1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
26 @c readline appendices use @vindex, @findex and @ftable,
27 @c annotate.texi and gdbmi use @findex.
31 @c !!set GDB manual's edition---not the same as GDB version!
32 @c This is updated by GNU Press.
35 @c !!set GDB edit command default editor
38 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
40 @c This is a dir.info fragment to support semi-automated addition of
41 @c manuals to an info tree.
42 @dircategory Software development
44 * Gdb: (gdb). The GNU debugger.
48 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
49 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
50 Free Software Foundation, Inc.
52 Permission is granted to copy, distribute and/or modify this document
53 under the terms of the GNU Free Documentation License, Version 1.3 or
54 any later version published by the Free Software Foundation; with the
55 Invariant Sections being ``Free Software'' and ``Free Software Needs
56 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
57 and with the Back-Cover Texts as in (a) below.
59 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
60 this GNU Manual. Buying copies from GNU Press supports the FSF in
61 developing GNU and promoting software freedom.''
65 This file documents the @sc{gnu} debugger @value{GDBN}.
67 This is the @value{EDITION} Edition, of @cite{Debugging with
68 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
69 @ifset VERSION_PACKAGE
70 @value{VERSION_PACKAGE}
72 Version @value{GDBVN}.
78 @title Debugging with @value{GDBN}
79 @subtitle The @sc{gnu} Source-Level Debugger
81 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
82 @ifset VERSION_PACKAGE
84 @subtitle @value{VERSION_PACKAGE}
86 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
90 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
91 \hfill {\it Debugging with @value{GDBN}}\par
92 \hfill \TeX{}info \texinfoversion\par
96 @vskip 0pt plus 1filll
97 Published by the Free Software Foundation @*
98 51 Franklin Street, Fifth Floor,
99 Boston, MA 02110-1301, USA@*
100 ISBN 1-882114-77-9 @*
104 This edition of the GDB manual is dedicated to the memory of Fred
105 Fish. Fred was a long-standing contributor to GDB and to Free
106 software in general. We will miss him.
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2010 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
164 * GDB Bugs:: Reporting bugs in @value{GDBN}
166 @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 * Copying:: GNU General Public License says
185 how you can copy and share GDB
186 * GNU Free Documentation License:: The license for this documentation
195 @unnumbered Summary of @value{GDBN}
197 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
198 going on ``inside'' another program while it executes---or what another
199 program was doing at the moment it crashed.
201 @value{GDBN} can do four main kinds of things (plus other things in support of
202 these) to help you catch bugs in the act:
206 Start your program, specifying anything that might affect its behavior.
209 Make your program stop on specified conditions.
212 Examine what has happened, when your program has stopped.
215 Change things in your program, so you can experiment with correcting the
216 effects of one bug and go on to learn about another.
219 You can use @value{GDBN} to debug programs written in C and C@t{++}.
220 For more information, see @ref{Supported Languages,,Supported Languages}.
221 For more information, see @ref{C,,C and C++}.
223 Support for D is partial. For information on D, see
227 Support for Modula-2 is partial. For information on Modula-2, see
228 @ref{Modula-2,,Modula-2}.
230 Support for OpenCL C is partial. For information on OpenCL C, see
231 @ref{OpenCL C,,OpenCL C}.
234 Debugging Pascal programs which use sets, subranges, file variables, or
235 nested functions does not currently work. @value{GDBN} does not support
236 entering expressions, printing values, or similar features using Pascal
240 @value{GDBN} can be used to debug programs written in Fortran, although
241 it may be necessary to refer to some variables with a trailing
244 @value{GDBN} can be used to debug programs written in Objective-C,
245 using either the Apple/NeXT or the GNU Objective-C runtime.
248 * Free Software:: Freely redistributable software
249 * Contributors:: Contributors to GDB
253 @unnumberedsec Free Software
255 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
256 General Public License
257 (GPL). The GPL gives you the freedom to copy or adapt a licensed
258 program---but every person getting a copy also gets with it the
259 freedom to modify that copy (which means that they must get access to
260 the source code), and the freedom to distribute further copies.
261 Typical software companies use copyrights to limit your freedoms; the
262 Free Software Foundation uses the GPL to preserve these freedoms.
264 Fundamentally, the General Public License is a license which says that
265 you have these freedoms and that you cannot take these freedoms away
268 @unnumberedsec Free Software Needs Free Documentation
270 The biggest deficiency in the free software community today is not in
271 the software---it is the lack of good free documentation that we can
272 include with the free software. Many of our most important
273 programs do not come with free reference manuals and free introductory
274 texts. Documentation is an essential part of any software package;
275 when an important free software package does not come with a free
276 manual and a free tutorial, that is a major gap. We have many such
279 Consider Perl, for instance. The tutorial manuals that people
280 normally use are non-free. How did this come about? Because the
281 authors of those manuals published them with restrictive terms---no
282 copying, no modification, source files not available---which exclude
283 them from the free software world.
285 That wasn't the first time this sort of thing happened, and it was far
286 from the last. Many times we have heard a GNU user eagerly describe a
287 manual that he is writing, his intended contribution to the community,
288 only to learn that he had ruined everything by signing a publication
289 contract to make it non-free.
291 Free documentation, like free software, is a matter of freedom, not
292 price. The problem with the non-free manual is not that publishers
293 charge a price for printed copies---that in itself is fine. (The Free
294 Software Foundation sells printed copies of manuals, too.) The
295 problem is the restrictions on the use of the manual. Free manuals
296 are available in source code form, and give you permission to copy and
297 modify. Non-free manuals do not allow this.
299 The criteria of freedom for a free manual are roughly the same as for
300 free software. Redistribution (including the normal kinds of
301 commercial redistribution) must be permitted, so that the manual can
302 accompany every copy of the program, both on-line and on paper.
304 Permission for modification of the technical content is crucial too.
305 When people modify the software, adding or changing features, if they
306 are conscientious they will change the manual too---so they can
307 provide accurate and clear documentation for the modified program. A
308 manual that leaves you no choice but to write a new manual to document
309 a changed version of the program is not really available to our
312 Some kinds of limits on the way modification is handled are
313 acceptable. For example, requirements to preserve the original
314 author's copyright notice, the distribution terms, or the list of
315 authors, are ok. It is also no problem to require modified versions
316 to include notice that they were modified. Even entire sections that
317 may not be deleted or changed are acceptable, as long as they deal
318 with nontechnical topics (like this one). These kinds of restrictions
319 are acceptable because they don't obstruct the community's normal use
322 However, it must be possible to modify all the @emph{technical}
323 content of the manual, and then distribute the result in all the usual
324 media, through all the usual channels. Otherwise, the restrictions
325 obstruct the use of the manual, it is not free, and we need another
326 manual to replace it.
328 Please spread the word about this issue. Our community continues to
329 lose manuals to proprietary publishing. If we spread the word that
330 free software needs free reference manuals and free tutorials, perhaps
331 the next person who wants to contribute by writing documentation will
332 realize, before it is too late, that only free manuals contribute to
333 the free software community.
335 If you are writing documentation, please insist on publishing it under
336 the GNU Free Documentation License or another free documentation
337 license. Remember that this decision requires your approval---you
338 don't have to let the publisher decide. Some commercial publishers
339 will use a free license if you insist, but they will not propose the
340 option; it is up to you to raise the issue and say firmly that this is
341 what you want. If the publisher you are dealing with refuses, please
342 try other publishers. If you're not sure whether a proposed license
343 is free, write to @email{licensing@@gnu.org}.
345 You can encourage commercial publishers to sell more free, copylefted
346 manuals and tutorials by buying them, and particularly by buying
347 copies from the publishers that paid for their writing or for major
348 improvements. Meanwhile, try to avoid buying non-free documentation
349 at all. Check the distribution terms of a manual before you buy it,
350 and insist that whoever seeks your business must respect your freedom.
351 Check the history of the book, and try to reward the publishers that
352 have paid or pay the authors to work on it.
354 The Free Software Foundation maintains a list of free documentation
355 published by other publishers, at
356 @url{http://www.fsf.org/doc/other-free-books.html}.
359 @unnumberedsec Contributors to @value{GDBN}
361 Richard Stallman was the original author of @value{GDBN}, and of many
362 other @sc{gnu} programs. Many others have contributed to its
363 development. This section attempts to credit major contributors. One
364 of the virtues of free software is that everyone is free to contribute
365 to it; with regret, we cannot actually acknowledge everyone here. The
366 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
367 blow-by-blow account.
369 Changes much prior to version 2.0 are lost in the mists of time.
372 @emph{Plea:} Additions to this section are particularly welcome. If you
373 or your friends (or enemies, to be evenhanded) have been unfairly
374 omitted from this list, we would like to add your names!
377 So that they may not regard their many labors as thankless, we
378 particularly thank those who shepherded @value{GDBN} through major
380 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
381 Jim Blandy (release 4.18);
382 Jason Molenda (release 4.17);
383 Stan Shebs (release 4.14);
384 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
385 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
386 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
387 Jim Kingdon (releases 3.5, 3.4, and 3.3);
388 and Randy Smith (releases 3.2, 3.1, and 3.0).
390 Richard Stallman, assisted at various times by Peter TerMaat, Chris
391 Hanson, and Richard Mlynarik, handled releases through 2.8.
393 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
394 in @value{GDBN}, with significant additional contributions from Per
395 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
396 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
397 much general update work leading to release 3.0).
399 @value{GDBN} uses the BFD subroutine library to examine multiple
400 object-file formats; BFD was a joint project of David V.
401 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
403 David Johnson wrote the original COFF support; Pace Willison did
404 the original support for encapsulated COFF.
406 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
408 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
409 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
411 Jean-Daniel Fekete contributed Sun 386i support.
412 Chris Hanson improved the HP9000 support.
413 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
414 David Johnson contributed Encore Umax support.
415 Jyrki Kuoppala contributed Altos 3068 support.
416 Jeff Law contributed HP PA and SOM support.
417 Keith Packard contributed NS32K support.
418 Doug Rabson contributed Acorn Risc Machine support.
419 Bob Rusk contributed Harris Nighthawk CX-UX support.
420 Chris Smith contributed Convex support (and Fortran debugging).
421 Jonathan Stone contributed Pyramid support.
422 Michael Tiemann contributed SPARC support.
423 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
424 Pace Willison contributed Intel 386 support.
425 Jay Vosburgh contributed Symmetry support.
426 Marko Mlinar contributed OpenRISC 1000 support.
428 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
430 Rich Schaefer and Peter Schauer helped with support of SunOS shared
433 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
434 about several machine instruction sets.
436 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
437 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
438 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
439 and RDI targets, respectively.
441 Brian Fox is the author of the readline libraries providing
442 command-line editing and command history.
444 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
445 Modula-2 support, and contributed the Languages chapter of this manual.
447 Fred Fish wrote most of the support for Unix System Vr4.
448 He also enhanced the command-completion support to cover C@t{++} overloaded
451 Hitachi America (now Renesas America), Ltd. sponsored the support for
452 H8/300, H8/500, and Super-H processors.
454 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
456 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
459 Toshiba sponsored the support for the TX39 Mips processor.
461 Matsushita sponsored the support for the MN10200 and MN10300 processors.
463 Fujitsu sponsored the support for SPARClite and FR30 processors.
465 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
468 Michael Snyder added support for tracepoints.
470 Stu Grossman wrote gdbserver.
472 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
473 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
475 The following people at the Hewlett-Packard Company contributed
476 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
477 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
478 compiler, and the Text User Interface (nee Terminal User Interface):
479 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
480 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
481 provided HP-specific information in this manual.
483 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
484 Robert Hoehne made significant contributions to the DJGPP port.
486 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
487 development since 1991. Cygnus engineers who have worked on @value{GDBN}
488 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
489 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
490 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
491 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
492 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
493 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
494 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
495 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
496 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
497 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
498 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
499 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
500 Zuhn have made contributions both large and small.
502 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
503 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
505 Jim Blandy added support for preprocessor macros, while working for Red
508 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
509 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
510 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
511 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
512 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
513 with the migration of old architectures to this new framework.
515 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
516 unwinder framework, this consisting of a fresh new design featuring
517 frame IDs, independent frame sniffers, and the sentinel frame. Mark
518 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
519 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
520 trad unwinders. The architecture-specific changes, each involving a
521 complete rewrite of the architecture's frame code, were carried out by
522 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
523 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
524 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
525 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
528 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
529 Tensilica, Inc.@: contributed support for Xtensa processors. Others
530 who have worked on the Xtensa port of @value{GDBN} in the past include
531 Steve Tjiang, John Newlin, and Scott Foehner.
533 Michael Eager and staff of Xilinx, Inc., contributed support for the
534 Xilinx MicroBlaze architecture.
537 @chapter A Sample @value{GDBN} Session
539 You can use this manual at your leisure to read all about @value{GDBN}.
540 However, a handful of commands are enough to get started using the
541 debugger. This chapter illustrates those commands.
544 In this sample session, we emphasize user input like this: @b{input},
545 to make it easier to pick out from the surrounding output.
548 @c FIXME: this example may not be appropriate for some configs, where
549 @c FIXME...primary interest is in remote use.
551 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
552 processor) exhibits the following bug: sometimes, when we change its
553 quote strings from the default, the commands used to capture one macro
554 definition within another stop working. In the following short @code{m4}
555 session, we define a macro @code{foo} which expands to @code{0000}; we
556 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
557 same thing. However, when we change the open quote string to
558 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
559 procedure fails to define a new synonym @code{baz}:
568 @b{define(bar,defn(`foo'))}
572 @b{changequote(<QUOTE>,<UNQUOTE>)}
574 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
577 m4: End of input: 0: fatal error: EOF in string
581 Let us use @value{GDBN} to try to see what is going on.
584 $ @b{@value{GDBP} m4}
585 @c FIXME: this falsifies the exact text played out, to permit smallbook
586 @c FIXME... format to come out better.
587 @value{GDBN} is free software and you are welcome to distribute copies
588 of it under certain conditions; type "show copying" to see
590 There is absolutely no warranty for @value{GDBN}; type "show warranty"
593 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
598 @value{GDBN} reads only enough symbol data to know where to find the
599 rest when needed; as a result, the first prompt comes up very quickly.
600 We now tell @value{GDBN} to use a narrower display width than usual, so
601 that examples fit in this manual.
604 (@value{GDBP}) @b{set width 70}
608 We need to see how the @code{m4} built-in @code{changequote} works.
609 Having looked at the source, we know the relevant subroutine is
610 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
611 @code{break} command.
614 (@value{GDBP}) @b{break m4_changequote}
615 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
619 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
620 control; as long as control does not reach the @code{m4_changequote}
621 subroutine, the program runs as usual:
624 (@value{GDBP}) @b{run}
625 Starting program: /work/Editorial/gdb/gnu/m4/m4
633 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
634 suspends execution of @code{m4}, displaying information about the
635 context where it stops.
638 @b{changequote(<QUOTE>,<UNQUOTE>)}
640 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
642 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
646 Now we use the command @code{n} (@code{next}) to advance execution to
647 the next line of the current function.
651 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
656 @code{set_quotes} looks like a promising subroutine. We can go into it
657 by using the command @code{s} (@code{step}) instead of @code{next}.
658 @code{step} goes to the next line to be executed in @emph{any}
659 subroutine, so it steps into @code{set_quotes}.
663 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
665 530 if (lquote != def_lquote)
669 The display that shows the subroutine where @code{m4} is now
670 suspended (and its arguments) is called a stack frame display. It
671 shows a summary of the stack. We can use the @code{backtrace}
672 command (which can also be spelled @code{bt}), to see where we are
673 in the stack as a whole: the @code{backtrace} command displays a
674 stack frame for each active subroutine.
677 (@value{GDBP}) @b{bt}
678 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
680 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
682 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
683 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
685 #4 0x79dc in expand_input () at macro.c:40
686 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
690 We step through a few more lines to see what happens. The first two
691 times, we can use @samp{s}; the next two times we use @code{n} to avoid
692 falling into the @code{xstrdup} subroutine.
696 0x3b5c 532 if (rquote != def_rquote)
698 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
699 def_lquote : xstrdup(lq);
701 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
704 538 len_lquote = strlen(rquote);
708 The last line displayed looks a little odd; we can examine the variables
709 @code{lquote} and @code{rquote} to see if they are in fact the new left
710 and right quotes we specified. We use the command @code{p}
711 (@code{print}) to see their values.
714 (@value{GDBP}) @b{p lquote}
715 $1 = 0x35d40 "<QUOTE>"
716 (@value{GDBP}) @b{p rquote}
717 $2 = 0x35d50 "<UNQUOTE>"
721 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
722 To look at some context, we can display ten lines of source
723 surrounding the current line with the @code{l} (@code{list}) command.
729 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
731 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
734 538 len_lquote = strlen(rquote);
735 539 len_rquote = strlen(lquote);
742 Let us step past the two lines that set @code{len_lquote} and
743 @code{len_rquote}, and then examine the values of those variables.
747 539 len_rquote = strlen(lquote);
750 (@value{GDBP}) @b{p len_lquote}
752 (@value{GDBP}) @b{p len_rquote}
757 That certainly looks wrong, assuming @code{len_lquote} and
758 @code{len_rquote} are meant to be the lengths of @code{lquote} and
759 @code{rquote} respectively. We can set them to better values using
760 the @code{p} command, since it can print the value of
761 any expression---and that expression can include subroutine calls and
765 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
767 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
772 Is that enough to fix the problem of using the new quotes with the
773 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
774 executing with the @code{c} (@code{continue}) command, and then try the
775 example that caused trouble initially:
781 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
788 Success! The new quotes now work just as well as the default ones. The
789 problem seems to have been just the two typos defining the wrong
790 lengths. We allow @code{m4} exit by giving it an EOF as input:
794 Program exited normally.
798 The message @samp{Program exited normally.} is from @value{GDBN}; it
799 indicates @code{m4} has finished executing. We can end our @value{GDBN}
800 session with the @value{GDBN} @code{quit} command.
803 (@value{GDBP}) @b{quit}
807 @chapter Getting In and Out of @value{GDBN}
809 This chapter discusses how to start @value{GDBN}, and how to get out of it.
813 type @samp{@value{GDBP}} to start @value{GDBN}.
815 type @kbd{quit} or @kbd{Ctrl-d} to exit.
819 * Invoking GDB:: How to start @value{GDBN}
820 * Quitting GDB:: How to quit @value{GDBN}
821 * Shell Commands:: How to use shell commands inside @value{GDBN}
822 * Logging Output:: How to log @value{GDBN}'s output to a file
826 @section Invoking @value{GDBN}
828 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
829 @value{GDBN} reads commands from the terminal until you tell it to exit.
831 You can also run @code{@value{GDBP}} with a variety of arguments and options,
832 to specify more of your debugging environment at the outset.
834 The command-line options described here are designed
835 to cover a variety of situations; in some environments, some of these
836 options may effectively be unavailable.
838 The most usual way to start @value{GDBN} is with one argument,
839 specifying an executable program:
842 @value{GDBP} @var{program}
846 You can also start with both an executable program and a core file
850 @value{GDBP} @var{program} @var{core}
853 You can, instead, specify a process ID as a second argument, if you want
854 to debug a running process:
857 @value{GDBP} @var{program} 1234
861 would attach @value{GDBN} to process @code{1234} (unless you also have a file
862 named @file{1234}; @value{GDBN} does check for a core file first).
864 Taking advantage of the second command-line argument requires a fairly
865 complete operating system; when you use @value{GDBN} as a remote
866 debugger attached to a bare board, there may not be any notion of
867 ``process'', and there is often no way to get a core dump. @value{GDBN}
868 will warn you if it is unable to attach or to read core dumps.
870 You can optionally have @code{@value{GDBP}} pass any arguments after the
871 executable file to the inferior using @code{--args}. This option stops
874 @value{GDBP} --args gcc -O2 -c foo.c
876 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
877 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
879 You can run @code{@value{GDBP}} without printing the front material, which describes
880 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
887 You can further control how @value{GDBN} starts up by using command-line
888 options. @value{GDBN} itself can remind you of the options available.
898 to display all available options and briefly describe their use
899 (@samp{@value{GDBP} -h} is a shorter equivalent).
901 All options and command line arguments you give are processed
902 in sequential order. The order makes a difference when the
903 @samp{-x} option is used.
907 * File Options:: Choosing files
908 * Mode Options:: Choosing modes
909 * Startup:: What @value{GDBN} does during startup
913 @subsection Choosing Files
915 When @value{GDBN} starts, it reads any arguments other than options as
916 specifying an executable file and core file (or process ID). This is
917 the same as if the arguments were specified by the @samp{-se} and
918 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
919 first argument that does not have an associated option flag as
920 equivalent to the @samp{-se} option followed by that argument; and the
921 second argument that does not have an associated option flag, if any, as
922 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
923 If the second argument begins with a decimal digit, @value{GDBN} will
924 first attempt to attach to it as a process, and if that fails, attempt
925 to open it as a corefile. If you have a corefile whose name begins with
926 a digit, you can prevent @value{GDBN} from treating it as a pid by
927 prefixing it with @file{./}, e.g.@: @file{./12345}.
929 If @value{GDBN} has not been configured to included core file support,
930 such as for most embedded targets, then it will complain about a second
931 argument and ignore it.
933 Many options have both long and short forms; both are shown in the
934 following list. @value{GDBN} also recognizes the long forms if you truncate
935 them, so long as enough of the option is present to be unambiguous.
936 (If you prefer, you can flag option arguments with @samp{--} rather
937 than @samp{-}, though we illustrate the more usual convention.)
939 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
940 @c way, both those who look for -foo and --foo in the index, will find
944 @item -symbols @var{file}
946 @cindex @code{--symbols}
948 Read symbol table from file @var{file}.
950 @item -exec @var{file}
952 @cindex @code{--exec}
954 Use file @var{file} as the executable file to execute when appropriate,
955 and for examining pure data in conjunction with a core dump.
959 Read symbol table from file @var{file} and use it as the executable
962 @item -core @var{file}
964 @cindex @code{--core}
966 Use file @var{file} as a core dump to examine.
968 @item -pid @var{number}
969 @itemx -p @var{number}
972 Connect to process ID @var{number}, as with the @code{attach} command.
974 @item -command @var{file}
976 @cindex @code{--command}
978 Execute commands from file @var{file}. The contents of this file is
979 evaluated exactly as the @code{source} command would.
980 @xref{Command Files,, Command files}.
982 @item -eval-command @var{command}
983 @itemx -ex @var{command}
984 @cindex @code{--eval-command}
986 Execute a single @value{GDBN} command.
988 This option may be used multiple times to call multiple commands. It may
989 also be interleaved with @samp{-command} as required.
992 @value{GDBP} -ex 'target sim' -ex 'load' \
993 -x setbreakpoints -ex 'run' a.out
996 @item -directory @var{directory}
997 @itemx -d @var{directory}
998 @cindex @code{--directory}
1000 Add @var{directory} to the path to search for source and script files.
1004 @cindex @code{--readnow}
1006 Read each symbol file's entire symbol table immediately, rather than
1007 the default, which is to read it incrementally as it is needed.
1008 This makes startup slower, but makes future operations faster.
1013 @subsection Choosing Modes
1015 You can run @value{GDBN} in various alternative modes---for example, in
1016 batch mode or quiet mode.
1023 Do not execute commands found in any initialization files. Normally,
1024 @value{GDBN} executes the commands in these files after all the command
1025 options and arguments have been processed. @xref{Command Files,,Command
1031 @cindex @code{--quiet}
1032 @cindex @code{--silent}
1034 ``Quiet''. Do not print the introductory and copyright messages. These
1035 messages are also suppressed in batch mode.
1038 @cindex @code{--batch}
1039 Run in batch mode. Exit with status @code{0} after processing all the
1040 command files specified with @samp{-x} (and all commands from
1041 initialization files, if not inhibited with @samp{-n}). Exit with
1042 nonzero status if an error occurs in executing the @value{GDBN} commands
1043 in the command files. Batch mode also disables pagination, sets unlimited
1044 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1045 off} were in effect (@pxref{Messages/Warnings}).
1047 Batch mode may be useful for running @value{GDBN} as a filter, for
1048 example to download and run a program on another computer; in order to
1049 make this more useful, the message
1052 Program exited normally.
1056 (which is ordinarily issued whenever a program running under
1057 @value{GDBN} control terminates) is not issued when running in batch
1061 @cindex @code{--batch-silent}
1062 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1063 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1064 unaffected). This is much quieter than @samp{-silent} and would be useless
1065 for an interactive session.
1067 This is particularly useful when using targets that give @samp{Loading section}
1068 messages, for example.
1070 Note that targets that give their output via @value{GDBN}, as opposed to
1071 writing directly to @code{stdout}, will also be made silent.
1073 @item -return-child-result
1074 @cindex @code{--return-child-result}
1075 The return code from @value{GDBN} will be the return code from the child
1076 process (the process being debugged), with the following exceptions:
1080 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1081 internal error. In this case the exit code is the same as it would have been
1082 without @samp{-return-child-result}.
1084 The user quits with an explicit value. E.g., @samp{quit 1}.
1086 The child process never runs, or is not allowed to terminate, in which case
1087 the exit code will be -1.
1090 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1091 when @value{GDBN} is being used as a remote program loader or simulator
1096 @cindex @code{--nowindows}
1098 ``No windows''. If @value{GDBN} comes with a graphical user interface
1099 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1100 interface. If no GUI is available, this option has no effect.
1104 @cindex @code{--windows}
1106 If @value{GDBN} includes a GUI, then this option requires it to be
1109 @item -cd @var{directory}
1111 Run @value{GDBN} using @var{directory} as its working directory,
1112 instead of the current directory.
1116 @cindex @code{--fullname}
1118 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1119 subprocess. It tells @value{GDBN} to output the full file name and line
1120 number in a standard, recognizable fashion each time a stack frame is
1121 displayed (which includes each time your program stops). This
1122 recognizable format looks like two @samp{\032} characters, followed by
1123 the file name, line number and character position separated by colons,
1124 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1125 @samp{\032} characters as a signal to display the source code for the
1129 @cindex @code{--epoch}
1130 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1131 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1132 routines so as to allow Epoch to display values of expressions in a
1135 @item -annotate @var{level}
1136 @cindex @code{--annotate}
1137 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1138 effect is identical to using @samp{set annotate @var{level}}
1139 (@pxref{Annotations}). The annotation @var{level} controls how much
1140 information @value{GDBN} prints together with its prompt, values of
1141 expressions, source lines, and other types of output. Level 0 is the
1142 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1143 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1144 that control @value{GDBN}, and level 2 has been deprecated.
1146 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1150 @cindex @code{--args}
1151 Change interpretation of command line so that arguments following the
1152 executable file are passed as command line arguments to the inferior.
1153 This option stops option processing.
1155 @item -baud @var{bps}
1157 @cindex @code{--baud}
1159 Set the line speed (baud rate or bits per second) of any serial
1160 interface used by @value{GDBN} for remote debugging.
1162 @item -l @var{timeout}
1164 Set the timeout (in seconds) of any communication used by @value{GDBN}
1165 for remote debugging.
1167 @item -tty @var{device}
1168 @itemx -t @var{device}
1169 @cindex @code{--tty}
1171 Run using @var{device} for your program's standard input and output.
1172 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1174 @c resolve the situation of these eventually
1176 @cindex @code{--tui}
1177 Activate the @dfn{Text User Interface} when starting. The Text User
1178 Interface manages several text windows on the terminal, showing
1179 source, assembly, registers and @value{GDBN} command outputs
1180 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1181 Text User Interface can be enabled by invoking the program
1182 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1183 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1186 @c @cindex @code{--xdb}
1187 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1188 @c For information, see the file @file{xdb_trans.html}, which is usually
1189 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1192 @item -interpreter @var{interp}
1193 @cindex @code{--interpreter}
1194 Use the interpreter @var{interp} for interface with the controlling
1195 program or device. This option is meant to be set by programs which
1196 communicate with @value{GDBN} using it as a back end.
1197 @xref{Interpreters, , Command Interpreters}.
1199 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1200 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1201 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1202 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1203 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1204 @sc{gdb/mi} interfaces are no longer supported.
1207 @cindex @code{--write}
1208 Open the executable and core files for both reading and writing. This
1209 is equivalent to the @samp{set write on} command inside @value{GDBN}
1213 @cindex @code{--statistics}
1214 This option causes @value{GDBN} to print statistics about time and
1215 memory usage after it completes each command and returns to the prompt.
1218 @cindex @code{--version}
1219 This option causes @value{GDBN} to print its version number and
1220 no-warranty blurb, and exit.
1225 @subsection What @value{GDBN} Does During Startup
1226 @cindex @value{GDBN} startup
1228 Here's the description of what @value{GDBN} does during session startup:
1232 Sets up the command interpreter as specified by the command line
1233 (@pxref{Mode Options, interpreter}).
1237 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1238 used when building @value{GDBN}; @pxref{System-wide configuration,
1239 ,System-wide configuration and settings}) and executes all the commands in
1243 Reads the init file (if any) in your home directory@footnote{On
1244 DOS/Windows systems, the home directory is the one pointed to by the
1245 @code{HOME} environment variable.} and executes all the commands in
1249 Processes command line options and operands.
1252 Reads and executes the commands from init file (if any) in the current
1253 working directory. This is only done if the current directory is
1254 different from your home directory. Thus, you can have more than one
1255 init file, one generic in your home directory, and another, specific
1256 to the program you are debugging, in the directory where you invoke
1260 Reads command files specified by the @samp{-x} option. @xref{Command
1261 Files}, for more details about @value{GDBN} command files.
1264 Reads the command history recorded in the @dfn{history file}.
1265 @xref{Command History}, for more details about the command history and the
1266 files where @value{GDBN} records it.
1269 Init files use the same syntax as @dfn{command files} (@pxref{Command
1270 Files}) and are processed by @value{GDBN} in the same way. The init
1271 file in your home directory can set options (such as @samp{set
1272 complaints}) that affect subsequent processing of command line options
1273 and operands. Init files are not executed if you use the @samp{-nx}
1274 option (@pxref{Mode Options, ,Choosing Modes}).
1276 To display the list of init files loaded by gdb at startup, you
1277 can use @kbd{gdb --help}.
1279 @cindex init file name
1280 @cindex @file{.gdbinit}
1281 @cindex @file{gdb.ini}
1282 The @value{GDBN} init files are normally called @file{.gdbinit}.
1283 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1284 the limitations of file names imposed by DOS filesystems. The Windows
1285 ports of @value{GDBN} use the standard name, but if they find a
1286 @file{gdb.ini} file, they warn you about that and suggest to rename
1287 the file to the standard name.
1291 @section Quitting @value{GDBN}
1292 @cindex exiting @value{GDBN}
1293 @cindex leaving @value{GDBN}
1296 @kindex quit @r{[}@var{expression}@r{]}
1297 @kindex q @r{(@code{quit})}
1298 @item quit @r{[}@var{expression}@r{]}
1300 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1301 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1302 do not supply @var{expression}, @value{GDBN} will terminate normally;
1303 otherwise it will terminate using the result of @var{expression} as the
1308 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1309 terminates the action of any @value{GDBN} command that is in progress and
1310 returns to @value{GDBN} command level. It is safe to type the interrupt
1311 character at any time because @value{GDBN} does not allow it to take effect
1312 until a time when it is safe.
1314 If you have been using @value{GDBN} to control an attached process or
1315 device, you can release it with the @code{detach} command
1316 (@pxref{Attach, ,Debugging an Already-running Process}).
1318 @node Shell Commands
1319 @section Shell Commands
1321 If you need to execute occasional shell commands during your
1322 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1323 just use the @code{shell} command.
1327 @cindex shell escape
1328 @item shell @var{command string}
1329 Invoke a standard shell to execute @var{command string}.
1330 If it exists, the environment variable @code{SHELL} determines which
1331 shell to run. Otherwise @value{GDBN} uses the default shell
1332 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1335 The utility @code{make} is often needed in development environments.
1336 You do not have to use the @code{shell} command for this purpose in
1341 @cindex calling make
1342 @item make @var{make-args}
1343 Execute the @code{make} program with the specified
1344 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1347 @node Logging Output
1348 @section Logging Output
1349 @cindex logging @value{GDBN} output
1350 @cindex save @value{GDBN} output to a file
1352 You may want to save the output of @value{GDBN} commands to a file.
1353 There are several commands to control @value{GDBN}'s logging.
1357 @item set logging on
1359 @item set logging off
1361 @cindex logging file name
1362 @item set logging file @var{file}
1363 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1364 @item set logging overwrite [on|off]
1365 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1366 you want @code{set logging on} to overwrite the logfile instead.
1367 @item set logging redirect [on|off]
1368 By default, @value{GDBN} output will go to both the terminal and the logfile.
1369 Set @code{redirect} if you want output to go only to the log file.
1370 @kindex show logging
1372 Show the current values of the logging settings.
1376 @chapter @value{GDBN} Commands
1378 You can abbreviate a @value{GDBN} command to the first few letters of the command
1379 name, if that abbreviation is unambiguous; and you can repeat certain
1380 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1381 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1382 show you the alternatives available, if there is more than one possibility).
1385 * Command Syntax:: How to give commands to @value{GDBN}
1386 * Completion:: Command completion
1387 * Help:: How to ask @value{GDBN} for help
1390 @node Command Syntax
1391 @section Command Syntax
1393 A @value{GDBN} command is a single line of input. There is no limit on
1394 how long it can be. It starts with a command name, which is followed by
1395 arguments whose meaning depends on the command name. For example, the
1396 command @code{step} accepts an argument which is the number of times to
1397 step, as in @samp{step 5}. You can also use the @code{step} command
1398 with no arguments. Some commands do not allow any arguments.
1400 @cindex abbreviation
1401 @value{GDBN} command names may always be truncated if that abbreviation is
1402 unambiguous. Other possible command abbreviations are listed in the
1403 documentation for individual commands. In some cases, even ambiguous
1404 abbreviations are allowed; for example, @code{s} is specially defined as
1405 equivalent to @code{step} even though there are other commands whose
1406 names start with @code{s}. You can test abbreviations by using them as
1407 arguments to the @code{help} command.
1409 @cindex repeating commands
1410 @kindex RET @r{(repeat last command)}
1411 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1412 repeat the previous command. Certain commands (for example, @code{run})
1413 will not repeat this way; these are commands whose unintentional
1414 repetition might cause trouble and which you are unlikely to want to
1415 repeat. User-defined commands can disable this feature; see
1416 @ref{Define, dont-repeat}.
1418 The @code{list} and @code{x} commands, when you repeat them with
1419 @key{RET}, construct new arguments rather than repeating
1420 exactly as typed. This permits easy scanning of source or memory.
1422 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1423 output, in a way similar to the common utility @code{more}
1424 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1425 @key{RET} too many in this situation, @value{GDBN} disables command
1426 repetition after any command that generates this sort of display.
1428 @kindex # @r{(a comment)}
1430 Any text from a @kbd{#} to the end of the line is a comment; it does
1431 nothing. This is useful mainly in command files (@pxref{Command
1432 Files,,Command Files}).
1434 @cindex repeating command sequences
1435 @kindex Ctrl-o @r{(operate-and-get-next)}
1436 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1437 commands. This command accepts the current line, like @key{RET}, and
1438 then fetches the next line relative to the current line from the history
1442 @section Command Completion
1445 @cindex word completion
1446 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1447 only one possibility; it can also show you what the valid possibilities
1448 are for the next word in a command, at any time. This works for @value{GDBN}
1449 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1451 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1452 of a word. If there is only one possibility, @value{GDBN} fills in the
1453 word, and waits for you to finish the command (or press @key{RET} to
1454 enter it). For example, if you type
1456 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1457 @c complete accuracy in these examples; space introduced for clarity.
1458 @c If texinfo enhancements make it unnecessary, it would be nice to
1459 @c replace " @key" by "@key" in the following...
1461 (@value{GDBP}) info bre @key{TAB}
1465 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1466 the only @code{info} subcommand beginning with @samp{bre}:
1469 (@value{GDBP}) info breakpoints
1473 You can either press @key{RET} at this point, to run the @code{info
1474 breakpoints} command, or backspace and enter something else, if
1475 @samp{breakpoints} does not look like the command you expected. (If you
1476 were sure you wanted @code{info breakpoints} in the first place, you
1477 might as well just type @key{RET} immediately after @samp{info bre},
1478 to exploit command abbreviations rather than command completion).
1480 If there is more than one possibility for the next word when you press
1481 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1482 characters and try again, or just press @key{TAB} a second time;
1483 @value{GDBN} displays all the possible completions for that word. For
1484 example, you might want to set a breakpoint on a subroutine whose name
1485 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1486 just sounds the bell. Typing @key{TAB} again displays all the
1487 function names in your program that begin with those characters, for
1491 (@value{GDBP}) b make_ @key{TAB}
1492 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1493 make_a_section_from_file make_environ
1494 make_abs_section make_function_type
1495 make_blockvector make_pointer_type
1496 make_cleanup make_reference_type
1497 make_command make_symbol_completion_list
1498 (@value{GDBP}) b make_
1502 After displaying the available possibilities, @value{GDBN} copies your
1503 partial input (@samp{b make_} in the example) so you can finish the
1506 If you just want to see the list of alternatives in the first place, you
1507 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1508 means @kbd{@key{META} ?}. You can type this either by holding down a
1509 key designated as the @key{META} shift on your keyboard (if there is
1510 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1512 @cindex quotes in commands
1513 @cindex completion of quoted strings
1514 Sometimes the string you need, while logically a ``word'', may contain
1515 parentheses or other characters that @value{GDBN} normally excludes from
1516 its notion of a word. To permit word completion to work in this
1517 situation, you may enclose words in @code{'} (single quote marks) in
1518 @value{GDBN} commands.
1520 The most likely situation where you might need this is in typing the
1521 name of a C@t{++} function. This is because C@t{++} allows function
1522 overloading (multiple definitions of the same function, distinguished
1523 by argument type). For example, when you want to set a breakpoint you
1524 may need to distinguish whether you mean the version of @code{name}
1525 that takes an @code{int} parameter, @code{name(int)}, or the version
1526 that takes a @code{float} parameter, @code{name(float)}. To use the
1527 word-completion facilities in this situation, type a single quote
1528 @code{'} at the beginning of the function name. This alerts
1529 @value{GDBN} that it may need to consider more information than usual
1530 when you press @key{TAB} or @kbd{M-?} to request word completion:
1533 (@value{GDBP}) b 'bubble( @kbd{M-?}
1534 bubble(double,double) bubble(int,int)
1535 (@value{GDBP}) b 'bubble(
1538 In some cases, @value{GDBN} can tell that completing a name requires using
1539 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1540 completing as much as it can) if you do not type the quote in the first
1544 (@value{GDBP}) b bub @key{TAB}
1545 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1546 (@value{GDBP}) b 'bubble(
1550 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1551 you have not yet started typing the argument list when you ask for
1552 completion on an overloaded symbol.
1554 For more information about overloaded functions, see @ref{C Plus Plus
1555 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1556 overload-resolution off} to disable overload resolution;
1557 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1559 @cindex completion of structure field names
1560 @cindex structure field name completion
1561 @cindex completion of union field names
1562 @cindex union field name completion
1563 When completing in an expression which looks up a field in a
1564 structure, @value{GDBN} also tries@footnote{The completer can be
1565 confused by certain kinds of invalid expressions. Also, it only
1566 examines the static type of the expression, not the dynamic type.} to
1567 limit completions to the field names available in the type of the
1571 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1572 magic to_delete to_fputs to_put to_rewind
1573 to_data to_flush to_isatty to_read to_write
1577 This is because the @code{gdb_stdout} is a variable of the type
1578 @code{struct ui_file} that is defined in @value{GDBN} sources as
1585 ui_file_flush_ftype *to_flush;
1586 ui_file_write_ftype *to_write;
1587 ui_file_fputs_ftype *to_fputs;
1588 ui_file_read_ftype *to_read;
1589 ui_file_delete_ftype *to_delete;
1590 ui_file_isatty_ftype *to_isatty;
1591 ui_file_rewind_ftype *to_rewind;
1592 ui_file_put_ftype *to_put;
1599 @section Getting Help
1600 @cindex online documentation
1603 You can always ask @value{GDBN} itself for information on its commands,
1604 using the command @code{help}.
1607 @kindex h @r{(@code{help})}
1610 You can use @code{help} (abbreviated @code{h}) with no arguments to
1611 display a short list of named classes of commands:
1615 List of classes of commands:
1617 aliases -- Aliases of other commands
1618 breakpoints -- Making program stop at certain points
1619 data -- Examining data
1620 files -- Specifying and examining files
1621 internals -- Maintenance commands
1622 obscure -- Obscure features
1623 running -- Running the program
1624 stack -- Examining the stack
1625 status -- Status inquiries
1626 support -- Support facilities
1627 tracepoints -- Tracing of program execution without
1628 stopping the program
1629 user-defined -- User-defined commands
1631 Type "help" followed by a class name for a list of
1632 commands in that class.
1633 Type "help" followed by command name for full
1635 Command name abbreviations are allowed if unambiguous.
1638 @c the above line break eliminates huge line overfull...
1640 @item help @var{class}
1641 Using one of the general help classes as an argument, you can get a
1642 list of the individual commands in that class. For example, here is the
1643 help display for the class @code{status}:
1646 (@value{GDBP}) help status
1651 @c Line break in "show" line falsifies real output, but needed
1652 @c to fit in smallbook page size.
1653 info -- Generic command for showing things
1654 about the program being debugged
1655 show -- Generic command for showing things
1658 Type "help" followed by command name for full
1660 Command name abbreviations are allowed if unambiguous.
1664 @item help @var{command}
1665 With a command name as @code{help} argument, @value{GDBN} displays a
1666 short paragraph on how to use that command.
1669 @item apropos @var{args}
1670 The @code{apropos} command searches through all of the @value{GDBN}
1671 commands, and their documentation, for the regular expression specified in
1672 @var{args}. It prints out all matches found. For example:
1683 set symbol-reloading -- Set dynamic symbol table reloading
1684 multiple times in one run
1685 show symbol-reloading -- Show dynamic symbol table reloading
1686 multiple times in one run
1691 @item complete @var{args}
1692 The @code{complete @var{args}} command lists all the possible completions
1693 for the beginning of a command. Use @var{args} to specify the beginning of the
1694 command you want completed. For example:
1700 @noindent results in:
1711 @noindent This is intended for use by @sc{gnu} Emacs.
1714 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1715 and @code{show} to inquire about the state of your program, or the state
1716 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1717 manual introduces each of them in the appropriate context. The listings
1718 under @code{info} and under @code{show} in the Index point to
1719 all the sub-commands. @xref{Index}.
1724 @kindex i @r{(@code{info})}
1726 This command (abbreviated @code{i}) is for describing the state of your
1727 program. For example, you can show the arguments passed to a function
1728 with @code{info args}, list the registers currently in use with @code{info
1729 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1730 You can get a complete list of the @code{info} sub-commands with
1731 @w{@code{help info}}.
1735 You can assign the result of an expression to an environment variable with
1736 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1737 @code{set prompt $}.
1741 In contrast to @code{info}, @code{show} is for describing the state of
1742 @value{GDBN} itself.
1743 You can change most of the things you can @code{show}, by using the
1744 related command @code{set}; for example, you can control what number
1745 system is used for displays with @code{set radix}, or simply inquire
1746 which is currently in use with @code{show radix}.
1749 To display all the settable parameters and their current
1750 values, you can use @code{show} with no arguments; you may also use
1751 @code{info set}. Both commands produce the same display.
1752 @c FIXME: "info set" violates the rule that "info" is for state of
1753 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1754 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1758 Here are three miscellaneous @code{show} subcommands, all of which are
1759 exceptional in lacking corresponding @code{set} commands:
1762 @kindex show version
1763 @cindex @value{GDBN} version number
1765 Show what version of @value{GDBN} is running. You should include this
1766 information in @value{GDBN} bug-reports. If multiple versions of
1767 @value{GDBN} are in use at your site, you may need to determine which
1768 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1769 commands are introduced, and old ones may wither away. Also, many
1770 system vendors ship variant versions of @value{GDBN}, and there are
1771 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1772 The version number is the same as the one announced when you start
1775 @kindex show copying
1776 @kindex info copying
1777 @cindex display @value{GDBN} copyright
1780 Display information about permission for copying @value{GDBN}.
1782 @kindex show warranty
1783 @kindex info warranty
1785 @itemx info warranty
1786 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1787 if your version of @value{GDBN} comes with one.
1792 @chapter Running Programs Under @value{GDBN}
1794 When you run a program under @value{GDBN}, you must first generate
1795 debugging information when you compile it.
1797 You may start @value{GDBN} with its arguments, if any, in an environment
1798 of your choice. If you are doing native debugging, you may redirect
1799 your program's input and output, debug an already running process, or
1800 kill a child process.
1803 * Compilation:: Compiling for debugging
1804 * Starting:: Starting your program
1805 * Arguments:: Your program's arguments
1806 * Environment:: Your program's environment
1808 * Working Directory:: Your program's working directory
1809 * Input/Output:: Your program's input and output
1810 * Attach:: Debugging an already-running process
1811 * Kill Process:: Killing the child process
1813 * Inferiors and Programs:: Debugging multiple inferiors and programs
1814 * Threads:: Debugging programs with multiple threads
1815 * Forks:: Debugging forks
1816 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1820 @section Compiling for Debugging
1822 In order to debug a program effectively, you need to generate
1823 debugging information when you compile it. This debugging information
1824 is stored in the object file; it describes the data type of each
1825 variable or function and the correspondence between source line numbers
1826 and addresses in the executable code.
1828 To request debugging information, specify the @samp{-g} option when you run
1831 Programs that are to be shipped to your customers are compiled with
1832 optimizations, using the @samp{-O} compiler option. However, some
1833 compilers are unable to handle the @samp{-g} and @samp{-O} options
1834 together. Using those compilers, you cannot generate optimized
1835 executables containing debugging information.
1837 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1838 without @samp{-O}, making it possible to debug optimized code. We
1839 recommend that you @emph{always} use @samp{-g} whenever you compile a
1840 program. You may think your program is correct, but there is no sense
1841 in pushing your luck. For more information, see @ref{Optimized Code}.
1843 Older versions of the @sc{gnu} C compiler permitted a variant option
1844 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1845 format; if your @sc{gnu} C compiler has this option, do not use it.
1847 @value{GDBN} knows about preprocessor macros and can show you their
1848 expansion (@pxref{Macros}). Most compilers do not include information
1849 about preprocessor macros in the debugging information if you specify
1850 the @option{-g} flag alone, because this information is rather large.
1851 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1852 provides macro information if you specify the options
1853 @option{-gdwarf-2} and @option{-g3}; the former option requests
1854 debugging information in the Dwarf 2 format, and the latter requests
1855 ``extra information''. In the future, we hope to find more compact
1856 ways to represent macro information, so that it can be included with
1861 @section Starting your Program
1867 @kindex r @r{(@code{run})}
1870 Use the @code{run} command to start your program under @value{GDBN}.
1871 You must first specify the program name (except on VxWorks) with an
1872 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1873 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1874 (@pxref{Files, ,Commands to Specify Files}).
1878 If you are running your program in an execution environment that
1879 supports processes, @code{run} creates an inferior process and makes
1880 that process run your program. In some environments without processes,
1881 @code{run} jumps to the start of your program. Other targets,
1882 like @samp{remote}, are always running. If you get an error
1883 message like this one:
1886 The "remote" target does not support "run".
1887 Try "help target" or "continue".
1891 then use @code{continue} to run your program. You may need @code{load}
1892 first (@pxref{load}).
1894 The execution of a program is affected by certain information it
1895 receives from its superior. @value{GDBN} provides ways to specify this
1896 information, which you must do @emph{before} starting your program. (You
1897 can change it after starting your program, but such changes only affect
1898 your program the next time you start it.) This information may be
1899 divided into four categories:
1902 @item The @emph{arguments.}
1903 Specify the arguments to give your program as the arguments of the
1904 @code{run} command. If a shell is available on your target, the shell
1905 is used to pass the arguments, so that you may use normal conventions
1906 (such as wildcard expansion or variable substitution) in describing
1908 In Unix systems, you can control which shell is used with the
1909 @code{SHELL} environment variable.
1910 @xref{Arguments, ,Your Program's Arguments}.
1912 @item The @emph{environment.}
1913 Your program normally inherits its environment from @value{GDBN}, but you can
1914 use the @value{GDBN} commands @code{set environment} and @code{unset
1915 environment} to change parts of the environment that affect
1916 your program. @xref{Environment, ,Your Program's Environment}.
1918 @item The @emph{working directory.}
1919 Your program inherits its working directory from @value{GDBN}. You can set
1920 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1921 @xref{Working Directory, ,Your Program's Working Directory}.
1923 @item The @emph{standard input and output.}
1924 Your program normally uses the same device for standard input and
1925 standard output as @value{GDBN} is using. You can redirect input and output
1926 in the @code{run} command line, or you can use the @code{tty} command to
1927 set a different device for your program.
1928 @xref{Input/Output, ,Your Program's Input and Output}.
1931 @emph{Warning:} While input and output redirection work, you cannot use
1932 pipes to pass the output of the program you are debugging to another
1933 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1937 When you issue the @code{run} command, your program begins to execute
1938 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1939 of how to arrange for your program to stop. Once your program has
1940 stopped, you may call functions in your program, using the @code{print}
1941 or @code{call} commands. @xref{Data, ,Examining Data}.
1943 If the modification time of your symbol file has changed since the last
1944 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1945 table, and reads it again. When it does this, @value{GDBN} tries to retain
1946 your current breakpoints.
1951 @cindex run to main procedure
1952 The name of the main procedure can vary from language to language.
1953 With C or C@t{++}, the main procedure name is always @code{main}, but
1954 other languages such as Ada do not require a specific name for their
1955 main procedure. The debugger provides a convenient way to start the
1956 execution of the program and to stop at the beginning of the main
1957 procedure, depending on the language used.
1959 The @samp{start} command does the equivalent of setting a temporary
1960 breakpoint at the beginning of the main procedure and then invoking
1961 the @samp{run} command.
1963 @cindex elaboration phase
1964 Some programs contain an @dfn{elaboration} phase where some startup code is
1965 executed before the main procedure is called. This depends on the
1966 languages used to write your program. In C@t{++}, for instance,
1967 constructors for static and global objects are executed before
1968 @code{main} is called. It is therefore possible that the debugger stops
1969 before reaching the main procedure. However, the temporary breakpoint
1970 will remain to halt execution.
1972 Specify the arguments to give to your program as arguments to the
1973 @samp{start} command. These arguments will be given verbatim to the
1974 underlying @samp{run} command. Note that the same arguments will be
1975 reused if no argument is provided during subsequent calls to
1976 @samp{start} or @samp{run}.
1978 It is sometimes necessary to debug the program during elaboration. In
1979 these cases, using the @code{start} command would stop the execution of
1980 your program too late, as the program would have already completed the
1981 elaboration phase. Under these circumstances, insert breakpoints in your
1982 elaboration code before running your program.
1984 @kindex set exec-wrapper
1985 @item set exec-wrapper @var{wrapper}
1986 @itemx show exec-wrapper
1987 @itemx unset exec-wrapper
1988 When @samp{exec-wrapper} is set, the specified wrapper is used to
1989 launch programs for debugging. @value{GDBN} starts your program
1990 with a shell command of the form @kbd{exec @var{wrapper}
1991 @var{program}}. Quoting is added to @var{program} and its
1992 arguments, but not to @var{wrapper}, so you should add quotes if
1993 appropriate for your shell. The wrapper runs until it executes
1994 your program, and then @value{GDBN} takes control.
1996 You can use any program that eventually calls @code{execve} with
1997 its arguments as a wrapper. Several standard Unix utilities do
1998 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1999 with @code{exec "$@@"} will also work.
2001 For example, you can use @code{env} to pass an environment variable to
2002 the debugged program, without setting the variable in your shell's
2006 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2010 This command is available when debugging locally on most targets, excluding
2011 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2013 @kindex set disable-randomization
2014 @item set disable-randomization
2015 @itemx set disable-randomization on
2016 This option (enabled by default in @value{GDBN}) will turn off the native
2017 randomization of the virtual address space of the started program. This option
2018 is useful for multiple debugging sessions to make the execution better
2019 reproducible and memory addresses reusable across debugging sessions.
2021 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2025 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2028 @item set disable-randomization off
2029 Leave the behavior of the started executable unchanged. Some bugs rear their
2030 ugly heads only when the program is loaded at certain addresses. If your bug
2031 disappears when you run the program under @value{GDBN}, that might be because
2032 @value{GDBN} by default disables the address randomization on platforms, such
2033 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2034 disable-randomization off} to try to reproduce such elusive bugs.
2036 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2037 It protects the programs against some kinds of security attacks. In these
2038 cases the attacker needs to know the exact location of a concrete executable
2039 code. Randomizing its location makes it impossible to inject jumps misusing
2040 a code at its expected addresses.
2042 Prelinking shared libraries provides a startup performance advantage but it
2043 makes addresses in these libraries predictable for privileged processes by
2044 having just unprivileged access at the target system. Reading the shared
2045 library binary gives enough information for assembling the malicious code
2046 misusing it. Still even a prelinked shared library can get loaded at a new
2047 random address just requiring the regular relocation process during the
2048 startup. Shared libraries not already prelinked are always loaded at
2049 a randomly chosen address.
2051 Position independent executables (PIE) contain position independent code
2052 similar to the shared libraries and therefore such executables get loaded at
2053 a randomly chosen address upon startup. PIE executables always load even
2054 already prelinked shared libraries at a random address. You can build such
2055 executable using @command{gcc -fPIE -pie}.
2057 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2058 (as long as the randomization is enabled).
2060 @item show disable-randomization
2061 Show the current setting of the explicit disable of the native randomization of
2062 the virtual address space of the started program.
2067 @section Your Program's Arguments
2069 @cindex arguments (to your program)
2070 The arguments to your program can be specified by the arguments of the
2072 They are passed to a shell, which expands wildcard characters and
2073 performs redirection of I/O, and thence to your program. Your
2074 @code{SHELL} environment variable (if it exists) specifies what shell
2075 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2076 the default shell (@file{/bin/sh} on Unix).
2078 On non-Unix systems, the program is usually invoked directly by
2079 @value{GDBN}, which emulates I/O redirection via the appropriate system
2080 calls, and the wildcard characters are expanded by the startup code of
2081 the program, not by the shell.
2083 @code{run} with no arguments uses the same arguments used by the previous
2084 @code{run}, or those set by the @code{set args} command.
2089 Specify the arguments to be used the next time your program is run. If
2090 @code{set args} has no arguments, @code{run} executes your program
2091 with no arguments. Once you have run your program with arguments,
2092 using @code{set args} before the next @code{run} is the only way to run
2093 it again without arguments.
2097 Show the arguments to give your program when it is started.
2101 @section Your Program's Environment
2103 @cindex environment (of your program)
2104 The @dfn{environment} consists of a set of environment variables and
2105 their values. Environment variables conventionally record such things as
2106 your user name, your home directory, your terminal type, and your search
2107 path for programs to run. Usually you set up environment variables with
2108 the shell and they are inherited by all the other programs you run. When
2109 debugging, it can be useful to try running your program with a modified
2110 environment without having to start @value{GDBN} over again.
2114 @item path @var{directory}
2115 Add @var{directory} to the front of the @code{PATH} environment variable
2116 (the search path for executables) that will be passed to your program.
2117 The value of @code{PATH} used by @value{GDBN} does not change.
2118 You may specify several directory names, separated by whitespace or by a
2119 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2120 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2121 is moved to the front, so it is searched sooner.
2123 You can use the string @samp{$cwd} to refer to whatever is the current
2124 working directory at the time @value{GDBN} searches the path. If you
2125 use @samp{.} instead, it refers to the directory where you executed the
2126 @code{path} command. @value{GDBN} replaces @samp{.} in the
2127 @var{directory} argument (with the current path) before adding
2128 @var{directory} to the search path.
2129 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2130 @c document that, since repeating it would be a no-op.
2134 Display the list of search paths for executables (the @code{PATH}
2135 environment variable).
2137 @kindex show environment
2138 @item show environment @r{[}@var{varname}@r{]}
2139 Print the value of environment variable @var{varname} to be given to
2140 your program when it starts. If you do not supply @var{varname},
2141 print the names and values of all environment variables to be given to
2142 your program. You can abbreviate @code{environment} as @code{env}.
2144 @kindex set environment
2145 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2146 Set environment variable @var{varname} to @var{value}. The value
2147 changes for your program only, not for @value{GDBN} itself. @var{value} may
2148 be any string; the values of environment variables are just strings, and
2149 any interpretation is supplied by your program itself. The @var{value}
2150 parameter is optional; if it is eliminated, the variable is set to a
2152 @c "any string" here does not include leading, trailing
2153 @c blanks. Gnu asks: does anyone care?
2155 For example, this command:
2162 tells the debugged program, when subsequently run, that its user is named
2163 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2164 are not actually required.)
2166 @kindex unset environment
2167 @item unset environment @var{varname}
2168 Remove variable @var{varname} from the environment to be passed to your
2169 program. This is different from @samp{set env @var{varname} =};
2170 @code{unset environment} removes the variable from the environment,
2171 rather than assigning it an empty value.
2174 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2176 by your @code{SHELL} environment variable if it exists (or
2177 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2178 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2179 @file{.bashrc} for BASH---any variables you set in that file affect
2180 your program. You may wish to move setting of environment variables to
2181 files that are only run when you sign on, such as @file{.login} or
2184 @node Working Directory
2185 @section Your Program's Working Directory
2187 @cindex working directory (of your program)
2188 Each time you start your program with @code{run}, it inherits its
2189 working directory from the current working directory of @value{GDBN}.
2190 The @value{GDBN} working directory is initially whatever it inherited
2191 from its parent process (typically the shell), but you can specify a new
2192 working directory in @value{GDBN} with the @code{cd} command.
2194 The @value{GDBN} working directory also serves as a default for the commands
2195 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2200 @cindex change working directory
2201 @item cd @var{directory}
2202 Set the @value{GDBN} working directory to @var{directory}.
2206 Print the @value{GDBN} working directory.
2209 It is generally impossible to find the current working directory of
2210 the process being debugged (since a program can change its directory
2211 during its run). If you work on a system where @value{GDBN} is
2212 configured with the @file{/proc} support, you can use the @code{info
2213 proc} command (@pxref{SVR4 Process Information}) to find out the
2214 current working directory of the debuggee.
2217 @section Your Program's Input and Output
2222 By default, the program you run under @value{GDBN} does input and output to
2223 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2224 to its own terminal modes to interact with you, but it records the terminal
2225 modes your program was using and switches back to them when you continue
2226 running your program.
2229 @kindex info terminal
2231 Displays information recorded by @value{GDBN} about the terminal modes your
2235 You can redirect your program's input and/or output using shell
2236 redirection with the @code{run} command. For example,
2243 starts your program, diverting its output to the file @file{outfile}.
2246 @cindex controlling terminal
2247 Another way to specify where your program should do input and output is
2248 with the @code{tty} command. This command accepts a file name as
2249 argument, and causes this file to be the default for future @code{run}
2250 commands. It also resets the controlling terminal for the child
2251 process, for future @code{run} commands. For example,
2258 directs that processes started with subsequent @code{run} commands
2259 default to do input and output on the terminal @file{/dev/ttyb} and have
2260 that as their controlling terminal.
2262 An explicit redirection in @code{run} overrides the @code{tty} command's
2263 effect on the input/output device, but not its effect on the controlling
2266 When you use the @code{tty} command or redirect input in the @code{run}
2267 command, only the input @emph{for your program} is affected. The input
2268 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2269 for @code{set inferior-tty}.
2271 @cindex inferior tty
2272 @cindex set inferior controlling terminal
2273 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2274 display the name of the terminal that will be used for future runs of your
2278 @item set inferior-tty /dev/ttyb
2279 @kindex set inferior-tty
2280 Set the tty for the program being debugged to /dev/ttyb.
2282 @item show inferior-tty
2283 @kindex show inferior-tty
2284 Show the current tty for the program being debugged.
2288 @section Debugging an Already-running Process
2293 @item attach @var{process-id}
2294 This command attaches to a running process---one that was started
2295 outside @value{GDBN}. (@code{info files} shows your active
2296 targets.) The command takes as argument a process ID. The usual way to
2297 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2298 or with the @samp{jobs -l} shell command.
2300 @code{attach} does not repeat if you press @key{RET} a second time after
2301 executing the command.
2304 To use @code{attach}, your program must be running in an environment
2305 which supports processes; for example, @code{attach} does not work for
2306 programs on bare-board targets that lack an operating system. You must
2307 also have permission to send the process a signal.
2309 When you use @code{attach}, the debugger finds the program running in
2310 the process first by looking in the current working directory, then (if
2311 the program is not found) by using the source file search path
2312 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2313 the @code{file} command to load the program. @xref{Files, ,Commands to
2316 The first thing @value{GDBN} does after arranging to debug the specified
2317 process is to stop it. You can examine and modify an attached process
2318 with all the @value{GDBN} commands that are ordinarily available when
2319 you start processes with @code{run}. You can insert breakpoints; you
2320 can step and continue; you can modify storage. If you would rather the
2321 process continue running, you may use the @code{continue} command after
2322 attaching @value{GDBN} to the process.
2327 When you have finished debugging the attached process, you can use the
2328 @code{detach} command to release it from @value{GDBN} control. Detaching
2329 the process continues its execution. After the @code{detach} command,
2330 that process and @value{GDBN} become completely independent once more, and you
2331 are ready to @code{attach} another process or start one with @code{run}.
2332 @code{detach} does not repeat if you press @key{RET} again after
2333 executing the command.
2336 If you exit @value{GDBN} while you have an attached process, you detach
2337 that process. If you use the @code{run} command, you kill that process.
2338 By default, @value{GDBN} asks for confirmation if you try to do either of these
2339 things; you can control whether or not you need to confirm by using the
2340 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2344 @section Killing the Child Process
2349 Kill the child process in which your program is running under @value{GDBN}.
2352 This command is useful if you wish to debug a core dump instead of a
2353 running process. @value{GDBN} ignores any core dump file while your program
2356 On some operating systems, a program cannot be executed outside @value{GDBN}
2357 while you have breakpoints set on it inside @value{GDBN}. You can use the
2358 @code{kill} command in this situation to permit running your program
2359 outside the debugger.
2361 The @code{kill} command is also useful if you wish to recompile and
2362 relink your program, since on many systems it is impossible to modify an
2363 executable file while it is running in a process. In this case, when you
2364 next type @code{run}, @value{GDBN} notices that the file has changed, and
2365 reads the symbol table again (while trying to preserve your current
2366 breakpoint settings).
2368 @node Inferiors and Programs
2369 @section Debugging Multiple Inferiors and Programs
2371 @value{GDBN} lets you run and debug multiple programs in a single
2372 session. In addition, @value{GDBN} on some systems may let you run
2373 several programs simultaneously (otherwise you have to exit from one
2374 before starting another). In the most general case, you can have
2375 multiple threads of execution in each of multiple processes, launched
2376 from multiple executables.
2379 @value{GDBN} represents the state of each program execution with an
2380 object called an @dfn{inferior}. An inferior typically corresponds to
2381 a process, but is more general and applies also to targets that do not
2382 have processes. Inferiors may be created before a process runs, and
2383 may be retained after a process exits. Inferiors have unique
2384 identifiers that are different from process ids. Usually each
2385 inferior will also have its own distinct address space, although some
2386 embedded targets may have several inferiors running in different parts
2387 of a single address space. Each inferior may in turn have multiple
2388 threads running in it.
2390 To find out what inferiors exist at any moment, use @w{@code{info
2394 @kindex info inferiors
2395 @item info inferiors
2396 Print a list of all inferiors currently being managed by @value{GDBN}.
2398 @value{GDBN} displays for each inferior (in this order):
2402 the inferior number assigned by @value{GDBN}
2405 the target system's inferior identifier
2408 the name of the executable the inferior is running.
2413 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2414 indicates the current inferior.
2418 @c end table here to get a little more width for example
2421 (@value{GDBP}) info inferiors
2422 Num Description Executable
2423 2 process 2307 hello
2424 * 1 process 3401 goodbye
2427 To switch focus between inferiors, use the @code{inferior} command:
2430 @kindex inferior @var{infno}
2431 @item inferior @var{infno}
2432 Make inferior number @var{infno} the current inferior. The argument
2433 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2434 in the first field of the @samp{info inferiors} display.
2438 You can get multiple executables into a debugging session via the
2439 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2440 systems @value{GDBN} can add inferiors to the debug session
2441 automatically by following calls to @code{fork} and @code{exec}. To
2442 remove inferiors from the debugging session use the
2443 @w{@code{remove-inferior}} command.
2446 @kindex add-inferior
2447 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2448 Adds @var{n} inferiors to be run using @var{executable} as the
2449 executable. @var{n} defaults to 1. If no executable is specified,
2450 the inferiors begins empty, with no program. You can still assign or
2451 change the program assigned to the inferior at any time by using the
2452 @code{file} command with the executable name as its argument.
2454 @kindex clone-inferior
2455 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2456 Adds @var{n} inferiors ready to execute the same program as inferior
2457 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2458 number of the current inferior. This is a convenient command when you
2459 want to run another instance of the inferior you are debugging.
2462 (@value{GDBP}) info inferiors
2463 Num Description Executable
2464 * 1 process 29964 helloworld
2465 (@value{GDBP}) clone-inferior
2468 (@value{GDBP}) info inferiors
2469 Num Description Executable
2471 * 1 process 29964 helloworld
2474 You can now simply switch focus to inferior 2 and run it.
2476 @kindex remove-inferior
2477 @item remove-inferior @var{infno}
2478 Removes the inferior @var{infno}. It is not possible to remove an
2479 inferior that is running with this command. For those, use the
2480 @code{kill} or @code{detach} command first.
2484 To quit debugging one of the running inferiors that is not the current
2485 inferior, you can either detach from it by using the @w{@code{detach
2486 inferior}} command (allowing it to run independently), or kill it
2487 using the @w{@code{kill inferior}} command:
2490 @kindex detach inferior @var{infno}
2491 @item detach inferior @var{infno}
2492 Detach from the inferior identified by @value{GDBN} inferior number
2493 @var{infno}. Note that the inferior's entry still stays on the list
2494 of inferiors shown by @code{info inferiors}, but its Description will
2497 @kindex kill inferior @var{infno}
2498 @item kill inferior @var{infno}
2499 Kill the inferior identified by @value{GDBN} inferior number
2500 @var{infno}. Note that the inferior's entry still stays on the list
2501 of inferiors shown by @code{info inferiors}, but its Description will
2505 After the successful completion of a command such as @code{detach},
2506 @code{detach inferior}, @code{kill} or @code{kill inferior}, or after
2507 a normal process exit, the inferior is still valid and listed with
2508 @code{info inferiors}, ready to be restarted.
2511 To be notified when inferiors are started or exit under @value{GDBN}'s
2512 control use @w{@code{set print inferior-events}}:
2515 @kindex set print inferior-events
2516 @cindex print messages on inferior start and exit
2517 @item set print inferior-events
2518 @itemx set print inferior-events on
2519 @itemx set print inferior-events off
2520 The @code{set print inferior-events} command allows you to enable or
2521 disable printing of messages when @value{GDBN} notices that new
2522 inferiors have started or that inferiors have exited or have been
2523 detached. By default, these messages will not be printed.
2525 @kindex show print inferior-events
2526 @item show print inferior-events
2527 Show whether messages will be printed when @value{GDBN} detects that
2528 inferiors have started, exited or have been detached.
2531 Many commands will work the same with multiple programs as with a
2532 single program: e.g., @code{print myglobal} will simply display the
2533 value of @code{myglobal} in the current inferior.
2536 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2537 get more info about the relationship of inferiors, programs, address
2538 spaces in a debug session. You can do that with the @w{@code{maint
2539 info program-spaces}} command.
2542 @kindex maint info program-spaces
2543 @item maint info program-spaces
2544 Print a list of all program spaces currently being managed by
2547 @value{GDBN} displays for each program space (in this order):
2551 the program space number assigned by @value{GDBN}
2554 the name of the executable loaded into the program space, with e.g.,
2555 the @code{file} command.
2560 An asterisk @samp{*} preceding the @value{GDBN} program space number
2561 indicates the current program space.
2563 In addition, below each program space line, @value{GDBN} prints extra
2564 information that isn't suitable to display in tabular form. For
2565 example, the list of inferiors bound to the program space.
2568 (@value{GDBP}) maint info program-spaces
2571 Bound inferiors: ID 1 (process 21561)
2575 Here we can see that no inferior is running the program @code{hello},
2576 while @code{process 21561} is running the program @code{goodbye}. On
2577 some targets, it is possible that multiple inferiors are bound to the
2578 same program space. The most common example is that of debugging both
2579 the parent and child processes of a @code{vfork} call. For example,
2582 (@value{GDBP}) maint info program-spaces
2585 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2588 Here, both inferior 2 and inferior 1 are running in the same program
2589 space as a result of inferior 1 having executed a @code{vfork} call.
2593 @section Debugging Programs with Multiple Threads
2595 @cindex threads of execution
2596 @cindex multiple threads
2597 @cindex switching threads
2598 In some operating systems, such as HP-UX and Solaris, a single program
2599 may have more than one @dfn{thread} of execution. The precise semantics
2600 of threads differ from one operating system to another, but in general
2601 the threads of a single program are akin to multiple processes---except
2602 that they share one address space (that is, they can all examine and
2603 modify the same variables). On the other hand, each thread has its own
2604 registers and execution stack, and perhaps private memory.
2606 @value{GDBN} provides these facilities for debugging multi-thread
2610 @item automatic notification of new threads
2611 @item @samp{thread @var{threadno}}, a command to switch among threads
2612 @item @samp{info threads}, a command to inquire about existing threads
2613 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2614 a command to apply a command to a list of threads
2615 @item thread-specific breakpoints
2616 @item @samp{set print thread-events}, which controls printing of
2617 messages on thread start and exit.
2618 @item @samp{set libthread-db-search-path @var{path}}, which lets
2619 the user specify which @code{libthread_db} to use if the default choice
2620 isn't compatible with the program.
2624 @emph{Warning:} These facilities are not yet available on every
2625 @value{GDBN} configuration where the operating system supports threads.
2626 If your @value{GDBN} does not support threads, these commands have no
2627 effect. For example, a system without thread support shows no output
2628 from @samp{info threads}, and always rejects the @code{thread} command,
2632 (@value{GDBP}) info threads
2633 (@value{GDBP}) thread 1
2634 Thread ID 1 not known. Use the "info threads" command to
2635 see the IDs of currently known threads.
2637 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2638 @c doesn't support threads"?
2641 @cindex focus of debugging
2642 @cindex current thread
2643 The @value{GDBN} thread debugging facility allows you to observe all
2644 threads while your program runs---but whenever @value{GDBN} takes
2645 control, one thread in particular is always the focus of debugging.
2646 This thread is called the @dfn{current thread}. Debugging commands show
2647 program information from the perspective of the current thread.
2649 @cindex @code{New} @var{systag} message
2650 @cindex thread identifier (system)
2651 @c FIXME-implementors!! It would be more helpful if the [New...] message
2652 @c included GDB's numeric thread handle, so you could just go to that
2653 @c thread without first checking `info threads'.
2654 Whenever @value{GDBN} detects a new thread in your program, it displays
2655 the target system's identification for the thread with a message in the
2656 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2657 whose form varies depending on the particular system. For example, on
2658 @sc{gnu}/Linux, you might see
2661 [New Thread 46912507313328 (LWP 25582)]
2665 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2666 the @var{systag} is simply something like @samp{process 368}, with no
2669 @c FIXME!! (1) Does the [New...] message appear even for the very first
2670 @c thread of a program, or does it only appear for the
2671 @c second---i.e.@: when it becomes obvious we have a multithread
2673 @c (2) *Is* there necessarily a first thread always? Or do some
2674 @c multithread systems permit starting a program with multiple
2675 @c threads ab initio?
2677 @cindex thread number
2678 @cindex thread identifier (GDB)
2679 For debugging purposes, @value{GDBN} associates its own thread
2680 number---always a single integer---with each thread in your program.
2683 @kindex info threads
2685 Display a summary of all threads currently in your
2686 program. @value{GDBN} displays for each thread (in this order):
2690 the thread number assigned by @value{GDBN}
2693 the target system's thread identifier (@var{systag})
2696 the current stack frame summary for that thread
2700 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2701 indicates the current thread.
2705 @c end table here to get a little more width for example
2708 (@value{GDBP}) info threads
2709 3 process 35 thread 27 0x34e5 in sigpause ()
2710 2 process 35 thread 23 0x34e5 in sigpause ()
2711 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2717 @cindex debugging multithreaded programs (on HP-UX)
2718 @cindex thread identifier (GDB), on HP-UX
2719 For debugging purposes, @value{GDBN} associates its own thread
2720 number---a small integer assigned in thread-creation order---with each
2721 thread in your program.
2723 @cindex @code{New} @var{systag} message, on HP-UX
2724 @cindex thread identifier (system), on HP-UX
2725 @c FIXME-implementors!! It would be more helpful if the [New...] message
2726 @c included GDB's numeric thread handle, so you could just go to that
2727 @c thread without first checking `info threads'.
2728 Whenever @value{GDBN} detects a new thread in your program, it displays
2729 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2730 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2731 whose form varies depending on the particular system. For example, on
2735 [New thread 2 (system thread 26594)]
2739 when @value{GDBN} notices a new thread.
2742 @kindex info threads (HP-UX)
2744 Display a summary of all threads currently in your
2745 program. @value{GDBN} displays for each thread (in this order):
2748 @item the thread number assigned by @value{GDBN}
2750 @item the target system's thread identifier (@var{systag})
2752 @item the current stack frame summary for that thread
2756 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2757 indicates the current thread.
2761 @c end table here to get a little more width for example
2764 (@value{GDBP}) info threads
2765 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2767 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2768 from /usr/lib/libc.2
2769 1 system thread 27905 0x7b003498 in _brk () \@*
2770 from /usr/lib/libc.2
2773 On Solaris, you can display more information about user threads with a
2774 Solaris-specific command:
2777 @item maint info sol-threads
2778 @kindex maint info sol-threads
2779 @cindex thread info (Solaris)
2780 Display info on Solaris user threads.
2784 @kindex thread @var{threadno}
2785 @item thread @var{threadno}
2786 Make thread number @var{threadno} the current thread. The command
2787 argument @var{threadno} is the internal @value{GDBN} thread number, as
2788 shown in the first field of the @samp{info threads} display.
2789 @value{GDBN} responds by displaying the system identifier of the thread
2790 you selected, and its current stack frame summary:
2793 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2794 (@value{GDBP}) thread 2
2795 [Switching to process 35 thread 23]
2796 0x34e5 in sigpause ()
2800 As with the @samp{[New @dots{}]} message, the form of the text after
2801 @samp{Switching to} depends on your system's conventions for identifying
2804 @vindex $_thread@r{, convenience variable}
2805 The debugger convenience variable @samp{$_thread} contains the number
2806 of the current thread. You may find this useful in writing breakpoint
2807 conditional expressions, command scripts, and so forth. See
2808 @xref{Convenience Vars,, Convenience Variables}, for general
2809 information on convenience variables.
2811 @kindex thread apply
2812 @cindex apply command to several threads
2813 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2814 The @code{thread apply} command allows you to apply the named
2815 @var{command} to one or more threads. Specify the numbers of the
2816 threads that you want affected with the command argument
2817 @var{threadno}. It can be a single thread number, one of the numbers
2818 shown in the first field of the @samp{info threads} display; or it
2819 could be a range of thread numbers, as in @code{2-4}. To apply a
2820 command to all threads, type @kbd{thread apply all @var{command}}.
2822 @kindex set print thread-events
2823 @cindex print messages on thread start and exit
2824 @item set print thread-events
2825 @itemx set print thread-events on
2826 @itemx set print thread-events off
2827 The @code{set print thread-events} command allows you to enable or
2828 disable printing of messages when @value{GDBN} notices that new threads have
2829 started or that threads have exited. By default, these messages will
2830 be printed if detection of these events is supported by the target.
2831 Note that these messages cannot be disabled on all targets.
2833 @kindex show print thread-events
2834 @item show print thread-events
2835 Show whether messages will be printed when @value{GDBN} detects that threads
2836 have started and exited.
2839 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2840 more information about how @value{GDBN} behaves when you stop and start
2841 programs with multiple threads.
2843 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2844 watchpoints in programs with multiple threads.
2847 @kindex set libthread-db-search-path
2848 @cindex search path for @code{libthread_db}
2849 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2850 If this variable is set, @var{path} is a colon-separated list of
2851 directories @value{GDBN} will use to search for @code{libthread_db}.
2852 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2855 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2856 @code{libthread_db} library to obtain information about threads in the
2857 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2858 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2859 with default system shared library directories, and finally the directory
2860 from which @code{libpthread} was loaded in the inferior process.
2862 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2863 @value{GDBN} attempts to initialize it with the current inferior process.
2864 If this initialization fails (which could happen because of a version
2865 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2866 will unload @code{libthread_db}, and continue with the next directory.
2867 If none of @code{libthread_db} libraries initialize successfully,
2868 @value{GDBN} will issue a warning and thread debugging will be disabled.
2870 Setting @code{libthread-db-search-path} is currently implemented
2871 only on some platforms.
2873 @kindex show libthread-db-search-path
2874 @item show libthread-db-search-path
2875 Display current libthread_db search path.
2877 @kindex set debug libthread-db
2878 @kindex show debug libthread-db
2879 @cindex debugging @code{libthread_db}
2880 @item set debug libthread-db
2881 @itemx show debug libthread-db
2882 Turns on or off display of @code{libthread_db}-related events.
2883 Use @code{1} to enable, @code{0} to disable.
2887 @section Debugging Forks
2889 @cindex fork, debugging programs which call
2890 @cindex multiple processes
2891 @cindex processes, multiple
2892 On most systems, @value{GDBN} has no special support for debugging
2893 programs which create additional processes using the @code{fork}
2894 function. When a program forks, @value{GDBN} will continue to debug the
2895 parent process and the child process will run unimpeded. If you have
2896 set a breakpoint in any code which the child then executes, the child
2897 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2898 will cause it to terminate.
2900 However, if you want to debug the child process there is a workaround
2901 which isn't too painful. Put a call to @code{sleep} in the code which
2902 the child process executes after the fork. It may be useful to sleep
2903 only if a certain environment variable is set, or a certain file exists,
2904 so that the delay need not occur when you don't want to run @value{GDBN}
2905 on the child. While the child is sleeping, use the @code{ps} program to
2906 get its process ID. Then tell @value{GDBN} (a new invocation of
2907 @value{GDBN} if you are also debugging the parent process) to attach to
2908 the child process (@pxref{Attach}). From that point on you can debug
2909 the child process just like any other process which you attached to.
2911 On some systems, @value{GDBN} provides support for debugging programs that
2912 create additional processes using the @code{fork} or @code{vfork} functions.
2913 Currently, the only platforms with this feature are HP-UX (11.x and later
2914 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2916 By default, when a program forks, @value{GDBN} will continue to debug
2917 the parent process and the child process will run unimpeded.
2919 If you want to follow the child process instead of the parent process,
2920 use the command @w{@code{set follow-fork-mode}}.
2923 @kindex set follow-fork-mode
2924 @item set follow-fork-mode @var{mode}
2925 Set the debugger response to a program call of @code{fork} or
2926 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2927 process. The @var{mode} argument can be:
2931 The original process is debugged after a fork. The child process runs
2932 unimpeded. This is the default.
2935 The new process is debugged after a fork. The parent process runs
2940 @kindex show follow-fork-mode
2941 @item show follow-fork-mode
2942 Display the current debugger response to a @code{fork} or @code{vfork} call.
2945 @cindex debugging multiple processes
2946 On Linux, if you want to debug both the parent and child processes, use the
2947 command @w{@code{set detach-on-fork}}.
2950 @kindex set detach-on-fork
2951 @item set detach-on-fork @var{mode}
2952 Tells gdb whether to detach one of the processes after a fork, or
2953 retain debugger control over them both.
2957 The child process (or parent process, depending on the value of
2958 @code{follow-fork-mode}) will be detached and allowed to run
2959 independently. This is the default.
2962 Both processes will be held under the control of @value{GDBN}.
2963 One process (child or parent, depending on the value of
2964 @code{follow-fork-mode}) is debugged as usual, while the other
2969 @kindex show detach-on-fork
2970 @item show detach-on-fork
2971 Show whether detach-on-fork mode is on/off.
2974 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2975 will retain control of all forked processes (including nested forks).
2976 You can list the forked processes under the control of @value{GDBN} by
2977 using the @w{@code{info inferiors}} command, and switch from one fork
2978 to another by using the @code{inferior} command (@pxref{Inferiors and
2979 Programs, ,Debugging Multiple Inferiors and Programs}).
2981 To quit debugging one of the forked processes, you can either detach
2982 from it by using the @w{@code{detach inferior}} command (allowing it
2983 to run independently), or kill it using the @w{@code{kill inferior}}
2984 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
2987 If you ask to debug a child process and a @code{vfork} is followed by an
2988 @code{exec}, @value{GDBN} executes the new target up to the first
2989 breakpoint in the new target. If you have a breakpoint set on
2990 @code{main} in your original program, the breakpoint will also be set on
2991 the child process's @code{main}.
2993 On some systems, when a child process is spawned by @code{vfork}, you
2994 cannot debug the child or parent until an @code{exec} call completes.
2996 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2997 call executes, the new target restarts. To restart the parent
2998 process, use the @code{file} command with the parent executable name
2999 as its argument. By default, after an @code{exec} call executes,
3000 @value{GDBN} discards the symbols of the previous executable image.
3001 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3005 @kindex set follow-exec-mode
3006 @item set follow-exec-mode @var{mode}
3008 Set debugger response to a program call of @code{exec}. An
3009 @code{exec} call replaces the program image of a process.
3011 @code{follow-exec-mode} can be:
3015 @value{GDBN} creates a new inferior and rebinds the process to this
3016 new inferior. The program the process was running before the
3017 @code{exec} call can be restarted afterwards by restarting the
3023 (@value{GDBP}) info inferiors
3025 Id Description Executable
3028 process 12020 is executing new program: prog2
3029 Program exited normally.
3030 (@value{GDBP}) info inferiors
3031 Id Description Executable
3037 @value{GDBN} keeps the process bound to the same inferior. The new
3038 executable image replaces the previous executable loaded in the
3039 inferior. Restarting the inferior after the @code{exec} call, with
3040 e.g., the @code{run} command, restarts the executable the process was
3041 running after the @code{exec} call. This is the default mode.
3046 (@value{GDBP}) info inferiors
3047 Id Description Executable
3050 process 12020 is executing new program: prog2
3051 Program exited normally.
3052 (@value{GDBP}) info inferiors
3053 Id Description Executable
3060 You can use the @code{catch} command to make @value{GDBN} stop whenever
3061 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3062 Catchpoints, ,Setting Catchpoints}.
3064 @node Checkpoint/Restart
3065 @section Setting a @emph{Bookmark} to Return to Later
3070 @cindex snapshot of a process
3071 @cindex rewind program state
3073 On certain operating systems@footnote{Currently, only
3074 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3075 program's state, called a @dfn{checkpoint}, and come back to it
3078 Returning to a checkpoint effectively undoes everything that has
3079 happened in the program since the @code{checkpoint} was saved. This
3080 includes changes in memory, registers, and even (within some limits)
3081 system state. Effectively, it is like going back in time to the
3082 moment when the checkpoint was saved.
3084 Thus, if you're stepping thru a program and you think you're
3085 getting close to the point where things go wrong, you can save
3086 a checkpoint. Then, if you accidentally go too far and miss
3087 the critical statement, instead of having to restart your program
3088 from the beginning, you can just go back to the checkpoint and
3089 start again from there.
3091 This can be especially useful if it takes a lot of time or
3092 steps to reach the point where you think the bug occurs.
3094 To use the @code{checkpoint}/@code{restart} method of debugging:
3099 Save a snapshot of the debugged program's current execution state.
3100 The @code{checkpoint} command takes no arguments, but each checkpoint
3101 is assigned a small integer id, similar to a breakpoint id.
3103 @kindex info checkpoints
3104 @item info checkpoints
3105 List the checkpoints that have been saved in the current debugging
3106 session. For each checkpoint, the following information will be
3113 @item Source line, or label
3116 @kindex restart @var{checkpoint-id}
3117 @item restart @var{checkpoint-id}
3118 Restore the program state that was saved as checkpoint number
3119 @var{checkpoint-id}. All program variables, registers, stack frames
3120 etc.@: will be returned to the values that they had when the checkpoint
3121 was saved. In essence, gdb will ``wind back the clock'' to the point
3122 in time when the checkpoint was saved.
3124 Note that breakpoints, @value{GDBN} variables, command history etc.
3125 are not affected by restoring a checkpoint. In general, a checkpoint
3126 only restores things that reside in the program being debugged, not in
3129 @kindex delete checkpoint @var{checkpoint-id}
3130 @item delete checkpoint @var{checkpoint-id}
3131 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3135 Returning to a previously saved checkpoint will restore the user state
3136 of the program being debugged, plus a significant subset of the system
3137 (OS) state, including file pointers. It won't ``un-write'' data from
3138 a file, but it will rewind the file pointer to the previous location,
3139 so that the previously written data can be overwritten. For files
3140 opened in read mode, the pointer will also be restored so that the
3141 previously read data can be read again.
3143 Of course, characters that have been sent to a printer (or other
3144 external device) cannot be ``snatched back'', and characters received
3145 from eg.@: a serial device can be removed from internal program buffers,
3146 but they cannot be ``pushed back'' into the serial pipeline, ready to
3147 be received again. Similarly, the actual contents of files that have
3148 been changed cannot be restored (at this time).
3150 However, within those constraints, you actually can ``rewind'' your
3151 program to a previously saved point in time, and begin debugging it
3152 again --- and you can change the course of events so as to debug a
3153 different execution path this time.
3155 @cindex checkpoints and process id
3156 Finally, there is one bit of internal program state that will be
3157 different when you return to a checkpoint --- the program's process
3158 id. Each checkpoint will have a unique process id (or @var{pid}),
3159 and each will be different from the program's original @var{pid}.
3160 If your program has saved a local copy of its process id, this could
3161 potentially pose a problem.
3163 @subsection A Non-obvious Benefit of Using Checkpoints
3165 On some systems such as @sc{gnu}/Linux, address space randomization
3166 is performed on new processes for security reasons. This makes it
3167 difficult or impossible to set a breakpoint, or watchpoint, on an
3168 absolute address if you have to restart the program, since the
3169 absolute location of a symbol will change from one execution to the
3172 A checkpoint, however, is an @emph{identical} copy of a process.
3173 Therefore if you create a checkpoint at (eg.@:) the start of main,
3174 and simply return to that checkpoint instead of restarting the
3175 process, you can avoid the effects of address randomization and
3176 your symbols will all stay in the same place.
3179 @chapter Stopping and Continuing
3181 The principal purposes of using a debugger are so that you can stop your
3182 program before it terminates; or so that, if your program runs into
3183 trouble, you can investigate and find out why.
3185 Inside @value{GDBN}, your program may stop for any of several reasons,
3186 such as a signal, a breakpoint, or reaching a new line after a
3187 @value{GDBN} command such as @code{step}. You may then examine and
3188 change variables, set new breakpoints or remove old ones, and then
3189 continue execution. Usually, the messages shown by @value{GDBN} provide
3190 ample explanation of the status of your program---but you can also
3191 explicitly request this information at any time.
3194 @kindex info program
3196 Display information about the status of your program: whether it is
3197 running or not, what process it is, and why it stopped.
3201 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3202 * Continuing and Stepping:: Resuming execution
3204 * Thread Stops:: Stopping and starting multi-thread programs
3208 @section Breakpoints, Watchpoints, and Catchpoints
3211 A @dfn{breakpoint} makes your program stop whenever a certain point in
3212 the program is reached. For each breakpoint, you can add conditions to
3213 control in finer detail whether your program stops. You can set
3214 breakpoints with the @code{break} command and its variants (@pxref{Set
3215 Breaks, ,Setting Breakpoints}), to specify the place where your program
3216 should stop by line number, function name or exact address in the
3219 On some systems, you can set breakpoints in shared libraries before
3220 the executable is run. There is a minor limitation on HP-UX systems:
3221 you must wait until the executable is run in order to set breakpoints
3222 in shared library routines that are not called directly by the program
3223 (for example, routines that are arguments in a @code{pthread_create}
3227 @cindex data breakpoints
3228 @cindex memory tracing
3229 @cindex breakpoint on memory address
3230 @cindex breakpoint on variable modification
3231 A @dfn{watchpoint} is a special breakpoint that stops your program
3232 when the value of an expression changes. The expression may be a value
3233 of a variable, or it could involve values of one or more variables
3234 combined by operators, such as @samp{a + b}. This is sometimes called
3235 @dfn{data breakpoints}. You must use a different command to set
3236 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3237 from that, you can manage a watchpoint like any other breakpoint: you
3238 enable, disable, and delete both breakpoints and watchpoints using the
3241 You can arrange to have values from your program displayed automatically
3242 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3246 @cindex breakpoint on events
3247 A @dfn{catchpoint} is another special breakpoint that stops your program
3248 when a certain kind of event occurs, such as the throwing of a C@t{++}
3249 exception or the loading of a library. As with watchpoints, you use a
3250 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3251 Catchpoints}), but aside from that, you can manage a catchpoint like any
3252 other breakpoint. (To stop when your program receives a signal, use the
3253 @code{handle} command; see @ref{Signals, ,Signals}.)
3255 @cindex breakpoint numbers
3256 @cindex numbers for breakpoints
3257 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3258 catchpoint when you create it; these numbers are successive integers
3259 starting with one. In many of the commands for controlling various
3260 features of breakpoints you use the breakpoint number to say which
3261 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3262 @dfn{disabled}; if disabled, it has no effect on your program until you
3265 @cindex breakpoint ranges
3266 @cindex ranges of breakpoints
3267 Some @value{GDBN} commands accept a range of breakpoints on which to
3268 operate. A breakpoint range is either a single breakpoint number, like
3269 @samp{5}, or two such numbers, in increasing order, separated by a
3270 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3271 all breakpoints in that range are operated on.
3274 * Set Breaks:: Setting breakpoints
3275 * Set Watchpoints:: Setting watchpoints
3276 * Set Catchpoints:: Setting catchpoints
3277 * Delete Breaks:: Deleting breakpoints
3278 * Disabling:: Disabling breakpoints
3279 * Conditions:: Break conditions
3280 * Break Commands:: Breakpoint command lists
3281 * Save Breakpoints:: How to save breakpoints in a file
3282 * Error in Breakpoints:: ``Cannot insert breakpoints''
3283 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3287 @subsection Setting Breakpoints
3289 @c FIXME LMB what does GDB do if no code on line of breakpt?
3290 @c consider in particular declaration with/without initialization.
3292 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3295 @kindex b @r{(@code{break})}
3296 @vindex $bpnum@r{, convenience variable}
3297 @cindex latest breakpoint
3298 Breakpoints are set with the @code{break} command (abbreviated
3299 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3300 number of the breakpoint you've set most recently; see @ref{Convenience
3301 Vars,, Convenience Variables}, for a discussion of what you can do with
3302 convenience variables.
3305 @item break @var{location}
3306 Set a breakpoint at the given @var{location}, which can specify a
3307 function name, a line number, or an address of an instruction.
3308 (@xref{Specify Location}, for a list of all the possible ways to
3309 specify a @var{location}.) The breakpoint will stop your program just
3310 before it executes any of the code in the specified @var{location}.
3312 When using source languages that permit overloading of symbols, such as
3313 C@t{++}, a function name may refer to more than one possible place to break.
3314 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3317 It is also possible to insert a breakpoint that will stop the program
3318 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3319 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3322 When called without any arguments, @code{break} sets a breakpoint at
3323 the next instruction to be executed in the selected stack frame
3324 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3325 innermost, this makes your program stop as soon as control
3326 returns to that frame. This is similar to the effect of a
3327 @code{finish} command in the frame inside the selected frame---except
3328 that @code{finish} does not leave an active breakpoint. If you use
3329 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3330 the next time it reaches the current location; this may be useful
3333 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3334 least one instruction has been executed. If it did not do this, you
3335 would be unable to proceed past a breakpoint without first disabling the
3336 breakpoint. This rule applies whether or not the breakpoint already
3337 existed when your program stopped.
3339 @item break @dots{} if @var{cond}
3340 Set a breakpoint with condition @var{cond}; evaluate the expression
3341 @var{cond} each time the breakpoint is reached, and stop only if the
3342 value is nonzero---that is, if @var{cond} evaluates as true.
3343 @samp{@dots{}} stands for one of the possible arguments described
3344 above (or no argument) specifying where to break. @xref{Conditions,
3345 ,Break Conditions}, for more information on breakpoint conditions.
3348 @item tbreak @var{args}
3349 Set a breakpoint enabled only for one stop. @var{args} are the
3350 same as for the @code{break} command, and the breakpoint is set in the same
3351 way, but the breakpoint is automatically deleted after the first time your
3352 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3355 @cindex hardware breakpoints
3356 @item hbreak @var{args}
3357 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3358 @code{break} command and the breakpoint is set in the same way, but the
3359 breakpoint requires hardware support and some target hardware may not
3360 have this support. The main purpose of this is EPROM/ROM code
3361 debugging, so you can set a breakpoint at an instruction without
3362 changing the instruction. This can be used with the new trap-generation
3363 provided by SPARClite DSU and most x86-based targets. These targets
3364 will generate traps when a program accesses some data or instruction
3365 address that is assigned to the debug registers. However the hardware
3366 breakpoint registers can take a limited number of breakpoints. For
3367 example, on the DSU, only two data breakpoints can be set at a time, and
3368 @value{GDBN} will reject this command if more than two are used. Delete
3369 or disable unused hardware breakpoints before setting new ones
3370 (@pxref{Disabling, ,Disabling Breakpoints}).
3371 @xref{Conditions, ,Break Conditions}.
3372 For remote targets, you can restrict the number of hardware
3373 breakpoints @value{GDBN} will use, see @ref{set remote
3374 hardware-breakpoint-limit}.
3377 @item thbreak @var{args}
3378 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3379 are the same as for the @code{hbreak} command and the breakpoint is set in
3380 the same way. However, like the @code{tbreak} command,
3381 the breakpoint is automatically deleted after the
3382 first time your program stops there. Also, like the @code{hbreak}
3383 command, the breakpoint requires hardware support and some target hardware
3384 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3385 See also @ref{Conditions, ,Break Conditions}.
3388 @cindex regular expression
3389 @cindex breakpoints at functions matching a regexp
3390 @cindex set breakpoints in many functions
3391 @item rbreak @var{regex}
3392 Set breakpoints on all functions matching the regular expression
3393 @var{regex}. This command sets an unconditional breakpoint on all
3394 matches, printing a list of all breakpoints it set. Once these
3395 breakpoints are set, they are treated just like the breakpoints set with
3396 the @code{break} command. You can delete them, disable them, or make
3397 them conditional the same way as any other breakpoint.
3399 The syntax of the regular expression is the standard one used with tools
3400 like @file{grep}. Note that this is different from the syntax used by
3401 shells, so for instance @code{foo*} matches all functions that include
3402 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3403 @code{.*} leading and trailing the regular expression you supply, so to
3404 match only functions that begin with @code{foo}, use @code{^foo}.
3406 @cindex non-member C@t{++} functions, set breakpoint in
3407 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3408 breakpoints on overloaded functions that are not members of any special
3411 @cindex set breakpoints on all functions
3412 The @code{rbreak} command can be used to set breakpoints in
3413 @strong{all} the functions in a program, like this:
3416 (@value{GDBP}) rbreak .
3419 @item rbreak @var{file}:@var{regex}
3420 If @code{rbreak} is called with a filename qualification, it limits
3421 the search for functions matching the given regular expression to the
3422 specified @var{file}. This can be used, for example, to set breakpoints on
3423 every function in a given file:
3426 (@value{GDBP}) rbreak file.c:.
3429 The colon separating the filename qualifier from the regex may
3430 optionally be surrounded by spaces.
3432 @kindex info breakpoints
3433 @cindex @code{$_} and @code{info breakpoints}
3434 @item info breakpoints @r{[}@var{n}@r{]}
3435 @itemx info break @r{[}@var{n}@r{]}
3436 Print a table of all breakpoints, watchpoints, and catchpoints set and
3437 not deleted. Optional argument @var{n} means print information only
3438 about the specified breakpoint (or watchpoint or catchpoint). For
3439 each breakpoint, following columns are printed:
3442 @item Breakpoint Numbers
3444 Breakpoint, watchpoint, or catchpoint.
3446 Whether the breakpoint is marked to be disabled or deleted when hit.
3447 @item Enabled or Disabled
3448 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3449 that are not enabled.
3451 Where the breakpoint is in your program, as a memory address. For a
3452 pending breakpoint whose address is not yet known, this field will
3453 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3454 library that has the symbol or line referred by breakpoint is loaded.
3455 See below for details. A breakpoint with several locations will
3456 have @samp{<MULTIPLE>} in this field---see below for details.
3458 Where the breakpoint is in the source for your program, as a file and
3459 line number. For a pending breakpoint, the original string passed to
3460 the breakpoint command will be listed as it cannot be resolved until
3461 the appropriate shared library is loaded in the future.
3465 If a breakpoint is conditional, @code{info break} shows the condition on
3466 the line following the affected breakpoint; breakpoint commands, if any,
3467 are listed after that. A pending breakpoint is allowed to have a condition
3468 specified for it. The condition is not parsed for validity until a shared
3469 library is loaded that allows the pending breakpoint to resolve to a
3473 @code{info break} with a breakpoint
3474 number @var{n} as argument lists only that breakpoint. The
3475 convenience variable @code{$_} and the default examining-address for
3476 the @code{x} command are set to the address of the last breakpoint
3477 listed (@pxref{Memory, ,Examining Memory}).
3480 @code{info break} displays a count of the number of times the breakpoint
3481 has been hit. This is especially useful in conjunction with the
3482 @code{ignore} command. You can ignore a large number of breakpoint
3483 hits, look at the breakpoint info to see how many times the breakpoint
3484 was hit, and then run again, ignoring one less than that number. This
3485 will get you quickly to the last hit of that breakpoint.
3488 @value{GDBN} allows you to set any number of breakpoints at the same place in
3489 your program. There is nothing silly or meaningless about this. When
3490 the breakpoints are conditional, this is even useful
3491 (@pxref{Conditions, ,Break Conditions}).
3493 @cindex multiple locations, breakpoints
3494 @cindex breakpoints, multiple locations
3495 It is possible that a breakpoint corresponds to several locations
3496 in your program. Examples of this situation are:
3500 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3501 instances of the function body, used in different cases.
3504 For a C@t{++} template function, a given line in the function can
3505 correspond to any number of instantiations.
3508 For an inlined function, a given source line can correspond to
3509 several places where that function is inlined.
3512 In all those cases, @value{GDBN} will insert a breakpoint at all
3513 the relevant locations@footnote{
3514 As of this writing, multiple-location breakpoints work only if there's
3515 line number information for all the locations. This means that they
3516 will generally not work in system libraries, unless you have debug
3517 info with line numbers for them.}.
3519 A breakpoint with multiple locations is displayed in the breakpoint
3520 table using several rows---one header row, followed by one row for
3521 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3522 address column. The rows for individual locations contain the actual
3523 addresses for locations, and show the functions to which those
3524 locations belong. The number column for a location is of the form
3525 @var{breakpoint-number}.@var{location-number}.
3530 Num Type Disp Enb Address What
3531 1 breakpoint keep y <MULTIPLE>
3533 breakpoint already hit 1 time
3534 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3535 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3538 Each location can be individually enabled or disabled by passing
3539 @var{breakpoint-number}.@var{location-number} as argument to the
3540 @code{enable} and @code{disable} commands. Note that you cannot
3541 delete the individual locations from the list, you can only delete the
3542 entire list of locations that belong to their parent breakpoint (with
3543 the @kbd{delete @var{num}} command, where @var{num} is the number of
3544 the parent breakpoint, 1 in the above example). Disabling or enabling
3545 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3546 that belong to that breakpoint.
3548 @cindex pending breakpoints
3549 It's quite common to have a breakpoint inside a shared library.
3550 Shared libraries can be loaded and unloaded explicitly,
3551 and possibly repeatedly, as the program is executed. To support
3552 this use case, @value{GDBN} updates breakpoint locations whenever
3553 any shared library is loaded or unloaded. Typically, you would
3554 set a breakpoint in a shared library at the beginning of your
3555 debugging session, when the library is not loaded, and when the
3556 symbols from the library are not available. When you try to set
3557 breakpoint, @value{GDBN} will ask you if you want to set
3558 a so called @dfn{pending breakpoint}---breakpoint whose address
3559 is not yet resolved.
3561 After the program is run, whenever a new shared library is loaded,
3562 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3563 shared library contains the symbol or line referred to by some
3564 pending breakpoint, that breakpoint is resolved and becomes an
3565 ordinary breakpoint. When a library is unloaded, all breakpoints
3566 that refer to its symbols or source lines become pending again.
3568 This logic works for breakpoints with multiple locations, too. For
3569 example, if you have a breakpoint in a C@t{++} template function, and
3570 a newly loaded shared library has an instantiation of that template,
3571 a new location is added to the list of locations for the breakpoint.
3573 Except for having unresolved address, pending breakpoints do not
3574 differ from regular breakpoints. You can set conditions or commands,
3575 enable and disable them and perform other breakpoint operations.
3577 @value{GDBN} provides some additional commands for controlling what
3578 happens when the @samp{break} command cannot resolve breakpoint
3579 address specification to an address:
3581 @kindex set breakpoint pending
3582 @kindex show breakpoint pending
3584 @item set breakpoint pending auto
3585 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3586 location, it queries you whether a pending breakpoint should be created.
3588 @item set breakpoint pending on
3589 This indicates that an unrecognized breakpoint location should automatically
3590 result in a pending breakpoint being created.
3592 @item set breakpoint pending off
3593 This indicates that pending breakpoints are not to be created. Any
3594 unrecognized breakpoint location results in an error. This setting does
3595 not affect any pending breakpoints previously created.
3597 @item show breakpoint pending
3598 Show the current behavior setting for creating pending breakpoints.
3601 The settings above only affect the @code{break} command and its
3602 variants. Once breakpoint is set, it will be automatically updated
3603 as shared libraries are loaded and unloaded.
3605 @cindex automatic hardware breakpoints
3606 For some targets, @value{GDBN} can automatically decide if hardware or
3607 software breakpoints should be used, depending on whether the
3608 breakpoint address is read-only or read-write. This applies to
3609 breakpoints set with the @code{break} command as well as to internal
3610 breakpoints set by commands like @code{next} and @code{finish}. For
3611 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3614 You can control this automatic behaviour with the following commands::
3616 @kindex set breakpoint auto-hw
3617 @kindex show breakpoint auto-hw
3619 @item set breakpoint auto-hw on
3620 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3621 will try to use the target memory map to decide if software or hardware
3622 breakpoint must be used.
3624 @item set breakpoint auto-hw off
3625 This indicates @value{GDBN} should not automatically select breakpoint
3626 type. If the target provides a memory map, @value{GDBN} will warn when
3627 trying to set software breakpoint at a read-only address.
3630 @value{GDBN} normally implements breakpoints by replacing the program code
3631 at the breakpoint address with a special instruction, which, when
3632 executed, given control to the debugger. By default, the program
3633 code is so modified only when the program is resumed. As soon as
3634 the program stops, @value{GDBN} restores the original instructions. This
3635 behaviour guards against leaving breakpoints inserted in the
3636 target should gdb abrubptly disconnect. However, with slow remote
3637 targets, inserting and removing breakpoint can reduce the performance.
3638 This behavior can be controlled with the following commands::
3640 @kindex set breakpoint always-inserted
3641 @kindex show breakpoint always-inserted
3643 @item set breakpoint always-inserted off
3644 All breakpoints, including newly added by the user, are inserted in
3645 the target only when the target is resumed. All breakpoints are
3646 removed from the target when it stops.
3648 @item set breakpoint always-inserted on
3649 Causes all breakpoints to be inserted in the target at all times. If
3650 the user adds a new breakpoint, or changes an existing breakpoint, the
3651 breakpoints in the target are updated immediately. A breakpoint is
3652 removed from the target only when breakpoint itself is removed.
3654 @cindex non-stop mode, and @code{breakpoint always-inserted}
3655 @item set breakpoint always-inserted auto
3656 This is the default mode. If @value{GDBN} is controlling the inferior
3657 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3658 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3659 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3660 @code{breakpoint always-inserted} mode is off.
3663 @cindex negative breakpoint numbers
3664 @cindex internal @value{GDBN} breakpoints
3665 @value{GDBN} itself sometimes sets breakpoints in your program for
3666 special purposes, such as proper handling of @code{longjmp} (in C
3667 programs). These internal breakpoints are assigned negative numbers,
3668 starting with @code{-1}; @samp{info breakpoints} does not display them.
3669 You can see these breakpoints with the @value{GDBN} maintenance command
3670 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3673 @node Set Watchpoints
3674 @subsection Setting Watchpoints
3676 @cindex setting watchpoints
3677 You can use a watchpoint to stop execution whenever the value of an
3678 expression changes, without having to predict a particular place where
3679 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3680 The expression may be as simple as the value of a single variable, or
3681 as complex as many variables combined by operators. Examples include:
3685 A reference to the value of a single variable.
3688 An address cast to an appropriate data type. For example,
3689 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3690 address (assuming an @code{int} occupies 4 bytes).
3693 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3694 expression can use any operators valid in the program's native
3695 language (@pxref{Languages}).
3698 You can set a watchpoint on an expression even if the expression can
3699 not be evaluated yet. For instance, you can set a watchpoint on
3700 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3701 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3702 the expression produces a valid value. If the expression becomes
3703 valid in some other way than changing a variable (e.g.@: if the memory
3704 pointed to by @samp{*global_ptr} becomes readable as the result of a
3705 @code{malloc} call), @value{GDBN} may not stop until the next time
3706 the expression changes.
3708 @cindex software watchpoints
3709 @cindex hardware watchpoints
3710 Depending on your system, watchpoints may be implemented in software or
3711 hardware. @value{GDBN} does software watchpointing by single-stepping your
3712 program and testing the variable's value each time, which is hundreds of
3713 times slower than normal execution. (But this may still be worth it, to
3714 catch errors where you have no clue what part of your program is the
3717 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3718 x86-based targets, @value{GDBN} includes support for hardware
3719 watchpoints, which do not slow down the running of your program.
3723 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3724 Set a watchpoint for an expression. @value{GDBN} will break when the
3725 expression @var{expr} is written into by the program and its value
3726 changes. The simplest (and the most popular) use of this command is
3727 to watch the value of a single variable:
3730 (@value{GDBP}) watch foo
3733 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3734 clause, @value{GDBN} breaks only when the thread identified by
3735 @var{threadnum} changes the value of @var{expr}. If any other threads
3736 change the value of @var{expr}, @value{GDBN} will not break. Note
3737 that watchpoints restricted to a single thread in this way only work
3738 with Hardware Watchpoints.
3740 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3741 (see below). The @code{-location} argument tells @value{GDBN} to
3742 instead watch the memory referred to by @var{expr}. In this case,
3743 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3744 and watch the memory at that address. The type of the result is used
3745 to determine the size of the watched memory. If the expression's
3746 result does not have an address, then @value{GDBN} will print an
3750 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3751 Set a watchpoint that will break when the value of @var{expr} is read
3755 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3756 Set a watchpoint that will break when @var{expr} is either read from
3757 or written into by the program.
3759 @kindex info watchpoints @r{[}@var{n}@r{]}
3760 @item info watchpoints
3761 This command prints a list of watchpoints, using the same format as
3762 @code{info break} (@pxref{Set Breaks}).
3765 If you watch for a change in a numerically entered address you need to
3766 dereference it, as the address itself is just a constant number which will
3767 never change. @value{GDBN} refuses to create a watchpoint that watches
3768 a never-changing value:
3771 (@value{GDBP}) watch 0x600850
3772 Cannot watch constant value 0x600850.
3773 (@value{GDBP}) watch *(int *) 0x600850
3774 Watchpoint 1: *(int *) 6293584
3777 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3778 watchpoints execute very quickly, and the debugger reports a change in
3779 value at the exact instruction where the change occurs. If @value{GDBN}
3780 cannot set a hardware watchpoint, it sets a software watchpoint, which
3781 executes more slowly and reports the change in value at the next
3782 @emph{statement}, not the instruction, after the change occurs.
3784 @cindex use only software watchpoints
3785 You can force @value{GDBN} to use only software watchpoints with the
3786 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3787 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3788 the underlying system supports them. (Note that hardware-assisted
3789 watchpoints that were set @emph{before} setting
3790 @code{can-use-hw-watchpoints} to zero will still use the hardware
3791 mechanism of watching expression values.)
3794 @item set can-use-hw-watchpoints
3795 @kindex set can-use-hw-watchpoints
3796 Set whether or not to use hardware watchpoints.
3798 @item show can-use-hw-watchpoints
3799 @kindex show can-use-hw-watchpoints
3800 Show the current mode of using hardware watchpoints.
3803 For remote targets, you can restrict the number of hardware
3804 watchpoints @value{GDBN} will use, see @ref{set remote
3805 hardware-breakpoint-limit}.
3807 When you issue the @code{watch} command, @value{GDBN} reports
3810 Hardware watchpoint @var{num}: @var{expr}
3814 if it was able to set a hardware watchpoint.
3816 Currently, the @code{awatch} and @code{rwatch} commands can only set
3817 hardware watchpoints, because accesses to data that don't change the
3818 value of the watched expression cannot be detected without examining
3819 every instruction as it is being executed, and @value{GDBN} does not do
3820 that currently. If @value{GDBN} finds that it is unable to set a
3821 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3822 will print a message like this:
3825 Expression cannot be implemented with read/access watchpoint.
3828 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3829 data type of the watched expression is wider than what a hardware
3830 watchpoint on the target machine can handle. For example, some systems
3831 can only watch regions that are up to 4 bytes wide; on such systems you
3832 cannot set hardware watchpoints for an expression that yields a
3833 double-precision floating-point number (which is typically 8 bytes
3834 wide). As a work-around, it might be possible to break the large region
3835 into a series of smaller ones and watch them with separate watchpoints.
3837 If you set too many hardware watchpoints, @value{GDBN} might be unable
3838 to insert all of them when you resume the execution of your program.
3839 Since the precise number of active watchpoints is unknown until such
3840 time as the program is about to be resumed, @value{GDBN} might not be
3841 able to warn you about this when you set the watchpoints, and the
3842 warning will be printed only when the program is resumed:
3845 Hardware watchpoint @var{num}: Could not insert watchpoint
3849 If this happens, delete or disable some of the watchpoints.
3851 Watching complex expressions that reference many variables can also
3852 exhaust the resources available for hardware-assisted watchpoints.
3853 That's because @value{GDBN} needs to watch every variable in the
3854 expression with separately allocated resources.
3856 If you call a function interactively using @code{print} or @code{call},
3857 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3858 kind of breakpoint or the call completes.
3860 @value{GDBN} automatically deletes watchpoints that watch local
3861 (automatic) variables, or expressions that involve such variables, when
3862 they go out of scope, that is, when the execution leaves the block in
3863 which these variables were defined. In particular, when the program
3864 being debugged terminates, @emph{all} local variables go out of scope,
3865 and so only watchpoints that watch global variables remain set. If you
3866 rerun the program, you will need to set all such watchpoints again. One
3867 way of doing that would be to set a code breakpoint at the entry to the
3868 @code{main} function and when it breaks, set all the watchpoints.
3870 @cindex watchpoints and threads
3871 @cindex threads and watchpoints
3872 In multi-threaded programs, watchpoints will detect changes to the
3873 watched expression from every thread.
3876 @emph{Warning:} In multi-threaded programs, software watchpoints
3877 have only limited usefulness. If @value{GDBN} creates a software
3878 watchpoint, it can only watch the value of an expression @emph{in a
3879 single thread}. If you are confident that the expression can only
3880 change due to the current thread's activity (and if you are also
3881 confident that no other thread can become current), then you can use
3882 software watchpoints as usual. However, @value{GDBN} may not notice
3883 when a non-current thread's activity changes the expression. (Hardware
3884 watchpoints, in contrast, watch an expression in all threads.)
3887 @xref{set remote hardware-watchpoint-limit}.
3889 @node Set Catchpoints
3890 @subsection Setting Catchpoints
3891 @cindex catchpoints, setting
3892 @cindex exception handlers
3893 @cindex event handling
3895 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3896 kinds of program events, such as C@t{++} exceptions or the loading of a
3897 shared library. Use the @code{catch} command to set a catchpoint.
3901 @item catch @var{event}
3902 Stop when @var{event} occurs. @var{event} can be any of the following:
3905 @cindex stop on C@t{++} exceptions
3906 The throwing of a C@t{++} exception.
3909 The catching of a C@t{++} exception.
3912 @cindex Ada exception catching
3913 @cindex catch Ada exceptions
3914 An Ada exception being raised. If an exception name is specified
3915 at the end of the command (eg @code{catch exception Program_Error}),
3916 the debugger will stop only when this specific exception is raised.
3917 Otherwise, the debugger stops execution when any Ada exception is raised.
3919 When inserting an exception catchpoint on a user-defined exception whose
3920 name is identical to one of the exceptions defined by the language, the
3921 fully qualified name must be used as the exception name. Otherwise,
3922 @value{GDBN} will assume that it should stop on the pre-defined exception
3923 rather than the user-defined one. For instance, assuming an exception
3924 called @code{Constraint_Error} is defined in package @code{Pck}, then
3925 the command to use to catch such exceptions is @kbd{catch exception
3926 Pck.Constraint_Error}.
3928 @item exception unhandled
3929 An exception that was raised but is not handled by the program.
3932 A failed Ada assertion.
3935 @cindex break on fork/exec
3936 A call to @code{exec}. This is currently only available for HP-UX
3940 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3941 @cindex break on a system call.
3942 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3943 syscall is a mechanism for application programs to request a service
3944 from the operating system (OS) or one of the OS system services.
3945 @value{GDBN} can catch some or all of the syscalls issued by the
3946 debuggee, and show the related information for each syscall. If no
3947 argument is specified, calls to and returns from all system calls
3950 @var{name} can be any system call name that is valid for the
3951 underlying OS. Just what syscalls are valid depends on the OS. On
3952 GNU and Unix systems, you can find the full list of valid syscall
3953 names on @file{/usr/include/asm/unistd.h}.
3955 @c For MS-Windows, the syscall names and the corresponding numbers
3956 @c can be found, e.g., on this URL:
3957 @c http://www.metasploit.com/users/opcode/syscalls.html
3958 @c but we don't support Windows syscalls yet.
3960 Normally, @value{GDBN} knows in advance which syscalls are valid for
3961 each OS, so you can use the @value{GDBN} command-line completion
3962 facilities (@pxref{Completion,, command completion}) to list the
3965 You may also specify the system call numerically. A syscall's
3966 number is the value passed to the OS's syscall dispatcher to
3967 identify the requested service. When you specify the syscall by its
3968 name, @value{GDBN} uses its database of syscalls to convert the name
3969 into the corresponding numeric code, but using the number directly
3970 may be useful if @value{GDBN}'s database does not have the complete
3971 list of syscalls on your system (e.g., because @value{GDBN} lags
3972 behind the OS upgrades).
3974 The example below illustrates how this command works if you don't provide
3978 (@value{GDBP}) catch syscall
3979 Catchpoint 1 (syscall)
3981 Starting program: /tmp/catch-syscall
3983 Catchpoint 1 (call to syscall 'close'), \
3984 0xffffe424 in __kernel_vsyscall ()
3988 Catchpoint 1 (returned from syscall 'close'), \
3989 0xffffe424 in __kernel_vsyscall ()
3993 Here is an example of catching a system call by name:
3996 (@value{GDBP}) catch syscall chroot
3997 Catchpoint 1 (syscall 'chroot' [61])
3999 Starting program: /tmp/catch-syscall
4001 Catchpoint 1 (call to syscall 'chroot'), \
4002 0xffffe424 in __kernel_vsyscall ()
4006 Catchpoint 1 (returned from syscall 'chroot'), \
4007 0xffffe424 in __kernel_vsyscall ()
4011 An example of specifying a system call numerically. In the case
4012 below, the syscall number has a corresponding entry in the XML
4013 file, so @value{GDBN} finds its name and prints it:
4016 (@value{GDBP}) catch syscall 252
4017 Catchpoint 1 (syscall(s) 'exit_group')
4019 Starting program: /tmp/catch-syscall
4021 Catchpoint 1 (call to syscall 'exit_group'), \
4022 0xffffe424 in __kernel_vsyscall ()
4026 Program exited normally.
4030 However, there can be situations when there is no corresponding name
4031 in XML file for that syscall number. In this case, @value{GDBN} prints
4032 a warning message saying that it was not able to find the syscall name,
4033 but the catchpoint will be set anyway. See the example below:
4036 (@value{GDBP}) catch syscall 764
4037 warning: The number '764' does not represent a known syscall.
4038 Catchpoint 2 (syscall 764)
4042 If you configure @value{GDBN} using the @samp{--without-expat} option,
4043 it will not be able to display syscall names. Also, if your
4044 architecture does not have an XML file describing its system calls,
4045 you will not be able to see the syscall names. It is important to
4046 notice that these two features are used for accessing the syscall
4047 name database. In either case, you will see a warning like this:
4050 (@value{GDBP}) catch syscall
4051 warning: Could not open "syscalls/i386-linux.xml"
4052 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4053 GDB will not be able to display syscall names.
4054 Catchpoint 1 (syscall)
4058 Of course, the file name will change depending on your architecture and system.
4060 Still using the example above, you can also try to catch a syscall by its
4061 number. In this case, you would see something like:
4064 (@value{GDBP}) catch syscall 252
4065 Catchpoint 1 (syscall(s) 252)
4068 Again, in this case @value{GDBN} would not be able to display syscall's names.
4071 A call to @code{fork}. This is currently only available for HP-UX
4075 A call to @code{vfork}. This is currently only available for HP-UX
4080 @item tcatch @var{event}
4081 Set a catchpoint that is enabled only for one stop. The catchpoint is
4082 automatically deleted after the first time the event is caught.
4086 Use the @code{info break} command to list the current catchpoints.
4088 There are currently some limitations to C@t{++} exception handling
4089 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4093 If you call a function interactively, @value{GDBN} normally returns
4094 control to you when the function has finished executing. If the call
4095 raises an exception, however, the call may bypass the mechanism that
4096 returns control to you and cause your program either to abort or to
4097 simply continue running until it hits a breakpoint, catches a signal
4098 that @value{GDBN} is listening for, or exits. This is the case even if
4099 you set a catchpoint for the exception; catchpoints on exceptions are
4100 disabled within interactive calls.
4103 You cannot raise an exception interactively.
4106 You cannot install an exception handler interactively.
4109 @cindex raise exceptions
4110 Sometimes @code{catch} is not the best way to debug exception handling:
4111 if you need to know exactly where an exception is raised, it is better to
4112 stop @emph{before} the exception handler is called, since that way you
4113 can see the stack before any unwinding takes place. If you set a
4114 breakpoint in an exception handler instead, it may not be easy to find
4115 out where the exception was raised.
4117 To stop just before an exception handler is called, you need some
4118 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4119 raised by calling a library function named @code{__raise_exception}
4120 which has the following ANSI C interface:
4123 /* @var{addr} is where the exception identifier is stored.
4124 @var{id} is the exception identifier. */
4125 void __raise_exception (void **addr, void *id);
4129 To make the debugger catch all exceptions before any stack
4130 unwinding takes place, set a breakpoint on @code{__raise_exception}
4131 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4133 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4134 that depends on the value of @var{id}, you can stop your program when
4135 a specific exception is raised. You can use multiple conditional
4136 breakpoints to stop your program when any of a number of exceptions are
4141 @subsection Deleting Breakpoints
4143 @cindex clearing breakpoints, watchpoints, catchpoints
4144 @cindex deleting breakpoints, watchpoints, catchpoints
4145 It is often necessary to eliminate a breakpoint, watchpoint, or
4146 catchpoint once it has done its job and you no longer want your program
4147 to stop there. This is called @dfn{deleting} the breakpoint. A
4148 breakpoint that has been deleted no longer exists; it is forgotten.
4150 With the @code{clear} command you can delete breakpoints according to
4151 where they are in your program. With the @code{delete} command you can
4152 delete individual breakpoints, watchpoints, or catchpoints by specifying
4153 their breakpoint numbers.
4155 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4156 automatically ignores breakpoints on the first instruction to be executed
4157 when you continue execution without changing the execution address.
4162 Delete any breakpoints at the next instruction to be executed in the
4163 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4164 the innermost frame is selected, this is a good way to delete a
4165 breakpoint where your program just stopped.
4167 @item clear @var{location}
4168 Delete any breakpoints set at the specified @var{location}.
4169 @xref{Specify Location}, for the various forms of @var{location}; the
4170 most useful ones are listed below:
4173 @item clear @var{function}
4174 @itemx clear @var{filename}:@var{function}
4175 Delete any breakpoints set at entry to the named @var{function}.
4177 @item clear @var{linenum}
4178 @itemx clear @var{filename}:@var{linenum}
4179 Delete any breakpoints set at or within the code of the specified
4180 @var{linenum} of the specified @var{filename}.
4183 @cindex delete breakpoints
4185 @kindex d @r{(@code{delete})}
4186 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4187 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4188 ranges specified as arguments. If no argument is specified, delete all
4189 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4190 confirm off}). You can abbreviate this command as @code{d}.
4194 @subsection Disabling Breakpoints
4196 @cindex enable/disable a breakpoint
4197 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4198 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4199 it had been deleted, but remembers the information on the breakpoint so
4200 that you can @dfn{enable} it again later.
4202 You disable and enable breakpoints, watchpoints, and catchpoints with
4203 the @code{enable} and @code{disable} commands, optionally specifying
4204 one or more breakpoint numbers as arguments. Use @code{info break} to
4205 print a list of all breakpoints, watchpoints, and catchpoints if you
4206 do not know which numbers to use.
4208 Disabling and enabling a breakpoint that has multiple locations
4209 affects all of its locations.
4211 A breakpoint, watchpoint, or catchpoint can have any of four different
4212 states of enablement:
4216 Enabled. The breakpoint stops your program. A breakpoint set
4217 with the @code{break} command starts out in this state.
4219 Disabled. The breakpoint has no effect on your program.
4221 Enabled once. The breakpoint stops your program, but then becomes
4224 Enabled for deletion. The breakpoint stops your program, but
4225 immediately after it does so it is deleted permanently. A breakpoint
4226 set with the @code{tbreak} command starts out in this state.
4229 You can use the following commands to enable or disable breakpoints,
4230 watchpoints, and catchpoints:
4234 @kindex dis @r{(@code{disable})}
4235 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4236 Disable the specified breakpoints---or all breakpoints, if none are
4237 listed. A disabled breakpoint has no effect but is not forgotten. All
4238 options such as ignore-counts, conditions and commands are remembered in
4239 case the breakpoint is enabled again later. You may abbreviate
4240 @code{disable} as @code{dis}.
4243 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4244 Enable the specified breakpoints (or all defined breakpoints). They
4245 become effective once again in stopping your program.
4247 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4248 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4249 of these breakpoints immediately after stopping your program.
4251 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4252 Enable the specified breakpoints to work once, then die. @value{GDBN}
4253 deletes any of these breakpoints as soon as your program stops there.
4254 Breakpoints set by the @code{tbreak} command start out in this state.
4257 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4258 @c confusing: tbreak is also initially enabled.
4259 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4260 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4261 subsequently, they become disabled or enabled only when you use one of
4262 the commands above. (The command @code{until} can set and delete a
4263 breakpoint of its own, but it does not change the state of your other
4264 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4268 @subsection Break Conditions
4269 @cindex conditional breakpoints
4270 @cindex breakpoint conditions
4272 @c FIXME what is scope of break condition expr? Context where wanted?
4273 @c in particular for a watchpoint?
4274 The simplest sort of breakpoint breaks every time your program reaches a
4275 specified place. You can also specify a @dfn{condition} for a
4276 breakpoint. A condition is just a Boolean expression in your
4277 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4278 a condition evaluates the expression each time your program reaches it,
4279 and your program stops only if the condition is @emph{true}.
4281 This is the converse of using assertions for program validation; in that
4282 situation, you want to stop when the assertion is violated---that is,
4283 when the condition is false. In C, if you want to test an assertion expressed
4284 by the condition @var{assert}, you should set the condition
4285 @samp{! @var{assert}} on the appropriate breakpoint.
4287 Conditions are also accepted for watchpoints; you may not need them,
4288 since a watchpoint is inspecting the value of an expression anyhow---but
4289 it might be simpler, say, to just set a watchpoint on a variable name,
4290 and specify a condition that tests whether the new value is an interesting
4293 Break conditions can have side effects, and may even call functions in
4294 your program. This can be useful, for example, to activate functions
4295 that log program progress, or to use your own print functions to
4296 format special data structures. The effects are completely predictable
4297 unless there is another enabled breakpoint at the same address. (In
4298 that case, @value{GDBN} might see the other breakpoint first and stop your
4299 program without checking the condition of this one.) Note that
4300 breakpoint commands are usually more convenient and flexible than break
4302 purpose of performing side effects when a breakpoint is reached
4303 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4305 Break conditions can be specified when a breakpoint is set, by using
4306 @samp{if} in the arguments to the @code{break} command. @xref{Set
4307 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4308 with the @code{condition} command.
4310 You can also use the @code{if} keyword with the @code{watch} command.
4311 The @code{catch} command does not recognize the @code{if} keyword;
4312 @code{condition} is the only way to impose a further condition on a
4317 @item condition @var{bnum} @var{expression}
4318 Specify @var{expression} as the break condition for breakpoint,
4319 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4320 breakpoint @var{bnum} stops your program only if the value of
4321 @var{expression} is true (nonzero, in C). When you use
4322 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4323 syntactic correctness, and to determine whether symbols in it have
4324 referents in the context of your breakpoint. If @var{expression} uses
4325 symbols not referenced in the context of the breakpoint, @value{GDBN}
4326 prints an error message:
4329 No symbol "foo" in current context.
4334 not actually evaluate @var{expression} at the time the @code{condition}
4335 command (or a command that sets a breakpoint with a condition, like
4336 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4338 @item condition @var{bnum}
4339 Remove the condition from breakpoint number @var{bnum}. It becomes
4340 an ordinary unconditional breakpoint.
4343 @cindex ignore count (of breakpoint)
4344 A special case of a breakpoint condition is to stop only when the
4345 breakpoint has been reached a certain number of times. This is so
4346 useful that there is a special way to do it, using the @dfn{ignore
4347 count} of the breakpoint. Every breakpoint has an ignore count, which
4348 is an integer. Most of the time, the ignore count is zero, and
4349 therefore has no effect. But if your program reaches a breakpoint whose
4350 ignore count is positive, then instead of stopping, it just decrements
4351 the ignore count by one and continues. As a result, if the ignore count
4352 value is @var{n}, the breakpoint does not stop the next @var{n} times
4353 your program reaches it.
4357 @item ignore @var{bnum} @var{count}
4358 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4359 The next @var{count} times the breakpoint is reached, your program's
4360 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4363 To make the breakpoint stop the next time it is reached, specify
4366 When you use @code{continue} to resume execution of your program from a
4367 breakpoint, you can specify an ignore count directly as an argument to
4368 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4369 Stepping,,Continuing and Stepping}.
4371 If a breakpoint has a positive ignore count and a condition, the
4372 condition is not checked. Once the ignore count reaches zero,
4373 @value{GDBN} resumes checking the condition.
4375 You could achieve the effect of the ignore count with a condition such
4376 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4377 is decremented each time. @xref{Convenience Vars, ,Convenience
4381 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4384 @node Break Commands
4385 @subsection Breakpoint Command Lists
4387 @cindex breakpoint commands
4388 You can give any breakpoint (or watchpoint or catchpoint) a series of
4389 commands to execute when your program stops due to that breakpoint. For
4390 example, you might want to print the values of certain expressions, or
4391 enable other breakpoints.
4395 @kindex end@r{ (breakpoint commands)}
4396 @item commands @r{[}@var{range}@dots{}@r{]}
4397 @itemx @dots{} @var{command-list} @dots{}
4399 Specify a list of commands for the given breakpoints. The commands
4400 themselves appear on the following lines. Type a line containing just
4401 @code{end} to terminate the commands.
4403 To remove all commands from a breakpoint, type @code{commands} and
4404 follow it immediately with @code{end}; that is, give no commands.
