callee4",args=[],
25903 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25904 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
25907 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25908 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25909 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25910 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25911 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25912 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25913 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25914 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25915 addr="0x00010734",func="callee4",
25916 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25917 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
25918 bkpt=@{number="2",type="watchpoint",disp="keep",
25919 enabled="y",addr="",what="C",times="-5"@}]@}
25923 ^done,reason="watchpoint-scope",wpnum="2",
25924 frame=@{func="callee3",args=[@{name="strarg",
25925 value="0x11940 \"A string argument.\""@}],
25926 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25927 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25930 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25931 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25932 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25933 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25934 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25935 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25936 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25937 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25938 addr="0x00010734",func="callee4",
25939 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25940 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
25945 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25946 @node GDB/MI Program Context
25947 @section @sc{gdb/mi} Program Context
25949 @subheading The @code{-exec-arguments} Command
25950 @findex -exec-arguments
25953 @subsubheading Synopsis
25956 -exec-arguments @var{args}
25959 Set the inferior program arguments, to be used in the next
25962 @subsubheading @value{GDBN} Command
25964 The corresponding @value{GDBN} command is @samp{set args}.
25966 @subsubheading Example
25970 -exec-arguments -v word
25977 @subheading The @code{-exec-show-arguments} Command
25978 @findex -exec-show-arguments
25980 @subsubheading Synopsis
25983 -exec-show-arguments
25986 Print the arguments of the program.
25988 @subsubheading @value{GDBN} Command
25990 The corresponding @value{GDBN} command is @samp{show args}.
25992 @subsubheading Example
25997 @subheading The @code{-environment-cd} Command
25998 @findex -environment-cd
26000 @subsubheading Synopsis
26003 -environment-cd @var{pathdir}
26006 Set @value{GDBN}'s working directory.
26008 @subsubheading @value{GDBN} Command
26010 The corresponding @value{GDBN} command is @samp{cd}.
26012 @subsubheading Example
26016 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26022 @subheading The @code{-environment-directory} Command
26023 @findex -environment-directory
26025 @subsubheading Synopsis
26028 -environment-directory [ -r ] [ @var{pathdir} ]+
26031 Add directories @var{pathdir} to beginning of search path for source files.
26032 If the @samp{-r} option is used, the search path is reset to the default
26033 search path. If directories @var{pathdir} are supplied in addition to the
26034 @samp{-r} option, the search path is first reset and then addition
26036 Multiple directories may be specified, separated by blanks. Specifying
26037 multiple directories in a single command
26038 results in the directories added to the beginning of the
26039 search path in the same order they were presented in the command.
26040 If blanks are needed as
26041 part of a directory name, double-quotes should be used around
26042 the name. In the command output, the path will show up separated
26043 by the system directory-separator character. The directory-separator
26044 character must not be used
26045 in any directory name.
26046 If no directories are specified, the current search path is displayed.
26048 @subsubheading @value{GDBN} Command
26050 The corresponding @value{GDBN} command is @samp{dir}.
26052 @subsubheading Example
26056 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26057 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26059 -environment-directory ""
26060 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26062 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
26063 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
26065 -environment-directory -r
26066 ^done,source-path="$cdir:$cwd"
26071 @subheading The @code{-environment-path} Command
26072 @findex -environment-path
26074 @subsubheading Synopsis
26077 -environment-path [ -r ] [ @var{pathdir} ]+
26080 Add directories @var{pathdir} to beginning of search path for object files.
26081 If the @samp{-r} option is used, the search path is reset to the original
26082 search path that existed at gdb start-up. If directories @var{pathdir} are
26083 supplied in addition to the
26084 @samp{-r} option, the search path is first reset and then addition
26086 Multiple directories may be specified, separated by blanks. Specifying
26087 multiple directories in a single command
26088 results in the directories added to the beginning of the
26089 search path in the same order they were presented in the command.
26090 If blanks are needed as
26091 part of a directory name, double-quotes should be used around
26092 the name. In the command output, the path will show up separated
26093 by the system directory-separator character. The directory-separator
26094 character must not be used
26095 in any directory name.
26096 If no directories are specified, the current path is displayed.
26099 @subsubheading @value{GDBN} Command
26101 The corresponding @value{GDBN} command is @samp{path}.
26103 @subsubheading Example
26108 ^done,path="/usr/bin"
26110 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
26111 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
26113 -environment-path -r /usr/local/bin
26114 ^done,path="/usr/local/bin:/usr/bin"
26119 @subheading The @code{-environment-pwd} Command
26120 @findex -environment-pwd
26122 @subsubheading Synopsis
26128 Show the current working directory.
26130 @subsubheading @value{GDBN} Command
26132 The corresponding @value{GDBN} command is @samp{pwd}.
26134 @subsubheading Example
26139 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
26143 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26144 @node GDB/MI Thread Commands
26145 @section @sc{gdb/mi} Thread Commands
26148 @subheading The @code{-thread-info} Command
26149 @findex -thread-info
26151 @subsubheading Synopsis
26154 -thread-info [ @var{thread-id} ]
26157 Reports information about either a specific thread, if
26158 the @var{thread-id} parameter is present, or about all
26159 threads. When printing information about all threads,
26160 also reports the current thread.
26162 @subsubheading @value{GDBN} Command
26164 The @samp{info thread} command prints the same information
26167 @subsubheading Result
26169 The result is a list of threads. The following attributes are
26170 defined for a given thread:
26174 This field exists only for the current thread. It has the value @samp{*}.
26177 The identifier that @value{GDBN} uses to refer to the thread.
26180 The identifier that the target uses to refer to the thread.
26183 Extra information about the thread, in a target-specific format. This
26187 The name of the thread. If the user specified a name using the
26188 @code{thread name} command, then this name is given. Otherwise, if
26189 @value{GDBN} can extract the thread name from the target, then that
26190 name is given. If @value{GDBN} cannot find the thread name, then this
26194 The stack frame currently executing in the thread.
26197 The thread's state. The @samp{state} field may have the following
26202 The thread is stopped. Frame information is available for stopped
26206 The thread is running. There's no frame information for running
26212 If @value{GDBN} can find the CPU core on which this thread is running,
26213 then this field is the core identifier. This field is optional.
26217 @subsubheading Example
26222 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
26223 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
26224 args=[]@},state="running"@},
26225 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
26226 frame=@{level="0",addr="0x0804891f",func="foo",
26227 args=[@{name="i",value="10"@}],
26228 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
26229 state="running"@}],
26230 current-thread-id="1"
26234 @subheading The @code{-thread-list-ids} Command
26235 @findex -thread-list-ids
26237 @subsubheading Synopsis
26243 Produces a list of the currently known @value{GDBN} thread ids. At the
26244 end of the list it also prints the total number of such threads.
26246 This command is retained for historical reasons, the
26247 @code{-thread-info} command should be used instead.
26249 @subsubheading @value{GDBN} Command
26251 Part of @samp{info threads} supplies the same information.
26253 @subsubheading Example
26258 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26259 current-thread-id="1",number-of-threads="3"
26264 @subheading The @code{-thread-select} Command
26265 @findex -thread-select
26267 @subsubheading Synopsis
26270 -thread-select @var{threadnum}
26273 Make @var{threadnum} the current thread. It prints the number of the new
26274 current thread, and the topmost frame for that thread.
26276 This command is deprecated in favor of explicitly using the
26277 @samp{--thread} option to each command.
26279 @subsubheading @value{GDBN} Command
26281 The corresponding @value{GDBN} command is @samp{thread}.
26283 @subsubheading Example
26290 *stopped,reason="end-stepping-range",thread-id="2",line="187",
26291 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
26295 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26296 number-of-threads="3"
26299 ^done,new-thread-id="3",
26300 frame=@{level="0",func="vprintf",
26301 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
26302 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
26306 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26307 @node GDB/MI Program Execution
26308 @section @sc{gdb/mi} Program Execution
26310 These are the asynchronous commands which generate the out-of-band
26311 record @samp{*stopped}. Currently @value{GDBN} only really executes
26312 asynchronously with remote targets and this interaction is mimicked in
26315 @subheading The @code{-exec-continue} Command
26316 @findex -exec-continue
26318 @subsubheading Synopsis
26321 -exec-continue [--reverse] [--all|--thread-group N]
26324 Resumes the execution of the inferior program, which will continue
26325 to execute until it reaches a debugger stop event. If the
26326 @samp{--reverse} option is specified, execution resumes in reverse until
26327 it reaches a stop event. Stop events may include
26330 breakpoints or watchpoints
26332 signals or exceptions
26334 the end of the process (or its beginning under @samp{--reverse})
26336 the end or beginning of a replay log if one is being used.
26338 In all-stop mode (@pxref{All-Stop
26339 Mode}), may resume only one thread, or all threads, depending on the
26340 value of the @samp{scheduler-locking} variable. If @samp{--all} is
26341 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
26342 ignored in all-stop mode. If the @samp{--thread-group} options is
26343 specified, then all threads in that thread group are resumed.
26345 @subsubheading @value{GDBN} Command
26347 The corresponding @value{GDBN} corresponding is @samp{continue}.
26349 @subsubheading Example
26356 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
26357 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
26363 @subheading The @code{-exec-finish} Command
26364 @findex -exec-finish
26366 @subsubheading Synopsis
26369 -exec-finish [--reverse]
26372 Resumes the execution of the inferior program until the current
26373 function is exited. Displays the results returned by the function.
26374 If the @samp{--reverse} option is specified, resumes the reverse
26375 execution of the inferior program until the point where current
26376 function was called.
26378 @subsubheading @value{GDBN} Command
26380 The corresponding @value{GDBN} command is @samp{finish}.
26382 @subsubheading Example
26384 Function returning @code{void}.
26391 *stopped,reason="function-finished",frame=@{func="main",args=[],
26392 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
26396 Function returning other than @code{void}. The name of the internal
26397 @value{GDBN} variable storing the result is printed, together with the
26404 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
26405 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
26406 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26407 gdb-result-var="$1",return-value="0"
26412 @subheading The @code{-exec-interrupt} Command
26413 @findex -exec-interrupt
26415 @subsubheading Synopsis
26418 -exec-interrupt [--all|--thread-group N]
26421 Interrupts the background execution of the target. Note how the token
26422 associated with the stop message is the one for the execution command
26423 that has been interrupted. The token for the interrupt itself only
26424 appears in the @samp{^done} output. If the user is trying to
26425 interrupt a non-running program, an error message will be printed.
26427 Note that when asynchronous execution is enabled, this command is
26428 asynchronous just like other execution commands. That is, first the
26429 @samp{^done} response will be printed, and the target stop will be
26430 reported after that using the @samp{*stopped} notification.
26432 In non-stop mode, only the context thread is interrupted by default.
26433 All threads (in all inferiors) will be interrupted if the
26434 @samp{--all} option is specified. If the @samp{--thread-group}
26435 option is specified, all threads in that group will be interrupted.
26437 @subsubheading @value{GDBN} Command
26439 The corresponding @value{GDBN} command is @samp{interrupt}.
26441 @subsubheading Example
26452 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
26453 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
26454 fullname="/home/foo/bar/try.c",line="13"@}
26459 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
26463 @subheading The @code{-exec-jump} Command
26466 @subsubheading Synopsis
26469 -exec-jump @var{location}
26472 Resumes execution of the inferior program at the location specified by
26473 parameter. @xref{Specify Location}, for a description of the
26474 different forms of @var{location}.
26476 @subsubheading @value{GDBN} Command
26478 The corresponding @value{GDBN} command is @samp{jump}.
26480 @subsubheading Example
26483 -exec-jump foo.c:10
26484 *running,thread-id="all"
26489 @subheading The @code{-exec-next} Command
26492 @subsubheading Synopsis
26495 -exec-next [--reverse]
26498 Resumes execution of the inferior program, stopping when the beginning
26499 of the next source line is reached.
26501 If the @samp{--reverse} option is specified, resumes reverse execution
26502 of the inferior program, stopping at the beginning of the previous
26503 source line. If you issue this command on the first line of a
26504 function, it will take you back to the caller of that function, to the
26505 source line where the function was called.
26508 @subsubheading @value{GDBN} Command
26510 The corresponding @value{GDBN} command is @samp{next}.
26512 @subsubheading Example
26518 *stopped,reason="end-stepping-range",line="8",file="hello.c"
26523 @subheading The @code{-exec-next-instruction} Command
26524 @findex -exec-next-instruction
26526 @subsubheading Synopsis
26529 -exec-next-instruction [--reverse]
26532 Executes one machine instruction. If the instruction is a function
26533 call, continues until the function returns. If the program stops at an
26534 instruction in the middle of a source line, the address will be
26537 If the @samp{--reverse} option is specified, resumes reverse execution
26538 of the inferior program, stopping at the previous instruction. If the
26539 previously executed instruction was a return from another function,
26540 it will continue to execute in reverse until the call to that function
26541 (from the current stack frame) is reached.
26543 @subsubheading @value{GDBN} Command
26545 The corresponding @value{GDBN} command is @samp{nexti}.
26547 @subsubheading Example
26551 -exec-next-instruction
26555 *stopped,reason="end-stepping-range",
26556 addr="0x000100d4",line="5",file="hello.c"
26561 @subheading The @code{-exec-return} Command
26562 @findex -exec-return
26564 @subsubheading Synopsis
26570 Makes current function return immediately. Doesn't execute the inferior.
26571 Displays the new current frame.
26573 @subsubheading @value{GDBN} Command
26575 The corresponding @value{GDBN} command is @samp{return}.
26577 @subsubheading Example
26581 200-break-insert callee4
26582 200^done,bkpt=@{number="1",addr="0x00010734",
26583 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
26588 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
26589 frame=@{func="callee4",args=[],
26590 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26591 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
26597 111^done,frame=@{level="0",func="callee3",
26598 args=[@{name="strarg",
26599 value="0x11940 \"A string argument.\""@}],
26600 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26601 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26606 @subheading The @code{-exec-run} Command
26609 @subsubheading Synopsis
26612 -exec-run [--all | --thread-group N]
26615 Starts execution of the inferior from the beginning. The inferior
26616 executes until either a breakpoint is encountered or the program
26617 exits. In the latter case the output will include an exit code, if
26618 the program has exited exceptionally.
26620 When no option is specified, the current inferior is started. If the
26621 @samp{--thread-group} option is specified, it should refer to a thread
26622 group of type @samp{process}, and that thread group will be started.
26623 If the @samp{--all} option is specified, then all inferiors will be started.
26625 @subsubheading @value{GDBN} Command
26627 The corresponding @value{GDBN} command is @samp{run}.
26629 @subsubheading Examples
26634 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
26639 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
26640 frame=@{func="main",args=[],file="recursive2.c",
26641 fullname="/home/foo/bar/recursive2.c",line="4"@}
26646 Program exited normally:
26654 *stopped,reason="exited-normally"
26659 Program exited exceptionally:
26667 *stopped,reason="exited",exit-code="01"
26671 Another way the program can terminate is if it receives a signal such as
26672 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
26676 *stopped,reason="exited-signalled",signal-name="SIGINT",
26677 signal-meaning="Interrupt"
26681 @c @subheading -exec-signal
26684 @subheading The @code{-exec-step} Command
26687 @subsubheading Synopsis
26690 -exec-step [--reverse]
26693 Resumes execution of the inferior program, stopping when the beginning
26694 of the next source line is reached, if the next source line is not a
26695 function call. If it is, stop at the first instruction of the called
26696 function. If the @samp{--reverse} option is specified, resumes reverse
26697 execution of the inferior program, stopping at the beginning of the
26698 previously executed source line.
26700 @subsubheading @value{GDBN} Command
26702 The corresponding @value{GDBN} command is @samp{step}.
26704 @subsubheading Example
26706 Stepping into a function:
26712 *stopped,reason="end-stepping-range",
26713 frame=@{func="foo",args=[@{name="a",value="10"@},
26714 @{name="b",value="0"@}],file="recursive2.c",
26715 fullname="/home/foo/bar/recursive2.c",line="11"@}
26725 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
26730 @subheading The @code{-exec-step-instruction} Command
26731 @findex -exec-step-instruction
26733 @subsubheading Synopsis
26736 -exec-step-instruction [--reverse]
26739 Resumes the inferior which executes one machine instruction. If the
26740 @samp{--reverse} option is specified, resumes reverse execution of the
26741 inferior program, stopping at the previously executed instruction.
26742 The output, once @value{GDBN} has stopped, will vary depending on
26743 whether we have stopped in the middle of a source line or not. In the
26744 former case, the address at which the program stopped will be printed
26747 @subsubheading @value{GDBN} Command
26749 The corresponding @value{GDBN} command is @samp{stepi}.
26751 @subsubheading Example
26755 -exec-step-instruction
26759 *stopped,reason="end-stepping-range",
26760 frame=@{func="foo",args=[],file="try.c",
26761 fullname="/home/foo/bar/try.c",line="10"@}
26763 -exec-step-instruction
26767 *stopped,reason="end-stepping-range",
26768 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
26769 fullname="/home/foo/bar/try.c",line="10"@}
26774 @subheading The @code{-exec-until} Command
26775 @findex -exec-until
26777 @subsubheading Synopsis
26780 -exec-until [ @var{location} ]
26783 Executes the inferior until the @var{location} specified in the
26784 argument is reached. If there is no argument, the inferior executes
26785 until a source line greater than the current one is reached. The
26786 reason for stopping in this case will be @samp{location-reached}.
26788 @subsubheading @value{GDBN} Command
26790 The corresponding @value{GDBN} command is @samp{until}.
26792 @subsubheading Example
26796 -exec-until recursive2.c:6
26800 *stopped,reason="location-reached",frame=@{func="main",args=[],
26801 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
26806 @subheading -file-clear
26807 Is this going away????
26810 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26811 @node GDB/MI Stack Manipulation
26812 @section @sc{gdb/mi} Stack Manipulation Commands
26815 @subheading The @code{-stack-info-frame} Command
26816 @findex -stack-info-frame
26818 @subsubheading Synopsis
26824 Get info on the selected frame.
26826 @subsubheading @value{GDBN} Command
26828 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
26829 (without arguments).
26831 @subsubheading Example
26836 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
26837 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26838 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
26842 @subheading The @code{-stack-info-depth} Command
26843 @findex -stack-info-depth
26845 @subsubheading Synopsis
26848 -stack-info-depth [ @var{max-depth} ]
26851 Return the depth of the stack. If the integer argument @var{max-depth}
26852 is specified, do not count beyond @var{max-depth} frames.
26854 @subsubheading @value{GDBN} Command
26856 There's no equivalent @value{GDBN} command.
26858 @subsubheading Example
26860 For a stack with frame levels 0 through 11:
26867 -stack-info-depth 4
26870 -stack-info-depth 12
26873 -stack-info-depth 11
26876 -stack-info-depth 13
26881 @subheading The @code{-stack-list-arguments} Command
26882 @findex -stack-list-arguments
26884 @subsubheading Synopsis
26887 -stack-list-arguments @var{print-values}
26888 [ @var{low-frame} @var{high-frame} ]
26891 Display a list of the arguments for the frames between @var{low-frame}
26892 and @var{high-frame} (inclusive). If @var{low-frame} and
26893 @var{high-frame} are not provided, list the arguments for the whole
26894 call stack. If the two arguments are equal, show the single frame
26895 at the corresponding level. It is an error if @var{low-frame} is
26896 larger than the actual number of frames. On the other hand,
26897 @var{high-frame} may be larger than the actual number of frames, in
26898 which case only existing frames will be returned.
26900 If @var{print-values} is 0 or @code{--no-values}, print only the names of
26901 the variables; if it is 1 or @code{--all-values}, print also their
26902 values; and if it is 2 or @code{--simple-values}, print the name,
26903 type and value for simple data types, and the name and type for arrays,
26904 structures and unions.
26906 Use of this command to obtain arguments in a single frame is
26907 deprecated in favor of the @samp{-stack-list-variables} command.
26909 @subsubheading @value{GDBN} Command
26911 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
26912 @samp{gdb_get_args} command which partially overlaps with the
26913 functionality of @samp{-stack-list-arguments}.
26915 @subsubheading Example
26922 frame=@{level="0",addr="0x00010734",func="callee4",
26923 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26924 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
26925 frame=@{level="1",addr="0x0001076c",func="callee3",
26926 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26927 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
26928 frame=@{level="2",addr="0x0001078c",func="callee2",
26929 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26930 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
26931 frame=@{level="3",addr="0x000107b4",func="callee1",
26932 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26933 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
26934 frame=@{level="4",addr="0x000107e0",func="main",
26935 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26936 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
26938 -stack-list-arguments 0
26941 frame=@{level="0",args=[]@},
26942 frame=@{level="1",args=[name="strarg"]@},
26943 frame=@{level="2",args=[name="intarg",name="strarg"]@},
26944 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
26945 frame=@{level="4",args=[]@}]
26947 -stack-list-arguments 1
26950 frame=@{level="0",args=[]@},
26952 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
26953 frame=@{level="2",args=[
26954 @{name="intarg",value="2"@},
26955 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
26956 @{frame=@{level="3",args=[
26957 @{name="intarg",value="2"@},
26958 @{name="strarg",value="0x11940 \"A string argument.\""@},
26959 @{name="fltarg",value="3.5"@}]@},
26960 frame=@{level="4",args=[]@}]
26962 -stack-list-arguments 0 2 2
26963 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
26965 -stack-list-arguments 1 2 2
26966 ^done,stack-args=[frame=@{level="2",
26967 args=[@{name="intarg",value="2"@},
26968 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
26972 @c @subheading -stack-list-exception-handlers
26975 @subheading The @code{-stack-list-frames} Command
26976 @findex -stack-list-frames
26978 @subsubheading Synopsis
26981 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
26984 List the frames currently on the stack. For each frame it displays the
26989 The frame number, 0 being the topmost frame, i.e., the innermost function.
26991 The @code{$pc} value for that frame.
26995 File name of the source file where the function lives.
26996 @item @var{fullname}
26997 The full file name of the source file where the function lives.
26999 Line number corresponding to the @code{$pc}.
27001 The shared library where this function is defined. This is only given
27002 if the frame's function is not known.
27005 If invoked without arguments, this command prints a backtrace for the
27006 whole stack. If given two integer arguments, it shows the frames whose
27007 levels are between the two arguments (inclusive). If the two arguments
27008 are equal, it shows the single frame at the corresponding level. It is
27009 an error if @var{low-frame} is larger than the actual number of
27010 frames. On the other hand, @var{high-frame} may be larger than the
27011 actual number of frames, in which case only existing frames will be returned.
27013 @subsubheading @value{GDBN} Command
27015 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
27017 @subsubheading Example
27019 Full stack backtrace:
27025 [frame=@{level="0",addr="0x0001076c",func="foo",
27026 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
27027 frame=@{level="1",addr="0x000107a4",func="foo",
27028 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27029 frame=@{level="2",addr="0x000107a4",func="foo",
27030 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27031 frame=@{level="3",addr="0x000107a4",func="foo",
27032 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27033 frame=@{level="4",addr="0x000107a4",func="foo",
27034 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27035 frame=@{level="5",addr="0x000107a4",func="foo",
27036 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27037 frame=@{level="6",addr="0x000107a4",func="foo",
27038 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27039 frame=@{level="7",addr="0x000107a4",func="foo",
27040 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27041 frame=@{level="8",addr="0x000107a4",func="foo",
27042 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27043 frame=@{level="9",addr="0x000107a4",func="foo",
27044 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27045 frame=@{level="10",addr="0x000107a4",func="foo",
27046 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27047 frame=@{level="11",addr="0x00010738",func="main",
27048 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
27052 Show frames between @var{low_frame} and @var{high_frame}:
27056 -stack-list-frames 3 5
27058 [frame=@{level="3",addr="0x000107a4",func="foo",
27059 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27060 frame=@{level="4",addr="0x000107a4",func="foo",
27061 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27062 frame=@{level="5",addr="0x000107a4",func="foo",
27063 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27067 Show a single frame:
27071 -stack-list-frames 3 3
27073 [frame=@{level="3",addr="0x000107a4",func="foo",
27074 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27079 @subheading The @code{-stack-list-locals} Command
27080 @findex -stack-list-locals
27082 @subsubheading Synopsis
27085 -stack-list-locals @var{print-values}
27088 Display the local variable names for the selected frame. If
27089 @var{print-values} is 0 or @code{--no-values}, print only the names of
27090 the variables; if it is 1 or @code{--all-values}, print also their
27091 values; and if it is 2 or @code{--simple-values}, print the name,
27092 type and value for simple data types, and the name and type for arrays,
27093 structures and unions. In this last case, a frontend can immediately
27094 display the value of simple data types and create variable objects for
27095 other data types when the user wishes to explore their values in
27098 This command is deprecated in favor of the
27099 @samp{-stack-list-variables} command.
27101 @subsubheading @value{GDBN} Command
27103 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
27105 @subsubheading Example
27109 -stack-list-locals 0
27110 ^done,locals=[name="A",name="B",name="C"]
27112 -stack-list-locals --all-values
27113 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
27114 @{name="C",value="@{1, 2, 3@}"@}]
27115 -stack-list-locals --simple-values
27116 ^done,locals=[@{name="A",type="int",value="1"@},
27117 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
27121 @subheading The @code{-stack-list-variables} Command
27122 @findex -stack-list-variables
27124 @subsubheading Synopsis
27127 -stack-list-variables @var{print-values}
27130 Display the names of local variables and function arguments for the selected frame. If
27131 @var{print-values} is 0 or @code{--no-values}, print only the names of
27132 the variables; if it is 1 or @code{--all-values}, print also their
27133 values; and if it is 2 or @code{--simple-values}, print the name,
27134 type and value for simple data types, and the name and type for arrays,
27135 structures and unions.
27137 @subsubheading Example
27141 -stack-list-variables --thread 1 --frame 0 --all-values
27142 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
27147 @subheading The @code{-stack-select-frame} Command
27148 @findex -stack-select-frame
27150 @subsubheading Synopsis
27153 -stack-select-frame @var{framenum}
27156 Change the selected frame. Select a different frame @var{framenum} on
27159 This command in deprecated in favor of passing the @samp{--frame}
27160 option to every command.
27162 @subsubheading @value{GDBN} Command
27164 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
27165 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
27167 @subsubheading Example
27171 -stack-select-frame 2
27176 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27177 @node GDB/MI Variable Objects
27178 @section @sc{gdb/mi} Variable Objects
27182 @subheading Motivation for Variable Objects in @sc{gdb/mi}
27184 For the implementation of a variable debugger window (locals, watched
27185 expressions, etc.), we are proposing the adaptation of the existing code
27186 used by @code{Insight}.
27188 The two main reasons for that are:
27192 It has been proven in practice (it is already on its second generation).
27195 It will shorten development time (needless to say how important it is
27199 The original interface was designed to be used by Tcl code, so it was
27200 slightly changed so it could be used through @sc{gdb/mi}. This section
27201 describes the @sc{gdb/mi} operations that will be available and gives some
27202 hints about their use.
27204 @emph{Note}: In addition to the set of operations described here, we
27205 expect the @sc{gui} implementation of a variable window to require, at
27206 least, the following operations:
27209 @item @code{-gdb-show} @code{output-radix}
27210 @item @code{-stack-list-arguments}
27211 @item @code{-stack-list-locals}
27212 @item @code{-stack-select-frame}
27217 @subheading Introduction to Variable Objects
27219 @cindex variable objects in @sc{gdb/mi}
27221 Variable objects are "object-oriented" MI interface for examining and
27222 changing values of expressions. Unlike some other MI interfaces that
27223 work with expressions, variable objects are specifically designed for
27224 simple and efficient presentation in the frontend. A variable object
27225 is identified by string name. When a variable object is created, the
27226 frontend specifies the expression for that variable object. The
27227 expression can be a simple variable, or it can be an arbitrary complex
27228 expression, and can even involve CPU registers. After creating a
27229 variable object, the frontend can invoke other variable object
27230 operations---for example to obtain or change the value of a variable
27231 object, or to change display format.
27233 Variable objects have hierarchical tree structure. Any variable object
27234 that corresponds to a composite type, such as structure in C, has
27235 a number of child variable objects, for example corresponding to each
27236 element of a structure. A child variable object can itself have
27237 children, recursively. Recursion ends when we reach
27238 leaf variable objects, which always have built-in types. Child variable
27239 objects are created only by explicit request, so if a frontend
27240 is not interested in the children of a particular variable object, no
27241 child will be created.
27243 For a leaf variable object it is possible to obtain its value as a
27244 string, or set the value from a string. String value can be also
27245 obtained for a non-leaf variable object, but it's generally a string
27246 that only indicates the type of the object, and does not list its
27247 contents. Assignment to a non-leaf variable object is not allowed.
27249 A frontend does not need to read the values of all variable objects each time
27250 the program stops. Instead, MI provides an update command that lists all
27251 variable objects whose values has changed since the last update
27252 operation. This considerably reduces the amount of data that must
27253 be transferred to the frontend. As noted above, children variable
27254 objects are created on demand, and only leaf variable objects have a
27255 real value. As result, gdb will read target memory only for leaf
27256 variables that frontend has created.
27258 The automatic update is not always desirable. For example, a frontend
27259 might want to keep a value of some expression for future reference,
27260 and never update it. For another example, fetching memory is
27261 relatively slow for embedded targets, so a frontend might want
27262 to disable automatic update for the variables that are either not
27263 visible on the screen, or ``closed''. This is possible using so
27264 called ``frozen variable objects''. Such variable objects are never
27265 implicitly updated.
27267 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
27268 fixed variable object, the expression is parsed when the variable
27269 object is created, including associating identifiers to specific
27270 variables. The meaning of expression never changes. For a floating
27271 variable object the values of variables whose names appear in the
27272 expressions are re-evaluated every time in the context of the current
27273 frame. Consider this example:
27278 struct work_state state;
27285 If a fixed variable object for the @code{state} variable is created in
27286 this function, and we enter the recursive call, the variable
27287 object will report the value of @code{state} in the top-level
27288 @code{do_work} invocation. On the other hand, a floating variable
27289 object will report the value of @code{state} in the current frame.
27291 If an expression specified when creating a fixed variable object
27292 refers to a local variable, the variable object becomes bound to the
27293 thread and frame in which the variable object is created. When such
27294 variable object is updated, @value{GDBN} makes sure that the
27295 thread/frame combination the variable object is bound to still exists,
27296 and re-evaluates the variable object in context of that thread/frame.
27298 The following is the complete set of @sc{gdb/mi} operations defined to
27299 access this functionality:
27301 @multitable @columnfractions .4 .6
27302 @item @strong{Operation}
27303 @tab @strong{Description}
27305 @item @code{-enable-pretty-printing}
27306 @tab enable Python-based pretty-printing
27307 @item @code{-var-create}
27308 @tab create a variable object
27309 @item @code{-var-delete}
27310 @tab delete the variable object and/or its children
27311 @item @code{-var-set-format}
27312 @tab set the display format of this variable
27313 @item @code{-var-show-format}
27314 @tab show the display format of this variable
27315 @item @code{-var-info-num-children}
27316 @tab tells how many children this object has
27317 @item @code{-var-list-children}
27318 @tab return a list of the object's children
27319 @item @code{-var-info-type}
27320 @tab show the type of this variable object
27321 @item @code{-var-info-expression}
27322 @tab print parent-relative expression that this variable object represents
27323 @item @code{-var-info-path-expression}
27324 @tab print full expression that this variable object represents
27325 @item @code{-var-show-attributes}
27326 @tab is this variable editable? does it exist here?
27327 @item @code{-var-evaluate-expression}
27328 @tab get the value of this variable
27329 @item @code{-var-assign}
27330 @tab set the value of this variable
27331 @item @code{-var-update}
27332 @tab update the variable and its children
27333 @item @code{-var-set-frozen}
27334 @tab set frozeness attribute
27335 @item @code{-var-set-update-range}
27336 @tab set range of children to display on update
27339 In the next subsection we describe each operation in detail and suggest
27340 how it can be used.
27342 @subheading Description And Use of Operations on Variable Objects
27344 @subheading The @code{-enable-pretty-printing} Command
27345 @findex -enable-pretty-printing
27348 -enable-pretty-printing
27351 @value{GDBN} allows Python-based visualizers to affect the output of the
27352 MI variable object commands. However, because there was no way to
27353 implement this in a fully backward-compatible way, a front end must
27354 request that this functionality be enabled.
27356 Once enabled, this feature cannot be disabled.
27358 Note that if Python support has not been compiled into @value{GDBN},
27359 this command will still succeed (and do nothing).
27361 This feature is currently (as of @value{GDBN} 7.0) experimental, and
27362 may work differently in future versions of @value{GDBN}.
27364 @subheading The @code{-var-create} Command
27365 @findex -var-create
27367 @subsubheading Synopsis
27370 -var-create @{@var{name} | "-"@}
27371 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
27374 This operation creates a variable object, which allows the monitoring of
27375 a variable, the result of an expression, a memory cell or a CPU
27378 The @var{name} parameter is the string by which the object can be
27379 referenced. It must be unique. If @samp{-} is specified, the varobj
27380 system will generate a string ``varNNNNNN'' automatically. It will be
27381 unique provided that one does not specify @var{name} of that format.
27382 The command fails if a duplicate name is found.
27384 The frame under which the expression should be evaluated can be
27385 specified by @var{frame-addr}. A @samp{*} indicates that the current
27386 frame should be used. A @samp{@@} indicates that a floating variable
27387 object must be created.
27389 @var{expression} is any expression valid on the current language set (must not
27390 begin with a @samp{*}), or one of the following:
27394 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
27397 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
27400 @samp{$@var{regname}} --- a CPU register name
27403 @cindex dynamic varobj
27404 A varobj's contents may be provided by a Python-based pretty-printer. In this
27405 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
27406 have slightly different semantics in some cases. If the
27407 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
27408 will never create a dynamic varobj. This ensures backward
27409 compatibility for existing clients.
27411 @subsubheading Result
27413 This operation returns attributes of the newly-created varobj. These
27418 The name of the varobj.
27421 The number of children of the varobj. This number is not necessarily
27422 reliable for a dynamic varobj. Instead, you must examine the
27423 @samp{has_more} attribute.
27426 The varobj's scalar value. For a varobj whose type is some sort of
27427 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
27428 will not be interesting.
27431 The varobj's type. This is a string representation of the type, as
27432 would be printed by the @value{GDBN} CLI.
27435 If a variable object is bound to a specific thread, then this is the
27436 thread's identifier.
27439 For a dynamic varobj, this indicates whether there appear to be any
27440 children available. For a non-dynamic varobj, this will be 0.
27443 This attribute will be present and have the value @samp{1} if the
27444 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
27445 then this attribute will not be present.
27448 A dynamic varobj can supply a display hint to the front end. The
27449 value comes directly from the Python pretty-printer object's
27450 @code{display_hint} method. @xref{Pretty Printing API}.
27453 Typical output will look like this:
27456 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
27457 has_more="@var{has_more}"
27461 @subheading The @code{-var-delete} Command
27462 @findex -var-delete
27464 @subsubheading Synopsis
27467 -var-delete [ -c ] @var{name}
27470 Deletes a previously created variable object and all of its children.
27471 With the @samp{-c} option, just deletes the children.
27473 Returns an error if the object @var{name} is not found.
27476 @subheading The @code{-var-set-format} Command
27477 @findex -var-set-format
27479 @subsubheading Synopsis
27482 -var-set-format @var{name} @var{format-spec}
27485 Sets the output format for the value of the object @var{name} to be
27488 @anchor{-var-set-format}
27489 The syntax for the @var{format-spec} is as follows:
27492 @var{format-spec} @expansion{}
27493 @{binary | decimal | hexadecimal | octal | natural@}
27496 The natural format is the default format choosen automatically
27497 based on the variable type (like decimal for an @code{int}, hex
27498 for pointers, etc.).
27500 For a variable with children, the format is set only on the
27501 variable itself, and the children are not affected.
