1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
3 @c 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
4 @c 2010, 2011 Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
26 @c readline appendices use @vindex, @findex and @ftable,
27 @c annotate.texi and gdbmi use @findex.
31 @c !!set GDB manual's edition---not the same as GDB version!
32 @c This is updated by GNU Press.
35 @c !!set GDB edit command default editor
38 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
40 @c This is a dir.info fragment to support semi-automated addition of
41 @c manuals to an info tree.
42 @dircategory Software development
44 * Gdb: (gdb). The GNU debugger.
48 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
49 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
50 Free Software Foundation, Inc.
52 Permission is granted to copy, distribute and/or modify this document
53 under the terms of the GNU Free Documentation License, Version 1.3 or
54 any later version published by the Free Software Foundation; with the
55 Invariant Sections being ``Free Software'' and ``Free Software Needs
56 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
57 and with the Back-Cover Texts as in (a) below.
59 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
60 this GNU Manual. Buying copies from GNU Press supports the FSF in
61 developing GNU and promoting software freedom.''
65 This file documents the @sc{gnu} debugger @value{GDBN}.
67 This is the @value{EDITION} Edition, of @cite{Debugging with
68 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
69 @ifset VERSION_PACKAGE
70 @value{VERSION_PACKAGE}
72 Version @value{GDBVN}.
78 @title Debugging with @value{GDBN}
79 @subtitle The @sc{gnu} Source-Level Debugger
81 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
82 @ifset VERSION_PACKAGE
84 @subtitle @value{VERSION_PACKAGE}
86 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
90 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
91 \hfill {\it Debugging with @value{GDBN}}\par
92 \hfill \TeX{}info \texinfoversion\par
96 @vskip 0pt plus 1filll
97 Published by the Free Software Foundation @*
98 51 Franklin Street, Fifth Floor,
99 Boston, MA 02110-1301, USA@*
100 ISBN 1-882114-77-9 @*
104 This edition of the GDB manual is dedicated to the memory of Fred
105 Fish. Fred was a long-standing contributor to GDB and to Free
106 software in general. We will miss him.
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2010 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
164 * GDB Bugs:: Reporting bugs in @value{GDBN}
166 @ifset SYSTEM_READLINE
167 * Command Line Editing: (rluserman). Command Line Editing
168 * Using History Interactively: (history). Using History Interactively
170 @ifclear SYSTEM_READLINE
171 * Command Line Editing:: Command Line Editing
172 * Using History Interactively:: Using History Interactively
174 * Formatting Documentation:: How to format and print @value{GDBN} documentation
175 * Installing GDB:: Installing GDB
176 * Maintenance Commands:: Maintenance Commands
177 * Remote Protocol:: GDB Remote Serial Protocol
178 * Agent Expressions:: The GDB Agent Expression Mechanism
179 * Target Descriptions:: How targets can describe themselves to
181 * Operating System Information:: Getting additional information from
183 * Trace File Format:: GDB trace file format
184 * 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.
1114 @item -data-directory @var{directory}
1115 @cindex @code{--data-directory}
1116 Run @value{GDBN} using @var{directory} as its data directory.
1117 The data directory is where @value{GDBN} searches for its
1118 auxiliary files. @xref{Data Files}.
1122 @cindex @code{--fullname}
1124 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1125 subprocess. It tells @value{GDBN} to output the full file name and line
1126 number in a standard, recognizable fashion each time a stack frame is
1127 displayed (which includes each time your program stops). This
1128 recognizable format looks like two @samp{\032} characters, followed by
1129 the file name, line number and character position separated by colons,
1130 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1131 @samp{\032} characters as a signal to display the source code for the
1135 @cindex @code{--epoch}
1136 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1137 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1138 routines so as to allow Epoch to display values of expressions in a
1141 @item -annotate @var{level}
1142 @cindex @code{--annotate}
1143 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1144 effect is identical to using @samp{set annotate @var{level}}
1145 (@pxref{Annotations}). The annotation @var{level} controls how much
1146 information @value{GDBN} prints together with its prompt, values of
1147 expressions, source lines, and other types of output. Level 0 is the
1148 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1149 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1150 that control @value{GDBN}, and level 2 has been deprecated.
1152 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1156 @cindex @code{--args}
1157 Change interpretation of command line so that arguments following the
1158 executable file are passed as command line arguments to the inferior.
1159 This option stops option processing.
1161 @item -baud @var{bps}
1163 @cindex @code{--baud}
1165 Set the line speed (baud rate or bits per second) of any serial
1166 interface used by @value{GDBN} for remote debugging.
1168 @item -l @var{timeout}
1170 Set the timeout (in seconds) of any communication used by @value{GDBN}
1171 for remote debugging.
1173 @item -tty @var{device}
1174 @itemx -t @var{device}
1175 @cindex @code{--tty}
1177 Run using @var{device} for your program's standard input and output.
1178 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1180 @c resolve the situation of these eventually
1182 @cindex @code{--tui}
1183 Activate the @dfn{Text User Interface} when starting. The Text User
1184 Interface manages several text windows on the terminal, showing
1185 source, assembly, registers and @value{GDBN} command outputs
1186 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1187 Text User Interface can be enabled by invoking the program
1188 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1189 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1192 @c @cindex @code{--xdb}
1193 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1194 @c For information, see the file @file{xdb_trans.html}, which is usually
1195 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1198 @item -interpreter @var{interp}
1199 @cindex @code{--interpreter}
1200 Use the interpreter @var{interp} for interface with the controlling
1201 program or device. This option is meant to be set by programs which
1202 communicate with @value{GDBN} using it as a back end.
1203 @xref{Interpreters, , Command Interpreters}.
1205 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1206 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1207 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1208 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1209 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1210 @sc{gdb/mi} interfaces are no longer supported.
1213 @cindex @code{--write}
1214 Open the executable and core files for both reading and writing. This
1215 is equivalent to the @samp{set write on} command inside @value{GDBN}
1219 @cindex @code{--statistics}
1220 This option causes @value{GDBN} to print statistics about time and
1221 memory usage after it completes each command and returns to the prompt.
1224 @cindex @code{--version}
1225 This option causes @value{GDBN} to print its version number and
1226 no-warranty blurb, and exit.
1231 @subsection What @value{GDBN} Does During Startup
1232 @cindex @value{GDBN} startup
1234 Here's the description of what @value{GDBN} does during session startup:
1238 Sets up the command interpreter as specified by the command line
1239 (@pxref{Mode Options, interpreter}).
1243 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1244 used when building @value{GDBN}; @pxref{System-wide configuration,
1245 ,System-wide configuration and settings}) and executes all the commands in
1249 Reads the init file (if any) in your home directory@footnote{On
1250 DOS/Windows systems, the home directory is the one pointed to by the
1251 @code{HOME} environment variable.} and executes all the commands in
1255 Processes command line options and operands.
1258 Reads and executes the commands from init file (if any) in the current
1259 working directory. This is only done if the current directory is
1260 different from your home directory. Thus, you can have more than one
1261 init file, one generic in your home directory, and another, specific
1262 to the program you are debugging, in the directory where you invoke
1266 If the command line specified a program to debug, or a process to
1267 attach to, or a core file, @value{GDBN} loads any auto-loaded
1268 scripts provided for the program or for its loaded shared libraries.
1269 @xref{Auto-loading}.
1271 If you wish to disable the auto-loading during startup,
1272 you must do something like the following:
1275 $ gdb -ex "set auto-load-scripts off" -ex "file myprogram"
1278 The following does not work because the auto-loading is turned off too late:
1281 $ gdb -ex "set auto-load-scripts off" myprogram
1285 Reads command files specified by the @samp{-x} option. @xref{Command
1286 Files}, for more details about @value{GDBN} command files.
1289 Reads the command history recorded in the @dfn{history file}.
1290 @xref{Command History}, for more details about the command history and the
1291 files where @value{GDBN} records it.
1294 Init files use the same syntax as @dfn{command files} (@pxref{Command
1295 Files}) and are processed by @value{GDBN} in the same way. The init
1296 file in your home directory can set options (such as @samp{set
1297 complaints}) that affect subsequent processing of command line options
1298 and operands. Init files are not executed if you use the @samp{-nx}
1299 option (@pxref{Mode Options, ,Choosing Modes}).
1301 To display the list of init files loaded by gdb at startup, you
1302 can use @kbd{gdb --help}.
1304 @cindex init file name
1305 @cindex @file{.gdbinit}
1306 @cindex @file{gdb.ini}
1307 The @value{GDBN} init files are normally called @file{.gdbinit}.
1308 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1309 the limitations of file names imposed by DOS filesystems. The Windows
1310 ports of @value{GDBN} use the standard name, but if they find a
1311 @file{gdb.ini} file, they warn you about that and suggest to rename
1312 the file to the standard name.
1316 @section Quitting @value{GDBN}
1317 @cindex exiting @value{GDBN}
1318 @cindex leaving @value{GDBN}
1321 @kindex quit @r{[}@var{expression}@r{]}
1322 @kindex q @r{(@code{quit})}
1323 @item quit @r{[}@var{expression}@r{]}
1325 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1326 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1327 do not supply @var{expression}, @value{GDBN} will terminate normally;
1328 otherwise it will terminate using the result of @var{expression} as the
1333 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1334 terminates the action of any @value{GDBN} command that is in progress and
1335 returns to @value{GDBN} command level. It is safe to type the interrupt
1336 character at any time because @value{GDBN} does not allow it to take effect
1337 until a time when it is safe.
1339 If you have been using @value{GDBN} to control an attached process or
1340 device, you can release it with the @code{detach} command
1341 (@pxref{Attach, ,Debugging an Already-running Process}).
1343 @node Shell Commands
1344 @section Shell Commands
1346 If you need to execute occasional shell commands during your
1347 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1348 just use the @code{shell} command.
1352 @cindex shell escape
1353 @item shell @var{command string}
1354 Invoke a standard shell to execute @var{command string}.
1355 If it exists, the environment variable @code{SHELL} determines which
1356 shell to run. Otherwise @value{GDBN} uses the default shell
1357 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1360 The utility @code{make} is often needed in development environments.
1361 You do not have to use the @code{shell} command for this purpose in
1366 @cindex calling make
1367 @item make @var{make-args}
1368 Execute the @code{make} program with the specified
1369 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1372 @node Logging Output
1373 @section Logging Output
1374 @cindex logging @value{GDBN} output
1375 @cindex save @value{GDBN} output to a file
1377 You may want to save the output of @value{GDBN} commands to a file.
1378 There are several commands to control @value{GDBN}'s logging.
1382 @item set logging on
1384 @item set logging off
1386 @cindex logging file name
1387 @item set logging file @var{file}
1388 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1389 @item set logging overwrite [on|off]
1390 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1391 you want @code{set logging on} to overwrite the logfile instead.
1392 @item set logging redirect [on|off]
1393 By default, @value{GDBN} output will go to both the terminal and the logfile.
1394 Set @code{redirect} if you want output to go only to the log file.
1395 @kindex show logging
1397 Show the current values of the logging settings.
1401 @chapter @value{GDBN} Commands
1403 You can abbreviate a @value{GDBN} command to the first few letters of the command
1404 name, if that abbreviation is unambiguous; and you can repeat certain
1405 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1406 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1407 show you the alternatives available, if there is more than one possibility).
1410 * Command Syntax:: How to give commands to @value{GDBN}
1411 * Completion:: Command completion
1412 * Help:: How to ask @value{GDBN} for help
1415 @node Command Syntax
1416 @section Command Syntax
1418 A @value{GDBN} command is a single line of input. There is no limit on
1419 how long it can be. It starts with a command name, which is followed by
1420 arguments whose meaning depends on the command name. For example, the
1421 command @code{step} accepts an argument which is the number of times to
1422 step, as in @samp{step 5}. You can also use the @code{step} command
1423 with no arguments. Some commands do not allow any arguments.
1425 @cindex abbreviation
1426 @value{GDBN} command names may always be truncated if that abbreviation is
1427 unambiguous. Other possible command abbreviations are listed in the
1428 documentation for individual commands. In some cases, even ambiguous
1429 abbreviations are allowed; for example, @code{s} is specially defined as
1430 equivalent to @code{step} even though there are other commands whose
1431 names start with @code{s}. You can test abbreviations by using them as
1432 arguments to the @code{help} command.
1434 @cindex repeating commands
1435 @kindex RET @r{(repeat last command)}
1436 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1437 repeat the previous command. Certain commands (for example, @code{run})
1438 will not repeat this way; these are commands whose unintentional
1439 repetition might cause trouble and which you are unlikely to want to
1440 repeat. User-defined commands can disable this feature; see
1441 @ref{Define, dont-repeat}.
1443 The @code{list} and @code{x} commands, when you repeat them with
1444 @key{RET}, construct new arguments rather than repeating
1445 exactly as typed. This permits easy scanning of source or memory.
1447 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1448 output, in a way similar to the common utility @code{more}
1449 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1450 @key{RET} too many in this situation, @value{GDBN} disables command
1451 repetition after any command that generates this sort of display.
1453 @kindex # @r{(a comment)}
1455 Any text from a @kbd{#} to the end of the line is a comment; it does
1456 nothing. This is useful mainly in command files (@pxref{Command
1457 Files,,Command Files}).
1459 @cindex repeating command sequences
1460 @kindex Ctrl-o @r{(operate-and-get-next)}
1461 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1462 commands. This command accepts the current line, like @key{RET}, and
1463 then fetches the next line relative to the current line from the history
1467 @section Command Completion
1470 @cindex word completion
1471 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1472 only one possibility; it can also show you what the valid possibilities
1473 are for the next word in a command, at any time. This works for @value{GDBN}
1474 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1476 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1477 of a word. If there is only one possibility, @value{GDBN} fills in the
1478 word, and waits for you to finish the command (or press @key{RET} to
1479 enter it). For example, if you type
1481 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1482 @c complete accuracy in these examples; space introduced for clarity.
1483 @c If texinfo enhancements make it unnecessary, it would be nice to
1484 @c replace " @key" by "@key" in the following...
1486 (@value{GDBP}) info bre @key{TAB}
1490 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1491 the only @code{info} subcommand beginning with @samp{bre}:
1494 (@value{GDBP}) info breakpoints
1498 You can either press @key{RET} at this point, to run the @code{info
1499 breakpoints} command, or backspace and enter something else, if
1500 @samp{breakpoints} does not look like the command you expected. (If you
1501 were sure you wanted @code{info breakpoints} in the first place, you
1502 might as well just type @key{RET} immediately after @samp{info bre},
1503 to exploit command abbreviations rather than command completion).
1505 If there is more than one possibility for the next word when you press
1506 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1507 characters and try again, or just press @key{TAB} a second time;
1508 @value{GDBN} displays all the possible completions for that word. For
1509 example, you might want to set a breakpoint on a subroutine whose name
1510 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1511 just sounds the bell. Typing @key{TAB} again displays all the
1512 function names in your program that begin with those characters, for
1516 (@value{GDBP}) b make_ @key{TAB}
1517 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1518 make_a_section_from_file make_environ
1519 make_abs_section make_function_type
1520 make_blockvector make_pointer_type
1521 make_cleanup make_reference_type
1522 make_command make_symbol_completion_list
1523 (@value{GDBP}) b make_
1527 After displaying the available possibilities, @value{GDBN} copies your
1528 partial input (@samp{b make_} in the example) so you can finish the
1531 If you just want to see the list of alternatives in the first place, you
1532 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1533 means @kbd{@key{META} ?}. You can type this either by holding down a
1534 key designated as the @key{META} shift on your keyboard (if there is
1535 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1537 @cindex quotes in commands
1538 @cindex completion of quoted strings
1539 Sometimes the string you need, while logically a ``word'', may contain
1540 parentheses or other characters that @value{GDBN} normally excludes from
1541 its notion of a word. To permit word completion to work in this
1542 situation, you may enclose words in @code{'} (single quote marks) in
1543 @value{GDBN} commands.
1545 The most likely situation where you might need this is in typing the
1546 name of a C@t{++} function. This is because C@t{++} allows function
1547 overloading (multiple definitions of the same function, distinguished
1548 by argument type). For example, when you want to set a breakpoint you
1549 may need to distinguish whether you mean the version of @code{name}
1550 that takes an @code{int} parameter, @code{name(int)}, or the version
1551 that takes a @code{float} parameter, @code{name(float)}. To use the
1552 word-completion facilities in this situation, type a single quote
1553 @code{'} at the beginning of the function name. This alerts
1554 @value{GDBN} that it may need to consider more information than usual
1555 when you press @key{TAB} or @kbd{M-?} to request word completion:
1558 (@value{GDBP}) b 'bubble( @kbd{M-?}
1559 bubble(double,double) bubble(int,int)
1560 (@value{GDBP}) b 'bubble(
1563 In some cases, @value{GDBN} can tell that completing a name requires using
1564 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1565 completing as much as it can) if you do not type the quote in the first
1569 (@value{GDBP}) b bub @key{TAB}
1570 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1571 (@value{GDBP}) b 'bubble(
1575 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1576 you have not yet started typing the argument list when you ask for
1577 completion on an overloaded symbol.
1579 For more information about overloaded functions, see @ref{C Plus Plus
1580 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1581 overload-resolution off} to disable overload resolution;
1582 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1584 @cindex completion of structure field names
1585 @cindex structure field name completion
1586 @cindex completion of union field names
1587 @cindex union field name completion
1588 When completing in an expression which looks up a field in a
1589 structure, @value{GDBN} also tries@footnote{The completer can be
1590 confused by certain kinds of invalid expressions. Also, it only
1591 examines the static type of the expression, not the dynamic type.} to
1592 limit completions to the field names available in the type of the
1596 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1597 magic to_delete to_fputs to_put to_rewind
1598 to_data to_flush to_isatty to_read to_write
1602 This is because the @code{gdb_stdout} is a variable of the type
1603 @code{struct ui_file} that is defined in @value{GDBN} sources as
1610 ui_file_flush_ftype *to_flush;
1611 ui_file_write_ftype *to_write;
1612 ui_file_fputs_ftype *to_fputs;
1613 ui_file_read_ftype *to_read;
1614 ui_file_delete_ftype *to_delete;
1615 ui_file_isatty_ftype *to_isatty;
1616 ui_file_rewind_ftype *to_rewind;
1617 ui_file_put_ftype *to_put;
1624 @section Getting Help
1625 @cindex online documentation
1628 You can always ask @value{GDBN} itself for information on its commands,
1629 using the command @code{help}.
1632 @kindex h @r{(@code{help})}
1635 You can use @code{help} (abbreviated @code{h}) with no arguments to
1636 display a short list of named classes of commands:
1640 List of classes of commands:
1642 aliases -- Aliases of other commands
1643 breakpoints -- Making program stop at certain points
1644 data -- Examining data
1645 files -- Specifying and examining files
1646 internals -- Maintenance commands
1647 obscure -- Obscure features
1648 running -- Running the program
1649 stack -- Examining the stack
1650 status -- Status inquiries
1651 support -- Support facilities
1652 tracepoints -- Tracing of program execution without
1653 stopping the program
1654 user-defined -- User-defined commands
1656 Type "help" followed by a class name for a list of
1657 commands in that class.
1658 Type "help" followed by command name for full
1660 Command name abbreviations are allowed if unambiguous.
1663 @c the above line break eliminates huge line overfull...
1665 @item help @var{class}
1666 Using one of the general help classes as an argument, you can get a
1667 list of the individual commands in that class. For example, here is the
1668 help display for the class @code{status}:
1671 (@value{GDBP}) help status
1676 @c Line break in "show" line falsifies real output, but needed
1677 @c to fit in smallbook page size.
1678 info -- Generic command for showing things
1679 about the program being debugged
1680 show -- Generic command for showing things
1683 Type "help" followed by command name for full
1685 Command name abbreviations are allowed if unambiguous.
1689 @item help @var{command}
1690 With a command name as @code{help} argument, @value{GDBN} displays a
1691 short paragraph on how to use that command.
1694 @item apropos @var{args}
1695 The @code{apropos} command searches through all of the @value{GDBN}
1696 commands, and their documentation, for the regular expression specified in
1697 @var{args}. It prints out all matches found. For example:
1708 set symbol-reloading -- Set dynamic symbol table reloading
1709 multiple times in one run
1710 show symbol-reloading -- Show dynamic symbol table reloading
1711 multiple times in one run
1716 @item complete @var{args}
1717 The @code{complete @var{args}} command lists all the possible completions
1718 for the beginning of a command. Use @var{args} to specify the beginning of the
1719 command you want completed. For example:
1725 @noindent results in:
1736 @noindent This is intended for use by @sc{gnu} Emacs.
1739 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1740 and @code{show} to inquire about the state of your program, or the state
1741 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1742 manual introduces each of them in the appropriate context. The listings
1743 under @code{info} and under @code{show} in the Index point to
1744 all the sub-commands. @xref{Index}.
1749 @kindex i @r{(@code{info})}
1751 This command (abbreviated @code{i}) is for describing the state of your
1752 program. For example, you can show the arguments passed to a function
1753 with @code{info args}, list the registers currently in use with @code{info
1754 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1755 You can get a complete list of the @code{info} sub-commands with
1756 @w{@code{help info}}.
1760 You can assign the result of an expression to an environment variable with
1761 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1762 @code{set prompt $}.
1766 In contrast to @code{info}, @code{show} is for describing the state of
1767 @value{GDBN} itself.
1768 You can change most of the things you can @code{show}, by using the
1769 related command @code{set}; for example, you can control what number
1770 system is used for displays with @code{set radix}, or simply inquire
1771 which is currently in use with @code{show radix}.
1774 To display all the settable parameters and their current
1775 values, you can use @code{show} with no arguments; you may also use
1776 @code{info set}. Both commands produce the same display.
1777 @c FIXME: "info set" violates the rule that "info" is for state of
1778 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1779 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1783 Here are three miscellaneous @code{show} subcommands, all of which are
1784 exceptional in lacking corresponding @code{set} commands:
1787 @kindex show version
1788 @cindex @value{GDBN} version number
1790 Show what version of @value{GDBN} is running. You should include this
1791 information in @value{GDBN} bug-reports. If multiple versions of
1792 @value{GDBN} are in use at your site, you may need to determine which
1793 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1794 commands are introduced, and old ones may wither away. Also, many
1795 system vendors ship variant versions of @value{GDBN}, and there are
1796 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1797 The version number is the same as the one announced when you start
1800 @kindex show copying
1801 @kindex info copying
1802 @cindex display @value{GDBN} copyright
1805 Display information about permission for copying @value{GDBN}.
1807 @kindex show warranty
1808 @kindex info warranty
1810 @itemx info warranty
1811 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1812 if your version of @value{GDBN} comes with one.
1817 @chapter Running Programs Under @value{GDBN}
1819 When you run a program under @value{GDBN}, you must first generate
1820 debugging information when you compile it.
1822 You may start @value{GDBN} with its arguments, if any, in an environment
1823 of your choice. If you are doing native debugging, you may redirect
1824 your program's input and output, debug an already running process, or
1825 kill a child process.
1828 * Compilation:: Compiling for debugging
1829 * Starting:: Starting your program
1830 * Arguments:: Your program's arguments
1831 * Environment:: Your program's environment
1833 * Working Directory:: Your program's working directory
1834 * Input/Output:: Your program's input and output
1835 * Attach:: Debugging an already-running process
1836 * Kill Process:: Killing the child process
1838 * Inferiors and Programs:: Debugging multiple inferiors and programs
1839 * Threads:: Debugging programs with multiple threads
1840 * Forks:: Debugging forks
1841 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1845 @section Compiling for Debugging
1847 In order to debug a program effectively, you need to generate
1848 debugging information when you compile it. This debugging information
1849 is stored in the object file; it describes the data type of each
1850 variable or function and the correspondence between source line numbers
1851 and addresses in the executable code.
1853 To request debugging information, specify the @samp{-g} option when you run
1856 Programs that are to be shipped to your customers are compiled with
1857 optimizations, using the @samp{-O} compiler option. However, some
1858 compilers are unable to handle the @samp{-g} and @samp{-O} options
1859 together. Using those compilers, you cannot generate optimized
1860 executables containing debugging information.
1862 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1863 without @samp{-O}, making it possible to debug optimized code. We
1864 recommend that you @emph{always} use @samp{-g} whenever you compile a
1865 program. You may think your program is correct, but there is no sense
1866 in pushing your luck. For more information, see @ref{Optimized Code}.
1868 Older versions of the @sc{gnu} C compiler permitted a variant option
1869 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1870 format; if your @sc{gnu} C compiler has this option, do not use it.
1872 @value{GDBN} knows about preprocessor macros and can show you their
1873 expansion (@pxref{Macros}). Most compilers do not include information
1874 about preprocessor macros in the debugging information if you specify
1875 the @option{-g} flag alone, because this information is rather large.
1876 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1877 provides macro information if you specify the options
1878 @option{-gdwarf-2} and @option{-g3}; the former option requests
1879 debugging information in the Dwarf 2 format, and the latter requests
1880 ``extra information''. In the future, we hope to find more compact
1881 ways to represent macro information, so that it can be included with
1886 @section Starting your Program
1892 @kindex r @r{(@code{run})}
1895 Use the @code{run} command to start your program under @value{GDBN}.
1896 You must first specify the program name (except on VxWorks) with an
1897 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1898 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1899 (@pxref{Files, ,Commands to Specify Files}).
1903 If you are running your program in an execution environment that
1904 supports processes, @code{run} creates an inferior process and makes
1905 that process run your program. In some environments without processes,
1906 @code{run} jumps to the start of your program. Other targets,
1907 like @samp{remote}, are always running. If you get an error
1908 message like this one:
1911 The "remote" target does not support "run".
1912 Try "help target" or "continue".
1916 then use @code{continue} to run your program. You may need @code{load}
1917 first (@pxref{load}).
1919 The execution of a program is affected by certain information it
1920 receives from its superior. @value{GDBN} provides ways to specify this
1921 information, which you must do @emph{before} starting your program. (You
1922 can change it after starting your program, but such changes only affect
1923 your program the next time you start it.) This information may be
1924 divided into four categories:
1927 @item The @emph{arguments.}
1928 Specify the arguments to give your program as the arguments of the
1929 @code{run} command. If a shell is available on your target, the shell
1930 is used to pass the arguments, so that you may use normal conventions
1931 (such as wildcard expansion or variable substitution) in describing
1933 In Unix systems, you can control which shell is used with the
1934 @code{SHELL} environment variable.
1935 @xref{Arguments, ,Your Program's Arguments}.
1937 @item The @emph{environment.}
1938 Your program normally inherits its environment from @value{GDBN}, but you can
1939 use the @value{GDBN} commands @code{set environment} and @code{unset
1940 environment} to change parts of the environment that affect
1941 your program. @xref{Environment, ,Your Program's Environment}.
1943 @item The @emph{working directory.}
1944 Your program inherits its working directory from @value{GDBN}. You can set
1945 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1946 @xref{Working Directory, ,Your Program's Working Directory}.
1948 @item The @emph{standard input and output.}
1949 Your program normally uses the same device for standard input and
1950 standard output as @value{GDBN} is using. You can redirect input and output
1951 in the @code{run} command line, or you can use the @code{tty} command to
1952 set a different device for your program.
1953 @xref{Input/Output, ,Your Program's Input and Output}.
1956 @emph{Warning:} While input and output redirection work, you cannot use
1957 pipes to pass the output of the program you are debugging to another
1958 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1962 When you issue the @code{run} command, your program begins to execute
1963 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1964 of how to arrange for your program to stop. Once your program has
1965 stopped, you may call functions in your program, using the @code{print}
1966 or @code{call} commands. @xref{Data, ,Examining Data}.
1968 If the modification time of your symbol file has changed since the last
1969 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1970 table, and reads it again. When it does this, @value{GDBN} tries to retain
1971 your current breakpoints.
1976 @cindex run to main procedure
1977 The name of the main procedure can vary from language to language.
1978 With C or C@t{++}, the main procedure name is always @code{main}, but
1979 other languages such as Ada do not require a specific name for their
1980 main procedure. The debugger provides a convenient way to start the
1981 execution of the program and to stop at the beginning of the main
1982 procedure, depending on the language used.
1984 The @samp{start} command does the equivalent of setting a temporary
1985 breakpoint at the beginning of the main procedure and then invoking
1986 the @samp{run} command.
1988 @cindex elaboration phase
1989 Some programs contain an @dfn{elaboration} phase where some startup code is
1990 executed before the main procedure is called. This depends on the
1991 languages used to write your program. In C@t{++}, for instance,
1992 constructors for static and global objects are executed before
1993 @code{main} is called. It is therefore possible that the debugger stops
1994 before reaching the main procedure. However, the temporary breakpoint
1995 will remain to halt execution.
1997 Specify the arguments to give to your program as arguments to the
1998 @samp{start} command. These arguments will be given verbatim to the
1999 underlying @samp{run} command. Note that the same arguments will be
2000 reused if no argument is provided during subsequent calls to
2001 @samp{start} or @samp{run}.
2003 It is sometimes necessary to debug the program during elaboration. In
2004 these cases, using the @code{start} command would stop the execution of
2005 your program too late, as the program would have already completed the
2006 elaboration phase. Under these circumstances, insert breakpoints in your
2007 elaboration code before running your program.
2009 @kindex set exec-wrapper
2010 @item set exec-wrapper @var{wrapper}
2011 @itemx show exec-wrapper
2012 @itemx unset exec-wrapper
2013 When @samp{exec-wrapper} is set, the specified wrapper is used to
2014 launch programs for debugging. @value{GDBN} starts your program
2015 with a shell command of the form @kbd{exec @var{wrapper}
2016 @var{program}}. Quoting is added to @var{program} and its
2017 arguments, but not to @var{wrapper}, so you should add quotes if
2018 appropriate for your shell. The wrapper runs until it executes
2019 your program, and then @value{GDBN} takes control.
2021 You can use any program that eventually calls @code{execve} with
2022 its arguments as a wrapper. Several standard Unix utilities do
2023 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2024 with @code{exec "$@@"} will also work.
2026 For example, you can use @code{env} to pass an environment variable to
2027 the debugged program, without setting the variable in your shell's
2031 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2035 This command is available when debugging locally on most targets, excluding
2036 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2038 @kindex set disable-randomization
2039 @item set disable-randomization
2040 @itemx set disable-randomization on
2041 This option (enabled by default in @value{GDBN}) will turn off the native
2042 randomization of the virtual address space of the started program. This option
2043 is useful for multiple debugging sessions to make the execution better
2044 reproducible and memory addresses reusable across debugging sessions.
2046 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2050 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2053 @item set disable-randomization off
2054 Leave the behavior of the started executable unchanged. Some bugs rear their
2055 ugly heads only when the program is loaded at certain addresses. If your bug
2056 disappears when you run the program under @value{GDBN}, that might be because
2057 @value{GDBN} by default disables the address randomization on platforms, such
2058 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2059 disable-randomization off} to try to reproduce such elusive bugs.
2061 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2062 It protects the programs against some kinds of security attacks. In these
2063 cases the attacker needs to know the exact location of a concrete executable
2064 code. Randomizing its location makes it impossible to inject jumps misusing
2065 a code at its expected addresses.
2067 Prelinking shared libraries provides a startup performance advantage but it
2068 makes addresses in these libraries predictable for privileged processes by
2069 having just unprivileged access at the target system. Reading the shared
2070 library binary gives enough information for assembling the malicious code
2071 misusing it. Still even a prelinked shared library can get loaded at a new
2072 random address just requiring the regular relocation process during the
2073 startup. Shared libraries not already prelinked are always loaded at
2074 a randomly chosen address.
2076 Position independent executables (PIE) contain position independent code
2077 similar to the shared libraries and therefore such executables get loaded at
2078 a randomly chosen address upon startup. PIE executables always load even
2079 already prelinked shared libraries at a random address. You can build such
2080 executable using @command{gcc -fPIE -pie}.
2082 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2083 (as long as the randomization is enabled).
2085 @item show disable-randomization
2086 Show the current setting of the explicit disable of the native randomization of
2087 the virtual address space of the started program.
2092 @section Your Program's Arguments
2094 @cindex arguments (to your program)
2095 The arguments to your program can be specified by the arguments of the
2097 They are passed to a shell, which expands wildcard characters and
2098 performs redirection of I/O, and thence to your program. Your
2099 @code{SHELL} environment variable (if it exists) specifies what shell
2100 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2101 the default shell (@file{/bin/sh} on Unix).
2103 On non-Unix systems, the program is usually invoked directly by
2104 @value{GDBN}, which emulates I/O redirection via the appropriate system
2105 calls, and the wildcard characters are expanded by the startup code of
2106 the program, not by the shell.
2108 @code{run} with no arguments uses the same arguments used by the previous
2109 @code{run}, or those set by the @code{set args} command.
2114 Specify the arguments to be used the next time your program is run. If
2115 @code{set args} has no arguments, @code{run} executes your program
2116 with no arguments. Once you have run your program with arguments,
2117 using @code{set args} before the next @code{run} is the only way to run
2118 it again without arguments.
2122 Show the arguments to give your program when it is started.
2126 @section Your Program's Environment
2128 @cindex environment (of your program)
2129 The @dfn{environment} consists of a set of environment variables and
2130 their values. Environment variables conventionally record such things as
2131 your user name, your home directory, your terminal type, and your search
2132 path for programs to run. Usually you set up environment variables with
2133 the shell and they are inherited by all the other programs you run. When
2134 debugging, it can be useful to try running your program with a modified
2135 environment without having to start @value{GDBN} over again.
2139 @item path @var{directory}
2140 Add @var{directory} to the front of the @code{PATH} environment variable
2141 (the search path for executables) that will be passed to your program.
2142 The value of @code{PATH} used by @value{GDBN} does not change.
2143 You may specify several directory names, separated by whitespace or by a
2144 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2145 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2146 is moved to the front, so it is searched sooner.
2148 You can use the string @samp{$cwd} to refer to whatever is the current
2149 working directory at the time @value{GDBN} searches the path. If you
2150 use @samp{.} instead, it refers to the directory where you executed the
2151 @code{path} command. @value{GDBN} replaces @samp{.} in the
2152 @var{directory} argument (with the current path) before adding
2153 @var{directory} to the search path.
2154 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2155 @c document that, since repeating it would be a no-op.
2159 Display the list of search paths for executables (the @code{PATH}
2160 environment variable).
2162 @kindex show environment
2163 @item show environment @r{[}@var{varname}@r{]}
2164 Print the value of environment variable @var{varname} to be given to
2165 your program when it starts. If you do not supply @var{varname},
2166 print the names and values of all environment variables to be given to
2167 your program. You can abbreviate @code{environment} as @code{env}.
2169 @kindex set environment
2170 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2171 Set environment variable @var{varname} to @var{value}. The value
2172 changes for your program only, not for @value{GDBN} itself. @var{value} may
2173 be any string; the values of environment variables are just strings, and
2174 any interpretation is supplied by your program itself. The @var{value}
2175 parameter is optional; if it is eliminated, the variable is set to a
2177 @c "any string" here does not include leading, trailing
2178 @c blanks. Gnu asks: does anyone care?
2180 For example, this command:
2187 tells the debugged program, when subsequently run, that its user is named
2188 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2189 are not actually required.)
2191 @kindex unset environment
2192 @item unset environment @var{varname}
2193 Remove variable @var{varname} from the environment to be passed to your
2194 program. This is different from @samp{set env @var{varname} =};
2195 @code{unset environment} removes the variable from the environment,
2196 rather than assigning it an empty value.
2199 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2201 by your @code{SHELL} environment variable if it exists (or
2202 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2203 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2204 @file{.bashrc} for BASH---any variables you set in that file affect
2205 your program. You may wish to move setting of environment variables to
2206 files that are only run when you sign on, such as @file{.login} or
2209 @node Working Directory
2210 @section Your Program's Working Directory
2212 @cindex working directory (of your program)
2213 Each time you start your program with @code{run}, it inherits its
2214 working directory from the current working directory of @value{GDBN}.
2215 The @value{GDBN} working directory is initially whatever it inherited
2216 from its parent process (typically the shell), but you can specify a new
2217 working directory in @value{GDBN} with the @code{cd} command.
2219 The @value{GDBN} working directory also serves as a default for the commands
2220 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2225 @cindex change working directory
2226 @item cd @var{directory}
2227 Set the @value{GDBN} working directory to @var{directory}.
2231 Print the @value{GDBN} working directory.
2234 It is generally impossible to find the current working directory of
2235 the process being debugged (since a program can change its directory
2236 during its run). If you work on a system where @value{GDBN} is
2237 configured with the @file{/proc} support, you can use the @code{info
2238 proc} command (@pxref{SVR4 Process Information}) to find out the
2239 current working directory of the debuggee.
2242 @section Your Program's Input and Output
2247 By default, the program you run under @value{GDBN} does input and output to
2248 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2249 to its own terminal modes to interact with you, but it records the terminal
2250 modes your program was using and switches back to them when you continue
2251 running your program.
2254 @kindex info terminal
2256 Displays information recorded by @value{GDBN} about the terminal modes your
2260 You can redirect your program's input and/or output using shell
2261 redirection with the @code{run} command. For example,
2268 starts your program, diverting its output to the file @file{outfile}.
2271 @cindex controlling terminal
2272 Another way to specify where your program should do input and output is
2273 with the @code{tty} command. This command accepts a file name as
2274 argument, and causes this file to be the default for future @code{run}
2275 commands. It also resets the controlling terminal for the child
2276 process, for future @code{run} commands. For example,
2283 directs that processes started with subsequent @code{run} commands
2284 default to do input and output on the terminal @file{/dev/ttyb} and have
2285 that as their controlling terminal.
2287 An explicit redirection in @code{run} overrides the @code{tty} command's
2288 effect on the input/output device, but not its effect on the controlling
2291 When you use the @code{tty} command or redirect input in the @code{run}
2292 command, only the input @emph{for your program} is affected. The input
2293 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2294 for @code{set inferior-tty}.
2296 @cindex inferior tty
2297 @cindex set inferior controlling terminal
2298 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2299 display the name of the terminal that will be used for future runs of your
2303 @item set inferior-tty /dev/ttyb
2304 @kindex set inferior-tty
2305 Set the tty for the program being debugged to /dev/ttyb.
2307 @item show inferior-tty
2308 @kindex show inferior-tty
2309 Show the current tty for the program being debugged.
2313 @section Debugging an Already-running Process
2318 @item attach @var{process-id}
2319 This command attaches to a running process---one that was started
2320 outside @value{GDBN}. (@code{info files} shows your active
2321 targets.) The command takes as argument a process ID. The usual way to
2322 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2323 or with the @samp{jobs -l} shell command.
2325 @code{attach} does not repeat if you press @key{RET} a second time after
2326 executing the command.
2329 To use @code{attach}, your program must be running in an environment
2330 which supports processes; for example, @code{attach} does not work for
2331 programs on bare-board targets that lack an operating system. You must
2332 also have permission to send the process a signal.
2334 When you use @code{attach}, the debugger finds the program running in
2335 the process first by looking in the current working directory, then (if
2336 the program is not found) by using the source file search path
2337 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2338 the @code{file} command to load the program. @xref{Files, ,Commands to
2341 The first thing @value{GDBN} does after arranging to debug the specified
2342 process is to stop it. You can examine and modify an attached process
2343 with all the @value{GDBN} commands that are ordinarily available when
2344 you start processes with @code{run}. You can insert breakpoints; you
2345 can step and continue; you can modify storage. If you would rather the
2346 process continue running, you may use the @code{continue} command after
2347 attaching @value{GDBN} to the process.
2352 When you have finished debugging the attached process, you can use the
2353 @code{detach} command to release it from @value{GDBN} control. Detaching
2354 the process continues its execution. After the @code{detach} command,
2355 that process and @value{GDBN} become completely independent once more, and you
2356 are ready to @code{attach} another process or start one with @code{run}.
2357 @code{detach} does not repeat if you press @key{RET} again after
2358 executing the command.
2361 If you exit @value{GDBN} while you have an attached process, you detach
2362 that process. If you use the @code{run} command, you kill that process.
2363 By default, @value{GDBN} asks for confirmation if you try to do either of these
2364 things; you can control whether or not you need to confirm by using the
2365 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2369 @section Killing the Child Process
2374 Kill the child process in which your program is running under @value{GDBN}.
2377 This command is useful if you wish to debug a core dump instead of a
2378 running process. @value{GDBN} ignores any core dump file while your program
2381 On some operating systems, a program cannot be executed outside @value{GDBN}
2382 while you have breakpoints set on it inside @value{GDBN}. You can use the
2383 @code{kill} command in this situation to permit running your program
2384 outside the debugger.
2386 The @code{kill} command is also useful if you wish to recompile and
2387 relink your program, since on many systems it is impossible to modify an
2388 executable file while it is running in a process. In this case, when you
2389 next type @code{run}, @value{GDBN} notices that the file has changed, and
2390 reads the symbol table again (while trying to preserve your current
2391 breakpoint settings).
2393 @node Inferiors and Programs
2394 @section Debugging Multiple Inferiors and Programs
2396 @value{GDBN} lets you run and debug multiple programs in a single
2397 session. In addition, @value{GDBN} on some systems may let you run
2398 several programs simultaneously (otherwise you have to exit from one
2399 before starting another). In the most general case, you can have
2400 multiple threads of execution in each of multiple processes, launched
2401 from multiple executables.
2404 @value{GDBN} represents the state of each program execution with an
2405 object called an @dfn{inferior}. An inferior typically corresponds to
2406 a process, but is more general and applies also to targets that do not
2407 have processes. Inferiors may be created before a process runs, and
2408 may be retained after a process exits. Inferiors have unique
2409 identifiers that are different from process ids. Usually each
2410 inferior will also have its own distinct address space, although some
2411 embedded targets may have several inferiors running in different parts
2412 of a single address space. Each inferior may in turn have multiple
2413 threads running in it.
2415 To find out what inferiors exist at any moment, use @w{@code{info
2419 @kindex info inferiors
2420 @item info inferiors
2421 Print a list of all inferiors currently being managed by @value{GDBN}.
2423 @value{GDBN} displays for each inferior (in this order):
2427 the inferior number assigned by @value{GDBN}
2430 the target system's inferior identifier
2433 the name of the executable the inferior is running.
2438 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2439 indicates the current inferior.
2443 @c end table here to get a little more width for example
2446 (@value{GDBP}) info inferiors
2447 Num Description Executable
2448 2 process 2307 hello
2449 * 1 process 3401 goodbye
2452 To switch focus between inferiors, use the @code{inferior} command:
2455 @kindex inferior @var{infno}
2456 @item inferior @var{infno}
2457 Make inferior number @var{infno} the current inferior. The argument
2458 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2459 in the first field of the @samp{info inferiors} display.
2463 You can get multiple executables into a debugging session via the
2464 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2465 systems @value{GDBN} can add inferiors to the debug session
2466 automatically by following calls to @code{fork} and @code{exec}. To
2467 remove inferiors from the debugging session use the
2468 @w{@code{remove-inferior}} command.
2471 @kindex add-inferior
2472 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2473 Adds @var{n} inferiors to be run using @var{executable} as the
2474 executable. @var{n} defaults to 1. If no executable is specified,
2475 the inferiors begins empty, with no program. You can still assign or
2476 change the program assigned to the inferior at any time by using the
2477 @code{file} command with the executable name as its argument.
2479 @kindex clone-inferior
2480 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2481 Adds @var{n} inferiors ready to execute the same program as inferior
2482 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2483 number of the current inferior. This is a convenient command when you
2484 want to run another instance of the inferior you are debugging.
2487 (@value{GDBP}) info inferiors
2488 Num Description Executable
2489 * 1 process 29964 helloworld
2490 (@value{GDBP}) clone-inferior
2493 (@value{GDBP}) info inferiors
2494 Num Description Executable
2496 * 1 process 29964 helloworld
2499 You can now simply switch focus to inferior 2 and run it.
2501 @kindex remove-inferior
2502 @item remove-inferior @var{infno}
2503 Removes the inferior @var{infno}. It is not possible to remove an
2504 inferior that is running with this command. For those, use the
2505 @code{kill} or @code{detach} command first.
2509 To quit debugging one of the running inferiors that is not the current
2510 inferior, you can either detach from it by using the @w{@code{detach
2511 inferior}} command (allowing it to run independently), or kill it
2512 using the @w{@code{kill inferior}} command:
2515 @kindex detach inferior @var{infno}
2516 @item detach inferior @var{infno}
2517 Detach from the inferior identified by @value{GDBN} inferior number
2518 @var{infno}. Note that the inferior's entry still stays on the list
2519 of inferiors shown by @code{info inferiors}, but its Description will
2522 @kindex kill inferior @var{infno}
2523 @item kill inferior @var{infno}
2524 Kill the inferior identified by @value{GDBN} inferior number
2525 @var{infno}. Note that the inferior's entry still stays on the list
2526 of inferiors shown by @code{info inferiors}, but its Description will
2530 After the successful completion of a command such as @code{detach},
2531 @code{detach inferior}, @code{kill} or @code{kill inferior}, or after
2532 a normal process exit, the inferior is still valid and listed with
2533 @code{info inferiors}, ready to be restarted.
2536 To be notified when inferiors are started or exit under @value{GDBN}'s
2537 control use @w{@code{set print inferior-events}}:
2540 @kindex set print inferior-events
2541 @cindex print messages on inferior start and exit
2542 @item set print inferior-events
2543 @itemx set print inferior-events on
2544 @itemx set print inferior-events off
2545 The @code{set print inferior-events} command allows you to enable or
2546 disable printing of messages when @value{GDBN} notices that new
2547 inferiors have started or that inferiors have exited or have been
2548 detached. By default, these messages will not be printed.
2550 @kindex show print inferior-events
2551 @item show print inferior-events
2552 Show whether messages will be printed when @value{GDBN} detects that
2553 inferiors have started, exited or have been detached.
2556 Many commands will work the same with multiple programs as with a
2557 single program: e.g., @code{print myglobal} will simply display the
2558 value of @code{myglobal} in the current inferior.
2561 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2562 get more info about the relationship of inferiors, programs, address
2563 spaces in a debug session. You can do that with the @w{@code{maint
2564 info program-spaces}} command.
2567 @kindex maint info program-spaces
2568 @item maint info program-spaces
2569 Print a list of all program spaces currently being managed by
2572 @value{GDBN} displays for each program space (in this order):
2576 the program space number assigned by @value{GDBN}
2579 the name of the executable loaded into the program space, with e.g.,
2580 the @code{file} command.
2585 An asterisk @samp{*} preceding the @value{GDBN} program space number
2586 indicates the current program space.
2588 In addition, below each program space line, @value{GDBN} prints extra
2589 information that isn't suitable to display in tabular form. For
2590 example, the list of inferiors bound to the program space.
2593 (@value{GDBP}) maint info program-spaces
2596 Bound inferiors: ID 1 (process 21561)
2600 Here we can see that no inferior is running the program @code{hello},
2601 while @code{process 21561} is running the program @code{goodbye}. On
2602 some targets, it is possible that multiple inferiors are bound to the
2603 same program space. The most common example is that of debugging both
2604 the parent and child processes of a @code{vfork} call. For example,
2607 (@value{GDBP}) maint info program-spaces
2610 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2613 Here, both inferior 2 and inferior 1 are running in the same program
2614 space as a result of inferior 1 having executed a @code{vfork} call.
2618 @section Debugging Programs with Multiple Threads
2620 @cindex threads of execution
2621 @cindex multiple threads
2622 @cindex switching threads
2623 In some operating systems, such as HP-UX and Solaris, a single program
2624 may have more than one @dfn{thread} of execution. The precise semantics
2625 of threads differ from one operating system to another, but in general
2626 the threads of a single program are akin to multiple processes---except
2627 that they share one address space (that is, they can all examine and
2628 modify the same variables). On the other hand, each thread has its own
2629 registers and execution stack, and perhaps private memory.
2631 @value{GDBN} provides these facilities for debugging multi-thread
2635 @item automatic notification of new threads
2636 @item @samp{thread @var{threadno}}, a command to switch among threads
2637 @item @samp{info threads}, a command to inquire about existing threads
2638 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2639 a command to apply a command to a list of threads
2640 @item thread-specific breakpoints
2641 @item @samp{set print thread-events}, which controls printing of
2642 messages on thread start and exit.
2643 @item @samp{set libthread-db-search-path @var{path}}, which lets
2644 the user specify which @code{libthread_db} to use if the default choice
2645 isn't compatible with the program.
2649 @emph{Warning:} These facilities are not yet available on every
2650 @value{GDBN} configuration where the operating system supports threads.
2651 If your @value{GDBN} does not support threads, these commands have no
2652 effect. For example, a system without thread support shows no output
2653 from @samp{info threads}, and always rejects the @code{thread} command,
2657 (@value{GDBP}) info threads
2658 (@value{GDBP}) thread 1
2659 Thread ID 1 not known. Use the "info threads" command to
2660 see the IDs of currently known threads.
2662 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2663 @c doesn't support threads"?
2666 @cindex focus of debugging
2667 @cindex current thread
2668 The @value{GDBN} thread debugging facility allows you to observe all
2669 threads while your program runs---but whenever @value{GDBN} takes
2670 control, one thread in particular is always the focus of debugging.
2671 This thread is called the @dfn{current thread}. Debugging commands show
2672 program information from the perspective of the current thread.
2674 @cindex @code{New} @var{systag} message
2675 @cindex thread identifier (system)
2676 @c FIXME-implementors!! It would be more helpful if the [New...] message
2677 @c included GDB's numeric thread handle, so you could just go to that
2678 @c thread without first checking `info threads'.
2679 Whenever @value{GDBN} detects a new thread in your program, it displays
2680 the target system's identification for the thread with a message in the
2681 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2682 whose form varies depending on the particular system. For example, on
2683 @sc{gnu}/Linux, you might see
2686 [New Thread 0x41e02940 (LWP 25582)]
2690 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2691 the @var{systag} is simply something like @samp{process 368}, with no
2694 @c FIXME!! (1) Does the [New...] message appear even for the very first
2695 @c thread of a program, or does it only appear for the
2696 @c second---i.e.@: when it becomes obvious we have a multithread
2698 @c (2) *Is* there necessarily a first thread always? Or do some
2699 @c multithread systems permit starting a program with multiple
2700 @c threads ab initio?
2702 @cindex thread number
2703 @cindex thread identifier (GDB)
2704 For debugging purposes, @value{GDBN} associates its own thread
2705 number---always a single integer---with each thread in your program.
2708 @kindex info threads
2709 @item info threads @r{[}@var{id}@dots{}@r{]}
2710 Display a summary of all threads currently in your program. Optional
2711 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2712 means to print information only about the specified thread or threads.
2713 @value{GDBN} displays for each thread (in this order):
2717 the thread number assigned by @value{GDBN}
2720 the target system's thread identifier (@var{systag})
2723 the thread's name, if one is known. A thread can either be named by
2724 the user (see @code{thread name}, below), or, in some cases, by the
2728 the current stack frame summary for that thread
2732 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2733 indicates the current thread.
2737 @c end table here to get a little more width for example
2740 (@value{GDBP}) info threads
2742 3 process 35 thread 27 0x34e5 in sigpause ()
2743 2 process 35 thread 23 0x34e5 in sigpause ()
2744 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2748 On Solaris, you can display more information about user threads with a
2749 Solaris-specific command:
2752 @item maint info sol-threads
2753 @kindex maint info sol-threads
2754 @cindex thread info (Solaris)
2755 Display info on Solaris user threads.
2759 @kindex thread @var{threadno}
2760 @item thread @var{threadno}
2761 Make thread number @var{threadno} the current thread. The command
2762 argument @var{threadno} is the internal @value{GDBN} thread number, as
2763 shown in the first field of the @samp{info threads} display.
2764 @value{GDBN} responds by displaying the system identifier of the thread
2765 you selected, and its current stack frame summary:
2768 (@value{GDBP}) thread 2
2769 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2770 #0 some_function (ignore=0x0) at example.c:8
2771 8 printf ("hello\n");
2775 As with the @samp{[New @dots{}]} message, the form of the text after
2776 @samp{Switching to} depends on your system's conventions for identifying
2779 @vindex $_thread@r{, convenience variable}
2780 The debugger convenience variable @samp{$_thread} contains the number
2781 of the current thread. You may find this useful in writing breakpoint
2782 conditional expressions, command scripts, and so forth. See
2783 @xref{Convenience Vars,, Convenience Variables}, for general
2784 information on convenience variables.
2786 @kindex thread apply
2787 @cindex apply command to several threads
2788 @item thread apply [@var{threadno} | all] @var{command}
2789 The @code{thread apply} command allows you to apply the named
2790 @var{command} to one or more threads. Specify the numbers of the
2791 threads that you want affected with the command argument
2792 @var{threadno}. It can be a single thread number, one of the numbers
2793 shown in the first field of the @samp{info threads} display; or it
2794 could be a range of thread numbers, as in @code{2-4}. To apply a
2795 command to all threads, type @kbd{thread apply all @var{command}}.
2798 @cindex name a thread
2799 @item thread name [@var{name}]
2800 This command assigns a name to the current thread. If no argument is
2801 given, any existing user-specified name is removed. The thread name
2802 appears in the @samp{info threads} display.
2804 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2805 determine the name of the thread as given by the OS. On these
2806 systems, a name specified with @samp{thread name} will override the
2807 system-give name, and removing the user-specified name will cause
2808 @value{GDBN} to once again display the system-specified name.
2811 @cindex search for a thread
2812 @item thread find [@var{regexp}]
2813 Search for and display thread ids whose name or @var{systag}
2814 matches the supplied regular expression.
2816 As well as being the complement to the @samp{thread name} command,
2817 this command also allows you to identify a thread by its target
2818 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2822 (@value{GDBN}) thread find 26688
2823 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2824 (@value{GDBN}) info thread 4
2826 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2829 @kindex set print thread-events
2830 @cindex print messages on thread start and exit
2831 @item set print thread-events
2832 @itemx set print thread-events on
2833 @itemx set print thread-events off
2834 The @code{set print thread-events} command allows you to enable or
2835 disable printing of messages when @value{GDBN} notices that new threads have
2836 started or that threads have exited. By default, these messages will
2837 be printed if detection of these events is supported by the target.
2838 Note that these messages cannot be disabled on all targets.
2840 @kindex show print thread-events
2841 @item show print thread-events
2842 Show whether messages will be printed when @value{GDBN} detects that threads
2843 have started and exited.
2846 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2847 more information about how @value{GDBN} behaves when you stop and start
2848 programs with multiple threads.
2850 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2851 watchpoints in programs with multiple threads.
2854 @kindex set libthread-db-search-path
2855 @cindex search path for @code{libthread_db}
2856 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2857 If this variable is set, @var{path} is a colon-separated list of
2858 directories @value{GDBN} will use to search for @code{libthread_db}.
2859 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2862 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2863 @code{libthread_db} library to obtain information about threads in the
2864 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2865 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2866 with default system shared library directories, and finally the directory
2867 from which @code{libpthread} was loaded in the inferior process.
2869 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2870 @value{GDBN} attempts to initialize it with the current inferior process.
2871 If this initialization fails (which could happen because of a version
2872 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2873 will unload @code{libthread_db}, and continue with the next directory.
2874 If none of @code{libthread_db} libraries initialize successfully,
2875 @value{GDBN} will issue a warning and thread debugging will be disabled.
2877 Setting @code{libthread-db-search-path} is currently implemented
2878 only on some platforms.
2880 @kindex show libthread-db-search-path
2881 @item show libthread-db-search-path
2882 Display current libthread_db search path.
2884 @kindex set debug libthread-db
2885 @kindex show debug libthread-db
2886 @cindex debugging @code{libthread_db}
2887 @item set debug libthread-db
2888 @itemx show debug libthread-db
2889 Turns on or off display of @code{libthread_db}-related events.
2890 Use @code{1} to enable, @code{0} to disable.
2894 @section Debugging Forks
2896 @cindex fork, debugging programs which call
2897 @cindex multiple processes
2898 @cindex processes, multiple
2899 On most systems, @value{GDBN} has no special support for debugging
2900 programs which create additional processes using the @code{fork}
2901 function. When a program forks, @value{GDBN} will continue to debug the
2902 parent process and the child process will run unimpeded. If you have
2903 set a breakpoint in any code which the child then executes, the child
2904 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2905 will cause it to terminate.
2907 However, if you want to debug the child process there is a workaround
2908 which isn't too painful. Put a call to @code{sleep} in the code which
2909 the child process executes after the fork. It may be useful to sleep
2910 only if a certain environment variable is set, or a certain file exists,
2911 so that the delay need not occur when you don't want to run @value{GDBN}
2912 on the child. While the child is sleeping, use the @code{ps} program to
2913 get its process ID. Then tell @value{GDBN} (a new invocation of
2914 @value{GDBN} if you are also debugging the parent process) to attach to
2915 the child process (@pxref{Attach}). From that point on you can debug
2916 the child process just like any other process which you attached to.
2918 On some systems, @value{GDBN} provides support for debugging programs that
2919 create additional processes using the @code{fork} or @code{vfork} functions.
2920 Currently, the only platforms with this feature are HP-UX (11.x and later
2921 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2923 By default, when a program forks, @value{GDBN} will continue to debug
2924 the parent process and the child process will run unimpeded.
2926 If you want to follow the child process instead of the parent process,
2927 use the command @w{@code{set follow-fork-mode}}.
2930 @kindex set follow-fork-mode
2931 @item set follow-fork-mode @var{mode}
2932 Set the debugger response to a program call of @code{fork} or
2933 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2934 process. The @var{mode} argument can be:
2938 The original process is debugged after a fork. The child process runs
2939 unimpeded. This is the default.
2942 The new process is debugged after a fork. The parent process runs
2947 @kindex show follow-fork-mode
2948 @item show follow-fork-mode
2949 Display the current debugger response to a @code{fork} or @code{vfork} call.
2952 @cindex debugging multiple processes
2953 On Linux, if you want to debug both the parent and child processes, use the
2954 command @w{@code{set detach-on-fork}}.
2957 @kindex set detach-on-fork
2958 @item set detach-on-fork @var{mode}
2959 Tells gdb whether to detach one of the processes after a fork, or
2960 retain debugger control over them both.
2964 The child process (or parent process, depending on the value of
2965 @code{follow-fork-mode}) will be detached and allowed to run
2966 independently. This is the default.
2969 Both processes will be held under the control of @value{GDBN}.
2970 One process (child or parent, depending on the value of
2971 @code{follow-fork-mode}) is debugged as usual, while the other
2976 @kindex show detach-on-fork
2977 @item show detach-on-fork
2978 Show whether detach-on-fork mode is on/off.
2981 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2982 will retain control of all forked processes (including nested forks).
2983 You can list the forked processes under the control of @value{GDBN} by
2984 using the @w{@code{info inferiors}} command, and switch from one fork
2985 to another by using the @code{inferior} command (@pxref{Inferiors and
2986 Programs, ,Debugging Multiple Inferiors and Programs}).
2988 To quit debugging one of the forked processes, you can either detach
2989 from it by using the @w{@code{detach inferior}} command (allowing it
2990 to run independently), or kill it using the @w{@code{kill inferior}}
2991 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
2994 If you ask to debug a child process and a @code{vfork} is followed by an
2995 @code{exec}, @value{GDBN} executes the new target up to the first
2996 breakpoint in the new target. If you have a breakpoint set on
2997 @code{main} in your original program, the breakpoint will also be set on
2998 the child process's @code{main}.
3000 On some systems, when a child process is spawned by @code{vfork}, you
3001 cannot debug the child or parent until an @code{exec} call completes.
3003 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3004 call executes, the new target restarts. To restart the parent
3005 process, use the @code{file} command with the parent executable name
3006 as its argument. By default, after an @code{exec} call executes,
3007 @value{GDBN} discards the symbols of the previous executable image.
3008 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3012 @kindex set follow-exec-mode
3013 @item set follow-exec-mode @var{mode}
3015 Set debugger response to a program call of @code{exec}. An
3016 @code{exec} call replaces the program image of a process.
3018 @code{follow-exec-mode} can be:
3022 @value{GDBN} creates a new inferior and rebinds the process to this
3023 new inferior. The program the process was running before the
3024 @code{exec} call can be restarted afterwards by restarting the
3030 (@value{GDBP}) info inferiors
3032 Id Description Executable
3035 process 12020 is executing new program: prog2
3036 Program exited normally.
3037 (@value{GDBP}) info inferiors
3038 Id Description Executable
3044 @value{GDBN} keeps the process bound to the same inferior. The new
3045 executable image replaces the previous executable loaded in the
3046 inferior. Restarting the inferior after the @code{exec} call, with
3047 e.g., the @code{run} command, restarts the executable the process was
3048 running after the @code{exec} call. This is the default mode.
3053 (@value{GDBP}) info inferiors
3054 Id Description Executable
3057 process 12020 is executing new program: prog2
3058 Program exited normally.
3059 (@value{GDBP}) info inferiors
3060 Id Description Executable
3067 You can use the @code{catch} command to make @value{GDBN} stop whenever
3068 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3069 Catchpoints, ,Setting Catchpoints}.
3071 @node Checkpoint/Restart
3072 @section Setting a @emph{Bookmark} to Return to Later
3077 @cindex snapshot of a process
3078 @cindex rewind program state
3080 On certain operating systems@footnote{Currently, only
3081 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3082 program's state, called a @dfn{checkpoint}, and come back to it
3085 Returning to a checkpoint effectively undoes everything that has
3086 happened in the program since the @code{checkpoint} was saved. This
3087 includes changes in memory, registers, and even (within some limits)
3088 system state. Effectively, it is like going back in time to the
3089 moment when the checkpoint was saved.
3091 Thus, if you're stepping thru a program and you think you're
3092 getting close to the point where things go wrong, you can save
3093 a checkpoint. Then, if you accidentally go too far and miss
3094 the critical statement, instead of having to restart your program
3095 from the beginning, you can just go back to the checkpoint and
3096 start again from there.
3098 This can be especially useful if it takes a lot of time or
3099 steps to reach the point where you think the bug occurs.
3101 To use the @code{checkpoint}/@code{restart} method of debugging:
3106 Save a snapshot of the debugged program's current execution state.
3107 The @code{checkpoint} command takes no arguments, but each checkpoint
3108 is assigned a small integer id, similar to a breakpoint id.
3110 @kindex info checkpoints
3111 @item info checkpoints
3112 List the checkpoints that have been saved in the current debugging
3113 session. For each checkpoint, the following information will be
3120 @item Source line, or label
3123 @kindex restart @var{checkpoint-id}
3124 @item restart @var{checkpoint-id}
3125 Restore the program state that was saved as checkpoint number
3126 @var{checkpoint-id}. All program variables, registers, stack frames
3127 etc.@: will be returned to the values that they had when the checkpoint
3128 was saved. In essence, gdb will ``wind back the clock'' to the point
3129 in time when the checkpoint was saved.
3131 Note that breakpoints, @value{GDBN} variables, command history etc.
3132 are not affected by restoring a checkpoint. In general, a checkpoint
3133 only restores things that reside in the program being debugged, not in
3136 @kindex delete checkpoint @var{checkpoint-id}
3137 @item delete checkpoint @var{checkpoint-id}
3138 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3142 Returning to a previously saved checkpoint will restore the user state
3143 of the program being debugged, plus a significant subset of the system
3144 (OS) state, including file pointers. It won't ``un-write'' data from
3145 a file, but it will rewind the file pointer to the previous location,
3146 so that the previously written data can be overwritten. For files
3147 opened in read mode, the pointer will also be restored so that the
3148 previously read data can be read again.
3150 Of course, characters that have been sent to a printer (or other
3151 external device) cannot be ``snatched back'', and characters received
3152 from eg.@: a serial device can be removed from internal program buffers,
3153 but they cannot be ``pushed back'' into the serial pipeline, ready to
3154 be received again. Similarly, the actual contents of files that have
3155 been changed cannot be restored (at this time).
3157 However, within those constraints, you actually can ``rewind'' your
3158 program to a previously saved point in time, and begin debugging it
3159 again --- and you can change the course of events so as to debug a
3160 different execution path this time.
3162 @cindex checkpoints and process id
3163 Finally, there is one bit of internal program state that will be
3164 different when you return to a checkpoint --- the program's process
3165 id. Each checkpoint will have a unique process id (or @var{pid}),
3166 and each will be different from the program's original @var{pid}.
3167 If your program has saved a local copy of its process id, this could
3168 potentially pose a problem.
3170 @subsection A Non-obvious Benefit of Using Checkpoints
3172 On some systems such as @sc{gnu}/Linux, address space randomization
3173 is performed on new processes for security reasons. This makes it
3174 difficult or impossible to set a breakpoint, or watchpoint, on an
3175 absolute address if you have to restart the program, since the
3176 absolute location of a symbol will change from one execution to the
3179 A checkpoint, however, is an @emph{identical} copy of a process.
3180 Therefore if you create a checkpoint at (eg.@:) the start of main,
3181 and simply return to that checkpoint instead of restarting the
3182 process, you can avoid the effects of address randomization and
3183 your symbols will all stay in the same place.
3186 @chapter Stopping and Continuing
3188 The principal purposes of using a debugger are so that you can stop your
3189 program before it terminates; or so that, if your program runs into
3190 trouble, you can investigate and find out why.
3192 Inside @value{GDBN}, your program may stop for any of several reasons,
3193 such as a signal, a breakpoint, or reaching a new line after a
3194 @value{GDBN} command such as @code{step}. You may then examine and
3195 change variables, set new breakpoints or remove old ones, and then
3196 continue execution. Usually, the messages shown by @value{GDBN} provide
3197 ample explanation of the status of your program---but you can also
3198 explicitly request this information at any time.
3201 @kindex info program
3203 Display information about the status of your program: whether it is
3204 running or not, what process it is, and why it stopped.
3208 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3209 * Continuing and Stepping:: Resuming execution
3211 * Thread Stops:: Stopping and starting multi-thread programs
3215 @section Breakpoints, Watchpoints, and Catchpoints
3218 A @dfn{breakpoint} makes your program stop whenever a certain point in
3219 the program is reached. For each breakpoint, you can add conditions to
3220 control in finer detail whether your program stops. You can set
3221 breakpoints with the @code{break} command and its variants (@pxref{Set
3222 Breaks, ,Setting Breakpoints}), to specify the place where your program
3223 should stop by line number, function name or exact address in the
3226 On some systems, you can set breakpoints in shared libraries before
3227 the executable is run. There is a minor limitation on HP-UX systems:
3228 you must wait until the executable is run in order to set breakpoints
3229 in shared library routines that are not called directly by the program
3230 (for example, routines that are arguments in a @code{pthread_create}
3234 @cindex data breakpoints
3235 @cindex memory tracing
3236 @cindex breakpoint on memory address
3237 @cindex breakpoint on variable modification
3238 A @dfn{watchpoint} is a special breakpoint that stops your program
3239 when the value of an expression changes. The expression may be a value
3240 of a variable, or it could involve values of one or more variables
3241 combined by operators, such as @samp{a + b}. This is sometimes called
3242 @dfn{data breakpoints}. You must use a different command to set
3243 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3244 from that, you can manage a watchpoint like any other breakpoint: you
3245 enable, disable, and delete both breakpoints and watchpoints using the
3248 You can arrange to have values from your program displayed automatically
3249 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3253 @cindex breakpoint on events
3254 A @dfn{catchpoint} is another special breakpoint that stops your program
3255 when a certain kind of event occurs, such as the throwing of a C@t{++}
3256 exception or the loading of a library. As with watchpoints, you use a
3257 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3258 Catchpoints}), but aside from that, you can manage a catchpoint like any
3259 other breakpoint. (To stop when your program receives a signal, use the
3260 @code{handle} command; see @ref{Signals, ,Signals}.)
3262 @cindex breakpoint numbers
3263 @cindex numbers for breakpoints
3264 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3265 catchpoint when you create it; these numbers are successive integers
3266 starting with one. In many of the commands for controlling various
3267 features of breakpoints you use the breakpoint number to say which
3268 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3269 @dfn{disabled}; if disabled, it has no effect on your program until you
3272 @cindex breakpoint ranges
3273 @cindex ranges of breakpoints
3274 Some @value{GDBN} commands accept a range of breakpoints on which to
3275 operate. A breakpoint range is either a single breakpoint number, like
3276 @samp{5}, or two such numbers, in increasing order, separated by a
3277 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3278 all breakpoints in that range are operated on.
3281 * Set Breaks:: Setting breakpoints
3282 * Set Watchpoints:: Setting watchpoints
3283 * Set Catchpoints:: Setting catchpoints
3284 * Delete Breaks:: Deleting breakpoints
3285 * Disabling:: Disabling breakpoints
3286 * Conditions:: Break conditions
3287 * Break Commands:: Breakpoint command lists
3288 * Save Breakpoints:: How to save breakpoints in a file
3289 * Error in Breakpoints:: ``Cannot insert breakpoints''
3290 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3294 @subsection Setting Breakpoints
3296 @c FIXME LMB what does GDB do if no code on line of breakpt?
3297 @c consider in particular declaration with/without initialization.
3299 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3302 @kindex b @r{(@code{break})}
3303 @vindex $bpnum@r{, convenience variable}
3304 @cindex latest breakpoint
3305 Breakpoints are set with the @code{break} command (abbreviated
3306 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3307 number of the breakpoint you've set most recently; see @ref{Convenience
3308 Vars,, Convenience Variables}, for a discussion of what you can do with
3309 convenience variables.
3312 @item break @var{location}
3313 Set a breakpoint at the given @var{location}, which can specify a
3314 function name, a line number, or an address of an instruction.
3315 (@xref{Specify Location}, for a list of all the possible ways to
3316 specify a @var{location}.) The breakpoint will stop your program just
3317 before it executes any of the code in the specified @var{location}.
3319 When using source languages that permit overloading of symbols, such as
3320 C@t{++}, a function name may refer to more than one possible place to break.
3321 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3324 It is also possible to insert a breakpoint that will stop the program
3325 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3326 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3329 When called without any arguments, @code{break} sets a breakpoint at
3330 the next instruction to be executed in the selected stack frame
3331 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3332 innermost, this makes your program stop as soon as control
3333 returns to that frame. This is similar to the effect of a
3334 @code{finish} command in the frame inside the selected frame---except
3335 that @code{finish} does not leave an active breakpoint. If you use
3336 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3337 the next time it reaches the current location; this may be useful
3340 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3341 least one instruction has been executed. If it did not do this, you
3342 would be unable to proceed past a breakpoint without first disabling the
3343 breakpoint. This rule applies whether or not the breakpoint already
3344 existed when your program stopped.
3346 @item break @dots{} if @var{cond}
3347 Set a breakpoint with condition @var{cond}; evaluate the expression
3348 @var{cond} each time the breakpoint is reached, and stop only if the
3349 value is nonzero---that is, if @var{cond} evaluates as true.
3350 @samp{@dots{}} stands for one of the possible arguments described
3351 above (or no argument) specifying where to break. @xref{Conditions,
3352 ,Break Conditions}, for more information on breakpoint conditions.
3355 @item tbreak @var{args}
3356 Set a breakpoint enabled only for one stop. @var{args} are the
3357 same as for the @code{break} command, and the breakpoint is set in the same
3358 way, but the breakpoint is automatically deleted after the first time your
3359 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3362 @cindex hardware breakpoints
3363 @item hbreak @var{args}
3364 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3365 @code{break} command and the breakpoint is set in the same way, but the
3366 breakpoint requires hardware support and some target hardware may not
3367 have this support. The main purpose of this is EPROM/ROM code
3368 debugging, so you can set a breakpoint at an instruction without
3369 changing the instruction. This can be used with the new trap-generation
3370 provided by SPARClite DSU and most x86-based targets. These targets
3371 will generate traps when a program accesses some data or instruction
3372 address that is assigned to the debug registers. However the hardware
3373 breakpoint registers can take a limited number of breakpoints. For
3374 example, on the DSU, only two data breakpoints can be set at a time, and
3375 @value{GDBN} will reject this command if more than two are used. Delete
3376 or disable unused hardware breakpoints before setting new ones
3377 (@pxref{Disabling, ,Disabling Breakpoints}).
3378 @xref{Conditions, ,Break Conditions}.
3379 For remote targets, you can restrict the number of hardware
3380 breakpoints @value{GDBN} will use, see @ref{set remote
3381 hardware-breakpoint-limit}.
3384 @item thbreak @var{args}
3385 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3386 are the same as for the @code{hbreak} command and the breakpoint is set in
3387 the same way. However, like the @code{tbreak} command,
3388 the breakpoint is automatically deleted after the
3389 first time your program stops there. Also, like the @code{hbreak}
3390 command, the breakpoint requires hardware support and some target hardware
3391 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3392 See also @ref{Conditions, ,Break Conditions}.
3395 @cindex regular expression
3396 @cindex breakpoints at functions matching a regexp
3397 @cindex set breakpoints in many functions
3398 @item rbreak @var{regex}
3399 Set breakpoints on all functions matching the regular expression
3400 @var{regex}. This command sets an unconditional breakpoint on all
3401 matches, printing a list of all breakpoints it set. Once these
3402 breakpoints are set, they are treated just like the breakpoints set with
3403 the @code{break} command. You can delete them, disable them, or make
3404 them conditional the same way as any other breakpoint.
3406 The syntax of the regular expression is the standard one used with tools
3407 like @file{grep}. Note that this is different from the syntax used by
3408 shells, so for instance @code{foo*} matches all functions that include
3409 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3410 @code{.*} leading and trailing the regular expression you supply, so to
3411 match only functions that begin with @code{foo}, use @code{^foo}.
3413 @cindex non-member C@t{++} functions, set breakpoint in
3414 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3415 breakpoints on overloaded functions that are not members of any special
3418 @cindex set breakpoints on all functions
3419 The @code{rbreak} command can be used to set breakpoints in
3420 @strong{all} the functions in a program, like this:
3423 (@value{GDBP}) rbreak .
3426 @item rbreak @var{file}:@var{regex}
3427 If @code{rbreak} is called with a filename qualification, it limits
3428 the search for functions matching the given regular expression to the
3429 specified @var{file}. This can be used, for example, to set breakpoints on
3430 every function in a given file:
3433 (@value{GDBP}) rbreak file.c:.
3436 The colon separating the filename qualifier from the regex may
3437 optionally be surrounded by spaces.
3439 @kindex info breakpoints
3440 @cindex @code{$_} and @code{info breakpoints}
3441 @item info breakpoints @r{[}@var{n}@r{]}
3442 @itemx info break @r{[}@var{n}@r{]}
3443 Print a table of all breakpoints, watchpoints, and catchpoints set and
3444 not deleted. Optional argument @var{n} means print information only
3445 about the specified breakpoint (or watchpoint or catchpoint). For
3446 each breakpoint, following columns are printed:
3449 @item Breakpoint Numbers
3451 Breakpoint, watchpoint, or catchpoint.
3453 Whether the breakpoint is marked to be disabled or deleted when hit.
3454 @item Enabled or Disabled
3455 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3456 that are not enabled.
3458 Where the breakpoint is in your program, as a memory address. For a
3459 pending breakpoint whose address is not yet known, this field will
3460 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3461 library that has the symbol or line referred by breakpoint is loaded.
3462 See below for details. A breakpoint with several locations will
3463 have @samp{<MULTIPLE>} in this field---see below for details.
3465 Where the breakpoint is in the source for your program, as a file and
3466 line number. For a pending breakpoint, the original string passed to
3467 the breakpoint command will be listed as it cannot be resolved until
3468 the appropriate shared library is loaded in the future.
3472 If a breakpoint is conditional, @code{info break} shows the condition on
3473 the line following the affected breakpoint; breakpoint commands, if any,
3474 are listed after that. A pending breakpoint is allowed to have a condition
3475 specified for it. The condition is not parsed for validity until a shared
3476 library is loaded that allows the pending breakpoint to resolve to a
3480 @code{info break} with a breakpoint
3481 number @var{n} as argument lists only that breakpoint. The
3482 convenience variable @code{$_} and the default examining-address for
3483 the @code{x} command are set to the address of the last breakpoint
3484 listed (@pxref{Memory, ,Examining Memory}).
3487 @code{info break} displays a count of the number of times the breakpoint
3488 has been hit. This is especially useful in conjunction with the
3489 @code{ignore} command. You can ignore a large number of breakpoint
3490 hits, look at the breakpoint info to see how many times the breakpoint
3491 was hit, and then run again, ignoring one less than that number. This
3492 will get you quickly to the last hit of that breakpoint.
3495 @value{GDBN} allows you to set any number of breakpoints at the same place in
3496 your program. There is nothing silly or meaningless about this. When
3497 the breakpoints are conditional, this is even useful
3498 (@pxref{Conditions, ,Break Conditions}).
3500 @cindex multiple locations, breakpoints
3501 @cindex breakpoints, multiple locations
3502 It is possible that a breakpoint corresponds to several locations
3503 in your program. Examples of this situation are:
3507 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3508 instances of the function body, used in different cases.
3511 For a C@t{++} template function, a given line in the function can
3512 correspond to any number of instantiations.
3515 For an inlined function, a given source line can correspond to
3516 several places where that function is inlined.
3519 In all those cases, @value{GDBN} will insert a breakpoint at all
3520 the relevant locations@footnote{
3521 As of this writing, multiple-location breakpoints work only if there's
3522 line number information for all the locations. This means that they
3523 will generally not work in system libraries, unless you have debug
3524 info with line numbers for them.}.
3526 A breakpoint with multiple locations is displayed in the breakpoint
3527 table using several rows---one header row, followed by one row for
3528 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3529 address column. The rows for individual locations contain the actual
3530 addresses for locations, and show the functions to which those
3531 locations belong. The number column for a location is of the form
3532 @var{breakpoint-number}.@var{location-number}.
3537 Num Type Disp Enb Address What
3538 1 breakpoint keep y <MULTIPLE>
3540 breakpoint already hit 1 time
3541 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3542 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3545 Each location can be individually enabled or disabled by passing
3546 @var{breakpoint-number}.@var{location-number} as argument to the
3547 @code{enable} and @code{disable} commands. Note that you cannot
3548 delete the individual locations from the list, you can only delete the
3549 entire list of locations that belong to their parent breakpoint (with
3550 the @kbd{delete @var{num}} command, where @var{num} is the number of
3551 the parent breakpoint, 1 in the above example). Disabling or enabling
3552 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3553 that belong to that breakpoint.
3555 @cindex pending breakpoints
3556 It's quite common to have a breakpoint inside a shared library.
3557 Shared libraries can be loaded and unloaded explicitly,
3558 and possibly repeatedly, as the program is executed. To support
3559 this use case, @value{GDBN} updates breakpoint locations whenever
3560 any shared library is loaded or unloaded. Typically, you would
3561 set a breakpoint in a shared library at the beginning of your
3562 debugging session, when the library is not loaded, and when the
3563 symbols from the library are not available. When you try to set
3564 breakpoint, @value{GDBN} will ask you if you want to set
3565 a so called @dfn{pending breakpoint}---breakpoint whose address
3566 is not yet resolved.
3568 After the program is run, whenever a new shared library is loaded,
3569 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3570 shared library contains the symbol or line referred to by some
3571 pending breakpoint, that breakpoint is resolved and becomes an
3572 ordinary breakpoint. When a library is unloaded, all breakpoints
3573 that refer to its symbols or source lines become pending again.
3575 This logic works for breakpoints with multiple locations, too. For
3576 example, if you have a breakpoint in a C@t{++} template function, and
3577 a newly loaded shared library has an instantiation of that template,
3578 a new location is added to the list of locations for the breakpoint.
3580 Except for having unresolved address, pending breakpoints do not
3581 differ from regular breakpoints. You can set conditions or commands,
3582 enable and disable them and perform other breakpoint operations.
3584 @value{GDBN} provides some additional commands for controlling what
3585 happens when the @samp{break} command cannot resolve breakpoint
3586 address specification to an address:
3588 @kindex set breakpoint pending
3589 @kindex show breakpoint pending
3591 @item set breakpoint pending auto
3592 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3593 location, it queries you whether a pending breakpoint should be created.
3595 @item set breakpoint pending on
3596 This indicates that an unrecognized breakpoint location should automatically
3597 result in a pending breakpoint being created.
3599 @item set breakpoint pending off
3600 This indicates that pending breakpoints are not to be created. Any
3601 unrecognized breakpoint location results in an error. This setting does
3602 not affect any pending breakpoints previously created.
3604 @item show breakpoint pending
3605 Show the current behavior setting for creating pending breakpoints.
3608 The settings above only affect the @code{break} command and its
3609 variants. Once breakpoint is set, it will be automatically updated
3610 as shared libraries are loaded and unloaded.
3612 @cindex automatic hardware breakpoints
3613 For some targets, @value{GDBN} can automatically decide if hardware or
3614 software breakpoints should be used, depending on whether the
3615 breakpoint address is read-only or read-write. This applies to
3616 breakpoints set with the @code{break} command as well as to internal
3617 breakpoints set by commands like @code{next} and @code{finish}. For
3618 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3621 You can control this automatic behaviour with the following commands::
3623 @kindex set breakpoint auto-hw
3624 @kindex show breakpoint auto-hw
3626 @item set breakpoint auto-hw on
3627 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3628 will try to use the target memory map to decide if software or hardware
3629 breakpoint must be used.
3631 @item set breakpoint auto-hw off
3632 This indicates @value{GDBN} should not automatically select breakpoint
3633 type. If the target provides a memory map, @value{GDBN} will warn when
3634 trying to set software breakpoint at a read-only address.
3637 @value{GDBN} normally implements breakpoints by replacing the program code
3638 at the breakpoint address with a special instruction, which, when
3639 executed, given control to the debugger. By default, the program
3640 code is so modified only when the program is resumed. As soon as
3641 the program stops, @value{GDBN} restores the original instructions. This
3642 behaviour guards against leaving breakpoints inserted in the
3643 target should gdb abrubptly disconnect. However, with slow remote
3644 targets, inserting and removing breakpoint can reduce the performance.
3645 This behavior can be controlled with the following commands::
3647 @kindex set breakpoint always-inserted
3648 @kindex show breakpoint always-inserted
3650 @item set breakpoint always-inserted off
3651 All breakpoints, including newly added by the user, are inserted in
3652 the target only when the target is resumed. All breakpoints are
3653 removed from the target when it stops.
3655 @item set breakpoint always-inserted on
3656 Causes all breakpoints to be inserted in the target at all times. If
3657 the user adds a new breakpoint, or changes an existing breakpoint, the
3658 breakpoints in the target are updated immediately. A breakpoint is
3659 removed from the target only when breakpoint itself is removed.
3661 @cindex non-stop mode, and @code{breakpoint always-inserted}
3662 @item set breakpoint always-inserted auto
3663 This is the default mode. If @value{GDBN} is controlling the inferior
3664 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3665 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3666 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3667 @code{breakpoint always-inserted} mode is off.
3670 @cindex negative breakpoint numbers
3671 @cindex internal @value{GDBN} breakpoints
3672 @value{GDBN} itself sometimes sets breakpoints in your program for
3673 special purposes, such as proper handling of @code{longjmp} (in C
3674 programs). These internal breakpoints are assigned negative numbers,
3675 starting with @code{-1}; @samp{info breakpoints} does not display them.
3676 You can see these breakpoints with the @value{GDBN} maintenance command
3677 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3680 @node Set Watchpoints
3681 @subsection Setting Watchpoints
3683 @cindex setting watchpoints
3684 You can use a watchpoint to stop execution whenever the value of an
3685 expression changes, without having to predict a particular place where
3686 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3687 The expression may be as simple as the value of a single variable, or
3688 as complex as many variables combined by operators. Examples include:
3692 A reference to the value of a single variable.
3695 An address cast to an appropriate data type. For example,
3696 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3697 address (assuming an @code{int} occupies 4 bytes).
3700 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3701 expression can use any operators valid in the program's native
3702 language (@pxref{Languages}).
3705 You can set a watchpoint on an expression even if the expression can
3706 not be evaluated yet. For instance, you can set a watchpoint on
3707 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3708 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3709 the expression produces a valid value. If the expression becomes
3710 valid in some other way than changing a variable (e.g.@: if the memory
3711 pointed to by @samp{*global_ptr} becomes readable as the result of a
3712 @code{malloc} call), @value{GDBN} may not stop until the next time
3713 the expression changes.
3715 @cindex software watchpoints
3716 @cindex hardware watchpoints
3717 Depending on your system, watchpoints may be implemented in software or
3718 hardware. @value{GDBN} does software watchpointing by single-stepping your
3719 program and testing the variable's value each time, which is hundreds of
3720 times slower than normal execution. (But this may still be worth it, to
3721 catch errors where you have no clue what part of your program is the
3724 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3725 x86-based targets, @value{GDBN} includes support for hardware
3726 watchpoints, which do not slow down the running of your program.
3730 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3731 Set a watchpoint for an expression. @value{GDBN} will break when the
3732 expression @var{expr} is written into by the program and its value
3733 changes. The simplest (and the most popular) use of this command is
3734 to watch the value of a single variable:
3737 (@value{GDBP}) watch foo
3740 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3741 clause, @value{GDBN} breaks only when the thread identified by
3742 @var{threadnum} changes the value of @var{expr}. If any other threads
3743 change the value of @var{expr}, @value{GDBN} will not break. Note
3744 that watchpoints restricted to a single thread in this way only work
3745 with Hardware Watchpoints.
3747 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3748 (see below). The @code{-location} argument tells @value{GDBN} to
3749 instead watch the memory referred to by @var{expr}. In this case,
3750 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3751 and watch the memory at that address. The type of the result is used
3752 to determine the size of the watched memory. If the expression's
3753 result does not have an address, then @value{GDBN} will print an
3757 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3758 Set a watchpoint that will break when the value of @var{expr} is read
3762 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3763 Set a watchpoint that will break when @var{expr} is either read from
3764 or written into by the program.
3766 @kindex info watchpoints @r{[}@var{n}@r{]}
3767 @item info watchpoints
3768 This command prints a list of watchpoints, using the same format as
3769 @code{info break} (@pxref{Set Breaks}).
3772 If you watch for a change in a numerically entered address you need to
3773 dereference it, as the address itself is just a constant number which will
3774 never change. @value{GDBN} refuses to create a watchpoint that watches
3775 a never-changing value:
3778 (@value{GDBP}) watch 0x600850
3779 Cannot watch constant value 0x600850.
3780 (@value{GDBP}) watch *(int *) 0x600850
3781 Watchpoint 1: *(int *) 6293584
3784 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3785 watchpoints execute very quickly, and the debugger reports a change in
3786 value at the exact instruction where the change occurs. If @value{GDBN}
3787 cannot set a hardware watchpoint, it sets a software watchpoint, which
3788 executes more slowly and reports the change in value at the next
3789 @emph{statement}, not the instruction, after the change occurs.
3791 @cindex use only software watchpoints
3792 You can force @value{GDBN} to use only software watchpoints with the
3793 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3794 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3795 the underlying system supports them. (Note that hardware-assisted
3796 watchpoints that were set @emph{before} setting
3797 @code{can-use-hw-watchpoints} to zero will still use the hardware
3798 mechanism of watching expression values.)
3801 @item set can-use-hw-watchpoints
3802 @kindex set can-use-hw-watchpoints
3803 Set whether or not to use hardware watchpoints.
3805 @item show can-use-hw-watchpoints
3806 @kindex show can-use-hw-watchpoints
3807 Show the current mode of using hardware watchpoints.
3810 For remote targets, you can restrict the number of hardware
3811 watchpoints @value{GDBN} will use, see @ref{set remote
3812 hardware-breakpoint-limit}.
3814 When you issue the @code{watch} command, @value{GDBN} reports
3817 Hardware watchpoint @var{num}: @var{expr}
3821 if it was able to set a hardware watchpoint.
3823 Currently, the @code{awatch} and @code{rwatch} commands can only set
3824 hardware watchpoints, because accesses to data that don't change the
3825 value of the watched expression cannot be detected without examining
3826 every instruction as it is being executed, and @value{GDBN} does not do
3827 that currently. If @value{GDBN} finds that it is unable to set a
3828 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3829 will print a message like this:
3832 Expression cannot be implemented with read/access watchpoint.
3835 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3836 data type of the watched expression is wider than what a hardware
3837 watchpoint on the target machine can handle. For example, some systems
3838 can only watch regions that are up to 4 bytes wide; on such systems you
3839 cannot set hardware watchpoints for an expression that yields a
3840 double-precision floating-point number (which is typically 8 bytes
3841 wide). As a work-around, it might be possible to break the large region
3842 into a series of smaller ones and watch them with separate watchpoints.
3844 If you set too many hardware watchpoints, @value{GDBN} might be unable
3845 to insert all of them when you resume the execution of your program.
3846 Since the precise number of active watchpoints is unknown until such
3847 time as the program is about to be resumed, @value{GDBN} might not be
3848 able to warn you about this when you set the watchpoints, and the
3849 warning will be printed only when the program is resumed:
3852 Hardware watchpoint @var{num}: Could not insert watchpoint
3856 If this happens, delete or disable some of the watchpoints.
3858 Watching complex expressions that reference many variables can also
3859 exhaust the resources available for hardware-assisted watchpoints.
3860 That's because @value{GDBN} needs to watch every variable in the
3861 expression with separately allocated resources.
3863 If you call a function interactively using @code{print} or @code{call},
3864 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3865 kind of breakpoint or the call completes.
3867 @value{GDBN} automatically deletes watchpoints that watch local
3868 (automatic) variables, or expressions that involve such variables, when
3869 they go out of scope, that is, when the execution leaves the block in
3870 which these variables were defined. In particular, when the program
3871 being debugged terminates, @emph{all} local variables go out of scope,
3872 and so only watchpoints that watch global variables remain set. If you
3873 rerun the program, you will need to set all such watchpoints again. One
3874 way of doing that would be to set a code breakpoint at the entry to the
3875 @code{main} function and when it breaks, set all the watchpoints.
3877 @cindex watchpoints and threads
3878 @cindex threads and watchpoints
3879 In multi-threaded programs, watchpoints will detect changes to the
3880 watched expression from every thread.
3883 @emph{Warning:} In multi-threaded programs, software watchpoints
3884 have only limited usefulness. If @value{GDBN} creates a software
3885 watchpoint, it can only watch the value of an expression @emph{in a
3886 single thread}. If you are confident that the expression can only
3887 change due to the current thread's activity (and if you are also
3888 confident that no other thread can become current), then you can use
3889 software watchpoints as usual. However, @value{GDBN} may not notice
3890 when a non-current thread's activity changes the expression. (Hardware
3891 watchpoints, in contrast, watch an expression in all threads.)
3894 @xref{set remote hardware-watchpoint-limit}.
3896 @node Set Catchpoints
3897 @subsection Setting Catchpoints
3898 @cindex catchpoints, setting
3899 @cindex exception handlers
3900 @cindex event handling
3902 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3903 kinds of program events, such as C@t{++} exceptions or the loading of a
3904 shared library. Use the @code{catch} command to set a catchpoint.
3908 @item catch @var{event}
3909 Stop when @var{event} occurs. @var{event} can be any of the following:
3912 @cindex stop on C@t{++} exceptions
3913 The throwing of a C@t{++} exception.
3916 The catching of a C@t{++} exception.
3919 @cindex Ada exception catching
3920 @cindex catch Ada exceptions
3921 An Ada exception being raised. If an exception name is specified
3922 at the end of the command (eg @code{catch exception Program_Error}),
3923 the debugger will stop only when this specific exception is raised.
3924 Otherwise, the debugger stops execution when any Ada exception is raised.
3926 When inserting an exception catchpoint on a user-defined exception whose
3927 name is identical to one of the exceptions defined by the language, the
3928 fully qualified name must be used as the exception name. Otherwise,
3929 @value{GDBN} will assume that it should stop on the pre-defined exception
3930 rather than the user-defined one. For instance, assuming an exception
3931 called @code{Constraint_Error} is defined in package @code{Pck}, then
3932 the command to use to catch such exceptions is @kbd{catch exception
3933 Pck.Constraint_Error}.
3935 @item exception unhandled
3936 An exception that was raised but is not handled by the program.
3939 A failed Ada assertion.
3942 @cindex break on fork/exec
3943 A call to @code{exec}. This is currently only available for HP-UX
3947 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3948 @cindex break on a system call.
3949 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3950 syscall is a mechanism for application programs to request a service
3951 from the operating system (OS) or one of the OS system services.
3952 @value{GDBN} can catch some or all of the syscalls issued by the
3953 debuggee, and show the related information for each syscall. If no
3954 argument is specified, calls to and returns from all system calls
3957 @var{name} can be any system call name that is valid for the
3958 underlying OS. Just what syscalls are valid depends on the OS. On
3959 GNU and Unix systems, you can find the full list of valid syscall
3960 names on @file{/usr/include/asm/unistd.h}.
3962 @c For MS-Windows, the syscall names and the corresponding numbers
3963 @c can be found, e.g., on this URL:
3964 @c http://www.metasploit.com/users/opcode/syscalls.html
3965 @c but we don't support Windows syscalls yet.
3967 Normally, @value{GDBN} knows in advance which syscalls are valid for
3968 each OS, so you can use the @value{GDBN} command-line completion
3969 facilities (@pxref{Completion,, command completion}) to list the
3972 You may also specify the system call numerically. A syscall's
3973 number is the value passed to the OS's syscall dispatcher to
3974 identify the requested service. When you specify the syscall by its
3975 name, @value{GDBN} uses its database of syscalls to convert the name
3976 into the corresponding numeric code, but using the number directly
3977 may be useful if @value{GDBN}'s database does not have the complete
3978 list of syscalls on your system (e.g., because @value{GDBN} lags
3979 behind the OS upgrades).
3981 The example below illustrates how this command works if you don't provide
3985 (@value{GDBP}) catch syscall
3986 Catchpoint 1 (syscall)
3988 Starting program: /tmp/catch-syscall
3990 Catchpoint 1 (call to syscall 'close'), \
3991 0xffffe424 in __kernel_vsyscall ()
3995 Catchpoint 1 (returned from syscall 'close'), \
3996 0xffffe424 in __kernel_vsyscall ()
4000 Here is an example of catching a system call by name:
4003 (@value{GDBP}) catch syscall chroot
4004 Catchpoint 1 (syscall 'chroot' [61])
4006 Starting program: /tmp/catch-syscall
4008 Catchpoint 1 (call to syscall 'chroot'), \
4009 0xffffe424 in __kernel_vsyscall ()
4013 Catchpoint 1 (returned from syscall 'chroot'), \
4014 0xffffe424 in __kernel_vsyscall ()
4018 An example of specifying a system call numerically. In the case
4019 below, the syscall number has a corresponding entry in the XML
4020 file, so @value{GDBN} finds its name and prints it:
4023 (@value{GDBP}) catch syscall 252
4024 Catchpoint 1 (syscall(s) 'exit_group')
4026 Starting program: /tmp/catch-syscall
4028 Catchpoint 1 (call to syscall 'exit_group'), \
4029 0xffffe424 in __kernel_vsyscall ()
4033 Program exited normally.
4037 However, there can be situations when there is no corresponding name
4038 in XML file for that syscall number. In this case, @value{GDBN} prints
4039 a warning message saying that it was not able to find the syscall name,
4040 but the catchpoint will be set anyway. See the example below:
4043 (@value{GDBP}) catch syscall 764
4044 warning: The number '764' does not represent a known syscall.
4045 Catchpoint 2 (syscall 764)
4049 If you configure @value{GDBN} using the @samp{--without-expat} option,
4050 it will not be able to display syscall names. Also, if your
4051 architecture does not have an XML file describing its system calls,
4052 you will not be able to see the syscall names. It is important to
4053 notice that these two features are used for accessing the syscall
4054 name database. In either case, you will see a warning like this:
4057 (@value{GDBP}) catch syscall
4058 warning: Could not open "syscalls/i386-linux.xml"
4059 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4060 GDB will not be able to display syscall names.
4061 Catchpoint 1 (syscall)
4065 Of course, the file name will change depending on your architecture and system.
4067 Still using the example above, you can also try to catch a syscall by its
4068 number. In this case, you would see something like:
4071 (@value{GDBP}) catch syscall 252
4072 Catchpoint 1 (syscall(s) 252)
4075 Again, in this case @value{GDBN} would not be able to display syscall's names.
4078 A call to @code{fork}. This is currently only available for HP-UX
4082 A call to @code{vfork}. This is currently only available for HP-UX
4087 @item tcatch @var{event}
4088 Set a catchpoint that is enabled only for one stop. The catchpoint is
4089 automatically deleted after the first time the event is caught.
4093 Use the @code{info break} command to list the current catchpoints.
4095 There are currently some limitations to C@t{++} exception handling
4096 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4100 If you call a function interactively, @value{GDBN} normally returns
4101 control to you when the function has finished executing. If the call
4102 raises an exception, however, the call may bypass the mechanism that
4103 returns control to you and cause your program either to abort or to
4104 simply continue running until it hits a breakpoint, catches a signal
4105 that @value{GDBN} is listening for, or exits. This is the case even if
4106 you set a catchpoint for the exception; catchpoints on exceptions are
4107 disabled within interactive calls.
4110 You cannot raise an exception interactively.
4113 You cannot install an exception handler interactively.
4116 @cindex raise exceptions
4117 Sometimes @code{catch} is not the best way to debug exception handling:
4118 if you need to know exactly where an exception is raised, it is better to
4119 stop @emph{before} the exception handler is called, since that way you
4120 can see the stack before any unwinding takes place. If you set a
4121 breakpoint in an exception handler instead, it may not be easy to find
4122 out where the exception was raised.
4124 To stop just before an exception handler is called, you need some
4125 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4126 raised by calling a library function named @code{__raise_exception}
4127 which has the following ANSI C interface:
4130 /* @var{addr} is where the exception identifier is stored.
4131 @var{id} is the exception identifier. */
4132 void __raise_exception (void **addr, void *id);
4136 To make the debugger catch all exceptions before any stack
4137 unwinding takes place, set a breakpoint on @code{__raise_exception}
4138 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4140 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4141 that depends on the value of @var{id}, you can stop your program when
4142 a specific exception is raised. You can use multiple conditional
4143 breakpoints to stop your program when any of a number of exceptions are
4148 @subsection Deleting Breakpoints
4150 @cindex clearing breakpoints, watchpoints, catchpoints
4151 @cindex deleting breakpoints, watchpoints, catchpoints
4152 It is often necessary to eliminate a breakpoint, watchpoint, or
4153 catchpoint once it has done its job and you no longer want your program
4154 to stop there. This is called @dfn{deleting} the breakpoint. A
4155 breakpoint that has been deleted no longer exists; it is forgotten.
4157 With the @code{clear} command you can delete breakpoints according to
4158 where they are in your program. With the @code{delete} command you can
4159 delete individual breakpoints, watchpoints, or catchpoints by specifying
4160 their breakpoint numbers.
4162 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4163 automatically ignores breakpoints on the first instruction to be executed
4164 when you continue execution without changing the execution address.
4169 Delete any breakpoints at the next instruction to be executed in the
4170 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4171 the innermost frame is selected, this is a good way to delete a
4172 breakpoint where your program just stopped.
4174 @item clear @var{location}
4175 Delete any breakpoints set at the specified @var{location}.
4176 @xref{Specify Location}, for the various forms of @var{location}; the
4177 most useful ones are listed below:
4180 @item clear @var{function}
4181 @itemx clear @var{filename}:@var{function}
4182 Delete any breakpoints set at entry to the named @var{function}.
4184 @item clear @var{linenum}
4185 @itemx clear @var{filename}:@var{linenum}
4186 Delete any breakpoints set at or within the code of the specified
4187 @var{linenum} of the specified @var{filename}.
4190 @cindex delete breakpoints
4192 @kindex d @r{(@code{delete})}
4193 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4194 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4195 ranges specified as arguments. If no argument is specified, delete all
4196 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4197 confirm off}). You can abbreviate this command as @code{d}.
4201 @subsection Disabling Breakpoints
4203 @cindex enable/disable a breakpoint
4204 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4205 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4206 it had been deleted, but remembers the information on the breakpoint so
4207 that you can @dfn{enable} it again later.
4209 You disable and enable breakpoints, watchpoints, and catchpoints with
4210 the @code{enable} and @code{disable} commands, optionally specifying
4211 one or more breakpoint numbers as arguments. Use @code{info break} to
4212 print a list of all breakpoints, watchpoints, and catchpoints if you
4213 do not know which numbers to use.
4215 Disabling and enabling a breakpoint that has multiple locations
4216 affects all of its locations.
4218 A breakpoint, watchpoint, or catchpoint can have any of four different
4219 states of enablement:
4223 Enabled. The breakpoint stops your program. A breakpoint set
4224 with the @code{break} command starts out in this state.
4226 Disabled. The breakpoint has no effect on your program.
4228 Enabled once. The breakpoint stops your program, but then becomes
4231 Enabled for deletion. The breakpoint stops your program, but
4232 immediately after it does so it is deleted permanently. A breakpoint
4233 set with the @code{tbreak} command starts out in this state.
4236 You can use the following commands to enable or disable breakpoints,
4237 watchpoints, and catchpoints:
4241 @kindex dis @r{(@code{disable})}
4242 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4243 Disable the specified breakpoints---or all breakpoints, if none are
4244 listed. A disabled breakpoint has no effect but is not forgotten. All
4245 options such as ignore-counts, conditions and commands are remembered in
4246 case the breakpoint is enabled again later. You may abbreviate
4247 @code{disable} as @code{dis}.
4250 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4251 Enable the specified breakpoints (or all defined breakpoints). They
4252 become effective once again in stopping your program.
4254 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4255 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4256 of these breakpoints immediately after stopping your program.