4406 With no argument, @code{commands} refers to the last breakpoint,
4407 watchpoint, or catchpoint set (not to the breakpoint most recently
4408 encountered). If the most recent breakpoints were set with a single
4409 command, then the @code{commands} will apply to all the breakpoints
4410 set by that command. This applies to breakpoints set by
4411 @code{rbreak}, and also applies when a single @code{break} command
4412 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4416 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4417 disabled within a @var{command-list}.
4419 You can use breakpoint commands to start your program up again. Simply
4420 use the @code{continue} command, or @code{step}, or any other command
4421 that resumes execution.
4423 Any other commands in the command list, after a command that resumes
4424 execution, are ignored. This is because any time you resume execution
4425 (even with a simple @code{next} or @code{step}), you may encounter
4426 another breakpoint---which could have its own command list, leading to
4427 ambiguities about which list to execute.
4430 If the first command you specify in a command list is @code{silent}, the
4431 usual message about stopping at a breakpoint is not printed. This may
4432 be desirable for breakpoints that are to print a specific message and
4433 then continue. If none of the remaining commands print anything, you
4434 see no sign that the breakpoint was reached. @code{silent} is
4435 meaningful only at the beginning of a breakpoint command list.
4437 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4438 print precisely controlled output, and are often useful in silent
4439 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4441 For example, here is how you could use breakpoint commands to print the
4442 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4448 printf "x is %d\n",x
4453 One application for breakpoint commands is to compensate for one bug so
4454 you can test for another. Put a breakpoint just after the erroneous line
4455 of code, give it a condition to detect the case in which something
4456 erroneous has been done, and give it commands to assign correct values
4457 to any variables that need them. End with the @code{continue} command
4458 so that your program does not stop, and start with the @code{silent}
4459 command so that no output is produced. Here is an example:
4470 @node Save Breakpoints
4471 @subsection How to save breakpoints to a file
4473 To save breakpoint definitions to a file use the @w{@code{save
4474 breakpoints}} command.
4477 @kindex save breakpoints
4478 @cindex save breakpoints to a file for future sessions
4479 @item save breakpoints [@var{filename}]
4480 This command saves all current breakpoint definitions together with
4481 their commands and ignore counts, into a file @file{@var{filename}}
4482 suitable for use in a later debugging session. This includes all
4483 types of breakpoints (breakpoints, watchpoints, catchpoints,
4484 tracepoints). To read the saved breakpoint definitions, use the
4485 @code{source} command (@pxref{Command Files}). Note that watchpoints
4486 with expressions involving local variables may fail to be recreated
4487 because it may not be possible to access the context where the
4488 watchpoint is valid anymore. Because the saved breakpoint definitions
4489 are simply a sequence of @value{GDBN} commands that recreate the
4490 breakpoints, you can edit the file in your favorite editing program,
4491 and remove the breakpoint definitions you're not interested in, or
4492 that can no longer be recreated.
4495 @c @ifclear BARETARGET
4496 @node Error in Breakpoints
4497 @subsection ``Cannot insert breakpoints''
4499 If you request too many active hardware-assisted breakpoints and
4500 watchpoints, you will see this error message:
4502 @c FIXME: the precise wording of this message may change; the relevant
4503 @c source change is not committed yet (Sep 3, 1999).
4505 Stopped; cannot insert breakpoints.
4506 You may have requested too many hardware breakpoints and watchpoints.
4510 This message is printed when you attempt to resume the program, since
4511 only then @value{GDBN} knows exactly how many hardware breakpoints and
4512 watchpoints it needs to insert.
4514 When this message is printed, you need to disable or remove some of the
4515 hardware-assisted breakpoints and watchpoints, and then continue.
4517 @node Breakpoint-related Warnings
4518 @subsection ``Breakpoint address adjusted...''
4519 @cindex breakpoint address adjusted
4521 Some processor architectures place constraints on the addresses at
4522 which breakpoints may be placed. For architectures thus constrained,
4523 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4524 with the constraints dictated by the architecture.
4526 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4527 a VLIW architecture in which a number of RISC-like instructions may be
4528 bundled together for parallel execution. The FR-V architecture
4529 constrains the location of a breakpoint instruction within such a
4530 bundle to the instruction with the lowest address. @value{GDBN}
4531 honors this constraint by adjusting a breakpoint's address to the
4532 first in the bundle.
4534 It is not uncommon for optimized code to have bundles which contain
4535 instructions from different source statements, thus it may happen that
4536 a breakpoint's address will be adjusted from one source statement to
4537 another. Since this adjustment may significantly alter @value{GDBN}'s
4538 breakpoint related behavior from what the user expects, a warning is
4539 printed when the breakpoint is first set and also when the breakpoint
4542 A warning like the one below is printed when setting a breakpoint
4543 that's been subject to address adjustment:
4546 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4549 Such warnings are printed both for user settable and @value{GDBN}'s
4550 internal breakpoints. If you see one of these warnings, you should
4551 verify that a breakpoint set at the adjusted address will have the
4552 desired affect. If not, the breakpoint in question may be removed and
4553 other breakpoints may be set which will have the desired behavior.
4554 E.g., it may be sufficient to place the breakpoint at a later
4555 instruction. A conditional breakpoint may also be useful in some
4556 cases to prevent the breakpoint from triggering too often.
4558 @value{GDBN} will also issue a warning when stopping at one of these
4559 adjusted breakpoints:
4562 warning: Breakpoint 1 address previously adjusted from 0x00010414
4566 When this warning is encountered, it may be too late to take remedial
4567 action except in cases where the breakpoint is hit earlier or more
4568 frequently than expected.
4570 @node Continuing and Stepping
4571 @section Continuing and Stepping
4575 @cindex resuming execution
4576 @dfn{Continuing} means resuming program execution until your program
4577 completes normally. In contrast, @dfn{stepping} means executing just
4578 one more ``step'' of your program, where ``step'' may mean either one
4579 line of source code, or one machine instruction (depending on what
4580 particular command you use). Either when continuing or when stepping,
4581 your program may stop even sooner, due to a breakpoint or a signal. (If
4582 it stops due to a signal, you may want to use @code{handle}, or use
4583 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4587 @kindex c @r{(@code{continue})}
4588 @kindex fg @r{(resume foreground execution)}
4589 @item continue @r{[}@var{ignore-count}@r{]}
4590 @itemx c @r{[}@var{ignore-count}@r{]}
4591 @itemx fg @r{[}@var{ignore-count}@r{]}
4592 Resume program execution, at the address where your program last stopped;
4593 any breakpoints set at that address are bypassed. The optional argument
4594 @var{ignore-count} allows you to specify a further number of times to
4595 ignore a breakpoint at this location; its effect is like that of
4596 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4598 The argument @var{ignore-count} is meaningful only when your program
4599 stopped due to a breakpoint. At other times, the argument to
4600 @code{continue} is ignored.
4602 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4603 debugged program is deemed to be the foreground program) are provided
4604 purely for convenience, and have exactly the same behavior as
4608 To resume execution at a different place, you can use @code{return}
4609 (@pxref{Returning, ,Returning from a Function}) to go back to the
4610 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4611 Different Address}) to go to an arbitrary location in your program.
4613 A typical technique for using stepping is to set a breakpoint
4614 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4615 beginning of the function or the section of your program where a problem
4616 is believed to lie, run your program until it stops at that breakpoint,
4617 and then step through the suspect area, examining the variables that are
4618 interesting, until you see the problem happen.
4622 @kindex s @r{(@code{step})}
4624 Continue running your program until control reaches a different source
4625 line, then stop it and return control to @value{GDBN}. This command is
4626 abbreviated @code{s}.
4629 @c "without debugging information" is imprecise; actually "without line
4630 @c numbers in the debugging information". (gcc -g1 has debugging info but
4631 @c not line numbers). But it seems complex to try to make that
4632 @c distinction here.
4633 @emph{Warning:} If you use the @code{step} command while control is
4634 within a function that was compiled without debugging information,
4635 execution proceeds until control reaches a function that does have
4636 debugging information. Likewise, it will not step into a function which
4637 is compiled without debugging information. To step through functions
4638 without debugging information, use the @code{stepi} command, described
4642 The @code{step} command only stops at the first instruction of a source
4643 line. This prevents the multiple stops that could otherwise occur in
4644 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4645 to stop if a function that has debugging information is called within
4646 the line. In other words, @code{step} @emph{steps inside} any functions
4647 called within the line.
4649 Also, the @code{step} command only enters a function if there is line
4650 number information for the function. Otherwise it acts like the
4651 @code{next} command. This avoids problems when using @code{cc -gl}
4652 on MIPS machines. Previously, @code{step} entered subroutines if there
4653 was any debugging information about the routine.
4655 @item step @var{count}
4656 Continue running as in @code{step}, but do so @var{count} times. If a
4657 breakpoint is reached, or a signal not related to stepping occurs before
4658 @var{count} steps, stepping stops right away.
4661 @kindex n @r{(@code{next})}
4662 @item next @r{[}@var{count}@r{]}
4663 Continue to the next source line in the current (innermost) stack frame.
4664 This is similar to @code{step}, but function calls that appear within
4665 the line of code are executed without stopping. Execution stops when
4666 control reaches a different line of code at the original stack level
4667 that was executing when you gave the @code{next} command. This command
4668 is abbreviated @code{n}.
4670 An argument @var{count} is a repeat count, as for @code{step}.
4673 @c FIX ME!! Do we delete this, or is there a way it fits in with
4674 @c the following paragraph? --- Vctoria
4676 @c @code{next} within a function that lacks debugging information acts like
4677 @c @code{step}, but any function calls appearing within the code of the
4678 @c function are executed without stopping.
4680 The @code{next} command only stops at the first instruction of a
4681 source line. This prevents multiple stops that could otherwise occur in
4682 @code{switch} statements, @code{for} loops, etc.
4684 @kindex set step-mode
4686 @cindex functions without line info, and stepping
4687 @cindex stepping into functions with no line info
4688 @itemx set step-mode on
4689 The @code{set step-mode on} command causes the @code{step} command to
4690 stop at the first instruction of a function which contains no debug line
4691 information rather than stepping over it.
4693 This is useful in cases where you may be interested in inspecting the
4694 machine instructions of a function which has no symbolic info and do not
4695 want @value{GDBN} to automatically skip over this function.
4697 @item set step-mode off
4698 Causes the @code{step} command to step over any functions which contains no
4699 debug information. This is the default.
4701 @item show step-mode
4702 Show whether @value{GDBN} will stop in or step over functions without
4703 source line debug information.
4706 @kindex fin @r{(@code{finish})}
4708 Continue running until just after function in the selected stack frame
4709 returns. Print the returned value (if any). This command can be
4710 abbreviated as @code{fin}.
4712 Contrast this with the @code{return} command (@pxref{Returning,
4713 ,Returning from a Function}).
4716 @kindex u @r{(@code{until})}
4717 @cindex run until specified location
4720 Continue running until a source line past the current line, in the
4721 current stack frame, is reached. This command is used to avoid single
4722 stepping through a loop more than once. It is like the @code{next}
4723 command, except that when @code{until} encounters a jump, it
4724 automatically continues execution until the program counter is greater
4725 than the address of the jump.
4727 This means that when you reach the end of a loop after single stepping
4728 though it, @code{until} makes your program continue execution until it
4729 exits the loop. In contrast, a @code{next} command at the end of a loop
4730 simply steps back to the beginning of the loop, which forces you to step
4731 through the next iteration.
4733 @code{until} always stops your program if it attempts to exit the current
4736 @code{until} may produce somewhat counterintuitive results if the order
4737 of machine code does not match the order of the source lines. For
4738 example, in the following excerpt from a debugging session, the @code{f}
4739 (@code{frame}) command shows that execution is stopped at line
4740 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4744 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4746 (@value{GDBP}) until
4747 195 for ( ; argc > 0; NEXTARG) @{
4750 This happened because, for execution efficiency, the compiler had
4751 generated code for the loop closure test at the end, rather than the
4752 start, of the loop---even though the test in a C @code{for}-loop is
4753 written before the body of the loop. The @code{until} command appeared
4754 to step back to the beginning of the loop when it advanced to this
4755 expression; however, it has not really gone to an earlier
4756 statement---not in terms of the actual machine code.
4758 @code{until} with no argument works by means of single
4759 instruction stepping, and hence is slower than @code{until} with an
4762 @item until @var{location}
4763 @itemx u @var{location}
4764 Continue running your program until either the specified location is
4765 reached, or the current stack frame returns. @var{location} is any of
4766 the forms described in @ref{Specify Location}.
4767 This form of the command uses temporary breakpoints, and
4768 hence is quicker than @code{until} without an argument. The specified
4769 location is actually reached only if it is in the current frame. This
4770 implies that @code{until} can be used to skip over recursive function
4771 invocations. For instance in the code below, if the current location is
4772 line @code{96}, issuing @code{until 99} will execute the program up to
4773 line @code{99} in the same invocation of factorial, i.e., after the inner
4774 invocations have returned.
4777 94 int factorial (int value)
4779 96 if (value > 1) @{
4780 97 value *= factorial (value - 1);
4787 @kindex advance @var{location}
4788 @itemx advance @var{location}
4789 Continue running the program up to the given @var{location}. An argument is
4790 required, which should be of one of the forms described in
4791 @ref{Specify Location}.
4792 Execution will also stop upon exit from the current stack
4793 frame. This command is similar to @code{until}, but @code{advance} will
4794 not skip over recursive function calls, and the target location doesn't
4795 have to be in the same frame as the current one.
4799 @kindex si @r{(@code{stepi})}
4801 @itemx stepi @var{arg}
4803 Execute one machine instruction, then stop and return to the debugger.
4805 It is often useful to do @samp{display/i $pc} when stepping by machine
4806 instructions. This makes @value{GDBN} automatically display the next
4807 instruction to be executed, each time your program stops. @xref{Auto
4808 Display,, Automatic Display}.
4810 An argument is a repeat count, as in @code{step}.
4814 @kindex ni @r{(@code{nexti})}
4816 @itemx nexti @var{arg}
4818 Execute one machine instruction, but if it is a function call,
4819 proceed until the function returns.
4821 An argument is a repeat count, as in @code{next}.
4828 A signal is an asynchronous event that can happen in a program. The
4829 operating system defines the possible kinds of signals, and gives each
4830 kind a name and a number. For example, in Unix @code{SIGINT} is the
4831 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4832 @code{SIGSEGV} is the signal a program gets from referencing a place in
4833 memory far away from all the areas in use; @code{SIGALRM} occurs when
4834 the alarm clock timer goes off (which happens only if your program has
4835 requested an alarm).
4837 @cindex fatal signals
4838 Some signals, including @code{SIGALRM}, are a normal part of the
4839 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4840 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4841 program has not specified in advance some other way to handle the signal.
4842 @code{SIGINT} does not indicate an error in your program, but it is normally
4843 fatal so it can carry out the purpose of the interrupt: to kill the program.
4845 @value{GDBN} has the ability to detect any occurrence of a signal in your
4846 program. You can tell @value{GDBN} in advance what to do for each kind of
4849 @cindex handling signals
4850 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4851 @code{SIGALRM} be silently passed to your program
4852 (so as not to interfere with their role in the program's functioning)
4853 but to stop your program immediately whenever an error signal happens.
4854 You can change these settings with the @code{handle} command.
4857 @kindex info signals
4861 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4862 handle each one. You can use this to see the signal numbers of all
4863 the defined types of signals.
4865 @item info signals @var{sig}
4866 Similar, but print information only about the specified signal number.
4868 @code{info handle} is an alias for @code{info signals}.
4871 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4872 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4873 can be the number of a signal or its name (with or without the
4874 @samp{SIG} at the beginning); a list of signal numbers of the form
4875 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4876 known signals. Optional arguments @var{keywords}, described below,
4877 say what change to make.
4881 The keywords allowed by the @code{handle} command can be abbreviated.
4882 Their full names are:
4886 @value{GDBN} should not stop your program when this signal happens. It may
4887 still print a message telling you that the signal has come in.
4890 @value{GDBN} should stop your program when this signal happens. This implies
4891 the @code{print} keyword as well.
4894 @value{GDBN} should print a message when this signal happens.
4897 @value{GDBN} should not mention the occurrence of the signal at all. This
4898 implies the @code{nostop} keyword as well.
4902 @value{GDBN} should allow your program to see this signal; your program
4903 can handle the signal, or else it may terminate if the signal is fatal
4904 and not handled. @code{pass} and @code{noignore} are synonyms.
4908 @value{GDBN} should not allow your program to see this signal.
4909 @code{nopass} and @code{ignore} are synonyms.
4913 When a signal stops your program, the signal is not visible to the
4915 continue. Your program sees the signal then, if @code{pass} is in
4916 effect for the signal in question @emph{at that time}. In other words,
4917 after @value{GDBN} reports a signal, you can use the @code{handle}
4918 command with @code{pass} or @code{nopass} to control whether your
4919 program sees that signal when you continue.
4921 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4922 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4923 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4926 You can also use the @code{signal} command to prevent your program from
4927 seeing a signal, or cause it to see a signal it normally would not see,
4928 or to give it any signal at any time. For example, if your program stopped
4929 due to some sort of memory reference error, you might store correct
4930 values into the erroneous variables and continue, hoping to see more
4931 execution; but your program would probably terminate immediately as
4932 a result of the fatal signal once it saw the signal. To prevent this,
4933 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4936 @cindex extra signal information
4937 @anchor{extra signal information}
4939 On some targets, @value{GDBN} can inspect extra signal information
4940 associated with the intercepted signal, before it is actually
4941 delivered to the program being debugged. This information is exported
4942 by the convenience variable @code{$_siginfo}, and consists of data
4943 that is passed by the kernel to the signal handler at the time of the
4944 receipt of a signal. The data type of the information itself is
4945 target dependent. You can see the data type using the @code{ptype
4946 $_siginfo} command. On Unix systems, it typically corresponds to the
4947 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4950 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4951 referenced address that raised a segmentation fault.
4955 (@value{GDBP}) continue
4956 Program received signal SIGSEGV, Segmentation fault.
4957 0x0000000000400766 in main ()
4959 (@value{GDBP}) ptype $_siginfo
4966 struct @{...@} _kill;
4967 struct @{...@} _timer;
4969 struct @{...@} _sigchld;
4970 struct @{...@} _sigfault;
4971 struct @{...@} _sigpoll;
4974 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4978 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4979 $1 = (void *) 0x7ffff7ff7000
4983 Depending on target support, @code{$_siginfo} may also be writable.
4986 @section Stopping and Starting Multi-thread Programs
4988 @cindex stopped threads
4989 @cindex threads, stopped
4991 @cindex continuing threads
4992 @cindex threads, continuing
4994 @value{GDBN} supports debugging programs with multiple threads
4995 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4996 are two modes of controlling execution of your program within the
4997 debugger. In the default mode, referred to as @dfn{all-stop mode},
4998 when any thread in your program stops (for example, at a breakpoint
4999 or while being stepped), all other threads in the program are also stopped by
5000 @value{GDBN}. On some targets, @value{GDBN} also supports
5001 @dfn{non-stop mode}, in which other threads can continue to run freely while
5002 you examine the stopped thread in the debugger.
5005 * All-Stop Mode:: All threads stop when GDB takes control
5006 * Non-Stop Mode:: Other threads continue to execute
5007 * Background Execution:: Running your program asynchronously
5008 * Thread-Specific Breakpoints:: Controlling breakpoints
5009 * Interrupted System Calls:: GDB may interfere with system calls
5010 * Observer Mode:: GDB does not alter program behavior
5014 @subsection All-Stop Mode
5016 @cindex all-stop mode
5018 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5019 @emph{all} threads of execution stop, not just the current thread. This
5020 allows you to examine the overall state of the program, including
5021 switching between threads, without worrying that things may change
5024 Conversely, whenever you restart the program, @emph{all} threads start
5025 executing. @emph{This is true even when single-stepping} with commands
5026 like @code{step} or @code{next}.
5028 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5029 Since thread scheduling is up to your debugging target's operating
5030 system (not controlled by @value{GDBN}), other threads may
5031 execute more than one statement while the current thread completes a
5032 single step. Moreover, in general other threads stop in the middle of a
5033 statement, rather than at a clean statement boundary, when the program
5036 You might even find your program stopped in another thread after
5037 continuing or even single-stepping. This happens whenever some other
5038 thread runs into a breakpoint, a signal, or an exception before the
5039 first thread completes whatever you requested.
5041 @cindex automatic thread selection
5042 @cindex switching threads automatically
5043 @cindex threads, automatic switching
5044 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5045 signal, it automatically selects the thread where that breakpoint or
5046 signal happened. @value{GDBN} alerts you to the context switch with a
5047 message such as @samp{[Switching to Thread @var{n}]} to identify the
5050 On some OSes, you can modify @value{GDBN}'s default behavior by
5051 locking the OS scheduler to allow only a single thread to run.
5054 @item set scheduler-locking @var{mode}
5055 @cindex scheduler locking mode
5056 @cindex lock scheduler
5057 Set the scheduler locking mode. If it is @code{off}, then there is no
5058 locking and any thread may run at any time. If @code{on}, then only the
5059 current thread may run when the inferior is resumed. The @code{step}
5060 mode optimizes for single-stepping; it prevents other threads
5061 from preempting the current thread while you are stepping, so that
5062 the focus of debugging does not change unexpectedly.
5063 Other threads only rarely (or never) get a chance to run
5064 when you step. They are more likely to run when you @samp{next} over a
5065 function call, and they are completely free to run when you use commands
5066 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5067 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5068 the current thread away from the thread that you are debugging.
5070 @item show scheduler-locking
5071 Display the current scheduler locking mode.
5074 @cindex resume threads of multiple processes simultaneously
5075 By default, when you issue one of the execution commands such as
5076 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5077 threads of the current inferior to run. For example, if @value{GDBN}
5078 is attached to two inferiors, each with two threads, the
5079 @code{continue} command resumes only the two threads of the current
5080 inferior. This is useful, for example, when you debug a program that
5081 forks and you want to hold the parent stopped (so that, for instance,
5082 it doesn't run to exit), while you debug the child. In other
5083 situations, you may not be interested in inspecting the current state
5084 of any of the processes @value{GDBN} is attached to, and you may want
5085 to resume them all until some breakpoint is hit. In the latter case,
5086 you can instruct @value{GDBN} to allow all threads of all the
5087 inferiors to run with the @w{@code{set schedule-multiple}} command.
5090 @kindex set schedule-multiple
5091 @item set schedule-multiple
5092 Set the mode for allowing threads of multiple processes to be resumed
5093 when an execution command is issued. When @code{on}, all threads of
5094 all processes are allowed to run. When @code{off}, only the threads
5095 of the current process are resumed. The default is @code{off}. The
5096 @code{scheduler-locking} mode takes precedence when set to @code{on},
5097 or while you are stepping and set to @code{step}.
5099 @item show schedule-multiple
5100 Display the current mode for resuming the execution of threads of
5105 @subsection Non-Stop Mode
5107 @cindex non-stop mode
5109 @c This section is really only a place-holder, and needs to be expanded
5110 @c with more details.
5112 For some multi-threaded targets, @value{GDBN} supports an optional
5113 mode of operation in which you can examine stopped program threads in
5114 the debugger while other threads continue to execute freely. This
5115 minimizes intrusion when debugging live systems, such as programs
5116 where some threads have real-time constraints or must continue to
5117 respond to external events. This is referred to as @dfn{non-stop} mode.
5119 In non-stop mode, when a thread stops to report a debugging event,
5120 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5121 threads as well, in contrast to the all-stop mode behavior. Additionally,
5122 execution commands such as @code{continue} and @code{step} apply by default
5123 only to the current thread in non-stop mode, rather than all threads as
5124 in all-stop mode. This allows you to control threads explicitly in
5125 ways that are not possible in all-stop mode --- for example, stepping
5126 one thread while allowing others to run freely, stepping
5127 one thread while holding all others stopped, or stepping several threads
5128 independently and simultaneously.
5130 To enter non-stop mode, use this sequence of commands before you run
5131 or attach to your program:
5134 # Enable the async interface.
5137 # If using the CLI, pagination breaks non-stop.
5140 # Finally, turn it on!
5144 You can use these commands to manipulate the non-stop mode setting:
5147 @kindex set non-stop
5148 @item set non-stop on
5149 Enable selection of non-stop mode.
5150 @item set non-stop off
5151 Disable selection of non-stop mode.
5152 @kindex show non-stop
5154 Show the current non-stop enablement setting.
5157 Note these commands only reflect whether non-stop mode is enabled,
5158 not whether the currently-executing program is being run in non-stop mode.
5159 In particular, the @code{set non-stop} preference is only consulted when
5160 @value{GDBN} starts or connects to the target program, and it is generally
5161 not possible to switch modes once debugging has started. Furthermore,
5162 since not all targets support non-stop mode, even when you have enabled
5163 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5166 In non-stop mode, all execution commands apply only to the current thread
5167 by default. That is, @code{continue} only continues one thread.
5168 To continue all threads, issue @code{continue -a} or @code{c -a}.
5170 You can use @value{GDBN}'s background execution commands
5171 (@pxref{Background Execution}) to run some threads in the background
5172 while you continue to examine or step others from @value{GDBN}.
5173 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5174 always executed asynchronously in non-stop mode.
5176 Suspending execution is done with the @code{interrupt} command when
5177 running in the background, or @kbd{Ctrl-c} during foreground execution.
5178 In all-stop mode, this stops the whole process;
5179 but in non-stop mode the interrupt applies only to the current thread.
5180 To stop the whole program, use @code{interrupt -a}.
5182 Other execution commands do not currently support the @code{-a} option.
5184 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5185 that thread current, as it does in all-stop mode. This is because the
5186 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5187 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5188 changed to a different thread just as you entered a command to operate on the
5189 previously current thread.
5191 @node Background Execution
5192 @subsection Background Execution
5194 @cindex foreground execution
5195 @cindex background execution
5196 @cindex asynchronous execution
5197 @cindex execution, foreground, background and asynchronous
5199 @value{GDBN}'s execution commands have two variants: the normal
5200 foreground (synchronous) behavior, and a background
5201 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5202 the program to report that some thread has stopped before prompting for
5203 another command. In background execution, @value{GDBN} immediately gives
5204 a command prompt so that you can issue other commands while your program runs.
5206 You need to explicitly enable asynchronous mode before you can use
5207 background execution commands. You can use these commands to
5208 manipulate the asynchronous mode setting:
5211 @kindex set target-async
5212 @item set target-async on
5213 Enable asynchronous mode.
5214 @item set target-async off
5215 Disable asynchronous mode.
5216 @kindex show target-async
5217 @item show target-async
5218 Show the current target-async setting.
5221 If the target doesn't support async mode, @value{GDBN} issues an error
5222 message if you attempt to use the background execution commands.
5224 To specify background execution, add a @code{&} to the command. For example,
5225 the background form of the @code{continue} command is @code{continue&}, or
5226 just @code{c&}. The execution commands that accept background execution
5232 @xref{Starting, , Starting your Program}.
5236 @xref{Attach, , Debugging an Already-running Process}.
5240 @xref{Continuing and Stepping, step}.
5244 @xref{Continuing and Stepping, stepi}.
5248 @xref{Continuing and Stepping, next}.
5252 @xref{Continuing and Stepping, nexti}.
5256 @xref{Continuing and Stepping, continue}.
5260 @xref{Continuing and Stepping, finish}.
5264 @xref{Continuing and Stepping, until}.
5268 Background execution is especially useful in conjunction with non-stop
5269 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5270 However, you can also use these commands in the normal all-stop mode with
5271 the restriction that you cannot issue another execution command until the
5272 previous one finishes. Examples of commands that are valid in all-stop
5273 mode while the program is running include @code{help} and @code{info break}.
5275 You can interrupt your program while it is running in the background by
5276 using the @code{interrupt} command.
5283 Suspend execution of the running program. In all-stop mode,
5284 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5285 only the current thread. To stop the whole program in non-stop mode,
5286 use @code{interrupt -a}.
5289 @node Thread-Specific Breakpoints
5290 @subsection Thread-Specific Breakpoints
5292 When your program has multiple threads (@pxref{Threads,, Debugging
5293 Programs with Multiple Threads}), you can choose whether to set
5294 breakpoints on all threads, or on a particular thread.
5297 @cindex breakpoints and threads
5298 @cindex thread breakpoints
5299 @kindex break @dots{} thread @var{threadno}
5300 @item break @var{linespec} thread @var{threadno}
5301 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5302 @var{linespec} specifies source lines; there are several ways of
5303 writing them (@pxref{Specify Location}), but the effect is always to
5304 specify some source line.
5306 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5307 to specify that you only want @value{GDBN} to stop the program when a
5308 particular thread reaches this breakpoint. @var{threadno} is one of the
5309 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5310 column of the @samp{info threads} display.
5312 If you do not specify @samp{thread @var{threadno}} when you set a
5313 breakpoint, the breakpoint applies to @emph{all} threads of your
5316 You can use the @code{thread} qualifier on conditional breakpoints as
5317 well; in this case, place @samp{thread @var{threadno}} before or
5318 after the breakpoint condition, like this:
5321 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5326 @node Interrupted System Calls
5327 @subsection Interrupted System Calls
5329 @cindex thread breakpoints and system calls
5330 @cindex system calls and thread breakpoints
5331 @cindex premature return from system calls
5332 There is an unfortunate side effect when using @value{GDBN} to debug
5333 multi-threaded programs. If one thread stops for a
5334 breakpoint, or for some other reason, and another thread is blocked in a
5335 system call, then the system call may return prematurely. This is a
5336 consequence of the interaction between multiple threads and the signals
5337 that @value{GDBN} uses to implement breakpoints and other events that
5340 To handle this problem, your program should check the return value of
5341 each system call and react appropriately. This is good programming
5344 For example, do not write code like this:
5350 The call to @code{sleep} will return early if a different thread stops
5351 at a breakpoint or for some other reason.
5353 Instead, write this:
5358 unslept = sleep (unslept);
5361 A system call is allowed to return early, so the system is still
5362 conforming to its specification. But @value{GDBN} does cause your
5363 multi-threaded program to behave differently than it would without
5366 Also, @value{GDBN} uses internal breakpoints in the thread library to
5367 monitor certain events such as thread creation and thread destruction.
5368 When such an event happens, a system call in another thread may return
5369 prematurely, even though your program does not appear to stop.
5372 @subsection Observer Mode
5374 If you want to build on non-stop mode and observe program behavior
5375 without any chance of disruption by @value{GDBN}, you can set
5376 variables to disable all of the debugger's attempts to modify state,
5377 whether by writing memory, inserting breakpoints, etc. These operate
5378 at a low level, intercepting operations from all commands.
5380 When all of these are set to @code{off}, then @value{GDBN} is said to
5381 be @dfn{observer mode}. As a convenience, the variable
5382 @code{observer} can be set to disable these, plus enable non-stop
5385 Note that @value{GDBN} will not prevent you from making nonsensical
5386 combinations of these settings. For instance, if you have enabled
5387 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5388 then breakpoints that work by writing trap instructions into the code
5389 stream will still not be able to be placed.
5394 @item set observer on
5395 @itemx set observer off
5396 When set to @code{on}, this disables all the permission variables
5397 below (except for @code{insert-fast-tracepoints}), plus enables
5398 non-stop debugging. Setting this to @code{off} switches back to
5399 normal debugging, though remaining in non-stop mode.
5402 Show whether observer mode is on or off.
5404 @kindex may-write-registers
5405 @item set may-write-registers on
5406 @itemx set may-write-registers off
5407 This controls whether @value{GDBN} will attempt to alter the values of
5408 registers, such as with assignment expressions in @code{print}, or the
5409 @code{jump} command. It defaults to @code{on}.
5411 @item show may-write-registers
5412 Show the current permission to write registers.
5414 @kindex may-write-memory
5415 @item set may-write-memory on
5416 @itemx set may-write-memory off
5417 This controls whether @value{GDBN} will attempt to alter the contents
5418 of memory, such as with assignment expressions in @code{print}. It
5419 defaults to @code{on}.
5421 @item show may-write-memory
5422 Show the current permission to write memory.
5424 @kindex may-insert-breakpoints
5425 @item set may-insert-breakpoints on
5426 @itemx set may-insert-breakpoints off
5427 This controls whether @value{GDBN} will attempt to insert breakpoints.
5428 This affects all breakpoints, including internal breakpoints defined
5429 by @value{GDBN}. It defaults to @code{on}.
5431 @item show may-insert-breakpoints
5432 Show the current permission to insert breakpoints.
5434 @kindex may-insert-tracepoints
5435 @item set may-insert-tracepoints on
5436 @itemx set may-insert-tracepoints off
5437 This controls whether @value{GDBN} will attempt to insert (regular)
5438 tracepoints at the beginning of a tracing experiment. It affects only
5439 non-fast tracepoints, fast tracepoints being under the control of
5440 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5442 @item show may-insert-tracepoints
5443 Show the current permission to insert tracepoints.
5445 @kindex may-insert-fast-tracepoints
5446 @item set may-insert-fast-tracepoints on
5447 @itemx set may-insert-fast-tracepoints off
5448 This controls whether @value{GDBN} will attempt to insert fast
5449 tracepoints at the beginning of a tracing experiment. It affects only
5450 fast tracepoints, regular (non-fast) tracepoints being under the
5451 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5453 @item show may-insert-fast-tracepoints
5454 Show the current permission to insert fast tracepoints.
5456 @kindex may-interrupt
5457 @item set may-interrupt on
5458 @itemx set may-interrupt off
5459 This controls whether @value{GDBN} will attempt to interrupt or stop
5460 program execution. When this variable is @code{off}, the
5461 @code{interrupt} command will have no effect, nor will
5462 @kbd{Ctrl-c}. It defaults to @code{on}.
5464 @item show may-interrupt
5465 Show the current permission to interrupt or stop the program.
5469 @node Reverse Execution
5470 @chapter Running programs backward
5471 @cindex reverse execution
5472 @cindex running programs backward
5474 When you are debugging a program, it is not unusual to realize that
5475 you have gone too far, and some event of interest has already happened.
5476 If the target environment supports it, @value{GDBN} can allow you to
5477 ``rewind'' the program by running it backward.
5479 A target environment that supports reverse execution should be able
5480 to ``undo'' the changes in machine state that have taken place as the
5481 program was executing normally. Variables, registers etc.@: should
5482 revert to their previous values. Obviously this requires a great
5483 deal of sophistication on the part of the target environment; not
5484 all target environments can support reverse execution.
5486 When a program is executed in reverse, the instructions that
5487 have most recently been executed are ``un-executed'', in reverse
5488 order. The program counter runs backward, following the previous
5489 thread of execution in reverse. As each instruction is ``un-executed'',
5490 the values of memory and/or registers that were changed by that
5491 instruction are reverted to their previous states. After executing
5492 a piece of source code in reverse, all side effects of that code
5493 should be ``undone'', and all variables should be returned to their
5494 prior values@footnote{
5495 Note that some side effects are easier to undo than others. For instance,
5496 memory and registers are relatively easy, but device I/O is hard. Some
5497 targets may be able undo things like device I/O, and some may not.
5499 The contract between @value{GDBN} and the reverse executing target
5500 requires only that the target do something reasonable when
5501 @value{GDBN} tells it to execute backwards, and then report the
5502 results back to @value{GDBN}. Whatever the target reports back to
5503 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5504 assumes that the memory and registers that the target reports are in a
5505 consistant state, but @value{GDBN} accepts whatever it is given.
5508 If you are debugging in a target environment that supports
5509 reverse execution, @value{GDBN} provides the following commands.
5512 @kindex reverse-continue
5513 @kindex rc @r{(@code{reverse-continue})}
5514 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5515 @itemx rc @r{[}@var{ignore-count}@r{]}
5516 Beginning at the point where your program last stopped, start executing
5517 in reverse. Reverse execution will stop for breakpoints and synchronous
5518 exceptions (signals), just like normal execution. Behavior of
5519 asynchronous signals depends on the target environment.
5521 @kindex reverse-step
5522 @kindex rs @r{(@code{step})}
5523 @item reverse-step @r{[}@var{count}@r{]}
5524 Run the program backward until control reaches the start of a
5525 different source line; then stop it, and return control to @value{GDBN}.
5527 Like the @code{step} command, @code{reverse-step} will only stop
5528 at the beginning of a source line. It ``un-executes'' the previously
5529 executed source line. If the previous source line included calls to
5530 debuggable functions, @code{reverse-step} will step (backward) into
5531 the called function, stopping at the beginning of the @emph{last}
5532 statement in the called function (typically a return statement).
5534 Also, as with the @code{step} command, if non-debuggable functions are
5535 called, @code{reverse-step} will run thru them backward without stopping.
5537 @kindex reverse-stepi
5538 @kindex rsi @r{(@code{reverse-stepi})}
5539 @item reverse-stepi @r{[}@var{count}@r{]}
5540 Reverse-execute one machine instruction. Note that the instruction
5541 to be reverse-executed is @emph{not} the one pointed to by the program
5542 counter, but the instruction executed prior to that one. For instance,
5543 if the last instruction was a jump, @code{reverse-stepi} will take you
5544 back from the destination of the jump to the jump instruction itself.
5546 @kindex reverse-next
5547 @kindex rn @r{(@code{reverse-next})}
5548 @item reverse-next @r{[}@var{count}@r{]}
5549 Run backward to the beginning of the previous line executed in
5550 the current (innermost) stack frame. If the line contains function
5551 calls, they will be ``un-executed'' without stopping. Starting from
5552 the first line of a function, @code{reverse-next} will take you back
5553 to the caller of that function, @emph{before} the function was called,
5554 just as the normal @code{next} command would take you from the last
5555 line of a function back to its return to its caller
5556 @footnote{Unless the code is too heavily optimized.}.
5558 @kindex reverse-nexti
5559 @kindex rni @r{(@code{reverse-nexti})}
5560 @item reverse-nexti @r{[}@var{count}@r{]}
5561 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5562 in reverse, except that called functions are ``un-executed'' atomically.
5563 That is, if the previously executed instruction was a return from
5564 another function, @code{reverse-nexti} will continue to execute
5565 in reverse until the call to that function (from the current stack
5568 @kindex reverse-finish
5569 @item reverse-finish
5570 Just as the @code{finish} command takes you to the point where the
5571 current function returns, @code{reverse-finish} takes you to the point
5572 where it was called. Instead of ending up at the end of the current
5573 function invocation, you end up at the beginning.
5575 @kindex set exec-direction
5576 @item set exec-direction
5577 Set the direction of target execution.
5578 @itemx set exec-direction reverse
5579 @cindex execute forward or backward in time
5580 @value{GDBN} will perform all execution commands in reverse, until the
5581 exec-direction mode is changed to ``forward''. Affected commands include
5582 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5583 command cannot be used in reverse mode.
5584 @item set exec-direction forward
5585 @value{GDBN} will perform all execution commands in the normal fashion.
5586 This is the default.
5590 @node Process Record and Replay
5591 @chapter Recording Inferior's Execution and Replaying It
5592 @cindex process record and replay
5593 @cindex recording inferior's execution and replaying it
5595 On some platforms, @value{GDBN} provides a special @dfn{process record
5596 and replay} target that can record a log of the process execution, and
5597 replay it later with both forward and reverse execution commands.
5600 When this target is in use, if the execution log includes the record
5601 for the next instruction, @value{GDBN} will debug in @dfn{replay
5602 mode}. In the replay mode, the inferior does not really execute code
5603 instructions. Instead, all the events that normally happen during
5604 code execution are taken from the execution log. While code is not
5605 really executed in replay mode, the values of registers (including the
5606 program counter register) and the memory of the inferior are still
5607 changed as they normally would. Their contents are taken from the
5611 If the record for the next instruction is not in the execution log,
5612 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5613 inferior executes normally, and @value{GDBN} records the execution log
5616 The process record and replay target supports reverse execution
5617 (@pxref{Reverse Execution}), even if the platform on which the
5618 inferior runs does not. However, the reverse execution is limited in
5619 this case by the range of the instructions recorded in the execution
5620 log. In other words, reverse execution on platforms that don't
5621 support it directly can only be done in the replay mode.
5623 When debugging in the reverse direction, @value{GDBN} will work in
5624 replay mode as long as the execution log includes the record for the
5625 previous instruction; otherwise, it will work in record mode, if the
5626 platform supports reverse execution, or stop if not.
5628 For architecture environments that support process record and replay,
5629 @value{GDBN} provides the following commands:
5632 @kindex target record
5636 This command starts the process record and replay target. The process
5637 record and replay target can only debug a process that is already
5638 running. Therefore, you need first to start the process with the
5639 @kbd{run} or @kbd{start} commands, and then start the recording with
5640 the @kbd{target record} command.
5642 Both @code{record} and @code{rec} are aliases of @code{target record}.
5644 @cindex displaced stepping, and process record and replay
5645 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5646 will be automatically disabled when process record and replay target
5647 is started. That's because the process record and replay target
5648 doesn't support displaced stepping.
5650 @cindex non-stop mode, and process record and replay
5651 @cindex asynchronous execution, and process record and replay
5652 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5653 the asynchronous execution mode (@pxref{Background Execution}), the
5654 process record and replay target cannot be started because it doesn't
5655 support these two modes.
5660 Stop the process record and replay target. When process record and
5661 replay target stops, the entire execution log will be deleted and the
5662 inferior will either be terminated, or will remain in its final state.
5664 When you stop the process record and replay target in record mode (at
5665 the end of the execution log), the inferior will be stopped at the
5666 next instruction that would have been recorded. In other words, if
5667 you record for a while and then stop recording, the inferior process
5668 will be left in the same state as if the recording never happened.
5670 On the other hand, if the process record and replay target is stopped
5671 while in replay mode (that is, not at the end of the execution log,
5672 but at some earlier point), the inferior process will become ``live''
5673 at that earlier state, and it will then be possible to continue the
5674 usual ``live'' debugging of the process from that state.
5676 When the inferior process exits, or @value{GDBN} detaches from it,
5677 process record and replay target will automatically stop itself.
5680 @item record save @var{filename}
5681 Save the execution log to a file @file{@var{filename}}.
5682 Default filename is @file{gdb_record.@var{process_id}}, where
5683 @var{process_id} is the process ID of the inferior.
5685 @kindex record restore
5686 @item record restore @var{filename}
5687 Restore the execution log from a file @file{@var{filename}}.
5688 File must have been created with @code{record save}.
5690 @kindex set record insn-number-max
5691 @item set record insn-number-max @var{limit}
5692 Set the limit of instructions to be recorded. Default value is 200000.
5694 If @var{limit} is a positive number, then @value{GDBN} will start
5695 deleting instructions from the log once the number of the record
5696 instructions becomes greater than @var{limit}. For every new recorded
5697 instruction, @value{GDBN} will delete the earliest recorded
5698 instruction to keep the number of recorded instructions at the limit.
5699 (Since deleting recorded instructions loses information, @value{GDBN}
5700 lets you control what happens when the limit is reached, by means of
5701 the @code{stop-at-limit} option, described below.)
5703 If @var{limit} is zero, @value{GDBN} will never delete recorded
5704 instructions from the execution log. The number of recorded
5705 instructions is unlimited in this case.
5707 @kindex show record insn-number-max
5708 @item show record insn-number-max
5709 Show the limit of instructions to be recorded.
5711 @kindex set record stop-at-limit
5712 @item set record stop-at-limit
5713 Control the behavior when the number of recorded instructions reaches
5714 the limit. If ON (the default), @value{GDBN} will stop when the limit
5715 is reached for the first time and ask you whether you want to stop the
5716 inferior or continue running it and recording the execution log. If
5717 you decide to continue recording, each new recorded instruction will
5718 cause the oldest one to be deleted.
5720 If this option is OFF, @value{GDBN} will automatically delete the
5721 oldest record to make room for each new one, without asking.
5723 @kindex show record stop-at-limit
5724 @item show record stop-at-limit
5725 Show the current setting of @code{stop-at-limit}.
5727 @kindex set record memory-query
5728 @item set record memory-query
5729 Control the behavior when @value{GDBN} is unable to record memory
5730 changes caused by an instruction. If ON, @value{GDBN} will query
5731 whether to stop the inferior in that case.
5733 If this option is OFF (the default), @value{GDBN} will automatically
5734 ignore the effect of such instructions on memory. Later, when
5735 @value{GDBN} replays this execution log, it will mark the log of this
5736 instruction as not accessible, and it will not affect the replay
5739 @kindex show record memory-query
5740 @item show record memory-query
5741 Show the current setting of @code{memory-query}.
5745 Show various statistics about the state of process record and its
5746 in-memory execution log buffer, including:
5750 Whether in record mode or replay mode.
5752 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5754 Highest recorded instruction number.
5756 Current instruction about to be replayed (if in replay mode).
5758 Number of instructions contained in the execution log.
5760 Maximum number of instructions that may be contained in the execution log.
5763 @kindex record delete
5766 When record target runs in replay mode (``in the past''), delete the
5767 subsequent execution log and begin to record a new execution log starting
5768 from the current address. This means you will abandon the previously
5769 recorded ``future'' and begin recording a new ``future''.
5774 @chapter Examining the Stack
5776 When your program has stopped, the first thing you need to know is where it
5777 stopped and how it got there.
5780 Each time your program performs a function call, information about the call
5782 That information includes the location of the call in your program,
5783 the arguments of the call,
5784 and the local variables of the function being called.
5785 The information is saved in a block of data called a @dfn{stack frame}.
5786 The stack frames are allocated in a region of memory called the @dfn{call
5789 When your program stops, the @value{GDBN} commands for examining the
5790 stack allow you to see all of this information.
5792 @cindex selected frame
5793 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5794 @value{GDBN} commands refer implicitly to the selected frame. In
5795 particular, whenever you ask @value{GDBN} for the value of a variable in
5796 your program, the value is found in the selected frame. There are
5797 special @value{GDBN} commands to select whichever frame you are
5798 interested in. @xref{Selection, ,Selecting a Frame}.
5800 When your program stops, @value{GDBN} automatically selects the
5801 currently executing frame and describes it briefly, similar to the
5802 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5805 * Frames:: Stack frames
5806 * Backtrace:: Backtraces
5807 * Selection:: Selecting a frame
5808 * Frame Info:: Information on a frame
5813 @section Stack Frames
5815 @cindex frame, definition
5817 The call stack is divided up into contiguous pieces called @dfn{stack
5818 frames}, or @dfn{frames} for short; each frame is the data associated
5819 with one call to one function. The frame contains the arguments given
5820 to the function, the function's local variables, and the address at
5821 which the function is executing.
5823 @cindex initial frame
5824 @cindex outermost frame
5825 @cindex innermost frame
5826 When your program is started, the stack has only one frame, that of the
5827 function @code{main}. This is called the @dfn{initial} frame or the
5828 @dfn{outermost} frame. Each time a function is called, a new frame is
5829 made. Each time a function returns, the frame for that function invocation
5830 is eliminated. If a function is recursive, there can be many frames for
5831 the same function. The frame for the function in which execution is
5832 actually occurring is called the @dfn{innermost} frame. This is the most
5833 recently created of all the stack frames that still exist.
5835 @cindex frame pointer
5836 Inside your program, stack frames are identified by their addresses. A
5837 stack frame consists of many bytes, each of which has its own address; each
5838 kind of computer has a convention for choosing one byte whose
5839 address serves as the address of the frame. Usually this address is kept
5840 in a register called the @dfn{frame pointer register}
5841 (@pxref{Registers, $fp}) while execution is going on in that frame.
5843 @cindex frame number
5844 @value{GDBN} assigns numbers to all existing stack frames, starting with
5845 zero for the innermost frame, one for the frame that called it,
5846 and so on upward. These numbers do not really exist in your program;
5847 they are assigned by @value{GDBN} to give you a way of designating stack
5848 frames in @value{GDBN} commands.
5850 @c The -fomit-frame-pointer below perennially causes hbox overflow
5851 @c underflow problems.
5852 @cindex frameless execution
5853 Some compilers provide a way to compile functions so that they operate
5854 without stack frames. (For example, the @value{NGCC} option
5856 @samp{-fomit-frame-pointer}
5858 generates functions without a frame.)
5859 This is occasionally done with heavily used library functions to save
5860 the frame setup time. @value{GDBN} has limited facilities for dealing
5861 with these function invocations. If the innermost function invocation
5862 has no stack frame, @value{GDBN} nevertheless regards it as though
5863 it had a separate frame, which is numbered zero as usual, allowing
5864 correct tracing of the function call chain. However, @value{GDBN} has
5865 no provision for frameless functions elsewhere in the stack.
5868 @kindex frame@r{, command}
5869 @cindex current stack frame
5870 @item frame @var{args}
5871 The @code{frame} command allows you to move from one stack frame to another,
5872 and to print the stack frame you select. @var{args} may be either the
5873 address of the frame or the stack frame number. Without an argument,
5874 @code{frame} prints the current stack frame.
5876 @kindex select-frame
5877 @cindex selecting frame silently
5879 The @code{select-frame} command allows you to move from one stack frame
5880 to another without printing the frame. This is the silent version of
5888 @cindex call stack traces
5889 A backtrace is a summary of how your program got where it is. It shows one
5890 line per frame, for many frames, starting with the currently executing
5891 frame (frame zero), followed by its caller (frame one), and on up the
5896 @kindex bt @r{(@code{backtrace})}
5899 Print a backtrace of the entire stack: one line per frame for all
5900 frames in the stack.
5902 You can stop the backtrace at any time by typing the system interrupt
5903 character, normally @kbd{Ctrl-c}.
5905 @item backtrace @var{n}
5907 Similar, but print only the innermost @var{n} frames.
5909 @item backtrace -@var{n}
5911 Similar, but print only the outermost @var{n} frames.
5913 @item backtrace full
5915 @itemx bt full @var{n}
5916 @itemx bt full -@var{n}
5917 Print the values of the local variables also. @var{n} specifies the
5918 number of frames to print, as described above.
5923 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5924 are additional aliases for @code{backtrace}.
5926 @cindex multiple threads, backtrace
5927 In a multi-threaded program, @value{GDBN} by default shows the
5928 backtrace only for the current thread. To display the backtrace for
5929 several or all of the threads, use the command @code{thread apply}
5930 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5931 apply all backtrace}, @value{GDBN} will display the backtrace for all
5932 the threads; this is handy when you debug a core dump of a
5933 multi-threaded program.
5935 Each line in the backtrace shows the frame number and the function name.
5936 The program counter value is also shown---unless you use @code{set
5937 print address off}. The backtrace also shows the source file name and
5938 line number, as well as the arguments to the function. The program
5939 counter value is omitted if it is at the beginning of the code for that
5942 Here is an example of a backtrace. It was made with the command
5943 @samp{bt 3}, so it shows the innermost three frames.
5947 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5949 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5950 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5952 (More stack frames follow...)
5957 The display for frame zero does not begin with a program counter
5958 value, indicating that your program has stopped at the beginning of the
5959 code for line @code{993} of @code{builtin.c}.
5962 The value of parameter @code{data} in frame 1 has been replaced by
5963 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5964 only if it is a scalar (integer, pointer, enumeration, etc). See command
5965 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5966 on how to configure the way function parameter values are printed.
5968 @cindex value optimized out, in backtrace
5969 @cindex function call arguments, optimized out
5970 If your program was compiled with optimizations, some compilers will
5971 optimize away arguments passed to functions if those arguments are
5972 never used after the call. Such optimizations generate code that
5973 passes arguments through registers, but doesn't store those arguments
5974 in the stack frame. @value{GDBN} has no way of displaying such
5975 arguments in stack frames other than the innermost one. Here's what
5976 such a backtrace might look like:
5980 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5982 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5983 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5985 (More stack frames follow...)
5990 The values of arguments that were not saved in their stack frames are
5991 shown as @samp{<value optimized out>}.
5993 If you need to display the values of such optimized-out arguments,
5994 either deduce that from other variables whose values depend on the one
5995 you are interested in, or recompile without optimizations.
5997 @cindex backtrace beyond @code{main} function
5998 @cindex program entry point
5999 @cindex startup code, and backtrace
6000 Most programs have a standard user entry point---a place where system
6001 libraries and startup code transition into user code. For C this is
6002 @code{main}@footnote{
6003 Note that embedded programs (the so-called ``free-standing''
6004 environment) are not required to have a @code{main} function as the
6005 entry point. They could even have multiple entry points.}.
6006 When @value{GDBN} finds the entry function in a backtrace
6007 it will terminate the backtrace, to avoid tracing into highly
6008 system-specific (and generally uninteresting) code.
6010 If you need to examine the startup code, or limit the number of levels
6011 in a backtrace, you can change this behavior:
6014 @item set backtrace past-main
6015 @itemx set backtrace past-main on
6016 @kindex set backtrace
6017 Backtraces will continue past the user entry point.
6019 @item set backtrace past-main off
6020 Backtraces will stop when they encounter the user entry point. This is the
6023 @item show backtrace past-main
6024 @kindex show backtrace
6025 Display the current user entry point backtrace policy.
6027 @item set backtrace past-entry
6028 @itemx set backtrace past-entry on
6029 Backtraces will continue past the internal entry point of an application.
6030 This entry point is encoded by the linker when the application is built,
6031 and is likely before the user entry point @code{main} (or equivalent) is called.
6033 @item set backtrace past-entry off
6034 Backtraces will stop when they encounter the internal entry point of an
6035 application. This is the default.
6037 @item show backtrace past-entry
6038 Display the current internal entry point backtrace policy.
6040 @item set backtrace limit @var{n}
6041 @itemx set backtrace limit 0
6042 @cindex backtrace limit
6043 Limit the backtrace to @var{n} levels. A value of zero means
6046 @item show backtrace limit
6047 Display the current limit on backtrace levels.
6051 @section Selecting a Frame
6053 Most commands for examining the stack and other data in your program work on
6054 whichever stack frame is selected at the moment. Here are the commands for
6055 selecting a stack frame; all of them finish by printing a brief description
6056 of the stack frame just selected.
6059 @kindex frame@r{, selecting}
6060 @kindex f @r{(@code{frame})}
6063 Select frame number @var{n}. Recall that frame zero is the innermost
6064 (currently executing) frame, frame one is the frame that called the
6065 innermost one, and so on. The highest-numbered frame is the one for
6068 @item frame @var{addr}
6070 Select the frame at address @var{addr}. This is useful mainly if the
6071 chaining of stack frames has been damaged by a bug, making it
6072 impossible for @value{GDBN} to assign numbers properly to all frames. In
6073 addition, this can be useful when your program has multiple stacks and
6074 switches between them.
6076 On the SPARC architecture, @code{frame} needs two addresses to
6077 select an arbitrary frame: a frame pointer and a stack pointer.
6079 On the MIPS and Alpha architecture, it needs two addresses: a stack
6080 pointer and a program counter.
6082 On the 29k architecture, it needs three addresses: a register stack
6083 pointer, a program counter, and a memory stack pointer.
6087 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6088 advances toward the outermost frame, to higher frame numbers, to frames
6089 that have existed longer. @var{n} defaults to one.
6092 @kindex do @r{(@code{down})}
6094 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6095 advances toward the innermost frame, to lower frame numbers, to frames
6096 that were created more recently. @var{n} defaults to one. You may
6097 abbreviate @code{down} as @code{do}.
6100 All of these commands end by printing two lines of output describing the
6101 frame. The first line shows the frame number, the function name, the
6102 arguments, and the source file and line number of execution in that
6103 frame. The second line shows the text of that source line.
6111 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6113 10 read_input_file (argv[i]);
6117 After such a printout, the @code{list} command with no arguments
6118 prints ten lines centered on the point of execution in the frame.
6119 You can also edit the program at the point of execution with your favorite
6120 editing program by typing @code{edit}.
6121 @xref{List, ,Printing Source Lines},
6125 @kindex down-silently
6127 @item up-silently @var{n}
6128 @itemx down-silently @var{n}
6129 These two commands are variants of @code{up} and @code{down},
6130 respectively; they differ in that they do their work silently, without
6131 causing display of the new frame. They are intended primarily for use
6132 in @value{GDBN} command scripts, where the output might be unnecessary and
6137 @section Information About a Frame
6139 There are several other commands to print information about the selected
6145 When used without any argument, this command does not change which
6146 frame is selected, but prints a brief description of the currently
6147 selected stack frame. It can be abbreviated @code{f}. With an
6148 argument, this command is used to select a stack frame.
6149 @xref{Selection, ,Selecting a Frame}.
6152 @kindex info f @r{(@code{info frame})}
6155 This command prints a verbose description of the selected stack frame,
6160 the address of the frame
6162 the address of the next frame down (called by this frame)
6164 the address of the next frame up (caller of this frame)
6166 the language in which the source code corresponding to this frame is written
6168 the address of the frame's arguments
6170 the address of the frame's local variables
6172 the program counter saved in it (the address of execution in the caller frame)
6174 which registers were saved in the frame
6177 @noindent The verbose description is useful when
6178 something has gone wrong that has made the stack format fail to fit
6179 the usual conventions.
6181 @item info frame @var{addr}
6182 @itemx info f @var{addr}
6183 Print a verbose description of the frame at address @var{addr}, without
6184 selecting that frame. The selected frame remains unchanged by this
6185 command. This requires the same kind of address (more than one for some
6186 architectures) that you specify in the @code{frame} command.
6187 @xref{Selection, ,Selecting a Frame}.
6191 Print the arguments of the selected frame, each on a separate line.
6195 Print the local variables of the selected frame, each on a separate
6196 line. These are all variables (declared either static or automatic)
6197 accessible at the point of execution of the selected frame.
6200 @cindex catch exceptions, list active handlers
6201 @cindex exception handlers, how to list
6203 Print a list of all the exception handlers that are active in the
6204 current stack frame at the current point of execution. To see other
6205 exception handlers, visit the associated frame (using the @code{up},
6206 @code{down}, or @code{frame} commands); then type @code{info catch}.
6207 @xref{Set Catchpoints, , Setting Catchpoints}.
6213 @chapter Examining Source Files
6215 @value{GDBN} can print parts of your program's source, since the debugging
6216 information recorded in the program tells @value{GDBN} what source files were
6217 used to build it. When your program stops, @value{GDBN} spontaneously prints
6218 the line where it stopped. Likewise, when you select a stack frame
6219 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6220 execution in that frame has stopped. You can print other portions of
6221 source files by explicit command.
6223 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6224 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6225 @value{GDBN} under @sc{gnu} Emacs}.
6228 * List:: Printing source lines
6229 * Specify Location:: How to specify code locations
6230 * Edit:: Editing source files
6231 * Search:: Searching source files
6232 * Source Path:: Specifying source directories
6233 * Machine Code:: Source and machine code
6237 @section Printing Source Lines
6240 @kindex l @r{(@code{list})}
6241 To print lines from a source file, use the @code{list} command
6242 (abbreviated @code{l}). By default, ten lines are printed.
6243 There are several ways to specify what part of the file you want to
6244 print; see @ref{Specify Location}, for the full list.
6246 Here are the forms of the @code{list} command most commonly used:
6249 @item list @var{linenum}
6250 Print lines centered around line number @var{linenum} in the
6251 current source file.
6253 @item list @var{function}
6254 Print lines centered around the beginning of function
6258 Print more lines. If the last lines printed were printed with a
6259 @code{list} command, this prints lines following the last lines
6260 printed; however, if the last line printed was a solitary line printed
6261 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6262 Stack}), this prints lines centered around that line.
6265 Print lines just before the lines last printed.
6268 @cindex @code{list}, how many lines to display
6269 By default, @value{GDBN} prints ten source lines with any of these forms of
6270 the @code{list} command. You can change this using @code{set listsize}:
6273 @kindex set listsize
6274 @item set listsize @var{count}
6275 Make the @code{list} command display @var{count} source lines (unless
6276 the @code{list} argument explicitly specifies some other number).
6278 @kindex show listsize
6280 Display the number of lines that @code{list} prints.
6283 Repeating a @code{list} command with @key{RET} discards the argument,
6284 so it is equivalent to typing just @code{list}. This is more useful
6285 than listing the same lines again. An exception is made for an
6286 argument of @samp{-}; that argument is preserved in repetition so that
6287 each repetition moves up in the source file.
6289 In general, the @code{list} command expects you to supply zero, one or two
6290 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6291 of writing them (@pxref{Specify Location}), but the effect is always
6292 to specify some source line.
6294 Here is a complete description of the possible arguments for @code{list}:
6297 @item list @var{linespec}
6298 Print lines centered around the line specified by @var{linespec}.
6300 @item list @var{first},@var{last}
6301 Print lines from @var{first} to @var{last}. Both arguments are
6302 linespecs. When a @code{list} command has two linespecs, and the
6303 source file of the second linespec is omitted, this refers to
6304 the same source file as the first linespec.
6306 @item list ,@var{last}
6307 Print lines ending with @var{last}.
6309 @item list @var{first},
6310 Print lines starting with @var{first}.
6313 Print lines just after the lines last printed.
6316 Print lines just before the lines last printed.
6319 As described in the preceding table.
6322 @node Specify Location
6323 @section Specifying a Location
6324 @cindex specifying location
6327 Several @value{GDBN} commands accept arguments that specify a location
6328 of your program's code. Since @value{GDBN} is a source-level
6329 debugger, a location usually specifies some line in the source code;
6330 for that reason, locations are also known as @dfn{linespecs}.
6332 Here are all the different ways of specifying a code location that
6333 @value{GDBN} understands:
6337 Specifies the line number @var{linenum} of the current source file.
6340 @itemx +@var{offset}
6341 Specifies the line @var{offset} lines before or after the @dfn{current
6342 line}. For the @code{list} command, the current line is the last one
6343 printed; for the breakpoint commands, this is the line at which
6344 execution stopped in the currently selected @dfn{stack frame}
6345 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6346 used as the second of the two linespecs in a @code{list} command,
6347 this specifies the line @var{offset} lines up or down from the first
6350 @item @var{filename}:@var{linenum}
6351 Specifies the line @var{linenum} in the source file @var{filename}.
6353 @item @var{function}
6354 Specifies the line that begins the body of the function @var{function}.
6355 For example, in C, this is the line with the open brace.
6357 @item @var{filename}:@var{function}
6358 Specifies the line that begins the body of the function @var{function}
6359 in the file @var{filename}. You only need the file name with a
6360 function name to avoid ambiguity when there are identically named
6361 functions in different source files.
6364 Specifies the line at which the label named @var{label} appears.
6365 @value{GDBN} searches for the label in the function corresponding to
6366 the currently selected stack frame. If there is no current selected
6367 stack frame (for instance, if the inferior is not running), then
6368 @value{GDBN} will not search for a label.
6370 @item *@var{address}
6371 Specifies the program address @var{address}. For line-oriented
6372 commands, such as @code{list} and @code{edit}, this specifies a source
6373 line that contains @var{address}. For @code{break} and other
6374 breakpoint oriented commands, this can be used to set breakpoints in
6375 parts of your program which do not have debugging information or
6378 Here @var{address} may be any expression valid in the current working
6379 language (@pxref{Languages, working language}) that specifies a code
6380 address. In addition, as a convenience, @value{GDBN} extends the
6381 semantics of expressions used in locations to cover the situations
6382 that frequently happen during debugging. Here are the various forms
6386 @item @var{expression}
6387 Any expression valid in the current working language.
6389 @item @var{funcaddr}
6390 An address of a function or procedure derived from its name. In C,
6391 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6392 simply the function's name @var{function} (and actually a special case
6393 of a valid expression). In Pascal and Modula-2, this is
6394 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6395 (although the Pascal form also works).
6397 This form specifies the address of the function's first instruction,
6398 before the stack frame and arguments have been set up.
6400 @item '@var{filename}'::@var{funcaddr}
6401 Like @var{funcaddr} above, but also specifies the name of the source
6402 file explicitly. This is useful if the name of the function does not
6403 specify the function unambiguously, e.g., if there are several
6404 functions with identical names in different source files.
6411 @section Editing Source Files
6412 @cindex editing source files
6415 @kindex e @r{(@code{edit})}
6416 To edit the lines in a source file, use the @code{edit} command.
6417 The editing program of your choice
6418 is invoked with the current line set to
6419 the active line in the program.
6420 Alternatively, there are several ways to specify what part of the file you
6421 want to print if you want to see other parts of the program:
6424 @item edit @var{location}
6425 Edit the source file specified by @code{location}. Editing starts at
6426 that @var{location}, e.g., at the specified source line of the
6427 specified file. @xref{Specify Location}, for all the possible forms
6428 of the @var{location} argument; here are the forms of the @code{edit}
6429 command most commonly used:
6432 @item edit @var{number}
6433 Edit the current source file with @var{number} as the active line number.
6435 @item edit @var{function}
6436 Edit the file containing @var{function} at the beginning of its definition.
6441 @subsection Choosing your Editor
6442 You can customize @value{GDBN} to use any editor you want
6444 The only restriction is that your editor (say @code{ex}), recognizes the
6445 following command-line syntax:
6447 ex +@var{number} file
6449 The optional numeric value +@var{number} specifies the number of the line in
6450 the file where to start editing.}.
6451 By default, it is @file{@value{EDITOR}}, but you can change this
6452 by setting the environment variable @code{EDITOR} before using
6453 @value{GDBN}. For example, to configure @value{GDBN} to use the
6454 @code{vi} editor, you could use these commands with the @code{sh} shell:
6460 or in the @code{csh} shell,
6462 setenv EDITOR /usr/bin/vi
6467 @section Searching Source Files
6468 @cindex searching source files
6470 There are two commands for searching through the current source file for a
6475 @kindex forward-search
6476 @item forward-search @var{regexp}
6477 @itemx search @var{regexp}
6478 The command @samp{forward-search @var{regexp}} checks each line,
6479 starting with the one following the last line listed, for a match for
6480 @var{regexp}. It lists the line that is found. You can use the
6481 synonym @samp{search @var{regexp}} or abbreviate the command name as
6484 @kindex reverse-search
6485 @item reverse-search @var{regexp}
6486 The command @samp{reverse-search @var{regexp}} checks each line, starting
6487 with the one before the last line listed and going backward, for a match
6488 for @var{regexp}. It lists the line that is found. You can abbreviate
6489 this command as @code{rev}.
6493 @section Specifying Source Directories
6496 @cindex directories for source files
6497 Executable programs sometimes do not record the directories of the source
6498 files from which they were compiled, just the names. Even when they do,
6499 the directories could be moved between the compilation and your debugging
6500 session. @value{GDBN} has a list of directories to search for source files;
6501 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6502 it tries all the directories in the list, in the order they are present
6503 in the list, until it finds a file with the desired name.
6505 For example, suppose an executable references the file
6506 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6507 @file{/mnt/cross}. The file is first looked up literally; if this
6508 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6509 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6510 message is printed. @value{GDBN} does not look up the parts of the
6511 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6512 Likewise, the subdirectories of the source path are not searched: if
6513 the source path is @file{/mnt/cross}, and the binary refers to
6514 @file{foo.c}, @value{GDBN} would not find it under
6515 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6517 Plain file names, relative file names with leading directories, file
6518 names containing dots, etc.@: are all treated as described above; for
6519 instance, if the source path is @file{/mnt/cross}, and the source file
6520 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6521 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6522 that---@file{/mnt/cross/foo.c}.
6524 Note that the executable search path is @emph{not} used to locate the
6527 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6528 any information it has cached about where source files are found and where
6529 each line is in the file.
6533 When you start @value{GDBN}, its source path includes only @samp{cdir}
6534 and @samp{cwd}, in that order.
6535 To add other directories, use the @code{directory} command.
6537 The search path is used to find both program source files and @value{GDBN}
6538 script files (read using the @samp{-command} option and @samp{source} command).
6540 In addition to the source path, @value{GDBN} provides a set of commands
6541 that manage a list of source path substitution rules. A @dfn{substitution
6542 rule} specifies how to rewrite source directories stored in the program's
6543 debug information in case the sources were moved to a different
6544 directory between compilation and debugging. A rule is made of
6545 two strings, the first specifying what needs to be rewritten in
6546 the path, and the second specifying how it should be rewritten.
6547 In @ref{set substitute-path}, we name these two parts @var{from} and
6548 @var{to} respectively. @value{GDBN} does a simple string replacement
6549 of @var{from} with @var{to} at the start of the directory part of the
6550 source file name, and uses that result instead of the original file
6551 name to look up the sources.
6553 Using the previous example, suppose the @file{foo-1.0} tree has been
6554 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6555 @value{GDBN} to replace @file{/usr/src} in all source path names with
6556 @file{/mnt/cross}. The first lookup will then be
6557 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6558 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6559 substitution rule, use the @code{set substitute-path} command
6560 (@pxref{set substitute-path}).
6562 To avoid unexpected substitution results, a rule is applied only if the
6563 @var{from} part of the directory name ends at a directory separator.
6564 For instance, a rule substituting @file{/usr/source} into
6565 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6566 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6567 is applied only at the beginning of the directory name, this rule will
6568 not be applied to @file{/root/usr/source/baz.c} either.
6570 In many cases, you can achieve the same result using the @code{directory}
6571 command. However, @code{set substitute-path} can be more efficient in
6572 the case where the sources are organized in a complex tree with multiple
6573 subdirectories. With the @code{directory} command, you need to add each
6574 subdirectory of your project. If you moved the entire tree while
6575 preserving its internal organization, then @code{set substitute-path}
6576 allows you to direct the debugger to all the sources with one single
6579 @code{set substitute-path} is also more than just a shortcut command.
6580 The source path is only used if the file at the original location no
6581 longer exists. On the other hand, @code{set substitute-path} modifies
6582 the debugger behavior to look at the rewritten location instead. So, if
6583 for any reason a source file that is not relevant to your executable is
6584 located at the original location, a substitution rule is the only
6585 method available to point @value{GDBN} at the new location.
6587 @cindex @samp{--with-relocated-sources}
6588 @cindex default source path substitution
6589 You can configure a default source path substitution rule by
6590 configuring @value{GDBN} with the
6591 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6592 should be the name of a directory under @value{GDBN}'s configured
6593 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6594 directory names in debug information under @var{dir} will be adjusted
6595 automatically if the installed @value{GDBN} is moved to a new
6596 location. This is useful if @value{GDBN}, libraries or executables
6597 with debug information and corresponding source code are being moved
6601 @item directory @var{dirname} @dots{}
6602 @item dir @var{dirname} @dots{}
6603 Add directory @var{dirname} to the front of the source path. Several
6604 directory names may be given to this command, separated by @samp{:}
6605 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6606 part of absolute file names) or
6607 whitespace. You may specify a directory that is already in the source
6608 path; this moves it forward, so @value{GDBN} searches it sooner.
6612 @vindex $cdir@r{, convenience variable}
6613 @vindex $cwd@r{, convenience variable}
6614 @cindex compilation directory
6615 @cindex current directory
6616 @cindex working directory
6617 @cindex directory, current
6618 @cindex directory, compilation
6619 You can use the string @samp{$cdir} to refer to the compilation
6620 directory (if one is recorded), and @samp{$cwd} to refer to the current
6621 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6622 tracks the current working directory as it changes during your @value{GDBN}
6623 session, while the latter is immediately expanded to the current
6624 directory at the time you add an entry to the source path.
6627 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6629 @c RET-repeat for @code{directory} is explicitly disabled, but since
6630 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6632 @item set directories @var{path-list}
6633 @kindex set directories
6634 Set the source path to @var{path-list}.
6635 @samp{$cdir:$cwd} are added if missing.
6637 @item show directories
6638 @kindex show directories
6639 Print the source path: show which directories it contains.
6641 @anchor{set substitute-path}
6642 @item set substitute-path @var{from} @var{to}
6643 @kindex set substitute-path
6644 Define a source path substitution rule, and add it at the end of the
6645 current list of existing substitution rules. If a rule with the same
6646 @var{from} was already defined, then the old rule is also deleted.
6648 For example, if the file @file{/foo/bar/baz.c} was moved to
6649 @file{/mnt/cross/baz.c}, then the command
6652 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6656 will tell @value{GDBN} to replace @samp{/usr/src} with
6657 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6658 @file{baz.c} even though it was moved.
6660 In the case when more than one substitution rule have been defined,
6661 the rules are evaluated one by one in the order where they have been
6662 defined. The first one matching, if any, is selected to perform
6665 For instance, if we had entered the following commands:
6668 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6669 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6673 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6674 @file{/mnt/include/defs.h} by using the first rule. However, it would
6675 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6676 @file{/mnt/src/lib/foo.c}.
6679 @item unset substitute-path [path]
6680 @kindex unset substitute-path
6681 If a path is specified, search the current list of substitution rules
6682 for a rule that would rewrite that path. Delete that rule if found.
6683 A warning is emitted by the debugger if no rule could be found.
6685 If no path is specified, then all substitution rules are deleted.
6687 @item show substitute-path [path]
6688 @kindex show substitute-path
6689 If a path is specified, then print the source path substitution rule
6690 which would rewrite that path, if any.
6692 If no path is specified, then print all existing source path substitution
6697 If your source path is cluttered with directories that are no longer of
6698 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6699 versions of source. You can correct the situation as follows:
6703 Use @code{directory} with no argument to reset the source path to its default value.
6706 Use @code{directory} with suitable arguments to reinstall the
6707 directories you want in the source path. You can add all the
6708 directories in one command.
6712 @section Source and Machine Code
6713 @cindex source line and its code address
6715 You can use the command @code{info line} to map source lines to program
6716 addresses (and vice versa), and the command @code{disassemble} to display
6717 a range of addresses as machine instructions. You can use the command
6718 @code{set disassemble-next-line} to set whether to disassemble next
6719 source line when execution stops. When run under @sc{gnu} Emacs
6720 mode, the @code{info line} command causes the arrow to point to the
6721 line specified. Also, @code{info line} prints addresses in symbolic form as
6726 @item info line @var{linespec}
6727 Print the starting and ending addresses of the compiled code for
6728 source line @var{linespec}. You can specify source lines in any of
6729 the ways documented in @ref{Specify Location}.
6732 For example, we can use @code{info line} to discover the location of
6733 the object code for the first line of function
6734 @code{m4_changequote}:
6736 @c FIXME: I think this example should also show the addresses in
6737 @c symbolic form, as they usually would be displayed.
6739 (@value{GDBP}) info line m4_changequote
6740 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6744 @cindex code address and its source line
6745 We can also inquire (using @code{*@var{addr}} as the form for
6746 @var{linespec}) what source line covers a particular address:
6748 (@value{GDBP}) info line *0x63ff
6749 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6752 @cindex @code{$_} and @code{info line}
6753 @cindex @code{x} command, default address
6754 @kindex x@r{(examine), and} info line
6755 After @code{info line}, the default address for the @code{x} command
6756 is changed to the starting address of the line, so that @samp{x/i} is
6757 sufficient to begin examining the machine code (@pxref{Memory,
6758 ,Examining Memory}). Also, this address is saved as the value of the
6759 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6764 @cindex assembly instructions
6765 @cindex instructions, assembly
6766 @cindex machine instructions
6767 @cindex listing machine instructions
6769 @itemx disassemble /m
6770 @itemx disassemble /r
6771 This specialized command dumps a range of memory as machine
6772 instructions. It can also print mixed source+disassembly by specifying
6773 the @code{/m} modifier and print the raw instructions in hex as well as
6774 in symbolic form by specifying the @code{/r}.
6775 The default memory range is the function surrounding the
6776 program counter of the selected frame. A single argument to this
6777 command is a program counter value; @value{GDBN} dumps the function
6778 surrounding this value. When two arguments are given, they should
6779 be separated by a comma, possibly surrounded by whitespace. The
6780 arguments specify a range of addresses to dump, in one of two forms:
6783 @item @var{start},@var{end}
6784 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6785 @item @var{start},+@var{length}
6786 the addresses from @var{start} (inclusive) to
6787 @code{@var{start}+@var{length}} (exclusive).
6791 When 2 arguments are specified, the name of the function is also
6792 printed (since there could be several functions in the given range).
6794 The argument(s) can be any expression yielding a numeric value, such as
6795 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6797 If the range of memory being disassembled contains current program counter,
6798 the instruction at that location is shown with a @code{=>} marker.
6801 The following example shows the disassembly of a range of addresses of
6802 HP PA-RISC 2.0 code:
6805 (@value{GDBP}) disas 0x32c4, 0x32e4
6806 Dump of assembler code from 0x32c4 to 0x32e4:
6807 0x32c4 <main+204>: addil 0,dp
6808 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6809 0x32cc <main+212>: ldil 0x3000,r31
6810 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6811 0x32d4 <main+220>: ldo 0(r31),rp
6812 0x32d8 <main+224>: addil -0x800,dp
6813 0x32dc <main+228>: ldo 0x588(r1),r26
6814 0x32e0 <main+232>: ldil 0x3000,r31
6815 End of assembler dump.
6818 Here is an example showing mixed source+assembly for Intel x86, when the
6819 program is stopped just after function prologue:
6822 (@value{GDBP}) disas /m main
6823 Dump of assembler code for function main:
6825 0x08048330 <+0>: push %ebp
6826 0x08048331 <+1>: mov %esp,%ebp
6827 0x08048333 <+3>: sub $0x8,%esp
6828 0x08048336 <+6>: and $0xfffffff0,%esp
6829 0x08048339 <+9>: sub $0x10,%esp
6831 6 printf ("Hello.\n");
6832 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6833 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6837 0x08048348 <+24>: mov $0x0,%eax
6838 0x0804834d <+29>: leave
6839 0x0804834e <+30>: ret
6841 End of assembler dump.
6844 Here is another example showing raw instructions in hex for AMD x86-64,
6847 (gdb) disas /r 0x400281,+10
6848 Dump of assembler code from 0x400281 to 0x40028b:
6849 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6850 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6851 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
6852 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
6853 End of assembler dump.
6856 Some architectures have more than one commonly-used set of instruction
6857 mnemonics or other syntax.
6859 For programs that were dynamically linked and use shared libraries,
6860 instructions that call functions or branch to locations in the shared
6861 libraries might show a seemingly bogus location---it's actually a
6862 location of the relocation table. On some architectures, @value{GDBN}
6863 might be able to resolve these to actual function names.
6866 @kindex set disassembly-flavor
6867 @cindex Intel disassembly flavor
6868 @cindex AT&T disassembly flavor
6869 @item set disassembly-flavor @var{instruction-set}
6870 Select the instruction set to use when disassembling the
6871 program via the @code{disassemble} or @code{x/i} commands.
6873 Currently this command is only defined for the Intel x86 family. You
6874 can set @var{instruction-set} to either @code{intel} or @code{att}.
6875 The default is @code{att}, the AT&T flavor used by default by Unix
6876 assemblers for x86-based targets.
6878 @kindex show disassembly-flavor
6879 @item show disassembly-flavor
6880 Show the current setting of the disassembly flavor.
6884 @kindex set disassemble-next-line
6885 @kindex show disassemble-next-line
6886 @item set disassemble-next-line
6887 @itemx show disassemble-next-line
6888 Control whether or not @value{GDBN} will disassemble the next source
6889 line or instruction when execution stops. If ON, @value{GDBN} will
6890 display disassembly of the next source line when execution of the
6891 program being debugged stops. This is @emph{in addition} to
6892 displaying the source line itself, which @value{GDBN} always does if
6893 possible. If the next source line cannot be displayed for some reason
6894 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6895 info in the debug info), @value{GDBN} will display disassembly of the
6896 next @emph{instruction} instead of showing the next source line. If
6897 AUTO, @value{GDBN} will display disassembly of next instruction only
6898 if the source line cannot be displayed. This setting causes
6899 @value{GDBN} to display some feedback when you step through a function
6900 with no line info or whose source file is unavailable. The default is
6901 OFF, which means never display the disassembly of the next line or
6907 @chapter Examining Data
6909 @cindex printing data
6910 @cindex examining data
6913 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6914 @c document because it is nonstandard... Under Epoch it displays in a
6915 @c different window or something like that.
6916 The usual way to examine data in your program is with the @code{print}
6917 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6918 evaluates and prints the value of an expression of the language your
6919 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6920 Different Languages}). It may also print the expression using a
6921 Python-based pretty-printer (@pxref{Pretty Printing}).
6924 @item print @var{expr}
6925 @itemx print /@var{f} @var{expr}
6926 @var{expr} is an expression (in the source language). By default the
6927 value of @var{expr} is printed in a format appropriate to its data type;
6928 you can choose a different format by specifying @samp{/@var{f}}, where
6929 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6933 @itemx print /@var{f}
6934 @cindex reprint the last value
6935 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6936 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6937 conveniently inspect the same value in an alternative format.
6940 A more low-level way of examining data is with the @code{x} command.
6941 It examines data in memory at a specified address and prints it in a
6942 specified format. @xref{Memory, ,Examining Memory}.
6944 If you are interested in information about types, or about how the
6945 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6946 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6950 * Expressions:: Expressions
6951 * Ambiguous Expressions:: Ambiguous Expressions
6952 * Variables:: Program variables
6953 * Arrays:: Artificial arrays
6954 * Output Formats:: Output formats
6955 * Memory:: Examining memory
6956 * Auto Display:: Automatic display
6957 * Print Settings:: Print settings
6958 * Pretty Printing:: Python pretty printing
6959 * Value History:: Value history
6960 * Convenience Vars:: Convenience variables
6961 * Registers:: Registers
6962 * Floating Point Hardware:: Floating point hardware
6963 * Vector Unit:: Vector Unit
6964 * OS Information:: Auxiliary data provided by operating system
6965 * Memory Region Attributes:: Memory region attributes
6966 * Dump/Restore Files:: Copy between memory and a file
6967 * Core File Generation:: Cause a program dump its core
6968 * Character Sets:: Debugging programs that use a different
6969 character set than GDB does
6970 * Caching Remote Data:: Data caching for remote targets
6971 * Searching Memory:: Searching memory for a sequence of bytes
6975 @section Expressions
6978 @code{print} and many other @value{GDBN} commands accept an expression and
6979 compute its value. Any kind of constant, variable or operator defined
6980 by the programming language you are using is valid in an expression in
6981 @value{GDBN}. This includes conditional expressions, function calls,
6982 casts, and string constants. It also includes preprocessor macros, if
6983 you compiled your program to include this information; see
6986 @cindex arrays in expressions
6987 @value{GDBN} supports array constants in expressions input by
6988 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6989 you can use the command @code{print @{1, 2, 3@}} to create an array
6990 of three integers. If you pass an array to a function or assign it
6991 to a program variable, @value{GDBN} copies the array to memory that
6992 is @code{malloc}ed in the target program.
6994 Because C is so widespread, most of the expressions shown in examples in
6995 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6996 Languages}, for information on how to use expressions in other
6999 In this section, we discuss operators that you can use in @value{GDBN}
7000 expressions regardless of your programming language.
7002 @cindex casts, in expressions
7003 Casts are supported in all languages, not just in C, because it is so
7004 useful to cast a number into a pointer in order to examine a structure
7005 at that address in memory.
7006 @c FIXME: casts supported---Mod2 true?
7008 @value{GDBN} supports these operators, in addition to those common
7009 to programming languages:
7013 @samp{@@} is a binary operator for treating parts of memory as arrays.
7014 @xref{Arrays, ,Artificial Arrays}, for more information.
7017 @samp{::} allows you to specify a variable in terms of the file or
7018 function where it is defined. @xref{Variables, ,Program Variables}.
7020 @cindex @{@var{type}@}
7021 @cindex type casting memory
7022 @cindex memory, viewing as typed object
7023 @cindex casts, to view memory
7024 @item @{@var{type}@} @var{addr}
7025 Refers to an object of type @var{type} stored at address @var{addr} in
7026 memory. @var{addr} may be any expression whose value is an integer or
7027 pointer (but parentheses are required around binary operators, just as in
7028 a cast). This construct is allowed regardless of what kind of data is
7029 normally supposed to reside at @var{addr}.
7032 @node Ambiguous Expressions
7033 @section Ambiguous Expressions
7034 @cindex ambiguous expressions
7036 Expressions can sometimes contain some ambiguous elements. For instance,
7037 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7038 a single function name to be defined several times, for application in
7039 different contexts. This is called @dfn{overloading}. Another example
7040 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7041 templates and is typically instantiated several times, resulting in
7042 the same function name being defined in different contexts.
7044 In some cases and depending on the language, it is possible to adjust
7045 the expression to remove the ambiguity. For instance in C@t{++}, you
7046 can specify the signature of the function you want to break on, as in
7047 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7048 qualified name of your function often makes the expression unambiguous
7051 When an ambiguity that needs to be resolved is detected, the debugger
7052 has the capability to display a menu of numbered choices for each
7053 possibility, and then waits for the selection with the prompt @samp{>}.
7054 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7055 aborts the current command. If the command in which the expression was
7056 used allows more than one choice to be selected, the next option in the
7057 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7060 For example, the following session excerpt shows an attempt to set a
7061 breakpoint at the overloaded symbol @code{String::after}.
7062 We choose three particular definitions of that function name:
7064 @c FIXME! This is likely to change to show arg type lists, at least
7067 (@value{GDBP}) b String::after
7070 [2] file:String.cc; line number:867
7071 [3] file:String.cc; line number:860
7072 [4] file:String.cc; line number:875
7073 [5] file:String.cc; line number:853
7074 [6] file:String.cc; line number:846
7075 [7] file:String.cc; line number:735
7077 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7078 Breakpoint 2 at 0xb344: file String.cc, line 875.
7079 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7080 Multiple breakpoints were set.
7081 Use the "delete" command to delete unwanted
7088 @kindex set multiple-symbols
7089 @item set multiple-symbols @var{mode}
7090 @cindex multiple-symbols menu
7092 This option allows you to adjust the debugger behavior when an expression
7095 By default, @var{mode} is set to @code{all}. If the command with which
7096 the expression is used allows more than one choice, then @value{GDBN}
7097 automatically selects all possible choices. For instance, inserting
7098 a breakpoint on a function using an ambiguous name results in a breakpoint
7099 inserted on each possible match. However, if a unique choice must be made,
7100 then @value{GDBN} uses the menu to help you disambiguate the expression.
7101 For instance, printing the address of an overloaded function will result
7102 in the use of the menu.
7104 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7105 when an ambiguity is detected.
7107 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7108 an error due to the ambiguity and the command is aborted.
7110 @kindex show multiple-symbols
7111 @item show multiple-symbols
7112 Show the current value of the @code{multiple-symbols} setting.
7116 @section Program Variables
7118 The most common kind of expression to use is the name of a variable
7121 Variables in expressions are understood in the selected stack frame
7122 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7126 global (or file-static)
7133 visible according to the scope rules of the
7134 programming language from the point of execution in that frame
7137 @noindent This means that in the function
7152 you can examine and use the variable @code{a} whenever your program is
7153 executing within the function @code{foo}, but you can only use or
7154 examine the variable @code{b} while your program is executing inside
7155 the block where @code{b} is declared.
7157 @cindex variable name conflict
7158 There is an exception: you can refer to a variable or function whose
7159 scope is a single source file even if the current execution point is not
7160 in this file. But it is possible to have more than one such variable or
7161 function with the same name (in different source files). If that
7162 happens, referring to that name has unpredictable effects. If you wish,
7163 you can specify a static variable in a particular function or file,
7164 using the colon-colon (@code{::}) notation:
7166 @cindex colon-colon, context for variables/functions
7168 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7169 @cindex @code{::}, context for variables/functions
7172 @var{file}::@var{variable}
7173 @var{function}::@var{variable}
7177 Here @var{file} or @var{function} is the name of the context for the
7178 static @var{variable}. In the case of file names, you can use quotes to
7179 make sure @value{GDBN} parses the file name as a single word---for example,
7180 to print a global value of @code{x} defined in @file{f2.c}:
7183 (@value{GDBP}) p 'f2.c'::x
7186 @cindex C@t{++} scope resolution
7187 This use of @samp{::} is very rarely in conflict with the very similar
7188 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7189 scope resolution operator in @value{GDBN} expressions.
7190 @c FIXME: Um, so what happens in one of those rare cases where it's in
7193 @cindex wrong values
7194 @cindex variable values, wrong
7195 @cindex function entry/exit, wrong values of variables
7196 @cindex optimized code, wrong values of variables
7198 @emph{Warning:} Occasionally, a local variable may appear to have the
7199 wrong value at certain points in a function---just after entry to a new
7200 scope, and just before exit.
7202 You may see this problem when you are stepping by machine instructions.
7203 This is because, on most machines, it takes more than one instruction to
7204 set up a stack frame (including local variable definitions); if you are
7205 stepping by machine instructions, variables may appear to have the wrong
7206 values until the stack frame is completely built. On exit, it usually
7207 also takes more than one machine instruction to destroy a stack frame;
7208 after you begin stepping through that group of instructions, local
7209 variable definitions may be gone.
7211 This may also happen when the compiler does significant optimizations.
7212 To be sure of always seeing accurate values, turn off all optimization
7215 @cindex ``No symbol "foo" in current context''
7216 Another possible effect of compiler optimizations is to optimize
7217 unused variables out of existence, or assign variables to registers (as
7218 opposed to memory addresses). Depending on the support for such cases
7219 offered by the debug info format used by the compiler, @value{GDBN}
7220 might not be able to display values for such local variables. If that
7221 happens, @value{GDBN} will print a message like this:
7224 No symbol "foo" in current context.
7227 To solve such problems, either recompile without optimizations, or use a
7228 different debug info format, if the compiler supports several such
7229 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7230 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7231 produces debug info in a format that is superior to formats such as
7232 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7233 an effective form for debug info. @xref{Debugging Options,,Options
7234 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7235 Compiler Collection (GCC)}.
7236 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7237 that are best suited to C@t{++} programs.
7239 If you ask to print an object whose contents are unknown to
7240 @value{GDBN}, e.g., because its data type is not completely specified
7241 by the debug information, @value{GDBN} will say @samp{<incomplete
7242 type>}. @xref{Symbols, incomplete type}, for more about this.
7244 Strings are identified as arrays of @code{char} values without specified
7245 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7246 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7247 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7248 defines literal string type @code{"char"} as @code{char} without a sign.
7253 signed char var1[] = "A";
7256 You get during debugging
7261 $2 = @{65 'A', 0 '\0'@}
7265 @section Artificial Arrays
7267 @cindex artificial array
7269 @kindex @@@r{, referencing memory as an array}
7270 It is often useful to print out several successive objects of the
7271 same type in memory; a section of an array, or an array of
7272 dynamically determined size for which only a pointer exists in the
7275 You can do this by referring to a contiguous span of memory as an
7276 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7277 operand of @samp{@@} should be the first element of the desired array
7278 and be an individual object. The right operand should be the desired length
7279 of the array. The result is an array value whose elements are all of
7280 the type of the left argument. The first element is actually the left
7281 argument; the second element comes from bytes of memory immediately
7282 following those that hold the first element, and so on. Here is an
7283 example. If a program says
7286 int *array = (int *) malloc (len * sizeof (int));
7290 you can print the contents of @code{array} with
7296 The left operand of @samp{@@} must reside in memory. Array values made
7297 with @samp{@@} in this way behave just like other arrays in terms of
7298 subscripting, and are coerced to pointers when used in expressions.
7299 Artificial arrays most often appear in expressions via the value history
7300 (@pxref{Value History, ,Value History}), after printing one out.
7302 Another way to create an artificial array is to use a cast.
7303 This re-interprets a value as if it were an array.
7304 The value need not be in memory:
7306 (@value{GDBP}) p/x (short[2])0x12345678
7307 $1 = @{0x1234, 0x5678@}
7310 As a convenience, if you leave the array length out (as in
7311 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7312 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7314 (@value{GDBP}) p/x (short[])0x12345678
7315 $2 = @{0x1234, 0x5678@}
7318 Sometimes the artificial array mechanism is not quite enough; in
7319 moderately complex data structures, the elements of interest may not
7320 actually be adjacent---for example, if you are interested in the values
7321 of pointers in an array. One useful work-around in this situation is
7322 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7323 Variables}) as a counter in an expression that prints the first
7324 interesting value, and then repeat that expression via @key{RET}. For
7325 instance, suppose you have an array @code{dtab} of pointers to
7326 structures, and you are interested in the values of a field @code{fv}
7327 in each structure. Here is an example of what you might type:
7337 @node Output Formats
7338 @section Output Formats
7340 @cindex formatted output
7341 @cindex output formats
7342 By default, @value{GDBN} prints a value according to its data type. Sometimes
7343 this is not what you want. For example, you might want to print a number
7344 in hex, or a pointer in decimal. Or you might want to view data in memory
7345 at a certain address as a character string or as an instruction. To do
7346 these things, specify an @dfn{output format} when you print a value.
7348 The simplest use of output formats is to say how to print a value
7349 already computed. This is done by starting the arguments of the
7350 @code{print} command with a slash and a format letter. The format
7351 letters supported are:
7355 Regard the bits of the value as an integer, and print the integer in
7359 Print as integer in signed decimal.
7362 Print as integer in unsigned decimal.
7365 Print as integer in octal.
7368 Print as integer in binary. The letter @samp{t} stands for ``two''.
7369 @footnote{@samp{b} cannot be used because these format letters are also
7370 used with the @code{x} command, where @samp{b} stands for ``byte'';
7371 see @ref{Memory,,Examining Memory}.}
7374 @cindex unknown address, locating
7375 @cindex locate address
7376 Print as an address, both absolute in hexadecimal and as an offset from
7377 the nearest preceding symbol. You can use this format used to discover
7378 where (in what function) an unknown address is located:
7381 (@value{GDBP}) p/a 0x54320
7382 $3 = 0x54320 <_initialize_vx+396>
7386 The command @code{info symbol 0x54320} yields similar results.
7387 @xref{Symbols, info symbol}.
7390 Regard as an integer and print it as a character constant. This
7391 prints both the numerical value and its character representation. The
7392 character representation is replaced with the octal escape @samp{\nnn}
7393 for characters outside the 7-bit @sc{ascii} range.
7395 Without this format, @value{GDBN} displays @code{char},
7396 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7397 constants. Single-byte members of vectors are displayed as integer
7401 Regard the bits of the value as a floating point number and print
7402 using typical floating point syntax.
7405 @cindex printing strings
7406 @cindex printing byte arrays
7407 Regard as a string, if possible. With this format, pointers to single-byte
7408 data are displayed as null-terminated strings and arrays of single-byte data
7409 are displayed as fixed-length strings. Other values are displayed in their
7412 Without this format, @value{GDBN} displays pointers to and arrays of
7413 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7414 strings. Single-byte members of a vector are displayed as an integer
7418 @cindex raw printing
7419 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7420 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7421 Printing}). This typically results in a higher-level display of the
7422 value's contents. The @samp{r} format bypasses any Python
7423 pretty-printer which might exist.
7426 For example, to print the program counter in hex (@pxref{Registers}), type
7433 Note that no space is required before the slash; this is because command
7434 names in @value{GDBN} cannot contain a slash.
7436 To reprint the last value in the value history with a different format,
7437 you can use the @code{print} command with just a format and no
7438 expression. For example, @samp{p/x} reprints the last value in hex.
7441 @section Examining Memory
7443 You can use the command @code{x} (for ``examine'') to examine memory in
7444 any of several formats, independently of your program's data types.
7446 @cindex examining memory
7448 @kindex x @r{(examine memory)}
7449 @item x/@var{nfu} @var{addr}
7452 Use the @code{x} command to examine memory.
7455 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7456 much memory to display and how to format it; @var{addr} is an
7457 expression giving the address where you want to start displaying memory.
7458 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7459 Several commands set convenient defaults for @var{addr}.
7462 @item @var{n}, the repeat count
7463 The repeat count is a decimal integer; the default is 1. It specifies
7464 how much memory (counting by units @var{u}) to display.
7465 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7468 @item @var{f}, the display format
7469 The display format is one of the formats used by @code{print}
7470 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7471 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7472 The default is @samp{x} (hexadecimal) initially. The default changes
7473 each time you use either @code{x} or @code{print}.
7475 @item @var{u}, the unit size
7476 The unit size is any of
7482 Halfwords (two bytes).
7484 Words (four bytes). This is the initial default.
7486 Giant words (eight bytes).
7489 Each time you specify a unit size with @code{x}, that size becomes the
7490 default unit the next time you use @code{x}. For the @samp{i} format,
7491 the unit size is ignored and is normally not written. For the @samp{s} format,
7492 the unit size defaults to @samp{b}, unless it is explicitly given.
7493 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7494 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7495 Note that the results depend on the programming language of the
7496 current compilation unit. If the language is C, the @samp{s}
7497 modifier will use the UTF-16 encoding while @samp{w} will use
7498 UTF-32. The encoding is set by the programming language and cannot
7501 @item @var{addr}, starting display address
7502 @var{addr} is the address where you want @value{GDBN} to begin displaying
7503 memory. The expression need not have a pointer value (though it may);
7504 it is always interpreted as an integer address of a byte of memory.
7505 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7506 @var{addr} is usually just after the last address examined---but several
7507 other commands also set the default address: @code{info breakpoints} (to
7508 the address of the last breakpoint listed), @code{info line} (to the
7509 starting address of a line), and @code{print} (if you use it to display
7510 a value from memory).
7513 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7514 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7515 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7516 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7517 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7519 Since the letters indicating unit sizes are all distinct from the
7520 letters specifying output formats, you do not have to remember whether
7521 unit size or format comes first; either order works. The output
7522 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7523 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7525 Even though the unit size @var{u} is ignored for the formats @samp{s}
7526 and @samp{i}, you might still want to use a count @var{n}; for example,
7527 @samp{3i} specifies that you want to see three machine instructions,
7528 including any operands. For convenience, especially when used with
7529 the @code{display} command, the @samp{i} format also prints branch delay
7530 slot instructions, if any, beyond the count specified, which immediately
7531 follow the last instruction that is within the count. The command
7532 @code{disassemble} gives an alternative way of inspecting machine
7533 instructions; see @ref{Machine Code,,Source and Machine Code}.
7535 All the defaults for the arguments to @code{x} are designed to make it
7536 easy to continue scanning memory with minimal specifications each time
7537 you use @code{x}. For example, after you have inspected three machine
7538 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7539 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7540 the repeat count @var{n} is used again; the other arguments default as
7541 for successive uses of @code{x}.
7543 When examining machine instructions, the instruction at current program
7544 counter is shown with a @code{=>} marker. For example:
7547 (@value{GDBP}) x/5i $pc-6
7548 0x804837f <main+11>: mov %esp,%ebp
7549 0x8048381 <main+13>: push %ecx
7550 0x8048382 <main+14>: sub $0x4,%esp
7551 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7552 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7555 @cindex @code{$_}, @code{$__}, and value history
7556 The addresses and contents printed by the @code{x} command are not saved
7557 in the value history because there is often too much of them and they
7558 would get in the way. Instead, @value{GDBN} makes these values available for
7559 subsequent use in expressions as values of the convenience variables
7560 @code{$_} and @code{$__}. After an @code{x} command, the last address
7561 examined is available for use in expressions in the convenience variable
7562 @code{$_}. The contents of that address, as examined, are available in
7563 the convenience variable @code{$__}.
7565 If the @code{x} command has a repeat count, the address and contents saved
7566 are from the last memory unit printed; this is not the same as the last
7567 address printed if several units were printed on the last line of output.
7569 @cindex remote memory comparison
7570 @cindex verify remote memory image
7571 When you are debugging a program running on a remote target machine
7572 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7573 remote machine's memory against the executable file you downloaded to
7574 the target. The @code{compare-sections} command is provided for such
7578 @kindex compare-sections
7579 @item compare-sections @r{[}@var{section-name}@r{]}
7580 Compare the data of a loadable section @var{section-name} in the
7581 executable file of the program being debugged with the same section in
7582 the remote machine's memory, and report any mismatches. With no
7583 arguments, compares all loadable sections. This command's
7584 availability depends on the target's support for the @code{"qCRC"}
7589 @section Automatic Display
7590 @cindex automatic display
7591 @cindex display of expressions
7593 If you find that you want to print the value of an expression frequently
7594 (to see how it changes), you might want to add it to the @dfn{automatic
7595 display list} so that @value{GDBN} prints its value each time your program stops.
7596 Each expression added to the list is given a number to identify it;
7597 to remove an expression from the list, you specify that number.
7598 The automatic display looks like this:
7602 3: bar[5] = (struct hack *) 0x3804
7606 This display shows item numbers, expressions and their current values. As with
7607 displays you request manually using @code{x} or @code{print}, you can
7608 specify the output format you prefer; in fact, @code{display} decides
7609 whether to use @code{print} or @code{x} depending your format
7610 specification---it uses @code{x} if you specify either the @samp{i}
7611 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7615 @item display @var{expr}
7616 Add the expression @var{expr} to the list of expressions to display
7617 each time your program stops. @xref{Expressions, ,Expressions}.
7619 @code{display} does not repeat if you press @key{RET} again after using it.
7621 @item display/@var{fmt} @var{expr}
7622 For @var{fmt} specifying only a display format and not a size or
7623 count, add the expression @var{expr} to the auto-display list but
7624 arrange to display it each time in the specified format @var{fmt}.
7625 @xref{Output Formats,,Output Formats}.
7627 @item display/@var{fmt} @var{addr}
7628 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7629 number of units, add the expression @var{addr} as a memory address to
7630 be examined each time your program stops. Examining means in effect
7631 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7634 For example, @samp{display/i $pc} can be helpful, to see the machine
7635 instruction about to be executed each time execution stops (@samp{$pc}
7636 is a common name for the program counter; @pxref{Registers, ,Registers}).
7639 @kindex delete display
7641 @item undisplay @var{dnums}@dots{}
7642 @itemx delete display @var{dnums}@dots{}
7643 Remove item numbers @var{dnums} from the list of expressions to display.
7645 @code{undisplay} does not repeat if you press @key{RET} after using it.
7646 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7648 @kindex disable display
7649 @item disable display @var{dnums}@dots{}
7650 Disable the display of item numbers @var{dnums}. A disabled display
7651 item is not printed automatically, but is not forgotten. It may be
7652 enabled again later.
7654 @kindex enable display
7655 @item enable display @var{dnums}@dots{}
7656 Enable display of item numbers @var{dnums}. It becomes effective once
7657 again in auto display of its expression, until you specify otherwise.
7660 Display the current values of the expressions on the list, just as is
7661 done when your program stops.
7663 @kindex info display
7665 Print the list of expressions previously set up to display
7666 automatically, each one with its item number, but without showing the
7667 values. This includes disabled expressions, which are marked as such.
7668 It also includes expressions which would not be displayed right now
7669 because they refer to automatic variables not currently available.
7672 @cindex display disabled out of scope
7673 If a display expression refers to local variables, then it does not make
7674 sense outside the lexical context for which it was set up. Such an
7675 expression is disabled when execution enters a context where one of its
7676 variables is not defined. For example, if you give the command
7677 @code{display last_char} while inside a function with an argument
7678 @code{last_char}, @value{GDBN} displays this argument while your program
7679 continues to stop inside that function. When it stops elsewhere---where
7680 there is no variable @code{last_char}---the display is disabled
7681 automatically. The next time your program stops where @code{last_char}
7682 is meaningful, you can enable the display expression once again.
7684 @node Print Settings
7685 @section Print Settings
7687 @cindex format options
7688 @cindex print settings
7689 @value{GDBN} provides the following ways to control how arrays, structures,
7690 and symbols are printed.
7693 These settings are useful for debugging programs in any language:
7697 @item set print address
7698 @itemx set print address on
7699 @cindex print/don't print memory addresses
7700 @value{GDBN} prints memory addresses showing the location of stack
7701 traces, structure values, pointer values, breakpoints, and so forth,
7702 even when it also displays the contents of those addresses. The default
7703 is @code{on}. For example, this is what a stack frame display looks like with
7704 @code{set print address on}:
7709 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7711 530 if (lquote != def_lquote)
7715 @item set print address off
7716 Do not print addresses when displaying their contents. For example,
7717 this is the same stack frame displayed with @code{set print address off}:
7721 (@value{GDBP}) set print addr off
7723 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7724 530 if (lquote != def_lquote)
7728 You can use @samp{set print address off} to eliminate all machine
7729 dependent displays from the @value{GDBN} interface. For example, with
7730 @code{print address off}, you should get the same text for backtraces on
7731 all machines---whether or not they involve pointer arguments.
7734 @item show print address
7735 Show whether or not addresses are to be printed.
7738 When @value{GDBN} prints a symbolic address, it normally prints the
7739 closest earlier symbol plus an offset. If that symbol does not uniquely
7740 identify the address (for example, it is a name whose scope is a single
7741 source file), you may need to clarify. One way to do this is with
7742 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7743 you can set @value{GDBN} to print the source file and line number when
7744 it prints a symbolic address:
7747 @item set print symbol-filename on
7748 @cindex source file and line of a symbol
7749 @cindex symbol, source file and line
7750 Tell @value{GDBN} to print the source file name and line number of a
7751 symbol in the symbolic form of an address.
7753 @item set print symbol-filename off
7754 Do not print source file name and line number of a symbol. This is the
7757 @item show print symbol-filename
7758 Show whether or not @value{GDBN} will print the source file name and
7759 line number of a symbol in the symbolic form of an address.
7762 Another situation where it is helpful to show symbol filenames and line
7763 numbers is when disassembling code; @value{GDBN} shows you the line
7764 number and source file that corresponds to each instruction.
7766 Also, you may wish to see the symbolic form only if the address being
7767 printed is reasonably close to the closest earlier symbol:
7770 @item set print max-symbolic-offset @var{max-offset}
7771 @cindex maximum value for offset of closest symbol
7772 Tell @value{GDBN} to only display the symbolic form of an address if the
7773 offset between the closest earlier symbol and the address is less than
7774 @var{max-offset}. The default is 0, which tells @value{GDBN}
7775 to always print the symbolic form of an address if any symbol precedes it.
7777 @item show print max-symbolic-offset
7778 Ask how large the maximum offset is that @value{GDBN} prints in a
7782 @cindex wild pointer, interpreting
7783 @cindex pointer, finding referent
7784 If you have a pointer and you are not sure where it points, try
7785 @samp{set print symbol-filename on}. Then you can determine the name
7786 and source file location of the variable where it points, using
7787 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7788 For example, here @value{GDBN} shows that a variable @code{ptt} points
7789 at another variable @code{t}, defined in @file{hi2.c}:
7792 (@value{GDBP}) set print symbol-filename on
7793 (@value{GDBP}) p/a ptt
7794 $4 = 0xe008 <t in hi2.c>
7798 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7799 does not show the symbol name and filename of the referent, even with
7800 the appropriate @code{set print} options turned on.
7803 Other settings control how different kinds of objects are printed:
7806 @item set print array
7807 @itemx set print array on
7808 @cindex pretty print arrays
7809 Pretty print arrays. This format is more convenient to read,
7810 but uses more space. The default is off.
7812 @item set print array off
7813 Return to compressed format for arrays.
7815 @item show print array
7816 Show whether compressed or pretty format is selected for displaying
7819 @cindex print array indexes
7820 @item set print array-indexes
7821 @itemx set print array-indexes on
7822 Print the index of each element when displaying arrays. May be more
7823 convenient to locate a given element in the array or quickly find the
7824 index of a given element in that printed array. The default is off.
7826 @item set print array-indexes off
7827 Stop printing element indexes when displaying arrays.
7829 @item show print array-indexes
7830 Show whether the index of each element is printed when displaying
7833 @item set print elements @var{number-of-elements}
7834 @cindex number of array elements to print
7835 @cindex limit on number of printed array elements
7836 Set a limit on how many elements of an array @value{GDBN} will print.
7837 If @value{GDBN} is printing a large array, it stops printing after it has
7838 printed the number of elements set by the @code{set print elements} command.
7839 This limit also applies to the display of strings.
7840 When @value{GDBN} starts, this limit is set to 200.
7841 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7843 @item show print elements
7844 Display the number of elements of a large array that @value{GDBN} will print.
7845 If the number is 0, then the printing is unlimited.
7847 @item set print frame-arguments @var{value}
7848 @kindex set print frame-arguments
7849 @cindex printing frame argument values
7850 @cindex print all frame argument values
7851 @cindex print frame argument values for scalars only
7852 @cindex do not print frame argument values
7853 This command allows to control how the values of arguments are printed
7854 when the debugger prints a frame (@pxref{Frames}). The possible
7859 The values of all arguments are printed.
7862 Print the value of an argument only if it is a scalar. The value of more
7863 complex arguments such as arrays, structures, unions, etc, is replaced
7864 by @code{@dots{}}. This is the default. Here is an example where
7865 only scalar arguments are shown:
7868 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7873 None of the argument values are printed. Instead, the value of each argument
7874 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7877 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7882 By default, only scalar arguments are printed. This command can be used
7883 to configure the debugger to print the value of all arguments, regardless
7884 of their type. However, it is often advantageous to not print the value
7885 of more complex parameters. For instance, it reduces the amount of
7886 information printed in each frame, making the backtrace more readable.
7887 Also, it improves performance when displaying Ada frames, because
7888 the computation of large arguments can sometimes be CPU-intensive,
7889 especially in large applications. Setting @code{print frame-arguments}
7890 to @code{scalars} (the default) or @code{none} avoids this computation,
7891 thus speeding up the display of each Ada frame.
7893 @item show print frame-arguments
7894 Show how the value of arguments should be displayed when printing a frame.
7896 @item set print repeats
7897 @cindex repeated array elements
7898 Set the threshold for suppressing display of repeated array
7899 elements. When the number of consecutive identical elements of an
7900 array exceeds the threshold, @value{GDBN} prints the string
7901 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7902 identical repetitions, instead of displaying the identical elements
7903 themselves. Setting the threshold to zero will cause all elements to
7904 be individually printed. The default threshold is 10.
7906 @item show print repeats
7907 Display the current threshold for printing repeated identical
7910 @item set print null-stop
7911 @cindex @sc{null} elements in arrays
7912 Cause @value{GDBN} to stop printing the characters of an array when the first
7913 @sc{null} is encountered. This is useful when large arrays actually
7914 contain only short strings.
7917 @item show print null-stop
7918 Show whether @value{GDBN} stops printing an array on the first
7919 @sc{null} character.
7921 @item set print pretty on
7922 @cindex print structures in indented form
7923 @cindex indentation in structure display
7924 Cause @value{GDBN} to print structures in an indented format with one member
7925 per line, like this:
7940 @item set print pretty off
7941 Cause @value{GDBN} to print structures in a compact format, like this:
7945 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7946 meat = 0x54 "Pork"@}
7951 This is the default format.
7953 @item show print pretty
7954 Show which format @value{GDBN} is using to print structures.
7956 @item set print sevenbit-strings on
7957 @cindex eight-bit characters in strings
7958 @cindex octal escapes in strings
7959 Print using only seven-bit characters; if this option is set,
7960 @value{GDBN} displays any eight-bit characters (in strings or
7961 character values) using the notation @code{\}@var{nnn}. This setting is
7962 best if you are working in English (@sc{ascii}) and you use the
7963 high-order bit of characters as a marker or ``meta'' bit.
7965 @item set print sevenbit-strings off
7966 Print full eight-bit characters. This allows the use of more
7967 international character sets, and is the default.
7969 @item show print sevenbit-strings
7970 Show whether or not @value{GDBN} is printing only seven-bit characters.
7972 @item set print union on
7973 @cindex unions in structures, printing
7974 Tell @value{GDBN} to print unions which are contained in structures
7975 and other unions. This is the default setting.
7977 @item set print union off
7978 Tell @value{GDBN} not to print unions which are contained in
7979 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7982 @item show print union
7983 Ask @value{GDBN} whether or not it will print unions which are contained in
7984 structures and other unions.
7986 For example, given the declarations
7989 typedef enum @{Tree, Bug@} Species;
7990 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7991 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8002 struct thing foo = @{Tree, @{Acorn@}@};
8006 with @code{set print union on} in effect @samp{p foo} would print
8009 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8013 and with @code{set print union off} in effect it would print
8016 $1 = @{it = Tree, form = @{...@}@}
8020 @code{set print union} affects programs written in C-like languages
8026 These settings are of interest when debugging C@t{++} programs:
8029 @cindex demangling C@t{++} names
8030 @item set print demangle
8031 @itemx set print demangle on
8032 Print C@t{++} names in their source form rather than in the encoded
8033 (``mangled'') form passed to the assembler and linker for type-safe
8034 linkage. The default is on.
8036 @item show print demangle
8037 Show whether C@t{++} names are printed in mangled or demangled form.
8039 @item set print asm-demangle
8040 @itemx set print asm-demangle on
8041 Print C@t{++} names in their source form rather than their mangled form, even
8042 in assembler code printouts such as instruction disassemblies.
8045 @item show print asm-demangle
8046 Show whether C@t{++} names in assembly listings are printed in mangled
8049 @cindex C@t{++} symbol decoding style
8050 @cindex symbol decoding style, C@t{++}
8051 @kindex set demangle-style
8052 @item set demangle-style @var{style}
8053 Choose among several encoding schemes used by different compilers to
8054 represent C@t{++} names. The choices for @var{style} are currently:
8058 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8061 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8062 This is the default.
8065 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8068 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8071 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8072 @strong{Warning:} this setting alone is not sufficient to allow
8073 debugging @code{cfront}-generated executables. @value{GDBN} would
8074 require further enhancement to permit that.
8077 If you omit @var{style}, you will see a list of possible formats.
8079 @item show demangle-style
8080 Display the encoding style currently in use for decoding C@t{++} symbols.
8082 @item set print object
8083 @itemx set print object on
8084 @cindex derived type of an object, printing
8085 @cindex display derived types
8086 When displaying a pointer to an object, identify the @emph{actual}
8087 (derived) type of the object rather than the @emph{declared} type, using
8088 the virtual function table.
8090 @item set print object off
8091 Display only the declared type of objects, without reference to the
8092 virtual function table. This is the default setting.
8094 @item show print object
8095 Show whether actual, or declared, object types are displayed.
8097 @item set print static-members
8098 @itemx set print static-members on
8099 @cindex static members of C@t{++} objects
8100 Print static members when displaying a C@t{++} object. The default is on.
8102 @item set print static-members off
8103 Do not print static members when displaying a C@t{++} object.
8105 @item show print static-members
8106 Show whether C@t{++} static members are printed or not.
8108 @item set print pascal_static-members
8109 @itemx set print pascal_static-members on
8110 @cindex static members of Pascal objects
8111 @cindex Pascal objects, static members display
8112 Print static members when displaying a Pascal object. The default is on.
8114 @item set print pascal_static-members off
8115 Do not print static members when displaying a Pascal object.
8117 @item show print pascal_static-members
8118 Show whether Pascal static members are printed or not.
8120 @c These don't work with HP ANSI C++ yet.
8121 @item set print vtbl
8122 @itemx set print vtbl on
8123 @cindex pretty print C@t{++} virtual function tables
8124 @cindex virtual functions (C@t{++}) display
8125 @cindex VTBL display
8126 Pretty print C@t{++} virtual function tables. The default is off.
8127 (The @code{vtbl} commands do not work on programs compiled with the HP
8128 ANSI C@t{++} compiler (@code{aCC}).)
8130 @item set print vtbl off
8131 Do not pretty print C@t{++} virtual function tables.
8133 @item show print vtbl
8134 Show whether C@t{++} virtual function tables are pretty printed, or not.
8137 @node Pretty Printing
8138 @section Pretty Printing
8140 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8141 Python code. It greatly simplifies the display of complex objects. This
8142 mechanism works for both MI and the CLI.
8145 * Pretty-Printer Introduction:: Introduction to pretty-printers
8146 * Pretty-Printer Example:: An example pretty-printer
8147 * Pretty-Printer Commands:: Pretty-printer commands
8150 @node Pretty-Printer Introduction
8151 @subsection Pretty-Printer Introduction
8153 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8154 registered for the value. If there is then @value{GDBN} invokes the
8155 pretty-printer to print the value. Otherwise the value is printed normally.
8157 Pretty-printers are normally named. This makes them easy to manage.
8158 The @samp{info pretty-printer} command will list all the installed
8159 pretty-printers with their names.
8160 If a pretty-printer can handle multiple data types, then its
8161 @dfn{subprinters} are the printers for the individual data types.
8162 Each such subprinter has its own name.
8163 The format of the name is @var{printer-name}:@var{subprinter-name}.
8165 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8166 Typically they are automatically loaded and registered when the corresponding
8167 debug information is loaded, thus making them available without having to
8168 do anything special.
8170 There are three places where a pretty-printer can be registered.
8174 Pretty-printers registered globally are available when debugging
8178 Pretty-printers registered with a program space are available only
8179 when debugging that program.
8180 @xref{Progspaces In Python}, for more details on program spaces in Python.
8183 Pretty-printers registered with an objfile are loaded and unloaded
8184 with the corresponding objfile (e.g., shared library).
8185 @xref{Objfiles In Python}, for more details on objfiles in Python.
8188 @xref{Selecting Pretty-Printers}, for further information on how
8189 pretty-printers are selected,
8191 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8194 @node Pretty-Printer Example
8195 @subsection Pretty-Printer Example
8197 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8200 (@value{GDBP}) print s
8202 static npos = 4294967295,
8204 <std::allocator<char>> = @{
8205 <__gnu_cxx::new_allocator<char>> = @{
8206 <No data fields>@}, <No data fields>
8208 members of std::basic_string<char, std::char_traits<char>,
8209 std::allocator<char> >::_Alloc_hider:
8210 _M_p = 0x804a014 "abcd"
8215 With a pretty-printer for @code{std::string} only the contents are printed:
8218 (@value{GDBP}) print s
8222 @node Pretty-Printer Commands
8223 @subsection Pretty-Printer Commands
8224 @cindex pretty-printer commands
8227 @kindex info pretty-printer
8228 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8229 Print the list of installed pretty-printers.
8230 This includes disabled pretty-printers, which are marked as such.
8232 @var{object-regexp} is a regular expression matching the objects
8233 whose pretty-printers to list.
8234 Objects can be @code{global}, the program space's file
8235 (@pxref{Progspaces In Python}),
8236 and the object files within that program space (@pxref{Objfiles In Python}).
8237 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8238 looks up a printer from these three objects.
8240 @var{name-regexp} is a regular expression matching the name of the printers
8243 @kindex disable pretty-printer
8244 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8245 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8246 A disabled pretty-printer is not forgotten, it may be enabled again later.
8248 @kindex enable pretty-printer
8249 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8250 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8255 Suppose we have three pretty-printers installed: one from library1.so
8256 named @code{foo} that prints objects of type @code{foo}, and
8257 another from library2.so named @code{bar} that prints two types of objects,
8258 @code{bar1} and @code{bar2}.
8261 (gdb) info pretty-printer
8268 (gdb) info pretty-printer library2
8273 (gdb) disable pretty-printer library1
8275 2 of 3 printers enabled
8276 (gdb) info pretty-printer
8283 (gdb) disable pretty-printer library2 bar:bar1
8285 1 of 3 printers enabled
8286 (gdb) info pretty-printer library2
8293 (gdb) disable pretty-printer library2 bar
8295 0 of 3 printers enabled
8296 (gdb) info pretty-printer library2
8305 Note that for @code{bar} the entire printer can be disabled,
8306 as can each individual subprinter.
8309 @section Value History
8311 @cindex value history
8312 @cindex history of values printed by @value{GDBN}
8313 Values printed by the @code{print} command are saved in the @value{GDBN}
8314 @dfn{value history}. This allows you to refer to them in other expressions.
8315 Values are kept until the symbol table is re-read or discarded
8316 (for example with the @code{file} or @code{symbol-file} commands).
8317 When the symbol table changes, the value history is discarded,
8318 since the values may contain pointers back to the types defined in the
8323 @cindex history number
8324 The values printed are given @dfn{history numbers} by which you can
8325 refer to them. These are successive integers starting with one.
8326 @code{print} shows you the history number assigned to a value by
8327 printing @samp{$@var{num} = } before the value; here @var{num} is the
8330 To refer to any previous value, use @samp{$} followed by the value's
8331 history number. The way @code{print} labels its output is designed to
8332 remind you of this. Just @code{$} refers to the most recent value in
8333 the history, and @code{$$} refers to the value before that.
8334 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8335 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8336 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8338 For example, suppose you have just printed a pointer to a structure and
8339 want to see the contents of the structure. It suffices to type
8345 If you have a chain of structures where the component @code{next} points
8346 to the next one, you can print the contents of the next one with this:
8353 You can print successive links in the chain by repeating this
8354 command---which you can do by just typing @key{RET}.
8356 Note that the history records values, not expressions. If the value of
8357 @code{x} is 4 and you type these commands:
8365 then the value recorded in the value history by the @code{print} command
8366 remains 4 even though the value of @code{x} has changed.
8371 Print the last ten values in the value history, with their item numbers.
8372 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8373 values} does not change the history.
8375 @item show values @var{n}
8376 Print ten history values centered on history item number @var{n}.
8379 Print ten history values just after the values last printed. If no more
8380 values are available, @code{show values +} produces no display.
8383 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8384 same effect as @samp{show values +}.
8386 @node Convenience Vars
8387 @section Convenience Variables
8389 @cindex convenience variables
8390 @cindex user-defined variables
8391 @value{GDBN} provides @dfn{convenience variables} that you can use within
8392 @value{GDBN} to hold on to a value and refer to it later. These variables
8393 exist entirely within @value{GDBN}; they are not part of your program, and
8394 setting a convenience variable has no direct effect on further execution
8395 of your program. That is why you can use them freely.
8397 Convenience variables are prefixed with @samp{$}. Any name preceded by
8398 @samp{$} can be used for a convenience variable, unless it is one of
8399 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8400 (Value history references, in contrast, are @emph{numbers} preceded
8401 by @samp{$}. @xref{Value History, ,Value History}.)
8403 You can save a value in a convenience variable with an assignment
8404 expression, just as you would set a variable in your program.
8408 set $foo = *object_ptr
8412 would save in @code{$foo} the value contained in the object pointed to by
8415 Using a convenience variable for the first time creates it, but its
8416 value is @code{void} until you assign a new value. You can alter the
8417 value with another assignment at any time.
8419 Convenience variables have no fixed types. You can assign a convenience
8420 variable any type of value, including structures and arrays, even if
8421 that variable already has a value of a different type. The convenience
8422 variable, when used as an expression, has the type of its current value.
8425 @kindex show convenience
8426 @cindex show all user variables
8427 @item show convenience
8428 Print a list of convenience variables used so far, and their values.
8429 Abbreviated @code{show conv}.
8431 @kindex init-if-undefined
8432 @cindex convenience variables, initializing
8433 @item init-if-undefined $@var{variable} = @var{expression}
8434 Set a convenience variable if it has not already been set. This is useful
8435 for user-defined commands that keep some state. It is similar, in concept,
8436 to using local static variables with initializers in C (except that
8437 convenience variables are global). It can also be used to allow users to
8438 override default values used in a command script.
8440 If the variable is already defined then the expression is not evaluated so
8441 any side-effects do not occur.
8444 One of the ways to use a convenience variable is as a counter to be
8445 incremented or a pointer to be advanced. For example, to print
8446 a field from successive elements of an array of structures:
8450 print bar[$i++]->contents
8454 Repeat that command by typing @key{RET}.
8456 Some convenience variables are created automatically by @value{GDBN} and given
8457 values likely to be useful.
8460 @vindex $_@r{, convenience variable}
8462 The variable @code{$_} is automatically set by the @code{x} command to
8463 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8464 commands which provide a default address for @code{x} to examine also
8465 set @code{$_} to that address; these commands include @code{info line}
8466 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8467 except when set by the @code{x} command, in which case it is a pointer
8468 to the type of @code{$__}.
8470 @vindex $__@r{, convenience variable}
8472 The variable @code{$__} is automatically set by the @code{x} command
8473 to the value found in the last address examined. Its type is chosen
8474 to match the format in which the data was printed.
8477 @vindex $_exitcode@r{, convenience variable}
8478 The variable @code{$_exitcode} is automatically set to the exit code when
8479 the program being debugged terminates.
8482 @vindex $_sdata@r{, inspect, convenience variable}
8483 The variable @code{$_sdata} contains extra collected static tracepoint
8484 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8485 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8486 if extra static tracepoint data has not been collected.
8489 @vindex $_siginfo@r{, convenience variable}
8490 The variable @code{$_siginfo} contains extra signal information
8491 (@pxref{extra signal information}). Note that @code{$_siginfo}
8492 could be empty, if the application has not yet received any signals.
8493 For example, it will be empty before you execute the @code{run} command.
8496 @vindex $_tlb@r{, convenience variable}
8497 The variable @code{$_tlb} is automatically set when debugging
8498 applications running on MS-Windows in native mode or connected to
8499 gdbserver that supports the @code{qGetTIBAddr} request.
8500 @xref{General Query Packets}.
8501 This variable contains the address of the thread information block.
8505 On HP-UX systems, if you refer to a function or variable name that
8506 begins with a dollar sign, @value{GDBN} searches for a user or system
8507 name first, before it searches for a convenience variable.
8509 @cindex convenience functions
8510 @value{GDBN} also supplies some @dfn{convenience functions}. These
8511 have a syntax similar to convenience variables. A convenience
8512 function can be used in an expression just like an ordinary function;
8513 however, a convenience function is implemented internally to
8518 @kindex help function
8519 @cindex show all convenience functions
8520 Print a list of all convenience functions.
8527 You can refer to machine register contents, in expressions, as variables
8528 with names starting with @samp{$}. The names of registers are different
8529 for each machine; use @code{info registers} to see the names used on
8533 @kindex info registers
8534 @item info registers
8535 Print the names and values of all registers except floating-point
8536 and vector registers (in the selected stack frame).
8538 @kindex info all-registers
8539 @cindex floating point registers
8540 @item info all-registers
8541 Print the names and values of all registers, including floating-point
8542 and vector registers (in the selected stack frame).
8544 @item info registers @var{regname} @dots{}
8545 Print the @dfn{relativized} value of each specified register @var{regname}.
8546 As discussed in detail below, register values are normally relative to
8547 the selected stack frame. @var{regname} may be any register name valid on
8548 the machine you are using, with or without the initial @samp{$}.
8551 @cindex stack pointer register
8552 @cindex program counter register
8553 @cindex process status register
8554 @cindex frame pointer register
8555 @cindex standard registers
8556 @value{GDBN} has four ``standard'' register names that are available (in
8557 expressions) on most machines---whenever they do not conflict with an
8558 architecture's canonical mnemonics for registers. The register names
8559 @code{$pc} and @code{$sp} are used for the program counter register and
8560 the stack pointer. @code{$fp} is used for a register that contains a
8561 pointer to the current stack frame, and @code{$ps} is used for a
8562 register that contains the processor status. For example,
8563 you could print the program counter in hex with
8570 or print the instruction to be executed next with
8577 or add four to the stack pointer@footnote{This is a way of removing
8578 one word from the stack, on machines where stacks grow downward in
8579 memory (most machines, nowadays). This assumes that the innermost
8580 stack frame is selected; setting @code{$sp} is not allowed when other
8581 stack frames are selected. To pop entire frames off the stack,
8582 regardless of machine architecture, use @code{return};
8583 see @ref{Returning, ,Returning from a Function}.} with
8589 Whenever possible, these four standard register names are available on
8590 your machine even though the machine has different canonical mnemonics,
8591 so long as there is no conflict. The @code{info registers} command
8592 shows the canonical names. For example, on the SPARC, @code{info
8593 registers} displays the processor status register as @code{$psr} but you
8594 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8595 is an alias for the @sc{eflags} register.
8597 @value{GDBN} always considers the contents of an ordinary register as an
8598 integer when the register is examined in this way. Some machines have
8599 special registers which can hold nothing but floating point; these
8600 registers are considered to have floating point values. There is no way
8601 to refer to the contents of an ordinary register as floating point value
8602 (although you can @emph{print} it as a floating point value with
8603 @samp{print/f $@var{regname}}).
8605 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8606 means that the data format in which the register contents are saved by
8607 the operating system is not the same one that your program normally
8608 sees. For example, the registers of the 68881 floating point
8609 coprocessor are always saved in ``extended'' (raw) format, but all C
8610 programs expect to work with ``double'' (virtual) format. In such
8611 cases, @value{GDBN} normally works with the virtual format only (the format
8612 that makes sense for your program), but the @code{info registers} command
8613 prints the data in both formats.
8615 @cindex SSE registers (x86)
8616 @cindex MMX registers (x86)
8617 Some machines have special registers whose contents can be interpreted
8618 in several different ways. For example, modern x86-based machines
8619 have SSE and MMX registers that can hold several values packed
8620 together in several different formats. @value{GDBN} refers to such
8621 registers in @code{struct} notation:
8624 (@value{GDBP}) print $xmm1
8626 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8627 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8628 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8629 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8630 v4_int32 = @{0, 20657912, 11, 13@},
8631 v2_int64 = @{88725056443645952, 55834574859@},
8632 uint128 = 0x0000000d0000000b013b36f800000000
8637 To set values of such registers, you need to tell @value{GDBN} which
8638 view of the register you wish to change, as if you were assigning
8639 value to a @code{struct} member:
8642 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8645 Normally, register values are relative to the selected stack frame
8646 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8647 value that the register would contain if all stack frames farther in
8648 were exited and their saved registers restored. In order to see the
8649 true contents of hardware registers, you must select the innermost
8650 frame (with @samp{frame 0}).