27503 @subheading The @code{-var-show-format} Command
27504 @findex -var-show-format
27506 @subsubheading Synopsis
27509 -var-show-format @var{name}
27512 Returns the format used to display the value of the object @var{name}.
27515 @var{format} @expansion{}
27520 @subheading The @code{-var-info-num-children} Command
27521 @findex -var-info-num-children
27523 @subsubheading Synopsis
27526 -var-info-num-children @var{name}
27529 Returns the number of children of a variable object @var{name}:
27535 Note that this number is not completely reliable for a dynamic varobj.
27536 It will return the current number of children, but more children may
27540 @subheading The @code{-var-list-children} Command
27541 @findex -var-list-children
27543 @subsubheading Synopsis
27546 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
27548 @anchor{-var-list-children}
27550 Return a list of the children of the specified variable object and
27551 create variable objects for them, if they do not already exist. With
27552 a single argument or if @var{print-values} has a value of 0 or
27553 @code{--no-values}, print only the names of the variables; if
27554 @var{print-values} is 1 or @code{--all-values}, also print their
27555 values; and if it is 2 or @code{--simple-values} print the name and
27556 value for simple data types and just the name for arrays, structures
27559 @var{from} and @var{to}, if specified, indicate the range of children
27560 to report. If @var{from} or @var{to} is less than zero, the range is
27561 reset and all children will be reported. Otherwise, children starting
27562 at @var{from} (zero-based) and up to and excluding @var{to} will be
27565 If a child range is requested, it will only affect the current call to
27566 @code{-var-list-children}, but not future calls to @code{-var-update}.
27567 For this, you must instead use @code{-var-set-update-range}. The
27568 intent of this approach is to enable a front end to implement any
27569 update approach it likes; for example, scrolling a view may cause the
27570 front end to request more children with @code{-var-list-children}, and
27571 then the front end could call @code{-var-set-update-range} with a
27572 different range to ensure that future updates are restricted to just
27575 For each child the following results are returned:
27580 Name of the variable object created for this child.
27583 The expression to be shown to the user by the front end to designate this child.
27584 For example this may be the name of a structure member.
27586 For a dynamic varobj, this value cannot be used to form an
27587 expression. There is no way to do this at all with a dynamic varobj.
27589 For C/C@t{++} structures there are several pseudo children returned to
27590 designate access qualifiers. For these pseudo children @var{exp} is
27591 @samp{public}, @samp{private}, or @samp{protected}. In this case the
27592 type and value are not present.
27594 A dynamic varobj will not report the access qualifying
27595 pseudo-children, regardless of the language. This information is not
27596 available at all with a dynamic varobj.
27599 Number of children this child has. For a dynamic varobj, this will be
27603 The type of the child.
27606 If values were requested, this is the value.
27609 If this variable object is associated with a thread, this is the thread id.
27610 Otherwise this result is not present.
27613 If the variable object is frozen, this variable will be present with a value of 1.
27616 The result may have its own attributes:
27620 A dynamic varobj can supply a display hint to the front end. The
27621 value comes directly from the Python pretty-printer object's
27622 @code{display_hint} method. @xref{Pretty Printing API}.
27625 This is an integer attribute which is nonzero if there are children
27626 remaining after the end of the selected range.
27629 @subsubheading Example
27633 -var-list-children n
27634 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
27635 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
27637 -var-list-children --all-values n
27638 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
27639 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
27643 @subheading The @code{-var-info-type} Command
27644 @findex -var-info-type
27646 @subsubheading Synopsis
27649 -var-info-type @var{name}
27652 Returns the type of the specified variable @var{name}. The type is
27653 returned as a string in the same format as it is output by the
27657 type=@var{typename}
27661 @subheading The @code{-var-info-expression} Command
27662 @findex -var-info-expression
27664 @subsubheading Synopsis
27667 -var-info-expression @var{name}
27670 Returns a string that is suitable for presenting this
27671 variable object in user interface. The string is generally
27672 not valid expression in the current language, and cannot be evaluated.
27674 For example, if @code{a} is an array, and variable object
27675 @code{A} was created for @code{a}, then we'll get this output:
27678 (gdb) -var-info-expression A.1
27679 ^done,lang="C",exp="1"
27683 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
27685 Note that the output of the @code{-var-list-children} command also
27686 includes those expressions, so the @code{-var-info-expression} command
27689 @subheading The @code{-var-info-path-expression} Command
27690 @findex -var-info-path-expression
27692 @subsubheading Synopsis
27695 -var-info-path-expression @var{name}
27698 Returns an expression that can be evaluated in the current
27699 context and will yield the same value that a variable object has.
27700 Compare this with the @code{-var-info-expression} command, which
27701 result can be used only for UI presentation. Typical use of
27702 the @code{-var-info-path-expression} command is creating a
27703 watchpoint from a variable object.
27705 This command is currently not valid for children of a dynamic varobj,
27706 and will give an error when invoked on one.
27708 For example, suppose @code{C} is a C@t{++} class, derived from class
27709 @code{Base}, and that the @code{Base} class has a member called
27710 @code{m_size}. Assume a variable @code{c} is has the type of
27711 @code{C} and a variable object @code{C} was created for variable
27712 @code{c}. Then, we'll get this output:
27714 (gdb) -var-info-path-expression C.Base.public.m_size
27715 ^done,path_expr=((Base)c).m_size)
27718 @subheading The @code{-var-show-attributes} Command
27719 @findex -var-show-attributes
27721 @subsubheading Synopsis
27724 -var-show-attributes @var{name}
27727 List attributes of the specified variable object @var{name}:
27730 status=@var{attr} [ ( ,@var{attr} )* ]
27734 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
27736 @subheading The @code{-var-evaluate-expression} Command
27737 @findex -var-evaluate-expression
27739 @subsubheading Synopsis
27742 -var-evaluate-expression [-f @var{format-spec}] @var{name}
27745 Evaluates the expression that is represented by the specified variable
27746 object and returns its value as a string. The format of the string
27747 can be specified with the @samp{-f} option. The possible values of
27748 this option are the same as for @code{-var-set-format}
27749 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
27750 the current display format will be used. The current display format
27751 can be changed using the @code{-var-set-format} command.
27757 Note that one must invoke @code{-var-list-children} for a variable
27758 before the value of a child variable can be evaluated.
27760 @subheading The @code{-var-assign} Command
27761 @findex -var-assign
27763 @subsubheading Synopsis
27766 -var-assign @var{name} @var{expression}
27769 Assigns the value of @var{expression} to the variable object specified
27770 by @var{name}. The object must be @samp{editable}. If the variable's
27771 value is altered by the assign, the variable will show up in any
27772 subsequent @code{-var-update} list.
27774 @subsubheading Example
27782 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
27786 @subheading The @code{-var-update} Command
27787 @findex -var-update
27789 @subsubheading Synopsis
27792 -var-update [@var{print-values}] @{@var{name} | "*"@}
27795 Reevaluate the expressions corresponding to the variable object
27796 @var{name} and all its direct and indirect children, and return the
27797 list of variable objects whose values have changed; @var{name} must
27798 be a root variable object. Here, ``changed'' means that the result of
27799 @code{-var-evaluate-expression} before and after the
27800 @code{-var-update} is different. If @samp{*} is used as the variable
27801 object names, all existing variable objects are updated, except
27802 for frozen ones (@pxref{-var-set-frozen}). The option
27803 @var{print-values} determines whether both names and values, or just
27804 names are printed. The possible values of this option are the same
27805 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
27806 recommended to use the @samp{--all-values} option, to reduce the
27807 number of MI commands needed on each program stop.
27809 With the @samp{*} parameter, if a variable object is bound to a
27810 currently running thread, it will not be updated, without any
27813 If @code{-var-set-update-range} was previously used on a varobj, then
27814 only the selected range of children will be reported.
27816 @code{-var-update} reports all the changed varobjs in a tuple named
27819 Each item in the change list is itself a tuple holding:
27823 The name of the varobj.
27826 If values were requested for this update, then this field will be
27827 present and will hold the value of the varobj.
27830 @anchor{-var-update}
27831 This field is a string which may take one of three values:
27835 The variable object's current value is valid.
27838 The variable object does not currently hold a valid value but it may
27839 hold one in the future if its associated expression comes back into
27843 The variable object no longer holds a valid value.
27844 This can occur when the executable file being debugged has changed,
27845 either through recompilation or by using the @value{GDBN} @code{file}
27846 command. The front end should normally choose to delete these variable
27850 In the future new values may be added to this list so the front should
27851 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
27854 This is only present if the varobj is still valid. If the type
27855 changed, then this will be the string @samp{true}; otherwise it will
27859 If the varobj's type changed, then this field will be present and will
27862 @item new_num_children
27863 For a dynamic varobj, if the number of children changed, or if the
27864 type changed, this will be the new number of children.
27866 The @samp{numchild} field in other varobj responses is generally not
27867 valid for a dynamic varobj -- it will show the number of children that
27868 @value{GDBN} knows about, but because dynamic varobjs lazily
27869 instantiate their children, this will not reflect the number of
27870 children which may be available.
27872 The @samp{new_num_children} attribute only reports changes to the
27873 number of children known by @value{GDBN}. This is the only way to
27874 detect whether an update has removed children (which necessarily can
27875 only happen at the end of the update range).
27878 The display hint, if any.
27881 This is an integer value, which will be 1 if there are more children
27882 available outside the varobj's update range.
27885 This attribute will be present and have the value @samp{1} if the
27886 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
27887 then this attribute will not be present.
27890 If new children were added to a dynamic varobj within the selected
27891 update range (as set by @code{-var-set-update-range}), then they will
27892 be listed in this attribute.
27895 @subsubheading Example
27902 -var-update --all-values var1
27903 ^done,changelist=[@{name="var1",value="3",in_scope="true",
27904 type_changed="false"@}]
27908 @subheading The @code{-var-set-frozen} Command
27909 @findex -var-set-frozen
27910 @anchor{-var-set-frozen}
27912 @subsubheading Synopsis
27915 -var-set-frozen @var{name} @var{flag}
27918 Set the frozenness flag on the variable object @var{name}. The
27919 @var{flag} parameter should be either @samp{1} to make the variable
27920 frozen or @samp{0} to make it unfrozen. If a variable object is
27921 frozen, then neither itself, nor any of its children, are
27922 implicitly updated by @code{-var-update} of
27923 a parent variable or by @code{-var-update *}. Only
27924 @code{-var-update} of the variable itself will update its value and
27925 values of its children. After a variable object is unfrozen, it is
27926 implicitly updated by all subsequent @code{-var-update} operations.
27927 Unfreezing a variable does not update it, only subsequent
27928 @code{-var-update} does.
27930 @subsubheading Example
27934 -var-set-frozen V 1
27939 @subheading The @code{-var-set-update-range} command
27940 @findex -var-set-update-range
27941 @anchor{-var-set-update-range}
27943 @subsubheading Synopsis
27946 -var-set-update-range @var{name} @var{from} @var{to}
27949 Set the range of children to be returned by future invocations of
27950 @code{-var-update}.
27952 @var{from} and @var{to} indicate the range of children to report. If
27953 @var{from} or @var{to} is less than zero, the range is reset and all
27954 children will be reported. Otherwise, children starting at @var{from}
27955 (zero-based) and up to and excluding @var{to} will be reported.
27957 @subsubheading Example
27961 -var-set-update-range V 1 2
27965 @subheading The @code{-var-set-visualizer} command
27966 @findex -var-set-visualizer
27967 @anchor{-var-set-visualizer}
27969 @subsubheading Synopsis
27972 -var-set-visualizer @var{name} @var{visualizer}
27975 Set a visualizer for the variable object @var{name}.
27977 @var{visualizer} is the visualizer to use. The special value
27978 @samp{None} means to disable any visualizer in use.
27980 If not @samp{None}, @var{visualizer} must be a Python expression.
27981 This expression must evaluate to a callable object which accepts a
27982 single argument. @value{GDBN} will call this object with the value of
27983 the varobj @var{name} as an argument (this is done so that the same
27984 Python pretty-printing code can be used for both the CLI and MI).
27985 When called, this object must return an object which conforms to the
27986 pretty-printing interface (@pxref{Pretty Printing API}).
27988 The pre-defined function @code{gdb.default_visualizer} may be used to
27989 select a visualizer by following the built-in process
27990 (@pxref{Selecting Pretty-Printers}). This is done automatically when
27991 a varobj is created, and so ordinarily is not needed.
27993 This feature is only available if Python support is enabled. The MI
27994 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
27995 can be used to check this.
27997 @subsubheading Example
27999 Resetting the visualizer:
28003 -var-set-visualizer V None
28007 Reselecting the default (type-based) visualizer:
28011 -var-set-visualizer V gdb.default_visualizer
28015 Suppose @code{SomeClass} is a visualizer class. A lambda expression
28016 can be used to instantiate this class for a varobj:
28020 -var-set-visualizer V "lambda val: SomeClass()"
28024 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28025 @node GDB/MI Data Manipulation
28026 @section @sc{gdb/mi} Data Manipulation
28028 @cindex data manipulation, in @sc{gdb/mi}
28029 @cindex @sc{gdb/mi}, data manipulation
28030 This section describes the @sc{gdb/mi} commands that manipulate data:
28031 examine memory and registers, evaluate expressions, etc.
28033 @c REMOVED FROM THE INTERFACE.
28034 @c @subheading -data-assign
28035 @c Change the value of a program variable. Plenty of side effects.
28036 @c @subsubheading GDB Command
28038 @c @subsubheading Example
28041 @subheading The @code{-data-disassemble} Command
28042 @findex -data-disassemble
28044 @subsubheading Synopsis
28048 [ -s @var{start-addr} -e @var{end-addr} ]
28049 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
28057 @item @var{start-addr}
28058 is the beginning address (or @code{$pc})
28059 @item @var{end-addr}
28061 @item @var{filename}
28062 is the name of the file to disassemble
28063 @item @var{linenum}
28064 is the line number to disassemble around
28066 is the number of disassembly lines to be produced. If it is -1,
28067 the whole function will be disassembled, in case no @var{end-addr} is
28068 specified. If @var{end-addr} is specified as a non-zero value, and
28069 @var{lines} is lower than the number of disassembly lines between
28070 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
28071 displayed; if @var{lines} is higher than the number of lines between
28072 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
28075 is either 0 (meaning only disassembly), 1 (meaning mixed source and
28076 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
28077 mixed source and disassembly with raw opcodes).
28080 @subsubheading Result
28082 The output for each instruction is composed of four fields:
28091 Note that whatever included in the instruction field, is not manipulated
28092 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
28094 @subsubheading @value{GDBN} Command
28096 There's no direct mapping from this command to the CLI.
28098 @subsubheading Example
28100 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
28104 -data-disassemble -s $pc -e "$pc + 20" -- 0
28107 @{address="0x000107c0",func-name="main",offset="4",
28108 inst="mov 2, %o0"@},
28109 @{address="0x000107c4",func-name="main",offset="8",
28110 inst="sethi %hi(0x11800), %o2"@},
28111 @{address="0x000107c8",func-name="main",offset="12",
28112 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
28113 @{address="0x000107cc",func-name="main",offset="16",
28114 inst="sethi %hi(0x11800), %o2"@},
28115 @{address="0x000107d0",func-name="main",offset="20",
28116 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
28120 Disassemble the whole @code{main} function. Line 32 is part of
28124 -data-disassemble -f basics.c -l 32 -- 0
28126 @{address="0x000107bc",func-name="main",offset="0",
28127 inst="save %sp, -112, %sp"@},
28128 @{address="0x000107c0",func-name="main",offset="4",
28129 inst="mov 2, %o0"@},
28130 @{address="0x000107c4",func-name="main",offset="8",
28131 inst="sethi %hi(0x11800), %o2"@},
28133 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
28134 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
28138 Disassemble 3 instructions from the start of @code{main}:
28142 -data-disassemble -f basics.c -l 32 -n 3 -- 0
28144 @{address="0x000107bc",func-name="main",offset="0",
28145 inst="save %sp, -112, %sp"@},
28146 @{address="0x000107c0",func-name="main",offset="4",
28147 inst="mov 2, %o0"@},
28148 @{address="0x000107c4",func-name="main",offset="8",
28149 inst="sethi %hi(0x11800), %o2"@}]
28153 Disassemble 3 instructions from the start of @code{main} in mixed mode:
28157 -data-disassemble -f basics.c -l 32 -n 3 -- 1
28159 src_and_asm_line=@{line="31",
28160 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
28161 testsuite/gdb.mi/basics.c",line_asm_insn=[
28162 @{address="0x000107bc",func-name="main",offset="0",
28163 inst="save %sp, -112, %sp"@}]@},
28164 src_and_asm_line=@{line="32",
28165 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
28166 testsuite/gdb.mi/basics.c",line_asm_insn=[
28167 @{address="0x000107c0",func-name="main",offset="4",
28168 inst="mov 2, %o0"@},
28169 @{address="0x000107c4",func-name="main",offset="8",
28170 inst="sethi %hi(0x11800), %o2"@}]@}]
28175 @subheading The @code{-data-evaluate-expression} Command
28176 @findex -data-evaluate-expression
28178 @subsubheading Synopsis
28181 -data-evaluate-expression @var{expr}
28184 Evaluate @var{expr} as an expression. The expression could contain an
28185 inferior function call. The function call will execute synchronously.
28186 If the expression contains spaces, it must be enclosed in double quotes.
28188 @subsubheading @value{GDBN} Command
28190 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
28191 @samp{call}. In @code{gdbtk} only, there's a corresponding
28192 @samp{gdb_eval} command.
28194 @subsubheading Example
28196 In the following example, the numbers that precede the commands are the
28197 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
28198 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
28202 211-data-evaluate-expression A
28205 311-data-evaluate-expression &A
28206 311^done,value="0xefffeb7c"
28208 411-data-evaluate-expression A+3
28211 511-data-evaluate-expression "A + 3"
28217 @subheading The @code{-data-list-changed-registers} Command
28218 @findex -data-list-changed-registers
28220 @subsubheading Synopsis
28223 -data-list-changed-registers
28226 Display a list of the registers that have changed.
28228 @subsubheading @value{GDBN} Command
28230 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
28231 has the corresponding command @samp{gdb_changed_register_list}.
28233 @subsubheading Example
28235 On a PPC MBX board:
28243 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
28244 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
28247 -data-list-changed-registers
28248 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
28249 "10","11","13","14","15","16","17","18","19","20","21","22","23",
28250 "24","25","26","27","28","30","31","64","65","66","67","69"]
28255 @subheading The @code{-data-list-register-names} Command
28256 @findex -data-list-register-names
28258 @subsubheading Synopsis
28261 -data-list-register-names [ ( @var{regno} )+ ]
28264 Show a list of register names for the current target. If no arguments
28265 are given, it shows a list of the names of all the registers. If
28266 integer numbers are given as arguments, it will print a list of the
28267 names of the registers corresponding to the arguments. To ensure
28268 consistency between a register name and its number, the output list may
28269 include empty register names.
28271 @subsubheading @value{GDBN} Command
28273 @value{GDBN} does not have a command which corresponds to
28274 @samp{-data-list-register-names}. In @code{gdbtk} there is a
28275 corresponding command @samp{gdb_regnames}.
28277 @subsubheading Example
28279 For the PPC MBX board:
28282 -data-list-register-names
28283 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
28284 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
28285 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
28286 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
28287 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
28288 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
28289 "", "pc","ps","cr","lr","ctr","xer"]
28291 -data-list-register-names 1 2 3
28292 ^done,register-names=["r1","r2","r3"]
28296 @subheading The @code{-data-list-register-values} Command
28297 @findex -data-list-register-values
28299 @subsubheading Synopsis
28302 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
28305 Display the registers' contents. @var{fmt} is the format according to
28306 which the registers' contents are to be returned, followed by an optional
28307 list of numbers specifying the registers to display. A missing list of
28308 numbers indicates that the contents of all the registers must be returned.
28310 Allowed formats for @var{fmt} are:
28327 @subsubheading @value{GDBN} Command
28329 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
28330 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
28332 @subsubheading Example
28334 For a PPC MBX board (note: line breaks are for readability only, they
28335 don't appear in the actual output):
28339 -data-list-register-values r 64 65
28340 ^done,register-values=[@{number="64",value="0xfe00a300"@},
28341 @{number="65",value="0x00029002"@}]
28343 -data-list-register-values x
28344 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
28345 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
28346 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
28347 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
28348 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
28349 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
28350 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
28351 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
28352 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
28353 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
28354 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
28355 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
28356 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
28357 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
28358 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
28359 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
28360 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
28361 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
28362 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
28363 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
28364 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
28365 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
28366 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
28367 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
28368 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
28369 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
28370 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
28371 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
28372 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
28373 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
28374 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
28375 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
28376 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
28377 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
28378 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
28379 @{number="69",value="0x20002b03"@}]
28384 @subheading The @code{-data-read-memory} Command
28385 @findex -data-read-memory
28387 This command is deprecated, use @code{-data-read-memory-bytes} instead.
28389 @subsubheading Synopsis
28392 -data-read-memory [ -o @var{byte-offset} ]
28393 @var{address} @var{word-format} @var{word-size}
28394 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
28401 @item @var{address}
28402 An expression specifying the address of the first memory word to be
28403 read. Complex expressions containing embedded white space should be
28404 quoted using the C convention.
28406 @item @var{word-format}
28407 The format to be used to print the memory words. The notation is the
28408 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
28411 @item @var{word-size}
28412 The size of each memory word in bytes.
28414 @item @var{nr-rows}
28415 The number of rows in the output table.
28417 @item @var{nr-cols}
28418 The number of columns in the output table.
28421 If present, indicates that each row should include an @sc{ascii} dump. The
28422 value of @var{aschar} is used as a padding character when a byte is not a
28423 member of the printable @sc{ascii} character set (printable @sc{ascii}
28424 characters are those whose code is between 32 and 126, inclusively).
28426 @item @var{byte-offset}
28427 An offset to add to the @var{address} before fetching memory.
28430 This command displays memory contents as a table of @var{nr-rows} by
28431 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
28432 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
28433 (returned as @samp{total-bytes}). Should less than the requested number
28434 of bytes be returned by the target, the missing words are identified
28435 using @samp{N/A}. The number of bytes read from the target is returned
28436 in @samp{nr-bytes} and the starting address used to read memory in
28439 The address of the next/previous row or page is available in
28440 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
28443 @subsubheading @value{GDBN} Command
28445 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
28446 @samp{gdb_get_mem} memory read command.
28448 @subsubheading Example
28450 Read six bytes of memory starting at @code{bytes+6} but then offset by
28451 @code{-6} bytes. Format as three rows of two columns. One byte per
28452 word. Display each word in hex.
28456 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
28457 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
28458 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
28459 prev-page="0x0000138a",memory=[
28460 @{addr="0x00001390",data=["0x00","0x01"]@},
28461 @{addr="0x00001392",data=["0x02","0x03"]@},
28462 @{addr="0x00001394",data=["0x04","0x05"]@}]
28466 Read two bytes of memory starting at address @code{shorts + 64} and
28467 display as a single word formatted in decimal.
28471 5-data-read-memory shorts+64 d 2 1 1
28472 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
28473 next-row="0x00001512",prev-row="0x0000150e",
28474 next-page="0x00001512",prev-page="0x0000150e",memory=[
28475 @{addr="0x00001510",data=["128"]@}]
28479 Read thirty two bytes of memory starting at @code{bytes+16} and format
28480 as eight rows of four columns. Include a string encoding with @samp{x}
28481 used as the non-printable character.
28485 4-data-read-memory bytes+16 x 1 8 4 x
28486 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
28487 next-row="0x000013c0",prev-row="0x0000139c",
28488 next-page="0x000013c0",prev-page="0x00001380",memory=[
28489 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
28490 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
28491 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
28492 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
28493 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
28494 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
28495 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
28496 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
28500 @subheading The @code{-data-read-memory-bytes} Command
28501 @findex -data-read-memory-bytes
28503 @subsubheading Synopsis
28506 -data-read-memory-bytes [ -o @var{byte-offset} ]
28507 @var{address} @var{count}
28514 @item @var{address}
28515 An expression specifying the address of the first memory word to be
28516 read. Complex expressions containing embedded white space should be
28517 quoted using the C convention.
28520 The number of bytes to read. This should be an integer literal.
28522 @item @var{byte-offset}
28523 The offsets in bytes relative to @var{address} at which to start
28524 reading. This should be an integer literal. This option is provided
28525 so that a frontend is not required to first evaluate address and then
28526 perform address arithmetics itself.
28530 This command attempts to read all accessible memory regions in the
28531 specified range. First, all regions marked as unreadable in the memory
28532 map (if one is defined) will be skipped. @xref{Memory Region
28533 Attributes}. Second, @value{GDBN} will attempt to read the remaining
28534 regions. For each one, if reading full region results in an errors,
28535 @value{GDBN} will try to read a subset of the region.
28537 In general, every single byte in the region may be readable or not,
28538 and the only way to read every readable byte is to try a read at
28539 every address, which is not practical. Therefore, @value{GDBN} will
28540 attempt to read all accessible bytes at either beginning or the end
28541 of the region, using a binary division scheme. This heuristic works
28542 well for reading accross a memory map boundary. Note that if a region
28543 has a readable range that is neither at the beginning or the end,
28544 @value{GDBN} will not read it.
28546 The result record (@pxref{GDB/MI Result Records}) that is output of
28547 the command includes a field named @samp{memory} whose content is a
28548 list of tuples. Each tuple represent a successfully read memory block
28549 and has the following fields:
28553 The start address of the memory block, as hexadecimal literal.
28556 The end address of the memory block, as hexadecimal literal.
28559 The offset of the memory block, as hexadecimal literal, relative to
28560 the start address passed to @code{-data-read-memory-bytes}.
28563 The contents of the memory block, in hex.
28569 @subsubheading @value{GDBN} Command
28571 The corresponding @value{GDBN} command is @samp{x}.
28573 @subsubheading Example
28577 -data-read-memory-bytes &a 10
28578 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
28580 contents="01000000020000000300"@}]
28585 @subheading The @code{-data-write-memory-bytes} Command
28586 @findex -data-write-memory-bytes
28588 @subsubheading Synopsis
28591 -data-write-memory-bytes @var{address} @var{contents}
28598 @item @var{address}
28599 An expression specifying the address of the first memory word to be
28600 read. Complex expressions containing embedded white space should be
28601 quoted using the C convention.
28603 @item @var{contents}
28604 The hex-encoded bytes to write.
28608 @subsubheading @value{GDBN} Command
28610 There's no corresponding @value{GDBN} command.
28612 @subsubheading Example
28616 -data-write-memory-bytes &a "aabbccdd"
28622 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28623 @node GDB/MI Tracepoint Commands
28624 @section @sc{gdb/mi} Tracepoint Commands
28626 The commands defined in this section implement MI support for
28627 tracepoints. For detailed introduction, see @ref{Tracepoints}.
28629 @subheading The @code{-trace-find} Command
28630 @findex -trace-find
28632 @subsubheading Synopsis
28635 -trace-find @var{mode} [@var{parameters}@dots{}]
28638 Find a trace frame using criteria defined by @var{mode} and
28639 @var{parameters}. The following table lists permissible
28640 modes and their parameters. For details of operation, see @ref{tfind}.
28645 No parameters are required. Stops examining trace frames.
28648 An integer is required as parameter. Selects tracepoint frame with
28651 @item tracepoint-number
28652 An integer is required as parameter. Finds next
28653 trace frame that corresponds to tracepoint with the specified number.
28656 An address is required as parameter. Finds
28657 next trace frame that corresponds to any tracepoint at the specified
28660 @item pc-inside-range
28661 Two addresses are required as parameters. Finds next trace
28662 frame that corresponds to a tracepoint at an address inside the
28663 specified range. Both bounds are considered to be inside the range.
28665 @item pc-outside-range
28666 Two addresses are required as parameters. Finds
28667 next trace frame that corresponds to a tracepoint at an address outside
28668 the specified range. Both bounds are considered to be inside the range.
28671 Line specification is required as parameter. @xref{Specify Location}.
28672 Finds next trace frame that corresponds to a tracepoint at
28673 the specified location.
28677 If @samp{none} was passed as @var{mode}, the response does not
28678 have fields. Otherwise, the response may have the following fields:
28682 This field has either @samp{0} or @samp{1} as the value, depending
28683 on whether a matching tracepoint was found.
28686 The index of the found traceframe. This field is present iff
28687 the @samp{found} field has value of @samp{1}.
28690 The index of the found tracepoint. This field is present iff
28691 the @samp{found} field has value of @samp{1}.
28694 The information about the frame corresponding to the found trace
28695 frame. This field is present only if a trace frame was found.
28696 @xref{GDB/MI Frame Information}, for description of this field.
28700 @subsubheading @value{GDBN} Command
28702 The corresponding @value{GDBN} command is @samp{tfind}.
28704 @subheading -trace-define-variable
28705 @findex -trace-define-variable
28707 @subsubheading Synopsis
28710 -trace-define-variable @var{name} [ @var{value} ]
28713 Create trace variable @var{name} if it does not exist. If
28714 @var{value} is specified, sets the initial value of the specified
28715 trace variable to that value. Note that the @var{name} should start
28716 with the @samp{$} character.
28718 @subsubheading @value{GDBN} Command
28720 The corresponding @value{GDBN} command is @samp{tvariable}.
28722 @subheading -trace-list-variables
28723 @findex -trace-list-variables
28725 @subsubheading Synopsis
28728 -trace-list-variables
28731 Return a table of all defined trace variables. Each element of the
28732 table has the following fields:
28736 The name of the trace variable. This field is always present.
28739 The initial value. This is a 64-bit signed integer. This
28740 field is always present.
28743 The value the trace variable has at the moment. This is a 64-bit
28744 signed integer. This field is absent iff current value is
28745 not defined, for example if the trace was never run, or is
28750 @subsubheading @value{GDBN} Command
28752 The corresponding @value{GDBN} command is @samp{tvariables}.
28754 @subsubheading Example
28758 -trace-list-variables
28759 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
28760 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
28761 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
28762 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
28763 body=[variable=@{name="$trace_timestamp",initial="0"@}
28764 variable=@{name="$foo",initial="10",current="15"@}]@}
28768 @subheading -trace-save
28769 @findex -trace-save
28771 @subsubheading Synopsis
28774 -trace-save [-r ] @var{filename}
28777 Saves the collected trace data to @var{filename}. Without the
28778 @samp{-r} option, the data is downloaded from the target and saved
28779 in a local file. With the @samp{-r} option the target is asked
28780 to perform the save.
28782 @subsubheading @value{GDBN} Command
28784 The corresponding @value{GDBN} command is @samp{tsave}.
28787 @subheading -trace-start
28788 @findex -trace-start
28790 @subsubheading Synopsis
28796 Starts a tracing experiments. The result of this command does not
28799 @subsubheading @value{GDBN} Command
28801 The corresponding @value{GDBN} command is @samp{tstart}.
28803 @subheading -trace-status
28804 @findex -trace-status
28806 @subsubheading Synopsis
28812 Obtains the status of a tracing experiment. The result may include
28813 the following fields:
28818 May have a value of either @samp{0}, when no tracing operations are
28819 supported, @samp{1}, when all tracing operations are supported, or
28820 @samp{file} when examining trace file. In the latter case, examining
28821 of trace frame is possible but new tracing experiement cannot be
28822 started. This field is always present.
28825 May have a value of either @samp{0} or @samp{1} depending on whether
28826 tracing experiement is in progress on target. This field is present
28827 if @samp{supported} field is not @samp{0}.
28830 Report the reason why the tracing was stopped last time. This field
28831 may be absent iff tracing was never stopped on target yet. The
28832 value of @samp{request} means the tracing was stopped as result of
28833 the @code{-trace-stop} command. The value of @samp{overflow} means
28834 the tracing buffer is full. The value of @samp{disconnection} means
28835 tracing was automatically stopped when @value{GDBN} has disconnected.
28836 The value of @samp{passcount} means tracing was stopped when a
28837 tracepoint was passed a maximal number of times for that tracepoint.
28838 This field is present if @samp{supported} field is not @samp{0}.
28840 @item stopping-tracepoint
28841 The number of tracepoint whose passcount as exceeded. This field is
28842 present iff the @samp{stop-reason} field has the value of
28846 @itemx frames-created
28847 The @samp{frames} field is a count of the total number of trace frames
28848 in the trace buffer, while @samp{frames-created} is the total created
28849 during the run, including ones that were discarded, such as when a
28850 circular trace buffer filled up. Both fields are optional.
28854 These fields tell the current size of the tracing buffer and the
28855 remaining space. These fields are optional.
28858 The value of the circular trace buffer flag. @code{1} means that the
28859 trace buffer is circular and old trace frames will be discarded if
28860 necessary to make room, @code{0} means that the trace buffer is linear
28864 The value of the disconnected tracing flag. @code{1} means that
28865 tracing will continue after @value{GDBN} disconnects, @code{0} means
28866 that the trace run will stop.
28870 @subsubheading @value{GDBN} Command
28872 The corresponding @value{GDBN} command is @samp{tstatus}.
28874 @subheading -trace-stop
28875 @findex -trace-stop
28877 @subsubheading Synopsis
28883 Stops a tracing experiment. The result of this command has the same
28884 fields as @code{-trace-status}, except that the @samp{supported} and
28885 @samp{running} fields are not output.
28887 @subsubheading @value{GDBN} Command
28889 The corresponding @value{GDBN} command is @samp{tstop}.
28892 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28893 @node GDB/MI Symbol Query
28894 @section @sc{gdb/mi} Symbol Query Commands
28898 @subheading The @code{-symbol-info-address} Command
28899 @findex -symbol-info-address
28901 @subsubheading Synopsis
28904 -symbol-info-address @var{symbol}
28907 Describe where @var{symbol} is stored.
28909 @subsubheading @value{GDBN} Command
28911 The corresponding @value{GDBN} command is @samp{info address}.
28913 @subsubheading Example
28917 @subheading The @code{-symbol-info-file} Command
28918 @findex -symbol-info-file
28920 @subsubheading Synopsis
28926 Show the file for the symbol.
28928 @subsubheading @value{GDBN} Command
28930 There's no equivalent @value{GDBN} command. @code{gdbtk} has
28931 @samp{gdb_find_file}.
28933 @subsubheading Example
28937 @subheading The @code{-symbol-info-function} Command
28938 @findex -symbol-info-function
28940 @subsubheading Synopsis
28943 -symbol-info-function
28946 Show which function the symbol lives in.
28948 @subsubheading @value{GDBN} Command
28950 @samp{gdb_get_function} in @code{gdbtk}.
28952 @subsubheading Example
28956 @subheading The @code{-symbol-info-line} Command
28957 @findex -symbol-info-line
28959 @subsubheading Synopsis
28965 Show the core addresses of the code for a source line.
28967 @subsubheading @value{GDBN} Command
28969 The corresponding @value{GDBN} command is @samp{info line}.
28970 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
28972 @subsubheading Example
28976 @subheading The @code{-symbol-info-symbol} Command
28977 @findex -symbol-info-symbol
28979 @subsubheading Synopsis
28982 -symbol-info-symbol @var{addr}
28985 Describe what symbol is at location @var{addr}.
28987 @subsubheading @value{GDBN} Command
28989 The corresponding @value{GDBN} command is @samp{info symbol}.
28991 @subsubheading Example
28995 @subheading The @code{-symbol-list-functions} Command
28996 @findex -symbol-list-functions
28998 @subsubheading Synopsis
29001 -symbol-list-functions
29004 List the functions in the executable.
29006 @subsubheading @value{GDBN} Command
29008 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
29009 @samp{gdb_search} in @code{gdbtk}.
29011 @subsubheading Example
29016 @subheading The @code{-symbol-list-lines} Command
29017 @findex -symbol-list-lines
29019 @subsubheading Synopsis
29022 -symbol-list-lines @var{filename}
29025 Print the list of lines that contain code and their associated program
29026 addresses for the given source filename. The entries are sorted in
29027 ascending PC order.
29029 @subsubheading @value{GDBN} Command
29031 There is no corresponding @value{GDBN} command.
29033 @subsubheading Example
29036 -symbol-list-lines basics.c
29037 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
29043 @subheading The @code{-symbol-list-types} Command
29044 @findex -symbol-list-types
29046 @subsubheading Synopsis
29052 List all the type names.
29054 @subsubheading @value{GDBN} Command
29056 The corresponding commands are @samp{info types} in @value{GDBN},
29057 @samp{gdb_search} in @code{gdbtk}.