4258 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4259 Enable the specified breakpoints to work once, then die. @value{GDBN}
4260 deletes any of these breakpoints as soon as your program stops there.
4261 Breakpoints set by the @code{tbreak} command start out in this state.
4264 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4265 @c confusing: tbreak is also initially enabled.
4266 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4267 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4268 subsequently, they become disabled or enabled only when you use one of
4269 the commands above. (The command @code{until} can set and delete a
4270 breakpoint of its own, but it does not change the state of your other
4271 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4275 @subsection Break Conditions
4276 @cindex conditional breakpoints
4277 @cindex breakpoint conditions
4279 @c FIXME what is scope of break condition expr? Context where wanted?
4280 @c in particular for a watchpoint?
4281 The simplest sort of breakpoint breaks every time your program reaches a
4282 specified place. You can also specify a @dfn{condition} for a
4283 breakpoint. A condition is just a Boolean expression in your
4284 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4285 a condition evaluates the expression each time your program reaches it,
4286 and your program stops only if the condition is @emph{true}.
4288 This is the converse of using assertions for program validation; in that
4289 situation, you want to stop when the assertion is violated---that is,
4290 when the condition is false. In C, if you want to test an assertion expressed
4291 by the condition @var{assert}, you should set the condition
4292 @samp{! @var{assert}} on the appropriate breakpoint.
4294 Conditions are also accepted for watchpoints; you may not need them,
4295 since a watchpoint is inspecting the value of an expression anyhow---but
4296 it might be simpler, say, to just set a watchpoint on a variable name,
4297 and specify a condition that tests whether the new value is an interesting
4300 Break conditions can have side effects, and may even call functions in
4301 your program. This can be useful, for example, to activate functions
4302 that log program progress, or to use your own print functions to
4303 format special data structures. The effects are completely predictable
4304 unless there is another enabled breakpoint at the same address. (In
4305 that case, @value{GDBN} might see the other breakpoint first and stop your
4306 program without checking the condition of this one.) Note that
4307 breakpoint commands are usually more convenient and flexible than break
4309 purpose of performing side effects when a breakpoint is reached
4310 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4312 Break conditions can be specified when a breakpoint is set, by using
4313 @samp{if} in the arguments to the @code{break} command. @xref{Set
4314 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4315 with the @code{condition} command.
4317 You can also use the @code{if} keyword with the @code{watch} command.
4318 The @code{catch} command does not recognize the @code{if} keyword;
4319 @code{condition} is the only way to impose a further condition on a
4324 @item condition @var{bnum} @var{expression}
4325 Specify @var{expression} as the break condition for breakpoint,
4326 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4327 breakpoint @var{bnum} stops your program only if the value of
4328 @var{expression} is true (nonzero, in C). When you use
4329 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4330 syntactic correctness, and to determine whether symbols in it have
4331 referents in the context of your breakpoint. If @var{expression} uses
4332 symbols not referenced in the context of the breakpoint, @value{GDBN}
4333 prints an error message:
4336 No symbol "foo" in current context.
4341 not actually evaluate @var{expression} at the time the @code{condition}
4342 command (or a command that sets a breakpoint with a condition, like
4343 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4345 @item condition @var{bnum}
4346 Remove the condition from breakpoint number @var{bnum}. It becomes
4347 an ordinary unconditional breakpoint.
4350 @cindex ignore count (of breakpoint)
4351 A special case of a breakpoint condition is to stop only when the
4352 breakpoint has been reached a certain number of times. This is so
4353 useful that there is a special way to do it, using the @dfn{ignore
4354 count} of the breakpoint. Every breakpoint has an ignore count, which
4355 is an integer. Most of the time, the ignore count is zero, and
4356 therefore has no effect. But if your program reaches a breakpoint whose
4357 ignore count is positive, then instead of stopping, it just decrements
4358 the ignore count by one and continues. As a result, if the ignore count
4359 value is @var{n}, the breakpoint does not stop the next @var{n} times
4360 your program reaches it.
4364 @item ignore @var{bnum} @var{count}
4365 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4366 The next @var{count} times the breakpoint is reached, your program's
4367 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4370 To make the breakpoint stop the next time it is reached, specify
4373 When you use @code{continue} to resume execution of your program from a
4374 breakpoint, you can specify an ignore count directly as an argument to
4375 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4376 Stepping,,Continuing and Stepping}.
4378 If a breakpoint has a positive ignore count and a condition, the
4379 condition is not checked. Once the ignore count reaches zero,
4380 @value{GDBN} resumes checking the condition.
4382 You could achieve the effect of the ignore count with a condition such
4383 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4384 is decremented each time. @xref{Convenience Vars, ,Convenience
4388 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4391 @node Break Commands
4392 @subsection Breakpoint Command Lists
4394 @cindex breakpoint commands
4395 You can give any breakpoint (or watchpoint or catchpoint) a series of
4396 commands to execute when your program stops due to that breakpoint. For
4397 example, you might want to print the values of certain expressions, or
4398 enable other breakpoints.
4402 @kindex end@r{ (breakpoint commands)}
4403 @item commands @r{[}@var{range}@dots{}@r{]}
4404 @itemx @dots{} @var{command-list} @dots{}
4406 Specify a list of commands for the given breakpoints. The commands
4407 themselves appear on the following lines. Type a line containing just
4408 @code{end} to terminate the commands.
4410 To remove all commands from a breakpoint, type @code{commands} and
4411 follow it immediately with @code{end}; that is, give no commands.
4413 With no argument, @code{commands} refers to the last breakpoint,
4414 watchpoint, or catchpoint set (not to the breakpoint most recently
4415 encountered). If the most recent breakpoints were set with a single
4416 command, then the @code{commands} will apply to all the breakpoints
4417 set by that command. This applies to breakpoints set by
4418 @code{rbreak}, and also applies when a single @code{break} command
4419 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4423 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4424 disabled within a @var{command-list}.
4426 You can use breakpoint commands to start your program up again. Simply
4427 use the @code{continue} command, or @code{step}, or any other command
4428 that resumes execution.
4430 Any other commands in the command list, after a command that resumes
4431 execution, are ignored. This is because any time you resume execution
4432 (even with a simple @code{next} or @code{step}), you may encounter
4433 another breakpoint---which could have its own command list, leading to
4434 ambiguities about which list to execute.
4437 If the first command you specify in a command list is @code{silent}, the
4438 usual message about stopping at a breakpoint is not printed. This may
4439 be desirable for breakpoints that are to print a specific message and
4440 then continue. If none of the remaining commands print anything, you
4441 see no sign that the breakpoint was reached. @code{silent} is
4442 meaningful only at the beginning of a breakpoint command list.
4444 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4445 print precisely controlled output, and are often useful in silent
4446 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4448 For example, here is how you could use breakpoint commands to print the
4449 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4455 printf "x is %d\n",x
4460 One application for breakpoint commands is to compensate for one bug so
4461 you can test for another. Put a breakpoint just after the erroneous line
4462 of code, give it a condition to detect the case in which something
4463 erroneous has been done, and give it commands to assign correct values
4464 to any variables that need them. End with the @code{continue} command
4465 so that your program does not stop, and start with the @code{silent}
4466 command so that no output is produced. Here is an example:
4477 @node Save Breakpoints
4478 @subsection How to save breakpoints to a file
4480 To save breakpoint definitions to a file use the @w{@code{save
4481 breakpoints}} command.
4484 @kindex save breakpoints
4485 @cindex save breakpoints to a file for future sessions
4486 @item save breakpoints [@var{filename}]
4487 This command saves all current breakpoint definitions together with
4488 their commands and ignore counts, into a file @file{@var{filename}}
4489 suitable for use in a later debugging session. This includes all
4490 types of breakpoints (breakpoints, watchpoints, catchpoints,
4491 tracepoints). To read the saved breakpoint definitions, use the
4492 @code{source} command (@pxref{Command Files}). Note that watchpoints
4493 with expressions involving local variables may fail to be recreated
4494 because it may not be possible to access the context where the
4495 watchpoint is valid anymore. Because the saved breakpoint definitions
4496 are simply a sequence of @value{GDBN} commands that recreate the
4497 breakpoints, you can edit the file in your favorite editing program,
4498 and remove the breakpoint definitions you're not interested in, or
4499 that can no longer be recreated.
4502 @c @ifclear BARETARGET
4503 @node Error in Breakpoints
4504 @subsection ``Cannot insert breakpoints''
4506 If you request too many active hardware-assisted breakpoints and
4507 watchpoints, you will see this error message:
4509 @c FIXME: the precise wording of this message may change; the relevant
4510 @c source change is not committed yet (Sep 3, 1999).
4512 Stopped; cannot insert breakpoints.
4513 You may have requested too many hardware breakpoints and watchpoints.
4517 This message is printed when you attempt to resume the program, since
4518 only then @value{GDBN} knows exactly how many hardware breakpoints and
4519 watchpoints it needs to insert.
4521 When this message is printed, you need to disable or remove some of the
4522 hardware-assisted breakpoints and watchpoints, and then continue.
4524 @node Breakpoint-related Warnings
4525 @subsection ``Breakpoint address adjusted...''
4526 @cindex breakpoint address adjusted
4528 Some processor architectures place constraints on the addresses at
4529 which breakpoints may be placed. For architectures thus constrained,
4530 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4531 with the constraints dictated by the architecture.
4533 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4534 a VLIW architecture in which a number of RISC-like instructions may be
4535 bundled together for parallel execution. The FR-V architecture
4536 constrains the location of a breakpoint instruction within such a
4537 bundle to the instruction with the lowest address. @value{GDBN}
4538 honors this constraint by adjusting a breakpoint's address to the
4539 first in the bundle.
4541 It is not uncommon for optimized code to have bundles which contain
4542 instructions from different source statements, thus it may happen that
4543 a breakpoint's address will be adjusted from one source statement to
4544 another. Since this adjustment may significantly alter @value{GDBN}'s
4545 breakpoint related behavior from what the user expects, a warning is
4546 printed when the breakpoint is first set and also when the breakpoint
4549 A warning like the one below is printed when setting a breakpoint
4550 that's been subject to address adjustment:
4553 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4556 Such warnings are printed both for user settable and @value{GDBN}'s
4557 internal breakpoints. If you see one of these warnings, you should
4558 verify that a breakpoint set at the adjusted address will have the
4559 desired affect. If not, the breakpoint in question may be removed and
4560 other breakpoints may be set which will have the desired behavior.
4561 E.g., it may be sufficient to place the breakpoint at a later
4562 instruction. A conditional breakpoint may also be useful in some
4563 cases to prevent the breakpoint from triggering too often.
4565 @value{GDBN} will also issue a warning when stopping at one of these
4566 adjusted breakpoints:
4569 warning: Breakpoint 1 address previously adjusted from 0x00010414
4573 When this warning is encountered, it may be too late to take remedial
4574 action except in cases where the breakpoint is hit earlier or more
4575 frequently than expected.
4577 @node Continuing and Stepping
4578 @section Continuing and Stepping
4582 @cindex resuming execution
4583 @dfn{Continuing} means resuming program execution until your program
4584 completes normally. In contrast, @dfn{stepping} means executing just
4585 one more ``step'' of your program, where ``step'' may mean either one
4586 line of source code, or one machine instruction (depending on what
4587 particular command you use). Either when continuing or when stepping,
4588 your program may stop even sooner, due to a breakpoint or a signal. (If
4589 it stops due to a signal, you may want to use @code{handle}, or use
4590 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4594 @kindex c @r{(@code{continue})}
4595 @kindex fg @r{(resume foreground execution)}
4596 @item continue @r{[}@var{ignore-count}@r{]}
4597 @itemx c @r{[}@var{ignore-count}@r{]}
4598 @itemx fg @r{[}@var{ignore-count}@r{]}
4599 Resume program execution, at the address where your program last stopped;
4600 any breakpoints set at that address are bypassed. The optional argument
4601 @var{ignore-count} allows you to specify a further number of times to
4602 ignore a breakpoint at this location; its effect is like that of
4603 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4605 The argument @var{ignore-count} is meaningful only when your program
4606 stopped due to a breakpoint. At other times, the argument to
4607 @code{continue} is ignored.
4609 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4610 debugged program is deemed to be the foreground program) are provided
4611 purely for convenience, and have exactly the same behavior as
4615 To resume execution at a different place, you can use @code{return}
4616 (@pxref{Returning, ,Returning from a Function}) to go back to the
4617 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4618 Different Address}) to go to an arbitrary location in your program.
4620 A typical technique for using stepping is to set a breakpoint
4621 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4622 beginning of the function or the section of your program where a problem
4623 is believed to lie, run your program until it stops at that breakpoint,
4624 and then step through the suspect area, examining the variables that are
4625 interesting, until you see the problem happen.
4629 @kindex s @r{(@code{step})}
4631 Continue running your program until control reaches a different source
4632 line, then stop it and return control to @value{GDBN}. This command is
4633 abbreviated @code{s}.
4636 @c "without debugging information" is imprecise; actually "without line
4637 @c numbers in the debugging information". (gcc -g1 has debugging info but
4638 @c not line numbers). But it seems complex to try to make that
4639 @c distinction here.
4640 @emph{Warning:} If you use the @code{step} command while control is
4641 within a function that was compiled without debugging information,
4642 execution proceeds until control reaches a function that does have
4643 debugging information. Likewise, it will not step into a function which
4644 is compiled without debugging information. To step through functions
4645 without debugging information, use the @code{stepi} command, described
4649 The @code{step} command only stops at the first instruction of a source
4650 line. This prevents the multiple stops that could otherwise occur in
4651 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4652 to stop if a function that has debugging information is called within
4653 the line. In other words, @code{step} @emph{steps inside} any functions
4654 called within the line.
4656 Also, the @code{step} command only enters a function if there is line
4657 number information for the function. Otherwise it acts like the
4658 @code{next} command. This avoids problems when using @code{cc -gl}
4659 on MIPS machines. Previously, @code{step} entered subroutines if there
4660 was any debugging information about the routine.
4662 @item step @var{count}
4663 Continue running as in @code{step}, but do so @var{count} times. If a
4664 breakpoint is reached, or a signal not related to stepping occurs before
4665 @var{count} steps, stepping stops right away.
4668 @kindex n @r{(@code{next})}
4669 @item next @r{[}@var{count}@r{]}
4670 Continue to the next source line in the current (innermost) stack frame.
4671 This is similar to @code{step}, but function calls that appear within
4672 the line of code are executed without stopping. Execution stops when
4673 control reaches a different line of code at the original stack level
4674 that was executing when you gave the @code{next} command. This command
4675 is abbreviated @code{n}.
4677 An argument @var{count} is a repeat count, as for @code{step}.
4680 @c FIX ME!! Do we delete this, or is there a way it fits in with
4681 @c the following paragraph? --- Vctoria
4683 @c @code{next} within a function that lacks debugging information acts like
4684 @c @code{step}, but any function calls appearing within the code of the
4685 @c function are executed without stopping.
4687 The @code{next} command only stops at the first instruction of a
4688 source line. This prevents multiple stops that could otherwise occur in
4689 @code{switch} statements, @code{for} loops, etc.
4691 @kindex set step-mode
4693 @cindex functions without line info, and stepping
4694 @cindex stepping into functions with no line info
4695 @itemx set step-mode on
4696 The @code{set step-mode on} command causes the @code{step} command to
4697 stop at the first instruction of a function which contains no debug line
4698 information rather than stepping over it.
4700 This is useful in cases where you may be interested in inspecting the
4701 machine instructions of a function which has no symbolic info and do not
4702 want @value{GDBN} to automatically skip over this function.
4704 @item set step-mode off
4705 Causes the @code{step} command to step over any functions which contains no
4706 debug information. This is the default.
4708 @item show step-mode
4709 Show whether @value{GDBN} will stop in or step over functions without
4710 source line debug information.
4713 @kindex fin @r{(@code{finish})}
4715 Continue running until just after function in the selected stack frame
4716 returns. Print the returned value (if any). This command can be
4717 abbreviated as @code{fin}.
4719 Contrast this with the @code{return} command (@pxref{Returning,
4720 ,Returning from a Function}).
4723 @kindex u @r{(@code{until})}
4724 @cindex run until specified location
4727 Continue running until a source line past the current line, in the
4728 current stack frame, is reached. This command is used to avoid single
4729 stepping through a loop more than once. It is like the @code{next}
4730 command, except that when @code{until} encounters a jump, it
4731 automatically continues execution until the program counter is greater
4732 than the address of the jump.
4734 This means that when you reach the end of a loop after single stepping
4735 though it, @code{until} makes your program continue execution until it
4736 exits the loop. In contrast, a @code{next} command at the end of a loop
4737 simply steps back to the beginning of the loop, which forces you to step
4738 through the next iteration.
4740 @code{until} always stops your program if it attempts to exit the current
4743 @code{until} may produce somewhat counterintuitive results if the order
4744 of machine code does not match the order of the source lines. For
4745 example, in the following excerpt from a debugging session, the @code{f}
4746 (@code{frame}) command shows that execution is stopped at line
4747 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4751 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4753 (@value{GDBP}) until
4754 195 for ( ; argc > 0; NEXTARG) @{
4757 This happened because, for execution efficiency, the compiler had
4758 generated code for the loop closure test at the end, rather than the
4759 start, of the loop---even though the test in a C @code{for}-loop is
4760 written before the body of the loop. The @code{until} command appeared
4761 to step back to the beginning of the loop when it advanced to this
4762 expression; however, it has not really gone to an earlier
4763 statement---not in terms of the actual machine code.
4765 @code{until} with no argument works by means of single
4766 instruction stepping, and hence is slower than @code{until} with an
4769 @item until @var{location}
4770 @itemx u @var{location}
4771 Continue running your program until either the specified location is
4772 reached, or the current stack frame returns. @var{location} is any of
4773 the forms described in @ref{Specify Location}.
4774 This form of the command uses temporary breakpoints, and
4775 hence is quicker than @code{until} without an argument. The specified
4776 location is actually reached only if it is in the current frame. This
4777 implies that @code{until} can be used to skip over recursive function
4778 invocations. For instance in the code below, if the current location is
4779 line @code{96}, issuing @code{until 99} will execute the program up to
4780 line @code{99} in the same invocation of factorial, i.e., after the inner
4781 invocations have returned.
4784 94 int factorial (int value)
4786 96 if (value > 1) @{
4787 97 value *= factorial (value - 1);
4794 @kindex advance @var{location}
4795 @itemx advance @var{location}
4796 Continue running the program up to the given @var{location}. An argument is
4797 required, which should be of one of the forms described in
4798 @ref{Specify Location}.
4799 Execution will also stop upon exit from the current stack
4800 frame. This command is similar to @code{until}, but @code{advance} will
4801 not skip over recursive function calls, and the target location doesn't
4802 have to be in the same frame as the current one.
4806 @kindex si @r{(@code{stepi})}
4808 @itemx stepi @var{arg}
4810 Execute one machine instruction, then stop and return to the debugger.
4812 It is often useful to do @samp{display/i $pc} when stepping by machine
4813 instructions. This makes @value{GDBN} automatically display the next
4814 instruction to be executed, each time your program stops. @xref{Auto
4815 Display,, Automatic Display}.
4817 An argument is a repeat count, as in @code{step}.
4821 @kindex ni @r{(@code{nexti})}
4823 @itemx nexti @var{arg}
4825 Execute one machine instruction, but if it is a function call,
4826 proceed until the function returns.
4828 An argument is a repeat count, as in @code{next}.
4835 A signal is an asynchronous event that can happen in a program. The
4836 operating system defines the possible kinds of signals, and gives each
4837 kind a name and a number. For example, in Unix @code{SIGINT} is the
4838 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4839 @code{SIGSEGV} is the signal a program gets from referencing a place in
4840 memory far away from all the areas in use; @code{SIGALRM} occurs when
4841 the alarm clock timer goes off (which happens only if your program has
4842 requested an alarm).
4844 @cindex fatal signals
4845 Some signals, including @code{SIGALRM}, are a normal part of the
4846 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4847 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4848 program has not specified in advance some other way to handle the signal.
4849 @code{SIGINT} does not indicate an error in your program, but it is normally
4850 fatal so it can carry out the purpose of the interrupt: to kill the program.
4852 @value{GDBN} has the ability to detect any occurrence of a signal in your
4853 program. You can tell @value{GDBN} in advance what to do for each kind of
4856 @cindex handling signals
4857 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4858 @code{SIGALRM} be silently passed to your program
4859 (so as not to interfere with their role in the program's functioning)
4860 but to stop your program immediately whenever an error signal happens.
4861 You can change these settings with the @code{handle} command.
4864 @kindex info signals
4868 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4869 handle each one. You can use this to see the signal numbers of all
4870 the defined types of signals.
4872 @item info signals @var{sig}
4873 Similar, but print information only about the specified signal number.
4875 @code{info handle} is an alias for @code{info signals}.
4878 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4879 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4880 can be the number of a signal or its name (with or without the
4881 @samp{SIG} at the beginning); a list of signal numbers of the form
4882 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4883 known signals. Optional arguments @var{keywords}, described below,
4884 say what change to make.
4888 The keywords allowed by the @code{handle} command can be abbreviated.
4889 Their full names are:
4893 @value{GDBN} should not stop your program when this signal happens. It may
4894 still print a message telling you that the signal has come in.
4897 @value{GDBN} should stop your program when this signal happens. This implies
4898 the @code{print} keyword as well.
4901 @value{GDBN} should print a message when this signal happens.
4904 @value{GDBN} should not mention the occurrence of the signal at all. This
4905 implies the @code{nostop} keyword as well.
4909 @value{GDBN} should allow your program to see this signal; your program
4910 can handle the signal, or else it may terminate if the signal is fatal
4911 and not handled. @code{pass} and @code{noignore} are synonyms.
4915 @value{GDBN} should not allow your program to see this signal.
4916 @code{nopass} and @code{ignore} are synonyms.
4920 When a signal stops your program, the signal is not visible to the
4922 continue. Your program sees the signal then, if @code{pass} is in
4923 effect for the signal in question @emph{at that time}. In other words,
4924 after @value{GDBN} reports a signal, you can use the @code{handle}
4925 command with @code{pass} or @code{nopass} to control whether your
4926 program sees that signal when you continue.
4928 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4929 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4930 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4933 You can also use the @code{signal} command to prevent your program from
4934 seeing a signal, or cause it to see a signal it normally would not see,
4935 or to give it any signal at any time. For example, if your program stopped
4936 due to some sort of memory reference error, you might store correct
4937 values into the erroneous variables and continue, hoping to see more
4938 execution; but your program would probably terminate immediately as
4939 a result of the fatal signal once it saw the signal. To prevent this,
4940 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4943 @cindex extra signal information
4944 @anchor{extra signal information}
4946 On some targets, @value{GDBN} can inspect extra signal information
4947 associated with the intercepted signal, before it is actually
4948 delivered to the program being debugged. This information is exported
4949 by the convenience variable @code{$_siginfo}, and consists of data
4950 that is passed by the kernel to the signal handler at the time of the
4951 receipt of a signal. The data type of the information itself is
4952 target dependent. You can see the data type using the @code{ptype
4953 $_siginfo} command. On Unix systems, it typically corresponds to the
4954 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4957 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4958 referenced address that raised a segmentation fault.
4962 (@value{GDBP}) continue
4963 Program received signal SIGSEGV, Segmentation fault.
4964 0x0000000000400766 in main ()
4966 (@value{GDBP}) ptype $_siginfo
4973 struct @{...@} _kill;
4974 struct @{...@} _timer;
4976 struct @{...@} _sigchld;
4977 struct @{...@} _sigfault;
4978 struct @{...@} _sigpoll;
4981 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4985 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4986 $1 = (void *) 0x7ffff7ff7000
4990 Depending on target support, @code{$_siginfo} may also be writable.
4993 @section Stopping and Starting Multi-thread Programs
4995 @cindex stopped threads
4996 @cindex threads, stopped
4998 @cindex continuing threads
4999 @cindex threads, continuing
5001 @value{GDBN} supports debugging programs with multiple threads
5002 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5003 are two modes of controlling execution of your program within the
5004 debugger. In the default mode, referred to as @dfn{all-stop mode},
5005 when any thread in your program stops (for example, at a breakpoint
5006 or while being stepped), all other threads in the program are also stopped by
5007 @value{GDBN}. On some targets, @value{GDBN} also supports
5008 @dfn{non-stop mode}, in which other threads can continue to run freely while
5009 you examine the stopped thread in the debugger.
5012 * All-Stop Mode:: All threads stop when GDB takes control
5013 * Non-Stop Mode:: Other threads continue to execute
5014 * Background Execution:: Running your program asynchronously
5015 * Thread-Specific Breakpoints:: Controlling breakpoints
5016 * Interrupted System Calls:: GDB may interfere with system calls
5017 * Observer Mode:: GDB does not alter program behavior
5021 @subsection All-Stop Mode
5023 @cindex all-stop mode
5025 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5026 @emph{all} threads of execution stop, not just the current thread. This
5027 allows you to examine the overall state of the program, including
5028 switching between threads, without worrying that things may change
5031 Conversely, whenever you restart the program, @emph{all} threads start
5032 executing. @emph{This is true even when single-stepping} with commands
5033 like @code{step} or @code{next}.
5035 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5036 Since thread scheduling is up to your debugging target's operating
5037 system (not controlled by @value{GDBN}), other threads may
5038 execute more than one statement while the current thread completes a
5039 single step. Moreover, in general other threads stop in the middle of a
5040 statement, rather than at a clean statement boundary, when the program
5043 You might even find your program stopped in another thread after
5044 continuing or even single-stepping. This happens whenever some other
5045 thread runs into a breakpoint, a signal, or an exception before the
5046 first thread completes whatever you requested.
5048 @cindex automatic thread selection
5049 @cindex switching threads automatically
5050 @cindex threads, automatic switching
5051 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5052 signal, it automatically selects the thread where that breakpoint or
5053 signal happened. @value{GDBN} alerts you to the context switch with a
5054 message such as @samp{[Switching to Thread @var{n}]} to identify the
5057 On some OSes, you can modify @value{GDBN}'s default behavior by
5058 locking the OS scheduler to allow only a single thread to run.
5061 @item set scheduler-locking @var{mode}
5062 @cindex scheduler locking mode
5063 @cindex lock scheduler
5064 Set the scheduler locking mode. If it is @code{off}, then there is no
5065 locking and any thread may run at any time. If @code{on}, then only the
5066 current thread may run when the inferior is resumed. The @code{step}
5067 mode optimizes for single-stepping; it prevents other threads
5068 from preempting the current thread while you are stepping, so that
5069 the focus of debugging does not change unexpectedly.
5070 Other threads only rarely (or never) get a chance to run
5071 when you step. They are more likely to run when you @samp{next} over a
5072 function call, and they are completely free to run when you use commands
5073 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5074 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5075 the current thread away from the thread that you are debugging.
5077 @item show scheduler-locking
5078 Display the current scheduler locking mode.
5081 @cindex resume threads of multiple processes simultaneously
5082 By default, when you issue one of the execution commands such as
5083 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5084 threads of the current inferior to run. For example, if @value{GDBN}
5085 is attached to two inferiors, each with two threads, the
5086 @code{continue} command resumes only the two threads of the current
5087 inferior. This is useful, for example, when you debug a program that
5088 forks and you want to hold the parent stopped (so that, for instance,
5089 it doesn't run to exit), while you debug the child. In other
5090 situations, you may not be interested in inspecting the current state
5091 of any of the processes @value{GDBN} is attached to, and you may want
5092 to resume them all until some breakpoint is hit. In the latter case,
5093 you can instruct @value{GDBN} to allow all threads of all the
5094 inferiors to run with the @w{@code{set schedule-multiple}} command.
5097 @kindex set schedule-multiple
5098 @item set schedule-multiple
5099 Set the mode for allowing threads of multiple processes to be resumed
5100 when an execution command is issued. When @code{on}, all threads of
5101 all processes are allowed to run. When @code{off}, only the threads
5102 of the current process are resumed. The default is @code{off}. The
5103 @code{scheduler-locking} mode takes precedence when set to @code{on},
5104 or while you are stepping and set to @code{step}.
5106 @item show schedule-multiple
5107 Display the current mode for resuming the execution of threads of
5112 @subsection Non-Stop Mode
5114 @cindex non-stop mode
5116 @c This section is really only a place-holder, and needs to be expanded
5117 @c with more details.
5119 For some multi-threaded targets, @value{GDBN} supports an optional
5120 mode of operation in which you can examine stopped program threads in
5121 the debugger while other threads continue to execute freely. This
5122 minimizes intrusion when debugging live systems, such as programs
5123 where some threads have real-time constraints or must continue to
5124 respond to external events. This is referred to as @dfn{non-stop} mode.
5126 In non-stop mode, when a thread stops to report a debugging event,
5127 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5128 threads as well, in contrast to the all-stop mode behavior. Additionally,
5129 execution commands such as @code{continue} and @code{step} apply by default
5130 only to the current thread in non-stop mode, rather than all threads as
5131 in all-stop mode. This allows you to control threads explicitly in
5132 ways that are not possible in all-stop mode --- for example, stepping
5133 one thread while allowing others to run freely, stepping
5134 one thread while holding all others stopped, or stepping several threads
5135 independently and simultaneously.
5137 To enter non-stop mode, use this sequence of commands before you run
5138 or attach to your program:
5141 # Enable the async interface.
5144 # If using the CLI, pagination breaks non-stop.
5147 # Finally, turn it on!
5151 You can use these commands to manipulate the non-stop mode setting:
5154 @kindex set non-stop
5155 @item set non-stop on
5156 Enable selection of non-stop mode.
5157 @item set non-stop off
5158 Disable selection of non-stop mode.
5159 @kindex show non-stop
5161 Show the current non-stop enablement setting.
5164 Note these commands only reflect whether non-stop mode is enabled,
5165 not whether the currently-executing program is being run in non-stop mode.
5166 In particular, the @code{set non-stop} preference is only consulted when
5167 @value{GDBN} starts or connects to the target program, and it is generally
5168 not possible to switch modes once debugging has started. Furthermore,
5169 since not all targets support non-stop mode, even when you have enabled
5170 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5173 In non-stop mode, all execution commands apply only to the current thread
5174 by default. That is, @code{continue} only continues one thread.
5175 To continue all threads, issue @code{continue -a} or @code{c -a}.
5177 You can use @value{GDBN}'s background execution commands
5178 (@pxref{Background Execution}) to run some threads in the background
5179 while you continue to examine or step others from @value{GDBN}.
5180 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5181 always executed asynchronously in non-stop mode.
5183 Suspending execution is done with the @code{interrupt} command when
5184 running in the background, or @kbd{Ctrl-c} during foreground execution.
5185 In all-stop mode, this stops the whole process;
5186 but in non-stop mode the interrupt applies only to the current thread.
5187 To stop the whole program, use @code{interrupt -a}.
5189 Other execution commands do not currently support the @code{-a} option.
5191 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5192 that thread current, as it does in all-stop mode. This is because the
5193 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5194 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5195 changed to a different thread just as you entered a command to operate on the
5196 previously current thread.
5198 @node Background Execution
5199 @subsection Background Execution
5201 @cindex foreground execution
5202 @cindex background execution
5203 @cindex asynchronous execution
5204 @cindex execution, foreground, background and asynchronous
5206 @value{GDBN}'s execution commands have two variants: the normal
5207 foreground (synchronous) behavior, and a background
5208 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5209 the program to report that some thread has stopped before prompting for
5210 another command. In background execution, @value{GDBN} immediately gives
5211 a command prompt so that you can issue other commands while your program runs.
5213 You need to explicitly enable asynchronous mode before you can use
5214 background execution commands. You can use these commands to
5215 manipulate the asynchronous mode setting:
5218 @kindex set target-async
5219 @item set target-async on
5220 Enable asynchronous mode.
5221 @item set target-async off
5222 Disable asynchronous mode.
5223 @kindex show target-async
5224 @item show target-async
5225 Show the current target-async setting.
5228 If the target doesn't support async mode, @value{GDBN} issues an error
5229 message if you attempt to use the background execution commands.
5231 To specify background execution, add a @code{&} to the command. For example,
5232 the background form of the @code{continue} command is @code{continue&}, or
5233 just @code{c&}. The execution commands that accept background execution
5239 @xref{Starting, , Starting your Program}.
5243 @xref{Attach, , Debugging an Already-running Process}.
5247 @xref{Continuing and Stepping, step}.
5251 @xref{Continuing and Stepping, stepi}.
5255 @xref{Continuing and Stepping, next}.
5259 @xref{Continuing and Stepping, nexti}.
5263 @xref{Continuing and Stepping, continue}.
5267 @xref{Continuing and Stepping, finish}.
5271 @xref{Continuing and Stepping, until}.
5275 Background execution is especially useful in conjunction with non-stop
5276 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5277 However, you can also use these commands in the normal all-stop mode with
5278 the restriction that you cannot issue another execution command until the
5279 previous one finishes. Examples of commands that are valid in all-stop
5280 mode while the program is running include @code{help} and @code{info break}.
5282 You can interrupt your program while it is running in the background by
5283 using the @code{interrupt} command.
5290 Suspend execution of the running program. In all-stop mode,
5291 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5292 only the current thread. To stop the whole program in non-stop mode,
5293 use @code{interrupt -a}.
5296 @node Thread-Specific Breakpoints
5297 @subsection Thread-Specific Breakpoints
5299 When your program has multiple threads (@pxref{Threads,, Debugging
5300 Programs with Multiple Threads}), you can choose whether to set
5301 breakpoints on all threads, or on a particular thread.
5304 @cindex breakpoints and threads
5305 @cindex thread breakpoints
5306 @kindex break @dots{} thread @var{threadno}
5307 @item break @var{linespec} thread @var{threadno}
5308 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5309 @var{linespec} specifies source lines; there are several ways of
5310 writing them (@pxref{Specify Location}), but the effect is always to
5311 specify some source line.
5313 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5314 to specify that you only want @value{GDBN} to stop the program when a
5315 particular thread reaches this breakpoint. @var{threadno} is one of the
5316 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5317 column of the @samp{info threads} display.
5319 If you do not specify @samp{thread @var{threadno}} when you set a
5320 breakpoint, the breakpoint applies to @emph{all} threads of your
5323 You can use the @code{thread} qualifier on conditional breakpoints as
5324 well; in this case, place @samp{thread @var{threadno}} before or
5325 after the breakpoint condition, like this:
5328 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5333 @node Interrupted System Calls
5334 @subsection Interrupted System Calls
5336 @cindex thread breakpoints and system calls
5337 @cindex system calls and thread breakpoints
5338 @cindex premature return from system calls
5339 There is an unfortunate side effect when using @value{GDBN} to debug
5340 multi-threaded programs. If one thread stops for a
5341 breakpoint, or for some other reason, and another thread is blocked in a
5342 system call, then the system call may return prematurely. This is a
5343 consequence of the interaction between multiple threads and the signals
5344 that @value{GDBN} uses to implement breakpoints and other events that
5347 To handle this problem, your program should check the return value of
5348 each system call and react appropriately. This is good programming
5351 For example, do not write code like this:
5357 The call to @code{sleep} will return early if a different thread stops
5358 at a breakpoint or for some other reason.
5360 Instead, write this:
5365 unslept = sleep (unslept);
5368 A system call is allowed to return early, so the system is still
5369 conforming to its specification. But @value{GDBN} does cause your
5370 multi-threaded program to behave differently than it would without
5373 Also, @value{GDBN} uses internal breakpoints in the thread library to
5374 monitor certain events such as thread creation and thread destruction.
5375 When such an event happens, a system call in another thread may return
5376 prematurely, even though your program does not appear to stop.
5379 @subsection Observer Mode
5381 If you want to build on non-stop mode and observe program behavior
5382 without any chance of disruption by @value{GDBN}, you can set
5383 variables to disable all of the debugger's attempts to modify state,
5384 whether by writing memory, inserting breakpoints, etc. These operate
5385 at a low level, intercepting operations from all commands.
5387 When all of these are set to @code{off}, then @value{GDBN} is said to
5388 be @dfn{observer mode}. As a convenience, the variable
5389 @code{observer} can be set to disable these, plus enable non-stop
5392 Note that @value{GDBN} will not prevent you from making nonsensical
5393 combinations of these settings. For instance, if you have enabled
5394 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5395 then breakpoints that work by writing trap instructions into the code
5396 stream will still not be able to be placed.
5401 @item set observer on
5402 @itemx set observer off
5403 When set to @code{on}, this disables all the permission variables
5404 below (except for @code{insert-fast-tracepoints}), plus enables
5405 non-stop debugging. Setting this to @code{off} switches back to
5406 normal debugging, though remaining in non-stop mode.
5409 Show whether observer mode is on or off.
5411 @kindex may-write-registers
5412 @item set may-write-registers on
5413 @itemx set may-write-registers off
5414 This controls whether @value{GDBN} will attempt to alter the values of
5415 registers, such as with assignment expressions in @code{print}, or the
5416 @code{jump} command. It defaults to @code{on}.
5418 @item show may-write-registers
5419 Show the current permission to write registers.
5421 @kindex may-write-memory
5422 @item set may-write-memory on
5423 @itemx set may-write-memory off
5424 This controls whether @value{GDBN} will attempt to alter the contents
5425 of memory, such as with assignment expressions in @code{print}. It
5426 defaults to @code{on}.
5428 @item show may-write-memory
5429 Show the current permission to write memory.
5431 @kindex may-insert-breakpoints
5432 @item set may-insert-breakpoints on
5433 @itemx set may-insert-breakpoints off
5434 This controls whether @value{GDBN} will attempt to insert breakpoints.
5435 This affects all breakpoints, including internal breakpoints defined
5436 by @value{GDBN}. It defaults to @code{on}.
5438 @item show may-insert-breakpoints
5439 Show the current permission to insert breakpoints.
5441 @kindex may-insert-tracepoints
5442 @item set may-insert-tracepoints on
5443 @itemx set may-insert-tracepoints off
5444 This controls whether @value{GDBN} will attempt to insert (regular)
5445 tracepoints at the beginning of a tracing experiment. It affects only
5446 non-fast tracepoints, fast tracepoints being under the control of
5447 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5449 @item show may-insert-tracepoints
5450 Show the current permission to insert tracepoints.
5452 @kindex may-insert-fast-tracepoints
5453 @item set may-insert-fast-tracepoints on
5454 @itemx set may-insert-fast-tracepoints off
5455 This controls whether @value{GDBN} will attempt to insert fast
5456 tracepoints at the beginning of a tracing experiment. It affects only
5457 fast tracepoints, regular (non-fast) tracepoints being under the
5458 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5460 @item show may-insert-fast-tracepoints
5461 Show the current permission to insert fast tracepoints.
5463 @kindex may-interrupt
5464 @item set may-interrupt on
5465 @itemx set may-interrupt off
5466 This controls whether @value{GDBN} will attempt to interrupt or stop
5467 program execution. When this variable is @code{off}, the
5468 @code{interrupt} command will have no effect, nor will
5469 @kbd{Ctrl-c}. It defaults to @code{on}.
5471 @item show may-interrupt
5472 Show the current permission to interrupt or stop the program.
5476 @node Reverse Execution
5477 @chapter Running programs backward
5478 @cindex reverse execution
5479 @cindex running programs backward
5481 When you are debugging a program, it is not unusual to realize that
5482 you have gone too far, and some event of interest has already happened.
5483 If the target environment supports it, @value{GDBN} can allow you to
5484 ``rewind'' the program by running it backward.
5486 A target environment that supports reverse execution should be able
5487 to ``undo'' the changes in machine state that have taken place as the
5488 program was executing normally. Variables, registers etc.@: should
5489 revert to their previous values. Obviously this requires a great
5490 deal of sophistication on the part of the target environment; not
5491 all target environments can support reverse execution.
5493 When a program is executed in reverse, the instructions that
5494 have most recently been executed are ``un-executed'', in reverse
5495 order. The program counter runs backward, following the previous
5496 thread of execution in reverse. As each instruction is ``un-executed'',
5497 the values of memory and/or registers that were changed by that
5498 instruction are reverted to their previous states. After executing
5499 a piece of source code in reverse, all side effects of that code
5500 should be ``undone'', and all variables should be returned to their
5501 prior values@footnote{
5502 Note that some side effects are easier to undo than others. For instance,
5503 memory and registers are relatively easy, but device I/O is hard. Some
5504 targets may be able undo things like device I/O, and some may not.
5506 The contract between @value{GDBN} and the reverse executing target
5507 requires only that the target do something reasonable when
5508 @value{GDBN} tells it to execute backwards, and then report the
5509 results back to @value{GDBN}. Whatever the target reports back to
5510 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5511 assumes that the memory and registers that the target reports are in a
5512 consistant state, but @value{GDBN} accepts whatever it is given.
5515 If you are debugging in a target environment that supports
5516 reverse execution, @value{GDBN} provides the following commands.
5519 @kindex reverse-continue
5520 @kindex rc @r{(@code{reverse-continue})}
5521 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5522 @itemx rc @r{[}@var{ignore-count}@r{]}
5523 Beginning at the point where your program last stopped, start executing
5524 in reverse. Reverse execution will stop for breakpoints and synchronous
5525 exceptions (signals), just like normal execution. Behavior of
5526 asynchronous signals depends on the target environment.
5528 @kindex reverse-step
5529 @kindex rs @r{(@code{step})}
5530 @item reverse-step @r{[}@var{count}@r{]}
5531 Run the program backward until control reaches the start of a
5532 different source line; then stop it, and return control to @value{GDBN}.
5534 Like the @code{step} command, @code{reverse-step} will only stop
5535 at the beginning of a source line. It ``un-executes'' the previously
5536 executed source line. If the previous source line included calls to
5537 debuggable functions, @code{reverse-step} will step (backward) into
5538 the called function, stopping at the beginning of the @emph{last}
5539 statement in the called function (typically a return statement).
5541 Also, as with the @code{step} command, if non-debuggable functions are
5542 called, @code{reverse-step} will run thru them backward without stopping.
5544 @kindex reverse-stepi
5545 @kindex rsi @r{(@code{reverse-stepi})}
5546 @item reverse-stepi @r{[}@var{count}@r{]}
5547 Reverse-execute one machine instruction. Note that the instruction
5548 to be reverse-executed is @emph{not} the one pointed to by the program
5549 counter, but the instruction executed prior to that one. For instance,
5550 if the last instruction was a jump, @code{reverse-stepi} will take you
5551 back from the destination of the jump to the jump instruction itself.
5553 @kindex reverse-next
5554 @kindex rn @r{(@code{reverse-next})}
5555 @item reverse-next @r{[}@var{count}@r{]}
5556 Run backward to the beginning of the previous line executed in
5557 the current (innermost) stack frame. If the line contains function
5558 calls, they will be ``un-executed'' without stopping. Starting from
5559 the first line of a function, @code{reverse-next} will take you back
5560 to the caller of that function, @emph{before} the function was called,
5561 just as the normal @code{next} command would take you from the last
5562 line of a function back to its return to its caller
5563 @footnote{Unless the code is too heavily optimized.}.
5565 @kindex reverse-nexti
5566 @kindex rni @r{(@code{reverse-nexti})}
5567 @item reverse-nexti @r{[}@var{count}@r{]}
5568 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5569 in reverse, except that called functions are ``un-executed'' atomically.
5570 That is, if the previously executed instruction was a return from
5571 another function, @code{reverse-nexti} will continue to execute
5572 in reverse until the call to that function (from the current stack
5575 @kindex reverse-finish
5576 @item reverse-finish
5577 Just as the @code{finish} command takes you to the point where the
5578 current function returns, @code{reverse-finish} takes you to the point
5579 where it was called. Instead of ending up at the end of the current
5580 function invocation, you end up at the beginning.
5582 @kindex set exec-direction
5583 @item set exec-direction
5584 Set the direction of target execution.
5585 @itemx set exec-direction reverse
5586 @cindex execute forward or backward in time
5587 @value{GDBN} will perform all execution commands in reverse, until the
5588 exec-direction mode is changed to ``forward''. Affected commands include
5589 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5590 command cannot be used in reverse mode.
5591 @item set exec-direction forward
5592 @value{GDBN} will perform all execution commands in the normal fashion.
5593 This is the default.
5597 @node Process Record and Replay
5598 @chapter Recording Inferior's Execution and Replaying It
5599 @cindex process record and replay
5600 @cindex recording inferior's execution and replaying it
5602 On some platforms, @value{GDBN} provides a special @dfn{process record
5603 and replay} target that can record a log of the process execution, and
5604 replay it later with both forward and reverse execution commands.
5607 When this target is in use, if the execution log includes the record
5608 for the next instruction, @value{GDBN} will debug in @dfn{replay
5609 mode}. In the replay mode, the inferior does not really execute code
5610 instructions. Instead, all the events that normally happen during
5611 code execution are taken from the execution log. While code is not
5612 really executed in replay mode, the values of registers (including the
5613 program counter register) and the memory of the inferior are still
5614 changed as they normally would. Their contents are taken from the
5618 If the record for the next instruction is not in the execution log,
5619 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5620 inferior executes normally, and @value{GDBN} records the execution log
5623 The process record and replay target supports reverse execution
5624 (@pxref{Reverse Execution}), even if the platform on which the
5625 inferior runs does not. However, the reverse execution is limited in
5626 this case by the range of the instructions recorded in the execution
5627 log. In other words, reverse execution on platforms that don't
5628 support it directly can only be done in the replay mode.
5630 When debugging in the reverse direction, @value{GDBN} will work in
5631 replay mode as long as the execution log includes the record for the
5632 previous instruction; otherwise, it will work in record mode, if the
5633 platform supports reverse execution, or stop if not.
5635 For architecture environments that support process record and replay,
5636 @value{GDBN} provides the following commands:
5639 @kindex target record
5643 This command starts the process record and replay target. The process
5644 record and replay target can only debug a process that is already
5645 running. Therefore, you need first to start the process with the
5646 @kbd{run} or @kbd{start} commands, and then start the recording with
5647 the @kbd{target record} command.
5649 Both @code{record} and @code{rec} are aliases of @code{target record}.
5651 @cindex displaced stepping, and process record and replay
5652 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5653 will be automatically disabled when process record and replay target
5654 is started. That's because the process record and replay target
5655 doesn't support displaced stepping.
5657 @cindex non-stop mode, and process record and replay
5658 @cindex asynchronous execution, and process record and replay
5659 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5660 the asynchronous execution mode (@pxref{Background Execution}), the
5661 process record and replay target cannot be started because it doesn't
5662 support these two modes.
5667 Stop the process record and replay target. When process record and
5668 replay target stops, the entire execution log will be deleted and the
5669 inferior will either be terminated, or will remain in its final state.
5671 When you stop the process record and replay target in record mode (at
5672 the end of the execution log), the inferior will be stopped at the
5673 next instruction that would have been recorded. In other words, if
5674 you record for a while and then stop recording, the inferior process
5675 will be left in the same state as if the recording never happened.
5677 On the other hand, if the process record and replay target is stopped
5678 while in replay mode (that is, not at the end of the execution log,
5679 but at some earlier point), the inferior process will become ``live''
5680 at that earlier state, and it will then be possible to continue the
5681 usual ``live'' debugging of the process from that state.
5683 When the inferior process exits, or @value{GDBN} detaches from it,
5684 process record and replay target will automatically stop itself.
5687 @item record save @var{filename}
5688 Save the execution log to a file @file{@var{filename}}.
5689 Default filename is @file{gdb_record.@var{process_id}}, where
5690 @var{process_id} is the process ID of the inferior.
5692 @kindex record restore
5693 @item record restore @var{filename}
5694 Restore the execution log from a file @file{@var{filename}}.
5695 File must have been created with @code{record save}.
5697 @kindex set record insn-number-max
5698 @item set record insn-number-max @var{limit}
5699 Set the limit of instructions to be recorded. Default value is 200000.
5701 If @var{limit} is a positive number, then @value{GDBN} will start
5702 deleting instructions from the log once the number of the record
5703 instructions becomes greater than @var{limit}. For every new recorded
5704 instruction, @value{GDBN} will delete the earliest recorded
5705 instruction to keep the number of recorded instructions at the limit.
5706 (Since deleting recorded instructions loses information, @value{GDBN}
5707 lets you control what happens when the limit is reached, by means of
5708 the @code{stop-at-limit} option, described below.)
5710 If @var{limit} is zero, @value{GDBN} will never delete recorded
5711 instructions from the execution log. The number of recorded
5712 instructions is unlimited in this case.
5714 @kindex show record insn-number-max
5715 @item show record insn-number-max
5716 Show the limit of instructions to be recorded.
5718 @kindex set record stop-at-limit
5719 @item set record stop-at-limit
5720 Control the behavior when the number of recorded instructions reaches
5721 the limit. If ON (the default), @value{GDBN} will stop when the limit
5722 is reached for the first time and ask you whether you want to stop the
5723 inferior or continue running it and recording the execution log. If
5724 you decide to continue recording, each new recorded instruction will
5725 cause the oldest one to be deleted.
5727 If this option is OFF, @value{GDBN} will automatically delete the
5728 oldest record to make room for each new one, without asking.
5730 @kindex show record stop-at-limit
5731 @item show record stop-at-limit
5732 Show the current setting of @code{stop-at-limit}.
5734 @kindex set record memory-query
5735 @item set record memory-query
5736 Control the behavior when @value{GDBN} is unable to record memory
5737 changes caused by an instruction. If ON, @value{GDBN} will query
5738 whether to stop the inferior in that case.
5740 If this option is OFF (the default), @value{GDBN} will automatically
5741 ignore the effect of such instructions on memory. Later, when
5742 @value{GDBN} replays this execution log, it will mark the log of this
5743 instruction as not accessible, and it will not affect the replay
5746 @kindex show record memory-query
5747 @item show record memory-query
5748 Show the current setting of @code{memory-query}.
5752 Show various statistics about the state of process record and its
5753 in-memory execution log buffer, including:
5757 Whether in record mode or replay mode.
5759 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5761 Highest recorded instruction number.
5763 Current instruction about to be replayed (if in replay mode).
5765 Number of instructions contained in the execution log.
5767 Maximum number of instructions that may be contained in the execution log.
5770 @kindex record delete
5773 When record target runs in replay mode (``in the past''), delete the
5774 subsequent execution log and begin to record a new execution log starting
5775 from the current address. This means you will abandon the previously
5776 recorded ``future'' and begin recording a new ``future''.
5781 @chapter Examining the Stack
5783 When your program has stopped, the first thing you need to know is where it
5784 stopped and how it got there.
5787 Each time your program performs a function call, information about the call
5789 That information includes the location of the call in your program,
5790 the arguments of the call,
5791 and the local variables of the function being called.
5792 The information is saved in a block of data called a @dfn{stack frame}.
5793 The stack frames are allocated in a region of memory called the @dfn{call
5796 When your program stops, the @value{GDBN} commands for examining the
5797 stack allow you to see all of this information.
5799 @cindex selected frame
5800 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5801 @value{GDBN} commands refer implicitly to the selected frame. In
5802 particular, whenever you ask @value{GDBN} for the value of a variable in
5803 your program, the value is found in the selected frame. There are
5804 special @value{GDBN} commands to select whichever frame you are
5805 interested in. @xref{Selection, ,Selecting a Frame}.
5807 When your program stops, @value{GDBN} automatically selects the
5808 currently executing frame and describes it briefly, similar to the
5809 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5812 * Frames:: Stack frames
5813 * Backtrace:: Backtraces
5814 * Selection:: Selecting a frame
5815 * Frame Info:: Information on a frame
5820 @section Stack Frames
5822 @cindex frame, definition
5824 The call stack is divided up into contiguous pieces called @dfn{stack
5825 frames}, or @dfn{frames} for short; each frame is the data associated
5826 with one call to one function. The frame contains the arguments given
5827 to the function, the function's local variables, and the address at
5828 which the function is executing.
5830 @cindex initial frame
5831 @cindex outermost frame
5832 @cindex innermost frame
5833 When your program is started, the stack has only one frame, that of the
5834 function @code{main}. This is called the @dfn{initial} frame or the
5835 @dfn{outermost} frame. Each time a function is called, a new frame is
5836 made. Each time a function returns, the frame for that function invocation
5837 is eliminated. If a function is recursive, there can be many frames for
5838 the same function. The frame for the function in which execution is
5839 actually occurring is called the @dfn{innermost} frame. This is the most
5840 recently created of all the stack frames that still exist.
5842 @cindex frame pointer
5843 Inside your program, stack frames are identified by their addresses. A
5844 stack frame consists of many bytes, each of which has its own address; each
5845 kind of computer has a convention for choosing one byte whose
5846 address serves as the address of the frame. Usually this address is kept
5847 in a register called the @dfn{frame pointer register}
5848 (@pxref{Registers, $fp}) while execution is going on in that frame.
5850 @cindex frame number
5851 @value{GDBN} assigns numbers to all existing stack frames, starting with
5852 zero for the innermost frame, one for the frame that called it,
5853 and so on upward. These numbers do not really exist in your program;
5854 they are assigned by @value{GDBN} to give you a way of designating stack
5855 frames in @value{GDBN} commands.
5857 @c The -fomit-frame-pointer below perennially causes hbox overflow
5858 @c underflow problems.
5859 @cindex frameless execution
5860 Some compilers provide a way to compile functions so that they operate
5861 without stack frames. (For example, the @value{NGCC} option
5863 @samp{-fomit-frame-pointer}
5865 generates functions without a frame.)
5866 This is occasionally done with heavily used library functions to save
5867 the frame setup time. @value{GDBN} has limited facilities for dealing
5868 with these function invocations. If the innermost function invocation
5869 has no stack frame, @value{GDBN} nevertheless regards it as though
5870 it had a separate frame, which is numbered zero as usual, allowing
5871 correct tracing of the function call chain. However, @value{GDBN} has
5872 no provision for frameless functions elsewhere in the stack.
5875 @kindex frame@r{, command}
5876 @cindex current stack frame
5877 @item frame @var{args}
5878 The @code{frame} command allows you to move from one stack frame to another,
5879 and to print the stack frame you select. @var{args} may be either the
5880 address of the frame or the stack frame number. Without an argument,
5881 @code{frame} prints the current stack frame.
5883 @kindex select-frame
5884 @cindex selecting frame silently
5886 The @code{select-frame} command allows you to move from one stack frame
5887 to another without printing the frame. This is the silent version of
5895 @cindex call stack traces
5896 A backtrace is a summary of how your program got where it is. It shows one
5897 line per frame, for many frames, starting with the currently executing
5898 frame (frame zero), followed by its caller (frame one), and on up the
5903 @kindex bt @r{(@code{backtrace})}
5906 Print a backtrace of the entire stack: one line per frame for all
5907 frames in the stack.
5909 You can stop the backtrace at any time by typing the system interrupt
5910 character, normally @kbd{Ctrl-c}.
5912 @item backtrace @var{n}
5914 Similar, but print only the innermost @var{n} frames.
5916 @item backtrace -@var{n}
5918 Similar, but print only the outermost @var{n} frames.
5920 @item backtrace full
5922 @itemx bt full @var{n}
5923 @itemx bt full -@var{n}
5924 Print the values of the local variables also. @var{n} specifies the
5925 number of frames to print, as described above.
5930 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5931 are additional aliases for @code{backtrace}.
5933 @cindex multiple threads, backtrace
5934 In a multi-threaded program, @value{GDBN} by default shows the
5935 backtrace only for the current thread. To display the backtrace for
5936 several or all of the threads, use the command @code{thread apply}
5937 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5938 apply all backtrace}, @value{GDBN} will display the backtrace for all
5939 the threads; this is handy when you debug a core dump of a
5940 multi-threaded program.
5942 Each line in the backtrace shows the frame number and the function name.
5943 The program counter value is also shown---unless you use @code{set
5944 print address off}. The backtrace also shows the source file name and
5945 line number, as well as the arguments to the function. The program
5946 counter value is omitted if it is at the beginning of the code for that
5949 Here is an example of a backtrace. It was made with the command
5950 @samp{bt 3}, so it shows the innermost three frames.
5954 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5956 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5957 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5959 (More stack frames follow...)
5964 The display for frame zero does not begin with a program counter
5965 value, indicating that your program has stopped at the beginning of the
5966 code for line @code{993} of @code{builtin.c}.
5969 The value of parameter @code{data} in frame 1 has been replaced by
5970 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5971 only if it is a scalar (integer, pointer, enumeration, etc). See command
5972 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5973 on how to configure the way function parameter values are printed.
5975 @cindex optimized out, in backtrace
5976 @cindex function call arguments, optimized out
5977 If your program was compiled with optimizations, some compilers will
5978 optimize away arguments passed to functions if those arguments are
5979 never used after the call. Such optimizations generate code that
5980 passes arguments through registers, but doesn't store those arguments
5981 in the stack frame. @value{GDBN} has no way of displaying such
5982 arguments in stack frames other than the innermost one. Here's what
5983 such a backtrace might look like:
5987 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5989 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
5990 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
5992 (More stack frames follow...)
5997 The values of arguments that were not saved in their stack frames are
5998 shown as @samp{<optimized out>}.
6000 If you need to display the values of such optimized-out arguments,
6001 either deduce that from other variables whose values depend on the one
6002 you are interested in, or recompile without optimizations.
6004 @cindex backtrace beyond @code{main} function
6005 @cindex program entry point
6006 @cindex startup code, and backtrace
6007 Most programs have a standard user entry point---a place where system
6008 libraries and startup code transition into user code. For C this is
6009 @code{main}@footnote{
6010 Note that embedded programs (the so-called ``free-standing''
6011 environment) are not required to have a @code{main} function as the
6012 entry point. They could even have multiple entry points.}.
6013 When @value{GDBN} finds the entry function in a backtrace
6014 it will terminate the backtrace, to avoid tracing into highly
6015 system-specific (and generally uninteresting) code.
6017 If you need to examine the startup code, or limit the number of levels
6018 in a backtrace, you can change this behavior:
6021 @item set backtrace past-main
6022 @itemx set backtrace past-main on
6023 @kindex set backtrace
6024 Backtraces will continue past the user entry point.
6026 @item set backtrace past-main off
6027 Backtraces will stop when they encounter the user entry point. This is the
6030 @item show backtrace past-main
6031 @kindex show backtrace
6032 Display the current user entry point backtrace policy.
6034 @item set backtrace past-entry
6035 @itemx set backtrace past-entry on
6036 Backtraces will continue past the internal entry point of an application.
6037 This entry point is encoded by the linker when the application is built,
6038 and is likely before the user entry point @code{main} (or equivalent) is called.
6040 @item set backtrace past-entry off
6041 Backtraces will stop when they encounter the internal entry point of an
6042 application. This is the default.
6044 @item show backtrace past-entry
6045 Display the current internal entry point backtrace policy.
6047 @item set backtrace limit @var{n}
6048 @itemx set backtrace limit 0
6049 @cindex backtrace limit
6050 Limit the backtrace to @var{n} levels. A value of zero means
6053 @item show backtrace limit
6054 Display the current limit on backtrace levels.
6058 @section Selecting a Frame
6060 Most commands for examining the stack and other data in your program work on
6061 whichever stack frame is selected at the moment. Here are the commands for
6062 selecting a stack frame; all of them finish by printing a brief description
6063 of the stack frame just selected.
6066 @kindex frame@r{, selecting}
6067 @kindex f @r{(@code{frame})}
6070 Select frame number @var{n}. Recall that frame zero is the innermost
6071 (currently executing) frame, frame one is the frame that called the
6072 innermost one, and so on. The highest-numbered frame is the one for
6075 @item frame @var{addr}
6077 Select the frame at address @var{addr}. This is useful mainly if the
6078 chaining of stack frames has been damaged by a bug, making it
6079 impossible for @value{GDBN} to assign numbers properly to all frames. In
6080 addition, this can be useful when your program has multiple stacks and
6081 switches between them.
6083 On the SPARC architecture, @code{frame} needs two addresses to
6084 select an arbitrary frame: a frame pointer and a stack pointer.
6086 On the MIPS and Alpha architecture, it needs two addresses: a stack
6087 pointer and a program counter.
6089 On the 29k architecture, it needs three addresses: a register stack
6090 pointer, a program counter, and a memory stack pointer.
6094 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6095 advances toward the outermost frame, to higher frame numbers, to frames
6096 that have existed longer. @var{n} defaults to one.
6099 @kindex do @r{(@code{down})}
6101 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6102 advances toward the innermost frame, to lower frame numbers, to frames
6103 that were created more recently. @var{n} defaults to one. You may
6104 abbreviate @code{down} as @code{do}.
6107 All of these commands end by printing two lines of output describing the
6108 frame. The first line shows the frame number, the function name, the
6109 arguments, and the source file and line number of execution in that
6110 frame. The second line shows the text of that source line.
6118 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6120 10 read_input_file (argv[i]);
6124 After such a printout, the @code{list} command with no arguments
6125 prints ten lines centered on the point of execution in the frame.
6126 You can also edit the program at the point of execution with your favorite
6127 editing program by typing @code{edit}.
6128 @xref{List, ,Printing Source Lines},
6132 @kindex down-silently
6134 @item up-silently @var{n}
6135 @itemx down-silently @var{n}
6136 These two commands are variants of @code{up} and @code{down},
6137 respectively; they differ in that they do their work silently, without
6138 causing display of the new frame. They are intended primarily for use
6139 in @value{GDBN} command scripts, where the output might be unnecessary and
6144 @section Information About a Frame
6146 There are several other commands to print information about the selected
6152 When used without any argument, this command does not change which
6153 frame is selected, but prints a brief description of the currently
6154 selected stack frame. It can be abbreviated @code{f}. With an
6155 argument, this command is used to select a stack frame.
6156 @xref{Selection, ,Selecting a Frame}.
6159 @kindex info f @r{(@code{info frame})}
6162 This command prints a verbose description of the selected stack frame,
6167 the address of the frame
6169 the address of the next frame down (called by this frame)
6171 the address of the next frame up (caller of this frame)
6173 the language in which the source code corresponding to this frame is written
6175 the address of the frame's arguments
6177 the address of the frame's local variables
6179 the program counter saved in it (the address of execution in the caller frame)
6181 which registers were saved in the frame
6184 @noindent The verbose description is useful when
6185 something has gone wrong that has made the stack format fail to fit
6186 the usual conventions.
6188 @item info frame @var{addr}
6189 @itemx info f @var{addr}
6190 Print a verbose description of the frame at address @var{addr}, without
6191 selecting that frame. The selected frame remains unchanged by this
6192 command. This requires the same kind of address (more than one for some
6193 architectures) that you specify in the @code{frame} command.
6194 @xref{Selection, ,Selecting a Frame}.
6198 Print the arguments of the selected frame, each on a separate line.
6202 Print the local variables of the selected frame, each on a separate
6203 line. These are all variables (declared either static or automatic)
6204 accessible at the point of execution of the selected frame.
6207 @cindex catch exceptions, list active handlers
6208 @cindex exception handlers, how to list
6210 Print a list of all the exception handlers that are active in the
6211 current stack frame at the current point of execution. To see other
6212 exception handlers, visit the associated frame (using the @code{up},
6213 @code{down}, or @code{frame} commands); then type @code{info catch}.
6214 @xref{Set Catchpoints, , Setting Catchpoints}.
6220 @chapter Examining Source Files
6222 @value{GDBN} can print parts of your program's source, since the debugging
6223 information recorded in the program tells @value{GDBN} what source files were
6224 used to build it. When your program stops, @value{GDBN} spontaneously prints
6225 the line where it stopped. Likewise, when you select a stack frame
6226 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6227 execution in that frame has stopped. You can print other portions of
6228 source files by explicit command.
6230 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6231 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6232 @value{GDBN} under @sc{gnu} Emacs}.
6235 * List:: Printing source lines
6236 * Specify Location:: How to specify code locations
6237 * Edit:: Editing source files
6238 * Search:: Searching source files
6239 * Source Path:: Specifying source directories
6240 * Machine Code:: Source and machine code
6244 @section Printing Source Lines
6247 @kindex l @r{(@code{list})}
6248 To print lines from a source file, use the @code{list} command
6249 (abbreviated @code{l}). By default, ten lines are printed.
6250 There are several ways to specify what part of the file you want to
6251 print; see @ref{Specify Location}, for the full list.
6253 Here are the forms of the @code{list} command most commonly used:
6256 @item list @var{linenum}
6257 Print lines centered around line number @var{linenum} in the
6258 current source file.
6260 @item list @var{function}
6261 Print lines centered around the beginning of function
6265 Print more lines. If the last lines printed were printed with a
6266 @code{list} command, this prints lines following the last lines
6267 printed; however, if the last line printed was a solitary line printed
6268 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6269 Stack}), this prints lines centered around that line.
6272 Print lines just before the lines last printed.
6275 @cindex @code{list}, how many lines to display
6276 By default, @value{GDBN} prints ten source lines with any of these forms of
6277 the @code{list} command. You can change this using @code{set listsize}:
6280 @kindex set listsize
6281 @item set listsize @var{count}
6282 Make the @code{list} command display @var{count} source lines (unless
6283 the @code{list} argument explicitly specifies some other number).
6285 @kindex show listsize
6287 Display the number of lines that @code{list} prints.
6290 Repeating a @code{list} command with @key{RET} discards the argument,
6291 so it is equivalent to typing just @code{list}. This is more useful
6292 than listing the same lines again. An exception is made for an
6293 argument of @samp{-}; that argument is preserved in repetition so that
6294 each repetition moves up in the source file.
6296 In general, the @code{list} command expects you to supply zero, one or two
6297 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6298 of writing them (@pxref{Specify Location}), but the effect is always
6299 to specify some source line.
6301 Here is a complete description of the possible arguments for @code{list}:
6304 @item list @var{linespec}
6305 Print lines centered around the line specified by @var{linespec}.
6307 @item list @var{first},@var{last}
6308 Print lines from @var{first} to @var{last}. Both arguments are
6309 linespecs. When a @code{list} command has two linespecs, and the
6310 source file of the second linespec is omitted, this refers to
6311 the same source file as the first linespec.
6313 @item list ,@var{last}
6314 Print lines ending with @var{last}.
6316 @item list @var{first},
6317 Print lines starting with @var{first}.
6320 Print lines just after the lines last printed.
6323 Print lines just before the lines last printed.
6326 As described in the preceding table.
6329 @node Specify Location
6330 @section Specifying a Location
6331 @cindex specifying location
6334 Several @value{GDBN} commands accept arguments that specify a location
6335 of your program's code. Since @value{GDBN} is a source-level
6336 debugger, a location usually specifies some line in the source code;
6337 for that reason, locations are also known as @dfn{linespecs}.
6339 Here are all the different ways of specifying a code location that
6340 @value{GDBN} understands:
6344 Specifies the line number @var{linenum} of the current source file.
6347 @itemx +@var{offset}
6348 Specifies the line @var{offset} lines before or after the @dfn{current
6349 line}. For the @code{list} command, the current line is the last one
6350 printed; for the breakpoint commands, this is the line at which
6351 execution stopped in the currently selected @dfn{stack frame}
6352 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6353 used as the second of the two linespecs in a @code{list} command,
6354 this specifies the line @var{offset} lines up or down from the first
6357 @item @var{filename}:@var{linenum}
6358 Specifies the line @var{linenum} in the source file @var{filename}.
6360 @item @var{function}
6361 Specifies the line that begins the body of the function @var{function}.
6362 For example, in C, this is the line with the open brace.
6364 @item @var{filename}:@var{function}
6365 Specifies the line that begins the body of the function @var{function}
6366 in the file @var{filename}. You only need the file name with a
6367 function name to avoid ambiguity when there are identically named
6368 functions in different source files.
6371 Specifies the line at which the label named @var{label} appears.
6372 @value{GDBN} searches for the label in the function corresponding to
6373 the currently selected stack frame. If there is no current selected
6374 stack frame (for instance, if the inferior is not running), then
6375 @value{GDBN} will not search for a label.
6377 @item *@var{address}
6378 Specifies the program address @var{address}. For line-oriented
6379 commands, such as @code{list} and @code{edit}, this specifies a source
6380 line that contains @var{address}. For @code{break} and other
6381 breakpoint oriented commands, this can be used to set breakpoints in
6382 parts of your program which do not have debugging information or
6385 Here @var{address} may be any expression valid in the current working
6386 language (@pxref{Languages, working language}) that specifies a code
6387 address. In addition, as a convenience, @value{GDBN} extends the
6388 semantics of expressions used in locations to cover the situations
6389 that frequently happen during debugging. Here are the various forms
6393 @item @var{expression}
6394 Any expression valid in the current working language.
6396 @item @var{funcaddr}
6397 An address of a function or procedure derived from its name. In C,
6398 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6399 simply the function's name @var{function} (and actually a special case
6400 of a valid expression). In Pascal and Modula-2, this is
6401 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6402 (although the Pascal form also works).
6404 This form specifies the address of the function's first instruction,
6405 before the stack frame and arguments have been set up.
6407 @item '@var{filename}'::@var{funcaddr}
6408 Like @var{funcaddr} above, but also specifies the name of the source
6409 file explicitly. This is useful if the name of the function does not
6410 specify the function unambiguously, e.g., if there are several
6411 functions with identical names in different source files.
6418 @section Editing Source Files
6419 @cindex editing source files
6422 @kindex e @r{(@code{edit})}
6423 To edit the lines in a source file, use the @code{edit} command.
6424 The editing program of your choice
6425 is invoked with the current line set to
6426 the active line in the program.
6427 Alternatively, there are several ways to specify what part of the file you
6428 want to print if you want to see other parts of the program:
6431 @item edit @var{location}
6432 Edit the source file specified by @code{location}. Editing starts at
6433 that @var{location}, e.g., at the specified source line of the
6434 specified file. @xref{Specify Location}, for all the possible forms
6435 of the @var{location} argument; here are the forms of the @code{edit}
6436 command most commonly used:
6439 @item edit @var{number}
6440 Edit the current source file with @var{number} as the active line number.
6442 @item edit @var{function}
6443 Edit the file containing @var{function} at the beginning of its definition.
6448 @subsection Choosing your Editor
6449 You can customize @value{GDBN} to use any editor you want
6451 The only restriction is that your editor (say @code{ex}), recognizes the
6452 following command-line syntax:
6454 ex +@var{number} file
6456 The optional numeric value +@var{number} specifies the number of the line in
6457 the file where to start editing.}.
6458 By default, it is @file{@value{EDITOR}}, but you can change this
6459 by setting the environment variable @code{EDITOR} before using
6460 @value{GDBN}. For example, to configure @value{GDBN} to use the
6461 @code{vi} editor, you could use these commands with the @code{sh} shell:
6467 or in the @code{csh} shell,
6469 setenv EDITOR /usr/bin/vi
6474 @section Searching Source Files
6475 @cindex searching source files
6477 There are two commands for searching through the current source file for a
6482 @kindex forward-search
6483 @item forward-search @var{regexp}
6484 @itemx search @var{regexp}
6485 The command @samp{forward-search @var{regexp}} checks each line,
6486 starting with the one following the last line listed, for a match for
6487 @var{regexp}. It lists the line that is found. You can use the
6488 synonym @samp{search @var{regexp}} or abbreviate the command name as
6491 @kindex reverse-search
6492 @item reverse-search @var{regexp}
6493 The command @samp{reverse-search @var{regexp}} checks each line, starting
6494 with the one before the last line listed and going backward, for a match
6495 for @var{regexp}. It lists the line that is found. You can abbreviate
6496 this command as @code{rev}.
6500 @section Specifying Source Directories
6503 @cindex directories for source files
6504 Executable programs sometimes do not record the directories of the source
6505 files from which they were compiled, just the names. Even when they do,
6506 the directories could be moved between the compilation and your debugging
6507 session. @value{GDBN} has a list of directories to search for source files;
6508 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6509 it tries all the directories in the list, in the order they are present
6510 in the list, until it finds a file with the desired name.
6512 For example, suppose an executable references the file
6513 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6514 @file{/mnt/cross}. The file is first looked up literally; if this
6515 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6516 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6517 message is printed. @value{GDBN} does not look up the parts of the
6518 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6519 Likewise, the subdirectories of the source path are not searched: if
6520 the source path is @file{/mnt/cross}, and the binary refers to
6521 @file{foo.c}, @value{GDBN} would not find it under
6522 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6524 Plain file names, relative file names with leading directories, file
6525 names containing dots, etc.@: are all treated as described above; for
6526 instance, if the source path is @file{/mnt/cross}, and the source file
6527 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6528 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6529 that---@file{/mnt/cross/foo.c}.
6531 Note that the executable search path is @emph{not} used to locate the
6534 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6535 any information it has cached about where source files are found and where
6536 each line is in the file.
6540 When you start @value{GDBN}, its source path includes only @samp{cdir}
6541 and @samp{cwd}, in that order.
6542 To add other directories, use the @code{directory} command.
6544 The search path is used to find both program source files and @value{GDBN}
6545 script files (read using the @samp{-command} option and @samp{source} command).
6547 In addition to the source path, @value{GDBN} provides a set of commands
6548 that manage a list of source path substitution rules. A @dfn{substitution
6549 rule} specifies how to rewrite source directories stored in the program's
6550 debug information in case the sources were moved to a different
6551 directory between compilation and debugging. A rule is made of
6552 two strings, the first specifying what needs to be rewritten in
6553 the path, and the second specifying how it should be rewritten.
6554 In @ref{set substitute-path}, we name these two parts @var{from} and
6555 @var{to} respectively. @value{GDBN} does a simple string replacement
6556 of @var{from} with @var{to} at the start of the directory part of the
6557 source file name, and uses that result instead of the original file
6558 name to look up the sources.
6560 Using the previous example, suppose the @file{foo-1.0} tree has been
6561 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6562 @value{GDBN} to replace @file{/usr/src} in all source path names with
6563 @file{/mnt/cross}. The first lookup will then be
6564 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6565 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6566 substitution rule, use the @code{set substitute-path} command
6567 (@pxref{set substitute-path}).
6569 To avoid unexpected substitution results, a rule is applied only if the
6570 @var{from} part of the directory name ends at a directory separator.
6571 For instance, a rule substituting @file{/usr/source} into
6572 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6573 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6574 is applied only at the beginning of the directory name, this rule will
6575 not be applied to @file{/root/usr/source/baz.c} either.
6577 In many cases, you can achieve the same result using the @code{directory}
6578 command. However, @code{set substitute-path} can be more efficient in
6579 the case where the sources are organized in a complex tree with multiple
6580 subdirectories. With the @code{directory} command, you need to add each
6581 subdirectory of your project. If you moved the entire tree while
6582 preserving its internal organization, then @code{set substitute-path}
6583 allows you to direct the debugger to all the sources with one single
6586 @code{set substitute-path} is also more than just a shortcut command.
6587 The source path is only used if the file at the original location no
6588 longer exists. On the other hand, @code{set substitute-path} modifies
6589 the debugger behavior to look at the rewritten location instead. So, if
6590 for any reason a source file that is not relevant to your executable is
6591 located at the original location, a substitution rule is the only
6592 method available to point @value{GDBN} at the new location.
6594 @cindex @samp{--with-relocated-sources}
6595 @cindex default source path substitution
6596 You can configure a default source path substitution rule by
6597 configuring @value{GDBN} with the
6598 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6599 should be the name of a directory under @value{GDBN}'s configured
6600 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6601 directory names in debug information under @var{dir} will be adjusted
6602 automatically if the installed @value{GDBN} is moved to a new
6603 location. This is useful if @value{GDBN}, libraries or executables
6604 with debug information and corresponding source code are being moved
6608 @item directory @var{dirname} @dots{}
6609 @item dir @var{dirname} @dots{}
6610 Add directory @var{dirname} to the front of the source path. Several
6611 directory names may be given to this command, separated by @samp{:}
6612 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6613 part of absolute file names) or
6614 whitespace. You may specify a directory that is already in the source
6615 path; this moves it forward, so @value{GDBN} searches it sooner.
6619 @vindex $cdir@r{, convenience variable}
6620 @vindex $cwd@r{, convenience variable}
6621 @cindex compilation directory
6622 @cindex current directory
6623 @cindex working directory
6624 @cindex directory, current
6625 @cindex directory, compilation
6626 You can use the string @samp{$cdir} to refer to the compilation
6627 directory (if one is recorded), and @samp{$cwd} to refer to the current
6628 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6629 tracks the current working directory as it changes during your @value{GDBN}
6630 session, while the latter is immediately expanded to the current
6631 directory at the time you add an entry to the source path.
6634 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6636 @c RET-repeat for @code{directory} is explicitly disabled, but since
6637 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6639 @item set directories @var{path-list}
6640 @kindex set directories
6641 Set the source path to @var{path-list}.
6642 @samp{$cdir:$cwd} are added if missing.
6644 @item show directories
6645 @kindex show directories
6646 Print the source path: show which directories it contains.
6648 @anchor{set substitute-path}
6649 @item set substitute-path @var{from} @var{to}
6650 @kindex set substitute-path
6651 Define a source path substitution rule, and add it at the end of the
6652 current list of existing substitution rules. If a rule with the same
6653 @var{from} was already defined, then the old rule is also deleted.
6655 For example, if the file @file{/foo/bar/baz.c} was moved to
6656 @file{/mnt/cross/baz.c}, then the command
6659 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6663 will tell @value{GDBN} to replace @samp{/usr/src} with
6664 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6665 @file{baz.c} even though it was moved.
6667 In the case when more than one substitution rule have been defined,
6668 the rules are evaluated one by one in the order where they have been
6669 defined. The first one matching, if any, is selected to perform
6672 For instance, if we had entered the following commands:
6675 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6676 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6680 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6681 @file{/mnt/include/defs.h} by using the first rule. However, it would
6682 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6683 @file{/mnt/src/lib/foo.c}.
6686 @item unset substitute-path [path]
6687 @kindex unset substitute-path
6688 If a path is specified, search the current list of substitution rules
6689 for a rule that would rewrite that path. Delete that rule if found.
6690 A warning is emitted by the debugger if no rule could be found.
6692 If no path is specified, then all substitution rules are deleted.
6694 @item show substitute-path [path]
6695 @kindex show substitute-path
6696 If a path is specified, then print the source path substitution rule
6697 which would rewrite that path, if any.
6699 If no path is specified, then print all existing source path substitution
6704 If your source path is cluttered with directories that are no longer of
6705 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6706 versions of source. You can correct the situation as follows:
6710 Use @code{directory} with no argument to reset the source path to its default value.
6713 Use @code{directory} with suitable arguments to reinstall the
6714 directories you want in the source path. You can add all the
6715 directories in one command.
6719 @section Source and Machine Code
6720 @cindex source line and its code address
6722 You can use the command @code{info line} to map source lines to program
6723 addresses (and vice versa), and the command @code{disassemble} to display
6724 a range of addresses as machine instructions. You can use the command
6725 @code{set disassemble-next-line} to set whether to disassemble next
6726 source line when execution stops. When run under @sc{gnu} Emacs
6727 mode, the @code{info line} command causes the arrow to point to the
6728 line specified. Also, @code{info line} prints addresses in symbolic form as
6733 @item info line @var{linespec}
6734 Print the starting and ending addresses of the compiled code for
6735 source line @var{linespec}. You can specify source lines in any of
6736 the ways documented in @ref{Specify Location}.
6739 For example, we can use @code{info line} to discover the location of
6740 the object code for the first line of function
6741 @code{m4_changequote}:
6743 @c FIXME: I think this example should also show the addresses in
6744 @c symbolic form, as they usually would be displayed.
6746 (@value{GDBP}) info line m4_changequote
6747 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6751 @cindex code address and its source line
6752 We can also inquire (using @code{*@var{addr}} as the form for
6753 @var{linespec}) what source line covers a particular address:
6755 (@value{GDBP}) info line *0x63ff
6756 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6759 @cindex @code{$_} and @code{info line}
6760 @cindex @code{x} command, default address
6761 @kindex x@r{(examine), and} info line
6762 After @code{info line}, the default address for the @code{x} command
6763 is changed to the starting address of the line, so that @samp{x/i} is
6764 sufficient to begin examining the machine code (@pxref{Memory,
6765 ,Examining Memory}). Also, this address is saved as the value of the
6766 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6771 @cindex assembly instructions
6772 @cindex instructions, assembly
6773 @cindex machine instructions
6774 @cindex listing machine instructions
6776 @itemx disassemble /m
6777 @itemx disassemble /r
6778 This specialized command dumps a range of memory as machine
6779 instructions. It can also print mixed source+disassembly by specifying
6780 the @code{/m} modifier and print the raw instructions in hex as well as
6781 in symbolic form by specifying the @code{/r}.
6782 The default memory range is the function surrounding the
6783 program counter of the selected frame. A single argument to this
6784 command is a program counter value; @value{GDBN} dumps the function
6785 surrounding this value. When two arguments are given, they should
6786 be separated by a comma, possibly surrounded by whitespace. The
6787 arguments specify a range of addresses to dump, in one of two forms:
6790 @item @var{start},@var{end}
6791 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6792 @item @var{start},+@var{length}
6793 the addresses from @var{start} (inclusive) to
6794 @code{@var{start}+@var{length}} (exclusive).
6798 When 2 arguments are specified, the name of the function is also
6799 printed (since there could be several functions in the given range).
6801 The argument(s) can be any expression yielding a numeric value, such as
6802 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6804 If the range of memory being disassembled contains current program counter,
6805 the instruction at that location is shown with a @code{=>} marker.
6808 The following example shows the disassembly of a range of addresses of
6809 HP PA-RISC 2.0 code:
6812 (@value{GDBP}) disas 0x32c4, 0x32e4
6813 Dump of assembler code from 0x32c4 to 0x32e4:
6814 0x32c4 <main+204>: addil 0,dp
6815 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6816 0x32cc <main+212>: ldil 0x3000,r31
6817 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6818 0x32d4 <main+220>: ldo 0(r31),rp
6819 0x32d8 <main+224>: addil -0x800,dp
6820 0x32dc <main+228>: ldo 0x588(r1),r26
6821 0x32e0 <main+232>: ldil 0x3000,r31
6822 End of assembler dump.
6825 Here is an example showing mixed source+assembly for Intel x86, when the
6826 program is stopped just after function prologue:
6829 (@value{GDBP}) disas /m main
6830 Dump of assembler code for function main:
6832 0x08048330 <+0>: push %ebp
6833 0x08048331 <+1>: mov %esp,%ebp
6834 0x08048333 <+3>: sub $0x8,%esp
6835 0x08048336 <+6>: and $0xfffffff0,%esp
6836 0x08048339 <+9>: sub $0x10,%esp
6838 6 printf ("Hello.\n");
6839 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6840 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6844 0x08048348 <+24>: mov $0x0,%eax
6845 0x0804834d <+29>: leave
6846 0x0804834e <+30>: ret
6848 End of assembler dump.
6851 Here is another example showing raw instructions in hex for AMD x86-64,
6854 (gdb) disas /r 0x400281,+10
6855 Dump of assembler code from 0x400281 to 0x40028b:
6856 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6857 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6858 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
6859 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
6860 End of assembler dump.
6863 Some architectures have more than one commonly-used set of instruction
6864 mnemonics or other syntax.
6866 For programs that were dynamically linked and use shared libraries,
6867 instructions that call functions or branch to locations in the shared
6868 libraries might show a seemingly bogus location---it's actually a
6869 location of the relocation table. On some architectures, @value{GDBN}
6870 might be able to resolve these to actual function names.
6873 @kindex set disassembly-flavor
6874 @cindex Intel disassembly flavor
6875 @cindex AT&T disassembly flavor
6876 @item set disassembly-flavor @var{instruction-set}
6877 Select the instruction set to use when disassembling the
6878 program via the @code{disassemble} or @code{x/i} commands.
6880 Currently this command is only defined for the Intel x86 family. You
6881 can set @var{instruction-set} to either @code{intel} or @code{att}.
6882 The default is @code{att}, the AT&T flavor used by default by Unix
6883 assemblers for x86-based targets.
6885 @kindex show disassembly-flavor
6886 @item show disassembly-flavor
6887 Show the current setting of the disassembly flavor.
6891 @kindex set disassemble-next-line
6892 @kindex show disassemble-next-line
6893 @item set disassemble-next-line
6894 @itemx show disassemble-next-line
6895 Control whether or not @value{GDBN} will disassemble the next source
6896 line or instruction when execution stops. If ON, @value{GDBN} will
6897 display disassembly of the next source line when execution of the
6898 program being debugged stops. This is @emph{in addition} to
6899 displaying the source line itself, which @value{GDBN} always does if
6900 possible. If the next source line cannot be displayed for some reason
6901 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6902 info in the debug info), @value{GDBN} will display disassembly of the
6903 next @emph{instruction} instead of showing the next source line. If
6904 AUTO, @value{GDBN} will display disassembly of next instruction only
6905 if the source line cannot be displayed. This setting causes
6906 @value{GDBN} to display some feedback when you step through a function
6907 with no line info or whose source file is unavailable. The default is
6908 OFF, which means never display the disassembly of the next line or
6914 @chapter Examining Data
6916 @cindex printing data
6917 @cindex examining data
6920 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6921 @c document because it is nonstandard... Under Epoch it displays in a
6922 @c different window or something like that.
6923 The usual way to examine data in your program is with the @code{print}
6924 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6925 evaluates and prints the value of an expression of the language your
6926 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6927 Different Languages}). It may also print the expression using a
6928 Python-based pretty-printer (@pxref{Pretty Printing}).
6931 @item print @var{expr}
6932 @itemx print /@var{f} @var{expr}
6933 @var{expr} is an expression (in the source language). By default the
6934 value of @var{expr} is printed in a format appropriate to its data type;
6935 you can choose a different format by specifying @samp{/@var{f}}, where
6936 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6940 @itemx print /@var{f}
6941 @cindex reprint the last value
6942 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6943 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6944 conveniently inspect the same value in an alternative format.
6947 A more low-level way of examining data is with the @code{x} command.
6948 It examines data in memory at a specified address and prints it in a
6949 specified format. @xref{Memory, ,Examining Memory}.
6951 If you are interested in information about types, or about how the
6952 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6953 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6957 * Expressions:: Expressions
6958 * Ambiguous Expressions:: Ambiguous Expressions
6959 * Variables:: Program variables
6960 * Arrays:: Artificial arrays
6961 * Output Formats:: Output formats
6962 * Memory:: Examining memory
6963 * Auto Display:: Automatic display
6964 * Print Settings:: Print settings
6965 * Pretty Printing:: Python pretty printing
6966 * Value History:: Value history
6967 * Convenience Vars:: Convenience variables
6968 * Registers:: Registers
6969 * Floating Point Hardware:: Floating point hardware
6970 * Vector Unit:: Vector Unit
6971 * OS Information:: Auxiliary data provided by operating system
6972 * Memory Region Attributes:: Memory region attributes
6973 * Dump/Restore Files:: Copy between memory and a file
6974 * Core File Generation:: Cause a program dump its core
6975 * Character Sets:: Debugging programs that use a different
6976 character set than GDB does
6977 * Caching Remote Data:: Data caching for remote targets
6978 * Searching Memory:: Searching memory for a sequence of bytes
6982 @section Expressions
6985 @code{print} and many other @value{GDBN} commands accept an expression and
6986 compute its value. Any kind of constant, variable or operator defined
6987 by the programming language you are using is valid in an expression in
6988 @value{GDBN}. This includes conditional expressions, function calls,
6989 casts, and string constants. It also includes preprocessor macros, if
6990 you compiled your program to include this information; see
6993 @cindex arrays in expressions
6994 @value{GDBN} supports array constants in expressions input by
6995 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6996 you can use the command @code{print @{1, 2, 3@}} to create an array
6997 of three integers. If you pass an array to a function or assign it
6998 to a program variable, @value{GDBN} copies the array to memory that
6999 is @code{malloc}ed in the target program.
7001 Because C is so widespread, most of the expressions shown in examples in
7002 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7003 Languages}, for information on how to use expressions in other
7006 In this section, we discuss operators that you can use in @value{GDBN}
7007 expressions regardless of your programming language.
7009 @cindex casts, in expressions
7010 Casts are supported in all languages, not just in C, because it is so
7011 useful to cast a number into a pointer in order to examine a structure
7012 at that address in memory.
7013 @c FIXME: casts supported---Mod2 true?
7015 @value{GDBN} supports these operators, in addition to those common
7016 to programming languages:
7020 @samp{@@} is a binary operator for treating parts of memory as arrays.
7021 @xref{Arrays, ,Artificial Arrays}, for more information.
7024 @samp{::} allows you to specify a variable in terms of the file or
7025 function where it is defined. @xref{Variables, ,Program Variables}.
7027 @cindex @{@var{type}@}
7028 @cindex type casting memory
7029 @cindex memory, viewing as typed object
7030 @cindex casts, to view memory
7031 @item @{@var{type}@} @var{addr}
7032 Refers to an object of type @var{type} stored at address @var{addr} in
7033 memory. @var{addr} may be any expression whose value is an integer or
7034 pointer (but parentheses are required around binary operators, just as in
7035 a cast). This construct is allowed regardless of what kind of data is
7036 normally supposed to reside at @var{addr}.
7039 @node Ambiguous Expressions
7040 @section Ambiguous Expressions
7041 @cindex ambiguous expressions
7043 Expressions can sometimes contain some ambiguous elements. For instance,
7044 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7045 a single function name to be defined several times, for application in
7046 different contexts. This is called @dfn{overloading}. Another example
7047 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7048 templates and is typically instantiated several times, resulting in
7049 the same function name being defined in different contexts.
7051 In some cases and depending on the language, it is possible to adjust
7052 the expression to remove the ambiguity. For instance in C@t{++}, you
7053 can specify the signature of the function you want to break on, as in
7054 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7055 qualified name of your function often makes the expression unambiguous
7058 When an ambiguity that needs to be resolved is detected, the debugger
7059 has the capability to display a menu of numbered choices for each
7060 possibility, and then waits for the selection with the prompt @samp{>}.
7061 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7062 aborts the current command. If the command in which the expression was
7063 used allows more than one choice to be selected, the next option in the
7064 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7067 For example, the following session excerpt shows an attempt to set a
7068 breakpoint at the overloaded symbol @code{String::after}.
7069 We choose three particular definitions of that function name:
7071 @c FIXME! This is likely to change to show arg type lists, at least
7074 (@value{GDBP}) b String::after
7077 [2] file:String.cc; line number:867
7078 [3] file:String.cc; line number:860
7079 [4] file:String.cc; line number:875
7080 [5] file:String.cc; line number:853
7081 [6] file:String.cc; line number:846
7082 [7] file:String.cc; line number:735
7084 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7085 Breakpoint 2 at 0xb344: file String.cc, line 875.
7086 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7087 Multiple breakpoints were set.
7088 Use the "delete" command to delete unwanted
7095 @kindex set multiple-symbols
7096 @item set multiple-symbols @var{mode}
7097 @cindex multiple-symbols menu
7099 This option allows you to adjust the debugger behavior when an expression
7102 By default, @var{mode} is set to @code{all}. If the command with which
7103 the expression is used allows more than one choice, then @value{GDBN}
7104 automatically selects all possible choices. For instance, inserting
7105 a breakpoint on a function using an ambiguous name results in a breakpoint
7106 inserted on each possible match. However, if a unique choice must be made,
7107 then @value{GDBN} uses the menu to help you disambiguate the expression.
7108 For instance, printing the address of an overloaded function will result
7109 in the use of the menu.
7111 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7112 when an ambiguity is detected.
7114 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7115 an error due to the ambiguity and the command is aborted.
7117 @kindex show multiple-symbols
7118 @item show multiple-symbols
7119 Show the current value of the @code{multiple-symbols} setting.
7123 @section Program Variables
7125 The most common kind of expression to use is the name of a variable
7128 Variables in expressions are understood in the selected stack frame
7129 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7133 global (or file-static)
7140 visible according to the scope rules of the
7141 programming language from the point of execution in that frame
7144 @noindent This means that in the function
7159 you can examine and use the variable @code{a} whenever your program is
7160 executing within the function @code{foo}, but you can only use or
7161 examine the variable @code{b} while your program is executing inside
7162 the block where @code{b} is declared.
7164 @cindex variable name conflict
7165 There is an exception: you can refer to a variable or function whose
7166 scope is a single source file even if the current execution point is not
7167 in this file. But it is possible to have more than one such variable or
7168 function with the same name (in different source files). If that
7169 happens, referring to that name has unpredictable effects. If you wish,
7170 you can specify a static variable in a particular function or file,
7171 using the colon-colon (@code{::}) notation:
7173 @cindex colon-colon, context for variables/functions
7175 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7176 @cindex @code{::}, context for variables/functions
7179 @var{file}::@var{variable}
7180 @var{function}::@var{variable}
7184 Here @var{file} or @var{function} is the name of the context for the
7185 static @var{variable}. In the case of file names, you can use quotes to
7186 make sure @value{GDBN} parses the file name as a single word---for example,
7187 to print a global value of @code{x} defined in @file{f2.c}:
7190 (@value{GDBP}) p 'f2.c'::x
7193 @cindex C@t{++} scope resolution
7194 This use of @samp{::} is very rarely in conflict with the very similar
7195 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7196 scope resolution operator in @value{GDBN} expressions.
7197 @c FIXME: Um, so what happens in one of those rare cases where it's in
7200 @cindex wrong values
7201 @cindex variable values, wrong
7202 @cindex function entry/exit, wrong values of variables
7203 @cindex optimized code, wrong values of variables
7205 @emph{Warning:} Occasionally, a local variable may appear to have the
7206 wrong value at certain points in a function---just after entry to a new
7207 scope, and just before exit.
7209 You may see this problem when you are stepping by machine instructions.
7210 This is because, on most machines, it takes more than one instruction to
7211 set up a stack frame (including local variable definitions); if you are
7212 stepping by machine instructions, variables may appear to have the wrong
7213 values until the stack frame is completely built. On exit, it usually
7214 also takes more than one machine instruction to destroy a stack frame;
7215 after you begin stepping through that group of instructions, local
7216 variable definitions may be gone.
7218 This may also happen when the compiler does significant optimizations.
7219 To be sure of always seeing accurate values, turn off all optimization
7222 @cindex ``No symbol "foo" in current context''
7223 Another possible effect of compiler optimizations is to optimize
7224 unused variables out of existence, or assign variables to registers (as
7225 opposed to memory addresses). Depending on the support for such cases
7226 offered by the debug info format used by the compiler, @value{GDBN}
7227 might not be able to display values for such local variables. If that
7228 happens, @value{GDBN} will print a message like this:
7231 No symbol "foo" in current context.
7234 To solve such problems, either recompile without optimizations, or use a
7235 different debug info format, if the compiler supports several such
7236 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7237 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7238 produces debug info in a format that is superior to formats such as
7239 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7240 an effective form for debug info. @xref{Debugging Options,,Options
7241 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7242 Compiler Collection (GCC)}.
7243 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7244 that are best suited to C@t{++} programs.
7246 If you ask to print an object whose contents are unknown to
7247 @value{GDBN}, e.g., because its data type is not completely specified
7248 by the debug information, @value{GDBN} will say @samp{<incomplete
7249 type>}. @xref{Symbols, incomplete type}, for more about this.
7251 Strings are identified as arrays of @code{char} values without specified
7252 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7253 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7254 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7255 defines literal string type @code{"char"} as @code{char} without a sign.
7260 signed char var1[] = "A";
7263 You get during debugging
7268 $2 = @{65 'A', 0 '\0'@}
7272 @section Artificial Arrays
7274 @cindex artificial array
7276 @kindex @@@r{, referencing memory as an array}
7277 It is often useful to print out several successive objects of the
7278 same type in memory; a section of an array, or an array of
7279 dynamically determined size for which only a pointer exists in the
7282 You can do this by referring to a contiguous span of memory as an
7283 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7284 operand of @samp{@@} should be the first element of the desired array
7285 and be an individual object. The right operand should be the desired length
7286 of the array. The result is an array value whose elements are all of
7287 the type of the left argument. The first element is actually the left
7288 argument; the second element comes from bytes of memory immediately
7289 following those that hold the first element, and so on. Here is an
7290 example. If a program says
7293 int *array = (int *) malloc (len * sizeof (int));
7297 you can print the contents of @code{array} with
7303 The left operand of @samp{@@} must reside in memory. Array values made
7304 with @samp{@@} in this way behave just like other arrays in terms of
7305 subscripting, and are coerced to pointers when used in expressions.
7306 Artificial arrays most often appear in expressions via the value history
7307 (@pxref{Value History, ,Value History}), after printing one out.
7309 Another way to create an artificial array is to use a cast.
7310 This re-interprets a value as if it were an array.
7311 The value need not be in memory:
7313 (@value{GDBP}) p/x (short[2])0x12345678
7314 $1 = @{0x1234, 0x5678@}
7317 As a convenience, if you leave the array length out (as in
7318 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7319 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7321 (@value{GDBP}) p/x (short[])0x12345678
7322 $2 = @{0x1234, 0x5678@}
7325 Sometimes the artificial array mechanism is not quite enough; in
7326 moderately complex data structures, the elements of interest may not
7327 actually be adjacent---for example, if you are interested in the values
7328 of pointers in an array. One useful work-around in this situation is
7329 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7330 Variables}) as a counter in an expression that prints the first
7331 interesting value, and then repeat that expression via @key{RET}. For
7332 instance, suppose you have an array @code{dtab} of pointers to
7333 structures, and you are interested in the values of a field @code{fv}
7334 in each structure. Here is an example of what you might type:
7344 @node Output Formats
7345 @section Output Formats
7347 @cindex formatted output
7348 @cindex output formats
7349 By default, @value{GDBN} prints a value according to its data type. Sometimes
7350 this is not what you want. For example, you might want to print a number
7351 in hex, or a pointer in decimal. Or you might want to view data in memory
7352 at a certain address as a character string or as an instruction. To do
7353 these things, specify an @dfn{output format} when you print a value.
7355 The simplest use of output formats is to say how to print a value
7356 already computed. This is done by starting the arguments of the
7357 @code{print} command with a slash and a format letter. The format
7358 letters supported are:
7362 Regard the bits of the value as an integer, and print the integer in
7366 Print as integer in signed decimal.
7369 Print as integer in unsigned decimal.
7372 Print as integer in octal.
7375 Print as integer in binary. The letter @samp{t} stands for ``two''.
7376 @footnote{@samp{b} cannot be used because these format letters are also
7377 used with the @code{x} command, where @samp{b} stands for ``byte'';
7378 see @ref{Memory,,Examining Memory}.}
7381 @cindex unknown address, locating
7382 @cindex locate address
7383 Print as an address, both absolute in hexadecimal and as an offset from
7384 the nearest preceding symbol. You can use this format used to discover
7385 where (in what function) an unknown address is located:
7388 (@value{GDBP}) p/a 0x54320
7389 $3 = 0x54320 <_initialize_vx+396>
7393 The command @code{info symbol 0x54320} yields similar results.
7394 @xref{Symbols, info symbol}.
7397 Regard as an integer and print it as a character constant. This
7398 prints both the numerical value and its character representation. The
7399 character representation is replaced with the octal escape @samp{\nnn}
7400 for characters outside the 7-bit @sc{ascii} range.
7402 Without this format, @value{GDBN} displays @code{char},
7403 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7404 constants. Single-byte members of vectors are displayed as integer
7408 Regard the bits of the value as a floating point number and print
7409 using typical floating point syntax.
7412 @cindex printing strings
7413 @cindex printing byte arrays
7414 Regard as a string, if possible. With this format, pointers to single-byte
7415 data are displayed as null-terminated strings and arrays of single-byte data
7416 are displayed as fixed-length strings. Other values are displayed in their
7419 Without this format, @value{GDBN} displays pointers to and arrays of
7420 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7421 strings. Single-byte members of a vector are displayed as an integer
7425 @cindex raw printing
7426 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7427 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7428 Printing}). This typically results in a higher-level display of the
7429 value's contents. The @samp{r} format bypasses any Python
7430 pretty-printer which might exist.
7433 For example, to print the program counter in hex (@pxref{Registers}), type
7440 Note that no space is required before the slash; this is because command
7441 names in @value{GDBN} cannot contain a slash.
7443 To reprint the last value in the value history with a different format,
7444 you can use the @code{print} command with just a format and no
7445 expression. For example, @samp{p/x} reprints the last value in hex.
7448 @section Examining Memory
7450 You can use the command @code{x} (for ``examine'') to examine memory in
7451 any of several formats, independently of your program's data types.
7453 @cindex examining memory
7455 @kindex x @r{(examine memory)}
7456 @item x/@var{nfu} @var{addr}
7459 Use the @code{x} command to examine memory.
7462 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7463 much memory to display and how to format it; @var{addr} is an
7464 expression giving the address where you want to start displaying memory.
7465 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7466 Several commands set convenient defaults for @var{addr}.
7469 @item @var{n}, the repeat count
7470 The repeat count is a decimal integer; the default is 1. It specifies
7471 how much memory (counting by units @var{u}) to display.
7472 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7475 @item @var{f}, the display format
7476 The display format is one of the formats used by @code{print}
7477 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7478 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7479 The default is @samp{x} (hexadecimal) initially. The default changes
7480 each time you use either @code{x} or @code{print}.
7482 @item @var{u}, the unit size
7483 The unit size is any of
7489 Halfwords (two bytes).
7491 Words (four bytes). This is the initial default.
7493 Giant words (eight bytes).
7496 Each time you specify a unit size with @code{x}, that size becomes the
7497 default unit the next time you use @code{x}. For the @samp{i} format,
7498 the unit size is ignored and is normally not written. For the @samp{s} format,
7499 the unit size defaults to @samp{b}, unless it is explicitly given.