8652 However, @value{GDBN} must deduce where registers are saved, from the machine
8653 code generated by your compiler. If some registers are not saved, or if
8654 @value{GDBN} is unable to locate the saved registers, the selected stack
8655 frame makes no difference.
8657 @node Floating Point Hardware
8658 @section Floating Point Hardware
8659 @cindex floating point
8661 Depending on the configuration, @value{GDBN} may be able to give
8662 you more information about the status of the floating point hardware.
8667 Display hardware-dependent information about the floating
8668 point unit. The exact contents and layout vary depending on the
8669 floating point chip. Currently, @samp{info float} is supported on
8670 the ARM and x86 machines.
8674 @section Vector Unit
8677 Depending on the configuration, @value{GDBN} may be able to give you
8678 more information about the status of the vector unit.
8683 Display information about the vector unit. The exact contents and
8684 layout vary depending on the hardware.
8687 @node OS Information
8688 @section Operating System Auxiliary Information
8689 @cindex OS information
8691 @value{GDBN} provides interfaces to useful OS facilities that can help
8692 you debug your program.
8694 @cindex @code{ptrace} system call
8695 @cindex @code{struct user} contents
8696 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8697 machines), it interfaces with the inferior via the @code{ptrace}
8698 system call. The operating system creates a special sata structure,
8699 called @code{struct user}, for this interface. You can use the
8700 command @code{info udot} to display the contents of this data
8706 Display the contents of the @code{struct user} maintained by the OS
8707 kernel for the program being debugged. @value{GDBN} displays the
8708 contents of @code{struct user} as a list of hex numbers, similar to
8709 the @code{examine} command.
8712 @cindex auxiliary vector
8713 @cindex vector, auxiliary
8714 Some operating systems supply an @dfn{auxiliary vector} to programs at
8715 startup. This is akin to the arguments and environment that you
8716 specify for a program, but contains a system-dependent variety of
8717 binary values that tell system libraries important details about the
8718 hardware, operating system, and process. Each value's purpose is
8719 identified by an integer tag; the meanings are well-known but system-specific.
8720 Depending on the configuration and operating system facilities,
8721 @value{GDBN} may be able to show you this information. For remote
8722 targets, this functionality may further depend on the remote stub's
8723 support of the @samp{qXfer:auxv:read} packet, see
8724 @ref{qXfer auxiliary vector read}.
8729 Display the auxiliary vector of the inferior, which can be either a
8730 live process or a core dump file. @value{GDBN} prints each tag value
8731 numerically, and also shows names and text descriptions for recognized
8732 tags. Some values in the vector are numbers, some bit masks, and some
8733 pointers to strings or other data. @value{GDBN} displays each value in the
8734 most appropriate form for a recognized tag, and in hexadecimal for
8735 an unrecognized tag.
8738 On some targets, @value{GDBN} can access operating-system-specific information
8739 and display it to user, without interpretation. For remote targets,
8740 this functionality depends on the remote stub's support of the
8741 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8746 List the types of OS information available for the target. If the
8747 target does not return a list of possible types, this command will
8750 @kindex info os processes
8751 @item info os processes
8752 Display the list of processes on the target. For each process,
8753 @value{GDBN} prints the process identifier, the name of the user, and
8754 the command corresponding to the process.
8757 @node Memory Region Attributes
8758 @section Memory Region Attributes
8759 @cindex memory region attributes
8761 @dfn{Memory region attributes} allow you to describe special handling
8762 required by regions of your target's memory. @value{GDBN} uses
8763 attributes to determine whether to allow certain types of memory
8764 accesses; whether to use specific width accesses; and whether to cache
8765 target memory. By default the description of memory regions is
8766 fetched from the target (if the current target supports this), but the
8767 user can override the fetched regions.
8769 Defined memory regions can be individually enabled and disabled. When a
8770 memory region is disabled, @value{GDBN} uses the default attributes when
8771 accessing memory in that region. Similarly, if no memory regions have
8772 been defined, @value{GDBN} uses the default attributes when accessing
8775 When a memory region is defined, it is given a number to identify it;
8776 to enable, disable, or remove a memory region, you specify that number.
8780 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8781 Define a memory region bounded by @var{lower} and @var{upper} with
8782 attributes @var{attributes}@dots{}, and add it to the list of regions
8783 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8784 case: it is treated as the target's maximum memory address.
8785 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8788 Discard any user changes to the memory regions and use target-supplied
8789 regions, if available, or no regions if the target does not support.
8792 @item delete mem @var{nums}@dots{}
8793 Remove memory regions @var{nums}@dots{} from the list of regions
8794 monitored by @value{GDBN}.
8797 @item disable mem @var{nums}@dots{}
8798 Disable monitoring of memory regions @var{nums}@dots{}.
8799 A disabled memory region is not forgotten.
8800 It may be enabled again later.
8803 @item enable mem @var{nums}@dots{}
8804 Enable monitoring of memory regions @var{nums}@dots{}.
8808 Print a table of all defined memory regions, with the following columns
8812 @item Memory Region Number
8813 @item Enabled or Disabled.
8814 Enabled memory regions are marked with @samp{y}.
8815 Disabled memory regions are marked with @samp{n}.
8818 The address defining the inclusive lower bound of the memory region.
8821 The address defining the exclusive upper bound of the memory region.
8824 The list of attributes set for this memory region.
8829 @subsection Attributes
8831 @subsubsection Memory Access Mode
8832 The access mode attributes set whether @value{GDBN} may make read or
8833 write accesses to a memory region.
8835 While these attributes prevent @value{GDBN} from performing invalid
8836 memory accesses, they do nothing to prevent the target system, I/O DMA,
8837 etc.@: from accessing memory.
8841 Memory is read only.
8843 Memory is write only.
8845 Memory is read/write. This is the default.
8848 @subsubsection Memory Access Size
8849 The access size attribute tells @value{GDBN} to use specific sized
8850 accesses in the memory region. Often memory mapped device registers
8851 require specific sized accesses. If no access size attribute is
8852 specified, @value{GDBN} may use accesses of any size.
8856 Use 8 bit memory accesses.
8858 Use 16 bit memory accesses.
8860 Use 32 bit memory accesses.
8862 Use 64 bit memory accesses.
8865 @c @subsubsection Hardware/Software Breakpoints
8866 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8867 @c will use hardware or software breakpoints for the internal breakpoints
8868 @c used by the step, next, finish, until, etc. commands.
8872 @c Always use hardware breakpoints
8873 @c @item swbreak (default)
8876 @subsubsection Data Cache
8877 The data cache attributes set whether @value{GDBN} will cache target
8878 memory. While this generally improves performance by reducing debug
8879 protocol overhead, it can lead to incorrect results because @value{GDBN}
8880 does not know about volatile variables or memory mapped device
8885 Enable @value{GDBN} to cache target memory.
8887 Disable @value{GDBN} from caching target memory. This is the default.
8890 @subsection Memory Access Checking
8891 @value{GDBN} can be instructed to refuse accesses to memory that is
8892 not explicitly described. This can be useful if accessing such
8893 regions has undesired effects for a specific target, or to provide
8894 better error checking. The following commands control this behaviour.
8897 @kindex set mem inaccessible-by-default
8898 @item set mem inaccessible-by-default [on|off]
8899 If @code{on} is specified, make @value{GDBN} treat memory not
8900 explicitly described by the memory ranges as non-existent and refuse accesses
8901 to such memory. The checks are only performed if there's at least one
8902 memory range defined. If @code{off} is specified, make @value{GDBN}
8903 treat the memory not explicitly described by the memory ranges as RAM.
8904 The default value is @code{on}.
8905 @kindex show mem inaccessible-by-default
8906 @item show mem inaccessible-by-default
8907 Show the current handling of accesses to unknown memory.
8911 @c @subsubsection Memory Write Verification
8912 @c The memory write verification attributes set whether @value{GDBN}
8913 @c will re-reads data after each write to verify the write was successful.
8917 @c @item noverify (default)
8920 @node Dump/Restore Files
8921 @section Copy Between Memory and a File
8922 @cindex dump/restore files
8923 @cindex append data to a file
8924 @cindex dump data to a file
8925 @cindex restore data from a file
8927 You can use the commands @code{dump}, @code{append}, and
8928 @code{restore} to copy data between target memory and a file. The
8929 @code{dump} and @code{append} commands write data to a file, and the
8930 @code{restore} command reads data from a file back into the inferior's
8931 memory. Files may be in binary, Motorola S-record, Intel hex, or
8932 Tektronix Hex format; however, @value{GDBN} can only append to binary
8938 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8939 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8940 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8941 or the value of @var{expr}, to @var{filename} in the given format.
8943 The @var{format} parameter may be any one of:
8950 Motorola S-record format.
8952 Tektronix Hex format.
8955 @value{GDBN} uses the same definitions of these formats as the
8956 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8957 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8961 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8962 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8963 Append the contents of memory from @var{start_addr} to @var{end_addr},
8964 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8965 (@value{GDBN} can only append data to files in raw binary form.)
8968 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8969 Restore the contents of file @var{filename} into memory. The
8970 @code{restore} command can automatically recognize any known @sc{bfd}
8971 file format, except for raw binary. To restore a raw binary file you
8972 must specify the optional keyword @code{binary} after the filename.
8974 If @var{bias} is non-zero, its value will be added to the addresses
8975 contained in the file. Binary files always start at address zero, so
8976 they will be restored at address @var{bias}. Other bfd files have
8977 a built-in location; they will be restored at offset @var{bias}
8980 If @var{start} and/or @var{end} are non-zero, then only data between
8981 file offset @var{start} and file offset @var{end} will be restored.
8982 These offsets are relative to the addresses in the file, before
8983 the @var{bias} argument is applied.
8987 @node Core File Generation
8988 @section How to Produce a Core File from Your Program
8989 @cindex dump core from inferior
8991 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8992 image of a running process and its process status (register values
8993 etc.). Its primary use is post-mortem debugging of a program that
8994 crashed while it ran outside a debugger. A program that crashes
8995 automatically produces a core file, unless this feature is disabled by
8996 the user. @xref{Files}, for information on invoking @value{GDBN} in
8997 the post-mortem debugging mode.
8999 Occasionally, you may wish to produce a core file of the program you
9000 are debugging in order to preserve a snapshot of its state.
9001 @value{GDBN} has a special command for that.
9005 @kindex generate-core-file
9006 @item generate-core-file [@var{file}]
9007 @itemx gcore [@var{file}]
9008 Produce a core dump of the inferior process. The optional argument
9009 @var{file} specifies the file name where to put the core dump. If not
9010 specified, the file name defaults to @file{core.@var{pid}}, where
9011 @var{pid} is the inferior process ID.
9013 Note that this command is implemented only for some systems (as of
9014 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9017 @node Character Sets
9018 @section Character Sets
9019 @cindex character sets
9021 @cindex translating between character sets
9022 @cindex host character set
9023 @cindex target character set
9025 If the program you are debugging uses a different character set to
9026 represent characters and strings than the one @value{GDBN} uses itself,
9027 @value{GDBN} can automatically translate between the character sets for
9028 you. The character set @value{GDBN} uses we call the @dfn{host
9029 character set}; the one the inferior program uses we call the
9030 @dfn{target character set}.
9032 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9033 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9034 remote protocol (@pxref{Remote Debugging}) to debug a program
9035 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9036 then the host character set is Latin-1, and the target character set is
9037 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9038 target-charset EBCDIC-US}, then @value{GDBN} translates between
9039 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9040 character and string literals in expressions.
9042 @value{GDBN} has no way to automatically recognize which character set
9043 the inferior program uses; you must tell it, using the @code{set
9044 target-charset} command, described below.
9046 Here are the commands for controlling @value{GDBN}'s character set
9050 @item set target-charset @var{charset}
9051 @kindex set target-charset
9052 Set the current target character set to @var{charset}. To display the
9053 list of supported target character sets, type
9054 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9056 @item set host-charset @var{charset}
9057 @kindex set host-charset
9058 Set the current host character set to @var{charset}.
9060 By default, @value{GDBN} uses a host character set appropriate to the
9061 system it is running on; you can override that default using the
9062 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9063 automatically determine the appropriate host character set. In this
9064 case, @value{GDBN} uses @samp{UTF-8}.
9066 @value{GDBN} can only use certain character sets as its host character
9067 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9068 @value{GDBN} will list the host character sets it supports.
9070 @item set charset @var{charset}
9072 Set the current host and target character sets to @var{charset}. As
9073 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9074 @value{GDBN} will list the names of the character sets that can be used
9075 for both host and target.
9078 @kindex show charset
9079 Show the names of the current host and target character sets.
9081 @item show host-charset
9082 @kindex show host-charset
9083 Show the name of the current host character set.
9085 @item show target-charset
9086 @kindex show target-charset
9087 Show the name of the current target character set.
9089 @item set target-wide-charset @var{charset}
9090 @kindex set target-wide-charset
9091 Set the current target's wide character set to @var{charset}. This is
9092 the character set used by the target's @code{wchar_t} type. To
9093 display the list of supported wide character sets, type
9094 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9096 @item show target-wide-charset
9097 @kindex show target-wide-charset
9098 Show the name of the current target's wide character set.
9101 Here is an example of @value{GDBN}'s character set support in action.
9102 Assume that the following source code has been placed in the file
9103 @file{charset-test.c}:
9109 = @{72, 101, 108, 108, 111, 44, 32, 119,
9110 111, 114, 108, 100, 33, 10, 0@};
9111 char ibm1047_hello[]
9112 = @{200, 133, 147, 147, 150, 107, 64, 166,
9113 150, 153, 147, 132, 90, 37, 0@};
9117 printf ("Hello, world!\n");
9121 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9122 containing the string @samp{Hello, world!} followed by a newline,
9123 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9125 We compile the program, and invoke the debugger on it:
9128 $ gcc -g charset-test.c -o charset-test
9129 $ gdb -nw charset-test
9130 GNU gdb 2001-12-19-cvs
9131 Copyright 2001 Free Software Foundation, Inc.
9136 We can use the @code{show charset} command to see what character sets
9137 @value{GDBN} is currently using to interpret and display characters and
9141 (@value{GDBP}) show charset
9142 The current host and target character set is `ISO-8859-1'.
9146 For the sake of printing this manual, let's use @sc{ascii} as our
9147 initial character set:
9149 (@value{GDBP}) set charset ASCII
9150 (@value{GDBP}) show charset
9151 The current host and target character set is `ASCII'.
9155 Let's assume that @sc{ascii} is indeed the correct character set for our
9156 host system --- in other words, let's assume that if @value{GDBN} prints
9157 characters using the @sc{ascii} character set, our terminal will display
9158 them properly. Since our current target character set is also
9159 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9162 (@value{GDBP}) print ascii_hello
9163 $1 = 0x401698 "Hello, world!\n"
9164 (@value{GDBP}) print ascii_hello[0]
9169 @value{GDBN} uses the target character set for character and string
9170 literals you use in expressions:
9173 (@value{GDBP}) print '+'
9178 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9181 @value{GDBN} relies on the user to tell it which character set the
9182 target program uses. If we print @code{ibm1047_hello} while our target
9183 character set is still @sc{ascii}, we get jibberish:
9186 (@value{GDBP}) print ibm1047_hello
9187 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9188 (@value{GDBP}) print ibm1047_hello[0]
9193 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9194 @value{GDBN} tells us the character sets it supports:
9197 (@value{GDBP}) set target-charset
9198 ASCII EBCDIC-US IBM1047 ISO-8859-1
9199 (@value{GDBP}) set target-charset
9202 We can select @sc{ibm1047} as our target character set, and examine the
9203 program's strings again. Now the @sc{ascii} string is wrong, but
9204 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9205 target character set, @sc{ibm1047}, to the host character set,
9206 @sc{ascii}, and they display correctly:
9209 (@value{GDBP}) set target-charset IBM1047
9210 (@value{GDBP}) show charset
9211 The current host character set is `ASCII'.
9212 The current target character set is `IBM1047'.
9213 (@value{GDBP}) print ascii_hello
9214 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9215 (@value{GDBP}) print ascii_hello[0]
9217 (@value{GDBP}) print ibm1047_hello
9218 $8 = 0x4016a8 "Hello, world!\n"
9219 (@value{GDBP}) print ibm1047_hello[0]
9224 As above, @value{GDBN} uses the target character set for character and
9225 string literals you use in expressions:
9228 (@value{GDBP}) print '+'
9233 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9236 @node Caching Remote Data
9237 @section Caching Data of Remote Targets
9238 @cindex caching data of remote targets
9240 @value{GDBN} caches data exchanged between the debugger and a
9241 remote target (@pxref{Remote Debugging}). Such caching generally improves
9242 performance, because it reduces the overhead of the remote protocol by
9243 bundling memory reads and writes into large chunks. Unfortunately, simply
9244 caching everything would lead to incorrect results, since @value{GDBN}
9245 does not necessarily know anything about volatile values, memory-mapped I/O
9246 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9247 memory can be changed @emph{while} a gdb command is executing.
9248 Therefore, by default, @value{GDBN} only caches data
9249 known to be on the stack@footnote{In non-stop mode, it is moderately
9250 rare for a running thread to modify the stack of a stopped thread
9251 in a way that would interfere with a backtrace, and caching of
9252 stack reads provides a significant speed up of remote backtraces.}.
9253 Other regions of memory can be explicitly marked as
9254 cacheable; see @pxref{Memory Region Attributes}.
9257 @kindex set remotecache
9258 @item set remotecache on
9259 @itemx set remotecache off
9260 This option no longer does anything; it exists for compatibility
9263 @kindex show remotecache
9264 @item show remotecache
9265 Show the current state of the obsolete remotecache flag.
9267 @kindex set stack-cache
9268 @item set stack-cache on
9269 @itemx set stack-cache off
9270 Enable or disable caching of stack accesses. When @code{ON}, use
9271 caching. By default, this option is @code{ON}.
9273 @kindex show stack-cache
9274 @item show stack-cache
9275 Show the current state of data caching for memory accesses.
9278 @item info dcache @r{[}line@r{]}
9279 Print the information about the data cache performance. The
9280 information displayed includes the dcache width and depth, and for
9281 each cache line, its number, address, and how many times it was
9282 referenced. This command is useful for debugging the data cache
9285 If a line number is specified, the contents of that line will be
9289 @node Searching Memory
9290 @section Search Memory
9291 @cindex searching memory
9293 Memory can be searched for a particular sequence of bytes with the
9294 @code{find} command.
9298 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9299 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9300 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9301 etc. The search begins at address @var{start_addr} and continues for either
9302 @var{len} bytes or through to @var{end_addr} inclusive.
9305 @var{s} and @var{n} are optional parameters.
9306 They may be specified in either order, apart or together.
9309 @item @var{s}, search query size
9310 The size of each search query value.
9316 halfwords (two bytes)
9320 giant words (eight bytes)
9323 All values are interpreted in the current language.
9324 This means, for example, that if the current source language is C/C@t{++}
9325 then searching for the string ``hello'' includes the trailing '\0'.
9327 If the value size is not specified, it is taken from the
9328 value's type in the current language.
9329 This is useful when one wants to specify the search
9330 pattern as a mixture of types.
9331 Note that this means, for example, that in the case of C-like languages
9332 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9333 which is typically four bytes.
9335 @item @var{n}, maximum number of finds
9336 The maximum number of matches to print. The default is to print all finds.
9339 You can use strings as search values. Quote them with double-quotes
9341 The string value is copied into the search pattern byte by byte,
9342 regardless of the endianness of the target and the size specification.
9344 The address of each match found is printed as well as a count of the
9345 number of matches found.
9347 The address of the last value found is stored in convenience variable
9349 A count of the number of matches is stored in @samp{$numfound}.
9351 For example, if stopped at the @code{printf} in this function:
9357 static char hello[] = "hello-hello";
9358 static struct @{ char c; short s; int i; @}
9359 __attribute__ ((packed)) mixed
9360 = @{ 'c', 0x1234, 0x87654321 @};
9361 printf ("%s\n", hello);
9366 you get during debugging:
9369 (gdb) find &hello[0], +sizeof(hello), "hello"
9370 0x804956d <hello.1620+6>
9372 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9373 0x8049567 <hello.1620>
9374 0x804956d <hello.1620+6>
9376 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9377 0x8049567 <hello.1620>
9379 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9380 0x8049560 <mixed.1625>
9382 (gdb) print $numfound
9385 $2 = (void *) 0x8049560
9388 @node Optimized Code
9389 @chapter Debugging Optimized Code
9390 @cindex optimized code, debugging
9391 @cindex debugging optimized code
9393 Almost all compilers support optimization. With optimization
9394 disabled, the compiler generates assembly code that corresponds
9395 directly to your source code, in a simplistic way. As the compiler
9396 applies more powerful optimizations, the generated assembly code
9397 diverges from your original source code. With help from debugging
9398 information generated by the compiler, @value{GDBN} can map from
9399 the running program back to constructs from your original source.
9401 @value{GDBN} is more accurate with optimization disabled. If you
9402 can recompile without optimization, it is easier to follow the
9403 progress of your program during debugging. But, there are many cases
9404 where you may need to debug an optimized version.
9406 When you debug a program compiled with @samp{-g -O}, remember that the
9407 optimizer has rearranged your code; the debugger shows you what is
9408 really there. Do not be too surprised when the execution path does not
9409 exactly match your source file! An extreme example: if you define a
9410 variable, but never use it, @value{GDBN} never sees that
9411 variable---because the compiler optimizes it out of existence.
9413 Some things do not work as well with @samp{-g -O} as with just
9414 @samp{-g}, particularly on machines with instruction scheduling. If in
9415 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9416 please report it to us as a bug (including a test case!).
9417 @xref{Variables}, for more information about debugging optimized code.
9420 * Inline Functions:: How @value{GDBN} presents inlining
9423 @node Inline Functions
9424 @section Inline Functions
9425 @cindex inline functions, debugging
9427 @dfn{Inlining} is an optimization that inserts a copy of the function
9428 body directly at each call site, instead of jumping to a shared
9429 routine. @value{GDBN} displays inlined functions just like
9430 non-inlined functions. They appear in backtraces. You can view their
9431 arguments and local variables, step into them with @code{step}, skip
9432 them with @code{next}, and escape from them with @code{finish}.
9433 You can check whether a function was inlined by using the
9434 @code{info frame} command.
9436 For @value{GDBN} to support inlined functions, the compiler must
9437 record information about inlining in the debug information ---
9438 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9439 other compilers do also. @value{GDBN} only supports inlined functions
9440 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9441 do not emit two required attributes (@samp{DW_AT_call_file} and
9442 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9443 function calls with earlier versions of @value{NGCC}. It instead
9444 displays the arguments and local variables of inlined functions as
9445 local variables in the caller.
9447 The body of an inlined function is directly included at its call site;
9448 unlike a non-inlined function, there are no instructions devoted to
9449 the call. @value{GDBN} still pretends that the call site and the
9450 start of the inlined function are different instructions. Stepping to
9451 the call site shows the call site, and then stepping again shows
9452 the first line of the inlined function, even though no additional
9453 instructions are executed.
9455 This makes source-level debugging much clearer; you can see both the
9456 context of the call and then the effect of the call. Only stepping by
9457 a single instruction using @code{stepi} or @code{nexti} does not do
9458 this; single instruction steps always show the inlined body.
9460 There are some ways that @value{GDBN} does not pretend that inlined
9461 function calls are the same as normal calls:
9465 You cannot set breakpoints on inlined functions. @value{GDBN}
9466 either reports that there is no symbol with that name, or else sets the
9467 breakpoint only on non-inlined copies of the function. This limitation
9468 will be removed in a future version of @value{GDBN}; until then,
9469 set a breakpoint by line number on the first line of the inlined
9473 Setting breakpoints at the call site of an inlined function may not
9474 work, because the call site does not contain any code. @value{GDBN}
9475 may incorrectly move the breakpoint to the next line of the enclosing
9476 function, after the call. This limitation will be removed in a future
9477 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9478 or inside the inlined function instead.
9481 @value{GDBN} cannot locate the return value of inlined calls after
9482 using the @code{finish} command. This is a limitation of compiler-generated
9483 debugging information; after @code{finish}, you can step to the next line
9484 and print a variable where your program stored the return value.
9490 @chapter C Preprocessor Macros
9492 Some languages, such as C and C@t{++}, provide a way to define and invoke
9493 ``preprocessor macros'' which expand into strings of tokens.
9494 @value{GDBN} can evaluate expressions containing macro invocations, show
9495 the result of macro expansion, and show a macro's definition, including
9496 where it was defined.
9498 You may need to compile your program specially to provide @value{GDBN}
9499 with information about preprocessor macros. Most compilers do not
9500 include macros in their debugging information, even when you compile
9501 with the @option{-g} flag. @xref{Compilation}.
9503 A program may define a macro at one point, remove that definition later,
9504 and then provide a different definition after that. Thus, at different
9505 points in the program, a macro may have different definitions, or have
9506 no definition at all. If there is a current stack frame, @value{GDBN}
9507 uses the macros in scope at that frame's source code line. Otherwise,
9508 @value{GDBN} uses the macros in scope at the current listing location;
9511 Whenever @value{GDBN} evaluates an expression, it always expands any
9512 macro invocations present in the expression. @value{GDBN} also provides
9513 the following commands for working with macros explicitly.
9517 @kindex macro expand
9518 @cindex macro expansion, showing the results of preprocessor
9519 @cindex preprocessor macro expansion, showing the results of
9520 @cindex expanding preprocessor macros
9521 @item macro expand @var{expression}
9522 @itemx macro exp @var{expression}
9523 Show the results of expanding all preprocessor macro invocations in
9524 @var{expression}. Since @value{GDBN} simply expands macros, but does
9525 not parse the result, @var{expression} need not be a valid expression;
9526 it can be any string of tokens.
9529 @item macro expand-once @var{expression}
9530 @itemx macro exp1 @var{expression}
9531 @cindex expand macro once
9532 @i{(This command is not yet implemented.)} Show the results of
9533 expanding those preprocessor macro invocations that appear explicitly in
9534 @var{expression}. Macro invocations appearing in that expansion are
9535 left unchanged. This command allows you to see the effect of a
9536 particular macro more clearly, without being confused by further
9537 expansions. Since @value{GDBN} simply expands macros, but does not
9538 parse the result, @var{expression} need not be a valid expression; it
9539 can be any string of tokens.
9542 @cindex macro definition, showing
9543 @cindex definition, showing a macro's
9544 @item info macro @var{macro}
9545 Show the definition of the macro named @var{macro}, and describe the
9546 source location or compiler command-line where that definition was established.
9548 @kindex macro define
9549 @cindex user-defined macros
9550 @cindex defining macros interactively
9551 @cindex macros, user-defined
9552 @item macro define @var{macro} @var{replacement-list}
9553 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9554 Introduce a definition for a preprocessor macro named @var{macro},
9555 invocations of which are replaced by the tokens given in
9556 @var{replacement-list}. The first form of this command defines an
9557 ``object-like'' macro, which takes no arguments; the second form
9558 defines a ``function-like'' macro, which takes the arguments given in
9561 A definition introduced by this command is in scope in every
9562 expression evaluated in @value{GDBN}, until it is removed with the
9563 @code{macro undef} command, described below. The definition overrides
9564 all definitions for @var{macro} present in the program being debugged,
9565 as well as any previous user-supplied definition.
9568 @item macro undef @var{macro}
9569 Remove any user-supplied definition for the macro named @var{macro}.
9570 This command only affects definitions provided with the @code{macro
9571 define} command, described above; it cannot remove definitions present
9572 in the program being debugged.
9576 List all the macros defined using the @code{macro define} command.
9579 @cindex macros, example of debugging with
9580 Here is a transcript showing the above commands in action. First, we
9581 show our source files:
9589 #define ADD(x) (M + x)
9594 printf ("Hello, world!\n");
9596 printf ("We're so creative.\n");
9598 printf ("Goodbye, world!\n");
9605 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9606 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9607 compiler includes information about preprocessor macros in the debugging
9611 $ gcc -gdwarf-2 -g3 sample.c -o sample
9615 Now, we start @value{GDBN} on our sample program:
9619 GNU gdb 2002-05-06-cvs
9620 Copyright 2002 Free Software Foundation, Inc.
9621 GDB is free software, @dots{}
9625 We can expand macros and examine their definitions, even when the
9626 program is not running. @value{GDBN} uses the current listing position
9627 to decide which macro definitions are in scope:
9630 (@value{GDBP}) list main
9633 5 #define ADD(x) (M + x)
9638 10 printf ("Hello, world!\n");
9640 12 printf ("We're so creative.\n");
9641 (@value{GDBP}) info macro ADD
9642 Defined at /home/jimb/gdb/macros/play/sample.c:5
9643 #define ADD(x) (M + x)
9644 (@value{GDBP}) info macro Q
9645 Defined at /home/jimb/gdb/macros/play/sample.h:1
9646 included at /home/jimb/gdb/macros/play/sample.c:2
9648 (@value{GDBP}) macro expand ADD(1)
9649 expands to: (42 + 1)
9650 (@value{GDBP}) macro expand-once ADD(1)
9651 expands to: once (M + 1)
9655 In the example above, note that @code{macro expand-once} expands only
9656 the macro invocation explicit in the original text --- the invocation of
9657 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9658 which was introduced by @code{ADD}.
9660 Once the program is running, @value{GDBN} uses the macro definitions in
9661 force at the source line of the current stack frame:
9664 (@value{GDBP}) break main
9665 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9667 Starting program: /home/jimb/gdb/macros/play/sample
9669 Breakpoint 1, main () at sample.c:10
9670 10 printf ("Hello, world!\n");
9674 At line 10, the definition of the macro @code{N} at line 9 is in force:
9677 (@value{GDBP}) info macro N
9678 Defined at /home/jimb/gdb/macros/play/sample.c:9
9680 (@value{GDBP}) macro expand N Q M
9682 (@value{GDBP}) print N Q M
9687 As we step over directives that remove @code{N}'s definition, and then
9688 give it a new definition, @value{GDBN} finds the definition (or lack
9689 thereof) in force at each point:
9694 12 printf ("We're so creative.\n");
9695 (@value{GDBP}) info macro N
9696 The symbol `N' has no definition as a C/C++ preprocessor macro
9697 at /home/jimb/gdb/macros/play/sample.c:12
9700 14 printf ("Goodbye, world!\n");
9701 (@value{GDBP}) info macro N
9702 Defined at /home/jimb/gdb/macros/play/sample.c:13
9704 (@value{GDBP}) macro expand N Q M
9705 expands to: 1729 < 42
9706 (@value{GDBP}) print N Q M
9711 In addition to source files, macros can be defined on the compilation command
9712 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9713 such a way, @value{GDBN} displays the location of their definition as line zero
9714 of the source file submitted to the compiler.
9717 (@value{GDBP}) info macro __STDC__
9718 Defined at /home/jimb/gdb/macros/play/sample.c:0
9725 @chapter Tracepoints
9726 @c This chapter is based on the documentation written by Michael
9727 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9730 In some applications, it is not feasible for the debugger to interrupt
9731 the program's execution long enough for the developer to learn
9732 anything helpful about its behavior. If the program's correctness
9733 depends on its real-time behavior, delays introduced by a debugger
9734 might cause the program to change its behavior drastically, or perhaps
9735 fail, even when the code itself is correct. It is useful to be able
9736 to observe the program's behavior without interrupting it.
9738 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9739 specify locations in the program, called @dfn{tracepoints}, and
9740 arbitrary expressions to evaluate when those tracepoints are reached.
9741 Later, using the @code{tfind} command, you can examine the values
9742 those expressions had when the program hit the tracepoints. The
9743 expressions may also denote objects in memory---structures or arrays,
9744 for example---whose values @value{GDBN} should record; while visiting
9745 a particular tracepoint, you may inspect those objects as if they were
9746 in memory at that moment. However, because @value{GDBN} records these
9747 values without interacting with you, it can do so quickly and
9748 unobtrusively, hopefully not disturbing the program's behavior.
9750 The tracepoint facility is currently available only for remote
9751 targets. @xref{Targets}. In addition, your remote target must know
9752 how to collect trace data. This functionality is implemented in the
9753 remote stub; however, none of the stubs distributed with @value{GDBN}
9754 support tracepoints as of this writing. The format of the remote
9755 packets used to implement tracepoints are described in @ref{Tracepoint
9758 It is also possible to get trace data from a file, in a manner reminiscent
9759 of corefiles; you specify the filename, and use @code{tfind} to search
9760 through the file. @xref{Trace Files}, for more details.
9762 This chapter describes the tracepoint commands and features.
9766 * Analyze Collected Data::
9767 * Tracepoint Variables::
9771 @node Set Tracepoints
9772 @section Commands to Set Tracepoints
9774 Before running such a @dfn{trace experiment}, an arbitrary number of
9775 tracepoints can be set. A tracepoint is actually a special type of
9776 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9777 standard breakpoint commands. For instance, as with breakpoints,
9778 tracepoint numbers are successive integers starting from one, and many
9779 of the commands associated with tracepoints take the tracepoint number
9780 as their argument, to identify which tracepoint to work on.
9782 For each tracepoint, you can specify, in advance, some arbitrary set
9783 of data that you want the target to collect in the trace buffer when
9784 it hits that tracepoint. The collected data can include registers,
9785 local variables, or global data. Later, you can use @value{GDBN}
9786 commands to examine the values these data had at the time the
9789 Tracepoints do not support every breakpoint feature. Ignore counts on
9790 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9791 commands when they are hit. Tracepoints may not be thread-specific
9794 @cindex fast tracepoints
9795 Some targets may support @dfn{fast tracepoints}, which are inserted in
9796 a different way (such as with a jump instead of a trap), that is
9797 faster but possibly restricted in where they may be installed.
9799 @cindex static tracepoints
9800 @cindex markers, static tracepoints
9801 @cindex probing markers, static tracepoints
9802 Regular and fast tracepoints are dynamic tracing facilities, meaning
9803 that they can be used to insert tracepoints at (almost) any location
9804 in the target. Some targets may also support controlling @dfn{static
9805 tracepoints} from @value{GDBN}. With static tracing, a set of
9806 instrumentation points, also known as @dfn{markers}, are embedded in
9807 the target program, and can be activated or deactivated by name or
9808 address. These are usually placed at locations which facilitate
9809 investigating what the target is actually doing. @value{GDBN}'s
9810 support for static tracing includes being able to list instrumentation
9811 points, and attach them with @value{GDBN} defined high level
9812 tracepoints that expose the whole range of convenience of
9813 @value{GDBN}'s tracepoints support. Namelly, support for collecting
9814 registers values and values of global or local (to the instrumentation
9815 point) variables; tracepoint conditions and trace state variables.
9816 The act of installing a @value{GDBN} static tracepoint on an
9817 instrumentation point, or marker, is referred to as @dfn{probing} a
9818 static tracepoint marker.
9820 @code{gdbserver} supports tracepoints on some target systems.
9821 @xref{Server,,Tracepoints support in @code{gdbserver}}.
9823 This section describes commands to set tracepoints and associated
9824 conditions and actions.
9827 * Create and Delete Tracepoints::
9828 * Enable and Disable Tracepoints::
9829 * Tracepoint Passcounts::
9830 * Tracepoint Conditions::
9831 * Trace State Variables::
9832 * Tracepoint Actions::
9833 * Listing Tracepoints::
9834 * Listing Static Tracepoint Markers::
9835 * Starting and Stopping Trace Experiments::
9836 * Tracepoint Restrictions::
9839 @node Create and Delete Tracepoints
9840 @subsection Create and Delete Tracepoints
9843 @cindex set tracepoint
9845 @item trace @var{location}
9846 The @code{trace} command is very similar to the @code{break} command.
9847 Its argument @var{location} can be a source line, a function name, or
9848 an address in the target program. @xref{Specify Location}. The
9849 @code{trace} command defines a tracepoint, which is a point in the
9850 target program where the debugger will briefly stop, collect some
9851 data, and then allow the program to continue. Setting a tracepoint or
9852 changing its actions doesn't take effect until the next @code{tstart}
9853 command, and once a trace experiment is running, further changes will
9854 not have any effect until the next trace experiment starts.
9856 Here are some examples of using the @code{trace} command:
9859 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9861 (@value{GDBP}) @b{trace +2} // 2 lines forward
9863 (@value{GDBP}) @b{trace my_function} // first source line of function
9865 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9867 (@value{GDBP}) @b{trace *0x2117c4} // an address
9871 You can abbreviate @code{trace} as @code{tr}.
9873 @item trace @var{location} if @var{cond}
9874 Set a tracepoint with condition @var{cond}; evaluate the expression
9875 @var{cond} each time the tracepoint is reached, and collect data only
9876 if the value is nonzero---that is, if @var{cond} evaluates as true.
9877 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9878 information on tracepoint conditions.
9880 @item ftrace @var{location} [ if @var{cond} ]
9881 @cindex set fast tracepoint
9882 @cindex fast tracepoints, setting
9884 The @code{ftrace} command sets a fast tracepoint. For targets that
9885 support them, fast tracepoints will use a more efficient but possibly
9886 less general technique to trigger data collection, such as a jump
9887 instruction instead of a trap, or some sort of hardware support. It
9888 may not be possible to create a fast tracepoint at the desired
9889 location, in which case the command will exit with an explanatory
9892 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9895 @item strace @var{location} [ if @var{cond} ]
9896 @cindex set static tracepoint
9897 @cindex static tracepoints, setting
9898 @cindex probe static tracepoint marker
9900 The @code{strace} command sets a static tracepoint. For targets that
9901 support it, setting a static tracepoint probes a static
9902 instrumentation point, or marker, found at @var{location}. It may not
9903 be possible to set a static tracepoint at the desired location, in
9904 which case the command will exit with an explanatory message.
9906 @value{GDBN} handles arguments to @code{strace} exactly as for
9907 @code{trace}, with the addition that the user can also specify
9908 @code{-m @var{marker}} as @var{location}. This probes the marker
9909 identified by the @var{marker} string identifier. This identifier
9910 depends on the static tracepoint backend library your program is
9911 using. You can find all the marker identifiers in the @samp{ID} field
9912 of the @code{info static-tracepoint-markers} command output.
9913 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
9914 Markers}. For example, in the following small program using the UST
9920 trace_mark(ust, bar33, "str %s", "FOOBAZ");
9925 the marker id is composed of joining the first two arguments to the
9926 @code{trace_mark} call with a slash, which translates to:
9929 (@value{GDBP}) info static-tracepoint-markers
9930 Cnt Enb ID Address What
9931 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
9937 so you may probe the marker above with:
9940 (@value{GDBP}) strace -m ust/bar33
9943 Static tracepoints accept an extra collect action --- @code{collect
9944 $_sdata}. This collects arbitrary user data passed in the probe point
9945 call to the tracing library. In the UST example above, you'll see
9946 that the third argument to @code{trace_mark} is a printf-like format
9947 string. The user data is then the result of running that formating
9948 string against the following arguments. Note that @code{info
9949 static-tracepoint-markers} command output lists that format string in
9950 the @samp{Data:} field.
9952 You can inspect this data when analyzing the trace buffer, by printing
9953 the $_sdata variable like any other variable available to
9954 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
9957 @cindex last tracepoint number
9958 @cindex recent tracepoint number
9959 @cindex tracepoint number
9960 The convenience variable @code{$tpnum} records the tracepoint number
9961 of the most recently set tracepoint.
9963 @kindex delete tracepoint
9964 @cindex tracepoint deletion
9965 @item delete tracepoint @r{[}@var{num}@r{]}
9966 Permanently delete one or more tracepoints. With no argument, the
9967 default is to delete all tracepoints. Note that the regular
9968 @code{delete} command can remove tracepoints also.
9973 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9975 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9979 You can abbreviate this command as @code{del tr}.
9982 @node Enable and Disable Tracepoints
9983 @subsection Enable and Disable Tracepoints
9985 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9988 @kindex disable tracepoint
9989 @item disable tracepoint @r{[}@var{num}@r{]}
9990 Disable tracepoint @var{num}, or all tracepoints if no argument
9991 @var{num} is given. A disabled tracepoint will have no effect during
9992 the next trace experiment, but it is not forgotten. You can re-enable
9993 a disabled tracepoint using the @code{enable tracepoint} command.
9995 @kindex enable tracepoint
9996 @item enable tracepoint @r{[}@var{num}@r{]}
9997 Enable tracepoint @var{num}, or all tracepoints. The enabled
9998 tracepoints will become effective the next time a trace experiment is
10002 @node Tracepoint Passcounts
10003 @subsection Tracepoint Passcounts
10007 @cindex tracepoint pass count
10008 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10009 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10010 automatically stop a trace experiment. If a tracepoint's passcount is
10011 @var{n}, then the trace experiment will be automatically stopped on
10012 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10013 @var{num} is not specified, the @code{passcount} command sets the
10014 passcount of the most recently defined tracepoint. If no passcount is
10015 given, the trace experiment will run until stopped explicitly by the
10021 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10022 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10024 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10025 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10026 (@value{GDBP}) @b{trace foo}
10027 (@value{GDBP}) @b{pass 3}
10028 (@value{GDBP}) @b{trace bar}
10029 (@value{GDBP}) @b{pass 2}
10030 (@value{GDBP}) @b{trace baz}
10031 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10032 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10033 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10034 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10038 @node Tracepoint Conditions
10039 @subsection Tracepoint Conditions
10040 @cindex conditional tracepoints
10041 @cindex tracepoint conditions
10043 The simplest sort of tracepoint collects data every time your program
10044 reaches a specified place. You can also specify a @dfn{condition} for
10045 a tracepoint. A condition is just a Boolean expression in your
10046 programming language (@pxref{Expressions, ,Expressions}). A
10047 tracepoint with a condition evaluates the expression each time your
10048 program reaches it, and data collection happens only if the condition
10051 Tracepoint conditions can be specified when a tracepoint is set, by
10052 using @samp{if} in the arguments to the @code{trace} command.
10053 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10054 also be set or changed at any time with the @code{condition} command,
10055 just as with breakpoints.
10057 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10058 the conditional expression itself. Instead, @value{GDBN} encodes the
10059 expression into an agent expression (@pxref{Agent Expressions}
10060 suitable for execution on the target, independently of @value{GDBN}.
10061 Global variables become raw memory locations, locals become stack
10062 accesses, and so forth.
10064 For instance, suppose you have a function that is usually called
10065 frequently, but should not be called after an error has occurred. You
10066 could use the following tracepoint command to collect data about calls
10067 of that function that happen while the error code is propagating
10068 through the program; an unconditional tracepoint could end up
10069 collecting thousands of useless trace frames that you would have to
10073 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10076 @node Trace State Variables
10077 @subsection Trace State Variables
10078 @cindex trace state variables
10080 A @dfn{trace state variable} is a special type of variable that is
10081 created and managed by target-side code. The syntax is the same as
10082 that for GDB's convenience variables (a string prefixed with ``$''),
10083 but they are stored on the target. They must be created explicitly,
10084 using a @code{tvariable} command. They are always 64-bit signed
10087 Trace state variables are remembered by @value{GDBN}, and downloaded
10088 to the target along with tracepoint information when the trace
10089 experiment starts. There are no intrinsic limits on the number of
10090 trace state variables, beyond memory limitations of the target.
10092 @cindex convenience variables, and trace state variables
10093 Although trace state variables are managed by the target, you can use
10094 them in print commands and expressions as if they were convenience
10095 variables; @value{GDBN} will get the current value from the target
10096 while the trace experiment is running. Trace state variables share
10097 the same namespace as other ``$'' variables, which means that you
10098 cannot have trace state variables with names like @code{$23} or
10099 @code{$pc}, nor can you have a trace state variable and a convenience
10100 variable with the same name.
10104 @item tvariable $@var{name} [ = @var{expression} ]
10106 The @code{tvariable} command creates a new trace state variable named
10107 @code{$@var{name}}, and optionally gives it an initial value of
10108 @var{expression}. @var{expression} is evaluated when this command is
10109 entered; the result will be converted to an integer if possible,
10110 otherwise @value{GDBN} will report an error. A subsequent
10111 @code{tvariable} command specifying the same name does not create a
10112 variable, but instead assigns the supplied initial value to the
10113 existing variable of that name, overwriting any previous initial
10114 value. The default initial value is 0.
10116 @item info tvariables
10117 @kindex info tvariables
10118 List all the trace state variables along with their initial values.
10119 Their current values may also be displayed, if the trace experiment is
10122 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10123 @kindex delete tvariable
10124 Delete the given trace state variables, or all of them if no arguments
10129 @node Tracepoint Actions
10130 @subsection Tracepoint Action Lists
10134 @cindex tracepoint actions
10135 @item actions @r{[}@var{num}@r{]}
10136 This command will prompt for a list of actions to be taken when the
10137 tracepoint is hit. If the tracepoint number @var{num} is not
10138 specified, this command sets the actions for the one that was most
10139 recently defined (so that you can define a tracepoint and then say
10140 @code{actions} without bothering about its number). You specify the
10141 actions themselves on the following lines, one action at a time, and
10142 terminate the actions list with a line containing just @code{end}. So
10143 far, the only defined actions are @code{collect}, @code{teval}, and
10144 @code{while-stepping}.
10146 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10147 Commands, ,Breakpoint Command Lists}), except that only the defined
10148 actions are allowed; any other @value{GDBN} command is rejected.
10150 @cindex remove actions from a tracepoint
10151 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10152 and follow it immediately with @samp{end}.
10155 (@value{GDBP}) @b{collect @var{data}} // collect some data
10157 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10159 (@value{GDBP}) @b{end} // signals the end of actions.
10162 In the following example, the action list begins with @code{collect}
10163 commands indicating the things to be collected when the tracepoint is
10164 hit. Then, in order to single-step and collect additional data
10165 following the tracepoint, a @code{while-stepping} command is used,
10166 followed by the list of things to be collected after each step in a
10167 sequence of single steps. The @code{while-stepping} command is
10168 terminated by its own separate @code{end} command. Lastly, the action
10169 list is terminated by an @code{end} command.
10172 (@value{GDBP}) @b{trace foo}
10173 (@value{GDBP}) @b{actions}
10174 Enter actions for tracepoint 1, one per line:
10177 > while-stepping 12
10178 > collect $pc, arr[i]
10183 @kindex collect @r{(tracepoints)}
10184 @item collect @var{expr1}, @var{expr2}, @dots{}
10185 Collect values of the given expressions when the tracepoint is hit.
10186 This command accepts a comma-separated list of any valid expressions.
10187 In addition to global, static, or local variables, the following
10188 special arguments are supported:
10192 Collect all registers.
10195 Collect all function arguments.
10198 Collect all local variables.
10201 @vindex $_sdata@r{, collect}
10202 Collect static tracepoint marker specific data. Only available for
10203 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10204 Lists}. On the UST static tracepoints library backend, an
10205 instrumentation point resembles a @code{printf} function call. The
10206 tracing library is able to collect user specified data formatted to a
10207 character string using the format provided by the programmer that
10208 instrumented the program. Other backends have similar mechanisms.
10209 Here's an example of a UST marker call:
10212 const char master_name[] = "$your_name";
10213 trace_mark(channel1, marker1, "hello %s", master_name)
10216 In this case, collecting @code{$_sdata} collects the string
10217 @samp{hello $yourname}. When analyzing the trace buffer, you can
10218 inspect @samp{$_sdata} like any other variable available to
10222 You can give several consecutive @code{collect} commands, each one
10223 with a single argument, or one @code{collect} command with several
10224 arguments separated by commas; the effect is the same.
10226 The command @code{info scope} (@pxref{Symbols, info scope}) is
10227 particularly useful for figuring out what data to collect.
10229 @kindex teval @r{(tracepoints)}
10230 @item teval @var{expr1}, @var{expr2}, @dots{}
10231 Evaluate the given expressions when the tracepoint is hit. This
10232 command accepts a comma-separated list of expressions. The results
10233 are discarded, so this is mainly useful for assigning values to trace
10234 state variables (@pxref{Trace State Variables}) without adding those
10235 values to the trace buffer, as would be the case if the @code{collect}
10238 @kindex while-stepping @r{(tracepoints)}
10239 @item while-stepping @var{n}
10240 Perform @var{n} single-step instruction traces after the tracepoint,
10241 collecting new data after each step. The @code{while-stepping}
10242 command is followed by the list of what to collect while stepping
10243 (followed by its own @code{end} command):
10246 > while-stepping 12
10247 > collect $regs, myglobal
10253 Note that @code{$pc} is not automatically collected by
10254 @code{while-stepping}; you need to explicitly collect that register if
10255 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10258 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10259 @kindex set default-collect
10260 @cindex default collection action
10261 This variable is a list of expressions to collect at each tracepoint
10262 hit. It is effectively an additional @code{collect} action prepended
10263 to every tracepoint action list. The expressions are parsed
10264 individually for each tracepoint, so for instance a variable named
10265 @code{xyz} may be interpreted as a global for one tracepoint, and a
10266 local for another, as appropriate to the tracepoint's location.
10268 @item show default-collect
10269 @kindex show default-collect
10270 Show the list of expressions that are collected by default at each
10275 @node Listing Tracepoints
10276 @subsection Listing Tracepoints
10279 @kindex info tracepoints
10281 @cindex information about tracepoints
10282 @item info tracepoints @r{[}@var{num}@r{]}
10283 Display information about the tracepoint @var{num}. If you don't
10284 specify a tracepoint number, displays information about all the
10285 tracepoints defined so far. The format is similar to that used for
10286 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10287 command, simply restricting itself to tracepoints.
10289 A tracepoint's listing may include additional information specific to
10294 its passcount as given by the @code{passcount @var{n}} command
10298 (@value{GDBP}) @b{info trace}
10299 Num Type Disp Enb Address What
10300 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10302 collect globfoo, $regs
10311 This command can be abbreviated @code{info tp}.
10314 @node Listing Static Tracepoint Markers
10315 @subsection Listing Static Tracepoint Markers
10318 @kindex info static-tracepoint-markers
10319 @cindex information about static tracepoint markers
10320 @item info static-tracepoint-markers
10321 Display information about all static tracepoint markers defined in the
10324 For each marker, the following columns are printed:
10328 An incrementing counter, output to help readability. This is not a
10331 The marker ID, as reported by the target.
10332 @item Enabled or Disabled
10333 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10334 that are not enabled.
10336 Where the marker is in your program, as a memory address.
10338 Where the marker is in the source for your program, as a file and line
10339 number. If the debug information included in the program does not
10340 allow @value{GDBN} to locate the source of the marker, this column
10341 will be left blank.
10345 In addition, the following information may be printed for each marker:
10349 User data passed to the tracing library by the marker call. In the
10350 UST backend, this is the format string passed as argument to the
10352 @item Static tracepoints probing the marker
10353 The list of static tracepoints attached to the marker.
10357 (@value{GDBP}) info static-tracepoint-markers
10358 Cnt ID Enb Address What
10359 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10360 Data: number1 %d number2 %d
10361 Probed by static tracepoints: #2
10362 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10368 @node Starting and Stopping Trace Experiments
10369 @subsection Starting and Stopping Trace Experiments
10373 @cindex start a new trace experiment
10374 @cindex collected data discarded
10376 This command takes no arguments. It starts the trace experiment, and
10377 begins collecting data. This has the side effect of discarding all
10378 the data collected in the trace buffer during the previous trace
10382 @cindex stop a running trace experiment
10384 This command takes no arguments. It ends the trace experiment, and
10385 stops collecting data.
10387 @strong{Note}: a trace experiment and data collection may stop
10388 automatically if any tracepoint's passcount is reached
10389 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10392 @cindex status of trace data collection
10393 @cindex trace experiment, status of
10395 This command displays the status of the current trace data
10399 Here is an example of the commands we described so far:
10402 (@value{GDBP}) @b{trace gdb_c_test}
10403 (@value{GDBP}) @b{actions}
10404 Enter actions for tracepoint #1, one per line.
10405 > collect $regs,$locals,$args
10406 > while-stepping 11
10410 (@value{GDBP}) @b{tstart}
10411 [time passes @dots{}]
10412 (@value{GDBP}) @b{tstop}
10415 @cindex disconnected tracing
10416 You can choose to continue running the trace experiment even if
10417 @value{GDBN} disconnects from the target, voluntarily or
10418 involuntarily. For commands such as @code{detach}, the debugger will
10419 ask what you want to do with the trace. But for unexpected
10420 terminations (@value{GDBN} crash, network outage), it would be
10421 unfortunate to lose hard-won trace data, so the variable
10422 @code{disconnected-tracing} lets you decide whether the trace should
10423 continue running without @value{GDBN}.
10426 @item set disconnected-tracing on
10427 @itemx set disconnected-tracing off
10428 @kindex set disconnected-tracing
10429 Choose whether a tracing run should continue to run if @value{GDBN}
10430 has disconnected from the target. Note that @code{detach} or
10431 @code{quit} will ask you directly what to do about a running trace no
10432 matter what this variable's setting, so the variable is mainly useful
10433 for handling unexpected situations, such as loss of the network.
10435 @item show disconnected-tracing
10436 @kindex show disconnected-tracing
10437 Show the current choice for disconnected tracing.
10441 When you reconnect to the target, the trace experiment may or may not
10442 still be running; it might have filled the trace buffer in the
10443 meantime, or stopped for one of the other reasons. If it is running,
10444 it will continue after reconnection.
10446 Upon reconnection, the target will upload information about the
10447 tracepoints in effect. @value{GDBN} will then compare that
10448 information to the set of tracepoints currently defined, and attempt
10449 to match them up, allowing for the possibility that the numbers may
10450 have changed due to creation and deletion in the meantime. If one of
10451 the target's tracepoints does not match any in @value{GDBN}, the
10452 debugger will create a new tracepoint, so that you have a number with
10453 which to specify that tracepoint. This matching-up process is
10454 necessarily heuristic, and it may result in useless tracepoints being
10455 created; you may simply delete them if they are of no use.
10457 @cindex circular trace buffer
10458 If your target agent supports a @dfn{circular trace buffer}, then you
10459 can run a trace experiment indefinitely without filling the trace
10460 buffer; when space runs out, the agent deletes already-collected trace
10461 frames, oldest first, until there is enough room to continue
10462 collecting. This is especially useful if your tracepoints are being
10463 hit too often, and your trace gets terminated prematurely because the
10464 buffer is full. To ask for a circular trace buffer, simply set
10465 @samp{circular_trace_buffer} to on. You can set this at any time,
10466 including during tracing; if the agent can do it, it will change
10467 buffer handling on the fly, otherwise it will not take effect until
10471 @item set circular-trace-buffer on
10472 @itemx set circular-trace-buffer off
10473 @kindex set circular-trace-buffer
10474 Choose whether a tracing run should use a linear or circular buffer
10475 for trace data. A linear buffer will not lose any trace data, but may
10476 fill up prematurely, while a circular buffer will discard old trace
10477 data, but it will have always room for the latest tracepoint hits.
10479 @item show circular-trace-buffer
10480 @kindex show circular-trace-buffer
10481 Show the current choice for the trace buffer. Note that this may not
10482 match the agent's current buffer handling, nor is it guaranteed to
10483 match the setting that might have been in effect during a past run,
10484 for instance if you are looking at frames from a trace file.
10488 @node Tracepoint Restrictions
10489 @subsection Tracepoint Restrictions
10491 @cindex tracepoint restrictions
10492 There are a number of restrictions on the use of tracepoints. As
10493 described above, tracepoint data gathering occurs on the target
10494 without interaction from @value{GDBN}. Thus the full capabilities of
10495 the debugger are not available during data gathering, and then at data
10496 examination time, you will be limited by only having what was
10497 collected. The following items describe some common problems, but it
10498 is not exhaustive, and you may run into additional difficulties not
10504 Tracepoint expressions are intended to gather objects (lvalues). Thus
10505 the full flexibility of GDB's expression evaluator is not available.
10506 You cannot call functions, cast objects to aggregate types, access
10507 convenience variables or modify values (except by assignment to trace
10508 state variables). Some language features may implicitly call
10509 functions (for instance Objective-C fields with accessors), and therefore
10510 cannot be collected either.
10513 Collection of local variables, either individually or in bulk with
10514 @code{$locals} or @code{$args}, during @code{while-stepping} may
10515 behave erratically. The stepping action may enter a new scope (for
10516 instance by stepping into a function), or the location of the variable
10517 may change (for instance it is loaded into a register). The
10518 tracepoint data recorded uses the location information for the
10519 variables that is correct for the tracepoint location. When the
10520 tracepoint is created, it is not possible, in general, to determine
10521 where the steps of a @code{while-stepping} sequence will advance the
10522 program---particularly if a conditional branch is stepped.
10525 Collection of an incompletely-initialized or partially-destroyed object
10526 may result in something that @value{GDBN} cannot display, or displays
10527 in a misleading way.
10530 When @value{GDBN} displays a pointer to character it automatically
10531 dereferences the pointer to also display characters of the string
10532 being pointed to. However, collecting the pointer during tracing does
10533 not automatically collect the string. You need to explicitly
10534 dereference the pointer and provide size information if you want to
10535 collect not only the pointer, but the memory pointed to. For example,
10536 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10540 It is not possible to collect a complete stack backtrace at a
10541 tracepoint. Instead, you may collect the registers and a few hundred
10542 bytes from the stack pointer with something like @code{*$esp@@300}
10543 (adjust to use the name of the actual stack pointer register on your
10544 target architecture, and the amount of stack you wish to capture).
10545 Then the @code{backtrace} command will show a partial backtrace when
10546 using a trace frame. The number of stack frames that can be examined
10547 depends on the sizes of the frames in the collected stack. Note that
10548 if you ask for a block so large that it goes past the bottom of the
10549 stack, the target agent may report an error trying to read from an
10553 If you do not collect registers at a tracepoint, @value{GDBN} can
10554 infer that the value of @code{$pc} must be the same as the address of
10555 the tracepoint and use that when you are looking at a trace frame
10556 for that tracepoint. However, this cannot work if the tracepoint has
10557 multiple locations (for instance if it was set in a function that was
10558 inlined), or if it has a @code{while-stepping} loop. In those cases
10559 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10564 @node Analyze Collected Data
10565 @section Using the Collected Data
10567 After the tracepoint experiment ends, you use @value{GDBN} commands
10568 for examining the trace data. The basic idea is that each tracepoint
10569 collects a trace @dfn{snapshot} every time it is hit and another
10570 snapshot every time it single-steps. All these snapshots are
10571 consecutively numbered from zero and go into a buffer, and you can
10572 examine them later. The way you examine them is to @dfn{focus} on a
10573 specific trace snapshot. When the remote stub is focused on a trace
10574 snapshot, it will respond to all @value{GDBN} requests for memory and
10575 registers by reading from the buffer which belongs to that snapshot,
10576 rather than from @emph{real} memory or registers of the program being
10577 debugged. This means that @strong{all} @value{GDBN} commands
10578 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10579 behave as if we were currently debugging the program state as it was
10580 when the tracepoint occurred. Any requests for data that are not in
10581 the buffer will fail.
10584 * tfind:: How to select a trace snapshot
10585 * tdump:: How to display all data for a snapshot
10586 * save tracepoints:: How to save tracepoints for a future run
10590 @subsection @code{tfind @var{n}}
10593 @cindex select trace snapshot
10594 @cindex find trace snapshot
10595 The basic command for selecting a trace snapshot from the buffer is
10596 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10597 counting from zero. If no argument @var{n} is given, the next
10598 snapshot is selected.
10600 Here are the various forms of using the @code{tfind} command.
10604 Find the first snapshot in the buffer. This is a synonym for
10605 @code{tfind 0} (since 0 is the number of the first snapshot).
10608 Stop debugging trace snapshots, resume @emph{live} debugging.
10611 Same as @samp{tfind none}.
10614 No argument means find the next trace snapshot.
10617 Find the previous trace snapshot before the current one. This permits
10618 retracing earlier steps.
10620 @item tfind tracepoint @var{num}
10621 Find the next snapshot associated with tracepoint @var{num}. Search
10622 proceeds forward from the last examined trace snapshot. If no
10623 argument @var{num} is given, it means find the next snapshot collected
10624 for the same tracepoint as the current snapshot.
10626 @item tfind pc @var{addr}
10627 Find the next snapshot associated with the value @var{addr} of the
10628 program counter. Search proceeds forward from the last examined trace
10629 snapshot. If no argument @var{addr} is given, it means find the next
10630 snapshot with the same value of PC as the current snapshot.
10632 @item tfind outside @var{addr1}, @var{addr2}
10633 Find the next snapshot whose PC is outside the given range of
10634 addresses (exclusive).
10636 @item tfind range @var{addr1}, @var{addr2}
10637 Find the next snapshot whose PC is between @var{addr1} and
10638 @var{addr2} (inclusive).
10640 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10641 Find the next snapshot associated with the source line @var{n}. If
10642 the optional argument @var{file} is given, refer to line @var{n} in
10643 that source file. Search proceeds forward from the last examined
10644 trace snapshot. If no argument @var{n} is given, it means find the
10645 next line other than the one currently being examined; thus saying
10646 @code{tfind line} repeatedly can appear to have the same effect as
10647 stepping from line to line in a @emph{live} debugging session.
10650 The default arguments for the @code{tfind} commands are specifically
10651 designed to make it easy to scan through the trace buffer. For
10652 instance, @code{tfind} with no argument selects the next trace
10653 snapshot, and @code{tfind -} with no argument selects the previous
10654 trace snapshot. So, by giving one @code{tfind} command, and then
10655 simply hitting @key{RET} repeatedly you can examine all the trace
10656 snapshots in order. Or, by saying @code{tfind -} and then hitting
10657 @key{RET} repeatedly you can examine the snapshots in reverse order.
10658 The @code{tfind line} command with no argument selects the snapshot
10659 for the next source line executed. The @code{tfind pc} command with
10660 no argument selects the next snapshot with the same program counter
10661 (PC) as the current frame. The @code{tfind tracepoint} command with
10662 no argument selects the next trace snapshot collected by the same
10663 tracepoint as the current one.
10665 In addition to letting you scan through the trace buffer manually,
10666 these commands make it easy to construct @value{GDBN} scripts that
10667 scan through the trace buffer and print out whatever collected data
10668 you are interested in. Thus, if we want to examine the PC, FP, and SP
10669 registers from each trace frame in the buffer, we can say this:
10672 (@value{GDBP}) @b{tfind start}
10673 (@value{GDBP}) @b{while ($trace_frame != -1)}
10674 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10675 $trace_frame, $pc, $sp, $fp
10679 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10680 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10681 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10682 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10683 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10684 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10685 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10686 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10687 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10688 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10689 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10692 Or, if we want to examine the variable @code{X} at each source line in
10696 (@value{GDBP}) @b{tfind start}
10697 (@value{GDBP}) @b{while ($trace_frame != -1)}
10698 > printf "Frame %d, X == %d\n", $trace_frame, X
10708 @subsection @code{tdump}
10710 @cindex dump all data collected at tracepoint
10711 @cindex tracepoint data, display
10713 This command takes no arguments. It prints all the data collected at
10714 the current trace snapshot.
10717 (@value{GDBP}) @b{trace 444}
10718 (@value{GDBP}) @b{actions}
10719 Enter actions for tracepoint #2, one per line:
10720 > collect $regs, $locals, $args, gdb_long_test
10723 (@value{GDBP}) @b{tstart}
10725 (@value{GDBP}) @b{tfind line 444}
10726 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10728 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10730 (@value{GDBP}) @b{tdump}
10731 Data collected at tracepoint 2, trace frame 1:
10732 d0 0xc4aa0085 -995491707
10736 d4 0x71aea3d 119204413
10739 d7 0x380035 3670069
10740 a0 0x19e24a 1696330
10741 a1 0x3000668 50333288
10743 a3 0x322000 3284992
10744 a4 0x3000698 50333336
10745 a5 0x1ad3cc 1758156
10746 fp 0x30bf3c 0x30bf3c
10747 sp 0x30bf34 0x30bf34
10749 pc 0x20b2c8 0x20b2c8
10753 p = 0x20e5b4 "gdb-test"
10760 gdb_long_test = 17 '\021'
10765 @code{tdump} works by scanning the tracepoint's current collection
10766 actions and printing the value of each expression listed. So
10767 @code{tdump} can fail, if after a run, you change the tracepoint's
10768 actions to mention variables that were not collected during the run.
10770 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10771 uses the collected value of @code{$pc} to distinguish between trace
10772 frames that were collected at the tracepoint hit, and frames that were
10773 collected while stepping. This allows it to correctly choose whether
10774 to display the basic list of collections, or the collections from the
10775 body of the while-stepping loop. However, if @code{$pc} was not collected,
10776 then @code{tdump} will always attempt to dump using the basic collection
10777 list, and may fail if a while-stepping frame does not include all the
10778 same data that is collected at the tracepoint hit.
10779 @c This is getting pretty arcane, example would be good.
10781 @node save tracepoints
10782 @subsection @code{save tracepoints @var{filename}}
10783 @kindex save tracepoints
10784 @kindex save-tracepoints
10785 @cindex save tracepoints for future sessions
10787 This command saves all current tracepoint definitions together with
10788 their actions and passcounts, into a file @file{@var{filename}}
10789 suitable for use in a later debugging session. To read the saved
10790 tracepoint definitions, use the @code{source} command (@pxref{Command
10791 Files}). The @w{@code{save-tracepoints}} command is a deprecated
10792 alias for @w{@code{save tracepoints}}
10794 @node Tracepoint Variables
10795 @section Convenience Variables for Tracepoints
10796 @cindex tracepoint variables
10797 @cindex convenience variables for tracepoints
10800 @vindex $trace_frame
10801 @item (int) $trace_frame
10802 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10803 snapshot is selected.
10805 @vindex $tracepoint
10806 @item (int) $tracepoint
10807 The tracepoint for the current trace snapshot.
10809 @vindex $trace_line
10810 @item (int) $trace_line
10811 The line number for the current trace snapshot.
10813 @vindex $trace_file
10814 @item (char []) $trace_file
10815 The source file for the current trace snapshot.
10817 @vindex $trace_func
10818 @item (char []) $trace_func
10819 The name of the function containing @code{$tracepoint}.
10822 Note: @code{$trace_file} is not suitable for use in @code{printf},
10823 use @code{output} instead.
10825 Here's a simple example of using these convenience variables for
10826 stepping through all the trace snapshots and printing some of their
10827 data. Note that these are not the same as trace state variables,
10828 which are managed by the target.
10831 (@value{GDBP}) @b{tfind start}
10833 (@value{GDBP}) @b{while $trace_frame != -1}
10834 > output $trace_file
10835 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10841 @section Using Trace Files
10842 @cindex trace files
10844 In some situations, the target running a trace experiment may no
10845 longer be available; perhaps it crashed, or the hardware was needed
10846 for a different activity. To handle these cases, you can arrange to
10847 dump the trace data into a file, and later use that file as a source
10848 of trace data, via the @code{target tfile} command.
10853 @item tsave [ -r ] @var{filename}
10854 Save the trace data to @var{filename}. By default, this command
10855 assumes that @var{filename} refers to the host filesystem, so if
10856 necessary @value{GDBN} will copy raw trace data up from the target and
10857 then save it. If the target supports it, you can also supply the
10858 optional argument @code{-r} (``remote'') to direct the target to save
10859 the data directly into @var{filename} in its own filesystem, which may be
10860 more efficient if the trace buffer is very large. (Note, however, that
10861 @code{target tfile} can only read from files accessible to the host.)
10863 @kindex target tfile
10865 @item target tfile @var{filename}
10866 Use the file named @var{filename} as a source of trace data. Commands
10867 that examine data work as they do with a live target, but it is not
10868 possible to run any new trace experiments. @code{tstatus} will report
10869 the state of the trace run at the moment the data was saved, as well
10870 as the current trace frame you are examining. @var{filename} must be
10871 on a filesystem accessible to the host.
10876 @chapter Debugging Programs That Use Overlays
10879 If your program is too large to fit completely in your target system's
10880 memory, you can sometimes use @dfn{overlays} to work around this
10881 problem. @value{GDBN} provides some support for debugging programs that
10885 * How Overlays Work:: A general explanation of overlays.
10886 * Overlay Commands:: Managing overlays in @value{GDBN}.
10887 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10888 mapped by asking the inferior.
10889 * Overlay Sample Program:: A sample program using overlays.
10892 @node How Overlays Work
10893 @section How Overlays Work
10894 @cindex mapped overlays
10895 @cindex unmapped overlays
10896 @cindex load address, overlay's
10897 @cindex mapped address
10898 @cindex overlay area
10900 Suppose you have a computer whose instruction address space is only 64
10901 kilobytes long, but which has much more memory which can be accessed by
10902 other means: special instructions, segment registers, or memory
10903 management hardware, for example. Suppose further that you want to
10904 adapt a program which is larger than 64 kilobytes to run on this system.
10906 One solution is to identify modules of your program which are relatively
10907 independent, and need not call each other directly; call these modules
10908 @dfn{overlays}. Separate the overlays from the main program, and place
10909 their machine code in the larger memory. Place your main program in
10910 instruction memory, but leave at least enough space there to hold the
10911 largest overlay as well.
10913 Now, to call a function located in an overlay, you must first copy that
10914 overlay's machine code from the large memory into the space set aside
10915 for it in the instruction memory, and then jump to its entry point
10918 @c NB: In the below the mapped area's size is greater or equal to the
10919 @c size of all overlays. This is intentional to remind the developer
10920 @c that overlays don't necessarily need to be the same size.
10924 Data Instruction Larger
10925 Address Space Address Space Address Space
10926 +-----------+ +-----------+ +-----------+
10928 +-----------+ +-----------+ +-----------+<-- overlay 1
10929 | program | | main | .----| overlay 1 | load address
10930 | variables | | program | | +-----------+
10931 | and heap | | | | | |
10932 +-----------+ | | | +-----------+<-- overlay 2
10933 | | +-----------+ | | | load address
10934 +-----------+ | | | .-| overlay 2 |
10936 mapped --->+-----------+ | | +-----------+
10937 address | | | | | |
10938 | overlay | <-' | | |
10939 | area | <---' +-----------+<-- overlay 3
10940 | | <---. | | load address
10941 +-----------+ `--| overlay 3 |
10948 @anchor{A code overlay}A code overlay
10952 The diagram (@pxref{A code overlay}) shows a system with separate data
10953 and instruction address spaces. To map an overlay, the program copies
10954 its code from the larger address space to the instruction address space.
10955 Since the overlays shown here all use the same mapped address, only one
10956 may be mapped at a time. For a system with a single address space for
10957 data and instructions, the diagram would be similar, except that the
10958 program variables and heap would share an address space with the main
10959 program and the overlay area.
10961 An overlay loaded into instruction memory and ready for use is called a
10962 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10963 instruction memory. An overlay not present (or only partially present)
10964 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10965 is its address in the larger memory. The mapped address is also called
10966 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10967 called the @dfn{load memory address}, or @dfn{LMA}.
10969 Unfortunately, overlays are not a completely transparent way to adapt a
10970 program to limited instruction memory. They introduce a new set of
10971 global constraints you must keep in mind as you design your program:
10976 Before calling or returning to a function in an overlay, your program
10977 must make sure that overlay is actually mapped. Otherwise, the call or
10978 return will transfer control to the right address, but in the wrong
10979 overlay, and your program will probably crash.
10982 If the process of mapping an overlay is expensive on your system, you
10983 will need to choose your overlays carefully to minimize their effect on
10984 your program's performance.
10987 The executable file you load onto your system must contain each
10988 overlay's instructions, appearing at the overlay's load address, not its
10989 mapped address. However, each overlay's instructions must be relocated
10990 and its symbols defined as if the overlay were at its mapped address.
10991 You can use GNU linker scripts to specify different load and relocation
10992 addresses for pieces of your program; see @ref{Overlay Description,,,
10993 ld.info, Using ld: the GNU linker}.
10996 The procedure for loading executable files onto your system must be able
10997 to load their contents into the larger address space as well as the
10998 instruction and data spaces.
11002 The overlay system described above is rather simple, and could be
11003 improved in many ways:
11008 If your system has suitable bank switch registers or memory management
11009 hardware, you could use those facilities to make an overlay's load area
11010 contents simply appear at their mapped address in instruction space.
11011 This would probably be faster than copying the overlay to its mapped
11012 area in the usual way.
11015 If your overlays are small enough, you could set aside more than one
11016 overlay area, and have more than one overlay mapped at a time.
11019 You can use overlays to manage data, as well as instructions. In
11020 general, data overlays are even less transparent to your design than
11021 code overlays: whereas code overlays only require care when you call or
11022 return to functions, data overlays require care every time you access
11023 the data. Also, if you change the contents of a data overlay, you
11024 must copy its contents back out to its load address before you can copy a
11025 different data overlay into the same mapped area.
11030 @node Overlay Commands
11031 @section Overlay Commands
11033 To use @value{GDBN}'s overlay support, each overlay in your program must
11034 correspond to a separate section of the executable file. The section's
11035 virtual memory address and load memory address must be the overlay's
11036 mapped and load addresses. Identifying overlays with sections allows
11037 @value{GDBN} to determine the appropriate address of a function or
11038 variable, depending on whether the overlay is mapped or not.
11040 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11041 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11046 Disable @value{GDBN}'s overlay support. When overlay support is
11047 disabled, @value{GDBN} assumes that all functions and variables are
11048 always present at their mapped addresses. By default, @value{GDBN}'s
11049 overlay support is disabled.
11051 @item overlay manual
11052 @cindex manual overlay debugging
11053 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11054 relies on you to tell it which overlays are mapped, and which are not,
11055 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11056 commands described below.
11058 @item overlay map-overlay @var{overlay}
11059 @itemx overlay map @var{overlay}
11060 @cindex map an overlay
11061 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11062 be the name of the object file section containing the overlay. When an
11063 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11064 functions and variables at their mapped addresses. @value{GDBN} assumes
11065 that any other overlays whose mapped ranges overlap that of
11066 @var{overlay} are now unmapped.
11068 @item overlay unmap-overlay @var{overlay}
11069 @itemx overlay unmap @var{overlay}
11070 @cindex unmap an overlay
11071 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11072 must be the name of the object file section containing the overlay.
11073 When an overlay is unmapped, @value{GDBN} assumes it can find the
11074 overlay's functions and variables at their load addresses.
11077 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11078 consults a data structure the overlay manager maintains in the inferior
11079 to see which overlays are mapped. For details, see @ref{Automatic
11080 Overlay Debugging}.
11082 @item overlay load-target
11083 @itemx overlay load
11084 @cindex reloading the overlay table
11085 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11086 re-reads the table @value{GDBN} automatically each time the inferior
11087 stops, so this command should only be necessary if you have changed the
11088 overlay mapping yourself using @value{GDBN}. This command is only
11089 useful when using automatic overlay debugging.
11091 @item overlay list-overlays
11092 @itemx overlay list
11093 @cindex listing mapped overlays
11094 Display a list of the overlays currently mapped, along with their mapped
11095 addresses, load addresses, and sizes.
11099 Normally, when @value{GDBN} prints a code address, it includes the name
11100 of the function the address falls in:
11103 (@value{GDBP}) print main
11104 $3 = @{int ()@} 0x11a0 <main>
11107 When overlay debugging is enabled, @value{GDBN} recognizes code in
11108 unmapped overlays, and prints the names of unmapped functions with
11109 asterisks around them. For example, if @code{foo} is a function in an
11110 unmapped overlay, @value{GDBN} prints it this way:
11113 (@value{GDBP}) overlay list
11114 No sections are mapped.
11115 (@value{GDBP}) print foo
11116 $5 = @{int (int)@} 0x100000 <*foo*>
11119 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11123 (@value{GDBP}) overlay list
11124 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11125 mapped at 0x1016 - 0x104a
11126 (@value{GDBP}) print foo
11127 $6 = @{int (int)@} 0x1016 <foo>
11130 When overlay debugging is enabled, @value{GDBN} can find the correct
11131 address for functions and variables in an overlay, whether or not the
11132 overlay is mapped. This allows most @value{GDBN} commands, like
11133 @code{break} and @code{disassemble}, to work normally, even on unmapped
11134 code. However, @value{GDBN}'s breakpoint support has some limitations:
11138 @cindex breakpoints in overlays
11139 @cindex overlays, setting breakpoints in
11140 You can set breakpoints in functions in unmapped overlays, as long as
11141 @value{GDBN} can write to the overlay at its load address.
11143 @value{GDBN} can not set hardware or simulator-based breakpoints in
11144 unmapped overlays. However, if you set a breakpoint at the end of your
11145 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11146 you are using manual overlay management), @value{GDBN} will re-set its
11147 breakpoints properly.
11151 @node Automatic Overlay Debugging
11152 @section Automatic Overlay Debugging
11153 @cindex automatic overlay debugging
11155 @value{GDBN} can automatically track which overlays are mapped and which
11156 are not, given some simple co-operation from the overlay manager in the
11157 inferior. If you enable automatic overlay debugging with the
11158 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11159 looks in the inferior's memory for certain variables describing the
11160 current state of the overlays.
11162 Here are the variables your overlay manager must define to support
11163 @value{GDBN}'s automatic overlay debugging:
11167 @item @code{_ovly_table}:
11168 This variable must be an array of the following structures:
11173 /* The overlay's mapped address. */
11176 /* The size of the overlay, in bytes. */
11177 unsigned long size;
11179 /* The overlay's load address. */
11182 /* Non-zero if the overlay is currently mapped;
11184 unsigned long mapped;
11188 @item @code{_novlys}:
11189 This variable must be a four-byte signed integer, holding the total
11190 number of elements in @code{_ovly_table}.
11194 To decide whether a particular overlay is mapped or not, @value{GDBN}
11195 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11196 @code{lma} members equal the VMA and LMA of the overlay's section in the
11197 executable file. When @value{GDBN} finds a matching entry, it consults
11198 the entry's @code{mapped} member to determine whether the overlay is
11201 In addition, your overlay manager may define a function called
11202 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11203 will silently set a breakpoint there. If the overlay manager then
11204 calls this function whenever it has changed the overlay table, this
11205 will enable @value{GDBN} to accurately keep track of which overlays
11206 are in program memory, and update any breakpoints that may be set
11207 in overlays. This will allow breakpoints to work even if the
11208 overlays are kept in ROM or other non-writable memory while they
11209 are not being executed.
11211 @node Overlay Sample Program
11212 @section Overlay Sample Program
11213 @cindex overlay example program
11215 When linking a program which uses overlays, you must place the overlays
11216 at their load addresses, while relocating them to run at their mapped
11217 addresses. To do this, you must write a linker script (@pxref{Overlay
11218 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11219 since linker scripts are specific to a particular host system, target
11220 architecture, and target memory layout, this manual cannot provide
11221 portable sample code demonstrating @value{GDBN}'s overlay support.
11223 However, the @value{GDBN} source distribution does contain an overlaid
11224 program, with linker scripts for a few systems, as part of its test
11225 suite. The program consists of the following files from
11226 @file{gdb/testsuite/gdb.base}:
11230 The main program file.
11232 A simple overlay manager, used by @file{overlays.c}.
11237 Overlay modules, loaded and used by @file{overlays.c}.
11240 Linker scripts for linking the test program on the @code{d10v-elf}
11241 and @code{m32r-elf} targets.
11244 You can build the test program using the @code{d10v-elf} GCC
11245 cross-compiler like this:
11248 $ d10v-elf-gcc -g -c overlays.c
11249 $ d10v-elf-gcc -g -c ovlymgr.c
11250 $ d10v-elf-gcc -g -c foo.c
11251 $ d10v-elf-gcc -g -c bar.c
11252 $ d10v-elf-gcc -g -c baz.c
11253 $ d10v-elf-gcc -g -c grbx.c
11254 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11255 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11258 The build process is identical for any other architecture, except that
11259 you must substitute the appropriate compiler and linker script for the
11260 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11264 @chapter Using @value{GDBN} with Different Languages
11267 Although programming languages generally have common aspects, they are
11268 rarely expressed in the same manner. For instance, in ANSI C,
11269 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11270 Modula-2, it is accomplished by @code{p^}. Values can also be
11271 represented (and displayed) differently. Hex numbers in C appear as
11272 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11274 @cindex working language
11275 Language-specific information is built into @value{GDBN} for some languages,
11276 allowing you to express operations like the above in your program's
11277 native language, and allowing @value{GDBN} to output values in a manner
11278 consistent with the syntax of your program's native language. The
11279 language you use to build expressions is called the @dfn{working
11283 * Setting:: Switching between source languages
11284 * Show:: Displaying the language
11285 * Checks:: Type and range checks
11286 * Supported Languages:: Supported languages
11287 * Unsupported Languages:: Unsupported languages
11291 @section Switching Between Source Languages
11293 There are two ways to control the working language---either have @value{GDBN}
11294 set it automatically, or select it manually yourself. You can use the
11295 @code{set language} command for either purpose. On startup, @value{GDBN}
11296 defaults to setting the language automatically. The working language is
11297 used to determine how expressions you type are interpreted, how values
11300 In addition to the working language, every source file that
11301 @value{GDBN} knows about has its own working language. For some object
11302 file formats, the compiler might indicate which language a particular
11303 source file is in. However, most of the time @value{GDBN} infers the
11304 language from the name of the file. The language of a source file
11305 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11306 show each frame appropriately for its own language. There is no way to
11307 set the language of a source file from within @value{GDBN}, but you can
11308 set the language associated with a filename extension. @xref{Show, ,
11309 Displaying the Language}.
11311 This is most commonly a problem when you use a program, such
11312 as @code{cfront} or @code{f2c}, that generates C but is written in
11313 another language. In that case, make the
11314 program use @code{#line} directives in its C output; that way
11315 @value{GDBN} will know the correct language of the source code of the original
11316 program, and will display that source code, not the generated C code.
11319 * Filenames:: Filename extensions and languages.
11320 * Manually:: Setting the working language manually
11321 * Automatically:: Having @value{GDBN} infer the source language
11325 @subsection List of Filename Extensions and Languages
11327 If a source file name ends in one of the following extensions, then
11328 @value{GDBN} infers that its language is the one indicated.
11346 C@t{++} source file
11352 Objective-C source file
11356 Fortran source file
11359 Modula-2 source file
11363 Assembler source file. This actually behaves almost like C, but
11364 @value{GDBN} does not skip over function prologues when stepping.
11367 In addition, you may set the language associated with a filename
11368 extension. @xref{Show, , Displaying the Language}.
11371 @subsection Setting the Working Language
11373 If you allow @value{GDBN} to set the language automatically,
11374 expressions are interpreted the same way in your debugging session and
11377 @kindex set language
11378 If you wish, you may set the language manually. To do this, issue the
11379 command @samp{set language @var{lang}}, where @var{lang} is the name of
11380 a language, such as
11381 @code{c} or @code{modula-2}.
11382 For a list of the supported languages, type @samp{set language}.
11384 Setting the language manually prevents @value{GDBN} from updating the working
11385 language automatically. This can lead to confusion if you try
11386 to debug a program when the working language is not the same as the
11387 source language, when an expression is acceptable to both
11388 languages---but means different things. For instance, if the current
11389 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11397 might not have the effect you intended. In C, this means to add
11398 @code{b} and @code{c} and place the result in @code{a}. The result
11399 printed would be the value of @code{a}. In Modula-2, this means to compare
11400 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11402 @node Automatically
11403 @subsection Having @value{GDBN} Infer the Source Language
11405 To have @value{GDBN} set the working language automatically, use
11406 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11407 then infers the working language. That is, when your program stops in a
11408 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11409 working language to the language recorded for the function in that
11410 frame. If the language for a frame is unknown (that is, if the function
11411 or block corresponding to the frame was defined in a source file that
11412 does not have a recognized extension), the current working language is
11413 not changed, and @value{GDBN} issues a warning.
11415 This may not seem necessary for most programs, which are written
11416 entirely in one source language. However, program modules and libraries
11417 written in one source language can be used by a main program written in
11418 a different source language. Using @samp{set language auto} in this
11419 case frees you from having to set the working language manually.
11422 @section Displaying the Language
11424 The following commands help you find out which language is the
11425 working language, and also what language source files were written in.
11428 @item show language
11429 @kindex show language
11430 Display the current working language. This is the
11431 language you can use with commands such as @code{print} to
11432 build and compute expressions that may involve variables in your program.
11435 @kindex info frame@r{, show the source language}
11436 Display the source language for this frame. This language becomes the
11437 working language if you use an identifier from this frame.
11438 @xref{Frame Info, ,Information about a Frame}, to identify the other
11439 information listed here.
11442 @kindex info source@r{, show the source language}
11443 Display the source language of this source file.
11444 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11445 information listed here.
11448 In unusual circumstances, you may have source files with extensions
11449 not in the standard list. You can then set the extension associated
11450 with a language explicitly:
11453 @item set extension-language @var{ext} @var{language}
11454 @kindex set extension-language
11455 Tell @value{GDBN} that source files with extension @var{ext} are to be
11456 assumed as written in the source language @var{language}.
11458 @item info extensions
11459 @kindex info extensions
11460 List all the filename extensions and the associated languages.
11464 @section Type and Range Checking
11467 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11468 checking are included, but they do not yet have any effect. This
11469 section documents the intended facilities.
11471 @c FIXME remove warning when type/range code added
11473 Some languages are designed to guard you against making seemingly common
11474 errors through a series of compile- and run-time checks. These include
11475 checking the type of arguments to functions and operators, and making
11476 sure mathematical overflows are caught at run time. Checks such as
11477 these help to ensure a program's correctness once it has been compiled
11478 by eliminating type mismatches, and providing active checks for range
11479 errors when your program is running.
11481 @value{GDBN} can check for conditions like the above if you wish.
11482 Although @value{GDBN} does not check the statements in your program,
11483 it can check expressions entered directly into @value{GDBN} for
11484 evaluation via the @code{print} command, for example. As with the
11485 working language, @value{GDBN} can also decide whether or not to check
11486 automatically based on your program's source language.
11487 @xref{Supported Languages, ,Supported Languages}, for the default
11488 settings of supported languages.
11491 * Type Checking:: An overview of type checking
11492 * Range Checking:: An overview of range checking
11495 @cindex type checking
11496 @cindex checks, type
11497 @node Type Checking
11498 @subsection An Overview of Type Checking
11500 Some languages, such as Modula-2, are strongly typed, meaning that the
11501 arguments to operators and functions have to be of the correct type,
11502 otherwise an error occurs. These checks prevent type mismatch
11503 errors from ever causing any run-time problems. For example,
11511 The second example fails because the @code{CARDINAL} 1 is not
11512 type-compatible with the @code{REAL} 2.3.
11514 For the expressions you use in @value{GDBN} commands, you can tell the
11515 @value{GDBN} type checker to skip checking;
11516 to treat any mismatches as errors and abandon the expression;
11517 or to only issue warnings when type mismatches occur,
11518 but evaluate the expression anyway. When you choose the last of
11519 these, @value{GDBN} evaluates expressions like the second example above, but
11520 also issues a warning.
11522 Even if you turn type checking off, there may be other reasons
11523 related to type that prevent @value{GDBN} from evaluating an expression.
11524 For instance, @value{GDBN} does not know how to add an @code{int} and
11525 a @code{struct foo}. These particular type errors have nothing to do
11526 with the language in use, and usually arise from expressions, such as
11527 the one described above, which make little sense to evaluate anyway.
11529 Each language defines to what degree it is strict about type. For
11530 instance, both Modula-2 and C require the arguments to arithmetical
11531 operators to be numbers. In C, enumerated types and pointers can be
11532 represented as numbers, so that they are valid arguments to mathematical
11533 operators. @xref{Supported Languages, ,Supported Languages}, for further
11534 details on specific languages.
11536 @value{GDBN} provides some additional commands for controlling the type checker:
11538 @kindex set check type
11539 @kindex show check type
11541 @item set check type auto
11542 Set type checking on or off based on the current working language.
11543 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11546 @item set check type on
11547 @itemx set check type off
11548 Set type checking on or off, overriding the default setting for the
11549 current working language. Issue a warning if the setting does not
11550 match the language default. If any type mismatches occur in
11551 evaluating an expression while type checking is on, @value{GDBN} prints a
11552 message and aborts evaluation of the expression.
11554 @item set check type warn
11555 Cause the type checker to issue warnings, but to always attempt to
11556 evaluate the expression. Evaluating the expression may still
11557 be impossible for other reasons. For example, @value{GDBN} cannot add
11558 numbers and structures.
11561 Show the current setting of the type checker, and whether or not @value{GDBN}
11562 is setting it automatically.
11565 @cindex range checking
11566 @cindex checks, range
11567 @node Range Checking
11568 @subsection An Overview of Range Checking
11570 In some languages (such as Modula-2), it is an error to exceed the
11571 bounds of a type; this is enforced with run-time checks. Such range
11572 checking is meant to ensure program correctness by making sure
11573 computations do not overflow, or indices on an array element access do
11574 not exceed the bounds of the array.
11576 For expressions you use in @value{GDBN} commands, you can tell
11577 @value{GDBN} to treat range errors in one of three ways: ignore them,
11578 always treat them as errors and abandon the expression, or issue
11579 warnings but evaluate the expression anyway.
11581 A range error can result from numerical overflow, from exceeding an
11582 array index bound, or when you type a constant that is not a member
11583 of any type. Some languages, however, do not treat overflows as an
11584 error. In many implementations of C, mathematical overflow causes the
11585 result to ``wrap around'' to lower values---for example, if @var{m} is
11586 the largest integer value, and @var{s} is the smallest, then
11589 @var{m} + 1 @result{} @var{s}
11592 This, too, is specific to individual languages, and in some cases
11593 specific to individual compilers or machines. @xref{Supported Languages, ,
11594 Supported Languages}, for further details on specific languages.
11596 @value{GDBN} provides some additional commands for controlling the range checker:
11598 @kindex set check range
11599 @kindex show check range
11601 @item set check range auto
11602 Set range checking on or off based on the current working language.
11603 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11606 @item set check range on
11607 @itemx set check range off
11608 Set range checking on or off, overriding the default setting for the
11609 current working language. A warning is issued if the setting does not
11610 match the language default. If a range error occurs and range checking is on,
11611 then a message is printed and evaluation of the expression is aborted.
11613 @item set check range warn
11614 Output messages when the @value{GDBN} range checker detects a range error,
11615 but attempt to evaluate the expression anyway. Evaluating the
11616 expression may still be impossible for other reasons, such as accessing
11617 memory that the process does not own (a typical example from many Unix
11621 Show the current setting of the range checker, and whether or not it is
11622 being set automatically by @value{GDBN}.
11625 @node Supported Languages
11626 @section Supported Languages
11628 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
11629 assembly, Modula-2, and Ada.
11630 @c This is false ...
11631 Some @value{GDBN} features may be used in expressions regardless of the
11632 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11633 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11634 ,Expressions}) can be used with the constructs of any supported
11637 The following sections detail to what degree each source language is
11638 supported by @value{GDBN}. These sections are not meant to be language
11639 tutorials or references, but serve only as a reference guide to what the
11640 @value{GDBN} expression parser accepts, and what input and output
11641 formats should look like for different languages. There are many good
11642 books written on each of these languages; please look to these for a
11643 language reference or tutorial.
11646 * C:: C and C@t{++}
11648 * Objective-C:: Objective-C
11649 * OpenCL C:: OpenCL C
11650 * Fortran:: Fortran
11652 * Modula-2:: Modula-2
11657 @subsection C and C@t{++}
11659 @cindex C and C@t{++}
11660 @cindex expressions in C or C@t{++}
11662 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11663 to both languages. Whenever this is the case, we discuss those languages
11667 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11668 @cindex @sc{gnu} C@t{++}
11669 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11670 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11671 effectively, you must compile your C@t{++} programs with a supported
11672 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11673 compiler (@code{aCC}).
11675 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11676 format; if it doesn't work on your system, try the stabs+ debugging
11677 format. You can select those formats explicitly with the @code{g++}
11678 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11679 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11680 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11683 * C Operators:: C and C@t{++} operators
11684 * C Constants:: C and C@t{++} constants
11685 * C Plus Plus Expressions:: C@t{++} expressions
11686 * C Defaults:: Default settings for C and C@t{++}
11687 * C Checks:: C and C@t{++} type and range checks
11688 * Debugging C:: @value{GDBN} and C
11689 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11690 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11694 @subsubsection C and C@t{++} Operators
11696 @cindex C and C@t{++} operators
11698 Operators must be defined on values of specific types. For instance,
11699 @code{+} is defined on numbers, but not on structures. Operators are
11700 often defined on groups of types.
11702 For the purposes of C and C@t{++}, the following definitions hold:
11707 @emph{Integral types} include @code{int} with any of its storage-class
11708 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11711 @emph{Floating-point types} include @code{float}, @code{double}, and
11712 @code{long double} (if supported by the target platform).
11715 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11718 @emph{Scalar types} include all of the above.
11723 The following operators are supported. They are listed here
11724 in order of increasing precedence:
11728 The comma or sequencing operator. Expressions in a comma-separated list
11729 are evaluated from left to right, with the result of the entire
11730 expression being the last expression evaluated.
11733 Assignment. The value of an assignment expression is the value
11734 assigned. Defined on scalar types.
11737 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11738 and translated to @w{@code{@var{a} = @var{a op b}}}.
11739 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11740 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11741 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11744 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11745 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11749 Logical @sc{or}. Defined on integral types.
11752 Logical @sc{and}. Defined on integral types.
11755 Bitwise @sc{or}. Defined on integral types.
11758 Bitwise exclusive-@sc{or}. Defined on integral types.
11761 Bitwise @sc{and}. Defined on integral types.
11764 Equality and inequality. Defined on scalar types. The value of these
11765 expressions is 0 for false and non-zero for true.
11767 @item <@r{, }>@r{, }<=@r{, }>=
11768 Less than, greater than, less than or equal, greater than or equal.
11769 Defined on scalar types. The value of these expressions is 0 for false
11770 and non-zero for true.
11773 left shift, and right shift. Defined on integral types.
11776 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11779 Addition and subtraction. Defined on integral types, floating-point types and
11782 @item *@r{, }/@r{, }%
11783 Multiplication, division, and modulus. Multiplication and division are
11784 defined on integral and floating-point types. Modulus is defined on
11788 Increment and decrement. When appearing before a variable, the
11789 operation is performed before the variable is used in an expression;
11790 when appearing after it, the variable's value is used before the
11791 operation takes place.
11794 Pointer dereferencing. Defined on pointer types. Same precedence as
11798 Address operator. Defined on variables. Same precedence as @code{++}.
11800 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11801 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11802 to examine the address
11803 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11807 Negative. Defined on integral and floating-point types. Same
11808 precedence as @code{++}.
11811 Logical negation. Defined on integral types. Same precedence as
11815 Bitwise complement operator. Defined on integral types. Same precedence as
11820 Structure member, and pointer-to-structure member. For convenience,
11821 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11822 pointer based on the stored type information.
11823 Defined on @code{struct} and @code{union} data.
11826 Dereferences of pointers to members.
11829 Array indexing. @code{@var{a}[@var{i}]} is defined as
11830 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11833 Function parameter list. Same precedence as @code{->}.
11836 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11837 and @code{class} types.
11840 Doubled colons also represent the @value{GDBN} scope operator
11841 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11845 If an operator is redefined in the user code, @value{GDBN} usually
11846 attempts to invoke the redefined version instead of using the operator's
11847 predefined meaning.
11850 @subsubsection C and C@t{++} Constants
11852 @cindex C and C@t{++} constants
11854 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11859 Integer constants are a sequence of digits. Octal constants are
11860 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11861 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11862 @samp{l}, specifying that the constant should be treated as a
11866 Floating point constants are a sequence of digits, followed by a decimal
11867 point, followed by a sequence of digits, and optionally followed by an
11868 exponent. An exponent is of the form:
11869 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11870 sequence of digits. The @samp{+} is optional for positive exponents.
11871 A floating-point constant may also end with a letter @samp{f} or
11872 @samp{F}, specifying that the constant should be treated as being of
11873 the @code{float} (as opposed to the default @code{double}) type; or with
11874 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11878 Enumerated constants consist of enumerated identifiers, or their
11879 integral equivalents.
11882 Character constants are a single character surrounded by single quotes
11883 (@code{'}), or a number---the ordinal value of the corresponding character
11884 (usually its @sc{ascii} value). Within quotes, the single character may
11885 be represented by a letter or by @dfn{escape sequences}, which are of
11886 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11887 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11888 @samp{@var{x}} is a predefined special character---for example,
11889 @samp{\n} for newline.
11892 String constants are a sequence of character constants surrounded by
11893 double quotes (@code{"}). Any valid character constant (as described
11894 above) may appear. Double quotes within the string must be preceded by
11895 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11899 Pointer constants are an integral value. You can also write pointers
11900 to constants using the C operator @samp{&}.
11903 Array constants are comma-separated lists surrounded by braces @samp{@{}
11904 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11905 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11906 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11909 @node C Plus Plus Expressions
11910 @subsubsection C@t{++} Expressions
11912 @cindex expressions in C@t{++}
11913 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11915 @cindex debugging C@t{++} programs
11916 @cindex C@t{++} compilers
11917 @cindex debug formats and C@t{++}
11918 @cindex @value{NGCC} and C@t{++}
11920 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11921 proper compiler and the proper debug format. Currently, @value{GDBN}
11922 works best when debugging C@t{++} code that is compiled with
11923 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11924 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11925 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11926 stabs+ as their default debug format, so you usually don't need to
11927 specify a debug format explicitly. Other compilers and/or debug formats
11928 are likely to work badly or not at all when using @value{GDBN} to debug
11934 @cindex member functions
11936 Member function calls are allowed; you can use expressions like
11939 count = aml->GetOriginal(x, y)
11942 @vindex this@r{, inside C@t{++} member functions}
11943 @cindex namespace in C@t{++}
11945 While a member function is active (in the selected stack frame), your
11946 expressions have the same namespace available as the member function;
11947 that is, @value{GDBN} allows implicit references to the class instance
11948 pointer @code{this} following the same rules as C@t{++}.
11950 @cindex call overloaded functions
11951 @cindex overloaded functions, calling
11952 @cindex type conversions in C@t{++}
11954 You can call overloaded functions; @value{GDBN} resolves the function
11955 call to the right definition, with some restrictions. @value{GDBN} does not
11956 perform overload resolution involving user-defined type conversions,
11957 calls to constructors, or instantiations of templates that do not exist
11958 in the program. It also cannot handle ellipsis argument lists or
11961 It does perform integral conversions and promotions, floating-point
11962 promotions, arithmetic conversions, pointer conversions, conversions of
11963 class objects to base classes, and standard conversions such as those of
11964 functions or arrays to pointers; it requires an exact match on the
11965 number of function arguments.
11967 Overload resolution is always performed, unless you have specified
11968 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11969 ,@value{GDBN} Features for C@t{++}}.
11971 You must specify @code{set overload-resolution off} in order to use an
11972 explicit function signature to call an overloaded function, as in
11974 p 'foo(char,int)'('x', 13)
11977 The @value{GDBN} command-completion facility can simplify this;
11978 see @ref{Completion, ,Command Completion}.
11980 @cindex reference declarations
11982 @value{GDBN} understands variables declared as C@t{++} references; you can use
11983 them in expressions just as you do in C@t{++} source---they are automatically
11986 In the parameter list shown when @value{GDBN} displays a frame, the values of
11987 reference variables are not displayed (unlike other variables); this
11988 avoids clutter, since references are often used for large structures.
11989 The @emph{address} of a reference variable is always shown, unless
11990 you have specified @samp{set print address off}.
11993 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
11994 expressions can use it just as expressions in your program do. Since
11995 one scope may be defined in another, you can use @code{::} repeatedly if
11996 necessary, for example in an expression like
11997 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
11998 resolving name scope by reference to source files, in both C and C@t{++}
11999 debugging (@pxref{Variables, ,Program Variables}).
12002 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
12003 calling virtual functions correctly, printing out virtual bases of
12004 objects, calling functions in a base subobject, casting objects, and
12005 invoking user-defined operators.
12008 @subsubsection C and C@t{++} Defaults
12010 @cindex C and C@t{++} defaults
12012 If you allow @value{GDBN} to set type and range checking automatically, they
12013 both default to @code{off} whenever the working language changes to
12014 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12015 selects the working language.
12017 If you allow @value{GDBN} to set the language automatically, it
12018 recognizes source files whose names end with @file{.c}, @file{.C}, or
12019 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12020 these files, it sets the working language to C or C@t{++}.
12021 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12022 for further details.
12024 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12025 @c unimplemented. If (b) changes, it might make sense to let this node
12026 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12029 @subsubsection C and C@t{++} Type and Range Checks
12031 @cindex C and C@t{++} checks
12033 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12034 is not used. However, if you turn type checking on, @value{GDBN}
12035 considers two variables type equivalent if:
12039 The two variables are structured and have the same structure, union, or
12043 The two variables have the same type name, or types that have been
12044 declared equivalent through @code{typedef}.
12047 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12050 The two @code{struct}, @code{union}, or @code{enum} variables are
12051 declared in the same declaration. (Note: this may not be true for all C
12056 Range checking, if turned on, is done on mathematical operations. Array
12057 indices are not checked, since they are often used to index a pointer
12058 that is not itself an array.
12061 @subsubsection @value{GDBN} and C
12063 The @code{set print union} and @code{show print union} commands apply to
12064 the @code{union} type. When set to @samp{on}, any @code{union} that is
12065 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12066 appears as @samp{@{...@}}.
12068 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12069 with pointers and a memory allocation function. @xref{Expressions,
12072 @node Debugging C Plus Plus
12073 @subsubsection @value{GDBN} Features for C@t{++}
12075 @cindex commands for C@t{++}
12077 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12078 designed specifically for use with C@t{++}. Here is a summary:
12081 @cindex break in overloaded functions
12082 @item @r{breakpoint menus}
12083 When you want a breakpoint in a function whose name is overloaded,
12084 @value{GDBN} has the capability to display a menu of possible breakpoint
12085 locations to help you specify which function definition you want.
12086 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12088 @cindex overloading in C@t{++}
12089 @item rbreak @var{regex}
12090 Setting breakpoints using regular expressions is helpful for setting
12091 breakpoints on overloaded functions that are not members of any special
12093 @xref{Set Breaks, ,Setting Breakpoints}.
12095 @cindex C@t{++} exception handling
12098 Debug C@t{++} exception handling using these commands. @xref{Set
12099 Catchpoints, , Setting Catchpoints}.
12101 @cindex inheritance
12102 @item ptype @var{typename}
12103 Print inheritance relationships as well as other information for type
12105 @xref{Symbols, ,Examining the Symbol Table}.
12107 @cindex C@t{++} symbol display
12108 @item set print demangle
12109 @itemx show print demangle
12110 @itemx set print asm-demangle
12111 @itemx show print asm-demangle
12112 Control whether C@t{++} symbols display in their source form, both when
12113 displaying code as C@t{++} source and when displaying disassemblies.
12114 @xref{Print Settings, ,Print Settings}.
12116 @item set print object
12117 @itemx show print object
12118 Choose whether to print derived (actual) or declared types of objects.
12119 @xref{Print Settings, ,Print Settings}.
12121 @item set print vtbl
12122 @itemx show print vtbl
12123 Control the format for printing virtual function tables.
12124 @xref{Print Settings, ,Print Settings}.
12125 (The @code{vtbl} commands do not work on programs compiled with the HP
12126 ANSI C@t{++} compiler (@code{aCC}).)
12128 @kindex set overload-resolution
12129 @cindex overloaded functions, overload resolution
12130 @item set overload-resolution on
12131 Enable overload resolution for C@t{++} expression evaluation. The default
12132 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12133 and searches for a function whose signature matches the argument types,
12134 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12135 Expressions, ,C@t{++} Expressions}, for details).
12136 If it cannot find a match, it emits a message.
12138 @item set overload-resolution off
12139 Disable overload resolution for C@t{++} expression evaluation. For
12140 overloaded functions that are not class member functions, @value{GDBN}
12141 chooses the first function of the specified name that it finds in the
12142 symbol table, whether or not its arguments are of the correct type. For
12143 overloaded functions that are class member functions, @value{GDBN}
12144 searches for a function whose signature @emph{exactly} matches the
12147 @kindex show overload-resolution
12148 @item show overload-resolution
12149 Show the current setting of overload resolution.
12151 @item @r{Overloaded symbol names}
12152 You can specify a particular definition of an overloaded symbol, using
12153 the same notation that is used to declare such symbols in C@t{++}: type
12154 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12155 also use the @value{GDBN} command-line word completion facilities to list the
12156 available choices, or to finish the type list for you.
12157 @xref{Completion,, Command Completion}, for details on how to do this.
12160 @node Decimal Floating Point
12161 @subsubsection Decimal Floating Point format
12162 @cindex decimal floating point format
12164 @value{GDBN} can examine, set and perform computations with numbers in
12165 decimal floating point format, which in the C language correspond to the
12166 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12167 specified by the extension to support decimal floating-point arithmetic.
12169 There are two encodings in use, depending on the architecture: BID (Binary
12170 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12171 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12174 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12175 to manipulate decimal floating point numbers, it is not possible to convert
12176 (using a cast, for example) integers wider than 32-bit to decimal float.
12178 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12179 point computations, error checking in decimal float operations ignores
12180 underflow, overflow and divide by zero exceptions.
12182 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12183 to inspect @code{_Decimal128} values stored in floating point registers.
12184 See @ref{PowerPC,,PowerPC} for more details.
12190 @value{GDBN} can be used to debug programs written in D and compiled with
12191 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12192 specific feature --- dynamic arrays.
12195 @subsection Objective-C
12197 @cindex Objective-C
12198 This section provides information about some commands and command
12199 options that are useful for debugging Objective-C code. See also
12200 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12201 few more commands specific to Objective-C support.
12204 * Method Names in Commands::
12205 * The Print Command with Objective-C::
12208 @node Method Names in Commands
12209 @subsubsection Method Names in Commands
12211 The following commands have been extended to accept Objective-C method
12212 names as line specifications:
12214 @kindex clear@r{, and Objective-C}
12215 @kindex break@r{, and Objective-C}
12216 @kindex info line@r{, and Objective-C}
12217 @kindex jump@r{, and Objective-C}
12218 @kindex list@r{, and Objective-C}
12222 @item @code{info line}
12227 A fully qualified Objective-C method name is specified as
12230 -[@var{Class} @var{methodName}]
12233 where the minus sign is used to indicate an instance method and a
12234 plus sign (not shown) is used to indicate a class method. The class
12235 name @var{Class} and method name @var{methodName} are enclosed in
12236 brackets, similar to the way messages are specified in Objective-C
12237 source code. For example, to set a breakpoint at the @code{create}
12238 instance method of class @code{Fruit} in the program currently being
12242 break -[Fruit create]
12245 To list ten program lines around the @code{initialize} class method,
12249 list +[NSText initialize]
12252 In the current version of @value{GDBN}, the plus or minus sign is
12253 required. In future versions of @value{GDBN}, the plus or minus
12254 sign will be optional, but you can use it to narrow the search. It
12255 is also possible to specify just a method name:
12261 You must specify the complete method name, including any colons. If
12262 your program's source files contain more than one @code{create} method,
12263 you'll be presented with a numbered list of classes that implement that
12264 method. Indicate your choice by number, or type @samp{0} to exit if
12267 As another example, to clear a breakpoint established at the
12268 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12271 clear -[NSWindow makeKeyAndOrderFront:]
12274 @node The Print Command with Objective-C
12275 @subsubsection The Print Command With Objective-C
12276 @cindex Objective-C, print objects
12277 @kindex print-object
12278 @kindex po @r{(@code{print-object})}
12280 The print command has also been extended to accept methods. For example:
12283 print -[@var{object} hash]
12286 @cindex print an Objective-C object description
12287 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12289 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12290 and print the result. Also, an additional command has been added,
12291 @code{print-object} or @code{po} for short, which is meant to print
12292 the description of an object. However, this command may only work
12293 with certain Objective-C libraries that have a particular hook
12294 function, @code{_NSPrintForDebugger}, defined.
12297 @subsection OpenCL C
12300 This section provides information about @value{GDBN}s OpenCL C support.
12303 * OpenCL C Datatypes::
12304 * OpenCL C Expressions::
12305 * OpenCL C Operators::
12308 @node OpenCL C Datatypes
12309 @subsubsection OpenCL C Datatypes
12311 @cindex OpenCL C Datatypes
12312 @value{GDBN} supports the builtin scalar and vector datatypes specified
12313 by OpenCL 1.1. In addition the half- and double-precision floating point
12314 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12315 extensions are also known to @value{GDBN}.
12317 @node OpenCL C Expressions
12318 @subsubsection OpenCL C Expressions
12320 @cindex OpenCL C Expressions
12321 @value{GDBN} supports accesses to vector components including the access as
12322 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12323 supported by @value{GDBN} can be used as well.
12325 @node OpenCL C Operators
12326 @subsubsection OpenCL C Operators
12328 @cindex OpenCL C Operators
12329 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12333 @subsection Fortran
12334 @cindex Fortran-specific support in @value{GDBN}
12336 @value{GDBN} can be used to debug programs written in Fortran, but it
12337 currently supports only the features of Fortran 77 language.
12339 @cindex trailing underscore, in Fortran symbols
12340 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12341 among them) append an underscore to the names of variables and
12342 functions. When you debug programs compiled by those compilers, you
12343 will need to refer to variables and functions with a trailing
12347 * Fortran Operators:: Fortran operators and expressions
12348 * Fortran Defaults:: Default settings for Fortran
12349 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12352 @node Fortran Operators
12353 @subsubsection Fortran Operators and Expressions
12355 @cindex Fortran operators and expressions
12357 Operators must be defined on values of specific types. For instance,
12358 @code{+} is defined on numbers, but not on characters or other non-
12359 arithmetic types. Operators are often defined on groups of types.
12363 The exponentiation operator. It raises the first operand to the power
12367 The range operator. Normally used in the form of array(low:high) to
12368 represent a section of array.
12371 The access component operator. Normally used to access elements in derived
12372 types. Also suitable for unions. As unions aren't part of regular Fortran,
12373 this can only happen when accessing a register that uses a gdbarch-defined
12377 @node Fortran Defaults
12378 @subsubsection Fortran Defaults
12380 @cindex Fortran Defaults
12382 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12383 default uses case-insensitive matches for Fortran symbols. You can
12384 change that with the @samp{set case-insensitive} command, see
12385 @ref{Symbols}, for the details.
12387 @node Special Fortran Commands
12388 @subsubsection Special Fortran Commands
12390 @cindex Special Fortran commands
12392 @value{GDBN} has some commands to support Fortran-specific features,
12393 such as displaying common blocks.
12396 @cindex @code{COMMON} blocks, Fortran
12397 @kindex info common
12398 @item info common @r{[}@var{common-name}@r{]}
12399 This command prints the values contained in the Fortran @code{COMMON}
12400 block whose name is @var{common-name}. With no argument, the names of
12401 all @code{COMMON} blocks visible at the current program location are
12408 @cindex Pascal support in @value{GDBN}, limitations
12409 Debugging Pascal programs which use sets, subranges, file variables, or
12410 nested functions does not currently work. @value{GDBN} does not support
12411 entering expressions, printing values, or similar features using Pascal
12414 The Pascal-specific command @code{set print pascal_static-members}
12415 controls whether static members of Pascal objects are displayed.
12416 @xref{Print Settings, pascal_static-members}.
12419 @subsection Modula-2
12421 @cindex Modula-2, @value{GDBN} support
12423 The extensions made to @value{GDBN} to support Modula-2 only support
12424 output from the @sc{gnu} Modula-2 compiler (which is currently being
12425 developed). Other Modula-2 compilers are not currently supported, and
12426 attempting to debug executables produced by them is most likely
12427 to give an error as @value{GDBN} reads in the executable's symbol
12430 @cindex expressions in Modula-2
12432 * M2 Operators:: Built-in operators
12433 * Built-In Func/Proc:: Built-in functions and procedures
12434 * M2 Constants:: Modula-2 constants
12435 * M2 Types:: Modula-2 types
12436 * M2 Defaults:: Default settings for Modula-2
12437 * Deviations:: Deviations from standard Modula-2
12438 * M2 Checks:: Modula-2 type and range checks
12439 * M2 Scope:: The scope operators @code{::} and @code{.}
12440 * GDB/M2:: @value{GDBN} and Modula-2
12444 @subsubsection Operators
12445 @cindex Modula-2 operators
12447 Operators must be defined on values of specific types. For instance,
12448 @code{+} is defined on numbers, but not on structures. Operators are
12449 often defined on groups of types. For the purposes of Modula-2, the
12450 following definitions hold:
12455 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12459 @emph{Character types} consist of @code{CHAR} and its subranges.
12462 @emph{Floating-point types} consist of @code{REAL}.
12465 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12469 @emph{Scalar types} consist of all of the above.
12472 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12475 @emph{Boolean types} consist of @code{BOOLEAN}.
12479 The following operators are supported, and appear in order of
12480 increasing precedence:
12484 Function argument or array index separator.
12487 Assignment. The value of @var{var} @code{:=} @var{value} is
12491 Less than, greater than on integral, floating-point, or enumerated
12495 Less than or equal to, greater than or equal to
12496 on integral, floating-point and enumerated types, or set inclusion on
12497 set types. Same precedence as @code{<}.
12499 @item =@r{, }<>@r{, }#
12500 Equality and two ways of expressing inequality, valid on scalar types.
12501 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
12502 available for inequality, since @code{#} conflicts with the script
12506 Set membership. Defined on set types and the types of their members.
12507 Same precedence as @code{<}.
12510 Boolean disjunction. Defined on boolean types.
12513 Boolean conjunction. Defined on boolean types.
12516 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12519 Addition and subtraction on integral and floating-point types, or union
12520 and difference on set types.
12523 Multiplication on integral and floating-point types, or set intersection
12527 Division on floating-point types, or symmetric set difference on set
12528 types. Same precedence as @code{*}.
12531 Integer division and remainder. Defined on integral types. Same
12532 precedence as @code{*}.
12535 Negative. Defined on @code{INTEGER} and @code{REAL} data.
12538 Pointer dereferencing. Defined on pointer types.
12541 Boolean negation. Defined on boolean types. Same precedence as
12545 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
12546 precedence as @code{^}.
12549 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
12552 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
12556 @value{GDBN} and Modula-2 scope operators.
12560 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
12561 treats the use of the operator @code{IN}, or the use of operators
12562 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
12563 @code{<=}, and @code{>=} on sets as an error.
12567 @node Built-In Func/Proc
12568 @subsubsection Built-in Functions and Procedures
12569 @cindex Modula-2 built-ins
12571 Modula-2 also makes available several built-in procedures and functions.
12572 In describing these, the following metavariables are used:
12577 represents an @code{ARRAY} variable.
12580 represents a @code{CHAR} constant or variable.
12583 represents a variable or constant of integral type.
12586 represents an identifier that belongs to a set. Generally used in the
12587 same function with the metavariable @var{s}. The type of @var{s} should
12588 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12591 represents a variable or constant of integral or floating-point type.
12594 represents a variable or constant of floating-point type.
12600 represents a variable.
12603 represents a variable or constant of one of many types. See the
12604 explanation of the function for details.
12607 All Modula-2 built-in procedures also return a result, described below.
12611 Returns the absolute value of @var{n}.
12614 If @var{c} is a lower case letter, it returns its upper case
12615 equivalent, otherwise it returns its argument.
12618 Returns the character whose ordinal value is @var{i}.
12621 Decrements the value in the variable @var{v} by one. Returns the new value.
12623 @item DEC(@var{v},@var{i})
12624 Decrements the value in the variable @var{v} by @var{i}. Returns the
12627 @item EXCL(@var{m},@var{s})
12628 Removes the element @var{m} from the set @var{s}. Returns the new
12631 @item FLOAT(@var{i})
12632 Returns the floating point equivalent of the integer @var{i}.
12634 @item HIGH(@var{a})
12635 Returns the index of the last member of @var{a}.
12638 Increments the value in the variable @var{v} by one. Returns the new value.
12640 @item INC(@var{v},@var{i})
12641 Increments the value in the variable @var{v} by @var{i}. Returns the
12644 @item INCL(@var{m},@var{s})
12645 Adds the element @var{m} to the set @var{s} if it is not already
12646 there. Returns the new set.
12649 Returns the maximum value of the type @var{t}.
12652 Returns the minimum value of the type @var{t}.
12655 Returns boolean TRUE if @var{i} is an odd number.
12658 Returns the ordinal value of its argument. For example, the ordinal
12659 value of a character is its @sc{ascii} value (on machines supporting the
12660 @sc{ascii} character set). @var{x} must be of an ordered type, which include
12661 integral, character and enumerated types.
12663 @item SIZE(@var{x})
12664 Returns the size of its argument. @var{x} can be a variable or a type.
12666 @item TRUNC(@var{r})
12667 Returns the integral part of @var{r}.
12669 @item TSIZE(@var{x})
12670 Returns the size of its argument. @var{x} can be a variable or a type.
12672 @item VAL(@var{t},@var{i})
12673 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12677 @emph{Warning:} Sets and their operations are not yet supported, so
12678 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12682 @cindex Modula-2 constants
12684 @subsubsection Constants
12686 @value{GDBN} allows you to express the constants of Modula-2 in the following
12692 Integer constants are simply a sequence of digits. When used in an
12693 expression, a constant is interpreted to be type-compatible with the
12694 rest of the expression. Hexadecimal integers are specified by a
12695 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12698 Floating point constants appear as a sequence of digits, followed by a
12699 decimal point and another sequence of digits. An optional exponent can
12700 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12701 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12702 digits of the floating point constant must be valid decimal (base 10)
12706 Character constants consist of a single character enclosed by a pair of
12707 like quotes, either single (@code{'}) or double (@code{"}). They may
12708 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12709 followed by a @samp{C}.
12712 String constants consist of a sequence of characters enclosed by a
12713 pair of like quotes, either single (@code{'}) or double (@code{"}).
12714 Escape sequences in the style of C are also allowed. @xref{C
12715 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12719 Enumerated constants consist of an enumerated identifier.
12722 Boolean constants consist of the identifiers @code{TRUE} and
12726 Pointer constants consist of integral values only.
12729 Set constants are not yet supported.
12733 @subsubsection Modula-2 Types
12734 @cindex Modula-2 types
12736 Currently @value{GDBN} can print the following data types in Modula-2
12737 syntax: array types, record types, set types, pointer types, procedure
12738 types, enumerated types, subrange types and base types. You can also
12739 print the contents of variables declared using these type.
12740 This section gives a number of simple source code examples together with
12741 sample @value{GDBN} sessions.
12743 The first example contains the following section of code:
12752 and you can request @value{GDBN} to interrogate the type and value of
12753 @code{r} and @code{s}.
12756 (@value{GDBP}) print s
12758 (@value{GDBP}) ptype s
12760 (@value{GDBP}) print r
12762 (@value{GDBP}) ptype r
12767 Likewise if your source code declares @code{s} as:
12771 s: SET ['A'..'Z'] ;
12775 then you may query the type of @code{s} by:
12778 (@value{GDBP}) ptype s
12779 type = SET ['A'..'Z']
12783 Note that at present you cannot interactively manipulate set
12784 expressions using the debugger.
12786 The following example shows how you might declare an array in Modula-2
12787 and how you can interact with @value{GDBN} to print its type and contents:
12791 s: ARRAY [-10..10] OF CHAR ;
12795 (@value{GDBP}) ptype s
12796 ARRAY [-10..10] OF CHAR
12799 Note that the array handling is not yet complete and although the type
12800 is printed correctly, expression handling still assumes that all
12801 arrays have a lower bound of zero and not @code{-10} as in the example
12804 Here are some more type related Modula-2 examples:
12808 colour = (blue, red, yellow, green) ;
12809 t = [blue..yellow] ;
12817 The @value{GDBN} interaction shows how you can query the data type
12818 and value of a variable.
12821 (@value{GDBP}) print s
12823 (@value{GDBP}) ptype t
12824 type = [blue..yellow]
12828 In this example a Modula-2 array is declared and its contents
12829 displayed. Observe that the contents are written in the same way as
12830 their @code{C} counterparts.
12834 s: ARRAY [1..5] OF CARDINAL ;
12840 (@value{GDBP}) print s
12841 $1 = @{1, 0, 0, 0, 0@}
12842 (@value{GDBP}) ptype s
12843 type = ARRAY [1..5] OF CARDINAL
12846 The Modula-2 language interface to @value{GDBN} also understands
12847 pointer types as shown in this example:
12851 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12858 and you can request that @value{GDBN} describes the type of @code{s}.
12861 (@value{GDBP}) ptype s
12862 type = POINTER TO ARRAY [1..5] OF CARDINAL
12865 @value{GDBN} handles compound types as we can see in this example.
12866 Here we combine array types, record types, pointer types and subrange
12877 myarray = ARRAY myrange OF CARDINAL ;
12878 myrange = [-2..2] ;
12880 s: POINTER TO ARRAY myrange OF foo ;
12884 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12888 (@value{GDBP}) ptype s
12889 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12892 f3 : ARRAY [-2..2] OF CARDINAL;
12897 @subsubsection Modula-2 Defaults
12898 @cindex Modula-2 defaults
12900 If type and range checking are set automatically by @value{GDBN}, they
12901 both default to @code{on} whenever the working language changes to
12902 Modula-2. This happens regardless of whether you or @value{GDBN}
12903 selected the working language.
12905 If you allow @value{GDBN} to set the language automatically, then entering
12906 code compiled from a file whose name ends with @file{.mod} sets the
12907 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12908 Infer the Source Language}, for further details.
12911 @subsubsection Deviations from Standard Modula-2
12912 @cindex Modula-2, deviations from
12914 A few changes have been made to make Modula-2 programs easier to debug.
12915 This is done primarily via loosening its type strictness:
12919 Unlike in standard Modula-2, pointer constants can be formed by
12920 integers. This allows you to modify pointer variables during
12921 debugging. (In standard Modula-2, the actual address contained in a
12922 pointer variable is hidden from you; it can only be modified
12923 through direct assignment to another pointer variable or expression that
12924 returned a pointer.)
12927 C escape sequences can be used in strings and characters to represent
12928 non-printable characters. @value{GDBN} prints out strings with these
12929 escape sequences embedded. Single non-printable characters are
12930 printed using the @samp{CHR(@var{nnn})} format.
12933 The assignment operator (@code{:=}) returns the value of its right-hand
12937 All built-in procedures both modify @emph{and} return their argument.
12941 @subsubsection Modula-2 Type and Range Checks
12942 @cindex Modula-2 checks
12945 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12948 @c FIXME remove warning when type/range checks added
12950 @value{GDBN} considers two Modula-2 variables type equivalent if:
12954 They are of types that have been declared equivalent via a @code{TYPE
12955 @var{t1} = @var{t2}} statement
12958 They have been declared on the same line. (Note: This is true of the
12959 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
12962 As long as type checking is enabled, any attempt to combine variables
12963 whose types are not equivalent is an error.
12965 Range checking is done on all mathematical operations, assignment, array
12966 index bounds, and all built-in functions and procedures.
12969 @subsubsection The Scope Operators @code{::} and @code{.}
12971 @cindex @code{.}, Modula-2 scope operator
12972 @cindex colon, doubled as scope operator
12974 @vindex colon-colon@r{, in Modula-2}
12975 @c Info cannot handle :: but TeX can.
12978 @vindex ::@r{, in Modula-2}
12981 There are a few subtle differences between the Modula-2 scope operator
12982 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
12987 @var{module} . @var{id}
12988 @var{scope} :: @var{id}
12992 where @var{scope} is the name of a module or a procedure,
12993 @var{module} the name of a module, and @var{id} is any declared
12994 identifier within your program, except another module.
12996 Using the @code{::} operator makes @value{GDBN} search the scope
12997 specified by @var{scope} for the identifier @var{id}. If it is not
12998 found in the specified scope, then @value{GDBN} searches all scopes
12999 enclosing the one specified by @var{scope}.
13001 Using the @code{.} operator makes @value{GDBN} search the current scope for
13002 the identifier specified by @var{id} that was imported from the
13003 definition module specified by @var{module}. With this operator, it is
13004 an error if the identifier @var{id} was not imported from definition
13005 module @var{module}, or if @var{id} is not an identifier in
13009 @subsubsection @value{GDBN} and Modula-2
13011 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13012 Five subcommands of @code{set print} and @code{show print} apply
13013 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13014 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13015 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13016 analogue in Modula-2.
13018 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13019 with any language, is not useful with Modula-2. Its
13020 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13021 created in Modula-2 as they can in C or C@t{++}. However, because an
13022 address can be specified by an integral constant, the construct
13023 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13025 @cindex @code{#} in Modula-2
13026 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13027 interpreted as the beginning of a comment. Use @code{<>} instead.
13033 The extensions made to @value{GDBN} for Ada only support
13034 output from the @sc{gnu} Ada (GNAT) compiler.
13035 Other Ada compilers are not currently supported, and
13036 attempting to debug executables produced by them is most likely
13040 @cindex expressions in Ada
13042 * Ada Mode Intro:: General remarks on the Ada syntax
13043 and semantics supported by Ada mode
13045 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13046 * Additions to Ada:: Extensions of the Ada expression syntax.
13047 * Stopping Before Main Program:: Debugging the program during elaboration.
13048 * Ada Tasks:: Listing and setting breakpoints in tasks.
13049 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13050 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13052 * Ada Glitches:: Known peculiarities of Ada mode.
13055 @node Ada Mode Intro
13056 @subsubsection Introduction
13057 @cindex Ada mode, general
13059 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13060 syntax, with some extensions.
13061 The philosophy behind the design of this subset is
13065 That @value{GDBN} should provide basic literals and access to operations for
13066 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13067 leaving more sophisticated computations to subprograms written into the
13068 program (which therefore may be called from @value{GDBN}).
13071 That type safety and strict adherence to Ada language restrictions
13072 are not particularly important to the @value{GDBN} user.
13075 That brevity is important to the @value{GDBN} user.
13078 Thus, for brevity, the debugger acts as if all names declared in
13079 user-written packages are directly visible, even if they are not visible
13080 according to Ada rules, thus making it unnecessary to fully qualify most
13081 names with their packages, regardless of context. Where this causes
13082 ambiguity, @value{GDBN} asks the user's intent.
13084 The debugger will start in Ada mode if it detects an Ada main program.
13085 As for other languages, it will enter Ada mode when stopped in a program that
13086 was translated from an Ada source file.
13088 While in Ada mode, you may use `@t{--}' for comments. This is useful
13089 mostly for documenting command files. The standard @value{GDBN} comment
13090 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13091 middle (to allow based literals).
13093 The debugger supports limited overloading. Given a subprogram call in which
13094 the function symbol has multiple definitions, it will use the number of
13095 actual parameters and some information about their types to attempt to narrow
13096 the set of definitions. It also makes very limited use of context, preferring
13097 procedures to functions in the context of the @code{call} command, and
13098 functions to procedures elsewhere.
13100 @node Omissions from Ada
13101 @subsubsection Omissions from Ada
13102 @cindex Ada, omissions from
13104 Here are the notable omissions from the subset:
13108 Only a subset of the attributes are supported:
13112 @t{'First}, @t{'Last}, and @t{'Length}
13113 on array objects (not on types and subtypes).
13116 @t{'Min} and @t{'Max}.
13119 @t{'Pos} and @t{'Val}.
13125 @t{'Range} on array objects (not subtypes), but only as the right
13126 operand of the membership (@code{in}) operator.
13129 @t{'Access}, @t{'Unchecked_Access}, and
13130 @t{'Unrestricted_Access} (a GNAT extension).
13138 @code{Characters.Latin_1} are not available and
13139 concatenation is not implemented. Thus, escape characters in strings are
13140 not currently available.
13143 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13144 equality of representations. They will generally work correctly
13145 for strings and arrays whose elements have integer or enumeration types.
13146 They may not work correctly for arrays whose element
13147 types have user-defined equality, for arrays of real values
13148 (in particular, IEEE-conformant floating point, because of negative
13149 zeroes and NaNs), and for arrays whose elements contain unused bits with
13150 indeterminate values.
13153 The other component-by-component array operations (@code{and}, @code{or},
13154 @code{xor}, @code{not}, and relational tests other than equality)
13155 are not implemented.
13158 @cindex array aggregates (Ada)
13159 @cindex record aggregates (Ada)
13160 @cindex aggregates (Ada)
13161 There is limited support for array and record aggregates. They are
13162 permitted only on the right sides of assignments, as in these examples:
13165 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13166 (@value{GDBP}) set An_Array := (1, others => 0)
13167 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13168 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13169 (@value{GDBP}) set A_Record := (1, "Peter", True);
13170 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13174 discriminant's value by assigning an aggregate has an
13175 undefined effect if that discriminant is used within the record.