29059 @subsubheading Example
29063 @subheading The @code{-symbol-list-variables} Command
29064 @findex -symbol-list-variables
29066 @subsubheading Synopsis
29069 -symbol-list-variables
29072 List all the global and static variable names.
29074 @subsubheading @value{GDBN} Command
29076 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
29078 @subsubheading Example
29082 @subheading The @code{-symbol-locate} Command
29083 @findex -symbol-locate
29085 @subsubheading Synopsis
29091 @subsubheading @value{GDBN} Command
29093 @samp{gdb_loc} in @code{gdbtk}.
29095 @subsubheading Example
29099 @subheading The @code{-symbol-type} Command
29100 @findex -symbol-type
29102 @subsubheading Synopsis
29105 -symbol-type @var{variable}
29108 Show type of @var{variable}.
29110 @subsubheading @value{GDBN} Command
29112 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
29113 @samp{gdb_obj_variable}.
29115 @subsubheading Example
29120 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29121 @node GDB/MI File Commands
29122 @section @sc{gdb/mi} File Commands
29124 This section describes the GDB/MI commands to specify executable file names
29125 and to read in and obtain symbol table information.
29127 @subheading The @code{-file-exec-and-symbols} Command
29128 @findex -file-exec-and-symbols
29130 @subsubheading Synopsis
29133 -file-exec-and-symbols @var{file}
29136 Specify the executable file to be debugged. This file is the one from
29137 which the symbol table is also read. If no file is specified, the
29138 command clears the executable and symbol information. If breakpoints
29139 are set when using this command with no arguments, @value{GDBN} will produce
29140 error messages. Otherwise, no output is produced, except a completion
29143 @subsubheading @value{GDBN} Command
29145 The corresponding @value{GDBN} command is @samp{file}.
29147 @subsubheading Example
29151 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
29157 @subheading The @code{-file-exec-file} Command
29158 @findex -file-exec-file
29160 @subsubheading Synopsis
29163 -file-exec-file @var{file}
29166 Specify the executable file to be debugged. Unlike
29167 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
29168 from this file. If used without argument, @value{GDBN} clears the information
29169 about the executable file. No output is produced, except a completion
29172 @subsubheading @value{GDBN} Command
29174 The corresponding @value{GDBN} command is @samp{exec-file}.
29176 @subsubheading Example
29180 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
29187 @subheading The @code{-file-list-exec-sections} Command
29188 @findex -file-list-exec-sections
29190 @subsubheading Synopsis
29193 -file-list-exec-sections
29196 List the sections of the current executable file.
29198 @subsubheading @value{GDBN} Command
29200 The @value{GDBN} command @samp{info file} shows, among the rest, the same
29201 information as this command. @code{gdbtk} has a corresponding command
29202 @samp{gdb_load_info}.
29204 @subsubheading Example
29209 @subheading The @code{-file-list-exec-source-file} Command
29210 @findex -file-list-exec-source-file
29212 @subsubheading Synopsis
29215 -file-list-exec-source-file
29218 List the line number, the current source file, and the absolute path
29219 to the current source file for the current executable. The macro
29220 information field has a value of @samp{1} or @samp{0} depending on
29221 whether or not the file includes preprocessor macro information.
29223 @subsubheading @value{GDBN} Command
29225 The @value{GDBN} equivalent is @samp{info source}
29227 @subsubheading Example
29231 123-file-list-exec-source-file
29232 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
29237 @subheading The @code{-file-list-exec-source-files} Command
29238 @findex -file-list-exec-source-files
29240 @subsubheading Synopsis
29243 -file-list-exec-source-files
29246 List the source files for the current executable.
29248 It will always output the filename, but only when @value{GDBN} can find
29249 the absolute file name of a source file, will it output the fullname.
29251 @subsubheading @value{GDBN} Command
29253 The @value{GDBN} equivalent is @samp{info sources}.
29254 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
29256 @subsubheading Example
29259 -file-list-exec-source-files
29261 @{file=foo.c,fullname=/home/foo.c@},
29262 @{file=/home/bar.c,fullname=/home/bar.c@},
29263 @{file=gdb_could_not_find_fullpath.c@}]
29268 @subheading The @code{-file-list-shared-libraries} Command
29269 @findex -file-list-shared-libraries
29271 @subsubheading Synopsis
29274 -file-list-shared-libraries
29277 List the shared libraries in the program.
29279 @subsubheading @value{GDBN} Command
29281 The corresponding @value{GDBN} command is @samp{info shared}.
29283 @subsubheading Example
29287 @subheading The @code{-file-list-symbol-files} Command
29288 @findex -file-list-symbol-files
29290 @subsubheading Synopsis
29293 -file-list-symbol-files
29298 @subsubheading @value{GDBN} Command
29300 The corresponding @value{GDBN} command is @samp{info file} (part of it).
29302 @subsubheading Example
29307 @subheading The @code{-file-symbol-file} Command
29308 @findex -file-symbol-file
29310 @subsubheading Synopsis
29313 -file-symbol-file @var{file}
29316 Read symbol table info from the specified @var{file} argument. When
29317 used without arguments, clears @value{GDBN}'s symbol table info. No output is
29318 produced, except for a completion notification.
29320 @subsubheading @value{GDBN} Command
29322 The corresponding @value{GDBN} command is @samp{symbol-file}.
29324 @subsubheading Example
29328 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
29334 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29335 @node GDB/MI Memory Overlay Commands
29336 @section @sc{gdb/mi} Memory Overlay Commands
29338 The memory overlay commands are not implemented.
29340 @c @subheading -overlay-auto
29342 @c @subheading -overlay-list-mapping-state
29344 @c @subheading -overlay-list-overlays
29346 @c @subheading -overlay-map
29348 @c @subheading -overlay-off
29350 @c @subheading -overlay-on
29352 @c @subheading -overlay-unmap
29354 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29355 @node GDB/MI Signal Handling Commands
29356 @section @sc{gdb/mi} Signal Handling Commands
29358 Signal handling commands are not implemented.
29360 @c @subheading -signal-handle
29362 @c @subheading -signal-list-handle-actions
29364 @c @subheading -signal-list-signal-types
29368 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29369 @node GDB/MI Target Manipulation
29370 @section @sc{gdb/mi} Target Manipulation Commands
29373 @subheading The @code{-target-attach} Command
29374 @findex -target-attach
29376 @subsubheading Synopsis
29379 -target-attach @var{pid} | @var{gid} | @var{file}
29382 Attach to a process @var{pid} or a file @var{file} outside of
29383 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
29384 group, the id previously returned by
29385 @samp{-list-thread-groups --available} must be used.
29387 @subsubheading @value{GDBN} Command
29389 The corresponding @value{GDBN} command is @samp{attach}.
29391 @subsubheading Example
29395 =thread-created,id="1"
29396 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
29402 @subheading The @code{-target-compare-sections} Command
29403 @findex -target-compare-sections
29405 @subsubheading Synopsis
29408 -target-compare-sections [ @var{section} ]
29411 Compare data of section @var{section} on target to the exec file.
29412 Without the argument, all sections are compared.
29414 @subsubheading @value{GDBN} Command
29416 The @value{GDBN} equivalent is @samp{compare-sections}.
29418 @subsubheading Example
29423 @subheading The @code{-target-detach} Command
29424 @findex -target-detach
29426 @subsubheading Synopsis
29429 -target-detach [ @var{pid} | @var{gid} ]
29432 Detach from the remote target which normally resumes its execution.
29433 If either @var{pid} or @var{gid} is specified, detaches from either
29434 the specified process, or specified thread group. There's no output.
29436 @subsubheading @value{GDBN} Command
29438 The corresponding @value{GDBN} command is @samp{detach}.
29440 @subsubheading Example
29450 @subheading The @code{-target-disconnect} Command
29451 @findex -target-disconnect
29453 @subsubheading Synopsis
29459 Disconnect from the remote target. There's no output and the target is
29460 generally not resumed.
29462 @subsubheading @value{GDBN} Command
29464 The corresponding @value{GDBN} command is @samp{disconnect}.
29466 @subsubheading Example
29476 @subheading The @code{-target-download} Command
29477 @findex -target-download
29479 @subsubheading Synopsis
29485 Loads the executable onto the remote target.
29486 It prints out an update message every half second, which includes the fields:
29490 The name of the section.
29492 The size of what has been sent so far for that section.
29494 The size of the section.
29496 The total size of what was sent so far (the current and the previous sections).
29498 The size of the overall executable to download.
29502 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
29503 @sc{gdb/mi} Output Syntax}).
29505 In addition, it prints the name and size of the sections, as they are
29506 downloaded. These messages include the following fields:
29510 The name of the section.
29512 The size of the section.
29514 The size of the overall executable to download.
29518 At the end, a summary is printed.
29520 @subsubheading @value{GDBN} Command
29522 The corresponding @value{GDBN} command is @samp{load}.
29524 @subsubheading Example
29526 Note: each status message appears on a single line. Here the messages
29527 have been broken down so that they can fit onto a page.
29532 +download,@{section=".text",section-size="6668",total-size="9880"@}
29533 +download,@{section=".text",section-sent="512",section-size="6668",
29534 total-sent="512",total-size="9880"@}
29535 +download,@{section=".text",section-sent="1024",section-size="6668",
29536 total-sent="1024",total-size="9880"@}
29537 +download,@{section=".text",section-sent="1536",section-size="6668",
29538 total-sent="1536",total-size="9880"@}
29539 +download,@{section=".text",section-sent="2048",section-size="6668",
29540 total-sent="2048",total-size="9880"@}
29541 +download,@{section=".text",section-sent="2560",section-size="6668",
29542 total-sent="2560",total-size="9880"@}
29543 +download,@{section=".text",section-sent="3072",section-size="6668",
29544 total-sent="3072",total-size="9880"@}
29545 +download,@{section=".text",section-sent="3584",section-size="6668",
29546 total-sent="3584",total-size="9880"@}
29547 +download,@{section=".text",section-sent="4096",section-size="6668",
29548 total-sent="4096",total-size="9880"@}
29549 +download,@{section=".text",section-sent="4608",section-size="6668",
29550 total-sent="4608",total-size="9880"@}
29551 +download,@{section=".text",section-sent="5120",section-size="6668",
29552 total-sent="5120",total-size="9880"@}
29553 +download,@{section=".text",section-sent="5632",section-size="6668",
29554 total-sent="5632",total-size="9880"@}
29555 +download,@{section=".text",section-sent="6144",section-size="6668",
29556 total-sent="6144",total-size="9880"@}
29557 +download,@{section=".text",section-sent="6656",section-size="6668",
29558 total-sent="6656",total-size="9880"@}
29559 +download,@{section=".init",section-size="28",total-size="9880"@}
29560 +download,@{section=".fini",section-size="28",total-size="9880"@}
29561 +download,@{section=".data",section-size="3156",total-size="9880"@}
29562 +download,@{section=".data",section-sent="512",section-size="3156",
29563 total-sent="7236",total-size="9880"@}
29564 +download,@{section=".data",section-sent="1024",section-size="3156",
29565 total-sent="7748",total-size="9880"@}
29566 +download,@{section=".data",section-sent="1536",section-size="3156",
29567 total-sent="8260",total-size="9880"@}
29568 +download,@{section=".data",section-sent="2048",section-size="3156",
29569 total-sent="8772",total-size="9880"@}
29570 +download,@{section=".data",section-sent="2560",section-size="3156",
29571 total-sent="9284",total-size="9880"@}
29572 +download,@{section=".data",section-sent="3072",section-size="3156",
29573 total-sent="9796",total-size="9880"@}
29574 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
29581 @subheading The @code{-target-exec-status} Command
29582 @findex -target-exec-status
29584 @subsubheading Synopsis
29587 -target-exec-status
29590 Provide information on the state of the target (whether it is running or
29591 not, for instance).
29593 @subsubheading @value{GDBN} Command
29595 There's no equivalent @value{GDBN} command.
29597 @subsubheading Example
29601 @subheading The @code{-target-list-available-targets} Command
29602 @findex -target-list-available-targets
29604 @subsubheading Synopsis
29607 -target-list-available-targets
29610 List the possible targets to connect to.
29612 @subsubheading @value{GDBN} Command
29614 The corresponding @value{GDBN} command is @samp{help target}.
29616 @subsubheading Example
29620 @subheading The @code{-target-list-current-targets} Command
29621 @findex -target-list-current-targets
29623 @subsubheading Synopsis
29626 -target-list-current-targets
29629 Describe the current target.
29631 @subsubheading @value{GDBN} Command
29633 The corresponding information is printed by @samp{info file} (among
29636 @subsubheading Example
29640 @subheading The @code{-target-list-parameters} Command
29641 @findex -target-list-parameters
29643 @subsubheading Synopsis
29646 -target-list-parameters
29652 @subsubheading @value{GDBN} Command
29656 @subsubheading Example
29660 @subheading The @code{-target-select} Command
29661 @findex -target-select
29663 @subsubheading Synopsis
29666 -target-select @var{type} @var{parameters @dots{}}
29669 Connect @value{GDBN} to the remote target. This command takes two args:
29673 The type of target, for instance @samp{remote}, etc.
29674 @item @var{parameters}
29675 Device names, host names and the like. @xref{Target Commands, ,
29676 Commands for Managing Targets}, for more details.
29679 The output is a connection notification, followed by the address at
29680 which the target program is, in the following form:
29683 ^connected,addr="@var{address}",func="@var{function name}",
29684 args=[@var{arg list}]
29687 @subsubheading @value{GDBN} Command
29689 The corresponding @value{GDBN} command is @samp{target}.
29691 @subsubheading Example
29695 -target-select remote /dev/ttya
29696 ^connected,addr="0xfe00a300",func="??",args=[]
29700 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29701 @node GDB/MI File Transfer Commands
29702 @section @sc{gdb/mi} File Transfer Commands
29705 @subheading The @code{-target-file-put} Command
29706 @findex -target-file-put
29708 @subsubheading Synopsis
29711 -target-file-put @var{hostfile} @var{targetfile}
29714 Copy file @var{hostfile} from the host system (the machine running
29715 @value{GDBN}) to @var{targetfile} on the target system.
29717 @subsubheading @value{GDBN} Command
29719 The corresponding @value{GDBN} command is @samp{remote put}.
29721 @subsubheading Example
29725 -target-file-put localfile remotefile
29731 @subheading The @code{-target-file-get} Command
29732 @findex -target-file-get
29734 @subsubheading Synopsis
29737 -target-file-get @var{targetfile} @var{hostfile}
29740 Copy file @var{targetfile} from the target system to @var{hostfile}
29741 on the host system.
29743 @subsubheading @value{GDBN} Command
29745 The corresponding @value{GDBN} command is @samp{remote get}.
29747 @subsubheading Example
29751 -target-file-get remotefile localfile
29757 @subheading The @code{-target-file-delete} Command
29758 @findex -target-file-delete
29760 @subsubheading Synopsis
29763 -target-file-delete @var{targetfile}
29766 Delete @var{targetfile} from the target system.
29768 @subsubheading @value{GDBN} Command
29770 The corresponding @value{GDBN} command is @samp{remote delete}.
29772 @subsubheading Example
29776 -target-file-delete remotefile
29782 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29783 @node GDB/MI Miscellaneous Commands
29784 @section Miscellaneous @sc{gdb/mi} Commands
29786 @c @subheading -gdb-complete
29788 @subheading The @code{-gdb-exit} Command
29791 @subsubheading Synopsis
29797 Exit @value{GDBN} immediately.
29799 @subsubheading @value{GDBN} Command
29801 Approximately corresponds to @samp{quit}.
29803 @subsubheading Example
29813 @subheading The @code{-exec-abort} Command
29814 @findex -exec-abort
29816 @subsubheading Synopsis
29822 Kill the inferior running program.
29824 @subsubheading @value{GDBN} Command
29826 The corresponding @value{GDBN} command is @samp{kill}.
29828 @subsubheading Example
29833 @subheading The @code{-gdb-set} Command
29836 @subsubheading Synopsis
29842 Set an internal @value{GDBN} variable.
29843 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
29845 @subsubheading @value{GDBN} Command
29847 The corresponding @value{GDBN} command is @samp{set}.
29849 @subsubheading Example
29859 @subheading The @code{-gdb-show} Command
29862 @subsubheading Synopsis
29868 Show the current value of a @value{GDBN} variable.
29870 @subsubheading @value{GDBN} Command
29872 The corresponding @value{GDBN} command is @samp{show}.
29874 @subsubheading Example
29883 @c @subheading -gdb-source
29886 @subheading The @code{-gdb-version} Command
29887 @findex -gdb-version
29889 @subsubheading Synopsis
29895 Show version information for @value{GDBN}. Used mostly in testing.
29897 @subsubheading @value{GDBN} Command
29899 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
29900 default shows this information when you start an interactive session.
29902 @subsubheading Example
29904 @c This example modifies the actual output from GDB to avoid overfull
29910 ~Copyright 2000 Free Software Foundation, Inc.
29911 ~GDB is free software, covered by the GNU General Public License, and
29912 ~you are welcome to change it and/or distribute copies of it under
29913 ~ certain conditions.
29914 ~Type "show copying" to see the conditions.
29915 ~There is absolutely no warranty for GDB. Type "show warranty" for
29917 ~This GDB was configured as
29918 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
29923 @subheading The @code{-list-features} Command
29924 @findex -list-features
29926 Returns a list of particular features of the MI protocol that
29927 this version of gdb implements. A feature can be a command,
29928 or a new field in an output of some command, or even an
29929 important bugfix. While a frontend can sometimes detect presence
29930 of a feature at runtime, it is easier to perform detection at debugger
29933 The command returns a list of strings, with each string naming an
29934 available feature. Each returned string is just a name, it does not
29935 have any internal structure. The list of possible feature names
29941 (gdb) -list-features
29942 ^done,result=["feature1","feature2"]
29945 The current list of features is:
29948 @item frozen-varobjs
29949 Indicates presence of the @code{-var-set-frozen} command, as well
29950 as possible presense of the @code{frozen} field in the output
29951 of @code{-varobj-create}.
29952 @item pending-breakpoints
29953 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
29955 Indicates presence of Python scripting support, Python-based
29956 pretty-printing commands, and possible presence of the
29957 @samp{display_hint} field in the output of @code{-var-list-children}
29959 Indicates presence of the @code{-thread-info} command.
29960 @item data-read-memory-bytes
29961 Indicates presense of the @code{-data-read-memory-bytes} and the
29962 @code{-data-write-memory-bytes} commands.
29966 @subheading The @code{-list-target-features} Command
29967 @findex -list-target-features
29969 Returns a list of particular features that are supported by the
29970 target. Those features affect the permitted MI commands, but
29971 unlike the features reported by the @code{-list-features} command, the
29972 features depend on which target GDB is using at the moment. Whenever
29973 a target can change, due to commands such as @code{-target-select},
29974 @code{-target-attach} or @code{-exec-run}, the list of target features
29975 may change, and the frontend should obtain it again.
29979 (gdb) -list-features
29980 ^done,result=["async"]
29983 The current list of features is:
29987 Indicates that the target is capable of asynchronous command
29988 execution, which means that @value{GDBN} will accept further commands
29989 while the target is running.
29992 Indicates that the target is capable of reverse execution.
29993 @xref{Reverse Execution}, for more information.
29997 @subheading The @code{-list-thread-groups} Command
29998 @findex -list-thread-groups
30000 @subheading Synopsis
30003 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
30006 Lists thread groups (@pxref{Thread groups}). When a single thread
30007 group is passed as the argument, lists the children of that group.
30008 When several thread group are passed, lists information about those
30009 thread groups. Without any parameters, lists information about all
30010 top-level thread groups.
30012 Normally, thread groups that are being debugged are reported.
30013 With the @samp{--available} option, @value{GDBN} reports thread groups
30014 available on the target.
30016 The output of this command may have either a @samp{threads} result or
30017 a @samp{groups} result. The @samp{thread} result has a list of tuples
30018 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
30019 Information}). The @samp{groups} result has a list of tuples as value,
30020 each tuple describing a thread group. If top-level groups are
30021 requested (that is, no parameter is passed), or when several groups
30022 are passed, the output always has a @samp{groups} result. The format
30023 of the @samp{group} result is described below.
30025 To reduce the number of roundtrips it's possible to list thread groups
30026 together with their children, by passing the @samp{--recurse} option
30027 and the recursion depth. Presently, only recursion depth of 1 is
30028 permitted. If this option is present, then every reported thread group
30029 will also include its children, either as @samp{group} or
30030 @samp{threads} field.
30032 In general, any combination of option and parameters is permitted, with
30033 the following caveats:
30037 When a single thread group is passed, the output will typically
30038 be the @samp{threads} result. Because threads may not contain
30039 anything, the @samp{recurse} option will be ignored.
30042 When the @samp{--available} option is passed, limited information may
30043 be available. In particular, the list of threads of a process might
30044 be inaccessible. Further, specifying specific thread groups might
30045 not give any performance advantage over listing all thread groups.
30046 The frontend should assume that @samp{-list-thread-groups --available}
30047 is always an expensive operation and cache the results.
30051 The @samp{groups} result is a list of tuples, where each tuple may
30052 have the following fields:
30056 Identifier of the thread group. This field is always present.
30057 The identifier is an opaque string; frontends should not try to
30058 convert it to an integer, even though it might look like one.
30061 The type of the thread group. At present, only @samp{process} is a
30065 The target-specific process identifier. This field is only present
30066 for thread groups of type @samp{process} and only if the process exists.
30069 The number of children this thread group has. This field may be
30070 absent for an available thread group.
30073 This field has a list of tuples as value, each tuple describing a
30074 thread. It may be present if the @samp{--recurse} option is
30075 specified, and it's actually possible to obtain the threads.
30078 This field is a list of integers, each identifying a core that one
30079 thread of the group is running on. This field may be absent if
30080 such information is not available.
30083 The name of the executable file that corresponds to this thread group.
30084 The field is only present for thread groups of type @samp{process},
30085 and only if there is a corresponding executable file.
30089 @subheading Example
30093 -list-thread-groups
30094 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
30095 -list-thread-groups 17
30096 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
30097 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
30098 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
30099 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
30100 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
30101 -list-thread-groups --available
30102 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
30103 -list-thread-groups --available --recurse 1
30104 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
30105 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
30106 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
30107 -list-thread-groups --available --recurse 1 17 18
30108 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
30109 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
30110 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
30114 @subheading The @code{-add-inferior} Command
30115 @findex -add-inferior
30117 @subheading Synopsis
30123 Creates a new inferior (@pxref{Inferiors and Programs}). The created
30124 inferior is not associated with any executable. Such association may
30125 be established with the @samp{-file-exec-and-symbols} command
30126 (@pxref{GDB/MI File Commands}). The command response has a single
30127 field, @samp{thread-group}, whose value is the identifier of the
30128 thread group corresponding to the new inferior.
30130 @subheading Example
30135 ^done,thread-group="i3"
30138 @subheading The @code{-interpreter-exec} Command
30139 @findex -interpreter-exec
30141 @subheading Synopsis
30144 -interpreter-exec @var{interpreter} @var{command}
30146 @anchor{-interpreter-exec}
30148 Execute the specified @var{command} in the given @var{interpreter}.
30150 @subheading @value{GDBN} Command
30152 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
30154 @subheading Example
30158 -interpreter-exec console "break main"
30159 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
30160 &"During symbol reading, bad structure-type format.\n"
30161 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
30166 @subheading The @code{-inferior-tty-set} Command
30167 @findex -inferior-tty-set
30169 @subheading Synopsis
30172 -inferior-tty-set /dev/pts/1
30175 Set terminal for future runs of the program being debugged.
30177 @subheading @value{GDBN} Command
30179 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
30181 @subheading Example
30185 -inferior-tty-set /dev/pts/1
30190 @subheading The @code{-inferior-tty-show} Command
30191 @findex -inferior-tty-show
30193 @subheading Synopsis
30199 Show terminal for future runs of program being debugged.
30201 @subheading @value{GDBN} Command
30203 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
30205 @subheading Example
30209 -inferior-tty-set /dev/pts/1
30213 ^done,inferior_tty_terminal="/dev/pts/1"
30217 @subheading The @code{-enable-timings} Command
30218 @findex -enable-timings
30220 @subheading Synopsis
30223 -enable-timings [yes | no]
30226 Toggle the printing of the wallclock, user and system times for an MI
30227 command as a field in its output. This command is to help frontend
30228 developers optimize the performance of their code. No argument is
30229 equivalent to @samp{yes}.
30231 @subheading @value{GDBN} Command
30235 @subheading Example
30243 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30244 addr="0x080484ed",func="main",file="myprog.c",
30245 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
30246 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
30254 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
30255 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
30256 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
30257 fullname="/home/nickrob/myprog.c",line="73"@}
30262 @chapter @value{GDBN} Annotations
30264 This chapter describes annotations in @value{GDBN}. Annotations were
30265 designed to interface @value{GDBN} to graphical user interfaces or other
30266 similar programs which want to interact with @value{GDBN} at a
30267 relatively high level.
30269 The annotation mechanism has largely been superseded by @sc{gdb/mi}
30273 This is Edition @value{EDITION}, @value{DATE}.
30277 * Annotations Overview:: What annotations are; the general syntax.
30278 * Server Prefix:: Issuing a command without affecting user state.
30279 * Prompting:: Annotations marking @value{GDBN}'s need for input.
30280 * Errors:: Annotations for error messages.
30281 * Invalidation:: Some annotations describe things now invalid.
30282 * Annotations for Running::
30283 Whether the program is running, how it stopped, etc.
30284 * Source Annotations:: Annotations describing source code.
30287 @node Annotations Overview
30288 @section What is an Annotation?
30289 @cindex annotations
30291 Annotations start with a newline character, two @samp{control-z}
30292 characters, and the name of the annotation. If there is no additional
30293 information associated with this annotation, the name of the annotation
30294 is followed immediately by a newline. If there is additional
30295 information, the name of the annotation is followed by a space, the
30296 additional information, and a newline. The additional information
30297 cannot contain newline characters.
30299 Any output not beginning with a newline and two @samp{control-z}
30300 characters denotes literal output from @value{GDBN}. Currently there is
30301 no need for @value{GDBN} to output a newline followed by two
30302 @samp{control-z} characters, but if there was such a need, the
30303 annotations could be extended with an @samp{escape} annotation which
30304 means those three characters as output.
30306 The annotation @var{level}, which is specified using the
30307 @option{--annotate} command line option (@pxref{Mode Options}), controls
30308 how much information @value{GDBN} prints together with its prompt,
30309 values of expressions, source lines, and other types of output. Level 0
30310 is for no annotations, level 1 is for use when @value{GDBN} is run as a
30311 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
30312 for programs that control @value{GDBN}, and level 2 annotations have
30313 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
30314 Interface, annotate, GDB's Obsolete Annotations}).
30317 @kindex set annotate
30318 @item set annotate @var{level}
30319 The @value{GDBN} command @code{set annotate} sets the level of
30320 annotations to the specified @var{level}.
30322 @item show annotate
30323 @kindex show annotate
30324 Show the current annotation level.
30327 This chapter describes level 3 annotations.
30329 A simple example of starting up @value{GDBN} with annotations is:
30332 $ @kbd{gdb --annotate=3}
30334 Copyright 2003 Free Software Foundation, Inc.
30335 GDB is free software, covered by the GNU General Public License,
30336 and you are welcome to change it and/or distribute copies of it
30337 under certain conditions.
30338 Type "show copying" to see the conditions.
30339 There is absolutely no warranty for GDB. Type "show warranty"
30341 This GDB was configured as "i386-pc-linux-gnu"
30352 Here @samp{quit} is input to @value{GDBN}; the rest is output from
30353 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
30354 denotes a @samp{control-z} character) are annotations; the rest is
30355 output from @value{GDBN}.
30357 @node Server Prefix
30358 @section The Server Prefix
30359 @cindex server prefix
30361 If you prefix a command with @samp{server } then it will not affect
30362 the command history, nor will it affect @value{GDBN}'s notion of which
30363 command to repeat if @key{RET} is pressed on a line by itself. This
30364 means that commands can be run behind a user's back by a front-end in
30365 a transparent manner.
30367 The @code{server } prefix does not affect the recording of values into
30368 the value history; to print a value without recording it into the
30369 value history, use the @code{output} command instead of the
30370 @code{print} command.
30372 Using this prefix also disables confirmation requests
30373 (@pxref{confirmation requests}).
30376 @section Annotation for @value{GDBN} Input
30378 @cindex annotations for prompts
30379 When @value{GDBN} prompts for input, it annotates this fact so it is possible
30380 to know when to send output, when the output from a given command is
30383 Different kinds of input each have a different @dfn{input type}. Each
30384 input type has three annotations: a @code{pre-} annotation, which
30385 denotes the beginning of any prompt which is being output, a plain
30386 annotation, which denotes the end of the prompt, and then a @code{post-}
30387 annotation which denotes the end of any echo which may (or may not) be
30388 associated with the input. For example, the @code{prompt} input type
30389 features the following annotations:
30397 The input types are
30400 @findex pre-prompt annotation
30401 @findex prompt annotation
30402 @findex post-prompt annotation
30404 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
30406 @findex pre-commands annotation
30407 @findex commands annotation
30408 @findex post-commands annotation
30410 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
30411 command. The annotations are repeated for each command which is input.
30413 @findex pre-overload-choice annotation
30414 @findex overload-choice annotation
30415 @findex post-overload-choice annotation
30416 @item overload-choice
30417 When @value{GDBN} wants the user to select between various overloaded functions.
30419 @findex pre-query annotation
30420 @findex query annotation
30421 @findex post-query annotation
30423 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
30425 @findex pre-prompt-for-continue annotation
30426 @findex prompt-for-continue annotation
30427 @findex post-prompt-for-continue annotation
30428 @item prompt-for-continue
30429 When @value{GDBN} is asking the user to press return to continue. Note: Don't
30430 expect this to work well; instead use @code{set height 0} to disable
30431 prompting. This is because the counting of lines is buggy in the
30432 presence of annotations.
30437 @cindex annotations for errors, warnings and interrupts
30439 @findex quit annotation
30444 This annotation occurs right before @value{GDBN} responds to an interrupt.
30446 @findex error annotation
30451 This annotation occurs right before @value{GDBN} responds to an error.
30453 Quit and error annotations indicate that any annotations which @value{GDBN} was
30454 in the middle of may end abruptly. For example, if a
30455 @code{value-history-begin} annotation is followed by a @code{error}, one
30456 cannot expect to receive the matching @code{value-history-end}. One
30457 cannot expect not to receive it either, however; an error annotation
30458 does not necessarily mean that @value{GDBN} is immediately returning all the way
30461 @findex error-begin annotation
30462 A quit or error annotation may be preceded by
30468 Any output between that and the quit or error annotation is the error
30471 Warning messages are not yet annotated.
30472 @c If we want to change that, need to fix warning(), type_error(),
30473 @c range_error(), and possibly other places.
30476 @section Invalidation Notices
30478 @cindex annotations for invalidation messages
30479 The following annotations say that certain pieces of state may have
30483 @findex frames-invalid annotation
30484 @item ^Z^Zframes-invalid
30486 The frames (for example, output from the @code{backtrace} command) may
30489 @findex breakpoints-invalid annotation
30490 @item ^Z^Zbreakpoints-invalid
30492 The breakpoints may have changed. For example, the user just added or
30493 deleted a breakpoint.
30496 @node Annotations for Running
30497 @section Running the Program
30498 @cindex annotations for running programs
30500 @findex starting annotation
30501 @findex stopping annotation
30502 When the program starts executing due to a @value{GDBN} command such as
30503 @code{step} or @code{continue},
30509 is output. When the program stops,
30515 is output. Before the @code{stopped} annotation, a variety of
30516 annotations describe how the program stopped.
30519 @findex exited annotation
30520 @item ^Z^Zexited @var{exit-status}
30521 The program exited, and @var{exit-status} is the exit status (zero for
30522 successful exit, otherwise nonzero).
30524 @findex signalled annotation
30525 @findex signal-name annotation
30526 @findex signal-name-end annotation
30527 @findex signal-string annotation
30528 @findex signal-string-end annotation
30529 @item ^Z^Zsignalled
30530 The program exited with a signal. After the @code{^Z^Zsignalled}, the
30531 annotation continues:
30537 ^Z^Zsignal-name-end
30541 ^Z^Zsignal-string-end
30546 where @var{name} is the name of the signal, such as @code{SIGILL} or
30547 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
30548 as @code{Illegal Instruction} or @code{Segmentation fault}.
30549 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
30550 user's benefit and have no particular format.
30552 @findex signal annotation
30554 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
30555 just saying that the program received the signal, not that it was
30556 terminated with it.
30558 @findex breakpoint annotation
30559 @item ^Z^Zbreakpoint @var{number}
30560 The program hit breakpoint number @var{number}.
30562 @findex watchpoint annotation
30563 @item ^Z^Zwatchpoint @var{number}
30564 The program hit watchpoint number @var{number}.
30567 @node Source Annotations
30568 @section Displaying Source
30569 @cindex annotations for source display
30571 @findex source annotation
30572 The following annotation is used instead of displaying source code:
30575 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
30578 where @var{filename} is an absolute file name indicating which source
30579 file, @var{line} is the line number within that file (where 1 is the
30580 first line in the file), @var{character} is the character position
30581 within the file (where 0 is the first character in the file) (for most
30582 debug formats this will necessarily point to the beginning of a line),
30583 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
30584 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
30585 @var{addr} is the address in the target program associated with the
30586 source which is being displayed. @var{addr} is in the form @samp{0x}
30587 followed by one or more lowercase hex digits (note that this does not
30588 depend on the language).
30590 @node JIT Interface
30591 @chapter JIT Compilation Interface
30592 @cindex just-in-time compilation
30593 @cindex JIT compilation interface
30595 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
30596 interface. A JIT compiler is a program or library that generates native
30597 executable code at runtime and executes it, usually in order to achieve good
30598 performance while maintaining platform independence.
30600 Programs that use JIT compilation are normally difficult to debug because
30601 portions of their code are generated at runtime, instead of being loaded from
30602 object files, which is where @value{GDBN} normally finds the program's symbols
30603 and debug information. In order to debug programs that use JIT compilation,
30604 @value{GDBN} has an interface that allows the program to register in-memory
30605 symbol files with @value{GDBN} at runtime.
30607 If you are using @value{GDBN} to debug a program that uses this interface, then
30608 it should work transparently so long as you have not stripped the binary. If
30609 you are developing a JIT compiler, then the interface is documented in the rest
30610 of this chapter. At this time, the only known client of this interface is the
30613 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
30614 JIT compiler communicates with @value{GDBN} by writing data into a global
30615 variable and calling a fuction at a well-known symbol. When @value{GDBN}
30616 attaches, it reads a linked list of symbol files from the global variable to
30617 find existing code, and puts a breakpoint in the function so that it can find
30618 out about additional code.
30621 * Declarations:: Relevant C struct declarations
30622 * Registering Code:: Steps to register code
30623 * Unregistering Code:: Steps to unregister code
30627 @section JIT Declarations
30629 These are the relevant struct declarations that a C program should include to
30630 implement the interface:
30640 struct jit_code_entry
30642 struct jit_code_entry *next_entry;
30643 struct jit_code_entry *prev_entry;
30644 const char *symfile_addr;
30645 uint64_t symfile_size;
30648 struct jit_descriptor
30651 /* This type should be jit_actions_t, but we use uint32_t
30652 to be explicit about the bitwidth. */
30653 uint32_t action_flag;
30654 struct jit_code_entry *relevant_entry;
30655 struct jit_code_entry *first_entry;
30658 /* GDB puts a breakpoint in this function. */
30659 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
30661 /* Make sure to specify the version statically, because the
30662 debugger may check the version before we can set it. */
30663 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
30666 If the JIT is multi-threaded, then it is important that the JIT synchronize any
30667 modifications to this global data properly, which can easily be done by putting
30668 a global mutex around modifications to these structures.