7500 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7501 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7502 Note that the results depend on the programming language of the
7503 current compilation unit. If the language is C, the @samp{s}
7504 modifier will use the UTF-16 encoding while @samp{w} will use
7505 UTF-32. The encoding is set by the programming language and cannot
7508 @item @var{addr}, starting display address
7509 @var{addr} is the address where you want @value{GDBN} to begin displaying
7510 memory. The expression need not have a pointer value (though it may);
7511 it is always interpreted as an integer address of a byte of memory.
7512 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7513 @var{addr} is usually just after the last address examined---but several
7514 other commands also set the default address: @code{info breakpoints} (to
7515 the address of the last breakpoint listed), @code{info line} (to the
7516 starting address of a line), and @code{print} (if you use it to display
7517 a value from memory).
7520 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7521 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7522 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7523 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7524 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7526 Since the letters indicating unit sizes are all distinct from the
7527 letters specifying output formats, you do not have to remember whether
7528 unit size or format comes first; either order works. The output
7529 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7530 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7532 Even though the unit size @var{u} is ignored for the formats @samp{s}
7533 and @samp{i}, you might still want to use a count @var{n}; for example,
7534 @samp{3i} specifies that you want to see three machine instructions,
7535 including any operands. For convenience, especially when used with
7536 the @code{display} command, the @samp{i} format also prints branch delay
7537 slot instructions, if any, beyond the count specified, which immediately
7538 follow the last instruction that is within the count. The command
7539 @code{disassemble} gives an alternative way of inspecting machine
7540 instructions; see @ref{Machine Code,,Source and Machine Code}.
7542 All the defaults for the arguments to @code{x} are designed to make it
7543 easy to continue scanning memory with minimal specifications each time
7544 you use @code{x}. For example, after you have inspected three machine
7545 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7546 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7547 the repeat count @var{n} is used again; the other arguments default as
7548 for successive uses of @code{x}.
7550 When examining machine instructions, the instruction at current program
7551 counter is shown with a @code{=>} marker. For example:
7554 (@value{GDBP}) x/5i $pc-6
7555 0x804837f <main+11>: mov %esp,%ebp
7556 0x8048381 <main+13>: push %ecx
7557 0x8048382 <main+14>: sub $0x4,%esp
7558 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7559 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7562 @cindex @code{$_}, @code{$__}, and value history
7563 The addresses and contents printed by the @code{x} command are not saved
7564 in the value history because there is often too much of them and they
7565 would get in the way. Instead, @value{GDBN} makes these values available for
7566 subsequent use in expressions as values of the convenience variables
7567 @code{$_} and @code{$__}. After an @code{x} command, the last address
7568 examined is available for use in expressions in the convenience variable
7569 @code{$_}. The contents of that address, as examined, are available in
7570 the convenience variable @code{$__}.
7572 If the @code{x} command has a repeat count, the address and contents saved
7573 are from the last memory unit printed; this is not the same as the last
7574 address printed if several units were printed on the last line of output.
7576 @cindex remote memory comparison
7577 @cindex verify remote memory image
7578 When you are debugging a program running on a remote target machine
7579 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7580 remote machine's memory against the executable file you downloaded to
7581 the target. The @code{compare-sections} command is provided for such
7585 @kindex compare-sections
7586 @item compare-sections @r{[}@var{section-name}@r{]}
7587 Compare the data of a loadable section @var{section-name} in the
7588 executable file of the program being debugged with the same section in
7589 the remote machine's memory, and report any mismatches. With no
7590 arguments, compares all loadable sections. This command's
7591 availability depends on the target's support for the @code{"qCRC"}
7596 @section Automatic Display
7597 @cindex automatic display
7598 @cindex display of expressions
7600 If you find that you want to print the value of an expression frequently
7601 (to see how it changes), you might want to add it to the @dfn{automatic
7602 display list} so that @value{GDBN} prints its value each time your program stops.
7603 Each expression added to the list is given a number to identify it;
7604 to remove an expression from the list, you specify that number.
7605 The automatic display looks like this:
7609 3: bar[5] = (struct hack *) 0x3804
7613 This display shows item numbers, expressions and their current values. As with
7614 displays you request manually using @code{x} or @code{print}, you can
7615 specify the output format you prefer; in fact, @code{display} decides
7616 whether to use @code{print} or @code{x} depending your format
7617 specification---it uses @code{x} if you specify either the @samp{i}
7618 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7622 @item display @var{expr}
7623 Add the expression @var{expr} to the list of expressions to display
7624 each time your program stops. @xref{Expressions, ,Expressions}.
7626 @code{display} does not repeat if you press @key{RET} again after using it.
7628 @item display/@var{fmt} @var{expr}
7629 For @var{fmt} specifying only a display format and not a size or
7630 count, add the expression @var{expr} to the auto-display list but
7631 arrange to display it each time in the specified format @var{fmt}.
7632 @xref{Output Formats,,Output Formats}.
7634 @item display/@var{fmt} @var{addr}
7635 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7636 number of units, add the expression @var{addr} as a memory address to
7637 be examined each time your program stops. Examining means in effect
7638 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7641 For example, @samp{display/i $pc} can be helpful, to see the machine
7642 instruction about to be executed each time execution stops (@samp{$pc}
7643 is a common name for the program counter; @pxref{Registers, ,Registers}).
7646 @kindex delete display
7648 @item undisplay @var{dnums}@dots{}
7649 @itemx delete display @var{dnums}@dots{}
7650 Remove item numbers @var{dnums} from the list of expressions to display.
7652 @code{undisplay} does not repeat if you press @key{RET} after using it.
7653 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7655 @kindex disable display
7656 @item disable display @var{dnums}@dots{}
7657 Disable the display of item numbers @var{dnums}. A disabled display
7658 item is not printed automatically, but is not forgotten. It may be
7659 enabled again later.
7661 @kindex enable display
7662 @item enable display @var{dnums}@dots{}
7663 Enable display of item numbers @var{dnums}. It becomes effective once
7664 again in auto display of its expression, until you specify otherwise.
7667 Display the current values of the expressions on the list, just as is
7668 done when your program stops.
7670 @kindex info display
7672 Print the list of expressions previously set up to display
7673 automatically, each one with its item number, but without showing the
7674 values. This includes disabled expressions, which are marked as such.
7675 It also includes expressions which would not be displayed right now
7676 because they refer to automatic variables not currently available.
7679 @cindex display disabled out of scope
7680 If a display expression refers to local variables, then it does not make
7681 sense outside the lexical context for which it was set up. Such an
7682 expression is disabled when execution enters a context where one of its
7683 variables is not defined. For example, if you give the command
7684 @code{display last_char} while inside a function with an argument
7685 @code{last_char}, @value{GDBN} displays this argument while your program
7686 continues to stop inside that function. When it stops elsewhere---where
7687 there is no variable @code{last_char}---the display is disabled
7688 automatically. The next time your program stops where @code{last_char}
7689 is meaningful, you can enable the display expression once again.
7691 @node Print Settings
7692 @section Print Settings
7694 @cindex format options
7695 @cindex print settings
7696 @value{GDBN} provides the following ways to control how arrays, structures,
7697 and symbols are printed.
7700 These settings are useful for debugging programs in any language:
7704 @item set print address
7705 @itemx set print address on
7706 @cindex print/don't print memory addresses
7707 @value{GDBN} prints memory addresses showing the location of stack
7708 traces, structure values, pointer values, breakpoints, and so forth,
7709 even when it also displays the contents of those addresses. The default
7710 is @code{on}. For example, this is what a stack frame display looks like with
7711 @code{set print address on}:
7716 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7718 530 if (lquote != def_lquote)
7722 @item set print address off
7723 Do not print addresses when displaying their contents. For example,
7724 this is the same stack frame displayed with @code{set print address off}:
7728 (@value{GDBP}) set print addr off
7730 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7731 530 if (lquote != def_lquote)
7735 You can use @samp{set print address off} to eliminate all machine
7736 dependent displays from the @value{GDBN} interface. For example, with
7737 @code{print address off}, you should get the same text for backtraces on
7738 all machines---whether or not they involve pointer arguments.
7741 @item show print address
7742 Show whether or not addresses are to be printed.
7745 When @value{GDBN} prints a symbolic address, it normally prints the
7746 closest earlier symbol plus an offset. If that symbol does not uniquely
7747 identify the address (for example, it is a name whose scope is a single
7748 source file), you may need to clarify. One way to do this is with
7749 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7750 you can set @value{GDBN} to print the source file and line number when
7751 it prints a symbolic address:
7754 @item set print symbol-filename on
7755 @cindex source file and line of a symbol
7756 @cindex symbol, source file and line
7757 Tell @value{GDBN} to print the source file name and line number of a
7758 symbol in the symbolic form of an address.
7760 @item set print symbol-filename off
7761 Do not print source file name and line number of a symbol. This is the
7764 @item show print symbol-filename
7765 Show whether or not @value{GDBN} will print the source file name and
7766 line number of a symbol in the symbolic form of an address.
7769 Another situation where it is helpful to show symbol filenames and line
7770 numbers is when disassembling code; @value{GDBN} shows you the line
7771 number and source file that corresponds to each instruction.
7773 Also, you may wish to see the symbolic form only if the address being
7774 printed is reasonably close to the closest earlier symbol:
7777 @item set print max-symbolic-offset @var{max-offset}
7778 @cindex maximum value for offset of closest symbol
7779 Tell @value{GDBN} to only display the symbolic form of an address if the
7780 offset between the closest earlier symbol and the address is less than
7781 @var{max-offset}. The default is 0, which tells @value{GDBN}
7782 to always print the symbolic form of an address if any symbol precedes it.
7784 @item show print max-symbolic-offset
7785 Ask how large the maximum offset is that @value{GDBN} prints in a
7789 @cindex wild pointer, interpreting
7790 @cindex pointer, finding referent
7791 If you have a pointer and you are not sure where it points, try
7792 @samp{set print symbol-filename on}. Then you can determine the name
7793 and source file location of the variable where it points, using
7794 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7795 For example, here @value{GDBN} shows that a variable @code{ptt} points
7796 at another variable @code{t}, defined in @file{hi2.c}:
7799 (@value{GDBP}) set print symbol-filename on
7800 (@value{GDBP}) p/a ptt
7801 $4 = 0xe008 <t in hi2.c>
7805 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7806 does not show the symbol name and filename of the referent, even with
7807 the appropriate @code{set print} options turned on.
7810 Other settings control how different kinds of objects are printed:
7813 @item set print array
7814 @itemx set print array on
7815 @cindex pretty print arrays
7816 Pretty print arrays. This format is more convenient to read,
7817 but uses more space. The default is off.
7819 @item set print array off
7820 Return to compressed format for arrays.
7822 @item show print array
7823 Show whether compressed or pretty format is selected for displaying
7826 @cindex print array indexes
7827 @item set print array-indexes
7828 @itemx set print array-indexes on
7829 Print the index of each element when displaying arrays. May be more
7830 convenient to locate a given element in the array or quickly find the
7831 index of a given element in that printed array. The default is off.
7833 @item set print array-indexes off
7834 Stop printing element indexes when displaying arrays.
7836 @item show print array-indexes
7837 Show whether the index of each element is printed when displaying
7840 @item set print elements @var{number-of-elements}
7841 @cindex number of array elements to print
7842 @cindex limit on number of printed array elements
7843 Set a limit on how many elements of an array @value{GDBN} will print.
7844 If @value{GDBN} is printing a large array, it stops printing after it has
7845 printed the number of elements set by the @code{set print elements} command.
7846 This limit also applies to the display of strings.
7847 When @value{GDBN} starts, this limit is set to 200.
7848 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7850 @item show print elements
7851 Display the number of elements of a large array that @value{GDBN} will print.
7852 If the number is 0, then the printing is unlimited.
7854 @item set print frame-arguments @var{value}
7855 @kindex set print frame-arguments
7856 @cindex printing frame argument values
7857 @cindex print all frame argument values
7858 @cindex print frame argument values for scalars only
7859 @cindex do not print frame argument values
7860 This command allows to control how the values of arguments are printed
7861 when the debugger prints a frame (@pxref{Frames}). The possible
7866 The values of all arguments are printed.
7869 Print the value of an argument only if it is a scalar. The value of more
7870 complex arguments such as arrays, structures, unions, etc, is replaced
7871 by @code{@dots{}}. This is the default. Here is an example where
7872 only scalar arguments are shown:
7875 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7880 None of the argument values are printed. Instead, the value of each argument
7881 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7884 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7889 By default, only scalar arguments are printed. This command can be used
7890 to configure the debugger to print the value of all arguments, regardless
7891 of their type. However, it is often advantageous to not print the value
7892 of more complex parameters. For instance, it reduces the amount of
7893 information printed in each frame, making the backtrace more readable.
7894 Also, it improves performance when displaying Ada frames, because
7895 the computation of large arguments can sometimes be CPU-intensive,
7896 especially in large applications. Setting @code{print frame-arguments}
7897 to @code{scalars} (the default) or @code{none} avoids this computation,
7898 thus speeding up the display of each Ada frame.
7900 @item show print frame-arguments
7901 Show how the value of arguments should be displayed when printing a frame.
7903 @item set print repeats
7904 @cindex repeated array elements
7905 Set the threshold for suppressing display of repeated array
7906 elements. When the number of consecutive identical elements of an
7907 array exceeds the threshold, @value{GDBN} prints the string
7908 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7909 identical repetitions, instead of displaying the identical elements
7910 themselves. Setting the threshold to zero will cause all elements to
7911 be individually printed. The default threshold is 10.
7913 @item show print repeats
7914 Display the current threshold for printing repeated identical
7917 @item set print null-stop
7918 @cindex @sc{null} elements in arrays
7919 Cause @value{GDBN} to stop printing the characters of an array when the first
7920 @sc{null} is encountered. This is useful when large arrays actually
7921 contain only short strings.
7924 @item show print null-stop
7925 Show whether @value{GDBN} stops printing an array on the first
7926 @sc{null} character.
7928 @item set print pretty on
7929 @cindex print structures in indented form
7930 @cindex indentation in structure display
7931 Cause @value{GDBN} to print structures in an indented format with one member
7932 per line, like this:
7947 @item set print pretty off
7948 Cause @value{GDBN} to print structures in a compact format, like this:
7952 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7953 meat = 0x54 "Pork"@}
7958 This is the default format.
7960 @item show print pretty
7961 Show which format @value{GDBN} is using to print structures.
7963 @item set print sevenbit-strings on
7964 @cindex eight-bit characters in strings
7965 @cindex octal escapes in strings
7966 Print using only seven-bit characters; if this option is set,
7967 @value{GDBN} displays any eight-bit characters (in strings or
7968 character values) using the notation @code{\}@var{nnn}. This setting is
7969 best if you are working in English (@sc{ascii}) and you use the
7970 high-order bit of characters as a marker or ``meta'' bit.
7972 @item set print sevenbit-strings off
7973 Print full eight-bit characters. This allows the use of more
7974 international character sets, and is the default.
7976 @item show print sevenbit-strings
7977 Show whether or not @value{GDBN} is printing only seven-bit characters.
7979 @item set print union on
7980 @cindex unions in structures, printing
7981 Tell @value{GDBN} to print unions which are contained in structures
7982 and other unions. This is the default setting.
7984 @item set print union off
7985 Tell @value{GDBN} not to print unions which are contained in
7986 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7989 @item show print union
7990 Ask @value{GDBN} whether or not it will print unions which are contained in
7991 structures and other unions.
7993 For example, given the declarations
7996 typedef enum @{Tree, Bug@} Species;
7997 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7998 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8009 struct thing foo = @{Tree, @{Acorn@}@};
8013 with @code{set print union on} in effect @samp{p foo} would print
8016 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8020 and with @code{set print union off} in effect it would print
8023 $1 = @{it = Tree, form = @{...@}@}
8027 @code{set print union} affects programs written in C-like languages
8033 These settings are of interest when debugging C@t{++} programs:
8036 @cindex demangling C@t{++} names
8037 @item set print demangle
8038 @itemx set print demangle on
8039 Print C@t{++} names in their source form rather than in the encoded
8040 (``mangled'') form passed to the assembler and linker for type-safe
8041 linkage. The default is on.
8043 @item show print demangle
8044 Show whether C@t{++} names are printed in mangled or demangled form.
8046 @item set print asm-demangle
8047 @itemx set print asm-demangle on
8048 Print C@t{++} names in their source form rather than their mangled form, even
8049 in assembler code printouts such as instruction disassemblies.
8052 @item show print asm-demangle
8053 Show whether C@t{++} names in assembly listings are printed in mangled
8056 @cindex C@t{++} symbol decoding style
8057 @cindex symbol decoding style, C@t{++}
8058 @kindex set demangle-style
8059 @item set demangle-style @var{style}
8060 Choose among several encoding schemes used by different compilers to
8061 represent C@t{++} names. The choices for @var{style} are currently:
8065 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8068 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8069 This is the default.
8072 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8075 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8078 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8079 @strong{Warning:} this setting alone is not sufficient to allow
8080 debugging @code{cfront}-generated executables. @value{GDBN} would
8081 require further enhancement to permit that.
8084 If you omit @var{style}, you will see a list of possible formats.
8086 @item show demangle-style
8087 Display the encoding style currently in use for decoding C@t{++} symbols.
8089 @item set print object
8090 @itemx set print object on
8091 @cindex derived type of an object, printing
8092 @cindex display derived types
8093 When displaying a pointer to an object, identify the @emph{actual}
8094 (derived) type of the object rather than the @emph{declared} type, using
8095 the virtual function table.
8097 @item set print object off
8098 Display only the declared type of objects, without reference to the
8099 virtual function table. This is the default setting.
8101 @item show print object
8102 Show whether actual, or declared, object types are displayed.
8104 @item set print static-members
8105 @itemx set print static-members on
8106 @cindex static members of C@t{++} objects
8107 Print static members when displaying a C@t{++} object. The default is on.
8109 @item set print static-members off
8110 Do not print static members when displaying a C@t{++} object.
8112 @item show print static-members
8113 Show whether C@t{++} static members are printed or not.
8115 @item set print pascal_static-members
8116 @itemx set print pascal_static-members on
8117 @cindex static members of Pascal objects
8118 @cindex Pascal objects, static members display
8119 Print static members when displaying a Pascal object. The default is on.
8121 @item set print pascal_static-members off
8122 Do not print static members when displaying a Pascal object.
8124 @item show print pascal_static-members
8125 Show whether Pascal static members are printed or not.
8127 @c These don't work with HP ANSI C++ yet.
8128 @item set print vtbl
8129 @itemx set print vtbl on
8130 @cindex pretty print C@t{++} virtual function tables
8131 @cindex virtual functions (C@t{++}) display
8132 @cindex VTBL display
8133 Pretty print C@t{++} virtual function tables. The default is off.
8134 (The @code{vtbl} commands do not work on programs compiled with the HP
8135 ANSI C@t{++} compiler (@code{aCC}).)
8137 @item set print vtbl off
8138 Do not pretty print C@t{++} virtual function tables.
8140 @item show print vtbl
8141 Show whether C@t{++} virtual function tables are pretty printed, or not.
8144 @node Pretty Printing
8145 @section Pretty Printing
8147 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8148 Python code. It greatly simplifies the display of complex objects. This
8149 mechanism works for both MI and the CLI.
8152 * Pretty-Printer Introduction:: Introduction to pretty-printers
8153 * Pretty-Printer Example:: An example pretty-printer
8154 * Pretty-Printer Commands:: Pretty-printer commands
8157 @node Pretty-Printer Introduction
8158 @subsection Pretty-Printer Introduction
8160 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8161 registered for the value. If there is then @value{GDBN} invokes the
8162 pretty-printer to print the value. Otherwise the value is printed normally.
8164 Pretty-printers are normally named. This makes them easy to manage.
8165 The @samp{info pretty-printer} command will list all the installed
8166 pretty-printers with their names.
8167 If a pretty-printer can handle multiple data types, then its
8168 @dfn{subprinters} are the printers for the individual data types.
8169 Each such subprinter has its own name.
8170 The format of the name is @var{printer-name};@var{subprinter-name}.
8172 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8173 Typically they are automatically loaded and registered when the corresponding
8174 debug information is loaded, thus making them available without having to
8175 do anything special.
8177 There are three places where a pretty-printer can be registered.
8181 Pretty-printers registered globally are available when debugging
8185 Pretty-printers registered with a program space are available only
8186 when debugging that program.
8187 @xref{Progspaces In Python}, for more details on program spaces in Python.
8190 Pretty-printers registered with an objfile are loaded and unloaded
8191 with the corresponding objfile (e.g., shared library).
8192 @xref{Objfiles In Python}, for more details on objfiles in Python.
8195 @xref{Selecting Pretty-Printers}, for further information on how
8196 pretty-printers are selected,
8198 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8201 @node Pretty-Printer Example
8202 @subsection Pretty-Printer Example
8204 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8207 (@value{GDBP}) print s
8209 static npos = 4294967295,
8211 <std::allocator<char>> = @{
8212 <__gnu_cxx::new_allocator<char>> = @{
8213 <No data fields>@}, <No data fields>
8215 members of std::basic_string<char, std::char_traits<char>,
8216 std::allocator<char> >::_Alloc_hider:
8217 _M_p = 0x804a014 "abcd"
8222 With a pretty-printer for @code{std::string} only the contents are printed:
8225 (@value{GDBP}) print s
8229 @node Pretty-Printer Commands
8230 @subsection Pretty-Printer Commands
8231 @cindex pretty-printer commands
8234 @kindex info pretty-printer
8235 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8236 Print the list of installed pretty-printers.
8237 This includes disabled pretty-printers, which are marked as such.
8239 @var{object-regexp} is a regular expression matching the objects
8240 whose pretty-printers to list.
8241 Objects can be @code{global}, the program space's file
8242 (@pxref{Progspaces In Python}),
8243 and the object files within that program space (@pxref{Objfiles In Python}).
8244 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8245 looks up a printer from these three objects.
8247 @var{name-regexp} is a regular expression matching the name of the printers
8250 @kindex disable pretty-printer
8251 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8252 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8253 A disabled pretty-printer is not forgotten, it may be enabled again later.
8255 @kindex enable pretty-printer
8256 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8257 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8262 Suppose we have three pretty-printers installed: one from library1.so
8263 named @code{foo} that prints objects of type @code{foo}, and
8264 another from library2.so named @code{bar} that prints two types of objects,
8265 @code{bar1} and @code{bar2}.
8268 (gdb) info pretty-printer
8275 (gdb) info pretty-printer library2
8280 (gdb) disable pretty-printer library1
8282 2 of 3 printers enabled
8283 (gdb) info pretty-printer
8290 (gdb) disable pretty-printer library2 bar:bar1
8292 1 of 3 printers enabled
8293 (gdb) info pretty-printer library2
8300 (gdb) disable pretty-printer library2 bar
8302 0 of 3 printers enabled
8303 (gdb) info pretty-printer library2
8312 Note that for @code{bar} the entire printer can be disabled,
8313 as can each individual subprinter.
8316 @section Value History
8318 @cindex value history
8319 @cindex history of values printed by @value{GDBN}
8320 Values printed by the @code{print} command are saved in the @value{GDBN}
8321 @dfn{value history}. This allows you to refer to them in other expressions.
8322 Values are kept until the symbol table is re-read or discarded
8323 (for example with the @code{file} or @code{symbol-file} commands).
8324 When the symbol table changes, the value history is discarded,
8325 since the values may contain pointers back to the types defined in the
8330 @cindex history number
8331 The values printed are given @dfn{history numbers} by which you can
8332 refer to them. These are successive integers starting with one.
8333 @code{print} shows you the history number assigned to a value by
8334 printing @samp{$@var{num} = } before the value; here @var{num} is the
8337 To refer to any previous value, use @samp{$} followed by the value's
8338 history number. The way @code{print} labels its output is designed to
8339 remind you of this. Just @code{$} refers to the most recent value in
8340 the history, and @code{$$} refers to the value before that.
8341 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8342 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8343 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8345 For example, suppose you have just printed a pointer to a structure and
8346 want to see the contents of the structure. It suffices to type
8352 If you have a chain of structures where the component @code{next} points
8353 to the next one, you can print the contents of the next one with this:
8360 You can print successive links in the chain by repeating this
8361 command---which you can do by just typing @key{RET}.
8363 Note that the history records values, not expressions. If the value of
8364 @code{x} is 4 and you type these commands:
8372 then the value recorded in the value history by the @code{print} command
8373 remains 4 even though the value of @code{x} has changed.
8378 Print the last ten values in the value history, with their item numbers.
8379 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8380 values} does not change the history.
8382 @item show values @var{n}
8383 Print ten history values centered on history item number @var{n}.
8386 Print ten history values just after the values last printed. If no more
8387 values are available, @code{show values +} produces no display.
8390 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8391 same effect as @samp{show values +}.
8393 @node Convenience Vars
8394 @section Convenience Variables
8396 @cindex convenience variables
8397 @cindex user-defined variables
8398 @value{GDBN} provides @dfn{convenience variables} that you can use within
8399 @value{GDBN} to hold on to a value and refer to it later. These variables
8400 exist entirely within @value{GDBN}; they are not part of your program, and
8401 setting a convenience variable has no direct effect on further execution
8402 of your program. That is why you can use them freely.
8404 Convenience variables are prefixed with @samp{$}. Any name preceded by
8405 @samp{$} can be used for a convenience variable, unless it is one of
8406 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8407 (Value history references, in contrast, are @emph{numbers} preceded
8408 by @samp{$}. @xref{Value History, ,Value History}.)
8410 You can save a value in a convenience variable with an assignment
8411 expression, just as you would set a variable in your program.
8415 set $foo = *object_ptr
8419 would save in @code{$foo} the value contained in the object pointed to by
8422 Using a convenience variable for the first time creates it, but its
8423 value is @code{void} until you assign a new value. You can alter the
8424 value with another assignment at any time.
8426 Convenience variables have no fixed types. You can assign a convenience
8427 variable any type of value, including structures and arrays, even if
8428 that variable already has a value of a different type. The convenience
8429 variable, when used as an expression, has the type of its current value.
8432 @kindex show convenience
8433 @cindex show all user variables
8434 @item show convenience
8435 Print a list of convenience variables used so far, and their values.
8436 Abbreviated @code{show conv}.
8438 @kindex init-if-undefined
8439 @cindex convenience variables, initializing
8440 @item init-if-undefined $@var{variable} = @var{expression}
8441 Set a convenience variable if it has not already been set. This is useful
8442 for user-defined commands that keep some state. It is similar, in concept,
8443 to using local static variables with initializers in C (except that
8444 convenience variables are global). It can also be used to allow users to
8445 override default values used in a command script.
8447 If the variable is already defined then the expression is not evaluated so
8448 any side-effects do not occur.
8451 One of the ways to use a convenience variable is as a counter to be
8452 incremented or a pointer to be advanced. For example, to print
8453 a field from successive elements of an array of structures:
8457 print bar[$i++]->contents
8461 Repeat that command by typing @key{RET}.
8463 Some convenience variables are created automatically by @value{GDBN} and given
8464 values likely to be useful.
8467 @vindex $_@r{, convenience variable}
8469 The variable @code{$_} is automatically set by the @code{x} command to
8470 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8471 commands which provide a default address for @code{x} to examine also
8472 set @code{$_} to that address; these commands include @code{info line}
8473 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8474 except when set by the @code{x} command, in which case it is a pointer
8475 to the type of @code{$__}.
8477 @vindex $__@r{, convenience variable}
8479 The variable @code{$__} is automatically set by the @code{x} command
8480 to the value found in the last address examined. Its type is chosen
8481 to match the format in which the data was printed.
8484 @vindex $_exitcode@r{, convenience variable}
8485 The variable @code{$_exitcode} is automatically set to the exit code when
8486 the program being debugged terminates.
8489 @vindex $_sdata@r{, inspect, convenience variable}
8490 The variable @code{$_sdata} contains extra collected static tracepoint
8491 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8492 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8493 if extra static tracepoint data has not been collected.
8496 @vindex $_siginfo@r{, convenience variable}
8497 The variable @code{$_siginfo} contains extra signal information
8498 (@pxref{extra signal information}). Note that @code{$_siginfo}
8499 could be empty, if the application has not yet received any signals.
8500 For example, it will be empty before you execute the @code{run} command.
8503 @vindex $_tlb@r{, convenience variable}
8504 The variable @code{$_tlb} is automatically set when debugging
8505 applications running on MS-Windows in native mode or connected to
8506 gdbserver that supports the @code{qGetTIBAddr} request.
8507 @xref{General Query Packets}.
8508 This variable contains the address of the thread information block.
8512 On HP-UX systems, if you refer to a function or variable name that
8513 begins with a dollar sign, @value{GDBN} searches for a user or system
8514 name first, before it searches for a convenience variable.
8516 @cindex convenience functions
8517 @value{GDBN} also supplies some @dfn{convenience functions}. These
8518 have a syntax similar to convenience variables. A convenience
8519 function can be used in an expression just like an ordinary function;
8520 however, a convenience function is implemented internally to
8525 @kindex help function
8526 @cindex show all convenience functions
8527 Print a list of all convenience functions.
8534 You can refer to machine register contents, in expressions, as variables
8535 with names starting with @samp{$}. The names of registers are different
8536 for each machine; use @code{info registers} to see the names used on
8540 @kindex info registers
8541 @item info registers
8542 Print the names and values of all registers except floating-point
8543 and vector registers (in the selected stack frame).
8545 @kindex info all-registers
8546 @cindex floating point registers
8547 @item info all-registers
8548 Print the names and values of all registers, including floating-point
8549 and vector registers (in the selected stack frame).
8551 @item info registers @var{regname} @dots{}
8552 Print the @dfn{relativized} value of each specified register @var{regname}.
8553 As discussed in detail below, register values are normally relative to
8554 the selected stack frame. @var{regname} may be any register name valid on
8555 the machine you are using, with or without the initial @samp{$}.
8558 @cindex stack pointer register
8559 @cindex program counter register
8560 @cindex process status register
8561 @cindex frame pointer register
8562 @cindex standard registers
8563 @value{GDBN} has four ``standard'' register names that are available (in
8564 expressions) on most machines---whenever they do not conflict with an
8565 architecture's canonical mnemonics for registers. The register names
8566 @code{$pc} and @code{$sp} are used for the program counter register and
8567 the stack pointer. @code{$fp} is used for a register that contains a
8568 pointer to the current stack frame, and @code{$ps} is used for a
8569 register that contains the processor status. For example,
8570 you could print the program counter in hex with
8577 or print the instruction to be executed next with
8584 or add four to the stack pointer@footnote{This is a way of removing
8585 one word from the stack, on machines where stacks grow downward in
8586 memory (most machines, nowadays). This assumes that the innermost
8587 stack frame is selected; setting @code{$sp} is not allowed when other
8588 stack frames are selected. To pop entire frames off the stack,
8589 regardless of machine architecture, use @code{return};
8590 see @ref{Returning, ,Returning from a Function}.} with
8596 Whenever possible, these four standard register names are available on
8597 your machine even though the machine has different canonical mnemonics,
8598 so long as there is no conflict. The @code{info registers} command
8599 shows the canonical names. For example, on the SPARC, @code{info
8600 registers} displays the processor status register as @code{$psr} but you
8601 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8602 is an alias for the @sc{eflags} register.
8604 @value{GDBN} always considers the contents of an ordinary register as an
8605 integer when the register is examined in this way. Some machines have
8606 special registers which can hold nothing but floating point; these
8607 registers are considered to have floating point values. There is no way
8608 to refer to the contents of an ordinary register as floating point value
8609 (although you can @emph{print} it as a floating point value with
8610 @samp{print/f $@var{regname}}).
8612 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8613 means that the data format in which the register contents are saved by
8614 the operating system is not the same one that your program normally
8615 sees. For example, the registers of the 68881 floating point
8616 coprocessor are always saved in ``extended'' (raw) format, but all C
8617 programs expect to work with ``double'' (virtual) format. In such
8618 cases, @value{GDBN} normally works with the virtual format only (the format
8619 that makes sense for your program), but the @code{info registers} command
8620 prints the data in both formats.
8622 @cindex SSE registers (x86)
8623 @cindex MMX registers (x86)
8624 Some machines have special registers whose contents can be interpreted
8625 in several different ways. For example, modern x86-based machines
8626 have SSE and MMX registers that can hold several values packed
8627 together in several different formats. @value{GDBN} refers to such
8628 registers in @code{struct} notation:
8631 (@value{GDBP}) print $xmm1
8633 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8634 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8635 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8636 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8637 v4_int32 = @{0, 20657912, 11, 13@},
8638 v2_int64 = @{88725056443645952, 55834574859@},
8639 uint128 = 0x0000000d0000000b013b36f800000000
8644 To set values of such registers, you need to tell @value{GDBN} which
8645 view of the register you wish to change, as if you were assigning
8646 value to a @code{struct} member:
8649 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8652 Normally, register values are relative to the selected stack frame
8653 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8654 value that the register would contain if all stack frames farther in
8655 were exited and their saved registers restored. In order to see the
8656 true contents of hardware registers, you must select the innermost
8657 frame (with @samp{frame 0}).
8659 However, @value{GDBN} must deduce where registers are saved, from the machine
8660 code generated by your compiler. If some registers are not saved, or if
8661 @value{GDBN} is unable to locate the saved registers, the selected stack
8662 frame makes no difference.
8664 @node Floating Point Hardware
8665 @section Floating Point Hardware
8666 @cindex floating point
8668 Depending on the configuration, @value{GDBN} may be able to give
8669 you more information about the status of the floating point hardware.
8674 Display hardware-dependent information about the floating
8675 point unit. The exact contents and layout vary depending on the
8676 floating point chip. Currently, @samp{info float} is supported on
8677 the ARM and x86 machines.
8681 @section Vector Unit
8684 Depending on the configuration, @value{GDBN} may be able to give you
8685 more information about the status of the vector unit.
8690 Display information about the vector unit. The exact contents and
8691 layout vary depending on the hardware.
8694 @node OS Information
8695 @section Operating System Auxiliary Information
8696 @cindex OS information
8698 @value{GDBN} provides interfaces to useful OS facilities that can help
8699 you debug your program.
8701 @cindex @code{ptrace} system call
8702 @cindex @code{struct user} contents
8703 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8704 machines), it interfaces with the inferior via the @code{ptrace}
8705 system call. The operating system creates a special sata structure,
8706 called @code{struct user}, for this interface. You can use the
8707 command @code{info udot} to display the contents of this data
8713 Display the contents of the @code{struct user} maintained by the OS
8714 kernel for the program being debugged. @value{GDBN} displays the
8715 contents of @code{struct user} as a list of hex numbers, similar to
8716 the @code{examine} command.
8719 @cindex auxiliary vector
8720 @cindex vector, auxiliary
8721 Some operating systems supply an @dfn{auxiliary vector} to programs at
8722 startup. This is akin to the arguments and environment that you
8723 specify for a program, but contains a system-dependent variety of
8724 binary values that tell system libraries important details about the
8725 hardware, operating system, and process. Each value's purpose is
8726 identified by an integer tag; the meanings are well-known but system-specific.
8727 Depending on the configuration and operating system facilities,
8728 @value{GDBN} may be able to show you this information. For remote
8729 targets, this functionality may further depend on the remote stub's
8730 support of the @samp{qXfer:auxv:read} packet, see
8731 @ref{qXfer auxiliary vector read}.
8736 Display the auxiliary vector of the inferior, which can be either a
8737 live process or a core dump file. @value{GDBN} prints each tag value
8738 numerically, and also shows names and text descriptions for recognized
8739 tags. Some values in the vector are numbers, some bit masks, and some
8740 pointers to strings or other data. @value{GDBN} displays each value in the
8741 most appropriate form for a recognized tag, and in hexadecimal for
8742 an unrecognized tag.
8745 On some targets, @value{GDBN} can access operating-system-specific information
8746 and display it to user, without interpretation. For remote targets,
8747 this functionality depends on the remote stub's support of the
8748 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8753 List the types of OS information available for the target. If the
8754 target does not return a list of possible types, this command will
8757 @kindex info os processes
8758 @item info os processes
8759 Display the list of processes on the target. For each process,
8760 @value{GDBN} prints the process identifier, the name of the user, and
8761 the command corresponding to the process.
8764 @node Memory Region Attributes
8765 @section Memory Region Attributes
8766 @cindex memory region attributes
8768 @dfn{Memory region attributes} allow you to describe special handling
8769 required by regions of your target's memory. @value{GDBN} uses
8770 attributes to determine whether to allow certain types of memory
8771 accesses; whether to use specific width accesses; and whether to cache
8772 target memory. By default the description of memory regions is
8773 fetched from the target (if the current target supports this), but the
8774 user can override the fetched regions.
8776 Defined memory regions can be individually enabled and disabled. When a
8777 memory region is disabled, @value{GDBN} uses the default attributes when
8778 accessing memory in that region. Similarly, if no memory regions have
8779 been defined, @value{GDBN} uses the default attributes when accessing
8782 When a memory region is defined, it is given a number to identify it;
8783 to enable, disable, or remove a memory region, you specify that number.
8787 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8788 Define a memory region bounded by @var{lower} and @var{upper} with
8789 attributes @var{attributes}@dots{}, and add it to the list of regions
8790 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8791 case: it is treated as the target's maximum memory address.
8792 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8795 Discard any user changes to the memory regions and use target-supplied
8796 regions, if available, or no regions if the target does not support.
8799 @item delete mem @var{nums}@dots{}
8800 Remove memory regions @var{nums}@dots{} from the list of regions
8801 monitored by @value{GDBN}.
8804 @item disable mem @var{nums}@dots{}
8805 Disable monitoring of memory regions @var{nums}@dots{}.
8806 A disabled memory region is not forgotten.
8807 It may be enabled again later.
8810 @item enable mem @var{nums}@dots{}
8811 Enable monitoring of memory regions @var{nums}@dots{}.
8815 Print a table of all defined memory regions, with the following columns
8819 @item Memory Region Number
8820 @item Enabled or Disabled.
8821 Enabled memory regions are marked with @samp{y}.
8822 Disabled memory regions are marked with @samp{n}.
8825 The address defining the inclusive lower bound of the memory region.
8828 The address defining the exclusive upper bound of the memory region.
8831 The list of attributes set for this memory region.
8836 @subsection Attributes
8838 @subsubsection Memory Access Mode
8839 The access mode attributes set whether @value{GDBN} may make read or
8840 write accesses to a memory region.
8842 While these attributes prevent @value{GDBN} from performing invalid
8843 memory accesses, they do nothing to prevent the target system, I/O DMA,
8844 etc.@: from accessing memory.
8848 Memory is read only.
8850 Memory is write only.
8852 Memory is read/write. This is the default.
8855 @subsubsection Memory Access Size
8856 The access size attribute tells @value{GDBN} to use specific sized
8857 accesses in the memory region. Often memory mapped device registers
8858 require specific sized accesses. If no access size attribute is
8859 specified, @value{GDBN} may use accesses of any size.
8863 Use 8 bit memory accesses.
8865 Use 16 bit memory accesses.
8867 Use 32 bit memory accesses.
8869 Use 64 bit memory accesses.
8872 @c @subsubsection Hardware/Software Breakpoints
8873 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8874 @c will use hardware or software breakpoints for the internal breakpoints
8875 @c used by the step, next, finish, until, etc. commands.
8879 @c Always use hardware breakpoints
8880 @c @item swbreak (default)
8883 @subsubsection Data Cache
8884 The data cache attributes set whether @value{GDBN} will cache target
8885 memory. While this generally improves performance by reducing debug
8886 protocol overhead, it can lead to incorrect results because @value{GDBN}
8887 does not know about volatile variables or memory mapped device
8892 Enable @value{GDBN} to cache target memory.
8894 Disable @value{GDBN} from caching target memory. This is the default.
8897 @subsection Memory Access Checking
8898 @value{GDBN} can be instructed to refuse accesses to memory that is
8899 not explicitly described. This can be useful if accessing such
8900 regions has undesired effects for a specific target, or to provide
8901 better error checking. The following commands control this behaviour.
8904 @kindex set mem inaccessible-by-default
8905 @item set mem inaccessible-by-default [on|off]
8906 If @code{on} is specified, make @value{GDBN} treat memory not
8907 explicitly described by the memory ranges as non-existent and refuse accesses
8908 to such memory. The checks are only performed if there's at least one
8909 memory range defined. If @code{off} is specified, make @value{GDBN}
8910 treat the memory not explicitly described by the memory ranges as RAM.
8911 The default value is @code{on}.
8912 @kindex show mem inaccessible-by-default
8913 @item show mem inaccessible-by-default
8914 Show the current handling of accesses to unknown memory.
8918 @c @subsubsection Memory Write Verification
8919 @c The memory write verification attributes set whether @value{GDBN}
8920 @c will re-reads data after each write to verify the write was successful.
8924 @c @item noverify (default)
8927 @node Dump/Restore Files
8928 @section Copy Between Memory and a File
8929 @cindex dump/restore files
8930 @cindex append data to a file
8931 @cindex dump data to a file
8932 @cindex restore data from a file
8934 You can use the commands @code{dump}, @code{append}, and
8935 @code{restore} to copy data between target memory and a file. The
8936 @code{dump} and @code{append} commands write data to a file, and the
8937 @code{restore} command reads data from a file back into the inferior's
8938 memory. Files may be in binary, Motorola S-record, Intel hex, or
8939 Tektronix Hex format; however, @value{GDBN} can only append to binary
8945 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8946 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8947 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8948 or the value of @var{expr}, to @var{filename} in the given format.
8950 The @var{format} parameter may be any one of:
8957 Motorola S-record format.
8959 Tektronix Hex format.
8962 @value{GDBN} uses the same definitions of these formats as the
8963 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8964 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8968 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8969 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8970 Append the contents of memory from @var{start_addr} to @var{end_addr},
8971 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8972 (@value{GDBN} can only append data to files in raw binary form.)
8975 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8976 Restore the contents of file @var{filename} into memory. The
8977 @code{restore} command can automatically recognize any known @sc{bfd}
8978 file format, except for raw binary. To restore a raw binary file you
8979 must specify the optional keyword @code{binary} after the filename.
8981 If @var{bias} is non-zero, its value will be added to the addresses
8982 contained in the file. Binary files always start at address zero, so
8983 they will be restored at address @var{bias}. Other bfd files have
8984 a built-in location; they will be restored at offset @var{bias}
8987 If @var{start} and/or @var{end} are non-zero, then only data between
8988 file offset @var{start} and file offset @var{end} will be restored.
8989 These offsets are relative to the addresses in the file, before
8990 the @var{bias} argument is applied.
8994 @node Core File Generation
8995 @section How to Produce a Core File from Your Program
8996 @cindex dump core from inferior
8998 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8999 image of a running process and its process status (register values
9000 etc.). Its primary use is post-mortem debugging of a program that
9001 crashed while it ran outside a debugger. A program that crashes
9002 automatically produces a core file, unless this feature is disabled by
9003 the user. @xref{Files}, for information on invoking @value{GDBN} in
9004 the post-mortem debugging mode.
9006 Occasionally, you may wish to produce a core file of the program you
9007 are debugging in order to preserve a snapshot of its state.
9008 @value{GDBN} has a special command for that.
9012 @kindex generate-core-file
9013 @item generate-core-file [@var{file}]
9014 @itemx gcore [@var{file}]
9015 Produce a core dump of the inferior process. The optional argument
9016 @var{file} specifies the file name where to put the core dump. If not
9017 specified, the file name defaults to @file{core.@var{pid}}, where
9018 @var{pid} is the inferior process ID.
9020 Note that this command is implemented only for some systems (as of
9021 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9024 @node Character Sets
9025 @section Character Sets
9026 @cindex character sets
9028 @cindex translating between character sets
9029 @cindex host character set
9030 @cindex target character set
9032 If the program you are debugging uses a different character set to
9033 represent characters and strings than the one @value{GDBN} uses itself,
9034 @value{GDBN} can automatically translate between the character sets for
9035 you. The character set @value{GDBN} uses we call the @dfn{host
9036 character set}; the one the inferior program uses we call the
9037 @dfn{target character set}.
9039 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9040 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9041 remote protocol (@pxref{Remote Debugging}) to debug a program
9042 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9043 then the host character set is Latin-1, and the target character set is
9044 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9045 target-charset EBCDIC-US}, then @value{GDBN} translates between
9046 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9047 character and string literals in expressions.
9049 @value{GDBN} has no way to automatically recognize which character set
9050 the inferior program uses; you must tell it, using the @code{set
9051 target-charset} command, described below.
9053 Here are the commands for controlling @value{GDBN}'s character set
9057 @item set target-charset @var{charset}
9058 @kindex set target-charset
9059 Set the current target character set to @var{charset}. To display the
9060 list of supported target character sets, type
9061 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9063 @item set host-charset @var{charset}
9064 @kindex set host-charset
9065 Set the current host character set to @var{charset}.
9067 By default, @value{GDBN} uses a host character set appropriate to the
9068 system it is running on; you can override that default using the
9069 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9070 automatically determine the appropriate host character set. In this
9071 case, @value{GDBN} uses @samp{UTF-8}.
9073 @value{GDBN} can only use certain character sets as its host character
9074 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9075 @value{GDBN} will list the host character sets it supports.
9077 @item set charset @var{charset}
9079 Set the current host and target character sets to @var{charset}. As
9080 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9081 @value{GDBN} will list the names of the character sets that can be used
9082 for both host and target.
9085 @kindex show charset
9086 Show the names of the current host and target character sets.
9088 @item show host-charset
9089 @kindex show host-charset
9090 Show the name of the current host character set.
9092 @item show target-charset
9093 @kindex show target-charset
9094 Show the name of the current target character set.
9096 @item set target-wide-charset @var{charset}
9097 @kindex set target-wide-charset
9098 Set the current target's wide character set to @var{charset}. This is
9099 the character set used by the target's @code{wchar_t} type. To
9100 display the list of supported wide character sets, type
9101 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9103 @item show target-wide-charset
9104 @kindex show target-wide-charset
9105 Show the name of the current target's wide character set.
9108 Here is an example of @value{GDBN}'s character set support in action.
9109 Assume that the following source code has been placed in the file
9110 @file{charset-test.c}:
9116 = @{72, 101, 108, 108, 111, 44, 32, 119,
9117 111, 114, 108, 100, 33, 10, 0@};
9118 char ibm1047_hello[]
9119 = @{200, 133, 147, 147, 150, 107, 64, 166,
9120 150, 153, 147, 132, 90, 37, 0@};
9124 printf ("Hello, world!\n");
9128 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9129 containing the string @samp{Hello, world!} followed by a newline,
9130 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9132 We compile the program, and invoke the debugger on it:
9135 $ gcc -g charset-test.c -o charset-test
9136 $ gdb -nw charset-test
9137 GNU gdb 2001-12-19-cvs
9138 Copyright 2001 Free Software Foundation, Inc.
9143 We can use the @code{show charset} command to see what character sets
9144 @value{GDBN} is currently using to interpret and display characters and
9148 (@value{GDBP}) show charset
9149 The current host and target character set is `ISO-8859-1'.
9153 For the sake of printing this manual, let's use @sc{ascii} as our
9154 initial character set:
9156 (@value{GDBP}) set charset ASCII
9157 (@value{GDBP}) show charset
9158 The current host and target character set is `ASCII'.
9162 Let's assume that @sc{ascii} is indeed the correct character set for our
9163 host system --- in other words, let's assume that if @value{GDBN} prints
9164 characters using the @sc{ascii} character set, our terminal will display
9165 them properly. Since our current target character set is also
9166 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9169 (@value{GDBP}) print ascii_hello
9170 $1 = 0x401698 "Hello, world!\n"
9171 (@value{GDBP}) print ascii_hello[0]
9176 @value{GDBN} uses the target character set for character and string
9177 literals you use in expressions:
9180 (@value{GDBP}) print '+'
9185 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9188 @value{GDBN} relies on the user to tell it which character set the
9189 target program uses. If we print @code{ibm1047_hello} while our target
9190 character set is still @sc{ascii}, we get jibberish:
9193 (@value{GDBP}) print ibm1047_hello
9194 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9195 (@value{GDBP}) print ibm1047_hello[0]
9200 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9201 @value{GDBN} tells us the character sets it supports:
9204 (@value{GDBP}) set target-charset
9205 ASCII EBCDIC-US IBM1047 ISO-8859-1
9206 (@value{GDBP}) set target-charset
9209 We can select @sc{ibm1047} as our target character set, and examine the
9210 program's strings again. Now the @sc{ascii} string is wrong, but
9211 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9212 target character set, @sc{ibm1047}, to the host character set,
9213 @sc{ascii}, and they display correctly:
9216 (@value{GDBP}) set target-charset IBM1047
9217 (@value{GDBP}) show charset
9218 The current host character set is `ASCII'.
9219 The current target character set is `IBM1047'.
9220 (@value{GDBP}) print ascii_hello
9221 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9222 (@value{GDBP}) print ascii_hello[0]
9224 (@value{GDBP}) print ibm1047_hello
9225 $8 = 0x4016a8 "Hello, world!\n"
9226 (@value{GDBP}) print ibm1047_hello[0]
9231 As above, @value{GDBN} uses the target character set for character and
9232 string literals you use in expressions:
9235 (@value{GDBP}) print '+'
9240 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9243 @node Caching Remote Data
9244 @section Caching Data of Remote Targets
9245 @cindex caching data of remote targets
9247 @value{GDBN} caches data exchanged between the debugger and a
9248 remote target (@pxref{Remote Debugging}). Such caching generally improves
9249 performance, because it reduces the overhead of the remote protocol by
9250 bundling memory reads and writes into large chunks. Unfortunately, simply
9251 caching everything would lead to incorrect results, since @value{GDBN}
9252 does not necessarily know anything about volatile values, memory-mapped I/O
9253 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9254 memory can be changed @emph{while} a gdb command is executing.
9255 Therefore, by default, @value{GDBN} only caches data
9256 known to be on the stack@footnote{In non-stop mode, it is moderately
9257 rare for a running thread to modify the stack of a stopped thread
9258 in a way that would interfere with a backtrace, and caching of
9259 stack reads provides a significant speed up of remote backtraces.}.
9260 Other regions of memory can be explicitly marked as
9261 cacheable; see @pxref{Memory Region Attributes}.
9264 @kindex set remotecache
9265 @item set remotecache on
9266 @itemx set remotecache off
9267 This option no longer does anything; it exists for compatibility
9270 @kindex show remotecache
9271 @item show remotecache
9272 Show the current state of the obsolete remotecache flag.
9274 @kindex set stack-cache
9275 @item set stack-cache on
9276 @itemx set stack-cache off
9277 Enable or disable caching of stack accesses. When @code{ON}, use
9278 caching. By default, this option is @code{ON}.
9280 @kindex show stack-cache
9281 @item show stack-cache
9282 Show the current state of data caching for memory accesses.
9285 @item info dcache @r{[}line@r{]}
9286 Print the information about the data cache performance. The
9287 information displayed includes the dcache width and depth, and for
9288 each cache line, its number, address, and how many times it was
9289 referenced. This command is useful for debugging the data cache
9292 If a line number is specified, the contents of that line will be
9296 @node Searching Memory
9297 @section Search Memory
9298 @cindex searching memory
9300 Memory can be searched for a particular sequence of bytes with the
9301 @code{find} command.
9305 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9306 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9307 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9308 etc. The search begins at address @var{start_addr} and continues for either
9309 @var{len} bytes or through to @var{end_addr} inclusive.
9312 @var{s} and @var{n} are optional parameters.
9313 They may be specified in either order, apart or together.
9316 @item @var{s}, search query size
9317 The size of each search query value.
9323 halfwords (two bytes)
9327 giant words (eight bytes)
9330 All values are interpreted in the current language.
9331 This means, for example, that if the current source language is C/C@t{++}
9332 then searching for the string ``hello'' includes the trailing '\0'.
9334 If the value size is not specified, it is taken from the
9335 value's type in the current language.
9336 This is useful when one wants to specify the search
9337 pattern as a mixture of types.
9338 Note that this means, for example, that in the case of C-like languages
9339 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9340 which is typically four bytes.
9342 @item @var{n}, maximum number of finds
9343 The maximum number of matches to print. The default is to print all finds.
9346 You can use strings as search values. Quote them with double-quotes
9348 The string value is copied into the search pattern byte by byte,
9349 regardless of the endianness of the target and the size specification.
9351 The address of each match found is printed as well as a count of the
9352 number of matches found.
9354 The address of the last value found is stored in convenience variable
9356 A count of the number of matches is stored in @samp{$numfound}.
9358 For example, if stopped at the @code{printf} in this function:
9364 static char hello[] = "hello-hello";
9365 static struct @{ char c; short s; int i; @}
9366 __attribute__ ((packed)) mixed
9367 = @{ 'c', 0x1234, 0x87654321 @};
9368 printf ("%s\n", hello);
9373 you get during debugging:
9376 (gdb) find &hello[0], +sizeof(hello), "hello"
9377 0x804956d <hello.1620+6>
9379 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9380 0x8049567 <hello.1620>
9381 0x804956d <hello.1620+6>
9383 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9384 0x8049567 <hello.1620>
9386 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9387 0x8049560 <mixed.1625>
9389 (gdb) print $numfound
9392 $2 = (void *) 0x8049560
9395 @node Optimized Code
9396 @chapter Debugging Optimized Code
9397 @cindex optimized code, debugging
9398 @cindex debugging optimized code
9400 Almost all compilers support optimization. With optimization
9401 disabled, the compiler generates assembly code that corresponds
9402 directly to your source code, in a simplistic way. As the compiler
9403 applies more powerful optimizations, the generated assembly code
9404 diverges from your original source code. With help from debugging
9405 information generated by the compiler, @value{GDBN} can map from
9406 the running program back to constructs from your original source.
9408 @value{GDBN} is more accurate with optimization disabled. If you
9409 can recompile without optimization, it is easier to follow the
9410 progress of your program during debugging. But, there are many cases
9411 where you may need to debug an optimized version.
9413 When you debug a program compiled with @samp{-g -O}, remember that the
9414 optimizer has rearranged your code; the debugger shows you what is
9415 really there. Do not be too surprised when the execution path does not
9416 exactly match your source file! An extreme example: if you define a
9417 variable, but never use it, @value{GDBN} never sees that
9418 variable---because the compiler optimizes it out of existence.
9420 Some things do not work as well with @samp{-g -O} as with just
9421 @samp{-g}, particularly on machines with instruction scheduling. If in
9422 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9423 please report it to us as a bug (including a test case!).
9424 @xref{Variables}, for more information about debugging optimized code.
9427 * Inline Functions:: How @value{GDBN} presents inlining
9430 @node Inline Functions
9431 @section Inline Functions
9432 @cindex inline functions, debugging
9434 @dfn{Inlining} is an optimization that inserts a copy of the function
9435 body directly at each call site, instead of jumping to a shared
9436 routine. @value{GDBN} displays inlined functions just like
9437 non-inlined functions. They appear in backtraces. You can view their
9438 arguments and local variables, step into them with @code{step}, skip
9439 them with @code{next}, and escape from them with @code{finish}.
9440 You can check whether a function was inlined by using the
9441 @code{info frame} command.
9443 For @value{GDBN} to support inlined functions, the compiler must
9444 record information about inlining in the debug information ---
9445 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9446 other compilers do also. @value{GDBN} only supports inlined functions
9447 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9448 do not emit two required attributes (@samp{DW_AT_call_file} and
9449 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9450 function calls with earlier versions of @value{NGCC}. It instead
9451 displays the arguments and local variables of inlined functions as
9452 local variables in the caller.
9454 The body of an inlined function is directly included at its call site;
9455 unlike a non-inlined function, there are no instructions devoted to
9456 the call. @value{GDBN} still pretends that the call site and the
9457 start of the inlined function are different instructions. Stepping to
9458 the call site shows the call site, and then stepping again shows
9459 the first line of the inlined function, even though no additional
9460 instructions are executed.
9462 This makes source-level debugging much clearer; you can see both the
9463 context of the call and then the effect of the call. Only stepping by
9464 a single instruction using @code{stepi} or @code{nexti} does not do
9465 this; single instruction steps always show the inlined body.
9467 There are some ways that @value{GDBN} does not pretend that inlined
9468 function calls are the same as normal calls:
9472 You cannot set breakpoints on inlined functions. @value{GDBN}
9473 either reports that there is no symbol with that name, or else sets the
9474 breakpoint only on non-inlined copies of the function. This limitation
9475 will be removed in a future version of @value{GDBN}; until then,
9476 set a breakpoint by line number on the first line of the inlined
9480 Setting breakpoints at the call site of an inlined function may not
9481 work, because the call site does not contain any code. @value{GDBN}
9482 may incorrectly move the breakpoint to the next line of the enclosing
9483 function, after the call. This limitation will be removed in a future
9484 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9485 or inside the inlined function instead.
9488 @value{GDBN} cannot locate the return value of inlined calls after
9489 using the @code{finish} command. This is a limitation of compiler-generated
9490 debugging information; after @code{finish}, you can step to the next line
9491 and print a variable where your program stored the return value.
9497 @chapter C Preprocessor Macros
9499 Some languages, such as C and C@t{++}, provide a way to define and invoke
9500 ``preprocessor macros'' which expand into strings of tokens.
9501 @value{GDBN} can evaluate expressions containing macro invocations, show
9502 the result of macro expansion, and show a macro's definition, including
9503 where it was defined.
9505 You may need to compile your program specially to provide @value{GDBN}
9506 with information about preprocessor macros. Most compilers do not
9507 include macros in their debugging information, even when you compile
9508 with the @option{-g} flag. @xref{Compilation}.
9510 A program may define a macro at one point, remove that definition later,
9511 and then provide a different definition after that. Thus, at different
9512 points in the program, a macro may have different definitions, or have
9513 no definition at all. If there is a current stack frame, @value{GDBN}
9514 uses the macros in scope at that frame's source code line. Otherwise,
9515 @value{GDBN} uses the macros in scope at the current listing location;
9518 Whenever @value{GDBN} evaluates an expression, it always expands any
9519 macro invocations present in the expression. @value{GDBN} also provides
9520 the following commands for working with macros explicitly.
9524 @kindex macro expand
9525 @cindex macro expansion, showing the results of preprocessor
9526 @cindex preprocessor macro expansion, showing the results of
9527 @cindex expanding preprocessor macros
9528 @item macro expand @var{expression}
9529 @itemx macro exp @var{expression}
9530 Show the results of expanding all preprocessor macro invocations in
9531 @var{expression}. Since @value{GDBN} simply expands macros, but does
9532 not parse the result, @var{expression} need not be a valid expression;
9533 it can be any string of tokens.
9536 @item macro expand-once @var{expression}
9537 @itemx macro exp1 @var{expression}
9538 @cindex expand macro once
9539 @i{(This command is not yet implemented.)} Show the results of
9540 expanding those preprocessor macro invocations that appear explicitly in
9541 @var{expression}. Macro invocations appearing in that expansion are
9542 left unchanged. This command allows you to see the effect of a
9543 particular macro more clearly, without being confused by further
9544 expansions. Since @value{GDBN} simply expands macros, but does not
9545 parse the result, @var{expression} need not be a valid expression; it
9546 can be any string of tokens.
9549 @cindex macro definition, showing
9550 @cindex definition, showing a macro's
9551 @item info macro @var{macro}
9552 Show the definition of the macro named @var{macro}, and describe the
9553 source location or compiler command-line where that definition was established.
9555 @kindex macro define
9556 @cindex user-defined macros
9557 @cindex defining macros interactively
9558 @cindex macros, user-defined
9559 @item macro define @var{macro} @var{replacement-list}
9560 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9561 Introduce a definition for a preprocessor macro named @var{macro},
9562 invocations of which are replaced by the tokens given in
9563 @var{replacement-list}. The first form of this command defines an
9564 ``object-like'' macro, which takes no arguments; the second form
9565 defines a ``function-like'' macro, which takes the arguments given in
9568 A definition introduced by this command is in scope in every
9569 expression evaluated in @value{GDBN}, until it is removed with the
9570 @code{macro undef} command, described below. The definition overrides
9571 all definitions for @var{macro} present in the program being debugged,
9572 as well as any previous user-supplied definition.
9575 @item macro undef @var{macro}
9576 Remove any user-supplied definition for the macro named @var{macro}.
9577 This command only affects definitions provided with the @code{macro
9578 define} command, described above; it cannot remove definitions present
9579 in the program being debugged.
9583 List all the macros defined using the @code{macro define} command.
9586 @cindex macros, example of debugging with
9587 Here is a transcript showing the above commands in action. First, we
9588 show our source files:
9596 #define ADD(x) (M + x)
9601 printf ("Hello, world!\n");
9603 printf ("We're so creative.\n");
9605 printf ("Goodbye, world!\n");
9612 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9613 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9614 compiler includes information about preprocessor macros in the debugging
9618 $ gcc -gdwarf-2 -g3 sample.c -o sample
9622 Now, we start @value{GDBN} on our sample program:
9626 GNU gdb 2002-05-06-cvs
9627 Copyright 2002 Free Software Foundation, Inc.
9628 GDB is free software, @dots{}
9632 We can expand macros and examine their definitions, even when the
9633 program is not running. @value{GDBN} uses the current listing position
9634 to decide which macro definitions are in scope:
9637 (@value{GDBP}) list main
9640 5 #define ADD(x) (M + x)
9645 10 printf ("Hello, world!\n");
9647 12 printf ("We're so creative.\n");
9648 (@value{GDBP}) info macro ADD
9649 Defined at /home/jimb/gdb/macros/play/sample.c:5
9650 #define ADD(x) (M + x)
9651 (@value{GDBP}) info macro Q
9652 Defined at /home/jimb/gdb/macros/play/sample.h:1
9653 included at /home/jimb/gdb/macros/play/sample.c:2
9655 (@value{GDBP}) macro expand ADD(1)
9656 expands to: (42 + 1)
9657 (@value{GDBP}) macro expand-once ADD(1)
9658 expands to: once (M + 1)
9662 In the example above, note that @code{macro expand-once} expands only
9663 the macro invocation explicit in the original text --- the invocation of
9664 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9665 which was introduced by @code{ADD}.
9667 Once the program is running, @value{GDBN} uses the macro definitions in
9668 force at the source line of the current stack frame:
9671 (@value{GDBP}) break main
9672 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9674 Starting program: /home/jimb/gdb/macros/play/sample
9676 Breakpoint 1, main () at sample.c:10
9677 10 printf ("Hello, world!\n");
9681 At line 10, the definition of the macro @code{N} at line 9 is in force:
9684 (@value{GDBP}) info macro N
9685 Defined at /home/jimb/gdb/macros/play/sample.c:9
9687 (@value{GDBP}) macro expand N Q M
9689 (@value{GDBP}) print N Q M
9694 As we step over directives that remove @code{N}'s definition, and then
9695 give it a new definition, @value{GDBN} finds the definition (or lack
9696 thereof) in force at each point:
9701 12 printf ("We're so creative.\n");
9702 (@value{GDBP}) info macro N
9703 The symbol `N' has no definition as a C/C++ preprocessor macro
9704 at /home/jimb/gdb/macros/play/sample.c:12
9707 14 printf ("Goodbye, world!\n");
9708 (@value{GDBP}) info macro N
9709 Defined at /home/jimb/gdb/macros/play/sample.c:13
9711 (@value{GDBP}) macro expand N Q M
9712 expands to: 1729 < 42
9713 (@value{GDBP}) print N Q M
9718 In addition to source files, macros can be defined on the compilation command
9719 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9720 such a way, @value{GDBN} displays the location of their definition as line zero
9721 of the source file submitted to the compiler.
9724 (@value{GDBP}) info macro __STDC__
9725 Defined at /home/jimb/gdb/macros/play/sample.c:0
9732 @chapter Tracepoints
9733 @c This chapter is based on the documentation written by Michael
9734 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9737 In some applications, it is not feasible for the debugger to interrupt
9738 the program's execution long enough for the developer to learn
9739 anything helpful about its behavior. If the program's correctness
9740 depends on its real-time behavior, delays introduced by a debugger
9741 might cause the program to change its behavior drastically, or perhaps
9742 fail, even when the code itself is correct. It is useful to be able
9743 to observe the program's behavior without interrupting it.
9745 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9746 specify locations in the program, called @dfn{tracepoints}, and
9747 arbitrary expressions to evaluate when those tracepoints are reached.
9748 Later, using the @code{tfind} command, you can examine the values
9749 those expressions had when the program hit the tracepoints. The
9750 expressions may also denote objects in memory---structures or arrays,
9751 for example---whose values @value{GDBN} should record; while visiting
9752 a particular tracepoint, you may inspect those objects as if they were
9753 in memory at that moment. However, because @value{GDBN} records these
9754 values without interacting with you, it can do so quickly and
9755 unobtrusively, hopefully not disturbing the program's behavior.
9757 The tracepoint facility is currently available only for remote
9758 targets. @xref{Targets}. In addition, your remote target must know
9759 how to collect trace data. This functionality is implemented in the
9760 remote stub; however, none of the stubs distributed with @value{GDBN}
9761 support tracepoints as of this writing. The format of the remote
9762 packets used to implement tracepoints are described in @ref{Tracepoint
9765 It is also possible to get trace data from a file, in a manner reminiscent
9766 of corefiles; you specify the filename, and use @code{tfind} to search
9767 through the file. @xref{Trace Files}, for more details.
9769 This chapter describes the tracepoint commands and features.
9773 * Analyze Collected Data::
9774 * Tracepoint Variables::
9778 @node Set Tracepoints
9779 @section Commands to Set Tracepoints
9781 Before running such a @dfn{trace experiment}, an arbitrary number of
9782 tracepoints can be set. A tracepoint is actually a special type of
9783 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9784 standard breakpoint commands. For instance, as with breakpoints,
9785 tracepoint numbers are successive integers starting from one, and many
9786 of the commands associated with tracepoints take the tracepoint number
9787 as their argument, to identify which tracepoint to work on.
9789 For each tracepoint, you can specify, in advance, some arbitrary set
9790 of data that you want the target to collect in the trace buffer when
9791 it hits that tracepoint. The collected data can include registers,
9792 local variables, or global data. Later, you can use @value{GDBN}
9793 commands to examine the values these data had at the time the
9796 Tracepoints do not support every breakpoint feature. Ignore counts on
9797 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9798 commands when they are hit. Tracepoints may not be thread-specific
9801 @cindex fast tracepoints
9802 Some targets may support @dfn{fast tracepoints}, which are inserted in
9803 a different way (such as with a jump instead of a trap), that is
9804 faster but possibly restricted in where they may be installed.
9806 @cindex static tracepoints
9807 @cindex markers, static tracepoints
9808 @cindex probing markers, static tracepoints
9809 Regular and fast tracepoints are dynamic tracing facilities, meaning
9810 that they can be used to insert tracepoints at (almost) any location
9811 in the target. Some targets may also support controlling @dfn{static
9812 tracepoints} from @value{GDBN}. With static tracing, a set of
9813 instrumentation points, also known as @dfn{markers}, are embedded in
9814 the target program, and can be activated or deactivated by name or
9815 address. These are usually placed at locations which facilitate
9816 investigating what the target is actually doing. @value{GDBN}'s
9817 support for static tracing includes being able to list instrumentation
9818 points, and attach them with @value{GDBN} defined high level
9819 tracepoints that expose the whole range of convenience of
9820 @value{GDBN}'s tracepoints support. Namelly, support for collecting
9821 registers values and values of global or local (to the instrumentation
9822 point) variables; tracepoint conditions and trace state variables.
9823 The act of installing a @value{GDBN} static tracepoint on an
9824 instrumentation point, or marker, is referred to as @dfn{probing} a
9825 static tracepoint marker.
9827 @code{gdbserver} supports tracepoints on some target systems.
9828 @xref{Server,,Tracepoints support in @code{gdbserver}}.
9830 This section describes commands to set tracepoints and associated
9831 conditions and actions.
9834 * Create and Delete Tracepoints::
9835 * Enable and Disable Tracepoints::
9836 * Tracepoint Passcounts::
9837 * Tracepoint Conditions::
9838 * Trace State Variables::
9839 * Tracepoint Actions::
9840 * Listing Tracepoints::
9841 * Listing Static Tracepoint Markers::
9842 * Starting and Stopping Trace Experiments::
9843 * Tracepoint Restrictions::
9846 @node Create and Delete Tracepoints
9847 @subsection Create and Delete Tracepoints
9850 @cindex set tracepoint
9852 @item trace @var{location}
9853 The @code{trace} command is very similar to the @code{break} command.
9854 Its argument @var{location} can be a source line, a function name, or
9855 an address in the target program. @xref{Specify Location}. The
9856 @code{trace} command defines a tracepoint, which is a point in the
9857 target program where the debugger will briefly stop, collect some
9858 data, and then allow the program to continue. Setting a tracepoint or
9859 changing its actions doesn't take effect until the next @code{tstart}
9860 command, and once a trace experiment is running, further changes will
9861 not have any effect until the next trace experiment starts.
9863 Here are some examples of using the @code{trace} command:
9866 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9868 (@value{GDBP}) @b{trace +2} // 2 lines forward
9870 (@value{GDBP}) @b{trace my_function} // first source line of function
9872 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9874 (@value{GDBP}) @b{trace *0x2117c4} // an address
9878 You can abbreviate @code{trace} as @code{tr}.
9880 @item trace @var{location} if @var{cond}
9881 Set a tracepoint with condition @var{cond}; evaluate the expression
9882 @var{cond} each time the tracepoint is reached, and collect data only
9883 if the value is nonzero---that is, if @var{cond} evaluates as true.
9884 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9885 information on tracepoint conditions.
9887 @item ftrace @var{location} [ if @var{cond} ]
9888 @cindex set fast tracepoint
9889 @cindex fast tracepoints, setting
9891 The @code{ftrace} command sets a fast tracepoint. For targets that
9892 support them, fast tracepoints will use a more efficient but possibly
9893 less general technique to trigger data collection, such as a jump
9894 instruction instead of a trap, or some sort of hardware support. It
9895 may not be possible to create a fast tracepoint at the desired
9896 location, in which case the command will exit with an explanatory
9899 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9902 @item strace @var{location} [ if @var{cond} ]
9903 @cindex set static tracepoint
9904 @cindex static tracepoints, setting
9905 @cindex probe static tracepoint marker
9907 The @code{strace} command sets a static tracepoint. For targets that
9908 support it, setting a static tracepoint probes a static
9909 instrumentation point, or marker, found at @var{location}. It may not
9910 be possible to set a static tracepoint at the desired location, in
9911 which case the command will exit with an explanatory message.
9913 @value{GDBN} handles arguments to @code{strace} exactly as for
9914 @code{trace}, with the addition that the user can also specify
9915 @code{-m @var{marker}} as @var{location}. This probes the marker
9916 identified by the @var{marker} string identifier. This identifier
9917 depends on the static tracepoint backend library your program is
9918 using. You can find all the marker identifiers in the @samp{ID} field
9919 of the @code{info static-tracepoint-markers} command output.
9920 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
9921 Markers}. For example, in the following small program using the UST
9927 trace_mark(ust, bar33, "str %s", "FOOBAZ");
9932 the marker id is composed of joining the first two arguments to the
9933 @code{trace_mark} call with a slash, which translates to:
9936 (@value{GDBP}) info static-tracepoint-markers
9937 Cnt Enb ID Address What
9938 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
9944 so you may probe the marker above with:
9947 (@value{GDBP}) strace -m ust/bar33
9950 Static tracepoints accept an extra collect action --- @code{collect
9951 $_sdata}. This collects arbitrary user data passed in the probe point
9952 call to the tracing library. In the UST example above, you'll see
9953 that the third argument to @code{trace_mark} is a printf-like format
9954 string. The user data is then the result of running that formating
9955 string against the following arguments. Note that @code{info
9956 static-tracepoint-markers} command output lists that format string in
9957 the @samp{Data:} field.
9959 You can inspect this data when analyzing the trace buffer, by printing
9960 the $_sdata variable like any other variable available to
9961 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
9964 @cindex last tracepoint number
9965 @cindex recent tracepoint number
9966 @cindex tracepoint number
9967 The convenience variable @code{$tpnum} records the tracepoint number
9968 of the most recently set tracepoint.
9970 @kindex delete tracepoint
9971 @cindex tracepoint deletion
9972 @item delete tracepoint @r{[}@var{num}@r{]}
9973 Permanently delete one or more tracepoints. With no argument, the
9974 default is to delete all tracepoints. Note that the regular
9975 @code{delete} command can remove tracepoints also.
9980 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9982 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9986 You can abbreviate this command as @code{del tr}.
9989 @node Enable and Disable Tracepoints
9990 @subsection Enable and Disable Tracepoints
9992 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9995 @kindex disable tracepoint
9996 @item disable tracepoint @r{[}@var{num}@r{]}
9997 Disable tracepoint @var{num}, or all tracepoints if no argument
9998 @var{num} is given. A disabled tracepoint will have no effect during
9999 the next trace experiment, but it is not forgotten. You can re-enable
10000 a disabled tracepoint using the @code{enable tracepoint} command.
10002 @kindex enable tracepoint
10003 @item enable tracepoint @r{[}@var{num}@r{]}
10004 Enable tracepoint @var{num}, or all tracepoints. The enabled
10005 tracepoints will become effective the next time a trace experiment is
10009 @node Tracepoint Passcounts
10010 @subsection Tracepoint Passcounts
10014 @cindex tracepoint pass count
10015 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10016 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10017 automatically stop a trace experiment. If a tracepoint's passcount is
10018 @var{n}, then the trace experiment will be automatically stopped on
10019 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10020 @var{num} is not specified, the @code{passcount} command sets the
10021 passcount of the most recently defined tracepoint. If no passcount is
10022 given, the trace experiment will run until stopped explicitly by the
10028 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10029 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10031 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10032 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10033 (@value{GDBP}) @b{trace foo}
10034 (@value{GDBP}) @b{pass 3}
10035 (@value{GDBP}) @b{trace bar}
10036 (@value{GDBP}) @b{pass 2}
10037 (@value{GDBP}) @b{trace baz}
10038 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10039 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10040 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10041 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10045 @node Tracepoint Conditions
10046 @subsection Tracepoint Conditions
10047 @cindex conditional tracepoints
10048 @cindex tracepoint conditions
10050 The simplest sort of tracepoint collects data every time your program
10051 reaches a specified place. You can also specify a @dfn{condition} for
10052 a tracepoint. A condition is just a Boolean expression in your
10053 programming language (@pxref{Expressions, ,Expressions}). A
10054 tracepoint with a condition evaluates the expression each time your
10055 program reaches it, and data collection happens only if the condition
10058 Tracepoint conditions can be specified when a tracepoint is set, by
10059 using @samp{if} in the arguments to the @code{trace} command.
10060 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10061 also be set or changed at any time with the @code{condition} command,
10062 just as with breakpoints.
10064 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10065 the conditional expression itself. Instead, @value{GDBN} encodes the
10066 expression into an agent expression (@pxref{Agent Expressions}
10067 suitable for execution on the target, independently of @value{GDBN}.
10068 Global variables become raw memory locations, locals become stack
10069 accesses, and so forth.
10071 For instance, suppose you have a function that is usually called
10072 frequently, but should not be called after an error has occurred. You
10073 could use the following tracepoint command to collect data about calls
10074 of that function that happen while the error code is propagating
10075 through the program; an unconditional tracepoint could end up
10076 collecting thousands of useless trace frames that you would have to
10080 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10083 @node Trace State Variables
10084 @subsection Trace State Variables
10085 @cindex trace state variables
10087 A @dfn{trace state variable} is a special type of variable that is
10088 created and managed by target-side code. The syntax is the same as
10089 that for GDB's convenience variables (a string prefixed with ``$''),
10090 but they are stored on the target. They must be created explicitly,
10091 using a @code{tvariable} command. They are always 64-bit signed
10094 Trace state variables are remembered by @value{GDBN}, and downloaded
10095 to the target along with tracepoint information when the trace
10096 experiment starts. There are no intrinsic limits on the number of
10097 trace state variables, beyond memory limitations of the target.
10099 @cindex convenience variables, and trace state variables
10100 Although trace state variables are managed by the target, you can use
10101 them in print commands and expressions as if they were convenience
10102 variables; @value{GDBN} will get the current value from the target
10103 while the trace experiment is running. Trace state variables share
10104 the same namespace as other ``$'' variables, which means that you
10105 cannot have trace state variables with names like @code{$23} or
10106 @code{$pc}, nor can you have a trace state variable and a convenience
10107 variable with the same name.
10111 @item tvariable $@var{name} [ = @var{expression} ]
10113 The @code{tvariable} command creates a new trace state variable named
10114 @code{$@var{name}}, and optionally gives it an initial value of
10115 @var{expression}. @var{expression} is evaluated when this command is
10116 entered; the result will be converted to an integer if possible,
10117 otherwise @value{GDBN} will report an error. A subsequent
10118 @code{tvariable} command specifying the same name does not create a
10119 variable, but instead assigns the supplied initial value to the
10120 existing variable of that name, overwriting any previous initial
10121 value. The default initial value is 0.
10123 @item info tvariables
10124 @kindex info tvariables
10125 List all the trace state variables along with their initial values.
10126 Their current values may also be displayed, if the trace experiment is
10129 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10130 @kindex delete tvariable
10131 Delete the given trace state variables, or all of them if no arguments
10136 @node Tracepoint Actions
10137 @subsection Tracepoint Action Lists
10141 @cindex tracepoint actions
10142 @item actions @r{[}@var{num}@r{]}
10143 This command will prompt for a list of actions to be taken when the
10144 tracepoint is hit. If the tracepoint number @var{num} is not
10145 specified, this command sets the actions for the one that was most
10146 recently defined (so that you can define a tracepoint and then say
10147 @code{actions} without bothering about its number). You specify the
10148 actions themselves on the following lines, one action at a time, and
10149 terminate the actions list with a line containing just @code{end}. So
10150 far, the only defined actions are @code{collect}, @code{teval}, and
10151 @code{while-stepping}.
10153 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10154 Commands, ,Breakpoint Command Lists}), except that only the defined
10155 actions are allowed; any other @value{GDBN} command is rejected.
10157 @cindex remove actions from a tracepoint
10158 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10159 and follow it immediately with @samp{end}.
10162 (@value{GDBP}) @b{collect @var{data}} // collect some data
10164 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10166 (@value{GDBP}) @b{end} // signals the end of actions.
10169 In the following example, the action list begins with @code{collect}
10170 commands indicating the things to be collected when the tracepoint is
10171 hit. Then, in order to single-step and collect additional data
10172 following the tracepoint, a @code{while-stepping} command is used,
10173 followed by the list of things to be collected after each step in a
10174 sequence of single steps. The @code{while-stepping} command is
10175 terminated by its own separate @code{end} command. Lastly, the action
10176 list is terminated by an @code{end} command.
10179 (@value{GDBP}) @b{trace foo}
10180 (@value{GDBP}) @b{actions}
10181 Enter actions for tracepoint 1, one per line:
10184 > while-stepping 12
10185 > collect $pc, arr[i]
10190 @kindex collect @r{(tracepoints)}
10191 @item collect @var{expr1}, @var{expr2}, @dots{}
10192 Collect values of the given expressions when the tracepoint is hit.
10193 This command accepts a comma-separated list of any valid expressions.
10194 In addition to global, static, or local variables, the following
10195 special arguments are supported:
10199 Collect all registers.
10202 Collect all function arguments.
10205 Collect all local variables.
10208 @vindex $_sdata@r{, collect}
10209 Collect static tracepoint marker specific data. Only available for
10210 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10211 Lists}. On the UST static tracepoints library backend, an
10212 instrumentation point resembles a @code{printf} function call. The
10213 tracing library is able to collect user specified data formatted to a
10214 character string using the format provided by the programmer that
10215 instrumented the program. Other backends have similar mechanisms.
10216 Here's an example of a UST marker call:
10219 const char master_name[] = "$your_name";
10220 trace_mark(channel1, marker1, "hello %s", master_name)
10223 In this case, collecting @code{$_sdata} collects the string
10224 @samp{hello $yourname}. When analyzing the trace buffer, you can
10225 inspect @samp{$_sdata} like any other variable available to
10229 You can give several consecutive @code{collect} commands, each one
10230 with a single argument, or one @code{collect} command with several
10231 arguments separated by commas; the effect is the same.
10233 The command @code{info scope} (@pxref{Symbols, info scope}) is
10234 particularly useful for figuring out what data to collect.
10236 @kindex teval @r{(tracepoints)}
10237 @item teval @var{expr1}, @var{expr2}, @dots{}
10238 Evaluate the given expressions when the tracepoint is hit. This
10239 command accepts a comma-separated list of expressions. The results
10240 are discarded, so this is mainly useful for assigning values to trace
10241 state variables (@pxref{Trace State Variables}) without adding those
10242 values to the trace buffer, as would be the case if the @code{collect}
10245 @kindex while-stepping @r{(tracepoints)}
10246 @item while-stepping @var{n}
10247 Perform @var{n} single-step instruction traces after the tracepoint,
10248 collecting new data after each step. The @code{while-stepping}
10249 command is followed by the list of what to collect while stepping
10250 (followed by its own @code{end} command):
10253 > while-stepping 12
10254 > collect $regs, myglobal
10260 Note that @code{$pc} is not automatically collected by
10261 @code{while-stepping}; you need to explicitly collect that register if
10262 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10265 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10266 @kindex set default-collect
10267 @cindex default collection action
10268 This variable is a list of expressions to collect at each tracepoint
10269 hit. It is effectively an additional @code{collect} action prepended
10270 to every tracepoint action list. The expressions are parsed
10271 individually for each tracepoint, so for instance a variable named
10272 @code{xyz} may be interpreted as a global for one tracepoint, and a
10273 local for another, as appropriate to the tracepoint's location.
10275 @item show default-collect
10276 @kindex show default-collect
10277 Show the list of expressions that are collected by default at each
10282 @node Listing Tracepoints
10283 @subsection Listing Tracepoints
10286 @kindex info tracepoints
10288 @cindex information about tracepoints
10289 @item info tracepoints @r{[}@var{num}@r{]}
10290 Display information about the tracepoint @var{num}. If you don't
10291 specify a tracepoint number, displays information about all the
10292 tracepoints defined so far. The format is similar to that used for
10293 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10294 command, simply restricting itself to tracepoints.
10296 A tracepoint's listing may include additional information specific to
10301 its passcount as given by the @code{passcount @var{n}} command
10305 (@value{GDBP}) @b{info trace}
10306 Num Type Disp Enb Address What
10307 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10309 collect globfoo, $regs
10318 This command can be abbreviated @code{info tp}.
10321 @node Listing Static Tracepoint Markers
10322 @subsection Listing Static Tracepoint Markers
10325 @kindex info static-tracepoint-markers
10326 @cindex information about static tracepoint markers
10327 @item info static-tracepoint-markers
10328 Display information about all static tracepoint markers defined in the
10331 For each marker, the following columns are printed:
10335 An incrementing counter, output to help readability. This is not a
10338 The marker ID, as reported by the target.
10339 @item Enabled or Disabled
10340 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10341 that are not enabled.
10343 Where the marker is in your program, as a memory address.
10345 Where the marker is in the source for your program, as a file and line
10346 number. If the debug information included in the program does not
10347 allow @value{GDBN} to locate the source of the marker, this column
10348 will be left blank.
10352 In addition, the following information may be printed for each marker:
10356 User data passed to the tracing library by the marker call. In the
10357 UST backend, this is the format string passed as argument to the
10359 @item Static tracepoints probing the marker
10360 The list of static tracepoints attached to the marker.
10364 (@value{GDBP}) info static-tracepoint-markers
10365 Cnt ID Enb Address What
10366 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10367 Data: number1 %d number2 %d
10368 Probed by static tracepoints: #2
10369 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10375 @node Starting and Stopping Trace Experiments
10376 @subsection Starting and Stopping Trace Experiments
10380 @cindex start a new trace experiment
10381 @cindex collected data discarded
10383 This command takes no arguments. It starts the trace experiment, and
10384 begins collecting data. This has the side effect of discarding all
10385 the data collected in the trace buffer during the previous trace
10389 @cindex stop a running trace experiment
10391 This command takes no arguments. It ends the trace experiment, and
10392 stops collecting data.
10394 @strong{Note}: a trace experiment and data collection may stop
10395 automatically if any tracepoint's passcount is reached
10396 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10399 @cindex status of trace data collection
10400 @cindex trace experiment, status of
10402 This command displays the status of the current trace data
10406 Here is an example of the commands we described so far:
10409 (@value{GDBP}) @b{trace gdb_c_test}
10410 (@value{GDBP}) @b{actions}
10411 Enter actions for tracepoint #1, one per line.
10412 > collect $regs,$locals,$args
10413 > while-stepping 11
10417 (@value{GDBP}) @b{tstart}
10418 [time passes @dots{}]
10419 (@value{GDBP}) @b{tstop}
10422 @cindex disconnected tracing
10423 You can choose to continue running the trace experiment even if
10424 @value{GDBN} disconnects from the target, voluntarily or
10425 involuntarily. For commands such as @code{detach}, the debugger will
10426 ask what you want to do with the trace. But for unexpected
10427 terminations (@value{GDBN} crash, network outage), it would be
10428 unfortunate to lose hard-won trace data, so the variable
10429 @code{disconnected-tracing} lets you decide whether the trace should
10430 continue running without @value{GDBN}.
10433 @item set disconnected-tracing on
10434 @itemx set disconnected-tracing off
10435 @kindex set disconnected-tracing
10436 Choose whether a tracing run should continue to run if @value{GDBN}
10437 has disconnected from the target. Note that @code{detach} or
10438 @code{quit} will ask you directly what to do about a running trace no
10439 matter what this variable's setting, so the variable is mainly useful
10440 for handling unexpected situations, such as loss of the network.
10442 @item show disconnected-tracing
10443 @kindex show disconnected-tracing
10444 Show the current choice for disconnected tracing.
10448 When you reconnect to the target, the trace experiment may or may not
10449 still be running; it might have filled the trace buffer in the
10450 meantime, or stopped for one of the other reasons. If it is running,
10451 it will continue after reconnection.
10453 Upon reconnection, the target will upload information about the
10454 tracepoints in effect. @value{GDBN} will then compare that
10455 information to the set of tracepoints currently defined, and attempt
10456 to match them up, allowing for the possibility that the numbers may
10457 have changed due to creation and deletion in the meantime. If one of
10458 the target's tracepoints does not match any in @value{GDBN}, the
10459 debugger will create a new tracepoint, so that you have a number with
10460 which to specify that tracepoint. This matching-up process is
10461 necessarily heuristic, and it may result in useless tracepoints being
10462 created; you may simply delete them if they are of no use.
10464 @cindex circular trace buffer
10465 If your target agent supports a @dfn{circular trace buffer}, then you
10466 can run a trace experiment indefinitely without filling the trace
10467 buffer; when space runs out, the agent deletes already-collected trace
10468 frames, oldest first, until there is enough room to continue
10469 collecting. This is especially useful if your tracepoints are being
10470 hit too often, and your trace gets terminated prematurely because the
10471 buffer is full. To ask for a circular trace buffer, simply set
10472 @samp{circular_trace_buffer} to on. You can set this at any time,
10473 including during tracing; if the agent can do it, it will change
10474 buffer handling on the fly, otherwise it will not take effect until
10478 @item set circular-trace-buffer on
10479 @itemx set circular-trace-buffer off
10480 @kindex set circular-trace-buffer
10481 Choose whether a tracing run should use a linear or circular buffer
10482 for trace data. A linear buffer will not lose any trace data, but may
10483 fill up prematurely, while a circular buffer will discard old trace
10484 data, but it will have always room for the latest tracepoint hits.
10486 @item show circular-trace-buffer
10487 @kindex show circular-trace-buffer
10488 Show the current choice for the trace buffer. Note that this may not
10489 match the agent's current buffer handling, nor is it guaranteed to
10490 match the setting that might have been in effect during a past run,
10491 for instance if you are looking at frames from a trace file.
10495 @node Tracepoint Restrictions
10496 @subsection Tracepoint Restrictions
10498 @cindex tracepoint restrictions
10499 There are a number of restrictions on the use of tracepoints. As
10500 described above, tracepoint data gathering occurs on the target
10501 without interaction from @value{GDBN}. Thus the full capabilities of
10502 the debugger are not available during data gathering, and then at data
10503 examination time, you will be limited by only having what was
10504 collected. The following items describe some common problems, but it
10505 is not exhaustive, and you may run into additional difficulties not
10511 Tracepoint expressions are intended to gather objects (lvalues). Thus
10512 the full flexibility of GDB's expression evaluator is not available.
10513 You cannot call functions, cast objects to aggregate types, access
10514 convenience variables or modify values (except by assignment to trace
10515 state variables). Some language features may implicitly call
10516 functions (for instance Objective-C fields with accessors), and therefore
10517 cannot be collected either.
10520 Collection of local variables, either individually or in bulk with
10521 @code{$locals} or @code{$args}, during @code{while-stepping} may
10522 behave erratically. The stepping action may enter a new scope (for
10523 instance by stepping into a function), or the location of the variable
10524 may change (for instance it is loaded into a register). The
10525 tracepoint data recorded uses the location information for the
10526 variables that is correct for the tracepoint location. When the
10527 tracepoint is created, it is not possible, in general, to determine
10528 where the steps of a @code{while-stepping} sequence will advance the
10529 program---particularly if a conditional branch is stepped.
10532 Collection of an incompletely-initialized or partially-destroyed object
10533 may result in something that @value{GDBN} cannot display, or displays
10534 in a misleading way.
10537 When @value{GDBN} displays a pointer to character it automatically
10538 dereferences the pointer to also display characters of the string
10539 being pointed to. However, collecting the pointer during tracing does
10540 not automatically collect the string. You need to explicitly
10541 dereference the pointer and provide size information if you want to
10542 collect not only the pointer, but the memory pointed to. For example,
10543 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10547 It is not possible to collect a complete stack backtrace at a
10548 tracepoint. Instead, you may collect the registers and a few hundred
10549 bytes from the stack pointer with something like @code{*$esp@@300}
10550 (adjust to use the name of the actual stack pointer register on your
10551 target architecture, and the amount of stack you wish to capture).
10552 Then the @code{backtrace} command will show a partial backtrace when
10553 using a trace frame. The number of stack frames that can be examined
10554 depends on the sizes of the frames in the collected stack. Note that
10555 if you ask for a block so large that it goes past the bottom of the
10556 stack, the target agent may report an error trying to read from an
10560 If you do not collect registers at a tracepoint, @value{GDBN} can
10561 infer that the value of @code{$pc} must be the same as the address of
10562 the tracepoint and use that when you are looking at a trace frame
10563 for that tracepoint. However, this cannot work if the tracepoint has
10564 multiple locations (for instance if it was set in a function that was
10565 inlined), or if it has a @code{while-stepping} loop. In those cases
10566 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10571 @node Analyze Collected Data
10572 @section Using the Collected Data
10574 After the tracepoint experiment ends, you use @value{GDBN} commands
10575 for examining the trace data. The basic idea is that each tracepoint
10576 collects a trace @dfn{snapshot} every time it is hit and another
10577 snapshot every time it single-steps. All these snapshots are
10578 consecutively numbered from zero and go into a buffer, and you can
10579 examine them later. The way you examine them is to @dfn{focus} on a
10580 specific trace snapshot. When the remote stub is focused on a trace
10581 snapshot, it will respond to all @value{GDBN} requests for memory and
10582 registers by reading from the buffer which belongs to that snapshot,
10583 rather than from @emph{real} memory or registers of the program being
10584 debugged. This means that @strong{all} @value{GDBN} commands
10585 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10586 behave as if we were currently debugging the program state as it was
10587 when the tracepoint occurred. Any requests for data that are not in
10588 the buffer will fail.
10591 * tfind:: How to select a trace snapshot
10592 * tdump:: How to display all data for a snapshot
10593 * save tracepoints:: How to save tracepoints for a future run
10597 @subsection @code{tfind @var{n}}
10600 @cindex select trace snapshot
10601 @cindex find trace snapshot
10602 The basic command for selecting a trace snapshot from the buffer is
10603 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10604 counting from zero. If no argument @var{n} is given, the next
10605 snapshot is selected.
10607 Here are the various forms of using the @code{tfind} command.
10611 Find the first snapshot in the buffer. This is a synonym for
10612 @code{tfind 0} (since 0 is the number of the first snapshot).
10615 Stop debugging trace snapshots, resume @emph{live} debugging.
10618 Same as @samp{tfind none}.
10621 No argument means find the next trace snapshot.
10624 Find the previous trace snapshot before the current one. This permits
10625 retracing earlier steps.
10627 @item tfind tracepoint @var{num}
10628 Find the next snapshot associated with tracepoint @var{num}. Search
10629 proceeds forward from the last examined trace snapshot. If no
10630 argument @var{num} is given, it means find the next snapshot collected
10631 for the same tracepoint as the current snapshot.
10633 @item tfind pc @var{addr}
10634 Find the next snapshot associated with the value @var{addr} of the
10635 program counter. Search proceeds forward from the last examined trace
10636 snapshot. If no argument @var{addr} is given, it means find the next
10637 snapshot with the same value of PC as the current snapshot.
10639 @item tfind outside @var{addr1}, @var{addr2}
10640 Find the next snapshot whose PC is outside the given range of
10641 addresses (exclusive).
10643 @item tfind range @var{addr1}, @var{addr2}
10644 Find the next snapshot whose PC is between @var{addr1} and
10645 @var{addr2} (inclusive).
10647 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10648 Find the next snapshot associated with the source line @var{n}. If
10649 the optional argument @var{file} is given, refer to line @var{n} in
10650 that source file. Search proceeds forward from the last examined
10651 trace snapshot. If no argument @var{n} is given, it means find the
10652 next line other than the one currently being examined; thus saying
10653 @code{tfind line} repeatedly can appear to have the same effect as
10654 stepping from line to line in a @emph{live} debugging session.
10657 The default arguments for the @code{tfind} commands are specifically
10658 designed to make it easy to scan through the trace buffer. For
10659 instance, @code{tfind} with no argument selects the next trace
10660 snapshot, and @code{tfind -} with no argument selects the previous
10661 trace snapshot. So, by giving one @code{tfind} command, and then
10662 simply hitting @key{RET} repeatedly you can examine all the trace
10663 snapshots in order. Or, by saying @code{tfind -} and then hitting
10664 @key{RET} repeatedly you can examine the snapshots in reverse order.
10665 The @code{tfind line} command with no argument selects the snapshot
10666 for the next source line executed. The @code{tfind pc} command with
10667 no argument selects the next snapshot with the same program counter
10668 (PC) as the current frame. The @code{tfind tracepoint} command with
10669 no argument selects the next trace snapshot collected by the same
10670 tracepoint as the current one.
10672 In addition to letting you scan through the trace buffer manually,
10673 these commands make it easy to construct @value{GDBN} scripts that
10674 scan through the trace buffer and print out whatever collected data
10675 you are interested in. Thus, if we want to examine the PC, FP, and SP
10676 registers from each trace frame in the buffer, we can say this:
10679 (@value{GDBP}) @b{tfind start}
10680 (@value{GDBP}) @b{while ($trace_frame != -1)}
10681 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10682 $trace_frame, $pc, $sp, $fp
10686 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10687 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10688 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10689 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10690 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10691 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10692 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10693 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10694 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10695 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10696 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10699 Or, if we want to examine the variable @code{X} at each source line in
10703 (@value{GDBP}) @b{tfind start}
10704 (@value{GDBP}) @b{while ($trace_frame != -1)}
10705 > printf "Frame %d, X == %d\n", $trace_frame, X
10715 @subsection @code{tdump}
10717 @cindex dump all data collected at tracepoint
10718 @cindex tracepoint data, display
10720 This command takes no arguments. It prints all the data collected at
10721 the current trace snapshot.
10724 (@value{GDBP}) @b{trace 444}
10725 (@value{GDBP}) @b{actions}
10726 Enter actions for tracepoint #2, one per line:
10727 > collect $regs, $locals, $args, gdb_long_test
10730 (@value{GDBP}) @b{tstart}
10732 (@value{GDBP}) @b{tfind line 444}
10733 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10735 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10737 (@value{GDBP}) @b{tdump}
10738 Data collected at tracepoint 2, trace frame 1:
10739 d0 0xc4aa0085 -995491707
10743 d4 0x71aea3d 119204413
10746 d7 0x380035 3670069
10747 a0 0x19e24a 1696330
10748 a1 0x3000668 50333288
10750 a3 0x322000 3284992
10751 a4 0x3000698 50333336
10752 a5 0x1ad3cc 1758156
10753 fp 0x30bf3c 0x30bf3c
10754 sp 0x30bf34 0x30bf34
10756 pc 0x20b2c8 0x20b2c8
10760 p = 0x20e5b4 "gdb-test"
10767 gdb_long_test = 17 '\021'
10772 @code{tdump} works by scanning the tracepoint's current collection
10773 actions and printing the value of each expression listed. So
10774 @code{tdump} can fail, if after a run, you change the tracepoint's
10775 actions to mention variables that were not collected during the run.
10777 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10778 uses the collected value of @code{$pc} to distinguish between trace
10779 frames that were collected at the tracepoint hit, and frames that were
10780 collected while stepping. This allows it to correctly choose whether
10781 to display the basic list of collections, or the collections from the
10782 body of the while-stepping loop. However, if @code{$pc} was not collected,
10783 then @code{tdump} will always attempt to dump using the basic collection
10784 list, and may fail if a while-stepping frame does not include all the
10785 same data that is collected at the tracepoint hit.
10786 @c This is getting pretty arcane, example would be good.
10788 @node save tracepoints
10789 @subsection @code{save tracepoints @var{filename}}
10790 @kindex save tracepoints
10791 @kindex save-tracepoints
10792 @cindex save tracepoints for future sessions
10794 This command saves all current tracepoint definitions together with
10795 their actions and passcounts, into a file @file{@var{filename}}
10796 suitable for use in a later debugging session. To read the saved
10797 tracepoint definitions, use the @code{source} command (@pxref{Command
10798 Files}). The @w{@code{save-tracepoints}} command is a deprecated
10799 alias for @w{@code{save tracepoints}}
10801 @node Tracepoint Variables
10802 @section Convenience Variables for Tracepoints
10803 @cindex tracepoint variables
10804 @cindex convenience variables for tracepoints
10807 @vindex $trace_frame
10808 @item (int) $trace_frame
10809 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10810 snapshot is selected.
10812 @vindex $tracepoint
10813 @item (int) $tracepoint
10814 The tracepoint for the current trace snapshot.
10816 @vindex $trace_line
10817 @item (int) $trace_line
10818 The line number for the current trace snapshot.
10820 @vindex $trace_file
10821 @item (char []) $trace_file
10822 The source file for the current trace snapshot.
10824 @vindex $trace_func
10825 @item (char []) $trace_func
10826 The name of the function containing @code{$tracepoint}.
10829 Note: @code{$trace_file} is not suitable for use in @code{printf},
10830 use @code{output} instead.
10832 Here's a simple example of using these convenience variables for
10833 stepping through all the trace snapshots and printing some of their
10834 data. Note that these are not the same as trace state variables,
10835 which are managed by the target.
10838 (@value{GDBP}) @b{tfind start}
10840 (@value{GDBP}) @b{while $trace_frame != -1}
10841 > output $trace_file
10842 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10848 @section Using Trace Files
10849 @cindex trace files
10851 In some situations, the target running a trace experiment may no
10852 longer be available; perhaps it crashed, or the hardware was needed
10853 for a different activity. To handle these cases, you can arrange to
10854 dump the trace data into a file, and later use that file as a source
10855 of trace data, via the @code{target tfile} command.
10860 @item tsave [ -r ] @var{filename}
10861 Save the trace data to @var{filename}. By default, this command
10862 assumes that @var{filename} refers to the host filesystem, so if
10863 necessary @value{GDBN} will copy raw trace data up from the target and
10864 then save it. If the target supports it, you can also supply the
10865 optional argument @code{-r} (``remote'') to direct the target to save
10866 the data directly into @var{filename} in its own filesystem, which may be
10867 more efficient if the trace buffer is very large. (Note, however, that
10868 @code{target tfile} can only read from files accessible to the host.)
10870 @kindex target tfile
10872 @item target tfile @var{filename}
10873 Use the file named @var{filename} as a source of trace data. Commands
10874 that examine data work as they do with a live target, but it is not
10875 possible to run any new trace experiments. @code{tstatus} will report
10876 the state of the trace run at the moment the data was saved, as well
10877 as the current trace frame you are examining. @var{filename} must be
10878 on a filesystem accessible to the host.
10883 @chapter Debugging Programs That Use Overlays
10886 If your program is too large to fit completely in your target system's
10887 memory, you can sometimes use @dfn{overlays} to work around this
10888 problem. @value{GDBN} provides some support for debugging programs that
10892 * How Overlays Work:: A general explanation of overlays.
10893 * Overlay Commands:: Managing overlays in @value{GDBN}.
10894 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10895 mapped by asking the inferior.
10896 * Overlay Sample Program:: A sample program using overlays.
10899 @node How Overlays Work
10900 @section How Overlays Work
10901 @cindex mapped overlays
10902 @cindex unmapped overlays
10903 @cindex load address, overlay's
10904 @cindex mapped address
10905 @cindex overlay area
10907 Suppose you have a computer whose instruction address space is only 64
10908 kilobytes long, but which has much more memory which can be accessed by
10909 other means: special instructions, segment registers, or memory
10910 management hardware, for example. Suppose further that you want to
10911 adapt a program which is larger than 64 kilobytes to run on this system.