13176 However, you can first modify discriminants by directly assigning to
13177 them (which normally would not be allowed in Ada), and then performing an
13178 aggregate assignment. For example, given a variable @code{A_Rec}
13179 declared to have a type such as:
13182 type Rec (Len : Small_Integer := 0) is record
13184 Vals : IntArray (1 .. Len);
13188 you can assign a value with a different size of @code{Vals} with two
13192 (@value{GDBP}) set A_Rec.Len := 4
13193 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13196 As this example also illustrates, @value{GDBN} is very loose about the usual
13197 rules concerning aggregates. You may leave out some of the
13198 components of an array or record aggregate (such as the @code{Len}
13199 component in the assignment to @code{A_Rec} above); they will retain their
13200 original values upon assignment. You may freely use dynamic values as
13201 indices in component associations. You may even use overlapping or
13202 redundant component associations, although which component values are
13203 assigned in such cases is not defined.
13206 Calls to dispatching subprograms are not implemented.
13209 The overloading algorithm is much more limited (i.e., less selective)
13210 than that of real Ada. It makes only limited use of the context in
13211 which a subexpression appears to resolve its meaning, and it is much
13212 looser in its rules for allowing type matches. As a result, some
13213 function calls will be ambiguous, and the user will be asked to choose
13214 the proper resolution.
13217 The @code{new} operator is not implemented.
13220 Entry calls are not implemented.
13223 Aside from printing, arithmetic operations on the native VAX floating-point
13224 formats are not supported.
13227 It is not possible to slice a packed array.
13230 The names @code{True} and @code{False}, when not part of a qualified name,
13231 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13233 Should your program
13234 redefine these names in a package or procedure (at best a dubious practice),
13235 you will have to use fully qualified names to access their new definitions.
13238 @node Additions to Ada
13239 @subsubsection Additions to Ada
13240 @cindex Ada, deviations from
13242 As it does for other languages, @value{GDBN} makes certain generic
13243 extensions to Ada (@pxref{Expressions}):
13247 If the expression @var{E} is a variable residing in memory (typically
13248 a local variable or array element) and @var{N} is a positive integer,
13249 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13250 @var{N}-1 adjacent variables following it in memory as an array. In
13251 Ada, this operator is generally not necessary, since its prime use is
13252 in displaying parts of an array, and slicing will usually do this in
13253 Ada. However, there are occasional uses when debugging programs in
13254 which certain debugging information has been optimized away.
13257 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13258 appears in function or file @var{B}.'' When @var{B} is a file name,
13259 you must typically surround it in single quotes.
13262 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13263 @var{type} that appears at address @var{addr}.''
13266 A name starting with @samp{$} is a convenience variable
13267 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13270 In addition, @value{GDBN} provides a few other shortcuts and outright
13271 additions specific to Ada:
13275 The assignment statement is allowed as an expression, returning
13276 its right-hand operand as its value. Thus, you may enter
13279 (@value{GDBP}) set x := y + 3
13280 (@value{GDBP}) print A(tmp := y + 1)
13284 The semicolon is allowed as an ``operator,'' returning as its value
13285 the value of its right-hand operand.
13286 This allows, for example,
13287 complex conditional breaks:
13290 (@value{GDBP}) break f
13291 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13295 Rather than use catenation and symbolic character names to introduce special
13296 characters into strings, one may instead use a special bracket notation,
13297 which is also used to print strings. A sequence of characters of the form
13298 @samp{["@var{XX}"]} within a string or character literal denotes the
13299 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13300 sequence of characters @samp{["""]} also denotes a single quotation mark
13301 in strings. For example,
13303 "One line.["0a"]Next line.["0a"]"
13306 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13310 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13311 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13315 (@value{GDBP}) print 'max(x, y)
13319 When printing arrays, @value{GDBN} uses positional notation when the
13320 array has a lower bound of 1, and uses a modified named notation otherwise.
13321 For example, a one-dimensional array of three integers with a lower bound
13322 of 3 might print as
13329 That is, in contrast to valid Ada, only the first component has a @code{=>}
13333 You may abbreviate attributes in expressions with any unique,
13334 multi-character subsequence of
13335 their names (an exact match gets preference).
13336 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13337 in place of @t{a'length}.
13340 @cindex quoting Ada internal identifiers
13341 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13342 to lower case. The GNAT compiler uses upper-case characters for
13343 some of its internal identifiers, which are normally of no interest to users.
13344 For the rare occasions when you actually have to look at them,
13345 enclose them in angle brackets to avoid the lower-case mapping.
13348 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13352 Printing an object of class-wide type or dereferencing an
13353 access-to-class-wide value will display all the components of the object's
13354 specific type (as indicated by its run-time tag). Likewise, component
13355 selection on such a value will operate on the specific type of the
13360 @node Stopping Before Main Program
13361 @subsubsection Stopping at the Very Beginning
13363 @cindex breakpointing Ada elaboration code
13364 It is sometimes necessary to debug the program during elaboration, and
13365 before reaching the main procedure.
13366 As defined in the Ada Reference
13367 Manual, the elaboration code is invoked from a procedure called
13368 @code{adainit}. To run your program up to the beginning of
13369 elaboration, simply use the following two commands:
13370 @code{tbreak adainit} and @code{run}.
13373 @subsubsection Extensions for Ada Tasks
13374 @cindex Ada, tasking
13376 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13377 @value{GDBN} provides the following task-related commands:
13382 This command shows a list of current Ada tasks, as in the following example:
13389 (@value{GDBP}) info tasks
13390 ID TID P-ID Pri State Name
13391 1 8088000 0 15 Child Activation Wait main_task
13392 2 80a4000 1 15 Accept Statement b
13393 3 809a800 1 15 Child Activation Wait a
13394 * 4 80ae800 3 15 Runnable c
13399 In this listing, the asterisk before the last task indicates it to be the
13400 task currently being inspected.
13404 Represents @value{GDBN}'s internal task number.
13410 The parent's task ID (@value{GDBN}'s internal task number).
13413 The base priority of the task.
13416 Current state of the task.
13420 The task has been created but has not been activated. It cannot be
13424 The task is not blocked for any reason known to Ada. (It may be waiting
13425 for a mutex, though.) It is conceptually "executing" in normal mode.
13428 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13429 that were waiting on terminate alternatives have been awakened and have
13430 terminated themselves.
13432 @item Child Activation Wait
13433 The task is waiting for created tasks to complete activation.
13435 @item Accept Statement
13436 The task is waiting on an accept or selective wait statement.
13438 @item Waiting on entry call
13439 The task is waiting on an entry call.
13441 @item Async Select Wait
13442 The task is waiting to start the abortable part of an asynchronous
13446 The task is waiting on a select statement with only a delay
13449 @item Child Termination Wait
13450 The task is sleeping having completed a master within itself, and is
13451 waiting for the tasks dependent on that master to become terminated or
13452 waiting on a terminate Phase.
13454 @item Wait Child in Term Alt
13455 The task is sleeping waiting for tasks on terminate alternatives to
13456 finish terminating.
13458 @item Accepting RV with @var{taskno}
13459 The task is accepting a rendez-vous with the task @var{taskno}.
13463 Name of the task in the program.
13467 @kindex info task @var{taskno}
13468 @item info task @var{taskno}
13469 This command shows detailled informations on the specified task, as in
13470 the following example:
13475 (@value{GDBP}) info tasks
13476 ID TID P-ID Pri State Name
13477 1 8077880 0 15 Child Activation Wait main_task
13478 * 2 807c468 1 15 Runnable task_1
13479 (@value{GDBP}) info task 2
13480 Ada Task: 0x807c468
13483 Parent: 1 (main_task)
13489 @kindex task@r{ (Ada)}
13490 @cindex current Ada task ID
13491 This command prints the ID of the current task.
13497 (@value{GDBP}) info tasks
13498 ID TID P-ID Pri State Name
13499 1 8077870 0 15 Child Activation Wait main_task
13500 * 2 807c458 1 15 Runnable t
13501 (@value{GDBP}) task
13502 [Current task is 2]
13505 @item task @var{taskno}
13506 @cindex Ada task switching
13507 This command is like the @code{thread @var{threadno}}
13508 command (@pxref{Threads}). It switches the context of debugging
13509 from the current task to the given task.
13515 (@value{GDBP}) info tasks
13516 ID TID P-ID Pri State Name
13517 1 8077870 0 15 Child Activation Wait main_task
13518 * 2 807c458 1 15 Runnable t
13519 (@value{GDBP}) task 1
13520 [Switching to task 1]
13521 #0 0x8067726 in pthread_cond_wait ()
13523 #0 0x8067726 in pthread_cond_wait ()
13524 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
13525 #2 0x805cb63 in system.task_primitives.operations.sleep ()
13526 #3 0x806153e in system.tasking.stages.activate_tasks ()
13527 #4 0x804aacc in un () at un.adb:5
13530 @item break @var{linespec} task @var{taskno}
13531 @itemx break @var{linespec} task @var{taskno} if @dots{}
13532 @cindex breakpoints and tasks, in Ada
13533 @cindex task breakpoints, in Ada
13534 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
13535 These commands are like the @code{break @dots{} thread @dots{}}
13536 command (@pxref{Thread Stops}).
13537 @var{linespec} specifies source lines, as described
13538 in @ref{Specify Location}.
13540 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
13541 to specify that you only want @value{GDBN} to stop the program when a
13542 particular Ada task reaches this breakpoint. @var{taskno} is one of the
13543 numeric task identifiers assigned by @value{GDBN}, shown in the first
13544 column of the @samp{info tasks} display.
13546 If you do not specify @samp{task @var{taskno}} when you set a
13547 breakpoint, the breakpoint applies to @emph{all} tasks of your
13550 You can use the @code{task} qualifier on conditional breakpoints as
13551 well; in this case, place @samp{task @var{taskno}} before the
13552 breakpoint condition (before the @code{if}).
13560 (@value{GDBP}) info tasks
13561 ID TID P-ID Pri State Name
13562 1 140022020 0 15 Child Activation Wait main_task
13563 2 140045060 1 15 Accept/Select Wait t2
13564 3 140044840 1 15 Runnable t1
13565 * 4 140056040 1 15 Runnable t3
13566 (@value{GDBP}) b 15 task 2
13567 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
13568 (@value{GDBP}) cont
13573 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13575 (@value{GDBP}) info tasks
13576 ID TID P-ID Pri State Name
13577 1 140022020 0 15 Child Activation Wait main_task
13578 * 2 140045060 1 15 Runnable t2
13579 3 140044840 1 15 Runnable t1
13580 4 140056040 1 15 Delay Sleep t3
13584 @node Ada Tasks and Core Files
13585 @subsubsection Tasking Support when Debugging Core Files
13586 @cindex Ada tasking and core file debugging
13588 When inspecting a core file, as opposed to debugging a live program,
13589 tasking support may be limited or even unavailable, depending on
13590 the platform being used.
13591 For instance, on x86-linux, the list of tasks is available, but task
13592 switching is not supported. On Tru64, however, task switching will work
13595 On certain platforms, including Tru64, the debugger needs to perform some
13596 memory writes in order to provide Ada tasking support. When inspecting
13597 a core file, this means that the core file must be opened with read-write
13598 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13599 Under these circumstances, you should make a backup copy of the core
13600 file before inspecting it with @value{GDBN}.
13602 @node Ravenscar Profile
13603 @subsubsection Tasking Support when using the Ravenscar Profile
13604 @cindex Ravenscar Profile
13606 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
13607 specifically designed for systems with safety-critical real-time
13611 @kindex set ravenscar task-switching on
13612 @cindex task switching with program using Ravenscar Profile
13613 @item set ravenscar task-switching on
13614 Allows task switching when debugging a program that uses the Ravenscar
13615 Profile. This is the default.
13617 @kindex set ravenscar task-switching off
13618 @item set ravenscar task-switching off
13619 Turn off task switching when debugging a program that uses the Ravenscar
13620 Profile. This is mostly intended to disable the code that adds support
13621 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
13622 the Ravenscar runtime is preventing @value{GDBN} from working properly.
13623 To be effective, this command should be run before the program is started.
13625 @kindex show ravenscar task-switching
13626 @item show ravenscar task-switching
13627 Show whether it is possible to switch from task to task in a program
13628 using the Ravenscar Profile.
13633 @subsubsection Known Peculiarities of Ada Mode
13634 @cindex Ada, problems
13636 Besides the omissions listed previously (@pxref{Omissions from Ada}),
13637 we know of several problems with and limitations of Ada mode in
13639 some of which will be fixed with planned future releases of the debugger
13640 and the GNU Ada compiler.
13644 Currently, the debugger
13645 has insufficient information to determine whether certain pointers represent
13646 pointers to objects or the objects themselves.
13647 Thus, the user may have to tack an extra @code{.all} after an expression
13648 to get it printed properly.
13651 Static constants that the compiler chooses not to materialize as objects in
13652 storage are invisible to the debugger.
13655 Named parameter associations in function argument lists are ignored (the
13656 argument lists are treated as positional).
13659 Many useful library packages are currently invisible to the debugger.
13662 Fixed-point arithmetic, conversions, input, and output is carried out using
13663 floating-point arithmetic, and may give results that only approximate those on
13667 The GNAT compiler never generates the prefix @code{Standard} for any of
13668 the standard symbols defined by the Ada language. @value{GDBN} knows about
13669 this: it will strip the prefix from names when you use it, and will never
13670 look for a name you have so qualified among local symbols, nor match against
13671 symbols in other packages or subprograms. If you have
13672 defined entities anywhere in your program other than parameters and
13673 local variables whose simple names match names in @code{Standard},
13674 GNAT's lack of qualification here can cause confusion. When this happens,
13675 you can usually resolve the confusion
13676 by qualifying the problematic names with package
13677 @code{Standard} explicitly.
13680 Older versions of the compiler sometimes generate erroneous debugging
13681 information, resulting in the debugger incorrectly printing the value
13682 of affected entities. In some cases, the debugger is able to work
13683 around an issue automatically. In other cases, the debugger is able
13684 to work around the issue, but the work-around has to be specifically
13687 @kindex set ada trust-PAD-over-XVS
13688 @kindex show ada trust-PAD-over-XVS
13691 @item set ada trust-PAD-over-XVS on
13692 Configure GDB to strictly follow the GNAT encoding when computing the
13693 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
13694 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
13695 a complete description of the encoding used by the GNAT compiler).
13696 This is the default.
13698 @item set ada trust-PAD-over-XVS off
13699 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
13700 sometimes prints the wrong value for certain entities, changing @code{ada
13701 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
13702 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
13703 @code{off}, but this incurs a slight performance penalty, so it is
13704 recommended to leave this setting to @code{on} unless necessary.
13708 @node Unsupported Languages
13709 @section Unsupported Languages
13711 @cindex unsupported languages
13712 @cindex minimal language
13713 In addition to the other fully-supported programming languages,
13714 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
13715 It does not represent a real programming language, but provides a set
13716 of capabilities close to what the C or assembly languages provide.
13717 This should allow most simple operations to be performed while debugging
13718 an application that uses a language currently not supported by @value{GDBN}.
13720 If the language is set to @code{auto}, @value{GDBN} will automatically
13721 select this language if the current frame corresponds to an unsupported
13725 @chapter Examining the Symbol Table
13727 The commands described in this chapter allow you to inquire about the
13728 symbols (names of variables, functions and types) defined in your
13729 program. This information is inherent in the text of your program and
13730 does not change as your program executes. @value{GDBN} finds it in your
13731 program's symbol table, in the file indicated when you started @value{GDBN}
13732 (@pxref{File Options, ,Choosing Files}), or by one of the
13733 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13735 @cindex symbol names
13736 @cindex names of symbols
13737 @cindex quoting names
13738 Occasionally, you may need to refer to symbols that contain unusual
13739 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13740 most frequent case is in referring to static variables in other
13741 source files (@pxref{Variables,,Program Variables}). File names
13742 are recorded in object files as debugging symbols, but @value{GDBN} would
13743 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13744 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13745 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13752 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13755 @cindex case-insensitive symbol names
13756 @cindex case sensitivity in symbol names
13757 @kindex set case-sensitive
13758 @item set case-sensitive on
13759 @itemx set case-sensitive off
13760 @itemx set case-sensitive auto
13761 Normally, when @value{GDBN} looks up symbols, it matches their names
13762 with case sensitivity determined by the current source language.
13763 Occasionally, you may wish to control that. The command @code{set
13764 case-sensitive} lets you do that by specifying @code{on} for
13765 case-sensitive matches or @code{off} for case-insensitive ones. If
13766 you specify @code{auto}, case sensitivity is reset to the default
13767 suitable for the source language. The default is case-sensitive
13768 matches for all languages except for Fortran, for which the default is
13769 case-insensitive matches.
13771 @kindex show case-sensitive
13772 @item show case-sensitive
13773 This command shows the current setting of case sensitivity for symbols
13776 @kindex info address
13777 @cindex address of a symbol
13778 @item info address @var{symbol}
13779 Describe where the data for @var{symbol} is stored. For a register
13780 variable, this says which register it is kept in. For a non-register
13781 local variable, this prints the stack-frame offset at which the variable
13784 Note the contrast with @samp{print &@var{symbol}}, which does not work
13785 at all for a register variable, and for a stack local variable prints
13786 the exact address of the current instantiation of the variable.
13788 @kindex info symbol
13789 @cindex symbol from address
13790 @cindex closest symbol and offset for an address
13791 @item info symbol @var{addr}
13792 Print the name of a symbol which is stored at the address @var{addr}.
13793 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13794 nearest symbol and an offset from it:
13797 (@value{GDBP}) info symbol 0x54320
13798 _initialize_vx + 396 in section .text
13802 This is the opposite of the @code{info address} command. You can use
13803 it to find out the name of a variable or a function given its address.
13805 For dynamically linked executables, the name of executable or shared
13806 library containing the symbol is also printed:
13809 (@value{GDBP}) info symbol 0x400225
13810 _start + 5 in section .text of /tmp/a.out
13811 (@value{GDBP}) info symbol 0x2aaaac2811cf
13812 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13816 @item whatis [@var{arg}]
13817 Print the data type of @var{arg}, which can be either an expression or
13818 a data type. With no argument, print the data type of @code{$}, the
13819 last value in the value history. If @var{arg} is an expression, it is
13820 not actually evaluated, and any side-effecting operations (such as
13821 assignments or function calls) inside it do not take place. If
13822 @var{arg} is a type name, it may be the name of a type or typedef, or
13823 for C code it may have the form @samp{class @var{class-name}},
13824 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13825 @samp{enum @var{enum-tag}}.
13826 @xref{Expressions, ,Expressions}.
13829 @item ptype [@var{arg}]
13830 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13831 detailed description of the type, instead of just the name of the type.
13832 @xref{Expressions, ,Expressions}.
13834 For example, for this variable declaration:
13837 struct complex @{double real; double imag;@} v;
13841 the two commands give this output:
13845 (@value{GDBP}) whatis v
13846 type = struct complex
13847 (@value{GDBP}) ptype v
13848 type = struct complex @{
13856 As with @code{whatis}, using @code{ptype} without an argument refers to
13857 the type of @code{$}, the last value in the value history.
13859 @cindex incomplete type
13860 Sometimes, programs use opaque data types or incomplete specifications
13861 of complex data structure. If the debug information included in the
13862 program does not allow @value{GDBN} to display a full declaration of
13863 the data type, it will say @samp{<incomplete type>}. For example,
13864 given these declarations:
13868 struct foo *fooptr;
13872 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13875 (@value{GDBP}) ptype foo
13876 $1 = <incomplete type>
13880 ``Incomplete type'' is C terminology for data types that are not
13881 completely specified.
13884 @item info types @var{regexp}
13886 Print a brief description of all types whose names match the regular
13887 expression @var{regexp} (or all types in your program, if you supply
13888 no argument). Each complete typename is matched as though it were a
13889 complete line; thus, @samp{i type value} gives information on all
13890 types in your program whose names include the string @code{value}, but
13891 @samp{i type ^value$} gives information only on types whose complete
13892 name is @code{value}.
13894 This command differs from @code{ptype} in two ways: first, like
13895 @code{whatis}, it does not print a detailed description; second, it
13896 lists all source files where a type is defined.
13899 @cindex local variables
13900 @item info scope @var{location}
13901 List all the variables local to a particular scope. This command
13902 accepts a @var{location} argument---a function name, a source line, or
13903 an address preceded by a @samp{*}, and prints all the variables local
13904 to the scope defined by that location. (@xref{Specify Location}, for
13905 details about supported forms of @var{location}.) For example:
13908 (@value{GDBP}) @b{info scope command_line_handler}
13909 Scope for command_line_handler:
13910 Symbol rl is an argument at stack/frame offset 8, length 4.
13911 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13912 Symbol linelength is in static storage at address 0x150a1c, length 4.
13913 Symbol p is a local variable in register $esi, length 4.
13914 Symbol p1 is a local variable in register $ebx, length 4.
13915 Symbol nline is a local variable in register $edx, length 4.
13916 Symbol repeat is a local variable at frame offset -8, length 4.
13920 This command is especially useful for determining what data to collect
13921 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13924 @kindex info source
13926 Show information about the current source file---that is, the source file for
13927 the function containing the current point of execution:
13930 the name of the source file, and the directory containing it,
13932 the directory it was compiled in,
13934 its length, in lines,
13936 which programming language it is written in,
13938 whether the executable includes debugging information for that file, and
13939 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13941 whether the debugging information includes information about
13942 preprocessor macros.
13946 @kindex info sources
13948 Print the names of all source files in your program for which there is
13949 debugging information, organized into two lists: files whose symbols
13950 have already been read, and files whose symbols will be read when needed.
13952 @kindex info functions
13953 @item info functions
13954 Print the names and data types of all defined functions.
13956 @item info functions @var{regexp}
13957 Print the names and data types of all defined functions
13958 whose names contain a match for regular expression @var{regexp}.
13959 Thus, @samp{info fun step} finds all functions whose names
13960 include @code{step}; @samp{info fun ^step} finds those whose names
13961 start with @code{step}. If a function name contains characters
13962 that conflict with the regular expression language (e.g.@:
13963 @samp{operator*()}), they may be quoted with a backslash.
13965 @kindex info variables
13966 @item info variables
13967 Print the names and data types of all variables that are defined
13968 outside of functions (i.e.@: excluding local variables).
13970 @item info variables @var{regexp}
13971 Print the names and data types of all variables (except for local
13972 variables) whose names contain a match for regular expression
13975 @kindex info classes
13976 @cindex Objective-C, classes and selectors
13978 @itemx info classes @var{regexp}
13979 Display all Objective-C classes in your program, or
13980 (with the @var{regexp} argument) all those matching a particular regular
13983 @kindex info selectors
13984 @item info selectors
13985 @itemx info selectors @var{regexp}
13986 Display all Objective-C selectors in your program, or
13987 (with the @var{regexp} argument) all those matching a particular regular
13991 This was never implemented.
13992 @kindex info methods
13994 @itemx info methods @var{regexp}
13995 The @code{info methods} command permits the user to examine all defined
13996 methods within C@t{++} program, or (with the @var{regexp} argument) a
13997 specific set of methods found in the various C@t{++} classes. Many
13998 C@t{++} classes provide a large number of methods. Thus, the output
13999 from the @code{ptype} command can be overwhelming and hard to use. The
14000 @code{info-methods} command filters the methods, printing only those
14001 which match the regular-expression @var{regexp}.
14004 @cindex reloading symbols
14005 Some systems allow individual object files that make up your program to
14006 be replaced without stopping and restarting your program. For example,
14007 in VxWorks you can simply recompile a defective object file and keep on
14008 running. If you are running on one of these systems, you can allow
14009 @value{GDBN} to reload the symbols for automatically relinked modules:
14012 @kindex set symbol-reloading
14013 @item set symbol-reloading on
14014 Replace symbol definitions for the corresponding source file when an
14015 object file with a particular name is seen again.
14017 @item set symbol-reloading off
14018 Do not replace symbol definitions when encountering object files of the
14019 same name more than once. This is the default state; if you are not
14020 running on a system that permits automatic relinking of modules, you
14021 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14022 may discard symbols when linking large programs, that may contain
14023 several modules (from different directories or libraries) with the same
14026 @kindex show symbol-reloading
14027 @item show symbol-reloading
14028 Show the current @code{on} or @code{off} setting.
14031 @cindex opaque data types
14032 @kindex set opaque-type-resolution
14033 @item set opaque-type-resolution on
14034 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14035 declared as a pointer to a @code{struct}, @code{class}, or
14036 @code{union}---for example, @code{struct MyType *}---that is used in one
14037 source file although the full declaration of @code{struct MyType} is in
14038 another source file. The default is on.
14040 A change in the setting of this subcommand will not take effect until
14041 the next time symbols for a file are loaded.
14043 @item set opaque-type-resolution off
14044 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14045 is printed as follows:
14047 @{<no data fields>@}
14050 @kindex show opaque-type-resolution
14051 @item show opaque-type-resolution
14052 Show whether opaque types are resolved or not.
14054 @kindex maint print symbols
14055 @cindex symbol dump
14056 @kindex maint print psymbols
14057 @cindex partial symbol dump
14058 @item maint print symbols @var{filename}
14059 @itemx maint print psymbols @var{filename}
14060 @itemx maint print msymbols @var{filename}
14061 Write a dump of debugging symbol data into the file @var{filename}.
14062 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14063 symbols with debugging data are included. If you use @samp{maint print
14064 symbols}, @value{GDBN} includes all the symbols for which it has already
14065 collected full details: that is, @var{filename} reflects symbols for
14066 only those files whose symbols @value{GDBN} has read. You can use the
14067 command @code{info sources} to find out which files these are. If you
14068 use @samp{maint print psymbols} instead, the dump shows information about
14069 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14070 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14071 @samp{maint print msymbols} dumps just the minimal symbol information
14072 required for each object file from which @value{GDBN} has read some symbols.
14073 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14074 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14076 @kindex maint info symtabs
14077 @kindex maint info psymtabs
14078 @cindex listing @value{GDBN}'s internal symbol tables
14079 @cindex symbol tables, listing @value{GDBN}'s internal
14080 @cindex full symbol tables, listing @value{GDBN}'s internal
14081 @cindex partial symbol tables, listing @value{GDBN}'s internal
14082 @item maint info symtabs @r{[} @var{regexp} @r{]}
14083 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14085 List the @code{struct symtab} or @code{struct partial_symtab}
14086 structures whose names match @var{regexp}. If @var{regexp} is not
14087 given, list them all. The output includes expressions which you can
14088 copy into a @value{GDBN} debugging this one to examine a particular
14089 structure in more detail. For example:
14092 (@value{GDBP}) maint info psymtabs dwarf2read
14093 @{ objfile /home/gnu/build/gdb/gdb
14094 ((struct objfile *) 0x82e69d0)
14095 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14096 ((struct partial_symtab *) 0x8474b10)
14099 text addresses 0x814d3c8 -- 0x8158074
14100 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14101 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14102 dependencies (none)
14105 (@value{GDBP}) maint info symtabs
14109 We see that there is one partial symbol table whose filename contains
14110 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14111 and we see that @value{GDBN} has not read in any symtabs yet at all.
14112 If we set a breakpoint on a function, that will cause @value{GDBN} to
14113 read the symtab for the compilation unit containing that function:
14116 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14117 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14119 (@value{GDBP}) maint info symtabs
14120 @{ objfile /home/gnu/build/gdb/gdb
14121 ((struct objfile *) 0x82e69d0)
14122 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14123 ((struct symtab *) 0x86c1f38)
14126 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14127 linetable ((struct linetable *) 0x8370fa0)
14128 debugformat DWARF 2
14137 @chapter Altering Execution
14139 Once you think you have found an error in your program, you might want to
14140 find out for certain whether correcting the apparent error would lead to
14141 correct results in the rest of the run. You can find the answer by
14142 experiment, using the @value{GDBN} features for altering execution of the
14145 For example, you can store new values into variables or memory
14146 locations, give your program a signal, restart it at a different
14147 address, or even return prematurely from a function.
14150 * Assignment:: Assignment to variables
14151 * Jumping:: Continuing at a different address
14152 * Signaling:: Giving your program a signal
14153 * Returning:: Returning from a function
14154 * Calling:: Calling your program's functions
14155 * Patching:: Patching your program
14159 @section Assignment to Variables
14162 @cindex setting variables
14163 To alter the value of a variable, evaluate an assignment expression.
14164 @xref{Expressions, ,Expressions}. For example,
14171 stores the value 4 into the variable @code{x}, and then prints the
14172 value of the assignment expression (which is 4).
14173 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14174 information on operators in supported languages.
14176 @kindex set variable
14177 @cindex variables, setting
14178 If you are not interested in seeing the value of the assignment, use the
14179 @code{set} command instead of the @code{print} command. @code{set} is
14180 really the same as @code{print} except that the expression's value is
14181 not printed and is not put in the value history (@pxref{Value History,
14182 ,Value History}). The expression is evaluated only for its effects.
14184 If the beginning of the argument string of the @code{set} command
14185 appears identical to a @code{set} subcommand, use the @code{set
14186 variable} command instead of just @code{set}. This command is identical
14187 to @code{set} except for its lack of subcommands. For example, if your
14188 program has a variable @code{width}, you get an error if you try to set
14189 a new value with just @samp{set width=13}, because @value{GDBN} has the
14190 command @code{set width}:
14193 (@value{GDBP}) whatis width
14195 (@value{GDBP}) p width
14197 (@value{GDBP}) set width=47
14198 Invalid syntax in expression.
14202 The invalid expression, of course, is @samp{=47}. In
14203 order to actually set the program's variable @code{width}, use
14206 (@value{GDBP}) set var width=47
14209 Because the @code{set} command has many subcommands that can conflict
14210 with the names of program variables, it is a good idea to use the
14211 @code{set variable} command instead of just @code{set}. For example, if
14212 your program has a variable @code{g}, you run into problems if you try
14213 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14214 the command @code{set gnutarget}, abbreviated @code{set g}:
14218 (@value{GDBP}) whatis g
14222 (@value{GDBP}) set g=4
14226 The program being debugged has been started already.
14227 Start it from the beginning? (y or n) y
14228 Starting program: /home/smith/cc_progs/a.out
14229 "/home/smith/cc_progs/a.out": can't open to read symbols:
14230 Invalid bfd target.
14231 (@value{GDBP}) show g
14232 The current BFD target is "=4".
14237 The program variable @code{g} did not change, and you silently set the
14238 @code{gnutarget} to an invalid value. In order to set the variable
14242 (@value{GDBP}) set var g=4
14245 @value{GDBN} allows more implicit conversions in assignments than C; you can
14246 freely store an integer value into a pointer variable or vice versa,
14247 and you can convert any structure to any other structure that is the
14248 same length or shorter.
14249 @comment FIXME: how do structs align/pad in these conversions?
14250 @comment /doc@cygnus.com 18dec1990
14252 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14253 construct to generate a value of specified type at a specified address
14254 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14255 to memory location @code{0x83040} as an integer (which implies a certain size
14256 and representation in memory), and
14259 set @{int@}0x83040 = 4
14263 stores the value 4 into that memory location.
14266 @section Continuing at a Different Address
14268 Ordinarily, when you continue your program, you do so at the place where
14269 it stopped, with the @code{continue} command. You can instead continue at
14270 an address of your own choosing, with the following commands:
14274 @item jump @var{linespec}
14275 @itemx jump @var{location}
14276 Resume execution at line @var{linespec} or at address given by
14277 @var{location}. Execution stops again immediately if there is a
14278 breakpoint there. @xref{Specify Location}, for a description of the
14279 different forms of @var{linespec} and @var{location}. It is common
14280 practice to use the @code{tbreak} command in conjunction with
14281 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14283 The @code{jump} command does not change the current stack frame, or
14284 the stack pointer, or the contents of any memory location or any
14285 register other than the program counter. If line @var{linespec} is in
14286 a different function from the one currently executing, the results may
14287 be bizarre if the two functions expect different patterns of arguments or
14288 of local variables. For this reason, the @code{jump} command requests
14289 confirmation if the specified line is not in the function currently
14290 executing. However, even bizarre results are predictable if you are
14291 well acquainted with the machine-language code of your program.
14294 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14295 On many systems, you can get much the same effect as the @code{jump}
14296 command by storing a new value into the register @code{$pc}. The
14297 difference is that this does not start your program running; it only
14298 changes the address of where it @emph{will} run when you continue. For
14306 makes the next @code{continue} command or stepping command execute at
14307 address @code{0x485}, rather than at the address where your program stopped.
14308 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14310 The most common occasion to use the @code{jump} command is to back
14311 up---perhaps with more breakpoints set---over a portion of a program
14312 that has already executed, in order to examine its execution in more
14317 @section Giving your Program a Signal
14318 @cindex deliver a signal to a program
14322 @item signal @var{signal}
14323 Resume execution where your program stopped, but immediately give it the
14324 signal @var{signal}. @var{signal} can be the name or the number of a
14325 signal. For example, on many systems @code{signal 2} and @code{signal
14326 SIGINT} are both ways of sending an interrupt signal.
14328 Alternatively, if @var{signal} is zero, continue execution without
14329 giving a signal. This is useful when your program stopped on account of
14330 a signal and would ordinary see the signal when resumed with the
14331 @code{continue} command; @samp{signal 0} causes it to resume without a
14334 @code{signal} does not repeat when you press @key{RET} a second time
14335 after executing the command.
14339 Invoking the @code{signal} command is not the same as invoking the
14340 @code{kill} utility from the shell. Sending a signal with @code{kill}
14341 causes @value{GDBN} to decide what to do with the signal depending on
14342 the signal handling tables (@pxref{Signals}). The @code{signal} command
14343 passes the signal directly to your program.
14347 @section Returning from a Function
14350 @cindex returning from a function
14353 @itemx return @var{expression}
14354 You can cancel execution of a function call with the @code{return}
14355 command. If you give an
14356 @var{expression} argument, its value is used as the function's return
14360 When you use @code{return}, @value{GDBN} discards the selected stack frame
14361 (and all frames within it). You can think of this as making the
14362 discarded frame return prematurely. If you wish to specify a value to
14363 be returned, give that value as the argument to @code{return}.
14365 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14366 Frame}), and any other frames inside of it, leaving its caller as the
14367 innermost remaining frame. That frame becomes selected. The
14368 specified value is stored in the registers used for returning values
14371 The @code{return} command does not resume execution; it leaves the
14372 program stopped in the state that would exist if the function had just
14373 returned. In contrast, the @code{finish} command (@pxref{Continuing
14374 and Stepping, ,Continuing and Stepping}) resumes execution until the
14375 selected stack frame returns naturally.
14377 @value{GDBN} needs to know how the @var{expression} argument should be set for
14378 the inferior. The concrete registers assignment depends on the OS ABI and the
14379 type being returned by the selected stack frame. For example it is common for
14380 OS ABI to return floating point values in FPU registers while integer values in
14381 CPU registers. Still some ABIs return even floating point values in CPU
14382 registers. Larger integer widths (such as @code{long long int}) also have
14383 specific placement rules. @value{GDBN} already knows the OS ABI from its
14384 current target so it needs to find out also the type being returned to make the
14385 assignment into the right register(s).
14387 Normally, the selected stack frame has debug info. @value{GDBN} will always
14388 use the debug info instead of the implicit type of @var{expression} when the
14389 debug info is available. For example, if you type @kbd{return -1}, and the
14390 function in the current stack frame is declared to return a @code{long long
14391 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14392 into a @code{long long int}:
14395 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14397 (@value{GDBP}) return -1
14398 Make func return now? (y or n) y
14399 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
14400 43 printf ("result=%lld\n", func ());
14404 However, if the selected stack frame does not have a debug info, e.g., if the
14405 function was compiled without debug info, @value{GDBN} has to find out the type
14406 to return from user. Specifying a different type by mistake may set the value
14407 in different inferior registers than the caller code expects. For example,
14408 typing @kbd{return -1} with its implicit type @code{int} would set only a part
14409 of a @code{long long int} result for a debug info less function (on 32-bit
14410 architectures). Therefore the user is required to specify the return type by
14411 an appropriate cast explicitly:
14414 Breakpoint 2, 0x0040050b in func ()
14415 (@value{GDBP}) return -1
14416 Return value type not available for selected stack frame.
14417 Please use an explicit cast of the value to return.
14418 (@value{GDBP}) return (long long int) -1
14419 Make selected stack frame return now? (y or n) y
14420 #0 0x00400526 in main ()
14425 @section Calling Program Functions
14428 @cindex calling functions
14429 @cindex inferior functions, calling
14430 @item print @var{expr}
14431 Evaluate the expression @var{expr} and display the resulting value.
14432 @var{expr} may include calls to functions in the program being
14436 @item call @var{expr}
14437 Evaluate the expression @var{expr} without displaying @code{void}
14440 You can use this variant of the @code{print} command if you want to
14441 execute a function from your program that does not return anything
14442 (a.k.a.@: @dfn{a void function}), but without cluttering the output
14443 with @code{void} returned values that @value{GDBN} will otherwise
14444 print. If the result is not void, it is printed and saved in the
14448 It is possible for the function you call via the @code{print} or
14449 @code{call} command to generate a signal (e.g., if there's a bug in
14450 the function, or if you passed it incorrect arguments). What happens
14451 in that case is controlled by the @code{set unwindonsignal} command.
14453 Similarly, with a C@t{++} program it is possible for the function you
14454 call via the @code{print} or @code{call} command to generate an
14455 exception that is not handled due to the constraints of the dummy
14456 frame. In this case, any exception that is raised in the frame, but has
14457 an out-of-frame exception handler will not be found. GDB builds a
14458 dummy-frame for the inferior function call, and the unwinder cannot
14459 seek for exception handlers outside of this dummy-frame. What happens
14460 in that case is controlled by the
14461 @code{set unwind-on-terminating-exception} command.
14464 @item set unwindonsignal
14465 @kindex set unwindonsignal
14466 @cindex unwind stack in called functions
14467 @cindex call dummy stack unwinding
14468 Set unwinding of the stack if a signal is received while in a function
14469 that @value{GDBN} called in the program being debugged. If set to on,
14470 @value{GDBN} unwinds the stack it created for the call and restores
14471 the context to what it was before the call. If set to off (the
14472 default), @value{GDBN} stops in the frame where the signal was
14475 @item show unwindonsignal
14476 @kindex show unwindonsignal
14477 Show the current setting of stack unwinding in the functions called by
14480 @item set unwind-on-terminating-exception
14481 @kindex set unwind-on-terminating-exception
14482 @cindex unwind stack in called functions with unhandled exceptions
14483 @cindex call dummy stack unwinding on unhandled exception.
14484 Set unwinding of the stack if a C@t{++} exception is raised, but left
14485 unhandled while in a function that @value{GDBN} called in the program being
14486 debugged. If set to on (the default), @value{GDBN} unwinds the stack
14487 it created for the call and restores the context to what it was before
14488 the call. If set to off, @value{GDBN} the exception is delivered to
14489 the default C@t{++} exception handler and the inferior terminated.
14491 @item show unwind-on-terminating-exception
14492 @kindex show unwind-on-terminating-exception
14493 Show the current setting of stack unwinding in the functions called by
14498 @cindex weak alias functions
14499 Sometimes, a function you wish to call is actually a @dfn{weak alias}
14500 for another function. In such case, @value{GDBN} might not pick up
14501 the type information, including the types of the function arguments,
14502 which causes @value{GDBN} to call the inferior function incorrectly.
14503 As a result, the called function will function erroneously and may
14504 even crash. A solution to that is to use the name of the aliased
14508 @section Patching Programs
14510 @cindex patching binaries
14511 @cindex writing into executables
14512 @cindex writing into corefiles
14514 By default, @value{GDBN} opens the file containing your program's
14515 executable code (or the corefile) read-only. This prevents accidental
14516 alterations to machine code; but it also prevents you from intentionally
14517 patching your program's binary.
14519 If you'd like to be able to patch the binary, you can specify that
14520 explicitly with the @code{set write} command. For example, you might
14521 want to turn on internal debugging flags, or even to make emergency
14527 @itemx set write off
14528 If you specify @samp{set write on}, @value{GDBN} opens executable and
14529 core files for both reading and writing; if you specify @kbd{set write
14530 off} (the default), @value{GDBN} opens them read-only.
14532 If you have already loaded a file, you must load it again (using the
14533 @code{exec-file} or @code{core-file} command) after changing @code{set
14534 write}, for your new setting to take effect.
14538 Display whether executable files and core files are opened for writing
14539 as well as reading.
14543 @chapter @value{GDBN} Files
14545 @value{GDBN} needs to know the file name of the program to be debugged,
14546 both in order to read its symbol table and in order to start your
14547 program. To debug a core dump of a previous run, you must also tell
14548 @value{GDBN} the name of the core dump file.
14551 * Files:: Commands to specify files
14552 * Separate Debug Files:: Debugging information in separate files
14553 * Index Files:: Index files speed up GDB
14554 * Symbol Errors:: Errors reading symbol files
14555 * Data Files:: GDB data files
14559 @section Commands to Specify Files
14561 @cindex symbol table
14562 @cindex core dump file
14564 You may want to specify executable and core dump file names. The usual
14565 way to do this is at start-up time, using the arguments to
14566 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
14567 Out of @value{GDBN}}).
14569 Occasionally it is necessary to change to a different file during a
14570 @value{GDBN} session. Or you may run @value{GDBN} and forget to
14571 specify a file you want to use. Or you are debugging a remote target
14572 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
14573 Program}). In these situations the @value{GDBN} commands to specify
14574 new files are useful.
14577 @cindex executable file
14579 @item file @var{filename}
14580 Use @var{filename} as the program to be debugged. It is read for its
14581 symbols and for the contents of pure memory. It is also the program
14582 executed when you use the @code{run} command. If you do not specify a
14583 directory and the file is not found in the @value{GDBN} working directory,
14584 @value{GDBN} uses the environment variable @code{PATH} as a list of
14585 directories to search, just as the shell does when looking for a program
14586 to run. You can change the value of this variable, for both @value{GDBN}
14587 and your program, using the @code{path} command.
14589 @cindex unlinked object files
14590 @cindex patching object files
14591 You can load unlinked object @file{.o} files into @value{GDBN} using
14592 the @code{file} command. You will not be able to ``run'' an object
14593 file, but you can disassemble functions and inspect variables. Also,
14594 if the underlying BFD functionality supports it, you could use
14595 @kbd{gdb -write} to patch object files using this technique. Note
14596 that @value{GDBN} can neither interpret nor modify relocations in this
14597 case, so branches and some initialized variables will appear to go to
14598 the wrong place. But this feature is still handy from time to time.
14601 @code{file} with no argument makes @value{GDBN} discard any information it
14602 has on both executable file and the symbol table.
14605 @item exec-file @r{[} @var{filename} @r{]}
14606 Specify that the program to be run (but not the symbol table) is found
14607 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
14608 if necessary to locate your program. Omitting @var{filename} means to
14609 discard information on the executable file.
14611 @kindex symbol-file
14612 @item symbol-file @r{[} @var{filename} @r{]}
14613 Read symbol table information from file @var{filename}. @code{PATH} is
14614 searched when necessary. Use the @code{file} command to get both symbol
14615 table and program to run from the same file.
14617 @code{symbol-file} with no argument clears out @value{GDBN} information on your
14618 program's symbol table.
14620 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
14621 some breakpoints and auto-display expressions. This is because they may
14622 contain pointers to the internal data recording symbols and data types,
14623 which are part of the old symbol table data being discarded inside
14626 @code{symbol-file} does not repeat if you press @key{RET} again after
14629 When @value{GDBN} is configured for a particular environment, it
14630 understands debugging information in whatever format is the standard
14631 generated for that environment; you may use either a @sc{gnu} compiler, or
14632 other compilers that adhere to the local conventions.
14633 Best results are usually obtained from @sc{gnu} compilers; for example,
14634 using @code{@value{NGCC}} you can generate debugging information for
14637 For most kinds of object files, with the exception of old SVR3 systems
14638 using COFF, the @code{symbol-file} command does not normally read the
14639 symbol table in full right away. Instead, it scans the symbol table
14640 quickly to find which source files and which symbols are present. The
14641 details are read later, one source file at a time, as they are needed.
14643 The purpose of this two-stage reading strategy is to make @value{GDBN}
14644 start up faster. For the most part, it is invisible except for
14645 occasional pauses while the symbol table details for a particular source
14646 file are being read. (The @code{set verbose} command can turn these
14647 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
14648 Warnings and Messages}.)
14650 We have not implemented the two-stage strategy for COFF yet. When the
14651 symbol table is stored in COFF format, @code{symbol-file} reads the
14652 symbol table data in full right away. Note that ``stabs-in-COFF''
14653 still does the two-stage strategy, since the debug info is actually
14657 @cindex reading symbols immediately
14658 @cindex symbols, reading immediately
14659 @item symbol-file @r{[} -readnow @r{]} @var{filename}
14660 @itemx file @r{[} -readnow @r{]} @var{filename}
14661 You can override the @value{GDBN} two-stage strategy for reading symbol
14662 tables by using the @samp{-readnow} option with any of the commands that
14663 load symbol table information, if you want to be sure @value{GDBN} has the
14664 entire symbol table available.
14666 @c FIXME: for now no mention of directories, since this seems to be in
14667 @c flux. 13mar1992 status is that in theory GDB would look either in
14668 @c current dir or in same dir as myprog; but issues like competing
14669 @c GDB's, or clutter in system dirs, mean that in practice right now
14670 @c only current dir is used. FFish says maybe a special GDB hierarchy
14671 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
14675 @item core-file @r{[}@var{filename}@r{]}
14677 Specify the whereabouts of a core dump file to be used as the ``contents
14678 of memory''. Traditionally, core files contain only some parts of the
14679 address space of the process that generated them; @value{GDBN} can access the
14680 executable file itself for other parts.
14682 @code{core-file} with no argument specifies that no core file is
14685 Note that the core file is ignored when your program is actually running
14686 under @value{GDBN}. So, if you have been running your program and you
14687 wish to debug a core file instead, you must kill the subprocess in which
14688 the program is running. To do this, use the @code{kill} command
14689 (@pxref{Kill Process, ,Killing the Child Process}).
14691 @kindex add-symbol-file
14692 @cindex dynamic linking
14693 @item add-symbol-file @var{filename} @var{address}
14694 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
14695 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
14696 The @code{add-symbol-file} command reads additional symbol table
14697 information from the file @var{filename}. You would use this command
14698 when @var{filename} has been dynamically loaded (by some other means)
14699 into the program that is running. @var{address} should be the memory
14700 address at which the file has been loaded; @value{GDBN} cannot figure
14701 this out for itself. You can additionally specify an arbitrary number
14702 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
14703 section name and base address for that section. You can specify any
14704 @var{address} as an expression.
14706 The symbol table of the file @var{filename} is added to the symbol table
14707 originally read with the @code{symbol-file} command. You can use the
14708 @code{add-symbol-file} command any number of times; the new symbol data
14709 thus read keeps adding to the old. To discard all old symbol data
14710 instead, use the @code{symbol-file} command without any arguments.
14712 @cindex relocatable object files, reading symbols from
14713 @cindex object files, relocatable, reading symbols from
14714 @cindex reading symbols from relocatable object files
14715 @cindex symbols, reading from relocatable object files
14716 @cindex @file{.o} files, reading symbols from
14717 Although @var{filename} is typically a shared library file, an
14718 executable file, or some other object file which has been fully
14719 relocated for loading into a process, you can also load symbolic
14720 information from relocatable @file{.o} files, as long as:
14724 the file's symbolic information refers only to linker symbols defined in
14725 that file, not to symbols defined by other object files,
14727 every section the file's symbolic information refers to has actually
14728 been loaded into the inferior, as it appears in the file, and
14730 you can determine the address at which every section was loaded, and
14731 provide these to the @code{add-symbol-file} command.
14735 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14736 relocatable files into an already running program; such systems
14737 typically make the requirements above easy to meet. However, it's
14738 important to recognize that many native systems use complex link
14739 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14740 assembly, for example) that make the requirements difficult to meet. In
14741 general, one cannot assume that using @code{add-symbol-file} to read a
14742 relocatable object file's symbolic information will have the same effect
14743 as linking the relocatable object file into the program in the normal
14746 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14748 @kindex add-symbol-file-from-memory
14749 @cindex @code{syscall DSO}
14750 @cindex load symbols from memory
14751 @item add-symbol-file-from-memory @var{address}
14752 Load symbols from the given @var{address} in a dynamically loaded
14753 object file whose image is mapped directly into the inferior's memory.
14754 For example, the Linux kernel maps a @code{syscall DSO} into each
14755 process's address space; this DSO provides kernel-specific code for
14756 some system calls. The argument can be any expression whose
14757 evaluation yields the address of the file's shared object file header.
14758 For this command to work, you must have used @code{symbol-file} or
14759 @code{exec-file} commands in advance.
14761 @kindex add-shared-symbol-files
14763 @item add-shared-symbol-files @var{library-file}
14764 @itemx assf @var{library-file}
14765 The @code{add-shared-symbol-files} command can currently be used only
14766 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14767 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14768 @value{GDBN} automatically looks for shared libraries, however if
14769 @value{GDBN} does not find yours, you can invoke
14770 @code{add-shared-symbol-files}. It takes one argument: the shared
14771 library's file name. @code{assf} is a shorthand alias for
14772 @code{add-shared-symbol-files}.
14775 @item section @var{section} @var{addr}
14776 The @code{section} command changes the base address of the named
14777 @var{section} of the exec file to @var{addr}. This can be used if the
14778 exec file does not contain section addresses, (such as in the
14779 @code{a.out} format), or when the addresses specified in the file
14780 itself are wrong. Each section must be changed separately. The
14781 @code{info files} command, described below, lists all the sections and
14785 @kindex info target
14788 @code{info files} and @code{info target} are synonymous; both print the
14789 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14790 including the names of the executable and core dump files currently in
14791 use by @value{GDBN}, and the files from which symbols were loaded. The
14792 command @code{help target} lists all possible targets rather than
14795 @kindex maint info sections
14796 @item maint info sections
14797 Another command that can give you extra information about program sections
14798 is @code{maint info sections}. In addition to the section information
14799 displayed by @code{info files}, this command displays the flags and file
14800 offset of each section in the executable and core dump files. In addition,
14801 @code{maint info sections} provides the following command options (which
14802 may be arbitrarily combined):
14806 Display sections for all loaded object files, including shared libraries.
14807 @item @var{sections}
14808 Display info only for named @var{sections}.
14809 @item @var{section-flags}
14810 Display info only for sections for which @var{section-flags} are true.
14811 The section flags that @value{GDBN} currently knows about are:
14814 Section will have space allocated in the process when loaded.
14815 Set for all sections except those containing debug information.
14817 Section will be loaded from the file into the child process memory.
14818 Set for pre-initialized code and data, clear for @code{.bss} sections.
14820 Section needs to be relocated before loading.
14822 Section cannot be modified by the child process.
14824 Section contains executable code only.
14826 Section contains data only (no executable code).
14828 Section will reside in ROM.
14830 Section contains data for constructor/destructor lists.
14832 Section is not empty.
14834 An instruction to the linker to not output the section.
14835 @item COFF_SHARED_LIBRARY
14836 A notification to the linker that the section contains
14837 COFF shared library information.
14839 Section contains common symbols.
14842 @kindex set trust-readonly-sections
14843 @cindex read-only sections
14844 @item set trust-readonly-sections on
14845 Tell @value{GDBN} that readonly sections in your object file
14846 really are read-only (i.e.@: that their contents will not change).
14847 In that case, @value{GDBN} can fetch values from these sections
14848 out of the object file, rather than from the target program.
14849 For some targets (notably embedded ones), this can be a significant
14850 enhancement to debugging performance.
14852 The default is off.
14854 @item set trust-readonly-sections off
14855 Tell @value{GDBN} not to trust readonly sections. This means that
14856 the contents of the section might change while the program is running,
14857 and must therefore be fetched from the target when needed.
14859 @item show trust-readonly-sections
14860 Show the current setting of trusting readonly sections.
14863 All file-specifying commands allow both absolute and relative file names
14864 as arguments. @value{GDBN} always converts the file name to an absolute file
14865 name and remembers it that way.
14867 @cindex shared libraries
14868 @anchor{Shared Libraries}
14869 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14870 and IBM RS/6000 AIX shared libraries.
14872 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14873 shared libraries. @xref{Expat}.
14875 @value{GDBN} automatically loads symbol definitions from shared libraries
14876 when you use the @code{run} command, or when you examine a core file.
14877 (Before you issue the @code{run} command, @value{GDBN} does not understand
14878 references to a function in a shared library, however---unless you are
14879 debugging a core file).
14881 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14882 automatically loads the symbols at the time of the @code{shl_load} call.
14884 @c FIXME: some @value{GDBN} release may permit some refs to undef
14885 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14886 @c FIXME...lib; check this from time to time when updating manual
14888 There are times, however, when you may wish to not automatically load
14889 symbol definitions from shared libraries, such as when they are
14890 particularly large or there are many of them.
14892 To control the automatic loading of shared library symbols, use the
14896 @kindex set auto-solib-add
14897 @item set auto-solib-add @var{mode}
14898 If @var{mode} is @code{on}, symbols from all shared object libraries
14899 will be loaded automatically when the inferior begins execution, you
14900 attach to an independently started inferior, or when the dynamic linker
14901 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14902 is @code{off}, symbols must be loaded manually, using the
14903 @code{sharedlibrary} command. The default value is @code{on}.
14905 @cindex memory used for symbol tables
14906 If your program uses lots of shared libraries with debug info that
14907 takes large amounts of memory, you can decrease the @value{GDBN}
14908 memory footprint by preventing it from automatically loading the
14909 symbols from shared libraries. To that end, type @kbd{set
14910 auto-solib-add off} before running the inferior, then load each
14911 library whose debug symbols you do need with @kbd{sharedlibrary
14912 @var{regexp}}, where @var{regexp} is a regular expression that matches
14913 the libraries whose symbols you want to be loaded.
14915 @kindex show auto-solib-add
14916 @item show auto-solib-add
14917 Display the current autoloading mode.
14920 @cindex load shared library
14921 To explicitly load shared library symbols, use the @code{sharedlibrary}
14925 @kindex info sharedlibrary
14927 @item info share @var{regex}
14928 @itemx info sharedlibrary @var{regex}
14929 Print the names of the shared libraries which are currently loaded
14930 that match @var{regex}. If @var{regex} is omitted then print
14931 all shared libraries that are loaded.
14933 @kindex sharedlibrary
14935 @item sharedlibrary @var{regex}
14936 @itemx share @var{regex}
14937 Load shared object library symbols for files matching a
14938 Unix regular expression.
14939 As with files loaded automatically, it only loads shared libraries
14940 required by your program for a core file or after typing @code{run}. If
14941 @var{regex} is omitted all shared libraries required by your program are
14944 @item nosharedlibrary
14945 @kindex nosharedlibrary
14946 @cindex unload symbols from shared libraries
14947 Unload all shared object library symbols. This discards all symbols
14948 that have been loaded from all shared libraries. Symbols from shared
14949 libraries that were loaded by explicit user requests are not
14953 Sometimes you may wish that @value{GDBN} stops and gives you control
14954 when any of shared library events happen. Use the @code{set
14955 stop-on-solib-events} command for this:
14958 @item set stop-on-solib-events
14959 @kindex set stop-on-solib-events
14960 This command controls whether @value{GDBN} should give you control
14961 when the dynamic linker notifies it about some shared library event.
14962 The most common event of interest is loading or unloading of a new
14965 @item show stop-on-solib-events
14966 @kindex show stop-on-solib-events
14967 Show whether @value{GDBN} stops and gives you control when shared
14968 library events happen.
14971 Shared libraries are also supported in many cross or remote debugging
14972 configurations. @value{GDBN} needs to have access to the target's libraries;
14973 this can be accomplished either by providing copies of the libraries
14974 on the host system, or by asking @value{GDBN} to automatically retrieve the
14975 libraries from the target. If copies of the target libraries are
14976 provided, they need to be the same as the target libraries, although the
14977 copies on the target can be stripped as long as the copies on the host are
14980 @cindex where to look for shared libraries
14981 For remote debugging, you need to tell @value{GDBN} where the target
14982 libraries are, so that it can load the correct copies---otherwise, it
14983 may try to load the host's libraries. @value{GDBN} has two variables
14984 to specify the search directories for target libraries.
14987 @cindex prefix for shared library file names
14988 @cindex system root, alternate
14989 @kindex set solib-absolute-prefix
14990 @kindex set sysroot
14991 @item set sysroot @var{path}
14992 Use @var{path} as the system root for the program being debugged. Any
14993 absolute shared library paths will be prefixed with @var{path}; many
14994 runtime loaders store the absolute paths to the shared library in the
14995 target program's memory. If you use @code{set sysroot} to find shared
14996 libraries, they need to be laid out in the same way that they are on
14997 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15000 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15001 retrieve the target libraries from the remote system. This is only
15002 supported when using a remote target that supports the @code{remote get}
15003 command (@pxref{File Transfer,,Sending files to a remote system}).
15004 The part of @var{path} following the initial @file{remote:}
15005 (if present) is used as system root prefix on the remote file system.
15006 @footnote{If you want to specify a local system root using a directory
15007 that happens to be named @file{remote:}, you need to use some equivalent
15008 variant of the name like @file{./remote:}.}
15010 For targets with an MS-DOS based filesystem, such as MS-Windows and
15011 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15012 absolute file name with @var{path}. But first, on Unix hosts,
15013 @value{GDBN} converts all backslash directory separators into forward
15014 slashes, because the backslash is not a directory separator on Unix:
15017 c:\foo\bar.dll @result{} c:/foo/bar.dll
15020 Then, @value{GDBN} attempts prefixing the target file name with
15021 @var{path}, and looks for the resulting file name in the host file
15025 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15028 If that does not find the shared library, @value{GDBN} tries removing
15029 the @samp{:} character from the drive spec, both for convenience, and,
15030 for the case of the host file system not supporting file names with
15034 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15037 This makes it possible to have a system root that mirrors a target
15038 with more than one drive. E.g., you may want to setup your local
15039 copies of the target system shared libraries like so (note @samp{c} vs
15043 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15044 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15045 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15049 and point the system root at @file{/path/to/sysroot}, so that
15050 @value{GDBN} can find the correct copies of both
15051 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15053 If that still does not find the shared library, @value{GDBN} tries
15054 removing the whole drive spec from the target file name:
15057 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15060 This last lookup makes it possible to not care about the drive name,
15061 if you don't want or need to.
15063 The @code{set solib-absolute-prefix} command is an alias for @code{set
15066 @cindex default system root
15067 @cindex @samp{--with-sysroot}
15068 You can set the default system root by using the configure-time
15069 @samp{--with-sysroot} option. If the system root is inside
15070 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15071 @samp{--exec-prefix}), then the default system root will be updated
15072 automatically if the installed @value{GDBN} is moved to a new
15075 @kindex show sysroot
15077 Display the current shared library prefix.
15079 @kindex set solib-search-path
15080 @item set solib-search-path @var{path}
15081 If this variable is set, @var{path} is a colon-separated list of
15082 directories to search for shared libraries. @samp{solib-search-path}
15083 is used after @samp{sysroot} fails to locate the library, or if the
15084 path to the library is relative instead of absolute. If you want to
15085 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15086 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15087 finding your host's libraries. @samp{sysroot} is preferred; setting
15088 it to a nonexistent directory may interfere with automatic loading
15089 of shared library symbols.
15091 @kindex show solib-search-path
15092 @item show solib-search-path
15093 Display the current shared library search path.
15095 @cindex DOS file-name semantics of file names.
15096 @kindex set target-file-system-kind (unix|dos-based|auto)
15097 @kindex show target-file-system-kind
15098 @item set target-file-system-kind @var{kind}
15099 Set assumed file system kind for target reported file names.
15101 Shared library file names as reported by the target system may not
15102 make sense as is on the system @value{GDBN} is running on. For
15103 example, when remote debugging a target that has MS-DOS based file
15104 system semantics, from a Unix host, the target may be reporting to
15105 @value{GDBN} a list of loaded shared libraries with file names such as
15106 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15107 drive letters, so the @samp{c:\} prefix is not normally understood as
15108 indicating an absolute file name, and neither is the backslash
15109 normally considered a directory separator character. In that case,
15110 the native file system would interpret this whole absolute file name
15111 as a relative file name with no directory components. This would make
15112 it impossible to point @value{GDBN} at a copy of the remote target's
15113 shared libraries on the host using @code{set sysroot}, and impractical
15114 with @code{set solib-search-path}. Setting
15115 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15116 to interpret such file names similarly to how the target would, and to
15117 map them to file names valid on @value{GDBN}'s native file system
15118 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15119 to one of the supported file system kinds. In that case, @value{GDBN}
15120 tries to determine the appropriate file system variant based on the
15121 current target's operating system (@pxref{ABI, ,Configuring the
15122 Current ABI}). The supported file system settings are:
15126 Instruct @value{GDBN} to assume the target file system is of Unix
15127 kind. Only file names starting the forward slash (@samp{/}) character
15128 are considered absolute, and the directory separator character is also
15132 Instruct @value{GDBN} to assume the target file system is DOS based.
15133 File names starting with either a forward slash, or a drive letter
15134 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15135 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15136 considered directory separators.
15139 Instruct @value{GDBN} to use the file system kind associated with the
15140 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15141 This is the default.
15146 @node Separate Debug Files
15147 @section Debugging Information in Separate Files
15148 @cindex separate debugging information files
15149 @cindex debugging information in separate files
15150 @cindex @file{.debug} subdirectories
15151 @cindex debugging information directory, global
15152 @cindex global debugging information directory
15153 @cindex build ID, and separate debugging files
15154 @cindex @file{.build-id} directory
15156 @value{GDBN} allows you to put a program's debugging information in a
15157 file separate from the executable itself, in a way that allows
15158 @value{GDBN} to find and load the debugging information automatically.
15159 Since debugging information can be very large---sometimes larger
15160 than the executable code itself---some systems distribute debugging
15161 information for their executables in separate files, which users can
15162 install only when they need to debug a problem.
15164 @value{GDBN} supports two ways of specifying the separate debug info
15169 The executable contains a @dfn{debug link} that specifies the name of
15170 the separate debug info file. The separate debug file's name is
15171 usually @file{@var{executable}.debug}, where @var{executable} is the
15172 name of the corresponding executable file without leading directories
15173 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15174 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15175 checksum for the debug file, which @value{GDBN} uses to validate that
15176 the executable and the debug file came from the same build.
15179 The executable contains a @dfn{build ID}, a unique bit string that is
15180 also present in the corresponding debug info file. (This is supported
15181 only on some operating systems, notably those which use the ELF format
15182 for binary files and the @sc{gnu} Binutils.) For more details about
15183 this feature, see the description of the @option{--build-id}
15184 command-line option in @ref{Options, , Command Line Options, ld.info,
15185 The GNU Linker}. The debug info file's name is not specified
15186 explicitly by the build ID, but can be computed from the build ID, see
15190 Depending on the way the debug info file is specified, @value{GDBN}
15191 uses two different methods of looking for the debug file:
15195 For the ``debug link'' method, @value{GDBN} looks up the named file in
15196 the directory of the executable file, then in a subdirectory of that
15197 directory named @file{.debug}, and finally under the global debug
15198 directory, in a subdirectory whose name is identical to the leading
15199 directories of the executable's absolute file name.
15202 For the ``build ID'' method, @value{GDBN} looks in the
15203 @file{.build-id} subdirectory of the global debug directory for a file
15204 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15205 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15206 are the rest of the bit string. (Real build ID strings are 32 or more
15207 hex characters, not 10.)
15210 So, for example, suppose you ask @value{GDBN} to debug
15211 @file{/usr/bin/ls}, which has a debug link that specifies the
15212 file @file{ls.debug}, and a build ID whose value in hex is
15213 @code{abcdef1234}. If the global debug directory is
15214 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15215 debug information files, in the indicated order:
15219 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15221 @file{/usr/bin/ls.debug}
15223 @file{/usr/bin/.debug/ls.debug}
15225 @file{/usr/lib/debug/usr/bin/ls.debug}.
15228 You can set the global debugging info directory's name, and view the
15229 name @value{GDBN} is currently using.
15233 @kindex set debug-file-directory
15234 @item set debug-file-directory @var{directories}
15235 Set the directories which @value{GDBN} searches for separate debugging
15236 information files to @var{directory}. Multiple directory components can be set
15237 concatenating them by a directory separator.
15239 @kindex show debug-file-directory
15240 @item show debug-file-directory
15241 Show the directories @value{GDBN} searches for separate debugging
15246 @cindex @code{.gnu_debuglink} sections
15247 @cindex debug link sections
15248 A debug link is a special section of the executable file named
15249 @code{.gnu_debuglink}. The section must contain:
15253 A filename, with any leading directory components removed, followed by
15256 zero to three bytes of padding, as needed to reach the next four-byte
15257 boundary within the section, and
15259 a four-byte CRC checksum, stored in the same endianness used for the
15260 executable file itself. The checksum is computed on the debugging
15261 information file's full contents by the function given below, passing
15262 zero as the @var{crc} argument.
15265 Any executable file format can carry a debug link, as long as it can
15266 contain a section named @code{.gnu_debuglink} with the contents
15269 @cindex @code{.note.gnu.build-id} sections
15270 @cindex build ID sections
15271 The build ID is a special section in the executable file (and in other
15272 ELF binary files that @value{GDBN} may consider). This section is
15273 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15274 It contains unique identification for the built files---the ID remains
15275 the same across multiple builds of the same build tree. The default
15276 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15277 content for the build ID string. The same section with an identical
15278 value is present in the original built binary with symbols, in its
15279 stripped variant, and in the separate debugging information file.
15281 The debugging information file itself should be an ordinary
15282 executable, containing a full set of linker symbols, sections, and
15283 debugging information. The sections of the debugging information file
15284 should have the same names, addresses, and sizes as the original file,
15285 but they need not contain any data---much like a @code{.bss} section
15286 in an ordinary executable.
15288 The @sc{gnu} binary utilities (Binutils) package includes the
15289 @samp{objcopy} utility that can produce
15290 the separated executable / debugging information file pairs using the
15291 following commands:
15294 @kbd{objcopy --only-keep-debug foo foo.debug}
15299 These commands remove the debugging
15300 information from the executable file @file{foo} and place it in the file
15301 @file{foo.debug}. You can use the first, second or both methods to link the
15306 The debug link method needs the following additional command to also leave
15307 behind a debug link in @file{foo}:
15310 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15313 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15314 a version of the @code{strip} command such that the command @kbd{strip foo -f
15315 foo.debug} has the same functionality as the two @code{objcopy} commands and
15316 the @code{ln -s} command above, together.
15319 Build ID gets embedded into the main executable using @code{ld --build-id} or
15320 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15321 compatibility fixes for debug files separation are present in @sc{gnu} binary
15322 utilities (Binutils) package since version 2.18.
15327 @cindex CRC algorithm definition
15328 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15329 IEEE 802.3 using the polynomial:
15331 @c TexInfo requires naked braces for multi-digit exponents for Tex
15332 @c output, but this causes HTML output to barf. HTML has to be set using
15333 @c raw commands. So we end up having to specify this equation in 2
15338 <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>
15339 + <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
15345 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15346 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15350 The function is computed byte at a time, taking the least
15351 significant bit of each byte first. The initial pattern
15352 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15353 the final result is inverted to ensure trailing zeros also affect the
15356 @emph{Note:} This is the same CRC polynomial as used in handling the
15357 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15358 , @value{GDBN} Remote Serial Protocol}). However in the
15359 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15360 significant bit first, and the result is not inverted, so trailing
15361 zeros have no effect on the CRC value.
15363 To complete the description, we show below the code of the function
15364 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15365 initially supplied @code{crc} argument means that an initial call to
15366 this function passing in zero will start computing the CRC using
15369 @kindex gnu_debuglink_crc32
15372 gnu_debuglink_crc32 (unsigned long crc,
15373 unsigned char *buf, size_t len)
15375 static const unsigned long crc32_table[256] =
15377 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
15378 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
15379 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
15380 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
15381 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
15382 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15383 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15384 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
15385 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
15386 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
15387 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
15388 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
15389 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
15390 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
15391 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
15392 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
15393 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
15394 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
15395 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
15396 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
15397 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
15398 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
15399 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
15400 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
15401 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
15402 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
15403 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
15404 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
15405 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
15406 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
15407 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
15408 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
15409 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
15410 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
15411 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
15412 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
15413 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
15414 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
15415 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
15416 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
15417 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
15418 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
15419 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
15420 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
15421 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
15422 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
15423 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
15424 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
15425 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
15426 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
15427 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
15430 unsigned char *end;
15432 crc = ~crc & 0xffffffff;
15433 for (end = buf + len; buf < end; ++buf)
15434 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15435 return ~crc & 0xffffffff;
15440 This computation does not apply to the ``build ID'' method.
15444 @section Index Files Speed Up @value{GDBN}
15445 @cindex index files
15446 @cindex @samp{.gdb_index} section
15448 When @value{GDBN} finds a symbol file, it scans the symbols in the
15449 file in order to construct an internal symbol table. This lets most
15450 @value{GDBN} operations work quickly---at the cost of a delay early
15451 on. For large programs, this delay can be quite lengthy, so
15452 @value{GDBN} provides a way to build an index, which speeds up
15455 The index is stored as a section in the symbol file. @value{GDBN} can
15456 write the index to a file, then you can put it into the symbol file
15457 using @command{objcopy}.
15459 To create an index file, use the @code{save gdb-index} command:
15462 @item save gdb-index @var{directory}
15463 @kindex save gdb-index
15464 Create an index file for each symbol file currently known by
15465 @value{GDBN}. Each file is named after its corresponding symbol file,
15466 with @samp{.gdb-index} appended, and is written into the given
15470 Once you have created an index file you can merge it into your symbol
15471 file, here named @file{symfile}, using @command{objcopy}:
15474 $ objcopy --add-section .gdb_index=symfile.gdb-index \
15475 --set-section-flags .gdb_index=readonly symfile symfile
15478 There are currently some limitation on indices. They only work when
15479 for DWARF debugging information, not stabs. And, they do not
15480 currently work for programs using Ada.
15482 @node Symbol Errors
15483 @section Errors Reading Symbol Files
15485 While reading a symbol file, @value{GDBN} occasionally encounters problems,
15486 such as symbol types it does not recognize, or known bugs in compiler
15487 output. By default, @value{GDBN} does not notify you of such problems, since
15488 they are relatively common and primarily of interest to people
15489 debugging compilers. If you are interested in seeing information
15490 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
15491 only one message about each such type of problem, no matter how many
15492 times the problem occurs; or you can ask @value{GDBN} to print more messages,
15493 to see how many times the problems occur, with the @code{set
15494 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
15497 The messages currently printed, and their meanings, include:
15500 @item inner block not inside outer block in @var{symbol}
15502 The symbol information shows where symbol scopes begin and end
15503 (such as at the start of a function or a block of statements). This
15504 error indicates that an inner scope block is not fully contained
15505 in its outer scope blocks.
15507 @value{GDBN} circumvents the problem by treating the inner block as if it had
15508 the same scope as the outer block. In the error message, @var{symbol}
15509 may be shown as ``@code{(don't know)}'' if the outer block is not a
15512 @item block at @var{address} out of order
15514 The symbol information for symbol scope blocks should occur in
15515 order of increasing addresses. This error indicates that it does not
15518 @value{GDBN} does not circumvent this problem, and has trouble
15519 locating symbols in the source file whose symbols it is reading. (You
15520 can often determine what source file is affected by specifying
15521 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
15524 @item bad block start address patched
15526 The symbol information for a symbol scope block has a start address
15527 smaller than the address of the preceding source line. This is known
15528 to occur in the SunOS 4.1.1 (and earlier) C compiler.
15530 @value{GDBN} circumvents the problem by treating the symbol scope block as
15531 starting on the previous source line.
15533 @item bad string table offset in symbol @var{n}
15536 Symbol number @var{n} contains a pointer into the string table which is
15537 larger than the size of the string table.
15539 @value{GDBN} circumvents the problem by considering the symbol to have the
15540 name @code{foo}, which may cause other problems if many symbols end up
15543 @item unknown symbol type @code{0x@var{nn}}
15545 The symbol information contains new data types that @value{GDBN} does
15546 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
15547 uncomprehended information, in hexadecimal.
15549 @value{GDBN} circumvents the error by ignoring this symbol information.
15550 This usually allows you to debug your program, though certain symbols
15551 are not accessible. If you encounter such a problem and feel like
15552 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
15553 on @code{complain}, then go up to the function @code{read_dbx_symtab}
15554 and examine @code{*bufp} to see the symbol.
15556 @item stub type has NULL name
15558 @value{GDBN} could not find the full definition for a struct or class.
15560 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
15561 The symbol information for a C@t{++} member function is missing some
15562 information that recent versions of the compiler should have output for
15565 @item info mismatch between compiler and debugger
15567 @value{GDBN} could not parse a type specification output by the compiler.
15572 @section GDB Data Files
15574 @cindex prefix for data files
15575 @value{GDBN} will sometimes read an auxiliary data file. These files
15576 are kept in a directory known as the @dfn{data directory}.
15578 You can set the data directory's name, and view the name @value{GDBN}
15579 is currently using.
15582 @kindex set data-directory
15583 @item set data-directory @var{directory}
15584 Set the directory which @value{GDBN} searches for auxiliary data files
15585 to @var{directory}.
15587 @kindex show data-directory
15588 @item show data-directory
15589 Show the directory @value{GDBN} searches for auxiliary data files.
15592 @cindex default data directory
15593 @cindex @samp{--with-gdb-datadir}
15594 You can set the default data directory by using the configure-time
15595 @samp{--with-gdb-datadir} option. If the data directory is inside
15596 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15597 @samp{--exec-prefix}), then the default data directory will be updated
15598 automatically if the installed @value{GDBN} is moved to a new
15602 @chapter Specifying a Debugging Target
15604 @cindex debugging target
15605 A @dfn{target} is the execution environment occupied by your program.
15607 Often, @value{GDBN} runs in the same host environment as your program;
15608 in that case, the debugging target is specified as a side effect when
15609 you use the @code{file} or @code{core} commands. When you need more
15610 flexibility---for example, running @value{GDBN} on a physically separate
15611 host, or controlling a standalone system over a serial port or a
15612 realtime system over a TCP/IP connection---you can use the @code{target}
15613 command to specify one of the target types configured for @value{GDBN}
15614 (@pxref{Target Commands, ,Commands for Managing Targets}).
15616 @cindex target architecture
15617 It is possible to build @value{GDBN} for several different @dfn{target
15618 architectures}. When @value{GDBN} is built like that, you can choose
15619 one of the available architectures with the @kbd{set architecture}
15623 @kindex set architecture
15624 @kindex show architecture
15625 @item set architecture @var{arch}
15626 This command sets the current target architecture to @var{arch}. The
15627 value of @var{arch} can be @code{"auto"}, in addition to one of the
15628 supported architectures.
15630 @item show architecture
15631 Show the current target architecture.
15633 @item set processor
15635 @kindex set processor
15636 @kindex show processor
15637 These are alias commands for, respectively, @code{set architecture}
15638 and @code{show architecture}.
15642 * Active Targets:: Active targets
15643 * Target Commands:: Commands for managing targets
15644 * Byte Order:: Choosing target byte order
15647 @node Active Targets
15648 @section Active Targets
15650 @cindex stacking targets
15651 @cindex active targets
15652 @cindex multiple targets
15654 There are multiple classes of targets such as: processes, executable files or
15655 recording sessions. Core files belong to the process class, making core file
15656 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
15657 on multiple active targets, one in each class. This allows you to (for
15658 example) start a process and inspect its activity, while still having access to
15659 the executable file after the process finishes. Or if you start process
15660 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
15661 presented a virtual layer of the recording target, while the process target
15662 remains stopped at the chronologically last point of the process execution.
15664 Use the @code{core-file} and @code{exec-file} commands to select a new core
15665 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
15666 specify as a target a process that is already running, use the @code{attach}
15667 command (@pxref{Attach, ,Debugging an Already-running Process}).
15669 @node Target Commands
15670 @section Commands for Managing Targets
15673 @item target @var{type} @var{parameters}
15674 Connects the @value{GDBN} host environment to a target machine or
15675 process. A target is typically a protocol for talking to debugging
15676 facilities. You use the argument @var{type} to specify the type or
15677 protocol of the target machine.
15679 Further @var{parameters} are interpreted by the target protocol, but
15680 typically include things like device names or host names to connect
15681 with, process numbers, and baud rates.
15683 The @code{target} command does not repeat if you press @key{RET} again
15684 after executing the command.
15686 @kindex help target
15688 Displays the names of all targets available. To display targets
15689 currently selected, use either @code{info target} or @code{info files}
15690 (@pxref{Files, ,Commands to Specify Files}).
15692 @item help target @var{name}
15693 Describe a particular target, including any parameters necessary to
15696 @kindex set gnutarget
15697 @item set gnutarget @var{args}
15698 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
15699 knows whether it is reading an @dfn{executable},
15700 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
15701 with the @code{set gnutarget} command. Unlike most @code{target} commands,
15702 with @code{gnutarget} the @code{target} refers to a program, not a machine.
15705 @emph{Warning:} To specify a file format with @code{set gnutarget},
15706 you must know the actual BFD name.
15710 @xref{Files, , Commands to Specify Files}.
15712 @kindex show gnutarget
15713 @item show gnutarget
15714 Use the @code{show gnutarget} command to display what file format
15715 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
15716 @value{GDBN} will determine the file format for each file automatically,
15717 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
15720 @cindex common targets
15721 Here are some common targets (available, or not, depending on the GDB
15726 @item target exec @var{program}
15727 @cindex executable file target
15728 An executable file. @samp{target exec @var{program}} is the same as
15729 @samp{exec-file @var{program}}.
15731 @item target core @var{filename}
15732 @cindex core dump file target
15733 A core dump file. @samp{target core @var{filename}} is the same as
15734 @samp{core-file @var{filename}}.
15736 @item target remote @var{medium}
15737 @cindex remote target
15738 A remote system connected to @value{GDBN} via a serial line or network
15739 connection. This command tells @value{GDBN} to use its own remote
15740 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
15742 For example, if you have a board connected to @file{/dev/ttya} on the
15743 machine running @value{GDBN}, you could say:
15746 target remote /dev/ttya
15749 @code{target remote} supports the @code{load} command. This is only
15750 useful if you have some other way of getting the stub to the target
15751 system, and you can put it somewhere in memory where it won't get
15752 clobbered by the download.
15754 @item target sim @r{[}@var{simargs}@r{]} @dots{}
15755 @cindex built-in simulator target
15756 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
15764 works; however, you cannot assume that a specific memory map, device
15765 drivers, or even basic I/O is available, although some simulators do
15766 provide these. For info about any processor-specific simulator details,
15767 see the appropriate section in @ref{Embedded Processors, ,Embedded
15772 Some configurations may include these targets as well:
15776 @item target nrom @var{dev}
15777 @cindex NetROM ROM emulator target
15778 NetROM ROM emulator. This target only supports downloading.
15782 Different targets are available on different configurations of @value{GDBN};
15783 your configuration may have more or fewer targets.
15785 Many remote targets require you to download the executable's code once
15786 you've successfully established a connection. You may wish to control
15787 various aspects of this process.
15792 @kindex set hash@r{, for remote monitors}
15793 @cindex hash mark while downloading
15794 This command controls whether a hash mark @samp{#} is displayed while
15795 downloading a file to the remote monitor. If on, a hash mark is
15796 displayed after each S-record is successfully downloaded to the
15800 @kindex show hash@r{, for remote monitors}
15801 Show the current status of displaying the hash mark.
15803 @item set debug monitor
15804 @kindex set debug monitor
15805 @cindex display remote monitor communications
15806 Enable or disable display of communications messages between
15807 @value{GDBN} and the remote monitor.
15809 @item show debug monitor
15810 @kindex show debug monitor
15811 Show the current status of displaying communications between
15812 @value{GDBN} and the remote monitor.
15817 @kindex load @var{filename}
15818 @item load @var{filename}
15820 Depending on what remote debugging facilities are configured into
15821 @value{GDBN}, the @code{load} command may be available. Where it exists, it
15822 is meant to make @var{filename} (an executable) available for debugging
15823 on the remote system---by downloading, or dynamic linking, for example.
15824 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15825 the @code{add-symbol-file} command.
15827 If your @value{GDBN} does not have a @code{load} command, attempting to
15828 execute it gets the error message ``@code{You can't do that when your
15829 target is @dots{}}''
15831 The file is loaded at whatever address is specified in the executable.
15832 For some object file formats, you can specify the load address when you
15833 link the program; for other formats, like a.out, the object file format
15834 specifies a fixed address.
15835 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15837 Depending on the remote side capabilities, @value{GDBN} may be able to
15838 load programs into flash memory.
15840 @code{load} does not repeat if you press @key{RET} again after using it.
15844 @section Choosing Target Byte Order
15846 @cindex choosing target byte order
15847 @cindex target byte order
15849 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15850 offer the ability to run either big-endian or little-endian byte
15851 orders. Usually the executable or symbol will include a bit to
15852 designate the endian-ness, and you will not need to worry about
15853 which to use. However, you may still find it useful to adjust
15854 @value{GDBN}'s idea of processor endian-ness manually.
15858 @item set endian big
15859 Instruct @value{GDBN} to assume the target is big-endian.
15861 @item set endian little
15862 Instruct @value{GDBN} to assume the target is little-endian.
15864 @item set endian auto
15865 Instruct @value{GDBN} to use the byte order associated with the
15869 Display @value{GDBN}'s current idea of the target byte order.
15873 Note that these commands merely adjust interpretation of symbolic
15874 data on the host, and that they have absolutely no effect on the
15878 @node Remote Debugging
15879 @chapter Debugging Remote Programs
15880 @cindex remote debugging
15882 If you are trying to debug a program running on a machine that cannot run
15883 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15884 For example, you might use remote debugging on an operating system kernel,
15885 or on a small system which does not have a general purpose operating system
15886 powerful enough to run a full-featured debugger.
15888 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15889 to make this work with particular debugging targets. In addition,
15890 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15891 but not specific to any particular target system) which you can use if you
15892 write the remote stubs---the code that runs on the remote system to
15893 communicate with @value{GDBN}.
15895 Other remote targets may be available in your
15896 configuration of @value{GDBN}; use @code{help target} to list them.
15899 * Connecting:: Connecting to a remote target
15900 * File Transfer:: Sending files to a remote system
15901 * Server:: Using the gdbserver program
15902 * Remote Configuration:: Remote configuration
15903 * Remote Stub:: Implementing a remote stub
15907 @section Connecting to a Remote Target
15909 On the @value{GDBN} host machine, you will need an unstripped copy of
15910 your program, since @value{GDBN} needs symbol and debugging information.
15911 Start up @value{GDBN} as usual, using the name of the local copy of your
15912 program as the first argument.
15914 @cindex @code{target remote}
15915 @value{GDBN} can communicate with the target over a serial line, or
15916 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15917 each case, @value{GDBN} uses the same protocol for debugging your
15918 program; only the medium carrying the debugging packets varies. The
15919 @code{target remote} command establishes a connection to the target.
15920 Its arguments indicate which medium to use:
15924 @item target remote @var{serial-device}
15925 @cindex serial line, @code{target remote}
15926 Use @var{serial-device} to communicate with the target. For example,
15927 to use a serial line connected to the device named @file{/dev/ttyb}:
15930 target remote /dev/ttyb
15933 If you're using a serial line, you may want to give @value{GDBN} the
15934 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15935 (@pxref{Remote Configuration, set remotebaud}) before the
15936 @code{target} command.
15938 @item target remote @code{@var{host}:@var{port}}
15939 @itemx target remote @code{tcp:@var{host}:@var{port}}
15940 @cindex @acronym{TCP} port, @code{target remote}
15941 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15942 The @var{host} may be either a host name or a numeric @acronym{IP}
15943 address; @var{port} must be a decimal number. The @var{host} could be
15944 the target machine itself, if it is directly connected to the net, or
15945 it might be a terminal server which in turn has a serial line to the
15948 For example, to connect to port 2828 on a terminal server named
15952 target remote manyfarms:2828
15955 If your remote target is actually running on the same machine as your
15956 debugger session (e.g.@: a simulator for your target running on the
15957 same host), you can omit the hostname. For example, to connect to
15958 port 1234 on your local machine:
15961 target remote :1234
15965 Note that the colon is still required here.
15967 @item target remote @code{udp:@var{host}:@var{port}}
15968 @cindex @acronym{UDP} port, @code{target remote}
15969 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
15970 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
15973 target remote udp:manyfarms:2828
15976 When using a @acronym{UDP} connection for remote debugging, you should
15977 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
15978 can silently drop packets on busy or unreliable networks, which will
15979 cause havoc with your debugging session.
15981 @item target remote | @var{command}
15982 @cindex pipe, @code{target remote} to
15983 Run @var{command} in the background and communicate with it using a
15984 pipe. The @var{command} is a shell command, to be parsed and expanded
15985 by the system's command shell, @code{/bin/sh}; it should expect remote
15986 protocol packets on its standard input, and send replies on its
15987 standard output. You could use this to run a stand-alone simulator
15988 that speaks the remote debugging protocol, to make net connections
15989 using programs like @code{ssh}, or for other similar tricks.
15991 If @var{command} closes its standard output (perhaps by exiting),
15992 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
15993 program has already exited, this will have no effect.)
15997 Once the connection has been established, you can use all the usual
15998 commands to examine and change data. The remote program is already
15999 running; you can use @kbd{step} and @kbd{continue}, and you do not
16000 need to use @kbd{run}.
16002 @cindex interrupting remote programs
16003 @cindex remote programs, interrupting
16004 Whenever @value{GDBN} is waiting for the remote program, if you type the
16005 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16006 program. This may or may not succeed, depending in part on the hardware
16007 and the serial drivers the remote system uses. If you type the
16008 interrupt character once again, @value{GDBN} displays this prompt:
16011 Interrupted while waiting for the program.
16012 Give up (and stop debugging it)? (y or n)
16015 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16016 (If you decide you want to try again later, you can use @samp{target
16017 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16018 goes back to waiting.
16021 @kindex detach (remote)
16023 When you have finished debugging the remote program, you can use the
16024 @code{detach} command to release it from @value{GDBN} control.
16025 Detaching from the target normally resumes its execution, but the results
16026 will depend on your particular remote stub. After the @code{detach}
16027 command, @value{GDBN} is free to connect to another target.
16031 The @code{disconnect} command behaves like @code{detach}, except that
16032 the target is generally not resumed. It will wait for @value{GDBN}
16033 (this instance or another one) to connect and continue debugging. After
16034 the @code{disconnect} command, @value{GDBN} is again free to connect to
16037 @cindex send command to remote monitor
16038 @cindex extend @value{GDBN} for remote targets
16039 @cindex add new commands for external monitor
16041 @item monitor @var{cmd}
16042 This command allows you to send arbitrary commands directly to the
16043 remote monitor. Since @value{GDBN} doesn't care about the commands it
16044 sends like this, this command is the way to extend @value{GDBN}---you
16045 can add new commands that only the external monitor will understand
16049 @node File Transfer
16050 @section Sending files to a remote system
16051 @cindex remote target, file transfer
16052 @cindex file transfer
16053 @cindex sending files to remote systems
16055 Some remote targets offer the ability to transfer files over the same
16056 connection used to communicate with @value{GDBN}. This is convenient
16057 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16058 running @code{gdbserver} over a network interface. For other targets,
16059 e.g.@: embedded devices with only a single serial port, this may be
16060 the only way to upload or download files.
16062 Not all remote targets support these commands.
16066 @item remote put @var{hostfile} @var{targetfile}
16067 Copy file @var{hostfile} from the host system (the machine running
16068 @value{GDBN}) to @var{targetfile} on the target system.
16071 @item remote get @var{targetfile} @var{hostfile}
16072 Copy file @var{targetfile} from the target system to @var{hostfile}
16073 on the host system.
16075 @kindex remote delete
16076 @item remote delete @var{targetfile}
16077 Delete @var{targetfile} from the target system.
16082 @section Using the @code{gdbserver} Program
16085 @cindex remote connection without stubs
16086 @code{gdbserver} is a control program for Unix-like systems, which
16087 allows you to connect your program with a remote @value{GDBN} via
16088 @code{target remote}---but without linking in the usual debugging stub.
16090 @code{gdbserver} is not a complete replacement for the debugging stubs,
16091 because it requires essentially the same operating-system facilities
16092 that @value{GDBN} itself does. In fact, a system that can run
16093 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16094 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16095 because it is a much smaller program than @value{GDBN} itself. It is
16096 also easier to port than all of @value{GDBN}, so you may be able to get
16097 started more quickly on a new system by using @code{gdbserver}.
16098 Finally, if you develop code for real-time systems, you may find that
16099 the tradeoffs involved in real-time operation make it more convenient to
16100 do as much development work as possible on another system, for example
16101 by cross-compiling. You can use @code{gdbserver} to make a similar
16102 choice for debugging.
16104 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16105 or a TCP connection, using the standard @value{GDBN} remote serial
16109 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16110 Do not run @code{gdbserver} connected to any public network; a
16111 @value{GDBN} connection to @code{gdbserver} provides access to the
16112 target system with the same privileges as the user running
16116 @subsection Running @code{gdbserver}
16117 @cindex arguments, to @code{gdbserver}
16119 Run @code{gdbserver} on the target system. You need a copy of the
16120 program you want to debug, including any libraries it requires.
16121 @code{gdbserver} does not need your program's symbol table, so you can
16122 strip the program if necessary to save space. @value{GDBN} on the host
16123 system does all the symbol handling.
16125 To use the server, you must tell it how to communicate with @value{GDBN};
16126 the name of your program; and the arguments for your program. The usual
16130 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16133 @var{comm} is either a device name (to use a serial line) or a TCP
16134 hostname and portnumber. For example, to debug Emacs with the argument
16135 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16139 target> gdbserver /dev/com1 emacs foo.txt
16142 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16145 To use a TCP connection instead of a serial line:
16148 target> gdbserver host:2345 emacs foo.txt
16151 The only difference from the previous example is the first argument,
16152 specifying that you are communicating with the host @value{GDBN} via
16153 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16154 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16155 (Currently, the @samp{host} part is ignored.) You can choose any number
16156 you want for the port number as long as it does not conflict with any
16157 TCP ports already in use on the target system (for example, @code{23} is
16158 reserved for @code{telnet}).@footnote{If you choose a port number that
16159 conflicts with another service, @code{gdbserver} prints an error message
16160 and exits.} You must use the same port number with the host @value{GDBN}
16161 @code{target remote} command.
16163 @subsubsection Attaching to a Running Program
16165 On some targets, @code{gdbserver} can also attach to running programs.
16166 This is accomplished via the @code{--attach} argument. The syntax is:
16169 target> gdbserver --attach @var{comm} @var{pid}
16172 @var{pid} is the process ID of a currently running process. It isn't necessary
16173 to point @code{gdbserver} at a binary for the running process.
16176 @cindex attach to a program by name
16177 You can debug processes by name instead of process ID if your target has the
16178 @code{pidof} utility:
16181 target> gdbserver --attach @var{comm} `pidof @var{program}`
16184 In case more than one copy of @var{program} is running, or @var{program}
16185 has multiple threads, most versions of @code{pidof} support the
16186 @code{-s} option to only return the first process ID.
16188 @subsubsection Multi-Process Mode for @code{gdbserver}
16189 @cindex gdbserver, multiple processes
16190 @cindex multiple processes with gdbserver
16192 When you connect to @code{gdbserver} using @code{target remote},
16193 @code{gdbserver} debugs the specified program only once. When the
16194 program exits, or you detach from it, @value{GDBN} closes the connection
16195 and @code{gdbserver} exits.
16197 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16198 enters multi-process mode. When the debugged program exits, or you
16199 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16200 though no program is running. The @code{run} and @code{attach}
16201 commands instruct @code{gdbserver} to run or attach to a new program.
16202 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16203 remote exec-file}) to select the program to run. Command line
16204 arguments are supported, except for wildcard expansion and I/O
16205 redirection (@pxref{Arguments}).
16207 To start @code{gdbserver} without supplying an initial command to run
16208 or process ID to attach, use the @option{--multi} command line option.
16209 Then you can connect using @kbd{target extended-remote} and start
16210 the program you want to debug.
16212 @code{gdbserver} does not automatically exit in multi-process mode.
16213 You can terminate it by using @code{monitor exit}
16214 (@pxref{Monitor Commands for gdbserver}).
16216 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16218 The @option{--debug} option tells @code{gdbserver} to display extra
16219 status information about the debugging process. The
16220 @option{--remote-debug} option tells @code{gdbserver} to display
16221 remote protocol debug output. These options are intended for
16222 @code{gdbserver} development and for bug reports to the developers.
16224 The @option{--wrapper} option specifies a wrapper to launch programs
16225 for debugging. The option should be followed by the name of the
16226 wrapper, then any command-line arguments to pass to the wrapper, then
16227 @kbd{--} indicating the end of the wrapper arguments.
16229 @code{gdbserver} runs the specified wrapper program with a combined
16230 command line including the wrapper arguments, then the name of the
16231 program to debug, then any arguments to the program. The wrapper
16232 runs until it executes your program, and then @value{GDBN} gains control.
16234 You can use any program that eventually calls @code{execve} with
16235 its arguments as a wrapper. Several standard Unix utilities do
16236 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16237 with @code{exec "$@@"} will also work.
16239 For example, you can use @code{env} to pass an environment variable to
16240 the debugged program, without setting the variable in @code{gdbserver}'s
16244 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16247 @subsection Connecting to @code{gdbserver}
16249 Run @value{GDBN} on the host system.
16251 First make sure you have the necessary symbol files. Load symbols for
16252 your application using the @code{file} command before you connect. Use
16253 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16254 was compiled with the correct sysroot using @code{--with-sysroot}).
16256 The symbol file and target libraries must exactly match the executable
16257 and libraries on the target, with one exception: the files on the host
16258 system should not be stripped, even if the files on the target system
16259 are. Mismatched or missing files will lead to confusing results
16260 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16261 files may also prevent @code{gdbserver} from debugging multi-threaded
16264 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16265 For TCP connections, you must start up @code{gdbserver} prior to using
16266 the @code{target remote} command. Otherwise you may get an error whose
16267 text depends on the host system, but which usually looks something like
16268 @samp{Connection refused}. Don't use the @code{load}
16269 command in @value{GDBN} when using @code{gdbserver}, since the program is
16270 already on the target.
16272 @subsection Monitor Commands for @code{gdbserver}
16273 @cindex monitor commands, for @code{gdbserver}
16274 @anchor{Monitor Commands for gdbserver}
16276 During a @value{GDBN} session using @code{gdbserver}, you can use the
16277 @code{monitor} command to send special requests to @code{gdbserver}.
16278 Here are the available commands.
16282 List the available monitor commands.
16284 @item monitor set debug 0
16285 @itemx monitor set debug 1
16286 Disable or enable general debugging messages.
16288 @item monitor set remote-debug 0
16289 @itemx monitor set remote-debug 1
16290 Disable or enable specific debugging messages associated with the remote
16291 protocol (@pxref{Remote Protocol}).
16293 @item monitor set libthread-db-search-path [PATH]
16294 @cindex gdbserver, search path for @code{libthread_db}
16295 When this command is issued, @var{path} is a colon-separated list of
16296 directories to search for @code{libthread_db} (@pxref{Threads,,set
16297 libthread-db-search-path}). If you omit @var{path},
16298 @samp{libthread-db-search-path} will be reset to an empty list.
16301 Tell gdbserver to exit immediately. This command should be followed by
16302 @code{disconnect} to close the debugging session. @code{gdbserver} will
16303 detach from any attached processes and kill any processes it created.
16304 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16305 of a multi-process mode debug session.
16309 @subsection Tracepoints support in @code{gdbserver}
16310 @cindex tracepoints support in @code{gdbserver}
16312 On some targets, @code{gdbserver} supports tracepoints, fast
16313 tracepoints and static tracepoints.
16315 For fast or static tracepoints to work, a special library called the
16316 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16317 This library is built and distributed as an integral part of
16318 @code{gdbserver}. In addition, support for static tracepoints
16319 requires building the in-process agent library with static tracepoints
16320 support. At present, the UST (LTTng Userspace Tracer,
16321 @url{http://lttng.org/ust}) tracing engine is supported. This support
16322 is automatically available if UST development headers are found in the
16323 standard include path when @code{gdbserver} is built, or if
16324 @code{gdbserver} was explicitly configured using @option{--with-ust}
16325 to point at such headers. You can explicitly disable the support
16326 using @option{--with-ust=no}.
16328 There are several ways to load the in-process agent in your program:
16331 @item Specifying it as dependency at link time
16333 You can link your program dynamically with the in-process agent
16334 library. On most systems, this is accomplished by adding
16335 @code{-linproctrace} to the link command.
16337 @item Using the system's preloading mechanisms
16339 You can force loading the in-process agent at startup time by using
16340 your system's support for preloading shared libraries. Many Unixes
16341 support the concept of preloading user defined libraries. In most
16342 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16343 in the environment. See also the description of @code{gdbserver}'s
16344 @option{--wrapper} command line option.
16346 @item Using @value{GDBN} to force loading the agent at run time
16348 On some systems, you can force the inferior to load a shared library,
16349 by calling a dynamic loader function in the inferior that takes care
16350 of dynamically looking up and loading a shared library. On most Unix
16351 systems, the function is @code{dlopen}. You'll use the @code{call}
16352 command for that. For example:
16355 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16358 Note that on most Unix systems, for the @code{dlopen} function to be
16359 available, the program needs to be linked with @code{-ldl}.
16362 On systems that have a userspace dynamic loader, like most Unix
16363 systems, when you connect to @code{gdbserver} using @code{target
16364 remote}, you'll find that the program is stopped at the dynamic
16365 loader's entry point, and no shared library has been loaded in the
16366 program's address space yet, including the in-process agent. In that
16367 case, before being able to use any of the fast or static tracepoints
16368 features, you need to let the loader run and load the shared
16369 libraries. The simplest way to do that is to run the program to the
16370 main procedure. E.g., if debugging a C or C@t{++} program, start
16371 @code{gdbserver} like so:
16374 $ gdbserver :9999 myprogram
16377 Start GDB and connect to @code{gdbserver} like so, and run to main:
16381 (@value{GDBP}) target remote myhost:9999
16382 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16383 (@value{GDBP}) b main
16384 (@value{GDBP}) continue
16387 The in-process tracing agent library should now be loaded into the
16388 process; you can confirm it with the @code{info sharedlibrary}
16389 command, which will list @file{libinproctrace.so} as loaded in the
16390 process. You are now ready to install fast tracepoints, list static
16391 tracepoint markers, probe static tracepoints markers, and start
16394 @node Remote Configuration
16395 @section Remote Configuration
16398 @kindex show remote
16399 This section documents the configuration options available when
16400 debugging remote programs. For the options related to the File I/O
16401 extensions of the remote protocol, see @ref{system,
16402 system-call-allowed}.
16405 @item set remoteaddresssize @var{bits}
16406 @cindex address size for remote targets
16407 @cindex bits in remote address
16408 Set the maximum size of address in a memory packet to the specified
16409 number of bits. @value{GDBN} will mask off the address bits above
16410 that number, when it passes addresses to the remote target. The
16411 default value is the number of bits in the target's address.
16413 @item show remoteaddresssize
16414 Show the current value of remote address size in bits.
16416 @item set remotebaud @var{n}
16417 @cindex baud rate for remote targets
16418 Set the baud rate for the remote serial I/O to @var{n} baud. The
16419 value is used to set the speed of the serial port used for debugging
16422 @item show remotebaud
16423 Show the current speed of the remote connection.
16425 @item set remotebreak
16426 @cindex interrupt remote programs
16427 @cindex BREAK signal instead of Ctrl-C
16428 @anchor{set remotebreak}
16429 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
16430 when you type @kbd{Ctrl-c} to interrupt the program running
16431 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
16432 character instead. The default is off, since most remote systems
16433 expect to see @samp{Ctrl-C} as the interrupt signal.
16435 @item show remotebreak
16436 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
16437 interrupt the remote program.
16439 @item set remoteflow on
16440 @itemx set remoteflow off
16441 @kindex set remoteflow
16442 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
16443 on the serial port used to communicate to the remote target.
16445 @item show remoteflow
16446 @kindex show remoteflow
16447 Show the current setting of hardware flow control.
16449 @item set remotelogbase @var{base}
16450 Set the base (a.k.a.@: radix) of logging serial protocol
16451 communications to @var{base}. Supported values of @var{base} are:
16452 @code{ascii}, @code{octal}, and @code{hex}. The default is
16455 @item show remotelogbase
16456 Show the current setting of the radix for logging remote serial
16459 @item set remotelogfile @var{file}
16460 @cindex record serial communications on file
16461 Record remote serial communications on the named @var{file}. The
16462 default is not to record at all.
16464 @item show remotelogfile.
16465 Show the current setting of the file name on which to record the
16466 serial communications.
16468 @item set remotetimeout @var{num}
16469 @cindex timeout for serial communications
16470 @cindex remote timeout
16471 Set the timeout limit to wait for the remote target to respond to
16472 @var{num} seconds. The default is 2 seconds.
16474 @item show remotetimeout
16475 Show the current number of seconds to wait for the remote target
16478 @cindex limit hardware breakpoints and watchpoints
16479 @cindex remote target, limit break- and watchpoints
16480 @anchor{set remote hardware-watchpoint-limit}
16481 @anchor{set remote hardware-breakpoint-limit}
16482 @item set remote hardware-watchpoint-limit @var{limit}
16483 @itemx set remote hardware-breakpoint-limit @var{limit}
16484 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
16485 watchpoints. A limit of -1, the default, is treated as unlimited.
16487 @item set remote exec-file @var{filename}
16488 @itemx show remote exec-file
16489 @anchor{set remote exec-file}
16490 @cindex executable file, for remote target
16491 Select the file used for @code{run} with @code{target
16492 extended-remote}. This should be set to a filename valid on the
16493 target system. If it is not set, the target will use a default
16494 filename (e.g.@: the last program run).
16496 @item set remote interrupt-sequence
16497 @cindex interrupt remote programs
16498 @cindex select Ctrl-C, BREAK or BREAK-g
16499 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
16500 @samp{BREAK-g} as the
16501 sequence to the remote target in order to interrupt the execution.
16502 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
16503 is high level of serial line for some certain time.
16504 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
16505 It is @code{BREAK} signal followed by character @code{g}.
16507 @item show interrupt-sequence
16508 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
16509 is sent by @value{GDBN} to interrupt the remote program.
16510 @code{BREAK-g} is BREAK signal followed by @code{g} and
16511 also known as Magic SysRq g.
16513 @item set remote interrupt-on-connect
16514 @cindex send interrupt-sequence on start
16515 Specify whether interrupt-sequence is sent to remote target when
16516 @value{GDBN} connects to it. This is mostly needed when you debug
16517 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
16518 which is known as Magic SysRq g in order to connect @value{GDBN}.
16520 @item show interrupt-on-connect
16521 Show whether interrupt-sequence is sent
16522 to remote target when @value{GDBN} connects to it.
16526 @item set tcp auto-retry on
16527 @cindex auto-retry, for remote TCP target
16528 Enable auto-retry for remote TCP connections. This is useful if the remote
16529 debugging agent is launched in parallel with @value{GDBN}; there is a race
16530 condition because the agent may not become ready to accept the connection
16531 before @value{GDBN} attempts to connect. When auto-retry is
16532 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
16533 to establish the connection using the timeout specified by
16534 @code{set tcp connect-timeout}.
16536 @item set tcp auto-retry off
16537 Do not auto-retry failed TCP connections.
16539 @item show tcp auto-retry
16540 Show the current auto-retry setting.
16542 @item set tcp connect-timeout @var{seconds}
16543 @cindex connection timeout, for remote TCP target
16544 @cindex timeout, for remote target connection
16545 Set the timeout for establishing a TCP connection to the remote target to
16546 @var{seconds}. The timeout affects both polling to retry failed connections
16547 (enabled by @code{set tcp auto-retry on}) and waiting for connections
16548 that are merely slow to complete, and represents an approximate cumulative
16551 @item show tcp connect-timeout
16552 Show the current connection timeout setting.
16555 @cindex remote packets, enabling and disabling
16556 The @value{GDBN} remote protocol autodetects the packets supported by
16557 your debugging stub. If you need to override the autodetection, you
16558 can use these commands to enable or disable individual packets. Each
16559 packet can be set to @samp{on} (the remote target supports this
16560 packet), @samp{off} (the remote target does not support this packet),
16561 or @samp{auto} (detect remote target support for this packet). They
16562 all default to @samp{auto}. For more information about each packet,
16563 see @ref{Remote Protocol}.
16565 During normal use, you should not have to use any of these commands.
16566 If you do, that may be a bug in your remote debugging stub, or a bug
16567 in @value{GDBN}. You may want to report the problem to the
16568 @value{GDBN} developers.
16570 For each packet @var{name}, the command to enable or disable the
16571 packet is @code{set remote @var{name}-packet}. The available settings
16574 @multitable @columnfractions 0.28 0.32 0.25
16577 @tab Related Features
16579 @item @code{fetch-register}
16581 @tab @code{info registers}
16583 @item @code{set-register}
16587 @item @code{binary-download}
16589 @tab @code{load}, @code{set}
16591 @item @code{read-aux-vector}
16592 @tab @code{qXfer:auxv:read}
16593 @tab @code{info auxv}
16595 @item @code{symbol-lookup}
16596 @tab @code{qSymbol}
16597 @tab Detecting multiple threads
16599 @item @code{attach}
16600 @tab @code{vAttach}
16603 @item @code{verbose-resume}
16605 @tab Stepping or resuming multiple threads
16611 @item @code{software-breakpoint}
16615 @item @code{hardware-breakpoint}
16619 @item @code{write-watchpoint}
16623 @item @code{read-watchpoint}
16627 @item @code{access-watchpoint}
16631 @item @code{target-features}
16632 @tab @code{qXfer:features:read}
16633 @tab @code{set architecture}
16635 @item @code{library-info}
16636 @tab @code{qXfer:libraries:read}
16637 @tab @code{info sharedlibrary}
16639 @item @code{memory-map}
16640 @tab @code{qXfer:memory-map:read}
16641 @tab @code{info mem}
16643 @item @code{read-sdata-object}
16644 @tab @code{qXfer:sdata:read}
16645 @tab @code{print $_sdata}
16647 @item @code{read-spu-object}
16648 @tab @code{qXfer:spu:read}
16649 @tab @code{info spu}
16651 @item @code{write-spu-object}
16652 @tab @code{qXfer:spu:write}
16653 @tab @code{info spu}
16655 @item @code{read-siginfo-object}
16656 @tab @code{qXfer:siginfo:read}
16657 @tab @code{print $_siginfo}
16659 @item @code{write-siginfo-object}
16660 @tab @code{qXfer:siginfo:write}
16661 @tab @code{set $_siginfo}
16663 @item @code{threads}
16664 @tab @code{qXfer:threads:read}
16665 @tab @code{info threads}
16667 @item @code{get-thread-local-@*storage-address}
16668 @tab @code{qGetTLSAddr}
16669 @tab Displaying @code{__thread} variables
16671 @item @code{get-thread-information-block-address}
16672 @tab @code{qGetTIBAddr}
16673 @tab Display MS-Windows Thread Information Block.
16675 @item @code{search-memory}
16676 @tab @code{qSearch:memory}
16679 @item @code{supported-packets}
16680 @tab @code{qSupported}
16681 @tab Remote communications parameters
16683 @item @code{pass-signals}
16684 @tab @code{QPassSignals}
16685 @tab @code{handle @var{signal}}
16687 @item @code{hostio-close-packet}
16688 @tab @code{vFile:close}
16689 @tab @code{remote get}, @code{remote put}
16691 @item @code{hostio-open-packet}
16692 @tab @code{vFile:open}
16693 @tab @code{remote get}, @code{remote put}
16695 @item @code{hostio-pread-packet}
16696 @tab @code{vFile:pread}
16697 @tab @code{remote get}, @code{remote put}
16699 @item @code{hostio-pwrite-packet}
16700 @tab @code{vFile:pwrite}
16701 @tab @code{remote get}, @code{remote put}
16703 @item @code{hostio-unlink-packet}
16704 @tab @code{vFile:unlink}
16705 @tab @code{remote delete}
16707 @item @code{noack-packet}
16708 @tab @code{QStartNoAckMode}
16709 @tab Packet acknowledgment
16711 @item @code{osdata}
16712 @tab @code{qXfer:osdata:read}
16713 @tab @code{info os}
16715 @item @code{query-attached}
16716 @tab @code{qAttached}
16717 @tab Querying remote process attach state.
16721 @section Implementing a Remote Stub
16723 @cindex debugging stub, example
16724 @cindex remote stub, example
16725 @cindex stub example, remote debugging
16726 The stub files provided with @value{GDBN} implement the target side of the
16727 communication protocol, and the @value{GDBN} side is implemented in the
16728 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
16729 these subroutines to communicate, and ignore the details. (If you're
16730 implementing your own stub file, you can still ignore the details: start
16731 with one of the existing stub files. @file{sparc-stub.c} is the best
16732 organized, and therefore the easiest to read.)
16734 @cindex remote serial debugging, overview
16735 To debug a program running on another machine (the debugging
16736 @dfn{target} machine), you must first arrange for all the usual
16737 prerequisites for the program to run by itself. For example, for a C
16742 A startup routine to set up the C runtime environment; these usually
16743 have a name like @file{crt0}. The startup routine may be supplied by
16744 your hardware supplier, or you may have to write your own.
16747 A C subroutine library to support your program's
16748 subroutine calls, notably managing input and output.
16751 A way of getting your program to the other machine---for example, a
16752 download program. These are often supplied by the hardware
16753 manufacturer, but you may have to write your own from hardware
16757 The next step is to arrange for your program to use a serial port to
16758 communicate with the machine where @value{GDBN} is running (the @dfn{host}
16759 machine). In general terms, the scheme looks like this:
16763 @value{GDBN} already understands how to use this protocol; when everything
16764 else is set up, you can simply use the @samp{target remote} command
16765 (@pxref{Targets,,Specifying a Debugging Target}).
16767 @item On the target,
16768 you must link with your program a few special-purpose subroutines that
16769 implement the @value{GDBN} remote serial protocol. The file containing these
16770 subroutines is called a @dfn{debugging stub}.
16772 On certain remote targets, you can use an auxiliary program
16773 @code{gdbserver} instead of linking a stub into your program.
16774 @xref{Server,,Using the @code{gdbserver} Program}, for details.
16777 The debugging stub is specific to the architecture of the remote
16778 machine; for example, use @file{sparc-stub.c} to debug programs on
16781 @cindex remote serial stub list
16782 These working remote stubs are distributed with @value{GDBN}:
16787 @cindex @file{i386-stub.c}
16790 For Intel 386 and compatible architectures.
16793 @cindex @file{m68k-stub.c}
16794 @cindex Motorola 680x0
16796 For Motorola 680x0 architectures.
16799 @cindex @file{sh-stub.c}
16802 For Renesas SH architectures.
16805 @cindex @file{sparc-stub.c}
16807 For @sc{sparc} architectures.
16809 @item sparcl-stub.c
16810 @cindex @file{sparcl-stub.c}
16813 For Fujitsu @sc{sparclite} architectures.
16817 The @file{README} file in the @value{GDBN} distribution may list other
16818 recently added stubs.
16821 * Stub Contents:: What the stub can do for you
16822 * Bootstrapping:: What you must do for the stub
16823 * Debug Session:: Putting it all together
16826 @node Stub Contents
16827 @subsection What the Stub Can Do for You
16829 @cindex remote serial stub
16830 The debugging stub for your architecture supplies these three
16834 @item set_debug_traps
16835 @findex set_debug_traps
16836 @cindex remote serial stub, initialization
16837 This routine arranges for @code{handle_exception} to run when your
16838 program stops. You must call this subroutine explicitly near the
16839 beginning of your program.
16841 @item handle_exception
16842 @findex handle_exception
16843 @cindex remote serial stub, main routine
16844 This is the central workhorse, but your program never calls it
16845 explicitly---the setup code arranges for @code{handle_exception} to
16846 run when a trap is triggered.
16848 @code{handle_exception} takes control when your program stops during
16849 execution (for example, on a breakpoint), and mediates communications
16850 with @value{GDBN} on the host machine. This is where the communications
16851 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
16852 representative on the target machine. It begins by sending summary
16853 information on the state of your program, then continues to execute,
16854 retrieving and transmitting any information @value{GDBN} needs, until you
16855 execute a @value{GDBN} command that makes your program resume; at that point,
16856 @code{handle_exception} returns control to your own code on the target
16860 @cindex @code{breakpoint} subroutine, remote
16861 Use this auxiliary subroutine to make your program contain a
16862 breakpoint. Depending on the particular situation, this may be the only
16863 way for @value{GDBN} to get control. For instance, if your target
16864 machine has some sort of interrupt button, you won't need to call this;
16865 pressing the interrupt button transfers control to
16866 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
16867 simply receiving characters on the serial port may also trigger a trap;
16868 again, in that situation, you don't need to call @code{breakpoint} from
16869 your own program---simply running @samp{target remote} from the host
16870 @value{GDBN} session gets control.
16872 Call @code{breakpoint} if none of these is true, or if you simply want
16873 to make certain your program stops at a predetermined point for the
16874 start of your debugging session.
16877 @node Bootstrapping
16878 @subsection What You Must Do for the Stub
16880 @cindex remote stub, support routines
16881 The debugging stubs that come with @value{GDBN} are set up for a particular
16882 chip architecture, but they have no information about the rest of your
16883 debugging target machine.
16885 First of all you need to tell the stub how to communicate with the
16889 @item int getDebugChar()
16890 @findex getDebugChar
16891 Write this subroutine to read a single character from the serial port.
16892 It may be identical to @code{getchar} for your target system; a
16893 different name is used to allow you to distinguish the two if you wish.
16895 @item void putDebugChar(int)
16896 @findex putDebugChar
16897 Write this subroutine to write a single character to the serial port.
16898 It may be identical to @code{putchar} for your target system; a
16899 different name is used to allow you to distinguish the two if you wish.
16902 @cindex control C, and remote debugging
16903 @cindex interrupting remote targets
16904 If you want @value{GDBN} to be able to stop your program while it is
16905 running, you need to use an interrupt-driven serial driver, and arrange
16906 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
16907 character). That is the character which @value{GDBN} uses to tell the
16908 remote system to stop.
16910 Getting the debugging target to return the proper status to @value{GDBN}
16911 probably requires changes to the standard stub; one quick and dirty way
16912 is to just execute a breakpoint instruction (the ``dirty'' part is that
16913 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
16915 Other routines you need to supply are:
16918 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
16919 @findex exceptionHandler
16920 Write this function to install @var{exception_address} in the exception
16921 handling tables. You need to do this because the stub does not have any
16922 way of knowing what the exception handling tables on your target system
16923 are like (for example, the processor's table might be in @sc{rom},
16924 containing entries which point to a table in @sc{ram}).
16925 @var{exception_number} is the exception number which should be changed;
16926 its meaning is architecture-dependent (for example, different numbers
16927 might represent divide by zero, misaligned access, etc). When this
16928 exception occurs, control should be transferred directly to
16929 @var{exception_address}, and the processor state (stack, registers,
16930 and so on) should be just as it is when a processor exception occurs. So if
16931 you want to use a jump instruction to reach @var{exception_address}, it
16932 should be a simple jump, not a jump to subroutine.
16934 For the 386, @var{exception_address} should be installed as an interrupt
16935 gate so that interrupts are masked while the handler runs. The gate
16936 should be at privilege level 0 (the most privileged level). The
16937 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
16938 help from @code{exceptionHandler}.
16940 @item void flush_i_cache()
16941 @findex flush_i_cache
16942 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
16943 instruction cache, if any, on your target machine. If there is no
16944 instruction cache, this subroutine may be a no-op.
16946 On target machines that have instruction caches, @value{GDBN} requires this
16947 function to make certain that the state of your program is stable.
16951 You must also make sure this library routine is available:
16954 @item void *memset(void *, int, int)
16956 This is the standard library function @code{memset} that sets an area of
16957 memory to a known value. If you have one of the free versions of
16958 @code{libc.a}, @code{memset} can be found there; otherwise, you must
16959 either obtain it from your hardware manufacturer, or write your own.
16962 If you do not use the GNU C compiler, you may need other standard
16963 library subroutines as well; this varies from one stub to another,
16964 but in general the stubs are likely to use any of the common library
16965 subroutines which @code{@value{NGCC}} generates as inline code.
16968 @node Debug Session
16969 @subsection Putting it All Together
16971 @cindex remote serial debugging summary
16972 In summary, when your program is ready to debug, you must follow these
16977 Make sure you have defined the supporting low-level routines
16978 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
16980 @code{getDebugChar}, @code{putDebugChar},
16981 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
16985 Insert these lines near the top of your program:
16993 For the 680x0 stub only, you need to provide a variable called
16994 @code{exceptionHook}. Normally you just use:
16997 void (*exceptionHook)() = 0;
17001 but if before calling @code{set_debug_traps}, you set it to point to a
17002 function in your program, that function is called when
17003 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17004 error). The function indicated by @code{exceptionHook} is called with
17005 one parameter: an @code{int} which is the exception number.
17008 Compile and link together: your program, the @value{GDBN} debugging stub for
17009 your target architecture, and the supporting subroutines.
17012 Make sure you have a serial connection between your target machine and
17013 the @value{GDBN} host, and identify the serial port on the host.
17016 @c The "remote" target now provides a `load' command, so we should
17017 @c document that. FIXME.
17018 Download your program to your target machine (or get it there by
17019 whatever means the manufacturer provides), and start it.
17022 Start @value{GDBN} on the host, and connect to the target
17023 (@pxref{Connecting,,Connecting to a Remote Target}).
17027 @node Configurations
17028 @chapter Configuration-Specific Information
17030 While nearly all @value{GDBN} commands are available for all native and
17031 cross versions of the debugger, there are some exceptions. This chapter
17032 describes things that are only available in certain configurations.
17034 There are three major categories of configurations: native
17035 configurations, where the host and target are the same, embedded
17036 operating system configurations, which are usually the same for several
17037 different processor architectures, and bare embedded processors, which
17038 are quite different from each other.
17043 * Embedded Processors::
17050 This section describes details specific to particular native
17055 * BSD libkvm Interface:: Debugging BSD kernel memory images
17056 * SVR4 Process Information:: SVR4 process information
17057 * DJGPP Native:: Features specific to the DJGPP port
17058 * Cygwin Native:: Features specific to the Cygwin port
17059 * Hurd Native:: Features specific to @sc{gnu} Hurd
17060 * Neutrino:: Features specific to QNX Neutrino
17061 * Darwin:: Features specific to Darwin
17067 On HP-UX systems, if you refer to a function or variable name that
17068 begins with a dollar sign, @value{GDBN} searches for a user or system
17069 name first, before it searches for a convenience variable.
17072 @node BSD libkvm Interface
17073 @subsection BSD libkvm Interface
17076 @cindex kernel memory image
17077 @cindex kernel crash dump
17079 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17080 interface that provides a uniform interface for accessing kernel virtual
17081 memory images, including live systems and crash dumps. @value{GDBN}
17082 uses this interface to allow you to debug live kernels and kernel crash
17083 dumps on many native BSD configurations. This is implemented as a
17084 special @code{kvm} debugging target. For debugging a live system, load
17085 the currently running kernel into @value{GDBN} and connect to the
17089 (@value{GDBP}) @b{target kvm}
17092 For debugging crash dumps, provide the file name of the crash dump as an
17096 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17099 Once connected to the @code{kvm} target, the following commands are
17105 Set current context from the @dfn{Process Control Block} (PCB) address.
17108 Set current context from proc address. This command isn't available on
17109 modern FreeBSD systems.
17112 @node SVR4 Process Information
17113 @subsection SVR4 Process Information
17115 @cindex examine process image
17116 @cindex process info via @file{/proc}
17118 Many versions of SVR4 and compatible systems provide a facility called
17119 @samp{/proc} that can be used to examine the image of a running
17120 process using file-system subroutines. If @value{GDBN} is configured
17121 for an operating system with this facility, the command @code{info
17122 proc} is available to report information about the process running
17123 your program, or about any process running on your system. @code{info
17124 proc} works only on SVR4 systems that include the @code{procfs} code.
17125 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17126 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17132 @itemx info proc @var{process-id}
17133 Summarize available information about any running process. If a
17134 process ID is specified by @var{process-id}, display information about
17135 that process; otherwise display information about the program being
17136 debugged. The summary includes the debugged process ID, the command
17137 line used to invoke it, its current working directory, and its
17138 executable file's absolute file name.
17140 On some systems, @var{process-id} can be of the form
17141 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17142 within a process. If the optional @var{pid} part is missing, it means
17143 a thread from the process being debugged (the leading @samp{/} still
17144 needs to be present, or else @value{GDBN} will interpret the number as
17145 a process ID rather than a thread ID).
17147 @item info proc mappings
17148 @cindex memory address space mappings
17149 Report the memory address space ranges accessible in the program, with
17150 information on whether the process has read, write, or execute access
17151 rights to each range. On @sc{gnu}/Linux systems, each memory range
17152 includes the object file which is mapped to that range, instead of the
17153 memory access rights to that range.
17155 @item info proc stat
17156 @itemx info proc status
17157 @cindex process detailed status information
17158 These subcommands are specific to @sc{gnu}/Linux systems. They show
17159 the process-related information, including the user ID and group ID;
17160 how many threads are there in the process; its virtual memory usage;
17161 the signals that are pending, blocked, and ignored; its TTY; its
17162 consumption of system and user time; its stack size; its @samp{nice}
17163 value; etc. For more information, see the @samp{proc} man page
17164 (type @kbd{man 5 proc} from your shell prompt).
17166 @item info proc all
17167 Show all the information about the process described under all of the
17168 above @code{info proc} subcommands.
17171 @comment These sub-options of 'info proc' were not included when
17172 @comment procfs.c was re-written. Keep their descriptions around
17173 @comment against the day when someone finds the time to put them back in.
17174 @kindex info proc times
17175 @item info proc times
17176 Starting time, user CPU time, and system CPU time for your program and
17179 @kindex info proc id
17181 Report on the process IDs related to your program: its own process ID,
17182 the ID of its parent, the process group ID, and the session ID.
17185 @item set procfs-trace
17186 @kindex set procfs-trace
17187 @cindex @code{procfs} API calls
17188 This command enables and disables tracing of @code{procfs} API calls.
17190 @item show procfs-trace
17191 @kindex show procfs-trace
17192 Show the current state of @code{procfs} API call tracing.
17194 @item set procfs-file @var{file}
17195 @kindex set procfs-file
17196 Tell @value{GDBN} to write @code{procfs} API trace to the named
17197 @var{file}. @value{GDBN} appends the trace info to the previous
17198 contents of the file. The default is to display the trace on the
17201 @item show procfs-file
17202 @kindex show procfs-file
17203 Show the file to which @code{procfs} API trace is written.
17205 @item proc-trace-entry
17206 @itemx proc-trace-exit
17207 @itemx proc-untrace-entry
17208 @itemx proc-untrace-exit
17209 @kindex proc-trace-entry
17210 @kindex proc-trace-exit
17211 @kindex proc-untrace-entry
17212 @kindex proc-untrace-exit
17213 These commands enable and disable tracing of entries into and exits
17214 from the @code{syscall} interface.
17217 @kindex info pidlist
17218 @cindex process list, QNX Neutrino
17219 For QNX Neutrino only, this command displays the list of all the
17220 processes and all the threads within each process.
17223 @kindex info meminfo
17224 @cindex mapinfo list, QNX Neutrino
17225 For QNX Neutrino only, this command displays the list of all mapinfos.
17229 @subsection Features for Debugging @sc{djgpp} Programs
17230 @cindex @sc{djgpp} debugging
17231 @cindex native @sc{djgpp} debugging
17232 @cindex MS-DOS-specific commands
17235 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17236 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17237 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17238 top of real-mode DOS systems and their emulations.
17240 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17241 defines a few commands specific to the @sc{djgpp} port. This
17242 subsection describes those commands.
17247 This is a prefix of @sc{djgpp}-specific commands which print
17248 information about the target system and important OS structures.
17251 @cindex MS-DOS system info
17252 @cindex free memory information (MS-DOS)
17253 @item info dos sysinfo
17254 This command displays assorted information about the underlying
17255 platform: the CPU type and features, the OS version and flavor, the
17256 DPMI version, and the available conventional and DPMI memory.
17261 @cindex segment descriptor tables
17262 @cindex descriptor tables display
17264 @itemx info dos ldt
17265 @itemx info dos idt
17266 These 3 commands display entries from, respectively, Global, Local,
17267 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17268 tables are data structures which store a descriptor for each segment
17269 that is currently in use. The segment's selector is an index into a
17270 descriptor table; the table entry for that index holds the
17271 descriptor's base address and limit, and its attributes and access
17274 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17275 segment (used for both data and the stack), and a DOS segment (which
17276 allows access to DOS/BIOS data structures and absolute addresses in
17277 conventional memory). However, the DPMI host will usually define
17278 additional segments in order to support the DPMI environment.
17280 @cindex garbled pointers
17281 These commands allow to display entries from the descriptor tables.
17282 Without an argument, all entries from the specified table are
17283 displayed. An argument, which should be an integer expression, means
17284 display a single entry whose index is given by the argument. For
17285 example, here's a convenient way to display information about the
17286 debugged program's data segment:
17289 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17290 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17294 This comes in handy when you want to see whether a pointer is outside
17295 the data segment's limit (i.e.@: @dfn{garbled}).
17297 @cindex page tables display (MS-DOS)
17299 @itemx info dos pte
17300 These two commands display entries from, respectively, the Page
17301 Directory and the Page Tables. Page Directories and Page Tables are
17302 data structures which control how virtual memory addresses are mapped
17303 into physical addresses. A Page Table includes an entry for every
17304 page of memory that is mapped into the program's address space; there
17305 may be several Page Tables, each one holding up to 4096 entries. A
17306 Page Directory has up to 4096 entries, one each for every Page Table
17307 that is currently in use.
17309 Without an argument, @kbd{info dos pde} displays the entire Page
17310 Directory, and @kbd{info dos pte} displays all the entries in all of
17311 the Page Tables. An argument, an integer expression, given to the
17312 @kbd{info dos pde} command means display only that entry from the Page
17313 Directory table. An argument given to the @kbd{info dos pte} command
17314 means display entries from a single Page Table, the one pointed to by
17315 the specified entry in the Page Directory.
17317 @cindex direct memory access (DMA) on MS-DOS
17318 These commands are useful when your program uses @dfn{DMA} (Direct
17319 Memory Access), which needs physical addresses to program the DMA
17322 These commands are supported only with some DPMI servers.
17324 @cindex physical address from linear address
17325 @item info dos address-pte @var{addr}
17326 This command displays the Page Table entry for a specified linear
17327 address. The argument @var{addr} is a linear address which should
17328 already have the appropriate segment's base address added to it,
17329 because this command accepts addresses which may belong to @emph{any}
17330 segment. For example, here's how to display the Page Table entry for
17331 the page where a variable @code{i} is stored:
17334 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17335 @exdent @code{Page Table entry for address 0x11a00d30:}
17336 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17340 This says that @code{i} is stored at offset @code{0xd30} from the page
17341 whose physical base address is @code{0x02698000}, and shows all the
17342 attributes of that page.
17344 Note that you must cast the addresses of variables to a @code{char *},
17345 since otherwise the value of @code{__djgpp_base_address}, the base
17346 address of all variables and functions in a @sc{djgpp} program, will
17347 be added using the rules of C pointer arithmetics: if @code{i} is
17348 declared an @code{int}, @value{GDBN} will add 4 times the value of
17349 @code{__djgpp_base_address} to the address of @code{i}.
17351 Here's another example, it displays the Page Table entry for the
17355 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17356 @exdent @code{Page Table entry for address 0x29110:}
17357 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17361 (The @code{+ 3} offset is because the transfer buffer's address is the
17362 3rd member of the @code{_go32_info_block} structure.) The output
17363 clearly shows that this DPMI server maps the addresses in conventional
17364 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17365 linear (@code{0x29110}) addresses are identical.
17367 This command is supported only with some DPMI servers.
17370 @cindex DOS serial data link, remote debugging
17371 In addition to native debugging, the DJGPP port supports remote
17372 debugging via a serial data link. The following commands are specific
17373 to remote serial debugging in the DJGPP port of @value{GDBN}.