30670 @node Registering Code
30671 @section Registering Code
30673 To register code with @value{GDBN}, the JIT should follow this protocol:
30677 Generate an object file in memory with symbols and other desired debug
30678 information. The file must include the virtual addresses of the sections.
30681 Create a code entry for the file, which gives the start and size of the symbol
30685 Add it to the linked list in the JIT descriptor.
30688 Point the relevant_entry field of the descriptor at the entry.
30691 Set @code{action_flag} to @code{JIT_REGISTER} and call
30692 @code{__jit_debug_register_code}.
30695 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
30696 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
30697 new code. However, the linked list must still be maintained in order to allow
30698 @value{GDBN} to attach to a running process and still find the symbol files.
30700 @node Unregistering Code
30701 @section Unregistering Code
30703 If code is freed, then the JIT should use the following protocol:
30707 Remove the code entry corresponding to the code from the linked list.
30710 Point the @code{relevant_entry} field of the descriptor at the code entry.
30713 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
30714 @code{__jit_debug_register_code}.
30717 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
30718 and the JIT will leak the memory used for the associated symbol files.
30721 @chapter Reporting Bugs in @value{GDBN}
30722 @cindex bugs in @value{GDBN}
30723 @cindex reporting bugs in @value{GDBN}
30725 Your bug reports play an essential role in making @value{GDBN} reliable.
30727 Reporting a bug may help you by bringing a solution to your problem, or it
30728 may not. But in any case the principal function of a bug report is to help
30729 the entire community by making the next version of @value{GDBN} work better. Bug
30730 reports are your contribution to the maintenance of @value{GDBN}.
30732 In order for a bug report to serve its purpose, you must include the
30733 information that enables us to fix the bug.
30736 * Bug Criteria:: Have you found a bug?
30737 * Bug Reporting:: How to report bugs
30741 @section Have You Found a Bug?
30742 @cindex bug criteria
30744 If you are not sure whether you have found a bug, here are some guidelines:
30747 @cindex fatal signal
30748 @cindex debugger crash
30749 @cindex crash of debugger
30751 If the debugger gets a fatal signal, for any input whatever, that is a
30752 @value{GDBN} bug. Reliable debuggers never crash.
30754 @cindex error on valid input
30756 If @value{GDBN} produces an error message for valid input, that is a
30757 bug. (Note that if you're cross debugging, the problem may also be
30758 somewhere in the connection to the target.)
30760 @cindex invalid input
30762 If @value{GDBN} does not produce an error message for invalid input,
30763 that is a bug. However, you should note that your idea of
30764 ``invalid input'' might be our idea of ``an extension'' or ``support
30765 for traditional practice''.
30768 If you are an experienced user of debugging tools, your suggestions
30769 for improvement of @value{GDBN} are welcome in any case.
30772 @node Bug Reporting
30773 @section How to Report Bugs
30774 @cindex bug reports
30775 @cindex @value{GDBN} bugs, reporting
30777 A number of companies and individuals offer support for @sc{gnu} products.
30778 If you obtained @value{GDBN} from a support organization, we recommend you
30779 contact that organization first.
30781 You can find contact information for many support companies and
30782 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
30784 @c should add a web page ref...
30787 @ifset BUGURL_DEFAULT
30788 In any event, we also recommend that you submit bug reports for
30789 @value{GDBN}. The preferred method is to submit them directly using
30790 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
30791 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
30794 @strong{Do not send bug reports to @samp{info-gdb}, or to
30795 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
30796 not want to receive bug reports. Those that do have arranged to receive
30799 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
30800 serves as a repeater. The mailing list and the newsgroup carry exactly
30801 the same messages. Often people think of posting bug reports to the
30802 newsgroup instead of mailing them. This appears to work, but it has one
30803 problem which can be crucial: a newsgroup posting often lacks a mail
30804 path back to the sender. Thus, if we need to ask for more information,
30805 we may be unable to reach you. For this reason, it is better to send
30806 bug reports to the mailing list.
30808 @ifclear BUGURL_DEFAULT
30809 In any event, we also recommend that you submit bug reports for
30810 @value{GDBN} to @value{BUGURL}.
30814 The fundamental principle of reporting bugs usefully is this:
30815 @strong{report all the facts}. If you are not sure whether to state a
30816 fact or leave it out, state it!
30818 Often people omit facts because they think they know what causes the
30819 problem and assume that some details do not matter. Thus, you might
30820 assume that the name of the variable you use in an example does not matter.
30821 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
30822 stray memory reference which happens to fetch from the location where that
30823 name is stored in memory; perhaps, if the name were different, the contents
30824 of that location would fool the debugger into doing the right thing despite
30825 the bug. Play it safe and give a specific, complete example. That is the
30826 easiest thing for you to do, and the most helpful.
30828 Keep in mind that the purpose of a bug report is to enable us to fix the
30829 bug. It may be that the bug has been reported previously, but neither
30830 you nor we can know that unless your bug report is complete and
30833 Sometimes people give a few sketchy facts and ask, ``Does this ring a
30834 bell?'' Those bug reports are useless, and we urge everyone to
30835 @emph{refuse to respond to them} except to chide the sender to report
30838 To enable us to fix the bug, you should include all these things:
30842 The version of @value{GDBN}. @value{GDBN} announces it if you start
30843 with no arguments; you can also print it at any time using @code{show
30846 Without this, we will not know whether there is any point in looking for
30847 the bug in the current version of @value{GDBN}.
30850 The type of machine you are using, and the operating system name and
30854 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
30855 ``@value{GCC}--2.8.1''.
30858 What compiler (and its version) was used to compile the program you are
30859 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
30860 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
30861 to get this information; for other compilers, see the documentation for
30865 The command arguments you gave the compiler to compile your example and
30866 observe the bug. For example, did you use @samp{-O}? To guarantee
30867 you will not omit something important, list them all. A copy of the
30868 Makefile (or the output from make) is sufficient.
30870 If we were to try to guess the arguments, we would probably guess wrong
30871 and then we might not encounter the bug.
30874 A complete input script, and all necessary source files, that will
30878 A description of what behavior you observe that you believe is
30879 incorrect. For example, ``It gets a fatal signal.''
30881 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
30882 will certainly notice it. But if the bug is incorrect output, we might
30883 not notice unless it is glaringly wrong. You might as well not give us
30884 a chance to make a mistake.
30886 Even if the problem you experience is a fatal signal, you should still
30887 say so explicitly. Suppose something strange is going on, such as, your
30888 copy of @value{GDBN} is out of synch, or you have encountered a bug in
30889 the C library on your system. (This has happened!) Your copy might
30890 crash and ours would not. If you told us to expect a crash, then when
30891 ours fails to crash, we would know that the bug was not happening for
30892 us. If you had not told us to expect a crash, then we would not be able
30893 to draw any conclusion from our observations.
30896 @cindex recording a session script
30897 To collect all this information, you can use a session recording program
30898 such as @command{script}, which is available on many Unix systems.
30899 Just run your @value{GDBN} session inside @command{script} and then
30900 include the @file{typescript} file with your bug report.
30902 Another way to record a @value{GDBN} session is to run @value{GDBN}
30903 inside Emacs and then save the entire buffer to a file.
30906 If you wish to suggest changes to the @value{GDBN} source, send us context
30907 diffs. If you even discuss something in the @value{GDBN} source, refer to
30908 it by context, not by line number.
30910 The line numbers in our development sources will not match those in your
30911 sources. Your line numbers would convey no useful information to us.
30915 Here are some things that are not necessary:
30919 A description of the envelope of the bug.
30921 Often people who encounter a bug spend a lot of time investigating
30922 which changes to the input file will make the bug go away and which
30923 changes will not affect it.
30925 This is often time consuming and not very useful, because the way we
30926 will find the bug is by running a single example under the debugger
30927 with breakpoints, not by pure deduction from a series of examples.
30928 We recommend that you save your time for something else.
30930 Of course, if you can find a simpler example to report @emph{instead}
30931 of the original one, that is a convenience for us. Errors in the
30932 output will be easier to spot, running under the debugger will take
30933 less time, and so on.
30935 However, simplification is not vital; if you do not want to do this,
30936 report the bug anyway and send us the entire test case you used.
30939 A patch for the bug.
30941 A patch for the bug does help us if it is a good one. But do not omit
30942 the necessary information, such as the test case, on the assumption that
30943 a patch is all we need. We might see problems with your patch and decide
30944 to fix the problem another way, or we might not understand it at all.
30946 Sometimes with a program as complicated as @value{GDBN} it is very hard to
30947 construct an example that will make the program follow a certain path
30948 through the code. If you do not send us the example, we will not be able
30949 to construct one, so we will not be able to verify that the bug is fixed.
30951 And if we cannot understand what bug you are trying to fix, or why your
30952 patch should be an improvement, we will not install it. A test case will
30953 help us to understand.
30956 A guess about what the bug is or what it depends on.
30958 Such guesses are usually wrong. Even we cannot guess right about such
30959 things without first using the debugger to find the facts.
30962 @c The readline documentation is distributed with the readline code
30963 @c and consists of the two following files:
30965 @c inc-hist.texinfo
30966 @c Use -I with makeinfo to point to the appropriate directory,
30967 @c environment var TEXINPUTS with TeX.
30968 @ifclear SYSTEM_READLINE
30969 @include rluser.texi
30970 @include inc-hist.texinfo
30974 @node Formatting Documentation
30975 @appendix Formatting Documentation
30977 @cindex @value{GDBN} reference card
30978 @cindex reference card
30979 The @value{GDBN} 4 release includes an already-formatted reference card, ready
30980 for printing with PostScript or Ghostscript, in the @file{gdb}
30981 subdirectory of the main source directory@footnote{In
30982 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
30983 release.}. If you can use PostScript or Ghostscript with your printer,
30984 you can print the reference card immediately with @file{refcard.ps}.
30986 The release also includes the source for the reference card. You
30987 can format it, using @TeX{}, by typing:
30993 The @value{GDBN} reference card is designed to print in @dfn{landscape}
30994 mode on US ``letter'' size paper;
30995 that is, on a sheet 11 inches wide by 8.5 inches
30996 high. You will need to specify this form of printing as an option to
30997 your @sc{dvi} output program.
30999 @cindex documentation
31001 All the documentation for @value{GDBN} comes as part of the machine-readable
31002 distribution. The documentation is written in Texinfo format, which is
31003 a documentation system that uses a single source file to produce both
31004 on-line information and a printed manual. You can use one of the Info
31005 formatting commands to create the on-line version of the documentation
31006 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
31008 @value{GDBN} includes an already formatted copy of the on-line Info
31009 version of this manual in the @file{gdb} subdirectory. The main Info
31010 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
31011 subordinate files matching @samp{gdb.info*} in the same directory. If
31012 necessary, you can print out these files, or read them with any editor;
31013 but they are easier to read using the @code{info} subsystem in @sc{gnu}
31014 Emacs or the standalone @code{info} program, available as part of the
31015 @sc{gnu} Texinfo distribution.
31017 If you want to format these Info files yourself, you need one of the
31018 Info formatting programs, such as @code{texinfo-format-buffer} or
31021 If you have @code{makeinfo} installed, and are in the top level
31022 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
31023 version @value{GDBVN}), you can make the Info file by typing:
31030 If you want to typeset and print copies of this manual, you need @TeX{},
31031 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
31032 Texinfo definitions file.
31034 @TeX{} is a typesetting program; it does not print files directly, but
31035 produces output files called @sc{dvi} files. To print a typeset
31036 document, you need a program to print @sc{dvi} files. If your system
31037 has @TeX{} installed, chances are it has such a program. The precise
31038 command to use depends on your system; @kbd{lpr -d} is common; another
31039 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
31040 require a file name without any extension or a @samp{.dvi} extension.
31042 @TeX{} also requires a macro definitions file called
31043 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
31044 written in Texinfo format. On its own, @TeX{} cannot either read or
31045 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
31046 and is located in the @file{gdb-@var{version-number}/texinfo}
31049 If you have @TeX{} and a @sc{dvi} printer program installed, you can
31050 typeset and print this manual. First switch to the @file{gdb}
31051 subdirectory of the main source directory (for example, to
31052 @file{gdb-@value{GDBVN}/gdb}) and type:
31058 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
31060 @node Installing GDB
31061 @appendix Installing @value{GDBN}
31062 @cindex installation
31065 * Requirements:: Requirements for building @value{GDBN}
31066 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
31067 * Separate Objdir:: Compiling @value{GDBN} in another directory
31068 * Config Names:: Specifying names for hosts and targets
31069 * Configure Options:: Summary of options for configure
31070 * System-wide configuration:: Having a system-wide init file
31074 @section Requirements for Building @value{GDBN}
31075 @cindex building @value{GDBN}, requirements for
31077 Building @value{GDBN} requires various tools and packages to be available.
31078 Other packages will be used only if they are found.
31080 @heading Tools/Packages Necessary for Building @value{GDBN}
31082 @item ISO C90 compiler
31083 @value{GDBN} is written in ISO C90. It should be buildable with any
31084 working C90 compiler, e.g.@: GCC.
31088 @heading Tools/Packages Optional for Building @value{GDBN}
31092 @value{GDBN} can use the Expat XML parsing library. This library may be
31093 included with your operating system distribution; if it is not, you
31094 can get the latest version from @url{http://expat.sourceforge.net}.
31095 The @file{configure} script will search for this library in several
31096 standard locations; if it is installed in an unusual path, you can
31097 use the @option{--with-libexpat-prefix} option to specify its location.
31103 Remote protocol memory maps (@pxref{Memory Map Format})
31105 Target descriptions (@pxref{Target Descriptions})
31107 Remote shared library lists (@pxref{Library List Format})
31109 MS-Windows shared libraries (@pxref{Shared Libraries})
31111 Traceframe info (@pxref{Traceframe Info Format})
31115 @cindex compressed debug sections
31116 @value{GDBN} will use the @samp{zlib} library, if available, to read
31117 compressed debug sections. Some linkers, such as GNU gold, are capable
31118 of producing binaries with compressed debug sections. If @value{GDBN}
31119 is compiled with @samp{zlib}, it will be able to read the debug
31120 information in such binaries.
31122 The @samp{zlib} library is likely included with your operating system
31123 distribution; if it is not, you can get the latest version from
31124 @url{http://zlib.net}.
31127 @value{GDBN}'s features related to character sets (@pxref{Character
31128 Sets}) require a functioning @code{iconv} implementation. If you are
31129 on a GNU system, then this is provided by the GNU C Library. Some
31130 other systems also provide a working @code{iconv}.
31132 On systems with @code{iconv}, you can install GNU Libiconv. If you
31133 have previously installed Libiconv, you can use the
31134 @option{--with-libiconv-prefix} option to configure.
31136 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
31137 arrange to build Libiconv if a directory named @file{libiconv} appears
31138 in the top-most source directory. If Libiconv is built this way, and
31139 if the operating system does not provide a suitable @code{iconv}
31140 implementation, then the just-built library will automatically be used
31141 by @value{GDBN}. One easy way to set this up is to download GNU
31142 Libiconv, unpack it, and then rename the directory holding the
31143 Libiconv source code to @samp{libiconv}.
31146 @node Running Configure
31147 @section Invoking the @value{GDBN} @file{configure} Script
31148 @cindex configuring @value{GDBN}
31149 @value{GDBN} comes with a @file{configure} script that automates the process
31150 of preparing @value{GDBN} for installation; you can then use @code{make} to
31151 build the @code{gdb} program.
31153 @c irrelevant in info file; it's as current as the code it lives with.
31154 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
31155 look at the @file{README} file in the sources; we may have improved the
31156 installation procedures since publishing this manual.}
31159 The @value{GDBN} distribution includes all the source code you need for
31160 @value{GDBN} in a single directory, whose name is usually composed by
31161 appending the version number to @samp{gdb}.
31163 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
31164 @file{gdb-@value{GDBVN}} directory. That directory contains:
31167 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
31168 script for configuring @value{GDBN} and all its supporting libraries
31170 @item gdb-@value{GDBVN}/gdb
31171 the source specific to @value{GDBN} itself
31173 @item gdb-@value{GDBVN}/bfd
31174 source for the Binary File Descriptor library
31176 @item gdb-@value{GDBVN}/include
31177 @sc{gnu} include files
31179 @item gdb-@value{GDBVN}/libiberty
31180 source for the @samp{-liberty} free software library
31182 @item gdb-@value{GDBVN}/opcodes
31183 source for the library of opcode tables and disassemblers
31185 @item gdb-@value{GDBVN}/readline
31186 source for the @sc{gnu} command-line interface
31188 @item gdb-@value{GDBVN}/glob
31189 source for the @sc{gnu} filename pattern-matching subroutine
31191 @item gdb-@value{GDBVN}/mmalloc
31192 source for the @sc{gnu} memory-mapped malloc package
31195 The simplest way to configure and build @value{GDBN} is to run @file{configure}
31196 from the @file{gdb-@var{version-number}} source directory, which in
31197 this example is the @file{gdb-@value{GDBVN}} directory.
31199 First switch to the @file{gdb-@var{version-number}} source directory
31200 if you are not already in it; then run @file{configure}. Pass the
31201 identifier for the platform on which @value{GDBN} will run as an
31207 cd gdb-@value{GDBVN}
31208 ./configure @var{host}
31213 where @var{host} is an identifier such as @samp{sun4} or
31214 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
31215 (You can often leave off @var{host}; @file{configure} tries to guess the
31216 correct value by examining your system.)
31218 Running @samp{configure @var{host}} and then running @code{make} builds the
31219 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
31220 libraries, then @code{gdb} itself. The configured source files, and the
31221 binaries, are left in the corresponding source directories.
31224 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
31225 system does not recognize this automatically when you run a different
31226 shell, you may need to run @code{sh} on it explicitly:
31229 sh configure @var{host}
31232 If you run @file{configure} from a directory that contains source
31233 directories for multiple libraries or programs, such as the
31234 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
31236 creates configuration files for every directory level underneath (unless
31237 you tell it not to, with the @samp{--norecursion} option).
31239 You should run the @file{configure} script from the top directory in the
31240 source tree, the @file{gdb-@var{version-number}} directory. If you run
31241 @file{configure} from one of the subdirectories, you will configure only
31242 that subdirectory. That is usually not what you want. In particular,
31243 if you run the first @file{configure} from the @file{gdb} subdirectory
31244 of the @file{gdb-@var{version-number}} directory, you will omit the
31245 configuration of @file{bfd}, @file{readline}, and other sibling
31246 directories of the @file{gdb} subdirectory. This leads to build errors
31247 about missing include files such as @file{bfd/bfd.h}.
31249 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
31250 However, you should make sure that the shell on your path (named by
31251 the @samp{SHELL} environment variable) is publicly readable. Remember
31252 that @value{GDBN} uses the shell to start your program---some systems refuse to
31253 let @value{GDBN} debug child processes whose programs are not readable.
31255 @node Separate Objdir
31256 @section Compiling @value{GDBN} in Another Directory
31258 If you want to run @value{GDBN} versions for several host or target machines,
31259 you need a different @code{gdb} compiled for each combination of
31260 host and target. @file{configure} is designed to make this easy by
31261 allowing you to generate each configuration in a separate subdirectory,
31262 rather than in the source directory. If your @code{make} program
31263 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
31264 @code{make} in each of these directories builds the @code{gdb}
31265 program specified there.
31267 To build @code{gdb} in a separate directory, run @file{configure}
31268 with the @samp{--srcdir} option to specify where to find the source.
31269 (You also need to specify a path to find @file{configure}
31270 itself from your working directory. If the path to @file{configure}
31271 would be the same as the argument to @samp{--srcdir}, you can leave out
31272 the @samp{--srcdir} option; it is assumed.)
31274 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
31275 separate directory for a Sun 4 like this:
31279 cd gdb-@value{GDBVN}
31282 ../gdb-@value{GDBVN}/configure sun4
31287 When @file{configure} builds a configuration using a remote source
31288 directory, it creates a tree for the binaries with the same structure
31289 (and using the same names) as the tree under the source directory. In
31290 the example, you'd find the Sun 4 library @file{libiberty.a} in the
31291 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
31292 @file{gdb-sun4/gdb}.
31294 Make sure that your path to the @file{configure} script has just one
31295 instance of @file{gdb} in it. If your path to @file{configure} looks
31296 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
31297 one subdirectory of @value{GDBN}, not the whole package. This leads to
31298 build errors about missing include files such as @file{bfd/bfd.h}.
31300 One popular reason to build several @value{GDBN} configurations in separate
31301 directories is to configure @value{GDBN} for cross-compiling (where
31302 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
31303 programs that run on another machine---the @dfn{target}).
31304 You specify a cross-debugging target by
31305 giving the @samp{--target=@var{target}} option to @file{configure}.
31307 When you run @code{make} to build a program or library, you must run
31308 it in a configured directory---whatever directory you were in when you
31309 called @file{configure} (or one of its subdirectories).
31311 The @code{Makefile} that @file{configure} generates in each source
31312 directory also runs recursively. If you type @code{make} in a source
31313 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
31314 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
31315 will build all the required libraries, and then build GDB.
31317 When you have multiple hosts or targets configured in separate
31318 directories, you can run @code{make} on them in parallel (for example,
31319 if they are NFS-mounted on each of the hosts); they will not interfere
31323 @section Specifying Names for Hosts and Targets
31325 The specifications used for hosts and targets in the @file{configure}
31326 script are based on a three-part naming scheme, but some short predefined
31327 aliases are also supported. The full naming scheme encodes three pieces
31328 of information in the following pattern:
31331 @var{architecture}-@var{vendor}-@var{os}
31334 For example, you can use the alias @code{sun4} as a @var{host} argument,
31335 or as the value for @var{target} in a @code{--target=@var{target}}
31336 option. The equivalent full name is @samp{sparc-sun-sunos4}.
31338 The @file{configure} script accompanying @value{GDBN} does not provide
31339 any query facility to list all supported host and target names or
31340 aliases. @file{configure} calls the Bourne shell script
31341 @code{config.sub} to map abbreviations to full names; you can read the
31342 script, if you wish, or you can use it to test your guesses on
31343 abbreviations---for example:
31346 % sh config.sub i386-linux
31348 % sh config.sub alpha-linux
31349 alpha-unknown-linux-gnu
31350 % sh config.sub hp9k700
31352 % sh config.sub sun4
31353 sparc-sun-sunos4.1.1
31354 % sh config.sub sun3
31355 m68k-sun-sunos4.1.1
31356 % sh config.sub i986v
31357 Invalid configuration `i986v': machine `i986v' not recognized
31361 @code{config.sub} is also distributed in the @value{GDBN} source
31362 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
31364 @node Configure Options
31365 @section @file{configure} Options
31367 Here is a summary of the @file{configure} options and arguments that
31368 are most often useful for building @value{GDBN}. @file{configure} also has
31369 several other options not listed here. @inforef{What Configure
31370 Does,,configure.info}, for a full explanation of @file{configure}.
31373 configure @r{[}--help@r{]}
31374 @r{[}--prefix=@var{dir}@r{]}
31375 @r{[}--exec-prefix=@var{dir}@r{]}
31376 @r{[}--srcdir=@var{dirname}@r{]}
31377 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
31378 @r{[}--target=@var{target}@r{]}
31383 You may introduce options with a single @samp{-} rather than
31384 @samp{--} if you prefer; but you may abbreviate option names if you use
31389 Display a quick summary of how to invoke @file{configure}.
31391 @item --prefix=@var{dir}
31392 Configure the source to install programs and files under directory
31395 @item --exec-prefix=@var{dir}
31396 Configure the source to install programs under directory
31399 @c avoid splitting the warning from the explanation:
31401 @item --srcdir=@var{dirname}
31402 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
31403 @code{make} that implements the @code{VPATH} feature.}@*
31404 Use this option to make configurations in directories separate from the
31405 @value{GDBN} source directories. Among other things, you can use this to
31406 build (or maintain) several configurations simultaneously, in separate
31407 directories. @file{configure} writes configuration-specific files in
31408 the current directory, but arranges for them to use the source in the
31409 directory @var{dirname}. @file{configure} creates directories under
31410 the working directory in parallel to the source directories below
31413 @item --norecursion
31414 Configure only the directory level where @file{configure} is executed; do not
31415 propagate configuration to subdirectories.
31417 @item --target=@var{target}
31418 Configure @value{GDBN} for cross-debugging programs running on the specified
31419 @var{target}. Without this option, @value{GDBN} is configured to debug
31420 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
31422 There is no convenient way to generate a list of all available targets.
31424 @item @var{host} @dots{}
31425 Configure @value{GDBN} to run on the specified @var{host}.
31427 There is no convenient way to generate a list of all available hosts.
31430 There are many other options available as well, but they are generally
31431 needed for special purposes only.
31433 @node System-wide configuration
31434 @section System-wide configuration and settings
31435 @cindex system-wide init file
31437 @value{GDBN} can be configured to have a system-wide init file;
31438 this file will be read and executed at startup (@pxref{Startup, , What
31439 @value{GDBN} does during startup}).
31441 Here is the corresponding configure option:
31444 @item --with-system-gdbinit=@var{file}
31445 Specify that the default location of the system-wide init file is
31449 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
31450 it may be subject to relocation. Two possible cases:
31454 If the default location of this init file contains @file{$prefix},
31455 it will be subject to relocation. Suppose that the configure options
31456 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
31457 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
31458 init file is looked for as @file{$install/etc/gdbinit} instead of
31459 @file{$prefix/etc/gdbinit}.
31462 By contrast, if the default location does not contain the prefix,
31463 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
31464 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
31465 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
31466 wherever @value{GDBN} is installed.
31469 @node Maintenance Commands
31470 @appendix Maintenance Commands
31471 @cindex maintenance commands
31472 @cindex internal commands
31474 In addition to commands intended for @value{GDBN} users, @value{GDBN}
31475 includes a number of commands intended for @value{GDBN} developers,
31476 that are not documented elsewhere in this manual. These commands are
31477 provided here for reference. (For commands that turn on debugging
31478 messages, see @ref{Debugging Output}.)
31481 @kindex maint agent
31482 @kindex maint agent-eval
31483 @item maint agent @var{expression}
31484 @itemx maint agent-eval @var{expression}
31485 Translate the given @var{expression} into remote agent bytecodes.
31486 This command is useful for debugging the Agent Expression mechanism
31487 (@pxref{Agent Expressions}). The @samp{agent} version produces an
31488 expression useful for data collection, such as by tracepoints, while
31489 @samp{maint agent-eval} produces an expression that evaluates directly
31490 to a result. For instance, a collection expression for @code{globa +
31491 globb} will include bytecodes to record four bytes of memory at each
31492 of the addresses of @code{globa} and @code{globb}, while discarding
31493 the result of the addition, while an evaluation expression will do the
31494 addition and return the sum.
31496 @kindex maint info breakpoints
31497 @item @anchor{maint info breakpoints}maint info breakpoints
31498 Using the same format as @samp{info breakpoints}, display both the
31499 breakpoints you've set explicitly, and those @value{GDBN} is using for
31500 internal purposes. Internal breakpoints are shown with negative
31501 breakpoint numbers. The type column identifies what kind of breakpoint
31506 Normal, explicitly set breakpoint.
31509 Normal, explicitly set watchpoint.
31512 Internal breakpoint, used to handle correctly stepping through
31513 @code{longjmp} calls.
31515 @item longjmp resume
31516 Internal breakpoint at the target of a @code{longjmp}.
31519 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
31522 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
31525 Shared library events.
31529 @kindex set displaced-stepping
31530 @kindex show displaced-stepping
31531 @cindex displaced stepping support
31532 @cindex out-of-line single-stepping
31533 @item set displaced-stepping
31534 @itemx show displaced-stepping
31535 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
31536 if the target supports it. Displaced stepping is a way to single-step
31537 over breakpoints without removing them from the inferior, by executing
31538 an out-of-line copy of the instruction that was originally at the
31539 breakpoint location. It is also known as out-of-line single-stepping.
31542 @item set displaced-stepping on
31543 If the target architecture supports it, @value{GDBN} will use
31544 displaced stepping to step over breakpoints.
31546 @item set displaced-stepping off
31547 @value{GDBN} will not use displaced stepping to step over breakpoints,
31548 even if such is supported by the target architecture.
31550 @cindex non-stop mode, and @samp{set displaced-stepping}
31551 @item set displaced-stepping auto
31552 This is the default mode. @value{GDBN} will use displaced stepping
31553 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
31554 architecture supports displaced stepping.
31557 @kindex maint check-symtabs
31558 @item maint check-symtabs
31559 Check the consistency of psymtabs and symtabs.
31561 @kindex maint cplus first_component
31562 @item maint cplus first_component @var{name}
31563 Print the first C@t{++} class/namespace component of @var{name}.
31565 @kindex maint cplus namespace
31566 @item maint cplus namespace
31567 Print the list of possible C@t{++} namespaces.
31569 @kindex maint demangle
31570 @item maint demangle @var{name}
31571 Demangle a C@t{++} or Objective-C mangled @var{name}.
31573 @kindex maint deprecate
31574 @kindex maint undeprecate
31575 @cindex deprecated commands
31576 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
31577 @itemx maint undeprecate @var{command}
31578 Deprecate or undeprecate the named @var{command}. Deprecated commands
31579 cause @value{GDBN} to issue a warning when you use them. The optional
31580 argument @var{replacement} says which newer command should be used in
31581 favor of the deprecated one; if it is given, @value{GDBN} will mention
31582 the replacement as part of the warning.
31584 @kindex maint dump-me
31585 @item maint dump-me
31586 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
31587 Cause a fatal signal in the debugger and force it to dump its core.
31588 This is supported only on systems which support aborting a program
31589 with the @code{SIGQUIT} signal.
31591 @kindex maint internal-error
31592 @kindex maint internal-warning
31593 @item maint internal-error @r{[}@var{message-text}@r{]}
31594 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
31595 Cause @value{GDBN} to call the internal function @code{internal_error}
31596 or @code{internal_warning} and hence behave as though an internal error
31597 or internal warning has been detected. In addition to reporting the
31598 internal problem, these functions give the user the opportunity to
31599 either quit @value{GDBN} or create a core file of the current
31600 @value{GDBN} session.
31602 These commands take an optional parameter @var{message-text} that is
31603 used as the text of the error or warning message.
31605 Here's an example of using @code{internal-error}:
31608 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
31609 @dots{}/maint.c:121: internal-error: testing, 1, 2
31610 A problem internal to GDB has been detected. Further
31611 debugging may prove unreliable.
31612 Quit this debugging session? (y or n) @kbd{n}
31613 Create a core file? (y or n) @kbd{n}
31617 @cindex @value{GDBN} internal error
31618 @cindex internal errors, control of @value{GDBN} behavior
31620 @kindex maint set internal-error
31621 @kindex maint show internal-error
31622 @kindex maint set internal-warning
31623 @kindex maint show internal-warning
31624 @item maint set internal-error @var{action} [ask|yes|no]
31625 @itemx maint show internal-error @var{action}
31626 @itemx maint set internal-warning @var{action} [ask|yes|no]
31627 @itemx maint show internal-warning @var{action}
31628 When @value{GDBN} reports an internal problem (error or warning) it
31629 gives the user the opportunity to both quit @value{GDBN} and create a
31630 core file of the current @value{GDBN} session. These commands let you
31631 override the default behaviour for each particular @var{action},
31632 described in the table below.
31636 You can specify that @value{GDBN} should always (yes) or never (no)
31637 quit. The default is to ask the user what to do.
31640 You can specify that @value{GDBN} should always (yes) or never (no)
31641 create a core file. The default is to ask the user what to do.
31644 @kindex maint packet
31645 @item maint packet @var{text}
31646 If @value{GDBN} is talking to an inferior via the serial protocol,
31647 then this command sends the string @var{text} to the inferior, and
31648 displays the response packet. @value{GDBN} supplies the initial
31649 @samp{$} character, the terminating @samp{#} character, and the
31652 @kindex maint print architecture
31653 @item maint print architecture @r{[}@var{file}@r{]}
31654 Print the entire architecture configuration. The optional argument
31655 @var{file} names the file where the output goes.
31657 @kindex maint print c-tdesc
31658 @item maint print c-tdesc
31659 Print the current target description (@pxref{Target Descriptions}) as
31660 a C source file. The created source file can be used in @value{GDBN}
31661 when an XML parser is not available to parse the description.
31663 @kindex maint print dummy-frames
31664 @item maint print dummy-frames
31665 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
31668 (@value{GDBP}) @kbd{b add}
31670 (@value{GDBP}) @kbd{print add(2,3)}
31671 Breakpoint 2, add (a=2, b=3) at @dots{}
31673 The program being debugged stopped while in a function called from GDB.
31675 (@value{GDBP}) @kbd{maint print dummy-frames}
31676 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
31677 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
31678 call_lo=0x01014000 call_hi=0x01014001
31682 Takes an optional file parameter.
31684 @kindex maint print registers
31685 @kindex maint print raw-registers
31686 @kindex maint print cooked-registers
31687 @kindex maint print register-groups
31688 @kindex maint print remote-registers
31689 @item maint print registers @r{[}@var{file}@r{]}
31690 @itemx maint print raw-registers @r{[}@var{file}@r{]}
31691 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
31692 @itemx maint print register-groups @r{[}@var{file}@r{]}
31693 @itemx maint print remote-registers @r{[}@var{file}@r{]}
31694 Print @value{GDBN}'s internal register data structures.
31696 The command @code{maint print raw-registers} includes the contents of
31697 the raw register cache; the command @code{maint print
31698 cooked-registers} includes the (cooked) value of all registers,
31699 including registers which aren't available on the target nor visible
31700 to user; the command @code{maint print register-groups} includes the
31701 groups that each register is a member of; and the command @code{maint
31702 print remote-registers} includes the remote target's register numbers
31703 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
31704 @value{GDBN} Internals}.
31706 These commands take an optional parameter, a file name to which to
31707 write the information.
31709 @kindex maint print reggroups
31710 @item maint print reggroups @r{[}@var{file}@r{]}
31711 Print @value{GDBN}'s internal register group data structures. The
31712 optional argument @var{file} tells to what file to write the
31715 The register groups info looks like this:
31718 (@value{GDBP}) @kbd{maint print reggroups}
31731 This command forces @value{GDBN} to flush its internal register cache.
31733 @kindex maint print objfiles
31734 @cindex info for known object files
31735 @item maint print objfiles
31736 Print a dump of all known object files. For each object file, this
31737 command prints its name, address in memory, and all of its psymtabs
31740 @kindex maint print section-scripts
31741 @cindex info for known .debug_gdb_scripts-loaded scripts
31742 @item maint print section-scripts [@var{regexp}]
31743 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
31744 If @var{regexp} is specified, only print scripts loaded by object files
31745 matching @var{regexp}.
31746 For each script, this command prints its name as specified in the objfile,
31747 and the full path if known.
31748 @xref{.debug_gdb_scripts section}.
31750 @kindex maint print statistics
31751 @cindex bcache statistics
31752 @item maint print statistics
31753 This command prints, for each object file in the program, various data
31754 about that object file followed by the byte cache (@dfn{bcache})
31755 statistics for the object file. The objfile data includes the number
31756 of minimal, partial, full, and stabs symbols, the number of types
31757 defined by the objfile, the number of as yet unexpanded psym tables,
31758 the number of line tables and string tables, and the amount of memory
31759 used by the various tables. The bcache statistics include the counts,
31760 sizes, and counts of duplicates of all and unique objects, max,
31761 average, and median entry size, total memory used and its overhead and
31762 savings, and various measures of the hash table size and chain
31765 @kindex maint print target-stack
31766 @cindex target stack description
31767 @item maint print target-stack
31768 A @dfn{target} is an interface between the debugger and a particular
31769 kind of file or process. Targets can be stacked in @dfn{strata},
31770 so that more than one target can potentially respond to a request.
31771 In particular, memory accesses will walk down the stack of targets
31772 until they find a target that is interested in handling that particular
31775 This command prints a short description of each layer that was pushed on
31776 the @dfn{target stack}, starting from the top layer down to the bottom one.
31778 @kindex maint print type
31779 @cindex type chain of a data type
31780 @item maint print type @var{expr}
31781 Print the type chain for a type specified by @var{expr}. The argument
31782 can be either a type name or a symbol. If it is a symbol, the type of
31783 that symbol is described. The type chain produced by this command is
31784 a recursive definition of the data type as stored in @value{GDBN}'s
31785 data structures, including its flags and contained types.