10913 One solution is to identify modules of your program which are relatively
10914 independent, and need not call each other directly; call these modules
10915 @dfn{overlays}. Separate the overlays from the main program, and place
10916 their machine code in the larger memory. Place your main program in
10917 instruction memory, but leave at least enough space there to hold the
10918 largest overlay as well.
10920 Now, to call a function located in an overlay, you must first copy that
10921 overlay's machine code from the large memory into the space set aside
10922 for it in the instruction memory, and then jump to its entry point
10925 @c NB: In the below the mapped area's size is greater or equal to the
10926 @c size of all overlays. This is intentional to remind the developer
10927 @c that overlays don't necessarily need to be the same size.
10931 Data Instruction Larger
10932 Address Space Address Space Address Space
10933 +-----------+ +-----------+ +-----------+
10935 +-----------+ +-----------+ +-----------+<-- overlay 1
10936 | program | | main | .----| overlay 1 | load address
10937 | variables | | program | | +-----------+
10938 | and heap | | | | | |
10939 +-----------+ | | | +-----------+<-- overlay 2
10940 | | +-----------+ | | | load address
10941 +-----------+ | | | .-| overlay 2 |
10943 mapped --->+-----------+ | | +-----------+
10944 address | | | | | |
10945 | overlay | <-' | | |
10946 | area | <---' +-----------+<-- overlay 3
10947 | | <---. | | load address
10948 +-----------+ `--| overlay 3 |
10955 @anchor{A code overlay}A code overlay
10959 The diagram (@pxref{A code overlay}) shows a system with separate data
10960 and instruction address spaces. To map an overlay, the program copies
10961 its code from the larger address space to the instruction address space.
10962 Since the overlays shown here all use the same mapped address, only one
10963 may be mapped at a time. For a system with a single address space for
10964 data and instructions, the diagram would be similar, except that the
10965 program variables and heap would share an address space with the main
10966 program and the overlay area.
10968 An overlay loaded into instruction memory and ready for use is called a
10969 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10970 instruction memory. An overlay not present (or only partially present)
10971 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10972 is its address in the larger memory. The mapped address is also called
10973 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10974 called the @dfn{load memory address}, or @dfn{LMA}.
10976 Unfortunately, overlays are not a completely transparent way to adapt a
10977 program to limited instruction memory. They introduce a new set of
10978 global constraints you must keep in mind as you design your program:
10983 Before calling or returning to a function in an overlay, your program
10984 must make sure that overlay is actually mapped. Otherwise, the call or
10985 return will transfer control to the right address, but in the wrong
10986 overlay, and your program will probably crash.
10989 If the process of mapping an overlay is expensive on your system, you
10990 will need to choose your overlays carefully to minimize their effect on
10991 your program's performance.
10994 The executable file you load onto your system must contain each
10995 overlay's instructions, appearing at the overlay's load address, not its
10996 mapped address. However, each overlay's instructions must be relocated
10997 and its symbols defined as if the overlay were at its mapped address.
10998 You can use GNU linker scripts to specify different load and relocation
10999 addresses for pieces of your program; see @ref{Overlay Description,,,
11000 ld.info, Using ld: the GNU linker}.
11003 The procedure for loading executable files onto your system must be able
11004 to load their contents into the larger address space as well as the
11005 instruction and data spaces.
11009 The overlay system described above is rather simple, and could be
11010 improved in many ways:
11015 If your system has suitable bank switch registers or memory management
11016 hardware, you could use those facilities to make an overlay's load area
11017 contents simply appear at their mapped address in instruction space.
11018 This would probably be faster than copying the overlay to its mapped
11019 area in the usual way.
11022 If your overlays are small enough, you could set aside more than one
11023 overlay area, and have more than one overlay mapped at a time.
11026 You can use overlays to manage data, as well as instructions. In
11027 general, data overlays are even less transparent to your design than
11028 code overlays: whereas code overlays only require care when you call or
11029 return to functions, data overlays require care every time you access
11030 the data. Also, if you change the contents of a data overlay, you
11031 must copy its contents back out to its load address before you can copy a
11032 different data overlay into the same mapped area.
11037 @node Overlay Commands
11038 @section Overlay Commands
11040 To use @value{GDBN}'s overlay support, each overlay in your program must
11041 correspond to a separate section of the executable file. The section's
11042 virtual memory address and load memory address must be the overlay's
11043 mapped and load addresses. Identifying overlays with sections allows
11044 @value{GDBN} to determine the appropriate address of a function or
11045 variable, depending on whether the overlay is mapped or not.
11047 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11048 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11053 Disable @value{GDBN}'s overlay support. When overlay support is
11054 disabled, @value{GDBN} assumes that all functions and variables are
11055 always present at their mapped addresses. By default, @value{GDBN}'s
11056 overlay support is disabled.
11058 @item overlay manual
11059 @cindex manual overlay debugging
11060 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11061 relies on you to tell it which overlays are mapped, and which are not,
11062 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11063 commands described below.
11065 @item overlay map-overlay @var{overlay}
11066 @itemx overlay map @var{overlay}
11067 @cindex map an overlay
11068 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11069 be the name of the object file section containing the overlay. When an
11070 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11071 functions and variables at their mapped addresses. @value{GDBN} assumes
11072 that any other overlays whose mapped ranges overlap that of
11073 @var{overlay} are now unmapped.
11075 @item overlay unmap-overlay @var{overlay}
11076 @itemx overlay unmap @var{overlay}
11077 @cindex unmap an overlay
11078 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11079 must be the name of the object file section containing the overlay.
11080 When an overlay is unmapped, @value{GDBN} assumes it can find the
11081 overlay's functions and variables at their load addresses.
11084 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11085 consults a data structure the overlay manager maintains in the inferior
11086 to see which overlays are mapped. For details, see @ref{Automatic
11087 Overlay Debugging}.
11089 @item overlay load-target
11090 @itemx overlay load
11091 @cindex reloading the overlay table
11092 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11093 re-reads the table @value{GDBN} automatically each time the inferior
11094 stops, so this command should only be necessary if you have changed the
11095 overlay mapping yourself using @value{GDBN}. This command is only
11096 useful when using automatic overlay debugging.
11098 @item overlay list-overlays
11099 @itemx overlay list
11100 @cindex listing mapped overlays
11101 Display a list of the overlays currently mapped, along with their mapped
11102 addresses, load addresses, and sizes.
11106 Normally, when @value{GDBN} prints a code address, it includes the name
11107 of the function the address falls in:
11110 (@value{GDBP}) print main
11111 $3 = @{int ()@} 0x11a0 <main>
11114 When overlay debugging is enabled, @value{GDBN} recognizes code in
11115 unmapped overlays, and prints the names of unmapped functions with
11116 asterisks around them. For example, if @code{foo} is a function in an
11117 unmapped overlay, @value{GDBN} prints it this way:
11120 (@value{GDBP}) overlay list
11121 No sections are mapped.
11122 (@value{GDBP}) print foo
11123 $5 = @{int (int)@} 0x100000 <*foo*>
11126 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11130 (@value{GDBP}) overlay list
11131 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11132 mapped at 0x1016 - 0x104a
11133 (@value{GDBP}) print foo
11134 $6 = @{int (int)@} 0x1016 <foo>
11137 When overlay debugging is enabled, @value{GDBN} can find the correct
11138 address for functions and variables in an overlay, whether or not the
11139 overlay is mapped. This allows most @value{GDBN} commands, like
11140 @code{break} and @code{disassemble}, to work normally, even on unmapped
11141 code. However, @value{GDBN}'s breakpoint support has some limitations:
11145 @cindex breakpoints in overlays
11146 @cindex overlays, setting breakpoints in
11147 You can set breakpoints in functions in unmapped overlays, as long as
11148 @value{GDBN} can write to the overlay at its load address.
11150 @value{GDBN} can not set hardware or simulator-based breakpoints in
11151 unmapped overlays. However, if you set a breakpoint at the end of your
11152 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11153 you are using manual overlay management), @value{GDBN} will re-set its
11154 breakpoints properly.
11158 @node Automatic Overlay Debugging
11159 @section Automatic Overlay Debugging
11160 @cindex automatic overlay debugging
11162 @value{GDBN} can automatically track which overlays are mapped and which
11163 are not, given some simple co-operation from the overlay manager in the
11164 inferior. If you enable automatic overlay debugging with the
11165 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11166 looks in the inferior's memory for certain variables describing the
11167 current state of the overlays.
11169 Here are the variables your overlay manager must define to support
11170 @value{GDBN}'s automatic overlay debugging:
11174 @item @code{_ovly_table}:
11175 This variable must be an array of the following structures:
11180 /* The overlay's mapped address. */
11183 /* The size of the overlay, in bytes. */
11184 unsigned long size;
11186 /* The overlay's load address. */
11189 /* Non-zero if the overlay is currently mapped;
11191 unsigned long mapped;
11195 @item @code{_novlys}:
11196 This variable must be a four-byte signed integer, holding the total
11197 number of elements in @code{_ovly_table}.
11201 To decide whether a particular overlay is mapped or not, @value{GDBN}
11202 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11203 @code{lma} members equal the VMA and LMA of the overlay's section in the
11204 executable file. When @value{GDBN} finds a matching entry, it consults
11205 the entry's @code{mapped} member to determine whether the overlay is
11208 In addition, your overlay manager may define a function called
11209 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11210 will silently set a breakpoint there. If the overlay manager then
11211 calls this function whenever it has changed the overlay table, this
11212 will enable @value{GDBN} to accurately keep track of which overlays
11213 are in program memory, and update any breakpoints that may be set
11214 in overlays. This will allow breakpoints to work even if the
11215 overlays are kept in ROM or other non-writable memory while they
11216 are not being executed.
11218 @node Overlay Sample Program
11219 @section Overlay Sample Program
11220 @cindex overlay example program
11222 When linking a program which uses overlays, you must place the overlays
11223 at their load addresses, while relocating them to run at their mapped
11224 addresses. To do this, you must write a linker script (@pxref{Overlay
11225 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11226 since linker scripts are specific to a particular host system, target
11227 architecture, and target memory layout, this manual cannot provide
11228 portable sample code demonstrating @value{GDBN}'s overlay support.
11230 However, the @value{GDBN} source distribution does contain an overlaid
11231 program, with linker scripts for a few systems, as part of its test
11232 suite. The program consists of the following files from
11233 @file{gdb/testsuite/gdb.base}:
11237 The main program file.
11239 A simple overlay manager, used by @file{overlays.c}.
11244 Overlay modules, loaded and used by @file{overlays.c}.
11247 Linker scripts for linking the test program on the @code{d10v-elf}
11248 and @code{m32r-elf} targets.
11251 You can build the test program using the @code{d10v-elf} GCC
11252 cross-compiler like this:
11255 $ d10v-elf-gcc -g -c overlays.c
11256 $ d10v-elf-gcc -g -c ovlymgr.c
11257 $ d10v-elf-gcc -g -c foo.c
11258 $ d10v-elf-gcc -g -c bar.c
11259 $ d10v-elf-gcc -g -c baz.c
11260 $ d10v-elf-gcc -g -c grbx.c
11261 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11262 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11265 The build process is identical for any other architecture, except that
11266 you must substitute the appropriate compiler and linker script for the
11267 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11271 @chapter Using @value{GDBN} with Different Languages
11274 Although programming languages generally have common aspects, they are
11275 rarely expressed in the same manner. For instance, in ANSI C,
11276 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11277 Modula-2, it is accomplished by @code{p^}. Values can also be
11278 represented (and displayed) differently. Hex numbers in C appear as
11279 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11281 @cindex working language
11282 Language-specific information is built into @value{GDBN} for some languages,
11283 allowing you to express operations like the above in your program's
11284 native language, and allowing @value{GDBN} to output values in a manner
11285 consistent with the syntax of your program's native language. The
11286 language you use to build expressions is called the @dfn{working
11290 * Setting:: Switching between source languages
11291 * Show:: Displaying the language
11292 * Checks:: Type and range checks
11293 * Supported Languages:: Supported languages
11294 * Unsupported Languages:: Unsupported languages
11298 @section Switching Between Source Languages
11300 There are two ways to control the working language---either have @value{GDBN}
11301 set it automatically, or select it manually yourself. You can use the
11302 @code{set language} command for either purpose. On startup, @value{GDBN}
11303 defaults to setting the language automatically. The working language is
11304 used to determine how expressions you type are interpreted, how values
11307 In addition to the working language, every source file that
11308 @value{GDBN} knows about has its own working language. For some object
11309 file formats, the compiler might indicate which language a particular
11310 source file is in. However, most of the time @value{GDBN} infers the
11311 language from the name of the file. The language of a source file
11312 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11313 show each frame appropriately for its own language. There is no way to
11314 set the language of a source file from within @value{GDBN}, but you can
11315 set the language associated with a filename extension. @xref{Show, ,
11316 Displaying the Language}.
11318 This is most commonly a problem when you use a program, such
11319 as @code{cfront} or @code{f2c}, that generates C but is written in
11320 another language. In that case, make the
11321 program use @code{#line} directives in its C output; that way
11322 @value{GDBN} will know the correct language of the source code of the original
11323 program, and will display that source code, not the generated C code.
11326 * Filenames:: Filename extensions and languages.
11327 * Manually:: Setting the working language manually
11328 * Automatically:: Having @value{GDBN} infer the source language
11332 @subsection List of Filename Extensions and Languages
11334 If a source file name ends in one of the following extensions, then
11335 @value{GDBN} infers that its language is the one indicated.
11353 C@t{++} source file
11359 Objective-C source file
11363 Fortran source file
11366 Modula-2 source file
11370 Assembler source file. This actually behaves almost like C, but
11371 @value{GDBN} does not skip over function prologues when stepping.
11374 In addition, you may set the language associated with a filename
11375 extension. @xref{Show, , Displaying the Language}.
11378 @subsection Setting the Working Language
11380 If you allow @value{GDBN} to set the language automatically,
11381 expressions are interpreted the same way in your debugging session and
11384 @kindex set language
11385 If you wish, you may set the language manually. To do this, issue the
11386 command @samp{set language @var{lang}}, where @var{lang} is the name of
11387 a language, such as
11388 @code{c} or @code{modula-2}.
11389 For a list of the supported languages, type @samp{set language}.
11391 Setting the language manually prevents @value{GDBN} from updating the working
11392 language automatically. This can lead to confusion if you try
11393 to debug a program when the working language is not the same as the
11394 source language, when an expression is acceptable to both
11395 languages---but means different things. For instance, if the current
11396 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11404 might not have the effect you intended. In C, this means to add
11405 @code{b} and @code{c} and place the result in @code{a}. The result
11406 printed would be the value of @code{a}. In Modula-2, this means to compare
11407 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11409 @node Automatically
11410 @subsection Having @value{GDBN} Infer the Source Language
11412 To have @value{GDBN} set the working language automatically, use
11413 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11414 then infers the working language. That is, when your program stops in a
11415 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11416 working language to the language recorded for the function in that
11417 frame. If the language for a frame is unknown (that is, if the function
11418 or block corresponding to the frame was defined in a source file that
11419 does not have a recognized extension), the current working language is
11420 not changed, and @value{GDBN} issues a warning.
11422 This may not seem necessary for most programs, which are written
11423 entirely in one source language. However, program modules and libraries
11424 written in one source language can be used by a main program written in
11425 a different source language. Using @samp{set language auto} in this
11426 case frees you from having to set the working language manually.
11429 @section Displaying the Language
11431 The following commands help you find out which language is the
11432 working language, and also what language source files were written in.
11435 @item show language
11436 @kindex show language
11437 Display the current working language. This is the
11438 language you can use with commands such as @code{print} to
11439 build and compute expressions that may involve variables in your program.
11442 @kindex info frame@r{, show the source language}
11443 Display the source language for this frame. This language becomes the
11444 working language if you use an identifier from this frame.
11445 @xref{Frame Info, ,Information about a Frame}, to identify the other
11446 information listed here.
11449 @kindex info source@r{, show the source language}
11450 Display the source language of this source file.
11451 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11452 information listed here.
11455 In unusual circumstances, you may have source files with extensions
11456 not in the standard list. You can then set the extension associated
11457 with a language explicitly:
11460 @item set extension-language @var{ext} @var{language}
11461 @kindex set extension-language
11462 Tell @value{GDBN} that source files with extension @var{ext} are to be
11463 assumed as written in the source language @var{language}.
11465 @item info extensions
11466 @kindex info extensions
11467 List all the filename extensions and the associated languages.
11471 @section Type and Range Checking
11474 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11475 checking are included, but they do not yet have any effect. This
11476 section documents the intended facilities.
11478 @c FIXME remove warning when type/range code added
11480 Some languages are designed to guard you against making seemingly common
11481 errors through a series of compile- and run-time checks. These include
11482 checking the type of arguments to functions and operators, and making
11483 sure mathematical overflows are caught at run time. Checks such as
11484 these help to ensure a program's correctness once it has been compiled
11485 by eliminating type mismatches, and providing active checks for range
11486 errors when your program is running.
11488 @value{GDBN} can check for conditions like the above if you wish.
11489 Although @value{GDBN} does not check the statements in your program,
11490 it can check expressions entered directly into @value{GDBN} for
11491 evaluation via the @code{print} command, for example. As with the
11492 working language, @value{GDBN} can also decide whether or not to check
11493 automatically based on your program's source language.
11494 @xref{Supported Languages, ,Supported Languages}, for the default
11495 settings of supported languages.
11498 * Type Checking:: An overview of type checking
11499 * Range Checking:: An overview of range checking
11502 @cindex type checking
11503 @cindex checks, type
11504 @node Type Checking
11505 @subsection An Overview of Type Checking
11507 Some languages, such as Modula-2, are strongly typed, meaning that the
11508 arguments to operators and functions have to be of the correct type,
11509 otherwise an error occurs. These checks prevent type mismatch
11510 errors from ever causing any run-time problems. For example,
11518 The second example fails because the @code{CARDINAL} 1 is not
11519 type-compatible with the @code{REAL} 2.3.
11521 For the expressions you use in @value{GDBN} commands, you can tell the
11522 @value{GDBN} type checker to skip checking;
11523 to treat any mismatches as errors and abandon the expression;
11524 or to only issue warnings when type mismatches occur,
11525 but evaluate the expression anyway. When you choose the last of
11526 these, @value{GDBN} evaluates expressions like the second example above, but
11527 also issues a warning.
11529 Even if you turn type checking off, there may be other reasons
11530 related to type that prevent @value{GDBN} from evaluating an expression.
11531 For instance, @value{GDBN} does not know how to add an @code{int} and
11532 a @code{struct foo}. These particular type errors have nothing to do
11533 with the language in use, and usually arise from expressions, such as
11534 the one described above, which make little sense to evaluate anyway.
11536 Each language defines to what degree it is strict about type. For
11537 instance, both Modula-2 and C require the arguments to arithmetical
11538 operators to be numbers. In C, enumerated types and pointers can be
11539 represented as numbers, so that they are valid arguments to mathematical
11540 operators. @xref{Supported Languages, ,Supported Languages}, for further
11541 details on specific languages.
11543 @value{GDBN} provides some additional commands for controlling the type checker:
11545 @kindex set check type
11546 @kindex show check type
11548 @item set check type auto
11549 Set type checking on or off based on the current working language.
11550 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11553 @item set check type on
11554 @itemx set check type off
11555 Set type checking on or off, overriding the default setting for the
11556 current working language. Issue a warning if the setting does not
11557 match the language default. If any type mismatches occur in
11558 evaluating an expression while type checking is on, @value{GDBN} prints a
11559 message and aborts evaluation of the expression.
11561 @item set check type warn
11562 Cause the type checker to issue warnings, but to always attempt to
11563 evaluate the expression. Evaluating the expression may still
11564 be impossible for other reasons. For example, @value{GDBN} cannot add
11565 numbers and structures.
11568 Show the current setting of the type checker, and whether or not @value{GDBN}
11569 is setting it automatically.
11572 @cindex range checking
11573 @cindex checks, range
11574 @node Range Checking
11575 @subsection An Overview of Range Checking
11577 In some languages (such as Modula-2), it is an error to exceed the
11578 bounds of a type; this is enforced with run-time checks. Such range
11579 checking is meant to ensure program correctness by making sure
11580 computations do not overflow, or indices on an array element access do
11581 not exceed the bounds of the array.
11583 For expressions you use in @value{GDBN} commands, you can tell
11584 @value{GDBN} to treat range errors in one of three ways: ignore them,
11585 always treat them as errors and abandon the expression, or issue
11586 warnings but evaluate the expression anyway.
11588 A range error can result from numerical overflow, from exceeding an
11589 array index bound, or when you type a constant that is not a member
11590 of any type. Some languages, however, do not treat overflows as an
11591 error. In many implementations of C, mathematical overflow causes the
11592 result to ``wrap around'' to lower values---for example, if @var{m} is
11593 the largest integer value, and @var{s} is the smallest, then
11596 @var{m} + 1 @result{} @var{s}
11599 This, too, is specific to individual languages, and in some cases
11600 specific to individual compilers or machines. @xref{Supported Languages, ,
11601 Supported Languages}, for further details on specific languages.
11603 @value{GDBN} provides some additional commands for controlling the range checker:
11605 @kindex set check range
11606 @kindex show check range
11608 @item set check range auto
11609 Set range checking on or off based on the current working language.
11610 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11613 @item set check range on
11614 @itemx set check range off
11615 Set range checking on or off, overriding the default setting for the
11616 current working language. A warning is issued if the setting does not
11617 match the language default. If a range error occurs and range checking is on,
11618 then a message is printed and evaluation of the expression is aborted.
11620 @item set check range warn
11621 Output messages when the @value{GDBN} range checker detects a range error,
11622 but attempt to evaluate the expression anyway. Evaluating the
11623 expression may still be impossible for other reasons, such as accessing
11624 memory that the process does not own (a typical example from many Unix
11628 Show the current setting of the range checker, and whether or not it is
11629 being set automatically by @value{GDBN}.
11632 @node Supported Languages
11633 @section Supported Languages
11635 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
11636 assembly, Modula-2, and Ada.
11637 @c This is false ...
11638 Some @value{GDBN} features may be used in expressions regardless of the
11639 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11640 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11641 ,Expressions}) can be used with the constructs of any supported
11644 The following sections detail to what degree each source language is
11645 supported by @value{GDBN}. These sections are not meant to be language
11646 tutorials or references, but serve only as a reference guide to what the
11647 @value{GDBN} expression parser accepts, and what input and output
11648 formats should look like for different languages. There are many good
11649 books written on each of these languages; please look to these for a
11650 language reference or tutorial.
11653 * C:: C and C@t{++}
11655 * Objective-C:: Objective-C
11656 * OpenCL C:: OpenCL C
11657 * Fortran:: Fortran
11659 * Modula-2:: Modula-2
11664 @subsection C and C@t{++}
11666 @cindex C and C@t{++}
11667 @cindex expressions in C or C@t{++}
11669 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11670 to both languages. Whenever this is the case, we discuss those languages
11674 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11675 @cindex @sc{gnu} C@t{++}
11676 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11677 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11678 effectively, you must compile your C@t{++} programs with a supported
11679 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11680 compiler (@code{aCC}).
11682 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11683 format; if it doesn't work on your system, try the stabs+ debugging
11684 format. You can select those formats explicitly with the @code{g++}
11685 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11686 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11687 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11690 * C Operators:: C and C@t{++} operators
11691 * C Constants:: C and C@t{++} constants
11692 * C Plus Plus Expressions:: C@t{++} expressions
11693 * C Defaults:: Default settings for C and C@t{++}
11694 * C Checks:: C and C@t{++} type and range checks
11695 * Debugging C:: @value{GDBN} and C
11696 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11697 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11701 @subsubsection C and C@t{++} Operators
11703 @cindex C and C@t{++} operators
11705 Operators must be defined on values of specific types. For instance,
11706 @code{+} is defined on numbers, but not on structures. Operators are
11707 often defined on groups of types.
11709 For the purposes of C and C@t{++}, the following definitions hold:
11714 @emph{Integral types} include @code{int} with any of its storage-class
11715 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11718 @emph{Floating-point types} include @code{float}, @code{double}, and
11719 @code{long double} (if supported by the target platform).
11722 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11725 @emph{Scalar types} include all of the above.
11730 The following operators are supported. They are listed here
11731 in order of increasing precedence:
11735 The comma or sequencing operator. Expressions in a comma-separated list
11736 are evaluated from left to right, with the result of the entire
11737 expression being the last expression evaluated.
11740 Assignment. The value of an assignment expression is the value
11741 assigned. Defined on scalar types.
11744 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11745 and translated to @w{@code{@var{a} = @var{a op b}}}.
11746 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11747 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11748 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11751 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11752 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11756 Logical @sc{or}. Defined on integral types.
11759 Logical @sc{and}. Defined on integral types.
11762 Bitwise @sc{or}. Defined on integral types.
11765 Bitwise exclusive-@sc{or}. Defined on integral types.
11768 Bitwise @sc{and}. Defined on integral types.
11771 Equality and inequality. Defined on scalar types. The value of these
11772 expressions is 0 for false and non-zero for true.
11774 @item <@r{, }>@r{, }<=@r{, }>=
11775 Less than, greater than, less than or equal, greater than or equal.
11776 Defined on scalar types. The value of these expressions is 0 for false
11777 and non-zero for true.
11780 left shift, and right shift. Defined on integral types.
11783 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11786 Addition and subtraction. Defined on integral types, floating-point types and
11789 @item *@r{, }/@r{, }%
11790 Multiplication, division, and modulus. Multiplication and division are
11791 defined on integral and floating-point types. Modulus is defined on
11795 Increment and decrement. When appearing before a variable, the
11796 operation is performed before the variable is used in an expression;
11797 when appearing after it, the variable's value is used before the
11798 operation takes place.
11801 Pointer dereferencing. Defined on pointer types. Same precedence as
11805 Address operator. Defined on variables. Same precedence as @code{++}.
11807 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11808 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11809 to examine the address
11810 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11814 Negative. Defined on integral and floating-point types. Same
11815 precedence as @code{++}.
11818 Logical negation. Defined on integral types. Same precedence as
11822 Bitwise complement operator. Defined on integral types. Same precedence as
11827 Structure member, and pointer-to-structure member. For convenience,
11828 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11829 pointer based on the stored type information.
11830 Defined on @code{struct} and @code{union} data.
11833 Dereferences of pointers to members.
11836 Array indexing. @code{@var{a}[@var{i}]} is defined as
11837 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11840 Function parameter list. Same precedence as @code{->}.
11843 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11844 and @code{class} types.
11847 Doubled colons also represent the @value{GDBN} scope operator
11848 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11852 If an operator is redefined in the user code, @value{GDBN} usually
11853 attempts to invoke the redefined version instead of using the operator's
11854 predefined meaning.
11857 @subsubsection C and C@t{++} Constants
11859 @cindex C and C@t{++} constants
11861 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11866 Integer constants are a sequence of digits. Octal constants are
11867 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11868 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11869 @samp{l}, specifying that the constant should be treated as a
11873 Floating point constants are a sequence of digits, followed by a decimal
11874 point, followed by a sequence of digits, and optionally followed by an
11875 exponent. An exponent is of the form:
11876 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11877 sequence of digits. The @samp{+} is optional for positive exponents.
11878 A floating-point constant may also end with a letter @samp{f} or
11879 @samp{F}, specifying that the constant should be treated as being of
11880 the @code{float} (as opposed to the default @code{double}) type; or with
11881 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11885 Enumerated constants consist of enumerated identifiers, or their
11886 integral equivalents.
11889 Character constants are a single character surrounded by single quotes
11890 (@code{'}), or a number---the ordinal value of the corresponding character
11891 (usually its @sc{ascii} value). Within quotes, the single character may
11892 be represented by a letter or by @dfn{escape sequences}, which are of
11893 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11894 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11895 @samp{@var{x}} is a predefined special character---for example,
11896 @samp{\n} for newline.
11899 String constants are a sequence of character constants surrounded by
11900 double quotes (@code{"}). Any valid character constant (as described
11901 above) may appear. Double quotes within the string must be preceded by
11902 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11906 Pointer constants are an integral value. You can also write pointers
11907 to constants using the C operator @samp{&}.
11910 Array constants are comma-separated lists surrounded by braces @samp{@{}
11911 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11912 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11913 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11916 @node C Plus Plus Expressions
11917 @subsubsection C@t{++} Expressions
11919 @cindex expressions in C@t{++}
11920 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11922 @cindex debugging C@t{++} programs
11923 @cindex C@t{++} compilers
11924 @cindex debug formats and C@t{++}
11925 @cindex @value{NGCC} and C@t{++}
11927 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11928 proper compiler and the proper debug format. Currently, @value{GDBN}
11929 works best when debugging C@t{++} code that is compiled with
11930 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11931 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11932 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11933 stabs+ as their default debug format, so you usually don't need to
11934 specify a debug format explicitly. Other compilers and/or debug formats
11935 are likely to work badly or not at all when using @value{GDBN} to debug
11941 @cindex member functions
11943 Member function calls are allowed; you can use expressions like
11946 count = aml->GetOriginal(x, y)
11949 @vindex this@r{, inside C@t{++} member functions}
11950 @cindex namespace in C@t{++}
11952 While a member function is active (in the selected stack frame), your
11953 expressions have the same namespace available as the member function;
11954 that is, @value{GDBN} allows implicit references to the class instance
11955 pointer @code{this} following the same rules as C@t{++}.
11957 @cindex call overloaded functions
11958 @cindex overloaded functions, calling
11959 @cindex type conversions in C@t{++}
11961 You can call overloaded functions; @value{GDBN} resolves the function
11962 call to the right definition, with some restrictions. @value{GDBN} does not
11963 perform overload resolution involving user-defined type conversions,
11964 calls to constructors, or instantiations of templates that do not exist
11965 in the program. It also cannot handle ellipsis argument lists or
11968 It does perform integral conversions and promotions, floating-point
11969 promotions, arithmetic conversions, pointer conversions, conversions of
11970 class objects to base classes, and standard conversions such as those of
11971 functions or arrays to pointers; it requires an exact match on the
11972 number of function arguments.
11974 Overload resolution is always performed, unless you have specified
11975 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11976 ,@value{GDBN} Features for C@t{++}}.
11978 You must specify @code{set overload-resolution off} in order to use an
11979 explicit function signature to call an overloaded function, as in
11981 p 'foo(char,int)'('x', 13)
11984 The @value{GDBN} command-completion facility can simplify this;
11985 see @ref{Completion, ,Command Completion}.
11987 @cindex reference declarations
11989 @value{GDBN} understands variables declared as C@t{++} references; you can use
11990 them in expressions just as you do in C@t{++} source---they are automatically
11993 In the parameter list shown when @value{GDBN} displays a frame, the values of
11994 reference variables are not displayed (unlike other variables); this
11995 avoids clutter, since references are often used for large structures.
11996 The @emph{address} of a reference variable is always shown, unless
11997 you have specified @samp{set print address off}.
12000 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12001 expressions can use it just as expressions in your program do. Since
12002 one scope may be defined in another, you can use @code{::} repeatedly if
12003 necessary, for example in an expression like
12004 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12005 resolving name scope by reference to source files, in both C and C@t{++}
12006 debugging (@pxref{Variables, ,Program Variables}).
12009 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
12010 calling virtual functions correctly, printing out virtual bases of
12011 objects, calling functions in a base subobject, casting objects, and
12012 invoking user-defined operators.
12015 @subsubsection C and C@t{++} Defaults
12017 @cindex C and C@t{++} defaults
12019 If you allow @value{GDBN} to set type and range checking automatically, they
12020 both default to @code{off} whenever the working language changes to
12021 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12022 selects the working language.
12024 If you allow @value{GDBN} to set the language automatically, it
12025 recognizes source files whose names end with @file{.c}, @file{.C}, or
12026 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12027 these files, it sets the working language to C or C@t{++}.
12028 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12029 for further details.
12031 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12032 @c unimplemented. If (b) changes, it might make sense to let this node
12033 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12036 @subsubsection C and C@t{++} Type and Range Checks
12038 @cindex C and C@t{++} checks
12040 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12041 is not used. However, if you turn type checking on, @value{GDBN}
12042 considers two variables type equivalent if:
12046 The two variables are structured and have the same structure, union, or
12050 The two variables have the same type name, or types that have been
12051 declared equivalent through @code{typedef}.
12054 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12057 The two @code{struct}, @code{union}, or @code{enum} variables are
12058 declared in the same declaration. (Note: this may not be true for all C
12063 Range checking, if turned on, is done on mathematical operations. Array
12064 indices are not checked, since they are often used to index a pointer
12065 that is not itself an array.
12068 @subsubsection @value{GDBN} and C
12070 The @code{set print union} and @code{show print union} commands apply to
12071 the @code{union} type. When set to @samp{on}, any @code{union} that is
12072 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12073 appears as @samp{@{...@}}.
12075 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12076 with pointers and a memory allocation function. @xref{Expressions,
12079 @node Debugging C Plus Plus
12080 @subsubsection @value{GDBN} Features for C@t{++}
12082 @cindex commands for C@t{++}
12084 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12085 designed specifically for use with C@t{++}. Here is a summary:
12088 @cindex break in overloaded functions
12089 @item @r{breakpoint menus}
12090 When you want a breakpoint in a function whose name is overloaded,
12091 @value{GDBN} has the capability to display a menu of possible breakpoint
12092 locations to help you specify which function definition you want.
12093 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12095 @cindex overloading in C@t{++}
12096 @item rbreak @var{regex}
12097 Setting breakpoints using regular expressions is helpful for setting
12098 breakpoints on overloaded functions that are not members of any special
12100 @xref{Set Breaks, ,Setting Breakpoints}.
12102 @cindex C@t{++} exception handling
12105 Debug C@t{++} exception handling using these commands. @xref{Set
12106 Catchpoints, , Setting Catchpoints}.
12108 @cindex inheritance
12109 @item ptype @var{typename}
12110 Print inheritance relationships as well as other information for type
12112 @xref{Symbols, ,Examining the Symbol Table}.
12114 @cindex C@t{++} symbol display
12115 @item set print demangle
12116 @itemx show print demangle
12117 @itemx set print asm-demangle
12118 @itemx show print asm-demangle
12119 Control whether C@t{++} symbols display in their source form, both when
12120 displaying code as C@t{++} source and when displaying disassemblies.
12121 @xref{Print Settings, ,Print Settings}.
12123 @item set print object
12124 @itemx show print object
12125 Choose whether to print derived (actual) or declared types of objects.
12126 @xref{Print Settings, ,Print Settings}.
12128 @item set print vtbl
12129 @itemx show print vtbl
12130 Control the format for printing virtual function tables.
12131 @xref{Print Settings, ,Print Settings}.
12132 (The @code{vtbl} commands do not work on programs compiled with the HP
12133 ANSI C@t{++} compiler (@code{aCC}).)
12135 @kindex set overload-resolution
12136 @cindex overloaded functions, overload resolution
12137 @item set overload-resolution on
12138 Enable overload resolution for C@t{++} expression evaluation. The default
12139 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12140 and searches for a function whose signature matches the argument types,
12141 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12142 Expressions, ,C@t{++} Expressions}, for details).
12143 If it cannot find a match, it emits a message.
12145 @item set overload-resolution off
12146 Disable overload resolution for C@t{++} expression evaluation. For
12147 overloaded functions that are not class member functions, @value{GDBN}
12148 chooses the first function of the specified name that it finds in the
12149 symbol table, whether or not its arguments are of the correct type. For
12150 overloaded functions that are class member functions, @value{GDBN}
12151 searches for a function whose signature @emph{exactly} matches the
12154 @kindex show overload-resolution
12155 @item show overload-resolution
12156 Show the current setting of overload resolution.
12158 @item @r{Overloaded symbol names}
12159 You can specify a particular definition of an overloaded symbol, using
12160 the same notation that is used to declare such symbols in C@t{++}: type
12161 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12162 also use the @value{GDBN} command-line word completion facilities to list the
12163 available choices, or to finish the type list for you.
12164 @xref{Completion,, Command Completion}, for details on how to do this.
12167 @node Decimal Floating Point
12168 @subsubsection Decimal Floating Point format
12169 @cindex decimal floating point format
12171 @value{GDBN} can examine, set and perform computations with numbers in
12172 decimal floating point format, which in the C language correspond to the
12173 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12174 specified by the extension to support decimal floating-point arithmetic.
12176 There are two encodings in use, depending on the architecture: BID (Binary
12177 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12178 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12181 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12182 to manipulate decimal floating point numbers, it is not possible to convert
12183 (using a cast, for example) integers wider than 32-bit to decimal float.
12185 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12186 point computations, error checking in decimal float operations ignores
12187 underflow, overflow and divide by zero exceptions.
12189 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12190 to inspect @code{_Decimal128} values stored in floating point registers.
12191 See @ref{PowerPC,,PowerPC} for more details.
12197 @value{GDBN} can be used to debug programs written in D and compiled with
12198 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12199 specific feature --- dynamic arrays.
12202 @subsection Objective-C
12204 @cindex Objective-C
12205 This section provides information about some commands and command
12206 options that are useful for debugging Objective-C code. See also
12207 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12208 few more commands specific to Objective-C support.
12211 * Method Names in Commands::
12212 * The Print Command with Objective-C::
12215 @node Method Names in Commands
12216 @subsubsection Method Names in Commands
12218 The following commands have been extended to accept Objective-C method
12219 names as line specifications:
12221 @kindex clear@r{, and Objective-C}
12222 @kindex break@r{, and Objective-C}
12223 @kindex info line@r{, and Objective-C}
12224 @kindex jump@r{, and Objective-C}
12225 @kindex list@r{, and Objective-C}
12229 @item @code{info line}
12234 A fully qualified Objective-C method name is specified as
12237 -[@var{Class} @var{methodName}]
12240 where the minus sign is used to indicate an instance method and a
12241 plus sign (not shown) is used to indicate a class method. The class
12242 name @var{Class} and method name @var{methodName} are enclosed in
12243 brackets, similar to the way messages are specified in Objective-C
12244 source code. For example, to set a breakpoint at the @code{create}
12245 instance method of class @code{Fruit} in the program currently being
12249 break -[Fruit create]
12252 To list ten program lines around the @code{initialize} class method,
12256 list +[NSText initialize]
12259 In the current version of @value{GDBN}, the plus or minus sign is
12260 required. In future versions of @value{GDBN}, the plus or minus
12261 sign will be optional, but you can use it to narrow the search. It
12262 is also possible to specify just a method name:
12268 You must specify the complete method name, including any colons. If
12269 your program's source files contain more than one @code{create} method,
12270 you'll be presented with a numbered list of classes that implement that
12271 method. Indicate your choice by number, or type @samp{0} to exit if
12274 As another example, to clear a breakpoint established at the
12275 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12278 clear -[NSWindow makeKeyAndOrderFront:]
12281 @node The Print Command with Objective-C
12282 @subsubsection The Print Command With Objective-C
12283 @cindex Objective-C, print objects
12284 @kindex print-object
12285 @kindex po @r{(@code{print-object})}
12287 The print command has also been extended to accept methods. For example:
12290 print -[@var{object} hash]
12293 @cindex print an Objective-C object description
12294 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12296 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12297 and print the result. Also, an additional command has been added,
12298 @code{print-object} or @code{po} for short, which is meant to print
12299 the description of an object. However, this command may only work
12300 with certain Objective-C libraries that have a particular hook
12301 function, @code{_NSPrintForDebugger}, defined.
12304 @subsection OpenCL C
12307 This section provides information about @value{GDBN}s OpenCL C support.
12310 * OpenCL C Datatypes::
12311 * OpenCL C Expressions::
12312 * OpenCL C Operators::
12315 @node OpenCL C Datatypes
12316 @subsubsection OpenCL C Datatypes
12318 @cindex OpenCL C Datatypes
12319 @value{GDBN} supports the builtin scalar and vector datatypes specified
12320 by OpenCL 1.1. In addition the half- and double-precision floating point
12321 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12322 extensions are also known to @value{GDBN}.
12324 @node OpenCL C Expressions
12325 @subsubsection OpenCL C Expressions
12327 @cindex OpenCL C Expressions
12328 @value{GDBN} supports accesses to vector components including the access as
12329 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12330 supported by @value{GDBN} can be used as well.
12332 @node OpenCL C Operators
12333 @subsubsection OpenCL C Operators
12335 @cindex OpenCL C Operators
12336 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12340 @subsection Fortran
12341 @cindex Fortran-specific support in @value{GDBN}
12343 @value{GDBN} can be used to debug programs written in Fortran, but it
12344 currently supports only the features of Fortran 77 language.
12346 @cindex trailing underscore, in Fortran symbols
12347 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12348 among them) append an underscore to the names of variables and
12349 functions. When you debug programs compiled by those compilers, you
12350 will need to refer to variables and functions with a trailing
12354 * Fortran Operators:: Fortran operators and expressions
12355 * Fortran Defaults:: Default settings for Fortran
12356 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12359 @node Fortran Operators
12360 @subsubsection Fortran Operators and Expressions
12362 @cindex Fortran operators and expressions
12364 Operators must be defined on values of specific types. For instance,
12365 @code{+} is defined on numbers, but not on characters or other non-
12366 arithmetic types. Operators are often defined on groups of types.
12370 The exponentiation operator. It raises the first operand to the power
12374 The range operator. Normally used in the form of array(low:high) to
12375 represent a section of array.
12378 The access component operator. Normally used to access elements in derived
12379 types. Also suitable for unions. As unions aren't part of regular Fortran,
12380 this can only happen when accessing a register that uses a gdbarch-defined
12384 @node Fortran Defaults
12385 @subsubsection Fortran Defaults
12387 @cindex Fortran Defaults
12389 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12390 default uses case-insensitive matches for Fortran symbols. You can
12391 change that with the @samp{set case-insensitive} command, see
12392 @ref{Symbols}, for the details.
12394 @node Special Fortran Commands
12395 @subsubsection Special Fortran Commands
12397 @cindex Special Fortran commands
12399 @value{GDBN} has some commands to support Fortran-specific features,
12400 such as displaying common blocks.
12403 @cindex @code{COMMON} blocks, Fortran
12404 @kindex info common
12405 @item info common @r{[}@var{common-name}@r{]}
12406 This command prints the values contained in the Fortran @code{COMMON}
12407 block whose name is @var{common-name}. With no argument, the names of
12408 all @code{COMMON} blocks visible at the current program location are
12415 @cindex Pascal support in @value{GDBN}, limitations
12416 Debugging Pascal programs which use sets, subranges, file variables, or
12417 nested functions does not currently work. @value{GDBN} does not support
12418 entering expressions, printing values, or similar features using Pascal
12421 The Pascal-specific command @code{set print pascal_static-members}
12422 controls whether static members of Pascal objects are displayed.
12423 @xref{Print Settings, pascal_static-members}.
12426 @subsection Modula-2
12428 @cindex Modula-2, @value{GDBN} support
12430 The extensions made to @value{GDBN} to support Modula-2 only support
12431 output from the @sc{gnu} Modula-2 compiler (which is currently being
12432 developed). Other Modula-2 compilers are not currently supported, and
12433 attempting to debug executables produced by them is most likely
12434 to give an error as @value{GDBN} reads in the executable's symbol
12437 @cindex expressions in Modula-2
12439 * M2 Operators:: Built-in operators
12440 * Built-In Func/Proc:: Built-in functions and procedures
12441 * M2 Constants:: Modula-2 constants
12442 * M2 Types:: Modula-2 types
12443 * M2 Defaults:: Default settings for Modula-2
12444 * Deviations:: Deviations from standard Modula-2
12445 * M2 Checks:: Modula-2 type and range checks
12446 * M2 Scope:: The scope operators @code{::} and @code{.}
12447 * GDB/M2:: @value{GDBN} and Modula-2
12451 @subsubsection Operators
12452 @cindex Modula-2 operators
12454 Operators must be defined on values of specific types. For instance,
12455 @code{+} is defined on numbers, but not on structures. Operators are
12456 often defined on groups of types. For the purposes of Modula-2, the
12457 following definitions hold:
12462 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12466 @emph{Character types} consist of @code{CHAR} and its subranges.
12469 @emph{Floating-point types} consist of @code{REAL}.
12472 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12476 @emph{Scalar types} consist of all of the above.
12479 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12482 @emph{Boolean types} consist of @code{BOOLEAN}.
12486 The following operators are supported, and appear in order of
12487 increasing precedence:
12491 Function argument or array index separator.
12494 Assignment. The value of @var{var} @code{:=} @var{value} is
12498 Less than, greater than on integral, floating-point, or enumerated
12502 Less than or equal to, greater than or equal to
12503 on integral, floating-point and enumerated types, or set inclusion on
12504 set types. Same precedence as @code{<}.
12506 @item =@r{, }<>@r{, }#
12507 Equality and two ways of expressing inequality, valid on scalar types.
12508 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
12509 available for inequality, since @code{#} conflicts with the script
12513 Set membership. Defined on set types and the types of their members.
12514 Same precedence as @code{<}.
12517 Boolean disjunction. Defined on boolean types.
12520 Boolean conjunction. Defined on boolean types.
12523 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12526 Addition and subtraction on integral and floating-point types, or union
12527 and difference on set types.
12530 Multiplication on integral and floating-point types, or set intersection
12534 Division on floating-point types, or symmetric set difference on set
12535 types. Same precedence as @code{*}.
12538 Integer division and remainder. Defined on integral types. Same
12539 precedence as @code{*}.
12542 Negative. Defined on @code{INTEGER} and @code{REAL} data.
12545 Pointer dereferencing. Defined on pointer types.
12548 Boolean negation. Defined on boolean types. Same precedence as
12552 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
12553 precedence as @code{^}.
12556 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
12559 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
12563 @value{GDBN} and Modula-2 scope operators.
12567 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
12568 treats the use of the operator @code{IN}, or the use of operators
12569 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
12570 @code{<=}, and @code{>=} on sets as an error.
12574 @node Built-In Func/Proc
12575 @subsubsection Built-in Functions and Procedures
12576 @cindex Modula-2 built-ins
12578 Modula-2 also makes available several built-in procedures and functions.
12579 In describing these, the following metavariables are used:
12584 represents an @code{ARRAY} variable.
12587 represents a @code{CHAR} constant or variable.
12590 represents a variable or constant of integral type.
12593 represents an identifier that belongs to a set. Generally used in the
12594 same function with the metavariable @var{s}. The type of @var{s} should
12595 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12598 represents a variable or constant of integral or floating-point type.
12601 represents a variable or constant of floating-point type.
12607 represents a variable.
12610 represents a variable or constant of one of many types. See the
12611 explanation of the function for details.
12614 All Modula-2 built-in procedures also return a result, described below.
12618 Returns the absolute value of @var{n}.
12621 If @var{c} is a lower case letter, it returns its upper case
12622 equivalent, otherwise it returns its argument.
12625 Returns the character whose ordinal value is @var{i}.
12628 Decrements the value in the variable @var{v} by one. Returns the new value.
12630 @item DEC(@var{v},@var{i})
12631 Decrements the value in the variable @var{v} by @var{i}. Returns the
12634 @item EXCL(@var{m},@var{s})
12635 Removes the element @var{m} from the set @var{s}. Returns the new
12638 @item FLOAT(@var{i})
12639 Returns the floating point equivalent of the integer @var{i}.
12641 @item HIGH(@var{a})
12642 Returns the index of the last member of @var{a}.
12645 Increments the value in the variable @var{v} by one. Returns the new value.
12647 @item INC(@var{v},@var{i})
12648 Increments the value in the variable @var{v} by @var{i}. Returns the
12651 @item INCL(@var{m},@var{s})
12652 Adds the element @var{m} to the set @var{s} if it is not already
12653 there. Returns the new set.
12656 Returns the maximum value of the type @var{t}.
12659 Returns the minimum value of the type @var{t}.
12662 Returns boolean TRUE if @var{i} is an odd number.
12665 Returns the ordinal value of its argument. For example, the ordinal
12666 value of a character is its @sc{ascii} value (on machines supporting the
12667 @sc{ascii} character set). @var{x} must be of an ordered type, which include
12668 integral, character and enumerated types.
12670 @item SIZE(@var{x})
12671 Returns the size of its argument. @var{x} can be a variable or a type.
12673 @item TRUNC(@var{r})
12674 Returns the integral part of @var{r}.
12676 @item TSIZE(@var{x})
12677 Returns the size of its argument. @var{x} can be a variable or a type.
12679 @item VAL(@var{t},@var{i})
12680 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12684 @emph{Warning:} Sets and their operations are not yet supported, so
12685 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12689 @cindex Modula-2 constants
12691 @subsubsection Constants
12693 @value{GDBN} allows you to express the constants of Modula-2 in the following
12699 Integer constants are simply a sequence of digits. When used in an
12700 expression, a constant is interpreted to be type-compatible with the
12701 rest of the expression. Hexadecimal integers are specified by a
12702 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12705 Floating point constants appear as a sequence of digits, followed by a
12706 decimal point and another sequence of digits. An optional exponent can
12707 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12708 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12709 digits of the floating point constant must be valid decimal (base 10)
12713 Character constants consist of a single character enclosed by a pair of
12714 like quotes, either single (@code{'}) or double (@code{"}). They may
12715 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12716 followed by a @samp{C}.
12719 String constants consist of a sequence of characters enclosed by a
12720 pair of like quotes, either single (@code{'}) or double (@code{"}).
12721 Escape sequences in the style of C are also allowed. @xref{C
12722 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12726 Enumerated constants consist of an enumerated identifier.
12729 Boolean constants consist of the identifiers @code{TRUE} and
12733 Pointer constants consist of integral values only.
12736 Set constants are not yet supported.
12740 @subsubsection Modula-2 Types
12741 @cindex Modula-2 types
12743 Currently @value{GDBN} can print the following data types in Modula-2
12744 syntax: array types, record types, set types, pointer types, procedure
12745 types, enumerated types, subrange types and base types. You can also
12746 print the contents of variables declared using these type.
12747 This section gives a number of simple source code examples together with
12748 sample @value{GDBN} sessions.
12750 The first example contains the following section of code:
12759 and you can request @value{GDBN} to interrogate the type and value of
12760 @code{r} and @code{s}.
12763 (@value{GDBP}) print s
12765 (@value{GDBP}) ptype s
12767 (@value{GDBP}) print r
12769 (@value{GDBP}) ptype r
12774 Likewise if your source code declares @code{s} as:
12778 s: SET ['A'..'Z'] ;
12782 then you may query the type of @code{s} by:
12785 (@value{GDBP}) ptype s
12786 type = SET ['A'..'Z']
12790 Note that at present you cannot interactively manipulate set
12791 expressions using the debugger.
12793 The following example shows how you might declare an array in Modula-2
12794 and how you can interact with @value{GDBN} to print its type and contents:
12798 s: ARRAY [-10..10] OF CHAR ;
12802 (@value{GDBP}) ptype s
12803 ARRAY [-10..10] OF CHAR
12806 Note that the array handling is not yet complete and although the type
12807 is printed correctly, expression handling still assumes that all
12808 arrays have a lower bound of zero and not @code{-10} as in the example
12811 Here are some more type related Modula-2 examples:
12815 colour = (blue, red, yellow, green) ;
12816 t = [blue..yellow] ;
12824 The @value{GDBN} interaction shows how you can query the data type
12825 and value of a variable.
12828 (@value{GDBP}) print s
12830 (@value{GDBP}) ptype t
12831 type = [blue..yellow]
12835 In this example a Modula-2 array is declared and its contents
12836 displayed. Observe that the contents are written in the same way as
12837 their @code{C} counterparts.
12841 s: ARRAY [1..5] OF CARDINAL ;
12847 (@value{GDBP}) print s
12848 $1 = @{1, 0, 0, 0, 0@}
12849 (@value{GDBP}) ptype s
12850 type = ARRAY [1..5] OF CARDINAL
12853 The Modula-2 language interface to @value{GDBN} also understands
12854 pointer types as shown in this example:
12858 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12865 and you can request that @value{GDBN} describes the type of @code{s}.
12868 (@value{GDBP}) ptype s
12869 type = POINTER TO ARRAY [1..5] OF CARDINAL
12872 @value{GDBN} handles compound types as we can see in this example.
12873 Here we combine array types, record types, pointer types and subrange
12884 myarray = ARRAY myrange OF CARDINAL ;
12885 myrange = [-2..2] ;
12887 s: POINTER TO ARRAY myrange OF foo ;
12891 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12895 (@value{GDBP}) ptype s
12896 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12899 f3 : ARRAY [-2..2] OF CARDINAL;
12904 @subsubsection Modula-2 Defaults
12905 @cindex Modula-2 defaults
12907 If type and range checking are set automatically by @value{GDBN}, they
12908 both default to @code{on} whenever the working language changes to
12909 Modula-2. This happens regardless of whether you or @value{GDBN}
12910 selected the working language.
12912 If you allow @value{GDBN} to set the language automatically, then entering
12913 code compiled from a file whose name ends with @file{.mod} sets the
12914 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12915 Infer the Source Language}, for further details.
12918 @subsubsection Deviations from Standard Modula-2
12919 @cindex Modula-2, deviations from
12921 A few changes have been made to make Modula-2 programs easier to debug.
12922 This is done primarily via loosening its type strictness:
12926 Unlike in standard Modula-2, pointer constants can be formed by
12927 integers. This allows you to modify pointer variables during
12928 debugging. (In standard Modula-2, the actual address contained in a
12929 pointer variable is hidden from you; it can only be modified
12930 through direct assignment to another pointer variable or expression that
12931 returned a pointer.)
12934 C escape sequences can be used in strings and characters to represent
12935 non-printable characters. @value{GDBN} prints out strings with these
12936 escape sequences embedded. Single non-printable characters are
12937 printed using the @samp{CHR(@var{nnn})} format.
12940 The assignment operator (@code{:=}) returns the value of its right-hand
12944 All built-in procedures both modify @emph{and} return their argument.
12948 @subsubsection Modula-2 Type and Range Checks
12949 @cindex Modula-2 checks
12952 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12955 @c FIXME remove warning when type/range checks added
12957 @value{GDBN} considers two Modula-2 variables type equivalent if:
12961 They are of types that have been declared equivalent via a @code{TYPE
12962 @var{t1} = @var{t2}} statement
12965 They have been declared on the same line. (Note: This is true of the
12966 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
12969 As long as type checking is enabled, any attempt to combine variables
12970 whose types are not equivalent is an error.
12972 Range checking is done on all mathematical operations, assignment, array
12973 index bounds, and all built-in functions and procedures.
12976 @subsubsection The Scope Operators @code{::} and @code{.}
12978 @cindex @code{.}, Modula-2 scope operator
12979 @cindex colon, doubled as scope operator
12981 @vindex colon-colon@r{, in Modula-2}
12982 @c Info cannot handle :: but TeX can.
12985 @vindex ::@r{, in Modula-2}
12988 There are a few subtle differences between the Modula-2 scope operator
12989 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
12994 @var{module} . @var{id}
12995 @var{scope} :: @var{id}
12999 where @var{scope} is the name of a module or a procedure,
13000 @var{module} the name of a module, and @var{id} is any declared
13001 identifier within your program, except another module.
13003 Using the @code{::} operator makes @value{GDBN} search the scope
13004 specified by @var{scope} for the identifier @var{id}. If it is not
13005 found in the specified scope, then @value{GDBN} searches all scopes
13006 enclosing the one specified by @var{scope}.
13008 Using the @code{.} operator makes @value{GDBN} search the current scope for
13009 the identifier specified by @var{id} that was imported from the
13010 definition module specified by @var{module}. With this operator, it is
13011 an error if the identifier @var{id} was not imported from definition
13012 module @var{module}, or if @var{id} is not an identifier in
13016 @subsubsection @value{GDBN} and Modula-2
13018 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13019 Five subcommands of @code{set print} and @code{show print} apply
13020 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13021 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13022 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13023 analogue in Modula-2.
13025 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13026 with any language, is not useful with Modula-2. Its
13027 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13028 created in Modula-2 as they can in C or C@t{++}. However, because an
13029 address can be specified by an integral constant, the construct
13030 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13032 @cindex @code{#} in Modula-2
13033 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13034 interpreted as the beginning of a comment. Use @code{<>} instead.
13040 The extensions made to @value{GDBN} for Ada only support
13041 output from the @sc{gnu} Ada (GNAT) compiler.
13042 Other Ada compilers are not currently supported, and
13043 attempting to debug executables produced by them is most likely
13047 @cindex expressions in Ada
13049 * Ada Mode Intro:: General remarks on the Ada syntax
13050 and semantics supported by Ada mode
13052 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13053 * Additions to Ada:: Extensions of the Ada expression syntax.
13054 * Stopping Before Main Program:: Debugging the program during elaboration.
13055 * Ada Tasks:: Listing and setting breakpoints in tasks.
13056 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13057 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13059 * Ada Glitches:: Known peculiarities of Ada mode.
13062 @node Ada Mode Intro
13063 @subsubsection Introduction
13064 @cindex Ada mode, general
13066 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13067 syntax, with some extensions.
13068 The philosophy behind the design of this subset is
13072 That @value{GDBN} should provide basic literals and access to operations for
13073 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13074 leaving more sophisticated computations to subprograms written into the
13075 program (which therefore may be called from @value{GDBN}).
13078 That type safety and strict adherence to Ada language restrictions
13079 are not particularly important to the @value{GDBN} user.
13082 That brevity is important to the @value{GDBN} user.
13085 Thus, for brevity, the debugger acts as if all names declared in
13086 user-written packages are directly visible, even if they are not visible
13087 according to Ada rules, thus making it unnecessary to fully qualify most
13088 names with their packages, regardless of context. Where this causes
13089 ambiguity, @value{GDBN} asks the user's intent.
13091 The debugger will start in Ada mode if it detects an Ada main program.
13092 As for other languages, it will enter Ada mode when stopped in a program that
13093 was translated from an Ada source file.
13095 While in Ada mode, you may use `@t{--}' for comments. This is useful
13096 mostly for documenting command files. The standard @value{GDBN} comment
13097 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13098 middle (to allow based literals).
13100 The debugger supports limited overloading. Given a subprogram call in which
13101 the function symbol has multiple definitions, it will use the number of
13102 actual parameters and some information about their types to attempt to narrow
13103 the set of definitions. It also makes very limited use of context, preferring
13104 procedures to functions in the context of the @code{call} command, and
13105 functions to procedures elsewhere.
13107 @node Omissions from Ada
13108 @subsubsection Omissions from Ada
13109 @cindex Ada, omissions from
13111 Here are the notable omissions from the subset:
13115 Only a subset of the attributes are supported:
13119 @t{'First}, @t{'Last}, and @t{'Length}
13120 on array objects (not on types and subtypes).
13123 @t{'Min} and @t{'Max}.
13126 @t{'Pos} and @t{'Val}.
13132 @t{'Range} on array objects (not subtypes), but only as the right
13133 operand of the membership (@code{in}) operator.
13136 @t{'Access}, @t{'Unchecked_Access}, and
13137 @t{'Unrestricted_Access} (a GNAT extension).
13145 @code{Characters.Latin_1} are not available and
13146 concatenation is not implemented. Thus, escape characters in strings are
13147 not currently available.
13150 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13151 equality of representations. They will generally work correctly
13152 for strings and arrays whose elements have integer or enumeration types.
13153 They may not work correctly for arrays whose element
13154 types have user-defined equality, for arrays of real values
13155 (in particular, IEEE-conformant floating point, because of negative
13156 zeroes and NaNs), and for arrays whose elements contain unused bits with
13157 indeterminate values.
13160 The other component-by-component array operations (@code{and}, @code{or},
13161 @code{xor}, @code{not}, and relational tests other than equality)
13162 are not implemented.
13165 @cindex array aggregates (Ada)
13166 @cindex record aggregates (Ada)
13167 @cindex aggregates (Ada)
13168 There is limited support for array and record aggregates. They are
13169 permitted only on the right sides of assignments, as in these examples:
13172 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13173 (@value{GDBP}) set An_Array := (1, others => 0)
13174 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13175 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13176 (@value{GDBP}) set A_Record := (1, "Peter", True);
13177 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13181 discriminant's value by assigning an aggregate has an
13182 undefined effect if that discriminant is used within the record.
13183 However, you can first modify discriminants by directly assigning to
13184 them (which normally would not be allowed in Ada), and then performing an
13185 aggregate assignment. For example, given a variable @code{A_Rec}
13186 declared to have a type such as:
13189 type Rec (Len : Small_Integer := 0) is record
13191 Vals : IntArray (1 .. Len);
13195 you can assign a value with a different size of @code{Vals} with two
13199 (@value{GDBP}) set A_Rec.Len := 4
13200 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13203 As this example also illustrates, @value{GDBN} is very loose about the usual
13204 rules concerning aggregates. You may leave out some of the
13205 components of an array or record aggregate (such as the @code{Len}
13206 component in the assignment to @code{A_Rec} above); they will retain their
13207 original values upon assignment. You may freely use dynamic values as
13208 indices in component associations. You may even use overlapping or
13209 redundant component associations, although which component values are
13210 assigned in such cases is not defined.
13213 Calls to dispatching subprograms are not implemented.
13216 The overloading algorithm is much more limited (i.e., less selective)
13217 than that of real Ada. It makes only limited use of the context in
13218 which a subexpression appears to resolve its meaning, and it is much
13219 looser in its rules for allowing type matches. As a result, some
13220 function calls will be ambiguous, and the user will be asked to choose
13221 the proper resolution.
13224 The @code{new} operator is not implemented.
13227 Entry calls are not implemented.
13230 Aside from printing, arithmetic operations on the native VAX floating-point
13231 formats are not supported.
13234 It is not possible to slice a packed array.
13237 The names @code{True} and @code{False}, when not part of a qualified name,
13238 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13240 Should your program
13241 redefine these names in a package or procedure (at best a dubious practice),
13242 you will have to use fully qualified names to access their new definitions.
13245 @node Additions to Ada
13246 @subsubsection Additions to Ada
13247 @cindex Ada, deviations from
13249 As it does for other languages, @value{GDBN} makes certain generic
13250 extensions to Ada (@pxref{Expressions}):
13254 If the expression @var{E} is a variable residing in memory (typically
13255 a local variable or array element) and @var{N} is a positive integer,
13256 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13257 @var{N}-1 adjacent variables following it in memory as an array. In
13258 Ada, this operator is generally not necessary, since its prime use is
13259 in displaying parts of an array, and slicing will usually do this in
13260 Ada. However, there are occasional uses when debugging programs in
13261 which certain debugging information has been optimized away.
13264 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13265 appears in function or file @var{B}.'' When @var{B} is a file name,
13266 you must typically surround it in single quotes.
13269 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13270 @var{type} that appears at address @var{addr}.''
13273 A name starting with @samp{$} is a convenience variable
13274 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13277 In addition, @value{GDBN} provides a few other shortcuts and outright
13278 additions specific to Ada:
13282 The assignment statement is allowed as an expression, returning
13283 its right-hand operand as its value. Thus, you may enter
13286 (@value{GDBP}) set x := y + 3
13287 (@value{GDBP}) print A(tmp := y + 1)
13291 The semicolon is allowed as an ``operator,'' returning as its value
13292 the value of its right-hand operand.
13293 This allows, for example,
13294 complex conditional breaks:
13297 (@value{GDBP}) break f
13298 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13302 Rather than use catenation and symbolic character names to introduce special
13303 characters into strings, one may instead use a special bracket notation,
13304 which is also used to print strings. A sequence of characters of the form
13305 @samp{["@var{XX}"]} within a string or character literal denotes the
13306 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13307 sequence of characters @samp{["""]} also denotes a single quotation mark
13308 in strings. For example,
13310 "One line.["0a"]Next line.["0a"]"
13313 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13317 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13318 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13322 (@value{GDBP}) print 'max(x, y)
13326 When printing arrays, @value{GDBN} uses positional notation when the
13327 array has a lower bound of 1, and uses a modified named notation otherwise.
13328 For example, a one-dimensional array of three integers with a lower bound
13329 of 3 might print as
13336 That is, in contrast to valid Ada, only the first component has a @code{=>}
13340 You may abbreviate attributes in expressions with any unique,
13341 multi-character subsequence of
13342 their names (an exact match gets preference).
13343 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13344 in place of @t{a'length}.
13347 @cindex quoting Ada internal identifiers
13348 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13349 to lower case. The GNAT compiler uses upper-case characters for
13350 some of its internal identifiers, which are normally of no interest to users.
13351 For the rare occasions when you actually have to look at them,
13352 enclose them in angle brackets to avoid the lower-case mapping.
13355 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13359 Printing an object of class-wide type or dereferencing an
13360 access-to-class-wide value will display all the components of the object's
13361 specific type (as indicated by its run-time tag). Likewise, component
13362 selection on such a value will operate on the specific type of the
13367 @node Stopping Before Main Program
13368 @subsubsection Stopping at the Very Beginning
13370 @cindex breakpointing Ada elaboration code
13371 It is sometimes necessary to debug the program during elaboration, and
13372 before reaching the main procedure.
13373 As defined in the Ada Reference
13374 Manual, the elaboration code is invoked from a procedure called
13375 @code{adainit}. To run your program up to the beginning of
13376 elaboration, simply use the following two commands:
13377 @code{tbreak adainit} and @code{run}.
13380 @subsubsection Extensions for Ada Tasks
13381 @cindex Ada, tasking
13383 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13384 @value{GDBN} provides the following task-related commands:
13389 This command shows a list of current Ada tasks, as in the following example:
13396 (@value{GDBP}) info tasks
13397 ID TID P-ID Pri State Name
13398 1 8088000 0 15 Child Activation Wait main_task
13399 2 80a4000 1 15 Accept Statement b
13400 3 809a800 1 15 Child Activation Wait a
13401 * 4 80ae800 3 15 Runnable c
13406 In this listing, the asterisk before the last task indicates it to be the
13407 task currently being inspected.
13411 Represents @value{GDBN}'s internal task number.
13417 The parent's task ID (@value{GDBN}'s internal task number).
13420 The base priority of the task.
13423 Current state of the task.
13427 The task has been created but has not been activated. It cannot be
13431 The task is not blocked for any reason known to Ada. (It may be waiting
13432 for a mutex, though.) It is conceptually "executing" in normal mode.
13435 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13436 that were waiting on terminate alternatives have been awakened and have
13437 terminated themselves.
13439 @item Child Activation Wait
13440 The task is waiting for created tasks to complete activation.
13442 @item Accept Statement
13443 The task is waiting on an accept or selective wait statement.
13445 @item Waiting on entry call
13446 The task is waiting on an entry call.
13448 @item Async Select Wait
13449 The task is waiting to start the abortable part of an asynchronous
13453 The task is waiting on a select statement with only a delay
13456 @item Child Termination Wait
13457 The task is sleeping having completed a master within itself, and is
13458 waiting for the tasks dependent on that master to become terminated or
13459 waiting on a terminate Phase.
13461 @item Wait Child in Term Alt
13462 The task is sleeping waiting for tasks on terminate alternatives to
13463 finish terminating.
13465 @item Accepting RV with @var{taskno}
13466 The task is accepting a rendez-vous with the task @var{taskno}.
13470 Name of the task in the program.
13474 @kindex info task @var{taskno}
13475 @item info task @var{taskno}
13476 This command shows detailled informations on the specified task, as in
13477 the following example:
13482 (@value{GDBP}) info tasks
13483 ID TID P-ID Pri State Name
13484 1 8077880 0 15 Child Activation Wait main_task
13485 * 2 807c468 1 15 Runnable task_1
13486 (@value{GDBP}) info task 2
13487 Ada Task: 0x807c468
13490 Parent: 1 (main_task)
13496 @kindex task@r{ (Ada)}
13497 @cindex current Ada task ID
13498 This command prints the ID of the current task.
13504 (@value{GDBP}) info tasks
13505 ID TID P-ID Pri State Name
13506 1 8077870 0 15 Child Activation Wait main_task
13507 * 2 807c458 1 15 Runnable t
13508 (@value{GDBP}) task
13509 [Current task is 2]
13512 @item task @var{taskno}
13513 @cindex Ada task switching
13514 This command is like the @code{thread @var{threadno}}
13515 command (@pxref{Threads}). It switches the context of debugging
13516 from the current task to the given task.
13522 (@value{GDBP}) info tasks
13523 ID TID P-ID Pri State Name
13524 1 8077870 0 15 Child Activation Wait main_task
13525 * 2 807c458 1 15 Runnable t
13526 (@value{GDBP}) task 1
13527 [Switching to task 1]
13528 #0 0x8067726 in pthread_cond_wait ()
13530 #0 0x8067726 in pthread_cond_wait ()
13531 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
13532 #2 0x805cb63 in system.task_primitives.operations.sleep ()
13533 #3 0x806153e in system.tasking.stages.activate_tasks ()
13534 #4 0x804aacc in un () at un.adb:5
13537 @item break @var{linespec} task @var{taskno}
13538 @itemx break @var{linespec} task @var{taskno} if @dots{}
13539 @cindex breakpoints and tasks, in Ada
13540 @cindex task breakpoints, in Ada
13541 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
13542 These commands are like the @code{break @dots{} thread @dots{}}
13543 command (@pxref{Thread Stops}).
13544 @var{linespec} specifies source lines, as described
13545 in @ref{Specify Location}.
13547 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
13548 to specify that you only want @value{GDBN} to stop the program when a
13549 particular Ada task reaches this breakpoint. @var{taskno} is one of the
13550 numeric task identifiers assigned by @value{GDBN}, shown in the first
13551 column of the @samp{info tasks} display.
13553 If you do not specify @samp{task @var{taskno}} when you set a
13554 breakpoint, the breakpoint applies to @emph{all} tasks of your
13557 You can use the @code{task} qualifier on conditional breakpoints as
13558 well; in this case, place @samp{task @var{taskno}} before the
13559 breakpoint condition (before the @code{if}).
13567 (@value{GDBP}) info tasks
13568 ID TID P-ID Pri State Name
13569 1 140022020 0 15 Child Activation Wait main_task
13570 2 140045060 1 15 Accept/Select Wait t2
13571 3 140044840 1 15 Runnable t1
13572 * 4 140056040 1 15 Runnable t3
13573 (@value{GDBP}) b 15 task 2
13574 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
13575 (@value{GDBP}) cont
13580 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13582 (@value{GDBP}) info tasks
13583 ID TID P-ID Pri State Name
13584 1 140022020 0 15 Child Activation Wait main_task
13585 * 2 140045060 1 15 Runnable t2
13586 3 140044840 1 15 Runnable t1
13587 4 140056040 1 15 Delay Sleep t3
13591 @node Ada Tasks and Core Files
13592 @subsubsection Tasking Support when Debugging Core Files
13593 @cindex Ada tasking and core file debugging
13595 When inspecting a core file, as opposed to debugging a live program,
13596 tasking support may be limited or even unavailable, depending on
13597 the platform being used.
13598 For instance, on x86-linux, the list of tasks is available, but task
13599 switching is not supported. On Tru64, however, task switching will work
13602 On certain platforms, including Tru64, the debugger needs to perform some
13603 memory writes in order to provide Ada tasking support. When inspecting
13604 a core file, this means that the core file must be opened with read-write
13605 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13606 Under these circumstances, you should make a backup copy of the core
13607 file before inspecting it with @value{GDBN}.
13609 @node Ravenscar Profile
13610 @subsubsection Tasking Support when using the Ravenscar Profile
13611 @cindex Ravenscar Profile
13613 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
13614 specifically designed for systems with safety-critical real-time
13618 @kindex set ravenscar task-switching on
13619 @cindex task switching with program using Ravenscar Profile
13620 @item set ravenscar task-switching on
13621 Allows task switching when debugging a program that uses the Ravenscar
13622 Profile. This is the default.
13624 @kindex set ravenscar task-switching off
13625 @item set ravenscar task-switching off
13626 Turn off task switching when debugging a program that uses the Ravenscar
13627 Profile. This is mostly intended to disable the code that adds support
13628 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
13629 the Ravenscar runtime is preventing @value{GDBN} from working properly.
13630 To be effective, this command should be run before the program is started.
13632 @kindex show ravenscar task-switching
13633 @item show ravenscar task-switching
13634 Show whether it is possible to switch from task to task in a program
13635 using the Ravenscar Profile.
13640 @subsubsection Known Peculiarities of Ada Mode
13641 @cindex Ada, problems
13643 Besides the omissions listed previously (@pxref{Omissions from Ada}),
13644 we know of several problems with and limitations of Ada mode in
13646 some of which will be fixed with planned future releases of the debugger
13647 and the GNU Ada compiler.
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
15601 The data directory may also be specified with the
15602 @code{--data-directory} command line option.
15603 @xref{Mode Options}.
15606 @chapter Specifying a Debugging Target
15608 @cindex debugging target
15609 A @dfn{target} is the execution environment occupied by your program.
15611 Often, @value{GDBN} runs in the same host environment as your program;
15612 in that case, the debugging target is specified as a side effect when
15613 you use the @code{file} or @code{core} commands. When you need more
15614 flexibility---for example, running @value{GDBN} on a physically separate
15615 host, or controlling a standalone system over a serial port or a
15616 realtime system over a TCP/IP connection---you can use the @code{target}
15617 command to specify one of the target types configured for @value{GDBN}
15618 (@pxref{Target Commands, ,Commands for Managing Targets}).
15620 @cindex target architecture
15621 It is possible to build @value{GDBN} for several different @dfn{target
15622 architectures}. When @value{GDBN} is built like that, you can choose
15623 one of the available architectures with the @kbd{set architecture}
15627 @kindex set architecture
15628 @kindex show architecture
15629 @item set architecture @var{arch}
15630 This command sets the current target architecture to @var{arch}. The
15631 value of @var{arch} can be @code{"auto"}, in addition to one of the
15632 supported architectures.
15634 @item show architecture
15635 Show the current target architecture.
15637 @item set processor
15639 @kindex set processor
15640 @kindex show processor
15641 These are alias commands for, respectively, @code{set architecture}
15642 and @code{show architecture}.
15646 * Active Targets:: Active targets
15647 * Target Commands:: Commands for managing targets
15648 * Byte Order:: Choosing target byte order
15651 @node Active Targets
15652 @section Active Targets
15654 @cindex stacking targets
15655 @cindex active targets
15656 @cindex multiple targets
15658 There are multiple classes of targets such as: processes, executable files or
15659 recording sessions. Core files belong to the process class, making core file
15660 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
15661 on multiple active targets, one in each class. This allows you to (for
15662 example) start a process and inspect its activity, while still having access to
15663 the executable file after the process finishes. Or if you start process
15664 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
15665 presented a virtual layer of the recording target, while the process target
15666 remains stopped at the chronologically last point of the process execution.
15668 Use the @code{core-file} and @code{exec-file} commands to select a new core
15669 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
15670 specify as a target a process that is already running, use the @code{attach}
15671 command (@pxref{Attach, ,Debugging an Already-running Process}).
15673 @node Target Commands
15674 @section Commands for Managing Targets
15677 @item target @var{type} @var{parameters}
15678 Connects the @value{GDBN} host environment to a target machine or
15679 process. A target is typically a protocol for talking to debugging
15680 facilities. You use the argument @var{type} to specify the type or
15681 protocol of the target machine.
15683 Further @var{parameters} are interpreted by the target protocol, but
15684 typically include things like device names or host names to connect
15685 with, process numbers, and baud rates.
15687 The @code{target} command does not repeat if you press @key{RET} again
15688 after executing the command.
15690 @kindex help target
15692 Displays the names of all targets available. To display targets
15693 currently selected, use either @code{info target} or @code{info files}
15694 (@pxref{Files, ,Commands to Specify Files}).
15696 @item help target @var{name}
15697 Describe a particular target, including any parameters necessary to
15700 @kindex set gnutarget
15701 @item set gnutarget @var{args}
15702 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
15703 knows whether it is reading an @dfn{executable},
15704 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
15705 with the @code{set gnutarget} command. Unlike most @code{target} commands,
15706 with @code{gnutarget} the @code{target} refers to a program, not a machine.
15709 @emph{Warning:} To specify a file format with @code{set gnutarget},
15710 you must know the actual BFD name.
15714 @xref{Files, , Commands to Specify Files}.
15716 @kindex show gnutarget
15717 @item show gnutarget
15718 Use the @code{show gnutarget} command to display what file format
15719 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
15720 @value{GDBN} will determine the file format for each file automatically,
15721 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
15724 @cindex common targets
15725 Here are some common targets (available, or not, depending on the GDB
15730 @item target exec @var{program}
15731 @cindex executable file target
15732 An executable file. @samp{target exec @var{program}} is the same as
15733 @samp{exec-file @var{program}}.
15735 @item target core @var{filename}
15736 @cindex core dump file target
15737 A core dump file. @samp{target core @var{filename}} is the same as
15738 @samp{core-file @var{filename}}.
15740 @item target remote @var{medium}
15741 @cindex remote target
15742 A remote system connected to @value{GDBN} via a serial line or network
15743 connection. This command tells @value{GDBN} to use its own remote
15744 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
15746 For example, if you have a board connected to @file{/dev/ttya} on the
15747 machine running @value{GDBN}, you could say:
15750 target remote /dev/ttya
15753 @code{target remote} supports the @code{load} command. This is only
15754 useful if you have some other way of getting the stub to the target
15755 system, and you can put it somewhere in memory where it won't get
15756 clobbered by the download.
15758 @item target sim @r{[}@var{simargs}@r{]} @dots{}
15759 @cindex built-in simulator target
15760 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
15768 works; however, you cannot assume that a specific memory map, device
15769 drivers, or even basic I/O is available, although some simulators do
15770 provide these. For info about any processor-specific simulator details,
15771 see the appropriate section in @ref{Embedded Processors, ,Embedded
15776 Some configurations may include these targets as well:
15780 @item target nrom @var{dev}
15781 @cindex NetROM ROM emulator target
15782 NetROM ROM emulator. This target only supports downloading.
15786 Different targets are available on different configurations of @value{GDBN};
15787 your configuration may have more or fewer targets.
15789 Many remote targets require you to download the executable's code once
15790 you've successfully established a connection. You may wish to control
15791 various aspects of this process.
15796 @kindex set hash@r{, for remote monitors}
15797 @cindex hash mark while downloading
15798 This command controls whether a hash mark @samp{#} is displayed while
15799 downloading a file to the remote monitor. If on, a hash mark is
15800 displayed after each S-record is successfully downloaded to the
15804 @kindex show hash@r{, for remote monitors}
15805 Show the current status of displaying the hash mark.
15807 @item set debug monitor
15808 @kindex set debug monitor
15809 @cindex display remote monitor communications
15810 Enable or disable display of communications messages between
15811 @value{GDBN} and the remote monitor.
15813 @item show debug monitor
15814 @kindex show debug monitor
15815 Show the current status of displaying communications between
15816 @value{GDBN} and the remote monitor.
15821 @kindex load @var{filename}
15822 @item load @var{filename}
15824 Depending on what remote debugging facilities are configured into
15825 @value{GDBN}, the @code{load} command may be available. Where it exists, it
15826 is meant to make @var{filename} (an executable) available for debugging
15827 on the remote system---by downloading, or dynamic linking, for example.
15828 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15829 the @code{add-symbol-file} command.
15831 If your @value{GDBN} does not have a @code{load} command, attempting to
15832 execute it gets the error message ``@code{You can't do that when your
15833 target is @dots{}}''
15835 The file is loaded at whatever address is specified in the executable.
15836 For some object file formats, you can specify the load address when you
15837 link the program; for other formats, like a.out, the object file format
15838 specifies a fixed address.
15839 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15841 Depending on the remote side capabilities, @value{GDBN} may be able to
15842 load programs into flash memory.
15844 @code{load} does not repeat if you press @key{RET} again after using it.
15848 @section Choosing Target Byte Order
15850 @cindex choosing target byte order
15851 @cindex target byte order
15853 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15854 offer the ability to run either big-endian or little-endian byte
15855 orders. Usually the executable or symbol will include a bit to
15856 designate the endian-ness, and you will not need to worry about
15857 which to use. However, you may still find it useful to adjust
15858 @value{GDBN}'s idea of processor endian-ness manually.
15862 @item set endian big
15863 Instruct @value{GDBN} to assume the target is big-endian.
15865 @item set endian little
15866 Instruct @value{GDBN} to assume the target is little-endian.
15868 @item set endian auto
15869 Instruct @value{GDBN} to use the byte order associated with the
15873 Display @value{GDBN}'s current idea of the target byte order.
15877 Note that these commands merely adjust interpretation of symbolic
15878 data on the host, and that they have absolutely no effect on the
15882 @node Remote Debugging
15883 @chapter Debugging Remote Programs
15884 @cindex remote debugging
15886 If you are trying to debug a program running on a machine that cannot run
15887 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15888 For example, you might use remote debugging on an operating system kernel,
15889 or on a small system which does not have a general purpose operating system
15890 powerful enough to run a full-featured debugger.
15892 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15893 to make this work with particular debugging targets. In addition,
15894 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15895 but not specific to any particular target system) which you can use if you
15896 write the remote stubs---the code that runs on the remote system to
15897 communicate with @value{GDBN}.
15899 Other remote targets may be available in your
15900 configuration of @value{GDBN}; use @code{help target} to list them.
15903 * Connecting:: Connecting to a remote target
15904 * File Transfer:: Sending files to a remote system
15905 * Server:: Using the gdbserver program
15906 * Remote Configuration:: Remote configuration
15907 * Remote Stub:: Implementing a remote stub
15911 @section Connecting to a Remote Target
15913 On the @value{GDBN} host machine, you will need an unstripped copy of
15914 your program, since @value{GDBN} needs symbol and debugging information.
15915 Start up @value{GDBN} as usual, using the name of the local copy of your
15916 program as the first argument.
15918 @cindex @code{target remote}
15919 @value{GDBN} can communicate with the target over a serial line, or
15920 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15921 each case, @value{GDBN} uses the same protocol for debugging your
15922 program; only the medium carrying the debugging packets varies. The
15923 @code{target remote} command establishes a connection to the target.
15924 Its arguments indicate which medium to use:
15928 @item target remote @var{serial-device}
15929 @cindex serial line, @code{target remote}
15930 Use @var{serial-device} to communicate with the target. For example,
15931 to use a serial line connected to the device named @file{/dev/ttyb}:
15934 target remote /dev/ttyb
15937 If you're using a serial line, you may want to give @value{GDBN} the
15938 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15939 (@pxref{Remote Configuration, set remotebaud}) before the
15940 @code{target} command.
15942 @item target remote @code{@var{host}:@var{port}}
15943 @itemx target remote @code{tcp:@var{host}:@var{port}}
15944 @cindex @acronym{TCP} port, @code{target remote}
15945 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15946 The @var{host} may be either a host name or a numeric @acronym{IP}
15947 address; @var{port} must be a decimal number. The @var{host} could be
15948 the target machine itself, if it is directly connected to the net, or
15949 it might be a terminal server which in turn has a serial line to the
15952 For example, to connect to port 2828 on a terminal server named
15956 target remote manyfarms:2828
15959 If your remote target is actually running on the same machine as your
15960 debugger session (e.g.@: a simulator for your target running on the
15961 same host), you can omit the hostname. For example, to connect to
15962 port 1234 on your local machine:
15965 target remote :1234
15969 Note that the colon is still required here.
15971 @item target remote @code{udp:@var{host}:@var{port}}
15972 @cindex @acronym{UDP} port, @code{target remote}
15973 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
15974 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
15977 target remote udp:manyfarms:2828
15980 When using a @acronym{UDP} connection for remote debugging, you should
15981 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
15982 can silently drop packets on busy or unreliable networks, which will
15983 cause havoc with your debugging session.
15985 @item target remote | @var{command}
15986 @cindex pipe, @code{target remote} to
15987 Run @var{command} in the background and communicate with it using a
15988 pipe. The @var{command} is a shell command, to be parsed and expanded
15989 by the system's command shell, @code{/bin/sh}; it should expect remote
15990 protocol packets on its standard input, and send replies on its
15991 standard output. You could use this to run a stand-alone simulator
15992 that speaks the remote debugging protocol, to make net connections
15993 using programs like @code{ssh}, or for other similar tricks.
15995 If @var{command} closes its standard output (perhaps by exiting),
15996 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
15997 program has already exited, this will have no effect.)
16001 Once the connection has been established, you can use all the usual
16002 commands to examine and change data. The remote program is already
16003 running; you can use @kbd{step} and @kbd{continue}, and you do not
16004 need to use @kbd{run}.
16006 @cindex interrupting remote programs
16007 @cindex remote programs, interrupting
16008 Whenever @value{GDBN} is waiting for the remote program, if you type the
16009 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16010 program. This may or may not succeed, depending in part on the hardware
16011 and the serial drivers the remote system uses. If you type the
16012 interrupt character once again, @value{GDBN} displays this prompt:
16015 Interrupted while waiting for the program.
16016 Give up (and stop debugging it)? (y or n)
16019 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16020 (If you decide you want to try again later, you can use @samp{target
16021 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16022 goes back to waiting.
16025 @kindex detach (remote)
16027 When you have finished debugging the remote program, you can use the
16028 @code{detach} command to release it from @value{GDBN} control.
16029 Detaching from the target normally resumes its execution, but the results
16030 will depend on your particular remote stub. After the @code{detach}
16031 command, @value{GDBN} is free to connect to another target.
16035 The @code{disconnect} command behaves like @code{detach}, except that
16036 the target is generally not resumed. It will wait for @value{GDBN}
16037 (this instance or another one) to connect and continue debugging. After
16038 the @code{disconnect} command, @value{GDBN} is again free to connect to
16041 @cindex send command to remote monitor
16042 @cindex extend @value{GDBN} for remote targets
16043 @cindex add new commands for external monitor
16045 @item monitor @var{cmd}
16046 This command allows you to send arbitrary commands directly to the
16047 remote monitor. Since @value{GDBN} doesn't care about the commands it
16048 sends like this, this command is the way to extend @value{GDBN}---you
16049 can add new commands that only the external monitor will understand
16053 @node File Transfer
16054 @section Sending files to a remote system
16055 @cindex remote target, file transfer
16056 @cindex file transfer
16057 @cindex sending files to remote systems
16059 Some remote targets offer the ability to transfer files over the same
16060 connection used to communicate with @value{GDBN}. This is convenient
16061 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16062 running @code{gdbserver} over a network interface. For other targets,
16063 e.g.@: embedded devices with only a single serial port, this may be
16064 the only way to upload or download files.
16066 Not all remote targets support these commands.
16070 @item remote put @var{hostfile} @var{targetfile}
16071 Copy file @var{hostfile} from the host system (the machine running
16072 @value{GDBN}) to @var{targetfile} on the target system.
16075 @item remote get @var{targetfile} @var{hostfile}
16076 Copy file @var{targetfile} from the target system to @var{hostfile}
16077 on the host system.
16079 @kindex remote delete
16080 @item remote delete @var{targetfile}
16081 Delete @var{targetfile} from the target system.
16086 @section Using the @code{gdbserver} Program
16089 @cindex remote connection without stubs
16090 @code{gdbserver} is a control program for Unix-like systems, which
16091 allows you to connect your program with a remote @value{GDBN} via
16092 @code{target remote}---but without linking in the usual debugging stub.
16094 @code{gdbserver} is not a complete replacement for the debugging stubs,
16095 because it requires essentially the same operating-system facilities
16096 that @value{GDBN} itself does. In fact, a system that can run
16097 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16098 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16099 because it is a much smaller program than @value{GDBN} itself. It is
16100 also easier to port than all of @value{GDBN}, so you may be able to get
16101 started more quickly on a new system by using @code{gdbserver}.
16102 Finally, if you develop code for real-time systems, you may find that
16103 the tradeoffs involved in real-time operation make it more convenient to
16104 do as much development work as possible on another system, for example
16105 by cross-compiling. You can use @code{gdbserver} to make a similar
16106 choice for debugging.
16108 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16109 or a TCP connection, using the standard @value{GDBN} remote serial
16113 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16114 Do not run @code{gdbserver} connected to any public network; a
16115 @value{GDBN} connection to @code{gdbserver} provides access to the
16116 target system with the same privileges as the user running
16120 @subsection Running @code{gdbserver}
16121 @cindex arguments, to @code{gdbserver}
16123 Run @code{gdbserver} on the target system. You need a copy of the
16124 program you want to debug, including any libraries it requires.
16125 @code{gdbserver} does not need your program's symbol table, so you can
16126 strip the program if necessary to save space. @value{GDBN} on the host
16127 system does all the symbol handling.
16129 To use the server, you must tell it how to communicate with @value{GDBN};
16130 the name of your program; and the arguments for your program. The usual
16134 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16137 @var{comm} is either a device name (to use a serial line) or a TCP
16138 hostname and portnumber. For example, to debug Emacs with the argument
16139 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16143 target> gdbserver /dev/com1 emacs foo.txt
16146 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16149 To use a TCP connection instead of a serial line:
16152 target> gdbserver host:2345 emacs foo.txt
16155 The only difference from the previous example is the first argument,
16156 specifying that you are communicating with the host @value{GDBN} via
16157 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16158 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16159 (Currently, the @samp{host} part is ignored.) You can choose any number
16160 you want for the port number as long as it does not conflict with any
16161 TCP ports already in use on the target system (for example, @code{23} is
16162 reserved for @code{telnet}).@footnote{If you choose a port number that
16163 conflicts with another service, @code{gdbserver} prints an error message
16164 and exits.} You must use the same port number with the host @value{GDBN}
16165 @code{target remote} command.
16167 @subsubsection Attaching to a Running Program
16169 On some targets, @code{gdbserver} can also attach to running programs.
16170 This is accomplished via the @code{--attach} argument. The syntax is:
16173 target> gdbserver --attach @var{comm} @var{pid}
16176 @var{pid} is the process ID of a currently running process. It isn't necessary
16177 to point @code{gdbserver} at a binary for the running process.
16180 @cindex attach to a program by name
16181 You can debug processes by name instead of process ID if your target has the
16182 @code{pidof} utility:
16185 target> gdbserver --attach @var{comm} `pidof @var{program}`
16188 In case more than one copy of @var{program} is running, or @var{program}
16189 has multiple threads, most versions of @code{pidof} support the
16190 @code{-s} option to only return the first process ID.
16192 @subsubsection Multi-Process Mode for @code{gdbserver}
16193 @cindex gdbserver, multiple processes
16194 @cindex multiple processes with gdbserver
16196 When you connect to @code{gdbserver} using @code{target remote},
16197 @code{gdbserver} debugs the specified program only once. When the
16198 program exits, or you detach from it, @value{GDBN} closes the connection
16199 and @code{gdbserver} exits.
16201 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16202 enters multi-process mode. When the debugged program exits, or you
16203 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16204 though no program is running. The @code{run} and @code{attach}
16205 commands instruct @code{gdbserver} to run or attach to a new program.
16206 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16207 remote exec-file}) to select the program to run. Command line
16208 arguments are supported, except for wildcard expansion and I/O
16209 redirection (@pxref{Arguments}).
16211 To start @code{gdbserver} without supplying an initial command to run
16212 or process ID to attach, use the @option{--multi} command line option.
16213 Then you can connect using @kbd{target extended-remote} and start
16214 the program you want to debug.
16216 @code{gdbserver} does not automatically exit in multi-process mode.
16217 You can terminate it by using @code{monitor exit}
16218 (@pxref{Monitor Commands for gdbserver}).
16220 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16222 The @option{--debug} option tells @code{gdbserver} to display extra
16223 status information about the debugging process. The
16224 @option{--remote-debug} option tells @code{gdbserver} to display
16225 remote protocol debug output. These options are intended for
16226 @code{gdbserver} development and for bug reports to the developers.
16228 The @option{--wrapper} option specifies a wrapper to launch programs
16229 for debugging. The option should be followed by the name of the
16230 wrapper, then any command-line arguments to pass to the wrapper, then
16231 @kbd{--} indicating the end of the wrapper arguments.
16233 @code{gdbserver} runs the specified wrapper program with a combined
16234 command line including the wrapper arguments, then the name of the
16235 program to debug, then any arguments to the program. The wrapper
16236 runs until it executes your program, and then @value{GDBN} gains control.
16238 You can use any program that eventually calls @code{execve} with
16239 its arguments as a wrapper. Several standard Unix utilities do
16240 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16241 with @code{exec "$@@"} will also work.
16243 For example, you can use @code{env} to pass an environment variable to
16244 the debugged program, without setting the variable in @code{gdbserver}'s
16248 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16251 @subsection Connecting to @code{gdbserver}
16253 Run @value{GDBN} on the host system.
16255 First make sure you have the necessary symbol files. Load symbols for
16256 your application using the @code{file} command before you connect. Use
16257 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16258 was compiled with the correct sysroot using @code{--with-sysroot}).
16260 The symbol file and target libraries must exactly match the executable
16261 and libraries on the target, with one exception: the files on the host
16262 system should not be stripped, even if the files on the target system
16263 are. Mismatched or missing files will lead to confusing results
16264 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16265 files may also prevent @code{gdbserver} from debugging multi-threaded
16268 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16269 For TCP connections, you must start up @code{gdbserver} prior to using
16270 the @code{target remote} command. Otherwise you may get an error whose
16271 text depends on the host system, but which usually looks something like
16272 @samp{Connection refused}. Don't use the @code{load}
16273 command in @value{GDBN} when using @code{gdbserver}, since the program is
16274 already on the target.
16276 @subsection Monitor Commands for @code{gdbserver}
16277 @cindex monitor commands, for @code{gdbserver}
16278 @anchor{Monitor Commands for gdbserver}
16280 During a @value{GDBN} session using @code{gdbserver}, you can use the
16281 @code{monitor} command to send special requests to @code{gdbserver}.
16282 Here are the available commands.
16286 List the available monitor commands.
16288 @item monitor set debug 0
16289 @itemx monitor set debug 1
16290 Disable or enable general debugging messages.
16292 @item monitor set remote-debug 0
16293 @itemx monitor set remote-debug 1
16294 Disable or enable specific debugging messages associated with the remote
16295 protocol (@pxref{Remote Protocol}).
16297 @item monitor set libthread-db-search-path [PATH]
16298 @cindex gdbserver, search path for @code{libthread_db}
16299 When this command is issued, @var{path} is a colon-separated list of
16300 directories to search for @code{libthread_db} (@pxref{Threads,,set
16301 libthread-db-search-path}). If you omit @var{path},
16302 @samp{libthread-db-search-path} will be reset to an empty list.
16305 Tell gdbserver to exit immediately. This command should be followed by
16306 @code{disconnect} to close the debugging session. @code{gdbserver} will
16307 detach from any attached processes and kill any processes it created.
16308 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16309 of a multi-process mode debug session.
16313 @subsection Tracepoints support in @code{gdbserver}
16314 @cindex tracepoints support in @code{gdbserver}
16316 On some targets, @code{gdbserver} supports tracepoints, fast
16317 tracepoints and static tracepoints.
16319 For fast or static tracepoints to work, a special library called the
16320 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16321 This library is built and distributed as an integral part of
16322 @code{gdbserver}. In addition, support for static tracepoints
16323 requires building the in-process agent library with static tracepoints
16324 support. At present, the UST (LTTng Userspace Tracer,
16325 @url{http://lttng.org/ust}) tracing engine is supported. This support
16326 is automatically available if UST development headers are found in the
16327 standard include path when @code{gdbserver} is built, or if
16328 @code{gdbserver} was explicitly configured using @option{--with-ust}
16329 to point at such headers. You can explicitly disable the support
16330 using @option{--with-ust=no}.
16332 There are several ways to load the in-process agent in your program:
16335 @item Specifying it as dependency at link time
16337 You can link your program dynamically with the in-process agent
16338 library. On most systems, this is accomplished by adding
16339 @code{-linproctrace} to the link command.
16341 @item Using the system's preloading mechanisms
16343 You can force loading the in-process agent at startup time by using
16344 your system's support for preloading shared libraries. Many Unixes
16345 support the concept of preloading user defined libraries. In most
16346 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16347 in the environment. See also the description of @code{gdbserver}'s
16348 @option{--wrapper} command line option.
16350 @item Using @value{GDBN} to force loading the agent at run time
16352 On some systems, you can force the inferior to load a shared library,
16353 by calling a dynamic loader function in the inferior that takes care
16354 of dynamically looking up and loading a shared library. On most Unix
16355 systems, the function is @code{dlopen}. You'll use the @code{call}
16356 command for that. For example:
16359 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16362 Note that on most Unix systems, for the @code{dlopen} function to be
16363 available, the program needs to be linked with @code{-ldl}.
16366 On systems that have a userspace dynamic loader, like most Unix
16367 systems, when you connect to @code{gdbserver} using @code{target
16368 remote}, you'll find that the program is stopped at the dynamic
16369 loader's entry point, and no shared library has been loaded in the
16370 program's address space yet, including the in-process agent. In that
16371 case, before being able to use any of the fast or static tracepoints
16372 features, you need to let the loader run and load the shared
16373 libraries. The simplest way to do that is to run the program to the
16374 main procedure. E.g., if debugging a C or C@t{++} program, start
16375 @code{gdbserver} like so:
16378 $ gdbserver :9999 myprogram
16381 Start GDB and connect to @code{gdbserver} like so, and run to main:
16385 (@value{GDBP}) target remote myhost:9999
16386 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16387 (@value{GDBP}) b main
16388 (@value{GDBP}) continue
16391 The in-process tracing agent library should now be loaded into the
16392 process; you can confirm it with the @code{info sharedlibrary}
16393 command, which will list @file{libinproctrace.so} as loaded in the
16394 process. You are now ready to install fast tracepoints, list static
16395 tracepoint markers, probe static tracepoints markers, and start
16398 @node Remote Configuration
16399 @section Remote Configuration
16402 @kindex show remote
16403 This section documents the configuration options available when
16404 debugging remote programs. For the options related to the File I/O
16405 extensions of the remote protocol, see @ref{system,
16406 system-call-allowed}.
16409 @item set remoteaddresssize @var{bits}
16410 @cindex address size for remote targets
16411 @cindex bits in remote address
16412 Set the maximum size of address in a memory packet to the specified
16413 number of bits. @value{GDBN} will mask off the address bits above
16414 that number, when it passes addresses to the remote target. The
16415 default value is the number of bits in the target's address.
16417 @item show remoteaddresssize
16418 Show the current value of remote address size in bits.
16420 @item set remotebaud @var{n}
16421 @cindex baud rate for remote targets
16422 Set the baud rate for the remote serial I/O to @var{n} baud. The
16423 value is used to set the speed of the serial port used for debugging
16426 @item show remotebaud
16427 Show the current speed of the remote connection.
16429 @item set remotebreak
16430 @cindex interrupt remote programs
16431 @cindex BREAK signal instead of Ctrl-C
16432 @anchor{set remotebreak}
16433 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
16434 when you type @kbd{Ctrl-c} to interrupt the program running
16435 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
16436 character instead. The default is off, since most remote systems
16437 expect to see @samp{Ctrl-C} as the interrupt signal.
16439 @item show remotebreak
16440 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
16441 interrupt the remote program.
16443 @item set remoteflow on
16444 @itemx set remoteflow off
16445 @kindex set remoteflow
16446 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
16447 on the serial port used to communicate to the remote target.
16449 @item show remoteflow
16450 @kindex show remoteflow
16451 Show the current setting of hardware flow control.
16453 @item set remotelogbase @var{base}
16454 Set the base (a.k.a.@: radix) of logging serial protocol
16455 communications to @var{base}. Supported values of @var{base} are:
16456 @code{ascii}, @code{octal}, and @code{hex}. The default is
16459 @item show remotelogbase
16460 Show the current setting of the radix for logging remote serial
16463 @item set remotelogfile @var{file}
16464 @cindex record serial communications on file
16465 Record remote serial communications on the named @var{file}. The
16466 default is not to record at all.
16468 @item show remotelogfile.
16469 Show the current setting of the file name on which to record the
16470 serial communications.
16472 @item set remotetimeout @var{num}
16473 @cindex timeout for serial communications
16474 @cindex remote timeout
16475 Set the timeout limit to wait for the remote target to respond to
16476 @var{num} seconds. The default is 2 seconds.
16478 @item show remotetimeout
16479 Show the current number of seconds to wait for the remote target
16482 @cindex limit hardware breakpoints and watchpoints
16483 @cindex remote target, limit break- and watchpoints
16484 @anchor{set remote hardware-watchpoint-limit}
16485 @anchor{set remote hardware-breakpoint-limit}
16486 @item set remote hardware-watchpoint-limit @var{limit}
16487 @itemx set remote hardware-breakpoint-limit @var{limit}
16488 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
16489 watchpoints. A limit of -1, the default, is treated as unlimited.
16491 @item set remote exec-file @var{filename}
16492 @itemx show remote exec-file
16493 @anchor{set remote exec-file}
16494 @cindex executable file, for remote target
16495 Select the file used for @code{run} with @code{target
16496 extended-remote}. This should be set to a filename valid on the
16497 target system. If it is not set, the target will use a default
16498 filename (e.g.@: the last program run).
16500 @item set remote interrupt-sequence
16501 @cindex interrupt remote programs
16502 @cindex select Ctrl-C, BREAK or BREAK-g
16503 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
16504 @samp{BREAK-g} as the
16505 sequence to the remote target in order to interrupt the execution.
16506 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
16507 is high level of serial line for some certain time.
16508 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
16509 It is @code{BREAK} signal followed by character @code{g}.
16511 @item show interrupt-sequence
16512 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
16513 is sent by @value{GDBN} to interrupt the remote program.
16514 @code{BREAK-g} is BREAK signal followed by @code{g} and
16515 also known as Magic SysRq g.
16517 @item set remote interrupt-on-connect
16518 @cindex send interrupt-sequence on start
16519 Specify whether interrupt-sequence is sent to remote target when
16520 @value{GDBN} connects to it. This is mostly needed when you debug
16521 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
16522 which is known as Magic SysRq g in order to connect @value{GDBN}.