17376 @kindex set com1base
17377 @kindex set com1irq
17378 @kindex set com2base
17379 @kindex set com2irq
17380 @kindex set com3base
17381 @kindex set com3irq
17382 @kindex set com4base
17383 @kindex set com4irq
17384 @item set com1base @var{addr}
17385 This command sets the base I/O port address of the @file{COM1} serial
17388 @item set com1irq @var{irq}
17389 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
17390 for the @file{COM1} serial port.
17392 There are similar commands @samp{set com2base}, @samp{set com3irq},
17393 etc.@: for setting the port address and the @code{IRQ} lines for the
17396 @kindex show com1base
17397 @kindex show com1irq
17398 @kindex show com2base
17399 @kindex show com2irq
17400 @kindex show com3base
17401 @kindex show com3irq
17402 @kindex show com4base
17403 @kindex show com4irq
17404 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
17405 display the current settings of the base address and the @code{IRQ}
17406 lines used by the COM ports.
17409 @kindex info serial
17410 @cindex DOS serial port status
17411 This command prints the status of the 4 DOS serial ports. For each
17412 port, it prints whether it's active or not, its I/O base address and
17413 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
17414 counts of various errors encountered so far.
17418 @node Cygwin Native
17419 @subsection Features for Debugging MS Windows PE Executables
17420 @cindex MS Windows debugging
17421 @cindex native Cygwin debugging
17422 @cindex Cygwin-specific commands
17424 @value{GDBN} supports native debugging of MS Windows programs, including
17425 DLLs with and without symbolic debugging information.
17427 @cindex Ctrl-BREAK, MS-Windows
17428 @cindex interrupt debuggee on MS-Windows
17429 MS-Windows programs that call @code{SetConsoleMode} to switch off the
17430 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
17431 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
17432 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
17433 sequence, which can be used to interrupt the debuggee even if it
17436 There are various additional Cygwin-specific commands, described in
17437 this section. Working with DLLs that have no debugging symbols is
17438 described in @ref{Non-debug DLL Symbols}.
17443 This is a prefix of MS Windows-specific commands which print
17444 information about the target system and important OS structures.
17446 @item info w32 selector
17447 This command displays information returned by
17448 the Win32 API @code{GetThreadSelectorEntry} function.
17449 It takes an optional argument that is evaluated to
17450 a long value to give the information about this given selector.
17451 Without argument, this command displays information
17452 about the six segment registers.
17454 @item info w32 thread-information-block
17455 This command displays thread specific information stored in the
17456 Thread Information Block (readable on the X86 CPU family using @code{$fs}
17457 selector for 32-bit programs and @code{$gs} for 64-bit programs).
17461 This is a Cygwin-specific alias of @code{info shared}.
17463 @kindex dll-symbols
17465 This command loads symbols from a dll similarly to
17466 add-sym command but without the need to specify a base address.
17468 @kindex set cygwin-exceptions
17469 @cindex debugging the Cygwin DLL
17470 @cindex Cygwin DLL, debugging
17471 @item set cygwin-exceptions @var{mode}
17472 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
17473 happen inside the Cygwin DLL. If @var{mode} is @code{off},
17474 @value{GDBN} will delay recognition of exceptions, and may ignore some
17475 exceptions which seem to be caused by internal Cygwin DLL
17476 ``bookkeeping''. This option is meant primarily for debugging the
17477 Cygwin DLL itself; the default value is @code{off} to avoid annoying
17478 @value{GDBN} users with false @code{SIGSEGV} signals.
17480 @kindex show cygwin-exceptions
17481 @item show cygwin-exceptions
17482 Displays whether @value{GDBN} will break on exceptions that happen
17483 inside the Cygwin DLL itself.
17485 @kindex set new-console
17486 @item set new-console @var{mode}
17487 If @var{mode} is @code{on} the debuggee will
17488 be started in a new console on next start.
17489 If @var{mode} is @code{off}, the debuggee will
17490 be started in the same console as the debugger.
17492 @kindex show new-console
17493 @item show new-console
17494 Displays whether a new console is used
17495 when the debuggee is started.
17497 @kindex set new-group
17498 @item set new-group @var{mode}
17499 This boolean value controls whether the debuggee should
17500 start a new group or stay in the same group as the debugger.
17501 This affects the way the Windows OS handles
17504 @kindex show new-group
17505 @item show new-group
17506 Displays current value of new-group boolean.
17508 @kindex set debugevents
17509 @item set debugevents
17510 This boolean value adds debug output concerning kernel events related
17511 to the debuggee seen by the debugger. This includes events that
17512 signal thread and process creation and exit, DLL loading and
17513 unloading, console interrupts, and debugging messages produced by the
17514 Windows @code{OutputDebugString} API call.
17516 @kindex set debugexec
17517 @item set debugexec
17518 This boolean value adds debug output concerning execute events
17519 (such as resume thread) seen by the debugger.
17521 @kindex set debugexceptions
17522 @item set debugexceptions
17523 This boolean value adds debug output concerning exceptions in the
17524 debuggee seen by the debugger.
17526 @kindex set debugmemory
17527 @item set debugmemory
17528 This boolean value adds debug output concerning debuggee memory reads
17529 and writes by the debugger.
17533 This boolean values specifies whether the debuggee is called
17534 via a shell or directly (default value is on).
17538 Displays if the debuggee will be started with a shell.
17543 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
17546 @node Non-debug DLL Symbols
17547 @subsubsection Support for DLLs without Debugging Symbols
17548 @cindex DLLs with no debugging symbols
17549 @cindex Minimal symbols and DLLs
17551 Very often on windows, some of the DLLs that your program relies on do
17552 not include symbolic debugging information (for example,
17553 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
17554 symbols in a DLL, it relies on the minimal amount of symbolic
17555 information contained in the DLL's export table. This section
17556 describes working with such symbols, known internally to @value{GDBN} as
17557 ``minimal symbols''.
17559 Note that before the debugged program has started execution, no DLLs
17560 will have been loaded. The easiest way around this problem is simply to
17561 start the program --- either by setting a breakpoint or letting the
17562 program run once to completion. It is also possible to force
17563 @value{GDBN} to load a particular DLL before starting the executable ---
17564 see the shared library information in @ref{Files}, or the
17565 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
17566 explicitly loading symbols from a DLL with no debugging information will
17567 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
17568 which may adversely affect symbol lookup performance.
17570 @subsubsection DLL Name Prefixes
17572 In keeping with the naming conventions used by the Microsoft debugging
17573 tools, DLL export symbols are made available with a prefix based on the
17574 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
17575 also entered into the symbol table, so @code{CreateFileA} is often
17576 sufficient. In some cases there will be name clashes within a program
17577 (particularly if the executable itself includes full debugging symbols)
17578 necessitating the use of the fully qualified name when referring to the
17579 contents of the DLL. Use single-quotes around the name to avoid the
17580 exclamation mark (``!'') being interpreted as a language operator.
17582 Note that the internal name of the DLL may be all upper-case, even
17583 though the file name of the DLL is lower-case, or vice-versa. Since
17584 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
17585 some confusion. If in doubt, try the @code{info functions} and
17586 @code{info variables} commands or even @code{maint print msymbols}
17587 (@pxref{Symbols}). Here's an example:
17590 (@value{GDBP}) info function CreateFileA
17591 All functions matching regular expression "CreateFileA":
17593 Non-debugging symbols:
17594 0x77e885f4 CreateFileA
17595 0x77e885f4 KERNEL32!CreateFileA
17599 (@value{GDBP}) info function !
17600 All functions matching regular expression "!":
17602 Non-debugging symbols:
17603 0x6100114c cygwin1!__assert
17604 0x61004034 cygwin1!_dll_crt0@@0
17605 0x61004240 cygwin1!dll_crt0(per_process *)
17609 @subsubsection Working with Minimal Symbols
17611 Symbols extracted from a DLL's export table do not contain very much
17612 type information. All that @value{GDBN} can do is guess whether a symbol
17613 refers to a function or variable depending on the linker section that
17614 contains the symbol. Also note that the actual contents of the memory
17615 contained in a DLL are not available unless the program is running. This
17616 means that you cannot examine the contents of a variable or disassemble
17617 a function within a DLL without a running program.
17619 Variables are generally treated as pointers and dereferenced
17620 automatically. For this reason, it is often necessary to prefix a
17621 variable name with the address-of operator (``&'') and provide explicit
17622 type information in the command. Here's an example of the type of
17626 (@value{GDBP}) print 'cygwin1!__argv'
17631 (@value{GDBP}) x 'cygwin1!__argv'
17632 0x10021610: "\230y\""
17635 And two possible solutions:
17638 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
17639 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
17643 (@value{GDBP}) x/2x &'cygwin1!__argv'
17644 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
17645 (@value{GDBP}) x/x 0x10021608
17646 0x10021608: 0x0022fd98
17647 (@value{GDBP}) x/s 0x0022fd98
17648 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
17651 Setting a break point within a DLL is possible even before the program
17652 starts execution. However, under these circumstances, @value{GDBN} can't
17653 examine the initial instructions of the function in order to skip the
17654 function's frame set-up code. You can work around this by using ``*&''
17655 to set the breakpoint at a raw memory address:
17658 (@value{GDBP}) break *&'python22!PyOS_Readline'
17659 Breakpoint 1 at 0x1e04eff0
17662 The author of these extensions is not entirely convinced that setting a
17663 break point within a shared DLL like @file{kernel32.dll} is completely
17667 @subsection Commands Specific to @sc{gnu} Hurd Systems
17668 @cindex @sc{gnu} Hurd debugging
17670 This subsection describes @value{GDBN} commands specific to the
17671 @sc{gnu} Hurd native debugging.
17676 @kindex set signals@r{, Hurd command}
17677 @kindex set sigs@r{, Hurd command}
17678 This command toggles the state of inferior signal interception by
17679 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
17680 affected by this command. @code{sigs} is a shorthand alias for
17685 @kindex show signals@r{, Hurd command}
17686 @kindex show sigs@r{, Hurd command}
17687 Show the current state of intercepting inferior's signals.
17689 @item set signal-thread
17690 @itemx set sigthread
17691 @kindex set signal-thread
17692 @kindex set sigthread
17693 This command tells @value{GDBN} which thread is the @code{libc} signal
17694 thread. That thread is run when a signal is delivered to a running
17695 process. @code{set sigthread} is the shorthand alias of @code{set
17698 @item show signal-thread
17699 @itemx show sigthread
17700 @kindex show signal-thread
17701 @kindex show sigthread
17702 These two commands show which thread will run when the inferior is
17703 delivered a signal.
17706 @kindex set stopped@r{, Hurd command}
17707 This commands tells @value{GDBN} that the inferior process is stopped,
17708 as with the @code{SIGSTOP} signal. The stopped process can be
17709 continued by delivering a signal to it.
17712 @kindex show stopped@r{, Hurd command}
17713 This command shows whether @value{GDBN} thinks the debuggee is
17716 @item set exceptions
17717 @kindex set exceptions@r{, Hurd command}
17718 Use this command to turn off trapping of exceptions in the inferior.
17719 When exception trapping is off, neither breakpoints nor
17720 single-stepping will work. To restore the default, set exception
17723 @item show exceptions
17724 @kindex show exceptions@r{, Hurd command}
17725 Show the current state of trapping exceptions in the inferior.
17727 @item set task pause
17728 @kindex set task@r{, Hurd commands}
17729 @cindex task attributes (@sc{gnu} Hurd)
17730 @cindex pause current task (@sc{gnu} Hurd)
17731 This command toggles task suspension when @value{GDBN} has control.
17732 Setting it to on takes effect immediately, and the task is suspended
17733 whenever @value{GDBN} gets control. Setting it to off will take
17734 effect the next time the inferior is continued. If this option is set
17735 to off, you can use @code{set thread default pause on} or @code{set
17736 thread pause on} (see below) to pause individual threads.
17738 @item show task pause
17739 @kindex show task@r{, Hurd commands}
17740 Show the current state of task suspension.
17742 @item set task detach-suspend-count
17743 @cindex task suspend count
17744 @cindex detach from task, @sc{gnu} Hurd
17745 This command sets the suspend count the task will be left with when
17746 @value{GDBN} detaches from it.
17748 @item show task detach-suspend-count
17749 Show the suspend count the task will be left with when detaching.
17751 @item set task exception-port
17752 @itemx set task excp
17753 @cindex task exception port, @sc{gnu} Hurd
17754 This command sets the task exception port to which @value{GDBN} will
17755 forward exceptions. The argument should be the value of the @dfn{send
17756 rights} of the task. @code{set task excp} is a shorthand alias.
17758 @item set noninvasive
17759 @cindex noninvasive task options
17760 This command switches @value{GDBN} to a mode that is the least
17761 invasive as far as interfering with the inferior is concerned. This
17762 is the same as using @code{set task pause}, @code{set exceptions}, and
17763 @code{set signals} to values opposite to the defaults.
17765 @item info send-rights
17766 @itemx info receive-rights
17767 @itemx info port-rights
17768 @itemx info port-sets
17769 @itemx info dead-names
17772 @cindex send rights, @sc{gnu} Hurd
17773 @cindex receive rights, @sc{gnu} Hurd
17774 @cindex port rights, @sc{gnu} Hurd
17775 @cindex port sets, @sc{gnu} Hurd
17776 @cindex dead names, @sc{gnu} Hurd
17777 These commands display information about, respectively, send rights,
17778 receive rights, port rights, port sets, and dead names of a task.
17779 There are also shorthand aliases: @code{info ports} for @code{info
17780 port-rights} and @code{info psets} for @code{info port-sets}.
17782 @item set thread pause
17783 @kindex set thread@r{, Hurd command}
17784 @cindex thread properties, @sc{gnu} Hurd
17785 @cindex pause current thread (@sc{gnu} Hurd)
17786 This command toggles current thread suspension when @value{GDBN} has
17787 control. Setting it to on takes effect immediately, and the current
17788 thread is suspended whenever @value{GDBN} gets control. Setting it to
17789 off will take effect the next time the inferior is continued.
17790 Normally, this command has no effect, since when @value{GDBN} has
17791 control, the whole task is suspended. However, if you used @code{set
17792 task pause off} (see above), this command comes in handy to suspend
17793 only the current thread.
17795 @item show thread pause
17796 @kindex show thread@r{, Hurd command}
17797 This command shows the state of current thread suspension.
17799 @item set thread run
17800 This command sets whether the current thread is allowed to run.
17802 @item show thread run
17803 Show whether the current thread is allowed to run.
17805 @item set thread detach-suspend-count
17806 @cindex thread suspend count, @sc{gnu} Hurd
17807 @cindex detach from thread, @sc{gnu} Hurd
17808 This command sets the suspend count @value{GDBN} will leave on a
17809 thread when detaching. This number is relative to the suspend count
17810 found by @value{GDBN} when it notices the thread; use @code{set thread
17811 takeover-suspend-count} to force it to an absolute value.
17813 @item show thread detach-suspend-count
17814 Show the suspend count @value{GDBN} will leave on the thread when
17817 @item set thread exception-port
17818 @itemx set thread excp
17819 Set the thread exception port to which to forward exceptions. This
17820 overrides the port set by @code{set task exception-port} (see above).
17821 @code{set thread excp} is the shorthand alias.
17823 @item set thread takeover-suspend-count
17824 Normally, @value{GDBN}'s thread suspend counts are relative to the
17825 value @value{GDBN} finds when it notices each thread. This command
17826 changes the suspend counts to be absolute instead.
17828 @item set thread default
17829 @itemx show thread default
17830 @cindex thread default settings, @sc{gnu} Hurd
17831 Each of the above @code{set thread} commands has a @code{set thread
17832 default} counterpart (e.g., @code{set thread default pause}, @code{set
17833 thread default exception-port}, etc.). The @code{thread default}
17834 variety of commands sets the default thread properties for all
17835 threads; you can then change the properties of individual threads with
17836 the non-default commands.
17841 @subsection QNX Neutrino
17842 @cindex QNX Neutrino
17844 @value{GDBN} provides the following commands specific to the QNX
17848 @item set debug nto-debug
17849 @kindex set debug nto-debug
17850 When set to on, enables debugging messages specific to the QNX
17853 @item show debug nto-debug
17854 @kindex show debug nto-debug
17855 Show the current state of QNX Neutrino messages.
17862 @value{GDBN} provides the following commands specific to the Darwin target:
17865 @item set debug darwin @var{num}
17866 @kindex set debug darwin
17867 When set to a non zero value, enables debugging messages specific to
17868 the Darwin support. Higher values produce more verbose output.
17870 @item show debug darwin
17871 @kindex show debug darwin
17872 Show the current state of Darwin messages.
17874 @item set debug mach-o @var{num}
17875 @kindex set debug mach-o
17876 When set to a non zero value, enables debugging messages while
17877 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
17878 file format used on Darwin for object and executable files.) Higher
17879 values produce more verbose output. This is a command to diagnose
17880 problems internal to @value{GDBN} and should not be needed in normal
17883 @item show debug mach-o
17884 @kindex show debug mach-o
17885 Show the current state of Mach-O file messages.
17887 @item set mach-exceptions on
17888 @itemx set mach-exceptions off
17889 @kindex set mach-exceptions
17890 On Darwin, faults are first reported as a Mach exception and are then
17891 mapped to a Posix signal. Use this command to turn on trapping of
17892 Mach exceptions in the inferior. This might be sometimes useful to
17893 better understand the cause of a fault. The default is off.
17895 @item show mach-exceptions
17896 @kindex show mach-exceptions
17897 Show the current state of exceptions trapping.
17902 @section Embedded Operating Systems
17904 This section describes configurations involving the debugging of
17905 embedded operating systems that are available for several different
17909 * VxWorks:: Using @value{GDBN} with VxWorks
17912 @value{GDBN} includes the ability to debug programs running on
17913 various real-time operating systems.
17916 @subsection Using @value{GDBN} with VxWorks
17922 @kindex target vxworks
17923 @item target vxworks @var{machinename}
17924 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
17925 is the target system's machine name or IP address.
17929 On VxWorks, @code{load} links @var{filename} dynamically on the
17930 current target system as well as adding its symbols in @value{GDBN}.
17932 @value{GDBN} enables developers to spawn and debug tasks running on networked
17933 VxWorks targets from a Unix host. Already-running tasks spawned from
17934 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
17935 both the Unix host and on the VxWorks target. The program
17936 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
17937 installed with the name @code{vxgdb}, to distinguish it from a
17938 @value{GDBN} for debugging programs on the host itself.)
17941 @item VxWorks-timeout @var{args}
17942 @kindex vxworks-timeout
17943 All VxWorks-based targets now support the option @code{vxworks-timeout}.
17944 This option is set by the user, and @var{args} represents the number of
17945 seconds @value{GDBN} waits for responses to rpc's. You might use this if
17946 your VxWorks target is a slow software simulator or is on the far side
17947 of a thin network line.
17950 The following information on connecting to VxWorks was current when
17951 this manual was produced; newer releases of VxWorks may use revised
17954 @findex INCLUDE_RDB
17955 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
17956 to include the remote debugging interface routines in the VxWorks
17957 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
17958 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
17959 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
17960 source debugging task @code{tRdbTask} when VxWorks is booted. For more
17961 information on configuring and remaking VxWorks, see the manufacturer's
17963 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
17965 Once you have included @file{rdb.a} in your VxWorks system image and set
17966 your Unix execution search path to find @value{GDBN}, you are ready to
17967 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
17968 @code{vxgdb}, depending on your installation).
17970 @value{GDBN} comes up showing the prompt:
17977 * VxWorks Connection:: Connecting to VxWorks
17978 * VxWorks Download:: VxWorks download
17979 * VxWorks Attach:: Running tasks
17982 @node VxWorks Connection
17983 @subsubsection Connecting to VxWorks
17985 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
17986 network. To connect to a target whose host name is ``@code{tt}'', type:
17989 (vxgdb) target vxworks tt
17993 @value{GDBN} displays messages like these:
17996 Attaching remote machine across net...
18001 @value{GDBN} then attempts to read the symbol tables of any object modules
18002 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18003 these files by searching the directories listed in the command search
18004 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18005 to find an object file, it displays a message such as:
18008 prog.o: No such file or directory.
18011 When this happens, add the appropriate directory to the search path with
18012 the @value{GDBN} command @code{path}, and execute the @code{target}
18015 @node VxWorks Download
18016 @subsubsection VxWorks Download
18018 @cindex download to VxWorks
18019 If you have connected to the VxWorks target and you want to debug an
18020 object that has not yet been loaded, you can use the @value{GDBN}
18021 @code{load} command to download a file from Unix to VxWorks
18022 incrementally. The object file given as an argument to the @code{load}
18023 command is actually opened twice: first by the VxWorks target in order
18024 to download the code, then by @value{GDBN} in order to read the symbol
18025 table. This can lead to problems if the current working directories on
18026 the two systems differ. If both systems have NFS mounted the same
18027 filesystems, you can avoid these problems by using absolute paths.
18028 Otherwise, it is simplest to set the working directory on both systems
18029 to the directory in which the object file resides, and then to reference
18030 the file by its name, without any path. For instance, a program
18031 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18032 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18033 program, type this on VxWorks:
18036 -> cd "@var{vxpath}/vw/demo/rdb"
18040 Then, in @value{GDBN}, type:
18043 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18044 (vxgdb) load prog.o
18047 @value{GDBN} displays a response similar to this:
18050 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18053 You can also use the @code{load} command to reload an object module
18054 after editing and recompiling the corresponding source file. Note that
18055 this makes @value{GDBN} delete all currently-defined breakpoints,
18056 auto-displays, and convenience variables, and to clear the value
18057 history. (This is necessary in order to preserve the integrity of
18058 debugger's data structures that reference the target system's symbol
18061 @node VxWorks Attach
18062 @subsubsection Running Tasks
18064 @cindex running VxWorks tasks
18065 You can also attach to an existing task using the @code{attach} command as
18069 (vxgdb) attach @var{task}
18073 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18074 or suspended when you attach to it. Running tasks are suspended at
18075 the time of attachment.
18077 @node Embedded Processors
18078 @section Embedded Processors
18080 This section goes into details specific to particular embedded
18083 @cindex send command to simulator
18084 Whenever a specific embedded processor has a simulator, @value{GDBN}
18085 allows to send an arbitrary command to the simulator.
18088 @item sim @var{command}
18089 @kindex sim@r{, a command}
18090 Send an arbitrary @var{command} string to the simulator. Consult the
18091 documentation for the specific simulator in use for information about
18092 acceptable commands.
18098 * M32R/D:: Renesas M32R/D
18099 * M68K:: Motorola M68K
18100 * MicroBlaze:: Xilinx MicroBlaze
18101 * MIPS Embedded:: MIPS Embedded
18102 * OpenRISC 1000:: OpenRisc 1000
18103 * PA:: HP PA Embedded
18104 * PowerPC Embedded:: PowerPC Embedded
18105 * Sparclet:: Tsqware Sparclet
18106 * Sparclite:: Fujitsu Sparclite
18107 * Z8000:: Zilog Z8000
18110 * Super-H:: Renesas Super-H
18119 @item target rdi @var{dev}
18120 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18121 use this target to communicate with both boards running the Angel
18122 monitor, or with the EmbeddedICE JTAG debug device.
18125 @item target rdp @var{dev}
18130 @value{GDBN} provides the following ARM-specific commands:
18133 @item set arm disassembler
18135 This commands selects from a list of disassembly styles. The
18136 @code{"std"} style is the standard style.
18138 @item show arm disassembler
18140 Show the current disassembly style.
18142 @item set arm apcs32
18143 @cindex ARM 32-bit mode
18144 This command toggles ARM operation mode between 32-bit and 26-bit.
18146 @item show arm apcs32
18147 Display the current usage of the ARM 32-bit mode.
18149 @item set arm fpu @var{fputype}
18150 This command sets the ARM floating-point unit (FPU) type. The
18151 argument @var{fputype} can be one of these:
18155 Determine the FPU type by querying the OS ABI.
18157 Software FPU, with mixed-endian doubles on little-endian ARM
18160 GCC-compiled FPA co-processor.
18162 Software FPU with pure-endian doubles.
18168 Show the current type of the FPU.
18171 This command forces @value{GDBN} to use the specified ABI.
18174 Show the currently used ABI.
18176 @item set arm fallback-mode (arm|thumb|auto)
18177 @value{GDBN} uses the symbol table, when available, to determine
18178 whether instructions are ARM or Thumb. This command controls
18179 @value{GDBN}'s default behavior when the symbol table is not
18180 available. The default is @samp{auto}, which causes @value{GDBN} to
18181 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18184 @item show arm fallback-mode
18185 Show the current fallback instruction mode.
18187 @item set arm force-mode (arm|thumb|auto)
18188 This command overrides use of the symbol table to determine whether
18189 instructions are ARM or Thumb. The default is @samp{auto}, which
18190 causes @value{GDBN} to use the symbol table and then the setting
18191 of @samp{set arm fallback-mode}.
18193 @item show arm force-mode
18194 Show the current forced instruction mode.
18196 @item set debug arm
18197 Toggle whether to display ARM-specific debugging messages from the ARM
18198 target support subsystem.
18200 @item show debug arm
18201 Show whether ARM-specific debugging messages are enabled.
18204 The following commands are available when an ARM target is debugged
18205 using the RDI interface:
18208 @item rdilogfile @r{[}@var{file}@r{]}
18210 @cindex ADP (Angel Debugger Protocol) logging
18211 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18212 With an argument, sets the log file to the specified @var{file}. With
18213 no argument, show the current log file name. The default log file is
18216 @item rdilogenable @r{[}@var{arg}@r{]}
18217 @kindex rdilogenable
18218 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18219 enables logging, with an argument 0 or @code{"no"} disables it. With
18220 no arguments displays the current setting. When logging is enabled,
18221 ADP packets exchanged between @value{GDBN} and the RDI target device
18222 are logged to a file.
18224 @item set rdiromatzero
18225 @kindex set rdiromatzero
18226 @cindex ROM at zero address, RDI
18227 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18228 vector catching is disabled, so that zero address can be used. If off
18229 (the default), vector catching is enabled. For this command to take
18230 effect, it needs to be invoked prior to the @code{target rdi} command.
18232 @item show rdiromatzero
18233 @kindex show rdiromatzero
18234 Show the current setting of ROM at zero address.
18236 @item set rdiheartbeat
18237 @kindex set rdiheartbeat
18238 @cindex RDI heartbeat
18239 Enable or disable RDI heartbeat packets. It is not recommended to
18240 turn on this option, since it confuses ARM and EPI JTAG interface, as
18241 well as the Angel monitor.
18243 @item show rdiheartbeat
18244 @kindex show rdiheartbeat
18245 Show the setting of RDI heartbeat packets.
18249 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18250 The @value{GDBN} ARM simulator accepts the following optional arguments.
18253 @item --swi-support=@var{type}
18254 Tell the simulator which SWI interfaces to support.
18255 @var{type} may be a comma separated list of the following values.
18256 The default value is @code{all}.
18269 @subsection Renesas M32R/D and M32R/SDI
18272 @kindex target m32r
18273 @item target m32r @var{dev}
18274 Renesas M32R/D ROM monitor.
18276 @kindex target m32rsdi
18277 @item target m32rsdi @var{dev}
18278 Renesas M32R SDI server, connected via parallel port to the board.
18281 The following @value{GDBN} commands are specific to the M32R monitor:
18284 @item set download-path @var{path}
18285 @kindex set download-path
18286 @cindex find downloadable @sc{srec} files (M32R)
18287 Set the default path for finding downloadable @sc{srec} files.
18289 @item show download-path
18290 @kindex show download-path
18291 Show the default path for downloadable @sc{srec} files.
18293 @item set board-address @var{addr}
18294 @kindex set board-address
18295 @cindex M32-EVA target board address
18296 Set the IP address for the M32R-EVA target board.
18298 @item show board-address
18299 @kindex show board-address
18300 Show the current IP address of the target board.
18302 @item set server-address @var{addr}
18303 @kindex set server-address
18304 @cindex download server address (M32R)
18305 Set the IP address for the download server, which is the @value{GDBN}'s
18308 @item show server-address
18309 @kindex show server-address
18310 Display the IP address of the download server.
18312 @item upload @r{[}@var{file}@r{]}
18313 @kindex upload@r{, M32R}
18314 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18315 upload capability. If no @var{file} argument is given, the current
18316 executable file is uploaded.
18318 @item tload @r{[}@var{file}@r{]}
18319 @kindex tload@r{, M32R}
18320 Test the @code{upload} command.
18323 The following commands are available for M32R/SDI:
18328 @cindex reset SDI connection, M32R
18329 This command resets the SDI connection.
18333 This command shows the SDI connection status.
18336 @kindex debug_chaos
18337 @cindex M32R/Chaos debugging
18338 Instructs the remote that M32R/Chaos debugging is to be used.
18340 @item use_debug_dma
18341 @kindex use_debug_dma
18342 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18345 @kindex use_mon_code
18346 Instructs the remote to use the MON_CODE method of accessing memory.
18349 @kindex use_ib_break
18350 Instructs the remote to set breakpoints by IB break.
18352 @item use_dbt_break
18353 @kindex use_dbt_break
18354 Instructs the remote to set breakpoints by DBT.
18360 The Motorola m68k configuration includes ColdFire support, and a
18361 target command for the following ROM monitor.
18365 @kindex target dbug
18366 @item target dbug @var{dev}
18367 dBUG ROM monitor for Motorola ColdFire.
18372 @subsection MicroBlaze
18373 @cindex Xilinx MicroBlaze
18374 @cindex XMD, Xilinx Microprocessor Debugger
18376 The MicroBlaze is a soft-core processor supported on various Xilinx
18377 FPGAs, such as Spartan or Virtex series. Boards with these processors
18378 usually have JTAG ports which connect to a host system running the Xilinx
18379 Embedded Development Kit (EDK) or Software Development Kit (SDK).
18380 This host system is used to download the configuration bitstream to
18381 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
18382 communicates with the target board using the JTAG interface and
18383 presents a @code{gdbserver} interface to the board. By default
18384 @code{xmd} uses port @code{1234}. (While it is possible to change
18385 this default port, it requires the use of undocumented @code{xmd}
18386 commands. Contact Xilinx support if you need to do this.)
18388 Use these GDB commands to connect to the MicroBlaze target processor.
18391 @item target remote :1234
18392 Use this command to connect to the target if you are running @value{GDBN}
18393 on the same system as @code{xmd}.
18395 @item target remote @var{xmd-host}:1234
18396 Use this command to connect to the target if it is connected to @code{xmd}
18397 running on a different system named @var{xmd-host}.
18400 Use this command to download a program to the MicroBlaze target.
18402 @item set debug microblaze @var{n}
18403 Enable MicroBlaze-specific debugging messages if non-zero.
18405 @item show debug microblaze @var{n}
18406 Show MicroBlaze-specific debugging level.
18409 @node MIPS Embedded
18410 @subsection MIPS Embedded
18412 @cindex MIPS boards
18413 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
18414 MIPS board attached to a serial line. This is available when
18415 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
18418 Use these @value{GDBN} commands to specify the connection to your target board:
18421 @item target mips @var{port}
18422 @kindex target mips @var{port}
18423 To run a program on the board, start up @code{@value{GDBP}} with the
18424 name of your program as the argument. To connect to the board, use the
18425 command @samp{target mips @var{port}}, where @var{port} is the name of
18426 the serial port connected to the board. If the program has not already
18427 been downloaded to the board, you may use the @code{load} command to
18428 download it. You can then use all the usual @value{GDBN} commands.
18430 For example, this sequence connects to the target board through a serial
18431 port, and loads and runs a program called @var{prog} through the
18435 host$ @value{GDBP} @var{prog}
18436 @value{GDBN} is free software and @dots{}
18437 (@value{GDBP}) target mips /dev/ttyb
18438 (@value{GDBP}) load @var{prog}
18442 @item target mips @var{hostname}:@var{portnumber}
18443 On some @value{GDBN} host configurations, you can specify a TCP
18444 connection (for instance, to a serial line managed by a terminal
18445 concentrator) instead of a serial port, using the syntax
18446 @samp{@var{hostname}:@var{portnumber}}.
18448 @item target pmon @var{port}
18449 @kindex target pmon @var{port}
18452 @item target ddb @var{port}
18453 @kindex target ddb @var{port}
18454 NEC's DDB variant of PMON for Vr4300.
18456 @item target lsi @var{port}
18457 @kindex target lsi @var{port}
18458 LSI variant of PMON.
18460 @kindex target r3900
18461 @item target r3900 @var{dev}
18462 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
18464 @kindex target array
18465 @item target array @var{dev}
18466 Array Tech LSI33K RAID controller board.
18472 @value{GDBN} also supports these special commands for MIPS targets:
18475 @item set mipsfpu double
18476 @itemx set mipsfpu single
18477 @itemx set mipsfpu none
18478 @itemx set mipsfpu auto
18479 @itemx show mipsfpu
18480 @kindex set mipsfpu
18481 @kindex show mipsfpu
18482 @cindex MIPS remote floating point
18483 @cindex floating point, MIPS remote
18484 If your target board does not support the MIPS floating point
18485 coprocessor, you should use the command @samp{set mipsfpu none} (if you
18486 need this, you may wish to put the command in your @value{GDBN} init
18487 file). This tells @value{GDBN} how to find the return value of
18488 functions which return floating point values. It also allows
18489 @value{GDBN} to avoid saving the floating point registers when calling
18490 functions on the board. If you are using a floating point coprocessor
18491 with only single precision floating point support, as on the @sc{r4650}
18492 processor, use the command @samp{set mipsfpu single}. The default
18493 double precision floating point coprocessor may be selected using
18494 @samp{set mipsfpu double}.
18496 In previous versions the only choices were double precision or no
18497 floating point, so @samp{set mipsfpu on} will select double precision
18498 and @samp{set mipsfpu off} will select no floating point.
18500 As usual, you can inquire about the @code{mipsfpu} variable with
18501 @samp{show mipsfpu}.
18503 @item set timeout @var{seconds}
18504 @itemx set retransmit-timeout @var{seconds}
18505 @itemx show timeout
18506 @itemx show retransmit-timeout
18507 @cindex @code{timeout}, MIPS protocol
18508 @cindex @code{retransmit-timeout}, MIPS protocol
18509 @kindex set timeout
18510 @kindex show timeout
18511 @kindex set retransmit-timeout
18512 @kindex show retransmit-timeout
18513 You can control the timeout used while waiting for a packet, in the MIPS
18514 remote protocol, with the @code{set timeout @var{seconds}} command. The
18515 default is 5 seconds. Similarly, you can control the timeout used while
18516 waiting for an acknowledgment of a packet with the @code{set
18517 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
18518 You can inspect both values with @code{show timeout} and @code{show
18519 retransmit-timeout}. (These commands are @emph{only} available when
18520 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
18522 The timeout set by @code{set timeout} does not apply when @value{GDBN}
18523 is waiting for your program to stop. In that case, @value{GDBN} waits
18524 forever because it has no way of knowing how long the program is going
18525 to run before stopping.
18527 @item set syn-garbage-limit @var{num}
18528 @kindex set syn-garbage-limit@r{, MIPS remote}
18529 @cindex synchronize with remote MIPS target
18530 Limit the maximum number of characters @value{GDBN} should ignore when
18531 it tries to synchronize with the remote target. The default is 10
18532 characters. Setting the limit to -1 means there's no limit.
18534 @item show syn-garbage-limit
18535 @kindex show syn-garbage-limit@r{, MIPS remote}
18536 Show the current limit on the number of characters to ignore when
18537 trying to synchronize with the remote system.
18539 @item set monitor-prompt @var{prompt}
18540 @kindex set monitor-prompt@r{, MIPS remote}
18541 @cindex remote monitor prompt
18542 Tell @value{GDBN} to expect the specified @var{prompt} string from the
18543 remote monitor. The default depends on the target:
18553 @item show monitor-prompt
18554 @kindex show monitor-prompt@r{, MIPS remote}
18555 Show the current strings @value{GDBN} expects as the prompt from the
18558 @item set monitor-warnings
18559 @kindex set monitor-warnings@r{, MIPS remote}
18560 Enable or disable monitor warnings about hardware breakpoints. This
18561 has effect only for the @code{lsi} target. When on, @value{GDBN} will
18562 display warning messages whose codes are returned by the @code{lsi}
18563 PMON monitor for breakpoint commands.
18565 @item show monitor-warnings
18566 @kindex show monitor-warnings@r{, MIPS remote}
18567 Show the current setting of printing monitor warnings.
18569 @item pmon @var{command}
18570 @kindex pmon@r{, MIPS remote}
18571 @cindex send PMON command
18572 This command allows sending an arbitrary @var{command} string to the
18573 monitor. The monitor must be in debug mode for this to work.
18576 @node OpenRISC 1000
18577 @subsection OpenRISC 1000
18578 @cindex OpenRISC 1000
18580 @cindex or1k boards
18581 See OR1k Architecture document (@uref{www.opencores.org}) for more information
18582 about platform and commands.
18586 @kindex target jtag
18587 @item target jtag jtag://@var{host}:@var{port}
18589 Connects to remote JTAG server.
18590 JTAG remote server can be either an or1ksim or JTAG server,
18591 connected via parallel port to the board.
18593 Example: @code{target jtag jtag://localhost:9999}
18596 @item or1ksim @var{command}
18597 If connected to @code{or1ksim} OpenRISC 1000 Architectural
18598 Simulator, proprietary commands can be executed.
18600 @kindex info or1k spr
18601 @item info or1k spr
18602 Displays spr groups.
18604 @item info or1k spr @var{group}
18605 @itemx info or1k spr @var{groupno}
18606 Displays register names in selected group.
18608 @item info or1k spr @var{group} @var{register}
18609 @itemx info or1k spr @var{register}
18610 @itemx info or1k spr @var{groupno} @var{registerno}
18611 @itemx info or1k spr @var{registerno}
18612 Shows information about specified spr register.
18615 @item spr @var{group} @var{register} @var{value}
18616 @itemx spr @var{register @var{value}}
18617 @itemx spr @var{groupno} @var{registerno @var{value}}
18618 @itemx spr @var{registerno @var{value}}
18619 Writes @var{value} to specified spr register.
18622 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
18623 It is very similar to @value{GDBN} trace, except it does not interfere with normal
18624 program execution and is thus much faster. Hardware breakpoints/watchpoint
18625 triggers can be set using:
18628 Load effective address/data
18630 Store effective address/data
18632 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
18637 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
18638 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
18640 @code{htrace} commands:
18641 @cindex OpenRISC 1000 htrace
18644 @item hwatch @var{conditional}
18645 Set hardware watchpoint on combination of Load/Store Effective Address(es)
18646 or Data. For example:
18648 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18650 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18654 Display information about current HW trace configuration.
18656 @item htrace trigger @var{conditional}
18657 Set starting criteria for HW trace.
18659 @item htrace qualifier @var{conditional}
18660 Set acquisition qualifier for HW trace.
18662 @item htrace stop @var{conditional}
18663 Set HW trace stopping criteria.
18665 @item htrace record [@var{data}]*
18666 Selects the data to be recorded, when qualifier is met and HW trace was
18669 @item htrace enable
18670 @itemx htrace disable
18671 Enables/disables the HW trace.
18673 @item htrace rewind [@var{filename}]
18674 Clears currently recorded trace data.
18676 If filename is specified, new trace file is made and any newly collected data
18677 will be written there.
18679 @item htrace print [@var{start} [@var{len}]]
18680 Prints trace buffer, using current record configuration.
18682 @item htrace mode continuous
18683 Set continuous trace mode.
18685 @item htrace mode suspend
18686 Set suspend trace mode.
18690 @node PowerPC Embedded
18691 @subsection PowerPC Embedded
18693 @cindex DVC register
18694 @value{GDBN} supports using the DVC (Data Value Compare) register to
18695 implement in hardware simple hardware watchpoint conditions of the form:
18698 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
18699 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
18702 The DVC register will be automatically used whenever @value{GDBN} detects
18703 such pattern in a condition expression. This feature is available in native
18704 @value{GDBN} running on a Linux kernel version 2.6.34 or newer.
18706 @value{GDBN} provides the following PowerPC-specific commands:
18709 @kindex set powerpc
18710 @item set powerpc soft-float
18711 @itemx show powerpc soft-float
18712 Force @value{GDBN} to use (or not use) a software floating point calling
18713 convention. By default, @value{GDBN} selects the calling convention based
18714 on the selected architecture and the provided executable file.
18716 @item set powerpc vector-abi
18717 @itemx show powerpc vector-abi
18718 Force @value{GDBN} to use the specified calling convention for vector
18719 arguments and return values. The valid options are @samp{auto};
18720 @samp{generic}, to avoid vector registers even if they are present;
18721 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
18722 registers. By default, @value{GDBN} selects the calling convention
18723 based on the selected architecture and the provided executable file.
18725 @kindex target dink32
18726 @item target dink32 @var{dev}
18727 DINK32 ROM monitor.
18729 @kindex target ppcbug
18730 @item target ppcbug @var{dev}
18731 @kindex target ppcbug1
18732 @item target ppcbug1 @var{dev}
18733 PPCBUG ROM monitor for PowerPC.
18736 @item target sds @var{dev}
18737 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
18740 @cindex SDS protocol
18741 The following commands specific to the SDS protocol are supported
18745 @item set sdstimeout @var{nsec}
18746 @kindex set sdstimeout
18747 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
18748 default is 2 seconds.
18750 @item show sdstimeout
18751 @kindex show sdstimeout
18752 Show the current value of the SDS timeout.
18754 @item sds @var{command}
18755 @kindex sds@r{, a command}
18756 Send the specified @var{command} string to the SDS monitor.
18761 @subsection HP PA Embedded
18765 @kindex target op50n
18766 @item target op50n @var{dev}
18767 OP50N monitor, running on an OKI HPPA board.
18769 @kindex target w89k
18770 @item target w89k @var{dev}
18771 W89K monitor, running on a Winbond HPPA board.
18776 @subsection Tsqware Sparclet
18780 @value{GDBN} enables developers to debug tasks running on
18781 Sparclet targets from a Unix host.
18782 @value{GDBN} uses code that runs on
18783 both the Unix host and on the Sparclet target. The program
18784 @code{@value{GDBP}} is installed and executed on the Unix host.
18787 @item remotetimeout @var{args}
18788 @kindex remotetimeout
18789 @value{GDBN} supports the option @code{remotetimeout}.
18790 This option is set by the user, and @var{args} represents the number of
18791 seconds @value{GDBN} waits for responses.
18794 @cindex compiling, on Sparclet
18795 When compiling for debugging, include the options @samp{-g} to get debug
18796 information and @samp{-Ttext} to relocate the program to where you wish to
18797 load it on the target. You may also want to add the options @samp{-n} or
18798 @samp{-N} in order to reduce the size of the sections. Example:
18801 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
18804 You can use @code{objdump} to verify that the addresses are what you intended:
18807 sparclet-aout-objdump --headers --syms prog
18810 @cindex running, on Sparclet
18812 your Unix execution search path to find @value{GDBN}, you are ready to
18813 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
18814 (or @code{sparclet-aout-gdb}, depending on your installation).
18816 @value{GDBN} comes up showing the prompt:
18823 * Sparclet File:: Setting the file to debug
18824 * Sparclet Connection:: Connecting to Sparclet
18825 * Sparclet Download:: Sparclet download
18826 * Sparclet Execution:: Running and debugging
18829 @node Sparclet File
18830 @subsubsection Setting File to Debug
18832 The @value{GDBN} command @code{file} lets you choose with program to debug.
18835 (gdbslet) file prog
18839 @value{GDBN} then attempts to read the symbol table of @file{prog}.
18840 @value{GDBN} locates
18841 the file by searching the directories listed in the command search
18843 If the file was compiled with debug information (option @samp{-g}), source
18844 files will be searched as well.
18845 @value{GDBN} locates
18846 the source files by searching the directories listed in the directory search
18847 path (@pxref{Environment, ,Your Program's Environment}).
18849 to find a file, it displays a message such as:
18852 prog: No such file or directory.
18855 When this happens, add the appropriate directories to the search paths with
18856 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
18857 @code{target} command again.
18859 @node Sparclet Connection
18860 @subsubsection Connecting to Sparclet
18862 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
18863 To connect to a target on serial port ``@code{ttya}'', type:
18866 (gdbslet) target sparclet /dev/ttya
18867 Remote target sparclet connected to /dev/ttya
18868 main () at ../prog.c:3
18872 @value{GDBN} displays messages like these:
18878 @node Sparclet Download
18879 @subsubsection Sparclet Download
18881 @cindex download to Sparclet
18882 Once connected to the Sparclet target,
18883 you can use the @value{GDBN}
18884 @code{load} command to download the file from the host to the target.
18885 The file name and load offset should be given as arguments to the @code{load}
18887 Since the file format is aout, the program must be loaded to the starting
18888 address. You can use @code{objdump} to find out what this value is. The load
18889 offset is an offset which is added to the VMA (virtual memory address)
18890 of each of the file's sections.
18891 For instance, if the program
18892 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
18893 and bss at 0x12010170, in @value{GDBN}, type:
18896 (gdbslet) load prog 0x12010000
18897 Loading section .text, size 0xdb0 vma 0x12010000
18900 If the code is loaded at a different address then what the program was linked
18901 to, you may need to use the @code{section} and @code{add-symbol-file} commands
18902 to tell @value{GDBN} where to map the symbol table.
18904 @node Sparclet Execution
18905 @subsubsection Running and Debugging
18907 @cindex running and debugging Sparclet programs
18908 You can now begin debugging the task using @value{GDBN}'s execution control
18909 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
18910 manual for the list of commands.
18914 Breakpoint 1 at 0x12010000: file prog.c, line 3.
18916 Starting program: prog
18917 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
18918 3 char *symarg = 0;
18920 4 char *execarg = "hello!";
18925 @subsection Fujitsu Sparclite
18929 @kindex target sparclite
18930 @item target sparclite @var{dev}
18931 Fujitsu sparclite boards, used only for the purpose of loading.
18932 You must use an additional command to debug the program.
18933 For example: target remote @var{dev} using @value{GDBN} standard
18939 @subsection Zilog Z8000
18942 @cindex simulator, Z8000
18943 @cindex Zilog Z8000 simulator
18945 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
18948 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
18949 unsegmented variant of the Z8000 architecture) or the Z8001 (the
18950 segmented variant). The simulator recognizes which architecture is
18951 appropriate by inspecting the object code.
18954 @item target sim @var{args}
18956 @kindex target sim@r{, with Z8000}
18957 Debug programs on a simulated CPU. If the simulator supports setup
18958 options, specify them via @var{args}.
18962 After specifying this target, you can debug programs for the simulated
18963 CPU in the same style as programs for your host computer; use the
18964 @code{file} command to load a new program image, the @code{run} command
18965 to run your program, and so on.
18967 As well as making available all the usual machine registers
18968 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
18969 additional items of information as specially named registers:
18974 Counts clock-ticks in the simulator.
18977 Counts instructions run in the simulator.
18980 Execution time in 60ths of a second.
18984 You can refer to these values in @value{GDBN} expressions with the usual
18985 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
18986 conditional breakpoint that suspends only after at least 5000
18987 simulated clock ticks.
18990 @subsection Atmel AVR
18993 When configured for debugging the Atmel AVR, @value{GDBN} supports the
18994 following AVR-specific commands:
18997 @item info io_registers
18998 @kindex info io_registers@r{, AVR}
18999 @cindex I/O registers (Atmel AVR)
19000 This command displays information about the AVR I/O registers. For
19001 each register, @value{GDBN} prints its number and value.
19008 When configured for debugging CRIS, @value{GDBN} provides the
19009 following CRIS-specific commands:
19012 @item set cris-version @var{ver}
19013 @cindex CRIS version
19014 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19015 The CRIS version affects register names and sizes. This command is useful in
19016 case autodetection of the CRIS version fails.
19018 @item show cris-version
19019 Show the current CRIS version.
19021 @item set cris-dwarf2-cfi
19022 @cindex DWARF-2 CFI and CRIS
19023 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19024 Change to @samp{off} when using @code{gcc-cris} whose version is below
19027 @item show cris-dwarf2-cfi
19028 Show the current state of using DWARF-2 CFI.
19030 @item set cris-mode @var{mode}
19032 Set the current CRIS mode to @var{mode}. It should only be changed when
19033 debugging in guru mode, in which case it should be set to
19034 @samp{guru} (the default is @samp{normal}).
19036 @item show cris-mode
19037 Show the current CRIS mode.
19041 @subsection Renesas Super-H
19044 For the Renesas Super-H processor, @value{GDBN} provides these
19049 @kindex regs@r{, Super-H}
19050 Show the values of all Super-H registers.
19052 @item set sh calling-convention @var{convention}
19053 @kindex set sh calling-convention
19054 Set the calling-convention used when calling functions from @value{GDBN}.
19055 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19056 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19057 convention. If the DWARF-2 information of the called function specifies
19058 that the function follows the Renesas calling convention, the function
19059 is called using the Renesas calling convention. If the calling convention
19060 is set to @samp{renesas}, the Renesas calling convention is always used,
19061 regardless of the DWARF-2 information. This can be used to override the
19062 default of @samp{gcc} if debug information is missing, or the compiler
19063 does not emit the DWARF-2 calling convention entry for a function.
19065 @item show sh calling-convention
19066 @kindex show sh calling-convention
19067 Show the current calling convention setting.
19072 @node Architectures
19073 @section Architectures
19075 This section describes characteristics of architectures that affect
19076 all uses of @value{GDBN} with the architecture, both native and cross.
19083 * HPPA:: HP PA architecture
19084 * SPU:: Cell Broadband Engine SPU architecture
19089 @subsection x86 Architecture-specific Issues
19092 @item set struct-convention @var{mode}
19093 @kindex set struct-convention
19094 @cindex struct return convention
19095 @cindex struct/union returned in registers
19096 Set the convention used by the inferior to return @code{struct}s and
19097 @code{union}s from functions to @var{mode}. Possible values of
19098 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19099 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19100 are returned on the stack, while @code{"reg"} means that a
19101 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19102 be returned in a register.
19104 @item show struct-convention
19105 @kindex show struct-convention
19106 Show the current setting of the convention to return @code{struct}s
19115 @kindex set rstack_high_address
19116 @cindex AMD 29K register stack
19117 @cindex register stack, AMD29K
19118 @item set rstack_high_address @var{address}
19119 On AMD 29000 family processors, registers are saved in a separate
19120 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19121 extent of this stack. Normally, @value{GDBN} just assumes that the
19122 stack is ``large enough''. This may result in @value{GDBN} referencing
19123 memory locations that do not exist. If necessary, you can get around
19124 this problem by specifying the ending address of the register stack with
19125 the @code{set rstack_high_address} command. The argument should be an
19126 address, which you probably want to precede with @samp{0x} to specify in
19129 @kindex show rstack_high_address
19130 @item show rstack_high_address
19131 Display the current limit of the register stack, on AMD 29000 family
19139 See the following section.
19144 @cindex stack on Alpha
19145 @cindex stack on MIPS
19146 @cindex Alpha stack
19148 Alpha- and MIPS-based computers use an unusual stack frame, which
19149 sometimes requires @value{GDBN} to search backward in the object code to
19150 find the beginning of a function.
19152 @cindex response time, MIPS debugging
19153 To improve response time (especially for embedded applications, where
19154 @value{GDBN} may be restricted to a slow serial line for this search)
19155 you may want to limit the size of this search, using one of these
19159 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19160 @item set heuristic-fence-post @var{limit}
19161 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19162 search for the beginning of a function. A value of @var{0} (the
19163 default) means there is no limit. However, except for @var{0}, the
19164 larger the limit the more bytes @code{heuristic-fence-post} must search
19165 and therefore the longer it takes to run. You should only need to use
19166 this command when debugging a stripped executable.
19168 @item show heuristic-fence-post
19169 Display the current limit.
19173 These commands are available @emph{only} when @value{GDBN} is configured
19174 for debugging programs on Alpha or MIPS processors.
19176 Several MIPS-specific commands are available when debugging MIPS
19180 @item set mips abi @var{arg}
19181 @kindex set mips abi
19182 @cindex set ABI for MIPS
19183 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
19184 values of @var{arg} are:
19188 The default ABI associated with the current binary (this is the
19199 @item show mips abi
19200 @kindex show mips abi
19201 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
19204 @itemx show mipsfpu
19205 @xref{MIPS Embedded, set mipsfpu}.
19207 @item set mips mask-address @var{arg}
19208 @kindex set mips mask-address
19209 @cindex MIPS addresses, masking
19210 This command determines whether the most-significant 32 bits of 64-bit
19211 MIPS addresses are masked off. The argument @var{arg} can be
19212 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
19213 setting, which lets @value{GDBN} determine the correct value.
19215 @item show mips mask-address
19216 @kindex show mips mask-address
19217 Show whether the upper 32 bits of MIPS addresses are masked off or
19220 @item set remote-mips64-transfers-32bit-regs
19221 @kindex set remote-mips64-transfers-32bit-regs
19222 This command controls compatibility with 64-bit MIPS targets that
19223 transfer data in 32-bit quantities. If you have an old MIPS 64 target
19224 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
19225 and 64 bits for other registers, set this option to @samp{on}.
19227 @item show remote-mips64-transfers-32bit-regs
19228 @kindex show remote-mips64-transfers-32bit-regs
19229 Show the current setting of compatibility with older MIPS 64 targets.
19231 @item set debug mips
19232 @kindex set debug mips
19233 This command turns on and off debugging messages for the MIPS-specific
19234 target code in @value{GDBN}.
19236 @item show debug mips
19237 @kindex show debug mips
19238 Show the current setting of MIPS debugging messages.
19244 @cindex HPPA support
19246 When @value{GDBN} is debugging the HP PA architecture, it provides the
19247 following special commands:
19250 @item set debug hppa
19251 @kindex set debug hppa
19252 This command determines whether HPPA architecture-specific debugging
19253 messages are to be displayed.
19255 @item show debug hppa
19256 Show whether HPPA debugging messages are displayed.
19258 @item maint print unwind @var{address}
19259 @kindex maint print unwind@r{, HPPA}
19260 This command displays the contents of the unwind table entry at the
19261 given @var{address}.
19267 @subsection Cell Broadband Engine SPU architecture
19268 @cindex Cell Broadband Engine
19271 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
19272 it provides the following special commands:
19275 @item info spu event
19277 Display SPU event facility status. Shows current event mask
19278 and pending event status.
19280 @item info spu signal
19281 Display SPU signal notification facility status. Shows pending
19282 signal-control word and signal notification mode of both signal
19283 notification channels.
19285 @item info spu mailbox
19286 Display SPU mailbox facility status. Shows all pending entries,
19287 in order of processing, in each of the SPU Write Outbound,
19288 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
19291 Display MFC DMA status. Shows all pending commands in the MFC
19292 DMA queue. For each entry, opcode, tag, class IDs, effective
19293 and local store addresses and transfer size are shown.
19295 @item info spu proxydma
19296 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
19297 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
19298 and local store addresses and transfer size are shown.
19302 When @value{GDBN} is debugging a combined PowerPC/SPU application
19303 on the Cell Broadband Engine, it provides in addition the following
19307 @item set spu stop-on-load @var{arg}
19309 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
19310 will give control to the user when a new SPE thread enters its @code{main}
19311 function. The default is @code{off}.
19313 @item show spu stop-on-load
19315 Show whether to stop for new SPE threads.
19317 @item set spu auto-flush-cache @var{arg}
19318 Set whether to automatically flush the software-managed cache. When set to
19319 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19320 cache to be flushed whenever SPE execution stops. This provides a consistent
19321 view of PowerPC memory that is accessed via the cache. If an application
19322 does not use the software-managed cache, this option has no effect.
19324 @item show spu auto-flush-cache
19325 Show whether to automatically flush the software-managed cache.
19330 @subsection PowerPC
19331 @cindex PowerPC architecture
19333 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
19334 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
19335 numbers stored in the floating point registers. These values must be stored
19336 in two consecutive registers, always starting at an even register like
19337 @code{f0} or @code{f2}.
19339 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
19340 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
19341 @code{f2} and @code{f3} for @code{$dl1} and so on.
19343 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
19344 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
19347 @node Controlling GDB
19348 @chapter Controlling @value{GDBN}
19350 You can alter the way @value{GDBN} interacts with you by using the
19351 @code{set} command. For commands controlling how @value{GDBN} displays
19352 data, see @ref{Print Settings, ,Print Settings}. Other settings are
19357 * Editing:: Command editing
19358 * Command History:: Command history
19359 * Screen Size:: Screen size
19360 * Numbers:: Numbers
19361 * ABI:: Configuring the current ABI
19362 * Messages/Warnings:: Optional warnings and messages
19363 * Debugging Output:: Optional messages about internal happenings
19364 * Other Misc Settings:: Other Miscellaneous Settings
19372 @value{GDBN} indicates its readiness to read a command by printing a string
19373 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
19374 can change the prompt string with the @code{set prompt} command. For
19375 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
19376 the prompt in one of the @value{GDBN} sessions so that you can always tell
19377 which one you are talking to.
19379 @emph{Note:} @code{set prompt} does not add a space for you after the
19380 prompt you set. This allows you to set a prompt which ends in a space
19381 or a prompt that does not.
19385 @item set prompt @var{newprompt}
19386 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
19388 @kindex show prompt
19390 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
19394 @section Command Editing
19396 @cindex command line editing
19398 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
19399 @sc{gnu} library provides consistent behavior for programs which provide a
19400 command line interface to the user. Advantages are @sc{gnu} Emacs-style
19401 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
19402 substitution, and a storage and recall of command history across
19403 debugging sessions.
19405 You may control the behavior of command line editing in @value{GDBN} with the
19406 command @code{set}.
19409 @kindex set editing
19412 @itemx set editing on
19413 Enable command line editing (enabled by default).
19415 @item set editing off
19416 Disable command line editing.
19418 @kindex show editing
19420 Show whether command line editing is enabled.
19423 @ifset SYSTEM_READLINE
19424 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
19426 @ifclear SYSTEM_READLINE
19427 @xref{Command Line Editing},
19429 for more details about the Readline
19430 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
19431 encouraged to read that chapter.
19433 @node Command History
19434 @section Command History
19435 @cindex command history
19437 @value{GDBN} can keep track of the commands you type during your
19438 debugging sessions, so that you can be certain of precisely what
19439 happened. Use these commands to manage the @value{GDBN} command
19442 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
19443 package, to provide the history facility.
19444 @ifset SYSTEM_READLINE
19445 @xref{Using History Interactively, , , history, GNU History Library},
19447 @ifclear SYSTEM_READLINE
19448 @xref{Using History Interactively},
19450 for the detailed description of the History library.
19452 To issue a command to @value{GDBN} without affecting certain aspects of
19453 the state which is seen by users, prefix it with @samp{server }
19454 (@pxref{Server Prefix}). This
19455 means that this command will not affect the command history, nor will it
19456 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
19457 pressed on a line by itself.
19459 @cindex @code{server}, command prefix
19460 The server prefix does not affect the recording of values into the value
19461 history; to print a value without recording it into the value history,
19462 use the @code{output} command instead of the @code{print} command.
19464 Here is the description of @value{GDBN} commands related to command
19468 @cindex history substitution
19469 @cindex history file
19470 @kindex set history filename
19471 @cindex @env{GDBHISTFILE}, environment variable
19472 @item set history filename @var{fname}
19473 Set the name of the @value{GDBN} command history file to @var{fname}.
19474 This is the file where @value{GDBN} reads an initial command history
19475 list, and where it writes the command history from this session when it
19476 exits. You can access this list through history expansion or through
19477 the history command editing characters listed below. This file defaults
19478 to the value of the environment variable @code{GDBHISTFILE}, or to
19479 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
19482 @cindex save command history
19483 @kindex set history save
19484 @item set history save
19485 @itemx set history save on
19486 Record command history in a file, whose name may be specified with the
19487 @code{set history filename} command. By default, this option is disabled.
19489 @item set history save off
19490 Stop recording command history in a file.
19492 @cindex history size
19493 @kindex set history size
19494 @cindex @env{HISTSIZE}, environment variable
19495 @item set history size @var{size}
19496 Set the number of commands which @value{GDBN} keeps in its history list.
19497 This defaults to the value of the environment variable
19498 @code{HISTSIZE}, or to 256 if this variable is not set.
19501 History expansion assigns special meaning to the character @kbd{!}.
19502 @ifset SYSTEM_READLINE
19503 @xref{Event Designators, , , history, GNU History Library},
19505 @ifclear SYSTEM_READLINE
19506 @xref{Event Designators},
19510 @cindex history expansion, turn on/off
19511 Since @kbd{!} is also the logical not operator in C, history expansion
19512 is off by default. If you decide to enable history expansion with the
19513 @code{set history expansion on} command, you may sometimes need to
19514 follow @kbd{!} (when it is used as logical not, in an expression) with
19515 a space or a tab to prevent it from being expanded. The readline
19516 history facilities do not attempt substitution on the strings
19517 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
19519 The commands to control history expansion are:
19522 @item set history expansion on
19523 @itemx set history expansion
19524 @kindex set history expansion
19525 Enable history expansion. History expansion is off by default.
19527 @item set history expansion off
19528 Disable history expansion.
19531 @kindex show history
19533 @itemx show history filename
19534 @itemx show history save
19535 @itemx show history size
19536 @itemx show history expansion
19537 These commands display the state of the @value{GDBN} history parameters.
19538 @code{show history} by itself displays all four states.
19543 @kindex show commands
19544 @cindex show last commands
19545 @cindex display command history
19546 @item show commands
19547 Display the last ten commands in the command history.
19549 @item show commands @var{n}
19550 Print ten commands centered on command number @var{n}.
19552 @item show commands +
19553 Print ten commands just after the commands last printed.
19557 @section Screen Size
19558 @cindex size of screen
19559 @cindex pauses in output
19561 Certain commands to @value{GDBN} may produce large amounts of
19562 information output to the screen. To help you read all of it,
19563 @value{GDBN} pauses and asks you for input at the end of each page of
19564 output. Type @key{RET} when you want to continue the output, or @kbd{q}
19565 to discard the remaining output. Also, the screen width setting
19566 determines when to wrap lines of output. Depending on what is being
19567 printed, @value{GDBN} tries to break the line at a readable place,
19568 rather than simply letting it overflow onto the following line.
19570 Normally @value{GDBN} knows the size of the screen from the terminal
19571 driver software. For example, on Unix @value{GDBN} uses the termcap data base
19572 together with the value of the @code{TERM} environment variable and the
19573 @code{stty rows} and @code{stty cols} settings. If this is not correct,
19574 you can override it with the @code{set height} and @code{set
19581 @kindex show height
19582 @item set height @var{lpp}
19584 @itemx set width @var{cpl}
19586 These @code{set} commands specify a screen height of @var{lpp} lines and
19587 a screen width of @var{cpl} characters. The associated @code{show}
19588 commands display the current settings.
19590 If you specify a height of zero lines, @value{GDBN} does not pause during
19591 output no matter how long the output is. This is useful if output is to a
19592 file or to an editor buffer.
19594 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
19595 from wrapping its output.
19597 @item set pagination on
19598 @itemx set pagination off
19599 @kindex set pagination
19600 Turn the output pagination on or off; the default is on. Turning
19601 pagination off is the alternative to @code{set height 0}. Note that
19602 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
19603 Options, -batch}) also automatically disables pagination.
19605 @item show pagination
19606 @kindex show pagination
19607 Show the current pagination mode.
19612 @cindex number representation
19613 @cindex entering numbers
19615 You can always enter numbers in octal, decimal, or hexadecimal in
19616 @value{GDBN} by the usual conventions: octal numbers begin with
19617 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
19618 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
19619 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
19620 10; likewise, the default display for numbers---when no particular
19621 format is specified---is base 10. You can change the default base for
19622 both input and output with the commands described below.
19625 @kindex set input-radix
19626 @item set input-radix @var{base}
19627 Set the default base for numeric input. Supported choices
19628 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19629 specified either unambiguously or using the current input radix; for
19633 set input-radix 012
19634 set input-radix 10.
19635 set input-radix 0xa
19639 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
19640 leaves the input radix unchanged, no matter what it was, since
19641 @samp{10}, being without any leading or trailing signs of its base, is
19642 interpreted in the current radix. Thus, if the current radix is 16,
19643 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
19646 @kindex set output-radix
19647 @item set output-radix @var{base}
19648 Set the default base for numeric display. Supported choices
19649 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19650 specified either unambiguously or using the current input radix.
19652 @kindex show input-radix
19653 @item show input-radix
19654 Display the current default base for numeric input.
19656 @kindex show output-radix
19657 @item show output-radix
19658 Display the current default base for numeric display.
19660 @item set radix @r{[}@var{base}@r{]}
19664 These commands set and show the default base for both input and output
19665 of numbers. @code{set radix} sets the radix of input and output to
19666 the same base; without an argument, it resets the radix back to its
19667 default value of 10.
19672 @section Configuring the Current ABI
19674 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
19675 application automatically. However, sometimes you need to override its
19676 conclusions. Use these commands to manage @value{GDBN}'s view of the
19683 One @value{GDBN} configuration can debug binaries for multiple operating
19684 system targets, either via remote debugging or native emulation.
19685 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
19686 but you can override its conclusion using the @code{set osabi} command.
19687 One example where this is useful is in debugging of binaries which use
19688 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
19689 not have the same identifying marks that the standard C library for your
19694 Show the OS ABI currently in use.
19697 With no argument, show the list of registered available OS ABI's.
19699 @item set osabi @var{abi}
19700 Set the current OS ABI to @var{abi}.
19703 @cindex float promotion
19705 Generally, the way that an argument of type @code{float} is passed to a
19706 function depends on whether the function is prototyped. For a prototyped
19707 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
19708 according to the architecture's convention for @code{float}. For unprototyped
19709 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
19710 @code{double} and then passed.
19712 Unfortunately, some forms of debug information do not reliably indicate whether
19713 a function is prototyped. If @value{GDBN} calls a function that is not marked
19714 as prototyped, it consults @kbd{set coerce-float-to-double}.
19717 @kindex set coerce-float-to-double
19718 @item set coerce-float-to-double
19719 @itemx set coerce-float-to-double on
19720 Arguments of type @code{float} will be promoted to @code{double} when passed
19721 to an unprototyped function. This is the default setting.
19723 @item set coerce-float-to-double off
19724 Arguments of type @code{float} will be passed directly to unprototyped
19727 @kindex show coerce-float-to-double
19728 @item show coerce-float-to-double
19729 Show the current setting of promoting @code{float} to @code{double}.
19733 @kindex show cp-abi
19734 @value{GDBN} needs to know the ABI used for your program's C@t{++}
19735 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
19736 used to build your application. @value{GDBN} only fully supports
19737 programs with a single C@t{++} ABI; if your program contains code using
19738 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
19739 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
19740 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
19741 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
19742 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
19743 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
19748 Show the C@t{++} ABI currently in use.
19751 With no argument, show the list of supported C@t{++} ABI's.
19753 @item set cp-abi @var{abi}
19754 @itemx set cp-abi auto
19755 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
19758 @node Messages/Warnings
19759 @section Optional Warnings and Messages
19761 @cindex verbose operation
19762 @cindex optional warnings
19763 By default, @value{GDBN} is silent about its inner workings. If you are
19764 running on a slow machine, you may want to use the @code{set verbose}
19765 command. This makes @value{GDBN} tell you when it does a lengthy
19766 internal operation, so you will not think it has crashed.
19768 Currently, the messages controlled by @code{set verbose} are those
19769 which announce that the symbol table for a source file is being read;
19770 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
19773 @kindex set verbose
19774 @item set verbose on
19775 Enables @value{GDBN} output of certain informational messages.
19777 @item set verbose off
19778 Disables @value{GDBN} output of certain informational messages.
19780 @kindex show verbose
19782 Displays whether @code{set verbose} is on or off.
19785 By default, if @value{GDBN} encounters bugs in the symbol table of an
19786 object file, it is silent; but if you are debugging a compiler, you may
19787 find this information useful (@pxref{Symbol Errors, ,Errors Reading
19792 @kindex set complaints
19793 @item set complaints @var{limit}
19794 Permits @value{GDBN} to output @var{limit} complaints about each type of
19795 unusual symbols before becoming silent about the problem. Set
19796 @var{limit} to zero to suppress all complaints; set it to a large number
19797 to prevent complaints from being suppressed.
19799 @kindex show complaints
19800 @item show complaints
19801 Displays how many symbol complaints @value{GDBN} is permitted to produce.
19805 @anchor{confirmation requests}
19806 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
19807 lot of stupid questions to confirm certain commands. For example, if
19808 you try to run a program which is already running:
19812 The program being debugged has been started already.
19813 Start it from the beginning? (y or n)
19816 If you are willing to unflinchingly face the consequences of your own
19817 commands, you can disable this ``feature'':
19821 @kindex set confirm
19823 @cindex confirmation
19824 @cindex stupid questions
19825 @item set confirm off
19826 Disables confirmation requests. Note that running @value{GDBN} with
19827 the @option{--batch} option (@pxref{Mode Options, -batch}) also
19828 automatically disables confirmation requests.
19830 @item set confirm on
19831 Enables confirmation requests (the default).
19833 @kindex show confirm
19835 Displays state of confirmation requests.
19839 @cindex command tracing
19840 If you need to debug user-defined commands or sourced files you may find it
19841 useful to enable @dfn{command tracing}. In this mode each command will be
19842 printed as it is executed, prefixed with one or more @samp{+} symbols, the
19843 quantity denoting the call depth of each command.
19846 @kindex set trace-commands
19847 @cindex command scripts, debugging
19848 @item set trace-commands on
19849 Enable command tracing.
19850 @item set trace-commands off
19851 Disable command tracing.
19852 @item show trace-commands
19853 Display the current state of command tracing.
19856 @node Debugging Output
19857 @section Optional Messages about Internal Happenings
19858 @cindex optional debugging messages
19860 @value{GDBN} has commands that enable optional debugging messages from
19861 various @value{GDBN} subsystems; normally these commands are of
19862 interest to @value{GDBN} maintainers, or when reporting a bug. This
19863 section documents those commands.
19866 @kindex set exec-done-display
19867 @item set exec-done-display
19868 Turns on or off the notification of asynchronous commands'
19869 completion. When on, @value{GDBN} will print a message when an
19870 asynchronous command finishes its execution. The default is off.
19871 @kindex show exec-done-display
19872 @item show exec-done-display
19873 Displays the current setting of asynchronous command completion
19876 @cindex gdbarch debugging info
19877 @cindex architecture debugging info
19878 @item set debug arch
19879 Turns on or off display of gdbarch debugging info. The default is off
19881 @item show debug arch
19882 Displays the current state of displaying gdbarch debugging info.
19883 @item set debug aix-thread
19884 @cindex AIX threads
19885 Display debugging messages about inner workings of the AIX thread
19887 @item show debug aix-thread
19888 Show the current state of AIX thread debugging info display.
19889 @item set debug dwarf2-die
19890 @cindex DWARF2 DIEs
19891 Dump DWARF2 DIEs after they are read in.
19892 The value is the number of nesting levels to print.
19893 A value of zero turns off the display.
19894 @item show debug dwarf2-die
19895 Show the current state of DWARF2 DIE debugging.
19896 @item set debug displaced
19897 @cindex displaced stepping debugging info
19898 Turns on or off display of @value{GDBN} debugging info for the
19899 displaced stepping support. The default is off.
19900 @item show debug displaced
19901 Displays the current state of displaying @value{GDBN} debugging info
19902 related to displaced stepping.
19903 @item set debug event
19904 @cindex event debugging info
19905 Turns on or off display of @value{GDBN} event debugging info. The
19907 @item show debug event
19908 Displays the current state of displaying @value{GDBN} event debugging
19910 @item set debug expression
19911 @cindex expression debugging info
19912 Turns on or off display of debugging info about @value{GDBN}
19913 expression parsing. The default is off.
19914 @item show debug expression
19915 Displays the current state of displaying debugging info about
19916 @value{GDBN} expression parsing.
19917 @item set debug frame
19918 @cindex frame debugging info
19919 Turns on or off display of @value{GDBN} frame debugging info. The
19921 @item show debug frame
19922 Displays the current state of displaying @value{GDBN} frame debugging
19924 @item set debug gnu-nat
19925 @cindex @sc{gnu}/Hurd debug messages
19926 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
19927 @item show debug gnu-nat
19928 Show the current state of @sc{gnu}/Hurd debugging messages.
19929 @item set debug infrun
19930 @cindex inferior debugging info
19931 Turns on or off display of @value{GDBN} debugging info for running the inferior.
19932 The default is off. @file{infrun.c} contains GDB's runtime state machine used
19933 for implementing operations such as single-stepping the inferior.
19934 @item show debug infrun
19935 Displays the current state of @value{GDBN} inferior debugging.
19936 @item set debug lin-lwp
19937 @cindex @sc{gnu}/Linux LWP debug messages
19938 @cindex Linux lightweight processes
19939 Turns on or off debugging messages from the Linux LWP debug support.
19940 @item show debug lin-lwp
19941 Show the current state of Linux LWP debugging messages.
19942 @item set debug lin-lwp-async
19943 @cindex @sc{gnu}/Linux LWP async debug messages
19944 @cindex Linux lightweight processes
19945 Turns on or off debugging messages from the Linux LWP async debug support.
19946 @item show debug lin-lwp-async
19947 Show the current state of Linux LWP async debugging messages.
19948 @item set debug observer
19949 @cindex observer debugging info
19950 Turns on or off display of @value{GDBN} observer debugging. This
19951 includes info such as the notification of observable events.
19952 @item show debug observer
19953 Displays the current state of observer debugging.
19954 @item set debug overload
19955 @cindex C@t{++} overload debugging info
19956 Turns on or off display of @value{GDBN} C@t{++} overload debugging
19957 info. This includes info such as ranking of functions, etc. The default
19959 @item show debug overload
19960 Displays the current state of displaying @value{GDBN} C@t{++} overload
19962 @cindex expression parser, debugging info
19963 @cindex debug expression parser
19964 @item set debug parser
19965 Turns on or off the display of expression parser debugging output.
19966 Internally, this sets the @code{yydebug} variable in the expression
19967 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
19968 details. The default is off.
19969 @item show debug parser
19970 Show the current state of expression parser debugging.
19971 @cindex packets, reporting on stdout
19972 @cindex serial connections, debugging
19973 @cindex debug remote protocol
19974 @cindex remote protocol debugging
19975 @cindex display remote packets
19976 @item set debug remote
19977 Turns on or off display of reports on all packets sent back and forth across
19978 the serial line to the remote machine. The info is printed on the
19979 @value{GDBN} standard output stream. The default is off.
19980 @item show debug remote
19981 Displays the state of display of remote packets.
19982 @item set debug serial
19983 Turns on or off display of @value{GDBN} serial debugging info. The
19985 @item show debug serial
19986 Displays the current state of displaying @value{GDBN} serial debugging
19988 @item set debug solib-frv
19989 @cindex FR-V shared-library debugging
19990 Turns on or off debugging messages for FR-V shared-library code.
19991 @item show debug solib-frv
19992 Display the current state of FR-V shared-library code debugging
19994 @item set debug target
19995 @cindex target debugging info
19996 Turns on or off display of @value{GDBN} target debugging info. This info
19997 includes what is going on at the target level of GDB, as it happens. The
19998 default is 0. Set it to 1 to track events, and to 2 to also track the
19999 value of large memory transfers. Changes to this flag do not take effect
20000 until the next time you connect to a target or use the @code{run} command.
20001 @item show debug target
20002 Displays the current state of displaying @value{GDBN} target debugging
20004 @item set debug timestamp
20005 @cindex timestampping debugging info
20006 Turns on or off display of timestamps with @value{GDBN} debugging info.
20007 When enabled, seconds and microseconds are displayed before each debugging
20009 @item show debug timestamp
20010 Displays the current state of displaying timestamps with @value{GDBN}
20012 @item set debugvarobj
20013 @cindex variable object debugging info
20014 Turns on or off display of @value{GDBN} variable object debugging
20015 info. The default is off.
20016 @item show debugvarobj
20017 Displays the current state of displaying @value{GDBN} variable object
20019 @item set debug xml
20020 @cindex XML parser debugging
20021 Turns on or off debugging messages for built-in XML parsers.
20022 @item show debug xml
20023 Displays the current state of XML debugging messages.
20026 @node Other Misc Settings
20027 @section Other Miscellaneous Settings
20028 @cindex miscellaneous settings
20031 @kindex set interactive-mode
20032 @item set interactive-mode
20033 If @code{on}, forces @value{GDBN} to operate interactively.
20034 If @code{off}, forces @value{GDBN} to operate non-interactively,
20035 If @code{auto} (the default), @value{GDBN} guesses which mode to use,
20036 based on whether the debugger was started in a terminal or not.
20038 In the vast majority of cases, the debugger should be able to guess
20039 correctly which mode should be used. But this setting can be useful
20040 in certain specific cases, such as running a MinGW @value{GDBN}
20041 inside a cygwin window.
20043 @kindex show interactive-mode
20044 @item show interactive-mode
20045 Displays whether the debugger is operating in interactive mode or not.
20048 @node Extending GDB
20049 @chapter Extending @value{GDBN}
20050 @cindex extending GDB
20052 @value{GDBN} provides two mechanisms for extension. The first is based
20053 on composition of @value{GDBN} commands, and the second is based on the
20054 Python scripting language.
20056 To facilitate the use of these extensions, @value{GDBN} is capable
20057 of evaluating the contents of a file. When doing so, @value{GDBN}
20058 can recognize which scripting language is being used by looking at
20059 the filename extension. Files with an unrecognized filename extension
20060 are always treated as a @value{GDBN} Command Files.
20061 @xref{Command Files,, Command files}.
20063 You can control how @value{GDBN} evaluates these files with the following
20067 @kindex set script-extension
20068 @kindex show script-extension
20069 @item set script-extension off
20070 All scripts are always evaluated as @value{GDBN} Command Files.
20072 @item set script-extension soft
20073 The debugger determines the scripting language based on filename
20074 extension. If this scripting language is supported, @value{GDBN}
20075 evaluates the script using that language. Otherwise, it evaluates
20076 the file as a @value{GDBN} Command File.
20078 @item set script-extension strict
20079 The debugger determines the scripting language based on filename
20080 extension, and evaluates the script using that language. If the
20081 language is not supported, then the evaluation fails.
20083 @item show script-extension
20084 Display the current value of the @code{script-extension} option.
20089 * Sequences:: Canned Sequences of Commands
20090 * Python:: Scripting @value{GDBN} using Python
20094 @section Canned Sequences of Commands
20096 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20097 Command Lists}), @value{GDBN} provides two ways to store sequences of
20098 commands for execution as a unit: user-defined commands and command
20102 * Define:: How to define your own commands
20103 * Hooks:: Hooks for user-defined commands
20104 * Command Files:: How to write scripts of commands to be stored in a file
20105 * Output:: Commands for controlled output
20109 @subsection User-defined Commands
20111 @cindex user-defined command
20112 @cindex arguments, to user-defined commands
20113 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20114 which you assign a new name as a command. This is done with the
20115 @code{define} command. User commands may accept up to 10 arguments
20116 separated by whitespace. Arguments are accessed within the user command
20117 via @code{$arg0@dots{}$arg9}. A trivial example:
20121 print $arg0 + $arg1 + $arg2
20126 To execute the command use:
20133 This defines the command @code{adder}, which prints the sum of
20134 its three arguments. Note the arguments are text substitutions, so they may
20135 reference variables, use complex expressions, or even perform inferior
20138 @cindex argument count in user-defined commands
20139 @cindex how many arguments (user-defined commands)
20140 In addition, @code{$argc} may be used to find out how many arguments have
20141 been passed. This expands to a number in the range 0@dots{}10.
20146 print $arg0 + $arg1
20149 print $arg0 + $arg1 + $arg2
20157 @item define @var{commandname}
20158 Define a command named @var{commandname}. If there is already a command
20159 by that name, you are asked to confirm that you want to redefine it.
20160 @var{commandname} may be a bare command name consisting of letters,
20161 numbers, dashes, and underscores. It may also start with any predefined
20162 prefix command. For example, @samp{define target my-target} creates
20163 a user-defined @samp{target my-target} command.
20165 The definition of the command is made up of other @value{GDBN} command lines,
20166 which are given following the @code{define} command. The end of these
20167 commands is marked by a line containing @code{end}.
20170 @kindex end@r{ (user-defined commands)}
20171 @item document @var{commandname}
20172 Document the user-defined command @var{commandname}, so that it can be
20173 accessed by @code{help}. The command @var{commandname} must already be
20174 defined. This command reads lines of documentation just as @code{define}
20175 reads the lines of the command definition, ending with @code{end}.
20176 After the @code{document} command is finished, @code{help} on command
20177 @var{commandname} displays the documentation you have written.
20179 You may use the @code{document} command again to change the
20180 documentation of a command. Redefining the command with @code{define}
20181 does not change the documentation.
20183 @kindex dont-repeat
20184 @cindex don't repeat command
20186 Used inside a user-defined command, this tells @value{GDBN} that this
20187 command should not be repeated when the user hits @key{RET}
20188 (@pxref{Command Syntax, repeat last command}).
20190 @kindex help user-defined
20191 @item help user-defined
20192 List all user-defined commands, with the first line of the documentation
20197 @itemx show user @var{commandname}
20198 Display the @value{GDBN} commands used to define @var{commandname} (but
20199 not its documentation). If no @var{commandname} is given, display the
20200 definitions for all user-defined commands.
20202 @cindex infinite recursion in user-defined commands
20203 @kindex show max-user-call-depth
20204 @kindex set max-user-call-depth
20205 @item show max-user-call-depth
20206 @itemx set max-user-call-depth
20207 The value of @code{max-user-call-depth} controls how many recursion
20208 levels are allowed in user-defined commands before @value{GDBN} suspects an
20209 infinite recursion and aborts the command.
20212 In addition to the above commands, user-defined commands frequently
20213 use control flow commands, described in @ref{Command Files}.
20215 When user-defined commands are executed, the
20216 commands of the definition are not printed. An error in any command
20217 stops execution of the user-defined command.
20219 If used interactively, commands that would ask for confirmation proceed
20220 without asking when used inside a user-defined command. Many @value{GDBN}
20221 commands that normally print messages to say what they are doing omit the
20222 messages when used in a user-defined command.
20225 @subsection User-defined Command Hooks
20226 @cindex command hooks
20227 @cindex hooks, for commands
20228 @cindex hooks, pre-command
20231 You may define @dfn{hooks}, which are a special kind of user-defined
20232 command. Whenever you run the command @samp{foo}, if the user-defined
20233 command @samp{hook-foo} exists, it is executed (with no arguments)
20234 before that command.
20236 @cindex hooks, post-command
20238 A hook may also be defined which is run after the command you executed.
20239 Whenever you run the command @samp{foo}, if the user-defined command
20240 @samp{hookpost-foo} exists, it is executed (with no arguments) after
20241 that command. Post-execution hooks may exist simultaneously with
20242 pre-execution hooks, for the same command.
20244 It is valid for a hook to call the command which it hooks. If this
20245 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
20247 @c It would be nice if hookpost could be passed a parameter indicating
20248 @c if the command it hooks executed properly or not. FIXME!
20250 @kindex stop@r{, a pseudo-command}
20251 In addition, a pseudo-command, @samp{stop} exists. Defining
20252 (@samp{hook-stop}) makes the associated commands execute every time
20253 execution stops in your program: before breakpoint commands are run,
20254 displays are printed, or the stack frame is printed.
20256 For example, to ignore @code{SIGALRM} signals while
20257 single-stepping, but treat them normally during normal execution,
20262 handle SIGALRM nopass
20266 handle SIGALRM pass
20269 define hook-continue
20270 handle SIGALRM pass
20274 As a further example, to hook at the beginning and end of the @code{echo}
20275 command, and to add extra text to the beginning and end of the message,
20283 define hookpost-echo
20287 (@value{GDBP}) echo Hello World
20288 <<<---Hello World--->>>
20293 You can define a hook for any single-word command in @value{GDBN}, but
20294 not for command aliases; you should define a hook for the basic command
20295 name, e.g.@: @code{backtrace} rather than @code{bt}.
20296 @c FIXME! So how does Joe User discover whether a command is an alias
20298 You can hook a multi-word command by adding @code{hook-} or
20299 @code{hookpost-} to the last word of the command, e.g.@:
20300 @samp{define target hook-remote} to add a hook to @samp{target remote}.
20302 If an error occurs during the execution of your hook, execution of
20303 @value{GDBN} commands stops and @value{GDBN} issues a prompt
20304 (before the command that you actually typed had a chance to run).
20306 If you try to define a hook which does not match any known command, you
20307 get a warning from the @code{define} command.
20309 @node Command Files
20310 @subsection Command Files
20312 @cindex command files
20313 @cindex scripting commands
20314 A command file for @value{GDBN} is a text file made of lines that are
20315 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
20316 also be included. An empty line in a command file does nothing; it
20317 does not mean to repeat the last command, as it would from the
20320 You can request the execution of a command file with the @code{source}
20321 command. Note that the @code{source} command is also used to evaluate
20322 scripts that are not Command Files. The exact behavior can be configured
20323 using the @code{script-extension} setting.
20324 @xref{Extending GDB,, Extending GDB}.
20328 @cindex execute commands from a file
20329 @item source [-s] [-v] @var{filename}
20330 Execute the command file @var{filename}.
20333 The lines in a command file are generally executed sequentially,
20334 unless the order of execution is changed by one of the
20335 @emph{flow-control commands} described below. The commands are not
20336 printed as they are executed. An error in any command terminates
20337 execution of the command file and control is returned to the console.
20339 @value{GDBN} first searches for @var{filename} in the current directory.
20340 If the file is not found there, and @var{filename} does not specify a
20341 directory, then @value{GDBN} also looks for the file on the source search path
20342 (specified with the @samp{directory} command);
20343 except that @file{$cdir} is not searched because the compilation directory
20344 is not relevant to scripts.
20346 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
20347 on the search path even if @var{filename} specifies a directory.
20348 The search is done by appending @var{filename} to each element of the
20349 search path. So, for example, if @var{filename} is @file{mylib/myscript}
20350 and the search path contains @file{/home/user} then @value{GDBN} will
20351 look for the script @file{/home/user/mylib/myscript}.
20352 The search is also done if @var{filename} is an absolute path.
20353 For example, if @var{filename} is @file{/tmp/myscript} and
20354 the search path contains @file{/home/user} then @value{GDBN} will
20355 look for the script @file{/home/user/tmp/myscript}.
20356 For DOS-like systems, if @var{filename} contains a drive specification,
20357 it is stripped before concatenation. For example, if @var{filename} is
20358 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
20359 will look for the script @file{c:/tmp/myscript}.
20361 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
20362 each command as it is executed. The option must be given before
20363 @var{filename}, and is interpreted as part of the filename anywhere else.
20365 Commands that would ask for confirmation if used interactively proceed
20366 without asking when used in a command file. Many @value{GDBN} commands that
20367 normally print messages to say what they are doing omit the messages
20368 when called from command files.
20370 @value{GDBN} also accepts command input from standard input. In this
20371 mode, normal output goes to standard output and error output goes to
20372 standard error. Errors in a command file supplied on standard input do
20373 not terminate execution of the command file---execution continues with
20377 gdb < cmds > log 2>&1
20380 (The syntax above will vary depending on the shell used.) This example
20381 will execute commands from the file @file{cmds}. All output and errors
20382 would be directed to @file{log}.
20384 Since commands stored on command files tend to be more general than
20385 commands typed interactively, they frequently need to deal with
20386 complicated situations, such as different or unexpected values of
20387 variables and symbols, changes in how the program being debugged is
20388 built, etc. @value{GDBN} provides a set of flow-control commands to
20389 deal with these complexities. Using these commands, you can write
20390 complex scripts that loop over data structures, execute commands
20391 conditionally, etc.
20398 This command allows to include in your script conditionally executed
20399 commands. The @code{if} command takes a single argument, which is an
20400 expression to evaluate. It is followed by a series of commands that
20401 are executed only if the expression is true (its value is nonzero).
20402 There can then optionally be an @code{else} line, followed by a series
20403 of commands that are only executed if the expression was false. The
20404 end of the list is marked by a line containing @code{end}.
20408 This command allows to write loops. Its syntax is similar to
20409 @code{if}: the command takes a single argument, which is an expression
20410 to evaluate, and must be followed by the commands to execute, one per
20411 line, terminated by an @code{end}. These commands are called the
20412 @dfn{body} of the loop. The commands in the body of @code{while} are
20413 executed repeatedly as long as the expression evaluates to true.
20417 This command exits the @code{while} loop in whose body it is included.
20418 Execution of the script continues after that @code{while}s @code{end}
20421 @kindex loop_continue
20422 @item loop_continue
20423 This command skips the execution of the rest of the body of commands
20424 in the @code{while} loop in whose body it is included. Execution
20425 branches to the beginning of the @code{while} loop, where it evaluates
20426 the controlling expression.
20428 @kindex end@r{ (if/else/while commands)}
20430 Terminate the block of commands that are the body of @code{if},
20431 @code{else}, or @code{while} flow-control commands.
20436 @subsection Commands for Controlled Output
20438 During the execution of a command file or a user-defined command, normal
20439 @value{GDBN} output is suppressed; the only output that appears is what is
20440 explicitly printed by the commands in the definition. This section
20441 describes three commands useful for generating exactly the output you
20446 @item echo @var{text}
20447 @c I do not consider backslash-space a standard C escape sequence
20448 @c because it is not in ANSI.
20449 Print @var{text}. Nonprinting characters can be included in
20450 @var{text} using C escape sequences, such as @samp{\n} to print a
20451 newline. @strong{No newline is printed unless you specify one.}
20452 In addition to the standard C escape sequences, a backslash followed
20453 by a space stands for a space. This is useful for displaying a
20454 string with spaces at the beginning or the end, since leading and
20455 trailing spaces are otherwise trimmed from all arguments.
20456 To print @samp{@w{ }and foo =@w{ }}, use the command
20457 @samp{echo \@w{ }and foo = \@w{ }}.
20459 A backslash at the end of @var{text} can be used, as in C, to continue
20460 the command onto subsequent lines. For example,
20463 echo This is some text\n\
20464 which is continued\n\
20465 onto several lines.\n
20468 produces the same output as
20471 echo This is some text\n
20472 echo which is continued\n
20473 echo onto several lines.\n
20477 @item output @var{expression}
20478 Print the value of @var{expression} and nothing but that value: no
20479 newlines, no @samp{$@var{nn} = }. The value is not entered in the
20480 value history either. @xref{Expressions, ,Expressions}, for more information
20483 @item output/@var{fmt} @var{expression}
20484 Print the value of @var{expression} in format @var{fmt}. You can use
20485 the same formats as for @code{print}. @xref{Output Formats,,Output
20486 Formats}, for more information.
20489 @item printf @var{template}, @var{expressions}@dots{}
20490 Print the values of one or more @var{expressions} under the control of
20491 the string @var{template}. To print several values, make
20492 @var{expressions} be a comma-separated list of individual expressions,
20493 which may be either numbers or pointers. Their values are printed as
20494 specified by @var{template}, exactly as a C program would do by
20495 executing the code below:
20498 printf (@var{template}, @var{expressions}@dots{});
20501 As in @code{C} @code{printf}, ordinary characters in @var{template}
20502 are printed verbatim, while @dfn{conversion specification} introduced
20503 by the @samp{%} character cause subsequent @var{expressions} to be
20504 evaluated, their values converted and formatted according to type and
20505 style information encoded in the conversion specifications, and then
20508 For example, you can print two values in hex like this:
20511 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
20514 @code{printf} supports all the standard @code{C} conversion
20515 specifications, including the flags and modifiers between the @samp{%}
20516 character and the conversion letter, with the following exceptions:
20520 The argument-ordering modifiers, such as @samp{2$}, are not supported.
20523 The modifier @samp{*} is not supported for specifying precision or
20527 The @samp{'} flag (for separation of digits into groups according to
20528 @code{LC_NUMERIC'}) is not supported.
20531 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
20535 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
20538 The conversion letters @samp{a} and @samp{A} are not supported.
20542 Note that the @samp{ll} type modifier is supported only if the
20543 underlying @code{C} implementation used to build @value{GDBN} supports
20544 the @code{long long int} type, and the @samp{L} type modifier is
20545 supported only if @code{long double} type is available.
20547 As in @code{C}, @code{printf} supports simple backslash-escape
20548 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
20549 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
20550 single character. Octal and hexadecimal escape sequences are not
20553 Additionally, @code{printf} supports conversion specifications for DFP
20554 (@dfn{Decimal Floating Point}) types using the following length modifiers
20555 together with a floating point specifier.
20560 @samp{H} for printing @code{Decimal32} types.
20563 @samp{D} for printing @code{Decimal64} types.
20566 @samp{DD} for printing @code{Decimal128} types.
20569 If the underlying @code{C} implementation used to build @value{GDBN} has
20570 support for the three length modifiers for DFP types, other modifiers
20571 such as width and precision will also be available for @value{GDBN} to use.
20573 In case there is no such @code{C} support, no additional modifiers will be
20574 available and the value will be printed in the standard way.
20576 Here's an example of printing DFP types using the above conversion letters:
20578 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
20582 @item eval @var{template}, @var{expressions}@dots{}
20583 Convert the values of one or more @var{expressions} under the control of
20584 the string @var{template} to a command line, and call it.
20589 @section Scripting @value{GDBN} using Python
20590 @cindex python scripting
20591 @cindex scripting with python
20593 You can script @value{GDBN} using the @uref{http://www.python.org/,
20594 Python programming language}. This feature is available only if
20595 @value{GDBN} was configured using @option{--with-python}.
20597 @cindex python directory
20598 Python scripts used by @value{GDBN} should be installed in
20599 @file{@var{data-directory}/python}, where @var{data-directory} is
20600 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
20601 This directory, known as the @dfn{python directory},
20602 is automatically added to the Python Search Path in order to allow
20603 the Python interpreter to locate all scripts installed at this location.
20606 * Python Commands:: Accessing Python from @value{GDBN}.
20607 * Python API:: Accessing @value{GDBN} from Python.
20608 * Auto-loading:: Automatically loading Python code.
20609 * Python modules:: Python modules provided by @value{GDBN}.
20612 @node Python Commands
20613 @subsection Python Commands
20614 @cindex python commands
20615 @cindex commands to access python
20617 @value{GDBN} provides one command for accessing the Python interpreter,
20618 and one related setting:
20622 @item python @r{[}@var{code}@r{]}
20623 The @code{python} command can be used to evaluate Python code.
20625 If given an argument, the @code{python} command will evaluate the
20626 argument as a Python command. For example:
20629 (@value{GDBP}) python print 23
20633 If you do not provide an argument to @code{python}, it will act as a
20634 multi-line command, like @code{define}. In this case, the Python
20635 script is made up of subsequent command lines, given after the
20636 @code{python} command. This command list is terminated using a line
20637 containing @code{end}. For example:
20640 (@value{GDBP}) python
20642 End with a line saying just "end".
20648 @kindex maint set python print-stack
20649 @item maint set python print-stack
20650 By default, @value{GDBN} will print a stack trace when an error occurs
20651 in a Python script. This can be controlled using @code{maint set
20652 python print-stack}: if @code{on}, the default, then Python stack
20653 printing is enabled; if @code{off}, then Python stack printing is
20657 It is also possible to execute a Python script from the @value{GDBN}
20661 @item source @file{script-name}
20662 The script name must end with @samp{.py} and @value{GDBN} must be configured
20663 to recognize the script language based on filename extension using
20664 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
20666 @item python execfile ("script-name")
20667 This method is based on the @code{execfile} Python built-in function,
20668 and thus is always available.
20672 @subsection Python API
20674 @cindex programming in python
20676 @cindex python stdout
20677 @cindex python pagination
20678 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
20679 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
20680 A Python program which outputs to one of these streams may have its
20681 output interrupted by the user (@pxref{Screen Size}). In this
20682 situation, a Python @code{KeyboardInterrupt} exception is thrown.
20685 * Basic Python:: Basic Python Functions.
20686 * Exception Handling::
20687 * Values From Inferior::
20688 * Types In Python:: Python representation of types.
20689 * Pretty Printing API:: Pretty-printing values.
20690 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
20691 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
20692 * Inferiors In Python:: Python representation of inferiors (processes)
20693 * Threads In Python:: Accessing inferior threads from Python.
20694 * Commands In Python:: Implementing new commands in Python.
20695 * Parameters In Python:: Adding new @value{GDBN} parameters.
20696 * Functions In Python:: Writing new convenience functions.
20697 * Progspaces In Python:: Program spaces.
20698 * Objfiles In Python:: Object files.
20699 * Frames In Python:: Accessing inferior stack frames from Python.
20700 * Blocks In Python:: Accessing frame blocks from Python.
20701 * Symbols In Python:: Python representation of symbols.
20702 * Symbol Tables In Python:: Python representation of symbol tables.
20703 * Lazy Strings In Python:: Python representation of lazy strings.
20704 * Breakpoints In Python:: Manipulating breakpoints using Python.
20708 @subsubsection Basic Python
20710 @cindex python functions
20711 @cindex python module
20713 @value{GDBN} introduces a new Python module, named @code{gdb}. All
20714 methods and classes added by @value{GDBN} are placed in this module.
20715 @value{GDBN} automatically @code{import}s the @code{gdb} module for
20716 use in all scripts evaluated by the @code{python} command.
20718 @findex gdb.PYTHONDIR
20720 A string containing the python directory (@pxref{Python}).
20723 @findex gdb.execute
20724 @defun execute command [from_tty] [to_string]
20725 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
20726 If a GDB exception happens while @var{command} runs, it is
20727 translated as described in @ref{Exception Handling,,Exception Handling}.
20729 @var{from_tty} specifies whether @value{GDBN} ought to consider this
20730 command as having originated from the user invoking it interactively.
20731 It must be a boolean value. If omitted, it defaults to @code{False}.
20733 By default, any output produced by @var{command} is sent to
20734 @value{GDBN}'s standard output. If the @var{to_string} parameter is
20735 @code{True}, then output will be collected by @code{gdb.execute} and
20736 returned as a string. The default is @code{False}, in which case the
20737 return value is @code{None}. If @var{to_string} is @code{True}, the
20738 @value{GDBN} virtual terminal will be temporarily set to unlimited width
20739 and height, and its pagination will be disabled; @pxref{Screen Size}.
20742 @findex gdb.breakpoints
20744 Return a sequence holding all of @value{GDBN}'s breakpoints.
20745 @xref{Breakpoints In Python}, for more information.
20748 @findex gdb.parameter
20749 @defun parameter parameter
20750 Return the value of a @value{GDBN} parameter. @var{parameter} is a
20751 string naming the parameter to look up; @var{parameter} may contain
20752 spaces if the parameter has a multi-part name. For example,
20753 @samp{print object} is a valid parameter name.
20755 If the named parameter does not exist, this function throws a
20756 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
20757 parameter's value is converted to a Python value of the appropriate
20758 type, and returned.
20761 @findex gdb.history
20762 @defun history number
20763 Return a value from @value{GDBN}'s value history (@pxref{Value
20764 History}). @var{number} indicates which history element to return.
20765 If @var{number} is negative, then @value{GDBN} will take its absolute value
20766 and count backward from the last element (i.e., the most recent element) to
20767 find the value to return. If @var{number} is zero, then @value{GDBN} will
20768 return the most recent element. If the element specified by @var{number}
20769 doesn't exist in the value history, a @code{gdb.error} exception will be
20772 If no exception is raised, the return value is always an instance of
20773 @code{gdb.Value} (@pxref{Values From Inferior}).
20776 @findex gdb.parse_and_eval
20777 @defun parse_and_eval expression
20778 Parse @var{expression} as an expression in the current language,
20779 evaluate it, and return the result as a @code{gdb.Value}.
20780 @var{expression} must be a string.
20782 This function can be useful when implementing a new command
20783 (@pxref{Commands In Python}), as it provides a way to parse the
20784 command's argument as an expression. It is also useful simply to
20785 compute values, for example, it is the only way to get the value of a
20786 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
20789 @findex gdb.post_event
20790 @defun post_event event
20791 Put @var{event}, a callable object taking no arguments, into
20792 @value{GDBN}'s internal event queue. This callable will be invoked at
20793 some later point, during @value{GDBN}'s event processing. Events
20794 posted using @code{post_event} will be run in the order in which they
20795 were posted; however, there is no way to know when they will be
20796 processed relative to other events inside @value{GDBN}.
20798 @value{GDBN} is not thread-safe. If your Python program uses multiple
20799 threads, you must be careful to only call @value{GDBN}-specific
20800 functions in the main @value{GDBN} thread. @code{post_event} ensures
20804 (@value{GDBP}) python
20808 > def __init__(self, message):
20809 > self.message = message;
20810 > def __call__(self):
20811 > gdb.write(self.message)
20813 >class MyThread1 (threading.Thread):
20815 > gdb.post_event(Writer("Hello "))
20817 >class MyThread2 (threading.Thread):
20819 > gdb.post_event(Writer("World\n"))
20821 >MyThread1().start()
20822 >MyThread2().start()
20824 (@value{GDBP}) Hello World
20829 @defun write string
20830 Print a string to @value{GDBN}'s paginated standard output stream.
20831 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
20832 call this function.
20837 Flush @value{GDBN}'s paginated standard output stream. Flushing
20838 @code{sys.stdout} or @code{sys.stderr} will automatically call this
20842 @findex gdb.target_charset
20843 @defun target_charset
20844 Return the name of the current target character set (@pxref{Character
20845 Sets}). This differs from @code{gdb.parameter('target-charset')} in
20846 that @samp{auto} is never returned.
20849 @findex gdb.target_wide_charset
20850 @defun target_wide_charset
20851 Return the name of the current target wide character set
20852 (@pxref{Character Sets}). This differs from
20853 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
20857 @findex gdb.solib_name
20858 @defun solib_name address
20859 Return the name of the shared library holding the given @var{address}
20860 as a string, or @code{None}.
20863 @findex gdb.decode_line
20864 @defun decode_line @r{[}expression@r{]}
20865 Return locations of the line specified by @var{expression}, or of the
20866 current line if no argument was given. This function returns a Python
20867 tuple containing two elements. The first element contains a string
20868 holding any unparsed section of @var{expression} (or @code{None} if
20869 the expression has been fully parsed). The second element contains
20870 either @code{None} or another tuple that contains all the locations
20871 that match the expression represented as @code{gdb.Symtab_and_line}
20872 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
20873 provided, it is decoded the way that @value{GDBN}'s inbuilt
20874 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
20877 @node Exception Handling
20878 @subsubsection Exception Handling
20879 @cindex python exceptions
20880 @cindex exceptions, python
20882 When executing the @code{python} command, Python exceptions
20883 uncaught within the Python code are translated to calls to
20884 @value{GDBN} error-reporting mechanism. If the command that called
20885 @code{python} does not handle the error, @value{GDBN} will
20886 terminate it and print an error message containing the Python
20887 exception name, the associated value, and the Python call stack
20888 backtrace at the point where the exception was raised. Example:
20891 (@value{GDBP}) python print foo
20892 Traceback (most recent call last):
20893 File "<string>", line 1, in <module>
20894 NameError: name 'foo' is not defined
20897 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
20898 Python code are converted to Python exceptions. The type of the
20899 Python exception depends on the error.
20903 This is the base class for most exceptions generated by @value{GDBN}.
20904 It is derived from @code{RuntimeError}, for compatibility with earlier
20905 versions of @value{GDBN}.
20907 If an error occurring in @value{GDBN} does not fit into some more
20908 specific category, then the generated exception will have this type.
20910 @item gdb.MemoryError
20911 This is a subclass of @code{gdb.error} which is thrown when an
20912 operation tried to access invalid memory in the inferior.
20914 @item KeyboardInterrupt
20915 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
20916 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
20919 In all cases, your exception handler will see the @value{GDBN} error
20920 message as its value and the Python call stack backtrace at the Python
20921 statement closest to where the @value{GDBN} error occured as the
20924 @findex gdb.GdbError
20925 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
20926 it is useful to be able to throw an exception that doesn't cause a
20927 traceback to be printed. For example, the user may have invoked the
20928 command incorrectly. Use the @code{gdb.GdbError} exception
20929 to handle this case. Example:
20933 >class HelloWorld (gdb.Command):
20934 > """Greet the whole world."""
20935 > def __init__ (self):
20936 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
20937 > def invoke (self, args, from_tty):
20938 > argv = gdb.string_to_argv (args)
20939 > if len (argv) != 0:
20940 > raise gdb.GdbError ("hello-world takes no arguments")
20941 > print "Hello, World!"
20944 (gdb) hello-world 42
20945 hello-world takes no arguments
20948 @node Values From Inferior
20949 @subsubsection Values From Inferior
20950 @cindex values from inferior, with Python
20951 @cindex python, working with values from inferior
20953 @cindex @code{gdb.Value}
20954 @value{GDBN} provides values it obtains from the inferior program in
20955 an object of type @code{gdb.Value}. @value{GDBN} uses this object
20956 for its internal bookkeeping of the inferior's values, and for
20957 fetching values when necessary.
20959 Inferior values that are simple scalars can be used directly in
20960 Python expressions that are valid for the value's data type. Here's
20961 an example for an integer or floating-point value @code{some_val}:
20968 As result of this, @code{bar} will also be a @code{gdb.Value} object
20969 whose values are of the same type as those of @code{some_val}.
20971 Inferior values that are structures or instances of some class can
20972 be accessed using the Python @dfn{dictionary syntax}. For example, if
20973 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
20974 can access its @code{foo} element with:
20977 bar = some_val['foo']
20980 Again, @code{bar} will also be a @code{gdb.Value} object.
20982 A @code{gdb.Value} that represents a function can be executed via
20983 inferior function call. Any arguments provided to the call must match
20984 the function's prototype, and must be provided in the order specified
20987 For example, @code{some_val} is a @code{gdb.Value} instance
20988 representing a function that takes two integers as arguments. To
20989 execute this function, call it like so:
20992 result = some_val (10,20)
20995 Any values returned from a function call will be stored as a
20998 The following attributes are provided:
21001 @defivar Value address
21002 If this object is addressable, this read-only attribute holds a
21003 @code{gdb.Value} object representing the address. Otherwise,
21004 this attribute holds @code{None}.
21007 @cindex optimized out value in Python
21008 @defivar Value is_optimized_out
21009 This read-only boolean attribute is true if the compiler optimized out
21010 this value, thus it is not available for fetching from the inferior.
21013 @defivar Value type
21014 The type of this @code{gdb.Value}. The value of this attribute is a
21015 @code{gdb.Type} object (@pxref{Types In Python}).
21018 @defivar Value dynamic_type
21019 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21020 type information (@acronym{RTTI}) to determine the dynamic type of the
21021 value. If this value is of class type, it will return the class in
21022 which the value is embedded, if any. If this value is of pointer or
21023 reference to a class type, it will compute the dynamic type of the
21024 referenced object, and return a pointer or reference to that type,
21025 respectively. In all other cases, it will return the value's static
21028 Note that this feature will only work when debugging a C@t{++} program
21029 that includes @acronym{RTTI} for the object in question. Otherwise,
21030 it will just return the static type of the value as in @kbd{ptype foo}
21031 (@pxref{Symbols, ptype}).
21035 The following methods are provided:
21038 @defmethod Value __init__ @var{val}
21039 Many Python values can be converted directly to a @code{gdb.Value} via
21040 this object initializer. Specifically:
21043 @item Python boolean
21044 A Python boolean is converted to the boolean type from the current
21047 @item Python integer
21048 A Python integer is converted to the C @code{long} type for the
21049 current architecture.
21052 A Python long is converted to the C @code{long long} type for the
21053 current architecture.
21056 A Python float is converted to the C @code{double} type for the
21057 current architecture.
21059 @item Python string
21060 A Python string is converted to a target string, using the current
21063 @item @code{gdb.Value}
21064 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
21066 @item @code{gdb.LazyString}
21067 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
21068 Python}), then the lazy string's @code{value} method is called, and
21069 its result is used.
21073 @defmethod Value cast type
21074 Return a new instance of @code{gdb.Value} that is the result of
21075 casting this instance to the type described by @var{type}, which must
21076 be a @code{gdb.Type} object. If the cast cannot be performed for some
21077 reason, this method throws an exception.
21080 @defmethod Value dereference
21081 For pointer data types, this method returns a new @code{gdb.Value} object
21082 whose contents is the object pointed to by the pointer. For example, if
21083 @code{foo} is a C pointer to an @code{int}, declared in your C program as
21090 then you can use the corresponding @code{gdb.Value} to access what
21091 @code{foo} points to like this:
21094 bar = foo.dereference ()
21097 The result @code{bar} will be a @code{gdb.Value} object holding the
21098 value pointed to by @code{foo}.
21101 @defmethod Value dynamic_cast type
21102 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
21103 operator were used. Consult a C@t{++} reference for details.
21106 @defmethod Value reinterpret_cast type
21107 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
21108 operator were used. Consult a C@t{++} reference for details.
21111 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
21112 If this @code{gdb.Value} represents a string, then this method
21113 converts the contents to a Python string. Otherwise, this method will
21114 throw an exception.
21116 Strings are recognized in a language-specific way; whether a given
21117 @code{gdb.Value} represents a string is determined by the current
21120 For C-like languages, a value is a string if it is a pointer to or an
21121 array of characters or ints. The string is assumed to be terminated
21122 by a zero of the appropriate width. However if the optional length
21123 argument is given, the string will be converted to that given length,
21124 ignoring any embedded zeros that the string may contain.
21126 If the optional @var{encoding} argument is given, it must be a string
21127 naming the encoding of the string in the @code{gdb.Value}, such as
21128 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
21129 the same encodings as the corresponding argument to Python's
21130 @code{string.decode} method, and the Python codec machinery will be used
21131 to convert the string. If @var{encoding} is not given, or if
21132 @var{encoding} is the empty string, then either the @code{target-charset}
21133 (@pxref{Character Sets}) will be used, or a language-specific encoding
21134 will be used, if the current language is able to supply one.
21136 The optional @var{errors} argument is the same as the corresponding
21137 argument to Python's @code{string.decode} method.
21139 If the optional @var{length} argument is given, the string will be
21140 fetched and converted to the given length.
21143 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
21144 If this @code{gdb.Value} represents a string, then this method
21145 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
21146 In Python}). Otherwise, this method will throw an exception.
21148 If the optional @var{encoding} argument is given, it must be a string
21149 naming the encoding of the @code{gdb.LazyString}. Some examples are:
21150 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
21151 @var{encoding} argument is an encoding that @value{GDBN} does
21152 recognize, @value{GDBN} will raise an error.
21154 When a lazy string is printed, the @value{GDBN} encoding machinery is
21155 used to convert the string during printing. If the optional
21156 @var{encoding} argument is not provided, or is an empty string,
21157 @value{GDBN} will automatically select the encoding most suitable for
21158 the string type. For further information on encoding in @value{GDBN}
21159 please see @ref{Character Sets}.
21161 If the optional @var{length} argument is given, the string will be
21162 fetched and encoded to the length of characters specified. If
21163 the @var{length} argument is not provided, the string will be fetched
21164 and encoded until a null of appropriate width is found.
21168 @node Types In Python
21169 @subsubsection Types In Python
21170 @cindex types in Python
21171 @cindex Python, working with types
21174 @value{GDBN} represents types from the inferior using the class
21177 The following type-related functions are available in the @code{gdb}
21180 @findex gdb.lookup_type
21181 @defun lookup_type name [block]
21182 This function looks up a type by name. @var{name} is the name of the
21183 type to look up. It must be a string.
21185 If @var{block} is given, then @var{name} is looked up in that scope.
21186 Otherwise, it is searched for globally.
21188 Ordinarily, this function will return an instance of @code{gdb.Type}.
21189 If the named type cannot be found, it will throw an exception.
21192 An instance of @code{Type} has the following attributes:
21196 The type code for this type. The type code will be one of the
21197 @code{TYPE_CODE_} constants defined below.
21200 @defivar Type sizeof
21201 The size of this type, in target @code{char} units. Usually, a
21202 target's @code{char} type will be an 8-bit byte. However, on some
21203 unusual platforms, this type may have a different size.
21207 The tag name for this type. The tag name is the name after
21208 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
21209 languages have this concept. If this type has no tag name, then
21210 @code{None} is returned.
21214 The following methods are provided:
21217 @defmethod Type fields
21218 For structure and union types, this method returns the fields. Range
21219 types have two fields, the minimum and maximum values. Enum types
21220 have one field per enum constant. Function and method types have one
21221 field per parameter. The base types of C@t{++} classes are also
21222 represented as fields. If the type has no fields, or does not fit
21223 into one of these categories, an empty sequence will be returned.
21225 Each field is an object, with some pre-defined attributes:
21228 This attribute is not available for @code{static} fields (as in
21229 C@t{++} or Java). For non-@code{static} fields, the value is the bit
21230 position of the field.
21233 The name of the field, or @code{None} for anonymous fields.
21236 This is @code{True} if the field is artificial, usually meaning that
21237 it was provided by the compiler and not the user. This attribute is
21238 always provided, and is @code{False} if the field is not artificial.
21240 @item is_base_class
21241 This is @code{True} if the field represents a base class of a C@t{++}
21242 structure. This attribute is always provided, and is @code{False}
21243 if the field is not a base class of the type that is the argument of
21244 @code{fields}, or if that type was not a C@t{++} class.
21247 If the field is packed, or is a bitfield, then this will have a
21248 non-zero value, which is the size of the field in bits. Otherwise,
21249 this will be zero; in this case the field's size is given by its type.
21252 The type of the field. This is usually an instance of @code{Type},
21253 but it can be @code{None} in some situations.
21257 @defmethod Type array @var{n1} @r{[}@var{n2}@r{]}
21258 Return a new @code{gdb.Type} object which represents an array of this
21259 type. If one argument is given, it is the inclusive upper bound of
21260 the array; in this case the lower bound is zero. If two arguments are
21261 given, the first argument is the lower bound of the array, and the
21262 second argument is the upper bound of the array. An array's length
21263 must not be negative, but the bounds can be.
21266 @defmethod Type const
21267 Return a new @code{gdb.Type} object which represents a
21268 @code{const}-qualified variant of this type.
21271 @defmethod Type volatile
21272 Return a new @code{gdb.Type} object which represents a
21273 @code{volatile}-qualified variant of this type.
21276 @defmethod Type unqualified
21277 Return a new @code{gdb.Type} object which represents an unqualified
21278 variant of this type. That is, the result is neither @code{const} nor
21282 @defmethod Type range
21283 Return a Python @code{Tuple} object that contains two elements: the
21284 low bound of the argument type and the high bound of that type. If
21285 the type does not have a range, @value{GDBN} will raise a
21286 @code{gdb.error} exception (@pxref{Exception Handling}).
21289 @defmethod Type reference
21290 Return a new @code{gdb.Type} object which represents a reference to this
21294 @defmethod Type pointer
21295 Return a new @code{gdb.Type} object which represents a pointer to this
21299 @defmethod Type strip_typedefs
21300 Return a new @code{gdb.Type} that represents the real type,
21301 after removing all layers of typedefs.
21304 @defmethod Type target
21305 Return a new @code{gdb.Type} object which represents the target type
21308 For a pointer type, the target type is the type of the pointed-to
21309 object. For an array type (meaning C-like arrays), the target type is
21310 the type of the elements of the array. For a function or method type,
21311 the target type is the type of the return value. For a complex type,
21312 the target type is the type of the elements. For a typedef, the
21313 target type is the aliased type.
21315 If the type does not have a target, this method will throw an
21319 @defmethod Type template_argument n [block]
21320 If this @code{gdb.Type} is an instantiation of a template, this will
21321 return a new @code{gdb.Type} which represents the type of the
21322 @var{n}th template argument.
21324 If this @code{gdb.Type} is not a template type, this will throw an
21325 exception. Ordinarily, only C@t{++} code will have template types.
21327 If @var{block} is given, then @var{name} is looked up in that scope.
21328 Otherwise, it is searched for globally.
21333 Each type has a code, which indicates what category this type falls
21334 into. The available type categories are represented by constants
21335 defined in the @code{gdb} module:
21338 @findex TYPE_CODE_PTR
21339 @findex gdb.TYPE_CODE_PTR
21340 @item TYPE_CODE_PTR
21341 The type is a pointer.
21343 @findex TYPE_CODE_ARRAY
21344 @findex gdb.TYPE_CODE_ARRAY
21345 @item TYPE_CODE_ARRAY
21346 The type is an array.
21348 @findex TYPE_CODE_STRUCT
21349 @findex gdb.TYPE_CODE_STRUCT
21350 @item TYPE_CODE_STRUCT
21351 The type is a structure.
21353 @findex TYPE_CODE_UNION
21354 @findex gdb.TYPE_CODE_UNION
21355 @item TYPE_CODE_UNION
21356 The type is a union.
21358 @findex TYPE_CODE_ENUM
21359 @findex gdb.TYPE_CODE_ENUM
21360 @item TYPE_CODE_ENUM
21361 The type is an enum.
21363 @findex TYPE_CODE_FLAGS
21364 @findex gdb.TYPE_CODE_FLAGS
21365 @item TYPE_CODE_FLAGS
21366 A bit flags type, used for things such as status registers.
21368 @findex TYPE_CODE_FUNC
21369 @findex gdb.TYPE_CODE_FUNC
21370 @item TYPE_CODE_FUNC
21371 The type is a function.
21373 @findex TYPE_CODE_INT
21374 @findex gdb.TYPE_CODE_INT
21375 @item TYPE_CODE_INT
21376 The type is an integer type.
21378 @findex TYPE_CODE_FLT
21379 @findex gdb.TYPE_CODE_FLT
21380 @item TYPE_CODE_FLT
21381 A floating point type.
21383 @findex TYPE_CODE_VOID
21384 @findex gdb.TYPE_CODE_VOID
21385 @item TYPE_CODE_VOID
21386 The special type @code{void}.
21388 @findex TYPE_CODE_SET
21389 @findex gdb.TYPE_CODE_SET
21390 @item TYPE_CODE_SET
21393 @findex TYPE_CODE_RANGE
21394 @findex gdb.TYPE_CODE_RANGE
21395 @item TYPE_CODE_RANGE
21396 A range type, that is, an integer type with bounds.
21398 @findex TYPE_CODE_STRING
21399 @findex gdb.TYPE_CODE_STRING
21400 @item TYPE_CODE_STRING
21401 A string type. Note that this is only used for certain languages with
21402 language-defined string types; C strings are not represented this way.
21404 @findex TYPE_CODE_BITSTRING
21405 @findex gdb.TYPE_CODE_BITSTRING
21406 @item TYPE_CODE_BITSTRING
21409 @findex TYPE_CODE_ERROR
21410 @findex gdb.TYPE_CODE_ERROR
21411 @item TYPE_CODE_ERROR
21412 An unknown or erroneous type.
21414 @findex TYPE_CODE_METHOD
21415 @findex gdb.TYPE_CODE_METHOD
21416 @item TYPE_CODE_METHOD
21417 A method type, as found in C@t{++} or Java.
21419 @findex TYPE_CODE_METHODPTR
21420 @findex gdb.TYPE_CODE_METHODPTR
21421 @item TYPE_CODE_METHODPTR
21422 A pointer-to-member-function.
21424 @findex TYPE_CODE_MEMBERPTR
21425 @findex gdb.TYPE_CODE_MEMBERPTR
21426 @item TYPE_CODE_MEMBERPTR
21427 A pointer-to-member.
21429 @findex TYPE_CODE_REF
21430 @findex gdb.TYPE_CODE_REF
21431 @item TYPE_CODE_REF
21434 @findex TYPE_CODE_CHAR
21435 @findex gdb.TYPE_CODE_CHAR
21436 @item TYPE_CODE_CHAR
21439 @findex TYPE_CODE_BOOL
21440 @findex gdb.TYPE_CODE_BOOL
21441 @item TYPE_CODE_BOOL
21444 @findex TYPE_CODE_COMPLEX
21445 @findex gdb.TYPE_CODE_COMPLEX
21446 @item TYPE_CODE_COMPLEX
21447 A complex float type.
21449 @findex TYPE_CODE_TYPEDEF
21450 @findex gdb.TYPE_CODE_TYPEDEF
21451 @item TYPE_CODE_TYPEDEF
21452 A typedef to some other type.
21454 @findex TYPE_CODE_NAMESPACE
21455 @findex gdb.TYPE_CODE_NAMESPACE
21456 @item TYPE_CODE_NAMESPACE
21457 A C@t{++} namespace.
21459 @findex TYPE_CODE_DECFLOAT
21460 @findex gdb.TYPE_CODE_DECFLOAT
21461 @item TYPE_CODE_DECFLOAT
21462 A decimal floating point type.
21464 @findex TYPE_CODE_INTERNAL_FUNCTION
21465 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
21466 @item TYPE_CODE_INTERNAL_FUNCTION
21467 A function internal to @value{GDBN}. This is the type used to represent
21468 convenience functions.
21471 Further support for types is provided in the @code{gdb.types}
21472 Python module (@pxref{gdb.types}).
21474 @node Pretty Printing API
21475 @subsubsection Pretty Printing API
21477 An example output is provided (@pxref{Pretty Printing}).
21479 A pretty-printer is just an object that holds a value and implements a
21480 specific interface, defined here.
21482 @defop Operation {pretty printer} children (self)
21483 @value{GDBN} will call this method on a pretty-printer to compute the
21484 children of the pretty-printer's value.
21486 This method must return an object conforming to the Python iterator
21487 protocol. Each item returned by the iterator must be a tuple holding
21488 two elements. The first element is the ``name'' of the child; the
21489 second element is the child's value. The value can be any Python
21490 object which is convertible to a @value{GDBN} value.
21492 This method is optional. If it does not exist, @value{GDBN} will act
21493 as though the value has no children.
21496 @defop Operation {pretty printer} display_hint (self)
21497 The CLI may call this method and use its result to change the
21498 formatting of a value. The result will also be supplied to an MI
21499 consumer as a @samp{displayhint} attribute of the variable being
21502 This method is optional. If it does exist, this method must return a
21505 Some display hints are predefined by @value{GDBN}:
21509 Indicate that the object being printed is ``array-like''. The CLI
21510 uses this to respect parameters such as @code{set print elements} and
21511 @code{set print array}.
21514 Indicate that the object being printed is ``map-like'', and that the
21515 children of this value can be assumed to alternate between keys and
21519 Indicate that the object being printed is ``string-like''. If the
21520 printer's @code{to_string} method returns a Python string of some
21521 kind, then @value{GDBN} will call its internal language-specific
21522 string-printing function to format the string. For the CLI this means
21523 adding quotation marks, possibly escaping some characters, respecting
21524 @code{set print elements}, and the like.
21528 @defop Operation {pretty printer} to_string (self)
21529 @value{GDBN} will call this method to display the string
21530 representation of the value passed to the object's constructor.
21532 When printing from the CLI, if the @code{to_string} method exists,
21533 then @value{GDBN} will prepend its result to the values returned by
21534 @code{children}. Exactly how this formatting is done is dependent on
21535 the display hint, and may change as more hints are added. Also,
21536 depending on the print settings (@pxref{Print Settings}), the CLI may
21537 print just the result of @code{to_string} in a stack trace, omitting
21538 the result of @code{children}.
21540 If this method returns a string, it is printed verbatim.
21542 Otherwise, if this method returns an instance of @code{gdb.Value},
21543 then @value{GDBN} prints this value. This may result in a call to
21544 another pretty-printer.
21546 If instead the method returns a Python value which is convertible to a
21547 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
21548 the resulting value. Again, this may result in a call to another
21549 pretty-printer. Python scalars (integers, floats, and booleans) and
21550 strings are convertible to @code{gdb.Value}; other types are not.
21552 Finally, if this method returns @code{None} then no further operations
21553 are peformed in this method and nothing is printed.
21555 If the result is not one of these types, an exception is raised.
21558 @value{GDBN} provides a function which can be used to look up the
21559 default pretty-printer for a @code{gdb.Value}:
21561 @findex gdb.default_visualizer
21562 @defun default_visualizer value
21563 This function takes a @code{gdb.Value} object as an argument. If a
21564 pretty-printer for this value exists, then it is returned. If no such
21565 printer exists, then this returns @code{None}.
21568 @node Selecting Pretty-Printers
21569 @subsubsection Selecting Pretty-Printers
21571 The Python list @code{gdb.pretty_printers} contains an array of
21572 functions or callable objects that have been registered via addition
21573 as a pretty-printer. Printers in this list are called @code{global}
21574 printers, they're available when debugging all inferiors.
21575 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
21576 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
21579 Each function on these lists is passed a single @code{gdb.Value}
21580 argument and should return a pretty-printer object conforming to the
21581 interface definition above (@pxref{Pretty Printing API}). If a function
21582 cannot create a pretty-printer for the value, it should return
21585 @value{GDBN} first checks the @code{pretty_printers} attribute of each
21586 @code{gdb.Objfile} in the current program space and iteratively calls
21587 each enabled lookup routine in the list for that @code{gdb.Objfile}
21588 until it receives a pretty-printer object.
21589 If no pretty-printer is found in the objfile lists, @value{GDBN} then
21590 searches the pretty-printer list of the current program space,
21591 calling each enabled function until an object is returned.
21592 After these lists have been exhausted, it tries the global
21593 @code{gdb.pretty_printers} list, again calling each enabled function until an
21594 object is returned.
21596 The order in which the objfiles are searched is not specified. For a
21597 given list, functions are always invoked from the head of the list,
21598 and iterated over sequentially until the end of the list, or a printer
21599 object is returned.
21601 For various reasons a pretty-printer may not work.
21602 For example, the underlying data structure may have changed and
21603 the pretty-printer is out of date.
21605 The consequences of a broken pretty-printer are severe enough that
21606 @value{GDBN} provides support for enabling and disabling individual
21607 printers. For example, if @code{print frame-arguments} is on,
21608 a backtrace can become highly illegible if any argument is printed
21609 with a broken printer.
21611 Pretty-printers are enabled and disabled by attaching an @code{enabled}
21612 attribute to the registered function or callable object. If this attribute
21613 is present and its value is @code{False}, the printer is disabled, otherwise
21614 the printer is enabled.
21616 @node Writing a Pretty-Printer
21617 @subsubsection Writing a Pretty-Printer
21618 @cindex writing a pretty-printer
21620 A pretty-printer consists of two parts: a lookup function to detect
21621 if the type is supported, and the printer itself.
21623 Here is an example showing how a @code{std::string} printer might be
21624 written. @xref{Pretty Printing API}, for details on the API this class
21628 class StdStringPrinter(object):
21629 "Print a std::string"
21631 def __init__(self, val):
21634 def to_string(self):
21635 return self.val['_M_dataplus']['_M_p']
21637 def display_hint(self):
21641 And here is an example showing how a lookup function for the printer
21642 example above might be written.
21645 def str_lookup_function(val):
21646 lookup_tag = val.type.tag
21647 if lookup_tag == None:
21649 regex = re.compile("^std::basic_string<char,.*>$")
21650 if regex.match(lookup_tag):
21651 return StdStringPrinter(val)
21655 The example lookup function extracts the value's type, and attempts to
21656 match it to a type that it can pretty-print. If it is a type the
21657 printer can pretty-print, it will return a printer object. If not, it
21658 returns @code{None}.
21660 We recommend that you put your core pretty-printers into a Python
21661 package. If your pretty-printers are for use with a library, we
21662 further recommend embedding a version number into the package name.
21663 This practice will enable @value{GDBN} to load multiple versions of
21664 your pretty-printers at the same time, because they will have
21667 You should write auto-loaded code (@pxref{Auto-loading}) such that it
21668 can be evaluated multiple times without changing its meaning. An
21669 ideal auto-load file will consist solely of @code{import}s of your
21670 printer modules, followed by a call to a register pretty-printers with
21671 the current objfile.
21673 Taken as a whole, this approach will scale nicely to multiple
21674 inferiors, each potentially using a different library version.
21675 Embedding a version number in the Python package name will ensure that
21676 @value{GDBN} is able to load both sets of printers simultaneously.
21677 Then, because the search for pretty-printers is done by objfile, and
21678 because your auto-loaded code took care to register your library's
21679 printers with a specific objfile, @value{GDBN} will find the correct
21680 printers for the specific version of the library used by each
21683 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
21684 this code might appear in @code{gdb.libstdcxx.v6}:
21687 def register_printers(objfile):
21688 objfile.pretty_printers.add(str_lookup_function)
21692 And then the corresponding contents of the auto-load file would be:
21695 import gdb.libstdcxx.v6
21696 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
21699 The previous example illustrates a basic pretty-printer.
21700 There are a few things that can be improved on.
21701 The printer doesn't have a name, making it hard to identify in a
21702 list of installed printers. The lookup function has a name, but
21703 lookup functions can have arbitrary, even identical, names.