31787 @kindex maint set dwarf2 always-disassemble
31788 @kindex maint show dwarf2 always-disassemble
31789 @item maint set dwarf2 always-disassemble
31790 @item maint show dwarf2 always-disassemble
31791 Control the behavior of @code{info address} when using DWARF debugging
31794 The default is @code{off}, which means that @value{GDBN} should try to
31795 describe a variable's location in an easily readable format. When
31796 @code{on}, @value{GDBN} will instead display the DWARF location
31797 expression in an assembly-like format. Note that some locations are
31798 too complex for @value{GDBN} to describe simply; in this case you will
31799 always see the disassembly form.
31801 Here is an example of the resulting disassembly:
31804 (gdb) info addr argc
31805 Symbol "argc" is a complex DWARF expression:
31809 For more information on these expressions, see
31810 @uref{http://www.dwarfstd.org/, the DWARF standard}.
31812 @kindex maint set dwarf2 max-cache-age
31813 @kindex maint show dwarf2 max-cache-age
31814 @item maint set dwarf2 max-cache-age
31815 @itemx maint show dwarf2 max-cache-age
31816 Control the DWARF 2 compilation unit cache.
31818 @cindex DWARF 2 compilation units cache
31819 In object files with inter-compilation-unit references, such as those
31820 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
31821 reader needs to frequently refer to previously read compilation units.
31822 This setting controls how long a compilation unit will remain in the
31823 cache if it is not referenced. A higher limit means that cached
31824 compilation units will be stored in memory longer, and more total
31825 memory will be used. Setting it to zero disables caching, which will
31826 slow down @value{GDBN} startup, but reduce memory consumption.
31828 @kindex maint set profile
31829 @kindex maint show profile
31830 @cindex profiling GDB
31831 @item maint set profile
31832 @itemx maint show profile
31833 Control profiling of @value{GDBN}.
31835 Profiling will be disabled until you use the @samp{maint set profile}
31836 command to enable it. When you enable profiling, the system will begin
31837 collecting timing and execution count data; when you disable profiling or
31838 exit @value{GDBN}, the results will be written to a log file. Remember that
31839 if you use profiling, @value{GDBN} will overwrite the profiling log file
31840 (often called @file{gmon.out}). If you have a record of important profiling
31841 data in a @file{gmon.out} file, be sure to move it to a safe location.
31843 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
31844 compiled with the @samp{-pg} compiler option.
31846 @kindex maint set show-debug-regs
31847 @kindex maint show show-debug-regs
31848 @cindex hardware debug registers
31849 @item maint set show-debug-regs
31850 @itemx maint show show-debug-regs
31851 Control whether to show variables that mirror the hardware debug
31852 registers. Use @code{ON} to enable, @code{OFF} to disable. If
31853 enabled, the debug registers values are shown when @value{GDBN} inserts or
31854 removes a hardware breakpoint or watchpoint, and when the inferior
31855 triggers a hardware-assisted breakpoint or watchpoint.
31857 @kindex maint set show-all-tib
31858 @kindex maint show show-all-tib
31859 @item maint set show-all-tib
31860 @itemx maint show show-all-tib
31861 Control whether to show all non zero areas within a 1k block starting
31862 at thread local base, when using the @samp{info w32 thread-information-block}
31865 @kindex maint space
31866 @cindex memory used by commands
31868 Control whether to display memory usage for each command. If set to a
31869 nonzero value, @value{GDBN} will display how much memory each command
31870 took, following the command's own output. This can also be requested
31871 by invoking @value{GDBN} with the @option{--statistics} command-line
31872 switch (@pxref{Mode Options}).
31875 @cindex time of command execution
31877 Control whether to display the execution time for each command. If
31878 set to a nonzero value, @value{GDBN} will display how much time it
31879 took to execute each command, following the command's own output.
31880 The time is not printed for the commands that run the target, since
31881 there's no mechanism currently to compute how much time was spend
31882 by @value{GDBN} and how much time was spend by the program been debugged.
31883 it's not possibly currently
31884 This can also be requested by invoking @value{GDBN} with the
31885 @option{--statistics} command-line switch (@pxref{Mode Options}).
31887 @kindex maint translate-address
31888 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
31889 Find the symbol stored at the location specified by the address
31890 @var{addr} and an optional section name @var{section}. If found,
31891 @value{GDBN} prints the name of the closest symbol and an offset from
31892 the symbol's location to the specified address. This is similar to
31893 the @code{info address} command (@pxref{Symbols}), except that this
31894 command also allows to find symbols in other sections.
31896 If section was not specified, the section in which the symbol was found
31897 is also printed. For dynamically linked executables, the name of
31898 executable or shared library containing the symbol is printed as well.
31902 The following command is useful for non-interactive invocations of
31903 @value{GDBN}, such as in the test suite.
31906 @item set watchdog @var{nsec}
31907 @kindex set watchdog
31908 @cindex watchdog timer
31909 @cindex timeout for commands
31910 Set the maximum number of seconds @value{GDBN} will wait for the
31911 target operation to finish. If this time expires, @value{GDBN}
31912 reports and error and the command is aborted.
31914 @item show watchdog
31915 Show the current setting of the target wait timeout.
31918 @node Remote Protocol
31919 @appendix @value{GDBN} Remote Serial Protocol
31924 * Stop Reply Packets::
31925 * General Query Packets::
31926 * Architecture-Specific Protocol Details::
31927 * Tracepoint Packets::
31928 * Host I/O Packets::
31930 * Notification Packets::
31931 * Remote Non-Stop::
31932 * Packet Acknowledgment::
31934 * File-I/O Remote Protocol Extension::
31935 * Library List Format::
31936 * Memory Map Format::
31937 * Thread List Format::
31938 * Traceframe Info Format::
31944 There may be occasions when you need to know something about the
31945 protocol---for example, if there is only one serial port to your target
31946 machine, you might want your program to do something special if it
31947 recognizes a packet meant for @value{GDBN}.
31949 In the examples below, @samp{->} and @samp{<-} are used to indicate
31950 transmitted and received data, respectively.
31952 @cindex protocol, @value{GDBN} remote serial
31953 @cindex serial protocol, @value{GDBN} remote
31954 @cindex remote serial protocol
31955 All @value{GDBN} commands and responses (other than acknowledgments
31956 and notifications, see @ref{Notification Packets}) are sent as a
31957 @var{packet}. A @var{packet} is introduced with the character
31958 @samp{$}, the actual @var{packet-data}, and the terminating character
31959 @samp{#} followed by a two-digit @var{checksum}:
31962 @code{$}@var{packet-data}@code{#}@var{checksum}
31966 @cindex checksum, for @value{GDBN} remote
31968 The two-digit @var{checksum} is computed as the modulo 256 sum of all
31969 characters between the leading @samp{$} and the trailing @samp{#} (an
31970 eight bit unsigned checksum).
31972 Implementors should note that prior to @value{GDBN} 5.0 the protocol
31973 specification also included an optional two-digit @var{sequence-id}:
31976 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
31979 @cindex sequence-id, for @value{GDBN} remote
31981 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
31982 has never output @var{sequence-id}s. Stubs that handle packets added
31983 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
31985 When either the host or the target machine receives a packet, the first
31986 response expected is an acknowledgment: either @samp{+} (to indicate
31987 the package was received correctly) or @samp{-} (to request
31991 -> @code{$}@var{packet-data}@code{#}@var{checksum}
31996 The @samp{+}/@samp{-} acknowledgments can be disabled
31997 once a connection is established.
31998 @xref{Packet Acknowledgment}, for details.
32000 The host (@value{GDBN}) sends @var{command}s, and the target (the
32001 debugging stub incorporated in your program) sends a @var{response}. In
32002 the case of step and continue @var{command}s, the response is only sent
32003 when the operation has completed, and the target has again stopped all
32004 threads in all attached processes. This is the default all-stop mode
32005 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
32006 execution mode; see @ref{Remote Non-Stop}, for details.
32008 @var{packet-data} consists of a sequence of characters with the
32009 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
32012 @cindex remote protocol, field separator
32013 Fields within the packet should be separated using @samp{,} @samp{;} or
32014 @samp{:}. Except where otherwise noted all numbers are represented in
32015 @sc{hex} with leading zeros suppressed.
32017 Implementors should note that prior to @value{GDBN} 5.0, the character
32018 @samp{:} could not appear as the third character in a packet (as it
32019 would potentially conflict with the @var{sequence-id}).
32021 @cindex remote protocol, binary data
32022 @anchor{Binary Data}
32023 Binary data in most packets is encoded either as two hexadecimal
32024 digits per byte of binary data. This allowed the traditional remote
32025 protocol to work over connections which were only seven-bit clean.
32026 Some packets designed more recently assume an eight-bit clean
32027 connection, and use a more efficient encoding to send and receive
32030 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
32031 as an escape character. Any escaped byte is transmitted as the escape
32032 character followed by the original character XORed with @code{0x20}.
32033 For example, the byte @code{0x7d} would be transmitted as the two
32034 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
32035 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
32036 @samp{@}}) must always be escaped. Responses sent by the stub
32037 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
32038 is not interpreted as the start of a run-length encoded sequence
32041 Response @var{data} can be run-length encoded to save space.
32042 Run-length encoding replaces runs of identical characters with one
32043 instance of the repeated character, followed by a @samp{*} and a
32044 repeat count. The repeat count is itself sent encoded, to avoid
32045 binary characters in @var{data}: a value of @var{n} is sent as
32046 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
32047 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
32048 code 32) for a repeat count of 3. (This is because run-length
32049 encoding starts to win for counts 3 or more.) Thus, for example,
32050 @samp{0* } is a run-length encoding of ``0000'': the space character
32051 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
32054 The printable characters @samp{#} and @samp{$} or with a numeric value
32055 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
32056 seven repeats (@samp{$}) can be expanded using a repeat count of only
32057 five (@samp{"}). For example, @samp{00000000} can be encoded as
32060 The error response returned for some packets includes a two character
32061 error number. That number is not well defined.
32063 @cindex empty response, for unsupported packets
32064 For any @var{command} not supported by the stub, an empty response
32065 (@samp{$#00}) should be returned. That way it is possible to extend the
32066 protocol. A newer @value{GDBN} can tell if a packet is supported based
32069 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
32070 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
32076 The following table provides a complete list of all currently defined
32077 @var{command}s and their corresponding response @var{data}.
32078 @xref{File-I/O Remote Protocol Extension}, for details about the File
32079 I/O extension of the remote protocol.
32081 Each packet's description has a template showing the packet's overall
32082 syntax, followed by an explanation of the packet's meaning. We
32083 include spaces in some of the templates for clarity; these are not
32084 part of the packet's syntax. No @value{GDBN} packet uses spaces to
32085 separate its components. For example, a template like @samp{foo
32086 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
32087 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
32088 @var{baz}. @value{GDBN} does not transmit a space character between the
32089 @samp{foo} and the @var{bar}, or between the @var{bar} and the
32092 @cindex @var{thread-id}, in remote protocol
32093 @anchor{thread-id syntax}
32094 Several packets and replies include a @var{thread-id} field to identify
32095 a thread. Normally these are positive numbers with a target-specific
32096 interpretation, formatted as big-endian hex strings. A @var{thread-id}
32097 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
32100 In addition, the remote protocol supports a multiprocess feature in
32101 which the @var{thread-id} syntax is extended to optionally include both
32102 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
32103 The @var{pid} (process) and @var{tid} (thread) components each have the
32104 format described above: a positive number with target-specific
32105 interpretation formatted as a big-endian hex string, literal @samp{-1}
32106 to indicate all processes or threads (respectively), or @samp{0} to
32107 indicate an arbitrary process or thread. Specifying just a process, as
32108 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
32109 error to specify all processes but a specific thread, such as
32110 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
32111 for those packets and replies explicitly documented to include a process
32112 ID, rather than a @var{thread-id}.
32114 The multiprocess @var{thread-id} syntax extensions are only used if both
32115 @value{GDBN} and the stub report support for the @samp{multiprocess}
32116 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
32119 Note that all packet forms beginning with an upper- or lower-case
32120 letter, other than those described here, are reserved for future use.
32122 Here are the packet descriptions.
32127 @cindex @samp{!} packet
32128 @anchor{extended mode}
32129 Enable extended mode. In extended mode, the remote server is made
32130 persistent. The @samp{R} packet is used to restart the program being
32136 The remote target both supports and has enabled extended mode.
32140 @cindex @samp{?} packet
32141 Indicate the reason the target halted. The reply is the same as for
32142 step and continue. This packet has a special interpretation when the
32143 target is in non-stop mode; see @ref{Remote Non-Stop}.
32146 @xref{Stop Reply Packets}, for the reply specifications.
32148 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
32149 @cindex @samp{A} packet
32150 Initialized @code{argv[]} array passed into program. @var{arglen}
32151 specifies the number of bytes in the hex encoded byte stream
32152 @var{arg}. See @code{gdbserver} for more details.
32157 The arguments were set.
32163 @cindex @samp{b} packet
32164 (Don't use this packet; its behavior is not well-defined.)
32165 Change the serial line speed to @var{baud}.
32167 JTC: @emph{When does the transport layer state change? When it's
32168 received, or after the ACK is transmitted. In either case, there are
32169 problems if the command or the acknowledgment packet is dropped.}
32171 Stan: @emph{If people really wanted to add something like this, and get
32172 it working for the first time, they ought to modify ser-unix.c to send
32173 some kind of out-of-band message to a specially-setup stub and have the
32174 switch happen "in between" packets, so that from remote protocol's point
32175 of view, nothing actually happened.}
32177 @item B @var{addr},@var{mode}
32178 @cindex @samp{B} packet
32179 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
32180 breakpoint at @var{addr}.
32182 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
32183 (@pxref{insert breakpoint or watchpoint packet}).
32185 @cindex @samp{bc} packet
32188 Backward continue. Execute the target system in reverse. No parameter.
32189 @xref{Reverse Execution}, for more information.
32192 @xref{Stop Reply Packets}, for the reply specifications.
32194 @cindex @samp{bs} packet
32197 Backward single step. Execute one instruction in reverse. No parameter.
32198 @xref{Reverse Execution}, for more information.
32201 @xref{Stop Reply Packets}, for the reply specifications.
32203 @item c @r{[}@var{addr}@r{]}
32204 @cindex @samp{c} packet
32205 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
32206 resume at current address.
32209 @xref{Stop Reply Packets}, for the reply specifications.
32211 @item C @var{sig}@r{[};@var{addr}@r{]}
32212 @cindex @samp{C} packet
32213 Continue with signal @var{sig} (hex signal number). If
32214 @samp{;@var{addr}} is omitted, resume at same address.
32217 @xref{Stop Reply Packets}, for the reply specifications.
32220 @cindex @samp{d} packet
32223 Don't use this packet; instead, define a general set packet
32224 (@pxref{General Query Packets}).
32228 @cindex @samp{D} packet
32229 The first form of the packet is used to detach @value{GDBN} from the
32230 remote system. It is sent to the remote target
32231 before @value{GDBN} disconnects via the @code{detach} command.
32233 The second form, including a process ID, is used when multiprocess
32234 protocol extensions are enabled (@pxref{multiprocess extensions}), to
32235 detach only a specific process. The @var{pid} is specified as a
32236 big-endian hex string.
32246 @item F @var{RC},@var{EE},@var{CF};@var{XX}
32247 @cindex @samp{F} packet
32248 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
32249 This is part of the File-I/O protocol extension. @xref{File-I/O
32250 Remote Protocol Extension}, for the specification.
32253 @anchor{read registers packet}
32254 @cindex @samp{g} packet
32255 Read general registers.
32259 @item @var{XX@dots{}}
32260 Each byte of register data is described by two hex digits. The bytes
32261 with the register are transmitted in target byte order. The size of
32262 each register and their position within the @samp{g} packet are
32263 determined by the @value{GDBN} internal gdbarch functions
32264 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
32265 specification of several standard @samp{g} packets is specified below.
32267 When reading registers from a trace frame (@pxref{Analyze Collected
32268 Data,,Using the Collected Data}), the stub may also return a string of
32269 literal @samp{x}'s in place of the register data digits, to indicate
32270 that the corresponding register has not been collected, thus its value
32271 is unavailable. For example, for an architecture with 4 registers of
32272 4 bytes each, the following reply indicates to @value{GDBN} that
32273 registers 0 and 2 have not been collected, while registers 1 and 3
32274 have been collected, and both have zero value:
32278 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
32285 @item G @var{XX@dots{}}
32286 @cindex @samp{G} packet
32287 Write general registers. @xref{read registers packet}, for a
32288 description of the @var{XX@dots{}} data.
32298 @item H @var{c} @var{thread-id}
32299 @cindex @samp{H} packet
32300 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
32301 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
32302 should be @samp{c} for step and continue operations, @samp{g} for other
32303 operations. The thread designator @var{thread-id} has the format and
32304 interpretation described in @ref{thread-id syntax}.
32315 @c 'H': How restrictive (or permissive) is the thread model. If a
32316 @c thread is selected and stopped, are other threads allowed
32317 @c to continue to execute? As I mentioned above, I think the
32318 @c semantics of each command when a thread is selected must be
32319 @c described. For example:
32321 @c 'g': If the stub supports threads and a specific thread is
32322 @c selected, returns the register block from that thread;
32323 @c otherwise returns current registers.
32325 @c 'G' If the stub supports threads and a specific thread is
32326 @c selected, sets the registers of the register block of
32327 @c that thread; otherwise sets current registers.
32329 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
32330 @anchor{cycle step packet}
32331 @cindex @samp{i} packet
32332 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
32333 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
32334 step starting at that address.
32337 @cindex @samp{I} packet
32338 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
32342 @cindex @samp{k} packet
32345 FIXME: @emph{There is no description of how to operate when a specific
32346 thread context has been selected (i.e.@: does 'k' kill only that
32349 @item m @var{addr},@var{length}
32350 @cindex @samp{m} packet
32351 Read @var{length} bytes of memory starting at address @var{addr}.
32352 Note that @var{addr} may not be aligned to any particular boundary.
32354 The stub need not use any particular size or alignment when gathering
32355 data from memory for the response; even if @var{addr} is word-aligned
32356 and @var{length} is a multiple of the word size, the stub is free to
32357 use byte accesses, or not. For this reason, this packet may not be
32358 suitable for accessing memory-mapped I/O devices.
32359 @cindex alignment of remote memory accesses
32360 @cindex size of remote memory accesses
32361 @cindex memory, alignment and size of remote accesses
32365 @item @var{XX@dots{}}
32366 Memory contents; each byte is transmitted as a two-digit hexadecimal
32367 number. The reply may contain fewer bytes than requested if the
32368 server was able to read only part of the region of memory.
32373 @item M @var{addr},@var{length}:@var{XX@dots{}}
32374 @cindex @samp{M} packet
32375 Write @var{length} bytes of memory starting at address @var{addr}.
32376 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
32377 hexadecimal number.
32384 for an error (this includes the case where only part of the data was
32389 @cindex @samp{p} packet
32390 Read the value of register @var{n}; @var{n} is in hex.
32391 @xref{read registers packet}, for a description of how the returned
32392 register value is encoded.
32396 @item @var{XX@dots{}}
32397 the register's value
32401 Indicating an unrecognized @var{query}.
32404 @item P @var{n@dots{}}=@var{r@dots{}}
32405 @anchor{write register packet}
32406 @cindex @samp{P} packet
32407 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
32408 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
32409 digits for each byte in the register (target byte order).
32419 @item q @var{name} @var{params}@dots{}
32420 @itemx Q @var{name} @var{params}@dots{}
32421 @cindex @samp{q} packet
32422 @cindex @samp{Q} packet
32423 General query (@samp{q}) and set (@samp{Q}). These packets are
32424 described fully in @ref{General Query Packets}.
32427 @cindex @samp{r} packet
32428 Reset the entire system.
32430 Don't use this packet; use the @samp{R} packet instead.
32433 @cindex @samp{R} packet
32434 Restart the program being debugged. @var{XX}, while needed, is ignored.
32435 This packet is only available in extended mode (@pxref{extended mode}).
32437 The @samp{R} packet has no reply.
32439 @item s @r{[}@var{addr}@r{]}
32440 @cindex @samp{s} packet
32441 Single step. @var{addr} is the address at which to resume. If
32442 @var{addr} is omitted, resume at same address.
32445 @xref{Stop Reply Packets}, for the reply specifications.
32447 @item S @var{sig}@r{[};@var{addr}@r{]}
32448 @anchor{step with signal packet}
32449 @cindex @samp{S} packet
32450 Step with signal. This is analogous to the @samp{C} packet, but
32451 requests a single-step, rather than a normal resumption of execution.
32454 @xref{Stop Reply Packets}, for the reply specifications.
32456 @item t @var{addr}:@var{PP},@var{MM}
32457 @cindex @samp{t} packet
32458 Search backwards starting at address @var{addr} for a match with pattern
32459 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
32460 @var{addr} must be at least 3 digits.
32462 @item T @var{thread-id}
32463 @cindex @samp{T} packet
32464 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
32469 thread is still alive
32475 Packets starting with @samp{v} are identified by a multi-letter name,
32476 up to the first @samp{;} or @samp{?} (or the end of the packet).
32478 @item vAttach;@var{pid}
32479 @cindex @samp{vAttach} packet
32480 Attach to a new process with the specified process ID @var{pid}.
32481 The process ID is a
32482 hexadecimal integer identifying the process. In all-stop mode, all
32483 threads in the attached process are stopped; in non-stop mode, it may be
32484 attached without being stopped if that is supported by the target.
32486 @c In non-stop mode, on a successful vAttach, the stub should set the
32487 @c current thread to a thread of the newly-attached process. After
32488 @c attaching, GDB queries for the attached process's thread ID with qC.
32489 @c Also note that, from a user perspective, whether or not the
32490 @c target is stopped on attach in non-stop mode depends on whether you
32491 @c use the foreground or background version of the attach command, not
32492 @c on what vAttach does; GDB does the right thing with respect to either
32493 @c stopping or restarting threads.
32495 This packet is only available in extended mode (@pxref{extended mode}).
32501 @item @r{Any stop packet}
32502 for success in all-stop mode (@pxref{Stop Reply Packets})
32504 for success in non-stop mode (@pxref{Remote Non-Stop})
32507 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
32508 @cindex @samp{vCont} packet
32509 Resume the inferior, specifying different actions for each thread.
32510 If an action is specified with no @var{thread-id}, then it is applied to any
32511 threads that don't have a specific action specified; if no default action is
32512 specified then other threads should remain stopped in all-stop mode and
32513 in their current state in non-stop mode.
32514 Specifying multiple
32515 default actions is an error; specifying no actions is also an error.
32516 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
32518 Currently supported actions are:
32524 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
32528 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
32533 The optional argument @var{addr} normally associated with the
32534 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
32535 not supported in @samp{vCont}.
32537 The @samp{t} action is only relevant in non-stop mode
32538 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
32539 A stop reply should be generated for any affected thread not already stopped.
32540 When a thread is stopped by means of a @samp{t} action,
32541 the corresponding stop reply should indicate that the thread has stopped with
32542 signal @samp{0}, regardless of whether the target uses some other signal
32543 as an implementation detail.
32546 @xref{Stop Reply Packets}, for the reply specifications.
32549 @cindex @samp{vCont?} packet
32550 Request a list of actions supported by the @samp{vCont} packet.
32554 @item vCont@r{[};@var{action}@dots{}@r{]}
32555 The @samp{vCont} packet is supported. Each @var{action} is a supported
32556 command in the @samp{vCont} packet.
32558 The @samp{vCont} packet is not supported.
32561 @item vFile:@var{operation}:@var{parameter}@dots{}
32562 @cindex @samp{vFile} packet
32563 Perform a file operation on the target system. For details,
32564 see @ref{Host I/O Packets}.
32566 @item vFlashErase:@var{addr},@var{length}
32567 @cindex @samp{vFlashErase} packet
32568 Direct the stub to erase @var{length} bytes of flash starting at
32569 @var{addr}. The region may enclose any number of flash blocks, but
32570 its start and end must fall on block boundaries, as indicated by the
32571 flash block size appearing in the memory map (@pxref{Memory Map
32572 Format}). @value{GDBN} groups flash memory programming operations
32573 together, and sends a @samp{vFlashDone} request after each group; the
32574 stub is allowed to delay erase operation until the @samp{vFlashDone}
32575 packet is received.
32577 The stub must support @samp{vCont} if it reports support for
32578 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
32579 this case @samp{vCont} actions can be specified to apply to all threads
32580 in a process by using the @samp{p@var{pid}.-1} form of the
32591 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
32592 @cindex @samp{vFlashWrite} packet
32593 Direct the stub to write data to flash address @var{addr}. The data
32594 is passed in binary form using the same encoding as for the @samp{X}
32595 packet (@pxref{Binary Data}). The memory ranges specified by
32596 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
32597 not overlap, and must appear in order of increasing addresses
32598 (although @samp{vFlashErase} packets for higher addresses may already
32599 have been received; the ordering is guaranteed only between
32600 @samp{vFlashWrite} packets). If a packet writes to an address that was
32601 neither erased by a preceding @samp{vFlashErase} packet nor by some other
32602 target-specific method, the results are unpredictable.
32610 for vFlashWrite addressing non-flash memory
32616 @cindex @samp{vFlashDone} packet
32617 Indicate to the stub that flash programming operation is finished.
32618 The stub is permitted to delay or batch the effects of a group of
32619 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
32620 @samp{vFlashDone} packet is received. The contents of the affected
32621 regions of flash memory are unpredictable until the @samp{vFlashDone}
32622 request is completed.
32624 @item vKill;@var{pid}
32625 @cindex @samp{vKill} packet
32626 Kill the process with the specified process ID. @var{pid} is a
32627 hexadecimal integer identifying the process. This packet is used in
32628 preference to @samp{k} when multiprocess protocol extensions are
32629 supported; see @ref{multiprocess extensions}.
32639 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
32640 @cindex @samp{vRun} packet
32641 Run the program @var{filename}, passing it each @var{argument} on its
32642 command line. The file and arguments are hex-encoded strings. If
32643 @var{filename} is an empty string, the stub may use a default program
32644 (e.g.@: the last program run). The program is created in the stopped
32647 @c FIXME: What about non-stop mode?
32649 This packet is only available in extended mode (@pxref{extended mode}).
32655 @item @r{Any stop packet}
32656 for success (@pxref{Stop Reply Packets})
32660 @anchor{vStopped packet}
32661 @cindex @samp{vStopped} packet
32663 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
32664 reply and prompt for the stub to report another one.
32668 @item @r{Any stop packet}
32669 if there is another unreported stop event (@pxref{Stop Reply Packets})
32671 if there are no unreported stop events
32674 @item X @var{addr},@var{length}:@var{XX@dots{}}
32676 @cindex @samp{X} packet
32677 Write data to memory, where the data is transmitted in binary.
32678 @var{addr} is address, @var{length} is number of bytes,
32679 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
32689 @item z @var{type},@var{addr},@var{kind}
32690 @itemx Z @var{type},@var{addr},@var{kind}
32691 @anchor{insert breakpoint or watchpoint packet}
32692 @cindex @samp{z} packet
32693 @cindex @samp{Z} packets
32694 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
32695 watchpoint starting at address @var{address} of kind @var{kind}.
32697 Each breakpoint and watchpoint packet @var{type} is documented
32700 @emph{Implementation notes: A remote target shall return an empty string
32701 for an unrecognized breakpoint or watchpoint packet @var{type}. A
32702 remote target shall support either both or neither of a given
32703 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
32704 avoid potential problems with duplicate packets, the operations should
32705 be implemented in an idempotent way.}
32707 @item z0,@var{addr},@var{kind}
32708 @itemx Z0,@var{addr},@var{kind}
32709 @cindex @samp{z0} packet
32710 @cindex @samp{Z0} packet
32711 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
32712 @var{addr} of type @var{kind}.
32714 A memory breakpoint is implemented by replacing the instruction at
32715 @var{addr} with a software breakpoint or trap instruction. The
32716 @var{kind} is target-specific and typically indicates the size of
32717 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
32718 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
32719 architectures have additional meanings for @var{kind};
32720 see @ref{Architecture-Specific Protocol Details}.
32722 @emph{Implementation note: It is possible for a target to copy or move
32723 code that contains memory breakpoints (e.g., when implementing
32724 overlays). The behavior of this packet, in the presence of such a
32725 target, is not defined.}
32737 @item z1,@var{addr},@var{kind}
32738 @itemx Z1,@var{addr},@var{kind}
32739 @cindex @samp{z1} packet
32740 @cindex @samp{Z1} packet
32741 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
32742 address @var{addr}.
32744 A hardware breakpoint is implemented using a mechanism that is not
32745 dependant on being able to modify the target's memory. @var{kind}
32746 has the same meaning as in @samp{Z0} packets.
32748 @emph{Implementation note: A hardware breakpoint is not affected by code
32761 @item z2,@var{addr},@var{kind}
32762 @itemx Z2,@var{addr},@var{kind}
32763 @cindex @samp{z2} packet
32764 @cindex @samp{Z2} packet
32765 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
32766 @var{kind} is interpreted as the number of bytes to watch.
32778 @item z3,@var{addr},@var{kind}
32779 @itemx Z3,@var{addr},@var{kind}
32780 @cindex @samp{z3} packet
32781 @cindex @samp{Z3} packet
32782 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
32783 @var{kind} is interpreted as the number of bytes to watch.
32795 @item z4,@var{addr},@var{kind}
32796 @itemx Z4,@var{addr},@var{kind}
32797 @cindex @samp{z4} packet
32798 @cindex @samp{Z4} packet
32799 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
32800 @var{kind} is interpreted as the number of bytes to watch.
32814 @node Stop Reply Packets
32815 @section Stop Reply Packets
32816 @cindex stop reply packets
32818 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
32819 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
32820 receive any of the below as a reply. Except for @samp{?}
32821 and @samp{vStopped}, that reply is only returned
32822 when the target halts. In the below the exact meaning of @dfn{signal
32823 number} is defined by the header @file{include/gdb/signals.h} in the
32824 @value{GDBN} source code.
32826 As in the description of request packets, we include spaces in the
32827 reply templates for clarity; these are not part of the reply packet's
32828 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
32834 The program received signal number @var{AA} (a two-digit hexadecimal
32835 number). This is equivalent to a @samp{T} response with no
32836 @var{n}:@var{r} pairs.
32838 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
32839 @cindex @samp{T} packet reply
32840 The program received signal number @var{AA} (a two-digit hexadecimal
32841 number). This is equivalent to an @samp{S} response, except that the
32842 @samp{@var{n}:@var{r}} pairs can carry values of important registers
32843 and other information directly in the stop reply packet, reducing
32844 round-trip latency. Single-step and breakpoint traps are reported
32845 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
32849 If @var{n} is a hexadecimal number, it is a register number, and the
32850 corresponding @var{r} gives that register's value. @var{r} is a
32851 series of bytes in target byte order, with each byte given by a
32852 two-digit hex number.
32855 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
32856 the stopped thread, as specified in @ref{thread-id syntax}.
32859 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
32860 the core on which the stop event was detected.
32863 If @var{n} is a recognized @dfn{stop reason}, it describes a more
32864 specific event that stopped the target. The currently defined stop
32865 reasons are listed below. @var{aa} should be @samp{05}, the trap
32866 signal. At most one stop reason should be present.
32869 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
32870 and go on to the next; this allows us to extend the protocol in the
32874 The currently defined stop reasons are:
32880 The packet indicates a watchpoint hit, and @var{r} is the data address, in
32883 @cindex shared library events, remote reply
32885 The packet indicates that the loaded libraries have changed.
32886 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
32887 list of loaded libraries. @var{r} is ignored.
32889 @cindex replay log events, remote reply
32891 The packet indicates that the target cannot continue replaying
32892 logged execution events, because it has reached the end (or the
32893 beginning when executing backward) of the log. The value of @var{r}
32894 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
32895 for more information.
32899 @itemx W @var{AA} ; process:@var{pid}
32900 The process exited, and @var{AA} is the exit status. This is only
32901 applicable to certain targets.
32903 The second form of the response, including the process ID of the exited
32904 process, can be used only when @value{GDBN} has reported support for
32905 multiprocess protocol extensions; see @ref{multiprocess extensions}.
32906 The @var{pid} is formatted as a big-endian hex string.
32909 @itemx X @var{AA} ; process:@var{pid}
32910 The process terminated with signal @var{AA}.
32912 The second form of the response, including the process ID of the
32913 terminated process, can be used only when @value{GDBN} has reported
32914 support for multiprocess protocol extensions; see @ref{multiprocess
32915 extensions}. The @var{pid} is formatted as a big-endian hex string.
32917 @item O @var{XX}@dots{}
32918 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
32919 written as the program's console output. This can happen at any time
32920 while the program is running and the debugger should continue to wait
32921 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
32923 @item F @var{call-id},@var{parameter}@dots{}
32924 @var{call-id} is the identifier which says which host system call should
32925 be called. This is just the name of the function. Translation into the
32926 correct system call is only applicable as it's defined in @value{GDBN}.
32927 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
32930 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
32931 this very system call.
32933 The target replies with this packet when it expects @value{GDBN} to
32934 call a host system call on behalf of the target. @value{GDBN} replies
32935 with an appropriate @samp{F} packet and keeps up waiting for the next
32936 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
32937 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
32938 Protocol Extension}, for more details.
32942 @node General Query Packets
32943 @section General Query Packets
32944 @cindex remote query requests
32946 Packets starting with @samp{q} are @dfn{general query packets};
32947 packets starting with @samp{Q} are @dfn{general set packets}. General
32948 query and set packets are a semi-unified form for retrieving and
32949 sending information to and from the stub.
32951 The initial letter of a query or set packet is followed by a name
32952 indicating what sort of thing the packet applies to. For example,
32953 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
32954 definitions with the stub. These packet names follow some
32959 The name must not contain commas, colons or semicolons.
32961 Most @value{GDBN} query and set packets have a leading upper case
32964 The names of custom vendor packets should use a company prefix, in
32965 lower case, followed by a period. For example, packets designed at
32966 the Acme Corporation might begin with @samp{qacme.foo} (for querying
32967 foos) or @samp{Qacme.bar} (for setting bars).
32970 The name of a query or set packet should be separated from any
32971 parameters by a @samp{:}; the parameters themselves should be
32972 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
32973 full packet name, and check for a separator or the end of the packet,
32974 in case two packet names share a common prefix. New packets should not begin
32975 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
32976 packets predate these conventions, and have arguments without any terminator
32977 for the packet name; we suspect they are in widespread use in places that
32978 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
32979 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
32982 Like the descriptions of the other packets, each description here
32983 has a template showing the packet's overall syntax, followed by an
32984 explanation of the packet's meaning. We include spaces in some of the
32985 templates for clarity; these are not part of the packet's syntax. No
32986 @value{GDBN} packet uses spaces to separate its components.
32988 Here are the currently defined query and set packets:
32992 @item QAllow:@var{op}:@var{val}@dots{}
32993 @cindex @samp{QAllow} packet
32994 Specify which operations @value{GDBN} expects to request of the
32995 target, as a semicolon-separated list of operation name and value
32996 pairs. Possible values for @var{op} include @samp{WriteReg},
32997 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
32998 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
32999 indicating that @value{GDBN} will not request the operation, or 1,
33000 indicating that it may. (The target can then use this to set up its
33001 own internals optimally, for instance if the debugger never expects to
33002 insert breakpoints, it may not need to install its own trap handler.)
33005 @cindex current thread, remote request
33006 @cindex @samp{qC} packet
33007 Return the current thread ID.
33011 @item QC @var{thread-id}
33012 Where @var{thread-id} is a thread ID as documented in
33013 @ref{thread-id syntax}.