16524 @item show interrupt-on-connect
16525 Show whether interrupt-sequence is sent
16526 to remote target when @value{GDBN} connects to it.
16530 @item set tcp auto-retry on
16531 @cindex auto-retry, for remote TCP target
16532 Enable auto-retry for remote TCP connections. This is useful if the remote
16533 debugging agent is launched in parallel with @value{GDBN}; there is a race
16534 condition because the agent may not become ready to accept the connection
16535 before @value{GDBN} attempts to connect. When auto-retry is
16536 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
16537 to establish the connection using the timeout specified by
16538 @code{set tcp connect-timeout}.
16540 @item set tcp auto-retry off
16541 Do not auto-retry failed TCP connections.
16543 @item show tcp auto-retry
16544 Show the current auto-retry setting.
16546 @item set tcp connect-timeout @var{seconds}
16547 @cindex connection timeout, for remote TCP target
16548 @cindex timeout, for remote target connection
16549 Set the timeout for establishing a TCP connection to the remote target to
16550 @var{seconds}. The timeout affects both polling to retry failed connections
16551 (enabled by @code{set tcp auto-retry on}) and waiting for connections
16552 that are merely slow to complete, and represents an approximate cumulative
16555 @item show tcp connect-timeout
16556 Show the current connection timeout setting.
16559 @cindex remote packets, enabling and disabling
16560 The @value{GDBN} remote protocol autodetects the packets supported by
16561 your debugging stub. If you need to override the autodetection, you
16562 can use these commands to enable or disable individual packets. Each
16563 packet can be set to @samp{on} (the remote target supports this
16564 packet), @samp{off} (the remote target does not support this packet),
16565 or @samp{auto} (detect remote target support for this packet). They
16566 all default to @samp{auto}. For more information about each packet,
16567 see @ref{Remote Protocol}.
16569 During normal use, you should not have to use any of these commands.
16570 If you do, that may be a bug in your remote debugging stub, or a bug
16571 in @value{GDBN}. You may want to report the problem to the
16572 @value{GDBN} developers.
16574 For each packet @var{name}, the command to enable or disable the
16575 packet is @code{set remote @var{name}-packet}. The available settings
16578 @multitable @columnfractions 0.28 0.32 0.25
16581 @tab Related Features
16583 @item @code{fetch-register}
16585 @tab @code{info registers}
16587 @item @code{set-register}
16591 @item @code{binary-download}
16593 @tab @code{load}, @code{set}
16595 @item @code{read-aux-vector}
16596 @tab @code{qXfer:auxv:read}
16597 @tab @code{info auxv}
16599 @item @code{symbol-lookup}
16600 @tab @code{qSymbol}
16601 @tab Detecting multiple threads
16603 @item @code{attach}
16604 @tab @code{vAttach}
16607 @item @code{verbose-resume}
16609 @tab Stepping or resuming multiple threads
16615 @item @code{software-breakpoint}
16619 @item @code{hardware-breakpoint}
16623 @item @code{write-watchpoint}
16627 @item @code{read-watchpoint}
16631 @item @code{access-watchpoint}
16635 @item @code{target-features}
16636 @tab @code{qXfer:features:read}
16637 @tab @code{set architecture}
16639 @item @code{library-info}
16640 @tab @code{qXfer:libraries:read}
16641 @tab @code{info sharedlibrary}
16643 @item @code{memory-map}
16644 @tab @code{qXfer:memory-map:read}
16645 @tab @code{info mem}
16647 @item @code{read-sdata-object}
16648 @tab @code{qXfer:sdata:read}
16649 @tab @code{print $_sdata}
16651 @item @code{read-spu-object}
16652 @tab @code{qXfer:spu:read}
16653 @tab @code{info spu}
16655 @item @code{write-spu-object}
16656 @tab @code{qXfer:spu:write}
16657 @tab @code{info spu}
16659 @item @code{read-siginfo-object}
16660 @tab @code{qXfer:siginfo:read}
16661 @tab @code{print $_siginfo}
16663 @item @code{write-siginfo-object}
16664 @tab @code{qXfer:siginfo:write}
16665 @tab @code{set $_siginfo}
16667 @item @code{threads}
16668 @tab @code{qXfer:threads:read}
16669 @tab @code{info threads}
16671 @item @code{get-thread-local-@*storage-address}
16672 @tab @code{qGetTLSAddr}
16673 @tab Displaying @code{__thread} variables
16675 @item @code{get-thread-information-block-address}
16676 @tab @code{qGetTIBAddr}
16677 @tab Display MS-Windows Thread Information Block.
16679 @item @code{search-memory}
16680 @tab @code{qSearch:memory}
16683 @item @code{supported-packets}
16684 @tab @code{qSupported}
16685 @tab Remote communications parameters
16687 @item @code{pass-signals}
16688 @tab @code{QPassSignals}
16689 @tab @code{handle @var{signal}}
16691 @item @code{hostio-close-packet}
16692 @tab @code{vFile:close}
16693 @tab @code{remote get}, @code{remote put}
16695 @item @code{hostio-open-packet}
16696 @tab @code{vFile:open}
16697 @tab @code{remote get}, @code{remote put}
16699 @item @code{hostio-pread-packet}
16700 @tab @code{vFile:pread}
16701 @tab @code{remote get}, @code{remote put}
16703 @item @code{hostio-pwrite-packet}
16704 @tab @code{vFile:pwrite}
16705 @tab @code{remote get}, @code{remote put}
16707 @item @code{hostio-unlink-packet}
16708 @tab @code{vFile:unlink}
16709 @tab @code{remote delete}
16711 @item @code{noack-packet}
16712 @tab @code{QStartNoAckMode}
16713 @tab Packet acknowledgment
16715 @item @code{osdata}
16716 @tab @code{qXfer:osdata:read}
16717 @tab @code{info os}
16719 @item @code{query-attached}
16720 @tab @code{qAttached}
16721 @tab Querying remote process attach state.
16723 @item @code{traceframe-info}
16724 @tab @code{qXfer:traceframe-info:read}
16725 @tab Traceframe info
16729 @section Implementing a Remote Stub
16731 @cindex debugging stub, example
16732 @cindex remote stub, example
16733 @cindex stub example, remote debugging
16734 The stub files provided with @value{GDBN} implement the target side of the
16735 communication protocol, and the @value{GDBN} side is implemented in the
16736 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
16737 these subroutines to communicate, and ignore the details. (If you're
16738 implementing your own stub file, you can still ignore the details: start
16739 with one of the existing stub files. @file{sparc-stub.c} is the best
16740 organized, and therefore the easiest to read.)
16742 @cindex remote serial debugging, overview
16743 To debug a program running on another machine (the debugging
16744 @dfn{target} machine), you must first arrange for all the usual
16745 prerequisites for the program to run by itself. For example, for a C
16750 A startup routine to set up the C runtime environment; these usually
16751 have a name like @file{crt0}. The startup routine may be supplied by
16752 your hardware supplier, or you may have to write your own.
16755 A C subroutine library to support your program's
16756 subroutine calls, notably managing input and output.
16759 A way of getting your program to the other machine---for example, a
16760 download program. These are often supplied by the hardware
16761 manufacturer, but you may have to write your own from hardware
16765 The next step is to arrange for your program to use a serial port to
16766 communicate with the machine where @value{GDBN} is running (the @dfn{host}
16767 machine). In general terms, the scheme looks like this:
16771 @value{GDBN} already understands how to use this protocol; when everything
16772 else is set up, you can simply use the @samp{target remote} command
16773 (@pxref{Targets,,Specifying a Debugging Target}).
16775 @item On the target,
16776 you must link with your program a few special-purpose subroutines that
16777 implement the @value{GDBN} remote serial protocol. The file containing these
16778 subroutines is called a @dfn{debugging stub}.
16780 On certain remote targets, you can use an auxiliary program
16781 @code{gdbserver} instead of linking a stub into your program.
16782 @xref{Server,,Using the @code{gdbserver} Program}, for details.
16785 The debugging stub is specific to the architecture of the remote
16786 machine; for example, use @file{sparc-stub.c} to debug programs on
16789 @cindex remote serial stub list
16790 These working remote stubs are distributed with @value{GDBN}:
16795 @cindex @file{i386-stub.c}
16798 For Intel 386 and compatible architectures.
16801 @cindex @file{m68k-stub.c}
16802 @cindex Motorola 680x0
16804 For Motorola 680x0 architectures.
16807 @cindex @file{sh-stub.c}
16810 For Renesas SH architectures.
16813 @cindex @file{sparc-stub.c}
16815 For @sc{sparc} architectures.
16817 @item sparcl-stub.c
16818 @cindex @file{sparcl-stub.c}
16821 For Fujitsu @sc{sparclite} architectures.
16825 The @file{README} file in the @value{GDBN} distribution may list other
16826 recently added stubs.
16829 * Stub Contents:: What the stub can do for you
16830 * Bootstrapping:: What you must do for the stub
16831 * Debug Session:: Putting it all together
16834 @node Stub Contents
16835 @subsection What the Stub Can Do for You
16837 @cindex remote serial stub
16838 The debugging stub for your architecture supplies these three
16842 @item set_debug_traps
16843 @findex set_debug_traps
16844 @cindex remote serial stub, initialization
16845 This routine arranges for @code{handle_exception} to run when your
16846 program stops. You must call this subroutine explicitly near the
16847 beginning of your program.
16849 @item handle_exception
16850 @findex handle_exception
16851 @cindex remote serial stub, main routine
16852 This is the central workhorse, but your program never calls it
16853 explicitly---the setup code arranges for @code{handle_exception} to
16854 run when a trap is triggered.
16856 @code{handle_exception} takes control when your program stops during
16857 execution (for example, on a breakpoint), and mediates communications
16858 with @value{GDBN} on the host machine. This is where the communications
16859 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
16860 representative on the target machine. It begins by sending summary
16861 information on the state of your program, then continues to execute,
16862 retrieving and transmitting any information @value{GDBN} needs, until you
16863 execute a @value{GDBN} command that makes your program resume; at that point,
16864 @code{handle_exception} returns control to your own code on the target
16868 @cindex @code{breakpoint} subroutine, remote
16869 Use this auxiliary subroutine to make your program contain a
16870 breakpoint. Depending on the particular situation, this may be the only
16871 way for @value{GDBN} to get control. For instance, if your target
16872 machine has some sort of interrupt button, you won't need to call this;
16873 pressing the interrupt button transfers control to
16874 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
16875 simply receiving characters on the serial port may also trigger a trap;
16876 again, in that situation, you don't need to call @code{breakpoint} from
16877 your own program---simply running @samp{target remote} from the host
16878 @value{GDBN} session gets control.
16880 Call @code{breakpoint} if none of these is true, or if you simply want
16881 to make certain your program stops at a predetermined point for the
16882 start of your debugging session.
16885 @node Bootstrapping
16886 @subsection What You Must Do for the Stub
16888 @cindex remote stub, support routines
16889 The debugging stubs that come with @value{GDBN} are set up for a particular
16890 chip architecture, but they have no information about the rest of your
16891 debugging target machine.
16893 First of all you need to tell the stub how to communicate with the
16897 @item int getDebugChar()
16898 @findex getDebugChar
16899 Write this subroutine to read a single character from the serial port.
16900 It may be identical to @code{getchar} for your target system; a
16901 different name is used to allow you to distinguish the two if you wish.
16903 @item void putDebugChar(int)
16904 @findex putDebugChar
16905 Write this subroutine to write a single character to the serial port.
16906 It may be identical to @code{putchar} for your target system; a
16907 different name is used to allow you to distinguish the two if you wish.
16910 @cindex control C, and remote debugging
16911 @cindex interrupting remote targets
16912 If you want @value{GDBN} to be able to stop your program while it is
16913 running, you need to use an interrupt-driven serial driver, and arrange
16914 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
16915 character). That is the character which @value{GDBN} uses to tell the
16916 remote system to stop.
16918 Getting the debugging target to return the proper status to @value{GDBN}
16919 probably requires changes to the standard stub; one quick and dirty way
16920 is to just execute a breakpoint instruction (the ``dirty'' part is that
16921 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
16923 Other routines you need to supply are:
16926 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
16927 @findex exceptionHandler
16928 Write this function to install @var{exception_address} in the exception
16929 handling tables. You need to do this because the stub does not have any
16930 way of knowing what the exception handling tables on your target system
16931 are like (for example, the processor's table might be in @sc{rom},
16932 containing entries which point to a table in @sc{ram}).
16933 @var{exception_number} is the exception number which should be changed;
16934 its meaning is architecture-dependent (for example, different numbers
16935 might represent divide by zero, misaligned access, etc). When this
16936 exception occurs, control should be transferred directly to
16937 @var{exception_address}, and the processor state (stack, registers,
16938 and so on) should be just as it is when a processor exception occurs. So if
16939 you want to use a jump instruction to reach @var{exception_address}, it
16940 should be a simple jump, not a jump to subroutine.
16942 For the 386, @var{exception_address} should be installed as an interrupt
16943 gate so that interrupts are masked while the handler runs. The gate
16944 should be at privilege level 0 (the most privileged level). The
16945 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
16946 help from @code{exceptionHandler}.
16948 @item void flush_i_cache()
16949 @findex flush_i_cache
16950 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
16951 instruction cache, if any, on your target machine. If there is no
16952 instruction cache, this subroutine may be a no-op.
16954 On target machines that have instruction caches, @value{GDBN} requires this
16955 function to make certain that the state of your program is stable.
16959 You must also make sure this library routine is available:
16962 @item void *memset(void *, int, int)
16964 This is the standard library function @code{memset} that sets an area of
16965 memory to a known value. If you have one of the free versions of
16966 @code{libc.a}, @code{memset} can be found there; otherwise, you must
16967 either obtain it from your hardware manufacturer, or write your own.
16970 If you do not use the GNU C compiler, you may need other standard
16971 library subroutines as well; this varies from one stub to another,
16972 but in general the stubs are likely to use any of the common library
16973 subroutines which @code{@value{NGCC}} generates as inline code.
16976 @node Debug Session
16977 @subsection Putting it All Together
16979 @cindex remote serial debugging summary
16980 In summary, when your program is ready to debug, you must follow these
16985 Make sure you have defined the supporting low-level routines
16986 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
16988 @code{getDebugChar}, @code{putDebugChar},
16989 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
16993 Insert these lines near the top of your program:
17001 For the 680x0 stub only, you need to provide a variable called
17002 @code{exceptionHook}. Normally you just use:
17005 void (*exceptionHook)() = 0;
17009 but if before calling @code{set_debug_traps}, you set it to point to a
17010 function in your program, that function is called when
17011 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17012 error). The function indicated by @code{exceptionHook} is called with
17013 one parameter: an @code{int} which is the exception number.
17016 Compile and link together: your program, the @value{GDBN} debugging stub for
17017 your target architecture, and the supporting subroutines.
17020 Make sure you have a serial connection between your target machine and
17021 the @value{GDBN} host, and identify the serial port on the host.
17024 @c The "remote" target now provides a `load' command, so we should
17025 @c document that. FIXME.
17026 Download your program to your target machine (or get it there by
17027 whatever means the manufacturer provides), and start it.
17030 Start @value{GDBN} on the host, and connect to the target
17031 (@pxref{Connecting,,Connecting to a Remote Target}).
17035 @node Configurations
17036 @chapter Configuration-Specific Information
17038 While nearly all @value{GDBN} commands are available for all native and
17039 cross versions of the debugger, there are some exceptions. This chapter
17040 describes things that are only available in certain configurations.
17042 There are three major categories of configurations: native
17043 configurations, where the host and target are the same, embedded
17044 operating system configurations, which are usually the same for several
17045 different processor architectures, and bare embedded processors, which
17046 are quite different from each other.
17051 * Embedded Processors::
17058 This section describes details specific to particular native
17063 * BSD libkvm Interface:: Debugging BSD kernel memory images
17064 * SVR4 Process Information:: SVR4 process information
17065 * DJGPP Native:: Features specific to the DJGPP port
17066 * Cygwin Native:: Features specific to the Cygwin port
17067 * Hurd Native:: Features specific to @sc{gnu} Hurd
17068 * Neutrino:: Features specific to QNX Neutrino
17069 * Darwin:: Features specific to Darwin
17075 On HP-UX systems, if you refer to a function or variable name that
17076 begins with a dollar sign, @value{GDBN} searches for a user or system
17077 name first, before it searches for a convenience variable.
17080 @node BSD libkvm Interface
17081 @subsection BSD libkvm Interface
17084 @cindex kernel memory image
17085 @cindex kernel crash dump
17087 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17088 interface that provides a uniform interface for accessing kernel virtual
17089 memory images, including live systems and crash dumps. @value{GDBN}
17090 uses this interface to allow you to debug live kernels and kernel crash
17091 dumps on many native BSD configurations. This is implemented as a
17092 special @code{kvm} debugging target. For debugging a live system, load
17093 the currently running kernel into @value{GDBN} and connect to the
17097 (@value{GDBP}) @b{target kvm}
17100 For debugging crash dumps, provide the file name of the crash dump as an
17104 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17107 Once connected to the @code{kvm} target, the following commands are
17113 Set current context from the @dfn{Process Control Block} (PCB) address.
17116 Set current context from proc address. This command isn't available on
17117 modern FreeBSD systems.
17120 @node SVR4 Process Information
17121 @subsection SVR4 Process Information
17123 @cindex examine process image
17124 @cindex process info via @file{/proc}
17126 Many versions of SVR4 and compatible systems provide a facility called
17127 @samp{/proc} that can be used to examine the image of a running
17128 process using file-system subroutines. If @value{GDBN} is configured
17129 for an operating system with this facility, the command @code{info
17130 proc} is available to report information about the process running
17131 your program, or about any process running on your system. @code{info
17132 proc} works only on SVR4 systems that include the @code{procfs} code.
17133 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17134 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17140 @itemx info proc @var{process-id}
17141 Summarize available information about any running process. If a
17142 process ID is specified by @var{process-id}, display information about
17143 that process; otherwise display information about the program being
17144 debugged. The summary includes the debugged process ID, the command
17145 line used to invoke it, its current working directory, and its
17146 executable file's absolute file name.
17148 On some systems, @var{process-id} can be of the form
17149 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17150 within a process. If the optional @var{pid} part is missing, it means
17151 a thread from the process being debugged (the leading @samp{/} still
17152 needs to be present, or else @value{GDBN} will interpret the number as
17153 a process ID rather than a thread ID).
17155 @item info proc mappings
17156 @cindex memory address space mappings
17157 Report the memory address space ranges accessible in the program, with
17158 information on whether the process has read, write, or execute access
17159 rights to each range. On @sc{gnu}/Linux systems, each memory range
17160 includes the object file which is mapped to that range, instead of the
17161 memory access rights to that range.
17163 @item info proc stat
17164 @itemx info proc status
17165 @cindex process detailed status information
17166 These subcommands are specific to @sc{gnu}/Linux systems. They show
17167 the process-related information, including the user ID and group ID;
17168 how many threads are there in the process; its virtual memory usage;
17169 the signals that are pending, blocked, and ignored; its TTY; its
17170 consumption of system and user time; its stack size; its @samp{nice}
17171 value; etc. For more information, see the @samp{proc} man page
17172 (type @kbd{man 5 proc} from your shell prompt).
17174 @item info proc all
17175 Show all the information about the process described under all of the
17176 above @code{info proc} subcommands.
17179 @comment These sub-options of 'info proc' were not included when
17180 @comment procfs.c was re-written. Keep their descriptions around
17181 @comment against the day when someone finds the time to put them back in.
17182 @kindex info proc times
17183 @item info proc times
17184 Starting time, user CPU time, and system CPU time for your program and
17187 @kindex info proc id
17189 Report on the process IDs related to your program: its own process ID,
17190 the ID of its parent, the process group ID, and the session ID.
17193 @item set procfs-trace
17194 @kindex set procfs-trace
17195 @cindex @code{procfs} API calls
17196 This command enables and disables tracing of @code{procfs} API calls.
17198 @item show procfs-trace
17199 @kindex show procfs-trace
17200 Show the current state of @code{procfs} API call tracing.
17202 @item set procfs-file @var{file}
17203 @kindex set procfs-file
17204 Tell @value{GDBN} to write @code{procfs} API trace to the named
17205 @var{file}. @value{GDBN} appends the trace info to the previous
17206 contents of the file. The default is to display the trace on the
17209 @item show procfs-file
17210 @kindex show procfs-file
17211 Show the file to which @code{procfs} API trace is written.
17213 @item proc-trace-entry
17214 @itemx proc-trace-exit
17215 @itemx proc-untrace-entry
17216 @itemx proc-untrace-exit
17217 @kindex proc-trace-entry
17218 @kindex proc-trace-exit
17219 @kindex proc-untrace-entry
17220 @kindex proc-untrace-exit
17221 These commands enable and disable tracing of entries into and exits
17222 from the @code{syscall} interface.
17225 @kindex info pidlist
17226 @cindex process list, QNX Neutrino
17227 For QNX Neutrino only, this command displays the list of all the
17228 processes and all the threads within each process.
17231 @kindex info meminfo
17232 @cindex mapinfo list, QNX Neutrino
17233 For QNX Neutrino only, this command displays the list of all mapinfos.
17237 @subsection Features for Debugging @sc{djgpp} Programs
17238 @cindex @sc{djgpp} debugging
17239 @cindex native @sc{djgpp} debugging
17240 @cindex MS-DOS-specific commands
17243 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17244 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17245 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17246 top of real-mode DOS systems and their emulations.
17248 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17249 defines a few commands specific to the @sc{djgpp} port. This
17250 subsection describes those commands.
17255 This is a prefix of @sc{djgpp}-specific commands which print
17256 information about the target system and important OS structures.
17259 @cindex MS-DOS system info
17260 @cindex free memory information (MS-DOS)
17261 @item info dos sysinfo
17262 This command displays assorted information about the underlying
17263 platform: the CPU type and features, the OS version and flavor, the
17264 DPMI version, and the available conventional and DPMI memory.
17269 @cindex segment descriptor tables
17270 @cindex descriptor tables display
17272 @itemx info dos ldt
17273 @itemx info dos idt
17274 These 3 commands display entries from, respectively, Global, Local,
17275 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17276 tables are data structures which store a descriptor for each segment
17277 that is currently in use. The segment's selector is an index into a
17278 descriptor table; the table entry for that index holds the
17279 descriptor's base address and limit, and its attributes and access
17282 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17283 segment (used for both data and the stack), and a DOS segment (which
17284 allows access to DOS/BIOS data structures and absolute addresses in
17285 conventional memory). However, the DPMI host will usually define
17286 additional segments in order to support the DPMI environment.
17288 @cindex garbled pointers
17289 These commands allow to display entries from the descriptor tables.
17290 Without an argument, all entries from the specified table are
17291 displayed. An argument, which should be an integer expression, means
17292 display a single entry whose index is given by the argument. For
17293 example, here's a convenient way to display information about the
17294 debugged program's data segment:
17297 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17298 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17302 This comes in handy when you want to see whether a pointer is outside
17303 the data segment's limit (i.e.@: @dfn{garbled}).
17305 @cindex page tables display (MS-DOS)
17307 @itemx info dos pte
17308 These two commands display entries from, respectively, the Page
17309 Directory and the Page Tables. Page Directories and Page Tables are
17310 data structures which control how virtual memory addresses are mapped
17311 into physical addresses. A Page Table includes an entry for every
17312 page of memory that is mapped into the program's address space; there
17313 may be several Page Tables, each one holding up to 4096 entries. A
17314 Page Directory has up to 4096 entries, one each for every Page Table
17315 that is currently in use.
17317 Without an argument, @kbd{info dos pde} displays the entire Page
17318 Directory, and @kbd{info dos pte} displays all the entries in all of
17319 the Page Tables. An argument, an integer expression, given to the
17320 @kbd{info dos pde} command means display only that entry from the Page
17321 Directory table. An argument given to the @kbd{info dos pte} command
17322 means display entries from a single Page Table, the one pointed to by
17323 the specified entry in the Page Directory.
17325 @cindex direct memory access (DMA) on MS-DOS
17326 These commands are useful when your program uses @dfn{DMA} (Direct
17327 Memory Access), which needs physical addresses to program the DMA
17330 These commands are supported only with some DPMI servers.
17332 @cindex physical address from linear address
17333 @item info dos address-pte @var{addr}
17334 This command displays the Page Table entry for a specified linear
17335 address. The argument @var{addr} is a linear address which should
17336 already have the appropriate segment's base address added to it,
17337 because this command accepts addresses which may belong to @emph{any}
17338 segment. For example, here's how to display the Page Table entry for
17339 the page where a variable @code{i} is stored:
17342 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17343 @exdent @code{Page Table entry for address 0x11a00d30:}
17344 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17348 This says that @code{i} is stored at offset @code{0xd30} from the page
17349 whose physical base address is @code{0x02698000}, and shows all the
17350 attributes of that page.
17352 Note that you must cast the addresses of variables to a @code{char *},
17353 since otherwise the value of @code{__djgpp_base_address}, the base
17354 address of all variables and functions in a @sc{djgpp} program, will
17355 be added using the rules of C pointer arithmetics: if @code{i} is
17356 declared an @code{int}, @value{GDBN} will add 4 times the value of
17357 @code{__djgpp_base_address} to the address of @code{i}.
17359 Here's another example, it displays the Page Table entry for the
17363 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17364 @exdent @code{Page Table entry for address 0x29110:}
17365 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17369 (The @code{+ 3} offset is because the transfer buffer's address is the
17370 3rd member of the @code{_go32_info_block} structure.) The output
17371 clearly shows that this DPMI server maps the addresses in conventional
17372 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17373 linear (@code{0x29110}) addresses are identical.
17375 This command is supported only with some DPMI servers.
17378 @cindex DOS serial data link, remote debugging
17379 In addition to native debugging, the DJGPP port supports remote
17380 debugging via a serial data link. The following commands are specific
17381 to remote serial debugging in the DJGPP port of @value{GDBN}.
17384 @kindex set com1base
17385 @kindex set com1irq
17386 @kindex set com2base
17387 @kindex set com2irq
17388 @kindex set com3base
17389 @kindex set com3irq
17390 @kindex set com4base
17391 @kindex set com4irq
17392 @item set com1base @var{addr}
17393 This command sets the base I/O port address of the @file{COM1} serial
17396 @item set com1irq @var{irq}
17397 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
17398 for the @file{COM1} serial port.
17400 There are similar commands @samp{set com2base}, @samp{set com3irq},
17401 etc.@: for setting the port address and the @code{IRQ} lines for the
17404 @kindex show com1base
17405 @kindex show com1irq
17406 @kindex show com2base
17407 @kindex show com2irq
17408 @kindex show com3base
17409 @kindex show com3irq
17410 @kindex show com4base
17411 @kindex show com4irq
17412 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
17413 display the current settings of the base address and the @code{IRQ}
17414 lines used by the COM ports.
17417 @kindex info serial
17418 @cindex DOS serial port status
17419 This command prints the status of the 4 DOS serial ports. For each
17420 port, it prints whether it's active or not, its I/O base address and
17421 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
17422 counts of various errors encountered so far.
17426 @node Cygwin Native
17427 @subsection Features for Debugging MS Windows PE Executables
17428 @cindex MS Windows debugging
17429 @cindex native Cygwin debugging
17430 @cindex Cygwin-specific commands
17432 @value{GDBN} supports native debugging of MS Windows programs, including
17433 DLLs with and without symbolic debugging information.
17435 @cindex Ctrl-BREAK, MS-Windows
17436 @cindex interrupt debuggee on MS-Windows
17437 MS-Windows programs that call @code{SetConsoleMode} to switch off the
17438 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
17439 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
17440 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
17441 sequence, which can be used to interrupt the debuggee even if it
17444 There are various additional Cygwin-specific commands, described in
17445 this section. Working with DLLs that have no debugging symbols is
17446 described in @ref{Non-debug DLL Symbols}.
17451 This is a prefix of MS Windows-specific commands which print
17452 information about the target system and important OS structures.
17454 @item info w32 selector
17455 This command displays information returned by
17456 the Win32 API @code{GetThreadSelectorEntry} function.
17457 It takes an optional argument that is evaluated to
17458 a long value to give the information about this given selector.
17459 Without argument, this command displays information
17460 about the six segment registers.
17462 @item info w32 thread-information-block
17463 This command displays thread specific information stored in the
17464 Thread Information Block (readable on the X86 CPU family using @code{$fs}
17465 selector for 32-bit programs and @code{$gs} for 64-bit programs).
17469 This is a Cygwin-specific alias of @code{info shared}.
17471 @kindex dll-symbols
17473 This command loads symbols from a dll similarly to
17474 add-sym command but without the need to specify a base address.
17476 @kindex set cygwin-exceptions
17477 @cindex debugging the Cygwin DLL
17478 @cindex Cygwin DLL, debugging
17479 @item set cygwin-exceptions @var{mode}
17480 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
17481 happen inside the Cygwin DLL. If @var{mode} is @code{off},
17482 @value{GDBN} will delay recognition of exceptions, and may ignore some
17483 exceptions which seem to be caused by internal Cygwin DLL
17484 ``bookkeeping''. This option is meant primarily for debugging the
17485 Cygwin DLL itself; the default value is @code{off} to avoid annoying
17486 @value{GDBN} users with false @code{SIGSEGV} signals.
17488 @kindex show cygwin-exceptions
17489 @item show cygwin-exceptions
17490 Displays whether @value{GDBN} will break on exceptions that happen
17491 inside the Cygwin DLL itself.
17493 @kindex set new-console
17494 @item set new-console @var{mode}
17495 If @var{mode} is @code{on} the debuggee will
17496 be started in a new console on next start.
17497 If @var{mode} is @code{off}, the debuggee will
17498 be started in the same console as the debugger.
17500 @kindex show new-console
17501 @item show new-console
17502 Displays whether a new console is used
17503 when the debuggee is started.
17505 @kindex set new-group
17506 @item set new-group @var{mode}
17507 This boolean value controls whether the debuggee should
17508 start a new group or stay in the same group as the debugger.
17509 This affects the way the Windows OS handles
17512 @kindex show new-group
17513 @item show new-group
17514 Displays current value of new-group boolean.
17516 @kindex set debugevents
17517 @item set debugevents
17518 This boolean value adds debug output concerning kernel events related
17519 to the debuggee seen by the debugger. This includes events that
17520 signal thread and process creation and exit, DLL loading and
17521 unloading, console interrupts, and debugging messages produced by the
17522 Windows @code{OutputDebugString} API call.
17524 @kindex set debugexec
17525 @item set debugexec
17526 This boolean value adds debug output concerning execute events
17527 (such as resume thread) seen by the debugger.
17529 @kindex set debugexceptions
17530 @item set debugexceptions
17531 This boolean value adds debug output concerning exceptions in the
17532 debuggee seen by the debugger.
17534 @kindex set debugmemory
17535 @item set debugmemory
17536 This boolean value adds debug output concerning debuggee memory reads
17537 and writes by the debugger.
17541 This boolean values specifies whether the debuggee is called
17542 via a shell or directly (default value is on).
17546 Displays if the debuggee will be started with a shell.
17551 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
17554 @node Non-debug DLL Symbols
17555 @subsubsection Support for DLLs without Debugging Symbols
17556 @cindex DLLs with no debugging symbols
17557 @cindex Minimal symbols and DLLs
17559 Very often on windows, some of the DLLs that your program relies on do
17560 not include symbolic debugging information (for example,
17561 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
17562 symbols in a DLL, it relies on the minimal amount of symbolic
17563 information contained in the DLL's export table. This section
17564 describes working with such symbols, known internally to @value{GDBN} as
17565 ``minimal symbols''.
17567 Note that before the debugged program has started execution, no DLLs
17568 will have been loaded. The easiest way around this problem is simply to
17569 start the program --- either by setting a breakpoint or letting the
17570 program run once to completion. It is also possible to force
17571 @value{GDBN} to load a particular DLL before starting the executable ---
17572 see the shared library information in @ref{Files}, or the
17573 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
17574 explicitly loading symbols from a DLL with no debugging information will
17575 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
17576 which may adversely affect symbol lookup performance.
17578 @subsubsection DLL Name Prefixes
17580 In keeping with the naming conventions used by the Microsoft debugging
17581 tools, DLL export symbols are made available with a prefix based on the
17582 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
17583 also entered into the symbol table, so @code{CreateFileA} is often
17584 sufficient. In some cases there will be name clashes within a program
17585 (particularly if the executable itself includes full debugging symbols)
17586 necessitating the use of the fully qualified name when referring to the
17587 contents of the DLL. Use single-quotes around the name to avoid the
17588 exclamation mark (``!'') being interpreted as a language operator.
17590 Note that the internal name of the DLL may be all upper-case, even
17591 though the file name of the DLL is lower-case, or vice-versa. Since
17592 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
17593 some confusion. If in doubt, try the @code{info functions} and
17594 @code{info variables} commands or even @code{maint print msymbols}
17595 (@pxref{Symbols}). Here's an example:
17598 (@value{GDBP}) info function CreateFileA
17599 All functions matching regular expression "CreateFileA":
17601 Non-debugging symbols:
17602 0x77e885f4 CreateFileA
17603 0x77e885f4 KERNEL32!CreateFileA
17607 (@value{GDBP}) info function !
17608 All functions matching regular expression "!":
17610 Non-debugging symbols:
17611 0x6100114c cygwin1!__assert
17612 0x61004034 cygwin1!_dll_crt0@@0
17613 0x61004240 cygwin1!dll_crt0(per_process *)
17617 @subsubsection Working with Minimal Symbols
17619 Symbols extracted from a DLL's export table do not contain very much
17620 type information. All that @value{GDBN} can do is guess whether a symbol
17621 refers to a function or variable depending on the linker section that
17622 contains the symbol. Also note that the actual contents of the memory
17623 contained in a DLL are not available unless the program is running. This
17624 means that you cannot examine the contents of a variable or disassemble
17625 a function within a DLL without a running program.
17627 Variables are generally treated as pointers and dereferenced
17628 automatically. For this reason, it is often necessary to prefix a
17629 variable name with the address-of operator (``&'') and provide explicit
17630 type information in the command. Here's an example of the type of
17634 (@value{GDBP}) print 'cygwin1!__argv'
17639 (@value{GDBP}) x 'cygwin1!__argv'
17640 0x10021610: "\230y\""
17643 And two possible solutions:
17646 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
17647 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
17651 (@value{GDBP}) x/2x &'cygwin1!__argv'
17652 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
17653 (@value{GDBP}) x/x 0x10021608
17654 0x10021608: 0x0022fd98
17655 (@value{GDBP}) x/s 0x0022fd98
17656 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
17659 Setting a break point within a DLL is possible even before the program
17660 starts execution. However, under these circumstances, @value{GDBN} can't
17661 examine the initial instructions of the function in order to skip the
17662 function's frame set-up code. You can work around this by using ``*&''
17663 to set the breakpoint at a raw memory address:
17666 (@value{GDBP}) break *&'python22!PyOS_Readline'
17667 Breakpoint 1 at 0x1e04eff0
17670 The author of these extensions is not entirely convinced that setting a
17671 break point within a shared DLL like @file{kernel32.dll} is completely
17675 @subsection Commands Specific to @sc{gnu} Hurd Systems
17676 @cindex @sc{gnu} Hurd debugging
17678 This subsection describes @value{GDBN} commands specific to the
17679 @sc{gnu} Hurd native debugging.
17684 @kindex set signals@r{, Hurd command}
17685 @kindex set sigs@r{, Hurd command}
17686 This command toggles the state of inferior signal interception by
17687 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
17688 affected by this command. @code{sigs} is a shorthand alias for
17693 @kindex show signals@r{, Hurd command}
17694 @kindex show sigs@r{, Hurd command}
17695 Show the current state of intercepting inferior's signals.
17697 @item set signal-thread
17698 @itemx set sigthread
17699 @kindex set signal-thread
17700 @kindex set sigthread
17701 This command tells @value{GDBN} which thread is the @code{libc} signal
17702 thread. That thread is run when a signal is delivered to a running
17703 process. @code{set sigthread} is the shorthand alias of @code{set
17706 @item show signal-thread
17707 @itemx show sigthread
17708 @kindex show signal-thread
17709 @kindex show sigthread
17710 These two commands show which thread will run when the inferior is
17711 delivered a signal.
17714 @kindex set stopped@r{, Hurd command}
17715 This commands tells @value{GDBN} that the inferior process is stopped,
17716 as with the @code{SIGSTOP} signal. The stopped process can be
17717 continued by delivering a signal to it.
17720 @kindex show stopped@r{, Hurd command}
17721 This command shows whether @value{GDBN} thinks the debuggee is
17724 @item set exceptions
17725 @kindex set exceptions@r{, Hurd command}
17726 Use this command to turn off trapping of exceptions in the inferior.
17727 When exception trapping is off, neither breakpoints nor
17728 single-stepping will work. To restore the default, set exception
17731 @item show exceptions
17732 @kindex show exceptions@r{, Hurd command}
17733 Show the current state of trapping exceptions in the inferior.
17735 @item set task pause
17736 @kindex set task@r{, Hurd commands}
17737 @cindex task attributes (@sc{gnu} Hurd)
17738 @cindex pause current task (@sc{gnu} Hurd)
17739 This command toggles task suspension when @value{GDBN} has control.
17740 Setting it to on takes effect immediately, and the task is suspended
17741 whenever @value{GDBN} gets control. Setting it to off will take
17742 effect the next time the inferior is continued. If this option is set
17743 to off, you can use @code{set thread default pause on} or @code{set
17744 thread pause on} (see below) to pause individual threads.
17746 @item show task pause
17747 @kindex show task@r{, Hurd commands}
17748 Show the current state of task suspension.
17750 @item set task detach-suspend-count
17751 @cindex task suspend count
17752 @cindex detach from task, @sc{gnu} Hurd
17753 This command sets the suspend count the task will be left with when
17754 @value{GDBN} detaches from it.
17756 @item show task detach-suspend-count
17757 Show the suspend count the task will be left with when detaching.
17759 @item set task exception-port
17760 @itemx set task excp
17761 @cindex task exception port, @sc{gnu} Hurd
17762 This command sets the task exception port to which @value{GDBN} will
17763 forward exceptions. The argument should be the value of the @dfn{send
17764 rights} of the task. @code{set task excp} is a shorthand alias.
17766 @item set noninvasive
17767 @cindex noninvasive task options
17768 This command switches @value{GDBN} to a mode that is the least
17769 invasive as far as interfering with the inferior is concerned. This
17770 is the same as using @code{set task pause}, @code{set exceptions}, and
17771 @code{set signals} to values opposite to the defaults.
17773 @item info send-rights
17774 @itemx info receive-rights
17775 @itemx info port-rights
17776 @itemx info port-sets
17777 @itemx info dead-names
17780 @cindex send rights, @sc{gnu} Hurd
17781 @cindex receive rights, @sc{gnu} Hurd
17782 @cindex port rights, @sc{gnu} Hurd
17783 @cindex port sets, @sc{gnu} Hurd
17784 @cindex dead names, @sc{gnu} Hurd
17785 These commands display information about, respectively, send rights,
17786 receive rights, port rights, port sets, and dead names of a task.
17787 There are also shorthand aliases: @code{info ports} for @code{info
17788 port-rights} and @code{info psets} for @code{info port-sets}.
17790 @item set thread pause
17791 @kindex set thread@r{, Hurd command}
17792 @cindex thread properties, @sc{gnu} Hurd
17793 @cindex pause current thread (@sc{gnu} Hurd)
17794 This command toggles current thread suspension when @value{GDBN} has
17795 control. Setting it to on takes effect immediately, and the current
17796 thread is suspended whenever @value{GDBN} gets control. Setting it to
17797 off will take effect the next time the inferior is continued.
17798 Normally, this command has no effect, since when @value{GDBN} has
17799 control, the whole task is suspended. However, if you used @code{set
17800 task pause off} (see above), this command comes in handy to suspend
17801 only the current thread.
17803 @item show thread pause
17804 @kindex show thread@r{, Hurd command}
17805 This command shows the state of current thread suspension.
17807 @item set thread run
17808 This command sets whether the current thread is allowed to run.
17810 @item show thread run
17811 Show whether the current thread is allowed to run.
17813 @item set thread detach-suspend-count
17814 @cindex thread suspend count, @sc{gnu} Hurd
17815 @cindex detach from thread, @sc{gnu} Hurd
17816 This command sets the suspend count @value{GDBN} will leave on a
17817 thread when detaching. This number is relative to the suspend count
17818 found by @value{GDBN} when it notices the thread; use @code{set thread
17819 takeover-suspend-count} to force it to an absolute value.
17821 @item show thread detach-suspend-count
17822 Show the suspend count @value{GDBN} will leave on the thread when
17825 @item set thread exception-port
17826 @itemx set thread excp
17827 Set the thread exception port to which to forward exceptions. This
17828 overrides the port set by @code{set task exception-port} (see above).
17829 @code{set thread excp} is the shorthand alias.
17831 @item set thread takeover-suspend-count
17832 Normally, @value{GDBN}'s thread suspend counts are relative to the
17833 value @value{GDBN} finds when it notices each thread. This command
17834 changes the suspend counts to be absolute instead.
17836 @item set thread default
17837 @itemx show thread default
17838 @cindex thread default settings, @sc{gnu} Hurd
17839 Each of the above @code{set thread} commands has a @code{set thread
17840 default} counterpart (e.g., @code{set thread default pause}, @code{set
17841 thread default exception-port}, etc.). The @code{thread default}
17842 variety of commands sets the default thread properties for all
17843 threads; you can then change the properties of individual threads with
17844 the non-default commands.
17849 @subsection QNX Neutrino
17850 @cindex QNX Neutrino
17852 @value{GDBN} provides the following commands specific to the QNX
17856 @item set debug nto-debug
17857 @kindex set debug nto-debug
17858 When set to on, enables debugging messages specific to the QNX
17861 @item show debug nto-debug
17862 @kindex show debug nto-debug
17863 Show the current state of QNX Neutrino messages.
17870 @value{GDBN} provides the following commands specific to the Darwin target:
17873 @item set debug darwin @var{num}
17874 @kindex set debug darwin
17875 When set to a non zero value, enables debugging messages specific to
17876 the Darwin support. Higher values produce more verbose output.
17878 @item show debug darwin
17879 @kindex show debug darwin
17880 Show the current state of Darwin messages.
17882 @item set debug mach-o @var{num}
17883 @kindex set debug mach-o
17884 When set to a non zero value, enables debugging messages while
17885 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
17886 file format used on Darwin for object and executable files.) Higher
17887 values produce more verbose output. This is a command to diagnose
17888 problems internal to @value{GDBN} and should not be needed in normal
17891 @item show debug mach-o
17892 @kindex show debug mach-o
17893 Show the current state of Mach-O file messages.
17895 @item set mach-exceptions on
17896 @itemx set mach-exceptions off
17897 @kindex set mach-exceptions
17898 On Darwin, faults are first reported as a Mach exception and are then
17899 mapped to a Posix signal. Use this command to turn on trapping of
17900 Mach exceptions in the inferior. This might be sometimes useful to
17901 better understand the cause of a fault. The default is off.
17903 @item show mach-exceptions
17904 @kindex show mach-exceptions
17905 Show the current state of exceptions trapping.
17910 @section Embedded Operating Systems
17912 This section describes configurations involving the debugging of
17913 embedded operating systems that are available for several different
17917 * VxWorks:: Using @value{GDBN} with VxWorks
17920 @value{GDBN} includes the ability to debug programs running on
17921 various real-time operating systems.
17924 @subsection Using @value{GDBN} with VxWorks
17930 @kindex target vxworks
17931 @item target vxworks @var{machinename}
17932 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
17933 is the target system's machine name or IP address.
17937 On VxWorks, @code{load} links @var{filename} dynamically on the
17938 current target system as well as adding its symbols in @value{GDBN}.
17940 @value{GDBN} enables developers to spawn and debug tasks running on networked
17941 VxWorks targets from a Unix host. Already-running tasks spawned from
17942 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
17943 both the Unix host and on the VxWorks target. The program
17944 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
17945 installed with the name @code{vxgdb}, to distinguish it from a
17946 @value{GDBN} for debugging programs on the host itself.)
17949 @item VxWorks-timeout @var{args}
17950 @kindex vxworks-timeout
17951 All VxWorks-based targets now support the option @code{vxworks-timeout}.
17952 This option is set by the user, and @var{args} represents the number of
17953 seconds @value{GDBN} waits for responses to rpc's. You might use this if
17954 your VxWorks target is a slow software simulator or is on the far side
17955 of a thin network line.
17958 The following information on connecting to VxWorks was current when
17959 this manual was produced; newer releases of VxWorks may use revised
17962 @findex INCLUDE_RDB
17963 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
17964 to include the remote debugging interface routines in the VxWorks
17965 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
17966 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
17967 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
17968 source debugging task @code{tRdbTask} when VxWorks is booted. For more
17969 information on configuring and remaking VxWorks, see the manufacturer's
17971 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
17973 Once you have included @file{rdb.a} in your VxWorks system image and set
17974 your Unix execution search path to find @value{GDBN}, you are ready to
17975 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
17976 @code{vxgdb}, depending on your installation).
17978 @value{GDBN} comes up showing the prompt:
17985 * VxWorks Connection:: Connecting to VxWorks
17986 * VxWorks Download:: VxWorks download
17987 * VxWorks Attach:: Running tasks
17990 @node VxWorks Connection
17991 @subsubsection Connecting to VxWorks
17993 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
17994 network. To connect to a target whose host name is ``@code{tt}'', type:
17997 (vxgdb) target vxworks tt
18001 @value{GDBN} displays messages like these:
18004 Attaching remote machine across net...
18009 @value{GDBN} then attempts to read the symbol tables of any object modules
18010 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18011 these files by searching the directories listed in the command search
18012 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18013 to find an object file, it displays a message such as:
18016 prog.o: No such file or directory.
18019 When this happens, add the appropriate directory to the search path with
18020 the @value{GDBN} command @code{path}, and execute the @code{target}
18023 @node VxWorks Download
18024 @subsubsection VxWorks Download
18026 @cindex download to VxWorks
18027 If you have connected to the VxWorks target and you want to debug an
18028 object that has not yet been loaded, you can use the @value{GDBN}
18029 @code{load} command to download a file from Unix to VxWorks
18030 incrementally. The object file given as an argument to the @code{load}
18031 command is actually opened twice: first by the VxWorks target in order
18032 to download the code, then by @value{GDBN} in order to read the symbol
18033 table. This can lead to problems if the current working directories on
18034 the two systems differ. If both systems have NFS mounted the same
18035 filesystems, you can avoid these problems by using absolute paths.
18036 Otherwise, it is simplest to set the working directory on both systems
18037 to the directory in which the object file resides, and then to reference
18038 the file by its name, without any path. For instance, a program
18039 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18040 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18041 program, type this on VxWorks:
18044 -> cd "@var{vxpath}/vw/demo/rdb"
18048 Then, in @value{GDBN}, type:
18051 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18052 (vxgdb) load prog.o
18055 @value{GDBN} displays a response similar to this:
18058 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18061 You can also use the @code{load} command to reload an object module
18062 after editing and recompiling the corresponding source file. Note that
18063 this makes @value{GDBN} delete all currently-defined breakpoints,
18064 auto-displays, and convenience variables, and to clear the value
18065 history. (This is necessary in order to preserve the integrity of
18066 debugger's data structures that reference the target system's symbol
18069 @node VxWorks Attach
18070 @subsubsection Running Tasks
18072 @cindex running VxWorks tasks
18073 You can also attach to an existing task using the @code{attach} command as
18077 (vxgdb) attach @var{task}
18081 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18082 or suspended when you attach to it. Running tasks are suspended at
18083 the time of attachment.
18085 @node Embedded Processors
18086 @section Embedded Processors
18088 This section goes into details specific to particular embedded
18091 @cindex send command to simulator
18092 Whenever a specific embedded processor has a simulator, @value{GDBN}
18093 allows to send an arbitrary command to the simulator.
18096 @item sim @var{command}
18097 @kindex sim@r{, a command}
18098 Send an arbitrary @var{command} string to the simulator. Consult the
18099 documentation for the specific simulator in use for information about
18100 acceptable commands.
18106 * M32R/D:: Renesas M32R/D
18107 * M68K:: Motorola M68K
18108 * MicroBlaze:: Xilinx MicroBlaze
18109 * MIPS Embedded:: MIPS Embedded
18110 * OpenRISC 1000:: OpenRisc 1000
18111 * PA:: HP PA Embedded
18112 * PowerPC Embedded:: PowerPC Embedded
18113 * Sparclet:: Tsqware Sparclet
18114 * Sparclite:: Fujitsu Sparclite
18115 * Z8000:: Zilog Z8000
18118 * Super-H:: Renesas Super-H
18127 @item target rdi @var{dev}
18128 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18129 use this target to communicate with both boards running the Angel
18130 monitor, or with the EmbeddedICE JTAG debug device.
18133 @item target rdp @var{dev}
18138 @value{GDBN} provides the following ARM-specific commands:
18141 @item set arm disassembler
18143 This commands selects from a list of disassembly styles. The
18144 @code{"std"} style is the standard style.
18146 @item show arm disassembler
18148 Show the current disassembly style.
18150 @item set arm apcs32
18151 @cindex ARM 32-bit mode
18152 This command toggles ARM operation mode between 32-bit and 26-bit.
18154 @item show arm apcs32
18155 Display the current usage of the ARM 32-bit mode.
18157 @item set arm fpu @var{fputype}
18158 This command sets the ARM floating-point unit (FPU) type. The
18159 argument @var{fputype} can be one of these:
18163 Determine the FPU type by querying the OS ABI.
18165 Software FPU, with mixed-endian doubles on little-endian ARM
18168 GCC-compiled FPA co-processor.
18170 Software FPU with pure-endian doubles.
18176 Show the current type of the FPU.
18179 This command forces @value{GDBN} to use the specified ABI.
18182 Show the currently used ABI.
18184 @item set arm fallback-mode (arm|thumb|auto)
18185 @value{GDBN} uses the symbol table, when available, to determine
18186 whether instructions are ARM or Thumb. This command controls
18187 @value{GDBN}'s default behavior when the symbol table is not
18188 available. The default is @samp{auto}, which causes @value{GDBN} to
18189 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18192 @item show arm fallback-mode
18193 Show the current fallback instruction mode.
18195 @item set arm force-mode (arm|thumb|auto)
18196 This command overrides use of the symbol table to determine whether
18197 instructions are ARM or Thumb. The default is @samp{auto}, which
18198 causes @value{GDBN} to use the symbol table and then the setting
18199 of @samp{set arm fallback-mode}.
18201 @item show arm force-mode
18202 Show the current forced instruction mode.
18204 @item set debug arm
18205 Toggle whether to display ARM-specific debugging messages from the ARM
18206 target support subsystem.
18208 @item show debug arm
18209 Show whether ARM-specific debugging messages are enabled.
18212 The following commands are available when an ARM target is debugged
18213 using the RDI interface:
18216 @item rdilogfile @r{[}@var{file}@r{]}
18218 @cindex ADP (Angel Debugger Protocol) logging
18219 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18220 With an argument, sets the log file to the specified @var{file}. With
18221 no argument, show the current log file name. The default log file is
18224 @item rdilogenable @r{[}@var{arg}@r{]}
18225 @kindex rdilogenable
18226 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18227 enables logging, with an argument 0 or @code{"no"} disables it. With
18228 no arguments displays the current setting. When logging is enabled,
18229 ADP packets exchanged between @value{GDBN} and the RDI target device
18230 are logged to a file.
18232 @item set rdiromatzero
18233 @kindex set rdiromatzero
18234 @cindex ROM at zero address, RDI
18235 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18236 vector catching is disabled, so that zero address can be used. If off
18237 (the default), vector catching is enabled. For this command to take
18238 effect, it needs to be invoked prior to the @code{target rdi} command.
18240 @item show rdiromatzero
18241 @kindex show rdiromatzero
18242 Show the current setting of ROM at zero address.
18244 @item set rdiheartbeat
18245 @kindex set rdiheartbeat
18246 @cindex RDI heartbeat
18247 Enable or disable RDI heartbeat packets. It is not recommended to
18248 turn on this option, since it confuses ARM and EPI JTAG interface, as
18249 well as the Angel monitor.
18251 @item show rdiheartbeat
18252 @kindex show rdiheartbeat
18253 Show the setting of RDI heartbeat packets.
18257 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18258 The @value{GDBN} ARM simulator accepts the following optional arguments.
18261 @item --swi-support=@var{type}
18262 Tell the simulator which SWI interfaces to support.
18263 @var{type} may be a comma separated list of the following values.
18264 The default value is @code{all}.
18277 @subsection Renesas M32R/D and M32R/SDI
18280 @kindex target m32r
18281 @item target m32r @var{dev}
18282 Renesas M32R/D ROM monitor.
18284 @kindex target m32rsdi
18285 @item target m32rsdi @var{dev}
18286 Renesas M32R SDI server, connected via parallel port to the board.
18289 The following @value{GDBN} commands are specific to the M32R monitor:
18292 @item set download-path @var{path}
18293 @kindex set download-path
18294 @cindex find downloadable @sc{srec} files (M32R)
18295 Set the default path for finding downloadable @sc{srec} files.
18297 @item show download-path
18298 @kindex show download-path
18299 Show the default path for downloadable @sc{srec} files.
18301 @item set board-address @var{addr}
18302 @kindex set board-address
18303 @cindex M32-EVA target board address
18304 Set the IP address for the M32R-EVA target board.
18306 @item show board-address
18307 @kindex show board-address
18308 Show the current IP address of the target board.
18310 @item set server-address @var{addr}
18311 @kindex set server-address
18312 @cindex download server address (M32R)
18313 Set the IP address for the download server, which is the @value{GDBN}'s
18316 @item show server-address
18317 @kindex show server-address
18318 Display the IP address of the download server.
18320 @item upload @r{[}@var{file}@r{]}
18321 @kindex upload@r{, M32R}
18322 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18323 upload capability. If no @var{file} argument is given, the current
18324 executable file is uploaded.
18326 @item tload @r{[}@var{file}@r{]}
18327 @kindex tload@r{, M32R}
18328 Test the @code{upload} command.
18331 The following commands are available for M32R/SDI:
18336 @cindex reset SDI connection, M32R
18337 This command resets the SDI connection.
18341 This command shows the SDI connection status.
18344 @kindex debug_chaos
18345 @cindex M32R/Chaos debugging
18346 Instructs the remote that M32R/Chaos debugging is to be used.
18348 @item use_debug_dma
18349 @kindex use_debug_dma
18350 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18353 @kindex use_mon_code
18354 Instructs the remote to use the MON_CODE method of accessing memory.
18357 @kindex use_ib_break
18358 Instructs the remote to set breakpoints by IB break.
18360 @item use_dbt_break
18361 @kindex use_dbt_break
18362 Instructs the remote to set breakpoints by DBT.
18368 The Motorola m68k configuration includes ColdFire support, and a
18369 target command for the following ROM monitor.
18373 @kindex target dbug
18374 @item target dbug @var{dev}
18375 dBUG ROM monitor for Motorola ColdFire.
18380 @subsection MicroBlaze
18381 @cindex Xilinx MicroBlaze
18382 @cindex XMD, Xilinx Microprocessor Debugger
18384 The MicroBlaze is a soft-core processor supported on various Xilinx
18385 FPGAs, such as Spartan or Virtex series. Boards with these processors
18386 usually have JTAG ports which connect to a host system running the Xilinx
18387 Embedded Development Kit (EDK) or Software Development Kit (SDK).
18388 This host system is used to download the configuration bitstream to
18389 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
18390 communicates with the target board using the JTAG interface and
18391 presents a @code{gdbserver} interface to the board. By default
18392 @code{xmd} uses port @code{1234}. (While it is possible to change
18393 this default port, it requires the use of undocumented @code{xmd}
18394 commands. Contact Xilinx support if you need to do this.)
18396 Use these GDB commands to connect to the MicroBlaze target processor.
18399 @item target remote :1234
18400 Use this command to connect to the target if you are running @value{GDBN}
18401 on the same system as @code{xmd}.
18403 @item target remote @var{xmd-host}:1234
18404 Use this command to connect to the target if it is connected to @code{xmd}
18405 running on a different system named @var{xmd-host}.
18408 Use this command to download a program to the MicroBlaze target.
18410 @item set debug microblaze @var{n}
18411 Enable MicroBlaze-specific debugging messages if non-zero.
18413 @item show debug microblaze @var{n}
18414 Show MicroBlaze-specific debugging level.
18417 @node MIPS Embedded
18418 @subsection MIPS Embedded
18420 @cindex MIPS boards
18421 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
18422 MIPS board attached to a serial line. This is available when
18423 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
18426 Use these @value{GDBN} commands to specify the connection to your target board:
18429 @item target mips @var{port}
18430 @kindex target mips @var{port}
18431 To run a program on the board, start up @code{@value{GDBP}} with the
18432 name of your program as the argument. To connect to the board, use the
18433 command @samp{target mips @var{port}}, where @var{port} is the name of
18434 the serial port connected to the board. If the program has not already
18435 been downloaded to the board, you may use the @code{load} command to
18436 download it. You can then use all the usual @value{GDBN} commands.
18438 For example, this sequence connects to the target board through a serial
18439 port, and loads and runs a program called @var{prog} through the
18443 host$ @value{GDBP} @var{prog}
18444 @value{GDBN} is free software and @dots{}
18445 (@value{GDBP}) target mips /dev/ttyb
18446 (@value{GDBP}) load @var{prog}
18450 @item target mips @var{hostname}:@var{portnumber}
18451 On some @value{GDBN} host configurations, you can specify a TCP
18452 connection (for instance, to a serial line managed by a terminal
18453 concentrator) instead of a serial port, using the syntax
18454 @samp{@var{hostname}:@var{portnumber}}.
18456 @item target pmon @var{port}
18457 @kindex target pmon @var{port}
18460 @item target ddb @var{port}
18461 @kindex target ddb @var{port}
18462 NEC's DDB variant of PMON for Vr4300.
18464 @item target lsi @var{port}
18465 @kindex target lsi @var{port}
18466 LSI variant of PMON.
18468 @kindex target r3900
18469 @item target r3900 @var{dev}
18470 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
18472 @kindex target array
18473 @item target array @var{dev}
18474 Array Tech LSI33K RAID controller board.
18480 @value{GDBN} also supports these special commands for MIPS targets:
18483 @item set mipsfpu double
18484 @itemx set mipsfpu single
18485 @itemx set mipsfpu none
18486 @itemx set mipsfpu auto
18487 @itemx show mipsfpu
18488 @kindex set mipsfpu
18489 @kindex show mipsfpu
18490 @cindex MIPS remote floating point
18491 @cindex floating point, MIPS remote
18492 If your target board does not support the MIPS floating point
18493 coprocessor, you should use the command @samp{set mipsfpu none} (if you
18494 need this, you may wish to put the command in your @value{GDBN} init
18495 file). This tells @value{GDBN} how to find the return value of
18496 functions which return floating point values. It also allows
18497 @value{GDBN} to avoid saving the floating point registers when calling
18498 functions on the board. If you are using a floating point coprocessor
18499 with only single precision floating point support, as on the @sc{r4650}
18500 processor, use the command @samp{set mipsfpu single}. The default
18501 double precision floating point coprocessor may be selected using
18502 @samp{set mipsfpu double}.
18504 In previous versions the only choices were double precision or no
18505 floating point, so @samp{set mipsfpu on} will select double precision
18506 and @samp{set mipsfpu off} will select no floating point.
18508 As usual, you can inquire about the @code{mipsfpu} variable with
18509 @samp{show mipsfpu}.
18511 @item set timeout @var{seconds}
18512 @itemx set retransmit-timeout @var{seconds}
18513 @itemx show timeout
18514 @itemx show retransmit-timeout
18515 @cindex @code{timeout}, MIPS protocol
18516 @cindex @code{retransmit-timeout}, MIPS protocol
18517 @kindex set timeout
18518 @kindex show timeout
18519 @kindex set retransmit-timeout
18520 @kindex show retransmit-timeout
18521 You can control the timeout used while waiting for a packet, in the MIPS
18522 remote protocol, with the @code{set timeout @var{seconds}} command. The
18523 default is 5 seconds. Similarly, you can control the timeout used while
18524 waiting for an acknowledgment of a packet with the @code{set
18525 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
18526 You can inspect both values with @code{show timeout} and @code{show
18527 retransmit-timeout}. (These commands are @emph{only} available when
18528 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
18530 The timeout set by @code{set timeout} does not apply when @value{GDBN}
18531 is waiting for your program to stop. In that case, @value{GDBN} waits
18532 forever because it has no way of knowing how long the program is going
18533 to run before stopping.
18535 @item set syn-garbage-limit @var{num}
18536 @kindex set syn-garbage-limit@r{, MIPS remote}
18537 @cindex synchronize with remote MIPS target
18538 Limit the maximum number of characters @value{GDBN} should ignore when
18539 it tries to synchronize with the remote target. The default is 10
18540 characters. Setting the limit to -1 means there's no limit.
18542 @item show syn-garbage-limit
18543 @kindex show syn-garbage-limit@r{, MIPS remote}
18544 Show the current limit on the number of characters to ignore when
18545 trying to synchronize with the remote system.
18547 @item set monitor-prompt @var{prompt}
18548 @kindex set monitor-prompt@r{, MIPS remote}
18549 @cindex remote monitor prompt
18550 Tell @value{GDBN} to expect the specified @var{prompt} string from the
18551 remote monitor. The default depends on the target:
18561 @item show monitor-prompt
18562 @kindex show monitor-prompt@r{, MIPS remote}
18563 Show the current strings @value{GDBN} expects as the prompt from the
18566 @item set monitor-warnings
18567 @kindex set monitor-warnings@r{, MIPS remote}
18568 Enable or disable monitor warnings about hardware breakpoints. This
18569 has effect only for the @code{lsi} target. When on, @value{GDBN} will
18570 display warning messages whose codes are returned by the @code{lsi}
18571 PMON monitor for breakpoint commands.
18573 @item show monitor-warnings
18574 @kindex show monitor-warnings@r{, MIPS remote}
18575 Show the current setting of printing monitor warnings.
18577 @item pmon @var{command}
18578 @kindex pmon@r{, MIPS remote}
18579 @cindex send PMON command
18580 This command allows sending an arbitrary @var{command} string to the
18581 monitor. The monitor must be in debug mode for this to work.
18584 @node OpenRISC 1000
18585 @subsection OpenRISC 1000
18586 @cindex OpenRISC 1000
18588 @cindex or1k boards
18589 See OR1k Architecture document (@uref{www.opencores.org}) for more information
18590 about platform and commands.
18594 @kindex target jtag
18595 @item target jtag jtag://@var{host}:@var{port}
18597 Connects to remote JTAG server.
18598 JTAG remote server can be either an or1ksim or JTAG server,
18599 connected via parallel port to the board.
18601 Example: @code{target jtag jtag://localhost:9999}
18604 @item or1ksim @var{command}
18605 If connected to @code{or1ksim} OpenRISC 1000 Architectural
18606 Simulator, proprietary commands can be executed.
18608 @kindex info or1k spr
18609 @item info or1k spr
18610 Displays spr groups.
18612 @item info or1k spr @var{group}
18613 @itemx info or1k spr @var{groupno}
18614 Displays register names in selected group.
18616 @item info or1k spr @var{group} @var{register}
18617 @itemx info or1k spr @var{register}
18618 @itemx info or1k spr @var{groupno} @var{registerno}
18619 @itemx info or1k spr @var{registerno}
18620 Shows information about specified spr register.
18623 @item spr @var{group} @var{register} @var{value}
18624 @itemx spr @var{register @var{value}}
18625 @itemx spr @var{groupno} @var{registerno @var{value}}
18626 @itemx spr @var{registerno @var{value}}
18627 Writes @var{value} to specified spr register.
18630 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
18631 It is very similar to @value{GDBN} trace, except it does not interfere with normal
18632 program execution and is thus much faster. Hardware breakpoints/watchpoint
18633 triggers can be set using:
18636 Load effective address/data
18638 Store effective address/data
18640 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
18645 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
18646 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
18648 @code{htrace} commands:
18649 @cindex OpenRISC 1000 htrace
18652 @item hwatch @var{conditional}
18653 Set hardware watchpoint on combination of Load/Store Effective Address(es)
18654 or Data. For example:
18656 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18658 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18662 Display information about current HW trace configuration.
18664 @item htrace trigger @var{conditional}
18665 Set starting criteria for HW trace.
18667 @item htrace qualifier @var{conditional}
18668 Set acquisition qualifier for HW trace.
18670 @item htrace stop @var{conditional}
18671 Set HW trace stopping criteria.
18673 @item htrace record [@var{data}]*
18674 Selects the data to be recorded, when qualifier is met and HW trace was
18677 @item htrace enable
18678 @itemx htrace disable
18679 Enables/disables the HW trace.
18681 @item htrace rewind [@var{filename}]
18682 Clears currently recorded trace data.
18684 If filename is specified, new trace file is made and any newly collected data
18685 will be written there.
18687 @item htrace print [@var{start} [@var{len}]]
18688 Prints trace buffer, using current record configuration.
18690 @item htrace mode continuous
18691 Set continuous trace mode.
18693 @item htrace mode suspend
18694 Set suspend trace mode.
18698 @node PowerPC Embedded
18699 @subsection PowerPC Embedded
18701 @cindex DVC register
18702 @value{GDBN} supports using the DVC (Data Value Compare) register to
18703 implement in hardware simple hardware watchpoint conditions of the form:
18706 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
18707 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
18710 The DVC register will be automatically used when @value{GDBN} detects
18711 such pattern in a condition expression, and the created watchpoint uses one
18712 debug register (either the @code{exact-watchpoints} option is on and the
18713 variable is scalar, or the variable has a length of one byte). This feature
18714 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
18717 When running on PowerPC embedded processors, @value{GDBN} automatically uses
18718 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
18719 in which case watchpoints using only one debug register are created when
18720 watching variables of scalar types.
18722 You can create an artificial array to watch an arbitrary memory
18723 region using one of the following commands (@pxref{Expressions}):
18726 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
18727 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
18730 @value{GDBN} provides the following PowerPC-specific commands:
18733 @kindex set powerpc
18734 @item set powerpc soft-float
18735 @itemx show powerpc soft-float
18736 Force @value{GDBN} to use (or not use) a software floating point calling
18737 convention. By default, @value{GDBN} selects the calling convention based
18738 on the selected architecture and the provided executable file.
18740 @item set powerpc vector-abi
18741 @itemx show powerpc vector-abi
18742 Force @value{GDBN} to use the specified calling convention for vector
18743 arguments and return values. The valid options are @samp{auto};
18744 @samp{generic}, to avoid vector registers even if they are present;
18745 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
18746 registers. By default, @value{GDBN} selects the calling convention
18747 based on the selected architecture and the provided executable file.
18749 @item set powerpc exact-watchpoints
18750 @itemx show powerpc exact-watchpoints
18751 Allow @value{GDBN} to use only one debug register when watching a variable
18752 of scalar type, thus assuming that the variable is accessed through the
18753 address of its first byte.
18755 @kindex target dink32
18756 @item target dink32 @var{dev}
18757 DINK32 ROM monitor.
18759 @kindex target ppcbug
18760 @item target ppcbug @var{dev}
18761 @kindex target ppcbug1
18762 @item target ppcbug1 @var{dev}
18763 PPCBUG ROM monitor for PowerPC.
18766 @item target sds @var{dev}
18767 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
18770 @cindex SDS protocol
18771 The following commands specific to the SDS protocol are supported
18775 @item set sdstimeout @var{nsec}
18776 @kindex set sdstimeout
18777 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
18778 default is 2 seconds.
18780 @item show sdstimeout
18781 @kindex show sdstimeout
18782 Show the current value of the SDS timeout.
18784 @item sds @var{command}
18785 @kindex sds@r{, a command}
18786 Send the specified @var{command} string to the SDS monitor.
18791 @subsection HP PA Embedded
18795 @kindex target op50n
18796 @item target op50n @var{dev}
18797 OP50N monitor, running on an OKI HPPA board.
18799 @kindex target w89k
18800 @item target w89k @var{dev}
18801 W89K monitor, running on a Winbond HPPA board.
18806 @subsection Tsqware Sparclet
18810 @value{GDBN} enables developers to debug tasks running on
18811 Sparclet targets from a Unix host.
18812 @value{GDBN} uses code that runs on
18813 both the Unix host and on the Sparclet target. The program
18814 @code{@value{GDBP}} is installed and executed on the Unix host.
18817 @item remotetimeout @var{args}
18818 @kindex remotetimeout
18819 @value{GDBN} supports the option @code{remotetimeout}.
18820 This option is set by the user, and @var{args} represents the number of
18821 seconds @value{GDBN} waits for responses.
18824 @cindex compiling, on Sparclet
18825 When compiling for debugging, include the options @samp{-g} to get debug
18826 information and @samp{-Ttext} to relocate the program to where you wish to
18827 load it on the target. You may also want to add the options @samp{-n} or
18828 @samp{-N} in order to reduce the size of the sections. Example:
18831 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
18834 You can use @code{objdump} to verify that the addresses are what you intended:
18837 sparclet-aout-objdump --headers --syms prog
18840 @cindex running, on Sparclet
18842 your Unix execution search path to find @value{GDBN}, you are ready to
18843 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
18844 (or @code{sparclet-aout-gdb}, depending on your installation).
18846 @value{GDBN} comes up showing the prompt:
18853 * Sparclet File:: Setting the file to debug
18854 * Sparclet Connection:: Connecting to Sparclet
18855 * Sparclet Download:: Sparclet download
18856 * Sparclet Execution:: Running and debugging
18859 @node Sparclet File
18860 @subsubsection Setting File to Debug
18862 The @value{GDBN} command @code{file} lets you choose with program to debug.
18865 (gdbslet) file prog
18869 @value{GDBN} then attempts to read the symbol table of @file{prog}.
18870 @value{GDBN} locates
18871 the file by searching the directories listed in the command search
18873 If the file was compiled with debug information (option @samp{-g}), source
18874 files will be searched as well.
18875 @value{GDBN} locates
18876 the source files by searching the directories listed in the directory search
18877 path (@pxref{Environment, ,Your Program's Environment}).
18879 to find a file, it displays a message such as:
18882 prog: No such file or directory.
18885 When this happens, add the appropriate directories to the search paths with
18886 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
18887 @code{target} command again.
18889 @node Sparclet Connection
18890 @subsubsection Connecting to Sparclet
18892 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
18893 To connect to a target on serial port ``@code{ttya}'', type:
18896 (gdbslet) target sparclet /dev/ttya
18897 Remote target sparclet connected to /dev/ttya
18898 main () at ../prog.c:3
18902 @value{GDBN} displays messages like these:
18908 @node Sparclet Download
18909 @subsubsection Sparclet Download
18911 @cindex download to Sparclet
18912 Once connected to the Sparclet target,
18913 you can use the @value{GDBN}
18914 @code{load} command to download the file from the host to the target.
18915 The file name and load offset should be given as arguments to the @code{load}
18917 Since the file format is aout, the program must be loaded to the starting
18918 address. You can use @code{objdump} to find out what this value is. The load
18919 offset is an offset which is added to the VMA (virtual memory address)
18920 of each of the file's sections.
18921 For instance, if the program
18922 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
18923 and bss at 0x12010170, in @value{GDBN}, type:
18926 (gdbslet) load prog 0x12010000
18927 Loading section .text, size 0xdb0 vma 0x12010000
18930 If the code is loaded at a different address then what the program was linked
18931 to, you may need to use the @code{section} and @code{add-symbol-file} commands
18932 to tell @value{GDBN} where to map the symbol table.
18934 @node Sparclet Execution
18935 @subsubsection Running and Debugging
18937 @cindex running and debugging Sparclet programs
18938 You can now begin debugging the task using @value{GDBN}'s execution control
18939 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
18940 manual for the list of commands.
18944 Breakpoint 1 at 0x12010000: file prog.c, line 3.
18946 Starting program: prog
18947 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
18948 3 char *symarg = 0;
18950 4 char *execarg = "hello!";
18955 @subsection Fujitsu Sparclite
18959 @kindex target sparclite
18960 @item target sparclite @var{dev}
18961 Fujitsu sparclite boards, used only for the purpose of loading.
18962 You must use an additional command to debug the program.
18963 For example: target remote @var{dev} using @value{GDBN} standard
18969 @subsection Zilog Z8000
18972 @cindex simulator, Z8000
18973 @cindex Zilog Z8000 simulator
18975 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
18978 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
18979 unsegmented variant of the Z8000 architecture) or the Z8001 (the
18980 segmented variant). The simulator recognizes which architecture is
18981 appropriate by inspecting the object code.
18984 @item target sim @var{args}
18986 @kindex target sim@r{, with Z8000}
18987 Debug programs on a simulated CPU. If the simulator supports setup
18988 options, specify them via @var{args}.
18992 After specifying this target, you can debug programs for the simulated
18993 CPU in the same style as programs for your host computer; use the
18994 @code{file} command to load a new program image, the @code{run} command
18995 to run your program, and so on.
18997 As well as making available all the usual machine registers
18998 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
18999 additional items of information as specially named registers:
19004 Counts clock-ticks in the simulator.
19007 Counts instructions run in the simulator.
19010 Execution time in 60ths of a second.
19014 You can refer to these values in @value{GDBN} expressions with the usual
19015 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19016 conditional breakpoint that suspends only after at least 5000
19017 simulated clock ticks.
19020 @subsection Atmel AVR
19023 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19024 following AVR-specific commands:
19027 @item info io_registers
19028 @kindex info io_registers@r{, AVR}
19029 @cindex I/O registers (Atmel AVR)
19030 This command displays information about the AVR I/O registers. For
19031 each register, @value{GDBN} prints its number and value.
19038 When configured for debugging CRIS, @value{GDBN} provides the
19039 following CRIS-specific commands:
19042 @item set cris-version @var{ver}
19043 @cindex CRIS version
19044 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19045 The CRIS version affects register names and sizes. This command is useful in
19046 case autodetection of the CRIS version fails.
19048 @item show cris-version
19049 Show the current CRIS version.
19051 @item set cris-dwarf2-cfi
19052 @cindex DWARF-2 CFI and CRIS
19053 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19054 Change to @samp{off} when using @code{gcc-cris} whose version is below
19057 @item show cris-dwarf2-cfi
19058 Show the current state of using DWARF-2 CFI.
19060 @item set cris-mode @var{mode}
19062 Set the current CRIS mode to @var{mode}. It should only be changed when
19063 debugging in guru mode, in which case it should be set to
19064 @samp{guru} (the default is @samp{normal}).
19066 @item show cris-mode
19067 Show the current CRIS mode.
19071 @subsection Renesas Super-H
19074 For the Renesas Super-H processor, @value{GDBN} provides these
19079 @kindex regs@r{, Super-H}
19080 Show the values of all Super-H registers.
19082 @item set sh calling-convention @var{convention}
19083 @kindex set sh calling-convention
19084 Set the calling-convention used when calling functions from @value{GDBN}.
19085 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19086 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19087 convention. If the DWARF-2 information of the called function specifies
19088 that the function follows the Renesas calling convention, the function
19089 is called using the Renesas calling convention. If the calling convention
19090 is set to @samp{renesas}, the Renesas calling convention is always used,
19091 regardless of the DWARF-2 information. This can be used to override the
19092 default of @samp{gcc} if debug information is missing, or the compiler
19093 does not emit the DWARF-2 calling convention entry for a function.
19095 @item show sh calling-convention
19096 @kindex show sh calling-convention
19097 Show the current calling convention setting.
19102 @node Architectures
19103 @section Architectures
19105 This section describes characteristics of architectures that affect
19106 all uses of @value{GDBN} with the architecture, both native and cross.
19113 * HPPA:: HP PA architecture
19114 * SPU:: Cell Broadband Engine SPU architecture
19119 @subsection x86 Architecture-specific Issues
19122 @item set struct-convention @var{mode}
19123 @kindex set struct-convention
19124 @cindex struct return convention
19125 @cindex struct/union returned in registers
19126 Set the convention used by the inferior to return @code{struct}s and
19127 @code{union}s from functions to @var{mode}. Possible values of
19128 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19129 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19130 are returned on the stack, while @code{"reg"} means that a
19131 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19132 be returned in a register.
19134 @item show struct-convention
19135 @kindex show struct-convention
19136 Show the current setting of the convention to return @code{struct}s
19145 @kindex set rstack_high_address
19146 @cindex AMD 29K register stack
19147 @cindex register stack, AMD29K
19148 @item set rstack_high_address @var{address}
19149 On AMD 29000 family processors, registers are saved in a separate
19150 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19151 extent of this stack. Normally, @value{GDBN} just assumes that the
19152 stack is ``large enough''. This may result in @value{GDBN} referencing
19153 memory locations that do not exist. If necessary, you can get around
19154 this problem by specifying the ending address of the register stack with
19155 the @code{set rstack_high_address} command. The argument should be an
19156 address, which you probably want to precede with @samp{0x} to specify in
19159 @kindex show rstack_high_address
19160 @item show rstack_high_address
19161 Display the current limit of the register stack, on AMD 29000 family
19169 See the following section.
19174 @cindex stack on Alpha
19175 @cindex stack on MIPS
19176 @cindex Alpha stack
19178 Alpha- and MIPS-based computers use an unusual stack frame, which
19179 sometimes requires @value{GDBN} to search backward in the object code to
19180 find the beginning of a function.
19182 @cindex response time, MIPS debugging
19183 To improve response time (especially for embedded applications, where
19184 @value{GDBN} may be restricted to a slow serial line for this search)
19185 you may want to limit the size of this search, using one of these
19189 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19190 @item set heuristic-fence-post @var{limit}
19191 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19192 search for the beginning of a function. A value of @var{0} (the
19193 default) means there is no limit. However, except for @var{0}, the
19194 larger the limit the more bytes @code{heuristic-fence-post} must search
19195 and therefore the longer it takes to run. You should only need to use
19196 this command when debugging a stripped executable.
19198 @item show heuristic-fence-post
19199 Display the current limit.
19203 These commands are available @emph{only} when @value{GDBN} is configured
19204 for debugging programs on Alpha or MIPS processors.
19206 Several MIPS-specific commands are available when debugging MIPS
19210 @item set mips abi @var{arg}
19211 @kindex set mips abi
19212 @cindex set ABI for MIPS
19213 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
19214 values of @var{arg} are:
19218 The default ABI associated with the current binary (this is the
19229 @item show mips abi
19230 @kindex show mips abi
19231 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
19234 @itemx show mipsfpu
19235 @xref{MIPS Embedded, set mipsfpu}.
19237 @item set mips mask-address @var{arg}
19238 @kindex set mips mask-address
19239 @cindex MIPS addresses, masking
19240 This command determines whether the most-significant 32 bits of 64-bit
19241 MIPS addresses are masked off. The argument @var{arg} can be
19242 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
19243 setting, which lets @value{GDBN} determine the correct value.
19245 @item show mips mask-address
19246 @kindex show mips mask-address
19247 Show whether the upper 32 bits of MIPS addresses are masked off or
19250 @item set remote-mips64-transfers-32bit-regs
19251 @kindex set remote-mips64-transfers-32bit-regs
19252 This command controls compatibility with 64-bit MIPS targets that
19253 transfer data in 32-bit quantities. If you have an old MIPS 64 target
19254 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
19255 and 64 bits for other registers, set this option to @samp{on}.
19257 @item show remote-mips64-transfers-32bit-regs
19258 @kindex show remote-mips64-transfers-32bit-regs
19259 Show the current setting of compatibility with older MIPS 64 targets.
19261 @item set debug mips
19262 @kindex set debug mips
19263 This command turns on and off debugging messages for the MIPS-specific
19264 target code in @value{GDBN}.
19266 @item show debug mips
19267 @kindex show debug mips
19268 Show the current setting of MIPS debugging messages.
19274 @cindex HPPA support
19276 When @value{GDBN} is debugging the HP PA architecture, it provides the
19277 following special commands:
19280 @item set debug hppa
19281 @kindex set debug hppa
19282 This command determines whether HPPA architecture-specific debugging
19283 messages are to be displayed.
19285 @item show debug hppa
19286 Show whether HPPA debugging messages are displayed.
19288 @item maint print unwind @var{address}
19289 @kindex maint print unwind@r{, HPPA}
19290 This command displays the contents of the unwind table entry at the
19291 given @var{address}.
19297 @subsection Cell Broadband Engine SPU architecture
19298 @cindex Cell Broadband Engine
19301 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
19302 it provides the following special commands:
19305 @item info spu event
19307 Display SPU event facility status. Shows current event mask
19308 and pending event status.
19310 @item info spu signal
19311 Display SPU signal notification facility status. Shows pending
19312 signal-control word and signal notification mode of both signal
19313 notification channels.
19315 @item info spu mailbox
19316 Display SPU mailbox facility status. Shows all pending entries,
19317 in order of processing, in each of the SPU Write Outbound,
19318 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
19321 Display MFC DMA status. Shows all pending commands in the MFC
19322 DMA queue. For each entry, opcode, tag, class IDs, effective
19323 and local store addresses and transfer size are shown.
19325 @item info spu proxydma
19326 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
19327 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
19328 and local store addresses and transfer size are shown.
19332 When @value{GDBN} is debugging a combined PowerPC/SPU application
19333 on the Cell Broadband Engine, it provides in addition the following
19337 @item set spu stop-on-load @var{arg}
19339 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
19340 will give control to the user when a new SPE thread enters its @code{main}
19341 function. The default is @code{off}.
19343 @item show spu stop-on-load
19345 Show whether to stop for new SPE threads.
19347 @item set spu auto-flush-cache @var{arg}
19348 Set whether to automatically flush the software-managed cache. When set to
19349 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19350 cache to be flushed whenever SPE execution stops. This provides a consistent
19351 view of PowerPC memory that is accessed via the cache. If an application
19352 does not use the software-managed cache, this option has no effect.
19354 @item show spu auto-flush-cache
19355 Show whether to automatically flush the software-managed cache.
19360 @subsection PowerPC
19361 @cindex PowerPC architecture
19363 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
19364 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
19365 numbers stored in the floating point registers. These values must be stored
19366 in two consecutive registers, always starting at an even register like
19367 @code{f0} or @code{f2}.
19369 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
19370 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
19371 @code{f2} and @code{f3} for @code{$dl1} and so on.
19373 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
19374 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
19377 @node Controlling GDB
19378 @chapter Controlling @value{GDBN}
19380 You can alter the way @value{GDBN} interacts with you by using the
19381 @code{set} command. For commands controlling how @value{GDBN} displays
19382 data, see @ref{Print Settings, ,Print Settings}. Other settings are
19387 * Editing:: Command editing
19388 * Command History:: Command history
19389 * Screen Size:: Screen size
19390 * Numbers:: Numbers
19391 * ABI:: Configuring the current ABI
19392 * Messages/Warnings:: Optional warnings and messages
19393 * Debugging Output:: Optional messages about internal happenings
19394 * Other Misc Settings:: Other Miscellaneous Settings
19402 @value{GDBN} indicates its readiness to read a command by printing a string
19403 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
19404 can change the prompt string with the @code{set prompt} command. For
19405 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
19406 the prompt in one of the @value{GDBN} sessions so that you can always tell
19407 which one you are talking to.
19409 @emph{Note:} @code{set prompt} does not add a space for you after the
19410 prompt you set. This allows you to set a prompt which ends in a space
19411 or a prompt that does not.
19415 @item set prompt @var{newprompt}
19416 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
19418 @kindex show prompt
19420 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
19424 @section Command Editing
19426 @cindex command line editing
19428 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
19429 @sc{gnu} library provides consistent behavior for programs which provide a
19430 command line interface to the user. Advantages are @sc{gnu} Emacs-style
19431 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
19432 substitution, and a storage and recall of command history across
19433 debugging sessions.
19435 You may control the behavior of command line editing in @value{GDBN} with the
19436 command @code{set}.
19439 @kindex set editing
19442 @itemx set editing on
19443 Enable command line editing (enabled by default).
19445 @item set editing off
19446 Disable command line editing.
19448 @kindex show editing
19450 Show whether command line editing is enabled.
19453 @ifset SYSTEM_READLINE
19454 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
19456 @ifclear SYSTEM_READLINE
19457 @xref{Command Line Editing},
19459 for more details about the Readline
19460 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
19461 encouraged to read that chapter.
19463 @node Command History
19464 @section Command History
19465 @cindex command history
19467 @value{GDBN} can keep track of the commands you type during your
19468 debugging sessions, so that you can be certain of precisely what
19469 happened. Use these commands to manage the @value{GDBN} command
19472 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
19473 package, to provide the history facility.
19474 @ifset SYSTEM_READLINE
19475 @xref{Using History Interactively, , , history, GNU History Library},
19477 @ifclear SYSTEM_READLINE
19478 @xref{Using History Interactively},
19480 for the detailed description of the History library.
19482 To issue a command to @value{GDBN} without affecting certain aspects of
19483 the state which is seen by users, prefix it with @samp{server }
19484 (@pxref{Server Prefix}). This
19485 means that this command will not affect the command history, nor will it
19486 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
19487 pressed on a line by itself.
19489 @cindex @code{server}, command prefix
19490 The server prefix does not affect the recording of values into the value
19491 history; to print a value without recording it into the value history,
19492 use the @code{output} command instead of the @code{print} command.
19494 Here is the description of @value{GDBN} commands related to command
19498 @cindex history substitution
19499 @cindex history file
19500 @kindex set history filename
19501 @cindex @env{GDBHISTFILE}, environment variable
19502 @item set history filename @var{fname}
19503 Set the name of the @value{GDBN} command history file to @var{fname}.
19504 This is the file where @value{GDBN} reads an initial command history
19505 list, and where it writes the command history from this session when it
19506 exits. You can access this list through history expansion or through
19507 the history command editing characters listed below. This file defaults
19508 to the value of the environment variable @code{GDBHISTFILE}, or to
19509 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
19512 @cindex save command history
19513 @kindex set history save
19514 @item set history save
19515 @itemx set history save on
19516 Record command history in a file, whose name may be specified with the
19517 @code{set history filename} command. By default, this option is disabled.
19519 @item set history save off
19520 Stop recording command history in a file.
19522 @cindex history size
19523 @kindex set history size
19524 @cindex @env{HISTSIZE}, environment variable
19525 @item set history size @var{size}
19526 Set the number of commands which @value{GDBN} keeps in its history list.
19527 This defaults to the value of the environment variable
19528 @code{HISTSIZE}, or to 256 if this variable is not set.
19531 History expansion assigns special meaning to the character @kbd{!}.
19532 @ifset SYSTEM_READLINE
19533 @xref{Event Designators, , , history, GNU History Library},
19535 @ifclear SYSTEM_READLINE
19536 @xref{Event Designators},
19540 @cindex history expansion, turn on/off
19541 Since @kbd{!} is also the logical not operator in C, history expansion
19542 is off by default. If you decide to enable history expansion with the
19543 @code{set history expansion on} command, you may sometimes need to
19544 follow @kbd{!} (when it is used as logical not, in an expression) with
19545 a space or a tab to prevent it from being expanded. The readline
19546 history facilities do not attempt substitution on the strings
19547 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
19549 The commands to control history expansion are:
19552 @item set history expansion on
19553 @itemx set history expansion
19554 @kindex set history expansion
19555 Enable history expansion. History expansion is off by default.
19557 @item set history expansion off
19558 Disable history expansion.
19561 @kindex show history
19563 @itemx show history filename
19564 @itemx show history save
19565 @itemx show history size
19566 @itemx show history expansion
19567 These commands display the state of the @value{GDBN} history parameters.
19568 @code{show history} by itself displays all four states.
19573 @kindex show commands
19574 @cindex show last commands
19575 @cindex display command history
19576 @item show commands
19577 Display the last ten commands in the command history.
19579 @item show commands @var{n}
19580 Print ten commands centered on command number @var{n}.
19582 @item show commands +
19583 Print ten commands just after the commands last printed.
19587 @section Screen Size
19588 @cindex size of screen
19589 @cindex pauses in output
19591 Certain commands to @value{GDBN} may produce large amounts of
19592 information output to the screen. To help you read all of it,
19593 @value{GDBN} pauses and asks you for input at the end of each page of
19594 output. Type @key{RET} when you want to continue the output, or @kbd{q}
19595 to discard the remaining output. Also, the screen width setting
19596 determines when to wrap lines of output. Depending on what is being
19597 printed, @value{GDBN} tries to break the line at a readable place,
19598 rather than simply letting it overflow onto the following line.
19600 Normally @value{GDBN} knows the size of the screen from the terminal
19601 driver software. For example, on Unix @value{GDBN} uses the termcap data base
19602 together with the value of the @code{TERM} environment variable and the
19603 @code{stty rows} and @code{stty cols} settings. If this is not correct,
19604 you can override it with the @code{set height} and @code{set
19611 @kindex show height
19612 @item set height @var{lpp}
19614 @itemx set width @var{cpl}
19616 These @code{set} commands specify a screen height of @var{lpp} lines and
19617 a screen width of @var{cpl} characters. The associated @code{show}
19618 commands display the current settings.
19620 If you specify a height of zero lines, @value{GDBN} does not pause during
19621 output no matter how long the output is. This is useful if output is to a
19622 file or to an editor buffer.
19624 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
19625 from wrapping its output.
19627 @item set pagination on
19628 @itemx set pagination off
19629 @kindex set pagination
19630 Turn the output pagination on or off; the default is on. Turning
19631 pagination off is the alternative to @code{set height 0}. Note that
19632 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
19633 Options, -batch}) also automatically disables pagination.
19635 @item show pagination
19636 @kindex show pagination
19637 Show the current pagination mode.
19642 @cindex number representation
19643 @cindex entering numbers
19645 You can always enter numbers in octal, decimal, or hexadecimal in
19646 @value{GDBN} by the usual conventions: octal numbers begin with
19647 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
19648 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
19649 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
19650 10; likewise, the default display for numbers---when no particular
19651 format is specified---is base 10. You can change the default base for
19652 both input and output with the commands described below.
19655 @kindex set input-radix
19656 @item set input-radix @var{base}
19657 Set the default base for numeric input. Supported choices
19658 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19659 specified either unambiguously or using the current input radix; for
19663 set input-radix 012
19664 set input-radix 10.
19665 set input-radix 0xa
19669 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
19670 leaves the input radix unchanged, no matter what it was, since
19671 @samp{10}, being without any leading or trailing signs of its base, is
19672 interpreted in the current radix. Thus, if the current radix is 16,
19673 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
19676 @kindex set output-radix
19677 @item set output-radix @var{base}
19678 Set the default base for numeric display. Supported choices
19679 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19680 specified either unambiguously or using the current input radix.
19682 @kindex show input-radix
19683 @item show input-radix
19684 Display the current default base for numeric input.
19686 @kindex show output-radix
19687 @item show output-radix
19688 Display the current default base for numeric display.
19690 @item set radix @r{[}@var{base}@r{]}
19694 These commands set and show the default base for both input and output
19695 of numbers. @code{set radix} sets the radix of input and output to
19696 the same base; without an argument, it resets the radix back to its
19697 default value of 10.
19702 @section Configuring the Current ABI
19704 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
19705 application automatically. However, sometimes you need to override its
19706 conclusions. Use these commands to manage @value{GDBN}'s view of the
19713 One @value{GDBN} configuration can debug binaries for multiple operating
19714 system targets, either via remote debugging or native emulation.
19715 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
19716 but you can override its conclusion using the @code{set osabi} command.
19717 One example where this is useful is in debugging of binaries which use
19718 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
19719 not have the same identifying marks that the standard C library for your
19724 Show the OS ABI currently in use.
19727 With no argument, show the list of registered available OS ABI's.
19729 @item set osabi @var{abi}
19730 Set the current OS ABI to @var{abi}.
19733 @cindex float promotion
19735 Generally, the way that an argument of type @code{float} is passed to a
19736 function depends on whether the function is prototyped. For a prototyped
19737 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
19738 according to the architecture's convention for @code{float}. For unprototyped
19739 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
19740 @code{double} and then passed.
19742 Unfortunately, some forms of debug information do not reliably indicate whether
19743 a function is prototyped. If @value{GDBN} calls a function that is not marked
19744 as prototyped, it consults @kbd{set coerce-float-to-double}.
19747 @kindex set coerce-float-to-double
19748 @item set coerce-float-to-double
19749 @itemx set coerce-float-to-double on
19750 Arguments of type @code{float} will be promoted to @code{double} when passed
19751 to an unprototyped function. This is the default setting.
19753 @item set coerce-float-to-double off
19754 Arguments of type @code{float} will be passed directly to unprototyped
19757 @kindex show coerce-float-to-double
19758 @item show coerce-float-to-double
19759 Show the current setting of promoting @code{float} to @code{double}.
19763 @kindex show cp-abi
19764 @value{GDBN} needs to know the ABI used for your program's C@t{++}
19765 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
19766 used to build your application. @value{GDBN} only fully supports
19767 programs with a single C@t{++} ABI; if your program contains code using
19768 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
19769 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
19770 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
19771 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
19772 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
19773 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
19778 Show the C@t{++} ABI currently in use.
19781 With no argument, show the list of supported C@t{++} ABI's.
19783 @item set cp-abi @var{abi}
19784 @itemx set cp-abi auto
19785 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
19788 @node Messages/Warnings
19789 @section Optional Warnings and Messages
19791 @cindex verbose operation
19792 @cindex optional warnings
19793 By default, @value{GDBN} is silent about its inner workings. If you are
19794 running on a slow machine, you may want to use the @code{set verbose}
19795 command. This makes @value{GDBN} tell you when it does a lengthy
19796 internal operation, so you will not think it has crashed.
19798 Currently, the messages controlled by @code{set verbose} are those
19799 which announce that the symbol table for a source file is being read;
19800 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
19803 @kindex set verbose
19804 @item set verbose on
19805 Enables @value{GDBN} output of certain informational messages.
19807 @item set verbose off
19808 Disables @value{GDBN} output of certain informational messages.
19810 @kindex show verbose
19812 Displays whether @code{set verbose} is on or off.
19815 By default, if @value{GDBN} encounters bugs in the symbol table of an
19816 object file, it is silent; but if you are debugging a compiler, you may
19817 find this information useful (@pxref{Symbol Errors, ,Errors Reading
19822 @kindex set complaints
19823 @item set complaints @var{limit}
19824 Permits @value{GDBN} to output @var{limit} complaints about each type of
19825 unusual symbols before becoming silent about the problem. Set
19826 @var{limit} to zero to suppress all complaints; set it to a large number
19827 to prevent complaints from being suppressed.
19829 @kindex show complaints
19830 @item show complaints
19831 Displays how many symbol complaints @value{GDBN} is permitted to produce.
19835 @anchor{confirmation requests}
19836 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
19837 lot of stupid questions to confirm certain commands. For example, if
19838 you try to run a program which is already running:
19842 The program being debugged has been started already.
19843 Start it from the beginning? (y or n)
19846 If you are willing to unflinchingly face the consequences of your own
19847 commands, you can disable this ``feature'':
19851 @kindex set confirm
19853 @cindex confirmation
19854 @cindex stupid questions
19855 @item set confirm off
19856 Disables confirmation requests. Note that running @value{GDBN} with
19857 the @option{--batch} option (@pxref{Mode Options, -batch}) also
19858 automatically disables confirmation requests.
19860 @item set confirm on
19861 Enables confirmation requests (the default).
19863 @kindex show confirm
19865 Displays state of confirmation requests.
19869 @cindex command tracing
19870 If you need to debug user-defined commands or sourced files you may find it
19871 useful to enable @dfn{command tracing}. In this mode each command will be
19872 printed as it is executed, prefixed with one or more @samp{+} symbols, the
19873 quantity denoting the call depth of each command.
19876 @kindex set trace-commands
19877 @cindex command scripts, debugging
19878 @item set trace-commands on
19879 Enable command tracing.
19880 @item set trace-commands off
19881 Disable command tracing.
19882 @item show trace-commands
19883 Display the current state of command tracing.
19886 @node Debugging Output
19887 @section Optional Messages about Internal Happenings
19888 @cindex optional debugging messages
19890 @value{GDBN} has commands that enable optional debugging messages from
19891 various @value{GDBN} subsystems; normally these commands are of
19892 interest to @value{GDBN} maintainers, or when reporting a bug. This
19893 section documents those commands.
19896 @kindex set exec-done-display
19897 @item set exec-done-display
19898 Turns on or off the notification of asynchronous commands'
19899 completion. When on, @value{GDBN} will print a message when an
19900 asynchronous command finishes its execution. The default is off.
19901 @kindex show exec-done-display
19902 @item show exec-done-display
19903 Displays the current setting of asynchronous command completion
19906 @cindex gdbarch debugging info
19907 @cindex architecture debugging info
19908 @item set debug arch
19909 Turns on or off display of gdbarch debugging info. The default is off
19911 @item show debug arch
19912 Displays the current state of displaying gdbarch debugging info.
19913 @item set debug aix-thread
19914 @cindex AIX threads
19915 Display debugging messages about inner workings of the AIX thread
19917 @item show debug aix-thread
19918 Show the current state of AIX thread debugging info display.
19919 @item set debug dwarf2-die
19920 @cindex DWARF2 DIEs
19921 Dump DWARF2 DIEs after they are read in.
19922 The value is the number of nesting levels to print.
19923 A value of zero turns off the display.
19924 @item show debug dwarf2-die
19925 Show the current state of DWARF2 DIE debugging.
19926 @item set debug displaced
19927 @cindex displaced stepping debugging info
19928 Turns on or off display of @value{GDBN} debugging info for the
19929 displaced stepping support. The default is off.
19930 @item show debug displaced
19931 Displays the current state of displaying @value{GDBN} debugging info
19932 related to displaced stepping.
19933 @item set debug event
19934 @cindex event debugging info
19935 Turns on or off display of @value{GDBN} event debugging info. The
19937 @item show debug event
19938 Displays the current state of displaying @value{GDBN} event debugging
19940 @item set debug expression
19941 @cindex expression debugging info
19942 Turns on or off display of debugging info about @value{GDBN}
19943 expression parsing. The default is off.
19944 @item show debug expression
19945 Displays the current state of displaying debugging info about
19946 @value{GDBN} expression parsing.
19947 @item set debug frame
19948 @cindex frame debugging info
19949 Turns on or off display of @value{GDBN} frame debugging info. The
19951 @item show debug frame
19952 Displays the current state of displaying @value{GDBN} frame debugging
19954 @item set debug gnu-nat
19955 @cindex @sc{gnu}/Hurd debug messages
19956 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
19957 @item show debug gnu-nat
19958 Show the current state of @sc{gnu}/Hurd debugging messages.
19959 @item set debug infrun
19960 @cindex inferior debugging info
19961 Turns on or off display of @value{GDBN} debugging info for running the inferior.
19962 The default is off. @file{infrun.c} contains GDB's runtime state machine used
19963 for implementing operations such as single-stepping the inferior.
19964 @item show debug infrun
19965 Displays the current state of @value{GDBN} inferior debugging.
19966 @item set debug jit
19967 @cindex just-in-time compilation, debugging messages
19968 Turns on or off debugging messages from JIT debug support.
19969 @item show debug jit
19970 Displays the current state of @value{GDBN} JIT debugging.
19971 @item set debug lin-lwp
19972 @cindex @sc{gnu}/Linux LWP debug messages
19973 @cindex Linux lightweight processes
19974 Turns on or off debugging messages from the Linux LWP debug support.
19975 @item show debug lin-lwp
19976 Show the current state of Linux LWP debugging messages.
19977 @item set debug lin-lwp-async
19978 @cindex @sc{gnu}/Linux LWP async debug messages
19979 @cindex Linux lightweight processes
19980 Turns on or off debugging messages from the Linux LWP async debug support.
19981 @item show debug lin-lwp-async
19982 Show the current state of Linux LWP async debugging messages.
19983 @item set debug observer
19984 @cindex observer debugging info
19985 Turns on or off display of @value{GDBN} observer debugging. This
19986 includes info such as the notification of observable events.
19987 @item show debug observer
19988 Displays the current state of observer debugging.
19989 @item set debug overload
19990 @cindex C@t{++} overload debugging info
19991 Turns on or off display of @value{GDBN} C@t{++} overload debugging
19992 info. This includes info such as ranking of functions, etc. The default
19994 @item show debug overload
19995 Displays the current state of displaying @value{GDBN} C@t{++} overload
19997 @cindex expression parser, debugging info
19998 @cindex debug expression parser
19999 @item set debug parser
20000 Turns on or off the display of expression parser debugging output.
20001 Internally, this sets the @code{yydebug} variable in the expression
20002 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20003 details. The default is off.
20004 @item show debug parser
20005 Show the current state of expression parser debugging.
20006 @cindex packets, reporting on stdout
20007 @cindex serial connections, debugging
20008 @cindex debug remote protocol
20009 @cindex remote protocol debugging
20010 @cindex display remote packets
20011 @item set debug remote
20012 Turns on or off display of reports on all packets sent back and forth across
20013 the serial line to the remote machine. The info is printed on the
20014 @value{GDBN} standard output stream. The default is off.