21705 Second, the printer only handles one type, whereas a library typically has
21706 several types. One could install a lookup function for each desired type
21707 in the library, but one could also have a single lookup function recognize
21708 several types. The latter is the conventional way this is handled.
21709 If a pretty-printer can handle multiple data types, then its
21710 @dfn{subprinters} are the printers for the individual data types.
21712 The @code{gdb.printing} module provides a formal way of solving these
21713 problems (@pxref{gdb.printing}).
21714 Here is another example that handles multiple types.
21716 These are the types we are going to pretty-print:
21719 struct foo @{ int a, b; @};
21720 struct bar @{ struct foo x, y; @};
21723 Here are the printers:
21727 """Print a foo object."""
21729 def __init__(self, val):
21732 def to_string(self):
21733 return ("a=<" + str(self.val["a"]) +
21734 "> b=<" + str(self.val["b"]) + ">")
21737 """Print a bar object."""
21739 def __init__(self, val):
21742 def to_string(self):
21743 return ("x=<" + str(self.val["x"]) +
21744 "> y=<" + str(self.val["y"]) + ">")
21747 This example doesn't need a lookup function, that is handled by the
21748 @code{gdb.printing} module. Instead a function is provided to build up
21749 the object that handles the lookup.
21752 import gdb.printing
21754 def build_pretty_printer():
21755 pp = gdb.printing.RegexpCollectionPrettyPrinter(
21757 pp.add_printer('foo', '^foo$', fooPrinter)
21758 pp.add_printer('bar', '^bar$', barPrinter)
21762 And here is the autoload support:
21765 import gdb.printing
21767 gdb.printing.register_pretty_printer(
21768 gdb.current_objfile(),
21769 my_library.build_pretty_printer())
21772 Finally, when this printer is loaded into @value{GDBN}, here is the
21773 corresponding output of @samp{info pretty-printer}:
21776 (gdb) info pretty-printer
21783 @node Inferiors In Python
21784 @subsubsection Inferiors In Python
21785 @cindex inferiors in python
21787 @findex gdb.Inferior
21788 Programs which are being run under @value{GDBN} are called inferiors
21789 (@pxref{Inferiors and Programs}). Python scripts can access
21790 information about and manipulate inferiors controlled by @value{GDBN}
21791 via objects of the @code{gdb.Inferior} class.
21793 The following inferior-related functions are available in the @code{gdb}
21797 Return a tuple containing all inferior objects.
21800 A @code{gdb.Inferior} object has the following attributes:
21803 @defivar Inferior num
21804 ID of inferior, as assigned by GDB.
21807 @defivar Inferior pid
21808 Process ID of the inferior, as assigned by the underlying operating
21812 @defivar Inferior was_attached
21813 Boolean signaling whether the inferior was created using `attach', or
21814 started by @value{GDBN} itself.
21818 A @code{gdb.Inferior} object has the following methods:
21821 @defmethod Inferior threads
21822 This method returns a tuple holding all the threads which are valid
21823 when it is called. If there are no valid threads, the method will
21824 return an empty tuple.
21827 @findex gdb.read_memory
21828 @defmethod Inferior read_memory address length
21829 Read @var{length} bytes of memory from the inferior, starting at
21830 @var{address}. Returns a buffer object, which behaves much like an array
21831 or a string. It can be modified and given to the @code{gdb.write_memory}
21835 @findex gdb.write_memory
21836 @defmethod Inferior write_memory address buffer @r{[}length@r{]}
21837 Write the contents of @var{buffer} to the inferior, starting at
21838 @var{address}. The @var{buffer} parameter must be a Python object
21839 which supports the buffer protocol, i.e., a string, an array or the
21840 object returned from @code{gdb.read_memory}. If given, @var{length}
21841 determines the number of bytes from @var{buffer} to be written.
21844 @findex gdb.search_memory
21845 @defmethod Inferior search_memory address length pattern
21846 Search a region of the inferior memory starting at @var{address} with
21847 the given @var{length} using the search pattern supplied in
21848 @var{pattern}. The @var{pattern} parameter must be a Python object
21849 which supports the buffer protocol, i.e., a string, an array or the
21850 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
21851 containing the address where the pattern was found, or @code{None} if
21852 the pattern could not be found.
21856 @node Threads In Python
21857 @subsubsection Threads In Python
21858 @cindex threads in python
21860 @findex gdb.InferiorThread
21861 Python scripts can access information about, and manipulate inferior threads
21862 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
21864 The following thread-related functions are available in the @code{gdb}
21867 @findex gdb.selected_thread
21868 @defun selected_thread
21869 This function returns the thread object for the selected thread. If there
21870 is no selected thread, this will return @code{None}.
21873 A @code{gdb.InferiorThread} object has the following attributes:
21876 @defivar InferiorThread num
21877 ID of the thread, as assigned by GDB.
21880 @defivar InferiorThread ptid
21881 ID of the thread, as assigned by the operating system. This attribute is a
21882 tuple containing three integers. The first is the Process ID (PID); the second
21883 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
21884 Either the LWPID or TID may be 0, which indicates that the operating system
21885 does not use that identifier.
21889 A @code{gdb.InferiorThread} object has the following methods:
21892 @defmethod InferiorThread switch
21893 This changes @value{GDBN}'s currently selected thread to the one represented
21897 @defmethod InferiorThread is_stopped
21898 Return a Boolean indicating whether the thread is stopped.
21901 @defmethod InferiorThread is_running
21902 Return a Boolean indicating whether the thread is running.
21905 @defmethod InferiorThread is_exited
21906 Return a Boolean indicating whether the thread is exited.
21910 @node Commands In Python
21911 @subsubsection Commands In Python
21913 @cindex commands in python
21914 @cindex python commands
21915 You can implement new @value{GDBN} CLI commands in Python. A CLI
21916 command is implemented using an instance of the @code{gdb.Command}
21917 class, most commonly using a subclass.
21919 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
21920 The object initializer for @code{Command} registers the new command
21921 with @value{GDBN}. This initializer is normally invoked from the
21922 subclass' own @code{__init__} method.
21924 @var{name} is the name of the command. If @var{name} consists of
21925 multiple words, then the initial words are looked for as prefix
21926 commands. In this case, if one of the prefix commands does not exist,
21927 an exception is raised.
21929 There is no support for multi-line commands.
21931 @var{command_class} should be one of the @samp{COMMAND_} constants
21932 defined below. This argument tells @value{GDBN} how to categorize the
21933 new command in the help system.
21935 @var{completer_class} is an optional argument. If given, it should be
21936 one of the @samp{COMPLETE_} constants defined below. This argument
21937 tells @value{GDBN} how to perform completion for this command. If not
21938 given, @value{GDBN} will attempt to complete using the object's
21939 @code{complete} method (see below); if no such method is found, an
21940 error will occur when completion is attempted.
21942 @var{prefix} is an optional argument. If @code{True}, then the new
21943 command is a prefix command; sub-commands of this command may be
21946 The help text for the new command is taken from the Python
21947 documentation string for the command's class, if there is one. If no
21948 documentation string is provided, the default value ``This command is
21949 not documented.'' is used.
21952 @cindex don't repeat Python command
21953 @defmethod Command dont_repeat
21954 By default, a @value{GDBN} command is repeated when the user enters a
21955 blank line at the command prompt. A command can suppress this
21956 behavior by invoking the @code{dont_repeat} method. This is similar
21957 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
21960 @defmethod Command invoke argument from_tty
21961 This method is called by @value{GDBN} when this command is invoked.
21963 @var{argument} is a string. It is the argument to the command, after
21964 leading and trailing whitespace has been stripped.
21966 @var{from_tty} is a boolean argument. When true, this means that the
21967 command was entered by the user at the terminal; when false it means
21968 that the command came from elsewhere.
21970 If this method throws an exception, it is turned into a @value{GDBN}
21971 @code{error} call. Otherwise, the return value is ignored.
21973 @findex gdb.string_to_argv
21974 To break @var{argument} up into an argv-like string use
21975 @code{gdb.string_to_argv}. This function behaves identically to
21976 @value{GDBN}'s internal argument lexer @code{buildargv}.
21977 It is recommended to use this for consistency.
21978 Arguments are separated by spaces and may be quoted.
21982 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
21983 ['1', '2 "3', '4 "5', "6 '7"]
21988 @cindex completion of Python commands
21989 @defmethod Command complete text word
21990 This method is called by @value{GDBN} when the user attempts
21991 completion on this command. All forms of completion are handled by
21992 this method, that is, the @key{TAB} and @key{M-?} key bindings
21993 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
21996 The arguments @var{text} and @var{word} are both strings. @var{text}
21997 holds the complete command line up to the cursor's location.
21998 @var{word} holds the last word of the command line; this is computed
21999 using a word-breaking heuristic.
22001 The @code{complete} method can return several values:
22004 If the return value is a sequence, the contents of the sequence are
22005 used as the completions. It is up to @code{complete} to ensure that the
22006 contents actually do complete the word. A zero-length sequence is
22007 allowed, it means that there were no completions available. Only
22008 string elements of the sequence are used; other elements in the
22009 sequence are ignored.
22012 If the return value is one of the @samp{COMPLETE_} constants defined
22013 below, then the corresponding @value{GDBN}-internal completion
22014 function is invoked, and its result is used.
22017 All other results are treated as though there were no available
22022 When a new command is registered, it must be declared as a member of
22023 some general class of commands. This is used to classify top-level
22024 commands in the on-line help system; note that prefix commands are not
22025 listed under their own category but rather that of their top-level
22026 command. The available classifications are represented by constants
22027 defined in the @code{gdb} module:
22030 @findex COMMAND_NONE
22031 @findex gdb.COMMAND_NONE
22033 The command does not belong to any particular class. A command in
22034 this category will not be displayed in any of the help categories.
22036 @findex COMMAND_RUNNING
22037 @findex gdb.COMMAND_RUNNING
22038 @item COMMAND_RUNNING
22039 The command is related to running the inferior. For example,
22040 @code{start}, @code{step}, and @code{continue} are in this category.
22041 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
22042 commands in this category.
22044 @findex COMMAND_DATA
22045 @findex gdb.COMMAND_DATA
22047 The command is related to data or variables. For example,
22048 @code{call}, @code{find}, and @code{print} are in this category. Type
22049 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
22052 @findex COMMAND_STACK
22053 @findex gdb.COMMAND_STACK
22054 @item COMMAND_STACK
22055 The command has to do with manipulation of the stack. For example,
22056 @code{backtrace}, @code{frame}, and @code{return} are in this
22057 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
22058 list of commands in this category.
22060 @findex COMMAND_FILES
22061 @findex gdb.COMMAND_FILES
22062 @item COMMAND_FILES
22063 This class is used for file-related commands. For example,
22064 @code{file}, @code{list} and @code{section} are in this category.
22065 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
22066 commands in this category.
22068 @findex COMMAND_SUPPORT
22069 @findex gdb.COMMAND_SUPPORT
22070 @item COMMAND_SUPPORT
22071 This should be used for ``support facilities'', generally meaning
22072 things that are useful to the user when interacting with @value{GDBN},
22073 but not related to the state of the inferior. For example,
22074 @code{help}, @code{make}, and @code{shell} are in this category. Type
22075 @kbd{help support} at the @value{GDBN} prompt to see a list of
22076 commands in this category.
22078 @findex COMMAND_STATUS
22079 @findex gdb.COMMAND_STATUS
22080 @item COMMAND_STATUS
22081 The command is an @samp{info}-related command, that is, related to the
22082 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
22083 and @code{show} are in this category. Type @kbd{help status} at the
22084 @value{GDBN} prompt to see a list of commands in this category.
22086 @findex COMMAND_BREAKPOINTS
22087 @findex gdb.COMMAND_BREAKPOINTS
22088 @item COMMAND_BREAKPOINTS
22089 The command has to do with breakpoints. For example, @code{break},
22090 @code{clear}, and @code{delete} are in this category. Type @kbd{help
22091 breakpoints} at the @value{GDBN} prompt to see a list of commands in
22094 @findex COMMAND_TRACEPOINTS
22095 @findex gdb.COMMAND_TRACEPOINTS
22096 @item COMMAND_TRACEPOINTS
22097 The command has to do with tracepoints. For example, @code{trace},
22098 @code{actions}, and @code{tfind} are in this category. Type
22099 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
22100 commands in this category.
22102 @findex COMMAND_OBSCURE
22103 @findex gdb.COMMAND_OBSCURE
22104 @item COMMAND_OBSCURE
22105 The command is only used in unusual circumstances, or is not of
22106 general interest to users. For example, @code{checkpoint},
22107 @code{fork}, and @code{stop} are in this category. Type @kbd{help
22108 obscure} at the @value{GDBN} prompt to see a list of commands in this
22111 @findex COMMAND_MAINTENANCE
22112 @findex gdb.COMMAND_MAINTENANCE
22113 @item COMMAND_MAINTENANCE
22114 The command is only useful to @value{GDBN} maintainers. The
22115 @code{maintenance} and @code{flushregs} commands are in this category.
22116 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
22117 commands in this category.
22120 A new command can use a predefined completion function, either by
22121 specifying it via an argument at initialization, or by returning it
22122 from the @code{complete} method. These predefined completion
22123 constants are all defined in the @code{gdb} module:
22126 @findex COMPLETE_NONE
22127 @findex gdb.COMPLETE_NONE
22128 @item COMPLETE_NONE
22129 This constant means that no completion should be done.
22131 @findex COMPLETE_FILENAME
22132 @findex gdb.COMPLETE_FILENAME
22133 @item COMPLETE_FILENAME
22134 This constant means that filename completion should be performed.
22136 @findex COMPLETE_LOCATION
22137 @findex gdb.COMPLETE_LOCATION
22138 @item COMPLETE_LOCATION
22139 This constant means that location completion should be done.
22140 @xref{Specify Location}.
22142 @findex COMPLETE_COMMAND
22143 @findex gdb.COMPLETE_COMMAND
22144 @item COMPLETE_COMMAND
22145 This constant means that completion should examine @value{GDBN}
22148 @findex COMPLETE_SYMBOL
22149 @findex gdb.COMPLETE_SYMBOL
22150 @item COMPLETE_SYMBOL
22151 This constant means that completion should be done using symbol names
22155 The following code snippet shows how a trivial CLI command can be
22156 implemented in Python:
22159 class HelloWorld (gdb.Command):
22160 """Greet the whole world."""
22162 def __init__ (self):
22163 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
22165 def invoke (self, arg, from_tty):
22166 print "Hello, World!"
22171 The last line instantiates the class, and is necessary to trigger the
22172 registration of the command with @value{GDBN}. Depending on how the
22173 Python code is read into @value{GDBN}, you may need to import the
22174 @code{gdb} module explicitly.
22176 @node Parameters In Python
22177 @subsubsection Parameters In Python
22179 @cindex parameters in python
22180 @cindex python parameters
22181 @tindex gdb.Parameter
22183 You can implement new @value{GDBN} parameters using Python. A new
22184 parameter is implemented as an instance of the @code{gdb.Parameter}
22187 Parameters are exposed to the user via the @code{set} and
22188 @code{show} commands. @xref{Help}.
22190 There are many parameters that already exist and can be set in
22191 @value{GDBN}. Two examples are: @code{set follow fork} and
22192 @code{set charset}. Setting these parameters influences certain
22193 behavior in @value{GDBN}. Similarly, you can define parameters that
22194 can be used to influence behavior in custom Python scripts and commands.
22196 @defmethod Parameter __init__ name @var{command-class} @var{parameter-class} @r{[}@var{enum-sequence}@r{]}
22197 The object initializer for @code{Parameter} registers the new
22198 parameter with @value{GDBN}. This initializer is normally invoked
22199 from the subclass' own @code{__init__} method.
22201 @var{name} is the name of the new parameter. If @var{name} consists
22202 of multiple words, then the initial words are looked for as prefix
22203 parameters. An example of this can be illustrated with the
22204 @code{set print} set of parameters. If @var{name} is
22205 @code{print foo}, then @code{print} will be searched as the prefix
22206 parameter. In this case the parameter can subsequently be accessed in
22207 @value{GDBN} as @code{set print foo}.
22209 If @var{name} consists of multiple words, and no prefix parameter group
22210 can be found, an exception is raised.
22212 @var{command-class} should be one of the @samp{COMMAND_} constants
22213 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
22214 categorize the new parameter in the help system.
22216 @var{parameter-class} should be one of the @samp{PARAM_} constants
22217 defined below. This argument tells @value{GDBN} the type of the new
22218 parameter; this information is used for input validation and
22221 If @var{parameter-class} is @code{PARAM_ENUM}, then
22222 @var{enum-sequence} must be a sequence of strings. These strings
22223 represent the possible values for the parameter.
22225 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
22226 of a fourth argument will cause an exception to be thrown.
22228 The help text for the new parameter is taken from the Python
22229 documentation string for the parameter's class, if there is one. If
22230 there is no documentation string, a default value is used.
22233 @defivar Parameter set_doc
22234 If this attribute exists, and is a string, then its value is used as
22235 the help text for this parameter's @code{set} command. The value is
22236 examined when @code{Parameter.__init__} is invoked; subsequent changes
22240 @defivar Parameter show_doc
22241 If this attribute exists, and is a string, then its value is used as
22242 the help text for this parameter's @code{show} command. The value is
22243 examined when @code{Parameter.__init__} is invoked; subsequent changes
22247 @defivar Parameter value
22248 The @code{value} attribute holds the underlying value of the
22249 parameter. It can be read and assigned to just as any other
22250 attribute. @value{GDBN} does validation when assignments are made.
22254 When a new parameter is defined, its type must be specified. The
22255 available types are represented by constants defined in the @code{gdb}
22259 @findex PARAM_BOOLEAN
22260 @findex gdb.PARAM_BOOLEAN
22261 @item PARAM_BOOLEAN
22262 The value is a plain boolean. The Python boolean values, @code{True}
22263 and @code{False} are the only valid values.
22265 @findex PARAM_AUTO_BOOLEAN
22266 @findex gdb.PARAM_AUTO_BOOLEAN
22267 @item PARAM_AUTO_BOOLEAN
22268 The value has three possible states: true, false, and @samp{auto}. In
22269 Python, true and false are represented using boolean constants, and
22270 @samp{auto} is represented using @code{None}.
22272 @findex PARAM_UINTEGER
22273 @findex gdb.PARAM_UINTEGER
22274 @item PARAM_UINTEGER
22275 The value is an unsigned integer. The value of 0 should be
22276 interpreted to mean ``unlimited''.
22278 @findex PARAM_INTEGER
22279 @findex gdb.PARAM_INTEGER
22280 @item PARAM_INTEGER
22281 The value is a signed integer. The value of 0 should be interpreted
22282 to mean ``unlimited''.
22284 @findex PARAM_STRING
22285 @findex gdb.PARAM_STRING
22287 The value is a string. When the user modifies the string, any escape
22288 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
22289 translated into corresponding characters and encoded into the current
22292 @findex PARAM_STRING_NOESCAPE
22293 @findex gdb.PARAM_STRING_NOESCAPE
22294 @item PARAM_STRING_NOESCAPE
22295 The value is a string. When the user modifies the string, escapes are
22296 passed through untranslated.
22298 @findex PARAM_OPTIONAL_FILENAME
22299 @findex gdb.PARAM_OPTIONAL_FILENAME
22300 @item PARAM_OPTIONAL_FILENAME
22301 The value is a either a filename (a string), or @code{None}.
22303 @findex PARAM_FILENAME
22304 @findex gdb.PARAM_FILENAME
22305 @item PARAM_FILENAME
22306 The value is a filename. This is just like
22307 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
22309 @findex PARAM_ZINTEGER
22310 @findex gdb.PARAM_ZINTEGER
22311 @item PARAM_ZINTEGER
22312 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
22313 is interpreted as itself.
22316 @findex gdb.PARAM_ENUM
22318 The value is a string, which must be one of a collection string
22319 constants provided when the parameter is created.
22322 @node Functions In Python
22323 @subsubsection Writing new convenience functions
22325 @cindex writing convenience functions
22326 @cindex convenience functions in python
22327 @cindex python convenience functions
22328 @tindex gdb.Function
22330 You can implement new convenience functions (@pxref{Convenience Vars})
22331 in Python. A convenience function is an instance of a subclass of the
22332 class @code{gdb.Function}.
22334 @defmethod Function __init__ name
22335 The initializer for @code{Function} registers the new function with
22336 @value{GDBN}. The argument @var{name} is the name of the function,
22337 a string. The function will be visible to the user as a convenience
22338 variable of type @code{internal function}, whose name is the same as
22339 the given @var{name}.
22341 The documentation for the new function is taken from the documentation
22342 string for the new class.
22345 @defmethod Function invoke @var{*args}
22346 When a convenience function is evaluated, its arguments are converted
22347 to instances of @code{gdb.Value}, and then the function's
22348 @code{invoke} method is called. Note that @value{GDBN} does not
22349 predetermine the arity of convenience functions. Instead, all
22350 available arguments are passed to @code{invoke}, following the
22351 standard Python calling convention. In particular, a convenience
22352 function can have default values for parameters without ill effect.
22354 The return value of this method is used as its value in the enclosing
22355 expression. If an ordinary Python value is returned, it is converted
22356 to a @code{gdb.Value} following the usual rules.
22359 The following code snippet shows how a trivial convenience function can
22360 be implemented in Python:
22363 class Greet (gdb.Function):
22364 """Return string to greet someone.
22365 Takes a name as argument."""
22367 def __init__ (self):
22368 super (Greet, self).__init__ ("greet")
22370 def invoke (self, name):
22371 return "Hello, %s!" % name.string ()
22376 The last line instantiates the class, and is necessary to trigger the
22377 registration of the function with @value{GDBN}. Depending on how the
22378 Python code is read into @value{GDBN}, you may need to import the
22379 @code{gdb} module explicitly.
22381 @node Progspaces In Python
22382 @subsubsection Program Spaces In Python
22384 @cindex progspaces in python
22385 @tindex gdb.Progspace
22387 A program space, or @dfn{progspace}, represents a symbolic view
22388 of an address space.
22389 It consists of all of the objfiles of the program.
22390 @xref{Objfiles In Python}.
22391 @xref{Inferiors and Programs, program spaces}, for more details
22392 about program spaces.
22394 The following progspace-related functions are available in the
22397 @findex gdb.current_progspace
22398 @defun current_progspace
22399 This function returns the program space of the currently selected inferior.
22400 @xref{Inferiors and Programs}.
22403 @findex gdb.progspaces
22405 Return a sequence of all the progspaces currently known to @value{GDBN}.
22408 Each progspace is represented by an instance of the @code{gdb.Progspace}
22411 @defivar Progspace filename
22412 The file name of the progspace as a string.
22415 @defivar Progspace pretty_printers
22416 The @code{pretty_printers} attribute is a list of functions. It is
22417 used to look up pretty-printers. A @code{Value} is passed to each
22418 function in order; if the function returns @code{None}, then the
22419 search continues. Otherwise, the return value should be an object
22420 which is used to format the value. @xref{Pretty Printing API}, for more
22424 @node Objfiles In Python
22425 @subsubsection Objfiles In Python
22427 @cindex objfiles in python
22428 @tindex gdb.Objfile
22430 @value{GDBN} loads symbols for an inferior from various
22431 symbol-containing files (@pxref{Files}). These include the primary
22432 executable file, any shared libraries used by the inferior, and any
22433 separate debug info files (@pxref{Separate Debug Files}).
22434 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
22436 The following objfile-related functions are available in the
22439 @findex gdb.current_objfile
22440 @defun current_objfile
22441 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
22442 sets the ``current objfile'' to the corresponding objfile. This
22443 function returns the current objfile. If there is no current objfile,
22444 this function returns @code{None}.
22447 @findex gdb.objfiles
22449 Return a sequence of all the objfiles current known to @value{GDBN}.
22450 @xref{Objfiles In Python}.
22453 Each objfile is represented by an instance of the @code{gdb.Objfile}
22456 @defivar Objfile filename
22457 The file name of the objfile as a string.
22460 @defivar Objfile pretty_printers
22461 The @code{pretty_printers} attribute is a list of functions. It is
22462 used to look up pretty-printers. A @code{Value} is passed to each
22463 function in order; if the function returns @code{None}, then the
22464 search continues. Otherwise, the return value should be an object
22465 which is used to format the value. @xref{Pretty Printing API}, for more
22469 @node Frames In Python
22470 @subsubsection Accessing inferior stack frames from Python.
22472 @cindex frames in python
22473 When the debugged program stops, @value{GDBN} is able to analyze its call
22474 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
22475 represents a frame in the stack. A @code{gdb.Frame} object is only valid
22476 while its corresponding frame exists in the inferior's stack. If you try
22477 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
22478 exception (@pxref{Exception Handling}).
22480 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
22484 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
22488 The following frame-related functions are available in the @code{gdb} module:
22490 @findex gdb.selected_frame
22491 @defun selected_frame
22492 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
22495 @defun frame_stop_reason_string reason
22496 Return a string explaining the reason why @value{GDBN} stopped unwinding
22497 frames, as expressed by the given @var{reason} code (an integer, see the
22498 @code{unwind_stop_reason} method further down in this section).
22501 A @code{gdb.Frame} object has the following methods:
22504 @defmethod Frame is_valid
22505 Returns true if the @code{gdb.Frame} object is valid, false if not.
22506 A frame object can become invalid if the frame it refers to doesn't
22507 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
22508 an exception if it is invalid at the time the method is called.
22511 @defmethod Frame name
22512 Returns the function name of the frame, or @code{None} if it can't be
22516 @defmethod Frame type
22517 Returns the type of the frame. The value can be one of
22518 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
22519 or @code{gdb.SENTINEL_FRAME}.
22522 @defmethod Frame unwind_stop_reason
22523 Return an integer representing the reason why it's not possible to find
22524 more frames toward the outermost frame. Use
22525 @code{gdb.frame_stop_reason_string} to convert the value returned by this
22526 function to a string.
22529 @defmethod Frame pc
22530 Returns the frame's resume address.
22533 @defmethod Frame block
22534 Return the frame's code block. @xref{Blocks In Python}.
22537 @defmethod Frame function
22538 Return the symbol for the function corresponding to this frame.
22539 @xref{Symbols In Python}.
22542 @defmethod Frame older
22543 Return the frame that called this frame.
22546 @defmethod Frame newer
22547 Return the frame called by this frame.
22550 @defmethod Frame find_sal
22551 Return the frame's symtab and line object.
22552 @xref{Symbol Tables In Python}.
22555 @defmethod Frame read_var variable @r{[}block@r{]}
22556 Return the value of @var{variable} in this frame. If the optional
22557 argument @var{block} is provided, search for the variable from that
22558 block; otherwise start at the frame's current block (which is
22559 determined by the frame's current program counter). @var{variable}
22560 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
22561 @code{gdb.Block} object.
22564 @defmethod Frame select
22565 Set this frame to be the selected frame. @xref{Stack, ,Examining the
22570 @node Blocks In Python
22571 @subsubsection Accessing frame blocks from Python.
22573 @cindex blocks in python
22576 Within each frame, @value{GDBN} maintains information on each block
22577 stored in that frame. These blocks are organized hierarchically, and
22578 are represented individually in Python as a @code{gdb.Block}.
22579 Please see @ref{Frames In Python}, for a more in-depth discussion on
22580 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
22581 detailed technical information on @value{GDBN}'s book-keeping of the
22584 The following block-related functions are available in the @code{gdb}
22587 @findex gdb.block_for_pc
22588 @defun block_for_pc pc
22589 Return the @code{gdb.Block} containing the given @var{pc} value. If the
22590 block cannot be found for the @var{pc} value specified, the function
22591 will return @code{None}.
22594 A @code{gdb.Block} object has the following attributes:
22597 @defivar Block start
22598 The start address of the block. This attribute is not writable.
22602 The end address of the block. This attribute is not writable.
22605 @defivar Block function
22606 The name of the block represented as a @code{gdb.Symbol}. If the
22607 block is not named, then this attribute holds @code{None}. This
22608 attribute is not writable.
22611 @defivar Block superblock
22612 The block containing this block. If this parent block does not exist,
22613 this attribute holds @code{None}. This attribute is not writable.
22617 @node Symbols In Python
22618 @subsubsection Python representation of Symbols.
22620 @cindex symbols in python
22623 @value{GDBN} represents every variable, function and type as an
22624 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
22625 Similarly, Python represents these symbols in @value{GDBN} with the
22626 @code{gdb.Symbol} object.
22628 The following symbol-related functions are available in the @code{gdb}
22631 @findex gdb.lookup_symbol
22632 @defun lookup_symbol name [block] [domain]
22633 This function searches for a symbol by name. The search scope can be
22634 restricted to the parameters defined in the optional domain and block
22637 @var{name} is the name of the symbol. It must be a string. The
22638 optional @var{block} argument restricts the search to symbols visible
22639 in that @var{block}. The @var{block} argument must be a
22640 @code{gdb.Block} object. The optional @var{domain} argument restricts
22641 the search to the domain type. The @var{domain} argument must be a
22642 domain constant defined in the @code{gdb} module and described later
22646 A @code{gdb.Symbol} object has the following attributes:
22649 @defivar Symbol symtab
22650 The symbol table in which the symbol appears. This attribute is
22651 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
22652 Python}. This attribute is not writable.
22655 @defivar Symbol name
22656 The name of the symbol as a string. This attribute is not writable.
22659 @defivar Symbol linkage_name
22660 The name of the symbol, as used by the linker (i.e., may be mangled).
22661 This attribute is not writable.
22664 @defivar Symbol print_name
22665 The name of the symbol in a form suitable for output. This is either
22666 @code{name} or @code{linkage_name}, depending on whether the user
22667 asked @value{GDBN} to display demangled or mangled names.
22670 @defivar Symbol addr_class
22671 The address class of the symbol. This classifies how to find the value
22672 of a symbol. Each address class is a constant defined in the
22673 @code{gdb} module and described later in this chapter.
22676 @defivar Symbol is_argument
22677 @code{True} if the symbol is an argument of a function.
22680 @defivar Symbol is_constant
22681 @code{True} if the symbol is a constant.
22684 @defivar Symbol is_function
22685 @code{True} if the symbol is a function or a method.
22688 @defivar Symbol is_variable
22689 @code{True} if the symbol is a variable.
22693 The available domain categories in @code{gdb.Symbol} are represented
22694 as constants in the @code{gdb} module:
22697 @findex SYMBOL_UNDEF_DOMAIN
22698 @findex gdb.SYMBOL_UNDEF_DOMAIN
22699 @item SYMBOL_UNDEF_DOMAIN
22700 This is used when a domain has not been discovered or none of the
22701 following domains apply. This usually indicates an error either
22702 in the symbol information or in @value{GDBN}'s handling of symbols.
22703 @findex SYMBOL_VAR_DOMAIN
22704 @findex gdb.SYMBOL_VAR_DOMAIN
22705 @item SYMBOL_VAR_DOMAIN
22706 This domain contains variables, function names, typedef names and enum
22708 @findex SYMBOL_STRUCT_DOMAIN
22709 @findex gdb.SYMBOL_STRUCT_DOMAIN
22710 @item SYMBOL_STRUCT_DOMAIN
22711 This domain holds struct, union and enum type names.
22712 @findex SYMBOL_LABEL_DOMAIN
22713 @findex gdb.SYMBOL_LABEL_DOMAIN
22714 @item SYMBOL_LABEL_DOMAIN
22715 This domain contains names of labels (for gotos).
22716 @findex SYMBOL_VARIABLES_DOMAIN
22717 @findex gdb.SYMBOL_VARIABLES_DOMAIN
22718 @item SYMBOL_VARIABLES_DOMAIN
22719 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
22720 contains everything minus functions and types.
22721 @findex SYMBOL_FUNCTIONS_DOMAIN
22722 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
22723 @item SYMBOL_FUNCTION_DOMAIN
22724 This domain contains all functions.
22725 @findex SYMBOL_TYPES_DOMAIN
22726 @findex gdb.SYMBOL_TYPES_DOMAIN
22727 @item SYMBOL_TYPES_DOMAIN
22728 This domain contains all types.
22731 The available address class categories in @code{gdb.Symbol} are represented
22732 as constants in the @code{gdb} module:
22735 @findex SYMBOL_LOC_UNDEF
22736 @findex gdb.SYMBOL_LOC_UNDEF
22737 @item SYMBOL_LOC_UNDEF
22738 If this is returned by address class, it indicates an error either in
22739 the symbol information or in @value{GDBN}'s handling of symbols.
22740 @findex SYMBOL_LOC_CONST
22741 @findex gdb.SYMBOL_LOC_CONST
22742 @item SYMBOL_LOC_CONST
22743 Value is constant int.
22744 @findex SYMBOL_LOC_STATIC
22745 @findex gdb.SYMBOL_LOC_STATIC
22746 @item SYMBOL_LOC_STATIC
22747 Value is at a fixed address.
22748 @findex SYMBOL_LOC_REGISTER
22749 @findex gdb.SYMBOL_LOC_REGISTER
22750 @item SYMBOL_LOC_REGISTER
22751 Value is in a register.
22752 @findex SYMBOL_LOC_ARG
22753 @findex gdb.SYMBOL_LOC_ARG
22754 @item SYMBOL_LOC_ARG
22755 Value is an argument. This value is at the offset stored within the
22756 symbol inside the frame's argument list.
22757 @findex SYMBOL_LOC_REF_ARG
22758 @findex gdb.SYMBOL_LOC_REF_ARG
22759 @item SYMBOL_LOC_REF_ARG
22760 Value address is stored in the frame's argument list. Just like
22761 @code{LOC_ARG} except that the value's address is stored at the
22762 offset, not the value itself.
22763 @findex SYMBOL_LOC_REGPARM_ADDR
22764 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
22765 @item SYMBOL_LOC_REGPARM_ADDR
22766 Value is a specified register. Just like @code{LOC_REGISTER} except
22767 the register holds the address of the argument instead of the argument
22769 @findex SYMBOL_LOC_LOCAL
22770 @findex gdb.SYMBOL_LOC_LOCAL
22771 @item SYMBOL_LOC_LOCAL
22772 Value is a local variable.
22773 @findex SYMBOL_LOC_TYPEDEF
22774 @findex gdb.SYMBOL_LOC_TYPEDEF
22775 @item SYMBOL_LOC_TYPEDEF
22776 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
22778 @findex SYMBOL_LOC_BLOCK
22779 @findex gdb.SYMBOL_LOC_BLOCK
22780 @item SYMBOL_LOC_BLOCK
22782 @findex SYMBOL_LOC_CONST_BYTES
22783 @findex gdb.SYMBOL_LOC_CONST_BYTES
22784 @item SYMBOL_LOC_CONST_BYTES
22785 Value is a byte-sequence.
22786 @findex SYMBOL_LOC_UNRESOLVED
22787 @findex gdb.SYMBOL_LOC_UNRESOLVED
22788 @item SYMBOL_LOC_UNRESOLVED
22789 Value is at a fixed address, but the address of the variable has to be
22790 determined from the minimal symbol table whenever the variable is
22792 @findex SYMBOL_LOC_OPTIMIZED_OUT
22793 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
22794 @item SYMBOL_LOC_OPTIMIZED_OUT
22795 The value does not actually exist in the program.
22796 @findex SYMBOL_LOC_COMPUTED
22797 @findex gdb.SYMBOL_LOC_COMPUTED
22798 @item SYMBOL_LOC_COMPUTED
22799 The value's address is a computed location.
22802 @node Symbol Tables In Python
22803 @subsubsection Symbol table representation in Python.
22805 @cindex symbol tables in python
22807 @tindex gdb.Symtab_and_line
22809 Access to symbol table data maintained by @value{GDBN} on the inferior
22810 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
22811 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
22812 from the @code{find_sal} method in @code{gdb.Frame} object.
22813 @xref{Frames In Python}.
22815 For more information on @value{GDBN}'s symbol table management, see
22816 @ref{Symbols, ,Examining the Symbol Table}, for more information.
22818 A @code{gdb.Symtab_and_line} object has the following attributes:
22821 @defivar Symtab_and_line symtab
22822 The symbol table object (@code{gdb.Symtab}) for this frame.
22823 This attribute is not writable.
22826 @defivar Symtab_and_line pc
22827 Indicates the current program counter address. This attribute is not
22831 @defivar Symtab_and_line line
22832 Indicates the current line number for this object. This
22833 attribute is not writable.
22837 A @code{gdb.Symtab} object has the following attributes:
22840 @defivar Symtab filename
22841 The symbol table's source filename. This attribute is not writable.
22844 @defivar Symtab objfile
22845 The symbol table's backing object file. @xref{Objfiles In Python}.
22846 This attribute is not writable.
22850 The following methods are provided:
22853 @defmethod Symtab fullname
22854 Return the symbol table's source absolute file name.
22858 @node Breakpoints In Python
22859 @subsubsection Manipulating breakpoints using Python
22861 @cindex breakpoints in python
22862 @tindex gdb.Breakpoint
22864 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
22867 @defmethod Breakpoint __init__ spec @r{[}type@r{]} @r{[}wp_class@r{]} @r{[}internal@r{]}
22868 Create a new breakpoint. @var{spec} is a string naming the
22869 location of the breakpoint, or an expression that defines a
22870 watchpoint. The contents can be any location recognized by the
22871 @code{break} command, or in the case of a watchpoint, by the @code{watch}
22872 command. The optional @var{type} denotes the breakpoint to create
22873 from the types defined later in this chapter. This argument can be
22874 either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}. @var{type}
22875 defaults to @code{BP_BREAKPOINT}. The optional @var{internal} argument
22876 allows the breakpoint to become invisible to the user. The breakpoint
22877 will neither be reported when created, nor will it be listed in the
22878 output from @code{info breakpoints} (but will be listed with the
22879 @code{maint info breakpoints} command). The optional @var{wp_class}
22880 argument defines the class of watchpoint to create, if @var{type} is
22881 @code{BP_WATCHPOINT}. If a watchpoint class is not provided, it is
22882 assumed to be a @var{WP_WRITE} class.
22885 The available watchpoint types represented by constants are defined in the
22890 @findex gdb.WP_READ
22892 Read only watchpoint.
22895 @findex gdb.WP_WRITE
22897 Write only watchpoint.
22900 @findex gdb.WP_ACCESS
22902 Read/Write watchpoint.
22905 @defmethod Breakpoint is_valid
22906 Return @code{True} if this @code{Breakpoint} object is valid,
22907 @code{False} otherwise. A @code{Breakpoint} object can become invalid
22908 if the user deletes the breakpoint. In this case, the object still
22909 exists, but the underlying breakpoint does not. In the cases of
22910 watchpoint scope, the watchpoint remains valid even if execution of the
22911 inferior leaves the scope of that watchpoint.
22914 @defmethod Breakpoint delete
22915 Permanently deletes the @value{GDBN} breakpoint. This also
22916 invalidates the Python @code{Breakpoint} object. Any further access
22917 to this object's attributes or methods will raise an error.
22920 @defivar Breakpoint enabled
22921 This attribute is @code{True} if the breakpoint is enabled, and
22922 @code{False} otherwise. This attribute is writable.
22925 @defivar Breakpoint silent
22926 This attribute is @code{True} if the breakpoint is silent, and
22927 @code{False} otherwise. This attribute is writable.
22929 Note that a breakpoint can also be silent if it has commands and the
22930 first command is @code{silent}. This is not reported by the
22931 @code{silent} attribute.
22934 @defivar Breakpoint thread
22935 If the breakpoint is thread-specific, this attribute holds the thread
22936 id. If the breakpoint is not thread-specific, this attribute is
22937 @code{None}. This attribute is writable.
22940 @defivar Breakpoint task
22941 If the breakpoint is Ada task-specific, this attribute holds the Ada task
22942 id. If the breakpoint is not task-specific (or the underlying
22943 language is not Ada), this attribute is @code{None}. This attribute
22947 @defivar Breakpoint ignore_count
22948 This attribute holds the ignore count for the breakpoint, an integer.
22949 This attribute is writable.
22952 @defivar Breakpoint number
22953 This attribute holds the breakpoint's number --- the identifier used by
22954 the user to manipulate the breakpoint. This attribute is not writable.
22957 @defivar Breakpoint type
22958 This attribute holds the breakpoint's type --- the identifier used to
22959 determine the actual breakpoint type or use-case. This attribute is not
22963 @defivar Breakpoint visible
22964 This attribute tells whether the breakpoint is visible to the user
22965 when set, or when the @samp{info breakpoints} command is run. This
22966 attribute is not writable.
22969 The available types are represented by constants defined in the @code{gdb}
22973 @findex BP_BREAKPOINT
22974 @findex gdb.BP_BREAKPOINT
22975 @item BP_BREAKPOINT
22976 Normal code breakpoint.
22978 @findex BP_WATCHPOINT
22979 @findex gdb.BP_WATCHPOINT
22980 @item BP_WATCHPOINT
22981 Watchpoint breakpoint.
22983 @findex BP_HARDWARE_WATCHPOINT
22984 @findex gdb.BP_HARDWARE_WATCHPOINT
22985 @item BP_HARDWARE_WATCHPOINT
22986 Hardware assisted watchpoint.
22988 @findex BP_READ_WATCHPOINT
22989 @findex gdb.BP_READ_WATCHPOINT
22990 @item BP_READ_WATCHPOINT
22991 Hardware assisted read watchpoint.
22993 @findex BP_ACCESS_WATCHPOINT
22994 @findex gdb.BP_ACCESS_WATCHPOINT
22995 @item BP_ACCESS_WATCHPOINT
22996 Hardware assisted access watchpoint.
22999 @defivar Breakpoint hit_count
23000 This attribute holds the hit count for the breakpoint, an integer.
23001 This attribute is writable, but currently it can only be set to zero.
23004 @defivar Breakpoint location
23005 This attribute holds the location of the breakpoint, as specified by
23006 the user. It is a string. If the breakpoint does not have a location
23007 (that is, it is a watchpoint) the attribute's value is @code{None}. This
23008 attribute is not writable.
23011 @defivar Breakpoint expression
23012 This attribute holds a breakpoint expression, as specified by
23013 the user. It is a string. If the breakpoint does not have an
23014 expression (the breakpoint is not a watchpoint) the attribute's value
23015 is @code{None}. This attribute is not writable.
23018 @defivar Breakpoint condition
23019 This attribute holds the condition of the breakpoint, as specified by
23020 the user. It is a string. If there is no condition, this attribute's
23021 value is @code{None}. This attribute is writable.
23024 @defivar Breakpoint commands
23025 This attribute holds the commands attached to the breakpoint. If
23026 there are commands, this attribute's value is a string holding all the
23027 commands, separated by newlines. If there are no commands, this
23028 attribute is @code{None}. This attribute is not writable.
23031 @node Lazy Strings In Python
23032 @subsubsection Python representation of lazy strings.
23034 @cindex lazy strings in python
23035 @tindex gdb.LazyString
23037 A @dfn{lazy string} is a string whose contents is not retrieved or
23038 encoded until it is needed.
23040 A @code{gdb.LazyString} is represented in @value{GDBN} as an
23041 @code{address} that points to a region of memory, an @code{encoding}
23042 that will be used to encode that region of memory, and a @code{length}
23043 to delimit the region of memory that represents the string. The
23044 difference between a @code{gdb.LazyString} and a string wrapped within
23045 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
23046 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
23047 retrieved and encoded during printing, while a @code{gdb.Value}
23048 wrapping a string is immediately retrieved and encoded on creation.
23050 A @code{gdb.LazyString} object has the following functions:
23052 @defmethod LazyString value
23053 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
23054 will point to the string in memory, but will lose all the delayed
23055 retrieval, encoding and handling that @value{GDBN} applies to a
23056 @code{gdb.LazyString}.
23059 @defivar LazyString address
23060 This attribute holds the address of the string. This attribute is not
23064 @defivar LazyString length
23065 This attribute holds the length of the string in characters. If the
23066 length is -1, then the string will be fetched and encoded up to the
23067 first null of appropriate width. This attribute is not writable.
23070 @defivar LazyString encoding
23071 This attribute holds the encoding that will be applied to the string
23072 when the string is printed by @value{GDBN}. If the encoding is not
23073 set, or contains an empty string, then @value{GDBN} will select the
23074 most appropriate encoding when the string is printed. This attribute
23078 @defivar LazyString type
23079 This attribute holds the type that is represented by the lazy string's
23080 type. For a lazy string this will always be a pointer type. To
23081 resolve this to the lazy string's character type, use the type's
23082 @code{target} method. @xref{Types In Python}. This attribute is not
23087 @subsection Auto-loading
23088 @cindex auto-loading, Python
23090 When a new object file is read (for example, due to the @code{file}
23091 command, or because the inferior has loaded a shared library),
23092 @value{GDBN} will look for Python support scripts in several ways:
23093 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
23096 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
23097 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
23098 * Which flavor to choose?::
23101 The auto-loading feature is useful for supplying application-specific
23102 debugging commands and scripts.
23104 Auto-loading can be enabled or disabled.
23107 @kindex maint set python auto-load
23108 @item maint set python auto-load [yes|no]
23109 Enable or disable the Python auto-loading feature.
23111 @kindex maint show python auto-load
23112 @item maint show python auto-load
23113 Show whether Python auto-loading is enabled or disabled.
23116 When reading an auto-loaded file, @value{GDBN} sets the
23117 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
23118 function (@pxref{Objfiles In Python}). This can be useful for
23119 registering objfile-specific pretty-printers.
23121 @node objfile-gdb.py file
23122 @subsubsection The @file{@var{objfile}-gdb.py} file
23123 @cindex @file{@var{objfile}-gdb.py}
23125 When a new object file is read, @value{GDBN} looks for
23126 a file named @file{@var{objfile}-gdb.py},
23127 where @var{objfile} is the object file's real name, formed by ensuring
23128 that the file name is absolute, following all symlinks, and resolving
23129 @code{.} and @code{..} components. If this file exists and is
23130 readable, @value{GDBN} will evaluate it as a Python script.
23132 If this file does not exist, and if the parameter
23133 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
23134 then @value{GDBN} will look for @var{real-name} in all of the
23135 directories mentioned in the value of @code{debug-file-directory}.
23137 Finally, if this file does not exist, then @value{GDBN} will look for
23138 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
23139 @var{data-directory} is @value{GDBN}'s data directory (available via
23140 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
23141 is the object file's real name, as described above.
23143 @value{GDBN} does not track which files it has already auto-loaded this way.
23144 @value{GDBN} will load the associated script every time the corresponding
23145 @var{objfile} is opened.
23146 So your @file{-gdb.py} file should be careful to avoid errors if it
23147 is evaluated more than once.
23149 @node .debug_gdb_scripts section
23150 @subsubsection The @code{.debug_gdb_scripts} section
23151 @cindex @code{.debug_gdb_scripts} section
23153 For systems using file formats like ELF and COFF,
23154 when @value{GDBN} loads a new object file
23155 it will look for a special section named @samp{.debug_gdb_scripts}.
23156 If this section exists, its contents is a list of names of scripts to load.
23158 @value{GDBN} will look for each specified script file first in the
23159 current directory and then along the source search path
23160 (@pxref{Source Path, ,Specifying Source Directories}),
23161 except that @file{$cdir} is not searched, since the compilation
23162 directory is not relevant to scripts.
23164 Entries can be placed in section @code{.debug_gdb_scripts} with,
23165 for example, this GCC macro:
23168 /* Note: The "MS" section flags are to remove duplicates. */
23169 #define DEFINE_GDB_SCRIPT(script_name) \
23171 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
23173 .asciz \"" script_name "\"\n\
23179 Then one can reference the macro in a header or source file like this:
23182 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
23185 The script name may include directories if desired.
23187 If the macro is put in a header, any application or library
23188 using this header will get a reference to the specified script.
23190 @node Which flavor to choose?
23191 @subsubsection Which flavor to choose?
23193 Given the multiple ways of auto-loading Python scripts, it might not always
23194 be clear which one to choose. This section provides some guidance.
23196 Benefits of the @file{-gdb.py} way:
23200 Can be used with file formats that don't support multiple sections.
23203 Ease of finding scripts for public libraries.
23205 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
23206 in the source search path.
23207 For publicly installed libraries, e.g., @file{libstdc++}, there typically
23208 isn't a source directory in which to find the script.
23211 Doesn't require source code additions.
23214 Benefits of the @code{.debug_gdb_scripts} way:
23218 Works with static linking.
23220 Scripts for libraries done the @file{-gdb.py} way require an objfile to
23221 trigger their loading. When an application is statically linked the only
23222 objfile available is the executable, and it is cumbersome to attach all the
23223 scripts from all the input libraries to the executable's @file{-gdb.py} script.
23226 Works with classes that are entirely inlined.
23228 Some classes can be entirely inlined, and thus there may not be an associated
23229 shared library to attach a @file{-gdb.py} script to.
23232 Scripts needn't be copied out of the source tree.
23234 In some circumstances, apps can be built out of large collections of internal
23235 libraries, and the build infrastructure necessary to install the
23236 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
23237 cumbersome. It may be easier to specify the scripts in the
23238 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
23239 top of the source tree to the source search path.
23242 @node Python modules
23243 @subsection Python modules
23244 @cindex python modules
23246 @value{GDBN} comes with a module to assist writing Python code.
23249 * gdb.printing:: Building and registering pretty-printers.
23250 * gdb.types:: Utilities for working with types.
23254 @subsubsection gdb.printing
23255 @cindex gdb.printing
23257 This module provides a collection of utilities for working with
23261 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
23262 This class specifies the API that makes @samp{info pretty-printer},
23263 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
23264 Pretty-printers should generally inherit from this class.
23266 @item SubPrettyPrinter (@var{name})
23267 For printers that handle multiple types, this class specifies the
23268 corresponding API for the subprinters.
23270 @item RegexpCollectionPrettyPrinter (@var{name})
23271 Utility class for handling multiple printers, all recognized via
23272 regular expressions.
23273 @xref{Writing a Pretty-Printer}, for an example.
23275 @item register_pretty_printer (@var{obj}, @var{printer})
23276 Register @var{printer} with the pretty-printer list of @var{obj}.
23280 @subsubsection gdb.types
23283 This module provides a collection of utilities for working with
23284 @code{gdb.Types} objects.
23287 @item get_basic_type (@var{type})
23288 Return @var{type} with const and volatile qualifiers stripped,
23289 and with typedefs and C@t{++} references converted to the underlying type.
23294 typedef const int const_int;
23296 const_int& foo_ref (foo);
23297 int main () @{ return 0; @}
23304 (gdb) python import gdb.types
23305 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
23306 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
23310 @item has_field (@var{type}, @var{field})
23311 Return @code{True} if @var{type}, assumed to be a type with fields
23312 (e.g., a structure or union), has field @var{field}.
23314 @item make_enum_dict (@var{enum_type})
23315 Return a Python @code{dictionary} type produced from @var{enum_type}.
23319 @chapter Command Interpreters
23320 @cindex command interpreters
23322 @value{GDBN} supports multiple command interpreters, and some command
23323 infrastructure to allow users or user interface writers to switch
23324 between interpreters or run commands in other interpreters.
23326 @value{GDBN} currently supports two command interpreters, the console
23327 interpreter (sometimes called the command-line interpreter or @sc{cli})
23328 and the machine interface interpreter (or @sc{gdb/mi}). This manual
23329 describes both of these interfaces in great detail.
23331 By default, @value{GDBN} will start with the console interpreter.
23332 However, the user may choose to start @value{GDBN} with another
23333 interpreter by specifying the @option{-i} or @option{--interpreter}
23334 startup options. Defined interpreters include:
23338 @cindex console interpreter
23339 The traditional console or command-line interpreter. This is the most often
23340 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
23341 @value{GDBN} will use this interpreter.
23344 @cindex mi interpreter
23345 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
23346 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
23347 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
23351 @cindex mi2 interpreter
23352 The current @sc{gdb/mi} interface.
23355 @cindex mi1 interpreter
23356 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
23360 @cindex invoke another interpreter
23361 The interpreter being used by @value{GDBN} may not be dynamically
23362 switched at runtime. Although possible, this could lead to a very
23363 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
23364 enters the command "interpreter-set console" in a console view,
23365 @value{GDBN} would switch to using the console interpreter, rendering
23366 the IDE inoperable!
23368 @kindex interpreter-exec
23369 Although you may only choose a single interpreter at startup, you may execute
23370 commands in any interpreter from the current interpreter using the appropriate
23371 command. If you are running the console interpreter, simply use the
23372 @code{interpreter-exec} command:
23375 interpreter-exec mi "-data-list-register-names"
23378 @sc{gdb/mi} has a similar command, although it is only available in versions of
23379 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
23382 @chapter @value{GDBN} Text User Interface
23384 @cindex Text User Interface
23387 * TUI Overview:: TUI overview
23388 * TUI Keys:: TUI key bindings
23389 * TUI Single Key Mode:: TUI single key mode
23390 * TUI Commands:: TUI-specific commands
23391 * TUI Configuration:: TUI configuration variables
23394 The @value{GDBN} Text User Interface (TUI) is a terminal
23395 interface which uses the @code{curses} library to show the source
23396 file, the assembly output, the program registers and @value{GDBN}
23397 commands in separate text windows. The TUI mode is supported only
23398 on platforms where a suitable version of the @code{curses} library
23401 @pindex @value{GDBTUI}
23402 The TUI mode is enabled by default when you invoke @value{GDBN} as
23403 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
23404 You can also switch in and out of TUI mode while @value{GDBN} runs by
23405 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
23406 @xref{TUI Keys, ,TUI Key Bindings}.
23409 @section TUI Overview
23411 In TUI mode, @value{GDBN} can display several text windows:
23415 This window is the @value{GDBN} command window with the @value{GDBN}
23416 prompt and the @value{GDBN} output. The @value{GDBN} input is still
23417 managed using readline.
23420 The source window shows the source file of the program. The current
23421 line and active breakpoints are displayed in this window.
23424 The assembly window shows the disassembly output of the program.
23427 This window shows the processor registers. Registers are highlighted
23428 when their values change.
23431 The source and assembly windows show the current program position
23432 by highlighting the current line and marking it with a @samp{>} marker.
23433 Breakpoints are indicated with two markers. The first marker
23434 indicates the breakpoint type:
23438 Breakpoint which was hit at least once.
23441 Breakpoint which was never hit.
23444 Hardware breakpoint which was hit at least once.
23447 Hardware breakpoint which was never hit.
23450 The second marker indicates whether the breakpoint is enabled or not:
23454 Breakpoint is enabled.
23457 Breakpoint is disabled.
23460 The source, assembly and register windows are updated when the current
23461 thread changes, when the frame changes, or when the program counter
23464 These windows are not all visible at the same time. The command
23465 window is always visible. The others can be arranged in several
23476 source and assembly,
23479 source and registers, or
23482 assembly and registers.
23485 A status line above the command window shows the following information:
23489 Indicates the current @value{GDBN} target.
23490 (@pxref{Targets, ,Specifying a Debugging Target}).
23493 Gives the current process or thread number.
23494 When no process is being debugged, this field is set to @code{No process}.
23497 Gives the current function name for the selected frame.
23498 The name is demangled if demangling is turned on (@pxref{Print Settings}).
23499 When there is no symbol corresponding to the current program counter,
23500 the string @code{??} is displayed.
23503 Indicates the current line number for the selected frame.
23504 When the current line number is not known, the string @code{??} is displayed.
23507 Indicates the current program counter address.
23511 @section TUI Key Bindings
23512 @cindex TUI key bindings
23514 The TUI installs several key bindings in the readline keymaps
23515 @ifset SYSTEM_READLINE
23516 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
23518 @ifclear SYSTEM_READLINE
23519 (@pxref{Command Line Editing}).
23521 The following key bindings are installed for both TUI mode and the
23522 @value{GDBN} standard mode.
23531 Enter or leave the TUI mode. When leaving the TUI mode,
23532 the curses window management stops and @value{GDBN} operates using
23533 its standard mode, writing on the terminal directly. When reentering
23534 the TUI mode, control is given back to the curses windows.
23535 The screen is then refreshed.
23539 Use a TUI layout with only one window. The layout will
23540 either be @samp{source} or @samp{assembly}. When the TUI mode
23541 is not active, it will switch to the TUI mode.
23543 Think of this key binding as the Emacs @kbd{C-x 1} binding.
23547 Use a TUI layout with at least two windows. When the current
23548 layout already has two windows, the next layout with two windows is used.
23549 When a new layout is chosen, one window will always be common to the
23550 previous layout and the new one.
23552 Think of it as the Emacs @kbd{C-x 2} binding.
23556 Change the active window. The TUI associates several key bindings
23557 (like scrolling and arrow keys) with the active window. This command
23558 gives the focus to the next TUI window.
23560 Think of it as the Emacs @kbd{C-x o} binding.
23564 Switch in and out of the TUI SingleKey mode that binds single
23565 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
23568 The following key bindings only work in the TUI mode:
23573 Scroll the active window one page up.
23577 Scroll the active window one page down.
23581 Scroll the active window one line up.
23585 Scroll the active window one line down.
23589 Scroll the active window one column left.
23593 Scroll the active window one column right.
23597 Refresh the screen.
23600 Because the arrow keys scroll the active window in the TUI mode, they
23601 are not available for their normal use by readline unless the command
23602 window has the focus. When another window is active, you must use
23603 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
23604 and @kbd{C-f} to control the command window.
23606 @node TUI Single Key Mode
23607 @section TUI Single Key Mode
23608 @cindex TUI single key mode
23610 The TUI also provides a @dfn{SingleKey} mode, which binds several
23611 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
23612 switch into this mode, where the following key bindings are used:
23615 @kindex c @r{(SingleKey TUI key)}
23619 @kindex d @r{(SingleKey TUI key)}
23623 @kindex f @r{(SingleKey TUI key)}
23627 @kindex n @r{(SingleKey TUI key)}
23631 @kindex q @r{(SingleKey TUI key)}
23633 exit the SingleKey mode.
23635 @kindex r @r{(SingleKey TUI key)}
23639 @kindex s @r{(SingleKey TUI key)}
23643 @kindex u @r{(SingleKey TUI key)}
23647 @kindex v @r{(SingleKey TUI key)}
23651 @kindex w @r{(SingleKey TUI key)}
23656 Other keys temporarily switch to the @value{GDBN} command prompt.
23657 The key that was pressed is inserted in the editing buffer so that
23658 it is possible to type most @value{GDBN} commands without interaction
23659 with the TUI SingleKey mode. Once the command is entered the TUI
23660 SingleKey mode is restored. The only way to permanently leave
23661 this mode is by typing @kbd{q} or @kbd{C-x s}.
23665 @section TUI-specific Commands
23666 @cindex TUI commands
23668 The TUI has specific commands to control the text windows.
23669 These commands are always available, even when @value{GDBN} is not in
23670 the TUI mode. When @value{GDBN} is in the standard mode, most
23671 of these commands will automatically switch to the TUI mode.
23673 Note that if @value{GDBN}'s @code{stdout} is not connected to a
23674 terminal, or @value{GDBN} has been started with the machine interface
23675 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
23676 these commands will fail with an error, because it would not be
23677 possible or desirable to enable curses window management.
23682 List and give the size of all displayed windows.
23686 Display the next layout.
23689 Display the previous layout.
23692 Display the source window only.
23695 Display the assembly window only.
23698 Display the source and assembly window.
23701 Display the register window together with the source or assembly window.
23705 Make the next window active for scrolling.
23708 Make the previous window active for scrolling.
23711 Make the source window active for scrolling.
23714 Make the assembly window active for scrolling.
23717 Make the register window active for scrolling.
23720 Make the command window active for scrolling.
23724 Refresh the screen. This is similar to typing @kbd{C-L}.
23726 @item tui reg float
23728 Show the floating point registers in the register window.
23730 @item tui reg general
23731 Show the general registers in the register window.
23734 Show the next register group. The list of register groups as well as
23735 their order is target specific. The predefined register groups are the
23736 following: @code{general}, @code{float}, @code{system}, @code{vector},
23737 @code{all}, @code{save}, @code{restore}.
23739 @item tui reg system
23740 Show the system registers in the register window.
23744 Update the source window and the current execution point.
23746 @item winheight @var{name} +@var{count}
23747 @itemx winheight @var{name} -@var{count}
23749 Change the height of the window @var{name} by @var{count}
23750 lines. Positive counts increase the height, while negative counts
23753 @item tabset @var{nchars}
23755 Set the width of tab stops to be @var{nchars} characters.
23758 @node TUI Configuration
23759 @section TUI Configuration Variables
23760 @cindex TUI configuration variables
23762 Several configuration variables control the appearance of TUI windows.
23765 @item set tui border-kind @var{kind}
23766 @kindex set tui border-kind
23767 Select the border appearance for the source, assembly and register windows.
23768 The possible values are the following:
23771 Use a space character to draw the border.
23774 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
23777 Use the Alternate Character Set to draw the border. The border is
23778 drawn using character line graphics if the terminal supports them.
23781 @item set tui border-mode @var{mode}
23782 @kindex set tui border-mode
23783 @itemx set tui active-border-mode @var{mode}
23784 @kindex set tui active-border-mode
23785 Select the display attributes for the borders of the inactive windows
23786 or the active window. The @var{mode} can be one of the following:
23789 Use normal attributes to display the border.
23795 Use reverse video mode.
23798 Use half bright mode.
23800 @item half-standout
23801 Use half bright and standout mode.
23804 Use extra bright or bold mode.
23806 @item bold-standout
23807 Use extra bright or bold and standout mode.
23812 @chapter Using @value{GDBN} under @sc{gnu} Emacs
23815 @cindex @sc{gnu} Emacs
23816 A special interface allows you to use @sc{gnu} Emacs to view (and
23817 edit) the source files for the program you are debugging with
23820 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
23821 executable file you want to debug as an argument. This command starts
23822 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
23823 created Emacs buffer.
23824 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
23826 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
23831 All ``terminal'' input and output goes through an Emacs buffer, called
23834 This applies both to @value{GDBN} commands and their output, and to the input
23835 and output done by the program you are debugging.
23837 This is useful because it means that you can copy the text of previous
23838 commands and input them again; you can even use parts of the output
23841 All the facilities of Emacs' Shell mode are available for interacting
23842 with your program. In particular, you can send signals the usual
23843 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
23847 @value{GDBN} displays source code through Emacs.
23849 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
23850 source file for that frame and puts an arrow (@samp{=>}) at the
23851 left margin of the current line. Emacs uses a separate buffer for
23852 source display, and splits the screen to show both your @value{GDBN} session
23855 Explicit @value{GDBN} @code{list} or search commands still produce output as
23856 usual, but you probably have no reason to use them from Emacs.
23859 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
23860 a graphical mode, enabled by default, which provides further buffers
23861 that can control the execution and describe the state of your program.
23862 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
23864 If you specify an absolute file name when prompted for the @kbd{M-x
23865 gdb} argument, then Emacs sets your current working directory to where
23866 your program resides. If you only specify the file name, then Emacs
23867 sets your current working directory to to the directory associated
23868 with the previous buffer. In this case, @value{GDBN} may find your
23869 program by searching your environment's @code{PATH} variable, but on
23870 some operating systems it might not find the source. So, although the
23871 @value{GDBN} input and output session proceeds normally, the auxiliary
23872 buffer does not display the current source and line of execution.
23874 The initial working directory of @value{GDBN} is printed on the top
23875 line of the GUD buffer and this serves as a default for the commands
23876 that specify files for @value{GDBN} to operate on. @xref{Files,
23877 ,Commands to Specify Files}.
23879 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
23880 need to call @value{GDBN} by a different name (for example, if you
23881 keep several configurations around, with different names) you can
23882 customize the Emacs variable @code{gud-gdb-command-name} to run the
23885 In the GUD buffer, you can use these special Emacs commands in
23886 addition to the standard Shell mode commands:
23890 Describe the features of Emacs' GUD Mode.
23893 Execute to another source line, like the @value{GDBN} @code{step} command; also
23894 update the display window to show the current file and location.
23897 Execute to next source line in this function, skipping all function
23898 calls, like the @value{GDBN} @code{next} command. Then update the display window
23899 to show the current file and location.
23902 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
23903 display window accordingly.
23906 Execute until exit from the selected stack frame, like the @value{GDBN}
23907 @code{finish} command.
23910 Continue execution of your program, like the @value{GDBN} @code{continue}
23914 Go up the number of frames indicated by the numeric argument
23915 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
23916 like the @value{GDBN} @code{up} command.
23919 Go down the number of frames indicated by the numeric argument, like the
23920 @value{GDBN} @code{down} command.
23923 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
23924 tells @value{GDBN} to set a breakpoint on the source line point is on.
23926 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
23927 separate frame which shows a backtrace when the GUD buffer is current.
23928 Move point to any frame in the stack and type @key{RET} to make it
23929 become the current frame and display the associated source in the
23930 source buffer. Alternatively, click @kbd{Mouse-2} to make the
23931 selected frame become the current one. In graphical mode, the
23932 speedbar displays watch expressions.
23934 If you accidentally delete the source-display buffer, an easy way to get
23935 it back is to type the command @code{f} in the @value{GDBN} buffer, to
23936 request a frame display; when you run under Emacs, this recreates
23937 the source buffer if necessary to show you the context of the current
23940 The source files displayed in Emacs are in ordinary Emacs buffers
23941 which are visiting the source files in the usual way. You can edit
23942 the files with these buffers if you wish; but keep in mind that @value{GDBN}
23943 communicates with Emacs in terms of line numbers. If you add or
23944 delete lines from the text, the line numbers that @value{GDBN} knows cease
23945 to correspond properly with the code.
23947 A more detailed description of Emacs' interaction with @value{GDBN} is
23948 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
23951 @c The following dropped because Epoch is nonstandard. Reactivate
23952 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
23954 @kindex Emacs Epoch environment
23958 Version 18 of @sc{gnu} Emacs has a built-in window system
23959 called the @code{epoch}
23960 environment. Users of this environment can use a new command,
23961 @code{inspect} which performs identically to @code{print} except that
23962 each value is printed in its own window.
23967 @chapter The @sc{gdb/mi} Interface
23969 @unnumberedsec Function and Purpose
23971 @cindex @sc{gdb/mi}, its purpose
23972 @sc{gdb/mi} is a line based machine oriented text interface to
23973 @value{GDBN} and is activated by specifying using the
23974 @option{--interpreter} command line option (@pxref{Mode Options}). It
23975 is specifically intended to support the development of systems which
23976 use the debugger as just one small component of a larger system.
23978 This chapter is a specification of the @sc{gdb/mi} interface. It is written
23979 in the form of a reference manual.
23981 Note that @sc{gdb/mi} is still under construction, so some of the
23982 features described below are incomplete and subject to change
23983 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
23985 @unnumberedsec Notation and Terminology
23987 @cindex notational conventions, for @sc{gdb/mi}
23988 This chapter uses the following notation:
23992 @code{|} separates two alternatives.
23995 @code{[ @var{something} ]} indicates that @var{something} is optional:
23996 it may or may not be given.
23999 @code{( @var{group} )*} means that @var{group} inside the parentheses
24000 may repeat zero or more times.
24003 @code{( @var{group} )+} means that @var{group} inside the parentheses
24004 may repeat one or more times.
24007 @code{"@var{string}"} means a literal @var{string}.
24011 @heading Dependencies
24015 * GDB/MI General Design::
24016 * GDB/MI Command Syntax::
24017 * GDB/MI Compatibility with CLI::
24018 * GDB/MI Development and Front Ends::
24019 * GDB/MI Output Records::
24020 * GDB/MI Simple Examples::
24021 * GDB/MI Command Description Format::
24022 * GDB/MI Breakpoint Commands::
24023 * GDB/MI Program Context::
24024 * GDB/MI Thread Commands::
24025 * GDB/MI Program Execution::
24026 * GDB/MI Stack Manipulation::
24027 * GDB/MI Variable Objects::
24028 * GDB/MI Data Manipulation::
24029 * GDB/MI Tracepoint Commands::
24030 * GDB/MI Symbol Query::
24031 * GDB/MI File Commands::
24033 * GDB/MI Kod Commands::
24034 * GDB/MI Memory Overlay Commands::
24035 * GDB/MI Signal Handling Commands::
24037 * GDB/MI Target Manipulation::
24038 * GDB/MI File Transfer Commands::
24039 * GDB/MI Miscellaneous Commands::
24042 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24043 @node GDB/MI General Design
24044 @section @sc{gdb/mi} General Design
24045 @cindex GDB/MI General Design
24047 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
24048 parts---commands sent to @value{GDBN}, responses to those commands
24049 and notifications. Each command results in exactly one response,
24050 indicating either successful completion of the command, or an error.
24051 For the commands that do not resume the target, the response contains the
24052 requested information. For the commands that resume the target, the
24053 response only indicates whether the target was successfully resumed.
24054 Notifications is the mechanism for reporting changes in the state of the
24055 target, or in @value{GDBN} state, that cannot conveniently be associated with
24056 a command and reported as part of that command response.
24058 The important examples of notifications are:
24062 Exec notifications. These are used to report changes in
24063 target state---when a target is resumed, or stopped. It would not
24064 be feasible to include this information in response of resuming
24065 commands, because one resume commands can result in multiple events in
24066 different threads. Also, quite some time may pass before any event
24067 happens in the target, while a frontend needs to know whether the resuming
24068 command itself was successfully executed.
24071 Console output, and status notifications. Console output
24072 notifications are used to report output of CLI commands, as well as
24073 diagnostics for other commands. Status notifications are used to
24074 report the progress of a long-running operation. Naturally, including
24075 this information in command response would mean no output is produced
24076 until the command is finished, which is undesirable.
24079 General notifications. Commands may have various side effects on
24080 the @value{GDBN} or target state beyond their official purpose. For example,
24081 a command may change the selected thread. Although such changes can
24082 be included in command response, using notification allows for more
24083 orthogonal frontend design.
24087 There's no guarantee that whenever an MI command reports an error,
24088 @value{GDBN} or the target are in any specific state, and especially,
24089 the state is not reverted to the state before the MI command was
24090 processed. Therefore, whenever an MI command results in an error,
24091 we recommend that the frontend refreshes all the information shown in
24092 the user interface.
24096 * Context management::
24097 * Asynchronous and non-stop modes::
24101 @node Context management
24102 @subsection Context management
24104 In most cases when @value{GDBN} accesses the target, this access is
24105 done in context of a specific thread and frame (@pxref{Frames}).
24106 Often, even when accessing global data, the target requires that a thread
24107 be specified. The CLI interface maintains the selected thread and frame,
24108 and supplies them to target on each command. This is convenient,
24109 because a command line user would not want to specify that information
24110 explicitly on each command, and because user interacts with
24111 @value{GDBN} via a single terminal, so no confusion is possible as
24112 to what thread and frame are the current ones.
24114 In the case of MI, the concept of selected thread and frame is less
24115 useful. First, a frontend can easily remember this information
24116 itself. Second, a graphical frontend can have more than one window,
24117 each one used for debugging a different thread, and the frontend might
24118 want to access additional threads for internal purposes. This
24119 increases the risk that by relying on implicitly selected thread, the
24120 frontend may be operating on a wrong one. Therefore, each MI command
24121 should explicitly specify which thread and frame to operate on. To
24122 make it possible, each MI command accepts the @samp{--thread} and
24123 @samp{--frame} options, the value to each is @value{GDBN} identifier
24124 for thread and frame to operate on.
24126 Usually, each top-level window in a frontend allows the user to select
24127 a thread and a frame, and remembers the user selection for further
24128 operations. However, in some cases @value{GDBN} may suggest that the
24129 current thread be changed. For example, when stopping on a breakpoint
24130 it is reasonable to switch to the thread where breakpoint is hit. For
24131 another example, if the user issues the CLI @samp{thread} command via
24132 the frontend, it is desirable to change the frontend's selected thread to the
24133 one specified by user. @value{GDBN} communicates the suggestion to
24134 change current thread using the @samp{=thread-selected} notification.
24135 No such notification is available for the selected frame at the moment.
24137 Note that historically, MI shares the selected thread with CLI, so
24138 frontends used the @code{-thread-select} to execute commands in the
24139 right context. However, getting this to work right is cumbersome. The
24140 simplest way is for frontend to emit @code{-thread-select} command
24141 before every command. This doubles the number of commands that need
24142 to be sent. The alternative approach is to suppress @code{-thread-select}
24143 if the selected thread in @value{GDBN} is supposed to be identical to the
24144 thread the frontend wants to operate on. However, getting this
24145 optimization right can be tricky. In particular, if the frontend
24146 sends several commands to @value{GDBN}, and one of the commands changes the
24147 selected thread, then the behaviour of subsequent commands will
24148 change. So, a frontend should either wait for response from such
24149 problematic commands, or explicitly add @code{-thread-select} for
24150 all subsequent commands. No frontend is known to do this exactly
24151 right, so it is suggested to just always pass the @samp{--thread} and
24152 @samp{--frame} options.
24154 @node Asynchronous and non-stop modes
24155 @subsection Asynchronous command execution and non-stop mode
24157 On some targets, @value{GDBN} is capable of processing MI commands
24158 even while the target is running. This is called @dfn{asynchronous
24159 command execution} (@pxref{Background Execution}). The frontend may
24160 specify a preferrence for asynchronous execution using the
24161 @code{-gdb-set target-async 1} command, which should be emitted before
24162 either running the executable or attaching to the target. After the
24163 frontend has started the executable or attached to the target, it can
24164 find if asynchronous execution is enabled using the
24165 @code{-list-target-features} command.
24167 Even if @value{GDBN} can accept a command while target is running,
24168 many commands that access the target do not work when the target is
24169 running. Therefore, asynchronous command execution is most useful
24170 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
24171 it is possible to examine the state of one thread, while other threads
24174 When a given thread is running, MI commands that try to access the
24175 target in the context of that thread may not work, or may work only on
24176 some targets. In particular, commands that try to operate on thread's
24177 stack will not work, on any target. Commands that read memory, or
24178 modify breakpoints, may work or not work, depending on the target. Note
24179 that even commands that operate on global state, such as @code{print},
24180 @code{set}, and breakpoint commands, still access the target in the
24181 context of a specific thread, so frontend should try to find a
24182 stopped thread and perform the operation on that thread (using the
24183 @samp{--thread} option).
24185 Which commands will work in the context of a running thread is
24186 highly target dependent. However, the two commands
24187 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
24188 to find the state of a thread, will always work.
24190 @node Thread groups
24191 @subsection Thread groups
24192 @value{GDBN} may be used to debug several processes at the same time.
24193 On some platfroms, @value{GDBN} may support debugging of several
24194 hardware systems, each one having several cores with several different
24195 processes running on each core. This section describes the MI
24196 mechanism to support such debugging scenarios.
24198 The key observation is that regardless of the structure of the
24199 target, MI can have a global list of threads, because most commands that
24200 accept the @samp{--thread} option do not need to know what process that
24201 thread belongs to. Therefore, it is not necessary to introduce
24202 neither additional @samp{--process} option, nor an notion of the
24203 current process in the MI interface. The only strictly new feature
24204 that is required is the ability to find how the threads are grouped
24207 To allow the user to discover such grouping, and to support arbitrary
24208 hierarchy of machines/cores/processes, MI introduces the concept of a
24209 @dfn{thread group}. Thread group is a collection of threads and other
24210 thread groups. A thread group always has a string identifier, a type,
24211 and may have additional attributes specific to the type. A new
24212 command, @code{-list-thread-groups}, returns the list of top-level
24213 thread groups, which correspond to processes that @value{GDBN} is
24214 debugging at the moment. By passing an identifier of a thread group
24215 to the @code{-list-thread-groups} command, it is possible to obtain
24216 the members of specific thread group.
24218 To allow the user to easily discover processes, and other objects, he
24219 wishes to debug, a concept of @dfn{available thread group} is
24220 introduced. Available thread group is an thread group that
24221 @value{GDBN} is not debugging, but that can be attached to, using the
24222 @code{-target-attach} command. The list of available top-level thread
24223 groups can be obtained using @samp{-list-thread-groups --available}.
24224 In general, the content of a thread group may be only retrieved only
24225 after attaching to that thread group.
24227 Thread groups are related to inferiors (@pxref{Inferiors and
24228 Programs}). Each inferior corresponds to a thread group of a special
24229 type @samp{process}, and some additional operations are permitted on
24230 such thread groups.
24232 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24233 @node GDB/MI Command Syntax
24234 @section @sc{gdb/mi} Command Syntax
24237 * GDB/MI Input Syntax::
24238 * GDB/MI Output Syntax::
24241 @node GDB/MI Input Syntax
24242 @subsection @sc{gdb/mi} Input Syntax
24244 @cindex input syntax for @sc{gdb/mi}
24245 @cindex @sc{gdb/mi}, input syntax
24247 @item @var{command} @expansion{}
24248 @code{@var{cli-command} | @var{mi-command}}
24250 @item @var{cli-command} @expansion{}
24251 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
24252 @var{cli-command} is any existing @value{GDBN} CLI command.
24254 @item @var{mi-command} @expansion{}
24255 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
24256 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
24258 @item @var{token} @expansion{}
24259 "any sequence of digits"
24261 @item @var{option} @expansion{}
24262 @code{"-" @var{parameter} [ " " @var{parameter} ]}
24264 @item @var{parameter} @expansion{}
24265 @code{@var{non-blank-sequence} | @var{c-string}}
24267 @item @var{operation} @expansion{}
24268 @emph{any of the operations described in this chapter}
24270 @item @var{non-blank-sequence} @expansion{}
24271 @emph{anything, provided it doesn't contain special characters such as
24272 "-", @var{nl}, """ and of course " "}
24274 @item @var{c-string} @expansion{}
24275 @code{""" @var{seven-bit-iso-c-string-content} """}
24277 @item @var{nl} @expansion{}
24286 The CLI commands are still handled by the @sc{mi} interpreter; their
24287 output is described below.
24290 The @code{@var{token}}, when present, is passed back when the command
24294 Some @sc{mi} commands accept optional arguments as part of the parameter
24295 list. Each option is identified by a leading @samp{-} (dash) and may be
24296 followed by an optional argument parameter. Options occur first in the
24297 parameter list and can be delimited from normal parameters using
24298 @samp{--} (this is useful when some parameters begin with a dash).
24305 We want easy access to the existing CLI syntax (for debugging).
24308 We want it to be easy to spot a @sc{mi} operation.
24311 @node GDB/MI Output Syntax
24312 @subsection @sc{gdb/mi} Output Syntax
24314 @cindex output syntax of @sc{gdb/mi}
24315 @cindex @sc{gdb/mi}, output syntax
24316 The output from @sc{gdb/mi} consists of zero or more out-of-band records
24317 followed, optionally, by a single result record. This result record
24318 is for the most recent command. The sequence of output records is
24319 terminated by @samp{(gdb)}.
24321 If an input command was prefixed with a @code{@var{token}} then the
24322 corresponding output for that command will also be prefixed by that same
24326 @item @var{output} @expansion{}
24327 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
24329 @item @var{result-record} @expansion{}
24330 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
24332 @item @var{out-of-band-record} @expansion{}
24333 @code{@var{async-record} | @var{stream-record}}
24335 @item @var{async-record} @expansion{}
24336 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
24338 @item @var{exec-async-output} @expansion{}
24339 @code{[ @var{token} ] "*" @var{async-output}}
24341 @item @var{status-async-output} @expansion{}
24342 @code{[ @var{token} ] "+" @var{async-output}}
24344 @item @var{notify-async-output} @expansion{}
24345 @code{[ @var{token} ] "=" @var{async-output}}
24347 @item @var{async-output} @expansion{}
24348 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
24350 @item @var{result-class} @expansion{}
24351 @code{"done" | "running" | "connected" | "error" | "exit"}
24353 @item @var{async-class} @expansion{}
24354 @code{"stopped" | @var{others}} (where @var{others} will be added
24355 depending on the needs---this is still in development).
24357 @item @var{result} @expansion{}
24358 @code{ @var{variable} "=" @var{value}}
24360 @item @var{variable} @expansion{}
24361 @code{ @var{string} }
24363 @item @var{value} @expansion{}
24364 @code{ @var{const} | @var{tuple} | @var{list} }
24366 @item @var{const} @expansion{}
24367 @code{@var{c-string}}
24369 @item @var{tuple} @expansion{}
24370 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
24372 @item @var{list} @expansion{}
24373 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
24374 @var{result} ( "," @var{result} )* "]" }
24376 @item @var{stream-record} @expansion{}
24377 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
24379 @item @var{console-stream-output} @expansion{}
24380 @code{"~" @var{c-string}}
24382 @item @var{target-stream-output} @expansion{}
24383 @code{"@@" @var{c-string}}
24385 @item @var{log-stream-output} @expansion{}
24386 @code{"&" @var{c-string}}
24388 @item @var{nl} @expansion{}
24391 @item @var{token} @expansion{}
24392 @emph{any sequence of digits}.
24400 All output sequences end in a single line containing a period.
24403 The @code{@var{token}} is from the corresponding request. Note that
24404 for all async output, while the token is allowed by the grammar and
24405 may be output by future versions of @value{GDBN} for select async
24406 output messages, it is generally omitted. Frontends should treat
24407 all async output as reporting general changes in the state of the
24408 target and there should be no need to associate async output to any
24412 @cindex status output in @sc{gdb/mi}
24413 @var{status-async-output} contains on-going status information about the
24414 progress of a slow operation. It can be discarded. All status output is
24415 prefixed by @samp{+}.
24418 @cindex async output in @sc{gdb/mi}
24419 @var{exec-async-output} contains asynchronous state change on the target
24420 (stopped, started, disappeared). All async output is prefixed by
24424 @cindex notify output in @sc{gdb/mi}
24425 @var{notify-async-output} contains supplementary information that the
24426 client should handle (e.g., a new breakpoint information). All notify
24427 output is prefixed by @samp{=}.
24430 @cindex console output in @sc{gdb/mi}
24431 @var{console-stream-output} is output that should be displayed as is in the
24432 console. It is the textual response to a CLI command. All the console
24433 output is prefixed by @samp{~}.
24436 @cindex target output in @sc{gdb/mi}
24437 @var{target-stream-output} is the output produced by the target program.
24438 All the target output is prefixed by @samp{@@}.
24441 @cindex log output in @sc{gdb/mi}
24442 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
24443 instance messages that should be displayed as part of an error log. All
24444 the log output is prefixed by @samp{&}.
24447 @cindex list output in @sc{gdb/mi}
24448 New @sc{gdb/mi} commands should only output @var{lists} containing
24454 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
24455 details about the various output records.
24457 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24458 @node GDB/MI Compatibility with CLI
24459 @section @sc{gdb/mi} Compatibility with CLI
24461 @cindex compatibility, @sc{gdb/mi} and CLI
24462 @cindex @sc{gdb/mi}, compatibility with CLI
24464 For the developers convenience CLI commands can be entered directly,
24465 but there may be some unexpected behaviour. For example, commands
24466 that query the user will behave as if the user replied yes, breakpoint
24467 command lists are not executed and some CLI commands, such as
24468 @code{if}, @code{when} and @code{define}, prompt for further input with
24469 @samp{>}, which is not valid MI output.
24471 This feature may be removed at some stage in the future and it is
24472 recommended that front ends use the @code{-interpreter-exec} command
24473 (@pxref{-interpreter-exec}).
24475 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24476 @node GDB/MI Development and Front Ends
24477 @section @sc{gdb/mi} Development and Front Ends
24478 @cindex @sc{gdb/mi} development
24480 The application which takes the MI output and presents the state of the
24481 program being debugged to the user is called a @dfn{front end}.
24483 Although @sc{gdb/mi} is still incomplete, it is currently being used
24484 by a variety of front ends to @value{GDBN}. This makes it difficult
24485 to introduce new functionality without breaking existing usage. This
24486 section tries to minimize the problems by describing how the protocol
24489 Some changes in MI need not break a carefully designed front end, and
24490 for these the MI version will remain unchanged. The following is a
24491 list of changes that may occur within one level, so front ends should
24492 parse MI output in a way that can handle them:
24496 New MI commands may be added.
24499 New fields may be added to the output of any MI command.
24502 The range of values for fields with specified values, e.g.,
24503 @code{in_scope} (@pxref{-var-update}) may be extended.
24505 @c The format of field's content e.g type prefix, may change so parse it
24506 @c at your own risk. Yes, in general?
24508 @c The order of fields may change? Shouldn't really matter but it might
24509 @c resolve inconsistencies.
24512 If the changes are likely to break front ends, the MI version level
24513 will be increased by one. This will allow the front end to parse the
24514 output according to the MI version. Apart from mi0, new versions of
24515 @value{GDBN} will not support old versions of MI and it will be the
24516 responsibility of the front end to work with the new one.
24518 @c Starting with mi3, add a new command -mi-version that prints the MI
24521 The best way to avoid unexpected changes in MI that might break your front
24522 end is to make your project known to @value{GDBN} developers and
24523 follow development on @email{gdb@@sourceware.org} and
24524 @email{gdb-patches@@sourceware.org}.
24525 @cindex mailing lists
24527 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24528 @node GDB/MI Output Records
24529 @section @sc{gdb/mi} Output Records
24532 * GDB/MI Result Records::
24533 * GDB/MI Stream Records::
24534 * GDB/MI Async Records::
24535 * GDB/MI Frame Information::
24536 * GDB/MI Thread Information::
24539 @node GDB/MI Result Records
24540 @subsection @sc{gdb/mi} Result Records
24542 @cindex result records in @sc{gdb/mi}
24543 @cindex @sc{gdb/mi}, result records
24544 In addition to a number of out-of-band notifications, the response to a
24545 @sc{gdb/mi} command includes one of the following result indications:
24549 @item "^done" [ "," @var{results} ]
24550 The synchronous operation was successful, @code{@var{results}} are the return
24555 This result record is equivalent to @samp{^done}. Historically, it
24556 was output instead of @samp{^done} if the command has resumed the
24557 target. This behaviour is maintained for backward compatibility, but
24558 all frontends should treat @samp{^done} and @samp{^running}
24559 identically and rely on the @samp{*running} output record to determine
24560 which threads are resumed.
24564 @value{GDBN} has connected to a remote target.
24566 @item "^error" "," @var{c-string}
24568 The operation failed. The @code{@var{c-string}} contains the corresponding
24573 @value{GDBN} has terminated.
24577 @node GDB/MI Stream Records
24578 @subsection @sc{gdb/mi} Stream Records
24580 @cindex @sc{gdb/mi}, stream records
24581 @cindex stream records in @sc{gdb/mi}
24582 @value{GDBN} internally maintains a number of output streams: the console, the
24583 target, and the log. The output intended for each of these streams is
24584 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
24586 Each stream record begins with a unique @dfn{prefix character} which
24587 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
24588 Syntax}). In addition to the prefix, each stream record contains a
24589 @code{@var{string-output}}. This is either raw text (with an implicit new
24590 line) or a quoted C string (which does not contain an implicit newline).
24593 @item "~" @var{string-output}
24594 The console output stream contains text that should be displayed in the
24595 CLI console window. It contains the textual responses to CLI commands.
24597 @item "@@" @var{string-output}
24598 The target output stream contains any textual output from the running
24599 target. This is only present when GDB's event loop is truly
24600 asynchronous, which is currently only the case for remote targets.
24602 @item "&" @var{string-output}
24603 The log stream contains debugging messages being produced by @value{GDBN}'s
24607 @node GDB/MI Async Records
24608 @subsection @sc{gdb/mi} Async Records
24610 @cindex async records in @sc{gdb/mi}
24611 @cindex @sc{gdb/mi}, async records
24612 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
24613 additional changes that have occurred. Those changes can either be a
24614 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
24615 target activity (e.g., target stopped).
24617 The following is the list of possible async records:
24621 @item *running,thread-id="@var{thread}"
24622 The target is now running. The @var{thread} field tells which
24623 specific thread is now running, and can be @samp{all} if all threads
24624 are running. The frontend should assume that no interaction with a
24625 running thread is possible after this notification is produced.
24626 The frontend should not assume that this notification is output
24627 only once for any command. @value{GDBN} may emit this notification
24628 several times, either for different threads, because it cannot resume
24629 all threads together, or even for a single thread, if the thread must
24630 be stepped though some code before letting it run freely.
24632 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
24633 The target has stopped. The @var{reason} field can have one of the
24637 @item breakpoint-hit
24638 A breakpoint was reached.
24639 @item watchpoint-trigger
24640 A watchpoint was triggered.
24641 @item read-watchpoint-trigger
24642 A read watchpoint was triggered.
24643 @item access-watchpoint-trigger
24644 An access watchpoint was triggered.
24645 @item function-finished
24646 An -exec-finish or similar CLI command was accomplished.
24647 @item location-reached
24648 An -exec-until or similar CLI command was accomplished.
24649 @item watchpoint-scope
24650 A watchpoint has gone out of scope.
24651 @item end-stepping-range
24652 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
24653 similar CLI command was accomplished.
24654 @item exited-signalled
24655 The inferior exited because of a signal.
24657 The inferior exited.
24658 @item exited-normally
24659 The inferior exited normally.
24660 @item signal-received
24661 A signal was received by the inferior.
24664 The @var{id} field identifies the thread that directly caused the stop
24665 -- for example by hitting a breakpoint. Depending on whether all-stop
24666 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
24667 stop all threads, or only the thread that directly triggered the stop.
24668 If all threads are stopped, the @var{stopped} field will have the
24669 value of @code{"all"}. Otherwise, the value of the @var{stopped}
24670 field will be a list of thread identifiers. Presently, this list will
24671 always include a single thread, but frontend should be prepared to see
24672 several threads in the list. The @var{core} field reports the
24673 processor core on which the stop event has happened. This field may be absent
24674 if such information is not available.
24676 @item =thread-group-added,id="@var{id}"
24677 @itemx =thread-group-removed,id="@var{id}"
24678 A thread group was either added or removed. The @var{id} field
24679 contains the @value{GDBN} identifier of the thread group. When a thread
24680 group is added, it generally might not be associated with a running
24681 process. When a thread group is removed, its id becomes invalid and
24682 cannot be used in any way.
24684 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
24685 A thread group became associated with a running program,
24686 either because the program was just started or the thread group
24687 was attached to a program. The @var{id} field contains the
24688 @value{GDBN} identifier of the thread group. The @var{pid} field
24689 contains process identifier, specific to the operating system.
24691 @itemx =thread-group-exited,id="@var{id}"
24692 A thread group is no longer associated with a running program,
24693 either because the program has exited, or because it was detached
24694 from. The @var{id} field contains the @value{GDBN} identifier of the
24697 @item =thread-created,id="@var{id}",group-id="@var{gid}"
24698 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
24699 A thread either was created, or has exited. The @var{id} field
24700 contains the @value{GDBN} identifier of the thread. The @var{gid}
24701 field identifies the thread group this thread belongs to.
24703 @item =thread-selected,id="@var{id}"
24704 Informs that the selected thread was changed as result of the last
24705 command. This notification is not emitted as result of @code{-thread-select}
24706 command but is emitted whenever an MI command that is not documented
24707 to change the selected thread actually changes it. In particular,
24708 invoking, directly or indirectly (via user-defined command), the CLI
24709 @code{thread} command, will generate this notification.
24711 We suggest that in response to this notification, front ends
24712 highlight the selected thread and cause subsequent commands to apply to
24715 @item =library-loaded,...
24716 Reports that a new library file was loaded by the program. This
24717 notification has 4 fields---@var{id}, @var{target-name},
24718 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
24719 opaque identifier of the library. For remote debugging case,
24720 @var{target-name} and @var{host-name} fields give the name of the
24721 library file on the target, and on the host respectively. For native
24722 debugging, both those fields have the same value. The
24723 @var{symbols-loaded} field reports if the debug symbols for this
24724 library are loaded. The @var{thread-group} field, if present,
24725 specifies the id of the thread group in whose context the library was loaded.
24726 If the field is absent, it means the library was loaded in the context
24727 of all present thread groups.
24729 @item =library-unloaded,...
24730 Reports that a library was unloaded by the program. This notification
24731 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
24732 the same meaning as for the @code{=library-loaded} notification.
24733 The @var{thread-group} field, if present, specifies the id of the
24734 thread group in whose context the library was unloaded. If the field is
24735 absent, it means the library was unloaded in the context of all present
24740 @node GDB/MI Frame Information
24741 @subsection @sc{gdb/mi} Frame Information
24743 Response from many MI commands includes an information about stack
24744 frame. This information is a tuple that may have the following
24749 The level of the stack frame. The innermost frame has the level of
24750 zero. This field is always present.
24753 The name of the function corresponding to the frame. This field may
24754 be absent if @value{GDBN} is unable to determine the function name.
24757 The code address for the frame. This field is always present.
24760 The name of the source files that correspond to the frame's code
24761 address. This field may be absent.
24764 The source line corresponding to the frames' code address. This field
24768 The name of the binary file (either executable or shared library) the
24769 corresponds to the frame's code address. This field may be absent.
24773 @node GDB/MI Thread Information
24774 @subsection @sc{gdb/mi} Thread Information
24776 Whenever @value{GDBN} has to report an information about a thread, it
24777 uses a tuple with the following fields:
24781 The numeric id assigned to the thread by @value{GDBN}. This field is
24785 Target-specific string identifying the thread. This field is always present.
24788 Additional information about the thread provided by the target.
24789 It is supposed to be human-readable and not interpreted by the
24790 frontend. This field is optional.
24793 Either @samp{stopped} or @samp{running}, depending on whether the
24794 thread is presently running. This field is always present.
24797 The value of this field is an integer number of the processor core the
24798 thread was last seen on. This field is optional.
24802 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24803 @node GDB/MI Simple Examples
24804 @section Simple Examples of @sc{gdb/mi} Interaction
24805 @cindex @sc{gdb/mi}, simple examples
24807 This subsection presents several simple examples of interaction using
24808 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
24809 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
24810 the output received from @sc{gdb/mi}.
24812 Note the line breaks shown in the examples are here only for
24813 readability, they don't appear in the real output.
24815 @subheading Setting a Breakpoint
24817 Setting a breakpoint generates synchronous output which contains detailed
24818 information of the breakpoint.
24821 -> -break-insert main
24822 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24823 enabled="y",addr="0x08048564",func="main",file="myprog.c",
24824 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
24828 @subheading Program Execution
24830 Program execution generates asynchronous records and MI gives the
24831 reason that execution stopped.
24837 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
24838 frame=@{addr="0x08048564",func="main",
24839 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
24840 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
24845 <- *stopped,reason="exited-normally"
24849 @subheading Quitting @value{GDBN}
24851 Quitting @value{GDBN} just prints the result class @samp{^exit}.
24859 Please note that @samp{^exit} is printed immediately, but it might
24860 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
24861 performs necessary cleanups, including killing programs being debugged
24862 or disconnecting from debug hardware, so the frontend should wait till
24863 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
24864 fails to exit in reasonable time.
24866 @subheading A Bad Command
24868 Here's what happens if you pass a non-existent command:
24872 <- ^error,msg="Undefined MI command: rubbish"
24877 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24878 @node GDB/MI Command Description Format
24879 @section @sc{gdb/mi} Command Description Format
24881 The remaining sections describe blocks of commands. Each block of
24882 commands is laid out in a fashion similar to this section.
24884 @subheading Motivation
24886 The motivation for this collection of commands.
24888 @subheading Introduction
24890 A brief introduction to this collection of commands as a whole.
24892 @subheading Commands
24894 For each command in the block, the following is described:
24896 @subsubheading Synopsis
24899 -command @var{args}@dots{}
24902 @subsubheading Result
24904 @subsubheading @value{GDBN} Command
24906 The corresponding @value{GDBN} CLI command(s), if any.
24908 @subsubheading Example
24910 Example(s) formatted for readability. Some of the described commands have
24911 not been implemented yet and these are labeled N.A.@: (not available).
24914 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24915 @node GDB/MI Breakpoint Commands
24916 @section @sc{gdb/mi} Breakpoint Commands
24918 @cindex breakpoint commands for @sc{gdb/mi}
24919 @cindex @sc{gdb/mi}, breakpoint commands
24920 This section documents @sc{gdb/mi} commands for manipulating
24923 @subheading The @code{-break-after} Command
24924 @findex -break-after
24926 @subsubheading Synopsis
24929 -break-after @var{number} @var{count}
24932 The breakpoint number @var{number} is not in effect until it has been
24933 hit @var{count} times. To see how this is reflected in the output of
24934 the @samp{-break-list} command, see the description of the
24935 @samp{-break-list} command below.
24937 @subsubheading @value{GDBN} Command
24939 The corresponding @value{GDBN} command is @samp{ignore}.
24941 @subsubheading Example
24946 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24947 enabled="y",addr="0x000100d0",func="main",file="hello.c",
24948 fullname="/home/foo/hello.c",line="5",times="0"@}
24955 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24956 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24957 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24958 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24959 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24960 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24961 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24962 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24963 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24964 line="5",times="0",ignore="3"@}]@}
24969 @subheading The @code{-break-catch} Command
24970 @findex -break-catch
24973 @subheading The @code{-break-commands} Command
24974 @findex -break-commands
24976 @subsubheading Synopsis
24979 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
24982 Specifies the CLI commands that should be executed when breakpoint
24983 @var{number} is hit. The parameters @var{command1} to @var{commandN}
24984 are the commands. If no command is specified, any previously-set
24985 commands are cleared. @xref{Break Commands}. Typical use of this
24986 functionality is tracing a program, that is, printing of values of
24987 some variables whenever breakpoint is hit and then continuing.
24989 @subsubheading @value{GDBN} Command
24991 The corresponding @value{GDBN} command is @samp{commands}.
24993 @subsubheading Example
24998 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24999 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25000 fullname="/home/foo/hello.c",line="5",times="0"@}
25002 -break-commands 1 "print v" "continue"
25007 @subheading The @code{-break-condition} Command
25008 @findex -break-condition
25010 @subsubheading Synopsis
25013 -break-condition @var{number} @var{expr}
25016 Breakpoint @var{number} will stop the program only if the condition in
25017 @var{expr} is true. The condition becomes part of the
25018 @samp{-break-list} output (see the description of the @samp{-break-list}
25021 @subsubheading @value{GDBN} Command
25023 The corresponding @value{GDBN} command is @samp{condition}.
25025 @subsubheading Example
25029 -break-condition 1 1
25033 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25034 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25035 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25036 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25037 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25038 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25039 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25040 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25041 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25042 line="5",cond="1",times="0",ignore="3"@}]@}
25046 @subheading The @code{-break-delete} Command
25047 @findex -break-delete
25049 @subsubheading Synopsis
25052 -break-delete ( @var{breakpoint} )+
25055 Delete the breakpoint(s) whose number(s) are specified in the argument
25056 list. This is obviously reflected in the breakpoint list.
25058 @subsubheading @value{GDBN} Command
25060 The corresponding @value{GDBN} command is @samp{delete}.
25062 @subsubheading Example
25070 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
25071 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25072 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25073 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25074 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25075 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25076 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25081 @subheading The @code{-break-disable} Command
25082 @findex -break-disable
25084 @subsubheading Synopsis
25087 -break-disable ( @var{breakpoint} )+
25090 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
25091 break list is now set to @samp{n} for the named @var{breakpoint}(s).
25093 @subsubheading @value{GDBN} Command
25095 The corresponding @value{GDBN} command is @samp{disable}.
25097 @subsubheading Example
25105 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25106 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25107 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25108 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25109 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25110 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25111 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25112 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
25113 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25114 line="5",times="0"@}]@}
25118 @subheading The @code{-break-enable} Command
25119 @findex -break-enable
25121 @subsubheading Synopsis
25124 -break-enable ( @var{breakpoint} )+
25127 Enable (previously disabled) @var{breakpoint}(s).
25129 @subsubheading @value{GDBN} Command
25131 The corresponding @value{GDBN} command is @samp{enable}.
25133 @subsubheading Example
25141 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25142 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25143 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25144 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25145 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25146 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25147 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25148 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
25149 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25150 line="5",times="0"@}]@}
25154 @subheading The @code{-break-info} Command
25155 @findex -break-info
25157 @subsubheading Synopsis
25160 -break-info @var{breakpoint}
25164 Get information about a single breakpoint.
25166 @subsubheading @value{GDBN} Command
25168 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
25170 @subsubheading Example
25173 @subheading The @code{-break-insert} Command
25174 @findex -break-insert
25176 @subsubheading Synopsis
25179 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
25180 [ -c @var{condition} ] [ -i @var{ignore-count} ]
25181 [ -p @var{thread} ] [ @var{location} ]
25185 If specified, @var{location}, can be one of:
25192 @item filename:linenum
25193 @item filename:function
25197 The possible optional parameters of this command are:
25201 Insert a temporary breakpoint.
25203 Insert a hardware breakpoint.
25204 @item -c @var{condition}
25205 Make the breakpoint conditional on @var{condition}.
25206 @item -i @var{ignore-count}
25207 Initialize the @var{ignore-count}.
25209 If @var{location} cannot be parsed (for example if it
25210 refers to unknown files or functions), create a pending
25211 breakpoint. Without this flag, @value{GDBN} will report
25212 an error, and won't create a breakpoint, if @var{location}
25215 Create a disabled breakpoint.
25217 Create a tracepoint. @xref{Tracepoints}. When this parameter
25218 is used together with @samp{-h}, a fast tracepoint is created.
25221 @subsubheading Result
25223 The result is in the form:
25226 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
25227 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
25228 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
25229 times="@var{times}"@}
25233 where @var{number} is the @value{GDBN} number for this breakpoint,
25234 @var{funcname} is the name of the function where the breakpoint was
25235 inserted, @var{filename} is the name of the source file which contains
25236 this function, @var{lineno} is the source line number within that file
25237 and @var{times} the number of times that the breakpoint has been hit
25238 (always 0 for -break-insert but may be greater for -break-info or -break-list
25239 which use the same output).
25241 Note: this format is open to change.
25242 @c An out-of-band breakpoint instead of part of the result?
25244 @subsubheading @value{GDBN} Command
25246 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
25247 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
25249 @subsubheading Example
25254 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
25255 fullname="/home/foo/recursive2.c,line="4",times="0"@}
25257 -break-insert -t foo
25258 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
25259 fullname="/home/foo/recursive2.c,line="11",times="0"@}
25262 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25263 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25264 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25265 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25266 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25267 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25268 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25269 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25270 addr="0x0001072c", func="main",file="recursive2.c",
25271 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
25272 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
25273 addr="0x00010774",func="foo",file="recursive2.c",
25274 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
25276 -break-insert -r foo.*
25277 ~int foo(int, int);
25278 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
25279 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
25283 @subheading The @code{-break-list} Command
25284 @findex -break-list
25286 @subsubheading Synopsis
25292 Displays the list of inserted breakpoints, showing the following fields:
25296 number of the breakpoint
25298 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
25300 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
25303 is the breakpoint enabled or no: @samp{y} or @samp{n}
25305 memory location at which the breakpoint is set
25307 logical location of the breakpoint, expressed by function name, file
25310 number of times the breakpoint has been hit
25313 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
25314 @code{body} field is an empty list.
25316 @subsubheading @value{GDBN} Command
25318 The corresponding @value{GDBN} command is @samp{info break}.
25320 @subsubheading Example
25325 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25326 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25327 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25328 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25329 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25330 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25331 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25332 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25333 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
25334 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
25335 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
25336 line="13",times="0"@}]@}
25340 Here's an example of the result when there are no breakpoints:
25345 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
25346 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25347 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25348 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25349 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25350 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25351 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25356 @subheading The @code{-break-passcount} Command
25357 @findex -break-passcount
25359 @subsubheading Synopsis
25362 -break-passcount @var{tracepoint-number} @var{passcount}
25365 Set the passcount for tracepoint @var{tracepoint-number} to
25366 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
25367 is not a tracepoint, error is emitted. This corresponds to CLI
25368 command @samp{passcount}.
25370 @subheading The @code{-break-watch} Command
25371 @findex -break-watch
25373 @subsubheading Synopsis
25376 -break-watch [ -a | -r ]
25379 Create a watchpoint. With the @samp{-a} option it will create an
25380 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
25381 read from or on a write to the memory location. With the @samp{-r}
25382 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
25383 trigger only when the memory location is accessed for reading. Without
25384 either of the options, the watchpoint created is a regular watchpoint,
25385 i.e., it will trigger when the memory location is accessed for writing.
25386 @xref{Set Watchpoints, , Setting Watchpoints}.
25388 Note that @samp{-break-list} will report a single list of watchpoints and
25389 breakpoints inserted.
25391 @subsubheading @value{GDBN} Command
25393 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
25396 @subsubheading Example
25398 Setting a watchpoint on a variable in the @code{main} function:
25403 ^done,wpt=@{number="2",exp="x"@}
25408 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
25409 value=@{old="-268439212",new="55"@},
25410 frame=@{func="main",args=[],file="recursive2.c",
25411 fullname="/home/foo/bar/recursive2.c",line="5"@}
25415 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
25416 the program execution twice: first for the variable changing value, then
25417 for the watchpoint going out of scope.
25422 ^done,wpt=@{number="5",exp="C"@}
25427 *stopped,reason="watchpoint-trigger",
25428 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
25429 frame=@{func="callee4",args=[],
25430 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25431 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
25436 *stopped,reason="watchpoint-scope",wpnum="5",
25437 frame=@{func="callee3",args=[@{name="strarg",
25438 value="0x11940 \"A string argument.\""@}],
25439 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25440 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25444 Listing breakpoints and watchpoints, at different points in the program
25445 execution. Note that once the watchpoint goes out of scope, it is
25451 ^done,wpt=@{number="2",exp="C"@}
25454 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25455 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25456 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25457 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25458 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25459 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25460 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25461 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25462 addr="0x00010734",func="callee4",
25463 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25464 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
25465 bkpt=@{number="2",type="watchpoint",disp="keep",
25466 enabled="y",addr="",what="C",times="0"@}]@}
25471 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
25472 value=@{old="-276895068",new="3"@},
25473 frame=@{func="callee4",args=[],
25474 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25475 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
25478 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25479 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25480 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25481 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25482 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25483 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25484 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25485 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25486 addr="0x00010734",func="callee4",
25487 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25488 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
25489 bkpt=@{number="2",type="watchpoint",disp="keep",
25490 enabled="y",addr="",what="C",times="-5"@}]@}
25494 ^done,reason="watchpoint-scope",wpnum="2",
25495 frame=@{func="callee3",args=[@{name="strarg",
25496 value="0x11940 \"A string argument.\""@}],
25497 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25498 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25501 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25502 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25503 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25504 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25505 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25506 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25507 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25508 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25509 addr="0x00010734",func="callee4",
25510 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25511 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
25516 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25517 @node GDB/MI Program Context
25518 @section @sc{gdb/mi} Program Context
25520 @subheading The @code{-exec-arguments} Command
25521 @findex -exec-arguments
25524 @subsubheading Synopsis
25527 -exec-arguments @var{args}
25530 Set the inferior program arguments, to be used in the next
25533 @subsubheading @value{GDBN} Command
25535 The corresponding @value{GDBN} command is @samp{set args}.
25537 @subsubheading Example
25541 -exec-arguments -v word
25548 @subheading The @code{-exec-show-arguments} Command
25549 @findex -exec-show-arguments
25551 @subsubheading Synopsis
25554 -exec-show-arguments
25557 Print the arguments of the program.
25559 @subsubheading @value{GDBN} Command
25561 The corresponding @value{GDBN} command is @samp{show args}.
25563 @subsubheading Example
25568 @subheading The @code{-environment-cd} Command
25569 @findex -environment-cd
25571 @subsubheading Synopsis
25574 -environment-cd @var{pathdir}
25577 Set @value{GDBN}'s working directory.
25579 @subsubheading @value{GDBN} Command
25581 The corresponding @value{GDBN} command is @samp{cd}.
25583 @subsubheading Example
25587 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
25593 @subheading The @code{-environment-directory} Command
25594 @findex -environment-directory
25596 @subsubheading Synopsis
25599 -environment-directory [ -r ] [ @var{pathdir} ]+
25602 Add directories @var{pathdir} to beginning of search path for source files.
25603 If the @samp{-r} option is used, the search path is reset to the default
25604 search path. If directories @var{pathdir} are supplied in addition to the
25605 @samp{-r} option, the search path is first reset and then addition
25607 Multiple directories may be specified, separated by blanks. Specifying
25608 multiple directories in a single command
25609 results in the directories added to the beginning of the
25610 search path in the same order they were presented in the command.
25611 If blanks are needed as
25612 part of a directory name, double-quotes should be used around
25613 the name. In the command output, the path will show up separated
25614 by the system directory-separator character. The directory-separator
25615 character must not be used
25616 in any directory name.
25617 If no directories are specified, the current search path is displayed.
25619 @subsubheading @value{GDBN} Command
25621 The corresponding @value{GDBN} command is @samp{dir}.
25623 @subsubheading Example
25627 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
25628 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
25630 -environment-directory ""
25631 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
25633 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
25634 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
25636 -environment-directory -r
25637 ^done,source-path="$cdir:$cwd"
25642 @subheading The @code{-environment-path} Command
25643 @findex -environment-path
25645 @subsubheading Synopsis
25648 -environment-path [ -r ] [ @var{pathdir} ]+
25651 Add directories @var{pathdir} to beginning of search path for object files.
25652 If the @samp{-r} option is used, the search path is reset to the original
25653 search path that existed at gdb start-up. If directories @var{pathdir} are
25654 supplied in addition to the
25655 @samp{-r} option, the search path is first reset and then addition
25657 Multiple directories may be specified, separated by blanks. Specifying
25658 multiple directories in a single command
25659 results in the directories added to the beginning of the
25660 search path in the same order they were presented in the command.
25661 If blanks are needed as
25662 part of a directory name, double-quotes should be used around
25663 the name. In the command output, the path will show up separated
25664 by the system directory-separator character. The directory-separator
25665 character must not be used
25666 in any directory name.
25667 If no directories are specified, the current path is displayed.
25670 @subsubheading @value{GDBN} Command
25672 The corresponding @value{GDBN} command is @samp{path}.
25674 @subsubheading Example
25679 ^done,path="/usr/bin"
25681 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
25682 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
25684 -environment-path -r /usr/local/bin
25685 ^done,path="/usr/local/bin:/usr/bin"
25690 @subheading The @code{-environment-pwd} Command
25691 @findex -environment-pwd
25693 @subsubheading Synopsis
25699 Show the current working directory.
25701 @subsubheading @value{GDBN} Command
25703 The corresponding @value{GDBN} command is @samp{pwd}.
25705 @subsubheading Example
25710 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
25714 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25715 @node GDB/MI Thread Commands
25716 @section @sc{gdb/mi} Thread Commands
25719 @subheading The @code{-thread-info} Command
25720 @findex -thread-info
25722 @subsubheading Synopsis
25725 -thread-info [ @var{thread-id} ]
25728 Reports information about either a specific thread, if
25729 the @var{thread-id} parameter is present, or about all
25730 threads. When printing information about all threads,
25731 also reports the current thread.
25733 @subsubheading @value{GDBN} Command
25735 The @samp{info thread} command prints the same information
25738 @subsubheading Example
25743 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
25744 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
25745 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
25746 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
25747 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
25748 current-thread-id="1"
25752 The @samp{state} field may have the following values:
25756 The thread is stopped. Frame information is available for stopped
25760 The thread is running. There's no frame information for running
25765 @subheading The @code{-thread-list-ids} Command
25766 @findex -thread-list-ids
25768 @subsubheading Synopsis
25774 Produces a list of the currently known @value{GDBN} thread ids. At the
25775 end of the list it also prints the total number of such threads.
25777 This command is retained for historical reasons, the
25778 @code{-thread-info} command should be used instead.
25780 @subsubheading @value{GDBN} Command
25782 Part of @samp{info threads} supplies the same information.
25784 @subsubheading Example
25789 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
25790 current-thread-id="1",number-of-threads="3"
25795 @subheading The @code{-thread-select} Command
25796 @findex -thread-select
25798 @subsubheading Synopsis
25801 -thread-select @var{threadnum}
25804 Make @var{threadnum} the current thread. It prints the number of the new
25805 current thread, and the topmost frame for that thread.
25807 This command is deprecated in favor of explicitly using the
25808 @samp{--thread} option to each command.
25810 @subsubheading @value{GDBN} Command
25812 The corresponding @value{GDBN} command is @samp{thread}.
25814 @subsubheading Example
25821 *stopped,reason="end-stepping-range",thread-id="2",line="187",
25822 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
25826 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
25827 number-of-threads="3"
25830 ^done,new-thread-id="3",
25831 frame=@{level="0",func="vprintf",
25832 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
25833 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
25837 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25838 @node GDB/MI Program Execution
25839 @section @sc{gdb/mi} Program Execution
25841 These are the asynchronous commands which generate the out-of-band
25842 record @samp{*stopped}. Currently @value{GDBN} only really executes
25843 asynchronously with remote targets and this interaction is mimicked in
25846 @subheading The @code{-exec-continue} Command
25847 @findex -exec-continue
25849 @subsubheading Synopsis
25852 -exec-continue [--reverse] [--all|--thread-group N]
25855 Resumes the execution of the inferior program, which will continue
25856 to execute until it reaches a debugger stop event. If the
25857 @samp{--reverse} option is specified, execution resumes in reverse until
25858 it reaches a stop event. Stop events may include
25861 breakpoints or watchpoints
25863 signals or exceptions
25865 the end of the process (or its beginning under @samp{--reverse})
25867 the end or beginning of a replay log if one is being used.
25869 In all-stop mode (@pxref{All-Stop
25870 Mode}), may resume only one thread, or all threads, depending on the
25871 value of the @samp{scheduler-locking} variable. If @samp{--all} is
25872 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
25873 ignored in all-stop mode. If the @samp{--thread-group} options is
25874 specified, then all threads in that thread group are resumed.
25876 @subsubheading @value{GDBN} Command
25878 The corresponding @value{GDBN} corresponding is @samp{continue}.
25880 @subsubheading Example
25887 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
25888 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
25894 @subheading The @code{-exec-finish} Command
25895 @findex -exec-finish
25897 @subsubheading Synopsis
25900 -exec-finish [--reverse]
25903 Resumes the execution of the inferior program until the current
25904 function is exited. Displays the results returned by the function.
25905 If the @samp{--reverse} option is specified, resumes the reverse
25906 execution of the inferior program until the point where current
25907 function was called.
25909 @subsubheading @value{GDBN} Command
25911 The corresponding @value{GDBN} command is @samp{finish}.
25913 @subsubheading Example
25915 Function returning @code{void}.
25922 *stopped,reason="function-finished",frame=@{func="main",args=[],
25923 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
25927 Function returning other than @code{void}. The name of the internal
25928 @value{GDBN} variable storing the result is printed, together with the
25935 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
25936 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
25937 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25938 gdb-result-var="$1",return-value="0"
25943 @subheading The @code{-exec-interrupt} Command
25944 @findex -exec-interrupt
25946 @subsubheading Synopsis
25949 -exec-interrupt [--all|--thread-group N]
25952 Interrupts the background execution of the target. Note how the token
25953 associated with the stop message is the one for the execution command
25954 that has been interrupted. The token for the interrupt itself only
25955 appears in the @samp{^done} output. If the user is trying to
25956 interrupt a non-running program, an error message will be printed.
25958 Note that when asynchronous execution is enabled, this command is
25959 asynchronous just like other execution commands. That is, first the
25960 @samp{^done} response will be printed, and the target stop will be
25961 reported after that using the @samp{*stopped} notification.
25963 In non-stop mode, only the context thread is interrupted by default.
25964 All threads (in all inferiors) will be interrupted if the
25965 @samp{--all} option is specified. If the @samp{--thread-group}
25966 option is specified, all threads in that group will be interrupted.
25968 @subsubheading @value{GDBN} Command
25970 The corresponding @value{GDBN} command is @samp{interrupt}.
25972 @subsubheading Example
25983 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
25984 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
25985 fullname="/home/foo/bar/try.c",line="13"@}
25990 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
25994 @subheading The @code{-exec-jump} Command
25997 @subsubheading Synopsis
26000 -exec-jump @var{location}
26003 Resumes execution of the inferior program at the location specified by
26004 parameter. @xref{Specify Location}, for a description of the
26005 different forms of @var{location}.
26007 @subsubheading @value{GDBN} Command
26009 The corresponding @value{GDBN} command is @samp{jump}.
26011 @subsubheading Example
26014 -exec-jump foo.c:10
26015 *running,thread-id="all"
26020 @subheading The @code{-exec-next} Command
26023 @subsubheading Synopsis
26026 -exec-next [--reverse]
26029 Resumes execution of the inferior program, stopping when the beginning
26030 of the next source line is reached.
26032 If the @samp{--reverse} option is specified, resumes reverse execution
26033 of the inferior program, stopping at the beginning of the previous
26034 source line. If you issue this command on the first line of a
26035 function, it will take you back to the caller of that function, to the
26036 source line where the function was called.
26039 @subsubheading @value{GDBN} Command
26041 The corresponding @value{GDBN} command is @samp{next}.
26043 @subsubheading Example
26049 *stopped,reason="end-stepping-range",line="8",file="hello.c"
26054 @subheading The @code{-exec-next-instruction} Command
26055 @findex -exec-next-instruction
26057 @subsubheading Synopsis
26060 -exec-next-instruction [--reverse]
26063 Executes one machine instruction. If the instruction is a function
26064 call, continues until the function returns. If the program stops at an
26065 instruction in the middle of a source line, the address will be
26068 If the @samp{--reverse} option is specified, resumes reverse execution
26069 of the inferior program, stopping at the previous instruction. If the
26070 previously executed instruction was a return from another function,
26071 it will continue to execute in reverse until the call to that function
26072 (from the current stack frame) is reached.
26074 @subsubheading @value{GDBN} Command
26076 The corresponding @value{GDBN} command is @samp{nexti}.
26078 @subsubheading Example
26082 -exec-next-instruction
26086 *stopped,reason="end-stepping-range",
26087 addr="0x000100d4",line="5",file="hello.c"
26092 @subheading The @code{-exec-return} Command
26093 @findex -exec-return
26095 @subsubheading Synopsis
26101 Makes current function return immediately. Doesn't execute the inferior.
26102 Displays the new current frame.
26104 @subsubheading @value{GDBN} Command
26106 The corresponding @value{GDBN} command is @samp{return}.
26108 @subsubheading Example
26112 200-break-insert callee4
26113 200^done,bkpt=@{number="1",addr="0x00010734",
26114 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
26119 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
26120 frame=@{func="callee4",args=[],
26121 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26122 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
26128 111^done,frame=@{level="0",func="callee3",
26129 args=[@{name="strarg",
26130 value="0x11940 \"A string argument.\""@}],
26131 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26132 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26137 @subheading The @code{-exec-run} Command
26140 @subsubheading Synopsis
26143 -exec-run [--all | --thread-group N]
26146 Starts execution of the inferior from the beginning. The inferior
26147 executes until either a breakpoint is encountered or the program
26148 exits. In the latter case the output will include an exit code, if
26149 the program has exited exceptionally.
26151 When no option is specified, the current inferior is started. If the
26152 @samp{--thread-group} option is specified, it should refer to a thread
26153 group of type @samp{process}, and that thread group will be started.
26154 If the @samp{--all} option is specified, then all inferiors will be started.
26156 @subsubheading @value{GDBN} Command
26158 The corresponding @value{GDBN} command is @samp{run}.
26160 @subsubheading Examples
26165 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
26170 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
26171 frame=@{func="main",args=[],file="recursive2.c",
26172 fullname="/home/foo/bar/recursive2.c",line="4"@}
26177 Program exited normally:
26185 *stopped,reason="exited-normally"
26190 Program exited exceptionally:
26198 *stopped,reason="exited",exit-code="01"
26202 Another way the program can terminate is if it receives a signal such as
26203 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
26207 *stopped,reason="exited-signalled",signal-name="SIGINT",
26208 signal-meaning="Interrupt"
26212 @c @subheading -exec-signal
26215 @subheading The @code{-exec-step} Command
26218 @subsubheading Synopsis
26221 -exec-step [--reverse]
26224 Resumes execution of the inferior program, stopping when the beginning
26225 of the next source line is reached, if the next source line is not a
26226 function call. If it is, stop at the first instruction of the called
26227 function. If the @samp{--reverse} option is specified, resumes reverse
26228 execution of the inferior program, stopping at the beginning of the
26229 previously executed source line.
26231 @subsubheading @value{GDBN} Command
26233 The corresponding @value{GDBN} command is @samp{step}.
26235 @subsubheading Example
26237 Stepping into a function:
26243 *stopped,reason="end-stepping-range",
26244 frame=@{func="foo",args=[@{name="a",value="10"@},
26245 @{name="b",value="0"@}],file="recursive2.c",
26246 fullname="/home/foo/bar/recursive2.c",line="11"@}
26256 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
26261 @subheading The @code{-exec-step-instruction} Command
26262 @findex -exec-step-instruction
26264 @subsubheading Synopsis
26267 -exec-step-instruction [--reverse]
26270 Resumes the inferior which executes one machine instruction. If the
26271 @samp{--reverse} option is specified, resumes reverse execution of the
26272 inferior program, stopping at the previously executed instruction.
26273 The output, once @value{GDBN} has stopped, will vary depending on
26274 whether we have stopped in the middle of a source line or not. In the
26275 former case, the address at which the program stopped will be printed
26278 @subsubheading @value{GDBN} Command
26280 The corresponding @value{GDBN} command is @samp{stepi}.
26282 @subsubheading Example
26286 -exec-step-instruction
26290 *stopped,reason="end-stepping-range",
26291 frame=@{func="foo",args=[],file="try.c",
26292 fullname="/home/foo/bar/try.c",line="10"@}
26294 -exec-step-instruction
26298 *stopped,reason="end-stepping-range",
26299 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
26300 fullname="/home/foo/bar/try.c",line="10"@}
26305 @subheading The @code{-exec-until} Command
26306 @findex -exec-until
26308 @subsubheading Synopsis
26311 -exec-until [ @var{location} ]
26314 Executes the inferior until the @var{location} specified in the
26315 argument is reached. If there is no argument, the inferior executes
26316 until a source line greater than the current one is reached. The
26317 reason for stopping in this case will be @samp{location-reached}.
26319 @subsubheading @value{GDBN} Command
26321 The corresponding @value{GDBN} command is @samp{until}.
26323 @subsubheading Example
26327 -exec-until recursive2.c:6
26331 *stopped,reason="location-reached",frame=@{func="main",args=[],
26332 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
26337 @subheading -file-clear
26338 Is this going away????
26341 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26342 @node GDB/MI Stack Manipulation
26343 @section @sc{gdb/mi} Stack Manipulation Commands
26346 @subheading The @code{-stack-info-frame} Command
26347 @findex -stack-info-frame
26349 @subsubheading Synopsis
26355 Get info on the selected frame.
26357 @subsubheading @value{GDBN} Command
26359 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
26360 (without arguments).
26362 @subsubheading Example
26367 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
26368 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26369 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
26373 @subheading The @code{-stack-info-depth} Command
26374 @findex -stack-info-depth
26376 @subsubheading Synopsis
26379 -stack-info-depth [ @var{max-depth} ]
26382 Return the depth of the stack. If the integer argument @var{max-depth}
26383 is specified, do not count beyond @var{max-depth} frames.
26385 @subsubheading @value{GDBN} Command
26387 There's no equivalent @value{GDBN} command.
26389 @subsubheading Example
26391 For a stack with frame levels 0 through 11:
26398 -stack-info-depth 4
26401 -stack-info-depth 12
26404 -stack-info-depth 11
26407 -stack-info-depth 13
26412 @subheading The @code{-stack-list-arguments} Command
26413 @findex -stack-list-arguments
26415 @subsubheading Synopsis
26418 -stack-list-arguments @var{print-values}
26419 [ @var{low-frame} @var{high-frame} ]
26422 Display a list of the arguments for the frames between @var{low-frame}
26423 and @var{high-frame} (inclusive). If @var{low-frame} and
26424 @var{high-frame} are not provided, list the arguments for the whole
26425 call stack. If the two arguments are equal, show the single frame
26426 at the corresponding level. It is an error if @var{low-frame} is
26427 larger than the actual number of frames. On the other hand,
26428 @var{high-frame} may be larger than the actual number of frames, in
26429 which case only existing frames will be returned.
26431 If @var{print-values} is 0 or @code{--no-values}, print only the names of
26432 the variables; if it is 1 or @code{--all-values}, print also their
26433 values; and if it is 2 or @code{--simple-values}, print the name,
26434 type and value for simple data types, and the name and type for arrays,
26435 structures and unions.
26437 Use of this command to obtain arguments in a single frame is
26438 deprecated in favor of the @samp{-stack-list-variables} command.
26440 @subsubheading @value{GDBN} Command
26442 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
26443 @samp{gdb_get_args} command which partially overlaps with the
26444 functionality of @samp{-stack-list-arguments}.
26446 @subsubheading Example
26453 frame=@{level="0",addr="0x00010734",func="callee4",
26454 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26455 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
26456 frame=@{level="1",addr="0x0001076c",func="callee3",
26457 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26458 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
26459 frame=@{level="2",addr="0x0001078c",func="callee2",
26460 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26461 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
26462 frame=@{level="3",addr="0x000107b4",func="callee1",
26463 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26464 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
26465 frame=@{level="4",addr="0x000107e0",func="main",
26466 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26467 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
26469 -stack-list-arguments 0
26472 frame=@{level="0",args=[]@},
26473 frame=@{level="1",args=[name="strarg"]@},
26474 frame=@{level="2",args=[name="intarg",name="strarg"]@},
26475 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
26476 frame=@{level="4",args=[]@}]
26478 -stack-list-arguments 1
26481 frame=@{level="0",args=[]@},
26483 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
26484 frame=@{level="2",args=[
26485 @{name="intarg",value="2"@},
26486 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
26487 @{frame=@{level="3",args=[
26488 @{name="intarg",value="2"@},
26489 @{name="strarg",value="0x11940 \"A string argument.\""@},
26490 @{name="fltarg",value="3.5"@}]@},
26491 frame=@{level="4",args=[]@}]
26493 -stack-list-arguments 0 2 2
26494 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
26496 -stack-list-arguments 1 2 2
26497 ^done,stack-args=[frame=@{level="2",
26498 args=[@{name="intarg",value="2"@},
26499 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
26503 @c @subheading -stack-list-exception-handlers
26506 @subheading The @code{-stack-list-frames} Command
26507 @findex -stack-list-frames
26509 @subsubheading Synopsis
26512 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
26515 List the frames currently on the stack. For each frame it displays the
26520 The frame number, 0 being the topmost frame, i.e., the innermost function.
26522 The @code{$pc} value for that frame.
26526 File name of the source file where the function lives.
26527 @item @var{fullname}
26528 The full file name of the source file where the function lives.
26530 Line number corresponding to the @code{$pc}.
26532 The shared library where this function is defined. This is only given
26533 if the frame's function is not known.
26536 If invoked without arguments, this command prints a backtrace for the
26537 whole stack. If given two integer arguments, it shows the frames whose
26538 levels are between the two arguments (inclusive). If the two arguments
26539 are equal, it shows the single frame at the corresponding level. It is
26540 an error if @var{low-frame} is larger than the actual number of
26541 frames. On the other hand, @var{high-frame} may be larger than the
26542 actual number of frames, in which case only existing frames will be returned.
26544 @subsubheading @value{GDBN} Command
26546 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
26548 @subsubheading Example
26550 Full stack backtrace:
26556 [frame=@{level="0",addr="0x0001076c",func="foo",
26557 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
26558 frame=@{level="1",addr="0x000107a4",func="foo",
26559 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26560 frame=@{level="2",addr="0x000107a4",func="foo",
26561 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26562 frame=@{level="3",addr="0x000107a4",func="foo",
26563 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26564 frame=@{level="4",addr="0x000107a4",func="foo",
26565 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26566 frame=@{level="5",addr="0x000107a4",func="foo",
26567 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26568 frame=@{level="6",addr="0x000107a4",func="foo",
26569 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26570 frame=@{level="7",addr="0x000107a4",func="foo",
26571 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26572 frame=@{level="8",addr="0x000107a4",func="foo",
26573 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26574 frame=@{level="9",addr="0x000107a4",func="foo",
26575 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26576 frame=@{level="10",addr="0x000107a4",func="foo",
26577 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26578 frame=@{level="11",addr="0x00010738",func="main",
26579 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
26583 Show frames between @var{low_frame} and @var{high_frame}:
26587 -stack-list-frames 3 5
26589 [frame=@{level="3",addr="0x000107a4",func="foo",
26590 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26591 frame=@{level="4",addr="0x000107a4",func="foo",
26592 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26593 frame=@{level="5",addr="0x000107a4",func="foo",
26594 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
26598 Show a single frame:
26602 -stack-list-frames 3 3
26604 [frame=@{level="3",addr="0x000107a4",func="foo",
26605 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
26610 @subheading The @code{-stack-list-locals} Command
26611 @findex -stack-list-locals
26613 @subsubheading Synopsis
26616 -stack-list-locals @var{print-values}
26619 Display the local variable names for the selected frame. If
26620 @var{print-values} is 0 or @code{--no-values}, print only the names of
26621 the variables; if it is 1 or @code{--all-values}, print also their
26622 values; and if it is 2 or @code{--simple-values}, print the name,
26623 type and value for simple data types, and the name and type for arrays,
26624 structures and unions. In this last case, a frontend can immediately
26625 display the value of simple data types and create variable objects for
26626 other data types when the user wishes to explore their values in
26629 This command is deprecated in favor of the
26630 @samp{-stack-list-variables} command.