33014 @item @r{(anything else)}
33015 Any other reply implies the old thread ID.
33018 @item qCRC:@var{addr},@var{length}
33019 @cindex CRC of memory block, remote request
33020 @cindex @samp{qCRC} packet
33021 Compute the CRC checksum of a block of memory using CRC-32 defined in
33022 IEEE 802.3. The CRC is computed byte at a time, taking the most
33023 significant bit of each byte first. The initial pattern code
33024 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
33026 @emph{Note:} This is the same CRC used in validating separate debug
33027 files (@pxref{Separate Debug Files, , Debugging Information in Separate
33028 Files}). However the algorithm is slightly different. When validating
33029 separate debug files, the CRC is computed taking the @emph{least}
33030 significant bit of each byte first, and the final result is inverted to
33031 detect trailing zeros.
33036 An error (such as memory fault)
33037 @item C @var{crc32}
33038 The specified memory region's checksum is @var{crc32}.
33042 @itemx qsThreadInfo
33043 @cindex list active threads, remote request
33044 @cindex @samp{qfThreadInfo} packet
33045 @cindex @samp{qsThreadInfo} packet
33046 Obtain a list of all active thread IDs from the target (OS). Since there
33047 may be too many active threads to fit into one reply packet, this query
33048 works iteratively: it may require more than one query/reply sequence to
33049 obtain the entire list of threads. The first query of the sequence will
33050 be the @samp{qfThreadInfo} query; subsequent queries in the
33051 sequence will be the @samp{qsThreadInfo} query.
33053 NOTE: This packet replaces the @samp{qL} query (see below).
33057 @item m @var{thread-id}
33059 @item m @var{thread-id},@var{thread-id}@dots{}
33060 a comma-separated list of thread IDs
33062 (lower case letter @samp{L}) denotes end of list.
33065 In response to each query, the target will reply with a list of one or
33066 more thread IDs, separated by commas.
33067 @value{GDBN} will respond to each reply with a request for more thread
33068 ids (using the @samp{qs} form of the query), until the target responds
33069 with @samp{l} (lower-case ell, for @dfn{last}).
33070 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
33073 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
33074 @cindex get thread-local storage address, remote request
33075 @cindex @samp{qGetTLSAddr} packet
33076 Fetch the address associated with thread local storage specified
33077 by @var{thread-id}, @var{offset}, and @var{lm}.
33079 @var{thread-id} is the thread ID associated with the
33080 thread for which to fetch the TLS address. @xref{thread-id syntax}.
33082 @var{offset} is the (big endian, hex encoded) offset associated with the
33083 thread local variable. (This offset is obtained from the debug
33084 information associated with the variable.)
33086 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
33087 load module associated with the thread local storage. For example,
33088 a @sc{gnu}/Linux system will pass the link map address of the shared
33089 object associated with the thread local storage under consideration.
33090 Other operating environments may choose to represent the load module
33091 differently, so the precise meaning of this parameter will vary.
33095 @item @var{XX}@dots{}
33096 Hex encoded (big endian) bytes representing the address of the thread
33097 local storage requested.
33100 An error occurred. @var{nn} are hex digits.
33103 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
33106 @item qGetTIBAddr:@var{thread-id}
33107 @cindex get thread information block address
33108 @cindex @samp{qGetTIBAddr} packet
33109 Fetch address of the Windows OS specific Thread Information Block.
33111 @var{thread-id} is the thread ID associated with the thread.
33115 @item @var{XX}@dots{}
33116 Hex encoded (big endian) bytes representing the linear address of the
33117 thread information block.
33120 An error occured. This means that either the thread was not found, or the
33121 address could not be retrieved.
33124 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
33127 @item qL @var{startflag} @var{threadcount} @var{nextthread}
33128 Obtain thread information from RTOS. Where: @var{startflag} (one hex
33129 digit) is one to indicate the first query and zero to indicate a
33130 subsequent query; @var{threadcount} (two hex digits) is the maximum
33131 number of threads the response packet can contain; and @var{nextthread}
33132 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
33133 returned in the response as @var{argthread}.
33135 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
33139 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
33140 Where: @var{count} (two hex digits) is the number of threads being
33141 returned; @var{done} (one hex digit) is zero to indicate more threads
33142 and one indicates no further threads; @var{argthreadid} (eight hex
33143 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
33144 is a sequence of thread IDs from the target. @var{threadid} (eight hex
33145 digits). See @code{remote.c:parse_threadlist_response()}.
33149 @cindex section offsets, remote request
33150 @cindex @samp{qOffsets} packet
33151 Get section offsets that the target used when relocating the downloaded
33156 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
33157 Relocate the @code{Text} section by @var{xxx} from its original address.
33158 Relocate the @code{Data} section by @var{yyy} from its original address.
33159 If the object file format provides segment information (e.g.@: @sc{elf}
33160 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
33161 segments by the supplied offsets.
33163 @emph{Note: while a @code{Bss} offset may be included in the response,
33164 @value{GDBN} ignores this and instead applies the @code{Data} offset
33165 to the @code{Bss} section.}
33167 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
33168 Relocate the first segment of the object file, which conventionally
33169 contains program code, to a starting address of @var{xxx}. If
33170 @samp{DataSeg} is specified, relocate the second segment, which
33171 conventionally contains modifiable data, to a starting address of
33172 @var{yyy}. @value{GDBN} will report an error if the object file
33173 does not contain segment information, or does not contain at least
33174 as many segments as mentioned in the reply. Extra segments are
33175 kept at fixed offsets relative to the last relocated segment.
33178 @item qP @var{mode} @var{thread-id}
33179 @cindex thread information, remote request
33180 @cindex @samp{qP} packet
33181 Returns information on @var{thread-id}. Where: @var{mode} is a hex
33182 encoded 32 bit mode; @var{thread-id} is a thread ID
33183 (@pxref{thread-id syntax}).
33185 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
33188 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
33192 @cindex non-stop mode, remote request
33193 @cindex @samp{QNonStop} packet
33195 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
33196 @xref{Remote Non-Stop}, for more information.
33201 The request succeeded.
33204 An error occurred. @var{nn} are hex digits.
33207 An empty reply indicates that @samp{QNonStop} is not supported by
33211 This packet is not probed by default; the remote stub must request it,
33212 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33213 Use of this packet is controlled by the @code{set non-stop} command;
33214 @pxref{Non-Stop Mode}.
33216 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
33217 @cindex pass signals to inferior, remote request
33218 @cindex @samp{QPassSignals} packet
33219 @anchor{QPassSignals}
33220 Each listed @var{signal} should be passed directly to the inferior process.
33221 Signals are numbered identically to continue packets and stop replies
33222 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
33223 strictly greater than the previous item. These signals do not need to stop
33224 the inferior, or be reported to @value{GDBN}. All other signals should be
33225 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
33226 combine; any earlier @samp{QPassSignals} list is completely replaced by the
33227 new list. This packet improves performance when using @samp{handle
33228 @var{signal} nostop noprint pass}.
33233 The request succeeded.
33236 An error occurred. @var{nn} are hex digits.
33239 An empty reply indicates that @samp{QPassSignals} is not supported by
33243 Use of this packet is controlled by the @code{set remote pass-signals}
33244 command (@pxref{Remote Configuration, set remote pass-signals}).
33245 This packet is not probed by default; the remote stub must request it,
33246 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33248 @item qRcmd,@var{command}
33249 @cindex execute remote command, remote request
33250 @cindex @samp{qRcmd} packet
33251 @var{command} (hex encoded) is passed to the local interpreter for
33252 execution. Invalid commands should be reported using the output
33253 string. Before the final result packet, the target may also respond
33254 with a number of intermediate @samp{O@var{output}} console output
33255 packets. @emph{Implementors should note that providing access to a
33256 stubs's interpreter may have security implications}.
33261 A command response with no output.
33263 A command response with the hex encoded output string @var{OUTPUT}.
33265 Indicate a badly formed request.
33267 An empty reply indicates that @samp{qRcmd} is not recognized.
33270 (Note that the @code{qRcmd} packet's name is separated from the
33271 command by a @samp{,}, not a @samp{:}, contrary to the naming
33272 conventions above. Please don't use this packet as a model for new
33275 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
33276 @cindex searching memory, in remote debugging
33277 @cindex @samp{qSearch:memory} packet
33278 @anchor{qSearch memory}
33279 Search @var{length} bytes at @var{address} for @var{search-pattern}.
33280 @var{address} and @var{length} are encoded in hex.
33281 @var{search-pattern} is a sequence of bytes, hex encoded.
33286 The pattern was not found.
33288 The pattern was found at @var{address}.
33290 A badly formed request or an error was encountered while searching memory.
33292 An empty reply indicates that @samp{qSearch:memory} is not recognized.
33295 @item QStartNoAckMode
33296 @cindex @samp{QStartNoAckMode} packet
33297 @anchor{QStartNoAckMode}
33298 Request that the remote stub disable the normal @samp{+}/@samp{-}
33299 protocol acknowledgments (@pxref{Packet Acknowledgment}).
33304 The stub has switched to no-acknowledgment mode.
33305 @value{GDBN} acknowledges this reponse,
33306 but neither the stub nor @value{GDBN} shall send or expect further
33307 @samp{+}/@samp{-} acknowledgments in the current connection.
33309 An empty reply indicates that the stub does not support no-acknowledgment mode.
33312 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
33313 @cindex supported packets, remote query
33314 @cindex features of the remote protocol
33315 @cindex @samp{qSupported} packet
33316 @anchor{qSupported}
33317 Tell the remote stub about features supported by @value{GDBN}, and
33318 query the stub for features it supports. This packet allows
33319 @value{GDBN} and the remote stub to take advantage of each others'
33320 features. @samp{qSupported} also consolidates multiple feature probes
33321 at startup, to improve @value{GDBN} performance---a single larger
33322 packet performs better than multiple smaller probe packets on
33323 high-latency links. Some features may enable behavior which must not
33324 be on by default, e.g.@: because it would confuse older clients or
33325 stubs. Other features may describe packets which could be
33326 automatically probed for, but are not. These features must be
33327 reported before @value{GDBN} will use them. This ``default
33328 unsupported'' behavior is not appropriate for all packets, but it
33329 helps to keep the initial connection time under control with new
33330 versions of @value{GDBN} which support increasing numbers of packets.
33334 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
33335 The stub supports or does not support each returned @var{stubfeature},
33336 depending on the form of each @var{stubfeature} (see below for the
33339 An empty reply indicates that @samp{qSupported} is not recognized,
33340 or that no features needed to be reported to @value{GDBN}.
33343 The allowed forms for each feature (either a @var{gdbfeature} in the
33344 @samp{qSupported} packet, or a @var{stubfeature} in the response)
33348 @item @var{name}=@var{value}
33349 The remote protocol feature @var{name} is supported, and associated
33350 with the specified @var{value}. The format of @var{value} depends
33351 on the feature, but it must not include a semicolon.
33353 The remote protocol feature @var{name} is supported, and does not
33354 need an associated value.
33356 The remote protocol feature @var{name} is not supported.
33358 The remote protocol feature @var{name} may be supported, and
33359 @value{GDBN} should auto-detect support in some other way when it is
33360 needed. This form will not be used for @var{gdbfeature} notifications,
33361 but may be used for @var{stubfeature} responses.
33364 Whenever the stub receives a @samp{qSupported} request, the
33365 supplied set of @value{GDBN} features should override any previous
33366 request. This allows @value{GDBN} to put the stub in a known
33367 state, even if the stub had previously been communicating with
33368 a different version of @value{GDBN}.
33370 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
33375 This feature indicates whether @value{GDBN} supports multiprocess
33376 extensions to the remote protocol. @value{GDBN} does not use such
33377 extensions unless the stub also reports that it supports them by
33378 including @samp{multiprocess+} in its @samp{qSupported} reply.
33379 @xref{multiprocess extensions}, for details.
33382 This feature indicates that @value{GDBN} supports the XML target
33383 description. If the stub sees @samp{xmlRegisters=} with target
33384 specific strings separated by a comma, it will report register
33388 This feature indicates whether @value{GDBN} supports the
33389 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
33390 instruction reply packet}).
33393 Stubs should ignore any unknown values for
33394 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
33395 packet supports receiving packets of unlimited length (earlier
33396 versions of @value{GDBN} may reject overly long responses). Additional values
33397 for @var{gdbfeature} may be defined in the future to let the stub take
33398 advantage of new features in @value{GDBN}, e.g.@: incompatible
33399 improvements in the remote protocol---the @samp{multiprocess} feature is
33400 an example of such a feature. The stub's reply should be independent
33401 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
33402 describes all the features it supports, and then the stub replies with
33403 all the features it supports.
33405 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
33406 responses, as long as each response uses one of the standard forms.
33408 Some features are flags. A stub which supports a flag feature
33409 should respond with a @samp{+} form response. Other features
33410 require values, and the stub should respond with an @samp{=}
33413 Each feature has a default value, which @value{GDBN} will use if
33414 @samp{qSupported} is not available or if the feature is not mentioned
33415 in the @samp{qSupported} response. The default values are fixed; a
33416 stub is free to omit any feature responses that match the defaults.
33418 Not all features can be probed, but for those which can, the probing
33419 mechanism is useful: in some cases, a stub's internal
33420 architecture may not allow the protocol layer to know some information
33421 about the underlying target in advance. This is especially common in
33422 stubs which may be configured for multiple targets.
33424 These are the currently defined stub features and their properties:
33426 @multitable @columnfractions 0.35 0.2 0.12 0.2
33427 @c NOTE: The first row should be @headitem, but we do not yet require
33428 @c a new enough version of Texinfo (4.7) to use @headitem.
33430 @tab Value Required
33434 @item @samp{PacketSize}
33439 @item @samp{qXfer:auxv:read}
33444 @item @samp{qXfer:features:read}
33449 @item @samp{qXfer:libraries:read}
33454 @item @samp{qXfer:memory-map:read}
33459 @item @samp{qXfer:sdata:read}
33464 @item @samp{qXfer:spu:read}
33469 @item @samp{qXfer:spu:write}
33474 @item @samp{qXfer:siginfo:read}
33479 @item @samp{qXfer:siginfo:write}
33484 @item @samp{qXfer:threads:read}
33489 @item @samp{qXfer:traceframe-info:read}
33495 @item @samp{QNonStop}
33500 @item @samp{QPassSignals}
33505 @item @samp{QStartNoAckMode}
33510 @item @samp{multiprocess}
33515 @item @samp{ConditionalTracepoints}
33520 @item @samp{ReverseContinue}
33525 @item @samp{ReverseStep}
33530 @item @samp{TracepointSource}
33535 @item @samp{QAllow}
33542 These are the currently defined stub features, in more detail:
33545 @cindex packet size, remote protocol
33546 @item PacketSize=@var{bytes}
33547 The remote stub can accept packets up to at least @var{bytes} in
33548 length. @value{GDBN} will send packets up to this size for bulk
33549 transfers, and will never send larger packets. This is a limit on the
33550 data characters in the packet, including the frame and checksum.
33551 There is no trailing NUL byte in a remote protocol packet; if the stub
33552 stores packets in a NUL-terminated format, it should allow an extra
33553 byte in its buffer for the NUL. If this stub feature is not supported,
33554 @value{GDBN} guesses based on the size of the @samp{g} packet response.
33556 @item qXfer:auxv:read
33557 The remote stub understands the @samp{qXfer:auxv:read} packet
33558 (@pxref{qXfer auxiliary vector read}).
33560 @item qXfer:features:read
33561 The remote stub understands the @samp{qXfer:features:read} packet
33562 (@pxref{qXfer target description read}).
33564 @item qXfer:libraries:read
33565 The remote stub understands the @samp{qXfer:libraries:read} packet
33566 (@pxref{qXfer library list read}).
33568 @item qXfer:memory-map:read
33569 The remote stub understands the @samp{qXfer:memory-map:read} packet
33570 (@pxref{qXfer memory map read}).
33572 @item qXfer:sdata:read
33573 The remote stub understands the @samp{qXfer:sdata:read} packet
33574 (@pxref{qXfer sdata read}).
33576 @item qXfer:spu:read
33577 The remote stub understands the @samp{qXfer:spu:read} packet
33578 (@pxref{qXfer spu read}).
33580 @item qXfer:spu:write
33581 The remote stub understands the @samp{qXfer:spu:write} packet
33582 (@pxref{qXfer spu write}).
33584 @item qXfer:siginfo:read
33585 The remote stub understands the @samp{qXfer:siginfo:read} packet
33586 (@pxref{qXfer siginfo read}).
33588 @item qXfer:siginfo:write
33589 The remote stub understands the @samp{qXfer:siginfo:write} packet
33590 (@pxref{qXfer siginfo write}).
33592 @item qXfer:threads:read
33593 The remote stub understands the @samp{qXfer:threads:read} packet
33594 (@pxref{qXfer threads read}).
33596 @item qXfer:traceframe-info:read
33597 The remote stub understands the @samp{qXfer:traceframe-info:read}
33598 packet (@pxref{qXfer traceframe info read}).
33601 The remote stub understands the @samp{QNonStop} packet
33602 (@pxref{QNonStop}).
33605 The remote stub understands the @samp{QPassSignals} packet
33606 (@pxref{QPassSignals}).
33608 @item QStartNoAckMode
33609 The remote stub understands the @samp{QStartNoAckMode} packet and
33610 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
33613 @anchor{multiprocess extensions}
33614 @cindex multiprocess extensions, in remote protocol
33615 The remote stub understands the multiprocess extensions to the remote
33616 protocol syntax. The multiprocess extensions affect the syntax of
33617 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
33618 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
33619 replies. Note that reporting this feature indicates support for the
33620 syntactic extensions only, not that the stub necessarily supports
33621 debugging of more than one process at a time. The stub must not use
33622 multiprocess extensions in packet replies unless @value{GDBN} has also
33623 indicated it supports them in its @samp{qSupported} request.
33625 @item qXfer:osdata:read
33626 The remote stub understands the @samp{qXfer:osdata:read} packet
33627 ((@pxref{qXfer osdata read}).
33629 @item ConditionalTracepoints
33630 The remote stub accepts and implements conditional expressions defined
33631 for tracepoints (@pxref{Tracepoint Conditions}).
33633 @item ReverseContinue
33634 The remote stub accepts and implements the reverse continue packet
33638 The remote stub accepts and implements the reverse step packet
33641 @item TracepointSource
33642 The remote stub understands the @samp{QTDPsrc} packet that supplies
33643 the source form of tracepoint definitions.
33646 The remote stub understands the @samp{QAllow} packet.
33648 @item StaticTracepoint
33649 @cindex static tracepoints, in remote protocol
33650 The remote stub supports static tracepoints.
33655 @cindex symbol lookup, remote request
33656 @cindex @samp{qSymbol} packet
33657 Notify the target that @value{GDBN} is prepared to serve symbol lookup
33658 requests. Accept requests from the target for the values of symbols.
33663 The target does not need to look up any (more) symbols.
33664 @item qSymbol:@var{sym_name}
33665 The target requests the value of symbol @var{sym_name} (hex encoded).
33666 @value{GDBN} may provide the value by using the
33667 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
33671 @item qSymbol:@var{sym_value}:@var{sym_name}
33672 Set the value of @var{sym_name} to @var{sym_value}.
33674 @var{sym_name} (hex encoded) is the name of a symbol whose value the
33675 target has previously requested.
33677 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
33678 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
33684 The target does not need to look up any (more) symbols.
33685 @item qSymbol:@var{sym_name}
33686 The target requests the value of a new symbol @var{sym_name} (hex
33687 encoded). @value{GDBN} will continue to supply the values of symbols
33688 (if available), until the target ceases to request them.
33693 @item QTDisconnected
33700 @xref{Tracepoint Packets}.
33702 @item qThreadExtraInfo,@var{thread-id}
33703 @cindex thread attributes info, remote request
33704 @cindex @samp{qThreadExtraInfo} packet
33705 Obtain a printable string description of a thread's attributes from
33706 the target OS. @var{thread-id} is a thread ID;
33707 see @ref{thread-id syntax}. This
33708 string may contain anything that the target OS thinks is interesting
33709 for @value{GDBN} to tell the user about the thread. The string is
33710 displayed in @value{GDBN}'s @code{info threads} display. Some
33711 examples of possible thread extra info strings are @samp{Runnable}, or
33712 @samp{Blocked on Mutex}.
33716 @item @var{XX}@dots{}
33717 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
33718 comprising the printable string containing the extra information about
33719 the thread's attributes.
33722 (Note that the @code{qThreadExtraInfo} packet's name is separated from
33723 the command by a @samp{,}, not a @samp{:}, contrary to the naming
33724 conventions above. Please don't use this packet as a model for new
33739 @xref{Tracepoint Packets}.
33741 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
33742 @cindex read special object, remote request
33743 @cindex @samp{qXfer} packet
33744 @anchor{qXfer read}
33745 Read uninterpreted bytes from the target's special data area
33746 identified by the keyword @var{object}. Request @var{length} bytes
33747 starting at @var{offset} bytes into the data. The content and
33748 encoding of @var{annex} is specific to @var{object}; it can supply
33749 additional details about what data to access.
33751 Here are the specific requests of this form defined so far. All
33752 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
33753 formats, listed below.
33756 @item qXfer:auxv:read::@var{offset},@var{length}
33757 @anchor{qXfer auxiliary vector read}
33758 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
33759 auxiliary vector}. Note @var{annex} must be empty.
33761 This packet is not probed by default; the remote stub must request it,
33762 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33764 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
33765 @anchor{qXfer target description read}
33766 Access the @dfn{target description}. @xref{Target Descriptions}. The
33767 annex specifies which XML document to access. The main description is
33768 always loaded from the @samp{target.xml} annex.
33770 This packet is not probed by default; the remote stub must request it,
33771 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33773 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
33774 @anchor{qXfer library list read}
33775 Access the target's list of loaded libraries. @xref{Library List Format}.
33776 The annex part of the generic @samp{qXfer} packet must be empty
33777 (@pxref{qXfer read}).
33779 Targets which maintain a list of libraries in the program's memory do
33780 not need to implement this packet; it is designed for platforms where
33781 the operating system manages the list of loaded libraries.
33783 This packet is not probed by default; the remote stub must request it,
33784 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33786 @item qXfer:memory-map:read::@var{offset},@var{length}
33787 @anchor{qXfer memory map read}
33788 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
33789 annex part of the generic @samp{qXfer} packet must be empty
33790 (@pxref{qXfer read}).
33792 This packet is not probed by default; the remote stub must request it,
33793 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33795 @item qXfer:sdata:read::@var{offset},@var{length}
33796 @anchor{qXfer sdata read}
33798 Read contents of the extra collected static tracepoint marker
33799 information. The annex part of the generic @samp{qXfer} packet must
33800 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
33803 This packet is not probed by default; the remote stub must request it,
33804 by supplying an appropriate @samp{qSupported} response
33805 (@pxref{qSupported}).
33807 @item qXfer:siginfo:read::@var{offset},@var{length}
33808 @anchor{qXfer siginfo read}
33809 Read contents of the extra signal information on the target
33810 system. The annex part of the generic @samp{qXfer} packet must be
33811 empty (@pxref{qXfer read}).
33813 This packet is not probed by default; the remote stub must request it,
33814 by supplying an appropriate @samp{qSupported} response
33815 (@pxref{qSupported}).
33817 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
33818 @anchor{qXfer spu read}
33819 Read contents of an @code{spufs} file on the target system. The
33820 annex specifies which file to read; it must be of the form
33821 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
33822 in the target process, and @var{name} identifes the @code{spufs} file
33823 in that context to be accessed.
33825 This packet is not probed by default; the remote stub must request it,
33826 by supplying an appropriate @samp{qSupported} response
33827 (@pxref{qSupported}).
33829 @item qXfer:threads:read::@var{offset},@var{length}
33830 @anchor{qXfer threads read}
33831 Access the list of threads on target. @xref{Thread List Format}. The
33832 annex part of the generic @samp{qXfer} packet must be empty
33833 (@pxref{qXfer read}).
33835 This packet is not probed by default; the remote stub must request it,
33836 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33838 @item qXfer:traceframe-info:read::@var{offset},@var{length}
33839 @anchor{qXfer traceframe info read}
33841 Return a description of the current traceframe's contents.
33842 @xref{Traceframe Info Format}. The annex part of the generic
33843 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
33845 This packet is not probed by default; the remote stub must request it,
33846 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33848 @item qXfer:osdata:read::@var{offset},@var{length}
33849 @anchor{qXfer osdata read}
33850 Access the target's @dfn{operating system information}.
33851 @xref{Operating System Information}.
33858 Data @var{data} (@pxref{Binary Data}) has been read from the
33859 target. There may be more data at a higher address (although
33860 it is permitted to return @samp{m} even for the last valid
33861 block of data, as long as at least one byte of data was read).
33862 @var{data} may have fewer bytes than the @var{length} in the
33866 Data @var{data} (@pxref{Binary Data}) has been read from the target.
33867 There is no more data to be read. @var{data} may have fewer bytes
33868 than the @var{length} in the request.
33871 The @var{offset} in the request is at the end of the data.
33872 There is no more data to be read.
33875 The request was malformed, or @var{annex} was invalid.
33878 The offset was invalid, or there was an error encountered reading the data.
33879 @var{nn} is a hex-encoded @code{errno} value.
33882 An empty reply indicates the @var{object} string was not recognized by
33883 the stub, or that the object does not support reading.
33886 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
33887 @cindex write data into object, remote request
33888 @anchor{qXfer write}
33889 Write uninterpreted bytes into the target's special data area
33890 identified by the keyword @var{object}, starting at @var{offset} bytes
33891 into the data. @var{data}@dots{} is the binary-encoded data
33892 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
33893 is specific to @var{object}; it can supply additional details about what data
33896 Here are the specific requests of this form defined so far. All
33897 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
33898 formats, listed below.
33901 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
33902 @anchor{qXfer siginfo write}
33903 Write @var{data} to the extra signal information on the target system.
33904 The annex part of the generic @samp{qXfer} packet must be
33905 empty (@pxref{qXfer write}).
33907 This packet is not probed by default; the remote stub must request it,
33908 by supplying an appropriate @samp{qSupported} response
33909 (@pxref{qSupported}).
33911 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
33912 @anchor{qXfer spu write}
33913 Write @var{data} to an @code{spufs} file on the target system. The
33914 annex specifies which file to write; it must be of the form
33915 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
33916 in the target process, and @var{name} identifes the @code{spufs} file
33917 in that context to be accessed.
33919 This packet is not probed by default; the remote stub must request it,
33920 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33926 @var{nn} (hex encoded) is the number of bytes written.
33927 This may be fewer bytes than supplied in the request.
33930 The request was malformed, or @var{annex} was invalid.
33933 The offset was invalid, or there was an error encountered writing the data.
33934 @var{nn} is a hex-encoded @code{errno} value.
33937 An empty reply indicates the @var{object} string was not
33938 recognized by the stub, or that the object does not support writing.
33941 @item qXfer:@var{object}:@var{operation}:@dots{}
33942 Requests of this form may be added in the future. When a stub does
33943 not recognize the @var{object} keyword, or its support for
33944 @var{object} does not recognize the @var{operation} keyword, the stub
33945 must respond with an empty packet.
33947 @item qAttached:@var{pid}
33948 @cindex query attached, remote request
33949 @cindex @samp{qAttached} packet
33950 Return an indication of whether the remote server attached to an
33951 existing process or created a new process. When the multiprocess
33952 protocol extensions are supported (@pxref{multiprocess extensions}),
33953 @var{pid} is an integer in hexadecimal format identifying the target
33954 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
33955 the query packet will be simplified as @samp{qAttached}.
33957 This query is used, for example, to know whether the remote process
33958 should be detached or killed when a @value{GDBN} session is ended with
33959 the @code{quit} command.
33964 The remote server attached to an existing process.
33966 The remote server created a new process.
33968 A badly formed request or an error was encountered.
33973 @node Architecture-Specific Protocol Details
33974 @section Architecture-Specific Protocol Details
33976 This section describes how the remote protocol is applied to specific
33977 target architectures. Also see @ref{Standard Target Features}, for
33978 details of XML target descriptions for each architecture.
33982 @subsubsection Breakpoint Kinds
33984 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
33989 16-bit Thumb mode breakpoint.
33992 32-bit Thumb mode (Thumb-2) breakpoint.
33995 32-bit ARM mode breakpoint.
34001 @subsubsection Register Packet Format
34003 The following @code{g}/@code{G} packets have previously been defined.
34004 In the below, some thirty-two bit registers are transferred as
34005 sixty-four bits. Those registers should be zero/sign extended (which?)
34006 to fill the space allocated. Register bytes are transferred in target
34007 byte order. The two nibbles within a register byte are transferred
34008 most-significant - least-significant.
34014 All registers are transferred as thirty-two bit quantities in the order:
34015 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
34016 registers; fsr; fir; fp.
34020 All registers are transferred as sixty-four bit quantities (including
34021 thirty-two bit registers such as @code{sr}). The ordering is the same
34026 @node Tracepoint Packets
34027 @section Tracepoint Packets
34028 @cindex tracepoint packets
34029 @cindex packets, tracepoint
34031 Here we describe the packets @value{GDBN} uses to implement
34032 tracepoints (@pxref{Tracepoints}).
34036 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
34037 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
34038 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
34039 the tracepoint is disabled. @var{step} is the tracepoint's step
34040 count, and @var{pass} is its pass count. If an @samp{F} is present,
34041 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
34042 the number of bytes that the target should copy elsewhere to make room
34043 for the tracepoint. If an @samp{X} is present, it introduces a
34044 tracepoint condition, which consists of a hexadecimal length, followed
34045 by a comma and hex-encoded bytes, in a manner similar to action
34046 encodings as described below. If the trailing @samp{-} is present,
34047 further @samp{QTDP} packets will follow to specify this tracepoint's
34053 The packet was understood and carried out.
34055 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
34057 The packet was not recognized.
34060 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
34061 Define actions to be taken when a tracepoint is hit. @var{n} and
34062 @var{addr} must be the same as in the initial @samp{QTDP} packet for
34063 this tracepoint. This packet may only be sent immediately after
34064 another @samp{QTDP} packet that ended with a @samp{-}. If the
34065 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
34066 specifying more actions for this tracepoint.
34068 In the series of action packets for a given tracepoint, at most one
34069 can have an @samp{S} before its first @var{action}. If such a packet
34070 is sent, it and the following packets define ``while-stepping''
34071 actions. Any prior packets define ordinary actions --- that is, those
34072 taken when the tracepoint is first hit. If no action packet has an
34073 @samp{S}, then all the packets in the series specify ordinary
34074 tracepoint actions.
34076 The @samp{@var{action}@dots{}} portion of the packet is a series of
34077 actions, concatenated without separators. Each action has one of the
34083 Collect the registers whose bits are set in @var{mask}. @var{mask} is
34084 a hexadecimal number whose @var{i}'th bit is set if register number
34085 @var{i} should be collected. (The least significant bit is numbered
34086 zero.) Note that @var{mask} may be any number of digits long; it may
34087 not fit in a 32-bit word.
34089 @item M @var{basereg},@var{offset},@var{len}
34090 Collect @var{len} bytes of memory starting at the address in register
34091 number @var{basereg}, plus @var{offset}. If @var{basereg} is
34092 @samp{-1}, then the range has a fixed address: @var{offset} is the
34093 address of the lowest byte to collect. The @var{basereg},
34094 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
34095 values (the @samp{-1} value for @var{basereg} is a special case).
34097 @item X @var{len},@var{expr}
34098 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
34099 it directs. @var{expr} is an agent expression, as described in
34100 @ref{Agent Expressions}. Each byte of the expression is encoded as a
34101 two-digit hex number in the packet; @var{len} is the number of bytes
34102 in the expression (and thus one-half the number of hex digits in the
34107 Any number of actions may be packed together in a single @samp{QTDP}
34108 packet, as long as the packet does not exceed the maximum packet
34109 length (400 bytes, for many stubs). There may be only one @samp{R}
34110 action per tracepoint, and it must precede any @samp{M} or @samp{X}
34111 actions. Any registers referred to by @samp{M} and @samp{X} actions
34112 must be collected by a preceding @samp{R} action. (The
34113 ``while-stepping'' actions are treated as if they were attached to a
34114 separate tracepoint, as far as these restrictions are concerned.)
34119 The packet was understood and carried out.
34121 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
34123 The packet was not recognized.
34126 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
34127 @cindex @samp{QTDPsrc} packet
34128 Specify a source string of tracepoint @var{n} at address @var{addr}.
34129 This is useful to get accurate reproduction of the tracepoints
34130 originally downloaded at the beginning of the trace run. @var{type}
34131 is the name of the tracepoint part, such as @samp{cond} for the
34132 tracepoint's conditional expression (see below for a list of types), while
34133 @var{bytes} is the string, encoded in hexadecimal.
34135 @var{start} is the offset of the @var{bytes} within the overall source
34136 string, while @var{slen} is the total length of the source string.
34137 This is intended for handling source strings that are longer than will
34138 fit in a single packet.
34139 @c Add detailed example when this info is moved into a dedicated
34140 @c tracepoint descriptions section.
34142 The available string types are @samp{at} for the location,
34143 @samp{cond} for the conditional, and @samp{cmd} for an action command.
34144 @value{GDBN} sends a separate packet for each command in the action
34145 list, in the same order in which the commands are stored in the list.
34147 The target does not need to do anything with source strings except
34148 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
34151 Although this packet is optional, and @value{GDBN} will only send it
34152 if the target replies with @samp{TracepointSource} @xref{General
34153 Query Packets}, it makes both disconnected tracing and trace files
34154 much easier to use. Otherwise the user must be careful that the
34155 tracepoints in effect while looking at trace frames are identical to
34156 the ones in effect during the trace run; even a small discrepancy
34157 could cause @samp{tdump} not to work, or a particular trace frame not
34160 @item QTDV:@var{n}:@var{value}
34161 @cindex define trace state variable, remote request
34162 @cindex @samp{QTDV} packet
34163 Create a new trace state variable, number @var{n}, with an initial
34164 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
34165 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
34166 the option of not using this packet for initial values of zero; the
34167 target should simply create the trace state variables as they are
34168 mentioned in expressions.
34170 @item QTFrame:@var{n}
34171 Select the @var{n}'th tracepoint frame from the buffer, and use the
34172 register and memory contents recorded there to answer subsequent
34173 request packets from @value{GDBN}.
34175 A successful reply from the stub indicates that the stub has found the
34176 requested frame. The response is a series of parts, concatenated
34177 without separators, describing the frame we selected. Each part has
34178 one of the following forms:
34182 The selected frame is number @var{n} in the trace frame buffer;
34183 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
34184 was no frame matching the criteria in the request packet.
34187 The selected trace frame records a hit of tracepoint number @var{t};
34188 @var{t} is a hexadecimal number.
34192 @item QTFrame:pc:@var{addr}
34193 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
34194 currently selected frame whose PC is @var{addr};
34195 @var{addr} is a hexadecimal number.
34197 @item QTFrame:tdp:@var{t}
34198 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
34199 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
34200 is a hexadecimal number.
34202 @item QTFrame:range:@var{start}:@var{end}
34203 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
34204 currently selected frame whose PC is between @var{start} (inclusive)
34205 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
34208 @item QTFrame:outside:@var{start}:@var{end}
34209 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
34210 frame @emph{outside} the given range of addresses (exclusive).
34213 Begin the tracepoint experiment. Begin collecting data from
34214 tracepoint hits in the trace frame buffer. This packet supports the
34215 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
34216 instruction reply packet}).
34219 End the tracepoint experiment. Stop collecting trace frames.
34222 Clear the table of tracepoints, and empty the trace frame buffer.
34224 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
34225 Establish the given ranges of memory as ``transparent''. The stub
34226 will answer requests for these ranges from memory's current contents,
34227 if they were not collected as part of the tracepoint hit.
34229 @value{GDBN} uses this to mark read-only regions of memory, like those
34230 containing program code. Since these areas never change, they should
34231 still have the same contents they did when the tracepoint was hit, so
34232 there's no reason for the stub to refuse to provide their contents.
34234 @item QTDisconnected:@var{value}
34235 Set the choice to what to do with the tracing run when @value{GDBN}
34236 disconnects from the target. A @var{value} of 1 directs the target to
34237 continue the tracing run, while 0 tells the target to stop tracing if
34238 @value{GDBN} is no longer in the picture.