20015 @item show debug remote
20016 Displays the state of display of remote packets.
20017 @item set debug serial
20018 Turns on or off display of @value{GDBN} serial debugging info. The
20020 @item show debug serial
20021 Displays the current state of displaying @value{GDBN} serial debugging
20023 @item set debug solib-frv
20024 @cindex FR-V shared-library debugging
20025 Turns on or off debugging messages for FR-V shared-library code.
20026 @item show debug solib-frv
20027 Display the current state of FR-V shared-library code debugging
20029 @item set debug target
20030 @cindex target debugging info
20031 Turns on or off display of @value{GDBN} target debugging info. This info
20032 includes what is going on at the target level of GDB, as it happens. The
20033 default is 0. Set it to 1 to track events, and to 2 to also track the
20034 value of large memory transfers. Changes to this flag do not take effect
20035 until the next time you connect to a target or use the @code{run} command.
20036 @item show debug target
20037 Displays the current state of displaying @value{GDBN} target debugging
20039 @item set debug timestamp
20040 @cindex timestampping debugging info
20041 Turns on or off display of timestamps with @value{GDBN} debugging info.
20042 When enabled, seconds and microseconds are displayed before each debugging
20044 @item show debug timestamp
20045 Displays the current state of displaying timestamps with @value{GDBN}
20047 @item set debugvarobj
20048 @cindex variable object debugging info
20049 Turns on or off display of @value{GDBN} variable object debugging
20050 info. The default is off.
20051 @item show debugvarobj
20052 Displays the current state of displaying @value{GDBN} variable object
20054 @item set debug xml
20055 @cindex XML parser debugging
20056 Turns on or off debugging messages for built-in XML parsers.
20057 @item show debug xml
20058 Displays the current state of XML debugging messages.
20061 @node Other Misc Settings
20062 @section Other Miscellaneous Settings
20063 @cindex miscellaneous settings
20066 @kindex set interactive-mode
20067 @item set interactive-mode
20068 If @code{on}, forces @value{GDBN} to assume that GDB was started
20069 in a terminal. In practice, this means that @value{GDBN} should wait
20070 for the user to answer queries generated by commands entered at
20071 the command prompt. If @code{off}, forces @value{GDBN} to operate
20072 in the opposite mode, and it uses the default answers to all queries.
20073 If @code{auto} (the default), @value{GDBN} tries to determine whether
20074 its standard input is a terminal, and works in interactive-mode if it
20075 is, non-interactively otherwise.
20077 In the vast majority of cases, the debugger should be able to guess
20078 correctly which mode should be used. But this setting can be useful
20079 in certain specific cases, such as running a MinGW @value{GDBN}
20080 inside a cygwin window.
20082 @kindex show interactive-mode
20083 @item show interactive-mode
20084 Displays whether the debugger is operating in interactive mode or not.
20087 @node Extending GDB
20088 @chapter Extending @value{GDBN}
20089 @cindex extending GDB
20091 @value{GDBN} provides two mechanisms for extension. The first is based
20092 on composition of @value{GDBN} commands, and the second is based on the
20093 Python scripting language.
20095 To facilitate the use of these extensions, @value{GDBN} is capable
20096 of evaluating the contents of a file. When doing so, @value{GDBN}
20097 can recognize which scripting language is being used by looking at
20098 the filename extension. Files with an unrecognized filename extension
20099 are always treated as a @value{GDBN} Command Files.
20100 @xref{Command Files,, Command files}.
20102 You can control how @value{GDBN} evaluates these files with the following
20106 @kindex set script-extension
20107 @kindex show script-extension
20108 @item set script-extension off
20109 All scripts are always evaluated as @value{GDBN} Command Files.
20111 @item set script-extension soft
20112 The debugger determines the scripting language based on filename
20113 extension. If this scripting language is supported, @value{GDBN}
20114 evaluates the script using that language. Otherwise, it evaluates
20115 the file as a @value{GDBN} Command File.
20117 @item set script-extension strict
20118 The debugger determines the scripting language based on filename
20119 extension, and evaluates the script using that language. If the
20120 language is not supported, then the evaluation fails.
20122 @item show script-extension
20123 Display the current value of the @code{script-extension} option.
20128 * Sequences:: Canned Sequences of Commands
20129 * Python:: Scripting @value{GDBN} using Python
20133 @section Canned Sequences of Commands
20135 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20136 Command Lists}), @value{GDBN} provides two ways to store sequences of
20137 commands for execution as a unit: user-defined commands and command
20141 * Define:: How to define your own commands
20142 * Hooks:: Hooks for user-defined commands
20143 * Command Files:: How to write scripts of commands to be stored in a file
20144 * Output:: Commands for controlled output
20148 @subsection User-defined Commands
20150 @cindex user-defined command
20151 @cindex arguments, to user-defined commands
20152 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20153 which you assign a new name as a command. This is done with the
20154 @code{define} command. User commands may accept up to 10 arguments
20155 separated by whitespace. Arguments are accessed within the user command
20156 via @code{$arg0@dots{}$arg9}. A trivial example:
20160 print $arg0 + $arg1 + $arg2
20165 To execute the command use:
20172 This defines the command @code{adder}, which prints the sum of
20173 its three arguments. Note the arguments are text substitutions, so they may
20174 reference variables, use complex expressions, or even perform inferior
20177 @cindex argument count in user-defined commands
20178 @cindex how many arguments (user-defined commands)
20179 In addition, @code{$argc} may be used to find out how many arguments have
20180 been passed. This expands to a number in the range 0@dots{}10.
20185 print $arg0 + $arg1
20188 print $arg0 + $arg1 + $arg2
20196 @item define @var{commandname}
20197 Define a command named @var{commandname}. If there is already a command
20198 by that name, you are asked to confirm that you want to redefine it.
20199 @var{commandname} may be a bare command name consisting of letters,
20200 numbers, dashes, and underscores. It may also start with any predefined
20201 prefix command. For example, @samp{define target my-target} creates
20202 a user-defined @samp{target my-target} command.
20204 The definition of the command is made up of other @value{GDBN} command lines,
20205 which are given following the @code{define} command. The end of these
20206 commands is marked by a line containing @code{end}.
20209 @kindex end@r{ (user-defined commands)}
20210 @item document @var{commandname}
20211 Document the user-defined command @var{commandname}, so that it can be
20212 accessed by @code{help}. The command @var{commandname} must already be
20213 defined. This command reads lines of documentation just as @code{define}
20214 reads the lines of the command definition, ending with @code{end}.
20215 After the @code{document} command is finished, @code{help} on command
20216 @var{commandname} displays the documentation you have written.
20218 You may use the @code{document} command again to change the
20219 documentation of a command. Redefining the command with @code{define}
20220 does not change the documentation.
20222 @kindex dont-repeat
20223 @cindex don't repeat command
20225 Used inside a user-defined command, this tells @value{GDBN} that this
20226 command should not be repeated when the user hits @key{RET}
20227 (@pxref{Command Syntax, repeat last command}).
20229 @kindex help user-defined
20230 @item help user-defined
20231 List all user-defined commands, with the first line of the documentation
20236 @itemx show user @var{commandname}
20237 Display the @value{GDBN} commands used to define @var{commandname} (but
20238 not its documentation). If no @var{commandname} is given, display the
20239 definitions for all user-defined commands.
20241 @cindex infinite recursion in user-defined commands
20242 @kindex show max-user-call-depth
20243 @kindex set max-user-call-depth
20244 @item show max-user-call-depth
20245 @itemx set max-user-call-depth
20246 The value of @code{max-user-call-depth} controls how many recursion
20247 levels are allowed in user-defined commands before @value{GDBN} suspects an
20248 infinite recursion and aborts the command.
20251 In addition to the above commands, user-defined commands frequently
20252 use control flow commands, described in @ref{Command Files}.
20254 When user-defined commands are executed, the
20255 commands of the definition are not printed. An error in any command
20256 stops execution of the user-defined command.
20258 If used interactively, commands that would ask for confirmation proceed
20259 without asking when used inside a user-defined command. Many @value{GDBN}
20260 commands that normally print messages to say what they are doing omit the
20261 messages when used in a user-defined command.
20264 @subsection User-defined Command Hooks
20265 @cindex command hooks
20266 @cindex hooks, for commands
20267 @cindex hooks, pre-command
20270 You may define @dfn{hooks}, which are a special kind of user-defined
20271 command. Whenever you run the command @samp{foo}, if the user-defined
20272 command @samp{hook-foo} exists, it is executed (with no arguments)
20273 before that command.
20275 @cindex hooks, post-command
20277 A hook may also be defined which is run after the command you executed.
20278 Whenever you run the command @samp{foo}, if the user-defined command
20279 @samp{hookpost-foo} exists, it is executed (with no arguments) after
20280 that command. Post-execution hooks may exist simultaneously with
20281 pre-execution hooks, for the same command.
20283 It is valid for a hook to call the command which it hooks. If this
20284 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
20286 @c It would be nice if hookpost could be passed a parameter indicating
20287 @c if the command it hooks executed properly or not. FIXME!
20289 @kindex stop@r{, a pseudo-command}
20290 In addition, a pseudo-command, @samp{stop} exists. Defining
20291 (@samp{hook-stop}) makes the associated commands execute every time
20292 execution stops in your program: before breakpoint commands are run,
20293 displays are printed, or the stack frame is printed.
20295 For example, to ignore @code{SIGALRM} signals while
20296 single-stepping, but treat them normally during normal execution,
20301 handle SIGALRM nopass
20305 handle SIGALRM pass
20308 define hook-continue
20309 handle SIGALRM pass
20313 As a further example, to hook at the beginning and end of the @code{echo}
20314 command, and to add extra text to the beginning and end of the message,
20322 define hookpost-echo
20326 (@value{GDBP}) echo Hello World
20327 <<<---Hello World--->>>
20332 You can define a hook for any single-word command in @value{GDBN}, but
20333 not for command aliases; you should define a hook for the basic command
20334 name, e.g.@: @code{backtrace} rather than @code{bt}.
20335 @c FIXME! So how does Joe User discover whether a command is an alias
20337 You can hook a multi-word command by adding @code{hook-} or
20338 @code{hookpost-} to the last word of the command, e.g.@:
20339 @samp{define target hook-remote} to add a hook to @samp{target remote}.
20341 If an error occurs during the execution of your hook, execution of
20342 @value{GDBN} commands stops and @value{GDBN} issues a prompt
20343 (before the command that you actually typed had a chance to run).
20345 If you try to define a hook which does not match any known command, you
20346 get a warning from the @code{define} command.
20348 @node Command Files
20349 @subsection Command Files
20351 @cindex command files
20352 @cindex scripting commands
20353 A command file for @value{GDBN} is a text file made of lines that are
20354 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
20355 also be included. An empty line in a command file does nothing; it
20356 does not mean to repeat the last command, as it would from the
20359 You can request the execution of a command file with the @code{source}
20360 command. Note that the @code{source} command is also used to evaluate
20361 scripts that are not Command Files. The exact behavior can be configured
20362 using the @code{script-extension} setting.
20363 @xref{Extending GDB,, Extending GDB}.
20367 @cindex execute commands from a file
20368 @item source [-s] [-v] @var{filename}
20369 Execute the command file @var{filename}.
20372 The lines in a command file are generally executed sequentially,
20373 unless the order of execution is changed by one of the
20374 @emph{flow-control commands} described below. The commands are not
20375 printed as they are executed. An error in any command terminates
20376 execution of the command file and control is returned to the console.
20378 @value{GDBN} first searches for @var{filename} in the current directory.
20379 If the file is not found there, and @var{filename} does not specify a
20380 directory, then @value{GDBN} also looks for the file on the source search path
20381 (specified with the @samp{directory} command);
20382 except that @file{$cdir} is not searched because the compilation directory
20383 is not relevant to scripts.
20385 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
20386 on the search path even if @var{filename} specifies a directory.
20387 The search is done by appending @var{filename} to each element of the
20388 search path. So, for example, if @var{filename} is @file{mylib/myscript}
20389 and the search path contains @file{/home/user} then @value{GDBN} will
20390 look for the script @file{/home/user/mylib/myscript}.
20391 The search is also done if @var{filename} is an absolute path.
20392 For example, if @var{filename} is @file{/tmp/myscript} and
20393 the search path contains @file{/home/user} then @value{GDBN} will
20394 look for the script @file{/home/user/tmp/myscript}.
20395 For DOS-like systems, if @var{filename} contains a drive specification,
20396 it is stripped before concatenation. For example, if @var{filename} is
20397 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
20398 will look for the script @file{c:/tmp/myscript}.
20400 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
20401 each command as it is executed. The option must be given before
20402 @var{filename}, and is interpreted as part of the filename anywhere else.
20404 Commands that would ask for confirmation if used interactively proceed
20405 without asking when used in a command file. Many @value{GDBN} commands that
20406 normally print messages to say what they are doing omit the messages
20407 when called from command files.
20409 @value{GDBN} also accepts command input from standard input. In this
20410 mode, normal output goes to standard output and error output goes to
20411 standard error. Errors in a command file supplied on standard input do
20412 not terminate execution of the command file---execution continues with
20416 gdb < cmds > log 2>&1
20419 (The syntax above will vary depending on the shell used.) This example
20420 will execute commands from the file @file{cmds}. All output and errors
20421 would be directed to @file{log}.
20423 Since commands stored on command files tend to be more general than
20424 commands typed interactively, they frequently need to deal with
20425 complicated situations, such as different or unexpected values of
20426 variables and symbols, changes in how the program being debugged is
20427 built, etc. @value{GDBN} provides a set of flow-control commands to
20428 deal with these complexities. Using these commands, you can write
20429 complex scripts that loop over data structures, execute commands
20430 conditionally, etc.
20437 This command allows to include in your script conditionally executed
20438 commands. The @code{if} command takes a single argument, which is an
20439 expression to evaluate. It is followed by a series of commands that
20440 are executed only if the expression is true (its value is nonzero).
20441 There can then optionally be an @code{else} line, followed by a series
20442 of commands that are only executed if the expression was false. The
20443 end of the list is marked by a line containing @code{end}.
20447 This command allows to write loops. Its syntax is similar to
20448 @code{if}: the command takes a single argument, which is an expression
20449 to evaluate, and must be followed by the commands to execute, one per
20450 line, terminated by an @code{end}. These commands are called the
20451 @dfn{body} of the loop. The commands in the body of @code{while} are
20452 executed repeatedly as long as the expression evaluates to true.
20456 This command exits the @code{while} loop in whose body it is included.
20457 Execution of the script continues after that @code{while}s @code{end}
20460 @kindex loop_continue
20461 @item loop_continue
20462 This command skips the execution of the rest of the body of commands
20463 in the @code{while} loop in whose body it is included. Execution
20464 branches to the beginning of the @code{while} loop, where it evaluates
20465 the controlling expression.
20467 @kindex end@r{ (if/else/while commands)}
20469 Terminate the block of commands that are the body of @code{if},
20470 @code{else}, or @code{while} flow-control commands.
20475 @subsection Commands for Controlled Output
20477 During the execution of a command file or a user-defined command, normal
20478 @value{GDBN} output is suppressed; the only output that appears is what is
20479 explicitly printed by the commands in the definition. This section
20480 describes three commands useful for generating exactly the output you
20485 @item echo @var{text}
20486 @c I do not consider backslash-space a standard C escape sequence
20487 @c because it is not in ANSI.
20488 Print @var{text}. Nonprinting characters can be included in
20489 @var{text} using C escape sequences, such as @samp{\n} to print a
20490 newline. @strong{No newline is printed unless you specify one.}
20491 In addition to the standard C escape sequences, a backslash followed
20492 by a space stands for a space. This is useful for displaying a
20493 string with spaces at the beginning or the end, since leading and
20494 trailing spaces are otherwise trimmed from all arguments.
20495 To print @samp{@w{ }and foo =@w{ }}, use the command
20496 @samp{echo \@w{ }and foo = \@w{ }}.
20498 A backslash at the end of @var{text} can be used, as in C, to continue
20499 the command onto subsequent lines. For example,
20502 echo This is some text\n\
20503 which is continued\n\
20504 onto several lines.\n
20507 produces the same output as
20510 echo This is some text\n
20511 echo which is continued\n
20512 echo onto several lines.\n
20516 @item output @var{expression}
20517 Print the value of @var{expression} and nothing but that value: no
20518 newlines, no @samp{$@var{nn} = }. The value is not entered in the
20519 value history either. @xref{Expressions, ,Expressions}, for more information
20522 @item output/@var{fmt} @var{expression}
20523 Print the value of @var{expression} in format @var{fmt}. You can use
20524 the same formats as for @code{print}. @xref{Output Formats,,Output
20525 Formats}, for more information.
20528 @item printf @var{template}, @var{expressions}@dots{}
20529 Print the values of one or more @var{expressions} under the control of
20530 the string @var{template}. To print several values, make
20531 @var{expressions} be a comma-separated list of individual expressions,
20532 which may be either numbers or pointers. Their values are printed as
20533 specified by @var{template}, exactly as a C program would do by
20534 executing the code below:
20537 printf (@var{template}, @var{expressions}@dots{});
20540 As in @code{C} @code{printf}, ordinary characters in @var{template}
20541 are printed verbatim, while @dfn{conversion specification} introduced
20542 by the @samp{%} character cause subsequent @var{expressions} to be
20543 evaluated, their values converted and formatted according to type and
20544 style information encoded in the conversion specifications, and then
20547 For example, you can print two values in hex like this:
20550 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
20553 @code{printf} supports all the standard @code{C} conversion
20554 specifications, including the flags and modifiers between the @samp{%}
20555 character and the conversion letter, with the following exceptions:
20559 The argument-ordering modifiers, such as @samp{2$}, are not supported.
20562 The modifier @samp{*} is not supported for specifying precision or
20566 The @samp{'} flag (for separation of digits into groups according to
20567 @code{LC_NUMERIC'}) is not supported.
20570 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
20574 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
20577 The conversion letters @samp{a} and @samp{A} are not supported.
20581 Note that the @samp{ll} type modifier is supported only if the
20582 underlying @code{C} implementation used to build @value{GDBN} supports
20583 the @code{long long int} type, and the @samp{L} type modifier is
20584 supported only if @code{long double} type is available.
20586 As in @code{C}, @code{printf} supports simple backslash-escape
20587 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
20588 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
20589 single character. Octal and hexadecimal escape sequences are not
20592 Additionally, @code{printf} supports conversion specifications for DFP
20593 (@dfn{Decimal Floating Point}) types using the following length modifiers
20594 together with a floating point specifier.
20599 @samp{H} for printing @code{Decimal32} types.
20602 @samp{D} for printing @code{Decimal64} types.
20605 @samp{DD} for printing @code{Decimal128} types.
20608 If the underlying @code{C} implementation used to build @value{GDBN} has
20609 support for the three length modifiers for DFP types, other modifiers
20610 such as width and precision will also be available for @value{GDBN} to use.
20612 In case there is no such @code{C} support, no additional modifiers will be
20613 available and the value will be printed in the standard way.
20615 Here's an example of printing DFP types using the above conversion letters:
20617 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
20621 @item eval @var{template}, @var{expressions}@dots{}
20622 Convert the values of one or more @var{expressions} under the control of
20623 the string @var{template} to a command line, and call it.
20628 @section Scripting @value{GDBN} using Python
20629 @cindex python scripting
20630 @cindex scripting with python
20632 You can script @value{GDBN} using the @uref{http://www.python.org/,
20633 Python programming language}. This feature is available only if
20634 @value{GDBN} was configured using @option{--with-python}.
20636 @cindex python directory
20637 Python scripts used by @value{GDBN} should be installed in
20638 @file{@var{data-directory}/python}, where @var{data-directory} is
20639 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
20640 This directory, known as the @dfn{python directory},
20641 is automatically added to the Python Search Path in order to allow
20642 the Python interpreter to locate all scripts installed at this location.
20645 * Python Commands:: Accessing Python from @value{GDBN}.
20646 * Python API:: Accessing @value{GDBN} from Python.
20647 * Auto-loading:: Automatically loading Python code.
20648 * Python modules:: Python modules provided by @value{GDBN}.
20651 @node Python Commands
20652 @subsection Python Commands
20653 @cindex python commands
20654 @cindex commands to access python
20656 @value{GDBN} provides one command for accessing the Python interpreter,
20657 and one related setting:
20661 @item python @r{[}@var{code}@r{]}
20662 The @code{python} command can be used to evaluate Python code.
20664 If given an argument, the @code{python} command will evaluate the
20665 argument as a Python command. For example:
20668 (@value{GDBP}) python print 23
20672 If you do not provide an argument to @code{python}, it will act as a
20673 multi-line command, like @code{define}. In this case, the Python
20674 script is made up of subsequent command lines, given after the
20675 @code{python} command. This command list is terminated using a line
20676 containing @code{end}. For example:
20679 (@value{GDBP}) python
20681 End with a line saying just "end".
20687 @kindex maint set python print-stack
20688 @item maint set python print-stack
20689 By default, @value{GDBN} will print a stack trace when an error occurs
20690 in a Python script. This can be controlled using @code{maint set
20691 python print-stack}: if @code{on}, the default, then Python stack
20692 printing is enabled; if @code{off}, then Python stack printing is
20696 It is also possible to execute a Python script from the @value{GDBN}
20700 @item source @file{script-name}
20701 The script name must end with @samp{.py} and @value{GDBN} must be configured
20702 to recognize the script language based on filename extension using
20703 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
20705 @item python execfile ("script-name")
20706 This method is based on the @code{execfile} Python built-in function,
20707 and thus is always available.
20711 @subsection Python API
20713 @cindex programming in python
20715 @cindex python stdout
20716 @cindex python pagination
20717 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
20718 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
20719 A Python program which outputs to one of these streams may have its
20720 output interrupted by the user (@pxref{Screen Size}). In this
20721 situation, a Python @code{KeyboardInterrupt} exception is thrown.
20724 * Basic Python:: Basic Python Functions.
20725 * Exception Handling:: How Python exceptions are translated.
20726 * Values From Inferior:: Python representation of values.
20727 * Types In Python:: Python representation of types.
20728 * Pretty Printing API:: Pretty-printing values.
20729 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
20730 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
20731 * Inferiors In Python:: Python representation of inferiors (processes)
20732 * Events In Python:: Listening for events from @value{GDBN}.
20733 * Threads In Python:: Accessing inferior threads from Python.
20734 * Commands In Python:: Implementing new commands in Python.
20735 * Parameters In Python:: Adding new @value{GDBN} parameters.
20736 * Functions In Python:: Writing new convenience functions.
20737 * Progspaces In Python:: Program spaces.
20738 * Objfiles In Python:: Object files.
20739 * Frames In Python:: Accessing inferior stack frames from Python.
20740 * Blocks In Python:: Accessing frame blocks from Python.
20741 * Symbols In Python:: Python representation of symbols.
20742 * Symbol Tables In Python:: Python representation of symbol tables.
20743 * Lazy Strings In Python:: Python representation of lazy strings.
20744 * Breakpoints In Python:: Manipulating breakpoints using Python.
20748 @subsubsection Basic Python
20750 @cindex python functions
20751 @cindex python module
20753 @value{GDBN} introduces a new Python module, named @code{gdb}. All
20754 methods and classes added by @value{GDBN} are placed in this module.
20755 @value{GDBN} automatically @code{import}s the @code{gdb} module for
20756 use in all scripts evaluated by the @code{python} command.
20758 @findex gdb.PYTHONDIR
20760 A string containing the python directory (@pxref{Python}).
20763 @findex gdb.execute
20764 @defun execute command [from_tty] [to_string]
20765 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
20766 If a GDB exception happens while @var{command} runs, it is
20767 translated as described in @ref{Exception Handling,,Exception Handling}.
20769 @var{from_tty} specifies whether @value{GDBN} ought to consider this
20770 command as having originated from the user invoking it interactively.
20771 It must be a boolean value. If omitted, it defaults to @code{False}.
20773 By default, any output produced by @var{command} is sent to
20774 @value{GDBN}'s standard output. If the @var{to_string} parameter is
20775 @code{True}, then output will be collected by @code{gdb.execute} and
20776 returned as a string. The default is @code{False}, in which case the
20777 return value is @code{None}. If @var{to_string} is @code{True}, the
20778 @value{GDBN} virtual terminal will be temporarily set to unlimited width
20779 and height, and its pagination will be disabled; @pxref{Screen Size}.
20782 @findex gdb.breakpoints
20784 Return a sequence holding all of @value{GDBN}'s breakpoints.
20785 @xref{Breakpoints In Python}, for more information.
20788 @findex gdb.parameter
20789 @defun parameter parameter
20790 Return the value of a @value{GDBN} parameter. @var{parameter} is a
20791 string naming the parameter to look up; @var{parameter} may contain
20792 spaces if the parameter has a multi-part name. For example,
20793 @samp{print object} is a valid parameter name.
20795 If the named parameter does not exist, this function throws a
20796 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
20797 parameter's value is converted to a Python value of the appropriate
20798 type, and returned.
20801 @findex gdb.history
20802 @defun history number
20803 Return a value from @value{GDBN}'s value history (@pxref{Value
20804 History}). @var{number} indicates which history element to return.
20805 If @var{number} is negative, then @value{GDBN} will take its absolute value
20806 and count backward from the last element (i.e., the most recent element) to
20807 find the value to return. If @var{number} is zero, then @value{GDBN} will
20808 return the most recent element. If the element specified by @var{number}
20809 doesn't exist in the value history, a @code{gdb.error} exception will be
20812 If no exception is raised, the return value is always an instance of
20813 @code{gdb.Value} (@pxref{Values From Inferior}).
20816 @findex gdb.parse_and_eval
20817 @defun parse_and_eval expression
20818 Parse @var{expression} as an expression in the current language,
20819 evaluate it, and return the result as a @code{gdb.Value}.
20820 @var{expression} must be a string.
20822 This function can be useful when implementing a new command
20823 (@pxref{Commands In Python}), as it provides a way to parse the
20824 command's argument as an expression. It is also useful simply to
20825 compute values, for example, it is the only way to get the value of a
20826 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
20829 @findex gdb.post_event
20830 @defun post_event event
20831 Put @var{event}, a callable object taking no arguments, into
20832 @value{GDBN}'s internal event queue. This callable will be invoked at
20833 some later point, during @value{GDBN}'s event processing. Events
20834 posted using @code{post_event} will be run in the order in which they
20835 were posted; however, there is no way to know when they will be
20836 processed relative to other events inside @value{GDBN}.
20838 @value{GDBN} is not thread-safe. If your Python program uses multiple
20839 threads, you must be careful to only call @value{GDBN}-specific
20840 functions in the main @value{GDBN} thread. @code{post_event} ensures
20844 (@value{GDBP}) python
20848 > def __init__(self, message):
20849 > self.message = message;
20850 > def __call__(self):
20851 > gdb.write(self.message)
20853 >class MyThread1 (threading.Thread):
20855 > gdb.post_event(Writer("Hello "))
20857 >class MyThread2 (threading.Thread):
20859 > gdb.post_event(Writer("World\n"))
20861 >MyThread1().start()
20862 >MyThread2().start()
20864 (@value{GDBP}) Hello World
20869 @defun write string
20870 Print a string to @value{GDBN}'s paginated standard output stream.
20871 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
20872 call this function.
20877 Flush @value{GDBN}'s paginated standard output stream. Flushing
20878 @code{sys.stdout} or @code{sys.stderr} will automatically call this
20882 @findex gdb.target_charset
20883 @defun target_charset
20884 Return the name of the current target character set (@pxref{Character
20885 Sets}). This differs from @code{gdb.parameter('target-charset')} in
20886 that @samp{auto} is never returned.
20889 @findex gdb.target_wide_charset
20890 @defun target_wide_charset
20891 Return the name of the current target wide character set
20892 (@pxref{Character Sets}). This differs from
20893 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
20897 @findex gdb.solib_name
20898 @defun solib_name address
20899 Return the name of the shared library holding the given @var{address}
20900 as a string, or @code{None}.
20903 @findex gdb.decode_line
20904 @defun decode_line @r{[}expression@r{]}
20905 Return locations of the line specified by @var{expression}, or of the
20906 current line if no argument was given. This function returns a Python
20907 tuple containing two elements. The first element contains a string
20908 holding any unparsed section of @var{expression} (or @code{None} if
20909 the expression has been fully parsed). The second element contains
20910 either @code{None} or another tuple that contains all the locations
20911 that match the expression represented as @code{gdb.Symtab_and_line}
20912 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
20913 provided, it is decoded the way that @value{GDBN}'s inbuilt
20914 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
20917 @node Exception Handling
20918 @subsubsection Exception Handling
20919 @cindex python exceptions
20920 @cindex exceptions, python
20922 When executing the @code{python} command, Python exceptions
20923 uncaught within the Python code are translated to calls to
20924 @value{GDBN} error-reporting mechanism. If the command that called
20925 @code{python} does not handle the error, @value{GDBN} will
20926 terminate it and print an error message containing the Python
20927 exception name, the associated value, and the Python call stack
20928 backtrace at the point where the exception was raised. Example:
20931 (@value{GDBP}) python print foo
20932 Traceback (most recent call last):
20933 File "<string>", line 1, in <module>
20934 NameError: name 'foo' is not defined
20937 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
20938 Python code are converted to Python exceptions. The type of the
20939 Python exception depends on the error.
20943 This is the base class for most exceptions generated by @value{GDBN}.
20944 It is derived from @code{RuntimeError}, for compatibility with earlier
20945 versions of @value{GDBN}.
20947 If an error occurring in @value{GDBN} does not fit into some more
20948 specific category, then the generated exception will have this type.
20950 @item gdb.MemoryError
20951 This is a subclass of @code{gdb.error} which is thrown when an
20952 operation tried to access invalid memory in the inferior.
20954 @item KeyboardInterrupt
20955 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
20956 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
20959 In all cases, your exception handler will see the @value{GDBN} error
20960 message as its value and the Python call stack backtrace at the Python
20961 statement closest to where the @value{GDBN} error occured as the
20964 @findex gdb.GdbError
20965 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
20966 it is useful to be able to throw an exception that doesn't cause a
20967 traceback to be printed. For example, the user may have invoked the
20968 command incorrectly. Use the @code{gdb.GdbError} exception
20969 to handle this case. Example:
20973 >class HelloWorld (gdb.Command):
20974 > """Greet the whole world."""
20975 > def __init__ (self):
20976 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
20977 > def invoke (self, args, from_tty):
20978 > argv = gdb.string_to_argv (args)
20979 > if len (argv) != 0:
20980 > raise gdb.GdbError ("hello-world takes no arguments")
20981 > print "Hello, World!"
20984 (gdb) hello-world 42
20985 hello-world takes no arguments
20988 @node Values From Inferior
20989 @subsubsection Values From Inferior
20990 @cindex values from inferior, with Python
20991 @cindex python, working with values from inferior
20993 @cindex @code{gdb.Value}
20994 @value{GDBN} provides values it obtains from the inferior program in
20995 an object of type @code{gdb.Value}. @value{GDBN} uses this object
20996 for its internal bookkeeping of the inferior's values, and for
20997 fetching values when necessary.
20999 Inferior values that are simple scalars can be used directly in
21000 Python expressions that are valid for the value's data type. Here's
21001 an example for an integer or floating-point value @code{some_val}:
21008 As result of this, @code{bar} will also be a @code{gdb.Value} object
21009 whose values are of the same type as those of @code{some_val}.
21011 Inferior values that are structures or instances of some class can
21012 be accessed using the Python @dfn{dictionary syntax}. For example, if
21013 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21014 can access its @code{foo} element with:
21017 bar = some_val['foo']
21020 Again, @code{bar} will also be a @code{gdb.Value} object.
21022 A @code{gdb.Value} that represents a function can be executed via
21023 inferior function call. Any arguments provided to the call must match
21024 the function's prototype, and must be provided in the order specified
21027 For example, @code{some_val} is a @code{gdb.Value} instance
21028 representing a function that takes two integers as arguments. To
21029 execute this function, call it like so:
21032 result = some_val (10,20)
21035 Any values returned from a function call will be stored as a
21038 The following attributes are provided:
21041 @defivar Value address
21042 If this object is addressable, this read-only attribute holds a
21043 @code{gdb.Value} object representing the address. Otherwise,
21044 this attribute holds @code{None}.
21047 @cindex optimized out value in Python
21048 @defivar Value is_optimized_out
21049 This read-only boolean attribute is true if the compiler optimized out
21050 this value, thus it is not available for fetching from the inferior.
21053 @defivar Value type
21054 The type of this @code{gdb.Value}. The value of this attribute is a
21055 @code{gdb.Type} object (@pxref{Types In Python}).
21058 @defivar Value dynamic_type
21059 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21060 type information (@acronym{RTTI}) to determine the dynamic type of the
21061 value. If this value is of class type, it will return the class in
21062 which the value is embedded, if any. If this value is of pointer or
21063 reference to a class type, it will compute the dynamic type of the
21064 referenced object, and return a pointer or reference to that type,
21065 respectively. In all other cases, it will return the value's static
21068 Note that this feature will only work when debugging a C@t{++} program
21069 that includes @acronym{RTTI} for the object in question. Otherwise,
21070 it will just return the static type of the value as in @kbd{ptype foo}
21071 (@pxref{Symbols, ptype}).
21075 The following methods are provided:
21078 @defmethod Value __init__ @var{val}
21079 Many Python values can be converted directly to a @code{gdb.Value} via
21080 this object initializer. Specifically:
21083 @item Python boolean
21084 A Python boolean is converted to the boolean type from the current
21087 @item Python integer
21088 A Python integer is converted to the C @code{long} type for the
21089 current architecture.
21092 A Python long is converted to the C @code{long long} type for the
21093 current architecture.
21096 A Python float is converted to the C @code{double} type for the
21097 current architecture.
21099 @item Python string
21100 A Python string is converted to a target string, using the current
21103 @item @code{gdb.Value}
21104 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
21106 @item @code{gdb.LazyString}
21107 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
21108 Python}), then the lazy string's @code{value} method is called, and
21109 its result is used.
21113 @defmethod Value cast type
21114 Return a new instance of @code{gdb.Value} that is the result of
21115 casting this instance to the type described by @var{type}, which must
21116 be a @code{gdb.Type} object. If the cast cannot be performed for some
21117 reason, this method throws an exception.
21120 @defmethod Value dereference
21121 For pointer data types, this method returns a new @code{gdb.Value} object
21122 whose contents is the object pointed to by the pointer. For example, if
21123 @code{foo} is a C pointer to an @code{int}, declared in your C program as
21130 then you can use the corresponding @code{gdb.Value} to access what
21131 @code{foo} points to like this:
21134 bar = foo.dereference ()
21137 The result @code{bar} will be a @code{gdb.Value} object holding the
21138 value pointed to by @code{foo}.
21141 @defmethod Value dynamic_cast type
21142 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
21143 operator were used. Consult a C@t{++} reference for details.
21146 @defmethod Value reinterpret_cast type
21147 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
21148 operator were used. Consult a C@t{++} reference for details.
21151 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
21152 If this @code{gdb.Value} represents a string, then this method
21153 converts the contents to a Python string. Otherwise, this method will
21154 throw an exception.
21156 Strings are recognized in a language-specific way; whether a given
21157 @code{gdb.Value} represents a string is determined by the current
21160 For C-like languages, a value is a string if it is a pointer to or an
21161 array of characters or ints. The string is assumed to be terminated
21162 by a zero of the appropriate width. However if the optional length
21163 argument is given, the string will be converted to that given length,
21164 ignoring any embedded zeros that the string may contain.
21166 If the optional @var{encoding} argument is given, it must be a string
21167 naming the encoding of the string in the @code{gdb.Value}, such as
21168 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
21169 the same encodings as the corresponding argument to Python's
21170 @code{string.decode} method, and the Python codec machinery will be used
21171 to convert the string. If @var{encoding} is not given, or if
21172 @var{encoding} is the empty string, then either the @code{target-charset}
21173 (@pxref{Character Sets}) will be used, or a language-specific encoding
21174 will be used, if the current language is able to supply one.
21176 The optional @var{errors} argument is the same as the corresponding
21177 argument to Python's @code{string.decode} method.
21179 If the optional @var{length} argument is given, the string will be
21180 fetched and converted to the given length.
21183 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
21184 If this @code{gdb.Value} represents a string, then this method
21185 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
21186 In Python}). Otherwise, this method will throw an exception.
21188 If the optional @var{encoding} argument is given, it must be a string
21189 naming the encoding of the @code{gdb.LazyString}. Some examples are:
21190 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
21191 @var{encoding} argument is an encoding that @value{GDBN} does
21192 recognize, @value{GDBN} will raise an error.
21194 When a lazy string is printed, the @value{GDBN} encoding machinery is
21195 used to convert the string during printing. If the optional
21196 @var{encoding} argument is not provided, or is an empty string,
21197 @value{GDBN} will automatically select the encoding most suitable for
21198 the string type. For further information on encoding in @value{GDBN}
21199 please see @ref{Character Sets}.
21201 If the optional @var{length} argument is given, the string will be
21202 fetched and encoded to the length of characters specified. If
21203 the @var{length} argument is not provided, the string will be fetched
21204 and encoded until a null of appropriate width is found.
21208 @node Types In Python
21209 @subsubsection Types In Python
21210 @cindex types in Python
21211 @cindex Python, working with types
21214 @value{GDBN} represents types from the inferior using the class
21217 The following type-related functions are available in the @code{gdb}
21220 @findex gdb.lookup_type
21221 @defun lookup_type name [block]
21222 This function looks up a type by name. @var{name} is the name of the
21223 type to look up. It must be a string.
21225 If @var{block} is given, then @var{name} is looked up in that scope.
21226 Otherwise, it is searched for globally.
21228 Ordinarily, this function will return an instance of @code{gdb.Type}.
21229 If the named type cannot be found, it will throw an exception.
21232 An instance of @code{Type} has the following attributes:
21236 The type code for this type. The type code will be one of the
21237 @code{TYPE_CODE_} constants defined below.
21240 @defivar Type sizeof
21241 The size of this type, in target @code{char} units. Usually, a
21242 target's @code{char} type will be an 8-bit byte. However, on some
21243 unusual platforms, this type may have a different size.
21247 The tag name for this type. The tag name is the name after
21248 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
21249 languages have this concept. If this type has no tag name, then
21250 @code{None} is returned.
21254 The following methods are provided:
21257 @defmethod Type fields
21258 For structure and union types, this method returns the fields. Range
21259 types have two fields, the minimum and maximum values. Enum types
21260 have one field per enum constant. Function and method types have one
21261 field per parameter. The base types of C@t{++} classes are also
21262 represented as fields. If the type has no fields, or does not fit
21263 into one of these categories, an empty sequence will be returned.
21265 Each field is an object, with some pre-defined attributes:
21268 This attribute is not available for @code{static} fields (as in
21269 C@t{++} or Java). For non-@code{static} fields, the value is the bit
21270 position of the field.
21273 The name of the field, or @code{None} for anonymous fields.
21276 This is @code{True} if the field is artificial, usually meaning that
21277 it was provided by the compiler and not the user. This attribute is
21278 always provided, and is @code{False} if the field is not artificial.
21280 @item is_base_class
21281 This is @code{True} if the field represents a base class of a C@t{++}
21282 structure. This attribute is always provided, and is @code{False}
21283 if the field is not a base class of the type that is the argument of
21284 @code{fields}, or if that type was not a C@t{++} class.
21287 If the field is packed, or is a bitfield, then this will have a
21288 non-zero value, which is the size of the field in bits. Otherwise,
21289 this will be zero; in this case the field's size is given by its type.
21292 The type of the field. This is usually an instance of @code{Type},
21293 but it can be @code{None} in some situations.
21297 @defmethod Type array @var{n1} @r{[}@var{n2}@r{]}
21298 Return a new @code{gdb.Type} object which represents an array of this
21299 type. If one argument is given, it is the inclusive upper bound of
21300 the array; in this case the lower bound is zero. If two arguments are
21301 given, the first argument is the lower bound of the array, and the
21302 second argument is the upper bound of the array. An array's length
21303 must not be negative, but the bounds can be.
21306 @defmethod Type const
21307 Return a new @code{gdb.Type} object which represents a
21308 @code{const}-qualified variant of this type.
21311 @defmethod Type volatile
21312 Return a new @code{gdb.Type} object which represents a
21313 @code{volatile}-qualified variant of this type.
21316 @defmethod Type unqualified
21317 Return a new @code{gdb.Type} object which represents an unqualified
21318 variant of this type. That is, the result is neither @code{const} nor
21322 @defmethod Type range
21323 Return a Python @code{Tuple} object that contains two elements: the
21324 low bound of the argument type and the high bound of that type. If
21325 the type does not have a range, @value{GDBN} will raise a
21326 @code{gdb.error} exception (@pxref{Exception Handling}).
21329 @defmethod Type reference
21330 Return a new @code{gdb.Type} object which represents a reference to this
21334 @defmethod Type pointer
21335 Return a new @code{gdb.Type} object which represents a pointer to this
21339 @defmethod Type strip_typedefs
21340 Return a new @code{gdb.Type} that represents the real type,
21341 after removing all layers of typedefs.
21344 @defmethod Type target
21345 Return a new @code{gdb.Type} object which represents the target type
21348 For a pointer type, the target type is the type of the pointed-to
21349 object. For an array type (meaning C-like arrays), the target type is
21350 the type of the elements of the array. For a function or method type,
21351 the target type is the type of the return value. For a complex type,
21352 the target type is the type of the elements. For a typedef, the
21353 target type is the aliased type.
21355 If the type does not have a target, this method will throw an
21359 @defmethod Type template_argument n [block]
21360 If this @code{gdb.Type} is an instantiation of a template, this will
21361 return a new @code{gdb.Type} which represents the type of the
21362 @var{n}th template argument.
21364 If this @code{gdb.Type} is not a template type, this will throw an
21365 exception. Ordinarily, only C@t{++} code will have template types.
21367 If @var{block} is given, then @var{name} is looked up in that scope.
21368 Otherwise, it is searched for globally.
21373 Each type has a code, which indicates what category this type falls
21374 into. The available type categories are represented by constants
21375 defined in the @code{gdb} module:
21378 @findex TYPE_CODE_PTR
21379 @findex gdb.TYPE_CODE_PTR
21380 @item TYPE_CODE_PTR
21381 The type is a pointer.
21383 @findex TYPE_CODE_ARRAY
21384 @findex gdb.TYPE_CODE_ARRAY
21385 @item TYPE_CODE_ARRAY
21386 The type is an array.
21388 @findex TYPE_CODE_STRUCT
21389 @findex gdb.TYPE_CODE_STRUCT
21390 @item TYPE_CODE_STRUCT
21391 The type is a structure.
21393 @findex TYPE_CODE_UNION
21394 @findex gdb.TYPE_CODE_UNION
21395 @item TYPE_CODE_UNION
21396 The type is a union.
21398 @findex TYPE_CODE_ENUM
21399 @findex gdb.TYPE_CODE_ENUM
21400 @item TYPE_CODE_ENUM
21401 The type is an enum.
21403 @findex TYPE_CODE_FLAGS
21404 @findex gdb.TYPE_CODE_FLAGS
21405 @item TYPE_CODE_FLAGS
21406 A bit flags type, used for things such as status registers.
21408 @findex TYPE_CODE_FUNC
21409 @findex gdb.TYPE_CODE_FUNC
21410 @item TYPE_CODE_FUNC
21411 The type is a function.
21413 @findex TYPE_CODE_INT
21414 @findex gdb.TYPE_CODE_INT
21415 @item TYPE_CODE_INT
21416 The type is an integer type.
21418 @findex TYPE_CODE_FLT
21419 @findex gdb.TYPE_CODE_FLT
21420 @item TYPE_CODE_FLT
21421 A floating point type.
21423 @findex TYPE_CODE_VOID
21424 @findex gdb.TYPE_CODE_VOID
21425 @item TYPE_CODE_VOID
21426 The special type @code{void}.
21428 @findex TYPE_CODE_SET
21429 @findex gdb.TYPE_CODE_SET
21430 @item TYPE_CODE_SET
21433 @findex TYPE_CODE_RANGE
21434 @findex gdb.TYPE_CODE_RANGE
21435 @item TYPE_CODE_RANGE
21436 A range type, that is, an integer type with bounds.
21438 @findex TYPE_CODE_STRING
21439 @findex gdb.TYPE_CODE_STRING
21440 @item TYPE_CODE_STRING
21441 A string type. Note that this is only used for certain languages with
21442 language-defined string types; C strings are not represented this way.
21444 @findex TYPE_CODE_BITSTRING
21445 @findex gdb.TYPE_CODE_BITSTRING
21446 @item TYPE_CODE_BITSTRING
21449 @findex TYPE_CODE_ERROR
21450 @findex gdb.TYPE_CODE_ERROR
21451 @item TYPE_CODE_ERROR
21452 An unknown or erroneous type.
21454 @findex TYPE_CODE_METHOD
21455 @findex gdb.TYPE_CODE_METHOD
21456 @item TYPE_CODE_METHOD
21457 A method type, as found in C@t{++} or Java.
21459 @findex TYPE_CODE_METHODPTR
21460 @findex gdb.TYPE_CODE_METHODPTR
21461 @item TYPE_CODE_METHODPTR
21462 A pointer-to-member-function.
21464 @findex TYPE_CODE_MEMBERPTR
21465 @findex gdb.TYPE_CODE_MEMBERPTR
21466 @item TYPE_CODE_MEMBERPTR
21467 A pointer-to-member.
21469 @findex TYPE_CODE_REF
21470 @findex gdb.TYPE_CODE_REF
21471 @item TYPE_CODE_REF
21474 @findex TYPE_CODE_CHAR
21475 @findex gdb.TYPE_CODE_CHAR
21476 @item TYPE_CODE_CHAR
21479 @findex TYPE_CODE_BOOL
21480 @findex gdb.TYPE_CODE_BOOL
21481 @item TYPE_CODE_BOOL
21484 @findex TYPE_CODE_COMPLEX
21485 @findex gdb.TYPE_CODE_COMPLEX
21486 @item TYPE_CODE_COMPLEX
21487 A complex float type.
21489 @findex TYPE_CODE_TYPEDEF
21490 @findex gdb.TYPE_CODE_TYPEDEF
21491 @item TYPE_CODE_TYPEDEF
21492 A typedef to some other type.
21494 @findex TYPE_CODE_NAMESPACE
21495 @findex gdb.TYPE_CODE_NAMESPACE
21496 @item TYPE_CODE_NAMESPACE
21497 A C@t{++} namespace.
21499 @findex TYPE_CODE_DECFLOAT
21500 @findex gdb.TYPE_CODE_DECFLOAT
21501 @item TYPE_CODE_DECFLOAT
21502 A decimal floating point type.
21504 @findex TYPE_CODE_INTERNAL_FUNCTION
21505 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
21506 @item TYPE_CODE_INTERNAL_FUNCTION
21507 A function internal to @value{GDBN}. This is the type used to represent
21508 convenience functions.
21511 Further support for types is provided in the @code{gdb.types}
21512 Python module (@pxref{gdb.types}).
21514 @node Pretty Printing API
21515 @subsubsection Pretty Printing API
21517 An example output is provided (@pxref{Pretty Printing}).
21519 A pretty-printer is just an object that holds a value and implements a
21520 specific interface, defined here.
21522 @defop Operation {pretty printer} children (self)
21523 @value{GDBN} will call this method on a pretty-printer to compute the
21524 children of the pretty-printer's value.
21526 This method must return an object conforming to the Python iterator
21527 protocol. Each item returned by the iterator must be a tuple holding
21528 two elements. The first element is the ``name'' of the child; the
21529 second element is the child's value. The value can be any Python
21530 object which is convertible to a @value{GDBN} value.
21532 This method is optional. If it does not exist, @value{GDBN} will act
21533 as though the value has no children.
21536 @defop Operation {pretty printer} display_hint (self)
21537 The CLI may call this method and use its result to change the
21538 formatting of a value. The result will also be supplied to an MI
21539 consumer as a @samp{displayhint} attribute of the variable being
21542 This method is optional. If it does exist, this method must return a
21545 Some display hints are predefined by @value{GDBN}:
21549 Indicate that the object being printed is ``array-like''. The CLI
21550 uses this to respect parameters such as @code{set print elements} and
21551 @code{set print array}.
21554 Indicate that the object being printed is ``map-like'', and that the
21555 children of this value can be assumed to alternate between keys and
21559 Indicate that the object being printed is ``string-like''. If the
21560 printer's @code{to_string} method returns a Python string of some
21561 kind, then @value{GDBN} will call its internal language-specific
21562 string-printing function to format the string. For the CLI this means
21563 adding quotation marks, possibly escaping some characters, respecting
21564 @code{set print elements}, and the like.
21568 @defop Operation {pretty printer} to_string (self)
21569 @value{GDBN} will call this method to display the string
21570 representation of the value passed to the object's constructor.
21572 When printing from the CLI, if the @code{to_string} method exists,
21573 then @value{GDBN} will prepend its result to the values returned by
21574 @code{children}. Exactly how this formatting is done is dependent on
21575 the display hint, and may change as more hints are added. Also,
21576 depending on the print settings (@pxref{Print Settings}), the CLI may
21577 print just the result of @code{to_string} in a stack trace, omitting
21578 the result of @code{children}.
21580 If this method returns a string, it is printed verbatim.
21582 Otherwise, if this method returns an instance of @code{gdb.Value},
21583 then @value{GDBN} prints this value. This may result in a call to
21584 another pretty-printer.
21586 If instead the method returns a Python value which is convertible to a
21587 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
21588 the resulting value. Again, this may result in a call to another
21589 pretty-printer. Python scalars (integers, floats, and booleans) and
21590 strings are convertible to @code{gdb.Value}; other types are not.
21592 Finally, if this method returns @code{None} then no further operations
21593 are peformed in this method and nothing is printed.
21595 If the result is not one of these types, an exception is raised.
21598 @value{GDBN} provides a function which can be used to look up the
21599 default pretty-printer for a @code{gdb.Value}:
21601 @findex gdb.default_visualizer
21602 @defun default_visualizer value
21603 This function takes a @code{gdb.Value} object as an argument. If a
21604 pretty-printer for this value exists, then it is returned. If no such
21605 printer exists, then this returns @code{None}.
21608 @node Selecting Pretty-Printers
21609 @subsubsection Selecting Pretty-Printers
21611 The Python list @code{gdb.pretty_printers} contains an array of
21612 functions or callable objects that have been registered via addition
21613 as a pretty-printer. Printers in this list are called @code{global}
21614 printers, they're available when debugging all inferiors.
21615 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
21616 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
21619 Each function on these lists is passed a single @code{gdb.Value}
21620 argument and should return a pretty-printer object conforming to the
21621 interface definition above (@pxref{Pretty Printing API}). If a function
21622 cannot create a pretty-printer for the value, it should return
21625 @value{GDBN} first checks the @code{pretty_printers} attribute of each
21626 @code{gdb.Objfile} in the current program space and iteratively calls
21627 each enabled lookup routine in the list for that @code{gdb.Objfile}
21628 until it receives a pretty-printer object.
21629 If no pretty-printer is found in the objfile lists, @value{GDBN} then
21630 searches the pretty-printer list of the current program space,
21631 calling each enabled function until an object is returned.
21632 After these lists have been exhausted, it tries the global
21633 @code{gdb.pretty_printers} list, again calling each enabled function until an
21634 object is returned.
21636 The order in which the objfiles are searched is not specified. For a
21637 given list, functions are always invoked from the head of the list,
21638 and iterated over sequentially until the end of the list, or a printer
21639 object is returned.
21641 For various reasons a pretty-printer may not work.
21642 For example, the underlying data structure may have changed and
21643 the pretty-printer is out of date.
21645 The consequences of a broken pretty-printer are severe enough that
21646 @value{GDBN} provides support for enabling and disabling individual
21647 printers. For example, if @code{print frame-arguments} is on,
21648 a backtrace can become highly illegible if any argument is printed
21649 with a broken printer.
21651 Pretty-printers are enabled and disabled by attaching an @code{enabled}
21652 attribute to the registered function or callable object. If this attribute
21653 is present and its value is @code{False}, the printer is disabled, otherwise
21654 the printer is enabled.
21656 @node Writing a Pretty-Printer
21657 @subsubsection Writing a Pretty-Printer
21658 @cindex writing a pretty-printer
21660 A pretty-printer consists of two parts: a lookup function to detect
21661 if the type is supported, and the printer itself.
21663 Here is an example showing how a @code{std::string} printer might be
21664 written. @xref{Pretty Printing API}, for details on the API this class
21668 class StdStringPrinter(object):
21669 "Print a std::string"
21671 def __init__(self, val):
21674 def to_string(self):
21675 return self.val['_M_dataplus']['_M_p']
21677 def display_hint(self):
21681 And here is an example showing how a lookup function for the printer
21682 example above might be written.
21685 def str_lookup_function(val):
21686 lookup_tag = val.type.tag
21687 if lookup_tag == None:
21689 regex = re.compile("^std::basic_string<char,.*>$")
21690 if regex.match(lookup_tag):
21691 return StdStringPrinter(val)
21695 The example lookup function extracts the value's type, and attempts to
21696 match it to a type that it can pretty-print. If it is a type the
21697 printer can pretty-print, it will return a printer object. If not, it
21698 returns @code{None}.
21700 We recommend that you put your core pretty-printers into a Python
21701 package. If your pretty-printers are for use with a library, we
21702 further recommend embedding a version number into the package name.
21703 This practice will enable @value{GDBN} to load multiple versions of
21704 your pretty-printers at the same time, because they will have
21707 You should write auto-loaded code (@pxref{Auto-loading}) such that it
21708 can be evaluated multiple times without changing its meaning. An
21709 ideal auto-load file will consist solely of @code{import}s of your
21710 printer modules, followed by a call to a register pretty-printers with
21711 the current objfile.
21713 Taken as a whole, this approach will scale nicely to multiple
21714 inferiors, each potentially using a different library version.
21715 Embedding a version number in the Python package name will ensure that
21716 @value{GDBN} is able to load both sets of printers simultaneously.
21717 Then, because the search for pretty-printers is done by objfile, and
21718 because your auto-loaded code took care to register your library's
21719 printers with a specific objfile, @value{GDBN} will find the correct
21720 printers for the specific version of the library used by each
21723 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
21724 this code might appear in @code{gdb.libstdcxx.v6}:
21727 def register_printers(objfile):
21728 objfile.pretty_printers.add(str_lookup_function)
21732 And then the corresponding contents of the auto-load file would be:
21735 import gdb.libstdcxx.v6
21736 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
21739 The previous example illustrates a basic pretty-printer.
21740 There are a few things that can be improved on.
21741 The printer doesn't have a name, making it hard to identify in a
21742 list of installed printers. The lookup function has a name, but
21743 lookup functions can have arbitrary, even identical, names.
21745 Second, the printer only handles one type, whereas a library typically has
21746 several types. One could install a lookup function for each desired type
21747 in the library, but one could also have a single lookup function recognize
21748 several types. The latter is the conventional way this is handled.
21749 If a pretty-printer can handle multiple data types, then its
21750 @dfn{subprinters} are the printers for the individual data types.
21752 The @code{gdb.printing} module provides a formal way of solving these
21753 problems (@pxref{gdb.printing}).
21754 Here is another example that handles multiple types.
21756 These are the types we are going to pretty-print:
21759 struct foo @{ int a, b; @};
21760 struct bar @{ struct foo x, y; @};
21763 Here are the printers:
21767 """Print a foo object."""
21769 def __init__(self, val):
21772 def to_string(self):
21773 return ("a=<" + str(self.val["a"]) +
21774 "> b=<" + str(self.val["b"]) + ">")
21777 """Print a bar object."""
21779 def __init__(self, val):
21782 def to_string(self):
21783 return ("x=<" + str(self.val["x"]) +
21784 "> y=<" + str(self.val["y"]) + ">")
21787 This example doesn't need a lookup function, that is handled by the
21788 @code{gdb.printing} module. Instead a function is provided to build up
21789 the object that handles the lookup.
21792 import gdb.printing
21794 def build_pretty_printer():
21795 pp = gdb.printing.RegexpCollectionPrettyPrinter(
21797 pp.add_printer('foo', '^foo$', fooPrinter)
21798 pp.add_printer('bar', '^bar$', barPrinter)
21802 And here is the autoload support:
21805 import gdb.printing
21807 gdb.printing.register_pretty_printer(
21808 gdb.current_objfile(),
21809 my_library.build_pretty_printer())
21812 Finally, when this printer is loaded into @value{GDBN}, here is the
21813 corresponding output of @samp{info pretty-printer}:
21816 (gdb) info pretty-printer
21823 @node Inferiors In Python
21824 @subsubsection Inferiors In Python
21825 @cindex inferiors in Python
21827 @findex gdb.Inferior
21828 Programs which are being run under @value{GDBN} are called inferiors
21829 (@pxref{Inferiors and Programs}). Python scripts can access
21830 information about and manipulate inferiors controlled by @value{GDBN}
21831 via objects of the @code{gdb.Inferior} class.
21833 The following inferior-related functions are available in the @code{gdb}
21837 Return a tuple containing all inferior objects.
21840 A @code{gdb.Inferior} object has the following attributes:
21843 @defivar Inferior num
21844 ID of inferior, as assigned by GDB.
21847 @defivar Inferior pid
21848 Process ID of the inferior, as assigned by the underlying operating
21852 @defivar Inferior was_attached
21853 Boolean signaling whether the inferior was created using `attach', or
21854 started by @value{GDBN} itself.
21858 A @code{gdb.Inferior} object has the following methods:
21861 @defmethod Inferior threads
21862 This method returns a tuple holding all the threads which are valid
21863 when it is called. If there are no valid threads, the method will
21864 return an empty tuple.
21867 @findex gdb.read_memory
21868 @defmethod Inferior read_memory address length
21869 Read @var{length} bytes of memory from the inferior, starting at
21870 @var{address}. Returns a buffer object, which behaves much like an array
21871 or a string. It can be modified and given to the @code{gdb.write_memory}
21875 @findex gdb.write_memory
21876 @defmethod Inferior write_memory address buffer @r{[}length@r{]}
21877 Write the contents of @var{buffer} to the inferior, starting at
21878 @var{address}. The @var{buffer} parameter must be a Python object
21879 which supports the buffer protocol, i.e., a string, an array or the
21880 object returned from @code{gdb.read_memory}. If given, @var{length}
21881 determines the number of bytes from @var{buffer} to be written.
21884 @findex gdb.search_memory
21885 @defmethod Inferior search_memory address length pattern
21886 Search a region of the inferior memory starting at @var{address} with
21887 the given @var{length} using the search pattern supplied in
21888 @var{pattern}. The @var{pattern} parameter must be a Python object
21889 which supports the buffer protocol, i.e., a string, an array or the
21890 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
21891 containing the address where the pattern was found, or @code{None} if
21892 the pattern could not be found.
21896 @node Events In Python
21897 @subsubsection Events In Python
21898 @cindex inferior events in Python
21900 @value{GDBN} provides a general event facility so that Python code can be
21901 notified of various state changes, particularly changes that occur in
21904 An @dfn{event} is just an object that describes some state change. The
21905 type of the object and its attributes will vary depending on the details
21906 of the change. All the existing events are described below.
21908 In order to be notified of an event, you must register an event handler
21909 with an @dfn{event registry}. An event registry is an object in the
21910 @code{gdb.events} module which dispatches particular events. A registry
21911 provides methods to register and unregister event handlers:
21914 @defmethod EventRegistry connect object
21915 Add the given callable @var{object} to the registry. This object will be
21916 called when an event corresponding to this registry occurs.
21919 @defmethod EventRegistry disconnect object
21920 Remove the given @var{object} from the registry. Once removed, the object
21921 will no longer receive notifications of events.
21925 Here is an example:
21928 def exit_handler (event):
21929 print "event type: exit"
21930 print "exit code: %d" % (event.exit_code)
21932 gdb.events.exited.connect (exit_handler)
21935 In the above example we connect our handler @code{exit_handler} to the
21936 registry @code{events.exited}. Once connected, @code{exit_handler} gets
21937 called when the inferior exits. The argument @dfn{event} in this example is
21938 of type @code{gdb.ExitedEvent}. As you can see in the example the
21939 @code{ExitedEvent} object has an attribute which indicates the exit code of
21942 The following is a listing of the event registries that are available and
21943 details of the events they emit:
21948 Emits @code{gdb.ThreadEvent}.
21950 Some events can be thread specific when @value{GDBN} is running in non-stop
21951 mode. When represented in Python, these events all extend
21952 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
21953 events which are emitted by this or other modules might extend this event.
21954 Examples of these events are @code{gdb.BreakpointEvent} and
21955 @code{gdb.ContinueEvent}.
21958 @defivar ThreadEvent inferior_thread
21959 In non-stop mode this attribute will be set to the specific thread which was
21960 involved in the emitted event. Otherwise, it will be set to @code{None}.
21964 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
21966 This event indicates that the inferior has been continued after a stop. For
21967 inherited attribute refer to @code{gdb.ThreadEvent} above.
21969 @item events.exited
21970 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
21971 @code{events.ExitedEvent} has one attribute:
21973 @defivar ExitedEvent exit_code
21974 An integer representing the exit code which the inferior has returned.
21979 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
21981 Indicates that the inferior has stopped. All events emitted by this registry
21982 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
21983 will indicate the stopped thread when @value{GDBN} is running in non-stop
21984 mode. Refer to @code{gdb.ThreadEvent} above for more details.
21986 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
21988 This event indicates that the inferior or one of its threads has received as
21989 signal. @code{gdb.SignalEvent} has the following attributes:
21992 @defivar SignalEvent stop_signal
21993 A string representing the signal received by the inferior. A list of possible
21994 signal values can be obtained by running the command @code{info signals} in
21995 the @value{GDBN} command prompt.
21999 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
22001 @code{gdb.BreakpointEvent} event indicates that a breakpoint has been hit, and
22002 has the following attributes:
22005 @defivar BreakpointEvent breakpoint
22006 A reference to the breakpoint that was hit of type @code{gdb.Breakpoint}.
22007 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
22013 @node Threads In Python
22014 @subsubsection Threads In Python
22015 @cindex threads in python
22017 @findex gdb.InferiorThread
22018 Python scripts can access information about, and manipulate inferior threads
22019 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
22021 The following thread-related functions are available in the @code{gdb}
22024 @findex gdb.selected_thread
22025 @defun selected_thread
22026 This function returns the thread object for the selected thread. If there
22027 is no selected thread, this will return @code{None}.
22030 A @code{gdb.InferiorThread} object has the following attributes:
22033 @defivar InferiorThread name
22034 The name of the thread. If the user specified a name using
22035 @code{thread name}, then this returns that name. Otherwise, if an
22036 OS-supplied name is available, then it is returned. Otherwise, this
22037 returns @code{None}.
22039 This attribute can be assigned to. The new value must be a string
22040 object, which sets the new name, or @code{None}, which removes any
22041 user-specified thread name.
22044 @defivar InferiorThread num
22045 ID of the thread, as assigned by GDB.
22048 @defivar InferiorThread ptid
22049 ID of the thread, as assigned by the operating system. This attribute is a
22050 tuple containing three integers. The first is the Process ID (PID); the second
22051 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
22052 Either the LWPID or TID may be 0, which indicates that the operating system
22053 does not use that identifier.
22057 A @code{gdb.InferiorThread} object has the following methods:
22060 @defmethod InferiorThread switch
22061 This changes @value{GDBN}'s currently selected thread to the one represented
22065 @defmethod InferiorThread is_stopped
22066 Return a Boolean indicating whether the thread is stopped.
22069 @defmethod InferiorThread is_running
22070 Return a Boolean indicating whether the thread is running.
22073 @defmethod InferiorThread is_exited
22074 Return a Boolean indicating whether the thread is exited.
22078 @node Commands In Python
22079 @subsubsection Commands In Python
22081 @cindex commands in python
22082 @cindex python commands
22083 You can implement new @value{GDBN} CLI commands in Python. A CLI
22084 command is implemented using an instance of the @code{gdb.Command}
22085 class, most commonly using a subclass.
22087 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
22088 The object initializer for @code{Command} registers the new command
22089 with @value{GDBN}. This initializer is normally invoked from the
22090 subclass' own @code{__init__} method.
22092 @var{name} is the name of the command. If @var{name} consists of
22093 multiple words, then the initial words are looked for as prefix
22094 commands. In this case, if one of the prefix commands does not exist,
22095 an exception is raised.
22097 There is no support for multi-line commands.
22099 @var{command_class} should be one of the @samp{COMMAND_} constants
22100 defined below. This argument tells @value{GDBN} how to categorize the
22101 new command in the help system.
22103 @var{completer_class} is an optional argument. If given, it should be
22104 one of the @samp{COMPLETE_} constants defined below. This argument
22105 tells @value{GDBN} how to perform completion for this command. If not
22106 given, @value{GDBN} will attempt to complete using the object's
22107 @code{complete} method (see below); if no such method is found, an
22108 error will occur when completion is attempted.
22110 @var{prefix} is an optional argument. If @code{True}, then the new
22111 command is a prefix command; sub-commands of this command may be
22114 The help text for the new command is taken from the Python
22115 documentation string for the command's class, if there is one. If no
22116 documentation string is provided, the default value ``This command is
22117 not documented.'' is used.
22120 @cindex don't repeat Python command
22121 @defmethod Command dont_repeat
22122 By default, a @value{GDBN} command is repeated when the user enters a
22123 blank line at the command prompt. A command can suppress this
22124 behavior by invoking the @code{dont_repeat} method. This is similar
22125 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
22128 @defmethod Command invoke argument from_tty
22129 This method is called by @value{GDBN} when this command is invoked.
22131 @var{argument} is a string. It is the argument to the command, after
22132 leading and trailing whitespace has been stripped.
22134 @var{from_tty} is a boolean argument. When true, this means that the
22135 command was entered by the user at the terminal; when false it means
22136 that the command came from elsewhere.
22138 If this method throws an exception, it is turned into a @value{GDBN}
22139 @code{error} call. Otherwise, the return value is ignored.
22141 @findex gdb.string_to_argv
22142 To break @var{argument} up into an argv-like string use
22143 @code{gdb.string_to_argv}. This function behaves identically to
22144 @value{GDBN}'s internal argument lexer @code{buildargv}.
22145 It is recommended to use this for consistency.
22146 Arguments are separated by spaces and may be quoted.
22150 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
22151 ['1', '2 "3', '4 "5', "6 '7"]
22156 @cindex completion of Python commands
22157 @defmethod Command complete text word
22158 This method is called by @value{GDBN} when the user attempts
22159 completion on this command. All forms of completion are handled by
22160 this method, that is, the @key{TAB} and @key{M-?} key bindings
22161 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
22164 The arguments @var{text} and @var{word} are both strings. @var{text}
22165 holds the complete command line up to the cursor's location.
22166 @var{word} holds the last word of the command line; this is computed
22167 using a word-breaking heuristic.
22169 The @code{complete} method can return several values:
22172 If the return value is a sequence, the contents of the sequence are
22173 used as the completions. It is up to @code{complete} to ensure that the
22174 contents actually do complete the word. A zero-length sequence is
22175 allowed, it means that there were no completions available. Only
22176 string elements of the sequence are used; other elements in the
22177 sequence are ignored.
22180 If the return value is one of the @samp{COMPLETE_} constants defined
22181 below, then the corresponding @value{GDBN}-internal completion
22182 function is invoked, and its result is used.
22185 All other results are treated as though there were no available
22190 When a new command is registered, it must be declared as a member of
22191 some general class of commands. This is used to classify top-level
22192 commands in the on-line help system; note that prefix commands are not
22193 listed under their own category but rather that of their top-level
22194 command. The available classifications are represented by constants
22195 defined in the @code{gdb} module:
22198 @findex COMMAND_NONE
22199 @findex gdb.COMMAND_NONE
22201 The command does not belong to any particular class. A command in
22202 this category will not be displayed in any of the help categories.
22204 @findex COMMAND_RUNNING
22205 @findex gdb.COMMAND_RUNNING
22206 @item COMMAND_RUNNING
22207 The command is related to running the inferior. For example,
22208 @code{start}, @code{step}, and @code{continue} are in this category.
22209 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
22210 commands in this category.
22212 @findex COMMAND_DATA
22213 @findex gdb.COMMAND_DATA
22215 The command is related to data or variables. For example,
22216 @code{call}, @code{find}, and @code{print} are in this category. Type
22217 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
22220 @findex COMMAND_STACK
22221 @findex gdb.COMMAND_STACK
22222 @item COMMAND_STACK
22223 The command has to do with manipulation of the stack. For example,
22224 @code{backtrace}, @code{frame}, and @code{return} are in this
22225 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
22226 list of commands in this category.
22228 @findex COMMAND_FILES
22229 @findex gdb.COMMAND_FILES
22230 @item COMMAND_FILES
22231 This class is used for file-related commands. For example,
22232 @code{file}, @code{list} and @code{section} are in this category.
22233 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
22234 commands in this category.
22236 @findex COMMAND_SUPPORT
22237 @findex gdb.COMMAND_SUPPORT
22238 @item COMMAND_SUPPORT
22239 This should be used for ``support facilities'', generally meaning
22240 things that are useful to the user when interacting with @value{GDBN},
22241 but not related to the state of the inferior. For example,
22242 @code{help}, @code{make}, and @code{shell} are in this category. Type
22243 @kbd{help support} at the @value{GDBN} prompt to see a list of
22244 commands in this category.
22246 @findex COMMAND_STATUS
22247 @findex gdb.COMMAND_STATUS
22248 @item COMMAND_STATUS
22249 The command is an @samp{info}-related command, that is, related to the
22250 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
22251 and @code{show} are in this category. Type @kbd{help status} at the
22252 @value{GDBN} prompt to see a list of commands in this category.
22254 @findex COMMAND_BREAKPOINTS
22255 @findex gdb.COMMAND_BREAKPOINTS
22256 @item COMMAND_BREAKPOINTS
22257 The command has to do with breakpoints. For example, @code{break},
22258 @code{clear}, and @code{delete} are in this category. Type @kbd{help
22259 breakpoints} at the @value{GDBN} prompt to see a list of commands in
22262 @findex COMMAND_TRACEPOINTS
22263 @findex gdb.COMMAND_TRACEPOINTS
22264 @item COMMAND_TRACEPOINTS
22265 The command has to do with tracepoints. For example, @code{trace},
22266 @code{actions}, and @code{tfind} are in this category. Type
22267 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
22268 commands in this category.
22270 @findex COMMAND_OBSCURE
22271 @findex gdb.COMMAND_OBSCURE
22272 @item COMMAND_OBSCURE
22273 The command is only used in unusual circumstances, or is not of
22274 general interest to users. For example, @code{checkpoint},
22275 @code{fork}, and @code{stop} are in this category. Type @kbd{help
22276 obscure} at the @value{GDBN} prompt to see a list of commands in this
22279 @findex COMMAND_MAINTENANCE
22280 @findex gdb.COMMAND_MAINTENANCE
22281 @item COMMAND_MAINTENANCE
22282 The command is only useful to @value{GDBN} maintainers. The
22283 @code{maintenance} and @code{flushregs} commands are in this category.
22284 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
22285 commands in this category.
22288 A new command can use a predefined completion function, either by
22289 specifying it via an argument at initialization, or by returning it
22290 from the @code{complete} method. These predefined completion
22291 constants are all defined in the @code{gdb} module:
22294 @findex COMPLETE_NONE
22295 @findex gdb.COMPLETE_NONE
22296 @item COMPLETE_NONE
22297 This constant means that no completion should be done.
22299 @findex COMPLETE_FILENAME
22300 @findex gdb.COMPLETE_FILENAME
22301 @item COMPLETE_FILENAME
22302 This constant means that filename completion should be performed.
22304 @findex COMPLETE_LOCATION
22305 @findex gdb.COMPLETE_LOCATION
22306 @item COMPLETE_LOCATION
22307 This constant means that location completion should be done.
22308 @xref{Specify Location}.
22310 @findex COMPLETE_COMMAND
22311 @findex gdb.COMPLETE_COMMAND
22312 @item COMPLETE_COMMAND
22313 This constant means that completion should examine @value{GDBN}
22316 @findex COMPLETE_SYMBOL
22317 @findex gdb.COMPLETE_SYMBOL
22318 @item COMPLETE_SYMBOL
22319 This constant means that completion should be done using symbol names
22323 The following code snippet shows how a trivial CLI command can be
22324 implemented in Python:
22327 class HelloWorld (gdb.Command):
22328 """Greet the whole world."""
22330 def __init__ (self):
22331 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
22333 def invoke (self, arg, from_tty):
22334 print "Hello, World!"
22339 The last line instantiates the class, and is necessary to trigger the
22340 registration of the command with @value{GDBN}. Depending on how the
22341 Python code is read into @value{GDBN}, you may need to import the
22342 @code{gdb} module explicitly.
22344 @node Parameters In Python
22345 @subsubsection Parameters In Python
22347 @cindex parameters in python
22348 @cindex python parameters
22349 @tindex gdb.Parameter
22351 You can implement new @value{GDBN} parameters using Python. A new
22352 parameter is implemented as an instance of the @code{gdb.Parameter}
22355 Parameters are exposed to the user via the @code{set} and
22356 @code{show} commands. @xref{Help}.
22358 There are many parameters that already exist and can be set in
22359 @value{GDBN}. Two examples are: @code{set follow fork} and
22360 @code{set charset}. Setting these parameters influences certain
22361 behavior in @value{GDBN}. Similarly, you can define parameters that
22362 can be used to influence behavior in custom Python scripts and commands.
22364 @defmethod Parameter __init__ name @var{command-class} @var{parameter-class} @r{[}@var{enum-sequence}@r{]}
22365 The object initializer for @code{Parameter} registers the new
22366 parameter with @value{GDBN}. This initializer is normally invoked
22367 from the subclass' own @code{__init__} method.
22369 @var{name} is the name of the new parameter. If @var{name} consists
22370 of multiple words, then the initial words are looked for as prefix
22371 parameters. An example of this can be illustrated with the
22372 @code{set print} set of parameters. If @var{name} is
22373 @code{print foo}, then @code{print} will be searched as the prefix
22374 parameter. In this case the parameter can subsequently be accessed in
22375 @value{GDBN} as @code{set print foo}.
22377 If @var{name} consists of multiple words, and no prefix parameter group
22378 can be found, an exception is raised.
22380 @var{command-class} should be one of the @samp{COMMAND_} constants
22381 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
22382 categorize the new parameter in the help system.
22384 @var{parameter-class} should be one of the @samp{PARAM_} constants
22385 defined below. This argument tells @value{GDBN} the type of the new
22386 parameter; this information is used for input validation and
22389 If @var{parameter-class} is @code{PARAM_ENUM}, then
22390 @var{enum-sequence} must be a sequence of strings. These strings
22391 represent the possible values for the parameter.
22393 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
22394 of a fourth argument will cause an exception to be thrown.
22396 The help text for the new parameter is taken from the Python
22397 documentation string for the parameter's class, if there is one. If
22398 there is no documentation string, a default value is used.
22401 @defivar Parameter set_doc
22402 If this attribute exists, and is a string, then its value is used as
22403 the help text for this parameter's @code{set} command. The value is
22404 examined when @code{Parameter.__init__} is invoked; subsequent changes
22408 @defivar Parameter show_doc
22409 If this attribute exists, and is a string, then its value is used as
22410 the help text for this parameter's @code{show} command. The value is
22411 examined when @code{Parameter.__init__} is invoked; subsequent changes
22415 @defivar Parameter value
22416 The @code{value} attribute holds the underlying value of the
22417 parameter. It can be read and assigned to just as any other
22418 attribute. @value{GDBN} does validation when assignments are made.
22422 When a new parameter is defined, its type must be specified. The
22423 available types are represented by constants defined in the @code{gdb}
22427 @findex PARAM_BOOLEAN
22428 @findex gdb.PARAM_BOOLEAN
22429 @item PARAM_BOOLEAN
22430 The value is a plain boolean. The Python boolean values, @code{True}
22431 and @code{False} are the only valid values.
22433 @findex PARAM_AUTO_BOOLEAN
22434 @findex gdb.PARAM_AUTO_BOOLEAN
22435 @item PARAM_AUTO_BOOLEAN
22436 The value has three possible states: true, false, and @samp{auto}. In
22437 Python, true and false are represented using boolean constants, and
22438 @samp{auto} is represented using @code{None}.
22440 @findex PARAM_UINTEGER
22441 @findex gdb.PARAM_UINTEGER
22442 @item PARAM_UINTEGER
22443 The value is an unsigned integer. The value of 0 should be
22444 interpreted to mean ``unlimited''.
22446 @findex PARAM_INTEGER
22447 @findex gdb.PARAM_INTEGER
22448 @item PARAM_INTEGER
22449 The value is a signed integer. The value of 0 should be interpreted
22450 to mean ``unlimited''.
22452 @findex PARAM_STRING
22453 @findex gdb.PARAM_STRING
22455 The value is a string. When the user modifies the string, any escape
22456 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
22457 translated into corresponding characters and encoded into the current
22460 @findex PARAM_STRING_NOESCAPE
22461 @findex gdb.PARAM_STRING_NOESCAPE
22462 @item PARAM_STRING_NOESCAPE
22463 The value is a string. When the user modifies the string, escapes are
22464 passed through untranslated.
22466 @findex PARAM_OPTIONAL_FILENAME
22467 @findex gdb.PARAM_OPTIONAL_FILENAME
22468 @item PARAM_OPTIONAL_FILENAME
22469 The value is a either a filename (a string), or @code{None}.
22471 @findex PARAM_FILENAME
22472 @findex gdb.PARAM_FILENAME
22473 @item PARAM_FILENAME
22474 The value is a filename. This is just like
22475 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
22477 @findex PARAM_ZINTEGER
22478 @findex gdb.PARAM_ZINTEGER
22479 @item PARAM_ZINTEGER
22480 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
22481 is interpreted as itself.
22484 @findex gdb.PARAM_ENUM
22486 The value is a string, which must be one of a collection string
22487 constants provided when the parameter is created.
22490 @node Functions In Python
22491 @subsubsection Writing new convenience functions
22493 @cindex writing convenience functions
22494 @cindex convenience functions in python
22495 @cindex python convenience functions
22496 @tindex gdb.Function
22498 You can implement new convenience functions (@pxref{Convenience Vars})
22499 in Python. A convenience function is an instance of a subclass of the
22500 class @code{gdb.Function}.
22502 @defmethod Function __init__ name
22503 The initializer for @code{Function} registers the new function with
22504 @value{GDBN}. The argument @var{name} is the name of the function,
22505 a string. The function will be visible to the user as a convenience
22506 variable of type @code{internal function}, whose name is the same as
22507 the given @var{name}.
22509 The documentation for the new function is taken from the documentation
22510 string for the new class.
22513 @defmethod Function invoke @var{*args}
22514 When a convenience function is evaluated, its arguments are converted
22515 to instances of @code{gdb.Value}, and then the function's
22516 @code{invoke} method is called. Note that @value{GDBN} does not
22517 predetermine the arity of convenience functions. Instead, all
22518 available arguments are passed to @code{invoke}, following the
22519 standard Python calling convention. In particular, a convenience
22520 function can have default values for parameters without ill effect.
22522 The return value of this method is used as its value in the enclosing
22523 expression. If an ordinary Python value is returned, it is converted
22524 to a @code{gdb.Value} following the usual rules.
22527 The following code snippet shows how a trivial convenience function can
22528 be implemented in Python:
22531 class Greet (gdb.Function):
22532 """Return string to greet someone.
22533 Takes a name as argument."""
22535 def __init__ (self):
22536 super (Greet, self).__init__ ("greet")
22538 def invoke (self, name):
22539 return "Hello, %s!" % name.string ()
22544 The last line instantiates the class, and is necessary to trigger the
22545 registration of the function with @value{GDBN}. Depending on how the
22546 Python code is read into @value{GDBN}, you may need to import the
22547 @code{gdb} module explicitly.
22549 @node Progspaces In Python
22550 @subsubsection Program Spaces In Python
22552 @cindex progspaces in python
22553 @tindex gdb.Progspace
22555 A program space, or @dfn{progspace}, represents a symbolic view
22556 of an address space.
22557 It consists of all of the objfiles of the program.
22558 @xref{Objfiles In Python}.
22559 @xref{Inferiors and Programs, program spaces}, for more details
22560 about program spaces.
22562 The following progspace-related functions are available in the
22565 @findex gdb.current_progspace
22566 @defun current_progspace
22567 This function returns the program space of the currently selected inferior.
22568 @xref{Inferiors and Programs}.
22571 @findex gdb.progspaces
22573 Return a sequence of all the progspaces currently known to @value{GDBN}.
22576 Each progspace is represented by an instance of the @code{gdb.Progspace}
22579 @defivar Progspace filename
22580 The file name of the progspace as a string.
22583 @defivar Progspace pretty_printers
22584 The @code{pretty_printers} attribute is a list of functions. It is
22585 used to look up pretty-printers. A @code{Value} is passed to each
22586 function in order; if the function returns @code{None}, then the
22587 search continues. Otherwise, the return value should be an object
22588 which is used to format the value. @xref{Pretty Printing API}, for more
22592 @node Objfiles In Python
22593 @subsubsection Objfiles In Python
22595 @cindex objfiles in python
22596 @tindex gdb.Objfile
22598 @value{GDBN} loads symbols for an inferior from various
22599 symbol-containing files (@pxref{Files}). These include the primary
22600 executable file, any shared libraries used by the inferior, and any
22601 separate debug info files (@pxref{Separate Debug Files}).
22602 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
22604 The following objfile-related functions are available in the
22607 @findex gdb.current_objfile
22608 @defun current_objfile
22609 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
22610 sets the ``current objfile'' to the corresponding objfile. This
22611 function returns the current objfile. If there is no current objfile,
22612 this function returns @code{None}.
22615 @findex gdb.objfiles
22617 Return a sequence of all the objfiles current known to @value{GDBN}.
22618 @xref{Objfiles In Python}.
22621 Each objfile is represented by an instance of the @code{gdb.Objfile}
22624 @defivar Objfile filename
22625 The file name of the objfile as a string.
22628 @defivar Objfile pretty_printers
22629 The @code{pretty_printers} attribute is a list of functions. It is
22630 used to look up pretty-printers. A @code{Value} is passed to each
22631 function in order; if the function returns @code{None}, then the
22632 search continues. Otherwise, the return value should be an object
22633 which is used to format the value. @xref{Pretty Printing API}, for more
22637 @node Frames In Python
22638 @subsubsection Accessing inferior stack frames from Python.
22640 @cindex frames in python
22641 When the debugged program stops, @value{GDBN} is able to analyze its call
22642 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
22643 represents a frame in the stack. A @code{gdb.Frame} object is only valid
22644 while its corresponding frame exists in the inferior's stack. If you try
22645 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
22646 exception (@pxref{Exception Handling}).
22648 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
22652 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
22656 The following frame-related functions are available in the @code{gdb} module:
22658 @findex gdb.selected_frame
22659 @defun selected_frame
22660 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
22663 @findex gdb.newest_frame
22664 @defun newest_frame
22665 Return the newest frame object for the selected thread.
22668 @defun frame_stop_reason_string reason
22669 Return a string explaining the reason why @value{GDBN} stopped unwinding
22670 frames, as expressed by the given @var{reason} code (an integer, see the
22671 @code{unwind_stop_reason} method further down in this section).
22674 A @code{gdb.Frame} object has the following methods:
22677 @defmethod Frame is_valid
22678 Returns true if the @code{gdb.Frame} object is valid, false if not.
22679 A frame object can become invalid if the frame it refers to doesn't
22680 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
22681 an exception if it is invalid at the time the method is called.
22684 @defmethod Frame name
22685 Returns the function name of the frame, or @code{None} if it can't be
22689 @defmethod Frame type
22690 Returns the type of the frame. The value can be one of:
22692 @item gdb.NORMAL_FRAME
22693 An ordinary stack frame.
22695 @item gdb.DUMMY_FRAME
22696 A fake stack frame that was created by @value{GDBN} when performing an
22697 inferior function call.
22699 @item gdb.INLINE_FRAME
22700 A frame representing an inlined function. The function was inlined
22701 into a @code{gdb.NORMAL_FRAME} that is older than this one.
22703 @item gdb.SIGTRAMP_FRAME
22704 A signal trampoline frame. This is the frame created by the OS when
22705 it calls into a signal handler.
22707 @item gdb.ARCH_FRAME
22708 A fake stack frame representing a cross-architecture call.
22710 @item gdb.SENTINEL_FRAME
22711 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
22716 @defmethod Frame unwind_stop_reason
22717 Return an integer representing the reason why it's not possible to find
22718 more frames toward the outermost frame. Use
22719 @code{gdb.frame_stop_reason_string} to convert the value returned by this
22720 function to a string.
22723 @defmethod Frame pc
22724 Returns the frame's resume address.
22727 @defmethod Frame block
22728 Return the frame's code block. @xref{Blocks In Python}.
22731 @defmethod Frame function
22732 Return the symbol for the function corresponding to this frame.
22733 @xref{Symbols In Python}.
22736 @defmethod Frame older
22737 Return the frame that called this frame.
22740 @defmethod Frame newer
22741 Return the frame called by this frame.
22744 @defmethod Frame find_sal
22745 Return the frame's symtab and line object.
22746 @xref{Symbol Tables In Python}.
22749 @defmethod Frame read_var variable @r{[}block@r{]}
22750 Return the value of @var{variable} in this frame. If the optional
22751 argument @var{block} is provided, search for the variable from that
22752 block; otherwise start at the frame's current block (which is
22753 determined by the frame's current program counter). @var{variable}
22754 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
22755 @code{gdb.Block} object.
22758 @defmethod Frame select
22759 Set this frame to be the selected frame. @xref{Stack, ,Examining the
22764 @node Blocks In Python
22765 @subsubsection Accessing frame blocks from Python.
22767 @cindex blocks in python
22770 Within each frame, @value{GDBN} maintains information on each block
22771 stored in that frame. These blocks are organized hierarchically, and
22772 are represented individually in Python as a @code{gdb.Block}.
22773 Please see @ref{Frames In Python}, for a more in-depth discussion on
22774 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
22775 detailed technical information on @value{GDBN}'s book-keeping of the
22778 The following block-related functions are available in the @code{gdb}
22781 @findex gdb.block_for_pc
22782 @defun block_for_pc pc
22783 Return the @code{gdb.Block} containing the given @var{pc} value. If the
22784 block cannot be found for the @var{pc} value specified, the function
22785 will return @code{None}.
22788 A @code{gdb.Block} object has the following attributes:
22791 @defivar Block start
22792 The start address of the block. This attribute is not writable.
22796 The end address of the block. This attribute is not writable.
22799 @defivar Block function
22800 The name of the block represented as a @code{gdb.Symbol}. If the
22801 block is not named, then this attribute holds @code{None}. This
22802 attribute is not writable.
22805 @defivar Block superblock
22806 The block containing this block. If this parent block does not exist,
22807 this attribute holds @code{None}. This attribute is not writable.
22811 @node Symbols In Python
22812 @subsubsection Python representation of Symbols.
22814 @cindex symbols in python
22817 @value{GDBN} represents every variable, function and type as an
22818 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
22819 Similarly, Python represents these symbols in @value{GDBN} with the
22820 @code{gdb.Symbol} object.
22822 The following symbol-related functions are available in the @code{gdb}
22825 @findex gdb.lookup_symbol
22826 @defun lookup_symbol name [block] [domain]
22827 This function searches for a symbol by name. The search scope can be
22828 restricted to the parameters defined in the optional domain and block
22831 @var{name} is the name of the symbol. It must be a string. The
22832 optional @var{block} argument restricts the search to symbols visible
22833 in that @var{block}. The @var{block} argument must be a
22834 @code{gdb.Block} object. The optional @var{domain} argument restricts
22835 the search to the domain type. The @var{domain} argument must be a
22836 domain constant defined in the @code{gdb} module and described later
22840 A @code{gdb.Symbol} object has the following attributes:
22843 @defivar Symbol symtab
22844 The symbol table in which the symbol appears. This attribute is
22845 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
22846 Python}. This attribute is not writable.
22849 @defivar Symbol name
22850 The name of the symbol as a string. This attribute is not writable.
22853 @defivar Symbol linkage_name
22854 The name of the symbol, as used by the linker (i.e., may be mangled).
22855 This attribute is not writable.
22858 @defivar Symbol print_name
22859 The name of the symbol in a form suitable for output. This is either
22860 @code{name} or @code{linkage_name}, depending on whether the user
22861 asked @value{GDBN} to display demangled or mangled names.
22864 @defivar Symbol addr_class
22865 The address class of the symbol. This classifies how to find the value
22866 of a symbol. Each address class is a constant defined in the
22867 @code{gdb} module and described later in this chapter.
22870 @defivar Symbol is_argument
22871 @code{True} if the symbol is an argument of a function.
22874 @defivar Symbol is_constant
22875 @code{True} if the symbol is a constant.
22878 @defivar Symbol is_function
22879 @code{True} if the symbol is a function or a method.
22882 @defivar Symbol is_variable
22883 @code{True} if the symbol is a variable.
22887 The available domain categories in @code{gdb.Symbol} are represented
22888 as constants in the @code{gdb} module:
22891 @findex SYMBOL_UNDEF_DOMAIN
22892 @findex gdb.SYMBOL_UNDEF_DOMAIN
22893 @item SYMBOL_UNDEF_DOMAIN
22894 This is used when a domain has not been discovered or none of the
22895 following domains apply. This usually indicates an error either
22896 in the symbol information or in @value{GDBN}'s handling of symbols.
22897 @findex SYMBOL_VAR_DOMAIN
22898 @findex gdb.SYMBOL_VAR_DOMAIN
22899 @item SYMBOL_VAR_DOMAIN
22900 This domain contains variables, function names, typedef names and enum
22902 @findex SYMBOL_STRUCT_DOMAIN
22903 @findex gdb.SYMBOL_STRUCT_DOMAIN
22904 @item SYMBOL_STRUCT_DOMAIN
22905 This domain holds struct, union and enum type names.
22906 @findex SYMBOL_LABEL_DOMAIN
22907 @findex gdb.SYMBOL_LABEL_DOMAIN
22908 @item SYMBOL_LABEL_DOMAIN
22909 This domain contains names of labels (for gotos).
22910 @findex SYMBOL_VARIABLES_DOMAIN
22911 @findex gdb.SYMBOL_VARIABLES_DOMAIN
22912 @item SYMBOL_VARIABLES_DOMAIN
22913 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
22914 contains everything minus functions and types.
22915 @findex SYMBOL_FUNCTIONS_DOMAIN
22916 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
22917 @item SYMBOL_FUNCTION_DOMAIN
22918 This domain contains all functions.
22919 @findex SYMBOL_TYPES_DOMAIN
22920 @findex gdb.SYMBOL_TYPES_DOMAIN
22921 @item SYMBOL_TYPES_DOMAIN
22922 This domain contains all types.
22925 The available address class categories in @code{gdb.Symbol} are represented
22926 as constants in the @code{gdb} module:
22929 @findex SYMBOL_LOC_UNDEF
22930 @findex gdb.SYMBOL_LOC_UNDEF
22931 @item SYMBOL_LOC_UNDEF
22932 If this is returned by address class, it indicates an error either in
22933 the symbol information or in @value{GDBN}'s handling of symbols.
22934 @findex SYMBOL_LOC_CONST
22935 @findex gdb.SYMBOL_LOC_CONST
22936 @item SYMBOL_LOC_CONST
22937 Value is constant int.
22938 @findex SYMBOL_LOC_STATIC
22939 @findex gdb.SYMBOL_LOC_STATIC
22940 @item SYMBOL_LOC_STATIC
22941 Value is at a fixed address.
22942 @findex SYMBOL_LOC_REGISTER
22943 @findex gdb.SYMBOL_LOC_REGISTER
22944 @item SYMBOL_LOC_REGISTER
22945 Value is in a register.
22946 @findex SYMBOL_LOC_ARG
22947 @findex gdb.SYMBOL_LOC_ARG
22948 @item SYMBOL_LOC_ARG
22949 Value is an argument. This value is at the offset stored within the
22950 symbol inside the frame's argument list.
22951 @findex SYMBOL_LOC_REF_ARG
22952 @findex gdb.SYMBOL_LOC_REF_ARG
22953 @item SYMBOL_LOC_REF_ARG
22954 Value address is stored in the frame's argument list. Just like
22955 @code{LOC_ARG} except that the value's address is stored at the
22956 offset, not the value itself.
22957 @findex SYMBOL_LOC_REGPARM_ADDR
22958 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
22959 @item SYMBOL_LOC_REGPARM_ADDR
22960 Value is a specified register. Just like @code{LOC_REGISTER} except
22961 the register holds the address of the argument instead of the argument
22963 @findex SYMBOL_LOC_LOCAL
22964 @findex gdb.SYMBOL_LOC_LOCAL
22965 @item SYMBOL_LOC_LOCAL
22966 Value is a local variable.
22967 @findex SYMBOL_LOC_TYPEDEF
22968 @findex gdb.SYMBOL_LOC_TYPEDEF
22969 @item SYMBOL_LOC_TYPEDEF
22970 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
22972 @findex SYMBOL_LOC_BLOCK
22973 @findex gdb.SYMBOL_LOC_BLOCK
22974 @item SYMBOL_LOC_BLOCK
22976 @findex SYMBOL_LOC_CONST_BYTES
22977 @findex gdb.SYMBOL_LOC_CONST_BYTES
22978 @item SYMBOL_LOC_CONST_BYTES
22979 Value is a byte-sequence.
22980 @findex SYMBOL_LOC_UNRESOLVED
22981 @findex gdb.SYMBOL_LOC_UNRESOLVED
22982 @item SYMBOL_LOC_UNRESOLVED
22983 Value is at a fixed address, but the address of the variable has to be
22984 determined from the minimal symbol table whenever the variable is
22986 @findex SYMBOL_LOC_OPTIMIZED_OUT
22987 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
22988 @item SYMBOL_LOC_OPTIMIZED_OUT
22989 The value does not actually exist in the program.
22990 @findex SYMBOL_LOC_COMPUTED
22991 @findex gdb.SYMBOL_LOC_COMPUTED
22992 @item SYMBOL_LOC_COMPUTED
22993 The value's address is a computed location.
22996 @node Symbol Tables In Python
22997 @subsubsection Symbol table representation in Python.
22999 @cindex symbol tables in python
23001 @tindex gdb.Symtab_and_line
23003 Access to symbol table data maintained by @value{GDBN} on the inferior
23004 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
23005 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
23006 from the @code{find_sal} method in @code{gdb.Frame} object.
23007 @xref{Frames In Python}.
23009 For more information on @value{GDBN}'s symbol table management, see
23010 @ref{Symbols, ,Examining the Symbol Table}, for more information.
23012 A @code{gdb.Symtab_and_line} object has the following attributes:
23015 @defivar Symtab_and_line symtab
23016 The symbol table object (@code{gdb.Symtab}) for this frame.
23017 This attribute is not writable.
23020 @defivar Symtab_and_line pc
23021 Indicates the current program counter address. This attribute is not
23025 @defivar Symtab_and_line line
23026 Indicates the current line number for this object. This
23027 attribute is not writable.
23031 A @code{gdb.Symtab} object has the following attributes:
23034 @defivar Symtab filename
23035 The symbol table's source filename. This attribute is not writable.
23038 @defivar Symtab objfile
23039 The symbol table's backing object file. @xref{Objfiles In Python}.
23040 This attribute is not writable.
23044 The following methods are provided:
23047 @defmethod Symtab fullname
23048 Return the symbol table's source absolute file name.
23052 @node Breakpoints In Python
23053 @subsubsection Manipulating breakpoints using Python
23055 @cindex breakpoints in python
23056 @tindex gdb.Breakpoint
23058 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
23061 @defmethod Breakpoint __init__ spec @r{[}type@r{]} @r{[}wp_class@r{]} @r{[}internal@r{]}
23062 Create a new breakpoint. @var{spec} is a string naming the
23063 location of the breakpoint, or an expression that defines a
23064 watchpoint. The contents can be any location recognized by the
23065 @code{break} command, or in the case of a watchpoint, by the @code{watch}
23066 command. The optional @var{type} denotes the breakpoint to create
23067 from the types defined later in this chapter. This argument can be
23068 either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}. @var{type}
23069 defaults to @code{BP_BREAKPOINT}. The optional @var{internal} argument
23070 allows the breakpoint to become invisible to the user. The breakpoint
23071 will neither be reported when created, nor will it be listed in the
23072 output from @code{info breakpoints} (but will be listed with the
23073 @code{maint info breakpoints} command). The optional @var{wp_class}
23074 argument defines the class of watchpoint to create, if @var{type} is
23075 @code{BP_WATCHPOINT}. If a watchpoint class is not provided, it is
23076 assumed to be a @var{WP_WRITE} class.
23079 The available watchpoint types represented by constants are defined in the
23084 @findex gdb.WP_READ
23086 Read only watchpoint.
23089 @findex gdb.WP_WRITE
23091 Write only watchpoint.
23094 @findex gdb.WP_ACCESS
23096 Read/Write watchpoint.
23099 @defmethod Breakpoint is_valid
23100 Return @code{True} if this @code{Breakpoint} object is valid,
23101 @code{False} otherwise. A @code{Breakpoint} object can become invalid
23102 if the user deletes the breakpoint. In this case, the object still
23103 exists, but the underlying breakpoint does not. In the cases of
23104 watchpoint scope, the watchpoint remains valid even if execution of the
23105 inferior leaves the scope of that watchpoint.
23108 @defmethod Breakpoint delete
23109 Permanently deletes the @value{GDBN} breakpoint. This also
23110 invalidates the Python @code{Breakpoint} object. Any further access
23111 to this object's attributes or methods will raise an error.
23114 @defivar Breakpoint enabled
23115 This attribute is @code{True} if the breakpoint is enabled, and
23116 @code{False} otherwise. This attribute is writable.
23119 @defivar Breakpoint silent
23120 This attribute is @code{True} if the breakpoint is silent, and
23121 @code{False} otherwise. This attribute is writable.
23123 Note that a breakpoint can also be silent if it has commands and the
23124 first command is @code{silent}. This is not reported by the
23125 @code{silent} attribute.
23128 @defivar Breakpoint thread
23129 If the breakpoint is thread-specific, this attribute holds the thread
23130 id. If the breakpoint is not thread-specific, this attribute is
23131 @code{None}. This attribute is writable.
23134 @defivar Breakpoint task
23135 If the breakpoint is Ada task-specific, this attribute holds the Ada task
23136 id. If the breakpoint is not task-specific (or the underlying
23137 language is not Ada), this attribute is @code{None}. This attribute
23141 @defivar Breakpoint ignore_count
23142 This attribute holds the ignore count for the breakpoint, an integer.
23143 This attribute is writable.
23146 @defivar Breakpoint number
23147 This attribute holds the breakpoint's number --- the identifier used by
23148 the user to manipulate the breakpoint. This attribute is not writable.
23151 @defivar Breakpoint type
23152 This attribute holds the breakpoint's type --- the identifier used to
23153 determine the actual breakpoint type or use-case. This attribute is not
23157 @defivar Breakpoint visible
23158 This attribute tells whether the breakpoint is visible to the user
23159 when set, or when the @samp{info breakpoints} command is run. This
23160 attribute is not writable.
23163 The available types are represented by constants defined in the @code{gdb}
23167 @findex BP_BREAKPOINT
23168 @findex gdb.BP_BREAKPOINT
23169 @item BP_BREAKPOINT
23170 Normal code breakpoint.
23172 @findex BP_WATCHPOINT
23173 @findex gdb.BP_WATCHPOINT
23174 @item BP_WATCHPOINT
23175 Watchpoint breakpoint.
23177 @findex BP_HARDWARE_WATCHPOINT
23178 @findex gdb.BP_HARDWARE_WATCHPOINT
23179 @item BP_HARDWARE_WATCHPOINT
23180 Hardware assisted watchpoint.
23182 @findex BP_READ_WATCHPOINT
23183 @findex gdb.BP_READ_WATCHPOINT
23184 @item BP_READ_WATCHPOINT
23185 Hardware assisted read watchpoint.
23187 @findex BP_ACCESS_WATCHPOINT
23188 @findex gdb.BP_ACCESS_WATCHPOINT
23189 @item BP_ACCESS_WATCHPOINT
23190 Hardware assisted access watchpoint.
23193 @defivar Breakpoint hit_count
23194 This attribute holds the hit count for the breakpoint, an integer.
23195 This attribute is writable, but currently it can only be set to zero.
23198 @defivar Breakpoint location
23199 This attribute holds the location of the breakpoint, as specified by
23200 the user. It is a string. If the breakpoint does not have a location
23201 (that is, it is a watchpoint) the attribute's value is @code{None}. This
23202 attribute is not writable.
23205 @defivar Breakpoint expression
23206 This attribute holds a breakpoint expression, as specified by
23207 the user. It is a string. If the breakpoint does not have an
23208 expression (the breakpoint is not a watchpoint) the attribute's value
23209 is @code{None}. This attribute is not writable.
23212 @defivar Breakpoint condition
23213 This attribute holds the condition of the breakpoint, as specified by
23214 the user. It is a string. If there is no condition, this attribute's
23215 value is @code{None}. This attribute is writable.
23218 @defivar Breakpoint commands
23219 This attribute holds the commands attached to the breakpoint. If
23220 there are commands, this attribute's value is a string holding all the
23221 commands, separated by newlines. If there are no commands, this
23222 attribute is @code{None}. This attribute is not writable.
23225 @node Lazy Strings In Python
23226 @subsubsection Python representation of lazy strings.
23228 @cindex lazy strings in python
23229 @tindex gdb.LazyString
23231 A @dfn{lazy string} is a string whose contents is not retrieved or
23232 encoded until it is needed.