26632 @subsubheading @value{GDBN} Command
26634 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
26636 @subsubheading Example
26640 -stack-list-locals 0
26641 ^done,locals=[name="A",name="B",name="C"]
26643 -stack-list-locals --all-values
26644 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
26645 @{name="C",value="@{1, 2, 3@}"@}]
26646 -stack-list-locals --simple-values
26647 ^done,locals=[@{name="A",type="int",value="1"@},
26648 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
26652 @subheading The @code{-stack-list-variables} Command
26653 @findex -stack-list-variables
26655 @subsubheading Synopsis
26658 -stack-list-variables @var{print-values}
26661 Display the names of local variables and function arguments for the selected frame. If
26662 @var{print-values} is 0 or @code{--no-values}, print only the names of
26663 the variables; if it is 1 or @code{--all-values}, print also their
26664 values; and if it is 2 or @code{--simple-values}, print the name,
26665 type and value for simple data types, and the name and type for arrays,
26666 structures and unions.
26668 @subsubheading Example
26672 -stack-list-variables --thread 1 --frame 0 --all-values
26673 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
26678 @subheading The @code{-stack-select-frame} Command
26679 @findex -stack-select-frame
26681 @subsubheading Synopsis
26684 -stack-select-frame @var{framenum}
26687 Change the selected frame. Select a different frame @var{framenum} on
26690 This command in deprecated in favor of passing the @samp{--frame}
26691 option to every command.
26693 @subsubheading @value{GDBN} Command
26695 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
26696 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
26698 @subsubheading Example
26702 -stack-select-frame 2
26707 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26708 @node GDB/MI Variable Objects
26709 @section @sc{gdb/mi} Variable Objects
26713 @subheading Motivation for Variable Objects in @sc{gdb/mi}
26715 For the implementation of a variable debugger window (locals, watched
26716 expressions, etc.), we are proposing the adaptation of the existing code
26717 used by @code{Insight}.
26719 The two main reasons for that are:
26723 It has been proven in practice (it is already on its second generation).
26726 It will shorten development time (needless to say how important it is
26730 The original interface was designed to be used by Tcl code, so it was
26731 slightly changed so it could be used through @sc{gdb/mi}. This section
26732 describes the @sc{gdb/mi} operations that will be available and gives some
26733 hints about their use.
26735 @emph{Note}: In addition to the set of operations described here, we
26736 expect the @sc{gui} implementation of a variable window to require, at
26737 least, the following operations:
26740 @item @code{-gdb-show} @code{output-radix}
26741 @item @code{-stack-list-arguments}
26742 @item @code{-stack-list-locals}
26743 @item @code{-stack-select-frame}
26748 @subheading Introduction to Variable Objects
26750 @cindex variable objects in @sc{gdb/mi}
26752 Variable objects are "object-oriented" MI interface for examining and
26753 changing values of expressions. Unlike some other MI interfaces that
26754 work with expressions, variable objects are specifically designed for
26755 simple and efficient presentation in the frontend. A variable object
26756 is identified by string name. When a variable object is created, the
26757 frontend specifies the expression for that variable object. The
26758 expression can be a simple variable, or it can be an arbitrary complex
26759 expression, and can even involve CPU registers. After creating a
26760 variable object, the frontend can invoke other variable object
26761 operations---for example to obtain or change the value of a variable
26762 object, or to change display format.
26764 Variable objects have hierarchical tree structure. Any variable object
26765 that corresponds to a composite type, such as structure in C, has
26766 a number of child variable objects, for example corresponding to each
26767 element of a structure. A child variable object can itself have
26768 children, recursively. Recursion ends when we reach
26769 leaf variable objects, which always have built-in types. Child variable
26770 objects are created only by explicit request, so if a frontend
26771 is not interested in the children of a particular variable object, no
26772 child will be created.
26774 For a leaf variable object it is possible to obtain its value as a
26775 string, or set the value from a string. String value can be also
26776 obtained for a non-leaf variable object, but it's generally a string
26777 that only indicates the type of the object, and does not list its
26778 contents. Assignment to a non-leaf variable object is not allowed.
26780 A frontend does not need to read the values of all variable objects each time
26781 the program stops. Instead, MI provides an update command that lists all
26782 variable objects whose values has changed since the last update
26783 operation. This considerably reduces the amount of data that must
26784 be transferred to the frontend. As noted above, children variable
26785 objects are created on demand, and only leaf variable objects have a
26786 real value. As result, gdb will read target memory only for leaf
26787 variables that frontend has created.
26789 The automatic update is not always desirable. For example, a frontend
26790 might want to keep a value of some expression for future reference,
26791 and never update it. For another example, fetching memory is
26792 relatively slow for embedded targets, so a frontend might want
26793 to disable automatic update for the variables that are either not
26794 visible on the screen, or ``closed''. This is possible using so
26795 called ``frozen variable objects''. Such variable objects are never
26796 implicitly updated.
26798 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
26799 fixed variable object, the expression is parsed when the variable
26800 object is created, including associating identifiers to specific
26801 variables. The meaning of expression never changes. For a floating
26802 variable object the values of variables whose names appear in the
26803 expressions are re-evaluated every time in the context of the current
26804 frame. Consider this example:
26809 struct work_state state;
26816 If a fixed variable object for the @code{state} variable is created in
26817 this function, and we enter the recursive call, the the variable
26818 object will report the value of @code{state} in the top-level
26819 @code{do_work} invocation. On the other hand, a floating variable
26820 object will report the value of @code{state} in the current frame.
26822 If an expression specified when creating a fixed variable object
26823 refers to a local variable, the variable object becomes bound to the
26824 thread and frame in which the variable object is created. When such
26825 variable object is updated, @value{GDBN} makes sure that the
26826 thread/frame combination the variable object is bound to still exists,
26827 and re-evaluates the variable object in context of that thread/frame.
26829 The following is the complete set of @sc{gdb/mi} operations defined to
26830 access this functionality:
26832 @multitable @columnfractions .4 .6
26833 @item @strong{Operation}
26834 @tab @strong{Description}
26836 @item @code{-enable-pretty-printing}
26837 @tab enable Python-based pretty-printing
26838 @item @code{-var-create}
26839 @tab create a variable object
26840 @item @code{-var-delete}
26841 @tab delete the variable object and/or its children
26842 @item @code{-var-set-format}
26843 @tab set the display format of this variable
26844 @item @code{-var-show-format}
26845 @tab show the display format of this variable
26846 @item @code{-var-info-num-children}
26847 @tab tells how many children this object has
26848 @item @code{-var-list-children}
26849 @tab return a list of the object's children
26850 @item @code{-var-info-type}
26851 @tab show the type of this variable object
26852 @item @code{-var-info-expression}
26853 @tab print parent-relative expression that this variable object represents
26854 @item @code{-var-info-path-expression}
26855 @tab print full expression that this variable object represents
26856 @item @code{-var-show-attributes}
26857 @tab is this variable editable? does it exist here?
26858 @item @code{-var-evaluate-expression}
26859 @tab get the value of this variable
26860 @item @code{-var-assign}
26861 @tab set the value of this variable
26862 @item @code{-var-update}
26863 @tab update the variable and its children
26864 @item @code{-var-set-frozen}
26865 @tab set frozeness attribute
26866 @item @code{-var-set-update-range}
26867 @tab set range of children to display on update
26870 In the next subsection we describe each operation in detail and suggest
26871 how it can be used.
26873 @subheading Description And Use of Operations on Variable Objects
26875 @subheading The @code{-enable-pretty-printing} Command
26876 @findex -enable-pretty-printing
26879 -enable-pretty-printing
26882 @value{GDBN} allows Python-based visualizers to affect the output of the
26883 MI variable object commands. However, because there was no way to
26884 implement this in a fully backward-compatible way, a front end must
26885 request that this functionality be enabled.
26887 Once enabled, this feature cannot be disabled.
26889 Note that if Python support has not been compiled into @value{GDBN},
26890 this command will still succeed (and do nothing).
26892 This feature is currently (as of @value{GDBN} 7.0) experimental, and
26893 may work differently in future versions of @value{GDBN}.
26895 @subheading The @code{-var-create} Command
26896 @findex -var-create
26898 @subsubheading Synopsis
26901 -var-create @{@var{name} | "-"@}
26902 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
26905 This operation creates a variable object, which allows the monitoring of
26906 a variable, the result of an expression, a memory cell or a CPU
26909 The @var{name} parameter is the string by which the object can be
26910 referenced. It must be unique. If @samp{-} is specified, the varobj
26911 system will generate a string ``varNNNNNN'' automatically. It will be
26912 unique provided that one does not specify @var{name} of that format.
26913 The command fails if a duplicate name is found.
26915 The frame under which the expression should be evaluated can be
26916 specified by @var{frame-addr}. A @samp{*} indicates that the current
26917 frame should be used. A @samp{@@} indicates that a floating variable
26918 object must be created.
26920 @var{expression} is any expression valid on the current language set (must not
26921 begin with a @samp{*}), or one of the following:
26925 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
26928 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
26931 @samp{$@var{regname}} --- a CPU register name
26934 @cindex dynamic varobj
26935 A varobj's contents may be provided by a Python-based pretty-printer. In this
26936 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
26937 have slightly different semantics in some cases. If the
26938 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
26939 will never create a dynamic varobj. This ensures backward
26940 compatibility for existing clients.
26942 @subsubheading Result
26944 This operation returns attributes of the newly-created varobj. These
26949 The name of the varobj.
26952 The number of children of the varobj. This number is not necessarily
26953 reliable for a dynamic varobj. Instead, you must examine the
26954 @samp{has_more} attribute.
26957 The varobj's scalar value. For a varobj whose type is some sort of
26958 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
26959 will not be interesting.
26962 The varobj's type. This is a string representation of the type, as
26963 would be printed by the @value{GDBN} CLI.
26966 If a variable object is bound to a specific thread, then this is the
26967 thread's identifier.
26970 For a dynamic varobj, this indicates whether there appear to be any
26971 children available. For a non-dynamic varobj, this will be 0.
26974 This attribute will be present and have the value @samp{1} if the
26975 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
26976 then this attribute will not be present.
26979 A dynamic varobj can supply a display hint to the front end. The
26980 value comes directly from the Python pretty-printer object's
26981 @code{display_hint} method. @xref{Pretty Printing API}.
26984 Typical output will look like this:
26987 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
26988 has_more="@var{has_more}"
26992 @subheading The @code{-var-delete} Command
26993 @findex -var-delete
26995 @subsubheading Synopsis
26998 -var-delete [ -c ] @var{name}
27001 Deletes a previously created variable object and all of its children.
27002 With the @samp{-c} option, just deletes the children.
27004 Returns an error if the object @var{name} is not found.
27007 @subheading The @code{-var-set-format} Command
27008 @findex -var-set-format
27010 @subsubheading Synopsis
27013 -var-set-format @var{name} @var{format-spec}
27016 Sets the output format for the value of the object @var{name} to be
27019 @anchor{-var-set-format}
27020 The syntax for the @var{format-spec} is as follows:
27023 @var{format-spec} @expansion{}
27024 @{binary | decimal | hexadecimal | octal | natural@}
27027 The natural format is the default format choosen automatically
27028 based on the variable type (like decimal for an @code{int}, hex
27029 for pointers, etc.).
27031 For a variable with children, the format is set only on the
27032 variable itself, and the children are not affected.
27034 @subheading The @code{-var-show-format} Command
27035 @findex -var-show-format
27037 @subsubheading Synopsis
27040 -var-show-format @var{name}
27043 Returns the format used to display the value of the object @var{name}.
27046 @var{format} @expansion{}
27051 @subheading The @code{-var-info-num-children} Command
27052 @findex -var-info-num-children
27054 @subsubheading Synopsis
27057 -var-info-num-children @var{name}
27060 Returns the number of children of a variable object @var{name}:
27066 Note that this number is not completely reliable for a dynamic varobj.
27067 It will return the current number of children, but more children may
27071 @subheading The @code{-var-list-children} Command
27072 @findex -var-list-children
27074 @subsubheading Synopsis
27077 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
27079 @anchor{-var-list-children}
27081 Return a list of the children of the specified variable object and
27082 create variable objects for them, if they do not already exist. With
27083 a single argument or if @var{print-values} has a value of 0 or
27084 @code{--no-values}, print only the names of the variables; if
27085 @var{print-values} is 1 or @code{--all-values}, also print their
27086 values; and if it is 2 or @code{--simple-values} print the name and
27087 value for simple data types and just the name for arrays, structures
27090 @var{from} and @var{to}, if specified, indicate the range of children
27091 to report. If @var{from} or @var{to} is less than zero, the range is
27092 reset and all children will be reported. Otherwise, children starting
27093 at @var{from} (zero-based) and up to and excluding @var{to} will be
27096 If a child range is requested, it will only affect the current call to
27097 @code{-var-list-children}, but not future calls to @code{-var-update}.
27098 For this, you must instead use @code{-var-set-update-range}. The
27099 intent of this approach is to enable a front end to implement any
27100 update approach it likes; for example, scrolling a view may cause the
27101 front end to request more children with @code{-var-list-children}, and
27102 then the front end could call @code{-var-set-update-range} with a
27103 different range to ensure that future updates are restricted to just
27106 For each child the following results are returned:
27111 Name of the variable object created for this child.
27114 The expression to be shown to the user by the front end to designate this child.
27115 For example this may be the name of a structure member.
27117 For a dynamic varobj, this value cannot be used to form an
27118 expression. There is no way to do this at all with a dynamic varobj.
27120 For C/C@t{++} structures there are several pseudo children returned to
27121 designate access qualifiers. For these pseudo children @var{exp} is
27122 @samp{public}, @samp{private}, or @samp{protected}. In this case the
27123 type and value are not present.
27125 A dynamic varobj will not report the access qualifying
27126 pseudo-children, regardless of the language. This information is not
27127 available at all with a dynamic varobj.
27130 Number of children this child has. For a dynamic varobj, this will be
27134 The type of the child.
27137 If values were requested, this is the value.
27140 If this variable object is associated with a thread, this is the thread id.
27141 Otherwise this result is not present.
27144 If the variable object is frozen, this variable will be present with a value of 1.
27147 The result may have its own attributes:
27151 A dynamic varobj can supply a display hint to the front end. The
27152 value comes directly from the Python pretty-printer object's
27153 @code{display_hint} method. @xref{Pretty Printing API}.
27156 This is an integer attribute which is nonzero if there are children
27157 remaining after the end of the selected range.
27160 @subsubheading Example
27164 -var-list-children n
27165 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
27166 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
27168 -var-list-children --all-values n
27169 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
27170 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
27174 @subheading The @code{-var-info-type} Command
27175 @findex -var-info-type
27177 @subsubheading Synopsis
27180 -var-info-type @var{name}
27183 Returns the type of the specified variable @var{name}. The type is
27184 returned as a string in the same format as it is output by the
27188 type=@var{typename}
27192 @subheading The @code{-var-info-expression} Command
27193 @findex -var-info-expression
27195 @subsubheading Synopsis
27198 -var-info-expression @var{name}
27201 Returns a string that is suitable for presenting this
27202 variable object in user interface. The string is generally
27203 not valid expression in the current language, and cannot be evaluated.
27205 For example, if @code{a} is an array, and variable object
27206 @code{A} was created for @code{a}, then we'll get this output:
27209 (gdb) -var-info-expression A.1
27210 ^done,lang="C",exp="1"
27214 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
27216 Note that the output of the @code{-var-list-children} command also
27217 includes those expressions, so the @code{-var-info-expression} command
27220 @subheading The @code{-var-info-path-expression} Command
27221 @findex -var-info-path-expression
27223 @subsubheading Synopsis
27226 -var-info-path-expression @var{name}
27229 Returns an expression that can be evaluated in the current
27230 context and will yield the same value that a variable object has.
27231 Compare this with the @code{-var-info-expression} command, which
27232 result can be used only for UI presentation. Typical use of
27233 the @code{-var-info-path-expression} command is creating a
27234 watchpoint from a variable object.
27236 This command is currently not valid for children of a dynamic varobj,
27237 and will give an error when invoked on one.
27239 For example, suppose @code{C} is a C@t{++} class, derived from class
27240 @code{Base}, and that the @code{Base} class has a member called
27241 @code{m_size}. Assume a variable @code{c} is has the type of
27242 @code{C} and a variable object @code{C} was created for variable
27243 @code{c}. Then, we'll get this output:
27245 (gdb) -var-info-path-expression C.Base.public.m_size
27246 ^done,path_expr=((Base)c).m_size)
27249 @subheading The @code{-var-show-attributes} Command
27250 @findex -var-show-attributes
27252 @subsubheading Synopsis
27255 -var-show-attributes @var{name}
27258 List attributes of the specified variable object @var{name}:
27261 status=@var{attr} [ ( ,@var{attr} )* ]
27265 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
27267 @subheading The @code{-var-evaluate-expression} Command
27268 @findex -var-evaluate-expression
27270 @subsubheading Synopsis
27273 -var-evaluate-expression [-f @var{format-spec}] @var{name}
27276 Evaluates the expression that is represented by the specified variable
27277 object and returns its value as a string. The format of the string
27278 can be specified with the @samp{-f} option. The possible values of
27279 this option are the same as for @code{-var-set-format}
27280 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
27281 the current display format will be used. The current display format
27282 can be changed using the @code{-var-set-format} command.
27288 Note that one must invoke @code{-var-list-children} for a variable
27289 before the value of a child variable can be evaluated.
27291 @subheading The @code{-var-assign} Command
27292 @findex -var-assign
27294 @subsubheading Synopsis
27297 -var-assign @var{name} @var{expression}
27300 Assigns the value of @var{expression} to the variable object specified
27301 by @var{name}. The object must be @samp{editable}. If the variable's
27302 value is altered by the assign, the variable will show up in any
27303 subsequent @code{-var-update} list.
27305 @subsubheading Example
27313 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
27317 @subheading The @code{-var-update} Command
27318 @findex -var-update
27320 @subsubheading Synopsis
27323 -var-update [@var{print-values}] @{@var{name} | "*"@}
27326 Reevaluate the expressions corresponding to the variable object
27327 @var{name} and all its direct and indirect children, and return the
27328 list of variable objects whose values have changed; @var{name} must
27329 be a root variable object. Here, ``changed'' means that the result of
27330 @code{-var-evaluate-expression} before and after the
27331 @code{-var-update} is different. If @samp{*} is used as the variable
27332 object names, all existing variable objects are updated, except
27333 for frozen ones (@pxref{-var-set-frozen}). The option
27334 @var{print-values} determines whether both names and values, or just
27335 names are printed. The possible values of this option are the same
27336 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
27337 recommended to use the @samp{--all-values} option, to reduce the
27338 number of MI commands needed on each program stop.
27340 With the @samp{*} parameter, if a variable object is bound to a
27341 currently running thread, it will not be updated, without any
27344 If @code{-var-set-update-range} was previously used on a varobj, then
27345 only the selected range of children will be reported.
27347 @code{-var-update} reports all the changed varobjs in a tuple named
27350 Each item in the change list is itself a tuple holding:
27354 The name of the varobj.
27357 If values were requested for this update, then this field will be
27358 present and will hold the value of the varobj.
27361 @anchor{-var-update}
27362 This field is a string which may take one of three values:
27366 The variable object's current value is valid.
27369 The variable object does not currently hold a valid value but it may
27370 hold one in the future if its associated expression comes back into
27374 The variable object no longer holds a valid value.
27375 This can occur when the executable file being debugged has changed,
27376 either through recompilation or by using the @value{GDBN} @code{file}
27377 command. The front end should normally choose to delete these variable
27381 In the future new values may be added to this list so the front should
27382 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
27385 This is only present if the varobj is still valid. If the type
27386 changed, then this will be the string @samp{true}; otherwise it will
27390 If the varobj's type changed, then this field will be present and will
27393 @item new_num_children
27394 For a dynamic varobj, if the number of children changed, or if the
27395 type changed, this will be the new number of children.
27397 The @samp{numchild} field in other varobj responses is generally not
27398 valid for a dynamic varobj -- it will show the number of children that
27399 @value{GDBN} knows about, but because dynamic varobjs lazily
27400 instantiate their children, this will not reflect the number of
27401 children which may be available.
27403 The @samp{new_num_children} attribute only reports changes to the
27404 number of children known by @value{GDBN}. This is the only way to
27405 detect whether an update has removed children (which necessarily can
27406 only happen at the end of the update range).
27409 The display hint, if any.
27412 This is an integer value, which will be 1 if there are more children
27413 available outside the varobj's update range.
27416 This attribute will be present and have the value @samp{1} if the
27417 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
27418 then this attribute will not be present.
27421 If new children were added to a dynamic varobj within the selected
27422 update range (as set by @code{-var-set-update-range}), then they will
27423 be listed in this attribute.
27426 @subsubheading Example
27433 -var-update --all-values var1
27434 ^done,changelist=[@{name="var1",value="3",in_scope="true",
27435 type_changed="false"@}]
27439 @subheading The @code{-var-set-frozen} Command
27440 @findex -var-set-frozen
27441 @anchor{-var-set-frozen}
27443 @subsubheading Synopsis
27446 -var-set-frozen @var{name} @var{flag}
27449 Set the frozenness flag on the variable object @var{name}. The
27450 @var{flag} parameter should be either @samp{1} to make the variable
27451 frozen or @samp{0} to make it unfrozen. If a variable object is
27452 frozen, then neither itself, nor any of its children, are
27453 implicitly updated by @code{-var-update} of
27454 a parent variable or by @code{-var-update *}. Only
27455 @code{-var-update} of the variable itself will update its value and
27456 values of its children. After a variable object is unfrozen, it is
27457 implicitly updated by all subsequent @code{-var-update} operations.
27458 Unfreezing a variable does not update it, only subsequent
27459 @code{-var-update} does.
27461 @subsubheading Example
27465 -var-set-frozen V 1
27470 @subheading The @code{-var-set-update-range} command
27471 @findex -var-set-update-range
27472 @anchor{-var-set-update-range}
27474 @subsubheading Synopsis
27477 -var-set-update-range @var{name} @var{from} @var{to}
27480 Set the range of children to be returned by future invocations of
27481 @code{-var-update}.
27483 @var{from} and @var{to} indicate the range of children to report. If
27484 @var{from} or @var{to} is less than zero, the range is reset and all
27485 children will be reported. Otherwise, children starting at @var{from}
27486 (zero-based) and up to and excluding @var{to} will be reported.
27488 @subsubheading Example
27492 -var-set-update-range V 1 2
27496 @subheading The @code{-var-set-visualizer} command
27497 @findex -var-set-visualizer
27498 @anchor{-var-set-visualizer}
27500 @subsubheading Synopsis
27503 -var-set-visualizer @var{name} @var{visualizer}
27506 Set a visualizer for the variable object @var{name}.
27508 @var{visualizer} is the visualizer to use. The special value
27509 @samp{None} means to disable any visualizer in use.
27511 If not @samp{None}, @var{visualizer} must be a Python expression.
27512 This expression must evaluate to a callable object which accepts a
27513 single argument. @value{GDBN} will call this object with the value of
27514 the varobj @var{name} as an argument (this is done so that the same
27515 Python pretty-printing code can be used for both the CLI and MI).
27516 When called, this object must return an object which conforms to the
27517 pretty-printing interface (@pxref{Pretty Printing API}).
27519 The pre-defined function @code{gdb.default_visualizer} may be used to
27520 select a visualizer by following the built-in process
27521 (@pxref{Selecting Pretty-Printers}). This is done automatically when
27522 a varobj is created, and so ordinarily is not needed.
27524 This feature is only available if Python support is enabled. The MI
27525 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
27526 can be used to check this.
27528 @subsubheading Example
27530 Resetting the visualizer:
27534 -var-set-visualizer V None
27538 Reselecting the default (type-based) visualizer:
27542 -var-set-visualizer V gdb.default_visualizer
27546 Suppose @code{SomeClass} is a visualizer class. A lambda expression
27547 can be used to instantiate this class for a varobj:
27551 -var-set-visualizer V "lambda val: SomeClass()"
27555 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27556 @node GDB/MI Data Manipulation
27557 @section @sc{gdb/mi} Data Manipulation
27559 @cindex data manipulation, in @sc{gdb/mi}
27560 @cindex @sc{gdb/mi}, data manipulation
27561 This section describes the @sc{gdb/mi} commands that manipulate data:
27562 examine memory and registers, evaluate expressions, etc.
27564 @c REMOVED FROM THE INTERFACE.
27565 @c @subheading -data-assign
27566 @c Change the value of a program variable. Plenty of side effects.
27567 @c @subsubheading GDB Command
27569 @c @subsubheading Example
27572 @subheading The @code{-data-disassemble} Command
27573 @findex -data-disassemble
27575 @subsubheading Synopsis
27579 [ -s @var{start-addr} -e @var{end-addr} ]
27580 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
27588 @item @var{start-addr}
27589 is the beginning address (or @code{$pc})
27590 @item @var{end-addr}
27592 @item @var{filename}
27593 is the name of the file to disassemble
27594 @item @var{linenum}
27595 is the line number to disassemble around
27597 is the number of disassembly lines to be produced. If it is -1,
27598 the whole function will be disassembled, in case no @var{end-addr} is
27599 specified. If @var{end-addr} is specified as a non-zero value, and
27600 @var{lines} is lower than the number of disassembly lines between
27601 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
27602 displayed; if @var{lines} is higher than the number of lines between
27603 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
27606 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
27610 @subsubheading Result
27612 The output for each instruction is composed of four fields:
27621 Note that whatever included in the instruction field, is not manipulated
27622 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
27624 @subsubheading @value{GDBN} Command
27626 There's no direct mapping from this command to the CLI.
27628 @subsubheading Example
27630 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
27634 -data-disassemble -s $pc -e "$pc + 20" -- 0
27637 @{address="0x000107c0",func-name="main",offset="4",
27638 inst="mov 2, %o0"@},
27639 @{address="0x000107c4",func-name="main",offset="8",
27640 inst="sethi %hi(0x11800), %o2"@},
27641 @{address="0x000107c8",func-name="main",offset="12",
27642 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
27643 @{address="0x000107cc",func-name="main",offset="16",
27644 inst="sethi %hi(0x11800), %o2"@},
27645 @{address="0x000107d0",func-name="main",offset="20",
27646 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
27650 Disassemble the whole @code{main} function. Line 32 is part of
27654 -data-disassemble -f basics.c -l 32 -- 0
27656 @{address="0x000107bc",func-name="main",offset="0",
27657 inst="save %sp, -112, %sp"@},
27658 @{address="0x000107c0",func-name="main",offset="4",
27659 inst="mov 2, %o0"@},
27660 @{address="0x000107c4",func-name="main",offset="8",
27661 inst="sethi %hi(0x11800), %o2"@},
27663 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
27664 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
27668 Disassemble 3 instructions from the start of @code{main}:
27672 -data-disassemble -f basics.c -l 32 -n 3 -- 0
27674 @{address="0x000107bc",func-name="main",offset="0",
27675 inst="save %sp, -112, %sp"@},
27676 @{address="0x000107c0",func-name="main",offset="4",
27677 inst="mov 2, %o0"@},
27678 @{address="0x000107c4",func-name="main",offset="8",
27679 inst="sethi %hi(0x11800), %o2"@}]
27683 Disassemble 3 instructions from the start of @code{main} in mixed mode:
27687 -data-disassemble -f basics.c -l 32 -n 3 -- 1
27689 src_and_asm_line=@{line="31",
27690 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
27691 testsuite/gdb.mi/basics.c",line_asm_insn=[
27692 @{address="0x000107bc",func-name="main",offset="0",
27693 inst="save %sp, -112, %sp"@}]@},
27694 src_and_asm_line=@{line="32",
27695 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
27696 testsuite/gdb.mi/basics.c",line_asm_insn=[
27697 @{address="0x000107c0",func-name="main",offset="4",
27698 inst="mov 2, %o0"@},
27699 @{address="0x000107c4",func-name="main",offset="8",
27700 inst="sethi %hi(0x11800), %o2"@}]@}]
27705 @subheading The @code{-data-evaluate-expression} Command
27706 @findex -data-evaluate-expression
27708 @subsubheading Synopsis
27711 -data-evaluate-expression @var{expr}
27714 Evaluate @var{expr} as an expression. The expression could contain an
27715 inferior function call. The function call will execute synchronously.
27716 If the expression contains spaces, it must be enclosed in double quotes.
27718 @subsubheading @value{GDBN} Command
27720 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
27721 @samp{call}. In @code{gdbtk} only, there's a corresponding
27722 @samp{gdb_eval} command.
27724 @subsubheading Example
27726 In the following example, the numbers that precede the commands are the
27727 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
27728 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
27732 211-data-evaluate-expression A
27735 311-data-evaluate-expression &A
27736 311^done,value="0xefffeb7c"
27738 411-data-evaluate-expression A+3
27741 511-data-evaluate-expression "A + 3"
27747 @subheading The @code{-data-list-changed-registers} Command
27748 @findex -data-list-changed-registers
27750 @subsubheading Synopsis
27753 -data-list-changed-registers
27756 Display a list of the registers that have changed.
27758 @subsubheading @value{GDBN} Command
27760 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
27761 has the corresponding command @samp{gdb_changed_register_list}.
27763 @subsubheading Example
27765 On a PPC MBX board:
27773 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
27774 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
27777 -data-list-changed-registers
27778 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
27779 "10","11","13","14","15","16","17","18","19","20","21","22","23",
27780 "24","25","26","27","28","30","31","64","65","66","67","69"]
27785 @subheading The @code{-data-list-register-names} Command
27786 @findex -data-list-register-names
27788 @subsubheading Synopsis
27791 -data-list-register-names [ ( @var{regno} )+ ]
27794 Show a list of register names for the current target. If no arguments
27795 are given, it shows a list of the names of all the registers. If
27796 integer numbers are given as arguments, it will print a list of the
27797 names of the registers corresponding to the arguments. To ensure
27798 consistency between a register name and its number, the output list may
27799 include empty register names.
27801 @subsubheading @value{GDBN} Command
27803 @value{GDBN} does not have a command which corresponds to
27804 @samp{-data-list-register-names}. In @code{gdbtk} there is a
27805 corresponding command @samp{gdb_regnames}.
27807 @subsubheading Example
27809 For the PPC MBX board:
27812 -data-list-register-names
27813 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
27814 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
27815 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
27816 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
27817 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
27818 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
27819 "", "pc","ps","cr","lr","ctr","xer"]
27821 -data-list-register-names 1 2 3
27822 ^done,register-names=["r1","r2","r3"]
27826 @subheading The @code{-data-list-register-values} Command
27827 @findex -data-list-register-values
27829 @subsubheading Synopsis
27832 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
27835 Display the registers' contents. @var{fmt} is the format according to
27836 which the registers' contents are to be returned, followed by an optional
27837 list of numbers specifying the registers to display. A missing list of
27838 numbers indicates that the contents of all the registers must be returned.
27840 Allowed formats for @var{fmt} are:
27857 @subsubheading @value{GDBN} Command
27859 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
27860 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
27862 @subsubheading Example
27864 For a PPC MBX board (note: line breaks are for readability only, they
27865 don't appear in the actual output):
27869 -data-list-register-values r 64 65
27870 ^done,register-values=[@{number="64",value="0xfe00a300"@},
27871 @{number="65",value="0x00029002"@}]
27873 -data-list-register-values x
27874 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
27875 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
27876 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
27877 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
27878 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
27879 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
27880 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
27881 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
27882 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
27883 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
27884 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
27885 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
27886 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
27887 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
27888 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
27889 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
27890 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
27891 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
27892 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
27893 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
27894 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
27895 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
27896 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
27897 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
27898 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
27899 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
27900 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
27901 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
27902 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
27903 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
27904 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
27905 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
27906 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
27907 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
27908 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
27909 @{number="69",value="0x20002b03"@}]
27914 @subheading The @code{-data-read-memory} Command
27915 @findex -data-read-memory
27917 This command is deprecated, use @code{-data-read-memory-bytes} instead.
27919 @subsubheading Synopsis
27922 -data-read-memory [ -o @var{byte-offset} ]
27923 @var{address} @var{word-format} @var{word-size}
27924 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
27931 @item @var{address}
27932 An expression specifying the address of the first memory word to be
27933 read. Complex expressions containing embedded white space should be
27934 quoted using the C convention.
27936 @item @var{word-format}
27937 The format to be used to print the memory words. The notation is the
27938 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
27941 @item @var{word-size}
27942 The size of each memory word in bytes.
27944 @item @var{nr-rows}
27945 The number of rows in the output table.
27947 @item @var{nr-cols}
27948 The number of columns in the output table.
27951 If present, indicates that each row should include an @sc{ascii} dump. The
27952 value of @var{aschar} is used as a padding character when a byte is not a
27953 member of the printable @sc{ascii} character set (printable @sc{ascii}
27954 characters are those whose code is between 32 and 126, inclusively).
27956 @item @var{byte-offset}
27957 An offset to add to the @var{address} before fetching memory.
27960 This command displays memory contents as a table of @var{nr-rows} by
27961 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
27962 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
27963 (returned as @samp{total-bytes}). Should less than the requested number
27964 of bytes be returned by the target, the missing words are identified
27965 using @samp{N/A}. The number of bytes read from the target is returned
27966 in @samp{nr-bytes} and the starting address used to read memory in
27969 The address of the next/previous row or page is available in
27970 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
27973 @subsubheading @value{GDBN} Command
27975 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
27976 @samp{gdb_get_mem} memory read command.
27978 @subsubheading Example
27980 Read six bytes of memory starting at @code{bytes+6} but then offset by
27981 @code{-6} bytes. Format as three rows of two columns. One byte per
27982 word. Display each word in hex.
27986 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
27987 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
27988 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
27989 prev-page="0x0000138a",memory=[
27990 @{addr="0x00001390",data=["0x00","0x01"]@},
27991 @{addr="0x00001392",data=["0x02","0x03"]@},
27992 @{addr="0x00001394",data=["0x04","0x05"]@}]
27996 Read two bytes of memory starting at address @code{shorts + 64} and
27997 display as a single word formatted in decimal.
28001 5-data-read-memory shorts+64 d 2 1 1
28002 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
28003 next-row="0x00001512",prev-row="0x0000150e",
28004 next-page="0x00001512",prev-page="0x0000150e",memory=[
28005 @{addr="0x00001510",data=["128"]@}]
28009 Read thirty two bytes of memory starting at @code{bytes+16} and format
28010 as eight rows of four columns. Include a string encoding with @samp{x}
28011 used as the non-printable character.
28015 4-data-read-memory bytes+16 x 1 8 4 x
28016 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
28017 next-row="0x000013c0",prev-row="0x0000139c",
28018 next-page="0x000013c0",prev-page="0x00001380",memory=[
28019 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
28020 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
28021 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
28022 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
28023 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
28024 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
28025 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
28026 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
28030 @subheading The @code{-data-read-memory-bytes} Command
28031 @findex -data-read-memory-bytes
28033 @subsubheading Synopsis
28036 -data-read-memory-bytes [ -o @var{byte-offset} ]
28037 @var{address} @var{count}
28044 @item @var{address}
28045 An expression specifying the address of the first memory word to be
28046 read. Complex expressions containing embedded white space should be
28047 quoted using the C convention.
28050 The number of bytes to read. This should be an integer literal.
28052 @item @var{byte-offset}
28053 The offsets in bytes relative to @var{address} at which to start
28054 reading. This should be an integer literal. This option is provided
28055 so that a frontend is not required to first evaluate address and then
28056 perform address arithmetics itself.
28060 This command attempts to read all accessible memory regions in the
28061 specified range. First, all regions marked as unreadable in the memory
28062 map (if one is defined) will be skipped. @xref{Memory Region
28063 Attributes}. Second, @value{GDBN} will attempt to read the remaining
28064 regions. For each one, if reading full region results in an errors,
28065 @value{GDBN} will try to read a subset of the region.
28067 In general, every single byte in the region may be readable or not,
28068 and the only way to read every readable byte is to try a read at
28069 every address, which is not practical. Therefore, @value{GDBN} will
28070 attempt to read all accessible bytes at either beginning or the end
28071 of the region, using a binary division scheme. This heuristic works
28072 well for reading accross a memory map boundary. Note that if a region
28073 has a readable range that is neither at the beginning or the end,
28074 @value{GDBN} will not read it.
28076 The result record (@pxref{GDB/MI Result Records}) that is output of
28077 the command includes a field named @samp{memory} whose content is a
28078 list of tuples. Each tuple represent a successfully read memory block
28079 and has the following fields:
28083 The start address of the memory block, as hexadecimal literal.
28086 The end address of the memory block, as hexadecimal literal.
28089 The offset of the memory block, as hexadecimal literal, relative to
28090 the start address passed to @code{-data-read-memory-bytes}.
28093 The contents of the memory block, in hex.
28099 @subsubheading @value{GDBN} Command
28101 The corresponding @value{GDBN} command is @samp{x}.
28103 @subsubheading Example
28107 -data-read-memory-bytes &a 10
28108 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
28110 contents="01000000020000000300"@}]
28115 @subheading The @code{-data-write-memory-bytes} Command
28116 @findex -data-write-memory-bytes
28118 @subsubheading Synopsis
28121 -data-write-memory-bytes @var{address} @var{contents}
28128 @item @var{address}
28129 An expression specifying the address of the first memory word to be
28130 read. Complex expressions containing embedded white space should be
28131 quoted using the C convention.
28133 @item @var{contents}
28134 The hex-encoded bytes to write.
28138 @subsubheading @value{GDBN} Command
28140 There's no corresponding @value{GDBN} command.
28142 @subsubheading Example
28146 -data-write-memory-bytes &a "aabbccdd"
28152 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28153 @node GDB/MI Tracepoint Commands
28154 @section @sc{gdb/mi} Tracepoint Commands
28156 The commands defined in this section implement MI support for
28157 tracepoints. For detailed introduction, see @ref{Tracepoints}.
28159 @subheading The @code{-trace-find} Command
28160 @findex -trace-find
28162 @subsubheading Synopsis
28165 -trace-find @var{mode} [@var{parameters}@dots{}]
28168 Find a trace frame using criteria defined by @var{mode} and
28169 @var{parameters}. The following table lists permissible
28170 modes and their parameters. For details of operation, see @ref{tfind}.
28175 No parameters are required. Stops examining trace frames.
28178 An integer is required as parameter. Selects tracepoint frame with
28181 @item tracepoint-number
28182 An integer is required as parameter. Finds next
28183 trace frame that corresponds to tracepoint with the specified number.
28186 An address is required as parameter. Finds
28187 next trace frame that corresponds to any tracepoint at the specified
28190 @item pc-inside-range
28191 Two addresses are required as parameters. Finds next trace
28192 frame that corresponds to a tracepoint at an address inside the
28193 specified range. Both bounds are considered to be inside the range.
28195 @item pc-outside-range
28196 Two addresses are required as parameters. Finds
28197 next trace frame that corresponds to a tracepoint at an address outside
28198 the specified range. Both bounds are considered to be inside the range.
28201 Line specification is required as parameter. @xref{Specify Location}.
28202 Finds next trace frame that corresponds to a tracepoint at
28203 the specified location.
28207 If @samp{none} was passed as @var{mode}, the response does not
28208 have fields. Otherwise, the response may have the following fields:
28212 This field has either @samp{0} or @samp{1} as the value, depending
28213 on whether a matching tracepoint was found.
28216 The index of the found traceframe. This field is present iff
28217 the @samp{found} field has value of @samp{1}.
28220 The index of the found tracepoint. This field is present iff
28221 the @samp{found} field has value of @samp{1}.
28224 The information about the frame corresponding to the found trace
28225 frame. This field is present only if a trace frame was found.
28226 @xref{GDB/MI Frame Information}, for description of this field.
28230 @subsubheading @value{GDBN} Command
28232 The corresponding @value{GDBN} command is @samp{tfind}.
28234 @subheading -trace-define-variable
28235 @findex -trace-define-variable
28237 @subsubheading Synopsis
28240 -trace-define-variable @var{name} [ @var{value} ]
28243 Create trace variable @var{name} if it does not exist. If
28244 @var{value} is specified, sets the initial value of the specified
28245 trace variable to that value. Note that the @var{name} should start
28246 with the @samp{$} character.
28248 @subsubheading @value{GDBN} Command
28250 The corresponding @value{GDBN} command is @samp{tvariable}.
28252 @subheading -trace-list-variables
28253 @findex -trace-list-variables
28255 @subsubheading Synopsis
28258 -trace-list-variables
28261 Return a table of all defined trace variables. Each element of the
28262 table has the following fields:
28266 The name of the trace variable. This field is always present.
28269 The initial value. This is a 64-bit signed integer. This
28270 field is always present.
28273 The value the trace variable has at the moment. This is a 64-bit
28274 signed integer. This field is absent iff current value is
28275 not defined, for example if the trace was never run, or is
28280 @subsubheading @value{GDBN} Command
28282 The corresponding @value{GDBN} command is @samp{tvariables}.
28284 @subsubheading Example
28288 -trace-list-variables
28289 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
28290 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
28291 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
28292 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
28293 body=[variable=@{name="$trace_timestamp",initial="0"@}
28294 variable=@{name="$foo",initial="10",current="15"@}]@}
28298 @subheading -trace-save
28299 @findex -trace-save
28301 @subsubheading Synopsis
28304 -trace-save [-r ] @var{filename}
28307 Saves the collected trace data to @var{filename}. Without the
28308 @samp{-r} option, the data is downloaded from the target and saved
28309 in a local file. With the @samp{-r} option the target is asked
28310 to perform the save.
28312 @subsubheading @value{GDBN} Command
28314 The corresponding @value{GDBN} command is @samp{tsave}.
28317 @subheading -trace-start
28318 @findex -trace-start
28320 @subsubheading Synopsis
28326 Starts a tracing experiments. The result of this command does not
28329 @subsubheading @value{GDBN} Command
28331 The corresponding @value{GDBN} command is @samp{tstart}.
28333 @subheading -trace-status
28334 @findex -trace-status
28336 @subsubheading Synopsis
28342 Obtains the status of a tracing experiment. The result may include
28343 the following fields:
28348 May have a value of either @samp{0}, when no tracing operations are
28349 supported, @samp{1}, when all tracing operations are supported, or
28350 @samp{file} when examining trace file. In the latter case, examining
28351 of trace frame is possible but new tracing experiement cannot be
28352 started. This field is always present.
28355 May have a value of either @samp{0} or @samp{1} depending on whether
28356 tracing experiement is in progress on target. This field is present
28357 if @samp{supported} field is not @samp{0}.
28360 Report the reason why the tracing was stopped last time. This field
28361 may be absent iff tracing was never stopped on target yet. The
28362 value of @samp{request} means the tracing was stopped as result of
28363 the @code{-trace-stop} command. The value of @samp{overflow} means
28364 the tracing buffer is full. The value of @samp{disconnection} means
28365 tracing was automatically stopped when @value{GDBN} has disconnected.
28366 The value of @samp{passcount} means tracing was stopped when a
28367 tracepoint was passed a maximal number of times for that tracepoint.
28368 This field is present if @samp{supported} field is not @samp{0}.
28370 @item stopping-tracepoint
28371 The number of tracepoint whose passcount as exceeded. This field is
28372 present iff the @samp{stop-reason} field has the value of
28376 @itemx frames-created
28377 The @samp{frames} field is a count of the total number of trace frames
28378 in the trace buffer, while @samp{frames-created} is the total created
28379 during the run, including ones that were discarded, such as when a
28380 circular trace buffer filled up. Both fields are optional.
28384 These fields tell the current size of the tracing buffer and the
28385 remaining space. These fields are optional.
28388 The value of the circular trace buffer flag. @code{1} means that the
28389 trace buffer is circular and old trace frames will be discarded if
28390 necessary to make room, @code{0} means that the trace buffer is linear
28394 The value of the disconnected tracing flag. @code{1} means that
28395 tracing will continue after @value{GDBN} disconnects, @code{0} means
28396 that the trace run will stop.
28400 @subsubheading @value{GDBN} Command
28402 The corresponding @value{GDBN} command is @samp{tstatus}.
28404 @subheading -trace-stop
28405 @findex -trace-stop
28407 @subsubheading Synopsis
28413 Stops a tracing experiment. The result of this command has the same
28414 fields as @code{-trace-status}, except that the @samp{supported} and
28415 @samp{running} fields are not output.
28417 @subsubheading @value{GDBN} Command
28419 The corresponding @value{GDBN} command is @samp{tstop}.
28422 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28423 @node GDB/MI Symbol Query
28424 @section @sc{gdb/mi} Symbol Query Commands
28428 @subheading The @code{-symbol-info-address} Command
28429 @findex -symbol-info-address
28431 @subsubheading Synopsis
28434 -symbol-info-address @var{symbol}
28437 Describe where @var{symbol} is stored.
28439 @subsubheading @value{GDBN} Command
28441 The corresponding @value{GDBN} command is @samp{info address}.
28443 @subsubheading Example
28447 @subheading The @code{-symbol-info-file} Command
28448 @findex -symbol-info-file
28450 @subsubheading Synopsis
28456 Show the file for the symbol.
28458 @subsubheading @value{GDBN} Command
28460 There's no equivalent @value{GDBN} command. @code{gdbtk} has
28461 @samp{gdb_find_file}.
28463 @subsubheading Example
28467 @subheading The @code{-symbol-info-function} Command
28468 @findex -symbol-info-function
28470 @subsubheading Synopsis
28473 -symbol-info-function
28476 Show which function the symbol lives in.
28478 @subsubheading @value{GDBN} Command
28480 @samp{gdb_get_function} in @code{gdbtk}.
28482 @subsubheading Example
28486 @subheading The @code{-symbol-info-line} Command
28487 @findex -symbol-info-line
28489 @subsubheading Synopsis
28495 Show the core addresses of the code for a source line.
28497 @subsubheading @value{GDBN} Command
28499 The corresponding @value{GDBN} command is @samp{info line}.
28500 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
28502 @subsubheading Example
28506 @subheading The @code{-symbol-info-symbol} Command
28507 @findex -symbol-info-symbol
28509 @subsubheading Synopsis
28512 -symbol-info-symbol @var{addr}
28515 Describe what symbol is at location @var{addr}.
28517 @subsubheading @value{GDBN} Command
28519 The corresponding @value{GDBN} command is @samp{info symbol}.
28521 @subsubheading Example
28525 @subheading The @code{-symbol-list-functions} Command
28526 @findex -symbol-list-functions
28528 @subsubheading Synopsis
28531 -symbol-list-functions
28534 List the functions in the executable.
28536 @subsubheading @value{GDBN} Command
28538 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
28539 @samp{gdb_search} in @code{gdbtk}.
28541 @subsubheading Example
28546 @subheading The @code{-symbol-list-lines} Command
28547 @findex -symbol-list-lines
28549 @subsubheading Synopsis
28552 -symbol-list-lines @var{filename}
28555 Print the list of lines that contain code and their associated program
28556 addresses for the given source filename. The entries are sorted in
28557 ascending PC order.
28559 @subsubheading @value{GDBN} Command
28561 There is no corresponding @value{GDBN} command.
28563 @subsubheading Example
28566 -symbol-list-lines basics.c
28567 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
28573 @subheading The @code{-symbol-list-types} Command
28574 @findex -symbol-list-types
28576 @subsubheading Synopsis
28582 List all the type names.
28584 @subsubheading @value{GDBN} Command
28586 The corresponding commands are @samp{info types} in @value{GDBN},
28587 @samp{gdb_search} in @code{gdbtk}.
28589 @subsubheading Example
28593 @subheading The @code{-symbol-list-variables} Command
28594 @findex -symbol-list-variables
28596 @subsubheading Synopsis
28599 -symbol-list-variables
28602 List all the global and static variable names.
28604 @subsubheading @value{GDBN} Command
28606 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
28608 @subsubheading Example
28612 @subheading The @code{-symbol-locate} Command
28613 @findex -symbol-locate
28615 @subsubheading Synopsis
28621 @subsubheading @value{GDBN} Command
28623 @samp{gdb_loc} in @code{gdbtk}.
28625 @subsubheading Example
28629 @subheading The @code{-symbol-type} Command
28630 @findex -symbol-type
28632 @subsubheading Synopsis
28635 -symbol-type @var{variable}
28638 Show type of @var{variable}.
28640 @subsubheading @value{GDBN} Command
28642 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
28643 @samp{gdb_obj_variable}.
28645 @subsubheading Example
28650 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28651 @node GDB/MI File Commands
28652 @section @sc{gdb/mi} File Commands
28654 This section describes the GDB/MI commands to specify executable file names
28655 and to read in and obtain symbol table information.
28657 @subheading The @code{-file-exec-and-symbols} Command
28658 @findex -file-exec-and-symbols
28660 @subsubheading Synopsis
28663 -file-exec-and-symbols @var{file}
28666 Specify the executable file to be debugged. This file is the one from
28667 which the symbol table is also read. If no file is specified, the
28668 command clears the executable and symbol information. If breakpoints
28669 are set when using this command with no arguments, @value{GDBN} will produce
28670 error messages. Otherwise, no output is produced, except a completion
28673 @subsubheading @value{GDBN} Command
28675 The corresponding @value{GDBN} command is @samp{file}.
28677 @subsubheading Example
28681 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
28687 @subheading The @code{-file-exec-file} Command
28688 @findex -file-exec-file
28690 @subsubheading Synopsis
28693 -file-exec-file @var{file}
28696 Specify the executable file to be debugged. Unlike
28697 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
28698 from this file. If used without argument, @value{GDBN} clears the information
28699 about the executable file. No output is produced, except a completion
28702 @subsubheading @value{GDBN} Command
28704 The corresponding @value{GDBN} command is @samp{exec-file}.
28706 @subsubheading Example
28710 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
28717 @subheading The @code{-file-list-exec-sections} Command
28718 @findex -file-list-exec-sections
28720 @subsubheading Synopsis
28723 -file-list-exec-sections
28726 List the sections of the current executable file.
28728 @subsubheading @value{GDBN} Command
28730 The @value{GDBN} command @samp{info file} shows, among the rest, the same
28731 information as this command. @code{gdbtk} has a corresponding command
28732 @samp{gdb_load_info}.
28734 @subsubheading Example
28739 @subheading The @code{-file-list-exec-source-file} Command
28740 @findex -file-list-exec-source-file
28742 @subsubheading Synopsis
28745 -file-list-exec-source-file
28748 List the line number, the current source file, and the absolute path
28749 to the current source file for the current executable. The macro
28750 information field has a value of @samp{1} or @samp{0} depending on
28751 whether or not the file includes preprocessor macro information.
28753 @subsubheading @value{GDBN} Command
28755 The @value{GDBN} equivalent is @samp{info source}
28757 @subsubheading Example
28761 123-file-list-exec-source-file
28762 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
28767 @subheading The @code{-file-list-exec-source-files} Command
28768 @findex -file-list-exec-source-files
28770 @subsubheading Synopsis
28773 -file-list-exec-source-files
28776 List the source files for the current executable.
28778 It will always output the filename, but only when @value{GDBN} can find
28779 the absolute file name of a source file, will it output the fullname.
28781 @subsubheading @value{GDBN} Command
28783 The @value{GDBN} equivalent is @samp{info sources}.
28784 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
28786 @subsubheading Example
28789 -file-list-exec-source-files
28791 @{file=foo.c,fullname=/home/foo.c@},
28792 @{file=/home/bar.c,fullname=/home/bar.c@},
28793 @{file=gdb_could_not_find_fullpath.c@}]
28798 @subheading The @code{-file-list-shared-libraries} Command
28799 @findex -file-list-shared-libraries
28801 @subsubheading Synopsis
28804 -file-list-shared-libraries
28807 List the shared libraries in the program.
28809 @subsubheading @value{GDBN} Command
28811 The corresponding @value{GDBN} command is @samp{info shared}.
28813 @subsubheading Example
28817 @subheading The @code{-file-list-symbol-files} Command
28818 @findex -file-list-symbol-files
28820 @subsubheading Synopsis
28823 -file-list-symbol-files
28828 @subsubheading @value{GDBN} Command
28830 The corresponding @value{GDBN} command is @samp{info file} (part of it).
28832 @subsubheading Example
28837 @subheading The @code{-file-symbol-file} Command
28838 @findex -file-symbol-file
28840 @subsubheading Synopsis
28843 -file-symbol-file @var{file}
28846 Read symbol table info from the specified @var{file} argument. When
28847 used without arguments, clears @value{GDBN}'s symbol table info. No output is
28848 produced, except for a completion notification.
28850 @subsubheading @value{GDBN} Command
28852 The corresponding @value{GDBN} command is @samp{symbol-file}.
28854 @subsubheading Example
28858 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
28864 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28865 @node GDB/MI Memory Overlay Commands
28866 @section @sc{gdb/mi} Memory Overlay Commands
28868 The memory overlay commands are not implemented.
28870 @c @subheading -overlay-auto
28872 @c @subheading -overlay-list-mapping-state
28874 @c @subheading -overlay-list-overlays
28876 @c @subheading -overlay-map
28878 @c @subheading -overlay-off
28880 @c @subheading -overlay-on
28882 @c @subheading -overlay-unmap
28884 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28885 @node GDB/MI Signal Handling Commands
28886 @section @sc{gdb/mi} Signal Handling Commands
28888 Signal handling commands are not implemented.
28890 @c @subheading -signal-handle
28892 @c @subheading -signal-list-handle-actions
28894 @c @subheading -signal-list-signal-types
28898 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28899 @node GDB/MI Target Manipulation
28900 @section @sc{gdb/mi} Target Manipulation Commands
28903 @subheading The @code{-target-attach} Command
28904 @findex -target-attach
28906 @subsubheading Synopsis
28909 -target-attach @var{pid} | @var{gid} | @var{file}
28912 Attach to a process @var{pid} or a file @var{file} outside of
28913 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
28914 group, the id previously returned by
28915 @samp{-list-thread-groups --available} must be used.
28917 @subsubheading @value{GDBN} Command
28919 The corresponding @value{GDBN} command is @samp{attach}.
28921 @subsubheading Example
28925 =thread-created,id="1"
28926 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
28932 @subheading The @code{-target-compare-sections} Command
28933 @findex -target-compare-sections
28935 @subsubheading Synopsis
28938 -target-compare-sections [ @var{section} ]
28941 Compare data of section @var{section} on target to the exec file.
28942 Without the argument, all sections are compared.
28944 @subsubheading @value{GDBN} Command
28946 The @value{GDBN} equivalent is @samp{compare-sections}.
28948 @subsubheading Example
28953 @subheading The @code{-target-detach} Command
28954 @findex -target-detach
28956 @subsubheading Synopsis
28959 -target-detach [ @var{pid} | @var{gid} ]
28962 Detach from the remote target which normally resumes its execution.
28963 If either @var{pid} or @var{gid} is specified, detaches from either
28964 the specified process, or specified thread group. There's no output.
28966 @subsubheading @value{GDBN} Command
28968 The corresponding @value{GDBN} command is @samp{detach}.
28970 @subsubheading Example
28980 @subheading The @code{-target-disconnect} Command
28981 @findex -target-disconnect
28983 @subsubheading Synopsis
28989 Disconnect from the remote target. There's no output and the target is
28990 generally not resumed.
28992 @subsubheading @value{GDBN} Command
28994 The corresponding @value{GDBN} command is @samp{disconnect}.
28996 @subsubheading Example
29006 @subheading The @code{-target-download} Command
29007 @findex -target-download
29009 @subsubheading Synopsis
29015 Loads the executable onto the remote target.
29016 It prints out an update message every half second, which includes the fields:
29020 The name of the section.
29022 The size of what has been sent so far for that section.
29024 The size of the section.
29026 The total size of what was sent so far (the current and the previous sections).
29028 The size of the overall executable to download.
29032 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
29033 @sc{gdb/mi} Output Syntax}).
29035 In addition, it prints the name and size of the sections, as they are
29036 downloaded. These messages include the following fields:
29040 The name of the section.
29042 The size of the section.
29044 The size of the overall executable to download.
29048 At the end, a summary is printed.
29050 @subsubheading @value{GDBN} Command
29052 The corresponding @value{GDBN} command is @samp{load}.
29054 @subsubheading Example
29056 Note: each status message appears on a single line. Here the messages
29057 have been broken down so that they can fit onto a page.
29062 +download,@{section=".text",section-size="6668",total-size="9880"@}
29063 +download,@{section=".text",section-sent="512",section-size="6668",
29064 total-sent="512",total-size="9880"@}
29065 +download,@{section=".text",section-sent="1024",section-size="6668",
29066 total-sent="1024",total-size="9880"@}
29067 +download,@{section=".text",section-sent="1536",section-size="6668",
29068 total-sent="1536",total-size="9880"@}
29069 +download,@{section=".text",section-sent="2048",section-size="6668",
29070 total-sent="2048",total-size="9880"@}
29071 +download,@{section=".text",section-sent="2560",section-size="6668",
29072 total-sent="2560",total-size="9880"@}
29073 +download,@{section=".text",section-sent="3072",section-size="6668",
29074 total-sent="3072",total-size="9880"@}
29075 +download,@{section=".text",section-sent="3584",section-size="6668",
29076 total-sent="3584",total-size="9880"@}
29077 +download,@{section=".text",section-sent="4096",section-size="6668",
29078 total-sent="4096",total-size="9880"@}
29079 +download,@{section=".text",section-sent="4608",section-size="6668",
29080 total-sent="4608",total-size="9880"@}
29081 +download,@{section=".text",section-sent="5120",section-size="6668",
29082 total-sent="5120",total-size="9880"@}
29083 +download,@{section=".text",section-sent="5632",section-size="6668",
29084 total-sent="5632",total-size="9880"@}
29085 +download,@{section=".text",section-sent="6144",section-size="6668",
29086 total-sent="6144",total-size="9880"@}
29087 +download,@{section=".text",section-sent="6656",section-size="6668",
29088 total-sent="6656",total-size="9880"@}
29089 +download,@{section=".init",section-size="28",total-size="9880"@}
29090 +download,@{section=".fini",section-size="28",total-size="9880"@}
29091 +download,@{section=".data",section-size="3156",total-size="9880"@}
29092 +download,@{section=".data",section-sent="512",section-size="3156",
29093 total-sent="7236",total-size="9880"@}
29094 +download,@{section=".data",section-sent="1024",section-size="3156",
29095 total-sent="7748",total-size="9880"@}
29096 +download,@{section=".data",section-sent="1536",section-size="3156",
29097 total-sent="8260",total-size="9880"@}
29098 +download,@{section=".data",section-sent="2048",section-size="3156",
29099 total-sent="8772",total-size="9880"@}
29100 +download,@{section=".data",section-sent="2560",section-size="3156",
29101 total-sent="9284",total-size="9880"@}
29102 +download,@{section=".data",section-sent="3072",section-size="3156",
29103 total-sent="9796",total-size="9880"@}
29104 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
29111 @subheading The @code{-target-exec-status} Command
29112 @findex -target-exec-status
29114 @subsubheading Synopsis
29117 -target-exec-status
29120 Provide information on the state of the target (whether it is running or
29121 not, for instance).
29123 @subsubheading @value{GDBN} Command
29125 There's no equivalent @value{GDBN} command.
29127 @subsubheading Example
29131 @subheading The @code{-target-list-available-targets} Command
29132 @findex -target-list-available-targets
29134 @subsubheading Synopsis
29137 -target-list-available-targets
29140 List the possible targets to connect to.
29142 @subsubheading @value{GDBN} Command
29144 The corresponding @value{GDBN} command is @samp{help target}.
29146 @subsubheading Example
29150 @subheading The @code{-target-list-current-targets} Command
29151 @findex -target-list-current-targets
29153 @subsubheading Synopsis
29156 -target-list-current-targets
29159 Describe the current target.
29161 @subsubheading @value{GDBN} Command
29163 The corresponding information is printed by @samp{info file} (among
29166 @subsubheading Example
29170 @subheading The @code{-target-list-parameters} Command
29171 @findex -target-list-parameters
29173 @subsubheading Synopsis
29176 -target-list-parameters
29182 @subsubheading @value{GDBN} Command
29186 @subsubheading Example
29190 @subheading The @code{-target-select} Command
29191 @findex -target-select
29193 @subsubheading Synopsis
29196 -target-select @var{type} @var{parameters @dots{}}
29199 Connect @value{GDBN} to the remote target. This command takes two args:
29203 The type of target, for instance @samp{remote}, etc.
29204 @item @var{parameters}
29205 Device names, host names and the like. @xref{Target Commands, ,
29206 Commands for Managing Targets}, for more details.
29209 The output is a connection notification, followed by the address at
29210 which the target program is, in the following form:
29213 ^connected,addr="@var{address}",func="@var{function name}",
29214 args=[@var{arg list}]
29217 @subsubheading @value{GDBN} Command
29219 The corresponding @value{GDBN} command is @samp{target}.
29221 @subsubheading Example
29225 -target-select remote /dev/ttya
29226 ^connected,addr="0xfe00a300",func="??",args=[]
29230 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29231 @node GDB/MI File Transfer Commands
29232 @section @sc{gdb/mi} File Transfer Commands
29235 @subheading The @code{-target-file-put} Command
29236 @findex -target-file-put
29238 @subsubheading Synopsis
29241 -target-file-put @var{hostfile} @var{targetfile}
29244 Copy file @var{hostfile} from the host system (the machine running
29245 @value{GDBN}) to @var{targetfile} on the target system.
29247 @subsubheading @value{GDBN} Command
29249 The corresponding @value{GDBN} command is @samp{remote put}.
29251 @subsubheading Example
29255 -target-file-put localfile remotefile
29261 @subheading The @code{-target-file-get} Command
29262 @findex -target-file-get
29264 @subsubheading Synopsis
29267 -target-file-get @var{targetfile} @var{hostfile}
29270 Copy file @var{targetfile} from the target system to @var{hostfile}
29271 on the host system.
29273 @subsubheading @value{GDBN} Command
29275 The corresponding @value{GDBN} command is @samp{remote get}.
29277 @subsubheading Example
29281 -target-file-get remotefile localfile
29287 @subheading The @code{-target-file-delete} Command
29288 @findex -target-file-delete
29290 @subsubheading Synopsis
29293 -target-file-delete @var{targetfile}
29296 Delete @var{targetfile} from the target system.
29298 @subsubheading @value{GDBN} Command
29300 The corresponding @value{GDBN} command is @samp{remote delete}.
29302 @subsubheading Example
29306 -target-file-delete remotefile
29312 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29313 @node GDB/MI Miscellaneous Commands
29314 @section Miscellaneous @sc{gdb/mi} Commands
29316 @c @subheading -gdb-complete
29318 @subheading The @code{-gdb-exit} Command
29321 @subsubheading Synopsis
29327 Exit @value{GDBN} immediately.
29329 @subsubheading @value{GDBN} Command
29331 Approximately corresponds to @samp{quit}.
29333 @subsubheading Example
29343 @subheading The @code{-exec-abort} Command
29344 @findex -exec-abort
29346 @subsubheading Synopsis
29352 Kill the inferior running program.
29354 @subsubheading @value{GDBN} Command
29356 The corresponding @value{GDBN} command is @samp{kill}.
29358 @subsubheading Example
29363 @subheading The @code{-gdb-set} Command
29366 @subsubheading Synopsis
29372 Set an internal @value{GDBN} variable.
29373 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
29375 @subsubheading @value{GDBN} Command
29377 The corresponding @value{GDBN} command is @samp{set}.
29379 @subsubheading Example
29389 @subheading The @code{-gdb-show} Command
29392 @subsubheading Synopsis
29398 Show the current value of a @value{GDBN} variable.
29400 @subsubheading @value{GDBN} Command
29402 The corresponding @value{GDBN} command is @samp{show}.
29404 @subsubheading Example
29413 @c @subheading -gdb-source
29416 @subheading The @code{-gdb-version} Command
29417 @findex -gdb-version
29419 @subsubheading Synopsis
29425 Show version information for @value{GDBN}. Used mostly in testing.
29427 @subsubheading @value{GDBN} Command
29429 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
29430 default shows this information when you start an interactive session.
29432 @subsubheading Example
29434 @c This example modifies the actual output from GDB to avoid overfull
29440 ~Copyright 2000 Free Software Foundation, Inc.
29441 ~GDB is free software, covered by the GNU General Public License, and
29442 ~you are welcome to change it and/or distribute copies of it under
29443 ~ certain conditions.
29444 ~Type "show copying" to see the conditions.
29445 ~There is absolutely no warranty for GDB. Type "show warranty" for
29447 ~This GDB was configured as
29448 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
29453 @subheading The @code{-list-features} Command
29454 @findex -list-features
29456 Returns a list of particular features of the MI protocol that
29457 this version of gdb implements. A feature can be a command,
29458 or a new field in an output of some command, or even an
29459 important bugfix. While a frontend can sometimes detect presence
29460 of a feature at runtime, it is easier to perform detection at debugger
29463 The command returns a list of strings, with each string naming an
29464 available feature. Each returned string is just a name, it does not
29465 have any internal structure. The list of possible feature names
29471 (gdb) -list-features
29472 ^done,result=["feature1","feature2"]
29475 The current list of features is:
29478 @item frozen-varobjs
29479 Indicates presence of the @code{-var-set-frozen} command, as well
29480 as possible presense of the @code{frozen} field in the output
29481 of @code{-varobj-create}.
29482 @item pending-breakpoints
29483 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
29485 Indicates presence of Python scripting support, Python-based
29486 pretty-printing commands, and possible presence of the
29487 @samp{display_hint} field in the output of @code{-var-list-children}
29489 Indicates presence of the @code{-thread-info} command.
29490 @item data-read-memory-bytes
29491 Indicates presense of the @code{-data-read-memory-bytes} and the
29492 @code{-data-write-memory-bytes} commands.
29496 @subheading The @code{-list-target-features} Command
29497 @findex -list-target-features
29499 Returns a list of particular features that are supported by the
29500 target. Those features affect the permitted MI commands, but
29501 unlike the features reported by the @code{-list-features} command, the
29502 features depend on which target GDB is using at the moment. Whenever
29503 a target can change, due to commands such as @code{-target-select},
29504 @code{-target-attach} or @code{-exec-run}, the list of target features
29505 may change, and the frontend should obtain it again.
29509 (gdb) -list-features
29510 ^done,result=["async"]
29513 The current list of features is:
29517 Indicates that the target is capable of asynchronous command
29518 execution, which means that @value{GDBN} will accept further commands
29519 while the target is running.
29522 Indicates that the target is capable of reverse execution.
29523 @xref{Reverse Execution}, for more information.
29527 @subheading The @code{-list-thread-groups} Command
29528 @findex -list-thread-groups
29530 @subheading Synopsis
29533 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
29536 Lists thread groups (@pxref{Thread groups}). When a single thread
29537 group is passed as the argument, lists the children of that group.
29538 When several thread group are passed, lists information about those
29539 thread groups. Without any parameters, lists information about all
29540 top-level thread groups.
29542 Normally, thread groups that are being debugged are reported.
29543 With the @samp{--available} option, @value{GDBN} reports thread groups
29544 available on the target.
29546 The output of this command may have either a @samp{threads} result or
29547 a @samp{groups} result. The @samp{thread} result has a list of tuples
29548 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
29549 Information}). The @samp{groups} result has a list of tuples as value,
29550 each tuple describing a thread group. If top-level groups are
29551 requested (that is, no parameter is passed), or when several groups
29552 are passed, the output always has a @samp{groups} result. The format
29553 of the @samp{group} result is described below.
29555 To reduce the number of roundtrips it's possible to list thread groups
29556 together with their children, by passing the @samp{--recurse} option
29557 and the recursion depth. Presently, only recursion depth of 1 is
29558 permitted. If this option is present, then every reported thread group
29559 will also include its children, either as @samp{group} or
29560 @samp{threads} field.
29562 In general, any combination of option and parameters is permitted, with
29563 the following caveats:
29567 When a single thread group is passed, the output will typically
29568 be the @samp{threads} result. Because threads may not contain
29569 anything, the @samp{recurse} option will be ignored.
29572 When the @samp{--available} option is passed, limited information may
29573 be available. In particular, the list of threads of a process might
29574 be inaccessible. Further, specifying specific thread groups might
29575 not give any performance advantage over listing all thread groups.
29576 The frontend should assume that @samp{-list-thread-groups --available}
29577 is always an expensive operation and cache the results.
29581 The @samp{groups} result is a list of tuples, where each tuple may
29582 have the following fields:
29586 Identifier of the thread group. This field is always present.
29587 The identifier is an opaque string; frontends should not try to
29588 convert it to an integer, even though it might look like one.
29591 The type of the thread group. At present, only @samp{process} is a
29595 The target-specific process identifier. This field is only present
29596 for thread groups of type @samp{process} and only if the process exists.
29599 The number of children this thread group has. This field may be
29600 absent for an available thread group.
29603 This field has a list of tuples as value, each tuple describing a
29604 thread. It may be present if the @samp{--recurse} option is
29605 specified, and it's actually possible to obtain the threads.
29608 This field is a list of integers, each identifying a core that one
29609 thread of the group is running on. This field may be absent if
29610 such information is not available.
29613 The name of the executable file that corresponds to this thread group.
29614 The field is only present for thread groups of type @samp{process},
29615 and only if there is a corresponding executable file.
29619 @subheading Example
29623 -list-thread-groups
29624 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
29625 -list-thread-groups 17
29626 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29627 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
29628 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29629 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
29630 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
29631 -list-thread-groups --available
29632 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
29633 -list-thread-groups --available --recurse 1
29634 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
29635 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
29636 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
29637 -list-thread-groups --available --recurse 1 17 18
29638 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
29639 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
29640 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
29644 @subheading The @code{-add-inferior} Command
29645 @findex -add-inferior
29647 @subheading Synopsis
29653 Creates a new inferior (@pxref{Inferiors and Programs}). The created
29654 inferior is not associated with any executable. Such association may
29655 be established with the @samp{-file-exec-and-symbols} command
29656 (@pxref{GDB/MI File Commands}). The command response has a single
29657 field, @samp{thread-group}, whose value is the identifier of the
29658 thread group corresponding to the new inferior.
29660 @subheading Example
29665 ^done,thread-group="i3"
29668 @subheading The @code{-interpreter-exec} Command
29669 @findex -interpreter-exec
29671 @subheading Synopsis
29674 -interpreter-exec @var{interpreter} @var{command}
29676 @anchor{-interpreter-exec}
29678 Execute the specified @var{command} in the given @var{interpreter}.
29680 @subheading @value{GDBN} Command
29682 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
29684 @subheading Example
29688 -interpreter-exec console "break main"
29689 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
29690 &"During symbol reading, bad structure-type format.\n"
29691 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
29696 @subheading The @code{-inferior-tty-set} Command
29697 @findex -inferior-tty-set
29699 @subheading Synopsis
29702 -inferior-tty-set /dev/pts/1
29705 Set terminal for future runs of the program being debugged.
29707 @subheading @value{GDBN} Command
29709 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
29711 @subheading Example
29715 -inferior-tty-set /dev/pts/1
29720 @subheading The @code{-inferior-tty-show} Command
29721 @findex -inferior-tty-show
29723 @subheading Synopsis
29729 Show terminal for future runs of program being debugged.
29731 @subheading @value{GDBN} Command
29733 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
29735 @subheading Example
29739 -inferior-tty-set /dev/pts/1
29743 ^done,inferior_tty_terminal="/dev/pts/1"
29747 @subheading The @code{-enable-timings} Command
29748 @findex -enable-timings
29750 @subheading Synopsis
29753 -enable-timings [yes | no]
29756 Toggle the printing of the wallclock, user and system times for an MI
29757 command as a field in its output. This command is to help frontend
29758 developers optimize the performance of their code. No argument is
29759 equivalent to @samp{yes}.
29761 @subheading @value{GDBN} Command
29765 @subheading Example
29773 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29774 addr="0x080484ed",func="main",file="myprog.c",
29775 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
29776 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
29784 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29785 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
29786 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
29787 fullname="/home/nickrob/myprog.c",line="73"@}
29792 @chapter @value{GDBN} Annotations
29794 This chapter describes annotations in @value{GDBN}. Annotations were
29795 designed to interface @value{GDBN} to graphical user interfaces or other
29796 similar programs which want to interact with @value{GDBN} at a
29797 relatively high level.
29799 The annotation mechanism has largely been superseded by @sc{gdb/mi}
29803 This is Edition @value{EDITION}, @value{DATE}.
29807 * Annotations Overview:: What annotations are; the general syntax.
29808 * Server Prefix:: Issuing a command without affecting user state.
29809 * Prompting:: Annotations marking @value{GDBN}'s need for input.
29810 * Errors:: Annotations for error messages.
29811 * Invalidation:: Some annotations describe things now invalid.
29812 * Annotations for Running::
29813 Whether the program is running, how it stopped, etc.
29814 * Source Annotations:: Annotations describing source code.
29817 @node Annotations Overview
29818 @section What is an Annotation?
29819 @cindex annotations
29821 Annotations start with a newline character, two @samp{control-z}
29822 characters, and the name of the annotation. If there is no additional
29823 information associated with this annotation, the name of the annotation
29824 is followed immediately by a newline. If there is additional
29825 information, the name of the annotation is followed by a space, the
29826 additional information, and a newline. The additional information
29827 cannot contain newline characters.
29829 Any output not beginning with a newline and two @samp{control-z}
29830 characters denotes literal output from @value{GDBN}. Currently there is
29831 no need for @value{GDBN} to output a newline followed by two
29832 @samp{control-z} characters, but if there was such a need, the
29833 annotations could be extended with an @samp{escape} annotation which
29834 means those three characters as output.
29836 The annotation @var{level}, which is specified using the
29837 @option{--annotate} command line option (@pxref{Mode Options}), controls
29838 how much information @value{GDBN} prints together with its prompt,
29839 values of expressions, source lines, and other types of output. Level 0
29840 is for no annotations, level 1 is for use when @value{GDBN} is run as a
29841 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
29842 for programs that control @value{GDBN}, and level 2 annotations have
29843 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
29844 Interface, annotate, GDB's Obsolete Annotations}).
29847 @kindex set annotate
29848 @item set annotate @var{level}
29849 The @value{GDBN} command @code{set annotate} sets the level of
29850 annotations to the specified @var{level}.
29852 @item show annotate
29853 @kindex show annotate
29854 Show the current annotation level.
29857 This chapter describes level 3 annotations.
29859 A simple example of starting up @value{GDBN} with annotations is:
29862 $ @kbd{gdb --annotate=3}
29864 Copyright 2003 Free Software Foundation, Inc.
29865 GDB is free software, covered by the GNU General Public License,
29866 and you are welcome to change it and/or distribute copies of it
29867 under certain conditions.
29868 Type "show copying" to see the conditions.
29869 There is absolutely no warranty for GDB. Type "show warranty"
29871 This GDB was configured as "i386-pc-linux-gnu"
29882 Here @samp{quit} is input to @value{GDBN}; the rest is output from
29883 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
29884 denotes a @samp{control-z} character) are annotations; the rest is
29885 output from @value{GDBN}.
29887 @node Server Prefix
29888 @section The Server Prefix
29889 @cindex server prefix
29891 If you prefix a command with @samp{server } then it will not affect
29892 the command history, nor will it affect @value{GDBN}'s notion of which
29893 command to repeat if @key{RET} is pressed on a line by itself. This
29894 means that commands can be run behind a user's back by a front-end in
29895 a transparent manner.
29897 The @code{server } prefix does not affect the recording of values into
29898 the value history; to print a value without recording it into the
29899 value history, use the @code{output} command instead of the
29900 @code{print} command.
29902 Using this prefix also disables confirmation requests
29903 (@pxref{confirmation requests}).
29906 @section Annotation for @value{GDBN} Input
29908 @cindex annotations for prompts
29909 When @value{GDBN} prompts for input, it annotates this fact so it is possible
29910 to know when to send output, when the output from a given command is
29913 Different kinds of input each have a different @dfn{input type}. Each
29914 input type has three annotations: a @code{pre-} annotation, which
29915 denotes the beginning of any prompt which is being output, a plain
29916 annotation, which denotes the end of the prompt, and then a @code{post-}
29917 annotation which denotes the end of any echo which may (or may not) be
29918 associated with the input. For example, the @code{prompt} input type
29919 features the following annotations:
29927 The input types are
29930 @findex pre-prompt annotation
29931 @findex prompt annotation
29932 @findex post-prompt annotation
29934 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
29936 @findex pre-commands annotation
29937 @findex commands annotation
29938 @findex post-commands annotation
29940 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
29941 command. The annotations are repeated for each command which is input.
29943 @findex pre-overload-choice annotation
29944 @findex overload-choice annotation
29945 @findex post-overload-choice annotation
29946 @item overload-choice
29947 When @value{GDBN} wants the user to select between various overloaded functions.
29949 @findex pre-query annotation
29950 @findex query annotation
29951 @findex post-query annotation
29953 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
29955 @findex pre-prompt-for-continue annotation
29956 @findex prompt-for-continue annotation
29957 @findex post-prompt-for-continue annotation
29958 @item prompt-for-continue
29959 When @value{GDBN} is asking the user to press return to continue. Note: Don't
29960 expect this to work well; instead use @code{set height 0} to disable
29961 prompting. This is because the counting of lines is buggy in the
29962 presence of annotations.
29967 @cindex annotations for errors, warnings and interrupts
29969 @findex quit annotation
29974 This annotation occurs right before @value{GDBN} responds to an interrupt.
29976 @findex error annotation
29981 This annotation occurs right before @value{GDBN} responds to an error.
29983 Quit and error annotations indicate that any annotations which @value{GDBN} was
29984 in the middle of may end abruptly. For example, if a
29985 @code{value-history-begin} annotation is followed by a @code{error}, one
29986 cannot expect to receive the matching @code{value-history-end}. One
29987 cannot expect not to receive it either, however; an error annotation
29988 does not necessarily mean that @value{GDBN} is immediately returning all the way
29991 @findex error-begin annotation
29992 A quit or error annotation may be preceded by
29998 Any output between that and the quit or error annotation is the error
30001 Warning messages are not yet annotated.
30002 @c If we want to change that, need to fix warning(), type_error(),
30003 @c range_error(), and possibly other places.
30006 @section Invalidation Notices
30008 @cindex annotations for invalidation messages
30009 The following annotations say that certain pieces of state may have
30013 @findex frames-invalid annotation
30014 @item ^Z^Zframes-invalid
30016 The frames (for example, output from the @code{backtrace} command) may
30019 @findex breakpoints-invalid annotation
30020 @item ^Z^Zbreakpoints-invalid
30022 The breakpoints may have changed. For example, the user just added or
30023 deleted a breakpoint.
30026 @node Annotations for Running
30027 @section Running the Program
30028 @cindex annotations for running programs
30030 @findex starting annotation
30031 @findex stopping annotation
30032 When the program starts executing due to a @value{GDBN} command such as
30033 @code{step} or @code{continue},
30039 is output. When the program stops,
30045 is output. Before the @code{stopped} annotation, a variety of
30046 annotations describe how the program stopped.
30049 @findex exited annotation
30050 @item ^Z^Zexited @var{exit-status}
30051 The program exited, and @var{exit-status} is the exit status (zero for
30052 successful exit, otherwise nonzero).
30054 @findex signalled annotation
30055 @findex signal-name annotation
30056 @findex signal-name-end annotation
30057 @findex signal-string annotation
30058 @findex signal-string-end annotation
30059 @item ^Z^Zsignalled
30060 The program exited with a signal. After the @code{^Z^Zsignalled}, the
30061 annotation continues:
30067 ^Z^Zsignal-name-end
30071 ^Z^Zsignal-string-end
30076 where @var{name} is the name of the signal, such as @code{SIGILL} or
30077 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
30078 as @code{Illegal Instruction} or @code{Segmentation fault}.
30079 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
30080 user's benefit and have no particular format.
30082 @findex signal annotation
30084 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
30085 just saying that the program received the signal, not that it was
30086 terminated with it.
30088 @findex breakpoint annotation
30089 @item ^Z^Zbreakpoint @var{number}
30090 The program hit breakpoint number @var{number}.
30092 @findex watchpoint annotation
30093 @item ^Z^Zwatchpoint @var{number}
30094 The program hit watchpoint number @var{number}.
30097 @node Source Annotations
30098 @section Displaying Source
30099 @cindex annotations for source display
30101 @findex source annotation
30102 The following annotation is used instead of displaying source code:
30105 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
30108 where @var{filename} is an absolute file name indicating which source
30109 file, @var{line} is the line number within that file (where 1 is the
30110 first line in the file), @var{character} is the character position
30111 within the file (where 0 is the first character in the file) (for most
30112 debug formats this will necessarily point to the beginning of a line),
30113 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
30114 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
30115 @var{addr} is the address in the target program associated with the
30116 source which is being displayed. @var{addr} is in the form @samp{0x}
30117 followed by one or more lowercase hex digits (note that this does not
30118 depend on the language).
30120 @node JIT Interface
30121 @chapter JIT Compilation Interface
30122 @cindex just-in-time compilation
30123 @cindex JIT compilation interface
30125 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
30126 interface. A JIT compiler is a program or library that generates native
30127 executable code at runtime and executes it, usually in order to achieve good
30128 performance while maintaining platform independence.
30130 Programs that use JIT compilation are normally difficult to debug because
30131 portions of their code are generated at runtime, instead of being loaded from
30132 object files, which is where @value{GDBN} normally finds the program's symbols
30133 and debug information. In order to debug programs that use JIT compilation,
30134 @value{GDBN} has an interface that allows the program to register in-memory
30135 symbol files with @value{GDBN} at runtime.
30137 If you are using @value{GDBN} to debug a program that uses this interface, then
30138 it should work transparently so long as you have not stripped the binary. If
30139 you are developing a JIT compiler, then the interface is documented in the rest
30140 of this chapter. At this time, the only known client of this interface is the
30143 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
30144 JIT compiler communicates with @value{GDBN} by writing data into a global
30145 variable and calling a fuction at a well-known symbol. When @value{GDBN}
30146 attaches, it reads a linked list of symbol files from the global variable to
30147 find existing code, and puts a breakpoint in the function so that it can find
30148 out about additional code.
30151 * Declarations:: Relevant C struct declarations
30152 * Registering Code:: Steps to register code
30153 * Unregistering Code:: Steps to unregister code
30157 @section JIT Declarations
30159 These are the relevant struct declarations that a C program should include to
30160 implement the interface:
30170 struct jit_code_entry
30172 struct jit_code_entry *next_entry;
30173 struct jit_code_entry *prev_entry;
30174 const char *symfile_addr;
30175 uint64_t symfile_size;
30178 struct jit_descriptor
30181 /* This type should be jit_actions_t, but we use uint32_t
30182 to be explicit about the bitwidth. */
30183 uint32_t action_flag;
30184 struct jit_code_entry *relevant_entry;
30185 struct jit_code_entry *first_entry;
30188 /* GDB puts a breakpoint in this function. */
30189 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
30191 /* Make sure to specify the version statically, because the
30192 debugger may check the version before we can set it. */
30193 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
30196 If the JIT is multi-threaded, then it is important that the JIT synchronize any
30197 modifications to this global data properly, which can easily be done by putting
30198 a global mutex around modifications to these structures.
30200 @node Registering Code
30201 @section Registering Code
30203 To register code with @value{GDBN}, the JIT should follow this protocol:
30207 Generate an object file in memory with symbols and other desired debug
30208 information. The file must include the virtual addresses of the sections.
30211 Create a code entry for the file, which gives the start and size of the symbol
30215 Add it to the linked list in the JIT descriptor.
30218 Point the relevant_entry field of the descriptor at the entry.
30221 Set @code{action_flag} to @code{JIT_REGISTER} and call
30222 @code{__jit_debug_register_code}.
30225 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
30226 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
30227 new code. However, the linked list must still be maintained in order to allow
30228 @value{GDBN} to attach to a running process and still find the symbol files.
30230 @node Unregistering Code
30231 @section Unregistering Code
30233 If code is freed, then the JIT should use the following protocol:
30237 Remove the code entry corresponding to the code from the linked list.
30240 Point the @code{relevant_entry} field of the descriptor at the code entry.
30243 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
30244 @code{__jit_debug_register_code}.
30247 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
30248 and the JIT will leak the memory used for the associated symbol files.
30251 @chapter Reporting Bugs in @value{GDBN}
30252 @cindex bugs in @value{GDBN}
30253 @cindex reporting bugs in @value{GDBN}
30255 Your bug reports play an essential role in making @value{GDBN} reliable.
30257 Reporting a bug may help you by bringing a solution to your problem, or it
30258 may not. But in any case the principal function of a bug report is to help
30259 the entire community by making the next version of @value{GDBN} work better. Bug
30260 reports are your contribution to the maintenance of @value{GDBN}.
30262 In order for a bug report to serve its purpose, you must include the
30263 information that enables us to fix the bug.
30266 * Bug Criteria:: Have you found a bug?
30267 * Bug Reporting:: How to report bugs
30271 @section Have You Found a Bug?
30272 @cindex bug criteria
30274 If you are not sure whether you have found a bug, here are some guidelines:
30277 @cindex fatal signal
30278 @cindex debugger crash
30279 @cindex crash of debugger
30281 If the debugger gets a fatal signal, for any input whatever, that is a
30282 @value{GDBN} bug. Reliable debuggers never crash.
30284 @cindex error on valid input
30286 If @value{GDBN} produces an error message for valid input, that is a
30287 bug. (Note that if you're cross debugging, the problem may also be
30288 somewhere in the connection to the target.)
30290 @cindex invalid input
30292 If @value{GDBN} does not produce an error message for invalid input,
30293 that is a bug. However, you should note that your idea of
30294 ``invalid input'' might be our idea of ``an extension'' or ``support
30295 for traditional practice''.
30298 If you are an experienced user of debugging tools, your suggestions
30299 for improvement of @value{GDBN} are welcome in any case.
30302 @node Bug Reporting
30303 @section How to Report Bugs
30304 @cindex bug reports
30305 @cindex @value{GDBN} bugs, reporting
30307 A number of companies and individuals offer support for @sc{gnu} products.
30308 If you obtained @value{GDBN} from a support organization, we recommend you
30309 contact that organization first.
30311 You can find contact information for many support companies and
30312 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
30314 @c should add a web page ref...
30317 @ifset BUGURL_DEFAULT
30318 In any event, we also recommend that you submit bug reports for
30319 @value{GDBN}. The preferred method is to submit them directly using
30320 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
30321 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
30324 @strong{Do not send bug reports to @samp{info-gdb}, or to
30325 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
30326 not want to receive bug reports. Those that do have arranged to receive
30329 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
30330 serves as a repeater. The mailing list and the newsgroup carry exactly
30331 the same messages. Often people think of posting bug reports to the
30332 newsgroup instead of mailing them. This appears to work, but it has one
30333 problem which can be crucial: a newsgroup posting often lacks a mail
30334 path back to the sender. Thus, if we need to ask for more information,
30335 we may be unable to reach you. For this reason, it is better to send
30336 bug reports to the mailing list.
30338 @ifclear BUGURL_DEFAULT
30339 In any event, we also recommend that you submit bug reports for
30340 @value{GDBN} to @value{BUGURL}.
30344 The fundamental principle of reporting bugs usefully is this:
30345 @strong{report all the facts}. If you are not sure whether to state a
30346 fact or leave it out, state it!
30348 Often people omit facts because they think they know what causes the
30349 problem and assume that some details do not matter. Thus, you might
30350 assume that the name of the variable you use in an example does not matter.
30351 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
30352 stray memory reference which happens to fetch from the location where that
30353 name is stored in memory; perhaps, if the name were different, the contents
30354 of that location would fool the debugger into doing the right thing despite
30355 the bug. Play it safe and give a specific, complete example. That is the
30356 easiest thing for you to do, and the most helpful.
30358 Keep in mind that the purpose of a bug report is to enable us to fix the
30359 bug. It may be that the bug has been reported previously, but neither
30360 you nor we can know that unless your bug report is complete and
30363 Sometimes people give a few sketchy facts and ask, ``Does this ring a
30364 bell?'' Those bug reports are useless, and we urge everyone to
30365 @emph{refuse to respond to them} except to chide the sender to report
30368 To enable us to fix the bug, you should include all these things:
30372 The version of @value{GDBN}. @value{GDBN} announces it if you start
30373 with no arguments; you can also print it at any time using @code{show
30376 Without this, we will not know whether there is any point in looking for
30377 the bug in the current version of @value{GDBN}.
30380 The type of machine you are using, and the operating system name and
30384 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
30385 ``@value{GCC}--2.8.1''.
30388 What compiler (and its version) was used to compile the program you are
30389 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
30390 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
30391 to get this information; for other compilers, see the documentation for
30395 The command arguments you gave the compiler to compile your example and
30396 observe the bug. For example, did you use @samp{-O}? To guarantee
30397 you will not omit something important, list them all. A copy of the
30398 Makefile (or the output from make) is sufficient.
30400 If we were to try to guess the arguments, we would probably guess wrong
30401 and then we might not encounter the bug.
30404 A complete input script, and all necessary source files, that will
30408 A description of what behavior you observe that you believe is
30409 incorrect. For example, ``It gets a fatal signal.''
30411 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
30412 will certainly notice it. But if the bug is incorrect output, we might
30413 not notice unless it is glaringly wrong. You might as well not give us
30414 a chance to make a mistake.
30416 Even if the problem you experience is a fatal signal, you should still
30417 say so explicitly. Suppose something strange is going on, such as, your
30418 copy of @value{GDBN} is out of synch, or you have encountered a bug in
30419 the C library on your system. (This has happened!) Your copy might
30420 crash and ours would not. If you told us to expect a crash, then when
30421 ours fails to crash, we would know that the bug was not happening for
30422 us. If you had not told us to expect a crash, then we would not be able
30423 to draw any conclusion from our observations.
30426 @cindex recording a session script
30427 To collect all this information, you can use a session recording program
30428 such as @command{script}, which is available on many Unix systems.
30429 Just run your @value{GDBN} session inside @command{script} and then
30430 include the @file{typescript} file with your bug report.
30432 Another way to record a @value{GDBN} session is to run @value{GDBN}
30433 inside Emacs and then save the entire buffer to a file.
30436 If you wish to suggest changes to the @value{GDBN} source, send us context
30437 diffs. If you even discuss something in the @value{GDBN} source, refer to
30438 it by context, not by line number.
30440 The line numbers in our development sources will not match those in your
30441 sources. Your line numbers would convey no useful information to us.
30445 Here are some things that are not necessary:
30449 A description of the envelope of the bug.
30451 Often people who encounter a bug spend a lot of time investigating
30452 which changes to the input file will make the bug go away and which
30453 changes will not affect it.
30455 This is often time consuming and not very useful, because the way we
30456 will find the bug is by running a single example under the debugger
30457 with breakpoints, not by pure deduction from a series of examples.
30458 We recommend that you save your time for something else.
30460 Of course, if you can find a simpler example to report @emph{instead}
30461 of the original one, that is a convenience for us. Errors in the
30462 output will be easier to spot, running under the debugger will take
30463 less time, and so on.
30465 However, simplification is not vital; if you do not want to do this,
30466 report the bug anyway and send us the entire test case you used.
30469 A patch for the bug.
30471 A patch for the bug does help us if it is a good one. But do not omit
30472 the necessary information, such as the test case, on the assumption that
30473 a patch is all we need. We might see problems with your patch and decide
30474 to fix the problem another way, or we might not understand it at all.
30476 Sometimes with a program as complicated as @value{GDBN} it is very hard to
30477 construct an example that will make the program follow a certain path
30478 through the code. If you do not send us the example, we will not be able
30479 to construct one, so we will not be able to verify that the bug is fixed.
30481 And if we cannot understand what bug you are trying to fix, or why your
30482 patch should be an improvement, we will not install it. A test case will
30483 help us to understand.
30486 A guess about what the bug is or what it depends on.
30488 Such guesses are usually wrong. Even we cannot guess right about such
30489 things without first using the debugger to find the facts.
30492 @c The readline documentation is distributed with the readline code
30493 @c and consists of the two following files:
30495 @c inc-hist.texinfo
30496 @c Use -I with makeinfo to point to the appropriate directory,
30497 @c environment var TEXINPUTS with TeX.
30498 @ifclear SYSTEM_READLINE
30499 @include rluser.texi
30500 @include inc-hist.texinfo
30504 @node Formatting Documentation
30505 @appendix Formatting Documentation
30507 @cindex @value{GDBN} reference card
30508 @cindex reference card
30509 The @value{GDBN} 4 release includes an already-formatted reference card, ready
30510 for printing with PostScript or Ghostscript, in the @file{gdb}
30511 subdirectory of the main source directory@footnote{In
30512 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
30513 release.}. If you can use PostScript or Ghostscript with your printer,
30514 you can print the reference card immediately with @file{refcard.ps}.
30516 The release also includes the source for the reference card. You
30517 can format it, using @TeX{}, by typing:
30523 The @value{GDBN} reference card is designed to print in @dfn{landscape}
30524 mode on US ``letter'' size paper;
30525 that is, on a sheet 11 inches wide by 8.5 inches
30526 high. You will need to specify this form of printing as an option to
30527 your @sc{dvi} output program.
30529 @cindex documentation
30531 All the documentation for @value{GDBN} comes as part of the machine-readable
30532 distribution. The documentation is written in Texinfo format, which is
30533 a documentation system that uses a single source file to produce both
30534 on-line information and a printed manual. You can use one of the Info
30535 formatting commands to create the on-line version of the documentation
30536 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
30538 @value{GDBN} includes an already formatted copy of the on-line Info
30539 version of this manual in the @file{gdb} subdirectory. The main Info
30540 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
30541 subordinate files matching @samp{gdb.info*} in the same directory. If
30542 necessary, you can print out these files, or read them with any editor;
30543 but they are easier to read using the @code{info} subsystem in @sc{gnu}
30544 Emacs or the standalone @code{info} program, available as part of the
30545 @sc{gnu} Texinfo distribution.
30547 If you want to format these Info files yourself, you need one of the
30548 Info formatting programs, such as @code{texinfo-format-buffer} or
30551 If you have @code{makeinfo} installed, and are in the top level
30552 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
30553 version @value{GDBVN}), you can make the Info file by typing:
30560 If you want to typeset and print copies of this manual, you need @TeX{},
30561 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
30562 Texinfo definitions file.
30564 @TeX{} is a typesetting program; it does not print files directly, but
30565 produces output files called @sc{dvi} files. To print a typeset
30566 document, you need a program to print @sc{dvi} files. If your system
30567 has @TeX{} installed, chances are it has such a program. The precise
30568 command to use depends on your system; @kbd{lpr -d} is common; another
30569 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
30570 require a file name without any extension or a @samp{.dvi} extension.
30572 @TeX{} also requires a macro definitions file called
30573 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
30574 written in Texinfo format. On its own, @TeX{} cannot either read or
30575 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
30576 and is located in the @file{gdb-@var{version-number}/texinfo}
30579 If you have @TeX{} and a @sc{dvi} printer program installed, you can
30580 typeset and print this manual. First switch to the @file{gdb}
30581 subdirectory of the main source directory (for example, to
30582 @file{gdb-@value{GDBVN}/gdb}) and type:
30588 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
30590 @node Installing GDB
30591 @appendix Installing @value{GDBN}
30592 @cindex installation
30595 * Requirements:: Requirements for building @value{GDBN}
30596 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
30597 * Separate Objdir:: Compiling @value{GDBN} in another directory
30598 * Config Names:: Specifying names for hosts and targets
30599 * Configure Options:: Summary of options for configure
30600 * System-wide configuration:: Having a system-wide init file
30604 @section Requirements for Building @value{GDBN}
30605 @cindex building @value{GDBN}, requirements for
30607 Building @value{GDBN} requires various tools and packages to be available.
30608 Other packages will be used only if they are found.
30610 @heading Tools/Packages Necessary for Building @value{GDBN}
30612 @item ISO C90 compiler
30613 @value{GDBN} is written in ISO C90. It should be buildable with any
30614 working C90 compiler, e.g.@: GCC.
30618 @heading Tools/Packages Optional for Building @value{GDBN}
30622 @value{GDBN} can use the Expat XML parsing library. This library may be
30623 included with your operating system distribution; if it is not, you
30624 can get the latest version from @url{http://expat.sourceforge.net}.
30625 The @file{configure} script will search for this library in several
30626 standard locations; if it is installed in an unusual path, you can
30627 use the @option{--with-libexpat-prefix} option to specify its location.
30633 Remote protocol memory maps (@pxref{Memory Map Format})
30635 Target descriptions (@pxref{Target Descriptions})
30637 Remote shared library lists (@pxref{Library List Format})
30639 MS-Windows shared libraries (@pxref{Shared Libraries})
30643 @cindex compressed debug sections
30644 @value{GDBN} will use the @samp{zlib} library, if available, to read
30645 compressed debug sections. Some linkers, such as GNU gold, are capable
30646 of producing binaries with compressed debug sections. If @value{GDBN}
30647 is compiled with @samp{zlib}, it will be able to read the debug
30648 information in such binaries.
30650 The @samp{zlib} library is likely included with your operating system
30651 distribution; if it is not, you can get the latest version from
30652 @url{http://zlib.net}.
30655 @value{GDBN}'s features related to character sets (@pxref{Character
30656 Sets}) require a functioning @code{iconv} implementation. If you are
30657 on a GNU system, then this is provided by the GNU C Library. Some
30658 other systems also provide a working @code{iconv}.
30660 On systems with @code{iconv}, you can install GNU Libiconv. If you
30661 have previously installed Libiconv, you can use the
30662 @option{--with-libiconv-prefix} option to configure.
30664 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
30665 arrange to build Libiconv if a directory named @file{libiconv} appears
30666 in the top-most source directory. If Libiconv is built this way, and
30667 if the operating system does not provide a suitable @code{iconv}
30668 implementation, then the just-built library will automatically be used
30669 by @value{GDBN}. One easy way to set this up is to download GNU
30670 Libiconv, unpack it, and then rename the directory holding the
30671 Libiconv source code to @samp{libiconv}.
30674 @node Running Configure
30675 @section Invoking the @value{GDBN} @file{configure} Script
30676 @cindex configuring @value{GDBN}
30677 @value{GDBN} comes with a @file{configure} script that automates the process
30678 of preparing @value{GDBN} for installation; you can then use @code{make} to
30679 build the @code{gdb} program.
30681 @c irrelevant in info file; it's as current as the code it lives with.
30682 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
30683 look at the @file{README} file in the sources; we may have improved the
30684 installation procedures since publishing this manual.}
30687 The @value{GDBN} distribution includes all the source code you need for
30688 @value{GDBN} in a single directory, whose name is usually composed by
30689 appending the version number to @samp{gdb}.
30691 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
30692 @file{gdb-@value{GDBVN}} directory. That directory contains:
30695 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
30696 script for configuring @value{GDBN} and all its supporting libraries
30698 @item gdb-@value{GDBVN}/gdb
30699 the source specific to @value{GDBN} itself
30701 @item gdb-@value{GDBVN}/bfd
30702 source for the Binary File Descriptor library
30704 @item gdb-@value{GDBVN}/include
30705 @sc{gnu} include files
30707 @item gdb-@value{GDBVN}/libiberty
30708 source for the @samp{-liberty} free software library
30710 @item gdb-@value{GDBVN}/opcodes
30711 source for the library of opcode tables and disassemblers
30713 @item gdb-@value{GDBVN}/readline
30714 source for the @sc{gnu} command-line interface
30716 @item gdb-@value{GDBVN}/glob
30717 source for the @sc{gnu} filename pattern-matching subroutine
30719 @item gdb-@value{GDBVN}/mmalloc
30720 source for the @sc{gnu} memory-mapped malloc package
30723 The simplest way to configure and build @value{GDBN} is to run @file{configure}
30724 from the @file{gdb-@var{version-number}} source directory, which in
30725 this example is the @file{gdb-@value{GDBVN}} directory.
30727 First switch to the @file{gdb-@var{version-number}} source directory
30728 if you are not already in it; then run @file{configure}. Pass the
30729 identifier for the platform on which @value{GDBN} will run as an
30735 cd gdb-@value{GDBVN}
30736 ./configure @var{host}
30741 where @var{host} is an identifier such as @samp{sun4} or
30742 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
30743 (You can often leave off @var{host}; @file{configure} tries to guess the
30744 correct value by examining your system.)
30746 Running @samp{configure @var{host}} and then running @code{make} builds the
30747 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
30748 libraries, then @code{gdb} itself. The configured source files, and the
30749 binaries, are left in the corresponding source directories.
30752 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
30753 system does not recognize this automatically when you run a different
30754 shell, you may need to run @code{sh} on it explicitly:
30757 sh configure @var{host}
30760 If you run @file{configure} from a directory that contains source
30761 directories for multiple libraries or programs, such as the
30762 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
30764 creates configuration files for every directory level underneath (unless
30765 you tell it not to, with the @samp{--norecursion} option).
30767 You should run the @file{configure} script from the top directory in the
30768 source tree, the @file{gdb-@var{version-number}} directory. If you run
30769 @file{configure} from one of the subdirectories, you will configure only
30770 that subdirectory. That is usually not what you want. In particular,
30771 if you run the first @file{configure} from the @file{gdb} subdirectory
30772 of the @file{gdb-@var{version-number}} directory, you will omit the
30773 configuration of @file{bfd}, @file{readline}, and other sibling
30774 directories of the @file{gdb} subdirectory. This leads to build errors
30775 about missing include files such as @file{bfd/bfd.h}.
30777 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
30778 However, you should make sure that the shell on your path (named by
30779 the @samp{SHELL} environment variable) is publicly readable. Remember
30780 that @value{GDBN} uses the shell to start your program---some systems refuse to
30781 let @value{GDBN} debug child processes whose programs are not readable.
30783 @node Separate Objdir
30784 @section Compiling @value{GDBN} in Another Directory
30786 If you want to run @value{GDBN} versions for several host or target machines,
30787 you need a different @code{gdb} compiled for each combination of
30788 host and target. @file{configure} is designed to make this easy by
30789 allowing you to generate each configuration in a separate subdirectory,
30790 rather than in the source directory. If your @code{make} program
30791 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
30792 @code{make} in each of these directories builds the @code{gdb}
30793 program specified there.
30795 To build @code{gdb} in a separate directory, run @file{configure}
30796 with the @samp{--srcdir} option to specify where to find the source.
30797 (You also need to specify a path to find @file{configure}
30798 itself from your working directory. If the path to @file{configure}
30799 would be the same as the argument to @samp{--srcdir}, you can leave out
30800 the @samp{--srcdir} option; it is assumed.)
30802 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
30803 separate directory for a Sun 4 like this:
30807 cd gdb-@value{GDBVN}
30810 ../gdb-@value{GDBVN}/configure sun4
30815 When @file{configure} builds a configuration using a remote source
30816 directory, it creates a tree for the binaries with the same structure
30817 (and using the same names) as the tree under the source directory. In
30818 the example, you'd find the Sun 4 library @file{libiberty.a} in the
30819 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
30820 @file{gdb-sun4/gdb}.
30822 Make sure that your path to the @file{configure} script has just one
30823 instance of @file{gdb} in it. If your path to @file{configure} looks
30824 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
30825 one subdirectory of @value{GDBN}, not the whole package. This leads to
30826 build errors about missing include files such as @file{bfd/bfd.h}.
30828 One popular reason to build several @value{GDBN} configurations in separate
30829 directories is to configure @value{GDBN} for cross-compiling (where
30830 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
30831 programs that run on another machine---the @dfn{target}).
30832 You specify a cross-debugging target by
30833 giving the @samp{--target=@var{target}} option to @file{configure}.
30835 When you run @code{make} to build a program or library, you must run
30836 it in a configured directory---whatever directory you were in when you
30837 called @file{configure} (or one of its subdirectories).
30839 The @code{Makefile} that @file{configure} generates in each source
30840 directory also runs recursively. If you type @code{make} in a source
30841 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
30842 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
30843 will build all the required libraries, and then build GDB.
30845 When you have multiple hosts or targets configured in separate
30846 directories, you can run @code{make} on them in parallel (for example,
30847 if they are NFS-mounted on each of the hosts); they will not interfere
30851 @section Specifying Names for Hosts and Targets
30853 The specifications used for hosts and targets in the @file{configure}
30854 script are based on a three-part naming scheme, but some short predefined
30855 aliases are also supported. The full naming scheme encodes three pieces
30856 of information in the following pattern:
30859 @var{architecture}-@var{vendor}-@var{os}
30862 For example, you can use the alias @code{sun4} as a @var{host} argument,
30863 or as the value for @var{target} in a @code{--target=@var{target}}
30864 option. The equivalent full name is @samp{sparc-sun-sunos4}.
30866 The @file{configure} script accompanying @value{GDBN} does not provide
30867 any query facility to list all supported host and target names or
30868 aliases. @file{configure} calls the Bourne shell script
30869 @code{config.sub} to map abbreviations to full names; you can read the
30870 script, if you wish, or you can use it to test your guesses on
30871 abbreviations---for example:
30874 % sh config.sub i386-linux
30876 % sh config.sub alpha-linux
30877 alpha-unknown-linux-gnu
30878 % sh config.sub hp9k700
30880 % sh config.sub sun4
30881 sparc-sun-sunos4.1.1
30882 % sh config.sub sun3
30883 m68k-sun-sunos4.1.1
30884 % sh config.sub i986v
30885 Invalid configuration `i986v': machine `i986v' not recognized
30889 @code{config.sub} is also distributed in the @value{GDBN} source
30890 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
30892 @node Configure Options
30893 @section @file{configure} Options
30895 Here is a summary of the @file{configure} options and arguments that
30896 are most often useful for building @value{GDBN}. @file{configure} also has
30897 several other options not listed here. @inforef{What Configure
30898 Does,,configure.info}, for a full explanation of @file{configure}.
30901 configure @r{[}--help@r{]}
30902 @r{[}--prefix=@var{dir}@r{]}
30903 @r{[}--exec-prefix=@var{dir}@r{]}
30904 @r{[}--srcdir=@var{dirname}@r{]}
30905 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
30906 @r{[}--target=@var{target}@r{]}
30911 You may introduce options with a single @samp{-} rather than
30912 @samp{--} if you prefer; but you may abbreviate option names if you use
30917 Display a quick summary of how to invoke @file{configure}.
30919 @item --prefix=@var{dir}
30920 Configure the source to install programs and files under directory
30923 @item --exec-prefix=@var{dir}
30924 Configure the source to install programs under directory
30927 @c avoid splitting the warning from the explanation:
30929 @item --srcdir=@var{dirname}
30930 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
30931 @code{make} that implements the @code{VPATH} feature.}@*
30932 Use this option to make configurations in directories separate from the
30933 @value{GDBN} source directories. Among other things, you can use this to
30934 build (or maintain) several configurations simultaneously, in separate
30935 directories. @file{configure} writes configuration-specific files in
30936 the current directory, but arranges for them to use the source in the
30937 directory @var{dirname}. @file{configure} creates directories under
30938 the working directory in parallel to the source directories below
30941 @item --norecursion
30942 Configure only the directory level where @file{configure} is executed; do not
30943 propagate configuration to subdirectories.
30945 @item --target=@var{target}
30946 Configure @value{GDBN} for cross-debugging programs running on the specified
30947 @var{target}. Without this option, @value{GDBN} is configured to debug
30948 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
30950 There is no convenient way to generate a list of all available targets.
30952 @item @var{host} @dots{}
30953 Configure @value{GDBN} to run on the specified @var{host}.
30955 There is no convenient way to generate a list of all available hosts.
30958 There are many other options available as well, but they are generally
30959 needed for special purposes only.
30961 @node System-wide configuration
30962 @section System-wide configuration and settings
30963 @cindex system-wide init file
30965 @value{GDBN} can be configured to have a system-wide init file;
30966 this file will be read and executed at startup (@pxref{Startup, , What
30967 @value{GDBN} does during startup}).
30969 Here is the corresponding configure option:
30972 @item --with-system-gdbinit=@var{file}
30973 Specify that the default location of the system-wide init file is
30977 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
30978 it may be subject to relocation. Two possible cases:
30982 If the default location of this init file contains @file{$prefix},
30983 it will be subject to relocation. Suppose that the configure options
30984 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
30985 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
30986 init file is looked for as @file{$install/etc/gdbinit} instead of
30987 @file{$prefix/etc/gdbinit}.
30990 By contrast, if the default location does not contain the prefix,
30991 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
30992 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
30993 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
30994 wherever @value{GDBN} is installed.
30997 @node Maintenance Commands
30998 @appendix Maintenance Commands
30999 @cindex maintenance commands
31000 @cindex internal commands
31002 In addition to commands intended for @value{GDBN} users, @value{GDBN}
31003 includes a number of commands intended for @value{GDBN} developers,
31004 that are not documented elsewhere in this manual. These commands are
31005 provided here for reference. (For commands that turn on debugging
31006 messages, see @ref{Debugging Output}.)
31009 @kindex maint agent
31010 @kindex maint agent-eval
31011 @item maint agent @var{expression}
31012 @itemx maint agent-eval @var{expression}
31013 Translate the given @var{expression} into remote agent bytecodes.
31014 This command is useful for debugging the Agent Expression mechanism
31015 (@pxref{Agent Expressions}). The @samp{agent} version produces an
31016 expression useful for data collection, such as by tracepoints, while
31017 @samp{maint agent-eval} produces an expression that evaluates directly
31018 to a result. For instance, a collection expression for @code{globa +
31019 globb} will include bytecodes to record four bytes of memory at each
31020 of the addresses of @code{globa} and @code{globb}, while discarding
31021 the result of the addition, while an evaluation expression will do the
31022 addition and return the sum.
31024 @kindex maint info breakpoints
31025 @item @anchor{maint info breakpoints}maint info breakpoints
31026 Using the same format as @samp{info breakpoints}, display both the
31027 breakpoints you've set explicitly, and those @value{GDBN} is using for
31028 internal purposes. Internal breakpoints are shown with negative
31029 breakpoint numbers. The type column identifies what kind of breakpoint
31034 Normal, explicitly set breakpoint.
31037 Normal, explicitly set watchpoint.
31040 Internal breakpoint, used to handle correctly stepping through
31041 @code{longjmp} calls.
31043 @item longjmp resume
31044 Internal breakpoint at the target of a @code{longjmp}.
31047 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
31050 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
31053 Shared library events.
31057 @kindex set displaced-stepping
31058 @kindex show displaced-stepping
31059 @cindex displaced stepping support
31060 @cindex out-of-line single-stepping
31061 @item set displaced-stepping
31062 @itemx show displaced-stepping
31063 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
31064 if the target supports it. Displaced stepping is a way to single-step
31065 over breakpoints without removing them from the inferior, by executing
31066 an out-of-line copy of the instruction that was originally at the
31067 breakpoint location. It is also known as out-of-line single-stepping.
31070 @item set displaced-stepping on
31071 If the target architecture supports it, @value{GDBN} will use
31072 displaced stepping to step over breakpoints.
31074 @item set displaced-stepping off
31075 @value{GDBN} will not use displaced stepping to step over breakpoints,
31076 even if such is supported by the target architecture.
31078 @cindex non-stop mode, and @samp{set displaced-stepping}
31079 @item set displaced-stepping auto
31080 This is the default mode. @value{GDBN} will use displaced stepping
31081 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
31082 architecture supports displaced stepping.
31085 @kindex maint check-symtabs
31086 @item maint check-symtabs
31087 Check the consistency of psymtabs and symtabs.
31089 @kindex maint cplus first_component
31090 @item maint cplus first_component @var{name}
31091 Print the first C@t{++} class/namespace component of @var{name}.
31093 @kindex maint cplus namespace
31094 @item maint cplus namespace
31095 Print the list of possible C@t{++} namespaces.
31097 @kindex maint demangle
31098 @item maint demangle @var{name}
31099 Demangle a C@t{++} or Objective-C mangled @var{name}.
31101 @kindex maint deprecate
31102 @kindex maint undeprecate
31103 @cindex deprecated commands
31104 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
31105 @itemx maint undeprecate @var{command}
31106 Deprecate or undeprecate the named @var{command}. Deprecated commands
31107 cause @value{GDBN} to issue a warning when you use them. The optional
31108 argument @var{replacement} says which newer command should be used in
31109 favor of the deprecated one; if it is given, @value{GDBN} will mention
31110 the replacement as part of the warning.
31112 @kindex maint dump-me
31113 @item maint dump-me
31114 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
31115 Cause a fatal signal in the debugger and force it to dump its core.
31116 This is supported only on systems which support aborting a program
31117 with the @code{SIGQUIT} signal.
31119 @kindex maint internal-error
31120 @kindex maint internal-warning
31121 @item maint internal-error @r{[}@var{message-text}@r{]}
31122 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
31123 Cause @value{GDBN} to call the internal function @code{internal_error}
31124 or @code{internal_warning} and hence behave as though an internal error
31125 or internal warning has been detected. In addition to reporting the
31126 internal problem, these functions give the user the opportunity to
31127 either quit @value{GDBN} or create a core file of the current
31128 @value{GDBN} session.
31130 These commands take an optional parameter @var{message-text} that is
31131 used as the text of the error or warning message.
31133 Here's an example of using @code{internal-error}:
31136 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
31137 @dots{}/maint.c:121: internal-error: testing, 1, 2
31138 A problem internal to GDB has been detected. Further
31139 debugging may prove unreliable.
31140 Quit this debugging session? (y or n) @kbd{n}
31141 Create a core file? (y or n) @kbd{n}
31145 @cindex @value{GDBN} internal error
31146 @cindex internal errors, control of @value{GDBN} behavior
31148 @kindex maint set internal-error
31149 @kindex maint show internal-error
31150 @kindex maint set internal-warning
31151 @kindex maint show internal-warning
31152 @item maint set internal-error @var{action} [ask|yes|no]
31153 @itemx maint show internal-error @var{action}
31154 @itemx maint set internal-warning @var{action} [ask|yes|no]
31155 @itemx maint show internal-warning @var{action}
31156 When @value{GDBN} reports an internal problem (error or warning) it
31157 gives the user the opportunity to both quit @value{GDBN} and create a
31158 core file of the current @value{GDBN} session. These commands let you
31159 override the default behaviour for each particular @var{action},
31160 described in the table below.
31164 You can specify that @value{GDBN} should always (yes) or never (no)
31165 quit. The default is to ask the user what to do.
31168 You can specify that @value{GDBN} should always (yes) or never (no)
31169 create a core file. The default is to ask the user what to do.
31172 @kindex maint packet
31173 @item maint packet @var{text}
31174 If @value{GDBN} is talking to an inferior via the serial protocol,
31175 then this command sends the string @var{text} to the inferior, and
31176 displays the response packet. @value{GDBN} supplies the initial
31177 @samp{$} character, the terminating @samp{#} character, and the
31180 @kindex maint print architecture
31181 @item maint print architecture @r{[}@var{file}@r{]}
31182 Print the entire architecture configuration. The optional argument
31183 @var{file} names the file where the output goes.
31185 @kindex maint print c-tdesc
31186 @item maint print c-tdesc
31187 Print the current target description (@pxref{Target Descriptions}) as
31188 a C source file. The created source file can be used in @value{GDBN}
31189 when an XML parser is not available to parse the description.
31191 @kindex maint print dummy-frames
31192 @item maint print dummy-frames
31193 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
31196 (@value{GDBP}) @kbd{b add}
31198 (@value{GDBP}) @kbd{print add(2,3)}
31199 Breakpoint 2, add (a=2, b=3) at @dots{}
31201 The program being debugged stopped while in a function called from GDB.
31203 (@value{GDBP}) @kbd{maint print dummy-frames}
31204 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
31205 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
31206 call_lo=0x01014000 call_hi=0x01014001
31210 Takes an optional file parameter.
31212 @kindex maint print registers
31213 @kindex maint print raw-registers
31214 @kindex maint print cooked-registers
31215 @kindex maint print register-groups
31216 @item maint print registers @r{[}@var{file}@r{]}
31217 @itemx maint print raw-registers @r{[}@var{file}@r{]}
31218 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
31219 @itemx maint print register-groups @r{[}@var{file}@r{]}
31220 Print @value{GDBN}'s internal register data structures.
31222 The command @code{maint print raw-registers} includes the contents of
31223 the raw register cache; the command @code{maint print cooked-registers}
31224 includes the (cooked) value of all registers, including registers which
31225 aren't available on the target nor visible to user; and the
31226 command @code{maint print register-groups} includes the groups that each
31227 register is a member of. @xref{Registers,, Registers, gdbint,
31228 @value{GDBN} Internals}.
31230 These commands take an optional parameter, a file name to which to
31231 write the information.
31233 @kindex maint print reggroups
31234 @item maint print reggroups @r{[}@var{file}@r{]}
31235 Print @value{GDBN}'s internal register group data structures. The
31236 optional argument @var{file} tells to what file to write the
31239 The register groups info looks like this:
31242 (@value{GDBP}) @kbd{maint print reggroups}
31255 This command forces @value{GDBN} to flush its internal register cache.
31257 @kindex maint print objfiles
31258 @cindex info for known object files
31259 @item maint print objfiles
31260 Print a dump of all known object files. For each object file, this
31261 command prints its name, address in memory, and all of its psymtabs
31264 @kindex maint print section-scripts
31265 @cindex info for known .debug_gdb_scripts-loaded scripts
31266 @item maint print section-scripts [@var{regexp}]
31267 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
31268 If @var{regexp} is specified, only print scripts loaded by object files
31269 matching @var{regexp}.
31270 For each script, this command prints its name as specified in the objfile,
31271 and the full path if known.
31272 @xref{.debug_gdb_scripts section}.
31274 @kindex maint print statistics
31275 @cindex bcache statistics
31276 @item maint print statistics
31277 This command prints, for each object file in the program, various data
31278 about that object file followed by the byte cache (@dfn{bcache})
31279 statistics for the object file. The objfile data includes the number
31280 of minimal, partial, full, and stabs symbols, the number of types
31281 defined by the objfile, the number of as yet unexpanded psym tables,
31282 the number of line tables and string tables, and the amount of memory
31283 used by the various tables. The bcache statistics include the counts,
31284 sizes, and counts of duplicates of all and unique objects, max,
31285 average, and median entry size, total memory used and its overhead and
31286 savings, and various measures of the hash table size and chain
31289 @kindex maint print target-stack
31290 @cindex target stack description
31291 @item maint print target-stack
31292 A @dfn{target} is an interface between the debugger and a particular
31293 kind of file or process. Targets can be stacked in @dfn{strata},
31294 so that more than one target can potentially respond to a request.
31295 In particular, memory accesses will walk down the stack of targets
31296 until they find a target that is interested in handling that particular
31299 This command prints a short description of each layer that was pushed on
31300 the @dfn{target stack}, starting from the top layer down to the bottom one.
31302 @kindex maint print type
31303 @cindex type chain of a data type
31304 @item maint print type @var{expr}
31305 Print the type chain for a type specified by @var{expr}. The argument
31306 can be either a type name or a symbol. If it is a symbol, the type of
31307 that symbol is described. The type chain produced by this command is
31308 a recursive definition of the data type as stored in @value{GDBN}'s
31309 data structures, including its flags and contained types.
31311 @kindex maint set dwarf2 always-disassemble
31312 @kindex maint show dwarf2 always-disassemble
31313 @item maint set dwarf2 always-disassemble
31314 @item maint show dwarf2 always-disassemble
31315 Control the behavior of @code{info address} when using DWARF debugging
31318 The default is @code{off}, which means that @value{GDBN} should try to
31319 describe a variable's location in an easily readable format. When
31320 @code{on}, @value{GDBN} will instead display the DWARF location
31321 expression in an assembly-like format. Note that some locations are
31322 too complex for @value{GDBN} to describe simply; in this case you will
31323 always see the disassembly form.
31325 Here is an example of the resulting disassembly:
31328 (gdb) info addr argc
31329 Symbol "argc" is a complex DWARF expression:
31333 For more information on these expressions, see
31334 @uref{http://www.dwarfstd.org/, the DWARF standard}.
31336 @kindex maint set dwarf2 max-cache-age
31337 @kindex maint show dwarf2 max-cache-age
31338 @item maint set dwarf2 max-cache-age
31339 @itemx maint show dwarf2 max-cache-age
31340 Control the DWARF 2 compilation unit cache.
31342 @cindex DWARF 2 compilation units cache
31343 In object files with inter-compilation-unit references, such as those
31344 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
31345 reader needs to frequently refer to previously read compilation units.
31346 This setting controls how long a compilation unit will remain in the
31347 cache if it is not referenced. A higher limit means that cached
31348 compilation units will be stored in memory longer, and more total
31349 memory will be used. Setting it to zero disables caching, which will
31350 slow down @value{GDBN} startup, but reduce memory consumption.
31352 @kindex maint set profile
31353 @kindex maint show profile
31354 @cindex profiling GDB
31355 @item maint set profile
31356 @itemx maint show profile
31357 Control profiling of @value{GDBN}.
31359 Profiling will be disabled until you use the @samp{maint set profile}
31360 command to enable it. When you enable profiling, the system will begin
31361 collecting timing and execution count data; when you disable profiling or
31362 exit @value{GDBN}, the results will be written to a log file. Remember that
31363 if you use profiling, @value{GDBN} will overwrite the profiling log file
31364 (often called @file{gmon.out}). If you have a record of important profiling
31365 data in a @file{gmon.out} file, be sure to move it to a safe location.
31367 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
31368 compiled with the @samp{-pg} compiler option.
31370 @kindex maint set show-debug-regs
31371 @kindex maint show show-debug-regs
31372 @cindex hardware debug registers
31373 @item maint set show-debug-regs
31374 @itemx maint show show-debug-regs
31375 Control whether to show variables that mirror the hardware debug
31376 registers. Use @code{ON} to enable, @code{OFF} to disable. If
31377 enabled, the debug registers values are shown when @value{GDBN} inserts or
31378 removes a hardware breakpoint or watchpoint, and when the inferior
31379 triggers a hardware-assisted breakpoint or watchpoint.
31381 @kindex maint set show-all-tib
31382 @kindex maint show show-all-tib
31383 @item maint set show-all-tib
31384 @itemx maint show show-all-tib
31385 Control whether to show all non zero areas within a 1k block starting
31386 at thread local base, when using the @samp{info w32 thread-information-block}
31389 @kindex maint space
31390 @cindex memory used by commands
31392 Control whether to display memory usage for each command. If set to a
31393 nonzero value, @value{GDBN} will display how much memory each command
31394 took, following the command's own output. This can also be requested
31395 by invoking @value{GDBN} with the @option{--statistics} command-line
31396 switch (@pxref{Mode Options}).
31399 @cindex time of command execution
31401 Control whether to display the execution time for each command. If
31402 set to a nonzero value, @value{GDBN} will display how much time it
31403 took to execute each command, following the command's own output.
31404 The time is not printed for the commands that run the target, since
31405 there's no mechanism currently to compute how much time was spend
31406 by @value{GDBN} and how much time was spend by the program been debugged.
31407 it's not possibly currently
31408 This can also be requested by invoking @value{GDBN} with the
31409 @option{--statistics} command-line switch (@pxref{Mode Options}).
31411 @kindex maint translate-address
31412 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
31413 Find the symbol stored at the location specified by the address
31414 @var{addr} and an optional section name @var{section}. If found,
31415 @value{GDBN} prints the name of the closest symbol and an offset from
31416 the symbol's location to the specified address. This is similar to
31417 the @code{info address} command (@pxref{Symbols}), except that this
31418 command also allows to find symbols in other sections.
31420 If section was not specified, the section in which the symbol was found
31421 is also printed. For dynamically linked executables, the name of
31422 executable or shared library containing the symbol is printed as well.
31426 The following command is useful for non-interactive invocations of
31427 @value{GDBN}, such as in the test suite.
31430 @item set watchdog @var{nsec}
31431 @kindex set watchdog
31432 @cindex watchdog timer
31433 @cindex timeout for commands
31434 Set the maximum number of seconds @value{GDBN} will wait for the
31435 target operation to finish. If this time expires, @value{GDBN}
31436 reports and error and the command is aborted.
31438 @item show watchdog
31439 Show the current setting of the target wait timeout.
31442 @node Remote Protocol
31443 @appendix @value{GDBN} Remote Serial Protocol
31448 * Stop Reply Packets::
31449 * General Query Packets::
31450 * Architecture-Specific Protocol Details::
31451 * Tracepoint Packets::
31452 * Host I/O Packets::
31454 * Notification Packets::
31455 * Remote Non-Stop::
31456 * Packet Acknowledgment::
31458 * File-I/O Remote Protocol Extension::
31459 * Library List Format::
31460 * Memory Map Format::
31461 * Thread List Format::
31467 There may be occasions when you need to know something about the
31468 protocol---for example, if there is only one serial port to your target
31469 machine, you might want your program to do something special if it
31470 recognizes a packet meant for @value{GDBN}.
31472 In the examples below, @samp{->} and @samp{<-} are used to indicate
31473 transmitted and received data, respectively.
31475 @cindex protocol, @value{GDBN} remote serial
31476 @cindex serial protocol, @value{GDBN} remote
31477 @cindex remote serial protocol
31478 All @value{GDBN} commands and responses (other than acknowledgments
31479 and notifications, see @ref{Notification Packets}) are sent as a
31480 @var{packet}. A @var{packet} is introduced with the character
31481 @samp{$}, the actual @var{packet-data}, and the terminating character
31482 @samp{#} followed by a two-digit @var{checksum}:
31485 @code{$}@var{packet-data}@code{#}@var{checksum}
31489 @cindex checksum, for @value{GDBN} remote
31491 The two-digit @var{checksum} is computed as the modulo 256 sum of all
31492 characters between the leading @samp{$} and the trailing @samp{#} (an
31493 eight bit unsigned checksum).
31495 Implementors should note that prior to @value{GDBN} 5.0 the protocol
31496 specification also included an optional two-digit @var{sequence-id}:
31499 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
31502 @cindex sequence-id, for @value{GDBN} remote
31504 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
31505 has never output @var{sequence-id}s. Stubs that handle packets added
31506 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
31508 When either the host or the target machine receives a packet, the first
31509 response expected is an acknowledgment: either @samp{+} (to indicate
31510 the package was received correctly) or @samp{-} (to request
31514 -> @code{$}@var{packet-data}@code{#}@var{checksum}
31519 The @samp{+}/@samp{-} acknowledgments can be disabled
31520 once a connection is established.
31521 @xref{Packet Acknowledgment}, for details.
31523 The host (@value{GDBN}) sends @var{command}s, and the target (the
31524 debugging stub incorporated in your program) sends a @var{response}. In
31525 the case of step and continue @var{command}s, the response is only sent
31526 when the operation has completed, and the target has again stopped all
31527 threads in all attached processes. This is the default all-stop mode
31528 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
31529 execution mode; see @ref{Remote Non-Stop}, for details.
31531 @var{packet-data} consists of a sequence of characters with the
31532 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
31535 @cindex remote protocol, field separator
31536 Fields within the packet should be separated using @samp{,} @samp{;} or
31537 @samp{:}. Except where otherwise noted all numbers are represented in
31538 @sc{hex} with leading zeros suppressed.
31540 Implementors should note that prior to @value{GDBN} 5.0, the character
31541 @samp{:} could not appear as the third character in a packet (as it
31542 would potentially conflict with the @var{sequence-id}).
31544 @cindex remote protocol, binary data
31545 @anchor{Binary Data}
31546 Binary data in most packets is encoded either as two hexadecimal
31547 digits per byte of binary data. This allowed the traditional remote
31548 protocol to work over connections which were only seven-bit clean.
31549 Some packets designed more recently assume an eight-bit clean
31550 connection, and use a more efficient encoding to send and receive
31553 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
31554 as an escape character. Any escaped byte is transmitted as the escape
31555 character followed by the original character XORed with @code{0x20}.