34241 Ask the stub if there is a trace experiment running right now.
34243 The reply has the form:
34247 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
34248 @var{running} is a single digit @code{1} if the trace is presently
34249 running, or @code{0} if not. It is followed by semicolon-separated
34250 optional fields that an agent may use to report additional status.
34254 If the trace is not running, the agent may report any of several
34255 explanations as one of the optional fields:
34260 No trace has been run yet.
34263 The trace was stopped by a user-originated stop command.
34266 The trace stopped because the trace buffer filled up.
34268 @item tdisconnected:0
34269 The trace stopped because @value{GDBN} disconnected from the target.
34271 @item tpasscount:@var{tpnum}
34272 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
34274 @item terror:@var{text}:@var{tpnum}
34275 The trace stopped because tracepoint @var{tpnum} had an error. The
34276 string @var{text} is available to describe the nature of the error
34277 (for instance, a divide by zero in the condition expression).
34278 @var{text} is hex encoded.
34281 The trace stopped for some other reason.
34285 Additional optional fields supply statistical and other information.
34286 Although not required, they are extremely useful for users monitoring
34287 the progress of a trace run. If a trace has stopped, and these
34288 numbers are reported, they must reflect the state of the just-stopped
34293 @item tframes:@var{n}
34294 The number of trace frames in the buffer.
34296 @item tcreated:@var{n}
34297 The total number of trace frames created during the run. This may
34298 be larger than the trace frame count, if the buffer is circular.
34300 @item tsize:@var{n}
34301 The total size of the trace buffer, in bytes.
34303 @item tfree:@var{n}
34304 The number of bytes still unused in the buffer.
34306 @item circular:@var{n}
34307 The value of the circular trace buffer flag. @code{1} means that the
34308 trace buffer is circular and old trace frames will be discarded if
34309 necessary to make room, @code{0} means that the trace buffer is linear
34312 @item disconn:@var{n}
34313 The value of the disconnected tracing flag. @code{1} means that
34314 tracing will continue after @value{GDBN} disconnects, @code{0} means
34315 that the trace run will stop.
34319 @item qTV:@var{var}
34320 @cindex trace state variable value, remote request
34321 @cindex @samp{qTV} packet
34322 Ask the stub for the value of the trace state variable number @var{var}.
34327 The value of the variable is @var{value}. This will be the current
34328 value of the variable if the user is examining a running target, or a
34329 saved value if the variable was collected in the trace frame that the
34330 user is looking at. Note that multiple requests may result in
34331 different reply values, such as when requesting values while the
34332 program is running.
34335 The value of the variable is unknown. This would occur, for example,
34336 if the user is examining a trace frame in which the requested variable
34342 These packets request data about tracepoints that are being used by
34343 the target. @value{GDBN} sends @code{qTfP} to get the first piece
34344 of data, and multiple @code{qTsP} to get additional pieces. Replies
34345 to these packets generally take the form of the @code{QTDP} packets
34346 that define tracepoints. (FIXME add detailed syntax)
34350 These packets request data about trace state variables that are on the
34351 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
34352 and multiple @code{qTsV} to get additional variables. Replies to
34353 these packets follow the syntax of the @code{QTDV} packets that define
34354 trace state variables.
34358 These packets request data about static tracepoint markers that exist
34359 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
34360 first piece of data, and multiple @code{qTsSTM} to get additional
34361 pieces. Replies to these packets take the following form:
34365 @item m @var{address}:@var{id}:@var{extra}
34367 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
34368 a comma-separated list of markers
34370 (lower case letter @samp{L}) denotes end of list.
34372 An error occurred. @var{nn} are hex digits.
34374 An empty reply indicates that the request is not supported by the
34378 @var{address} is encoded in hex.
34379 @var{id} and @var{extra} are strings encoded in hex.
34381 In response to each query, the target will reply with a list of one or
34382 more markers, separated by commas. @value{GDBN} will respond to each
34383 reply with a request for more markers (using the @samp{qs} form of the
34384 query), until the target responds with @samp{l} (lower-case ell, for
34387 @item qTSTMat:@var{address}
34388 This packets requests data about static tracepoint markers in the
34389 target program at @var{address}. Replies to this packet follow the
34390 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
34391 tracepoint markers.
34393 @item QTSave:@var{filename}
34394 This packet directs the target to save trace data to the file name
34395 @var{filename} in the target's filesystem. @var{filename} is encoded
34396 as a hex string; the interpretation of the file name (relative vs
34397 absolute, wild cards, etc) is up to the target.
34399 @item qTBuffer:@var{offset},@var{len}
34400 Return up to @var{len} bytes of the current contents of trace buffer,
34401 starting at @var{offset}. The trace buffer is treated as if it were
34402 a contiguous collection of traceframes, as per the trace file format.
34403 The reply consists as many hex-encoded bytes as the target can deliver
34404 in a packet; it is not an error to return fewer than were asked for.
34405 A reply consisting of just @code{l} indicates that no bytes are
34408 @item QTBuffer:circular:@var{value}
34409 This packet directs the target to use a circular trace buffer if
34410 @var{value} is 1, or a linear buffer if the value is 0.
34414 @subsection Relocate instruction reply packet
34415 When installing fast tracepoints in memory, the target may need to
34416 relocate the instruction currently at the tracepoint address to a
34417 different address in memory. For most instructions, a simple copy is
34418 enough, but, for example, call instructions that implicitly push the
34419 return address on the stack, and relative branches or other
34420 PC-relative instructions require offset adjustment, so that the effect
34421 of executing the instruction at a different address is the same as if
34422 it had executed in the original location.
34424 In response to several of the tracepoint packets, the target may also
34425 respond with a number of intermediate @samp{qRelocInsn} request
34426 packets before the final result packet, to have @value{GDBN} handle
34427 this relocation operation. If a packet supports this mechanism, its
34428 documentation will explicitly say so. See for example the above
34429 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
34430 format of the request is:
34433 @item qRelocInsn:@var{from};@var{to}
34435 This requests @value{GDBN} to copy instruction at address @var{from}
34436 to address @var{to}, possibly adjusted so that executing the
34437 instruction at @var{to} has the same effect as executing it at
34438 @var{from}. @value{GDBN} writes the adjusted instruction to target
34439 memory starting at @var{to}.
34444 @item qRelocInsn:@var{adjusted_size}
34445 Informs the stub the relocation is complete. @var{adjusted_size} is
34446 the length in bytes of resulting relocated instruction sequence.
34448 A badly formed request was detected, or an error was encountered while
34449 relocating the instruction.
34452 @node Host I/O Packets
34453 @section Host I/O Packets
34454 @cindex Host I/O, remote protocol
34455 @cindex file transfer, remote protocol
34457 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
34458 operations on the far side of a remote link. For example, Host I/O is
34459 used to upload and download files to a remote target with its own
34460 filesystem. Host I/O uses the same constant values and data structure
34461 layout as the target-initiated File-I/O protocol. However, the
34462 Host I/O packets are structured differently. The target-initiated
34463 protocol relies on target memory to store parameters and buffers.
34464 Host I/O requests are initiated by @value{GDBN}, and the
34465 target's memory is not involved. @xref{File-I/O Remote Protocol
34466 Extension}, for more details on the target-initiated protocol.
34468 The Host I/O request packets all encode a single operation along with
34469 its arguments. They have this format:
34473 @item vFile:@var{operation}: @var{parameter}@dots{}
34474 @var{operation} is the name of the particular request; the target
34475 should compare the entire packet name up to the second colon when checking
34476 for a supported operation. The format of @var{parameter} depends on
34477 the operation. Numbers are always passed in hexadecimal. Negative
34478 numbers have an explicit minus sign (i.e.@: two's complement is not
34479 used). Strings (e.g.@: filenames) are encoded as a series of
34480 hexadecimal bytes. The last argument to a system call may be a
34481 buffer of escaped binary data (@pxref{Binary Data}).
34485 The valid responses to Host I/O packets are:
34489 @item F @var{result} [, @var{errno}] [; @var{attachment}]
34490 @var{result} is the integer value returned by this operation, usually
34491 non-negative for success and -1 for errors. If an error has occured,
34492 @var{errno} will be included in the result. @var{errno} will have a
34493 value defined by the File-I/O protocol (@pxref{Errno Values}). For
34494 operations which return data, @var{attachment} supplies the data as a
34495 binary buffer. Binary buffers in response packets are escaped in the
34496 normal way (@pxref{Binary Data}). See the individual packet
34497 documentation for the interpretation of @var{result} and
34501 An empty response indicates that this operation is not recognized.
34505 These are the supported Host I/O operations:
34508 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
34509 Open a file at @var{pathname} and return a file descriptor for it, or
34510 return -1 if an error occurs. @var{pathname} is a string,
34511 @var{flags} is an integer indicating a mask of open flags
34512 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
34513 of mode bits to use if the file is created (@pxref{mode_t Values}).
34514 @xref{open}, for details of the open flags and mode values.
34516 @item vFile:close: @var{fd}
34517 Close the open file corresponding to @var{fd} and return 0, or
34518 -1 if an error occurs.
34520 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
34521 Read data from the open file corresponding to @var{fd}. Up to
34522 @var{count} bytes will be read from the file, starting at @var{offset}
34523 relative to the start of the file. The target may read fewer bytes;
34524 common reasons include packet size limits and an end-of-file
34525 condition. The number of bytes read is returned. Zero should only be
34526 returned for a successful read at the end of the file, or if
34527 @var{count} was zero.
34529 The data read should be returned as a binary attachment on success.
34530 If zero bytes were read, the response should include an empty binary
34531 attachment (i.e.@: a trailing semicolon). The return value is the
34532 number of target bytes read; the binary attachment may be longer if
34533 some characters were escaped.
34535 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
34536 Write @var{data} (a binary buffer) to the open file corresponding
34537 to @var{fd}. Start the write at @var{offset} from the start of the
34538 file. Unlike many @code{write} system calls, there is no
34539 separate @var{count} argument; the length of @var{data} in the
34540 packet is used. @samp{vFile:write} returns the number of bytes written,
34541 which may be shorter than the length of @var{data}, or -1 if an
34544 @item vFile:unlink: @var{pathname}
34545 Delete the file at @var{pathname} on the target. Return 0,
34546 or -1 if an error occurs. @var{pathname} is a string.
34551 @section Interrupts
34552 @cindex interrupts (remote protocol)
34554 When a program on the remote target is running, @value{GDBN} may
34555 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
34556 a @code{BREAK} followed by @code{g},
34557 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
34559 The precise meaning of @code{BREAK} is defined by the transport
34560 mechanism and may, in fact, be undefined. @value{GDBN} does not
34561 currently define a @code{BREAK} mechanism for any of the network
34562 interfaces except for TCP, in which case @value{GDBN} sends the
34563 @code{telnet} BREAK sequence.
34565 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
34566 transport mechanisms. It is represented by sending the single byte
34567 @code{0x03} without any of the usual packet overhead described in
34568 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
34569 transmitted as part of a packet, it is considered to be packet data
34570 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
34571 (@pxref{X packet}), used for binary downloads, may include an unescaped
34572 @code{0x03} as part of its packet.
34574 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
34575 When Linux kernel receives this sequence from serial port,
34576 it stops execution and connects to gdb.
34578 Stubs are not required to recognize these interrupt mechanisms and the
34579 precise meaning associated with receipt of the interrupt is
34580 implementation defined. If the target supports debugging of multiple
34581 threads and/or processes, it should attempt to interrupt all
34582 currently-executing threads and processes.
34583 If the stub is successful at interrupting the
34584 running program, it should send one of the stop
34585 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
34586 of successfully stopping the program in all-stop mode, and a stop reply
34587 for each stopped thread in non-stop mode.
34588 Interrupts received while the
34589 program is stopped are discarded.
34591 @node Notification Packets
34592 @section Notification Packets
34593 @cindex notification packets
34594 @cindex packets, notification
34596 The @value{GDBN} remote serial protocol includes @dfn{notifications},
34597 packets that require no acknowledgment. Both the GDB and the stub
34598 may send notifications (although the only notifications defined at
34599 present are sent by the stub). Notifications carry information
34600 without incurring the round-trip latency of an acknowledgment, and so
34601 are useful for low-impact communications where occasional packet loss
34604 A notification packet has the form @samp{% @var{data} #
34605 @var{checksum}}, where @var{data} is the content of the notification,
34606 and @var{checksum} is a checksum of @var{data}, computed and formatted
34607 as for ordinary @value{GDBN} packets. A notification's @var{data}
34608 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
34609 receiving a notification, the recipient sends no @samp{+} or @samp{-}
34610 to acknowledge the notification's receipt or to report its corruption.
34612 Every notification's @var{data} begins with a name, which contains no
34613 colon characters, followed by a colon character.
34615 Recipients should silently ignore corrupted notifications and
34616 notifications they do not understand. Recipients should restart
34617 timeout periods on receipt of a well-formed notification, whether or
34618 not they understand it.
34620 Senders should only send the notifications described here when this
34621 protocol description specifies that they are permitted. In the
34622 future, we may extend the protocol to permit existing notifications in
34623 new contexts; this rule helps older senders avoid confusing newer
34626 (Older versions of @value{GDBN} ignore bytes received until they see
34627 the @samp{$} byte that begins an ordinary packet, so new stubs may
34628 transmit notifications without fear of confusing older clients. There
34629 are no notifications defined for @value{GDBN} to send at the moment, but we
34630 assume that most older stubs would ignore them, as well.)
34632 The following notification packets from the stub to @value{GDBN} are
34636 @item Stop: @var{reply}
34637 Report an asynchronous stop event in non-stop mode.
34638 The @var{reply} has the form of a stop reply, as
34639 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
34640 for information on how these notifications are acknowledged by
34644 @node Remote Non-Stop
34645 @section Remote Protocol Support for Non-Stop Mode
34647 @value{GDBN}'s remote protocol supports non-stop debugging of
34648 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
34649 supports non-stop mode, it should report that to @value{GDBN} by including
34650 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
34652 @value{GDBN} typically sends a @samp{QNonStop} packet only when
34653 establishing a new connection with the stub. Entering non-stop mode
34654 does not alter the state of any currently-running threads, but targets
34655 must stop all threads in any already-attached processes when entering
34656 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
34657 probe the target state after a mode change.
34659 In non-stop mode, when an attached process encounters an event that
34660 would otherwise be reported with a stop reply, it uses the
34661 asynchronous notification mechanism (@pxref{Notification Packets}) to
34662 inform @value{GDBN}. In contrast to all-stop mode, where all threads
34663 in all processes are stopped when a stop reply is sent, in non-stop
34664 mode only the thread reporting the stop event is stopped. That is,
34665 when reporting a @samp{S} or @samp{T} response to indicate completion
34666 of a step operation, hitting a breakpoint, or a fault, only the
34667 affected thread is stopped; any other still-running threads continue
34668 to run. When reporting a @samp{W} or @samp{X} response, all running
34669 threads belonging to other attached processes continue to run.
34671 Only one stop reply notification at a time may be pending; if
34672 additional stop events occur before @value{GDBN} has acknowledged the
34673 previous notification, they must be queued by the stub for later
34674 synchronous transmission in response to @samp{vStopped} packets from
34675 @value{GDBN}. Because the notification mechanism is unreliable,
34676 the stub is permitted to resend a stop reply notification
34677 if it believes @value{GDBN} may not have received it. @value{GDBN}
34678 ignores additional stop reply notifications received before it has
34679 finished processing a previous notification and the stub has completed
34680 sending any queued stop events.
34682 Otherwise, @value{GDBN} must be prepared to receive a stop reply
34683 notification at any time. Specifically, they may appear when
34684 @value{GDBN} is not otherwise reading input from the stub, or when
34685 @value{GDBN} is expecting to read a normal synchronous response or a
34686 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
34687 Notification packets are distinct from any other communication from
34688 the stub so there is no ambiguity.
34690 After receiving a stop reply notification, @value{GDBN} shall
34691 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
34692 as a regular, synchronous request to the stub. Such acknowledgment
34693 is not required to happen immediately, as @value{GDBN} is permitted to
34694 send other, unrelated packets to the stub first, which the stub should
34697 Upon receiving a @samp{vStopped} packet, if the stub has other queued
34698 stop events to report to @value{GDBN}, it shall respond by sending a
34699 normal stop reply response. @value{GDBN} shall then send another
34700 @samp{vStopped} packet to solicit further responses; again, it is
34701 permitted to send other, unrelated packets as well which the stub
34702 should process normally.
34704 If the stub receives a @samp{vStopped} packet and there are no
34705 additional stop events to report, the stub shall return an @samp{OK}
34706 response. At this point, if further stop events occur, the stub shall
34707 send a new stop reply notification, @value{GDBN} shall accept the
34708 notification, and the process shall be repeated.
34710 In non-stop mode, the target shall respond to the @samp{?} packet as
34711 follows. First, any incomplete stop reply notification/@samp{vStopped}
34712 sequence in progress is abandoned. The target must begin a new
34713 sequence reporting stop events for all stopped threads, whether or not
34714 it has previously reported those events to @value{GDBN}. The first
34715 stop reply is sent as a synchronous reply to the @samp{?} packet, and
34716 subsequent stop replies are sent as responses to @samp{vStopped} packets
34717 using the mechanism described above. The target must not send
34718 asynchronous stop reply notifications until the sequence is complete.
34719 If all threads are running when the target receives the @samp{?} packet,
34720 or if the target is not attached to any process, it shall respond
34723 @node Packet Acknowledgment
34724 @section Packet Acknowledgment
34726 @cindex acknowledgment, for @value{GDBN} remote
34727 @cindex packet acknowledgment, for @value{GDBN} remote
34728 By default, when either the host or the target machine receives a packet,
34729 the first response expected is an acknowledgment: either @samp{+} (to indicate
34730 the package was received correctly) or @samp{-} (to request retransmission).
34731 This mechanism allows the @value{GDBN} remote protocol to operate over
34732 unreliable transport mechanisms, such as a serial line.
34734 In cases where the transport mechanism is itself reliable (such as a pipe or
34735 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
34736 It may be desirable to disable them in that case to reduce communication
34737 overhead, or for other reasons. This can be accomplished by means of the
34738 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
34740 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
34741 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
34742 and response format still includes the normal checksum, as described in
34743 @ref{Overview}, but the checksum may be ignored by the receiver.
34745 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
34746 no-acknowledgment mode, it should report that to @value{GDBN}
34747 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
34748 @pxref{qSupported}.
34749 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
34750 disabled via the @code{set remote noack-packet off} command
34751 (@pxref{Remote Configuration}),
34752 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
34753 Only then may the stub actually turn off packet acknowledgments.
34754 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
34755 response, which can be safely ignored by the stub.
34757 Note that @code{set remote noack-packet} command only affects negotiation
34758 between @value{GDBN} and the stub when subsequent connections are made;
34759 it does not affect the protocol acknowledgment state for any current
34761 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
34762 new connection is established,
34763 there is also no protocol request to re-enable the acknowledgments
34764 for the current connection, once disabled.
34769 Example sequence of a target being re-started. Notice how the restart
34770 does not get any direct output:
34775 @emph{target restarts}
34778 <- @code{T001:1234123412341234}
34782 Example sequence of a target being stepped by a single instruction:
34785 -> @code{G1445@dots{}}
34790 <- @code{T001:1234123412341234}
34794 <- @code{1455@dots{}}
34798 @node File-I/O Remote Protocol Extension
34799 @section File-I/O Remote Protocol Extension
34800 @cindex File-I/O remote protocol extension
34803 * File-I/O Overview::
34804 * Protocol Basics::
34805 * The F Request Packet::
34806 * The F Reply Packet::
34807 * The Ctrl-C Message::
34809 * List of Supported Calls::
34810 * Protocol-specific Representation of Datatypes::
34812 * File-I/O Examples::
34815 @node File-I/O Overview
34816 @subsection File-I/O Overview
34817 @cindex file-i/o overview
34819 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
34820 target to use the host's file system and console I/O to perform various
34821 system calls. System calls on the target system are translated into a
34822 remote protocol packet to the host system, which then performs the needed
34823 actions and returns a response packet to the target system.
34824 This simulates file system operations even on targets that lack file systems.
34826 The protocol is defined to be independent of both the host and target systems.
34827 It uses its own internal representation of datatypes and values. Both
34828 @value{GDBN} and the target's @value{GDBN} stub are responsible for
34829 translating the system-dependent value representations into the internal
34830 protocol representations when data is transmitted.
34832 The communication is synchronous. A system call is possible only when
34833 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
34834 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
34835 the target is stopped to allow deterministic access to the target's
34836 memory. Therefore File-I/O is not interruptible by target signals. On
34837 the other hand, it is possible to interrupt File-I/O by a user interrupt
34838 (@samp{Ctrl-C}) within @value{GDBN}.
34840 The target's request to perform a host system call does not finish
34841 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
34842 after finishing the system call, the target returns to continuing the
34843 previous activity (continue, step). No additional continue or step
34844 request from @value{GDBN} is required.
34847 (@value{GDBP}) continue
34848 <- target requests 'system call X'
34849 target is stopped, @value{GDBN} executes system call
34850 -> @value{GDBN} returns result
34851 ... target continues, @value{GDBN} returns to wait for the target
34852 <- target hits breakpoint and sends a Txx packet
34855 The protocol only supports I/O on the console and to regular files on
34856 the host file system. Character or block special devices, pipes,
34857 named pipes, sockets or any other communication method on the host
34858 system are not supported by this protocol.
34860 File I/O is not supported in non-stop mode.
34862 @node Protocol Basics
34863 @subsection Protocol Basics
34864 @cindex protocol basics, file-i/o
34866 The File-I/O protocol uses the @code{F} packet as the request as well
34867 as reply packet. Since a File-I/O system call can only occur when
34868 @value{GDBN} is waiting for a response from the continuing or stepping target,
34869 the File-I/O request is a reply that @value{GDBN} has to expect as a result
34870 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
34871 This @code{F} packet contains all information needed to allow @value{GDBN}
34872 to call the appropriate host system call:
34876 A unique identifier for the requested system call.
34879 All parameters to the system call. Pointers are given as addresses
34880 in the target memory address space. Pointers to strings are given as
34881 pointer/length pair. Numerical values are given as they are.
34882 Numerical control flags are given in a protocol-specific representation.
34886 At this point, @value{GDBN} has to perform the following actions.
34890 If the parameters include pointer values to data needed as input to a
34891 system call, @value{GDBN} requests this data from the target with a
34892 standard @code{m} packet request. This additional communication has to be
34893 expected by the target implementation and is handled as any other @code{m}
34897 @value{GDBN} translates all value from protocol representation to host
34898 representation as needed. Datatypes are coerced into the host types.
34901 @value{GDBN} calls the system call.
34904 It then coerces datatypes back to protocol representation.
34907 If the system call is expected to return data in buffer space specified
34908 by pointer parameters to the call, the data is transmitted to the
34909 target using a @code{M} or @code{X} packet. This packet has to be expected
34910 by the target implementation and is handled as any other @code{M} or @code{X}
34915 Eventually @value{GDBN} replies with another @code{F} packet which contains all
34916 necessary information for the target to continue. This at least contains
34923 @code{errno}, if has been changed by the system call.
34930 After having done the needed type and value coercion, the target continues
34931 the latest continue or step action.
34933 @node The F Request Packet
34934 @subsection The @code{F} Request Packet
34935 @cindex file-i/o request packet
34936 @cindex @code{F} request packet
34938 The @code{F} request packet has the following format:
34941 @item F@var{call-id},@var{parameter@dots{}}
34943 @var{call-id} is the identifier to indicate the host system call to be called.
34944 This is just the name of the function.
34946 @var{parameter@dots{}} are the parameters to the system call.
34947 Parameters are hexadecimal integer values, either the actual values in case
34948 of scalar datatypes, pointers to target buffer space in case of compound
34949 datatypes and unspecified memory areas, or pointer/length pairs in case
34950 of string parameters. These are appended to the @var{call-id} as a
34951 comma-delimited list. All values are transmitted in ASCII
34952 string representation, pointer/length pairs separated by a slash.
34958 @node The F Reply Packet
34959 @subsection The @code{F} Reply Packet
34960 @cindex file-i/o reply packet
34961 @cindex @code{F} reply packet
34963 The @code{F} reply packet has the following format:
34967 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
34969 @var{retcode} is the return code of the system call as hexadecimal value.
34971 @var{errno} is the @code{errno} set by the call, in protocol-specific
34973 This parameter can be omitted if the call was successful.
34975 @var{Ctrl-C flag} is only sent if the user requested a break. In this
34976 case, @var{errno} must be sent as well, even if the call was successful.
34977 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
34984 or, if the call was interrupted before the host call has been performed:
34991 assuming 4 is the protocol-specific representation of @code{EINTR}.
34996 @node The Ctrl-C Message
34997 @subsection The @samp{Ctrl-C} Message
34998 @cindex ctrl-c message, in file-i/o protocol
35000 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
35001 reply packet (@pxref{The F Reply Packet}),
35002 the target should behave as if it had
35003 gotten a break message. The meaning for the target is ``system call
35004 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
35005 (as with a break message) and return to @value{GDBN} with a @code{T02}
35008 It's important for the target to know in which
35009 state the system call was interrupted. There are two possible cases:
35013 The system call hasn't been performed on the host yet.
35016 The system call on the host has been finished.
35020 These two states can be distinguished by the target by the value of the
35021 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
35022 call hasn't been performed. This is equivalent to the @code{EINTR} handling
35023 on POSIX systems. In any other case, the target may presume that the
35024 system call has been finished --- successfully or not --- and should behave
35025 as if the break message arrived right after the system call.
35027 @value{GDBN} must behave reliably. If the system call has not been called
35028 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
35029 @code{errno} in the packet. If the system call on the host has been finished
35030 before the user requests a break, the full action must be finished by
35031 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
35032 The @code{F} packet may only be sent when either nothing has happened
35033 or the full action has been completed.
35036 @subsection Console I/O
35037 @cindex console i/o as part of file-i/o
35039 By default and if not explicitly closed by the target system, the file
35040 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
35041 on the @value{GDBN} console is handled as any other file output operation
35042 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
35043 by @value{GDBN} so that after the target read request from file descriptor
35044 0 all following typing is buffered until either one of the following
35049 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
35051 system call is treated as finished.
35054 The user presses @key{RET}. This is treated as end of input with a trailing
35058 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
35059 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
35063 If the user has typed more characters than fit in the buffer given to
35064 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
35065 either another @code{read(0, @dots{})} is requested by the target, or debugging
35066 is stopped at the user's request.
35069 @node List of Supported Calls
35070 @subsection List of Supported Calls
35071 @cindex list of supported file-i/o calls
35088 @unnumberedsubsubsec open
35089 @cindex open, file-i/o system call
35094 int open(const char *pathname, int flags);
35095 int open(const char *pathname, int flags, mode_t mode);
35099 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
35102 @var{flags} is the bitwise @code{OR} of the following values:
35106 If the file does not exist it will be created. The host
35107 rules apply as far as file ownership and time stamps
35111 When used with @code{O_CREAT}, if the file already exists it is
35112 an error and open() fails.
35115 If the file already exists and the open mode allows
35116 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
35117 truncated to zero length.
35120 The file is opened in append mode.
35123 The file is opened for reading only.
35126 The file is opened for writing only.
35129 The file is opened for reading and writing.
35133 Other bits are silently ignored.
35137 @var{mode} is the bitwise @code{OR} of the following values:
35141 User has read permission.
35144 User has write permission.
35147 Group has read permission.
35150 Group has write permission.
35153 Others have read permission.
35156 Others have write permission.
35160 Other bits are silently ignored.
35163 @item Return value:
35164 @code{open} returns the new file descriptor or -1 if an error
35171 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
35174 @var{pathname} refers to a directory.
35177 The requested access is not allowed.
35180 @var{pathname} was too long.
35183 A directory component in @var{pathname} does not exist.
35186 @var{pathname} refers to a device, pipe, named pipe or socket.
35189 @var{pathname} refers to a file on a read-only filesystem and
35190 write access was requested.
35193 @var{pathname} is an invalid pointer value.
35196 No space on device to create the file.
35199 The process already has the maximum number of files open.
35202 The limit on the total number of files open on the system
35206 The call was interrupted by the user.
35212 @unnumberedsubsubsec close
35213 @cindex close, file-i/o system call
35222 @samp{Fclose,@var{fd}}
35224 @item Return value:
35225 @code{close} returns zero on success, or -1 if an error occurred.
35231 @var{fd} isn't a valid open file descriptor.
35234 The call was interrupted by the user.
35240 @unnumberedsubsubsec read
35241 @cindex read, file-i/o system call
35246 int read(int fd, void *buf, unsigned int count);
35250 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
35252 @item Return value:
35253 On success, the number of bytes read is returned.
35254 Zero indicates end of file. If count is zero, read
35255 returns zero as well. On error, -1 is returned.
35261 @var{fd} is not a valid file descriptor or is not open for
35265 @var{bufptr} is an invalid pointer value.
35268 The call was interrupted by the user.
35274 @unnumberedsubsubsec write
35275 @cindex write, file-i/o system call
35280 int write(int fd, const void *buf, unsigned int count);
35284 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
35286 @item Return value:
35287 On success, the number of bytes written are returned.
35288 Zero indicates nothing was written. On error, -1
35295 @var{fd} is not a valid file descriptor or is not open for
35299 @var{bufptr} is an invalid pointer value.
35302 An attempt was made to write a file that exceeds the
35303 host-specific maximum file size allowed.
35306 No space on device to write the data.
35309 The call was interrupted by the user.
35315 @unnumberedsubsubsec lseek
35316 @cindex lseek, file-i/o system call
35321 long lseek (int fd, long offset, int flag);
35325 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
35327 @var{flag} is one of:
35331 The offset is set to @var{offset} bytes.
35334 The offset is set to its current location plus @var{offset}
35338 The offset is set to the size of the file plus @var{offset}
35342 @item Return value:
35343 On success, the resulting unsigned offset in bytes from
35344 the beginning of the file is returned. Otherwise, a
35345 value of -1 is returned.
35351 @var{fd} is not a valid open file descriptor.
35354 @var{fd} is associated with the @value{GDBN} console.
35357 @var{flag} is not a proper value.
35360 The call was interrupted by the user.
35366 @unnumberedsubsubsec rename
35367 @cindex rename, file-i/o system call
35372 int rename(const char *oldpath, const char *newpath);
35376 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
35378 @item Return value:
35379 On success, zero is returned. On error, -1 is returned.
35385 @var{newpath} is an existing directory, but @var{oldpath} is not a
35389 @var{newpath} is a non-empty directory.
35392 @var{oldpath} or @var{newpath} is a directory that is in use by some
35396 An attempt was made to make a directory a subdirectory
35400 A component used as a directory in @var{oldpath} or new
35401 path is not a directory. Or @var{oldpath} is a directory
35402 and @var{newpath} exists but is not a directory.
35405 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
35408 No access to the file or the path of the file.
35412 @var{oldpath} or @var{newpath} was too long.
35415 A directory component in @var{oldpath} or @var{newpath} does not exist.
35418 The file is on a read-only filesystem.
35421 The device containing the file has no room for the new
35425 The call was interrupted by the user.
35431 @unnumberedsubsubsec unlink
35432 @cindex unlink, file-i/o system call
35437 int unlink(const char *pathname);
35441 @samp{Funlink,@var{pathnameptr}/@var{len}}
35443 @item Return value:
35444 On success, zero is returned. On error, -1 is returned.
35450 No access to the file or the path of the file.
35453 The system does not allow unlinking of directories.
35456 The file @var{pathname} cannot be unlinked because it's
35457 being used by another process.
35460 @var{pathnameptr} is an invalid pointer value.
35463 @var{pathname} was too long.
35466 A directory component in @var{pathname} does not exist.
35469 A component of the path is not a directory.
35472 The file is on a read-only filesystem.
35475 The call was interrupted by the user.
35481 @unnumberedsubsubsec stat/fstat
35482 @cindex fstat, file-i/o system call
35483 @cindex stat, file-i/o system call
35488 int stat(const char *pathname, struct stat *buf);
35489 int fstat(int fd, struct stat *buf);
35493 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
35494 @samp{Ffstat,@var{fd},@var{bufptr}}
35496 @item Return value:
35497 On success, zero is returned. On error, -1 is returned.
35503 @var{fd} is not a valid open file.
35506 A directory component in @var{pathname} does not exist or the
35507 path is an empty string.
35510 A component of the path is not a directory.
35513 @var{pathnameptr} is an invalid pointer value.
35516 No access to the file or the path of the file.
35519 @var{pathname} was too long.
35522 The call was interrupted by the user.
35528 @unnumberedsubsubsec gettimeofday
35529 @cindex gettimeofday, file-i/o system call
35534 int gettimeofday(struct timeval *tv, void *tz);
35538 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
35540 @item Return value:
35541 On success, 0 is returned, -1 otherwise.
35547 @var{tz} is a non-NULL pointer.
35550 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
35556 @unnumberedsubsubsec isatty
35557 @cindex isatty, file-i/o system call
35562 int isatty(int fd);
35566 @samp{Fisatty,@var{fd}}
35568 @item Return value:
35569 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
35575 The call was interrupted by the user.
35580 Note that the @code{isatty} call is treated as a special case: it returns
35581 1 to the target if the file descriptor is attached
35582 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
35583 would require implementing @code{ioctl} and would be more complex than
35588 @unnumberedsubsubsec system
35589 @cindex system, file-i/o system call
35594 int system(const char *command);
35598 @samp{Fsystem,@var{commandptr}/@var{len}}
35600 @item Return value:
35601 If @var{len} is zero, the return value indicates whether a shell is
35602 available. A zero return value indicates a shell is not available.
35603 For non-zero @var{len}, the value returned is -1 on error and the
35604 return status of the command otherwise. Only the exit status of the
35605 command is returned, which is extracted from the host's @code{system}
35606 return value by calling @code{WEXITSTATUS(retval)}. In case
35607 @file{/bin/sh} could not be executed, 127 is returned.
35613 The call was interrupted by the user.
35618 @value{GDBN} takes over the full task of calling the necessary host calls
35619 to perform the @code{system} call. The return value of @code{system} on
35620 the host is simplified before it's returned
35621 to the target. Any termination signal information from the child process
35622 is discarded, and the return value consists
35623 entirely of the exit status of the called command.
35625 Due to security concerns, the @code{system} call is by default refused
35626 by @value{GDBN}. The user has to allow this call explicitly with the
35627 @code{set remote system-call-allowed 1} command.
35630 @item set remote system-call-allowed
35631 @kindex set remote system-call-allowed
35632 Control whether to allow the @code{system} calls in the File I/O
35633 protocol for the remote target. The default is zero (disabled).
35635 @item show remote system-call-allowed
35636 @kindex show remote system-call-allowed
35637 Show whether the @code{system} calls are allowed in the File I/O
35641 @node Protocol-specific Representation of Datatypes
35642 @subsection Protocol-specific Representation of Datatypes
35643 @cindex protocol-specific representation of datatypes, in file-i/o protocol
35646 * Integral Datatypes::
35648 * Memory Transfer::
35653 @node Integral Datatypes
35654 @unnumberedsubsubsec Integral Datatypes
35655 @cindex integral datatypes, in file-i/o protocol
35657 The integral datatypes used in the system calls are @code{int},
35658 @code{unsigned int}, @code{long}, @code{unsigned long},
35659 @code{mode_t}, and @code{time_t}.
35661 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
35662 implemented as 32 bit values in this protocol.
35664 @code{long} and @code{unsigned long} are implemented as 64 bit types.
35666 @xref{Limits}, for corresponding MIN and MAX values (similar to those
35667 in @file{limits.h}) to allow range checking on host and target.
35669 @code{time_t} datatypes are defined as seconds since the Epoch.
35671 All integral datatypes transferred as part of a memory read or write of a
35672 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
35675 @node Pointer Values
35676 @unnumberedsubsubsec Pointer Values
35677 @cindex pointer values, in file-i/o protocol
35679 Pointers to target data are transmitted as they are. An exception
35680 is made for pointers to buffers for which the length isn't
35681 transmitted as part of the function call, namely strings. Strings
35682 are transmitted as a pointer/length pair, both as hex values, e.g.@:
35689 which is a pointer to data of length 18 bytes at position 0x1aaf.