23234 A @code{gdb.LazyString} is represented in @value{GDBN} as an
23235 @code{address} that points to a region of memory, an @code{encoding}
23236 that will be used to encode that region of memory, and a @code{length}
23237 to delimit the region of memory that represents the string. The
23238 difference between a @code{gdb.LazyString} and a string wrapped within
23239 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
23240 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
23241 retrieved and encoded during printing, while a @code{gdb.Value}
23242 wrapping a string is immediately retrieved and encoded on creation.
23244 A @code{gdb.LazyString} object has the following functions:
23246 @defmethod LazyString value
23247 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
23248 will point to the string in memory, but will lose all the delayed
23249 retrieval, encoding and handling that @value{GDBN} applies to a
23250 @code{gdb.LazyString}.
23253 @defivar LazyString address
23254 This attribute holds the address of the string. This attribute is not
23258 @defivar LazyString length
23259 This attribute holds the length of the string in characters. If the
23260 length is -1, then the string will be fetched and encoded up to the
23261 first null of appropriate width. This attribute is not writable.
23264 @defivar LazyString encoding
23265 This attribute holds the encoding that will be applied to the string
23266 when the string is printed by @value{GDBN}. If the encoding is not
23267 set, or contains an empty string, then @value{GDBN} will select the
23268 most appropriate encoding when the string is printed. This attribute
23272 @defivar LazyString type
23273 This attribute holds the type that is represented by the lazy string's
23274 type. For a lazy string this will always be a pointer type. To
23275 resolve this to the lazy string's character type, use the type's
23276 @code{target} method. @xref{Types In Python}. This attribute is not
23281 @subsection Auto-loading
23282 @cindex auto-loading, Python
23284 When a new object file is read (for example, due to the @code{file}
23285 command, or because the inferior has loaded a shared library),
23286 @value{GDBN} will look for Python support scripts in several ways:
23287 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
23290 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
23291 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
23292 * Which flavor to choose?::
23295 The auto-loading feature is useful for supplying application-specific
23296 debugging commands and scripts.
23298 Auto-loading can be enabled or disabled.
23301 @kindex set auto-load-scripts
23302 @item set auto-load-scripts [yes|no]
23303 Enable or disable the auto-loading of Python scripts.
23305 @kindex show auto-load-scripts
23306 @item show auto-load-scripts
23307 Show whether auto-loading of Python scripts is enabled or disabled.
23310 When reading an auto-loaded file, @value{GDBN} sets the
23311 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
23312 function (@pxref{Objfiles In Python}). This can be useful for
23313 registering objfile-specific pretty-printers.
23315 @node objfile-gdb.py file
23316 @subsubsection The @file{@var{objfile}-gdb.py} file
23317 @cindex @file{@var{objfile}-gdb.py}
23319 When a new object file is read, @value{GDBN} looks for
23320 a file named @file{@var{objfile}-gdb.py},
23321 where @var{objfile} is the object file's real name, formed by ensuring
23322 that the file name is absolute, following all symlinks, and resolving
23323 @code{.} and @code{..} components. If this file exists and is
23324 readable, @value{GDBN} will evaluate it as a Python script.
23326 If this file does not exist, and if the parameter
23327 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
23328 then @value{GDBN} will look for @var{real-name} in all of the
23329 directories mentioned in the value of @code{debug-file-directory}.
23331 Finally, if this file does not exist, then @value{GDBN} will look for
23332 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
23333 @var{data-directory} is @value{GDBN}'s data directory (available via
23334 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
23335 is the object file's real name, as described above.
23337 @value{GDBN} does not track which files it has already auto-loaded this way.
23338 @value{GDBN} will load the associated script every time the corresponding
23339 @var{objfile} is opened.
23340 So your @file{-gdb.py} file should be careful to avoid errors if it
23341 is evaluated more than once.
23343 @node .debug_gdb_scripts section
23344 @subsubsection The @code{.debug_gdb_scripts} section
23345 @cindex @code{.debug_gdb_scripts} section
23347 For systems using file formats like ELF and COFF,
23348 when @value{GDBN} loads a new object file
23349 it will look for a special section named @samp{.debug_gdb_scripts}.
23350 If this section exists, its contents is a list of names of scripts to load.
23352 @value{GDBN} will look for each specified script file first in the
23353 current directory and then along the source search path
23354 (@pxref{Source Path, ,Specifying Source Directories}),
23355 except that @file{$cdir} is not searched, since the compilation
23356 directory is not relevant to scripts.
23358 Entries can be placed in section @code{.debug_gdb_scripts} with,
23359 for example, this GCC macro:
23362 /* Note: The "MS" section flags are to remove duplicates. */
23363 #define DEFINE_GDB_SCRIPT(script_name) \
23365 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
23367 .asciz \"" script_name "\"\n\
23373 Then one can reference the macro in a header or source file like this:
23376 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
23379 The script name may include directories if desired.
23381 If the macro is put in a header, any application or library
23382 using this header will get a reference to the specified script.
23384 @node Which flavor to choose?
23385 @subsubsection Which flavor to choose?
23387 Given the multiple ways of auto-loading Python scripts, it might not always
23388 be clear which one to choose. This section provides some guidance.
23390 Benefits of the @file{-gdb.py} way:
23394 Can be used with file formats that don't support multiple sections.
23397 Ease of finding scripts for public libraries.
23399 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
23400 in the source search path.
23401 For publicly installed libraries, e.g., @file{libstdc++}, there typically
23402 isn't a source directory in which to find the script.
23405 Doesn't require source code additions.
23408 Benefits of the @code{.debug_gdb_scripts} way:
23412 Works with static linking.
23414 Scripts for libraries done the @file{-gdb.py} way require an objfile to
23415 trigger their loading. When an application is statically linked the only
23416 objfile available is the executable, and it is cumbersome to attach all the
23417 scripts from all the input libraries to the executable's @file{-gdb.py} script.
23420 Works with classes that are entirely inlined.
23422 Some classes can be entirely inlined, and thus there may not be an associated
23423 shared library to attach a @file{-gdb.py} script to.
23426 Scripts needn't be copied out of the source tree.
23428 In some circumstances, apps can be built out of large collections of internal
23429 libraries, and the build infrastructure necessary to install the
23430 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
23431 cumbersome. It may be easier to specify the scripts in the
23432 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
23433 top of the source tree to the source search path.
23436 @node Python modules
23437 @subsection Python modules
23438 @cindex python modules
23440 @value{GDBN} comes with a module to assist writing Python code.
23443 * gdb.printing:: Building and registering pretty-printers.
23444 * gdb.types:: Utilities for working with types.
23448 @subsubsection gdb.printing
23449 @cindex gdb.printing
23451 This module provides a collection of utilities for working with
23455 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
23456 This class specifies the API that makes @samp{info pretty-printer},
23457 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
23458 Pretty-printers should generally inherit from this class.
23460 @item SubPrettyPrinter (@var{name})
23461 For printers that handle multiple types, this class specifies the
23462 corresponding API for the subprinters.
23464 @item RegexpCollectionPrettyPrinter (@var{name})
23465 Utility class for handling multiple printers, all recognized via
23466 regular expressions.
23467 @xref{Writing a Pretty-Printer}, for an example.
23469 @item register_pretty_printer (@var{obj}, @var{printer})
23470 Register @var{printer} with the pretty-printer list of @var{obj}.
23474 @subsubsection gdb.types
23477 This module provides a collection of utilities for working with
23478 @code{gdb.Types} objects.
23481 @item get_basic_type (@var{type})
23482 Return @var{type} with const and volatile qualifiers stripped,
23483 and with typedefs and C@t{++} references converted to the underlying type.
23488 typedef const int const_int;
23490 const_int& foo_ref (foo);
23491 int main () @{ return 0; @}
23498 (gdb) python import gdb.types
23499 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
23500 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
23504 @item has_field (@var{type}, @var{field})
23505 Return @code{True} if @var{type}, assumed to be a type with fields
23506 (e.g., a structure or union), has field @var{field}.
23508 @item make_enum_dict (@var{enum_type})
23509 Return a Python @code{dictionary} type produced from @var{enum_type}.
23513 @chapter Command Interpreters
23514 @cindex command interpreters
23516 @value{GDBN} supports multiple command interpreters, and some command
23517 infrastructure to allow users or user interface writers to switch
23518 between interpreters or run commands in other interpreters.
23520 @value{GDBN} currently supports two command interpreters, the console
23521 interpreter (sometimes called the command-line interpreter or @sc{cli})
23522 and the machine interface interpreter (or @sc{gdb/mi}). This manual
23523 describes both of these interfaces in great detail.
23525 By default, @value{GDBN} will start with the console interpreter.
23526 However, the user may choose to start @value{GDBN} with another
23527 interpreter by specifying the @option{-i} or @option{--interpreter}
23528 startup options. Defined interpreters include:
23532 @cindex console interpreter
23533 The traditional console or command-line interpreter. This is the most often
23534 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
23535 @value{GDBN} will use this interpreter.
23538 @cindex mi interpreter
23539 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
23540 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
23541 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
23545 @cindex mi2 interpreter
23546 The current @sc{gdb/mi} interface.
23549 @cindex mi1 interpreter
23550 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
23554 @cindex invoke another interpreter
23555 The interpreter being used by @value{GDBN} may not be dynamically
23556 switched at runtime. Although possible, this could lead to a very
23557 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
23558 enters the command "interpreter-set console" in a console view,
23559 @value{GDBN} would switch to using the console interpreter, rendering
23560 the IDE inoperable!
23562 @kindex interpreter-exec
23563 Although you may only choose a single interpreter at startup, you may execute
23564 commands in any interpreter from the current interpreter using the appropriate
23565 command. If you are running the console interpreter, simply use the
23566 @code{interpreter-exec} command:
23569 interpreter-exec mi "-data-list-register-names"
23572 @sc{gdb/mi} has a similar command, although it is only available in versions of
23573 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
23576 @chapter @value{GDBN} Text User Interface
23578 @cindex Text User Interface
23581 * TUI Overview:: TUI overview
23582 * TUI Keys:: TUI key bindings
23583 * TUI Single Key Mode:: TUI single key mode
23584 * TUI Commands:: TUI-specific commands
23585 * TUI Configuration:: TUI configuration variables
23588 The @value{GDBN} Text User Interface (TUI) is a terminal
23589 interface which uses the @code{curses} library to show the source
23590 file, the assembly output, the program registers and @value{GDBN}
23591 commands in separate text windows. The TUI mode is supported only
23592 on platforms where a suitable version of the @code{curses} library
23595 @pindex @value{GDBTUI}
23596 The TUI mode is enabled by default when you invoke @value{GDBN} as
23597 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
23598 You can also switch in and out of TUI mode while @value{GDBN} runs by
23599 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
23600 @xref{TUI Keys, ,TUI Key Bindings}.
23603 @section TUI Overview
23605 In TUI mode, @value{GDBN} can display several text windows:
23609 This window is the @value{GDBN} command window with the @value{GDBN}
23610 prompt and the @value{GDBN} output. The @value{GDBN} input is still
23611 managed using readline.
23614 The source window shows the source file of the program. The current
23615 line and active breakpoints are displayed in this window.
23618 The assembly window shows the disassembly output of the program.
23621 This window shows the processor registers. Registers are highlighted
23622 when their values change.
23625 The source and assembly windows show the current program position
23626 by highlighting the current line and marking it with a @samp{>} marker.
23627 Breakpoints are indicated with two markers. The first marker
23628 indicates the breakpoint type:
23632 Breakpoint which was hit at least once.
23635 Breakpoint which was never hit.
23638 Hardware breakpoint which was hit at least once.
23641 Hardware breakpoint which was never hit.
23644 The second marker indicates whether the breakpoint is enabled or not:
23648 Breakpoint is enabled.
23651 Breakpoint is disabled.
23654 The source, assembly and register windows are updated when the current
23655 thread changes, when the frame changes, or when the program counter
23658 These windows are not all visible at the same time. The command
23659 window is always visible. The others can be arranged in several
23670 source and assembly,
23673 source and registers, or
23676 assembly and registers.
23679 A status line above the command window shows the following information:
23683 Indicates the current @value{GDBN} target.
23684 (@pxref{Targets, ,Specifying a Debugging Target}).
23687 Gives the current process or thread number.
23688 When no process is being debugged, this field is set to @code{No process}.
23691 Gives the current function name for the selected frame.
23692 The name is demangled if demangling is turned on (@pxref{Print Settings}).
23693 When there is no symbol corresponding to the current program counter,
23694 the string @code{??} is displayed.
23697 Indicates the current line number for the selected frame.
23698 When the current line number is not known, the string @code{??} is displayed.
23701 Indicates the current program counter address.
23705 @section TUI Key Bindings
23706 @cindex TUI key bindings
23708 The TUI installs several key bindings in the readline keymaps
23709 @ifset SYSTEM_READLINE
23710 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
23712 @ifclear SYSTEM_READLINE
23713 (@pxref{Command Line Editing}).
23715 The following key bindings are installed for both TUI mode and the
23716 @value{GDBN} standard mode.
23725 Enter or leave the TUI mode. When leaving the TUI mode,
23726 the curses window management stops and @value{GDBN} operates using
23727 its standard mode, writing on the terminal directly. When reentering
23728 the TUI mode, control is given back to the curses windows.
23729 The screen is then refreshed.
23733 Use a TUI layout with only one window. The layout will
23734 either be @samp{source} or @samp{assembly}. When the TUI mode
23735 is not active, it will switch to the TUI mode.
23737 Think of this key binding as the Emacs @kbd{C-x 1} binding.
23741 Use a TUI layout with at least two windows. When the current
23742 layout already has two windows, the next layout with two windows is used.
23743 When a new layout is chosen, one window will always be common to the
23744 previous layout and the new one.
23746 Think of it as the Emacs @kbd{C-x 2} binding.
23750 Change the active window. The TUI associates several key bindings
23751 (like scrolling and arrow keys) with the active window. This command
23752 gives the focus to the next TUI window.
23754 Think of it as the Emacs @kbd{C-x o} binding.
23758 Switch in and out of the TUI SingleKey mode that binds single
23759 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
23762 The following key bindings only work in the TUI mode:
23767 Scroll the active window one page up.
23771 Scroll the active window one page down.
23775 Scroll the active window one line up.
23779 Scroll the active window one line down.
23783 Scroll the active window one column left.
23787 Scroll the active window one column right.
23791 Refresh the screen.
23794 Because the arrow keys scroll the active window in the TUI mode, they
23795 are not available for their normal use by readline unless the command
23796 window has the focus. When another window is active, you must use
23797 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
23798 and @kbd{C-f} to control the command window.
23800 @node TUI Single Key Mode
23801 @section TUI Single Key Mode
23802 @cindex TUI single key mode
23804 The TUI also provides a @dfn{SingleKey} mode, which binds several
23805 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
23806 switch into this mode, where the following key bindings are used:
23809 @kindex c @r{(SingleKey TUI key)}
23813 @kindex d @r{(SingleKey TUI key)}
23817 @kindex f @r{(SingleKey TUI key)}
23821 @kindex n @r{(SingleKey TUI key)}
23825 @kindex q @r{(SingleKey TUI key)}
23827 exit the SingleKey mode.
23829 @kindex r @r{(SingleKey TUI key)}
23833 @kindex s @r{(SingleKey TUI key)}
23837 @kindex u @r{(SingleKey TUI key)}
23841 @kindex v @r{(SingleKey TUI key)}
23845 @kindex w @r{(SingleKey TUI key)}
23850 Other keys temporarily switch to the @value{GDBN} command prompt.
23851 The key that was pressed is inserted in the editing buffer so that
23852 it is possible to type most @value{GDBN} commands without interaction
23853 with the TUI SingleKey mode. Once the command is entered the TUI
23854 SingleKey mode is restored. The only way to permanently leave
23855 this mode is by typing @kbd{q} or @kbd{C-x s}.
23859 @section TUI-specific Commands
23860 @cindex TUI commands
23862 The TUI has specific commands to control the text windows.
23863 These commands are always available, even when @value{GDBN} is not in
23864 the TUI mode. When @value{GDBN} is in the standard mode, most
23865 of these commands will automatically switch to the TUI mode.
23867 Note that if @value{GDBN}'s @code{stdout} is not connected to a
23868 terminal, or @value{GDBN} has been started with the machine interface
23869 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
23870 these commands will fail with an error, because it would not be
23871 possible or desirable to enable curses window management.
23876 List and give the size of all displayed windows.
23880 Display the next layout.
23883 Display the previous layout.
23886 Display the source window only.
23889 Display the assembly window only.
23892 Display the source and assembly window.
23895 Display the register window together with the source or assembly window.
23899 Make the next window active for scrolling.
23902 Make the previous window active for scrolling.
23905 Make the source window active for scrolling.
23908 Make the assembly window active for scrolling.
23911 Make the register window active for scrolling.
23914 Make the command window active for scrolling.
23918 Refresh the screen. This is similar to typing @kbd{C-L}.
23920 @item tui reg float
23922 Show the floating point registers in the register window.
23924 @item tui reg general
23925 Show the general registers in the register window.
23928 Show the next register group. The list of register groups as well as
23929 their order is target specific. The predefined register groups are the
23930 following: @code{general}, @code{float}, @code{system}, @code{vector},
23931 @code{all}, @code{save}, @code{restore}.
23933 @item tui reg system
23934 Show the system registers in the register window.
23938 Update the source window and the current execution point.
23940 @item winheight @var{name} +@var{count}
23941 @itemx winheight @var{name} -@var{count}
23943 Change the height of the window @var{name} by @var{count}
23944 lines. Positive counts increase the height, while negative counts
23947 @item tabset @var{nchars}
23949 Set the width of tab stops to be @var{nchars} characters.
23952 @node TUI Configuration
23953 @section TUI Configuration Variables
23954 @cindex TUI configuration variables
23956 Several configuration variables control the appearance of TUI windows.
23959 @item set tui border-kind @var{kind}
23960 @kindex set tui border-kind
23961 Select the border appearance for the source, assembly and register windows.
23962 The possible values are the following:
23965 Use a space character to draw the border.
23968 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
23971 Use the Alternate Character Set to draw the border. The border is
23972 drawn using character line graphics if the terminal supports them.
23975 @item set tui border-mode @var{mode}
23976 @kindex set tui border-mode
23977 @itemx set tui active-border-mode @var{mode}
23978 @kindex set tui active-border-mode
23979 Select the display attributes for the borders of the inactive windows
23980 or the active window. The @var{mode} can be one of the following:
23983 Use normal attributes to display the border.
23989 Use reverse video mode.
23992 Use half bright mode.
23994 @item half-standout
23995 Use half bright and standout mode.
23998 Use extra bright or bold mode.
24000 @item bold-standout
24001 Use extra bright or bold and standout mode.
24006 @chapter Using @value{GDBN} under @sc{gnu} Emacs
24009 @cindex @sc{gnu} Emacs
24010 A special interface allows you to use @sc{gnu} Emacs to view (and
24011 edit) the source files for the program you are debugging with
24014 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
24015 executable file you want to debug as an argument. This command starts
24016 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
24017 created Emacs buffer.
24018 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
24020 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
24025 All ``terminal'' input and output goes through an Emacs buffer, called
24028 This applies both to @value{GDBN} commands and their output, and to the input
24029 and output done by the program you are debugging.
24031 This is useful because it means that you can copy the text of previous
24032 commands and input them again; you can even use parts of the output
24035 All the facilities of Emacs' Shell mode are available for interacting
24036 with your program. In particular, you can send signals the usual
24037 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
24041 @value{GDBN} displays source code through Emacs.
24043 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
24044 source file for that frame and puts an arrow (@samp{=>}) at the
24045 left margin of the current line. Emacs uses a separate buffer for
24046 source display, and splits the screen to show both your @value{GDBN} session
24049 Explicit @value{GDBN} @code{list} or search commands still produce output as
24050 usual, but you probably have no reason to use them from Emacs.
24053 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
24054 a graphical mode, enabled by default, which provides further buffers
24055 that can control the execution and describe the state of your program.
24056 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
24058 If you specify an absolute file name when prompted for the @kbd{M-x
24059 gdb} argument, then Emacs sets your current working directory to where
24060 your program resides. If you only specify the file name, then Emacs
24061 sets your current working directory to to the directory associated
24062 with the previous buffer. In this case, @value{GDBN} may find your
24063 program by searching your environment's @code{PATH} variable, but on
24064 some operating systems it might not find the source. So, although the
24065 @value{GDBN} input and output session proceeds normally, the auxiliary
24066 buffer does not display the current source and line of execution.
24068 The initial working directory of @value{GDBN} is printed on the top
24069 line of the GUD buffer and this serves as a default for the commands
24070 that specify files for @value{GDBN} to operate on. @xref{Files,
24071 ,Commands to Specify Files}.
24073 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
24074 need to call @value{GDBN} by a different name (for example, if you
24075 keep several configurations around, with different names) you can
24076 customize the Emacs variable @code{gud-gdb-command-name} to run the
24079 In the GUD buffer, you can use these special Emacs commands in
24080 addition to the standard Shell mode commands:
24084 Describe the features of Emacs' GUD Mode.
24087 Execute to another source line, like the @value{GDBN} @code{step} command; also
24088 update the display window to show the current file and location.
24091 Execute to next source line in this function, skipping all function
24092 calls, like the @value{GDBN} @code{next} command. Then update the display window
24093 to show the current file and location.
24096 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
24097 display window accordingly.
24100 Execute until exit from the selected stack frame, like the @value{GDBN}
24101 @code{finish} command.
24104 Continue execution of your program, like the @value{GDBN} @code{continue}
24108 Go up the number of frames indicated by the numeric argument
24109 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
24110 like the @value{GDBN} @code{up} command.
24113 Go down the number of frames indicated by the numeric argument, like the
24114 @value{GDBN} @code{down} command.
24117 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
24118 tells @value{GDBN} to set a breakpoint on the source line point is on.
24120 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
24121 separate frame which shows a backtrace when the GUD buffer is current.
24122 Move point to any frame in the stack and type @key{RET} to make it
24123 become the current frame and display the associated source in the
24124 source buffer. Alternatively, click @kbd{Mouse-2} to make the
24125 selected frame become the current one. In graphical mode, the
24126 speedbar displays watch expressions.
24128 If you accidentally delete the source-display buffer, an easy way to get
24129 it back is to type the command @code{f} in the @value{GDBN} buffer, to
24130 request a frame display; when you run under Emacs, this recreates
24131 the source buffer if necessary to show you the context of the current
24134 The source files displayed in Emacs are in ordinary Emacs buffers
24135 which are visiting the source files in the usual way. You can edit
24136 the files with these buffers if you wish; but keep in mind that @value{GDBN}
24137 communicates with Emacs in terms of line numbers. If you add or
24138 delete lines from the text, the line numbers that @value{GDBN} knows cease
24139 to correspond properly with the code.
24141 A more detailed description of Emacs' interaction with @value{GDBN} is
24142 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
24145 @c The following dropped because Epoch is nonstandard. Reactivate
24146 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
24148 @kindex Emacs Epoch environment
24152 Version 18 of @sc{gnu} Emacs has a built-in window system
24153 called the @code{epoch}
24154 environment. Users of this environment can use a new command,
24155 @code{inspect} which performs identically to @code{print} except that
24156 each value is printed in its own window.
24161 @chapter The @sc{gdb/mi} Interface
24163 @unnumberedsec Function and Purpose
24165 @cindex @sc{gdb/mi}, its purpose
24166 @sc{gdb/mi} is a line based machine oriented text interface to
24167 @value{GDBN} and is activated by specifying using the
24168 @option{--interpreter} command line option (@pxref{Mode Options}). It
24169 is specifically intended to support the development of systems which
24170 use the debugger as just one small component of a larger system.
24172 This chapter is a specification of the @sc{gdb/mi} interface. It is written
24173 in the form of a reference manual.
24175 Note that @sc{gdb/mi} is still under construction, so some of the
24176 features described below are incomplete and subject to change
24177 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
24179 @unnumberedsec Notation and Terminology
24181 @cindex notational conventions, for @sc{gdb/mi}
24182 This chapter uses the following notation:
24186 @code{|} separates two alternatives.
24189 @code{[ @var{something} ]} indicates that @var{something} is optional:
24190 it may or may not be given.
24193 @code{( @var{group} )*} means that @var{group} inside the parentheses
24194 may repeat zero or more times.
24197 @code{( @var{group} )+} means that @var{group} inside the parentheses
24198 may repeat one or more times.
24201 @code{"@var{string}"} means a literal @var{string}.
24205 @heading Dependencies
24209 * GDB/MI General Design::
24210 * GDB/MI Command Syntax::
24211 * GDB/MI Compatibility with CLI::
24212 * GDB/MI Development and Front Ends::
24213 * GDB/MI Output Records::
24214 * GDB/MI Simple Examples::
24215 * GDB/MI Command Description Format::
24216 * GDB/MI Breakpoint Commands::
24217 * GDB/MI Program Context::
24218 * GDB/MI Thread Commands::
24219 * GDB/MI Program Execution::
24220 * GDB/MI Stack Manipulation::
24221 * GDB/MI Variable Objects::
24222 * GDB/MI Data Manipulation::
24223 * GDB/MI Tracepoint Commands::
24224 * GDB/MI Symbol Query::
24225 * GDB/MI File Commands::
24227 * GDB/MI Kod Commands::
24228 * GDB/MI Memory Overlay Commands::
24229 * GDB/MI Signal Handling Commands::
24231 * GDB/MI Target Manipulation::
24232 * GDB/MI File Transfer Commands::
24233 * GDB/MI Miscellaneous Commands::
24236 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24237 @node GDB/MI General Design
24238 @section @sc{gdb/mi} General Design
24239 @cindex GDB/MI General Design
24241 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
24242 parts---commands sent to @value{GDBN}, responses to those commands
24243 and notifications. Each command results in exactly one response,
24244 indicating either successful completion of the command, or an error.
24245 For the commands that do not resume the target, the response contains the
24246 requested information. For the commands that resume the target, the
24247 response only indicates whether the target was successfully resumed.
24248 Notifications is the mechanism for reporting changes in the state of the
24249 target, or in @value{GDBN} state, that cannot conveniently be associated with
24250 a command and reported as part of that command response.
24252 The important examples of notifications are:
24256 Exec notifications. These are used to report changes in
24257 target state---when a target is resumed, or stopped. It would not
24258 be feasible to include this information in response of resuming
24259 commands, because one resume commands can result in multiple events in
24260 different threads. Also, quite some time may pass before any event
24261 happens in the target, while a frontend needs to know whether the resuming
24262 command itself was successfully executed.
24265 Console output, and status notifications. Console output
24266 notifications are used to report output of CLI commands, as well as
24267 diagnostics for other commands. Status notifications are used to
24268 report the progress of a long-running operation. Naturally, including
24269 this information in command response would mean no output is produced
24270 until the command is finished, which is undesirable.
24273 General notifications. Commands may have various side effects on
24274 the @value{GDBN} or target state beyond their official purpose. For example,
24275 a command may change the selected thread. Although such changes can
24276 be included in command response, using notification allows for more
24277 orthogonal frontend design.
24281 There's no guarantee that whenever an MI command reports an error,
24282 @value{GDBN} or the target are in any specific state, and especially,
24283 the state is not reverted to the state before the MI command was
24284 processed. Therefore, whenever an MI command results in an error,
24285 we recommend that the frontend refreshes all the information shown in
24286 the user interface.
24290 * Context management::
24291 * Asynchronous and non-stop modes::
24295 @node Context management
24296 @subsection Context management
24298 In most cases when @value{GDBN} accesses the target, this access is
24299 done in context of a specific thread and frame (@pxref{Frames}).
24300 Often, even when accessing global data, the target requires that a thread
24301 be specified. The CLI interface maintains the selected thread and frame,
24302 and supplies them to target on each command. This is convenient,
24303 because a command line user would not want to specify that information
24304 explicitly on each command, and because user interacts with
24305 @value{GDBN} via a single terminal, so no confusion is possible as
24306 to what thread and frame are the current ones.
24308 In the case of MI, the concept of selected thread and frame is less
24309 useful. First, a frontend can easily remember this information
24310 itself. Second, a graphical frontend can have more than one window,
24311 each one used for debugging a different thread, and the frontend might
24312 want to access additional threads for internal purposes. This
24313 increases the risk that by relying on implicitly selected thread, the
24314 frontend may be operating on a wrong one. Therefore, each MI command
24315 should explicitly specify which thread and frame to operate on. To
24316 make it possible, each MI command accepts the @samp{--thread} and
24317 @samp{--frame} options, the value to each is @value{GDBN} identifier
24318 for thread and frame to operate on.
24320 Usually, each top-level window in a frontend allows the user to select
24321 a thread and a frame, and remembers the user selection for further
24322 operations. However, in some cases @value{GDBN} may suggest that the
24323 current thread be changed. For example, when stopping on a breakpoint
24324 it is reasonable to switch to the thread where breakpoint is hit. For
24325 another example, if the user issues the CLI @samp{thread} command via
24326 the frontend, it is desirable to change the frontend's selected thread to the
24327 one specified by user. @value{GDBN} communicates the suggestion to
24328 change current thread using the @samp{=thread-selected} notification.
24329 No such notification is available for the selected frame at the moment.
24331 Note that historically, MI shares the selected thread with CLI, so
24332 frontends used the @code{-thread-select} to execute commands in the
24333 right context. However, getting this to work right is cumbersome. The
24334 simplest way is for frontend to emit @code{-thread-select} command
24335 before every command. This doubles the number of commands that need
24336 to be sent. The alternative approach is to suppress @code{-thread-select}
24337 if the selected thread in @value{GDBN} is supposed to be identical to the
24338 thread the frontend wants to operate on. However, getting this
24339 optimization right can be tricky. In particular, if the frontend
24340 sends several commands to @value{GDBN}, and one of the commands changes the
24341 selected thread, then the behaviour of subsequent commands will
24342 change. So, a frontend should either wait for response from such
24343 problematic commands, or explicitly add @code{-thread-select} for
24344 all subsequent commands. No frontend is known to do this exactly
24345 right, so it is suggested to just always pass the @samp{--thread} and
24346 @samp{--frame} options.
24348 @node Asynchronous and non-stop modes
24349 @subsection Asynchronous command execution and non-stop mode
24351 On some targets, @value{GDBN} is capable of processing MI commands
24352 even while the target is running. This is called @dfn{asynchronous
24353 command execution} (@pxref{Background Execution}). The frontend may
24354 specify a preferrence for asynchronous execution using the
24355 @code{-gdb-set target-async 1} command, which should be emitted before
24356 either running the executable or attaching to the target. After the
24357 frontend has started the executable or attached to the target, it can
24358 find if asynchronous execution is enabled using the
24359 @code{-list-target-features} command.
24361 Even if @value{GDBN} can accept a command while target is running,
24362 many commands that access the target do not work when the target is
24363 running. Therefore, asynchronous command execution is most useful
24364 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
24365 it is possible to examine the state of one thread, while other threads
24368 When a given thread is running, MI commands that try to access the
24369 target in the context of that thread may not work, or may work only on
24370 some targets. In particular, commands that try to operate on thread's
24371 stack will not work, on any target. Commands that read memory, or
24372 modify breakpoints, may work or not work, depending on the target. Note
24373 that even commands that operate on global state, such as @code{print},
24374 @code{set}, and breakpoint commands, still access the target in the
24375 context of a specific thread, so frontend should try to find a
24376 stopped thread and perform the operation on that thread (using the
24377 @samp{--thread} option).
24379 Which commands will work in the context of a running thread is
24380 highly target dependent. However, the two commands
24381 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
24382 to find the state of a thread, will always work.
24384 @node Thread groups
24385 @subsection Thread groups
24386 @value{GDBN} may be used to debug several processes at the same time.
24387 On some platfroms, @value{GDBN} may support debugging of several
24388 hardware systems, each one having several cores with several different
24389 processes running on each core. This section describes the MI
24390 mechanism to support such debugging scenarios.
24392 The key observation is that regardless of the structure of the
24393 target, MI can have a global list of threads, because most commands that
24394 accept the @samp{--thread} option do not need to know what process that
24395 thread belongs to. Therefore, it is not necessary to introduce
24396 neither additional @samp{--process} option, nor an notion of the
24397 current process in the MI interface. The only strictly new feature
24398 that is required is the ability to find how the threads are grouped
24401 To allow the user to discover such grouping, and to support arbitrary
24402 hierarchy of machines/cores/processes, MI introduces the concept of a
24403 @dfn{thread group}. Thread group is a collection of threads and other
24404 thread groups. A thread group always has a string identifier, a type,
24405 and may have additional attributes specific to the type. A new
24406 command, @code{-list-thread-groups}, returns the list of top-level
24407 thread groups, which correspond to processes that @value{GDBN} is
24408 debugging at the moment. By passing an identifier of a thread group
24409 to the @code{-list-thread-groups} command, it is possible to obtain
24410 the members of specific thread group.
24412 To allow the user to easily discover processes, and other objects, he
24413 wishes to debug, a concept of @dfn{available thread group} is
24414 introduced. Available thread group is an thread group that
24415 @value{GDBN} is not debugging, but that can be attached to, using the
24416 @code{-target-attach} command. The list of available top-level thread
24417 groups can be obtained using @samp{-list-thread-groups --available}.
24418 In general, the content of a thread group may be only retrieved only
24419 after attaching to that thread group.
24421 Thread groups are related to inferiors (@pxref{Inferiors and
24422 Programs}). Each inferior corresponds to a thread group of a special
24423 type @samp{process}, and some additional operations are permitted on
24424 such thread groups.
24426 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24427 @node GDB/MI Command Syntax
24428 @section @sc{gdb/mi} Command Syntax
24431 * GDB/MI Input Syntax::
24432 * GDB/MI Output Syntax::
24435 @node GDB/MI Input Syntax
24436 @subsection @sc{gdb/mi} Input Syntax
24438 @cindex input syntax for @sc{gdb/mi}
24439 @cindex @sc{gdb/mi}, input syntax
24441 @item @var{command} @expansion{}
24442 @code{@var{cli-command} | @var{mi-command}}
24444 @item @var{cli-command} @expansion{}
24445 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
24446 @var{cli-command} is any existing @value{GDBN} CLI command.
24448 @item @var{mi-command} @expansion{}
24449 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
24450 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
24452 @item @var{token} @expansion{}
24453 "any sequence of digits"
24455 @item @var{option} @expansion{}
24456 @code{"-" @var{parameter} [ " " @var{parameter} ]}
24458 @item @var{parameter} @expansion{}
24459 @code{@var{non-blank-sequence} | @var{c-string}}
24461 @item @var{operation} @expansion{}
24462 @emph{any of the operations described in this chapter}
24464 @item @var{non-blank-sequence} @expansion{}
24465 @emph{anything, provided it doesn't contain special characters such as
24466 "-", @var{nl}, """ and of course " "}
24468 @item @var{c-string} @expansion{}
24469 @code{""" @var{seven-bit-iso-c-string-content} """}
24471 @item @var{nl} @expansion{}
24480 The CLI commands are still handled by the @sc{mi} interpreter; their
24481 output is described below.
24484 The @code{@var{token}}, when present, is passed back when the command
24488 Some @sc{mi} commands accept optional arguments as part of the parameter
24489 list. Each option is identified by a leading @samp{-} (dash) and may be
24490 followed by an optional argument parameter. Options occur first in the
24491 parameter list and can be delimited from normal parameters using
24492 @samp{--} (this is useful when some parameters begin with a dash).
24499 We want easy access to the existing CLI syntax (for debugging).
24502 We want it to be easy to spot a @sc{mi} operation.
24505 @node GDB/MI Output Syntax
24506 @subsection @sc{gdb/mi} Output Syntax
24508 @cindex output syntax of @sc{gdb/mi}
24509 @cindex @sc{gdb/mi}, output syntax
24510 The output from @sc{gdb/mi} consists of zero or more out-of-band records
24511 followed, optionally, by a single result record. This result record
24512 is for the most recent command. The sequence of output records is
24513 terminated by @samp{(gdb)}.
24515 If an input command was prefixed with a @code{@var{token}} then the
24516 corresponding output for that command will also be prefixed by that same
24520 @item @var{output} @expansion{}
24521 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
24523 @item @var{result-record} @expansion{}
24524 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
24526 @item @var{out-of-band-record} @expansion{}
24527 @code{@var{async-record} | @var{stream-record}}
24529 @item @var{async-record} @expansion{}
24530 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
24532 @item @var{exec-async-output} @expansion{}
24533 @code{[ @var{token} ] "*" @var{async-output}}
24535 @item @var{status-async-output} @expansion{}
24536 @code{[ @var{token} ] "+" @var{async-output}}
24538 @item @var{notify-async-output} @expansion{}
24539 @code{[ @var{token} ] "=" @var{async-output}}
24541 @item @var{async-output} @expansion{}
24542 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
24544 @item @var{result-class} @expansion{}
24545 @code{"done" | "running" | "connected" | "error" | "exit"}
24547 @item @var{async-class} @expansion{}
24548 @code{"stopped" | @var{others}} (where @var{others} will be added
24549 depending on the needs---this is still in development).
24551 @item @var{result} @expansion{}
24552 @code{ @var{variable} "=" @var{value}}
24554 @item @var{variable} @expansion{}
24555 @code{ @var{string} }
24557 @item @var{value} @expansion{}
24558 @code{ @var{const} | @var{tuple} | @var{list} }
24560 @item @var{const} @expansion{}
24561 @code{@var{c-string}}
24563 @item @var{tuple} @expansion{}
24564 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
24566 @item @var{list} @expansion{}
24567 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
24568 @var{result} ( "," @var{result} )* "]" }
24570 @item @var{stream-record} @expansion{}
24571 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
24573 @item @var{console-stream-output} @expansion{}
24574 @code{"~" @var{c-string}}
24576 @item @var{target-stream-output} @expansion{}
24577 @code{"@@" @var{c-string}}
24579 @item @var{log-stream-output} @expansion{}
24580 @code{"&" @var{c-string}}
24582 @item @var{nl} @expansion{}
24585 @item @var{token} @expansion{}
24586 @emph{any sequence of digits}.
24594 All output sequences end in a single line containing a period.
24597 The @code{@var{token}} is from the corresponding request. Note that
24598 for all async output, while the token is allowed by the grammar and
24599 may be output by future versions of @value{GDBN} for select async
24600 output messages, it is generally omitted. Frontends should treat
24601 all async output as reporting general changes in the state of the
24602 target and there should be no need to associate async output to any
24606 @cindex status output in @sc{gdb/mi}
24607 @var{status-async-output} contains on-going status information about the
24608 progress of a slow operation. It can be discarded. All status output is
24609 prefixed by @samp{+}.
24612 @cindex async output in @sc{gdb/mi}
24613 @var{exec-async-output} contains asynchronous state change on the target
24614 (stopped, started, disappeared). All async output is prefixed by
24618 @cindex notify output in @sc{gdb/mi}
24619 @var{notify-async-output} contains supplementary information that the
24620 client should handle (e.g., a new breakpoint information). All notify
24621 output is prefixed by @samp{=}.
24624 @cindex console output in @sc{gdb/mi}
24625 @var{console-stream-output} is output that should be displayed as is in the
24626 console. It is the textual response to a CLI command. All the console
24627 output is prefixed by @samp{~}.
24630 @cindex target output in @sc{gdb/mi}
24631 @var{target-stream-output} is the output produced by the target program.
24632 All the target output is prefixed by @samp{@@}.
24635 @cindex log output in @sc{gdb/mi}
24636 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
24637 instance messages that should be displayed as part of an error log. All
24638 the log output is prefixed by @samp{&}.
24641 @cindex list output in @sc{gdb/mi}
24642 New @sc{gdb/mi} commands should only output @var{lists} containing
24648 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
24649 details about the various output records.
24651 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24652 @node GDB/MI Compatibility with CLI
24653 @section @sc{gdb/mi} Compatibility with CLI
24655 @cindex compatibility, @sc{gdb/mi} and CLI
24656 @cindex @sc{gdb/mi}, compatibility with CLI
24658 For the developers convenience CLI commands can be entered directly,
24659 but there may be some unexpected behaviour. For example, commands
24660 that query the user will behave as if the user replied yes, breakpoint
24661 command lists are not executed and some CLI commands, such as
24662 @code{if}, @code{when} and @code{define}, prompt for further input with
24663 @samp{>}, which is not valid MI output.
24665 This feature may be removed at some stage in the future and it is
24666 recommended that front ends use the @code{-interpreter-exec} command
24667 (@pxref{-interpreter-exec}).
24669 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24670 @node GDB/MI Development and Front Ends
24671 @section @sc{gdb/mi} Development and Front Ends
24672 @cindex @sc{gdb/mi} development
24674 The application which takes the MI output and presents the state of the
24675 program being debugged to the user is called a @dfn{front end}.
24677 Although @sc{gdb/mi} is still incomplete, it is currently being used
24678 by a variety of front ends to @value{GDBN}. This makes it difficult
24679 to introduce new functionality without breaking existing usage. This
24680 section tries to minimize the problems by describing how the protocol
24683 Some changes in MI need not break a carefully designed front end, and
24684 for these the MI version will remain unchanged. The following is a
24685 list of changes that may occur within one level, so front ends should
24686 parse MI output in a way that can handle them:
24690 New MI commands may be added.
24693 New fields may be added to the output of any MI command.
24696 The range of values for fields with specified values, e.g.,
24697 @code{in_scope} (@pxref{-var-update}) may be extended.
24699 @c The format of field's content e.g type prefix, may change so parse it
24700 @c at your own risk. Yes, in general?
24702 @c The order of fields may change? Shouldn't really matter but it might
24703 @c resolve inconsistencies.
24706 If the changes are likely to break front ends, the MI version level
24707 will be increased by one. This will allow the front end to parse the
24708 output according to the MI version. Apart from mi0, new versions of
24709 @value{GDBN} will not support old versions of MI and it will be the
24710 responsibility of the front end to work with the new one.
24712 @c Starting with mi3, add a new command -mi-version that prints the MI
24715 The best way to avoid unexpected changes in MI that might break your front
24716 end is to make your project known to @value{GDBN} developers and
24717 follow development on @email{gdb@@sourceware.org} and
24718 @email{gdb-patches@@sourceware.org}.
24719 @cindex mailing lists
24721 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24722 @node GDB/MI Output Records
24723 @section @sc{gdb/mi} Output Records
24726 * GDB/MI Result Records::
24727 * GDB/MI Stream Records::
24728 * GDB/MI Async Records::
24729 * GDB/MI Frame Information::
24730 * GDB/MI Thread Information::
24733 @node GDB/MI Result Records
24734 @subsection @sc{gdb/mi} Result Records
24736 @cindex result records in @sc{gdb/mi}
24737 @cindex @sc{gdb/mi}, result records
24738 In addition to a number of out-of-band notifications, the response to a
24739 @sc{gdb/mi} command includes one of the following result indications:
24743 @item "^done" [ "," @var{results} ]
24744 The synchronous operation was successful, @code{@var{results}} are the return
24749 This result record is equivalent to @samp{^done}. Historically, it
24750 was output instead of @samp{^done} if the command has resumed the
24751 target. This behaviour is maintained for backward compatibility, but
24752 all frontends should treat @samp{^done} and @samp{^running}
24753 identically and rely on the @samp{*running} output record to determine
24754 which threads are resumed.
24758 @value{GDBN} has connected to a remote target.
24760 @item "^error" "," @var{c-string}
24762 The operation failed. The @code{@var{c-string}} contains the corresponding
24767 @value{GDBN} has terminated.
24771 @node GDB/MI Stream Records
24772 @subsection @sc{gdb/mi} Stream Records
24774 @cindex @sc{gdb/mi}, stream records
24775 @cindex stream records in @sc{gdb/mi}
24776 @value{GDBN} internally maintains a number of output streams: the console, the
24777 target, and the log. The output intended for each of these streams is
24778 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
24780 Each stream record begins with a unique @dfn{prefix character} which
24781 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
24782 Syntax}). In addition to the prefix, each stream record contains a
24783 @code{@var{string-output}}. This is either raw text (with an implicit new
24784 line) or a quoted C string (which does not contain an implicit newline).
24787 @item "~" @var{string-output}
24788 The console output stream contains text that should be displayed in the
24789 CLI console window. It contains the textual responses to CLI commands.
24791 @item "@@" @var{string-output}
24792 The target output stream contains any textual output from the running
24793 target. This is only present when GDB's event loop is truly
24794 asynchronous, which is currently only the case for remote targets.
24796 @item "&" @var{string-output}
24797 The log stream contains debugging messages being produced by @value{GDBN}'s
24801 @node GDB/MI Async Records
24802 @subsection @sc{gdb/mi} Async Records
24804 @cindex async records in @sc{gdb/mi}
24805 @cindex @sc{gdb/mi}, async records
24806 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
24807 additional changes that have occurred. Those changes can either be a
24808 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
24809 target activity (e.g., target stopped).
24811 The following is the list of possible async records:
24815 @item *running,thread-id="@var{thread}"
24816 The target is now running. The @var{thread} field tells which
24817 specific thread is now running, and can be @samp{all} if all threads
24818 are running. The frontend should assume that no interaction with a
24819 running thread is possible after this notification is produced.
24820 The frontend should not assume that this notification is output
24821 only once for any command. @value{GDBN} may emit this notification
24822 several times, either for different threads, because it cannot resume
24823 all threads together, or even for a single thread, if the thread must
24824 be stepped though some code before letting it run freely.
24826 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
24827 The target has stopped. The @var{reason} field can have one of the
24831 @item breakpoint-hit
24832 A breakpoint was reached.
24833 @item watchpoint-trigger
24834 A watchpoint was triggered.
24835 @item read-watchpoint-trigger
24836 A read watchpoint was triggered.
24837 @item access-watchpoint-trigger
24838 An access watchpoint was triggered.
24839 @item function-finished
24840 An -exec-finish or similar CLI command was accomplished.
24841 @item location-reached
24842 An -exec-until or similar CLI command was accomplished.
24843 @item watchpoint-scope
24844 A watchpoint has gone out of scope.
24845 @item end-stepping-range
24846 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
24847 similar CLI command was accomplished.
24848 @item exited-signalled
24849 The inferior exited because of a signal.
24851 The inferior exited.
24852 @item exited-normally
24853 The inferior exited normally.
24854 @item signal-received
24855 A signal was received by the inferior.
24858 The @var{id} field identifies the thread that directly caused the stop
24859 -- for example by hitting a breakpoint. Depending on whether all-stop
24860 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
24861 stop all threads, or only the thread that directly triggered the stop.
24862 If all threads are stopped, the @var{stopped} field will have the
24863 value of @code{"all"}. Otherwise, the value of the @var{stopped}
24864 field will be a list of thread identifiers. Presently, this list will
24865 always include a single thread, but frontend should be prepared to see
24866 several threads in the list. The @var{core} field reports the
24867 processor core on which the stop event has happened. This field may be absent
24868 if such information is not available.
24870 @item =thread-group-added,id="@var{id}"
24871 @itemx =thread-group-removed,id="@var{id}"
24872 A thread group was either added or removed. The @var{id} field
24873 contains the @value{GDBN} identifier of the thread group. When a thread
24874 group is added, it generally might not be associated with a running
24875 process. When a thread group is removed, its id becomes invalid and
24876 cannot be used in any way.
24878 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
24879 A thread group became associated with a running program,
24880 either because the program was just started or the thread group
24881 was attached to a program. The @var{id} field contains the
24882 @value{GDBN} identifier of the thread group. The @var{pid} field
24883 contains process identifier, specific to the operating system.
24885 @itemx =thread-group-exited,id="@var{id}"
24886 A thread group is no longer associated with a running program,
24887 either because the program has exited, or because it was detached
24888 from. The @var{id} field contains the @value{GDBN} identifier of the
24891 @item =thread-created,id="@var{id}",group-id="@var{gid}"
24892 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
24893 A thread either was created, or has exited. The @var{id} field
24894 contains the @value{GDBN} identifier of the thread. The @var{gid}
24895 field identifies the thread group this thread belongs to.
24897 @item =thread-selected,id="@var{id}"
24898 Informs that the selected thread was changed as result of the last
24899 command. This notification is not emitted as result of @code{-thread-select}
24900 command but is emitted whenever an MI command that is not documented
24901 to change the selected thread actually changes it. In particular,
24902 invoking, directly or indirectly (via user-defined command), the CLI
24903 @code{thread} command, will generate this notification.
24905 We suggest that in response to this notification, front ends
24906 highlight the selected thread and cause subsequent commands to apply to
24909 @item =library-loaded,...
24910 Reports that a new library file was loaded by the program. This
24911 notification has 4 fields---@var{id}, @var{target-name},
24912 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
24913 opaque identifier of the library. For remote debugging case,
24914 @var{target-name} and @var{host-name} fields give the name of the
24915 library file on the target, and on the host respectively. For native
24916 debugging, both those fields have the same value. The
24917 @var{symbols-loaded} field is emitted only for backward compatibility
24918 and should not be relied on to convey any useful information. The
24919 @var{thread-group} field, if present, specifies the id of the thread
24920 group in whose context the library was loaded. If the field is
24921 absent, it means the library was loaded in the context of all present
24924 @item =library-unloaded,...
24925 Reports that a library was unloaded by the program. This notification
24926 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
24927 the same meaning as for the @code{=library-loaded} notification.
24928 The @var{thread-group} field, if present, specifies the id of the
24929 thread group in whose context the library was unloaded. If the field is
24930 absent, it means the library was unloaded in the context of all present
24935 @node GDB/MI Frame Information
24936 @subsection @sc{gdb/mi} Frame Information
24938 Response from many MI commands includes an information about stack
24939 frame. This information is a tuple that may have the following
24944 The level of the stack frame. The innermost frame has the level of
24945 zero. This field is always present.
24948 The name of the function corresponding to the frame. This field may
24949 be absent if @value{GDBN} is unable to determine the function name.
24952 The code address for the frame. This field is always present.
24955 The name of the source files that correspond to the frame's code
24956 address. This field may be absent.
24959 The source line corresponding to the frames' code address. This field
24963 The name of the binary file (either executable or shared library) the
24964 corresponds to the frame's code address. This field may be absent.
24968 @node GDB/MI Thread Information
24969 @subsection @sc{gdb/mi} Thread Information
24971 Whenever @value{GDBN} has to report an information about a thread, it
24972 uses a tuple with the following fields:
24976 The numeric id assigned to the thread by @value{GDBN}. This field is
24980 Target-specific string identifying the thread. This field is always present.
24983 Additional information about the thread provided by the target.
24984 It is supposed to be human-readable and not interpreted by the
24985 frontend. This field is optional.
24988 Either @samp{stopped} or @samp{running}, depending on whether the
24989 thread is presently running. This field is always present.
24992 The value of this field is an integer number of the processor core the
24993 thread was last seen on. This field is optional.
24997 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24998 @node GDB/MI Simple Examples
24999 @section Simple Examples of @sc{gdb/mi} Interaction
25000 @cindex @sc{gdb/mi}, simple examples
25002 This subsection presents several simple examples of interaction using
25003 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
25004 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
25005 the output received from @sc{gdb/mi}.
25007 Note the line breaks shown in the examples are here only for
25008 readability, they don't appear in the real output.
25010 @subheading Setting a Breakpoint
25012 Setting a breakpoint generates synchronous output which contains detailed
25013 information of the breakpoint.
25016 -> -break-insert main
25017 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25018 enabled="y",addr="0x08048564",func="main",file="myprog.c",
25019 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
25023 @subheading Program Execution
25025 Program execution generates asynchronous records and MI gives the
25026 reason that execution stopped.
25032 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
25033 frame=@{addr="0x08048564",func="main",
25034 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
25035 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
25040 <- *stopped,reason="exited-normally"
25044 @subheading Quitting @value{GDBN}
25046 Quitting @value{GDBN} just prints the result class @samp{^exit}.
25054 Please note that @samp{^exit} is printed immediately, but it might
25055 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
25056 performs necessary cleanups, including killing programs being debugged
25057 or disconnecting from debug hardware, so the frontend should wait till
25058 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
25059 fails to exit in reasonable time.
25061 @subheading A Bad Command
25063 Here's what happens if you pass a non-existent command:
25067 <- ^error,msg="Undefined MI command: rubbish"
25072 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25073 @node GDB/MI Command Description Format
25074 @section @sc{gdb/mi} Command Description Format
25076 The remaining sections describe blocks of commands. Each block of
25077 commands is laid out in a fashion similar to this section.
25079 @subheading Motivation
25081 The motivation for this collection of commands.
25083 @subheading Introduction
25085 A brief introduction to this collection of commands as a whole.
25087 @subheading Commands
25089 For each command in the block, the following is described:
25091 @subsubheading Synopsis
25094 -command @var{args}@dots{}
25097 @subsubheading Result
25099 @subsubheading @value{GDBN} Command
25101 The corresponding @value{GDBN} CLI command(s), if any.
25103 @subsubheading Example
25105 Example(s) formatted for readability. Some of the described commands have
25106 not been implemented yet and these are labeled N.A.@: (not available).
25109 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25110 @node GDB/MI Breakpoint Commands
25111 @section @sc{gdb/mi} Breakpoint Commands
25113 @cindex breakpoint commands for @sc{gdb/mi}
25114 @cindex @sc{gdb/mi}, breakpoint commands
25115 This section documents @sc{gdb/mi} commands for manipulating
25118 @subheading The @code{-break-after} Command
25119 @findex -break-after
25121 @subsubheading Synopsis
25124 -break-after @var{number} @var{count}
25127 The breakpoint number @var{number} is not in effect until it has been
25128 hit @var{count} times. To see how this is reflected in the output of
25129 the @samp{-break-list} command, see the description of the
25130 @samp{-break-list} command below.
25132 @subsubheading @value{GDBN} Command
25134 The corresponding @value{GDBN} command is @samp{ignore}.
25136 @subsubheading Example
25141 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25142 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25143 fullname="/home/foo/hello.c",line="5",times="0"@}
25150 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25151 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25152 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25153 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25154 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25155 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25156 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25157 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25158 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25159 line="5",times="0",ignore="3"@}]@}
25164 @subheading The @code{-break-catch} Command
25165 @findex -break-catch
25168 @subheading The @code{-break-commands} Command
25169 @findex -break-commands
25171 @subsubheading Synopsis
25174 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
25177 Specifies the CLI commands that should be executed when breakpoint
25178 @var{number} is hit. The parameters @var{command1} to @var{commandN}
25179 are the commands. If no command is specified, any previously-set
25180 commands are cleared. @xref{Break Commands}. Typical use of this
25181 functionality is tracing a program, that is, printing of values of
25182 some variables whenever breakpoint is hit and then continuing.
25184 @subsubheading @value{GDBN} Command
25186 The corresponding @value{GDBN} command is @samp{commands}.
25188 @subsubheading Example
25193 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25194 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25195 fullname="/home/foo/hello.c",line="5",times="0"@}
25197 -break-commands 1 "print v" "continue"
25202 @subheading The @code{-break-condition} Command
25203 @findex -break-condition
25205 @subsubheading Synopsis
25208 -break-condition @var{number} @var{expr}
25211 Breakpoint @var{number} will stop the program only if the condition in
25212 @var{expr} is true. The condition becomes part of the
25213 @samp{-break-list} output (see the description of the @samp{-break-list}
25216 @subsubheading @value{GDBN} Command
25218 The corresponding @value{GDBN} command is @samp{condition}.
25220 @subsubheading Example
25224 -break-condition 1 1
25228 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25229 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25230 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25231 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25232 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25233 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25234 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25235 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25236 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25237 line="5",cond="1",times="0",ignore="3"@}]@}
25241 @subheading The @code{-break-delete} Command
25242 @findex -break-delete
25244 @subsubheading Synopsis
25247 -break-delete ( @var{breakpoint} )+
25250 Delete the breakpoint(s) whose number(s) are specified in the argument
25251 list. This is obviously reflected in the breakpoint list.
25253 @subsubheading @value{GDBN} Command
25255 The corresponding @value{GDBN} command is @samp{delete}.
25257 @subsubheading Example
25265 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
25266 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25267 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25268 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25269 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25270 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25271 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25276 @subheading The @code{-break-disable} Command
25277 @findex -break-disable
25279 @subsubheading Synopsis
25282 -break-disable ( @var{breakpoint} )+
25285 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
25286 break list is now set to @samp{n} for the named @var{breakpoint}(s).
25288 @subsubheading @value{GDBN} Command
25290 The corresponding @value{GDBN} command is @samp{disable}.
25292 @subsubheading Example
25300 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25301 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25302 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25303 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25304 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25305 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25306 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25307 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
25308 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25309 line="5",times="0"@}]@}
25313 @subheading The @code{-break-enable} Command
25314 @findex -break-enable
25316 @subsubheading Synopsis
25319 -break-enable ( @var{breakpoint} )+
25322 Enable (previously disabled) @var{breakpoint}(s).
25324 @subsubheading @value{GDBN} Command
25326 The corresponding @value{GDBN} command is @samp{enable}.
25328 @subsubheading Example
25336 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25337 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25338 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25339 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25340 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25341 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25342 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25343 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
25344 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25345 line="5",times="0"@}]@}
25349 @subheading The @code{-break-info} Command
25350 @findex -break-info
25352 @subsubheading Synopsis
25355 -break-info @var{breakpoint}
25359 Get information about a single breakpoint.
25361 @subsubheading @value{GDBN} Command
25363 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
25365 @subsubheading Example
25368 @subheading The @code{-break-insert} Command
25369 @findex -break-insert
25371 @subsubheading Synopsis
25374 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
25375 [ -c @var{condition} ] [ -i @var{ignore-count} ]
25376 [ -p @var{thread} ] [ @var{location} ]
25380 If specified, @var{location}, can be one of:
25387 @item filename:linenum
25388 @item filename:function
25392 The possible optional parameters of this command are:
25396 Insert a temporary breakpoint.
25398 Insert a hardware breakpoint.
25399 @item -c @var{condition}
25400 Make the breakpoint conditional on @var{condition}.
25401 @item -i @var{ignore-count}
25402 Initialize the @var{ignore-count}.
25404 If @var{location} cannot be parsed (for example if it
25405 refers to unknown files or functions), create a pending
25406 breakpoint. Without this flag, @value{GDBN} will report
25407 an error, and won't create a breakpoint, if @var{location}
25410 Create a disabled breakpoint.
25412 Create a tracepoint. @xref{Tracepoints}. When this parameter
25413 is used together with @samp{-h}, a fast tracepoint is created.
25416 @subsubheading Result
25418 The result is in the form:
25421 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
25422 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
25423 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
25424 times="@var{times}"@}
25428 where @var{number} is the @value{GDBN} number for this breakpoint,
25429 @var{funcname} is the name of the function where the breakpoint was
25430 inserted, @var{filename} is the name of the source file which contains
25431 this function, @var{lineno} is the source line number within that file
25432 and @var{times} the number of times that the breakpoint has been hit
25433 (always 0 for -break-insert but may be greater for -break-info or -break-list
25434 which use the same output).
25436 Note: this format is open to change.
25437 @c An out-of-band breakpoint instead of part of the result?
25439 @subsubheading @value{GDBN} Command
25441 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
25442 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
25444 @subsubheading Example
25449 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
25450 fullname="/home/foo/recursive2.c,line="4",times="0"@}
25452 -break-insert -t foo
25453 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
25454 fullname="/home/foo/recursive2.c,line="11",times="0"@}
25457 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25458 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25459 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25460 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25461 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25462 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25463 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25464 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25465 addr="0x0001072c", func="main",file="recursive2.c",
25466 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
25467 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
25468 addr="0x00010774",func="foo",file="recursive2.c",
25469 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
25471 -break-insert -r foo.*
25472 ~int foo(int, int);
25473 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
25474 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
25478 @subheading The @code{-break-list} Command
25479 @findex -break-list
25481 @subsubheading Synopsis
25487 Displays the list of inserted breakpoints, showing the following fields:
25491 number of the breakpoint
25493 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
25495 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
25498 is the breakpoint enabled or no: @samp{y} or @samp{n}
25500 memory location at which the breakpoint is set
25502 logical location of the breakpoint, expressed by function name, file
25505 number of times the breakpoint has been hit
25508 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
25509 @code{body} field is an empty list.
25511 @subsubheading @value{GDBN} Command
25513 The corresponding @value{GDBN} command is @samp{info break}.
25515 @subsubheading Example
25520 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25521 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25522 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25523 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25524 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25525 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25526 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25527 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25528 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
25529 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
25530 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
25531 line="13",times="0"@}]@}
25535 Here's an example of the result when there are no breakpoints:
25540 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
25541 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25542 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25543 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25544 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25545 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25546 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25551 @subheading The @code{-break-passcount} Command
25552 @findex -break-passcount
25554 @subsubheading Synopsis
25557 -break-passcount @var{tracepoint-number} @var{passcount}
25560 Set the passcount for tracepoint @var{tracepoint-number} to
25561 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
25562 is not a tracepoint, error is emitted. This corresponds to CLI
25563 command @samp{passcount}.
25565 @subheading The @code{-break-watch} Command
25566 @findex -break-watch
25568 @subsubheading Synopsis
25571 -break-watch [ -a | -r ]
25574 Create a watchpoint. With the @samp{-a} option it will create an
25575 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
25576 read from or on a write to the memory location. With the @samp{-r}
25577 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
25578 trigger only when the memory location is accessed for reading. Without
25579 either of the options, the watchpoint created is a regular watchpoint,
25580 i.e., it will trigger when the memory location is accessed for writing.
25581 @xref{Set Watchpoints, , Setting Watchpoints}.
25583 Note that @samp{-break-list} will report a single list of watchpoints and
25584 breakpoints inserted.
25586 @subsubheading @value{GDBN} Command
25588 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
25591 @subsubheading Example
25593 Setting a watchpoint on a variable in the @code{main} function:
25598 ^done,wpt=@{number="2",exp="x"@}
25603 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
25604 value=@{old="-268439212",new="55"@},
25605 frame=@{func="main",args=[],file="recursive2.c",
25606 fullname="/home/foo/bar/recursive2.c",line="5"@}
25610 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
25611 the program execution twice: first for the variable changing value, then
25612 for the watchpoint going out of scope.
25617 ^done,wpt=@{number="5",exp="C"@}
25622 *stopped,reason="watchpoint-trigger",
25623 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
25624 frame=@{func="callee4",args=[],
25625 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25626 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
25631 *stopped,reason="watchpoint-scope",wpnum="5",
25632 frame=@{func="callee3",args=[@{name="strarg",
25633 value="0x11940 \"A string argument.\""@}],
25634 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25635 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25639 Listing breakpoints and watchpoints, at different points in the program
25640 execution. Note that once the watchpoint goes out of scope, it is
25646 ^done,wpt=@{number="2",exp="C"@}
25649 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25650 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25651 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25652 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25653 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25654 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25655 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25656 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25657 addr="0x00010734",func="callee4",
25658 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25659 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
25660 bkpt=@{number="2",type="watchpoint",disp="keep",
25661 enabled="y",addr="",what="C",times="0"@}]@}
25666 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
25667 value=@{old="-276895068",new="3"@},
25668 frame=@{func="callee4",args=[],
25669 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25670 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
25673 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25674 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25675 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25676 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25677 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25678 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25679 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25680 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25681 addr="0x00010734",func="callee4",
25682 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25683 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
25684 bkpt=@{number="2",type="watchpoint",disp="keep",
25685 enabled="y",addr="",what="C",times="-5"@}]@}
25689 ^done,reason="watchpoint-scope",wpnum="2",
25690 frame=@{func="callee3",args=[@{name="strarg",
25691 value="0x11940 \"A string argument.\""@}],
25692 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25693 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25696 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25697 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25698 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25699 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25700 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25701 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25702 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25703 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25704 addr="0x00010734",func="callee4",
25705 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25706 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
25711 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25712 @node GDB/MI Program Context
25713 @section @sc{gdb/mi} Program Context
25715 @subheading The @code{-exec-arguments} Command
25716 @findex -exec-arguments
25719 @subsubheading Synopsis
25722 -exec-arguments @var{args}
25725 Set the inferior program arguments, to be used in the next
25728 @subsubheading @value{GDBN} Command
25730 The corresponding @value{GDBN} command is @samp{set args}.
25732 @subsubheading Example
25736 -exec-arguments -v word
25743 @subheading The @code{-exec-show-arguments} Command
25744 @findex -exec-show-arguments
25746 @subsubheading Synopsis
25749 -exec-show-arguments
25752 Print the arguments of the program.
25754 @subsubheading @value{GDBN} Command
25756 The corresponding @value{GDBN} command is @samp{show args}.
25758 @subsubheading Example
25763 @subheading The @code{-environment-cd} Command
25764 @findex -environment-cd
25766 @subsubheading Synopsis
25769 -environment-cd @var{pathdir}
25772 Set @value{GDBN}'s working directory.
25774 @subsubheading @value{GDBN} Command
25776 The corresponding @value{GDBN} command is @samp{cd}.
25778 @subsubheading Example
25782 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
25788 @subheading The @code{-environment-directory} Command
25789 @findex -environment-directory
25791 @subsubheading Synopsis
25794 -environment-directory [ -r ] [ @var{pathdir} ]+
25797 Add directories @var{pathdir} to beginning of search path for source files.
25798 If the @samp{-r} option is used, the search path is reset to the default
25799 search path. If directories @var{pathdir} are supplied in addition to the
25800 @samp{-r} option, the search path is first reset and then addition
25802 Multiple directories may be specified, separated by blanks. Specifying
25803 multiple directories in a single command
25804 results in the directories added to the beginning of the
25805 search path in the same order they were presented in the command.
25806 If blanks are needed as
25807 part of a directory name, double-quotes should be used around
25808 the name. In the command output, the path will show up separated
25809 by the system directory-separator character. The directory-separator
25810 character must not be used
25811 in any directory name.
25812 If no directories are specified, the current search path is displayed.
25814 @subsubheading @value{GDBN} Command
25816 The corresponding @value{GDBN} command is @samp{dir}.
25818 @subsubheading Example
25822 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
25823 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
25825 -environment-directory ""
25826 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
25828 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
25829 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
25831 -environment-directory -r
25832 ^done,source-path="$cdir:$cwd"
25837 @subheading The @code{-environment-path} Command
25838 @findex -environment-path
25840 @subsubheading Synopsis
25843 -environment-path [ -r ] [ @var{pathdir} ]+
25846 Add directories @var{pathdir} to beginning of search path for object files.
25847 If the @samp{-r} option is used, the search path is reset to the original
25848 search path that existed at gdb start-up. If directories @var{pathdir} are
25849 supplied in addition to the
25850 @samp{-r} option, the search path is first reset and then addition
25852 Multiple directories may be specified, separated by blanks. Specifying
25853 multiple directories in a single command
25854 results in the directories added to the beginning of the
25855 search path in the same order they were presented in the command.
25856 If blanks are needed as
25857 part of a directory name, double-quotes should be used around
25858 the name. In the command output, the path will show up separated
25859 by the system directory-separator character. The directory-separator
25860 character must not be used
25861 in any directory name.
25862 If no directories are specified, the current path is displayed.
25865 @subsubheading @value{GDBN} Command
25867 The corresponding @value{GDBN} command is @samp{path}.
25869 @subsubheading Example
25874 ^done,path="/usr/bin"
25876 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
25877 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
25879 -environment-path -r /usr/local/bin
25880 ^done,path="/usr/local/bin:/usr/bin"
25885 @subheading The @code{-environment-pwd} Command
25886 @findex -environment-pwd
25888 @subsubheading Synopsis
25894 Show the current working directory.
25896 @subsubheading @value{GDBN} Command
25898 The corresponding @value{GDBN} command is @samp{pwd}.
25900 @subsubheading Example
25905 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
25909 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25910 @node GDB/MI Thread Commands
25911 @section @sc{gdb/mi} Thread Commands
25914 @subheading The @code{-thread-info} Command
25915 @findex -thread-info
25917 @subsubheading Synopsis
25920 -thread-info [ @var{thread-id} ]
25923 Reports information about either a specific thread, if
25924 the @var{thread-id} parameter is present, or about all
25925 threads. When printing information about all threads,
25926 also reports the current thread.
25928 @subsubheading @value{GDBN} Command
25930 The @samp{info thread} command prints the same information
25933 @subsubheading Result
25935 The result is a list of threads. The following attributes are
25936 defined for a given thread:
25940 This field exists only for the current thread. It has the value @samp{*}.
25943 The identifier that @value{GDBN} uses to refer to the thread.
25946 The identifier that the target uses to refer to the thread.
25949 Extra information about the thread, in a target-specific format. This
25953 The name of the thread. If the user specified a name using the
25954 @code{thread name} command, then this name is given. Otherwise, if
25955 @value{GDBN} can extract the thread name from the target, then that
25956 name is given. If @value{GDBN} cannot find the thread name, then this
25960 The stack frame currently executing in the thread.
25963 The thread's state. The @samp{state} field may have the following
25968 The thread is stopped. Frame information is available for stopped
25972 The thread is running. There's no frame information for running
25978 If @value{GDBN} can find the CPU core on which this thread is running,
25979 then this field is the core identifier. This field is optional.
25983 @subsubheading Example
25988 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
25989 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
25990 args=[]@},state="running"@},
25991 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
25992 frame=@{level="0",addr="0x0804891f",func="foo",
25993 args=[@{name="i",value="10"@}],
25994 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
25995 state="running"@}],
25996 current-thread-id="1"
26000 @subheading The @code{-thread-list-ids} Command
26001 @findex -thread-list-ids
26003 @subsubheading Synopsis
26009 Produces a list of the currently known @value{GDBN} thread ids. At the
26010 end of the list it also prints the total number of such threads.
26012 This command is retained for historical reasons, the
26013 @code{-thread-info} command should be used instead.
26015 @subsubheading @value{GDBN} Command
26017 Part of @samp{info threads} supplies the same information.
26019 @subsubheading Example
26024 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26025 current-thread-id="1",number-of-threads="3"
26030 @subheading The @code{-thread-select} Command
26031 @findex -thread-select
26033 @subsubheading Synopsis
26036 -thread-select @var{threadnum}
26039 Make @var{threadnum} the current thread. It prints the number of the new
26040 current thread, and the topmost frame for that thread.
26042 This command is deprecated in favor of explicitly using the
26043 @samp{--thread} option to each command.
26045 @subsubheading @value{GDBN} Command
26047 The corresponding @value{GDBN} command is @samp{thread}.
26049 @subsubheading Example
26056 *stopped,reason="end-stepping-range",thread-id="2",line="187",
26057 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
26061 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26062 number-of-threads="3"
26065 ^done,new-thread-id="3",
26066 frame=@{level="0",func="vprintf",
26067 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
26068 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
26072 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26073 @node GDB/MI Program Execution
26074 @section @sc{gdb/mi} Program Execution
26076 These are the asynchronous commands which generate the out-of-band
26077 record @samp{*stopped}. Currently @value{GDBN} only really executes
26078 asynchronously with remote targets and this interaction is mimicked in
26081 @subheading The @code{-exec-continue} Command
26082 @findex -exec-continue
26084 @subsubheading Synopsis
26087 -exec-continue [--reverse] [--all|--thread-group N]
26090 Resumes the execution of the inferior program, which will continue
26091 to execute until it reaches a debugger stop event. If the
26092 @samp{--reverse} option is specified, execution resumes in reverse until
26093 it reaches a stop event. Stop events may include
26096 breakpoints or watchpoints
26098 signals or exceptions
26100 the end of the process (or its beginning under @samp{--reverse})
26102 the end or beginning of a replay log if one is being used.
26104 In all-stop mode (@pxref{All-Stop
26105 Mode}), may resume only one thread, or all threads, depending on the
26106 value of the @samp{scheduler-locking} variable. If @samp{--all} is
26107 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
26108 ignored in all-stop mode. If the @samp{--thread-group} options is
26109 specified, then all threads in that thread group are resumed.
26111 @subsubheading @value{GDBN} Command
26113 The corresponding @value{GDBN} corresponding is @samp{continue}.
26115 @subsubheading Example
26122 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
26123 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
26129 @subheading The @code{-exec-finish} Command
26130 @findex -exec-finish
26132 @subsubheading Synopsis
26135 -exec-finish [--reverse]
26138 Resumes the execution of the inferior program until the current
26139 function is exited. Displays the results returned by the function.
26140 If the @samp{--reverse} option is specified, resumes the reverse
26141 execution of the inferior program until the point where current
26142 function was called.
26144 @subsubheading @value{GDBN} Command
26146 The corresponding @value{GDBN} command is @samp{finish}.
26148 @subsubheading Example
26150 Function returning @code{void}.
26157 *stopped,reason="function-finished",frame=@{func="main",args=[],
26158 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
26162 Function returning other than @code{void}. The name of the internal
26163 @value{GDBN} variable storing the result is printed, together with the
26170 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
26171 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
26172 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26173 gdb-result-var="$1",return-value="0"
26178 @subheading The @code{-exec-interrupt} Command
26179 @findex -exec-interrupt
26181 @subsubheading Synopsis
26184 -exec-interrupt [--all|--thread-group N]
26187 Interrupts the background execution of the target. Note how the token
26188 associated with the stop message is the one for the execution command
26189 that has been interrupted. The token for the interrupt itself only
26190 appears in the @samp{^done} output. If the user is trying to
26191 interrupt a non-running program, an error message will be printed.
26193 Note that when asynchronous execution is enabled, this command is
26194 asynchronous just like other execution commands. That is, first the
26195 @samp{^done} response will be printed, and the target stop will be
26196 reported after that using the @samp{*stopped} notification.
26198 In non-stop mode, only the context thread is interrupted by default.
26199 All threads (in all inferiors) will be interrupted if the
26200 @samp{--all} option is specified. If the @samp{--thread-group}
26201 option is specified, all threads in that group will be interrupted.
26203 @subsubheading @value{GDBN} Command
26205 The corresponding @value{GDBN} command is @samp{interrupt}.
26207 @subsubheading Example
26218 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
26219 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
26220 fullname="/home/foo/bar/try.c",line="13"@}
26225 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
26229 @subheading The @code{-exec-jump} Command
26232 @subsubheading Synopsis
26235 -exec-jump @var{location}
26238 Resumes execution of the inferior program at the location specified by
26239 parameter. @xref{Specify Location}, for a description of the
26240 different forms of @var{location}.
26242 @subsubheading @value{GDBN} Command
26244 The corresponding @value{GDBN} command is @samp{jump}.
26246 @subsubheading Example
26249 -exec-jump foo.c:10
26250 *running,thread-id="all"
26255 @subheading The @code{-exec-next} Command
26258 @subsubheading Synopsis
26261 -exec-next [--reverse]
26264 Resumes execution of the inferior program, stopping when the beginning
26265 of the next source line is reached.
26267 If the @samp{--reverse} option is specified, resumes reverse execution
26268 of the inferior program, stopping at the beginning of the previous
26269 source line. If you issue this command on the first line of a
26270 function, it will take you back to the caller of that function, to the
26271 source line where the function was called.
26274 @subsubheading @value{GDBN} Command
26276 The corresponding @value{GDBN} command is @samp{next}.
26278 @subsubheading Example
26284 *stopped,reason="end-stepping-range",line="8",file="hello.c"
26289 @subheading The @code{-exec-next-instruction} Command
26290 @findex -exec-next-instruction
26292 @subsubheading Synopsis
26295 -exec-next-instruction [--reverse]
26298 Executes one machine instruction. If the instruction is a function
26299 call, continues until the function returns. If the program stops at an
26300 instruction in the middle of a source line, the address will be
26303 If the @samp{--reverse} option is specified, resumes reverse execution
26304 of the inferior program, stopping at the previous instruction. If the
26305 previously executed instruction was a return from another function,
26306 it will continue to execute in reverse until the call to that function
26307 (from the current stack frame) is reached.
26309 @subsubheading @value{GDBN} Command
26311 The corresponding @value{GDBN} command is @samp{nexti}.
26313 @subsubheading Example
26317 -exec-next-instruction
26321 *stopped,reason="end-stepping-range",
26322 addr="0x000100d4",line="5",file="hello.c"
26327 @subheading The @code{-exec-return} Command
26328 @findex -exec-return
26330 @subsubheading Synopsis
26336 Makes current function return immediately. Doesn't execute the inferior.
26337 Displays the new current frame.
26339 @subsubheading @value{GDBN} Command
26341 The corresponding @value{GDBN} command is @samp{return}.
26343 @subsubheading Example
26347 200-break-insert callee4
26348 200^done,bkpt=@{number="1",addr="0x00010734",
26349 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
26354 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
26355 frame=@{func="callee4",args=[],
26356 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26357 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
26363 111^done,frame=@{level="0",func="callee3",
26364 args=[@{name="strarg",
26365 value="0x11940 \"A string argument.\""@}],
26366 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26367 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26372 @subheading The @code{-exec-run} Command
26375 @subsubheading Synopsis
26378 -exec-run [--all | --thread-group N]
26381 Starts execution of the inferior from the beginning. The inferior
26382 executes until either a breakpoint is encountered or the program
26383 exits. In the latter case the output will include an exit code, if
26384 the program has exited exceptionally.
26386 When no option is specified, the current inferior is started. If the
26387 @samp{--thread-group} option is specified, it should refer to a thread
26388 group of type @samp{process}, and that thread group will be started.
26389 If the @samp{--all} option is specified, then all inferiors will be started.
26391 @subsubheading @value{GDBN} Command
26393 The corresponding @value{GDBN} command is @samp{run}.
26395 @subsubheading Examples
26400 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
26405 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
26406 frame=@{func="main",args=[],file="recursive2.c",
26407 fullname="/home/foo/bar/recursive2.c",line="4"@}
26412 Program exited normally:
26420 *stopped,reason="exited-normally"
26425 Program exited exceptionally:
26433 *stopped,reason="exited",exit-code="01"
26437 Another way the program can terminate is if it receives a signal such as
26438 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
26442 *stopped,reason="exited-signalled",signal-name="SIGINT",
26443 signal-meaning="Interrupt"
26447 @c @subheading -exec-signal
26450 @subheading The @code{-exec-step} Command
26453 @subsubheading Synopsis
26456 -exec-step [--reverse]
26459 Resumes execution of the inferior program, stopping when the beginning
26460 of the next source line is reached, if the next source line is not a
26461 function call. If it is, stop at the first instruction of the called
26462 function. If the @samp{--reverse} option is specified, resumes reverse
26463 execution of the inferior program, stopping at the beginning of the
26464 previously executed source line.
26466 @subsubheading @value{GDBN} Command
26468 The corresponding @value{GDBN} command is @samp{step}.
26470 @subsubheading Example
26472 Stepping into a function:
26478 *stopped,reason="end-stepping-range",
26479 frame=@{func="foo",args=[@{name="a",value="10"@},
26480 @{name="b",value="0"@}],file="recursive2.c",
26481 fullname="/home/foo/bar/recursive2.c",line="11"@}
26491 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
26496 @subheading The @code{-exec-step-instruction} Command
26497 @findex -exec-step-instruction
26499 @subsubheading Synopsis
26502 -exec-step-instruction [--reverse]
26505 Resumes the inferior which executes one machine instruction. If the
26506 @samp{--reverse} option is specified, resumes reverse execution of the
26507 inferior program, stopping at the previously executed instruction.
26508 The output, once @value{GDBN} has stopped, will vary depending on
26509 whether we have stopped in the middle of a source line or not. In the
26510 former case, the address at which the program stopped will be printed
26513 @subsubheading @value{GDBN} Command
26515 The corresponding @value{GDBN} command is @samp{stepi}.
26517 @subsubheading Example
26521 -exec-step-instruction
26525 *stopped,reason="end-stepping-range",
26526 frame=@{func="foo",args=[],file="try.c",
26527 fullname="/home/foo/bar/try.c",line="10"@}
26529 -exec-step-instruction
26533 *stopped,reason="end-stepping-range",
26534 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
26535 fullname="/home/foo/bar/try.c",line="10"@}
26540 @subheading The @code{-exec-until} Command
26541 @findex -exec-until
26543 @subsubheading Synopsis
26546 -exec-until [ @var{location} ]
26549 Executes the inferior until the @var{location} specified in the
26550 argument is reached. If there is no argument, the inferior executes
26551 until a source line greater than the current one is reached. The
26552 reason for stopping in this case will be @samp{location-reached}.
26554 @subsubheading @value{GDBN} Command
26556 The corresponding @value{GDBN} command is @samp{until}.
26558 @subsubheading Example
26562 -exec-until recursive2.c:6
26566 *stopped,reason="location-reached",frame=@{func="main",args=[],
26567 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
26572 @subheading -file-clear
26573 Is this going away????
26576 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26577 @node GDB/MI Stack Manipulation
26578 @section @sc{gdb/mi} Stack Manipulation Commands
26581 @subheading The @code{-stack-info-frame} Command
26582 @findex -stack-info-frame
26584 @subsubheading Synopsis
26590 Get info on the selected frame.
26592 @subsubheading @value{GDBN} Command
26594 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
26595 (without arguments).
26597 @subsubheading Example
26602 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
26603 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26604 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
26608 @subheading The @code{-stack-info-depth} Command
26609 @findex -stack-info-depth
26611 @subsubheading Synopsis
26614 -stack-info-depth [ @var{max-depth} ]
26617 Return the depth of the stack. If the integer argument @var{max-depth}
26618 is specified, do not count beyond @var{max-depth} frames.
26620 @subsubheading @value{GDBN} Command
26622 There's no equivalent @value{GDBN} command.
26624 @subsubheading Example
26626 For a stack with frame levels 0 through 11:
26633 -stack-info-depth 4
26636 -stack-info-depth 12
26639 -stack-info-depth 11
26642 -stack-info-depth 13
26647 @subheading The @code{-stack-list-arguments} Command
26648 @findex -stack-list-arguments
26650 @subsubheading Synopsis
26653 -stack-list-arguments @var{print-values}
26654 [ @var{low-frame} @var{high-frame} ]
26657 Display a list of the arguments for the frames between @var{low-frame}
26658 and @var{high-frame} (inclusive). If @var{low-frame} and
26659 @var{high-frame} are not provided, list the arguments for the whole
26660 call stack. If the two arguments are equal, show the single frame
26661 at the corresponding level. It is an error if @var{low-frame} is
26662 larger than the actual number of frames. On the other hand,
26663 @var{high-frame} may be larger than the actual number of frames, in
26664 which case only existing frames will be returned.
26666 If @var{print-values} is 0 or @code{--no-values}, print only the names of
26667 the variables; if it is 1 or @code{--all-values}, print also their
26668 values; and if it is 2 or @code{--simple-values}, print the name,
26669 type and value for simple data types, and the name and type for arrays,
26670 structures and unions.
26672 Use of this command to obtain arguments in a single frame is
26673 deprecated in favor of the @samp{-stack-list-variables} command.
26675 @subsubheading @value{GDBN} Command
26677 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
26678 @samp{gdb_get_args} command which partially overlaps with the
26679 functionality of @samp{-stack-list-arguments}.
26681 @subsubheading Example
26688 frame=@{level="0",addr="0x00010734",func="callee4",
26689 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26690 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
26691 frame=@{level="1",addr="0x0001076c",func="callee3",
26692 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26693 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
26694 frame=@{level="2",addr="0x0001078c",func="callee2",
26695 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26696 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
26697 frame=@{level="3",addr="0x000107b4",func="callee1",
26698 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26699 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
26700 frame=@{level="4",addr="0x000107e0",func="main",
26701 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26702 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
26704 -stack-list-arguments 0
26707 frame=@{level="0",args=[]@},
26708 frame=@{level="1",args=[name="strarg"]@},
26709 frame=@{level="2",args=[name="intarg",name="strarg"]@},
26710 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
26711 frame=@{level="4",args=[]@}]
26713 -stack-list-arguments 1
26716 frame=@{level="0",args=[]@},
26718 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
26719 frame=@{level="2",args=[
26720 @{name="intarg",value="2"@},
26721 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
26722 @{frame=@{level="3",args=[
26723 @{name="intarg",value="2"@},
26724 @{name="strarg",value="0x11940 \"A string argument.\""@},
26725 @{name="fltarg",value="3.5"@}]@},
26726 frame=@{level="4",args=[]@}]
26728 -stack-list-arguments 0 2 2
26729 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
26731 -stack-list-arguments 1 2 2
26732 ^done,stack-args=[frame=@{level="2",
26733 args=[@{name="intarg",value="2"@},
26734 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
26738 @c @subheading -stack-list-exception-handlers
26741 @subheading The @code{-stack-list-frames} Command
26742 @findex -stack-list-frames
26744 @subsubheading Synopsis
26747 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
26750 List the frames currently on the stack. For each frame it displays the
26755 The frame number, 0 being the topmost frame, i.e., the innermost function.
26757 The @code{$pc} value for that frame.
26761 File name of the source file where the function lives.
26762 @item @var{fullname}
26763 The full file name of the source file where the function lives.
26765 Line number corresponding to the @code{$pc}.
26767 The shared library where this function is defined. This is only given
26768 if the frame's function is not known.
26771 If invoked without arguments, this command prints a backtrace for the
26772 whole stack. If given two integer arguments, it shows the frames whose
26773 levels are between the two arguments (inclusive). If the two arguments
26774 are equal, it shows the single frame at the corresponding level. It is
26775 an error if @var{low-frame} is larger than the actual number of
26776 frames. On the other hand, @var{high-frame} may be larger than the
26777 actual number of frames, in which case only existing frames will be returned.
26779 @subsubheading @value{GDBN} Command
26781 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
26783 @subsubheading Example
26785 Full stack backtrace:
26791 [frame=@{level="0",addr="0x0001076c",func="foo",
26792 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
26793 frame=@{level="1",addr="0x000107a4",func="foo",
26794 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26795 frame=@{level="2",addr="0x000107a4",func="foo",
26796 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26797 frame=@{level="3",addr="0x000107a4",func="foo",
26798 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26799 frame=@{level="4",addr="0x000107a4",func="foo",
26800 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26801 frame=@{level="5",addr="0x000107a4",func="foo",
26802 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26803 frame=@{level="6",addr="0x000107a4",func="foo",
26804 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26805 frame=@{level="7",addr="0x000107a4",func="foo",
26806 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26807 frame=@{level="8",addr="0x000107a4",func="foo",
26808 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26809 frame=@{level="9",addr="0x000107a4",func="foo",
26810 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26811 frame=@{level="10",addr="0x000107a4",func="foo",
26812 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26813 frame=@{level="11",addr="0x00010738",func="main",
26814 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
26818 Show frames between @var{low_frame} and @var{high_frame}:
26822 -stack-list-frames 3 5
26824 [frame=@{level="3",addr="0x000107a4",func="foo",
26825 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26826 frame=@{level="4",addr="0x000107a4",func="foo",
26827 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26828 frame=@{level="5",addr="0x000107a4",func="foo",
26829 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
26833 Show a single frame:
26837 -stack-list-frames 3 3
26839 [frame=@{level="3",addr="0x000107a4",func="foo",
26840 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
26845 @subheading The @code{-stack-list-locals} Command
26846 @findex -stack-list-locals
26848 @subsubheading Synopsis
26851 -stack-list-locals @var{print-values}
26854 Display the local variable names for the selected frame. If
26855 @var{print-values} is 0 or @code{--no-values}, print only the names of
26856 the variables; if it is 1 or @code{--all-values}, print also their
26857 values; and if it is 2 or @code{--simple-values}, print the name,
26858 type and value for simple data types, and the name and type for arrays,
26859 structures and unions. In this last case, a frontend can immediately
26860 display the value of simple data types and create variable objects for
26861 other data types when the user wishes to explore their values in
26864 This command is deprecated in favor of the
26865 @samp{-stack-list-variables} command.
26867 @subsubheading @value{GDBN} Command
26869 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
26871 @subsubheading Example
26875 -stack-list-locals 0
26876 ^done,locals=[name="A",name="B",name="C"]
26878 -stack-list-locals --all-values
26879 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
26880 @{name="C",value="@{1, 2, 3@}"@}]
26881 -stack-list-locals --simple-values
26882 ^done,locals=[@{name="A",type="int",value="1"@},
26883 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
26887 @subheading The @code{-stack-list-variables} Command
26888 @findex -stack-list-variables
26890 @subsubheading Synopsis
26893 -stack-list-variables @var{print-values}
26896 Display the names of local variables and function arguments for the selected frame. If
26897 @var{print-values} is 0 or @code{--no-values}, print only the names of
26898 the variables; if it is 1 or @code{--all-values}, print also their
26899 values; and if it is 2 or @code{--simple-values}, print the name,
26900 type and value for simple data types, and the name and type for arrays,
26901 structures and unions.
26903 @subsubheading Example
26907 -stack-list-variables --thread 1 --frame 0 --all-values
26908 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
26913 @subheading The @code{-stack-select-frame} Command
26914 @findex -stack-select-frame
26916 @subsubheading Synopsis
26919 -stack-select-frame @var{framenum}
26922 Change the selected frame. Select a different frame @var{framenum} on
26925 This command in deprecated in favor of passing the @samp{--frame}
26926 option to every command.
26928 @subsubheading @value{GDBN} Command
26930 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
26931 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
26933 @subsubheading Example
26937 -stack-select-frame 2
26942 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26943 @node GDB/MI Variable Objects
26944 @section @sc{gdb/mi} Variable Objects
26948 @subheading Motivation for Variable Objects in @sc{gdb/mi}
26950 For the implementation of a variable debugger window (locals, watched
26951 expressions, etc.), we are proposing the adaptation of the existing code
26952 used by @code{Insight}.
26954 The two main reasons for that are:
26958 It has been proven in practice (it is already on its second generation).
26961 It will shorten development time (needless to say how important it is
26965 The original interface was designed to be used by Tcl code, so it was
26966 slightly changed so it could be used through @sc{gdb/mi}. This section
26967 describes the @sc{gdb/mi} operations that will be available and gives some
26968 hints about their use.
26970 @emph{Note}: In addition to the set of operations described here, we
26971 expect the @sc{gui} implementation of a variable window to require, at
26972 least, the following operations:
26975 @item @code{-gdb-show} @code{output-radix}
26976 @item @code{-stack-list-arguments}
26977 @item @code{-stack-list-locals}
26978 @item @code{-stack-select-frame}
26983 @subheading Introduction to Variable Objects
26985 @cindex variable objects in @sc{gdb/mi}
26987 Variable objects are "object-oriented" MI interface for examining and
26988 changing values of expressions. Unlike some other MI interfaces that
26989 work with expressions, variable objects are specifically designed for
26990 simple and efficient presentation in the frontend. A variable object
26991 is identified by string name. When a variable object is created, the
26992 frontend specifies the expression for that variable object. The
26993 expression can be a simple variable, or it can be an arbitrary complex
26994 expression, and can even involve CPU registers. After creating a
26995 variable object, the frontend can invoke other variable object
26996 operations---for example to obtain or change the value of a variable
26997 object, or to change display format.
26999 Variable objects have hierarchical tree structure. Any variable object
27000 that corresponds to a composite type, such as structure in C, has
27001 a number of child variable objects, for example corresponding to each
27002 element of a structure. A child variable object can itself have
27003 children, recursively. Recursion ends when we reach
27004 leaf variable objects, which always have built-in types. Child variable
27005 objects are created only by explicit request, so if a frontend
27006 is not interested in the children of a particular variable object, no
27007 child will be created.
27009 For a leaf variable object it is possible to obtain its value as a
27010 string, or set the value from a string. String value can be also
27011 obtained for a non-leaf variable object, but it's generally a string
27012 that only indicates the type of the object, and does not list its
27013 contents. Assignment to a non-leaf variable object is not allowed.
27015 A frontend does not need to read the values of all variable objects each time
27016 the program stops. Instead, MI provides an update command that lists all
27017 variable objects whose values has changed since the last update
27018 operation. This considerably reduces the amount of data that must
27019 be transferred to the frontend. As noted above, children variable
27020 objects are created on demand, and only leaf variable objects have a
27021 real value. As result, gdb will read target memory only for leaf
27022 variables that frontend has created.
27024 The automatic update is not always desirable. For example, a frontend
27025 might want to keep a value of some expression for future reference,
27026 and never update it. For another example, fetching memory is
27027 relatively slow for embedded targets, so a frontend might want
27028 to disable automatic update for the variables that are either not
27029 visible on the screen, or ``closed''. This is possible using so
27030 called ``frozen variable objects''. Such variable objects are never
27031 implicitly updated.
27033 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
27034 fixed variable object, the expression is parsed when the variable
27035 object is created, including associating identifiers to specific
27036 variables. The meaning of expression never changes. For a floating
27037 variable object the values of variables whose names appear in the
27038 expressions are re-evaluated every time in the context of the current
27039 frame. Consider this example:
27044 struct work_state state;
27051 If a fixed variable object for the @code{state} variable is created in
27052 this function, and we enter the recursive call, the the variable
27053 object will report the value of @code{state} in the top-level
27054 @code{do_work} invocation. On the other hand, a floating variable
27055 object will report the value of @code{state} in the current frame.
27057 If an expression specified when creating a fixed variable object
27058 refers to a local variable, the variable object becomes bound to the
27059 thread and frame in which the variable object is created. When such
27060 variable object is updated, @value{GDBN} makes sure that the
27061 thread/frame combination the variable object is bound to still exists,
27062 and re-evaluates the variable object in context of that thread/frame.
27064 The following is the complete set of @sc{gdb/mi} operations defined to
27065 access this functionality:
27067 @multitable @columnfractions .4 .6
27068 @item @strong{Operation}
27069 @tab @strong{Description}
27071 @item @code{-enable-pretty-printing}
27072 @tab enable Python-based pretty-printing
27073 @item @code{-var-create}
27074 @tab create a variable object
27075 @item @code{-var-delete}
27076 @tab delete the variable object and/or its children
27077 @item @code{-var-set-format}
27078 @tab set the display format of this variable
27079 @item @code{-var-show-format}
27080 @tab show the display format of this variable
27081 @item @code{-var-info-num-children}
27082 @tab tells how many children this object has
27083 @item @code{-var-list-children}
27084 @tab return a list of the object's children
27085 @item @code{-var-info-type}
27086 @tab show the type of this variable object
27087 @item @code{-var-info-expression}
27088 @tab print parent-relative expression that this variable object represents
27089 @item @code{-var-info-path-expression}
27090 @tab print full expression that this variable object represents
27091 @item @code{-var-show-attributes}
27092 @tab is this variable editable? does it exist here?
27093 @item @code{-var-evaluate-expression}
27094 @tab get the value of this variable
27095 @item @code{-var-assign}
27096 @tab set the value of this variable
27097 @item @code{-var-update}
27098 @tab update the variable and its children
27099 @item @code{-var-set-frozen}
27100 @tab set frozeness attribute
27101 @item @code{-var-set-update-range}
27102 @tab set range of children to display on update
27105 In the next subsection we describe each operation in detail and suggest
27106 how it can be used.
27108 @subheading Description And Use of Operations on Variable Objects
27110 @subheading The @code{-enable-pretty-printing} Command
27111 @findex -enable-pretty-printing
27114 -enable-pretty-printing
27117 @value{GDBN} allows Python-based visualizers to affect the output of the
27118 MI variable object commands. However, because there was no way to
27119 implement this in a fully backward-compatible way, a front end must
27120 request that this functionality be enabled.
27122 Once enabled, this feature cannot be disabled.
27124 Note that if Python support has not been compiled into @value{GDBN},
27125 this command will still succeed (and do nothing).
27127 This feature is currently (as of @value{GDBN} 7.0) experimental, and
27128 may work differently in future versions of @value{GDBN}.
27130 @subheading The @code{-var-create} Command
27131 @findex -var-create
27133 @subsubheading Synopsis
27136 -var-create @{@var{name} | "-"@}
27137 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
27140 This operation creates a variable object, which allows the monitoring of
27141 a variable, the result of an expression, a memory cell or a CPU
27144 The @var{name} parameter is the string by which the object can be
27145 referenced. It must be unique. If @samp{-} is specified, the varobj
27146 system will generate a string ``varNNNNNN'' automatically. It will be
27147 unique provided that one does not specify @var{name} of that format.
27148 The command fails if a duplicate name is found.
27150 The frame under which the expression should be evaluated can be
27151 specified by @var{frame-addr}. A @samp{*} indicates that the current
27152 frame should be used. A @samp{@@} indicates that a floating variable
27153 object must be created.
27155 @var{expression} is any expression valid on the current language set (must not
27156 begin with a @samp{*}), or one of the following:
27160 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
27163 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
27166 @samp{$@var{regname}} --- a CPU register name
27169 @cindex dynamic varobj
27170 A varobj's contents may be provided by a Python-based pretty-printer. In this
27171 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
27172 have slightly different semantics in some cases. If the
27173 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
27174 will never create a dynamic varobj. This ensures backward
27175 compatibility for existing clients.
27177 @subsubheading Result
27179 This operation returns attributes of the newly-created varobj. These
27184 The name of the varobj.
27187 The number of children of the varobj. This number is not necessarily
27188 reliable for a dynamic varobj. Instead, you must examine the
27189 @samp{has_more} attribute.
27192 The varobj's scalar value. For a varobj whose type is some sort of
27193 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
27194 will not be interesting.
27197 The varobj's type. This is a string representation of the type, as
27198 would be printed by the @value{GDBN} CLI.
27201 If a variable object is bound to a specific thread, then this is the
27202 thread's identifier.
27205 For a dynamic varobj, this indicates whether there appear to be any
27206 children available. For a non-dynamic varobj, this will be 0.
27209 This attribute will be present and have the value @samp{1} if the
27210 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
27211 then this attribute will not be present.
27214 A dynamic varobj can supply a display hint to the front end. The
27215 value comes directly from the Python pretty-printer object's
27216 @code{display_hint} method. @xref{Pretty Printing API}.
27219 Typical output will look like this:
27222 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
27223 has_more="@var{has_more}"
27227 @subheading The @code{-var-delete} Command
27228 @findex -var-delete
27230 @subsubheading Synopsis
27233 -var-delete [ -c ] @var{name}
27236 Deletes a previously created variable object and all of its children.
27237 With the @samp{-c} option, just deletes the children.
27239 Returns an error if the object @var{name} is not found.
27242 @subheading The @code{-var-set-format} Command
27243 @findex -var-set-format
27245 @subsubheading Synopsis
27248 -var-set-format @var{name} @var{format-spec}
27251 Sets the output format for the value of the object @var{name} to be
27254 @anchor{-var-set-format}
27255 The syntax for the @var{format-spec} is as follows:
27258 @var{format-spec} @expansion{}
27259 @{binary | decimal | hexadecimal | octal | natural@}
27262 The natural format is the default format choosen automatically
27263 based on the variable type (like decimal for an @code{int}, hex
27264 for pointers, etc.).
27266 For a variable with children, the format is set only on the
27267 variable itself, and the children are not affected.
27269 @subheading The @code{-var-show-format} Command
27270 @findex -var-show-format
27272 @subsubheading Synopsis
27275 -var-show-format @var{name}
27278 Returns the format used to display the value of the object @var{name}.
27281 @var{format} @expansion{}
27286 @subheading The @code{-var-info-num-children} Command
27287 @findex -var-info-num-children
27289 @subsubheading Synopsis
27292 -var-info-num-children @var{name}
27295 Returns the number of children of a variable object @var{name}:
27301 Note that this number is not completely reliable for a dynamic varobj.
27302 It will return the current number of children, but more children may
27306 @subheading The @code{-var-list-children} Command
27307 @findex -var-list-children
27309 @subsubheading Synopsis
27312 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
27314 @anchor{-var-list-children}
27316 Return a list of the children of the specified variable object and
27317 create variable objects for them, if they do not already exist. With
27318 a single argument or if @var{print-values} has a value of 0 or
27319 @code{--no-values}, print only the names of the variables; if
27320 @var{print-values} is 1 or @code{--all-values}, also print their
27321 values; and if it is 2 or @code{--simple-values} print the name and
27322 value for simple data types and just the name for arrays, structures
27325 @var{from} and @var{to}, if specified, indicate the range of children
27326 to report. If @var{from} or @var{to} is less than zero, the range is
27327 reset and all children will be reported. Otherwise, children starting
27328 at @var{from} (zero-based) and up to and excluding @var{to} will be
27331 If a child range is requested, it will only affect the current call to
27332 @code{-var-list-children}, but not future calls to @code{-var-update}.
27333 For this, you must instead use @code{-var-set-update-range}. The
27334 intent of this approach is to enable a front end to implement any
27335 update approach it likes; for example, scrolling a view may cause the
27336 front end to request more children with @code{-var-list-children}, and
27337 then the front end could call @code{-var-set-update-range} with a
27338 different range to ensure that future updates are restricted to just
27341 For each child the following results are returned:
27346 Name of the variable object created for this child.
27349 The expression to be shown to the user by the front end to designate this child.
27350 For example this may be the name of a structure member.
27352 For a dynamic varobj, this value cannot be used to form an
27353 expression. There is no way to do this at all with a dynamic varobj.
27355 For C/C@t{++} structures there are several pseudo children returned to
27356 designate access qualifiers. For these pseudo children @var{exp} is
27357 @samp{public}, @samp{private}, or @samp{protected}. In this case the
27358 type and value are not present.
27360 A dynamic varobj will not report the access qualifying
27361 pseudo-children, regardless of the language. This information is not
27362 available at all with a dynamic varobj.
27365 Number of children this child has. For a dynamic varobj, this will be
27369 The type of the child.
27372 If values were requested, this is the value.
27375 If this variable object is associated with a thread, this is the thread id.
27376 Otherwise this result is not present.
27379 If the variable object is frozen, this variable will be present with a value of 1.
27382 The result may have its own attributes:
27386 A dynamic varobj can supply a display hint to the front end. The
27387 value comes directly from the Python pretty-printer object's
27388 @code{display_hint} method. @xref{Pretty Printing API}.