31556 For example, the byte @code{0x7d} would be transmitted as the two
31557 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
31558 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
31559 @samp{@}}) must always be escaped. Responses sent by the stub
31560 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
31561 is not interpreted as the start of a run-length encoded sequence
31564 Response @var{data} can be run-length encoded to save space.
31565 Run-length encoding replaces runs of identical characters with one
31566 instance of the repeated character, followed by a @samp{*} and a
31567 repeat count. The repeat count is itself sent encoded, to avoid
31568 binary characters in @var{data}: a value of @var{n} is sent as
31569 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
31570 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
31571 code 32) for a repeat count of 3. (This is because run-length
31572 encoding starts to win for counts 3 or more.) Thus, for example,
31573 @samp{0* } is a run-length encoding of ``0000'': the space character
31574 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
31577 The printable characters @samp{#} and @samp{$} or with a numeric value
31578 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
31579 seven repeats (@samp{$}) can be expanded using a repeat count of only
31580 five (@samp{"}). For example, @samp{00000000} can be encoded as
31583 The error response returned for some packets includes a two character
31584 error number. That number is not well defined.
31586 @cindex empty response, for unsupported packets
31587 For any @var{command} not supported by the stub, an empty response
31588 (@samp{$#00}) should be returned. That way it is possible to extend the
31589 protocol. A newer @value{GDBN} can tell if a packet is supported based
31592 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
31593 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
31599 The following table provides a complete list of all currently defined
31600 @var{command}s and their corresponding response @var{data}.
31601 @xref{File-I/O Remote Protocol Extension}, for details about the File
31602 I/O extension of the remote protocol.
31604 Each packet's description has a template showing the packet's overall
31605 syntax, followed by an explanation of the packet's meaning. We
31606 include spaces in some of the templates for clarity; these are not
31607 part of the packet's syntax. No @value{GDBN} packet uses spaces to
31608 separate its components. For example, a template like @samp{foo
31609 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
31610 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
31611 @var{baz}. @value{GDBN} does not transmit a space character between the
31612 @samp{foo} and the @var{bar}, or between the @var{bar} and the
31615 @cindex @var{thread-id}, in remote protocol
31616 @anchor{thread-id syntax}
31617 Several packets and replies include a @var{thread-id} field to identify
31618 a thread. Normally these are positive numbers with a target-specific
31619 interpretation, formatted as big-endian hex strings. A @var{thread-id}
31620 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
31623 In addition, the remote protocol supports a multiprocess feature in
31624 which the @var{thread-id} syntax is extended to optionally include both
31625 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
31626 The @var{pid} (process) and @var{tid} (thread) components each have the
31627 format described above: a positive number with target-specific
31628 interpretation formatted as a big-endian hex string, literal @samp{-1}
31629 to indicate all processes or threads (respectively), or @samp{0} to
31630 indicate an arbitrary process or thread. Specifying just a process, as
31631 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
31632 error to specify all processes but a specific thread, such as
31633 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
31634 for those packets and replies explicitly documented to include a process
31635 ID, rather than a @var{thread-id}.
31637 The multiprocess @var{thread-id} syntax extensions are only used if both
31638 @value{GDBN} and the stub report support for the @samp{multiprocess}
31639 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
31642 Note that all packet forms beginning with an upper- or lower-case
31643 letter, other than those described here, are reserved for future use.
31645 Here are the packet descriptions.
31650 @cindex @samp{!} packet
31651 @anchor{extended mode}
31652 Enable extended mode. In extended mode, the remote server is made
31653 persistent. The @samp{R} packet is used to restart the program being
31659 The remote target both supports and has enabled extended mode.
31663 @cindex @samp{?} packet
31664 Indicate the reason the target halted. The reply is the same as for
31665 step and continue. This packet has a special interpretation when the
31666 target is in non-stop mode; see @ref{Remote Non-Stop}.
31669 @xref{Stop Reply Packets}, for the reply specifications.
31671 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
31672 @cindex @samp{A} packet
31673 Initialized @code{argv[]} array passed into program. @var{arglen}
31674 specifies the number of bytes in the hex encoded byte stream
31675 @var{arg}. See @code{gdbserver} for more details.
31680 The arguments were set.
31686 @cindex @samp{b} packet
31687 (Don't use this packet; its behavior is not well-defined.)
31688 Change the serial line speed to @var{baud}.
31690 JTC: @emph{When does the transport layer state change? When it's
31691 received, or after the ACK is transmitted. In either case, there are
31692 problems if the command or the acknowledgment packet is dropped.}
31694 Stan: @emph{If people really wanted to add something like this, and get
31695 it working for the first time, they ought to modify ser-unix.c to send
31696 some kind of out-of-band message to a specially-setup stub and have the
31697 switch happen "in between" packets, so that from remote protocol's point
31698 of view, nothing actually happened.}
31700 @item B @var{addr},@var{mode}
31701 @cindex @samp{B} packet
31702 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
31703 breakpoint at @var{addr}.
31705 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
31706 (@pxref{insert breakpoint or watchpoint packet}).
31708 @cindex @samp{bc} packet
31711 Backward continue. Execute the target system in reverse. No parameter.
31712 @xref{Reverse Execution}, for more information.
31715 @xref{Stop Reply Packets}, for the reply specifications.
31717 @cindex @samp{bs} packet
31720 Backward single step. Execute one instruction in reverse. No parameter.
31721 @xref{Reverse Execution}, for more information.
31724 @xref{Stop Reply Packets}, for the reply specifications.
31726 @item c @r{[}@var{addr}@r{]}
31727 @cindex @samp{c} packet
31728 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
31729 resume at current address.
31732 @xref{Stop Reply Packets}, for the reply specifications.
31734 @item C @var{sig}@r{[};@var{addr}@r{]}
31735 @cindex @samp{C} packet
31736 Continue with signal @var{sig} (hex signal number). If
31737 @samp{;@var{addr}} is omitted, resume at same address.
31740 @xref{Stop Reply Packets}, for the reply specifications.
31743 @cindex @samp{d} packet
31746 Don't use this packet; instead, define a general set packet
31747 (@pxref{General Query Packets}).
31751 @cindex @samp{D} packet
31752 The first form of the packet is used to detach @value{GDBN} from the
31753 remote system. It is sent to the remote target
31754 before @value{GDBN} disconnects via the @code{detach} command.
31756 The second form, including a process ID, is used when multiprocess
31757 protocol extensions are enabled (@pxref{multiprocess extensions}), to
31758 detach only a specific process. The @var{pid} is specified as a
31759 big-endian hex string.
31769 @item F @var{RC},@var{EE},@var{CF};@var{XX}
31770 @cindex @samp{F} packet
31771 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
31772 This is part of the File-I/O protocol extension. @xref{File-I/O
31773 Remote Protocol Extension}, for the specification.
31776 @anchor{read registers packet}
31777 @cindex @samp{g} packet
31778 Read general registers.
31782 @item @var{XX@dots{}}
31783 Each byte of register data is described by two hex digits. The bytes
31784 with the register are transmitted in target byte order. The size of
31785 each register and their position within the @samp{g} packet are
31786 determined by the @value{GDBN} internal gdbarch functions
31787 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
31788 specification of several standard @samp{g} packets is specified below.
31793 @item G @var{XX@dots{}}
31794 @cindex @samp{G} packet
31795 Write general registers. @xref{read registers packet}, for a
31796 description of the @var{XX@dots{}} data.
31806 @item H @var{c} @var{thread-id}
31807 @cindex @samp{H} packet
31808 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
31809 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
31810 should be @samp{c} for step and continue operations, @samp{g} for other
31811 operations. The thread designator @var{thread-id} has the format and
31812 interpretation described in @ref{thread-id syntax}.
31823 @c 'H': How restrictive (or permissive) is the thread model. If a
31824 @c thread is selected and stopped, are other threads allowed
31825 @c to continue to execute? As I mentioned above, I think the
31826 @c semantics of each command when a thread is selected must be
31827 @c described. For example:
31829 @c 'g': If the stub supports threads and a specific thread is
31830 @c selected, returns the register block from that thread;
31831 @c otherwise returns current registers.
31833 @c 'G' If the stub supports threads and a specific thread is
31834 @c selected, sets the registers of the register block of
31835 @c that thread; otherwise sets current registers.
31837 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
31838 @anchor{cycle step packet}
31839 @cindex @samp{i} packet
31840 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
31841 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
31842 step starting at that address.
31845 @cindex @samp{I} packet
31846 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
31850 @cindex @samp{k} packet
31853 FIXME: @emph{There is no description of how to operate when a specific
31854 thread context has been selected (i.e.@: does 'k' kill only that
31857 @item m @var{addr},@var{length}
31858 @cindex @samp{m} packet
31859 Read @var{length} bytes of memory starting at address @var{addr}.
31860 Note that @var{addr} may not be aligned to any particular boundary.
31862 The stub need not use any particular size or alignment when gathering
31863 data from memory for the response; even if @var{addr} is word-aligned
31864 and @var{length} is a multiple of the word size, the stub is free to
31865 use byte accesses, or not. For this reason, this packet may not be
31866 suitable for accessing memory-mapped I/O devices.
31867 @cindex alignment of remote memory accesses
31868 @cindex size of remote memory accesses
31869 @cindex memory, alignment and size of remote accesses
31873 @item @var{XX@dots{}}
31874 Memory contents; each byte is transmitted as a two-digit hexadecimal
31875 number. The reply may contain fewer bytes than requested if the
31876 server was able to read only part of the region of memory.
31881 @item M @var{addr},@var{length}:@var{XX@dots{}}
31882 @cindex @samp{M} packet
31883 Write @var{length} bytes of memory starting at address @var{addr}.
31884 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
31885 hexadecimal number.
31892 for an error (this includes the case where only part of the data was
31897 @cindex @samp{p} packet
31898 Read the value of register @var{n}; @var{n} is in hex.
31899 @xref{read registers packet}, for a description of how the returned
31900 register value is encoded.
31904 @item @var{XX@dots{}}
31905 the register's value
31909 Indicating an unrecognized @var{query}.
31912 @item P @var{n@dots{}}=@var{r@dots{}}
31913 @anchor{write register packet}
31914 @cindex @samp{P} packet
31915 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
31916 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
31917 digits for each byte in the register (target byte order).
31927 @item q @var{name} @var{params}@dots{}
31928 @itemx Q @var{name} @var{params}@dots{}
31929 @cindex @samp{q} packet
31930 @cindex @samp{Q} packet
31931 General query (@samp{q}) and set (@samp{Q}). These packets are
31932 described fully in @ref{General Query Packets}.
31935 @cindex @samp{r} packet
31936 Reset the entire system.
31938 Don't use this packet; use the @samp{R} packet instead.
31941 @cindex @samp{R} packet
31942 Restart the program being debugged. @var{XX}, while needed, is ignored.
31943 This packet is only available in extended mode (@pxref{extended mode}).
31945 The @samp{R} packet has no reply.
31947 @item s @r{[}@var{addr}@r{]}
31948 @cindex @samp{s} packet
31949 Single step. @var{addr} is the address at which to resume. If
31950 @var{addr} is omitted, resume at same address.
31953 @xref{Stop Reply Packets}, for the reply specifications.
31955 @item S @var{sig}@r{[};@var{addr}@r{]}
31956 @anchor{step with signal packet}
31957 @cindex @samp{S} packet
31958 Step with signal. This is analogous to the @samp{C} packet, but
31959 requests a single-step, rather than a normal resumption of execution.
31962 @xref{Stop Reply Packets}, for the reply specifications.
31964 @item t @var{addr}:@var{PP},@var{MM}
31965 @cindex @samp{t} packet
31966 Search backwards starting at address @var{addr} for a match with pattern
31967 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
31968 @var{addr} must be at least 3 digits.
31970 @item T @var{thread-id}
31971 @cindex @samp{T} packet
31972 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
31977 thread is still alive
31983 Packets starting with @samp{v} are identified by a multi-letter name,
31984 up to the first @samp{;} or @samp{?} (or the end of the packet).
31986 @item vAttach;@var{pid}
31987 @cindex @samp{vAttach} packet
31988 Attach to a new process with the specified process ID @var{pid}.
31989 The process ID is a
31990 hexadecimal integer identifying the process. In all-stop mode, all
31991 threads in the attached process are stopped; in non-stop mode, it may be
31992 attached without being stopped if that is supported by the target.
31994 @c In non-stop mode, on a successful vAttach, the stub should set the
31995 @c current thread to a thread of the newly-attached process. After
31996 @c attaching, GDB queries for the attached process's thread ID with qC.
31997 @c Also note that, from a user perspective, whether or not the
31998 @c target is stopped on attach in non-stop mode depends on whether you
31999 @c use the foreground or background version of the attach command, not
32000 @c on what vAttach does; GDB does the right thing with respect to either
32001 @c stopping or restarting threads.
32003 This packet is only available in extended mode (@pxref{extended mode}).
32009 @item @r{Any stop packet}
32010 for success in all-stop mode (@pxref{Stop Reply Packets})
32012 for success in non-stop mode (@pxref{Remote Non-Stop})
32015 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
32016 @cindex @samp{vCont} packet
32017 Resume the inferior, specifying different actions for each thread.
32018 If an action is specified with no @var{thread-id}, then it is applied to any
32019 threads that don't have a specific action specified; if no default action is
32020 specified then other threads should remain stopped in all-stop mode and
32021 in their current state in non-stop mode.
32022 Specifying multiple
32023 default actions is an error; specifying no actions is also an error.
32024 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
32026 Currently supported actions are:
32032 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
32036 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
32041 The optional argument @var{addr} normally associated with the
32042 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
32043 not supported in @samp{vCont}.
32045 The @samp{t} action is only relevant in non-stop mode
32046 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
32047 A stop reply should be generated for any affected thread not already stopped.
32048 When a thread is stopped by means of a @samp{t} action,
32049 the corresponding stop reply should indicate that the thread has stopped with
32050 signal @samp{0}, regardless of whether the target uses some other signal
32051 as an implementation detail.
32054 @xref{Stop Reply Packets}, for the reply specifications.
32057 @cindex @samp{vCont?} packet
32058 Request a list of actions supported by the @samp{vCont} packet.
32062 @item vCont@r{[};@var{action}@dots{}@r{]}
32063 The @samp{vCont} packet is supported. Each @var{action} is a supported
32064 command in the @samp{vCont} packet.
32066 The @samp{vCont} packet is not supported.
32069 @item vFile:@var{operation}:@var{parameter}@dots{}
32070 @cindex @samp{vFile} packet
32071 Perform a file operation on the target system. For details,
32072 see @ref{Host I/O Packets}.
32074 @item vFlashErase:@var{addr},@var{length}
32075 @cindex @samp{vFlashErase} packet
32076 Direct the stub to erase @var{length} bytes of flash starting at
32077 @var{addr}. The region may enclose any number of flash blocks, but
32078 its start and end must fall on block boundaries, as indicated by the
32079 flash block size appearing in the memory map (@pxref{Memory Map
32080 Format}). @value{GDBN} groups flash memory programming operations
32081 together, and sends a @samp{vFlashDone} request after each group; the
32082 stub is allowed to delay erase operation until the @samp{vFlashDone}
32083 packet is received.
32085 The stub must support @samp{vCont} if it reports support for
32086 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
32087 this case @samp{vCont} actions can be specified to apply to all threads
32088 in a process by using the @samp{p@var{pid}.-1} form of the
32099 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
32100 @cindex @samp{vFlashWrite} packet
32101 Direct the stub to write data to flash address @var{addr}. The data
32102 is passed in binary form using the same encoding as for the @samp{X}
32103 packet (@pxref{Binary Data}). The memory ranges specified by
32104 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
32105 not overlap, and must appear in order of increasing addresses
32106 (although @samp{vFlashErase} packets for higher addresses may already
32107 have been received; the ordering is guaranteed only between
32108 @samp{vFlashWrite} packets). If a packet writes to an address that was
32109 neither erased by a preceding @samp{vFlashErase} packet nor by some other
32110 target-specific method, the results are unpredictable.
32118 for vFlashWrite addressing non-flash memory
32124 @cindex @samp{vFlashDone} packet
32125 Indicate to the stub that flash programming operation is finished.
32126 The stub is permitted to delay or batch the effects of a group of
32127 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
32128 @samp{vFlashDone} packet is received. The contents of the affected
32129 regions of flash memory are unpredictable until the @samp{vFlashDone}
32130 request is completed.
32132 @item vKill;@var{pid}
32133 @cindex @samp{vKill} packet
32134 Kill the process with the specified process ID. @var{pid} is a
32135 hexadecimal integer identifying the process. This packet is used in
32136 preference to @samp{k} when multiprocess protocol extensions are
32137 supported; see @ref{multiprocess extensions}.
32147 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
32148 @cindex @samp{vRun} packet
32149 Run the program @var{filename}, passing it each @var{argument} on its
32150 command line. The file and arguments are hex-encoded strings. If
32151 @var{filename} is an empty string, the stub may use a default program
32152 (e.g.@: the last program run). The program is created in the stopped
32155 @c FIXME: What about non-stop mode?
32157 This packet is only available in extended mode (@pxref{extended mode}).
32163 @item @r{Any stop packet}
32164 for success (@pxref{Stop Reply Packets})
32168 @anchor{vStopped packet}
32169 @cindex @samp{vStopped} packet
32171 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
32172 reply and prompt for the stub to report another one.
32176 @item @r{Any stop packet}
32177 if there is another unreported stop event (@pxref{Stop Reply Packets})
32179 if there are no unreported stop events
32182 @item X @var{addr},@var{length}:@var{XX@dots{}}
32184 @cindex @samp{X} packet
32185 Write data to memory, where the data is transmitted in binary.
32186 @var{addr} is address, @var{length} is number of bytes,
32187 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
32197 @item z @var{type},@var{addr},@var{kind}
32198 @itemx Z @var{type},@var{addr},@var{kind}
32199 @anchor{insert breakpoint or watchpoint packet}
32200 @cindex @samp{z} packet
32201 @cindex @samp{Z} packets
32202 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
32203 watchpoint starting at address @var{address} of kind @var{kind}.
32205 Each breakpoint and watchpoint packet @var{type} is documented
32208 @emph{Implementation notes: A remote target shall return an empty string
32209 for an unrecognized breakpoint or watchpoint packet @var{type}. A
32210 remote target shall support either both or neither of a given
32211 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
32212 avoid potential problems with duplicate packets, the operations should
32213 be implemented in an idempotent way.}
32215 @item z0,@var{addr},@var{kind}
32216 @itemx Z0,@var{addr},@var{kind}
32217 @cindex @samp{z0} packet
32218 @cindex @samp{Z0} packet
32219 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
32220 @var{addr} of type @var{kind}.
32222 A memory breakpoint is implemented by replacing the instruction at
32223 @var{addr} with a software breakpoint or trap instruction. The
32224 @var{kind} is target-specific and typically indicates the size of
32225 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
32226 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
32227 architectures have additional meanings for @var{kind};
32228 see @ref{Architecture-Specific Protocol Details}.
32230 @emph{Implementation note: It is possible for a target to copy or move
32231 code that contains memory breakpoints (e.g., when implementing
32232 overlays). The behavior of this packet, in the presence of such a
32233 target, is not defined.}
32245 @item z1,@var{addr},@var{kind}
32246 @itemx Z1,@var{addr},@var{kind}
32247 @cindex @samp{z1} packet
32248 @cindex @samp{Z1} packet
32249 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
32250 address @var{addr}.
32252 A hardware breakpoint is implemented using a mechanism that is not
32253 dependant on being able to modify the target's memory. @var{kind}
32254 has the same meaning as in @samp{Z0} packets.
32256 @emph{Implementation note: A hardware breakpoint is not affected by code
32269 @item z2,@var{addr},@var{kind}
32270 @itemx Z2,@var{addr},@var{kind}
32271 @cindex @samp{z2} packet
32272 @cindex @samp{Z2} packet
32273 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
32274 @var{kind} is interpreted as the number of bytes to watch.
32286 @item z3,@var{addr},@var{kind}
32287 @itemx Z3,@var{addr},@var{kind}
32288 @cindex @samp{z3} packet
32289 @cindex @samp{Z3} packet
32290 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
32291 @var{kind} is interpreted as the number of bytes to watch.
32303 @item z4,@var{addr},@var{kind}
32304 @itemx Z4,@var{addr},@var{kind}
32305 @cindex @samp{z4} packet
32306 @cindex @samp{Z4} packet
32307 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
32308 @var{kind} is interpreted as the number of bytes to watch.
32322 @node Stop Reply Packets
32323 @section Stop Reply Packets
32324 @cindex stop reply packets
32326 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
32327 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
32328 receive any of the below as a reply. Except for @samp{?}
32329 and @samp{vStopped}, that reply is only returned
32330 when the target halts. In the below the exact meaning of @dfn{signal
32331 number} is defined by the header @file{include/gdb/signals.h} in the
32332 @value{GDBN} source code.
32334 As in the description of request packets, we include spaces in the
32335 reply templates for clarity; these are not part of the reply packet's
32336 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
32342 The program received signal number @var{AA} (a two-digit hexadecimal
32343 number). This is equivalent to a @samp{T} response with no
32344 @var{n}:@var{r} pairs.
32346 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
32347 @cindex @samp{T} packet reply
32348 The program received signal number @var{AA} (a two-digit hexadecimal
32349 number). This is equivalent to an @samp{S} response, except that the
32350 @samp{@var{n}:@var{r}} pairs can carry values of important registers
32351 and other information directly in the stop reply packet, reducing
32352 round-trip latency. Single-step and breakpoint traps are reported
32353 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
32357 If @var{n} is a hexadecimal number, it is a register number, and the
32358 corresponding @var{r} gives that register's value. @var{r} is a
32359 series of bytes in target byte order, with each byte given by a
32360 two-digit hex number.
32363 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
32364 the stopped thread, as specified in @ref{thread-id syntax}.
32367 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
32368 the core on which the stop event was detected.
32371 If @var{n} is a recognized @dfn{stop reason}, it describes a more
32372 specific event that stopped the target. The currently defined stop
32373 reasons are listed below. @var{aa} should be @samp{05}, the trap
32374 signal. At most one stop reason should be present.
32377 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
32378 and go on to the next; this allows us to extend the protocol in the
32382 The currently defined stop reasons are:
32388 The packet indicates a watchpoint hit, and @var{r} is the data address, in
32391 @cindex shared library events, remote reply
32393 The packet indicates that the loaded libraries have changed.
32394 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
32395 list of loaded libraries. @var{r} is ignored.
32397 @cindex replay log events, remote reply
32399 The packet indicates that the target cannot continue replaying
32400 logged execution events, because it has reached the end (or the
32401 beginning when executing backward) of the log. The value of @var{r}
32402 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
32403 for more information.
32407 @itemx W @var{AA} ; process:@var{pid}
32408 The process exited, and @var{AA} is the exit status. This is only
32409 applicable to certain targets.
32411 The second form of the response, including the process ID of the exited
32412 process, can be used only when @value{GDBN} has reported support for
32413 multiprocess protocol extensions; see @ref{multiprocess extensions}.
32414 The @var{pid} is formatted as a big-endian hex string.
32417 @itemx X @var{AA} ; process:@var{pid}
32418 The process terminated with signal @var{AA}.
32420 The second form of the response, including the process ID of the
32421 terminated process, can be used only when @value{GDBN} has reported
32422 support for multiprocess protocol extensions; see @ref{multiprocess
32423 extensions}. The @var{pid} is formatted as a big-endian hex string.
32425 @item O @var{XX}@dots{}
32426 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
32427 written as the program's console output. This can happen at any time
32428 while the program is running and the debugger should continue to wait
32429 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
32431 @item F @var{call-id},@var{parameter}@dots{}
32432 @var{call-id} is the identifier which says which host system call should
32433 be called. This is just the name of the function. Translation into the
32434 correct system call is only applicable as it's defined in @value{GDBN}.
32435 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
32438 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
32439 this very system call.
32441 The target replies with this packet when it expects @value{GDBN} to
32442 call a host system call on behalf of the target. @value{GDBN} replies
32443 with an appropriate @samp{F} packet and keeps up waiting for the next
32444 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
32445 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
32446 Protocol Extension}, for more details.
32450 @node General Query Packets
32451 @section General Query Packets
32452 @cindex remote query requests
32454 Packets starting with @samp{q} are @dfn{general query packets};
32455 packets starting with @samp{Q} are @dfn{general set packets}. General
32456 query and set packets are a semi-unified form for retrieving and
32457 sending information to and from the stub.
32459 The initial letter of a query or set packet is followed by a name
32460 indicating what sort of thing the packet applies to. For example,
32461 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
32462 definitions with the stub. These packet names follow some
32467 The name must not contain commas, colons or semicolons.
32469 Most @value{GDBN} query and set packets have a leading upper case
32472 The names of custom vendor packets should use a company prefix, in
32473 lower case, followed by a period. For example, packets designed at
32474 the Acme Corporation might begin with @samp{qacme.foo} (for querying
32475 foos) or @samp{Qacme.bar} (for setting bars).
32478 The name of a query or set packet should be separated from any
32479 parameters by a @samp{:}; the parameters themselves should be
32480 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
32481 full packet name, and check for a separator or the end of the packet,
32482 in case two packet names share a common prefix. New packets should not begin
32483 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
32484 packets predate these conventions, and have arguments without any terminator
32485 for the packet name; we suspect they are in widespread use in places that
32486 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
32487 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
32490 Like the descriptions of the other packets, each description here
32491 has a template showing the packet's overall syntax, followed by an
32492 explanation of the packet's meaning. We include spaces in some of the
32493 templates for clarity; these are not part of the packet's syntax. No
32494 @value{GDBN} packet uses spaces to separate its components.
32496 Here are the currently defined query and set packets:
32500 @item QAllow:@var{op}:@var{val}@dots{}
32501 @cindex @samp{QAllow} packet
32502 Specify which operations @value{GDBN} expects to request of the
32503 target, as a semicolon-separated list of operation name and value
32504 pairs. Possible values for @var{op} include @samp{WriteReg},
32505 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
32506 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
32507 indicating that @value{GDBN} will not request the operation, or 1,
32508 indicating that it may. (The target can then use this to set up its
32509 own internals optimally, for instance if the debugger never expects to
32510 insert breakpoints, it may not need to install its own trap handler.)
32513 @cindex current thread, remote request
32514 @cindex @samp{qC} packet
32515 Return the current thread ID.
32519 @item QC @var{thread-id}
32520 Where @var{thread-id} is a thread ID as documented in
32521 @ref{thread-id syntax}.
32522 @item @r{(anything else)}
32523 Any other reply implies the old thread ID.
32526 @item qCRC:@var{addr},@var{length}
32527 @cindex CRC of memory block, remote request
32528 @cindex @samp{qCRC} packet
32529 Compute the CRC checksum of a block of memory using CRC-32 defined in
32530 IEEE 802.3. The CRC is computed byte at a time, taking the most
32531 significant bit of each byte first. The initial pattern code
32532 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
32534 @emph{Note:} This is the same CRC used in validating separate debug
32535 files (@pxref{Separate Debug Files, , Debugging Information in Separate
32536 Files}). However the algorithm is slightly different. When validating
32537 separate debug files, the CRC is computed taking the @emph{least}
32538 significant bit of each byte first, and the final result is inverted to
32539 detect trailing zeros.
32544 An error (such as memory fault)
32545 @item C @var{crc32}
32546 The specified memory region's checksum is @var{crc32}.
32550 @itemx qsThreadInfo
32551 @cindex list active threads, remote request
32552 @cindex @samp{qfThreadInfo} packet
32553 @cindex @samp{qsThreadInfo} packet
32554 Obtain a list of all active thread IDs from the target (OS). Since there
32555 may be too many active threads to fit into one reply packet, this query
32556 works iteratively: it may require more than one query/reply sequence to
32557 obtain the entire list of threads. The first query of the sequence will
32558 be the @samp{qfThreadInfo} query; subsequent queries in the
32559 sequence will be the @samp{qsThreadInfo} query.
32561 NOTE: This packet replaces the @samp{qL} query (see below).
32565 @item m @var{thread-id}
32567 @item m @var{thread-id},@var{thread-id}@dots{}
32568 a comma-separated list of thread IDs
32570 (lower case letter @samp{L}) denotes end of list.
32573 In response to each query, the target will reply with a list of one or
32574 more thread IDs, separated by commas.
32575 @value{GDBN} will respond to each reply with a request for more thread
32576 ids (using the @samp{qs} form of the query), until the target responds
32577 with @samp{l} (lower-case ell, for @dfn{last}).
32578 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
32581 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
32582 @cindex get thread-local storage address, remote request
32583 @cindex @samp{qGetTLSAddr} packet
32584 Fetch the address associated with thread local storage specified
32585 by @var{thread-id}, @var{offset}, and @var{lm}.
32587 @var{thread-id} is the thread ID associated with the
32588 thread for which to fetch the TLS address. @xref{thread-id syntax}.
32590 @var{offset} is the (big endian, hex encoded) offset associated with the
32591 thread local variable. (This offset is obtained from the debug
32592 information associated with the variable.)
32594 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
32595 the load module associated with the thread local storage. For example,
32596 a @sc{gnu}/Linux system will pass the link map address of the shared
32597 object associated with the thread local storage under consideration.
32598 Other operating environments may choose to represent the load module
32599 differently, so the precise meaning of this parameter will vary.
32603 @item @var{XX}@dots{}
32604 Hex encoded (big endian) bytes representing the address of the thread
32605 local storage requested.
32608 An error occurred. @var{nn} are hex digits.
32611 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
32614 @item qGetTIBAddr:@var{thread-id}
32615 @cindex get thread information block address
32616 @cindex @samp{qGetTIBAddr} packet
32617 Fetch address of the Windows OS specific Thread Information Block.
32619 @var{thread-id} is the thread ID associated with the thread.
32623 @item @var{XX}@dots{}
32624 Hex encoded (big endian) bytes representing the linear address of the
32625 thread information block.
32628 An error occured. This means that either the thread was not found, or the
32629 address could not be retrieved.
32632 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
32635 @item qL @var{startflag} @var{threadcount} @var{nextthread}
32636 Obtain thread information from RTOS. Where: @var{startflag} (one hex
32637 digit) is one to indicate the first query and zero to indicate a
32638 subsequent query; @var{threadcount} (two hex digits) is the maximum
32639 number of threads the response packet can contain; and @var{nextthread}
32640 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
32641 returned in the response as @var{argthread}.
32643 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
32647 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
32648 Where: @var{count} (two hex digits) is the number of threads being
32649 returned; @var{done} (one hex digit) is zero to indicate more threads
32650 and one indicates no further threads; @var{argthreadid} (eight hex
32651 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
32652 is a sequence of thread IDs from the target. @var{threadid} (eight hex
32653 digits). See @code{remote.c:parse_threadlist_response()}.
32657 @cindex section offsets, remote request
32658 @cindex @samp{qOffsets} packet
32659 Get section offsets that the target used when relocating the downloaded
32664 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
32665 Relocate the @code{Text} section by @var{xxx} from its original address.
32666 Relocate the @code{Data} section by @var{yyy} from its original address.
32667 If the object file format provides segment information (e.g.@: @sc{elf}
32668 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
32669 segments by the supplied offsets.
32671 @emph{Note: while a @code{Bss} offset may be included in the response,
32672 @value{GDBN} ignores this and instead applies the @code{Data} offset
32673 to the @code{Bss} section.}
32675 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
32676 Relocate the first segment of the object file, which conventionally
32677 contains program code, to a starting address of @var{xxx}. If
32678 @samp{DataSeg} is specified, relocate the second segment, which
32679 conventionally contains modifiable data, to a starting address of
32680 @var{yyy}. @value{GDBN} will report an error if the object file
32681 does not contain segment information, or does not contain at least
32682 as many segments as mentioned in the reply. Extra segments are
32683 kept at fixed offsets relative to the last relocated segment.
32686 @item qP @var{mode} @var{thread-id}
32687 @cindex thread information, remote request
32688 @cindex @samp{qP} packet
32689 Returns information on @var{thread-id}. Where: @var{mode} is a hex
32690 encoded 32 bit mode; @var{thread-id} is a thread ID
32691 (@pxref{thread-id syntax}).
32693 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
32696 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
32700 @cindex non-stop mode, remote request
32701 @cindex @samp{QNonStop} packet
32703 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
32704 @xref{Remote Non-Stop}, for more information.
32709 The request succeeded.
32712 An error occurred. @var{nn} are hex digits.
32715 An empty reply indicates that @samp{QNonStop} is not supported by
32719 This packet is not probed by default; the remote stub must request it,
32720 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32721 Use of this packet is controlled by the @code{set non-stop} command;
32722 @pxref{Non-Stop Mode}.
32724 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
32725 @cindex pass signals to inferior, remote request
32726 @cindex @samp{QPassSignals} packet
32727 @anchor{QPassSignals}
32728 Each listed @var{signal} should be passed directly to the inferior process.
32729 Signals are numbered identically to continue packets and stop replies
32730 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
32731 strictly greater than the previous item. These signals do not need to stop
32732 the inferior, or be reported to @value{GDBN}. All other signals should be
32733 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
32734 combine; any earlier @samp{QPassSignals} list is completely replaced by the
32735 new list. This packet improves performance when using @samp{handle
32736 @var{signal} nostop noprint pass}.
32741 The request succeeded.
32744 An error occurred. @var{nn} are hex digits.
32747 An empty reply indicates that @samp{QPassSignals} is not supported by
32751 Use of this packet is controlled by the @code{set remote pass-signals}
32752 command (@pxref{Remote Configuration, set remote pass-signals}).
32753 This packet is not probed by default; the remote stub must request it,
32754 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32756 @item qRcmd,@var{command}
32757 @cindex execute remote command, remote request
32758 @cindex @samp{qRcmd} packet
32759 @var{command} (hex encoded) is passed to the local interpreter for
32760 execution. Invalid commands should be reported using the output
32761 string. Before the final result packet, the target may also respond
32762 with a number of intermediate @samp{O@var{output}} console output
32763 packets. @emph{Implementors should note that providing access to a
32764 stubs's interpreter may have security implications}.
32769 A command response with no output.
32771 A command response with the hex encoded output string @var{OUTPUT}.
32773 Indicate a badly formed request.
32775 An empty reply indicates that @samp{qRcmd} is not recognized.
32778 (Note that the @code{qRcmd} packet's name is separated from the
32779 command by a @samp{,}, not a @samp{:}, contrary to the naming
32780 conventions above. Please don't use this packet as a model for new
32783 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
32784 @cindex searching memory, in remote debugging
32785 @cindex @samp{qSearch:memory} packet
32786 @anchor{qSearch memory}
32787 Search @var{length} bytes at @var{address} for @var{search-pattern}.
32788 @var{address} and @var{length} are encoded in hex.
32789 @var{search-pattern} is a sequence of bytes, hex encoded.
32794 The pattern was not found.
32796 The pattern was found at @var{address}.
32798 A badly formed request or an error was encountered while searching memory.
32800 An empty reply indicates that @samp{qSearch:memory} is not recognized.
32803 @item QStartNoAckMode
32804 @cindex @samp{QStartNoAckMode} packet
32805 @anchor{QStartNoAckMode}
32806 Request that the remote stub disable the normal @samp{+}/@samp{-}
32807 protocol acknowledgments (@pxref{Packet Acknowledgment}).
32812 The stub has switched to no-acknowledgment mode.
32813 @value{GDBN} acknowledges this reponse,
32814 but neither the stub nor @value{GDBN} shall send or expect further
32815 @samp{+}/@samp{-} acknowledgments in the current connection.
32817 An empty reply indicates that the stub does not support no-acknowledgment mode.
32820 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
32821 @cindex supported packets, remote query
32822 @cindex features of the remote protocol
32823 @cindex @samp{qSupported} packet
32824 @anchor{qSupported}
32825 Tell the remote stub about features supported by @value{GDBN}, and
32826 query the stub for features it supports. This packet allows
32827 @value{GDBN} and the remote stub to take advantage of each others'
32828 features. @samp{qSupported} also consolidates multiple feature probes
32829 at startup, to improve @value{GDBN} performance---a single larger
32830 packet performs better than multiple smaller probe packets on
32831 high-latency links. Some features may enable behavior which must not
32832 be on by default, e.g.@: because it would confuse older clients or
32833 stubs. Other features may describe packets which could be
32834 automatically probed for, but are not. These features must be
32835 reported before @value{GDBN} will use them. This ``default
32836 unsupported'' behavior is not appropriate for all packets, but it
32837 helps to keep the initial connection time under control with new
32838 versions of @value{GDBN} which support increasing numbers of packets.
32842 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
32843 The stub supports or does not support each returned @var{stubfeature},
32844 depending on the form of each @var{stubfeature} (see below for the
32847 An empty reply indicates that @samp{qSupported} is not recognized,
32848 or that no features needed to be reported to @value{GDBN}.
32851 The allowed forms for each feature (either a @var{gdbfeature} in the
32852 @samp{qSupported} packet, or a @var{stubfeature} in the response)
32856 @item @var{name}=@var{value}
32857 The remote protocol feature @var{name} is supported, and associated
32858 with the specified @var{value}. The format of @var{value} depends
32859 on the feature, but it must not include a semicolon.
32861 The remote protocol feature @var{name} is supported, and does not
32862 need an associated value.
32864 The remote protocol feature @var{name} is not supported.
32866 The remote protocol feature @var{name} may be supported, and
32867 @value{GDBN} should auto-detect support in some other way when it is
32868 needed. This form will not be used for @var{gdbfeature} notifications,
32869 but may be used for @var{stubfeature} responses.
32872 Whenever the stub receives a @samp{qSupported} request, the
32873 supplied set of @value{GDBN} features should override any previous
32874 request. This allows @value{GDBN} to put the stub in a known
32875 state, even if the stub had previously been communicating with
32876 a different version of @value{GDBN}.
32878 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
32883 This feature indicates whether @value{GDBN} supports multiprocess
32884 extensions to the remote protocol. @value{GDBN} does not use such
32885 extensions unless the stub also reports that it supports them by
32886 including @samp{multiprocess+} in its @samp{qSupported} reply.
32887 @xref{multiprocess extensions}, for details.
32890 This feature indicates that @value{GDBN} supports the XML target
32891 description. If the stub sees @samp{xmlRegisters=} with target
32892 specific strings separated by a comma, it will report register
32896 This feature indicates whether @value{GDBN} supports the
32897 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
32898 instruction reply packet}).
32901 Stubs should ignore any unknown values for
32902 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
32903 packet supports receiving packets of unlimited length (earlier
32904 versions of @value{GDBN} may reject overly long responses). Additional values
32905 for @var{gdbfeature} may be defined in the future to let the stub take
32906 advantage of new features in @value{GDBN}, e.g.@: incompatible
32907 improvements in the remote protocol---the @samp{multiprocess} feature is
32908 an example of such a feature. The stub's reply should be independent
32909 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
32910 describes all the features it supports, and then the stub replies with
32911 all the features it supports.
32913 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
32914 responses, as long as each response uses one of the standard forms.
32916 Some features are flags. A stub which supports a flag feature
32917 should respond with a @samp{+} form response. Other features
32918 require values, and the stub should respond with an @samp{=}
32921 Each feature has a default value, which @value{GDBN} will use if
32922 @samp{qSupported} is not available or if the feature is not mentioned
32923 in the @samp{qSupported} response. The default values are fixed; a
32924 stub is free to omit any feature responses that match the defaults.
32926 Not all features can be probed, but for those which can, the probing
32927 mechanism is useful: in some cases, a stub's internal
32928 architecture may not allow the protocol layer to know some information
32929 about the underlying target in advance. This is especially common in
32930 stubs which may be configured for multiple targets.
32932 These are the currently defined stub features and their properties:
32934 @multitable @columnfractions 0.35 0.2 0.12 0.2
32935 @c NOTE: The first row should be @headitem, but we do not yet require
32936 @c a new enough version of Texinfo (4.7) to use @headitem.
32938 @tab Value Required
32942 @item @samp{PacketSize}
32947 @item @samp{qXfer:auxv:read}
32952 @item @samp{qXfer:features:read}
32957 @item @samp{qXfer:libraries:read}
32962 @item @samp{qXfer:memory-map:read}
32967 @item @samp{qXfer:sdata:read}
32972 @item @samp{qXfer:spu:read}
32977 @item @samp{qXfer:spu:write}
32982 @item @samp{qXfer:siginfo:read}
32987 @item @samp{qXfer:siginfo:write}
32992 @item @samp{qXfer:threads:read}
32998 @item @samp{QNonStop}
33003 @item @samp{QPassSignals}
33008 @item @samp{QStartNoAckMode}
33013 @item @samp{multiprocess}
33018 @item @samp{ConditionalTracepoints}
33023 @item @samp{ReverseContinue}
33028 @item @samp{ReverseStep}
33033 @item @samp{TracepointSource}
33038 @item @samp{QAllow}
33045 These are the currently defined stub features, in more detail:
33048 @cindex packet size, remote protocol
33049 @item PacketSize=@var{bytes}
33050 The remote stub can accept packets up to at least @var{bytes} in
33051 length. @value{GDBN} will send packets up to this size for bulk
33052 transfers, and will never send larger packets. This is a limit on the
33053 data characters in the packet, including the frame and checksum.
33054 There is no trailing NUL byte in a remote protocol packet; if the stub
33055 stores packets in a NUL-terminated format, it should allow an extra
33056 byte in its buffer for the NUL. If this stub feature is not supported,
33057 @value{GDBN} guesses based on the size of the @samp{g} packet response.
33059 @item qXfer:auxv:read
33060 The remote stub understands the @samp{qXfer:auxv:read} packet
33061 (@pxref{qXfer auxiliary vector read}).
33063 @item qXfer:features:read
33064 The remote stub understands the @samp{qXfer:features:read} packet
33065 (@pxref{qXfer target description read}).
33067 @item qXfer:libraries:read
33068 The remote stub understands the @samp{qXfer:libraries:read} packet
33069 (@pxref{qXfer library list read}).
33071 @item qXfer:memory-map:read
33072 The remote stub understands the @samp{qXfer:memory-map:read} packet
33073 (@pxref{qXfer memory map read}).
33075 @item qXfer:sdata:read
33076 The remote stub understands the @samp{qXfer:sdata:read} packet
33077 (@pxref{qXfer sdata read}).
33079 @item qXfer:spu:read
33080 The remote stub understands the @samp{qXfer:spu:read} packet
33081 (@pxref{qXfer spu read}).
33083 @item qXfer:spu:write
33084 The remote stub understands the @samp{qXfer:spu:write} packet
33085 (@pxref{qXfer spu write}).
33087 @item qXfer:siginfo:read
33088 The remote stub understands the @samp{qXfer:siginfo:read} packet
33089 (@pxref{qXfer siginfo read}).
33091 @item qXfer:siginfo:write
33092 The remote stub understands the @samp{qXfer:siginfo:write} packet
33093 (@pxref{qXfer siginfo write}).
33095 @item qXfer:threads:read
33096 The remote stub understands the @samp{qXfer:threads:read} packet
33097 (@pxref{qXfer threads read}).
33100 The remote stub understands the @samp{QNonStop} packet
33101 (@pxref{QNonStop}).
33104 The remote stub understands the @samp{QPassSignals} packet
33105 (@pxref{QPassSignals}).
33107 @item QStartNoAckMode
33108 The remote stub understands the @samp{QStartNoAckMode} packet and
33109 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
33112 @anchor{multiprocess extensions}
33113 @cindex multiprocess extensions, in remote protocol
33114 The remote stub understands the multiprocess extensions to the remote
33115 protocol syntax. The multiprocess extensions affect the syntax of
33116 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
33117 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
33118 replies. Note that reporting this feature indicates support for the
33119 syntactic extensions only, not that the stub necessarily supports
33120 debugging of more than one process at a time. The stub must not use
33121 multiprocess extensions in packet replies unless @value{GDBN} has also
33122 indicated it supports them in its @samp{qSupported} request.
33124 @item qXfer:osdata:read
33125 The remote stub understands the @samp{qXfer:osdata:read} packet
33126 ((@pxref{qXfer osdata read}).
33128 @item ConditionalTracepoints
33129 The remote stub accepts and implements conditional expressions defined
33130 for tracepoints (@pxref{Tracepoint Conditions}).
33132 @item ReverseContinue
33133 The remote stub accepts and implements the reverse continue packet
33137 The remote stub accepts and implements the reverse step packet
33140 @item TracepointSource
33141 The remote stub understands the @samp{QTDPsrc} packet that supplies
33142 the source form of tracepoint definitions.
33145 The remote stub understands the @samp{QAllow} packet.
33147 @item StaticTracepoint
33148 @cindex static tracepoints, in remote protocol
33149 The remote stub supports static tracepoints.
33154 @cindex symbol lookup, remote request
33155 @cindex @samp{qSymbol} packet
33156 Notify the target that @value{GDBN} is prepared to serve symbol lookup
33157 requests. Accept requests from the target for the values of symbols.
33162 The target does not need to look up any (more) symbols.
33163 @item qSymbol:@var{sym_name}
33164 The target requests the value of symbol @var{sym_name} (hex encoded).
33165 @value{GDBN} may provide the value by using the
33166 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
33170 @item qSymbol:@var{sym_value}:@var{sym_name}
33171 Set the value of @var{sym_name} to @var{sym_value}.
33173 @var{sym_name} (hex encoded) is the name of a symbol whose value the
33174 target has previously requested.
33176 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
33177 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
33183 The target does not need to look up any (more) symbols.
33184 @item qSymbol:@var{sym_name}
33185 The target requests the value of a new symbol @var{sym_name} (hex
33186 encoded). @value{GDBN} will continue to supply the values of symbols
33187 (if available), until the target ceases to request them.
33192 @item QTDisconnected
33199 @xref{Tracepoint Packets}.
33201 @item qThreadExtraInfo,@var{thread-id}
33202 @cindex thread attributes info, remote request
33203 @cindex @samp{qThreadExtraInfo} packet
33204 Obtain a printable string description of a thread's attributes from
33205 the target OS. @var{thread-id} is a thread ID;
33206 see @ref{thread-id syntax}. This
33207 string may contain anything that the target OS thinks is interesting
33208 for @value{GDBN} to tell the user about the thread. The string is
33209 displayed in @value{GDBN}'s @code{info threads} display. Some
33210 examples of possible thread extra info strings are @samp{Runnable}, or
33211 @samp{Blocked on Mutex}.
33215 @item @var{XX}@dots{}
33216 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
33217 comprising the printable string containing the extra information about
33218 the thread's attributes.
33221 (Note that the @code{qThreadExtraInfo} packet's name is separated from
33222 the command by a @samp{,}, not a @samp{:}, contrary to the naming
33223 conventions above. Please don't use this packet as a model for new
33238 @xref{Tracepoint Packets}.
33240 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
33241 @cindex read special object, remote request
33242 @cindex @samp{qXfer} packet
33243 @anchor{qXfer read}
33244 Read uninterpreted bytes from the target's special data area
33245 identified by the keyword @var{object}. Request @var{length} bytes
33246 starting at @var{offset} bytes into the data. The content and
33247 encoding of @var{annex} is specific to @var{object}; it can supply
33248 additional details about what data to access.
33250 Here are the specific requests of this form defined so far. All
33251 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
33252 formats, listed below.
33255 @item qXfer:auxv:read::@var{offset},@var{length}
33256 @anchor{qXfer auxiliary vector read}
33257 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
33258 auxiliary vector}. Note @var{annex} must be empty.
33260 This packet is not probed by default; the remote stub must request it,
33261 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33263 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
33264 @anchor{qXfer target description read}
33265 Access the @dfn{target description}. @xref{Target Descriptions}. The
33266 annex specifies which XML document to access. The main description is
33267 always loaded from the @samp{target.xml} annex.
33269 This packet is not probed by default; the remote stub must request it,
33270 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33272 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
33273 @anchor{qXfer library list read}
33274 Access the target's list of loaded libraries. @xref{Library List Format}.
33275 The annex part of the generic @samp{qXfer} packet must be empty
33276 (@pxref{qXfer read}).
33278 Targets which maintain a list of libraries in the program's memory do
33279 not need to implement this packet; it is designed for platforms where
33280 the operating system manages the list of loaded libraries.
33282 This packet is not probed by default; the remote stub must request it,
33283 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33285 @item qXfer:memory-map:read::@var{offset},@var{length}
33286 @anchor{qXfer memory map read}
33287 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
33288 annex part of the generic @samp{qXfer} packet must be empty
33289 (@pxref{qXfer read}).
33291 This packet is not probed by default; the remote stub must request it,
33292 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33294 @item qXfer:sdata:read::@var{offset},@var{length}
33295 @anchor{qXfer sdata read}
33297 Read contents of the extra collected static tracepoint marker
33298 information. The annex part of the generic @samp{qXfer} packet must
33299 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
33302 This packet is not probed by default; the remote stub must request it,
33303 by supplying an appropriate @samp{qSupported} response
33304 (@pxref{qSupported}).
33306 @item qXfer:siginfo:read::@var{offset},@var{length}
33307 @anchor{qXfer siginfo read}
33308 Read contents of the extra signal information on the target
33309 system. The annex part of the generic @samp{qXfer} packet must be
33310 empty (@pxref{qXfer read}).
33312 This packet is not probed by default; the remote stub must request it,
33313 by supplying an appropriate @samp{qSupported} response
33314 (@pxref{qSupported}).
33316 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
33317 @anchor{qXfer spu read}
33318 Read contents of an @code{spufs} file on the target system. The
33319 annex specifies which file to read; it must be of the form
33320 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
33321 in the target process, and @var{name} identifes the @code{spufs} file
33322 in that context to be accessed.
33324 This packet is not probed by default; the remote stub must request it,
33325 by supplying an appropriate @samp{qSupported} response
33326 (@pxref{qSupported}).
33328 @item qXfer:threads:read::@var{offset},@var{length}
33329 @anchor{qXfer threads read}
33330 Access the list of threads on target. @xref{Thread List Format}. The
33331 annex part of the generic @samp{qXfer} packet must be empty
33332 (@pxref{qXfer read}).
33334 This packet is not probed by default; the remote stub must request it,
33335 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33337 @item qXfer:osdata:read::@var{offset},@var{length}
33338 @anchor{qXfer osdata read}
33339 Access the target's @dfn{operating system information}.
33340 @xref{Operating System Information}.
33347 Data @var{data} (@pxref{Binary Data}) has been read from the
33348 target. There may be more data at a higher address (although
33349 it is permitted to return @samp{m} even for the last valid
33350 block of data, as long as at least one byte of data was read).
33351 @var{data} may have fewer bytes than the @var{length} in the
33355 Data @var{data} (@pxref{Binary Data}) has been read from the target.
33356 There is no more data to be read. @var{data} may have fewer bytes
33357 than the @var{length} in the request.
33360 The @var{offset} in the request is at the end of the data.
33361 There is no more data to be read.
33364 The request was malformed, or @var{annex} was invalid.
33367 The offset was invalid, or there was an error encountered reading the data.
33368 @var{nn} is a hex-encoded @code{errno} value.
33371 An empty reply indicates the @var{object} string was not recognized by
33372 the stub, or that the object does not support reading.
33375 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
33376 @cindex write data into object, remote request
33377 @anchor{qXfer write}
33378 Write uninterpreted bytes into the target's special data area
33379 identified by the keyword @var{object}, starting at @var{offset} bytes
33380 into the data. @var{data}@dots{} is the binary-encoded data
33381 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
33382 is specific to @var{object}; it can supply additional details about what data
33385 Here are the specific requests of this form defined so far. All
33386 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
33387 formats, listed below.
33390 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
33391 @anchor{qXfer siginfo write}
33392 Write @var{data} to the extra signal information on the target system.
33393 The annex part of the generic @samp{qXfer} packet must be
33394 empty (@pxref{qXfer write}).
33396 This packet is not probed by default; the remote stub must request it,
33397 by supplying an appropriate @samp{qSupported} response
33398 (@pxref{qSupported}).
33400 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
33401 @anchor{qXfer spu write}
33402 Write @var{data} to an @code{spufs} file on the target system. The
33403 annex specifies which file to write; it must be of the form
33404 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
33405 in the target process, and @var{name} identifes the @code{spufs} file
33406 in that context to be accessed.
33408 This packet is not probed by default; the remote stub must request it,
33409 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33415 @var{nn} (hex encoded) is the number of bytes written.
33416 This may be fewer bytes than supplied in the request.
33419 The request was malformed, or @var{annex} was invalid.
33422 The offset was invalid, or there was an error encountered writing the data.
33423 @var{nn} is a hex-encoded @code{errno} value.
33426 An empty reply indicates the @var{object} string was not
33427 recognized by the stub, or that the object does not support writing.
33430 @item qXfer:@var{object}:@var{operation}:@dots{}
33431 Requests of this form may be added in the future. When a stub does
33432 not recognize the @var{object} keyword, or its support for
33433 @var{object} does not recognize the @var{operation} keyword, the stub
33434 must respond with an empty packet.
33436 @item qAttached:@var{pid}
33437 @cindex query attached, remote request
33438 @cindex @samp{qAttached} packet
33439 Return an indication of whether the remote server attached to an
33440 existing process or created a new process. When the multiprocess
33441 protocol extensions are supported (@pxref{multiprocess extensions}),
33442 @var{pid} is an integer in hexadecimal format identifying the target
33443 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
33444 the query packet will be simplified as @samp{qAttached}.
33446 This query is used, for example, to know whether the remote process
33447 should be detached or killed when a @value{GDBN} session is ended with
33448 the @code{quit} command.
33453 The remote server attached to an existing process.
33455 The remote server created a new process.
33457 A badly formed request or an error was encountered.
33462 @node Architecture-Specific Protocol Details
33463 @section Architecture-Specific Protocol Details
33465 This section describes how the remote protocol is applied to specific
33466 target architectures. Also see @ref{Standard Target Features}, for
33467 details of XML target descriptions for each architecture.
33471 @subsubsection Breakpoint Kinds
33473 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
33478 16-bit Thumb mode breakpoint.
33481 32-bit Thumb mode (Thumb-2) breakpoint.
33484 32-bit ARM mode breakpoint.
33490 @subsubsection Register Packet Format
33492 The following @code{g}/@code{G} packets have previously been defined.
33493 In the below, some thirty-two bit registers are transferred as
33494 sixty-four bits. Those registers should be zero/sign extended (which?)
33495 to fill the space allocated. Register bytes are transferred in target
33496 byte order. The two nibbles within a register byte are transferred
33497 most-significant - least-significant.
33503 All registers are transferred as thirty-two bit quantities in the order:
33504 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
33505 registers; fsr; fir; fp.
33509 All registers are transferred as sixty-four bit quantities (including
33510 thirty-two bit registers such as @code{sr}). The ordering is the same
33515 @node Tracepoint Packets
33516 @section Tracepoint Packets
33517 @cindex tracepoint packets
33518 @cindex packets, tracepoint
33520 Here we describe the packets @value{GDBN} uses to implement
33521 tracepoints (@pxref{Tracepoints}).
33525 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
33526 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
33527 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
33528 the tracepoint is disabled. @var{step} is the tracepoint's step
33529 count, and @var{pass} is its pass count. If an @samp{F} is present,
33530 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
33531 the number of bytes that the target should copy elsewhere to make room
33532 for the tracepoint. If an @samp{X} is present, it introduces a
33533 tracepoint condition, which consists of a hexadecimal length, followed
33534 by a comma and hex-encoded bytes, in a manner similar to action
33535 encodings as described below. If the trailing @samp{-} is present,
33536 further @samp{QTDP} packets will follow to specify this tracepoint's
33542 The packet was understood and carried out.
33544 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
33546 The packet was not recognized.
33549 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
33550 Define actions to be taken when a tracepoint is hit. @var{n} and
33551 @var{addr} must be the same as in the initial @samp{QTDP} packet for
33552 this tracepoint. This packet may only be sent immediately after
33553 another @samp{QTDP} packet that ended with a @samp{-}. If the
33554 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
33555 specifying more actions for this tracepoint.
33557 In the series of action packets for a given tracepoint, at most one
33558 can have an @samp{S} before its first @var{action}. If such a packet
33559 is sent, it and the following packets define ``while-stepping''
33560 actions. Any prior packets define ordinary actions --- that is, those
33561 taken when the tracepoint is first hit. If no action packet has an
33562 @samp{S}, then all the packets in the series specify ordinary
33563 tracepoint actions.
33565 The @samp{@var{action}@dots{}} portion of the packet is a series of
33566 actions, concatenated without separators. Each action has one of the
33572 Collect the registers whose bits are set in @var{mask}. @var{mask} is
33573 a hexadecimal number whose @var{i}'th bit is set if register number
33574 @var{i} should be collected. (The least significant bit is numbered
33575 zero.) Note that @var{mask} may be any number of digits long; it may
33576 not fit in a 32-bit word.
33578 @item M @var{basereg},@var{offset},@var{len}
33579 Collect @var{len} bytes of memory starting at the address in register
33580 number @var{basereg}, plus @var{offset}. If @var{basereg} is
33581 @samp{-1}, then the range has a fixed address: @var{offset} is the
33582 address of the lowest byte to collect. The @var{basereg},
33583 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
33584 values (the @samp{-1} value for @var{basereg} is a special case).
33586 @item X @var{len},@var{expr}
33587 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
33588 it directs. @var{expr} is an agent expression, as described in
33589 @ref{Agent Expressions}. Each byte of the expression is encoded as a
33590 two-digit hex number in the packet; @var{len} is the number of bytes
33591 in the expression (and thus one-half the number of hex digits in the
33596 Any number of actions may be packed together in a single @samp{QTDP}
33597 packet, as long as the packet does not exceed the maximum packet
33598 length (400 bytes, for many stubs). There may be only one @samp{R}
33599 action per tracepoint, and it must precede any @samp{M} or @samp{X}
33600 actions. Any registers referred to by @samp{M} and @samp{X} actions
33601 must be collected by a preceding @samp{R} action. (The
33602 ``while-stepping'' actions are treated as if they were attached to a
33603 separate tracepoint, as far as these restrictions are concerned.)
33608 The packet was understood and carried out.
33610 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
33612 The packet was not recognized.
33615 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
33616 @cindex @samp{QTDPsrc} packet
33617 Specify a source string of tracepoint @var{n} at address @var{addr}.
33618 This is useful to get accurate reproduction of the tracepoints
33619 originally downloaded at the beginning of the trace run. @var{type}
33620 is the name of the tracepoint part, such as @samp{cond} for the
33621 tracepoint's conditional expression (see below for a list of types), while
33622 @var{bytes} is the string, encoded in hexadecimal.
33624 @var{start} is the offset of the @var{bytes} within the overall source
33625 string, while @var{slen} is the total length of the source string.
33626 This is intended for handling source strings that are longer than will
33627 fit in a single packet.
33628 @c Add detailed example when this info is moved into a dedicated
33629 @c tracepoint descriptions section.
33631 The available string types are @samp{at} for the location,
33632 @samp{cond} for the conditional, and @samp{cmd} for an action command.
33633 @value{GDBN} sends a separate packet for each command in the action
33634 list, in the same order in which the commands are stored in the list.
33636 The target does not need to do anything with source strings except
33637 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
33640 Although this packet is optional, and @value{GDBN} will only send it
33641 if the target replies with @samp{TracepointSource} @xref{General
33642 Query Packets}, it makes both disconnected tracing and trace files
33643 much easier to use. Otherwise the user must be careful that the
33644 tracepoints in effect while looking at trace frames are identical to
33645 the ones in effect during the trace run; even a small discrepancy
33646 could cause @samp{tdump} not to work, or a particular trace frame not
33649 @item QTDV:@var{n}:@var{value}
33650 @cindex define trace state variable, remote request
33651 @cindex @samp{QTDV} packet
33652 Create a new trace state variable, number @var{n}, with an initial
33653 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
33654 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
33655 the option of not using this packet for initial values of zero; the
33656 target should simply create the trace state variables as they are
33657 mentioned in expressions.
33659 @item QTFrame:@var{n}
33660 Select the @var{n}'th tracepoint frame from the buffer, and use the
33661 register and memory contents recorded there to answer subsequent
33662 request packets from @value{GDBN}.
33664 A successful reply from the stub indicates that the stub has found the
33665 requested frame. The response is a series of parts, concatenated
33666 without separators, describing the frame we selected. Each part has
33667 one of the following forms:
33671 The selected frame is number @var{n} in the trace frame buffer;
33672 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
33673 was no frame matching the criteria in the request packet.
33676 The selected trace frame records a hit of tracepoint number @var{t};
33677 @var{t} is a hexadecimal number.
33681 @item QTFrame:pc:@var{addr}
33682 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
33683 currently selected frame whose PC is @var{addr};
33684 @var{addr} is a hexadecimal number.
33686 @item QTFrame:tdp:@var{t}
33687 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
33688 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
33689 is a hexadecimal number.
33691 @item QTFrame:range:@var{start}:@var{end}
33692 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
33693 currently selected frame whose PC is between @var{start} (inclusive)
33694 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
33697 @item QTFrame:outside:@var{start}:@var{end}
33698 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
33699 frame @emph{outside} the given range of addresses (exclusive).
33702 Begin the tracepoint experiment. Begin collecting data from
33703 tracepoint hits in the trace frame buffer. This packet supports the
33704 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
33705 instruction reply packet}).
33708 End the tracepoint experiment. Stop collecting trace frames.
33711 Clear the table of tracepoints, and empty the trace frame buffer.
33713 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
33714 Establish the given ranges of memory as ``transparent''. The stub
33715 will answer requests for these ranges from memory's current contents,
33716 if they were not collected as part of the tracepoint hit.
33718 @value{GDBN} uses this to mark read-only regions of memory, like those
33719 containing program code. Since these areas never change, they should
33720 still have the same contents they did when the tracepoint was hit, so
33721 there's no reason for the stub to refuse to provide their contents.
33723 @item QTDisconnected:@var{value}
33724 Set the choice to what to do with the tracing run when @value{GDBN}
33725 disconnects from the target. A @var{value} of 1 directs the target to
33726 continue the tracing run, while 0 tells the target to stop tracing if
33727 @value{GDBN} is no longer in the picture.
33730 Ask the stub if there is a trace experiment running right now.
33732 The reply has the form:
33736 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
33737 @var{running} is a single digit @code{1} if the trace is presently
33738 running, or @code{0} if not. It is followed by semicolon-separated
33739 optional fields that an agent may use to report additional status.
33743 If the trace is not running, the agent may report any of several
33744 explanations as one of the optional fields:
33749 No trace has been run yet.
33752 The trace was stopped by a user-originated stop command.
33755 The trace stopped because the trace buffer filled up.
33757 @item tdisconnected:0
33758 The trace stopped because @value{GDBN} disconnected from the target.
33760 @item tpasscount:@var{tpnum}
33761 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
33763 @item terror:@var{text}:@var{tpnum}
33764 The trace stopped because tracepoint @var{tpnum} had an error. The
33765 string @var{text} is available to describe the nature of the error
33766 (for instance, a divide by zero in the condition expression).
33767 @var{text} is hex encoded.
33770 The trace stopped for some other reason.
33774 Additional optional fields supply statistical and other information.
33775 Although not required, they are extremely useful for users monitoring
33776 the progress of a trace run. If a trace has stopped, and these
33777 numbers are reported, they must reflect the state of the just-stopped
33782 @item tframes:@var{n}
33783 The number of trace frames in the buffer.
33785 @item tcreated:@var{n}
33786 The total number of trace frames created during the run. This may
33787 be larger than the trace frame count, if the buffer is circular.
33789 @item tsize:@var{n}
33790 The total size of the trace buffer, in bytes.
33792 @item tfree:@var{n}
33793 The number of bytes still unused in the buffer.
33795 @item circular:@var{n}
33796 The value of the circular trace buffer flag. @code{1} means that the
33797 trace buffer is circular and old trace frames will be discarded if
33798 necessary to make room, @code{0} means that the trace buffer is linear
33801 @item disconn:@var{n}
33802 The value of the disconnected tracing flag. @code{1} means that
33803 tracing will continue after @value{GDBN} disconnects, @code{0} means
33804 that the trace run will stop.
33808 @item qTV:@var{var}
33809 @cindex trace state variable value, remote request
33810 @cindex @samp{qTV} packet
33811 Ask the stub for the value of the trace state variable number @var{var}.
33816 The value of the variable is @var{value}. This will be the current
33817 value of the variable if the user is examining a running target, or a
33818 saved value if the variable was collected in the trace frame that the
33819 user is looking at. Note that multiple requests may result in
33820 different reply values, such as when requesting values while the
33821 program is running.
33824 The value of the variable is unknown. This would occur, for example,
33825 if the user is examining a trace frame in which the requested variable
33831 These packets request data about tracepoints that are being used by
33832 the target. @value{GDBN} sends @code{qTfP} to get the first piece
33833 of data, and multiple @code{qTsP} to get additional pieces. Replies
33834 to these packets generally take the form of the @code{QTDP} packets
33835 that define tracepoints. (FIXME add detailed syntax)
33839 These packets request data about trace state variables that are on the
33840 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
33841 and multiple @code{qTsV} to get additional variables. Replies to
33842 these packets follow the syntax of the @code{QTDV} packets that define
33843 trace state variables.
33847 These packets request data about static tracepoint markers that exist
33848 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
33849 first piece of data, and multiple @code{qTsSTM} to get additional
33850 pieces. Replies to these packets take the following form:
33854 @item m @var{address}:@var{id}:@var{extra}
33856 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
33857 a comma-separated list of markers
33859 (lower case letter @samp{L}) denotes end of list.
33861 An error occurred. @var{nn} are hex digits.
33863 An empty reply indicates that the request is not supported by the
33867 @var{address} is encoded in hex.
33868 @var{id} and @var{extra} are strings encoded in hex.
33870 In response to each query, the target will reply with a list of one or
33871 more markers, separated by commas. @value{GDBN} will respond to each
33872 reply with a request for more markers (using the @samp{qs} form of the
33873 query), until the target responds with @samp{l} (lower-case ell, for
33876 @item qTSTMat:@var{address}
33877 This packets requests data about static tracepoint markers in the
33878 target program at @var{address}. Replies to this packet follow the
33879 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
33880 tracepoint markers.
33882 @item QTSave:@var{filename}
33883 This packet directs the target to save trace data to the file name
33884 @var{filename} in the target's filesystem. @var{filename} is encoded
33885 as a hex string; the interpretation of the file name (relative vs
33886 absolute, wild cards, etc) is up to the target.
33888 @item qTBuffer:@var{offset},@var{len}
33889 Return up to @var{len} bytes of the current contents of trace buffer,
33890 starting at @var{offset}. The trace buffer is treated as if it were
33891 a contiguous collection of traceframes, as per the trace file format.
33892 The reply consists as many hex-encoded bytes as the target can deliver
33893 in a packet; it is not an error to return fewer than were asked for.
33894 A reply consisting of just @code{l} indicates that no bytes are
33897 @item QTBuffer:circular:@var{value}
33898 This packet directs the target to use a circular trace buffer if
33899 @var{value} is 1, or a linear buffer if the value is 0.
33903 @subsection Relocate instruction reply packet
33904 When installing fast tracepoints in memory, the target may need to
33905 relocate the instruction currently at the tracepoint address to a
33906 different address in memory. For most instructions, a simple copy is
33907 enough, but, for example, call instructions that implicitly push the
33908 return address on the stack, and relative branches or other
33909 PC-relative instructions require offset adjustment, so that the effect
33910 of executing the instruction at a different address is the same as if
33911 it had executed in the original location.
33913 In response to several of the tracepoint packets, the target may also
33914 respond with a number of intermediate @samp{qRelocInsn} request
33915 packets before the final result packet, to have @value{GDBN} handle
33916 this relocation operation. If a packet supports this mechanism, its
33917 documentation will explicitly say so. See for example the above
33918 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
33919 format of the request is:
33922 @item qRelocInsn:@var{from};@var{to}
33924 This requests @value{GDBN} to copy instruction at address @var{from}
33925 to address @var{to}, possibly adjusted so that executing the
33926 instruction at @var{to} has the same effect as executing it at
33927 @var{from}. @value{GDBN} writes the adjusted instruction to target
33928 memory starting at @var{to}.
33933 @item qRelocInsn:@var{adjusted_size}
33934 Informs the stub the relocation is complete. @var{adjusted_size} is
33935 the length in bytes of resulting relocated instruction sequence.
33937 A badly formed request was detected, or an error was encountered while
33938 relocating the instruction.
33941 @node Host I/O Packets
33942 @section Host I/O Packets
33943 @cindex Host I/O, remote protocol
33944 @cindex file transfer, remote protocol
33946 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
33947 operations on the far side of a remote link. For example, Host I/O is
33948 used to upload and download files to a remote target with its own
33949 filesystem. Host I/O uses the same constant values and data structure
33950 layout as the target-initiated File-I/O protocol. However, the
33951 Host I/O packets are structured differently. The target-initiated
33952 protocol relies on target memory to store parameters and buffers.
33953 Host I/O requests are initiated by @value{GDBN}, and the
33954 target's memory is not involved. @xref{File-I/O Remote Protocol
33955 Extension}, for more details on the target-initiated protocol.
33957 The Host I/O request packets all encode a single operation along with
33958 its arguments. They have this format:
33962 @item vFile:@var{operation}: @var{parameter}@dots{}
33963 @var{operation} is the name of the particular request; the target
33964 should compare the entire packet name up to the second colon when checking
33965 for a supported operation. The format of @var{parameter} depends on
33966 the operation. Numbers are always passed in hexadecimal. Negative
33967 numbers have an explicit minus sign (i.e.@: two's complement is not
33968 used). Strings (e.g.@: filenames) are encoded as a series of
33969 hexadecimal bytes. The last argument to a system call may be a
33970 buffer of escaped binary data (@pxref{Binary Data}).
33974 The valid responses to Host I/O packets are:
33978 @item F @var{result} [, @var{errno}] [; @var{attachment}]
33979 @var{result} is the integer value returned by this operation, usually
33980 non-negative for success and -1 for errors. If an error has occured,
33981 @var{errno} will be included in the result. @var{errno} will have a
33982 value defined by the File-I/O protocol (@pxref{Errno Values}). For
33983 operations which return data, @var{attachment} supplies the data as a
33984 binary buffer. Binary buffers in response packets are escaped in the
33985 normal way (@pxref{Binary Data}). See the individual packet
33986 documentation for the interpretation of @var{result} and
33990 An empty response indicates that this operation is not recognized.
33994 These are the supported Host I/O operations:
33997 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
33998 Open a file at @var{pathname} and return a file descriptor for it, or
33999 return -1 if an error occurs. @var{pathname} is a string,
34000 @var{flags} is an integer indicating a mask of open flags
34001 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
34002 of mode bits to use if the file is created (@pxref{mode_t Values}).
34003 @xref{open}, for details of the open flags and mode values.
34005 @item vFile:close: @var{fd}
34006 Close the open file corresponding to @var{fd} and return 0, or
34007 -1 if an error occurs.
34009 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
34010 Read data from the open file corresponding to @var{fd}. Up to
34011 @var{count} bytes will be read from the file, starting at @var{offset}
34012 relative to the start of the file. The target may read fewer bytes;
34013 common reasons include packet size limits and an end-of-file
34014 condition. The number of bytes read is returned. Zero should only be
34015 returned for a successful read at the end of the file, or if
34016 @var{count} was zero.
34018 The data read should be returned as a binary attachment on success.
34019 If zero bytes were read, the response should include an empty binary
34020 attachment (i.e.@: a trailing semicolon). The return value is the
34021 number of target bytes read; the binary attachment may be longer if
34022 some characters were escaped.
34024 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
34025 Write @var{data} (a binary buffer) to the open file corresponding
34026 to @var{fd}. Start the write at @var{offset} from the start of the
34027 file. Unlike many @code{write} system calls, there is no
34028 separate @var{count} argument; the length of @var{data} in the
34029 packet is used. @samp{vFile:write} returns the number of bytes written,
34030 which may be shorter than the length of @var{data}, or -1 if an
34033 @item vFile:unlink: @var{pathname}
34034 Delete the file at @var{pathname} on the target. Return 0,
34035 or -1 if an error occurs. @var{pathname} is a string.
34040 @section Interrupts
34041 @cindex interrupts (remote protocol)
34043 When a program on the remote target is running, @value{GDBN} may
34044 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
34045 a @code{BREAK} followed by @code{g},
34046 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
34048 The precise meaning of @code{BREAK} is defined by the transport
34049 mechanism and may, in fact, be undefined. @value{GDBN} does not
34050 currently define a @code{BREAK} mechanism for any of the network
34051 interfaces except for TCP, in which case @value{GDBN} sends the
34052 @code{telnet} BREAK sequence.
34054 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
34055 transport mechanisms. It is represented by sending the single byte
34056 @code{0x03} without any of the usual packet overhead described in
34057 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
34058 transmitted as part of a packet, it is considered to be packet data
34059 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
34060 (@pxref{X packet}), used for binary downloads, may include an unescaped
34061 @code{0x03} as part of its packet.
34063 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
34064 When Linux kernel receives this sequence from serial port,
34065 it stops execution and connects to gdb.
34067 Stubs are not required to recognize these interrupt mechanisms and the
34068 precise meaning associated with receipt of the interrupt is
34069 implementation defined. If the target supports debugging of multiple
34070 threads and/or processes, it should attempt to interrupt all
34071 currently-executing threads and processes.
34072 If the stub is successful at interrupting the
34073 running program, it should send one of the stop
34074 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
34075 of successfully stopping the program in all-stop mode, and a stop reply
34076 for each stopped thread in non-stop mode.
34077 Interrupts received while the
34078 program is stopped are discarded.
34080 @node Notification Packets
34081 @section Notification Packets
34082 @cindex notification packets
34083 @cindex packets, notification
34085 The @value{GDBN} remote serial protocol includes @dfn{notifications},
34086 packets that require no acknowledgment. Both the GDB and the stub
34087 may send notifications (although the only notifications defined at
34088 present are sent by the stub). Notifications carry information
34089 without incurring the round-trip latency of an acknowledgment, and so
34090 are useful for low-impact communications where occasional packet loss
34093 A notification packet has the form @samp{% @var{data} #
34094 @var{checksum}}, where @var{data} is the content of the notification,
34095 and @var{checksum} is a checksum of @var{data}, computed and formatted
34096 as for ordinary @value{GDBN} packets. A notification's @var{data}
34097 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
34098 receiving a notification, the recipient sends no @samp{+} or @samp{-}
34099 to acknowledge the notification's receipt or to report its corruption.
34101 Every notification's @var{data} begins with a name, which contains no
34102 colon characters, followed by a colon character.
34104 Recipients should silently ignore corrupted notifications and
34105 notifications they do not understand. Recipients should restart
34106 timeout periods on receipt of a well-formed notification, whether or
34107 not they understand it.
34109 Senders should only send the notifications described here when this
34110 protocol description specifies that they are permitted. In the
34111 future, we may extend the protocol to permit existing notifications in
34112 new contexts; this rule helps older senders avoid confusing newer
34115 (Older versions of @value{GDBN} ignore bytes received until they see
34116 the @samp{$} byte that begins an ordinary packet, so new stubs may
34117 transmit notifications without fear of confusing older clients. There
34118 are no notifications defined for @value{GDBN} to send at the moment, but we
34119 assume that most older stubs would ignore them, as well.)
34121 The following notification packets from the stub to @value{GDBN} are
34125 @item Stop: @var{reply}
34126 Report an asynchronous stop event in non-stop mode.
34127 The @var{reply} has the form of a stop reply, as
34128 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
34129 for information on how these notifications are acknowledged by
34133 @node Remote Non-Stop
34134 @section Remote Protocol Support for Non-Stop Mode
34136 @value{GDBN}'s remote protocol supports non-stop debugging of
34137 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
34138 supports non-stop mode, it should report that to @value{GDBN} by including
34139 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
34141 @value{GDBN} typically sends a @samp{QNonStop} packet only when
34142 establishing a new connection with the stub. Entering non-stop mode
34143 does not alter the state of any currently-running threads, but targets
34144 must stop all threads in any already-attached processes when entering
34145 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
34146 probe the target state after a mode change.
34148 In non-stop mode, when an attached process encounters an event that
34149 would otherwise be reported with a stop reply, it uses the
34150 asynchronous notification mechanism (@pxref{Notification Packets}) to
34151 inform @value{GDBN}. In contrast to all-stop mode, where all threads
34152 in all processes are stopped when a stop reply is sent, in non-stop
34153 mode only the thread reporting the stop event is stopped. That is,
34154 when reporting a @samp{S} or @samp{T} response to indicate completion
34155 of a step operation, hitting a breakpoint, or a fault, only the
34156 affected thread is stopped; any other still-running threads continue
34157 to run. When reporting a @samp{W} or @samp{X} response, all running
34158 threads belonging to other attached processes continue to run.
34160 Only one stop reply notification at a time may be pending; if
34161 additional stop events occur before @value{GDBN} has acknowledged the
34162 previous notification, they must be queued by the stub for later
34163 synchronous transmission in response to @samp{vStopped} packets from
34164 @value{GDBN}. Because the notification mechanism is unreliable,
34165 the stub is permitted to resend a stop reply notification
34166 if it believes @value{GDBN} may not have received it. @value{GDBN}
34167 ignores additional stop reply notifications received before it has
34168 finished processing a previous notification and the stub has completed
34169 sending any queued stop events.
34171 Otherwise, @value{GDBN} must be prepared to receive a stop reply
34172 notification at any time. Specifically, they may appear when
34173 @value{GDBN} is not otherwise reading input from the stub, or when
34174 @value{GDBN} is expecting to read a normal synchronous response or a
34175 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
34176 Notification packets are distinct from any other communication from
34177 the stub so there is no ambiguity.
34179 After receiving a stop reply notification, @value{GDBN} shall
34180 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
34181 as a regular, synchronous request to the stub. Such acknowledgment
34182 is not required to happen immediately, as @value{GDBN} is permitted to
34183 send other, unrelated packets to the stub first, which the stub should
34186 Upon receiving a @samp{vStopped} packet, if the stub has other queued
34187 stop events to report to @value{GDBN}, it shall respond by sending a
34188 normal stop reply response. @value{GDBN} shall then send another
34189 @samp{vStopped} packet to solicit further responses; again, it is
34190 permitted to send other, unrelated packets as well which the stub
34191 should process normally.
34193 If the stub receives a @samp{vStopped} packet and there are no
34194 additional stop events to report, the stub shall return an @samp{OK}
34195 response. At this point, if further stop events occur, the stub shall
34196 send a new stop reply notification, @value{GDBN} shall accept the
34197 notification, and the process shall be repeated.
34199 In non-stop mode, the target shall respond to the @samp{?} packet as
34200 follows. First, any incomplete stop reply notification/@samp{vStopped}
34201 sequence in progress is abandoned. The target must begin a new
34202 sequence reporting stop events for all stopped threads, whether or not
34203 it has previously reported those events to @value{GDBN}. The first
34204 stop reply is sent as a synchronous reply to the @samp{?} packet, and
34205 subsequent stop replies are sent as responses to @samp{vStopped} packets
34206 using the mechanism described above. The target must not send
34207 asynchronous stop reply notifications until the sequence is complete.
34208 If all threads are running when the target receives the @samp{?} packet,
34209 or if the target is not attached to any process, it shall respond
34212 @node Packet Acknowledgment
34213 @section Packet Acknowledgment
34215 @cindex acknowledgment, for @value{GDBN} remote
34216 @cindex packet acknowledgment, for @value{GDBN} remote
34217 By default, when either the host or the target machine receives a packet,
34218 the first response expected is an acknowledgment: either @samp{+} (to indicate
34219 the package was received correctly) or @samp{-} (to request retransmission).
34220 This mechanism allows the @value{GDBN} remote protocol to operate over
34221 unreliable transport mechanisms, such as a serial line.
34223 In cases where the transport mechanism is itself reliable (such as a pipe or
34224 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
34225 It may be desirable to disable them in that case to reduce communication
34226 overhead, or for other reasons. This can be accomplished by means of the
34227 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
34229 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
34230 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
34231 and response format still includes the normal checksum, as described in
34232 @ref{Overview}, but the checksum may be ignored by the receiver.
34234 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
34235 no-acknowledgment mode, it should report that to @value{GDBN}
34236 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
34237 @pxref{qSupported}.
34238 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
34239 disabled via the @code{set remote noack-packet off} command
34240 (@pxref{Remote Configuration}),
34241 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
34242 Only then may the stub actually turn off packet acknowledgments.
34243 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
34244 response, which can be safely ignored by the stub.
34246 Note that @code{set remote noack-packet} command only affects negotiation
34247 between @value{GDBN} and the stub when subsequent connections are made;
34248 it does not affect the protocol acknowledgment state for any current
34250 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
34251 new connection is established,
34252 there is also no protocol request to re-enable the acknowledgments
34253 for the current connection, once disabled.
34258 Example sequence of a target being re-started. Notice how the restart
34259 does not get any direct output:
34264 @emph{target restarts}
34267 <- @code{T001:1234123412341234}
34271 Example sequence of a target being stepped by a single instruction:
34274 -> @code{G1445@dots{}}
34279 <- @code{T001:1234123412341234}
34283 <- @code{1455@dots{}}
34287 @node File-I/O Remote Protocol Extension
34288 @section File-I/O Remote Protocol Extension
34289 @cindex File-I/O remote protocol extension
34292 * File-I/O Overview::
34293 * Protocol Basics::
34294 * The F Request Packet::
34295 * The F Reply Packet::
34296 * The Ctrl-C Message::
34298 * List of Supported Calls::
34299 * Protocol-specific Representation of Datatypes::
34301 * File-I/O Examples::
34304 @node File-I/O Overview
34305 @subsection File-I/O Overview
34306 @cindex file-i/o overview
34308 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
34309 target to use the host's file system and console I/O to perform various
34310 system calls. System calls on the target system are translated into a
34311 remote protocol packet to the host system, which then performs the needed
34312 actions and returns a response packet to the target system.
34313 This simulates file system operations even on targets that lack file systems.
34315 The protocol is defined to be independent of both the host and target systems.
34316 It uses its own internal representation of datatypes and values. Both
34317 @value{GDBN} and the target's @value{GDBN} stub are responsible for
34318 translating the system-dependent value representations into the internal
34319 protocol representations when data is transmitted.
34321 The communication is synchronous. A system call is possible only when
34322 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
34323 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
34324 the target is stopped to allow deterministic access to the target's
34325 memory. Therefore File-I/O is not interruptible by target signals. On
34326 the other hand, it is possible to interrupt File-I/O by a user interrupt
34327 (@samp{Ctrl-C}) within @value{GDBN}.
34329 The target's request to perform a host system call does not finish
34330 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
34331 after finishing the system call, the target returns to continuing the
34332 previous activity (continue, step). No additional continue or step
34333 request from @value{GDBN} is required.
34336 (@value{GDBP}) continue
34337 <- target requests 'system call X'
34338 target is stopped, @value{GDBN} executes system call
34339 -> @value{GDBN} returns result
34340 ... target continues, @value{GDBN} returns to wait for the target
34341 <- target hits breakpoint and sends a Txx packet
34344 The protocol only supports I/O on the console and to regular files on
34345 the host file system. Character or block special devices, pipes,
34346 named pipes, sockets or any other communication method on the host
34347 system are not supported by this protocol.
34349 File I/O is not supported in non-stop mode.
34351 @node Protocol Basics
34352 @subsection Protocol Basics
34353 @cindex protocol basics, file-i/o
34355 The File-I/O protocol uses the @code{F} packet as the request as well
34356 as reply packet. Since a File-I/O system call can only occur when
34357 @value{GDBN} is waiting for a response from the continuing or stepping target,
34358 the File-I/O request is a reply that @value{GDBN} has to expect as a result
34359 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
34360 This @code{F} packet contains all information needed to allow @value{GDBN}
34361 to call the appropriate host system call:
34365 A unique identifier for the requested system call.
34368 All parameters to the system call. Pointers are given as addresses
34369 in the target memory address space. Pointers to strings are given as
34370 pointer/length pair. Numerical values are given as they are.
34371 Numerical control flags are given in a protocol-specific representation.
34375 At this point, @value{GDBN} has to perform the following actions.
34379 If the parameters include pointer values to data needed as input to a
34380 system call, @value{GDBN} requests this data from the target with a
34381 standard @code{m} packet request. This additional communication has to be
34382 expected by the target implementation and is handled as any other @code{m}
34386 @value{GDBN} translates all value from protocol representation to host
34387 representation as needed. Datatypes are coerced into the host types.
34390 @value{GDBN} calls the system call.
34393 It then coerces datatypes back to protocol representation.
34396 If the system call is expected to return data in buffer space specified
34397 by pointer parameters to the call, the data is transmitted to the
34398 target using a @code{M} or @code{X} packet. This packet has to be expected
34399 by the target implementation and is handled as any other @code{M} or @code{X}
34404 Eventually @value{GDBN} replies with another @code{F} packet which contains all
34405 necessary information for the target to continue. This at least contains
34412 @code{errno}, if has been changed by the system call.
34419 After having done the needed type and value coercion, the target continues
34420 the latest continue or step action.
34422 @node The F Request Packet
34423 @subsection The @code{F} Request Packet
34424 @cindex file-i/o request packet
34425 @cindex @code{F} request packet
34427 The @code{F} request packet has the following format:
34430 @item F@var{call-id},@var{parameter@dots{}}
34432 @var{call-id} is the identifier to indicate the host system call to be called.
34433 This is just the name of the function.
34435 @var{parameter@dots{}} are the parameters to the system call.
34436 Parameters are hexadecimal integer values, either the actual values in case
34437 of scalar datatypes, pointers to target buffer space in case of compound
34438 datatypes and unspecified memory areas, or pointer/length pairs in case
34439 of string parameters. These are appended to the @var{call-id} as a
34440 comma-delimited list. All values are transmitted in ASCII
34441 string representation, pointer/length pairs separated by a slash.
34447 @node The F Reply Packet
34448 @subsection The @code{F} Reply Packet
34449 @cindex file-i/o reply packet
34450 @cindex @code{F} reply packet
34452 The @code{F} reply packet has the following format:
34456 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
34458 @var{retcode} is the return code of the system call as hexadecimal value.
34460 @var{errno} is the @code{errno} set by the call, in protocol-specific
34462 This parameter can be omitted if the call was successful.
34464 @var{Ctrl-C flag} is only sent if the user requested a break. In this
34465 case, @var{errno} must be sent as well, even if the call was successful.
34466 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
34473 or, if the call was interrupted before the host call has been performed:
34480 assuming 4 is the protocol-specific representation of @code{EINTR}.
34485 @node The Ctrl-C Message
34486 @subsection The @samp{Ctrl-C} Message
34487 @cindex ctrl-c message, in file-i/o protocol
34489 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
34490 reply packet (@pxref{The F Reply Packet}),
34491 the target should behave as if it had
34492 gotten a break message. The meaning for the target is ``system call
34493 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
34494 (as with a break message) and return to @value{GDBN} with a @code{T02}
34497 It's important for the target to know in which
34498 state the system call was interrupted. There are two possible cases:
34502 The system call hasn't been performed on the host yet.
34505 The system call on the host has been finished.
34509 These two states can be distinguished by the target by the value of the
34510 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
34511 call hasn't been performed. This is equivalent to the @code{EINTR} handling
34512 on POSIX systems. In any other case, the target may presume that the
34513 system call has been finished --- successfully or not --- and should behave
34514 as if the break message arrived right after the system call.
34516 @value{GDBN} must behave reliably. If the system call has not been called
34517 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
34518 @code{errno} in the packet. If the system call on the host has been finished
34519 before the user requests a break, the full action must be finished by
34520 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
34521 The @code{F} packet may only be sent when either nothing has happened
34522 or the full action has been completed.
34525 @subsection Console I/O
34526 @cindex console i/o as part of file-i/o
34528 By default and if not explicitly closed by the target system, the file
34529 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
34530 on the @value{GDBN} console is handled as any other file output operation
34531 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
34532 by @value{GDBN} so that after the target read request from file descriptor
34533 0 all following typing is buffered until either one of the following
34538 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
34540 system call is treated as finished.
34543 The user presses @key{RET}. This is treated as end of input with a trailing
34547 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
34548 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
34552 If the user has typed more characters than fit in the buffer given to
34553 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
34554 either another @code{read(0, @dots{})} is requested by the target, or debugging
34555 is stopped at the user's request.
34558 @node List of Supported Calls
34559 @subsection List of Supported Calls
34560 @cindex list of supported file-i/o calls
34577 @unnumberedsubsubsec open
34578 @cindex open, file-i/o system call
34583 int open(const char *pathname, int flags);
34584 int open(const char *pathname, int flags, mode_t mode);
34588 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
34591 @var{flags} is the bitwise @code{OR} of the following values:
34595 If the file does not exist it will be created. The host
34596 rules apply as far as file ownership and time stamps
34600 When used with @code{O_CREAT}, if the file already exists it is
34601 an error and open() fails.
34604 If the file already exists and the open mode allows
34605 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
34606 truncated to zero length.
34609 The file is opened in append mode.
34612 The file is opened for reading only.
34615 The file is opened for writing only.
34618 The file is opened for reading and writing.
34622 Other bits are silently ignored.
34626 @var{mode} is the bitwise @code{OR} of the following values:
34630 User has read permission.
34633 User has write permission.
34636 Group has read permission.
34639 Group has write permission.
34642 Others have read permission.
34645 Others have write permission.
34649 Other bits are silently ignored.
34652 @item Return value:
34653 @code{open} returns the new file descriptor or -1 if an error
34660 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
34663 @var{pathname} refers to a directory.
34666 The requested access is not allowed.
34669 @var{pathname} was too long.
34672 A directory component in @var{pathname} does not exist.
34675 @var{pathname} refers to a device, pipe, named pipe or socket.
34678 @var{pathname} refers to a file on a read-only filesystem and
34679 write access was requested.
34682 @var{pathname} is an invalid pointer value.
34685 No space on device to create the file.
34688 The process already has the maximum number of files open.
34691 The limit on the total number of files open on the system
34695 The call was interrupted by the user.
34701 @unnumberedsubsubsec close
34702 @cindex close, file-i/o system call
34711 @samp{Fclose,@var{fd}}
34713 @item Return value:
34714 @code{close} returns zero on success, or -1 if an error occurred.
34720 @var{fd} isn't a valid open file descriptor.
34723 The call was interrupted by the user.
34729 @unnumberedsubsubsec read
34730 @cindex read, file-i/o system call
34735 int read(int fd, void *buf, unsigned int count);
34739 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
34741 @item Return value:
34742 On success, the number of bytes read is returned.
34743 Zero indicates end of file. If count is zero, read
34744 returns zero as well. On error, -1 is returned.
34750 @var{fd} is not a valid file descriptor or is not open for
34754 @var{bufptr} is an invalid pointer value.
34757 The call was interrupted by the user.
34763 @unnumberedsubsubsec write
34764 @cindex write, file-i/o system call
34769 int write(int fd, const void *buf, unsigned int count);
34773 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
34775 @item Return value:
34776 On success, the number of bytes written are returned.
34777 Zero indicates nothing was written. On error, -1
34784 @var{fd} is not a valid file descriptor or is not open for
34788 @var{bufptr} is an invalid pointer value.
34791 An attempt was made to write a file that exceeds the
34792 host-specific maximum file size allowed.
34795 No space on device to write the data.
34798 The call was interrupted by the user.
34804 @unnumberedsubsubsec lseek
34805 @cindex lseek, file-i/o system call
34810 long lseek (int fd, long offset, int flag);
34814 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
34816 @var{flag} is one of:
34820 The offset is set to @var{offset} bytes.
34823 The offset is set to its current location plus @var{offset}
34827 The offset is set to the size of the file plus @var{offset}
34831 @item Return value:
34832 On success, the resulting unsigned offset in bytes from
34833 the beginning of the file is returned. Otherwise, a
34834 value of -1 is returned.
34840 @var{fd} is not a valid open file descriptor.
34843 @var{fd} is associated with the @value{GDBN} console.
34846 @var{flag} is not a proper value.
34849 The call was interrupted by the user.
34855 @unnumberedsubsubsec rename
34856 @cindex rename, file-i/o system call
34861 int rename(const char *oldpath, const char *newpath);
34865 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
34867 @item Return value:
34868 On success, zero is returned. On error, -1 is returned.
34874 @var{newpath} is an existing directory, but @var{oldpath} is not a
34878 @var{newpath} is a non-empty directory.
34881 @var{oldpath} or @var{newpath} is a directory that is in use by some
34885 An attempt was made to make a directory a subdirectory
34889 A component used as a directory in @var{oldpath} or new
34890 path is not a directory. Or @var{oldpath} is a directory
34891 and @var{newpath} exists but is not a directory.
34894 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
34897 No access to the file or the path of the file.
34901 @var{oldpath} or @var{newpath} was too long.
34904 A directory component in @var{oldpath} or @var{newpath} does not exist.
34907 The file is on a read-only filesystem.
34910 The device containing the file has no room for the new
34914 The call was interrupted by the user.
34920 @unnumberedsubsubsec unlink
34921 @cindex unlink, file-i/o system call
34926 int unlink(const char *pathname);
34930 @samp{Funlink,@var{pathnameptr}/@var{len}}
34932 @item Return value:
34933 On success, zero is returned. On error, -1 is returned.
34939 No access to the file or the path of the file.
34942 The system does not allow unlinking of directories.
34945 The file @var{pathname} cannot be unlinked because it's
34946 being used by another process.
34949 @var{pathnameptr} is an invalid pointer value.
34952 @var{pathname} was too long.
34955 A directory component in @var{pathname} does not exist.
34958 A component of the path is not a directory.
34961 The file is on a read-only filesystem.
34964 The call was interrupted by the user.
34970 @unnumberedsubsubsec stat/fstat
34971 @cindex fstat, file-i/o system call
34972 @cindex stat, file-i/o system call
34977 int stat(const char *pathname, struct stat *buf);
34978 int fstat(int fd, struct stat *buf);
34982 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
34983 @samp{Ffstat,@var{fd},@var{bufptr}}
34985 @item Return value:
34986 On success, zero is returned. On error, -1 is returned.
34992 @var{fd} is not a valid open file.
34995 A directory component in @var{pathname} does not exist or the
34996 path is an empty string.
34999 A component of the path is not a directory.
35002 @var{pathnameptr} is an invalid pointer value.
35005 No access to the file or the path of the file.
35008 @var{pathname} was too long.
35011 The call was interrupted by the user.
35017 @unnumberedsubsubsec gettimeofday
35018 @cindex gettimeofday, file-i/o system call
35023 int gettimeofday(struct timeval *tv, void *tz);
35027 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
35029 @item Return value:
35030 On success, 0 is returned, -1 otherwise.
35036 @var{tz} is a non-NULL pointer.
35039 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
35045 @unnumberedsubsubsec isatty
35046 @cindex isatty, file-i/o system call
35051 int isatty(int fd);
35055 @samp{Fisatty,@var{fd}}
35057 @item Return value:
35058 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
35064 The call was interrupted by the user.
35069 Note that the @code{isatty} call is treated as a special case: it returns
35070 1 to the target if the file descriptor is attached
35071 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
35072 would require implementing @code{ioctl} and would be more complex than
35077 @unnumberedsubsubsec system
35078 @cindex system, file-i/o system call
35083 int system(const char *command);
35087 @samp{Fsystem,@var{commandptr}/@var{len}}
35089 @item Return value:
35090 If @var{len} is zero, the return value indicates whether a shell is
35091 available. A zero return value indicates a shell is not available.
35092 For non-zero @var{len}, the value returned is -1 on error and the
35093 return status of the command otherwise. Only the exit status of the
35094 command is returned, which is extracted from the host's @code{system}
35095 return value by calling @code{WEXITSTATUS(retval)}. In case
35096 @file{/bin/sh} could not be executed, 127 is returned.
35102 The call was interrupted by the user.
35107 @value{GDBN} takes over the full task of calling the necessary host calls
35108 to perform the @code{system} call. The return value of @code{system} on
35109 the host is simplified before it's returned
35110 to the target. Any termination signal information from the child process
35111 is discarded, and the return value consists
35112 entirely of the exit status of the called command.
35114 Due to security concerns, the @code{system} call is by default refused
35115 by @value{GDBN}. The user has to allow this call explicitly with the
35116 @code{set remote system-call-allowed 1} command.
35119 @item set remote system-call-allowed
35120 @kindex set remote system-call-allowed
35121 Control whether to allow the @code{system} calls in the File I/O
35122 protocol for the remote target. The default is zero (disabled).
35124 @item show remote system-call-allowed
35125 @kindex show remote system-call-allowed
35126 Show whether the @code{system} calls are allowed in the File I/O
35130 @node Protocol-specific Representation of Datatypes
35131 @subsection Protocol-specific Representation of Datatypes
35132 @cindex protocol-specific representation of datatypes, in file-i/o protocol
35135 * Integral Datatypes::
35137 * Memory Transfer::
35142 @node Integral Datatypes
35143 @unnumberedsubsubsec Integral Datatypes
35144 @cindex integral datatypes, in file-i/o protocol
35146 The integral datatypes used in the system calls are @code{int},
35147 @code{unsigned int}, @code{long}, @code{unsigned long},
35148 @code{mode_t}, and @code{time_t}.
35150 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
35151 implemented as 32 bit values in this protocol.
35153 @code{long} and @code{unsigned long} are implemented as 64 bit types.
35155 @xref{Limits}, for corresponding MIN and MAX values (similar to those
35156 in @file{limits.h}) to allow range checking on host and target.
35158 @code{time_t} datatypes are defined as seconds since the Epoch.
35160 All integral datatypes transferred as part of a memory read or write of a
35161 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
35164 @node Pointer Values
35165 @unnumberedsubsubsec Pointer Values
35166 @cindex pointer values, in file-i/o protocol
35168 Pointers to target data are transmitted as they are. An exception
35169 is made for pointers to buffers for which the length isn't
35170 transmitted as part of the function call, namely strings. Strings
35171 are transmitted as a pointer/length pair, both as hex values, e.g.@:
35178 which is a pointer to data of length 18 bytes at position 0x1aaf.
35179 The length is defined as the full string length in bytes, including
35180 the trailing null byte. For example, the string @code{"hello world"}
35181 at address 0x123456 is transmitted as
35187 @node Memory Transfer
35188 @unnumberedsubsubsec Memory Transfer
35189 @cindex memory transfer, in file-i/o protocol
35191 Structured data which is transferred using a memory read or write (for
35192 example, a @code{struct stat}) is expected to be in a protocol-specific format
35193 with all scalar multibyte datatypes being big endian. Translation to
35194 this representation needs to be done both by the target before the @code{F}
35195 packet is sent, and by @value{GDBN} before
35196 it transfers memory to the target. Transferred pointers to structured
35197 data should point to the already-coerced data at any time.
35201 @unnumberedsubsubsec struct stat
35202 @cindex struct stat, in file-i/o protocol
35204 The buffer of type @code{struct stat} used by the target and @value{GDBN}
35205 is defined as follows:
35209 unsigned int st_dev; /* device */
35210 unsigned int st_ino; /* inode */
35211 mode_t st_mode; /* protection */
35212 unsigned int st_nlink; /* number of hard links */
35213 unsigned int st_uid; /* user ID of owner */
35214 unsigned int st_gid; /* group ID of owner */
35215 unsigned int st_rdev; /* device type (if inode device) */
35216 unsigned long st_size; /* total size, in bytes */
35217 unsigned long st_blksize; /* blocksize for filesystem I/O */
35218 unsigned long st_blocks; /* number of blocks allocated */
35219 time_t st_atime; /* time of last access */
35220 time_t st_mtime; /* time of last modification */
35221 time_t st_ctime; /* time of last change */
35225 The integral datatypes conform to the definitions given in the
35226 appropriate section (see @ref{Integral Datatypes}, for details) so this
35227 structure is of size 64 bytes.
35229 The values of several fields have a restricted meaning and/or
35235 A value of 0 represents a file, 1 the console.
35238 No valid meaning for the target. Transmitted unchanged.
35241 Valid mode bits are described in @ref{Constants}. Any other
35242 bits have currently no meaning for the target.
35247 No valid meaning for the target. Transmitted unchanged.
35252 These values have a host and file system dependent
35253 accuracy. Especially on Windows hosts, the file system may not
35254 support exact timing values.
35257 The target gets a @code{struct stat} of the above representation and is
35258 responsible for coercing it to the target representation before
35261 Note that due to size differences between the host, target, and protocol
35262 representations of @code{struct stat} members, these members could eventually
35263 get truncated on the target.
35265 @node struct timeval
35266 @unnumberedsubsubsec struct timeval
35267 @cindex struct timeval, in file-i/o protocol
35269 The buffer of type @code{struct timeval} used by the File-I/O protocol
35270 is defined as follows:
35274 time_t tv_sec; /* second */
35275 long tv_usec; /* microsecond */
35279 The integral datatypes conform to the definitions given in the
35280 appropriate section (see @ref{Integral Datatypes}, for details) so this
35281 structure is of size 8 bytes.
35284 @subsection Constants
35285 @cindex constants, in file-i/o protocol
35287 The following values are used for the constants inside of the
35288 protocol. @value{GDBN} and target are responsible for translating these
35289 values before and after the call as needed.
35300 @unnumberedsubsubsec Open Flags
35301 @cindex open flags, in file-i/o protocol
35303 All values are given in hexadecimal representation.
35315 @node mode_t Values
35316 @unnumberedsubsubsec mode_t Values
35317 @cindex mode_t values, in file-i/o protocol
35319 All values are given in octal representation.
35336 @unnumberedsubsubsec Errno Values
35337 @cindex errno values, in file-i/o protocol
35339 All values are given in decimal representation.
35364 @code{EUNKNOWN} is used as a fallback error value if a host system returns
35365 any error value not in the list of supported error numbers.
35368 @unnumberedsubsubsec Lseek Flags
35369 @cindex lseek flags, in file-i/o protocol
35378 @unnumberedsubsubsec Limits
35379 @cindex limits, in file-i/o protocol
35381 All values are given in decimal representation.
35384 INT_MIN -2147483648
35386 UINT_MAX 4294967295
35387 LONG_MIN -9223372036854775808
35388 LONG_MAX 9223372036854775807
35389 ULONG_MAX 18446744073709551615
35392 @node File-I/O Examples
35393 @subsection File-I/O Examples
35394 @cindex file-i/o examples
35396 Example sequence of a write call, file descriptor 3, buffer is at target
35397 address 0x1234, 6 bytes should be written:
35400 <- @code{Fwrite,3,1234,6}
35401 @emph{request memory read from target}
35404 @emph{return "6 bytes written"}
35408 Example sequence of a read call, file descriptor 3, buffer is at target
35409 address 0x1234, 6 bytes should be read:
35412 <- @code{Fread,3,1234,6}
35413 @emph{request memory write to target}
35414 -> @code{X1234,6:XXXXXX}
35415 @emph{return "6 bytes read"}
35419 Example sequence of a read call, call fails on the host due to invalid
35420 file descriptor (@code{EBADF}):
35423 <- @code{Fread,3,1234,6}
35427 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
35431 <- @code{Fread,3,1234,6}
35436 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
35440 <- @code{Fread,3,1234,6}
35441 -> @code{X1234,6:XXXXXX}
35445 @node Library List Format
35446 @section Library List Format
35447 @cindex library list format, remote protocol
35449 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
35450 same process as your application to manage libraries. In this case,
35451 @value{GDBN} can use the loader's symbol table and normal memory
35452 operations to maintain a list of shared libraries. On other
35453 platforms, the operating system manages loaded libraries.
35454 @value{GDBN} can not retrieve the list of currently loaded libraries
35455 through memory operations, so it uses the @samp{qXfer:libraries:read}
35456 packet (@pxref{qXfer library list read}) instead. The remote stub
35457 queries the target's operating system and reports which libraries
35460 The @samp{qXfer:libraries:read} packet returns an XML document which
35461 lists loaded libraries and their offsets. Each library has an
35462 associated name and one or more segment or section base addresses,
35463 which report where the library was loaded in memory.
35465 For the common case of libraries that are fully linked binaries, the
35466 library should have a list of segments. If the target supports
35467 dynamic linking of a relocatable object file, its library XML element
35468 should instead include a list of allocated sections. The segment or
35469 section bases are start addresses, not relocation offsets; they do not
35470 depend on the library's link-time base addresses.
35472 @value{GDBN} must be linked with the Expat library to support XML
35473 library lists. @xref{Expat}.
35475 A simple memory map, with one loaded library relocated by a single
35476 offset, looks like this:
35480 <library name="/lib/libc.so.6">
35481 <segment address="0x10000000"/>
35486 Another simple memory map, with one loaded library with three
35487 allocated sections (.text, .data, .bss), looks like this:
35491 <library name="sharedlib.o">
35492 <section address="0x10000000"/>
35493 <section address="0x20000000"/>
35494 <section address="0x30000000"/>
35499 The format of a library list is described by this DTD:
35502 <!-- library-list: Root element with versioning -->
35503 <!ELEMENT library-list (library)*>
35504 <!ATTLIST library-list version CDATA #FIXED "1.0">
35505 <!ELEMENT library (segment*, section*)>
35506 <!ATTLIST library name CDATA #REQUIRED>
35507 <!ELEMENT segment EMPTY>
35508 <!ATTLIST segment address CDATA #REQUIRED>
35509 <!ELEMENT section EMPTY>
35510 <!ATTLIST section address CDATA #REQUIRED>
35513 In addition, segments and section descriptors cannot be mixed within a
35514 single library element, and you must supply at least one segment or
35515 section for each library.
35517 @node Memory Map Format
35518 @section Memory Map Format
35519 @cindex memory map format
35521 To be able to write into flash memory, @value{GDBN} needs to obtain a
35522 memory map from the target. This section describes the format of the
35525 The memory map is obtained using the @samp{qXfer:memory-map:read}
35526 (@pxref{qXfer memory map read}) packet and is an XML document that
35527 lists memory regions.
35529 @value{GDBN} must be linked with the Expat library to support XML
35530 memory maps. @xref{Expat}.
35532 The top-level structure of the document is shown below:
35535 <?xml version="1.0"?>
35536 <!DOCTYPE memory-map
35537 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
35538 "http://sourceware.org/gdb/gdb-memory-map.dtd">
35544 Each region can be either:
35549 A region of RAM starting at @var{addr} and extending for @var{length}
35553 <memory type="ram" start="@var{addr}" length="@var{length}"/>
35558 A region of read-only memory:
35561 <memory type="rom" start="@var{addr}" length="@var{length}"/>
35566 A region of flash memory, with erasure blocks @var{blocksize}
35570 <memory type="flash" start="@var{addr}" length="@var{length}">
35571 <property name="blocksize">@var{blocksize}</property>
35577 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
35578 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
35579 packets to write to addresses in such ranges.
35581 The formal DTD for memory map format is given below:
35584 <!-- ................................................... -->
35585 <!-- Memory Map XML DTD ................................ -->
35586 <!-- File: memory-map.dtd .............................. -->
35587 <!-- .................................... .............. -->
35588 <!-- memory-map.dtd -->
35589 <!-- memory-map: Root element with versioning -->
35590 <!ELEMENT memory-map (memory | property)>
35591 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
35592 <!ELEMENT memory (property)>
35593 <!-- memory: Specifies a memory region,
35594 and its type, or device. -->
35595 <!ATTLIST memory type CDATA #REQUIRED
35596 start CDATA #REQUIRED
35597 length CDATA #REQUIRED
35598 device CDATA #IMPLIED>
35599 <!-- property: Generic attribute tag -->
35600 <!ELEMENT property (#PCDATA | property)*>
35601 <!ATTLIST property name CDATA #REQUIRED>
35604 @node Thread List Format
35605 @section Thread List Format
35606 @cindex thread list format
35608 To efficiently update the list of threads and their attributes,
35609 @value{GDBN} issues the @samp{qXfer:threads:read} packet
35610 (@pxref{qXfer threads read}) and obtains the XML document with
35611 the following structure:
35614 <?xml version="1.0"?>
35616 <thread id="id" core="0">
35617 ... description ...
35622 Each @samp{thread} element must have the @samp{id} attribute that
35623 identifies the thread (@pxref{thread-id syntax}). The
35624 @samp{core} attribute, if present, specifies which processor core
35625 the thread was last executing on. The content of the of @samp{thread}
35626 element is interpreted as human-readable auxilliary information.
35628 @include agentexpr.texi
35630 @node Trace File Format
35631 @appendix Trace File Format
35632 @cindex trace file format
35634 The trace file comes in three parts: a header, a textual description
35635 section, and a trace frame section with binary data.
35637 The header has the form @code{\x7fTRACE0\n}. The first byte is
35638 @code{0x7f} so as to indicate that the file contains binary data,
35639 while the @code{0} is a version number that may have different values
35642 The description section consists of multiple lines of @sc{ascii} text
35643 separated by newline characters (@code{0xa}). The lines may include a
35644 variety of optional descriptive or context-setting information, such
35645 as tracepoint definitions or register set size. @value{GDBN} will
35646 ignore any line that it does not recognize. An empty line marks the end
35649 @c FIXME add some specific types of data
35651 The trace frame section consists of a number of consecutive frames.
35652 Each frame begins with a two-byte tracepoint number, followed by a
35653 four-byte size giving the amount of data in the frame. The data in
35654 the frame consists of a number of blocks, each introduced by a
35655 character indicating its type (at least register, memory, and trace
35656 state variable). The data in this section is raw binary, not a
35657 hexadecimal or other encoding; its endianness matches the target's
35660 @c FIXME bi-arch may require endianness/arch info in description section
35663 @item R @var{bytes}
35664 Register block. The number and ordering of bytes matches that of a
35665 @code{g} packet in the remote protocol. Note that these are the
35666 actual bytes, in target order and @value{GDBN} register order, not a
35667 hexadecimal encoding.
35669 @item M @var{address} @var{length} @var{bytes}...
35670 Memory block. This is a contiguous block of memory, at the 8-byte
35671 address @var{address}, with a 2-byte length @var{length}, followed by
35672 @var{length} bytes.
35674 @item V @var{number} @var{value}
35675 Trace state variable block. This records the 8-byte signed value
35676 @var{value} of trace state variable numbered @var{number}.
35680 Future enhancements of the trace file format may include additional types
35683 @node Target Descriptions
35684 @appendix Target Descriptions
35685 @cindex target descriptions
35687 @strong{Warning:} target descriptions are still under active development,
35688 and the contents and format may change between @value{GDBN} releases.
35689 The format is expected to stabilize in the future.
35691 One of the challenges of using @value{GDBN} to debug embedded systems
35692 is that there are so many minor variants of each processor
35693 architecture in use. It is common practice for vendors to start with
35694 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
35695 and then make changes to adapt it to a particular market niche. Some
35696 architectures have hundreds of variants, available from dozens of
35697 vendors. This leads to a number of problems:
35701 With so many different customized processors, it is difficult for
35702 the @value{GDBN} maintainers to keep up with the changes.
35704 Since individual variants may have short lifetimes or limited
35705 audiences, it may not be worthwhile to carry information about every
35706 variant in the @value{GDBN} source tree.
35708 When @value{GDBN} does support the architecture of the embedded system
35709 at hand, the task of finding the correct architecture name to give the
35710 @command{set architecture} command can be error-prone.
35713 To address these problems, the @value{GDBN} remote protocol allows a
35714 target system to not only identify itself to @value{GDBN}, but to
35715 actually describe its own features. This lets @value{GDBN} support
35716 processor variants it has never seen before --- to the extent that the
35717 descriptions are accurate, and that @value{GDBN} understands them.
35719 @value{GDBN} must be linked with the Expat library to support XML
35720 target descriptions. @xref{Expat}.
35723 * Retrieving Descriptions:: How descriptions are fetched from a target.
35724 * Target Description Format:: The contents of a target description.
35725 * Predefined Target Types:: Standard types available for target
35727 * Standard Target Features:: Features @value{GDBN} knows about.
35730 @node Retrieving Descriptions
35731 @section Retrieving Descriptions
35733 Target descriptions can be read from the target automatically, or
35734 specified by the user manually. The default behavior is to read the
35735 description from the target. @value{GDBN} retrieves it via the remote
35736 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
35737 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
35738 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
35739 XML document, of the form described in @ref{Target Description
35742 Alternatively, you can specify a file to read for the target description.
35743 If a file is set, the target will not be queried. The commands to
35744 specify a file are:
35747 @cindex set tdesc filename
35748 @item set tdesc filename @var{path}
35749 Read the target description from @var{path}.
35751 @cindex unset tdesc filename
35752 @item unset tdesc filename
35753 Do not read the XML target description from a file. @value{GDBN}
35754 will use the description supplied by the current target.
35756 @cindex show tdesc filename
35757 @item show tdesc filename
35758 Show the filename to read for a target description, if any.
35762 @node Target Description Format
35763 @section Target Description Format
35764 @cindex target descriptions, XML format
35766 A target description annex is an @uref{http://www.w3.org/XML/, XML}
35767 document which complies with the Document Type Definition provided in
35768 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
35769 means you can use generally available tools like @command{xmllint} to
35770 check that your feature descriptions are well-formed and valid.
35771 However, to help people unfamiliar with XML write descriptions for
35772 their targets, we also describe the grammar here.
35774 Target descriptions can identify the architecture of the remote target
35775 and (for some architectures) provide information about custom register
35776 sets. They can also identify the OS ABI of the remote target.
35777 @value{GDBN} can use this information to autoconfigure for your
35778 target, or to warn you if you connect to an unsupported target.
35780 Here is a simple target description:
35783 <target version="1.0">
35784 <architecture>i386:x86-64</architecture>
35789 This minimal description only says that the target uses
35790 the x86-64 architecture.
35792 A target description has the following overall form, with [ ] marking
35793 optional elements and @dots{} marking repeatable elements. The elements
35794 are explained further below.
35797 <?xml version="1.0"?>
35798 <!DOCTYPE target SYSTEM "gdb-target.dtd">
35799 <target version="1.0">
35800 @r{[}@var{architecture}@r{]}
35801 @r{[}@var{osabi}@r{]}
35802 @r{[}@var{compatible}@r{]}
35803 @r{[}@var{feature}@dots{}@r{]}
35808 The description is generally insensitive to whitespace and line
35809 breaks, under the usual common-sense rules. The XML version
35810 declaration and document type declaration can generally be omitted
35811 (@value{GDBN} does not require them), but specifying them may be
35812 useful for XML validation tools. The @samp{version} attribute for
35813 @samp{<target>} may also be omitted, but we recommend
35814 including it; if future versions of @value{GDBN} use an incompatible
35815 revision of @file{gdb-target.dtd}, they will detect and report
35816 the version mismatch.
35818 @subsection Inclusion
35819 @cindex target descriptions, inclusion
35822 @cindex <xi:include>
35825 It can sometimes be valuable to split a target description up into
35826 several different annexes, either for organizational purposes, or to
35827 share files between different possible target descriptions. You can
35828 divide a description into multiple files by replacing any element of
35829 the target description with an inclusion directive of the form:
35832 <xi:include href="@var{document}"/>
35836 When @value{GDBN} encounters an element of this form, it will retrieve
35837 the named XML @var{document}, and replace the inclusion directive with
35838 the contents of that document. If the current description was read
35839 using @samp{qXfer}, then so will be the included document;
35840 @var{document} will be interpreted as the name of an annex. If the
35841 current description was read from a file, @value{GDBN} will look for
35842 @var{document} as a file in the same directory where it found the
35843 original description.
35845 @subsection Architecture
35846 @cindex <architecture>
35848 An @samp{<architecture>} element has this form:
35851 <architecture>@var{arch}</architecture>
35854 @var{arch} is one of the architectures from the set accepted by
35855 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
35858 @cindex @code{<osabi>}
35860 This optional field was introduced in @value{GDBN} version 7.0.
35861 Previous versions of @value{GDBN} ignore it.
35863 An @samp{<osabi>} element has this form:
35866 <osabi>@var{abi-name}</osabi>
35869 @var{abi-name} is an OS ABI name from the same selection accepted by
35870 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
35872 @subsection Compatible Architecture
35873 @cindex @code{<compatible>}
35875 This optional field was introduced in @value{GDBN} version 7.0.
35876 Previous versions of @value{GDBN} ignore it.
35878 A @samp{<compatible>} element has this form:
35881 <compatible>@var{arch}</compatible>
35884 @var{arch} is one of the architectures from the set accepted by
35885 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
35887 A @samp{<compatible>} element is used to specify that the target
35888 is able to run binaries in some other than the main target architecture
35889 given by the @samp{<architecture>} element. For example, on the
35890 Cell Broadband Engine, the main architecture is @code{powerpc:common}
35891 or @code{powerpc:common64}, but the system is able to run binaries
35892 in the @code{spu} architecture as well. The way to describe this
35893 capability with @samp{<compatible>} is as follows:
35896 <architecture>powerpc:common</architecture>
35897 <compatible>spu</compatible>
35900 @subsection Features
35903 Each @samp{<feature>} describes some logical portion of the target
35904 system. Features are currently used to describe available CPU
35905 registers and the types of their contents. A @samp{<feature>} element
35909 <feature name="@var{name}">
35910 @r{[}@var{type}@dots{}@r{]}
35916 Each feature's name should be unique within the description. The name
35917 of a feature does not matter unless @value{GDBN} has some special
35918 knowledge of the contents of that feature; if it does, the feature
35919 should have its standard name. @xref{Standard Target Features}.
35923 Any register's value is a collection of bits which @value{GDBN} must
35924 interpret. The default interpretation is a two's complement integer,
35925 but other types can be requested by name in the register description.
35926 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
35927 Target Types}), and the description can define additional composite types.
35929 Each type element must have an @samp{id} attribute, which gives
35930 a unique (within the containing @samp{<feature>}) name to the type.
35931 Types must be defined before they are used.
35934 Some targets offer vector registers, which can be treated as arrays
35935 of scalar elements. These types are written as @samp{<vector>} elements,
35936 specifying the array element type, @var{type}, and the number of elements,
35940 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
35944 If a register's value is usefully viewed in multiple ways, define it
35945 with a union type containing the useful representations. The
35946 @samp{<union>} element contains one or more @samp{<field>} elements,
35947 each of which has a @var{name} and a @var{type}:
35950 <union id="@var{id}">
35951 <field name="@var{name}" type="@var{type}"/>
35957 If a register's value is composed from several separate values, define
35958 it with a structure type. There are two forms of the @samp{<struct>}
35959 element; a @samp{<struct>} element must either contain only bitfields
35960 or contain no bitfields. If the structure contains only bitfields,
35961 its total size in bytes must be specified, each bitfield must have an
35962 explicit start and end, and bitfields are automatically assigned an
35963 integer type. The field's @var{start} should be less than or
35964 equal to its @var{end}, and zero represents the least significant bit.
35967 <struct id="@var{id}" size="@var{size}">
35968 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
35973 If the structure contains no bitfields, then each field has an
35974 explicit type, and no implicit padding is added.
35977 <struct id="@var{id}">
35978 <field name="@var{name}" type="@var{type}"/>
35984 If a register's value is a series of single-bit flags, define it with
35985 a flags type. The @samp{<flags>} element has an explicit @var{size}
35986 and contains one or more @samp{<field>} elements. Each field has a
35987 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
35991 <flags id="@var{id}" size="@var{size}">
35992 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
35997 @subsection Registers
36000 Each register is represented as an element with this form:
36003 <reg name="@var{name}"
36004 bitsize="@var{size}"
36005 @r{[}regnum="@var{num}"@r{]}
36006 @r{[}save-restore="@var{save-restore}"@r{]}
36007 @r{[}type="@var{type}"@r{]}
36008 @r{[}group="@var{group}"@r{]}/>
36012 The components are as follows:
36017 The register's name; it must be unique within the target description.
36020 The register's size, in bits.
36023 The register's number. If omitted, a register's number is one greater
36024 than that of the previous register (either in the current feature or in
36025 a preceeding feature); the first register in the target description
36026 defaults to zero. This register number is used to read or write
36027 the register; e.g.@: it is used in the remote @code{p} and @code{P}
36028 packets, and registers appear in the @code{g} and @code{G} packets
36029 in order of increasing register number.
36032 Whether the register should be preserved across inferior function
36033 calls; this must be either @code{yes} or @code{no}. The default is
36034 @code{yes}, which is appropriate for most registers except for
36035 some system control registers; this is not related to the target's
36039 The type of the register. @var{type} may be a predefined type, a type
36040 defined in the current feature, or one of the special types @code{int}
36041 and @code{float}. @code{int} is an integer type of the correct size
36042 for @var{bitsize}, and @code{float} is a floating point type (in the
36043 architecture's normal floating point format) of the correct size for
36044 @var{bitsize}. The default is @code{int}.
36047 The register group to which this register belongs. @var{group} must
36048 be either @code{general}, @code{float}, or @code{vector}. If no
36049 @var{group} is specified, @value{GDBN} will not display the register
36050 in @code{info registers}.
36054 @node Predefined Target Types
36055 @section Predefined Target Types
36056 @cindex target descriptions, predefined types
36058 Type definitions in the self-description can build up composite types
36059 from basic building blocks, but can not define fundamental types. Instead,
36060 standard identifiers are provided by @value{GDBN} for the fundamental
36061 types. The currently supported types are:
36070 Signed integer types holding the specified number of bits.
36077 Unsigned integer types holding the specified number of bits.
36081 Pointers to unspecified code and data. The program counter and
36082 any dedicated return address register may be marked as code
36083 pointers; printing a code pointer converts it into a symbolic
36084 address. The stack pointer and any dedicated address registers
36085 may be marked as data pointers.
36088 Single precision IEEE floating point.
36091 Double precision IEEE floating point.
36094 The 12-byte extended precision format used by ARM FPA registers.
36097 The 10-byte extended precision format used by x87 registers.
36100 32bit @sc{eflags} register used by x86.
36103 32bit @sc{mxcsr} register used by x86.
36107 @node Standard Target Features
36108 @section Standard Target Features
36109 @cindex target descriptions, standard features
36111 A target description must contain either no registers or all the
36112 target's registers. If the description contains no registers, then
36113 @value{GDBN} will assume a default register layout, selected based on
36114 the architecture. If the description contains any registers, the
36115 default layout will not be used; the standard registers must be
36116 described in the target description, in such a way that @value{GDBN}
36117 can recognize them.
36119 This is accomplished by giving specific names to feature elements
36120 which contain standard registers. @value{GDBN} will look for features
36121 with those names and verify that they contain the expected registers;
36122 if any known feature is missing required registers, or if any required
36123 feature is missing, @value{GDBN} will reject the target
36124 description. You can add additional registers to any of the
36125 standard features --- @value{GDBN} will display them just as if
36126 they were added to an unrecognized feature.
36128 This section lists the known features and their expected contents.
36129 Sample XML documents for these features are included in the
36130 @value{GDBN} source tree, in the directory @file{gdb/features}.
36132 Names recognized by @value{GDBN} should include the name of the
36133 company or organization which selected the name, and the overall
36134 architecture to which the feature applies; so e.g.@: the feature
36135 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
36137 The names of registers are not case sensitive for the purpose
36138 of recognizing standard features, but @value{GDBN} will only display
36139 registers using the capitalization used in the description.
36146 * PowerPC Features::
36151 @subsection ARM Features
36152 @cindex target descriptions, ARM features
36154 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
36156 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
36157 @samp{lr}, @samp{pc}, and @samp{cpsr}.
36159 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
36160 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
36161 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
36164 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
36165 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
36167 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
36168 it should contain at least registers @samp{wR0} through @samp{wR15} and
36169 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
36170 @samp{wCSSF}, and @samp{wCASF} registers are optional.
36172 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
36173 should contain at least registers @samp{d0} through @samp{d15}. If
36174 they are present, @samp{d16} through @samp{d31} should also be included.
36175 @value{GDBN} will synthesize the single-precision registers from
36176 halves of the double-precision registers.
36178 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
36179 need to contain registers; it instructs @value{GDBN} to display the
36180 VFP double-precision registers as vectors and to synthesize the
36181 quad-precision registers from pairs of double-precision registers.
36182 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
36183 be present and include 32 double-precision registers.
36185 @node i386 Features
36186 @subsection i386 Features
36187 @cindex target descriptions, i386 features
36189 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
36190 targets. It should describe the following registers:
36194 @samp{eax} through @samp{edi} plus @samp{eip} for i386
36196 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
36198 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
36199 @samp{fs}, @samp{gs}
36201 @samp{st0} through @samp{st7}
36203 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
36204 @samp{foseg}, @samp{fooff} and @samp{fop}
36207 The register sets may be different, depending on the target.
36209 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
36210 describe registers:
36214 @samp{xmm0} through @samp{xmm7} for i386
36216 @samp{xmm0} through @samp{xmm15} for amd64
36221 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
36222 @samp{org.gnu.gdb.i386.sse} feature. It should
36223 describe the upper 128 bits of @sc{ymm} registers:
36227 @samp{ymm0h} through @samp{ymm7h} for i386
36229 @samp{ymm0h} through @samp{ymm15h} for amd64
36232 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
36233 describe a single register, @samp{orig_eax}.
36235 @node MIPS Features
36236 @subsection MIPS Features
36237 @cindex target descriptions, MIPS features
36239 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
36240 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
36241 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
36244 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
36245 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
36246 registers. They may be 32-bit or 64-bit depending on the target.
36248 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
36249 it may be optional in a future version of @value{GDBN}. It should
36250 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
36251 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
36253 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
36254 contain a single register, @samp{restart}, which is used by the
36255 Linux kernel to control restartable syscalls.
36257 @node M68K Features
36258 @subsection M68K Features
36259 @cindex target descriptions, M68K features
36262 @item @samp{org.gnu.gdb.m68k.core}
36263 @itemx @samp{org.gnu.gdb.coldfire.core}
36264 @itemx @samp{org.gnu.gdb.fido.core}
36265 One of those features must be always present.
36266 The feature that is present determines which flavor of m68k is
36267 used. The feature that is present should contain registers
36268 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
36269 @samp{sp}, @samp{ps} and @samp{pc}.
36271 @item @samp{org.gnu.gdb.coldfire.fp}
36272 This feature is optional. If present, it should contain registers
36273 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
36277 @node PowerPC Features
36278 @subsection PowerPC Features
36279 @cindex target descriptions, PowerPC features
36281 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
36282 targets. It should contain registers @samp{r0} through @samp{r31},
36283 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
36284 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
36286 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
36287 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
36289 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
36290 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
36293 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
36294 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
36295 will combine these registers with the floating point registers
36296 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
36297 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
36298 through @samp{vs63}, the set of vector registers for POWER7.
36300 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
36301 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
36302 @samp{spefscr}. SPE targets should provide 32-bit registers in
36303 @samp{org.gnu.gdb.power.core} and provide the upper halves in
36304 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
36305 these to present registers @samp{ev0} through @samp{ev31} to the
36308 @node Operating System Information
36309 @appendix Operating System Information
36310 @cindex operating system information
36316 Users of @value{GDBN} often wish to obtain information about the state of
36317 the operating system running on the target---for example the list of
36318 processes, or the list of open files. This section describes the
36319 mechanism that makes it possible. This mechanism is similar to the
36320 target features mechanism (@pxref{Target Descriptions}), but focuses
36321 on a different aspect of target.
36323 Operating system information is retrived from the target via the
36324 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
36325 read}). The object name in the request should be @samp{osdata}, and
36326 the @var{annex} identifies the data to be fetched.
36329 @appendixsection Process list
36330 @cindex operating system information, process list
36332 When requesting the process list, the @var{annex} field in the
36333 @samp{qXfer} request should be @samp{processes}. The returned data is
36334 an XML document. The formal syntax of this document is defined in
36335 @file{gdb/features/osdata.dtd}.
36337 An example document is:
36340 <?xml version="1.0"?>
36341 <!DOCTYPE target SYSTEM "osdata.dtd">
36342 <osdata type="processes">
36344 <column name="pid">1</column>
36345 <column name="user">root</column>
36346 <column name="command">/sbin/init</column>
36347 <column name="cores">1,2,3</column>
36352 Each item should include a column whose name is @samp{pid}. The value
36353 of that column should identify the process on the target. The
36354 @samp{user} and @samp{command} columns are optional, and will be
36355 displayed by @value{GDBN}. The @samp{cores} column, if present,
36356 should contain a comma-separated list of cores that this process
36357 is running on. Target may provide additional columns,
36358 which @value{GDBN} currently ignores.
36362 @node GNU Free Documentation License
36363 @appendix GNU Free Documentation License
36372 % I think something like @colophon should be in texinfo. In the
36374 \long\def\colophon{\hbox to0pt{}\vfill
36375 \centerline{The body of this manual is set in}
36376 \centerline{\fontname\tenrm,}
36377 \centerline{with headings in {\bf\fontname\tenbf}}
36378 \centerline{and examples in {\tt\fontname\tentt}.}
36379 \centerline{{\it\fontname\tenit\/},}
36380 \centerline{{\bf\fontname\tenbf}, and}
36381 \centerline{{\sl\fontname\tensl\/}}
36382 \centerline{are used for emphasis.}\vfill}
36384 % Blame: doc@cygnus.com, 1991.