35690 The length is defined as the full string length in bytes, including
35691 the trailing null byte. For example, the string @code{"hello world"}
35692 at address 0x123456 is transmitted as
35698 @node Memory Transfer
35699 @unnumberedsubsubsec Memory Transfer
35700 @cindex memory transfer, in file-i/o protocol
35702 Structured data which is transferred using a memory read or write (for
35703 example, a @code{struct stat}) is expected to be in a protocol-specific format
35704 with all scalar multibyte datatypes being big endian. Translation to
35705 this representation needs to be done both by the target before the @code{F}
35706 packet is sent, and by @value{GDBN} before
35707 it transfers memory to the target. Transferred pointers to structured
35708 data should point to the already-coerced data at any time.
35712 @unnumberedsubsubsec struct stat
35713 @cindex struct stat, in file-i/o protocol
35715 The buffer of type @code{struct stat} used by the target and @value{GDBN}
35716 is defined as follows:
35720 unsigned int st_dev; /* device */
35721 unsigned int st_ino; /* inode */
35722 mode_t st_mode; /* protection */
35723 unsigned int st_nlink; /* number of hard links */
35724 unsigned int st_uid; /* user ID of owner */
35725 unsigned int st_gid; /* group ID of owner */
35726 unsigned int st_rdev; /* device type (if inode device) */
35727 unsigned long st_size; /* total size, in bytes */
35728 unsigned long st_blksize; /* blocksize for filesystem I/O */
35729 unsigned long st_blocks; /* number of blocks allocated */
35730 time_t st_atime; /* time of last access */
35731 time_t st_mtime; /* time of last modification */
35732 time_t st_ctime; /* time of last change */
35736 The integral datatypes conform to the definitions given in the
35737 appropriate section (see @ref{Integral Datatypes}, for details) so this
35738 structure is of size 64 bytes.
35740 The values of several fields have a restricted meaning and/or
35746 A value of 0 represents a file, 1 the console.
35749 No valid meaning for the target. Transmitted unchanged.
35752 Valid mode bits are described in @ref{Constants}. Any other
35753 bits have currently no meaning for the target.
35758 No valid meaning for the target. Transmitted unchanged.
35763 These values have a host and file system dependent
35764 accuracy. Especially on Windows hosts, the file system may not
35765 support exact timing values.
35768 The target gets a @code{struct stat} of the above representation and is
35769 responsible for coercing it to the target representation before
35772 Note that due to size differences between the host, target, and protocol
35773 representations of @code{struct stat} members, these members could eventually
35774 get truncated on the target.
35776 @node struct timeval
35777 @unnumberedsubsubsec struct timeval
35778 @cindex struct timeval, in file-i/o protocol
35780 The buffer of type @code{struct timeval} used by the File-I/O protocol
35781 is defined as follows:
35785 time_t tv_sec; /* second */
35786 long tv_usec; /* microsecond */
35790 The integral datatypes conform to the definitions given in the
35791 appropriate section (see @ref{Integral Datatypes}, for details) so this
35792 structure is of size 8 bytes.
35795 @subsection Constants
35796 @cindex constants, in file-i/o protocol
35798 The following values are used for the constants inside of the
35799 protocol. @value{GDBN} and target are responsible for translating these
35800 values before and after the call as needed.
35811 @unnumberedsubsubsec Open Flags
35812 @cindex open flags, in file-i/o protocol
35814 All values are given in hexadecimal representation.
35826 @node mode_t Values
35827 @unnumberedsubsubsec mode_t Values
35828 @cindex mode_t values, in file-i/o protocol
35830 All values are given in octal representation.
35847 @unnumberedsubsubsec Errno Values
35848 @cindex errno values, in file-i/o protocol
35850 All values are given in decimal representation.
35875 @code{EUNKNOWN} is used as a fallback error value if a host system returns
35876 any error value not in the list of supported error numbers.
35879 @unnumberedsubsubsec Lseek Flags
35880 @cindex lseek flags, in file-i/o protocol
35889 @unnumberedsubsubsec Limits
35890 @cindex limits, in file-i/o protocol
35892 All values are given in decimal representation.
35895 INT_MIN -2147483648
35897 UINT_MAX 4294967295
35898 LONG_MIN -9223372036854775808
35899 LONG_MAX 9223372036854775807
35900 ULONG_MAX 18446744073709551615
35903 @node File-I/O Examples
35904 @subsection File-I/O Examples
35905 @cindex file-i/o examples
35907 Example sequence of a write call, file descriptor 3, buffer is at target
35908 address 0x1234, 6 bytes should be written:
35911 <- @code{Fwrite,3,1234,6}
35912 @emph{request memory read from target}
35915 @emph{return "6 bytes written"}
35919 Example sequence of a read call, file descriptor 3, buffer is at target
35920 address 0x1234, 6 bytes should be read:
35923 <- @code{Fread,3,1234,6}
35924 @emph{request memory write to target}
35925 -> @code{X1234,6:XXXXXX}
35926 @emph{return "6 bytes read"}
35930 Example sequence of a read call, call fails on the host due to invalid
35931 file descriptor (@code{EBADF}):
35934 <- @code{Fread,3,1234,6}
35938 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
35942 <- @code{Fread,3,1234,6}
35947 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
35951 <- @code{Fread,3,1234,6}
35952 -> @code{X1234,6:XXXXXX}
35956 @node Library List Format
35957 @section Library List Format
35958 @cindex library list format, remote protocol
35960 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
35961 same process as your application to manage libraries. In this case,
35962 @value{GDBN} can use the loader's symbol table and normal memory
35963 operations to maintain a list of shared libraries. On other
35964 platforms, the operating system manages loaded libraries.
35965 @value{GDBN} can not retrieve the list of currently loaded libraries
35966 through memory operations, so it uses the @samp{qXfer:libraries:read}
35967 packet (@pxref{qXfer library list read}) instead. The remote stub
35968 queries the target's operating system and reports which libraries
35971 The @samp{qXfer:libraries:read} packet returns an XML document which
35972 lists loaded libraries and their offsets. Each library has an
35973 associated name and one or more segment or section base addresses,
35974 which report where the library was loaded in memory.
35976 For the common case of libraries that are fully linked binaries, the
35977 library should have a list of segments. If the target supports
35978 dynamic linking of a relocatable object file, its library XML element
35979 should instead include a list of allocated sections. The segment or
35980 section bases are start addresses, not relocation offsets; they do not
35981 depend on the library's link-time base addresses.
35983 @value{GDBN} must be linked with the Expat library to support XML
35984 library lists. @xref{Expat}.
35986 A simple memory map, with one loaded library relocated by a single
35987 offset, looks like this:
35991 <library name="/lib/libc.so.6">
35992 <segment address="0x10000000"/>
35997 Another simple memory map, with one loaded library with three
35998 allocated sections (.text, .data, .bss), looks like this:
36002 <library name="sharedlib.o">
36003 <section address="0x10000000"/>
36004 <section address="0x20000000"/>
36005 <section address="0x30000000"/>
36010 The format of a library list is described by this DTD:
36013 <!-- library-list: Root element with versioning -->
36014 <!ELEMENT library-list (library)*>
36015 <!ATTLIST library-list version CDATA #FIXED "1.0">
36016 <!ELEMENT library (segment*, section*)>
36017 <!ATTLIST library name CDATA #REQUIRED>
36018 <!ELEMENT segment EMPTY>
36019 <!ATTLIST segment address CDATA #REQUIRED>
36020 <!ELEMENT section EMPTY>
36021 <!ATTLIST section address CDATA #REQUIRED>
36024 In addition, segments and section descriptors cannot be mixed within a
36025 single library element, and you must supply at least one segment or
36026 section for each library.
36028 @node Memory Map Format
36029 @section Memory Map Format
36030 @cindex memory map format
36032 To be able to write into flash memory, @value{GDBN} needs to obtain a
36033 memory map from the target. This section describes the format of the
36036 The memory map is obtained using the @samp{qXfer:memory-map:read}
36037 (@pxref{qXfer memory map read}) packet and is an XML document that
36038 lists memory regions.
36040 @value{GDBN} must be linked with the Expat library to support XML
36041 memory maps. @xref{Expat}.
36043 The top-level structure of the document is shown below:
36046 <?xml version="1.0"?>
36047 <!DOCTYPE memory-map
36048 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
36049 "http://sourceware.org/gdb/gdb-memory-map.dtd">
36055 Each region can be either:
36060 A region of RAM starting at @var{addr} and extending for @var{length}
36064 <memory type="ram" start="@var{addr}" length="@var{length}"/>
36069 A region of read-only memory:
36072 <memory type="rom" start="@var{addr}" length="@var{length}"/>
36077 A region of flash memory, with erasure blocks @var{blocksize}
36081 <memory type="flash" start="@var{addr}" length="@var{length}">
36082 <property name="blocksize">@var{blocksize}</property>
36088 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
36089 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
36090 packets to write to addresses in such ranges.
36092 The formal DTD for memory map format is given below:
36095 <!-- ................................................... -->
36096 <!-- Memory Map XML DTD ................................ -->
36097 <!-- File: memory-map.dtd .............................. -->
36098 <!-- .................................... .............. -->
36099 <!-- memory-map.dtd -->
36100 <!-- memory-map: Root element with versioning -->
36101 <!ELEMENT memory-map (memory | property)>
36102 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
36103 <!ELEMENT memory (property)>
36104 <!-- memory: Specifies a memory region,
36105 and its type, or device. -->
36106 <!ATTLIST memory type CDATA #REQUIRED
36107 start CDATA #REQUIRED
36108 length CDATA #REQUIRED
36109 device CDATA #IMPLIED>
36110 <!-- property: Generic attribute tag -->
36111 <!ELEMENT property (#PCDATA | property)*>
36112 <!ATTLIST property name CDATA #REQUIRED>
36115 @node Thread List Format
36116 @section Thread List Format
36117 @cindex thread list format
36119 To efficiently update the list of threads and their attributes,
36120 @value{GDBN} issues the @samp{qXfer:threads:read} packet
36121 (@pxref{qXfer threads read}) and obtains the XML document with
36122 the following structure:
36125 <?xml version="1.0"?>
36127 <thread id="id" core="0">
36128 ... description ...
36133 Each @samp{thread} element must have the @samp{id} attribute that
36134 identifies the thread (@pxref{thread-id syntax}). The
36135 @samp{core} attribute, if present, specifies which processor core
36136 the thread was last executing on. The content of the of @samp{thread}
36137 element is interpreted as human-readable auxilliary information.
36139 @node Traceframe Info Format
36140 @section Traceframe Info Format
36141 @cindex traceframe info format
36143 To be able to know which objects in the inferior can be examined when
36144 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
36145 memory ranges, registers and trace state variables that have been
36146 collected in a traceframe.
36148 This list is obtained using the @samp{qXfer:traceframe-info:read}
36149 (@pxref{qXfer traceframe info read}) packet and is an XML document.
36151 @value{GDBN} must be linked with the Expat library to support XML
36152 traceframe info discovery. @xref{Expat}.
36154 The top-level structure of the document is shown below:
36157 <?xml version="1.0"?>
36158 <!DOCTYPE traceframe-info
36159 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
36160 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
36166 Each traceframe block can be either:
36171 A region of collected memory starting at @var{addr} and extending for
36172 @var{length} bytes from there:
36175 <memory start="@var{addr}" length="@var{length}"/>
36180 The formal DTD for the traceframe info format is given below:
36183 <!ELEMENT traceframe-info (memory)* >
36184 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
36186 <!ELEMENT memory EMPTY>
36187 <!ATTLIST memory start CDATA #REQUIRED
36188 length CDATA #REQUIRED>
36191 @include agentexpr.texi
36193 @node Target Descriptions
36194 @appendix Target Descriptions
36195 @cindex target descriptions
36197 @strong{Warning:} target descriptions are still under active development,
36198 and the contents and format may change between @value{GDBN} releases.
36199 The format is expected to stabilize in the future.
36201 One of the challenges of using @value{GDBN} to debug embedded systems
36202 is that there are so many minor variants of each processor
36203 architecture in use. It is common practice for vendors to start with
36204 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
36205 and then make changes to adapt it to a particular market niche. Some
36206 architectures have hundreds of variants, available from dozens of
36207 vendors. This leads to a number of problems:
36211 With so many different customized processors, it is difficult for
36212 the @value{GDBN} maintainers to keep up with the changes.
36214 Since individual variants may have short lifetimes or limited
36215 audiences, it may not be worthwhile to carry information about every
36216 variant in the @value{GDBN} source tree.
36218 When @value{GDBN} does support the architecture of the embedded system
36219 at hand, the task of finding the correct architecture name to give the
36220 @command{set architecture} command can be error-prone.
36223 To address these problems, the @value{GDBN} remote protocol allows a
36224 target system to not only identify itself to @value{GDBN}, but to
36225 actually describe its own features. This lets @value{GDBN} support
36226 processor variants it has never seen before --- to the extent that the
36227 descriptions are accurate, and that @value{GDBN} understands them.
36229 @value{GDBN} must be linked with the Expat library to support XML
36230 target descriptions. @xref{Expat}.
36233 * Retrieving Descriptions:: How descriptions are fetched from a target.
36234 * Target Description Format:: The contents of a target description.
36235 * Predefined Target Types:: Standard types available for target
36237 * Standard Target Features:: Features @value{GDBN} knows about.
36240 @node Retrieving Descriptions
36241 @section Retrieving Descriptions
36243 Target descriptions can be read from the target automatically, or
36244 specified by the user manually. The default behavior is to read the
36245 description from the target. @value{GDBN} retrieves it via the remote
36246 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
36247 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
36248 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
36249 XML document, of the form described in @ref{Target Description
36252 Alternatively, you can specify a file to read for the target description.
36253 If a file is set, the target will not be queried. The commands to
36254 specify a file are:
36257 @cindex set tdesc filename
36258 @item set tdesc filename @var{path}
36259 Read the target description from @var{path}.
36261 @cindex unset tdesc filename
36262 @item unset tdesc filename
36263 Do not read the XML target description from a file. @value{GDBN}
36264 will use the description supplied by the current target.
36266 @cindex show tdesc filename
36267 @item show tdesc filename
36268 Show the filename to read for a target description, if any.
36272 @node Target Description Format
36273 @section Target Description Format
36274 @cindex target descriptions, XML format
36276 A target description annex is an @uref{http://www.w3.org/XML/, XML}
36277 document which complies with the Document Type Definition provided in
36278 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
36279 means you can use generally available tools like @command{xmllint} to
36280 check that your feature descriptions are well-formed and valid.
36281 However, to help people unfamiliar with XML write descriptions for
36282 their targets, we also describe the grammar here.
36284 Target descriptions can identify the architecture of the remote target
36285 and (for some architectures) provide information about custom register
36286 sets. They can also identify the OS ABI of the remote target.
36287 @value{GDBN} can use this information to autoconfigure for your
36288 target, or to warn you if you connect to an unsupported target.
36290 Here is a simple target description:
36293 <target version="1.0">
36294 <architecture>i386:x86-64</architecture>
36299 This minimal description only says that the target uses
36300 the x86-64 architecture.
36302 A target description has the following overall form, with [ ] marking
36303 optional elements and @dots{} marking repeatable elements. The elements
36304 are explained further below.
36307 <?xml version="1.0"?>
36308 <!DOCTYPE target SYSTEM "gdb-target.dtd">
36309 <target version="1.0">
36310 @r{[}@var{architecture}@r{]}
36311 @r{[}@var{osabi}@r{]}
36312 @r{[}@var{compatible}@r{]}
36313 @r{[}@var{feature}@dots{}@r{]}
36318 The description is generally insensitive to whitespace and line
36319 breaks, under the usual common-sense rules. The XML version
36320 declaration and document type declaration can generally be omitted
36321 (@value{GDBN} does not require them), but specifying them may be
36322 useful for XML validation tools. The @samp{version} attribute for
36323 @samp{<target>} may also be omitted, but we recommend
36324 including it; if future versions of @value{GDBN} use an incompatible
36325 revision of @file{gdb-target.dtd}, they will detect and report
36326 the version mismatch.
36328 @subsection Inclusion
36329 @cindex target descriptions, inclusion
36332 @cindex <xi:include>
36335 It can sometimes be valuable to split a target description up into
36336 several different annexes, either for organizational purposes, or to
36337 share files between different possible target descriptions. You can
36338 divide a description into multiple files by replacing any element of
36339 the target description with an inclusion directive of the form:
36342 <xi:include href="@var{document}"/>
36346 When @value{GDBN} encounters an element of this form, it will retrieve
36347 the named XML @var{document}, and replace the inclusion directive with
36348 the contents of that document. If the current description was read
36349 using @samp{qXfer}, then so will be the included document;
36350 @var{document} will be interpreted as the name of an annex. If the
36351 current description was read from a file, @value{GDBN} will look for
36352 @var{document} as a file in the same directory where it found the
36353 original description.
36355 @subsection Architecture
36356 @cindex <architecture>
36358 An @samp{<architecture>} element has this form:
36361 <architecture>@var{arch}</architecture>
36364 @var{arch} is one of the architectures from the set accepted by
36365 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
36368 @cindex @code{<osabi>}
36370 This optional field was introduced in @value{GDBN} version 7.0.
36371 Previous versions of @value{GDBN} ignore it.
36373 An @samp{<osabi>} element has this form:
36376 <osabi>@var{abi-name}</osabi>
36379 @var{abi-name} is an OS ABI name from the same selection accepted by
36380 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
36382 @subsection Compatible Architecture
36383 @cindex @code{<compatible>}
36385 This optional field was introduced in @value{GDBN} version 7.0.
36386 Previous versions of @value{GDBN} ignore it.
36388 A @samp{<compatible>} element has this form:
36391 <compatible>@var{arch}</compatible>
36394 @var{arch} is one of the architectures from the set accepted by
36395 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
36397 A @samp{<compatible>} element is used to specify that the target
36398 is able to run binaries in some other than the main target architecture
36399 given by the @samp{<architecture>} element. For example, on the
36400 Cell Broadband Engine, the main architecture is @code{powerpc:common}
36401 or @code{powerpc:common64}, but the system is able to run binaries
36402 in the @code{spu} architecture as well. The way to describe this
36403 capability with @samp{<compatible>} is as follows:
36406 <architecture>powerpc:common</architecture>
36407 <compatible>spu</compatible>
36410 @subsection Features
36413 Each @samp{<feature>} describes some logical portion of the target
36414 system. Features are currently used to describe available CPU
36415 registers and the types of their contents. A @samp{<feature>} element
36419 <feature name="@var{name}">
36420 @r{[}@var{type}@dots{}@r{]}
36426 Each feature's name should be unique within the description. The name
36427 of a feature does not matter unless @value{GDBN} has some special
36428 knowledge of the contents of that feature; if it does, the feature
36429 should have its standard name. @xref{Standard Target Features}.
36433 Any register's value is a collection of bits which @value{GDBN} must
36434 interpret. The default interpretation is a two's complement integer,
36435 but other types can be requested by name in the register description.
36436 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
36437 Target Types}), and the description can define additional composite types.
36439 Each type element must have an @samp{id} attribute, which gives
36440 a unique (within the containing @samp{<feature>}) name to the type.
36441 Types must be defined before they are used.
36444 Some targets offer vector registers, which can be treated as arrays
36445 of scalar elements. These types are written as @samp{<vector>} elements,
36446 specifying the array element type, @var{type}, and the number of elements,
36450 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
36454 If a register's value is usefully viewed in multiple ways, define it
36455 with a union type containing the useful representations. The
36456 @samp{<union>} element contains one or more @samp{<field>} elements,
36457 each of which has a @var{name} and a @var{type}:
36460 <union id="@var{id}">
36461 <field name="@var{name}" type="@var{type}"/>
36467 If a register's value is composed from several separate values, define
36468 it with a structure type. There are two forms of the @samp{<struct>}
36469 element; a @samp{<struct>} element must either contain only bitfields
36470 or contain no bitfields. If the structure contains only bitfields,
36471 its total size in bytes must be specified, each bitfield must have an
36472 explicit start and end, and bitfields are automatically assigned an
36473 integer type. The field's @var{start} should be less than or
36474 equal to its @var{end}, and zero represents the least significant bit.
36477 <struct id="@var{id}" size="@var{size}">
36478 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
36483 If the structure contains no bitfields, then each field has an
36484 explicit type, and no implicit padding is added.
36487 <struct id="@var{id}">
36488 <field name="@var{name}" type="@var{type}"/>
36494 If a register's value is a series of single-bit flags, define it with
36495 a flags type. The @samp{<flags>} element has an explicit @var{size}
36496 and contains one or more @samp{<field>} elements. Each field has a
36497 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
36501 <flags id="@var{id}" size="@var{size}">
36502 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
36507 @subsection Registers
36510 Each register is represented as an element with this form:
36513 <reg name="@var{name}"
36514 bitsize="@var{size}"
36515 @r{[}regnum="@var{num}"@r{]}
36516 @r{[}save-restore="@var{save-restore}"@r{]}
36517 @r{[}type="@var{type}"@r{]}
36518 @r{[}group="@var{group}"@r{]}/>
36522 The components are as follows:
36527 The register's name; it must be unique within the target description.
36530 The register's size, in bits.
36533 The register's number. If omitted, a register's number is one greater
36534 than that of the previous register (either in the current feature or in
36535 a preceeding feature); the first register in the target description
36536 defaults to zero. This register number is used to read or write
36537 the register; e.g.@: it is used in the remote @code{p} and @code{P}
36538 packets, and registers appear in the @code{g} and @code{G} packets
36539 in order of increasing register number.
36542 Whether the register should be preserved across inferior function
36543 calls; this must be either @code{yes} or @code{no}. The default is
36544 @code{yes}, which is appropriate for most registers except for
36545 some system control registers; this is not related to the target's
36549 The type of the register. @var{type} may be a predefined type, a type
36550 defined in the current feature, or one of the special types @code{int}
36551 and @code{float}. @code{int} is an integer type of the correct size
36552 for @var{bitsize}, and @code{float} is a floating point type (in the
36553 architecture's normal floating point format) of the correct size for
36554 @var{bitsize}. The default is @code{int}.
36557 The register group to which this register belongs. @var{group} must
36558 be either @code{general}, @code{float}, or @code{vector}. If no
36559 @var{group} is specified, @value{GDBN} will not display the register
36560 in @code{info registers}.
36564 @node Predefined Target Types
36565 @section Predefined Target Types
36566 @cindex target descriptions, predefined types
36568 Type definitions in the self-description can build up composite types
36569 from basic building blocks, but can not define fundamental types. Instead,
36570 standard identifiers are provided by @value{GDBN} for the fundamental
36571 types. The currently supported types are:
36580 Signed integer types holding the specified number of bits.
36587 Unsigned integer types holding the specified number of bits.
36591 Pointers to unspecified code and data. The program counter and
36592 any dedicated return address register may be marked as code
36593 pointers; printing a code pointer converts it into a symbolic
36594 address. The stack pointer and any dedicated address registers
36595 may be marked as data pointers.
36598 Single precision IEEE floating point.
36601 Double precision IEEE floating point.
36604 The 12-byte extended precision format used by ARM FPA registers.
36607 The 10-byte extended precision format used by x87 registers.
36610 32bit @sc{eflags} register used by x86.
36613 32bit @sc{mxcsr} register used by x86.
36617 @node Standard Target Features
36618 @section Standard Target Features
36619 @cindex target descriptions, standard features
36621 A target description must contain either no registers or all the
36622 target's registers. If the description contains no registers, then
36623 @value{GDBN} will assume a default register layout, selected based on
36624 the architecture. If the description contains any registers, the
36625 default layout will not be used; the standard registers must be
36626 described in the target description, in such a way that @value{GDBN}
36627 can recognize them.
36629 This is accomplished by giving specific names to feature elements
36630 which contain standard registers. @value{GDBN} will look for features
36631 with those names and verify that they contain the expected registers;
36632 if any known feature is missing required registers, or if any required
36633 feature is missing, @value{GDBN} will reject the target
36634 description. You can add additional registers to any of the
36635 standard features --- @value{GDBN} will display them just as if
36636 they were added to an unrecognized feature.
36638 This section lists the known features and their expected contents.
36639 Sample XML documents for these features are included in the
36640 @value{GDBN} source tree, in the directory @file{gdb/features}.
36642 Names recognized by @value{GDBN} should include the name of the
36643 company or organization which selected the name, and the overall
36644 architecture to which the feature applies; so e.g.@: the feature
36645 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
36647 The names of registers are not case sensitive for the purpose
36648 of recognizing standard features, but @value{GDBN} will only display
36649 registers using the capitalization used in the description.
36656 * PowerPC Features::
36661 @subsection ARM Features
36662 @cindex target descriptions, ARM features
36664 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
36666 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
36667 @samp{lr}, @samp{pc}, and @samp{cpsr}.
36669 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
36670 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
36671 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
36674 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
36675 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
36677 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
36678 it should contain at least registers @samp{wR0} through @samp{wR15} and
36679 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
36680 @samp{wCSSF}, and @samp{wCASF} registers are optional.
36682 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
36683 should contain at least registers @samp{d0} through @samp{d15}. If
36684 they are present, @samp{d16} through @samp{d31} should also be included.
36685 @value{GDBN} will synthesize the single-precision registers from
36686 halves of the double-precision registers.
36688 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
36689 need to contain registers; it instructs @value{GDBN} to display the
36690 VFP double-precision registers as vectors and to synthesize the
36691 quad-precision registers from pairs of double-precision registers.
36692 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
36693 be present and include 32 double-precision registers.
36695 @node i386 Features
36696 @subsection i386 Features
36697 @cindex target descriptions, i386 features
36699 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
36700 targets. It should describe the following registers:
36704 @samp{eax} through @samp{edi} plus @samp{eip} for i386
36706 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
36708 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
36709 @samp{fs}, @samp{gs}
36711 @samp{st0} through @samp{st7}
36713 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
36714 @samp{foseg}, @samp{fooff} and @samp{fop}
36717 The register sets may be different, depending on the target.
36719 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
36720 describe registers:
36724 @samp{xmm0} through @samp{xmm7} for i386
36726 @samp{xmm0} through @samp{xmm15} for amd64
36731 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
36732 @samp{org.gnu.gdb.i386.sse} feature. It should
36733 describe the upper 128 bits of @sc{ymm} registers:
36737 @samp{ymm0h} through @samp{ymm7h} for i386
36739 @samp{ymm0h} through @samp{ymm15h} for amd64
36742 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
36743 describe a single register, @samp{orig_eax}.
36745 @node MIPS Features
36746 @subsection MIPS Features
36747 @cindex target descriptions, MIPS features
36749 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
36750 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
36751 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
36754 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
36755 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
36756 registers. They may be 32-bit or 64-bit depending on the target.
36758 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
36759 it may be optional in a future version of @value{GDBN}. It should
36760 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
36761 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
36763 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
36764 contain a single register, @samp{restart}, which is used by the
36765 Linux kernel to control restartable syscalls.
36767 @node M68K Features
36768 @subsection M68K Features
36769 @cindex target descriptions, M68K features
36772 @item @samp{org.gnu.gdb.m68k.core}
36773 @itemx @samp{org.gnu.gdb.coldfire.core}
36774 @itemx @samp{org.gnu.gdb.fido.core}
36775 One of those features must be always present.
36776 The feature that is present determines which flavor of m68k is
36777 used. The feature that is present should contain registers
36778 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
36779 @samp{sp}, @samp{ps} and @samp{pc}.
36781 @item @samp{org.gnu.gdb.coldfire.fp}
36782 This feature is optional. If present, it should contain registers
36783 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
36787 @node PowerPC Features
36788 @subsection PowerPC Features
36789 @cindex target descriptions, PowerPC features
36791 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
36792 targets. It should contain registers @samp{r0} through @samp{r31},
36793 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
36794 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
36796 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
36797 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
36799 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
36800 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
36803 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
36804 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
36805 will combine these registers with the floating point registers
36806 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
36807 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
36808 through @samp{vs63}, the set of vector registers for POWER7.
36810 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
36811 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
36812 @samp{spefscr}. SPE targets should provide 32-bit registers in
36813 @samp{org.gnu.gdb.power.core} and provide the upper halves in
36814 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
36815 these to present registers @samp{ev0} through @samp{ev31} to the
36818 @node Operating System Information
36819 @appendix Operating System Information
36820 @cindex operating system information
36826 Users of @value{GDBN} often wish to obtain information about the state of
36827 the operating system running on the target---for example the list of
36828 processes, or the list of open files. This section describes the
36829 mechanism that makes it possible. This mechanism is similar to the
36830 target features mechanism (@pxref{Target Descriptions}), but focuses
36831 on a different aspect of target.
36833 Operating system information is retrived from the target via the
36834 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
36835 read}). The object name in the request should be @samp{osdata}, and
36836 the @var{annex} identifies the data to be fetched.
36839 @appendixsection Process list
36840 @cindex operating system information, process list
36842 When requesting the process list, the @var{annex} field in the
36843 @samp{qXfer} request should be @samp{processes}. The returned data is
36844 an XML document. The formal syntax of this document is defined in
36845 @file{gdb/features/osdata.dtd}.
36847 An example document is:
36850 <?xml version="1.0"?>
36851 <!DOCTYPE target SYSTEM "osdata.dtd">
36852 <osdata type="processes">
36854 <column name="pid">1</column>
36855 <column name="user">root</column>
36856 <column name="command">/sbin/init</column>
36857 <column name="cores">1,2,3</column>
36862 Each item should include a column whose name is @samp{pid}. The value
36863 of that column should identify the process on the target. The
36864 @samp{user} and @samp{command} columns are optional, and will be
36865 displayed by @value{GDBN}. The @samp{cores} column, if present,
36866 should contain a comma-separated list of cores that this process
36867 is running on. Target may provide additional columns,
36868 which @value{GDBN} currently ignores.
36870 @node Trace File Format
36871 @appendix Trace File Format
36872 @cindex trace file format
36874 The trace file comes in three parts: a header, a textual description
36875 section, and a trace frame section with binary data.
36877 The header has the form @code{\x7fTRACE0\n}. The first byte is
36878 @code{0x7f} so as to indicate that the file contains binary data,
36879 while the @code{0} is a version number that may have different values
36882 The description section consists of multiple lines of @sc{ascii} text
36883 separated by newline characters (@code{0xa}). The lines may include a
36884 variety of optional descriptive or context-setting information, such
36885 as tracepoint definitions or register set size. @value{GDBN} will
36886 ignore any line that it does not recognize. An empty line marks the end
36889 @c FIXME add some specific types of data
36891 The trace frame section consists of a number of consecutive frames.
36892 Each frame begins with a two-byte tracepoint number, followed by a
36893 four-byte size giving the amount of data in the frame. The data in
36894 the frame consists of a number of blocks, each introduced by a
36895 character indicating its type (at least register, memory, and trace
36896 state variable). The data in this section is raw binary, not a
36897 hexadecimal or other encoding; its endianness matches the target's
36900 @c FIXME bi-arch may require endianness/arch info in description section
36903 @item R @var{bytes}
36904 Register block. The number and ordering of bytes matches that of a
36905 @code{g} packet in the remote protocol. Note that these are the
36906 actual bytes, in target order and @value{GDBN} register order, not a
36907 hexadecimal encoding.
36909 @item M @var{address} @var{length} @var{bytes}...
36910 Memory block. This is a contiguous block of memory, at the 8-byte
36911 address @var{address}, with a 2-byte length @var{length}, followed by
36912 @var{length} bytes.
36914 @item V @var{number} @var{value}
36915 Trace state variable block. This records the 8-byte signed value
36916 @var{value} of trace state variable numbered @var{number}.
36920 Future enhancements of the trace file format may include additional types
36923 @node Index Section Format
36924 @appendix @code{.gdb_index} section format
36925 @cindex .gdb_index section format
36926 @cindex index section format
36928 This section documents the index section that is created by @code{save
36929 gdb-index} (@pxref{Index Files}). The index section is
36930 DWARF-specific; some knowledge of DWARF is assumed in this
36933 The mapped index file format is designed to be directly
36934 @code{mmap}able on any architecture. In most cases, a datum is
36935 represented using a little-endian 32-bit integer value, called an
36936 @code{offset_type}. Big endian machines must byte-swap the values
36937 before using them. Exceptions to this rule are noted. The data is
36938 laid out such that alignment is always respected.
36940 A mapped index consists of several areas, laid out in order.
36944 The file header. This is a sequence of values, of @code{offset_type}
36945 unless otherwise noted:
36949 The version number, currently 4. Versions 1, 2 and 3 are obsolete.
36952 The offset, from the start of the file, of the CU list.
36955 The offset, from the start of the file, of the types CU list. Note
36956 that this area can be empty, in which case this offset will be equal
36957 to the next offset.
36960 The offset, from the start of the file, of the address area.
36963 The offset, from the start of the file, of the symbol table.
36966 The offset, from the start of the file, of the constant pool.
36970 The CU list. This is a sequence of pairs of 64-bit little-endian
36971 values, sorted by the CU offset. The first element in each pair is
36972 the offset of a CU in the @code{.debug_info} section. The second
36973 element in each pair is the length of that CU. References to a CU
36974 elsewhere in the map are done using a CU index, which is just the
36975 0-based index into this table. Note that if there are type CUs, then
36976 conceptually CUs and type CUs form a single list for the purposes of
36980 The types CU list. This is a sequence of triplets of 64-bit
36981 little-endian values. In a triplet, the first value is the CU offset,
36982 the second value is the type offset in the CU, and the third value is
36983 the type signature. The types CU list is not sorted.
36986 The address area. The address area consists of a sequence of address
36987 entries. Each address entry has three elements:
36991 The low address. This is a 64-bit little-endian value.
36994 The high address. This is a 64-bit little-endian value. Like
36995 @code{DW_AT_high_pc}, the value is one byte beyond the end.
36998 The CU index. This is an @code{offset_type} value.
37002 The symbol table. This is an open-addressed hash table. The size of
37003 the hash table is always a power of 2.
37005 Each slot in the hash table consists of a pair of @code{offset_type}
37006 values. The first value is the offset of the symbol's name in the
37007 constant pool. The second value is the offset of the CU vector in the
37010 If both values are 0, then this slot in the hash table is empty. This
37011 is ok because while 0 is a valid constant pool index, it cannot be a
37012 valid index for both a string and a CU vector.
37014 The hash value for a table entry is computed by applying an
37015 iterative hash function to the symbol's name. Starting with an
37016 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
37017 the string is incorporated into the hash using the formula
37018 @code{r = r * 67 + c - 113}. The terminating @samp{\0} is not
37019 incorporated into the hash.
37021 The step size used in the hash table is computed via
37022 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
37023 value, and @samp{size} is the size of the hash table. The step size
37024 is used to find the next candidate slot when handling a hash
37027 The names of C@t{++} symbols in the hash table are canonicalized. We
37028 don't currently have a simple description of the canonicalization
37029 algorithm; if you intend to create new index sections, you must read
37033 The constant pool. This is simply a bunch of bytes. It is organized
37034 so that alignment is correct: CU vectors are stored first, followed by
37037 A CU vector in the constant pool is a sequence of @code{offset_type}
37038 values. The first value is the number of CU indices in the vector.
37039 Each subsequent value is the index of a CU in the CU list. This
37040 element in the hash table is used to indicate which CUs define the
37043 A string in the constant pool is zero-terminated.
37048 @node GNU Free Documentation License
37049 @appendix GNU Free Documentation License
37058 % I think something like @colophon should be in texinfo. In the
37060 \long\def\colophon{\hbox to0pt{}\vfill
37061 \centerline{The body of this manual is set in}
37062 \centerline{\fontname\tenrm,}
37063 \centerline{with headings in {\bf\fontname\tenbf}}
37064 \centerline{and examples in {\tt\fontname\tentt}.}
37065 \centerline{{\it\fontname\tenit\/},}
37066 \centerline{{\bf\fontname\tenbf}, and}
37067 \centerline{{\sl\fontname\tensl\/}}
37068 \centerline{are used for emphasis.}\vfill}
37070 % Blame: doc@cygnus.com, 1991.