27391 This is an integer attribute which is nonzero if there are children
27392 remaining after the end of the selected range.
27395 @subsubheading Example
27399 -var-list-children n
27400 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
27401 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
27403 -var-list-children --all-values n
27404 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
27405 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
27409 @subheading The @code{-var-info-type} Command
27410 @findex -var-info-type
27412 @subsubheading Synopsis
27415 -var-info-type @var{name}
27418 Returns the type of the specified variable @var{name}. The type is
27419 returned as a string in the same format as it is output by the
27423 type=@var{typename}
27427 @subheading The @code{-var-info-expression} Command
27428 @findex -var-info-expression
27430 @subsubheading Synopsis
27433 -var-info-expression @var{name}
27436 Returns a string that is suitable for presenting this
27437 variable object in user interface. The string is generally
27438 not valid expression in the current language, and cannot be evaluated.
27440 For example, if @code{a} is an array, and variable object
27441 @code{A} was created for @code{a}, then we'll get this output:
27444 (gdb) -var-info-expression A.1
27445 ^done,lang="C",exp="1"
27449 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
27451 Note that the output of the @code{-var-list-children} command also
27452 includes those expressions, so the @code{-var-info-expression} command
27455 @subheading The @code{-var-info-path-expression} Command
27456 @findex -var-info-path-expression
27458 @subsubheading Synopsis
27461 -var-info-path-expression @var{name}
27464 Returns an expression that can be evaluated in the current
27465 context and will yield the same value that a variable object has.
27466 Compare this with the @code{-var-info-expression} command, which
27467 result can be used only for UI presentation. Typical use of
27468 the @code{-var-info-path-expression} command is creating a
27469 watchpoint from a variable object.
27471 This command is currently not valid for children of a dynamic varobj,
27472 and will give an error when invoked on one.
27474 For example, suppose @code{C} is a C@t{++} class, derived from class
27475 @code{Base}, and that the @code{Base} class has a member called
27476 @code{m_size}. Assume a variable @code{c} is has the type of
27477 @code{C} and a variable object @code{C} was created for variable
27478 @code{c}. Then, we'll get this output:
27480 (gdb) -var-info-path-expression C.Base.public.m_size
27481 ^done,path_expr=((Base)c).m_size)
27484 @subheading The @code{-var-show-attributes} Command
27485 @findex -var-show-attributes
27487 @subsubheading Synopsis
27490 -var-show-attributes @var{name}
27493 List attributes of the specified variable object @var{name}:
27496 status=@var{attr} [ ( ,@var{attr} )* ]
27500 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
27502 @subheading The @code{-var-evaluate-expression} Command
27503 @findex -var-evaluate-expression
27505 @subsubheading Synopsis
27508 -var-evaluate-expression [-f @var{format-spec}] @var{name}
27511 Evaluates the expression that is represented by the specified variable
27512 object and returns its value as a string. The format of the string
27513 can be specified with the @samp{-f} option. The possible values of
27514 this option are the same as for @code{-var-set-format}
27515 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
27516 the current display format will be used. The current display format
27517 can be changed using the @code{-var-set-format} command.
27523 Note that one must invoke @code{-var-list-children} for a variable
27524 before the value of a child variable can be evaluated.
27526 @subheading The @code{-var-assign} Command
27527 @findex -var-assign
27529 @subsubheading Synopsis
27532 -var-assign @var{name} @var{expression}
27535 Assigns the value of @var{expression} to the variable object specified
27536 by @var{name}. The object must be @samp{editable}. If the variable's
27537 value is altered by the assign, the variable will show up in any
27538 subsequent @code{-var-update} list.
27540 @subsubheading Example
27548 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
27552 @subheading The @code{-var-update} Command
27553 @findex -var-update
27555 @subsubheading Synopsis
27558 -var-update [@var{print-values}] @{@var{name} | "*"@}
27561 Reevaluate the expressions corresponding to the variable object
27562 @var{name} and all its direct and indirect children, and return the
27563 list of variable objects whose values have changed; @var{name} must
27564 be a root variable object. Here, ``changed'' means that the result of
27565 @code{-var-evaluate-expression} before and after the
27566 @code{-var-update} is different. If @samp{*} is used as the variable
27567 object names, all existing variable objects are updated, except
27568 for frozen ones (@pxref{-var-set-frozen}). The option
27569 @var{print-values} determines whether both names and values, or just
27570 names are printed. The possible values of this option are the same
27571 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
27572 recommended to use the @samp{--all-values} option, to reduce the
27573 number of MI commands needed on each program stop.
27575 With the @samp{*} parameter, if a variable object is bound to a
27576 currently running thread, it will not be updated, without any
27579 If @code{-var-set-update-range} was previously used on a varobj, then
27580 only the selected range of children will be reported.
27582 @code{-var-update} reports all the changed varobjs in a tuple named
27585 Each item in the change list is itself a tuple holding:
27589 The name of the varobj.
27592 If values were requested for this update, then this field will be
27593 present and will hold the value of the varobj.
27596 @anchor{-var-update}
27597 This field is a string which may take one of three values:
27601 The variable object's current value is valid.
27604 The variable object does not currently hold a valid value but it may
27605 hold one in the future if its associated expression comes back into
27609 The variable object no longer holds a valid value.
27610 This can occur when the executable file being debugged has changed,
27611 either through recompilation or by using the @value{GDBN} @code{file}
27612 command. The front end should normally choose to delete these variable
27616 In the future new values may be added to this list so the front should
27617 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
27620 This is only present if the varobj is still valid. If the type
27621 changed, then this will be the string @samp{true}; otherwise it will
27625 If the varobj's type changed, then this field will be present and will
27628 @item new_num_children
27629 For a dynamic varobj, if the number of children changed, or if the
27630 type changed, this will be the new number of children.
27632 The @samp{numchild} field in other varobj responses is generally not
27633 valid for a dynamic varobj -- it will show the number of children that
27634 @value{GDBN} knows about, but because dynamic varobjs lazily
27635 instantiate their children, this will not reflect the number of
27636 children which may be available.
27638 The @samp{new_num_children} attribute only reports changes to the
27639 number of children known by @value{GDBN}. This is the only way to
27640 detect whether an update has removed children (which necessarily can
27641 only happen at the end of the update range).
27644 The display hint, if any.
27647 This is an integer value, which will be 1 if there are more children
27648 available outside the varobj's update range.
27651 This attribute will be present and have the value @samp{1} if the
27652 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
27653 then this attribute will not be present.
27656 If new children were added to a dynamic varobj within the selected
27657 update range (as set by @code{-var-set-update-range}), then they will
27658 be listed in this attribute.
27661 @subsubheading Example
27668 -var-update --all-values var1
27669 ^done,changelist=[@{name="var1",value="3",in_scope="true",
27670 type_changed="false"@}]
27674 @subheading The @code{-var-set-frozen} Command
27675 @findex -var-set-frozen
27676 @anchor{-var-set-frozen}
27678 @subsubheading Synopsis
27681 -var-set-frozen @var{name} @var{flag}
27684 Set the frozenness flag on the variable object @var{name}. The
27685 @var{flag} parameter should be either @samp{1} to make the variable
27686 frozen or @samp{0} to make it unfrozen. If a variable object is
27687 frozen, then neither itself, nor any of its children, are
27688 implicitly updated by @code{-var-update} of
27689 a parent variable or by @code{-var-update *}. Only
27690 @code{-var-update} of the variable itself will update its value and
27691 values of its children. After a variable object is unfrozen, it is
27692 implicitly updated by all subsequent @code{-var-update} operations.
27693 Unfreezing a variable does not update it, only subsequent
27694 @code{-var-update} does.
27696 @subsubheading Example
27700 -var-set-frozen V 1
27705 @subheading The @code{-var-set-update-range} command
27706 @findex -var-set-update-range
27707 @anchor{-var-set-update-range}
27709 @subsubheading Synopsis
27712 -var-set-update-range @var{name} @var{from} @var{to}
27715 Set the range of children to be returned by future invocations of
27716 @code{-var-update}.
27718 @var{from} and @var{to} indicate the range of children to report. If
27719 @var{from} or @var{to} is less than zero, the range is reset and all
27720 children will be reported. Otherwise, children starting at @var{from}
27721 (zero-based) and up to and excluding @var{to} will be reported.
27723 @subsubheading Example
27727 -var-set-update-range V 1 2
27731 @subheading The @code{-var-set-visualizer} command
27732 @findex -var-set-visualizer
27733 @anchor{-var-set-visualizer}
27735 @subsubheading Synopsis
27738 -var-set-visualizer @var{name} @var{visualizer}
27741 Set a visualizer for the variable object @var{name}.
27743 @var{visualizer} is the visualizer to use. The special value
27744 @samp{None} means to disable any visualizer in use.
27746 If not @samp{None}, @var{visualizer} must be a Python expression.
27747 This expression must evaluate to a callable object which accepts a
27748 single argument. @value{GDBN} will call this object with the value of
27749 the varobj @var{name} as an argument (this is done so that the same
27750 Python pretty-printing code can be used for both the CLI and MI).
27751 When called, this object must return an object which conforms to the
27752 pretty-printing interface (@pxref{Pretty Printing API}).
27754 The pre-defined function @code{gdb.default_visualizer} may be used to
27755 select a visualizer by following the built-in process
27756 (@pxref{Selecting Pretty-Printers}). This is done automatically when
27757 a varobj is created, and so ordinarily is not needed.
27759 This feature is only available if Python support is enabled. The MI
27760 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
27761 can be used to check this.
27763 @subsubheading Example
27765 Resetting the visualizer:
27769 -var-set-visualizer V None
27773 Reselecting the default (type-based) visualizer:
27777 -var-set-visualizer V gdb.default_visualizer
27781 Suppose @code{SomeClass} is a visualizer class. A lambda expression
27782 can be used to instantiate this class for a varobj:
27786 -var-set-visualizer V "lambda val: SomeClass()"
27790 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27791 @node GDB/MI Data Manipulation
27792 @section @sc{gdb/mi} Data Manipulation
27794 @cindex data manipulation, in @sc{gdb/mi}
27795 @cindex @sc{gdb/mi}, data manipulation
27796 This section describes the @sc{gdb/mi} commands that manipulate data:
27797 examine memory and registers, evaluate expressions, etc.
27799 @c REMOVED FROM THE INTERFACE.
27800 @c @subheading -data-assign
27801 @c Change the value of a program variable. Plenty of side effects.
27802 @c @subsubheading GDB Command
27804 @c @subsubheading Example
27807 @subheading The @code{-data-disassemble} Command
27808 @findex -data-disassemble
27810 @subsubheading Synopsis
27814 [ -s @var{start-addr} -e @var{end-addr} ]
27815 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
27823 @item @var{start-addr}
27824 is the beginning address (or @code{$pc})
27825 @item @var{end-addr}
27827 @item @var{filename}
27828 is the name of the file to disassemble
27829 @item @var{linenum}
27830 is the line number to disassemble around
27832 is the number of disassembly lines to be produced. If it is -1,
27833 the whole function will be disassembled, in case no @var{end-addr} is
27834 specified. If @var{end-addr} is specified as a non-zero value, and
27835 @var{lines} is lower than the number of disassembly lines between
27836 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
27837 displayed; if @var{lines} is higher than the number of lines between
27838 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
27841 is either 0 (meaning only disassembly), 1 (meaning mixed source and
27842 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
27843 mixed source and disassembly with raw opcodes).
27846 @subsubheading Result
27848 The output for each instruction is composed of four fields:
27857 Note that whatever included in the instruction field, is not manipulated
27858 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
27860 @subsubheading @value{GDBN} Command
27862 There's no direct mapping from this command to the CLI.
27864 @subsubheading Example
27866 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
27870 -data-disassemble -s $pc -e "$pc + 20" -- 0
27873 @{address="0x000107c0",func-name="main",offset="4",
27874 inst="mov 2, %o0"@},
27875 @{address="0x000107c4",func-name="main",offset="8",
27876 inst="sethi %hi(0x11800), %o2"@},
27877 @{address="0x000107c8",func-name="main",offset="12",
27878 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
27879 @{address="0x000107cc",func-name="main",offset="16",
27880 inst="sethi %hi(0x11800), %o2"@},
27881 @{address="0x000107d0",func-name="main",offset="20",
27882 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
27886 Disassemble the whole @code{main} function. Line 32 is part of
27890 -data-disassemble -f basics.c -l 32 -- 0
27892 @{address="0x000107bc",func-name="main",offset="0",
27893 inst="save %sp, -112, %sp"@},
27894 @{address="0x000107c0",func-name="main",offset="4",
27895 inst="mov 2, %o0"@},
27896 @{address="0x000107c4",func-name="main",offset="8",
27897 inst="sethi %hi(0x11800), %o2"@},
27899 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
27900 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
27904 Disassemble 3 instructions from the start of @code{main}:
27908 -data-disassemble -f basics.c -l 32 -n 3 -- 0
27910 @{address="0x000107bc",func-name="main",offset="0",
27911 inst="save %sp, -112, %sp"@},
27912 @{address="0x000107c0",func-name="main",offset="4",
27913 inst="mov 2, %o0"@},
27914 @{address="0x000107c4",func-name="main",offset="8",
27915 inst="sethi %hi(0x11800), %o2"@}]
27919 Disassemble 3 instructions from the start of @code{main} in mixed mode:
27923 -data-disassemble -f basics.c -l 32 -n 3 -- 1
27925 src_and_asm_line=@{line="31",
27926 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
27927 testsuite/gdb.mi/basics.c",line_asm_insn=[
27928 @{address="0x000107bc",func-name="main",offset="0",
27929 inst="save %sp, -112, %sp"@}]@},
27930 src_and_asm_line=@{line="32",
27931 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
27932 testsuite/gdb.mi/basics.c",line_asm_insn=[
27933 @{address="0x000107c0",func-name="main",offset="4",
27934 inst="mov 2, %o0"@},
27935 @{address="0x000107c4",func-name="main",offset="8",
27936 inst="sethi %hi(0x11800), %o2"@}]@}]
27941 @subheading The @code{-data-evaluate-expression} Command
27942 @findex -data-evaluate-expression
27944 @subsubheading Synopsis
27947 -data-evaluate-expression @var{expr}
27950 Evaluate @var{expr} as an expression. The expression could contain an
27951 inferior function call. The function call will execute synchronously.
27952 If the expression contains spaces, it must be enclosed in double quotes.
27954 @subsubheading @value{GDBN} Command
27956 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
27957 @samp{call}. In @code{gdbtk} only, there's a corresponding
27958 @samp{gdb_eval} command.
27960 @subsubheading Example
27962 In the following example, the numbers that precede the commands are the
27963 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
27964 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
27968 211-data-evaluate-expression A
27971 311-data-evaluate-expression &A
27972 311^done,value="0xefffeb7c"
27974 411-data-evaluate-expression A+3
27977 511-data-evaluate-expression "A + 3"
27983 @subheading The @code{-data-list-changed-registers} Command
27984 @findex -data-list-changed-registers
27986 @subsubheading Synopsis
27989 -data-list-changed-registers
27992 Display a list of the registers that have changed.
27994 @subsubheading @value{GDBN} Command
27996 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
27997 has the corresponding command @samp{gdb_changed_register_list}.
27999 @subsubheading Example
28001 On a PPC MBX board:
28009 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
28010 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
28013 -data-list-changed-registers
28014 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
28015 "10","11","13","14","15","16","17","18","19","20","21","22","23",
28016 "24","25","26","27","28","30","31","64","65","66","67","69"]
28021 @subheading The @code{-data-list-register-names} Command
28022 @findex -data-list-register-names
28024 @subsubheading Synopsis
28027 -data-list-register-names [ ( @var{regno} )+ ]
28030 Show a list of register names for the current target. If no arguments
28031 are given, it shows a list of the names of all the registers. If
28032 integer numbers are given as arguments, it will print a list of the
28033 names of the registers corresponding to the arguments. To ensure
28034 consistency between a register name and its number, the output list may
28035 include empty register names.
28037 @subsubheading @value{GDBN} Command
28039 @value{GDBN} does not have a command which corresponds to
28040 @samp{-data-list-register-names}. In @code{gdbtk} there is a
28041 corresponding command @samp{gdb_regnames}.
28043 @subsubheading Example
28045 For the PPC MBX board:
28048 -data-list-register-names
28049 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
28050 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
28051 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
28052 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
28053 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
28054 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
28055 "", "pc","ps","cr","lr","ctr","xer"]
28057 -data-list-register-names 1 2 3
28058 ^done,register-names=["r1","r2","r3"]
28062 @subheading The @code{-data-list-register-values} Command
28063 @findex -data-list-register-values
28065 @subsubheading Synopsis
28068 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
28071 Display the registers' contents. @var{fmt} is the format according to
28072 which the registers' contents are to be returned, followed by an optional
28073 list of numbers specifying the registers to display. A missing list of
28074 numbers indicates that the contents of all the registers must be returned.
28076 Allowed formats for @var{fmt} are:
28093 @subsubheading @value{GDBN} Command
28095 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
28096 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
28098 @subsubheading Example
28100 For a PPC MBX board (note: line breaks are for readability only, they
28101 don't appear in the actual output):
28105 -data-list-register-values r 64 65
28106 ^done,register-values=[@{number="64",value="0xfe00a300"@},
28107 @{number="65",value="0x00029002"@}]
28109 -data-list-register-values x
28110 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
28111 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
28112 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
28113 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
28114 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
28115 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
28116 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
28117 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
28118 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
28119 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
28120 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
28121 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
28122 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
28123 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
28124 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
28125 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
28126 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
28127 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
28128 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
28129 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
28130 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
28131 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
28132 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
28133 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
28134 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
28135 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
28136 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
28137 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
28138 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
28139 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
28140 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
28141 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
28142 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
28143 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
28144 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
28145 @{number="69",value="0x20002b03"@}]
28150 @subheading The @code{-data-read-memory} Command
28151 @findex -data-read-memory
28153 This command is deprecated, use @code{-data-read-memory-bytes} instead.
28155 @subsubheading Synopsis
28158 -data-read-memory [ -o @var{byte-offset} ]
28159 @var{address} @var{word-format} @var{word-size}
28160 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
28167 @item @var{address}
28168 An expression specifying the address of the first memory word to be
28169 read. Complex expressions containing embedded white space should be
28170 quoted using the C convention.
28172 @item @var{word-format}
28173 The format to be used to print the memory words. The notation is the
28174 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
28177 @item @var{word-size}
28178 The size of each memory word in bytes.
28180 @item @var{nr-rows}
28181 The number of rows in the output table.
28183 @item @var{nr-cols}
28184 The number of columns in the output table.
28187 If present, indicates that each row should include an @sc{ascii} dump. The
28188 value of @var{aschar} is used as a padding character when a byte is not a
28189 member of the printable @sc{ascii} character set (printable @sc{ascii}
28190 characters are those whose code is between 32 and 126, inclusively).
28192 @item @var{byte-offset}
28193 An offset to add to the @var{address} before fetching memory.
28196 This command displays memory contents as a table of @var{nr-rows} by
28197 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
28198 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
28199 (returned as @samp{total-bytes}). Should less than the requested number
28200 of bytes be returned by the target, the missing words are identified
28201 using @samp{N/A}. The number of bytes read from the target is returned
28202 in @samp{nr-bytes} and the starting address used to read memory in
28205 The address of the next/previous row or page is available in
28206 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
28209 @subsubheading @value{GDBN} Command
28211 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
28212 @samp{gdb_get_mem} memory read command.
28214 @subsubheading Example
28216 Read six bytes of memory starting at @code{bytes+6} but then offset by
28217 @code{-6} bytes. Format as three rows of two columns. One byte per
28218 word. Display each word in hex.
28222 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
28223 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
28224 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
28225 prev-page="0x0000138a",memory=[
28226 @{addr="0x00001390",data=["0x00","0x01"]@},
28227 @{addr="0x00001392",data=["0x02","0x03"]@},
28228 @{addr="0x00001394",data=["0x04","0x05"]@}]
28232 Read two bytes of memory starting at address @code{shorts + 64} and
28233 display as a single word formatted in decimal.
28237 5-data-read-memory shorts+64 d 2 1 1
28238 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
28239 next-row="0x00001512",prev-row="0x0000150e",
28240 next-page="0x00001512",prev-page="0x0000150e",memory=[
28241 @{addr="0x00001510",data=["128"]@}]
28245 Read thirty two bytes of memory starting at @code{bytes+16} and format
28246 as eight rows of four columns. Include a string encoding with @samp{x}
28247 used as the non-printable character.
28251 4-data-read-memory bytes+16 x 1 8 4 x
28252 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
28253 next-row="0x000013c0",prev-row="0x0000139c",
28254 next-page="0x000013c0",prev-page="0x00001380",memory=[
28255 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
28256 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
28257 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
28258 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
28259 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
28260 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
28261 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
28262 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
28266 @subheading The @code{-data-read-memory-bytes} Command
28267 @findex -data-read-memory-bytes
28269 @subsubheading Synopsis
28272 -data-read-memory-bytes [ -o @var{byte-offset} ]
28273 @var{address} @var{count}
28280 @item @var{address}
28281 An expression specifying the address of the first memory word to be
28282 read. Complex expressions containing embedded white space should be
28283 quoted using the C convention.
28286 The number of bytes to read. This should be an integer literal.
28288 @item @var{byte-offset}
28289 The offsets in bytes relative to @var{address} at which to start
28290 reading. This should be an integer literal. This option is provided
28291 so that a frontend is not required to first evaluate address and then
28292 perform address arithmetics itself.
28296 This command attempts to read all accessible memory regions in the
28297 specified range. First, all regions marked as unreadable in the memory
28298 map (if one is defined) will be skipped. @xref{Memory Region
28299 Attributes}. Second, @value{GDBN} will attempt to read the remaining
28300 regions. For each one, if reading full region results in an errors,
28301 @value{GDBN} will try to read a subset of the region.
28303 In general, every single byte in the region may be readable or not,
28304 and the only way to read every readable byte is to try a read at
28305 every address, which is not practical. Therefore, @value{GDBN} will
28306 attempt to read all accessible bytes at either beginning or the end
28307 of the region, using a binary division scheme. This heuristic works
28308 well for reading accross a memory map boundary. Note that if a region
28309 has a readable range that is neither at the beginning or the end,
28310 @value{GDBN} will not read it.
28312 The result record (@pxref{GDB/MI Result Records}) that is output of
28313 the command includes a field named @samp{memory} whose content is a
28314 list of tuples. Each tuple represent a successfully read memory block
28315 and has the following fields:
28319 The start address of the memory block, as hexadecimal literal.
28322 The end address of the memory block, as hexadecimal literal.
28325 The offset of the memory block, as hexadecimal literal, relative to
28326 the start address passed to @code{-data-read-memory-bytes}.
28329 The contents of the memory block, in hex.
28335 @subsubheading @value{GDBN} Command
28337 The corresponding @value{GDBN} command is @samp{x}.
28339 @subsubheading Example
28343 -data-read-memory-bytes &a 10
28344 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
28346 contents="01000000020000000300"@}]
28351 @subheading The @code{-data-write-memory-bytes} Command
28352 @findex -data-write-memory-bytes
28354 @subsubheading Synopsis
28357 -data-write-memory-bytes @var{address} @var{contents}
28364 @item @var{address}
28365 An expression specifying the address of the first memory word to be
28366 read. Complex expressions containing embedded white space should be
28367 quoted using the C convention.
28369 @item @var{contents}
28370 The hex-encoded bytes to write.
28374 @subsubheading @value{GDBN} Command
28376 There's no corresponding @value{GDBN} command.
28378 @subsubheading Example
28382 -data-write-memory-bytes &a "aabbccdd"
28388 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28389 @node GDB/MI Tracepoint Commands
28390 @section @sc{gdb/mi} Tracepoint Commands
28392 The commands defined in this section implement MI support for
28393 tracepoints. For detailed introduction, see @ref{Tracepoints}.
28395 @subheading The @code{-trace-find} Command
28396 @findex -trace-find
28398 @subsubheading Synopsis
28401 -trace-find @var{mode} [@var{parameters}@dots{}]
28404 Find a trace frame using criteria defined by @var{mode} and
28405 @var{parameters}. The following table lists permissible
28406 modes and their parameters. For details of operation, see @ref{tfind}.
28411 No parameters are required. Stops examining trace frames.
28414 An integer is required as parameter. Selects tracepoint frame with
28417 @item tracepoint-number
28418 An integer is required as parameter. Finds next
28419 trace frame that corresponds to tracepoint with the specified number.
28422 An address is required as parameter. Finds
28423 next trace frame that corresponds to any tracepoint at the specified
28426 @item pc-inside-range
28427 Two addresses are required as parameters. Finds next trace
28428 frame that corresponds to a tracepoint at an address inside the
28429 specified range. Both bounds are considered to be inside the range.
28431 @item pc-outside-range
28432 Two addresses are required as parameters. Finds
28433 next trace frame that corresponds to a tracepoint at an address outside
28434 the specified range. Both bounds are considered to be inside the range.
28437 Line specification is required as parameter. @xref{Specify Location}.
28438 Finds next trace frame that corresponds to a tracepoint at
28439 the specified location.
28443 If @samp{none} was passed as @var{mode}, the response does not
28444 have fields. Otherwise, the response may have the following fields:
28448 This field has either @samp{0} or @samp{1} as the value, depending
28449 on whether a matching tracepoint was found.
28452 The index of the found traceframe. This field is present iff
28453 the @samp{found} field has value of @samp{1}.
28456 The index of the found tracepoint. This field is present iff
28457 the @samp{found} field has value of @samp{1}.
28460 The information about the frame corresponding to the found trace
28461 frame. This field is present only if a trace frame was found.
28462 @xref{GDB/MI Frame Information}, for description of this field.
28466 @subsubheading @value{GDBN} Command
28468 The corresponding @value{GDBN} command is @samp{tfind}.
28470 @subheading -trace-define-variable
28471 @findex -trace-define-variable
28473 @subsubheading Synopsis
28476 -trace-define-variable @var{name} [ @var{value} ]
28479 Create trace variable @var{name} if it does not exist. If
28480 @var{value} is specified, sets the initial value of the specified
28481 trace variable to that value. Note that the @var{name} should start
28482 with the @samp{$} character.
28484 @subsubheading @value{GDBN} Command
28486 The corresponding @value{GDBN} command is @samp{tvariable}.
28488 @subheading -trace-list-variables
28489 @findex -trace-list-variables
28491 @subsubheading Synopsis
28494 -trace-list-variables
28497 Return a table of all defined trace variables. Each element of the
28498 table has the following fields:
28502 The name of the trace variable. This field is always present.
28505 The initial value. This is a 64-bit signed integer. This
28506 field is always present.
28509 The value the trace variable has at the moment. This is a 64-bit
28510 signed integer. This field is absent iff current value is
28511 not defined, for example if the trace was never run, or is
28516 @subsubheading @value{GDBN} Command
28518 The corresponding @value{GDBN} command is @samp{tvariables}.
28520 @subsubheading Example
28524 -trace-list-variables
28525 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
28526 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
28527 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
28528 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
28529 body=[variable=@{name="$trace_timestamp",initial="0"@}
28530 variable=@{name="$foo",initial="10",current="15"@}]@}
28534 @subheading -trace-save
28535 @findex -trace-save
28537 @subsubheading Synopsis
28540 -trace-save [-r ] @var{filename}
28543 Saves the collected trace data to @var{filename}. Without the
28544 @samp{-r} option, the data is downloaded from the target and saved
28545 in a local file. With the @samp{-r} option the target is asked
28546 to perform the save.
28548 @subsubheading @value{GDBN} Command
28550 The corresponding @value{GDBN} command is @samp{tsave}.
28553 @subheading -trace-start
28554 @findex -trace-start
28556 @subsubheading Synopsis
28562 Starts a tracing experiments. The result of this command does not
28565 @subsubheading @value{GDBN} Command
28567 The corresponding @value{GDBN} command is @samp{tstart}.
28569 @subheading -trace-status
28570 @findex -trace-status
28572 @subsubheading Synopsis
28578 Obtains the status of a tracing experiment. The result may include
28579 the following fields:
28584 May have a value of either @samp{0}, when no tracing operations are
28585 supported, @samp{1}, when all tracing operations are supported, or
28586 @samp{file} when examining trace file. In the latter case, examining
28587 of trace frame is possible but new tracing experiement cannot be
28588 started. This field is always present.
28591 May have a value of either @samp{0} or @samp{1} depending on whether
28592 tracing experiement is in progress on target. This field is present
28593 if @samp{supported} field is not @samp{0}.
28596 Report the reason why the tracing was stopped last time. This field
28597 may be absent iff tracing was never stopped on target yet. The
28598 value of @samp{request} means the tracing was stopped as result of
28599 the @code{-trace-stop} command. The value of @samp{overflow} means
28600 the tracing buffer is full. The value of @samp{disconnection} means
28601 tracing was automatically stopped when @value{GDBN} has disconnected.
28602 The value of @samp{passcount} means tracing was stopped when a
28603 tracepoint was passed a maximal number of times for that tracepoint.
28604 This field is present if @samp{supported} field is not @samp{0}.
28606 @item stopping-tracepoint
28607 The number of tracepoint whose passcount as exceeded. This field is
28608 present iff the @samp{stop-reason} field has the value of
28612 @itemx frames-created
28613 The @samp{frames} field is a count of the total number of trace frames
28614 in the trace buffer, while @samp{frames-created} is the total created
28615 during the run, including ones that were discarded, such as when a
28616 circular trace buffer filled up. Both fields are optional.
28620 These fields tell the current size of the tracing buffer and the
28621 remaining space. These fields are optional.
28624 The value of the circular trace buffer flag. @code{1} means that the
28625 trace buffer is circular and old trace frames will be discarded if
28626 necessary to make room, @code{0} means that the trace buffer is linear
28630 The value of the disconnected tracing flag. @code{1} means that
28631 tracing will continue after @value{GDBN} disconnects, @code{0} means
28632 that the trace run will stop.
28636 @subsubheading @value{GDBN} Command
28638 The corresponding @value{GDBN} command is @samp{tstatus}.
28640 @subheading -trace-stop
28641 @findex -trace-stop
28643 @subsubheading Synopsis
28649 Stops a tracing experiment. The result of this command has the same
28650 fields as @code{-trace-status}, except that the @samp{supported} and
28651 @samp{running} fields are not output.
28653 @subsubheading @value{GDBN} Command
28655 The corresponding @value{GDBN} command is @samp{tstop}.
28658 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28659 @node GDB/MI Symbol Query
28660 @section @sc{gdb/mi} Symbol Query Commands
28664 @subheading The @code{-symbol-info-address} Command
28665 @findex -symbol-info-address
28667 @subsubheading Synopsis
28670 -symbol-info-address @var{symbol}
28673 Describe where @var{symbol} is stored.
28675 @subsubheading @value{GDBN} Command
28677 The corresponding @value{GDBN} command is @samp{info address}.
28679 @subsubheading Example
28683 @subheading The @code{-symbol-info-file} Command
28684 @findex -symbol-info-file
28686 @subsubheading Synopsis
28692 Show the file for the symbol.
28694 @subsubheading @value{GDBN} Command
28696 There's no equivalent @value{GDBN} command. @code{gdbtk} has
28697 @samp{gdb_find_file}.
28699 @subsubheading Example
28703 @subheading The @code{-symbol-info-function} Command
28704 @findex -symbol-info-function
28706 @subsubheading Synopsis
28709 -symbol-info-function
28712 Show which function the symbol lives in.
28714 @subsubheading @value{GDBN} Command
28716 @samp{gdb_get_function} in @code{gdbtk}.
28718 @subsubheading Example
28722 @subheading The @code{-symbol-info-line} Command
28723 @findex -symbol-info-line
28725 @subsubheading Synopsis
28731 Show the core addresses of the code for a source line.
28733 @subsubheading @value{GDBN} Command
28735 The corresponding @value{GDBN} command is @samp{info line}.
28736 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
28738 @subsubheading Example
28742 @subheading The @code{-symbol-info-symbol} Command
28743 @findex -symbol-info-symbol
28745 @subsubheading Synopsis
28748 -symbol-info-symbol @var{addr}
28751 Describe what symbol is at location @var{addr}.
28753 @subsubheading @value{GDBN} Command
28755 The corresponding @value{GDBN} command is @samp{info symbol}.
28757 @subsubheading Example
28761 @subheading The @code{-symbol-list-functions} Command
28762 @findex -symbol-list-functions
28764 @subsubheading Synopsis
28767 -symbol-list-functions
28770 List the functions in the executable.
28772 @subsubheading @value{GDBN} Command
28774 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
28775 @samp{gdb_search} in @code{gdbtk}.
28777 @subsubheading Example
28782 @subheading The @code{-symbol-list-lines} Command
28783 @findex -symbol-list-lines
28785 @subsubheading Synopsis
28788 -symbol-list-lines @var{filename}
28791 Print the list of lines that contain code and their associated program
28792 addresses for the given source filename. The entries are sorted in
28793 ascending PC order.
28795 @subsubheading @value{GDBN} Command
28797 There is no corresponding @value{GDBN} command.
28799 @subsubheading Example
28802 -symbol-list-lines basics.c
28803 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
28809 @subheading The @code{-symbol-list-types} Command
28810 @findex -symbol-list-types
28812 @subsubheading Synopsis
28818 List all the type names.
28820 @subsubheading @value{GDBN} Command
28822 The corresponding commands are @samp{info types} in @value{GDBN},
28823 @samp{gdb_search} in @code{gdbtk}.
28825 @subsubheading Example
28829 @subheading The @code{-symbol-list-variables} Command
28830 @findex -symbol-list-variables
28832 @subsubheading Synopsis
28835 -symbol-list-variables
28838 List all the global and static variable names.
28840 @subsubheading @value{GDBN} Command
28842 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
28844 @subsubheading Example
28848 @subheading The @code{-symbol-locate} Command
28849 @findex -symbol-locate
28851 @subsubheading Synopsis
28857 @subsubheading @value{GDBN} Command
28859 @samp{gdb_loc} in @code{gdbtk}.
28861 @subsubheading Example
28865 @subheading The @code{-symbol-type} Command
28866 @findex -symbol-type
28868 @subsubheading Synopsis
28871 -symbol-type @var{variable}
28874 Show type of @var{variable}.
28876 @subsubheading @value{GDBN} Command
28878 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
28879 @samp{gdb_obj_variable}.
28881 @subsubheading Example
28886 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28887 @node GDB/MI File Commands
28888 @section @sc{gdb/mi} File Commands
28890 This section describes the GDB/MI commands to specify executable file names
28891 and to read in and obtain symbol table information.
28893 @subheading The @code{-file-exec-and-symbols} Command
28894 @findex -file-exec-and-symbols
28896 @subsubheading Synopsis
28899 -file-exec-and-symbols @var{file}
28902 Specify the executable file to be debugged. This file is the one from
28903 which the symbol table is also read. If no file is specified, the
28904 command clears the executable and symbol information. If breakpoints
28905 are set when using this command with no arguments, @value{GDBN} will produce
28906 error messages. Otherwise, no output is produced, except a completion
28909 @subsubheading @value{GDBN} Command
28911 The corresponding @value{GDBN} command is @samp{file}.
28913 @subsubheading Example
28917 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
28923 @subheading The @code{-file-exec-file} Command
28924 @findex -file-exec-file
28926 @subsubheading Synopsis
28929 -file-exec-file @var{file}
28932 Specify the executable file to be debugged. Unlike
28933 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
28934 from this file. If used without argument, @value{GDBN} clears the information
28935 about the executable file. No output is produced, except a completion
28938 @subsubheading @value{GDBN} Command
28940 The corresponding @value{GDBN} command is @samp{exec-file}.
28942 @subsubheading Example
28946 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
28953 @subheading The @code{-file-list-exec-sections} Command
28954 @findex -file-list-exec-sections
28956 @subsubheading Synopsis
28959 -file-list-exec-sections
28962 List the sections of the current executable file.
28964 @subsubheading @value{GDBN} Command
28966 The @value{GDBN} command @samp{info file} shows, among the rest, the same
28967 information as this command. @code{gdbtk} has a corresponding command
28968 @samp{gdb_load_info}.
28970 @subsubheading Example
28975 @subheading The @code{-file-list-exec-source-file} Command
28976 @findex -file-list-exec-source-file
28978 @subsubheading Synopsis
28981 -file-list-exec-source-file
28984 List the line number, the current source file, and the absolute path
28985 to the current source file for the current executable. The macro
28986 information field has a value of @samp{1} or @samp{0} depending on
28987 whether or not the file includes preprocessor macro information.
28989 @subsubheading @value{GDBN} Command
28991 The @value{GDBN} equivalent is @samp{info source}
28993 @subsubheading Example
28997 123-file-list-exec-source-file
28998 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
29003 @subheading The @code{-file-list-exec-source-files} Command
29004 @findex -file-list-exec-source-files
29006 @subsubheading Synopsis
29009 -file-list-exec-source-files
29012 List the source files for the current executable.
29014 It will always output the filename, but only when @value{GDBN} can find
29015 the absolute file name of a source file, will it output the fullname.
29017 @subsubheading @value{GDBN} Command
29019 The @value{GDBN} equivalent is @samp{info sources}.
29020 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
29022 @subsubheading Example
29025 -file-list-exec-source-files
29027 @{file=foo.c,fullname=/home/foo.c@},
29028 @{file=/home/bar.c,fullname=/home/bar.c@},
29029 @{file=gdb_could_not_find_fullpath.c@}]
29034 @subheading The @code{-file-list-shared-libraries} Command
29035 @findex -file-list-shared-libraries
29037 @subsubheading Synopsis
29040 -file-list-shared-libraries
29043 List the shared libraries in the program.
29045 @subsubheading @value{GDBN} Command
29047 The corresponding @value{GDBN} command is @samp{info shared}.
29049 @subsubheading Example
29053 @subheading The @code{-file-list-symbol-files} Command
29054 @findex -file-list-symbol-files
29056 @subsubheading Synopsis
29059 -file-list-symbol-files
29064 @subsubheading @value{GDBN} Command
29066 The corresponding @value{GDBN} command is @samp{info file} (part of it).
29068 @subsubheading Example
29073 @subheading The @code{-file-symbol-file} Command
29074 @findex -file-symbol-file
29076 @subsubheading Synopsis
29079 -file-symbol-file @var{file}
29082 Read symbol table info from the specified @var{file} argument. When
29083 used without arguments, clears @value{GDBN}'s symbol table info. No output is
29084 produced, except for a completion notification.
29086 @subsubheading @value{GDBN} Command
29088 The corresponding @value{GDBN} command is @samp{symbol-file}.
29090 @subsubheading Example
29094 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
29100 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29101 @node GDB/MI Memory Overlay Commands
29102 @section @sc{gdb/mi} Memory Overlay Commands
29104 The memory overlay commands are not implemented.
29106 @c @subheading -overlay-auto
29108 @c @subheading -overlay-list-mapping-state
29110 @c @subheading -overlay-list-overlays
29112 @c @subheading -overlay-map
29114 @c @subheading -overlay-off
29116 @c @subheading -overlay-on
29118 @c @subheading -overlay-unmap
29120 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29121 @node GDB/MI Signal Handling Commands
29122 @section @sc{gdb/mi} Signal Handling Commands
29124 Signal handling commands are not implemented.
29126 @c @subheading -signal-handle
29128 @c @subheading -signal-list-handle-actions
29130 @c @subheading -signal-list-signal-types
29134 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29135 @node GDB/MI Target Manipulation
29136 @section @sc{gdb/mi} Target Manipulation Commands
29139 @subheading The @code{-target-attach} Command
29140 @findex -target-attach
29142 @subsubheading Synopsis
29145 -target-attach @var{pid} | @var{gid} | @var{file}
29148 Attach to a process @var{pid} or a file @var{file} outside of
29149 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
29150 group, the id previously returned by
29151 @samp{-list-thread-groups --available} must be used.
29153 @subsubheading @value{GDBN} Command
29155 The corresponding @value{GDBN} command is @samp{attach}.
29157 @subsubheading Example
29161 =thread-created,id="1"
29162 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
29168 @subheading The @code{-target-compare-sections} Command
29169 @findex -target-compare-sections
29171 @subsubheading Synopsis
29174 -target-compare-sections [ @var{section} ]
29177 Compare data of section @var{section} on target to the exec file.
29178 Without the argument, all sections are compared.
29180 @subsubheading @value{GDBN} Command
29182 The @value{GDBN} equivalent is @samp{compare-sections}.
29184 @subsubheading Example
29189 @subheading The @code{-target-detach} Command
29190 @findex -target-detach
29192 @subsubheading Synopsis
29195 -target-detach [ @var{pid} | @var{gid} ]
29198 Detach from the remote target which normally resumes its execution.
29199 If either @var{pid} or @var{gid} is specified, detaches from either
29200 the specified process, or specified thread group. There's no output.
29202 @subsubheading @value{GDBN} Command
29204 The corresponding @value{GDBN} command is @samp{detach}.
29206 @subsubheading Example
29216 @subheading The @code{-target-disconnect} Command
29217 @findex -target-disconnect
29219 @subsubheading Synopsis
29225 Disconnect from the remote target. There's no output and the target is
29226 generally not resumed.
29228 @subsubheading @value{GDBN} Command
29230 The corresponding @value{GDBN} command is @samp{disconnect}.
29232 @subsubheading Example
29242 @subheading The @code{-target-download} Command
29243 @findex -target-download
29245 @subsubheading Synopsis
29251 Loads the executable onto the remote target.
29252 It prints out an update message every half second, which includes the fields:
29256 The name of the section.
29258 The size of what has been sent so far for that section.
29260 The size of the section.
29262 The total size of what was sent so far (the current and the previous sections).
29264 The size of the overall executable to download.
29268 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
29269 @sc{gdb/mi} Output Syntax}).
29271 In addition, it prints the name and size of the sections, as they are
29272 downloaded. These messages include the following fields:
29276 The name of the section.
29278 The size of the section.
29280 The size of the overall executable to download.
29284 At the end, a summary is printed.
29286 @subsubheading @value{GDBN} Command
29288 The corresponding @value{GDBN} command is @samp{load}.
29290 @subsubheading Example
29292 Note: each status message appears on a single line. Here the messages
29293 have been broken down so that they can fit onto a page.
29298 +download,@{section=".text",section-size="6668",total-size="9880"@}
29299 +download,@{section=".text",section-sent="512",section-size="6668",
29300 total-sent="512",total-size="9880"@}
29301 +download,@{section=".text",section-sent="1024",section-size="6668",
29302 total-sent="1024",total-size="9880"@}
29303 +download,@{section=".text",section-sent="1536",section-size="6668",
29304 total-sent="1536",total-size="9880"@}
29305 +download,@{section=".text",section-sent="2048",section-size="6668",
29306 total-sent="2048",total-size="9880"@}
29307 +download,@{section=".text",section-sent="2560",section-size="6668",
29308 total-sent="2560",total-size="9880"@}
29309 +download,@{section=".text",section-sent="3072",section-size="6668",
29310 total-sent="3072",total-size="9880"@}
29311 +download,@{section=".text",section-sent="3584",section-size="6668",
29312 total-sent="3584",total-size="9880"@}
29313 +download,@{section=".text",section-sent="4096",section-size="6668",
29314 total-sent="4096",total-size="9880"@}
29315 +download,@{section=".text",section-sent="4608",section-size="6668",
29316 total-sent="4608",total-size="9880"@}
29317 +download,@{section=".text",section-sent="5120",section-size="6668",
29318 total-sent="5120",total-size="9880"@}
29319 +download,@{section=".text",section-sent="5632",section-size="6668",
29320 total-sent="5632",total-size="9880"@}
29321 +download,@{section=".text",section-sent="6144",section-size="6668",
29322 total-sent="6144",total-size="9880"@}
29323 +download,@{section=".text",section-sent="6656",section-size="6668",
29324 total-sent="6656",total-size="9880"@}
29325 +download,@{section=".init",section-size="28",total-size="9880"@}
29326 +download,@{section=".fini",section-size="28",total-size="9880"@}
29327 +download,@{section=".data",section-size="3156",total-size="9880"@}
29328 +download,@{section=".data",section-sent="512",section-size="3156",
29329 total-sent="7236",total-size="9880"@}
29330 +download,@{section=".data",section-sent="1024",section-size="3156",
29331 total-sent="7748",total-size="9880"@}
29332 +download,@{section=".data",section-sent="1536",section-size="3156",
29333 total-sent="8260",total-size="9880"@}
29334 +download,@{section=".data",section-sent="2048",section-size="3156",
29335 total-sent="8772",total-size="9880"@}
29336 +download,@{section=".data",section-sent="2560",section-size="3156",
29337 total-sent="9284",total-size="9880"@}
29338 +download,@{section=".data",section-sent="3072",section-size="3156",
29339 total-sent="9796",total-size="9880"@}
29340 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
29347 @subheading The @code{-target-exec-status} Command
29348 @findex -target-exec-status
29350 @subsubheading Synopsis
29353 -target-exec-status
29356 Provide information on the state of the target (whether it is running or
29357 not, for instance).
29359 @subsubheading @value{GDBN} Command
29361 There's no equivalent @value{GDBN} command.
29363 @subsubheading Example
29367 @subheading The @code{-target-list-available-targets} Command
29368 @findex -target-list-available-targets
29370 @subsubheading Synopsis
29373 -target-list-available-targets
29376 List the possible targets to connect to.
29378 @subsubheading @value{GDBN} Command
29380 The corresponding @value{GDBN} command is @samp{help target}.
29382 @subsubheading Example
29386 @subheading The @code{-target-list-current-targets} Command
29387 @findex -target-list-current-targets
29389 @subsubheading Synopsis
29392 -target-list-current-targets
29395 Describe the current target.
29397 @subsubheading @value{GDBN} Command
29399 The corresponding information is printed by @samp{info file} (among
29402 @subsubheading Example
29406 @subheading The @code{-target-list-parameters} Command
29407 @findex -target-list-parameters
29409 @subsubheading Synopsis
29412 -target-list-parameters
29418 @subsubheading @value{GDBN} Command
29422 @subsubheading Example
29426 @subheading The @code{-target-select} Command
29427 @findex -target-select
29429 @subsubheading Synopsis
29432 -target-select @var{type} @var{parameters @dots{}}
29435 Connect @value{GDBN} to the remote target. This command takes two args:
29439 The type of target, for instance @samp{remote}, etc.
29440 @item @var{parameters}
29441 Device names, host names and the like. @xref{Target Commands, ,
29442 Commands for Managing Targets}, for more details.
29445 The output is a connection notification, followed by the address at
29446 which the target program is, in the following form:
29449 ^connected,addr="@var{address}",func="@var{function name}",
29450 args=[@var{arg list}]
29453 @subsubheading @value{GDBN} Command
29455 The corresponding @value{GDBN} command is @samp{target}.
29457 @subsubheading Example
29461 -target-select remote /dev/ttya
29462 ^connected,addr="0xfe00a300",func="??",args=[]
29466 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29467 @node GDB/MI File Transfer Commands
29468 @section @sc{gdb/mi} File Transfer Commands
29471 @subheading The @code{-target-file-put} Command
29472 @findex -target-file-put
29474 @subsubheading Synopsis
29477 -target-file-put @var{hostfile} @var{targetfile}
29480 Copy file @var{hostfile} from the host system (the machine running
29481 @value{GDBN}) to @var{targetfile} on the target system.
29483 @subsubheading @value{GDBN} Command
29485 The corresponding @value{GDBN} command is @samp{remote put}.
29487 @subsubheading Example
29491 -target-file-put localfile remotefile
29497 @subheading The @code{-target-file-get} Command
29498 @findex -target-file-get
29500 @subsubheading Synopsis
29503 -target-file-get @var{targetfile} @var{hostfile}
29506 Copy file @var{targetfile} from the target system to @var{hostfile}
29507 on the host system.
29509 @subsubheading @value{GDBN} Command
29511 The corresponding @value{GDBN} command is @samp{remote get}.
29513 @subsubheading Example
29517 -target-file-get remotefile localfile
29523 @subheading The @code{-target-file-delete} Command
29524 @findex -target-file-delete
29526 @subsubheading Synopsis
29529 -target-file-delete @var{targetfile}
29532 Delete @var{targetfile} from the target system.
29534 @subsubheading @value{GDBN} Command
29536 The corresponding @value{GDBN} command is @samp{remote delete}.
29538 @subsubheading Example
29542 -target-file-delete remotefile
29548 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29549 @node GDB/MI Miscellaneous Commands
29550 @section Miscellaneous @sc{gdb/mi} Commands
29552 @c @subheading -gdb-complete
29554 @subheading The @code{-gdb-exit} Command
29557 @subsubheading Synopsis
29563 Exit @value{GDBN} immediately.
29565 @subsubheading @value{GDBN} Command
29567 Approximately corresponds to @samp{quit}.
29569 @subsubheading Example
29579 @subheading The @code{-exec-abort} Command
29580 @findex -exec-abort
29582 @subsubheading Synopsis
29588 Kill the inferior running program.
29590 @subsubheading @value{GDBN} Command
29592 The corresponding @value{GDBN} command is @samp{kill}.
29594 @subsubheading Example
29599 @subheading The @code{-gdb-set} Command
29602 @subsubheading Synopsis
29608 Set an internal @value{GDBN} variable.
29609 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
29611 @subsubheading @value{GDBN} Command
29613 The corresponding @value{GDBN} command is @samp{set}.
29615 @subsubheading Example
29625 @subheading The @code{-gdb-show} Command
29628 @subsubheading Synopsis
29634 Show the current value of a @value{GDBN} variable.
29636 @subsubheading @value{GDBN} Command
29638 The corresponding @value{GDBN} command is @samp{show}.
29640 @subsubheading Example
29649 @c @subheading -gdb-source
29652 @subheading The @code{-gdb-version} Command
29653 @findex -gdb-version
29655 @subsubheading Synopsis
29661 Show version information for @value{GDBN}. Used mostly in testing.
29663 @subsubheading @value{GDBN} Command
29665 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
29666 default shows this information when you start an interactive session.
29668 @subsubheading Example
29670 @c This example modifies the actual output from GDB to avoid overfull
29676 ~Copyright 2000 Free Software Foundation, Inc.
29677 ~GDB is free software, covered by the GNU General Public License, and
29678 ~you are welcome to change it and/or distribute copies of it under
29679 ~ certain conditions.
29680 ~Type "show copying" to see the conditions.
29681 ~There is absolutely no warranty for GDB. Type "show warranty" for
29683 ~This GDB was configured as
29684 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
29689 @subheading The @code{-list-features} Command
29690 @findex -list-features
29692 Returns a list of particular features of the MI protocol that
29693 this version of gdb implements. A feature can be a command,
29694 or a new field in an output of some command, or even an
29695 important bugfix. While a frontend can sometimes detect presence
29696 of a feature at runtime, it is easier to perform detection at debugger
29699 The command returns a list of strings, with each string naming an
29700 available feature. Each returned string is just a name, it does not
29701 have any internal structure. The list of possible feature names
29707 (gdb) -list-features
29708 ^done,result=["feature1","feature2"]
29711 The current list of features is:
29714 @item frozen-varobjs
29715 Indicates presence of the @code{-var-set-frozen} command, as well
29716 as possible presense of the @code{frozen} field in the output
29717 of @code{-varobj-create}.
29718 @item pending-breakpoints
29719 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
29721 Indicates presence of Python scripting support, Python-based
29722 pretty-printing commands, and possible presence of the
29723 @samp{display_hint} field in the output of @code{-var-list-children}
29725 Indicates presence of the @code{-thread-info} command.
29726 @item data-read-memory-bytes
29727 Indicates presense of the @code{-data-read-memory-bytes} and the
29728 @code{-data-write-memory-bytes} commands.
29732 @subheading The @code{-list-target-features} Command
29733 @findex -list-target-features
29735 Returns a list of particular features that are supported by the
29736 target. Those features affect the permitted MI commands, but
29737 unlike the features reported by the @code{-list-features} command, the
29738 features depend on which target GDB is using at the moment. Whenever
29739 a target can change, due to commands such as @code{-target-select},
29740 @code{-target-attach} or @code{-exec-run}, the list of target features
29741 may change, and the frontend should obtain it again.
29745 (gdb) -list-features
29746 ^done,result=["async"]
29749 The current list of features is:
29753 Indicates that the target is capable of asynchronous command
29754 execution, which means that @value{GDBN} will accept further commands
29755 while the target is running.
29758 Indicates that the target is capable of reverse execution.
29759 @xref{Reverse Execution}, for more information.
29763 @subheading The @code{-list-thread-groups} Command
29764 @findex -list-thread-groups
29766 @subheading Synopsis
29769 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
29772 Lists thread groups (@pxref{Thread groups}). When a single thread
29773 group is passed as the argument, lists the children of that group.
29774 When several thread group are passed, lists information about those
29775 thread groups. Without any parameters, lists information about all
29776 top-level thread groups.
29778 Normally, thread groups that are being debugged are reported.
29779 With the @samp{--available} option, @value{GDBN} reports thread groups
29780 available on the target.
29782 The output of this command may have either a @samp{threads} result or
29783 a @samp{groups} result. The @samp{thread} result has a list of tuples
29784 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
29785 Information}). The @samp{groups} result has a list of tuples as value,
29786 each tuple describing a thread group. If top-level groups are
29787 requested (that is, no parameter is passed), or when several groups
29788 are passed, the output always has a @samp{groups} result. The format
29789 of the @samp{group} result is described below.
29791 To reduce the number of roundtrips it's possible to list thread groups
29792 together with their children, by passing the @samp{--recurse} option
29793 and the recursion depth. Presently, only recursion depth of 1 is
29794 permitted. If this option is present, then every reported thread group
29795 will also include its children, either as @samp{group} or
29796 @samp{threads} field.
29798 In general, any combination of option and parameters is permitted, with
29799 the following caveats:
29803 When a single thread group is passed, the output will typically
29804 be the @samp{threads} result. Because threads may not contain
29805 anything, the @samp{recurse} option will be ignored.
29808 When the @samp{--available} option is passed, limited information may
29809 be available. In particular, the list of threads of a process might
29810 be inaccessible. Further, specifying specific thread groups might
29811 not give any performance advantage over listing all thread groups.
29812 The frontend should assume that @samp{-list-thread-groups --available}
29813 is always an expensive operation and cache the results.
29817 The @samp{groups} result is a list of tuples, where each tuple may
29818 have the following fields:
29822 Identifier of the thread group. This field is always present.
29823 The identifier is an opaque string; frontends should not try to
29824 convert it to an integer, even though it might look like one.
29827 The type of the thread group. At present, only @samp{process} is a
29831 The target-specific process identifier. This field is only present
29832 for thread groups of type @samp{process} and only if the process exists.
29835 The number of children this thread group has. This field may be
29836 absent for an available thread group.
29839 This field has a list of tuples as value, each tuple describing a
29840 thread. It may be present if the @samp{--recurse} option is
29841 specified, and it's actually possible to obtain the threads.
29844 This field is a list of integers, each identifying a core that one
29845 thread of the group is running on. This field may be absent if
29846 such information is not available.
29849 The name of the executable file that corresponds to this thread group.
29850 The field is only present for thread groups of type @samp{process},
29851 and only if there is a corresponding executable file.
29855 @subheading Example
29859 -list-thread-groups
29860 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
29861 -list-thread-groups 17
29862 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29863 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
29864 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29865 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
29866 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
29867 -list-thread-groups --available
29868 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
29869 -list-thread-groups --available --recurse 1
29870 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
29871 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
29872 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
29873 -list-thread-groups --available --recurse 1 17 18
29874 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
29875 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
29876 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
29880 @subheading The @code{-add-inferior} Command
29881 @findex -add-inferior
29883 @subheading Synopsis
29889 Creates a new inferior (@pxref{Inferiors and Programs}). The created
29890 inferior is not associated with any executable. Such association may
29891 be established with the @samp{-file-exec-and-symbols} command
29892 (@pxref{GDB/MI File Commands}). The command response has a single
29893 field, @samp{thread-group}, whose value is the identifier of the
29894 thread group corresponding to the new inferior.
29896 @subheading Example
29901 ^done,thread-group="i3"
29904 @subheading The @code{-interpreter-exec} Command
29905 @findex -interpreter-exec
29907 @subheading Synopsis
29910 -interpreter-exec @var{interpreter} @var{command}
29912 @anchor{-interpreter-exec}
29914 Execute the specified @var{command} in the given @var{interpreter}.
29916 @subheading @value{GDBN} Command
29918 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
29920 @subheading Example
29924 -interpreter-exec console "break main"
29925 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
29926 &"During symbol reading, bad structure-type format.\n"
29927 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
29932 @subheading The @code{-inferior-tty-set} Command
29933 @findex -inferior-tty-set
29935 @subheading Synopsis
29938 -inferior-tty-set /dev/pts/1
29941 Set terminal for future runs of the program being debugged.
29943 @subheading @value{GDBN} Command
29945 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
29947 @subheading Example
29951 -inferior-tty-set /dev/pts/1
29956 @subheading The @code{-inferior-tty-show} Command
29957 @findex -inferior-tty-show
29959 @subheading Synopsis
29965 Show terminal for future runs of program being debugged.
29967 @subheading @value{GDBN} Command
29969 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
29971 @subheading Example
29975 -inferior-tty-set /dev/pts/1
29979 ^done,inferior_tty_terminal="/dev/pts/1"
29983 @subheading The @code{-enable-timings} Command
29984 @findex -enable-timings
29986 @subheading Synopsis
29989 -enable-timings [yes | no]
29992 Toggle the printing of the wallclock, user and system times for an MI
29993 command as a field in its output. This command is to help frontend
29994 developers optimize the performance of their code. No argument is
29995 equivalent to @samp{yes}.
29997 @subheading @value{GDBN} Command
30001 @subheading Example
30009 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30010 addr="0x080484ed",func="main",file="myprog.c",
30011 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
30012 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
30020 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
30021 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
30022 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
30023 fullname="/home/nickrob/myprog.c",line="73"@}
30028 @chapter @value{GDBN} Annotations
30030 This chapter describes annotations in @value{GDBN}. Annotations were
30031 designed to interface @value{GDBN} to graphical user interfaces or other
30032 similar programs which want to interact with @value{GDBN} at a
30033 relatively high level.
30035 The annotation mechanism has largely been superseded by @sc{gdb/mi}
30039 This is Edition @value{EDITION}, @value{DATE}.
30043 * Annotations Overview:: What annotations are; the general syntax.
30044 * Server Prefix:: Issuing a command without affecting user state.
30045 * Prompting:: Annotations marking @value{GDBN}'s need for input.
30046 * Errors:: Annotations for error messages.
30047 * Invalidation:: Some annotations describe things now invalid.
30048 * Annotations for Running::
30049 Whether the program is running, how it stopped, etc.
30050 * Source Annotations:: Annotations describing source code.
30053 @node Annotations Overview
30054 @section What is an Annotation?
30055 @cindex annotations
30057 Annotations start with a newline character, two @samp{control-z}
30058 characters, and the name of the annotation. If there is no additional
30059 information associated with this annotation, the name of the annotation
30060 is followed immediately by a newline. If there is additional
30061 information, the name of the annotation is followed by a space, the
30062 additional information, and a newline. The additional information
30063 cannot contain newline characters.
30065 Any output not beginning with a newline and two @samp{control-z}
30066 characters denotes literal output from @value{GDBN}. Currently there is
30067 no need for @value{GDBN} to output a newline followed by two
30068 @samp{control-z} characters, but if there was such a need, the
30069 annotations could be extended with an @samp{escape} annotation which
30070 means those three characters as output.
30072 The annotation @var{level}, which is specified using the
30073 @option{--annotate} command line option (@pxref{Mode Options}), controls
30074 how much information @value{GDBN} prints together with its prompt,
30075 values of expressions, source lines, and other types of output. Level 0
30076 is for no annotations, level 1 is for use when @value{GDBN} is run as a
30077 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
30078 for programs that control @value{GDBN}, and level 2 annotations have
30079 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
30080 Interface, annotate, GDB's Obsolete Annotations}).
30083 @kindex set annotate
30084 @item set annotate @var{level}
30085 The @value{GDBN} command @code{set annotate} sets the level of
30086 annotations to the specified @var{level}.
30088 @item show annotate
30089 @kindex show annotate
30090 Show the current annotation level.
30093 This chapter describes level 3 annotations.
30095 A simple example of starting up @value{GDBN} with annotations is:
30098 $ @kbd{gdb --annotate=3}
30100 Copyright 2003 Free Software Foundation, Inc.
30101 GDB is free software, covered by the GNU General Public License,
30102 and you are welcome to change it and/or distribute copies of it
30103 under certain conditions.
30104 Type "show copying" to see the conditions.
30105 There is absolutely no warranty for GDB. Type "show warranty"
30107 This GDB was configured as "i386-pc-linux-gnu"
30118 Here @samp{quit} is input to @value{GDBN}; the rest is output from
30119 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
30120 denotes a @samp{control-z} character) are annotations; the rest is
30121 output from @value{GDBN}.
30123 @node Server Prefix
30124 @section The Server Prefix
30125 @cindex server prefix
30127 If you prefix a command with @samp{server } then it will not affect
30128 the command history, nor will it affect @value{GDBN}'s notion of which
30129 command to repeat if @key{RET} is pressed on a line by itself. This
30130 means that commands can be run behind a user's back by a front-end in
30131 a transparent manner.
30133 The @code{server } prefix does not affect the recording of values into
30134 the value history; to print a value without recording it into the
30135 value history, use the @code{output} command instead of the
30136 @code{print} command.
30138 Using this prefix also disables confirmation requests
30139 (@pxref{confirmation requests}).
30142 @section Annotation for @value{GDBN} Input
30144 @cindex annotations for prompts
30145 When @value{GDBN} prompts for input, it annotates this fact so it is possible
30146 to know when to send output, when the output from a given command is
30149 Different kinds of input each have a different @dfn{input type}. Each
30150 input type has three annotations: a @code{pre-} annotation, which
30151 denotes the beginning of any prompt which is being output, a plain
30152 annotation, which denotes the end of the prompt, and then a @code{post-}
30153 annotation which denotes the end of any echo which may (or may not) be
30154 associated with the input. For example, the @code{prompt} input type
30155 features the following annotations:
30163 The input types are
30166 @findex pre-prompt annotation
30167 @findex prompt annotation
30168 @findex post-prompt annotation
30170 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
30172 @findex pre-commands annotation
30173 @findex commands annotation
30174 @findex post-commands annotation
30176 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
30177 command. The annotations are repeated for each command which is input.
30179 @findex pre-overload-choice annotation
30180 @findex overload-choice annotation
30181 @findex post-overload-choice annotation
30182 @item overload-choice
30183 When @value{GDBN} wants the user to select between various overloaded functions.
30185 @findex pre-query annotation
30186 @findex query annotation
30187 @findex post-query annotation
30189 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
30191 @findex pre-prompt-for-continue annotation
30192 @findex prompt-for-continue annotation
30193 @findex post-prompt-for-continue annotation
30194 @item prompt-for-continue
30195 When @value{GDBN} is asking the user to press return to continue. Note: Don't
30196 expect this to work well; instead use @code{set height 0} to disable
30197 prompting. This is because the counting of lines is buggy in the
30198 presence of annotations.
30203 @cindex annotations for errors, warnings and interrupts
30205 @findex quit annotation
30210 This annotation occurs right before @value{GDBN} responds to an interrupt.
30212 @findex error annotation
30217 This annotation occurs right before @value{GDBN} responds to an error.
30219 Quit and error annotations indicate that any annotations which @value{GDBN} was
30220 in the middle of may end abruptly. For example, if a
30221 @code{value-history-begin} annotation is followed by a @code{error}, one
30222 cannot expect to receive the matching @code{value-history-end}. One
30223 cannot expect not to receive it either, however; an error annotation
30224 does not necessarily mean that @value{GDBN} is immediately returning all the way
30227 @findex error-begin annotation
30228 A quit or error annotation may be preceded by
30234 Any output between that and the quit or error annotation is the error
30237 Warning messages are not yet annotated.
30238 @c If we want to change that, need to fix warning(), type_error(),
30239 @c range_error(), and possibly other places.
30242 @section Invalidation Notices
30244 @cindex annotations for invalidation messages
30245 The following annotations say that certain pieces of state may have
30249 @findex frames-invalid annotation
30250 @item ^Z^Zframes-invalid
30252 The frames (for example, output from the @code{backtrace} command) may
30255 @findex breakpoints-invalid annotation
30256 @item ^Z^Zbreakpoints-invalid
30258 The breakpoints may have changed. For example, the user just added or
30259 deleted a breakpoint.
30262 @node Annotations for Running
30263 @section Running the Program
30264 @cindex annotations for running programs
30266 @findex starting annotation
30267 @findex stopping annotation
30268 When the program starts executing due to a @value{GDBN} command such as
30269 @code{step} or @code{continue},
30275 is output. When the program stops,
30281 is output. Before the @code{stopped} annotation, a variety of
30282 annotations describe how the program stopped.
30285 @findex exited annotation
30286 @item ^Z^Zexited @var{exit-status}
30287 The program exited, and @var{exit-status} is the exit status (zero for
30288 successful exit, otherwise nonzero).
30290 @findex signalled annotation
30291 @findex signal-name annotation
30292 @findex signal-name-end annotation
30293 @findex signal-string annotation
30294 @findex signal-string-end annotation
30295 @item ^Z^Zsignalled
30296 The program exited with a signal. After the @code{^Z^Zsignalled}, the
30297 annotation continues:
30303 ^Z^Zsignal-name-end
30307 ^Z^Zsignal-string-end
30312 where @var{name} is the name of the signal, such as @code{SIGILL} or
30313 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
30314 as @code{Illegal Instruction} or @code{Segmentation fault}.
30315 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
30316 user's benefit and have no particular format.
30318 @findex signal annotation
30320 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
30321 just saying that the program received the signal, not that it was
30322 terminated with it.
30324 @findex breakpoint annotation
30325 @item ^Z^Zbreakpoint @var{number}
30326 The program hit breakpoint number @var{number}.
30328 @findex watchpoint annotation
30329 @item ^Z^Zwatchpoint @var{number}
30330 The program hit watchpoint number @var{number}.
30333 @node Source Annotations
30334 @section Displaying Source
30335 @cindex annotations for source display
30337 @findex source annotation
30338 The following annotation is used instead of displaying source code:
30341 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
30344 where @var{filename} is an absolute file name indicating which source
30345 file, @var{line} is the line number within that file (where 1 is the
30346 first line in the file), @var{character} is the character position
30347 within the file (where 0 is the first character in the file) (for most
30348 debug formats this will necessarily point to the beginning of a line),
30349 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
30350 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
30351 @var{addr} is the address in the target program associated with the
30352 source which is being displayed. @var{addr} is in the form @samp{0x}
30353 followed by one or more lowercase hex digits (note that this does not
30354 depend on the language).
30356 @node JIT Interface
30357 @chapter JIT Compilation Interface
30358 @cindex just-in-time compilation
30359 @cindex JIT compilation interface
30361 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
30362 interface. A JIT compiler is a program or library that generates native
30363 executable code at runtime and executes it, usually in order to achieve good
30364 performance while maintaining platform independence.
30366 Programs that use JIT compilation are normally difficult to debug because
30367 portions of their code are generated at runtime, instead of being loaded from
30368 object files, which is where @value{GDBN} normally finds the program's symbols
30369 and debug information. In order to debug programs that use JIT compilation,
30370 @value{GDBN} has an interface that allows the program to register in-memory
30371 symbol files with @value{GDBN} at runtime.
30373 If you are using @value{GDBN} to debug a program that uses this interface, then
30374 it should work transparently so long as you have not stripped the binary. If
30375 you are developing a JIT compiler, then the interface is documented in the rest
30376 of this chapter. At this time, the only known client of this interface is the
30379 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
30380 JIT compiler communicates with @value{GDBN} by writing data into a global
30381 variable and calling a fuction at a well-known symbol. When @value{GDBN}
30382 attaches, it reads a linked list of symbol files from the global variable to
30383 find existing code, and puts a breakpoint in the function so that it can find
30384 out about additional code.
30387 * Declarations:: Relevant C struct declarations
30388 * Registering Code:: Steps to register code
30389 * Unregistering Code:: Steps to unregister code
30393 @section JIT Declarations
30395 These are the relevant struct declarations that a C program should include to
30396 implement the interface:
30406 struct jit_code_entry
30408 struct jit_code_entry *next_entry;
30409 struct jit_code_entry *prev_entry;
30410 const char *symfile_addr;
30411 uint64_t symfile_size;
30414 struct jit_descriptor
30417 /* This type should be jit_actions_t, but we use uint32_t
30418 to be explicit about the bitwidth. */
30419 uint32_t action_flag;
30420 struct jit_code_entry *relevant_entry;
30421 struct jit_code_entry *first_entry;
30424 /* GDB puts a breakpoint in this function. */
30425 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
30427 /* Make sure to specify the version statically, because the
30428 debugger may check the version before we can set it. */
30429 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
30432 If the JIT is multi-threaded, then it is important that the JIT synchronize any
30433 modifications to this global data properly, which can easily be done by putting
30434 a global mutex around modifications to these structures.
30436 @node Registering Code
30437 @section Registering Code
30439 To register code with @value{GDBN}, the JIT should follow this protocol:
30443 Generate an object file in memory with symbols and other desired debug
30444 information. The file must include the virtual addresses of the sections.
30447 Create a code entry for the file, which gives the start and size of the symbol
30451 Add it to the linked list in the JIT descriptor.
30454 Point the relevant_entry field of the descriptor at the entry.
30457 Set @code{action_flag} to @code{JIT_REGISTER} and call
30458 @code{__jit_debug_register_code}.
30461 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
30462 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
30463 new code. However, the linked list must still be maintained in order to allow
30464 @value{GDBN} to attach to a running process and still find the symbol files.
30466 @node Unregistering Code
30467 @section Unregistering Code
30469 If code is freed, then the JIT should use the following protocol:
30473 Remove the code entry corresponding to the code from the linked list.
30476 Point the @code{relevant_entry} field of the descriptor at the code entry.
30479 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
30480 @code{__jit_debug_register_code}.
30483 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
30484 and the JIT will leak the memory used for the associated symbol files.
30487 @chapter Reporting Bugs in @value{GDBN}
30488 @cindex bugs in @value{GDBN}
30489 @cindex reporting bugs in @value{GDBN}
30491 Your bug reports play an essential role in making @value{GDBN} reliable.
30493 Reporting a bug may help you by bringing a solution to your problem, or it
30494 may not. But in any case the principal function of a bug report is to help
30495 the entire community by making the next version of @value{GDBN} work better. Bug
30496 reports are your contribution to the maintenance of @value{GDBN}.
30498 In order for a bug report to serve its purpose, you must include the
30499 information that enables us to fix the bug.
30502 * Bug Criteria:: Have you found a bug?
30503 * Bug Reporting:: How to report bugs
30507 @section Have You Found a Bug?
30508 @cindex bug criteria
30510 If you are not sure whether you have found a bug, here are some guidelines:
30513 @cindex fatal signal
30514 @cindex debugger crash
30515 @cindex crash of debugger
30517 If the debugger gets a fatal signal, for any input whatever, that is a
30518 @value{GDBN} bug. Reliable debuggers never crash.
30520 @cindex error on valid input
30522 If @value{GDBN} produces an error message for valid input, that is a
30523 bug. (Note that if you're cross debugging, the problem may also be
30524 somewhere in the connection to the target.)
30526 @cindex invalid input
30528 If @value{GDBN} does not produce an error message for invalid input,
30529 that is a bug. However, you should note that your idea of
30530 ``invalid input'' might be our idea of ``an extension'' or ``support
30531 for traditional practice''.
30534 If you are an experienced user of debugging tools, your suggestions
30535 for improvement of @value{GDBN} are welcome in any case.
30538 @node Bug Reporting
30539 @section How to Report Bugs
30540 @cindex bug reports
30541 @cindex @value{GDBN} bugs, reporting
30543 A number of companies and individuals offer support for @sc{gnu} products.
30544 If you obtained @value{GDBN} from a support organization, we recommend you
30545 contact that organization first.
30547 You can find contact information for many support companies and
30548 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
30550 @c should add a web page ref...
30553 @ifset BUGURL_DEFAULT
30554 In any event, we also recommend that you submit bug reports for
30555 @value{GDBN}. The preferred method is to submit them directly using
30556 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
30557 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
30560 @strong{Do not send bug reports to @samp{info-gdb}, or to
30561 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
30562 not want to receive bug reports. Those that do have arranged to receive
30565 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
30566 serves as a repeater. The mailing list and the newsgroup carry exactly
30567 the same messages. Often people think of posting bug reports to the
30568 newsgroup instead of mailing them. This appears to work, but it has one
30569 problem which can be crucial: a newsgroup posting often lacks a mail
30570 path back to the sender. Thus, if we need to ask for more information,
30571 we may be unable to reach you. For this reason, it is better to send
30572 bug reports to the mailing list.
30574 @ifclear BUGURL_DEFAULT
30575 In any event, we also recommend that you submit bug reports for
30576 @value{GDBN} to @value{BUGURL}.
30580 The fundamental principle of reporting bugs usefully is this:
30581 @strong{report all the facts}. If you are not sure whether to state a
30582 fact or leave it out, state it!
30584 Often people omit facts because they think they know what causes the
30585 problem and assume that some details do not matter. Thus, you might
30586 assume that the name of the variable you use in an example does not matter.
30587 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
30588 stray memory reference which happens to fetch from the location where that
30589 name is stored in memory; perhaps, if the name were different, the contents
30590 of that location would fool the debugger into doing the right thing despite
30591 the bug. Play it safe and give a specific, complete example. That is the
30592 easiest thing for you to do, and the most helpful.
30594 Keep in mind that the purpose of a bug report is to enable us to fix the
30595 bug. It may be that the bug has been reported previously, but neither
30596 you nor we can know that unless your bug report is complete and
30599 Sometimes people give a few sketchy facts and ask, ``Does this ring a
30600 bell?'' Those bug reports are useless, and we urge everyone to
30601 @emph{refuse to respond to them} except to chide the sender to report
30604 To enable us to fix the bug, you should include all these things:
30608 The version of @value{GDBN}. @value{GDBN} announces it if you start
30609 with no arguments; you can also print it at any time using @code{show
30612 Without this, we will not know whether there is any point in looking for
30613 the bug in the current version of @value{GDBN}.
30616 The type of machine you are using, and the operating system name and
30620 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
30621 ``@value{GCC}--2.8.1''.
30624 What compiler (and its version) was used to compile the program you are
30625 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
30626 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
30627 to get this information; for other compilers, see the documentation for
30631 The command arguments you gave the compiler to compile your example and
30632 observe the bug. For example, did you use @samp{-O}? To guarantee
30633 you will not omit something important, list them all. A copy of the
30634 Makefile (or the output from make) is sufficient.
30636 If we were to try to guess the arguments, we would probably guess wrong
30637 and then we might not encounter the bug.
30640 A complete input script, and all necessary source files, that will
30644 A description of what behavior you observe that you believe is
30645 incorrect. For example, ``It gets a fatal signal.''
30647 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
30648 will certainly notice it. But if the bug is incorrect output, we might
30649 not notice unless it is glaringly wrong. You might as well not give us
30650 a chance to make a mistake.
30652 Even if the problem you experience is a fatal signal, you should still
30653 say so explicitly. Suppose something strange is going on, such as, your
30654 copy of @value{GDBN} is out of synch, or you have encountered a bug in
30655 the C library on your system. (This has happened!) Your copy might
30656 crash and ours would not. If you told us to expect a crash, then when
30657 ours fails to crash, we would know that the bug was not happening for
30658 us. If you had not told us to expect a crash, then we would not be able
30659 to draw any conclusion from our observations.
30662 @cindex recording a session script
30663 To collect all this information, you can use a session recording program
30664 such as @command{script}, which is available on many Unix systems.
30665 Just run your @value{GDBN} session inside @command{script} and then
30666 include the @file{typescript} file with your bug report.
30668 Another way to record a @value{GDBN} session is to run @value{GDBN}
30669 inside Emacs and then save the entire buffer to a file.
30672 If you wish to suggest changes to the @value{GDBN} source, send us context
30673 diffs. If you even discuss something in the @value{GDBN} source, refer to
30674 it by context, not by line number.
30676 The line numbers in our development sources will not match those in your
30677 sources. Your line numbers would convey no useful information to us.
30681 Here are some things that are not necessary:
30685 A description of the envelope of the bug.
30687 Often people who encounter a bug spend a lot of time investigating
30688 which changes to the input file will make the bug go away and which
30689 changes will not affect it.
30691 This is often time consuming and not very useful, because the way we
30692 will find the bug is by running a single example under the debugger
30693 with breakpoints, not by pure deduction from a series of examples.
30694 We recommend that you save your time for something else.
30696 Of course, if you can find a simpler example to report @emph{instead}
30697 of the original one, that is a convenience for us. Errors in the
30698 output will be easier to spot, running under the debugger will take
30699 less time, and so on.
30701 However, simplification is not vital; if you do not want to do this,
30702 report the bug anyway and send us the entire test case you used.
30705 A patch for the bug.
30707 A patch for the bug does help us if it is a good one. But do not omit
30708 the necessary information, such as the test case, on the assumption that
30709 a patch is all we need. We might see problems with your patch and decide
30710 to fix the problem another way, or we might not understand it at all.
30712 Sometimes with a program as complicated as @value{GDBN} it is very hard to
30713 construct an example that will make the program follow a certain path
30714 through the code. If you do not send us the example, we will not be able
30715 to construct one, so we will not be able to verify that the bug is fixed.
30717 And if we cannot understand what bug you are trying to fix, or why your
30718 patch should be an improvement, we will not install it. A test case will
30719 help us to understand.
30722 A guess about what the bug is or what it depends on.
30724 Such guesses are usually wrong. Even we cannot guess right about such
30725 things without first using the debugger to find the facts.
30728 @c The readline documentation is distributed with the readline code
30729 @c and consists of the two following files:
30731 @c inc-hist.texinfo
30732 @c Use -I with makeinfo to point to the appropriate directory,
30733 @c environment var TEXINPUTS with TeX.
30734 @ifclear SYSTEM_READLINE
30735 @include rluser.texi
30736 @include inc-hist.texinfo
30740 @node Formatting Documentation
30741 @appendix Formatting Documentation
30743 @cindex @value{GDBN} reference card
30744 @cindex reference card
30745 The @value{GDBN} 4 release includes an already-formatted reference card, ready
30746 for printing with PostScript or Ghostscript, in the @file{gdb}
30747 subdirectory of the main source directory@footnote{In
30748 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
30749 release.}. If you can use PostScript or Ghostscript with your printer,
30750 you can print the reference card immediately with @file{refcard.ps}.
30752 The release also includes the source for the reference card. You
30753 can format it, using @TeX{}, by typing:
30759 The @value{GDBN} reference card is designed to print in @dfn{landscape}
30760 mode on US ``letter'' size paper;
30761 that is, on a sheet 11 inches wide by 8.5 inches
30762 high. You will need to specify this form of printing as an option to
30763 your @sc{dvi} output program.
30765 @cindex documentation
30767 All the documentation for @value{GDBN} comes as part of the machine-readable
30768 distribution. The documentation is written in Texinfo format, which is
30769 a documentation system that uses a single source file to produce both
30770 on-line information and a printed manual. You can use one of the Info
30771 formatting commands to create the on-line version of the documentation
30772 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
30774 @value{GDBN} includes an already formatted copy of the on-line Info
30775 version of this manual in the @file{gdb} subdirectory. The main Info
30776 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
30777 subordinate files matching @samp{gdb.info*} in the same directory. If
30778 necessary, you can print out these files, or read them with any editor;
30779 but they are easier to read using the @code{info} subsystem in @sc{gnu}
30780 Emacs or the standalone @code{info} program, available as part of the
30781 @sc{gnu} Texinfo distribution.
30783 If you want to format these Info files yourself, you need one of the
30784 Info formatting programs, such as @code{texinfo-format-buffer} or
30787 If you have @code{makeinfo} installed, and are in the top level
30788 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
30789 version @value{GDBVN}), you can make the Info file by typing:
30796 If you want to typeset and print copies of this manual, you need @TeX{},
30797 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
30798 Texinfo definitions file.
30800 @TeX{} is a typesetting program; it does not print files directly, but
30801 produces output files called @sc{dvi} files. To print a typeset
30802 document, you need a program to print @sc{dvi} files. If your system
30803 has @TeX{} installed, chances are it has such a program. The precise
30804 command to use depends on your system; @kbd{lpr -d} is common; another
30805 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
30806 require a file name without any extension or a @samp{.dvi} extension.
30808 @TeX{} also requires a macro definitions file called
30809 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
30810 written in Texinfo format. On its own, @TeX{} cannot either read or
30811 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
30812 and is located in the @file{gdb-@var{version-number}/texinfo}
30815 If you have @TeX{} and a @sc{dvi} printer program installed, you can
30816 typeset and print this manual. First switch to the @file{gdb}
30817 subdirectory of the main source directory (for example, to
30818 @file{gdb-@value{GDBVN}/gdb}) and type:
30824 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
30826 @node Installing GDB
30827 @appendix Installing @value{GDBN}
30828 @cindex installation
30831 * Requirements:: Requirements for building @value{GDBN}
30832 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
30833 * Separate Objdir:: Compiling @value{GDBN} in another directory
30834 * Config Names:: Specifying names for hosts and targets
30835 * Configure Options:: Summary of options for configure
30836 * System-wide configuration:: Having a system-wide init file
30840 @section Requirements for Building @value{GDBN}
30841 @cindex building @value{GDBN}, requirements for
30843 Building @value{GDBN} requires various tools and packages to be available.
30844 Other packages will be used only if they are found.
30846 @heading Tools/Packages Necessary for Building @value{GDBN}
30848 @item ISO C90 compiler
30849 @value{GDBN} is written in ISO C90. It should be buildable with any
30850 working C90 compiler, e.g.@: GCC.
30854 @heading Tools/Packages Optional for Building @value{GDBN}
30858 @value{GDBN} can use the Expat XML parsing library. This library may be
30859 included with your operating system distribution; if it is not, you
30860 can get the latest version from @url{http://expat.sourceforge.net}.
30861 The @file{configure} script will search for this library in several
30862 standard locations; if it is installed in an unusual path, you can
30863 use the @option{--with-libexpat-prefix} option to specify its location.
30869 Remote protocol memory maps (@pxref{Memory Map Format})
30871 Target descriptions (@pxref{Target Descriptions})
30873 Remote shared library lists (@pxref{Library List Format})
30875 MS-Windows shared libraries (@pxref{Shared Libraries})
30877 Traceframe info (@pxref{Traceframe Info Format})
30881 @cindex compressed debug sections
30882 @value{GDBN} will use the @samp{zlib} library, if available, to read
30883 compressed debug sections. Some linkers, such as GNU gold, are capable
30884 of producing binaries with compressed debug sections. If @value{GDBN}
30885 is compiled with @samp{zlib}, it will be able to read the debug
30886 information in such binaries.
30888 The @samp{zlib} library is likely included with your operating system
30889 distribution; if it is not, you can get the latest version from
30890 @url{http://zlib.net}.
30893 @value{GDBN}'s features related to character sets (@pxref{Character
30894 Sets}) require a functioning @code{iconv} implementation. If you are
30895 on a GNU system, then this is provided by the GNU C Library. Some
30896 other systems also provide a working @code{iconv}.
30898 On systems with @code{iconv}, you can install GNU Libiconv. If you
30899 have previously installed Libiconv, you can use the
30900 @option{--with-libiconv-prefix} option to configure.
30902 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
30903 arrange to build Libiconv if a directory named @file{libiconv} appears
30904 in the top-most source directory. If Libiconv is built this way, and
30905 if the operating system does not provide a suitable @code{iconv}
30906 implementation, then the just-built library will automatically be used
30907 by @value{GDBN}. One easy way to set this up is to download GNU
30908 Libiconv, unpack it, and then rename the directory holding the
30909 Libiconv source code to @samp{libiconv}.
30912 @node Running Configure
30913 @section Invoking the @value{GDBN} @file{configure} Script
30914 @cindex configuring @value{GDBN}
30915 @value{GDBN} comes with a @file{configure} script that automates the process
30916 of preparing @value{GDBN} for installation; you can then use @code{make} to
30917 build the @code{gdb} program.
30919 @c irrelevant in info file; it's as current as the code it lives with.
30920 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
30921 look at the @file{README} file in the sources; we may have improved the
30922 installation procedures since publishing this manual.}
30925 The @value{GDBN} distribution includes all the source code you need for
30926 @value{GDBN} in a single directory, whose name is usually composed by
30927 appending the version number to @samp{gdb}.
30929 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
30930 @file{gdb-@value{GDBVN}} directory. That directory contains:
30933 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
30934 script for configuring @value{GDBN} and all its supporting libraries
30936 @item gdb-@value{GDBVN}/gdb
30937 the source specific to @value{GDBN} itself
30939 @item gdb-@value{GDBVN}/bfd
30940 source for the Binary File Descriptor library
30942 @item gdb-@value{GDBVN}/include
30943 @sc{gnu} include files
30945 @item gdb-@value{GDBVN}/libiberty
30946 source for the @samp{-liberty} free software library
30948 @item gdb-@value{GDBVN}/opcodes
30949 source for the library of opcode tables and disassemblers
30951 @item gdb-@value{GDBVN}/readline
30952 source for the @sc{gnu} command-line interface
30954 @item gdb-@value{GDBVN}/glob
30955 source for the @sc{gnu} filename pattern-matching subroutine
30957 @item gdb-@value{GDBVN}/mmalloc
30958 source for the @sc{gnu} memory-mapped malloc package
30961 The simplest way to configure and build @value{GDBN} is to run @file{configure}
30962 from the @file{gdb-@var{version-number}} source directory, which in
30963 this example is the @file{gdb-@value{GDBVN}} directory.
30965 First switch to the @file{gdb-@var{version-number}} source directory
30966 if you are not already in it; then run @file{configure}. Pass the
30967 identifier for the platform on which @value{GDBN} will run as an
30973 cd gdb-@value{GDBVN}
30974 ./configure @var{host}
30979 where @var{host} is an identifier such as @samp{sun4} or
30980 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
30981 (You can often leave off @var{host}; @file{configure} tries to guess the
30982 correct value by examining your system.)
30984 Running @samp{configure @var{host}} and then running @code{make} builds the
30985 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
30986 libraries, then @code{gdb} itself. The configured source files, and the
30987 binaries, are left in the corresponding source directories.
30990 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
30991 system does not recognize this automatically when you run a different
30992 shell, you may need to run @code{sh} on it explicitly:
30995 sh configure @var{host}
30998 If you run @file{configure} from a directory that contains source
30999 directories for multiple libraries or programs, such as the
31000 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
31002 creates configuration files for every directory level underneath (unless
31003 you tell it not to, with the @samp{--norecursion} option).
31005 You should run the @file{configure} script from the top directory in the
31006 source tree, the @file{gdb-@var{version-number}} directory. If you run
31007 @file{configure} from one of the subdirectories, you will configure only
31008 that subdirectory. That is usually not what you want. In particular,
31009 if you run the first @file{configure} from the @file{gdb} subdirectory
31010 of the @file{gdb-@var{version-number}} directory, you will omit the
31011 configuration of @file{bfd}, @file{readline}, and other sibling
31012 directories of the @file{gdb} subdirectory. This leads to build errors
31013 about missing include files such as @file{bfd/bfd.h}.
31015 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
31016 However, you should make sure that the shell on your path (named by
31017 the @samp{SHELL} environment variable) is publicly readable. Remember
31018 that @value{GDBN} uses the shell to start your program---some systems refuse to
31019 let @value{GDBN} debug child processes whose programs are not readable.
31021 @node Separate Objdir
31022 @section Compiling @value{GDBN} in Another Directory
31024 If you want to run @value{GDBN} versions for several host or target machines,
31025 you need a different @code{gdb} compiled for each combination of
31026 host and target. @file{configure} is designed to make this easy by
31027 allowing you to generate each configuration in a separate subdirectory,
31028 rather than in the source directory. If your @code{make} program
31029 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
31030 @code{make} in each of these directories builds the @code{gdb}
31031 program specified there.
31033 To build @code{gdb} in a separate directory, run @file{configure}
31034 with the @samp{--srcdir} option to specify where to find the source.
31035 (You also need to specify a path to find @file{configure}
31036 itself from your working directory. If the path to @file{configure}
31037 would be the same as the argument to @samp{--srcdir}, you can leave out
31038 the @samp{--srcdir} option; it is assumed.)
31040 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
31041 separate directory for a Sun 4 like this:
31045 cd gdb-@value{GDBVN}
31048 ../gdb-@value{GDBVN}/configure sun4
31053 When @file{configure} builds a configuration using a remote source
31054 directory, it creates a tree for the binaries with the same structure
31055 (and using the same names) as the tree under the source directory. In
31056 the example, you'd find the Sun 4 library @file{libiberty.a} in the
31057 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
31058 @file{gdb-sun4/gdb}.
31060 Make sure that your path to the @file{configure} script has just one
31061 instance of @file{gdb} in it. If your path to @file{configure} looks
31062 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
31063 one subdirectory of @value{GDBN}, not the whole package. This leads to
31064 build errors about missing include files such as @file{bfd/bfd.h}.
31066 One popular reason to build several @value{GDBN} configurations in separate
31067 directories is to configure @value{GDBN} for cross-compiling (where
31068 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
31069 programs that run on another machine---the @dfn{target}).
31070 You specify a cross-debugging target by
31071 giving the @samp{--target=@var{target}} option to @file{configure}.
31073 When you run @code{make} to build a program or library, you must run
31074 it in a configured directory---whatever directory you were in when you
31075 called @file{configure} (or one of its subdirectories).
31077 The @code{Makefile} that @file{configure} generates in each source
31078 directory also runs recursively. If you type @code{make} in a source
31079 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
31080 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
31081 will build all the required libraries, and then build GDB.
31083 When you have multiple hosts or targets configured in separate
31084 directories, you can run @code{make} on them in parallel (for example,
31085 if they are NFS-mounted on each of the hosts); they will not interfere
31089 @section Specifying Names for Hosts and Targets
31091 The specifications used for hosts and targets in the @file{configure}
31092 script are based on a three-part naming scheme, but some short predefined
31093 aliases are also supported. The full naming scheme encodes three pieces
31094 of information in the following pattern:
31097 @var{architecture}-@var{vendor}-@var{os}
31100 For example, you can use the alias @code{sun4} as a @var{host} argument,
31101 or as the value for @var{target} in a @code{--target=@var{target}}
31102 option. The equivalent full name is @samp{sparc-sun-sunos4}.
31104 The @file{configure} script accompanying @value{GDBN} does not provide
31105 any query facility to list all supported host and target names or
31106 aliases. @file{configure} calls the Bourne shell script
31107 @code{config.sub} to map abbreviations to full names; you can read the
31108 script, if you wish, or you can use it to test your guesses on
31109 abbreviations---for example:
31112 % sh config.sub i386-linux
31114 % sh config.sub alpha-linux
31115 alpha-unknown-linux-gnu
31116 % sh config.sub hp9k700
31118 % sh config.sub sun4
31119 sparc-sun-sunos4.1.1
31120 % sh config.sub sun3
31121 m68k-sun-sunos4.1.1
31122 % sh config.sub i986v
31123 Invalid configuration `i986v': machine `i986v' not recognized
31127 @code{config.sub} is also distributed in the @value{GDBN} source
31128 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
31130 @node Configure Options
31131 @section @file{configure} Options
31133 Here is a summary of the @file{configure} options and arguments that
31134 are most often useful for building @value{GDBN}. @file{configure} also has
31135 several other options not listed here. @inforef{What Configure
31136 Does,,configure.info}, for a full explanation of @file{configure}.
31139 configure @r{[}--help@r{]}
31140 @r{[}--prefix=@var{dir}@r{]}
31141 @r{[}--exec-prefix=@var{dir}@r{]}
31142 @r{[}--srcdir=@var{dirname}@r{]}
31143 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
31144 @r{[}--target=@var{target}@r{]}
31149 You may introduce options with a single @samp{-} rather than
31150 @samp{--} if you prefer; but you may abbreviate option names if you use
31155 Display a quick summary of how to invoke @file{configure}.
31157 @item --prefix=@var{dir}
31158 Configure the source to install programs and files under directory
31161 @item --exec-prefix=@var{dir}
31162 Configure the source to install programs under directory
31165 @c avoid splitting the warning from the explanation:
31167 @item --srcdir=@var{dirname}
31168 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
31169 @code{make} that implements the @code{VPATH} feature.}@*
31170 Use this option to make configurations in directories separate from the
31171 @value{GDBN} source directories. Among other things, you can use this to
31172 build (or maintain) several configurations simultaneously, in separate
31173 directories. @file{configure} writes configuration-specific files in
31174 the current directory, but arranges for them to use the source in the
31175 directory @var{dirname}. @file{configure} creates directories under
31176 the working directory in parallel to the source directories below
31179 @item --norecursion
31180 Configure only the directory level where @file{configure} is executed; do not
31181 propagate configuration to subdirectories.
31183 @item --target=@var{target}
31184 Configure @value{GDBN} for cross-debugging programs running on the specified
31185 @var{target}. Without this option, @value{GDBN} is configured to debug
31186 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
31188 There is no convenient way to generate a list of all available targets.
31190 @item @var{host} @dots{}
31191 Configure @value{GDBN} to run on the specified @var{host}.
31193 There is no convenient way to generate a list of all available hosts.
31196 There are many other options available as well, but they are generally
31197 needed for special purposes only.
31199 @node System-wide configuration
31200 @section System-wide configuration and settings
31201 @cindex system-wide init file
31203 @value{GDBN} can be configured to have a system-wide init file;
31204 this file will be read and executed at startup (@pxref{Startup, , What
31205 @value{GDBN} does during startup}).
31207 Here is the corresponding configure option:
31210 @item --with-system-gdbinit=@var{file}
31211 Specify that the default location of the system-wide init file is
31215 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
31216 it may be subject to relocation. Two possible cases:
31220 If the default location of this init file contains @file{$prefix},
31221 it will be subject to relocation. Suppose that the configure options
31222 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
31223 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
31224 init file is looked for as @file{$install/etc/gdbinit} instead of
31225 @file{$prefix/etc/gdbinit}.
31228 By contrast, if the default location does not contain the prefix,
31229 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
31230 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
31231 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
31232 wherever @value{GDBN} is installed.
31235 @node Maintenance Commands
31236 @appendix Maintenance Commands
31237 @cindex maintenance commands
31238 @cindex internal commands
31240 In addition to commands intended for @value{GDBN} users, @value{GDBN}
31241 includes a number of commands intended for @value{GDBN} developers,
31242 that are not documented elsewhere in this manual. These commands are
31243 provided here for reference. (For commands that turn on debugging
31244 messages, see @ref{Debugging Output}.)
31247 @kindex maint agent
31248 @kindex maint agent-eval
31249 @item maint agent @var{expression}
31250 @itemx maint agent-eval @var{expression}
31251 Translate the given @var{expression} into remote agent bytecodes.
31252 This command is useful for debugging the Agent Expression mechanism
31253 (@pxref{Agent Expressions}). The @samp{agent} version produces an
31254 expression useful for data collection, such as by tracepoints, while
31255 @samp{maint agent-eval} produces an expression that evaluates directly
31256 to a result. For instance, a collection expression for @code{globa +
31257 globb} will include bytecodes to record four bytes of memory at each
31258 of the addresses of @code{globa} and @code{globb}, while discarding
31259 the result of the addition, while an evaluation expression will do the
31260 addition and return the sum.
31262 @kindex maint info breakpoints
31263 @item @anchor{maint info breakpoints}maint info breakpoints
31264 Using the same format as @samp{info breakpoints}, display both the
31265 breakpoints you've set explicitly, and those @value{GDBN} is using for
31266 internal purposes. Internal breakpoints are shown with negative
31267 breakpoint numbers. The type column identifies what kind of breakpoint
31272 Normal, explicitly set breakpoint.
31275 Normal, explicitly set watchpoint.
31278 Internal breakpoint, used to handle correctly stepping through
31279 @code{longjmp} calls.
31281 @item longjmp resume
31282 Internal breakpoint at the target of a @code{longjmp}.
31285 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
31288 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
31291 Shared library events.
31295 @kindex set displaced-stepping
31296 @kindex show displaced-stepping
31297 @cindex displaced stepping support
31298 @cindex out-of-line single-stepping
31299 @item set displaced-stepping
31300 @itemx show displaced-stepping
31301 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
31302 if the target supports it. Displaced stepping is a way to single-step
31303 over breakpoints without removing them from the inferior, by executing
31304 an out-of-line copy of the instruction that was originally at the
31305 breakpoint location. It is also known as out-of-line single-stepping.
31308 @item set displaced-stepping on
31309 If the target architecture supports it, @value{GDBN} will use
31310 displaced stepping to step over breakpoints.
31312 @item set displaced-stepping off
31313 @value{GDBN} will not use displaced stepping to step over breakpoints,
31314 even if such is supported by the target architecture.
31316 @cindex non-stop mode, and @samp{set displaced-stepping}
31317 @item set displaced-stepping auto
31318 This is the default mode. @value{GDBN} will use displaced stepping
31319 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
31320 architecture supports displaced stepping.
31323 @kindex maint check-symtabs
31324 @item maint check-symtabs
31325 Check the consistency of psymtabs and symtabs.
31327 @kindex maint cplus first_component
31328 @item maint cplus first_component @var{name}
31329 Print the first C@t{++} class/namespace component of @var{name}.
31331 @kindex maint cplus namespace
31332 @item maint cplus namespace
31333 Print the list of possible C@t{++} namespaces.
31335 @kindex maint demangle
31336 @item maint demangle @var{name}
31337 Demangle a C@t{++} or Objective-C mangled @var{name}.
31339 @kindex maint deprecate
31340 @kindex maint undeprecate
31341 @cindex deprecated commands
31342 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
31343 @itemx maint undeprecate @var{command}
31344 Deprecate or undeprecate the named @var{command}. Deprecated commands
31345 cause @value{GDBN} to issue a warning when you use them. The optional
31346 argument @var{replacement} says which newer command should be used in
31347 favor of the deprecated one; if it is given, @value{GDBN} will mention
31348 the replacement as part of the warning.
31350 @kindex maint dump-me
31351 @item maint dump-me
31352 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
31353 Cause a fatal signal in the debugger and force it to dump its core.
31354 This is supported only on systems which support aborting a program
31355 with the @code{SIGQUIT} signal.
31357 @kindex maint internal-error
31358 @kindex maint internal-warning
31359 @item maint internal-error @r{[}@var{message-text}@r{]}
31360 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
31361 Cause @value{GDBN} to call the internal function @code{internal_error}
31362 or @code{internal_warning} and hence behave as though an internal error
31363 or internal warning has been detected. In addition to reporting the
31364 internal problem, these functions give the user the opportunity to
31365 either quit @value{GDBN} or create a core file of the current
31366 @value{GDBN} session.
31368 These commands take an optional parameter @var{message-text} that is
31369 used as the text of the error or warning message.
31371 Here's an example of using @code{internal-error}:
31374 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
31375 @dots{}/maint.c:121: internal-error: testing, 1, 2
31376 A problem internal to GDB has been detected. Further
31377 debugging may prove unreliable.
31378 Quit this debugging session? (y or n) @kbd{n}
31379 Create a core file? (y or n) @kbd{n}
31383 @cindex @value{GDBN} internal error
31384 @cindex internal errors, control of @value{GDBN} behavior
31386 @kindex maint set internal-error
31387 @kindex maint show internal-error
31388 @kindex maint set internal-warning
31389 @kindex maint show internal-warning
31390 @item maint set internal-error @var{action} [ask|yes|no]
31391 @itemx maint show internal-error @var{action}
31392 @itemx maint set internal-warning @var{action} [ask|yes|no]
31393 @itemx maint show internal-warning @var{action}
31394 When @value{GDBN} reports an internal problem (error or warning) it
31395 gives the user the opportunity to both quit @value{GDBN} and create a
31396 core file of the current @value{GDBN} session. These commands let you
31397 override the default behaviour for each particular @var{action},
31398 described in the table below.
31402 You can specify that @value{GDBN} should always (yes) or never (no)
31403 quit. The default is to ask the user what to do.
31406 You can specify that @value{GDBN} should always (yes) or never (no)
31407 create a core file. The default is to ask the user what to do.
31410 @kindex maint packet
31411 @item maint packet @var{text}
31412 If @value{GDBN} is talking to an inferior via the serial protocol,
31413 then this command sends the string @var{text} to the inferior, and
31414 displays the response packet. @value{GDBN} supplies the initial
31415 @samp{$} character, the terminating @samp{#} character, and the
31418 @kindex maint print architecture
31419 @item maint print architecture @r{[}@var{file}@r{]}
31420 Print the entire architecture configuration. The optional argument
31421 @var{file} names the file where the output goes.
31423 @kindex maint print c-tdesc
31424 @item maint print c-tdesc
31425 Print the current target description (@pxref{Target Descriptions}) as
31426 a C source file. The created source file can be used in @value{GDBN}
31427 when an XML parser is not available to parse the description.
31429 @kindex maint print dummy-frames
31430 @item maint print dummy-frames
31431 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
31434 (@value{GDBP}) @kbd{b add}
31436 (@value{GDBP}) @kbd{print add(2,3)}
31437 Breakpoint 2, add (a=2, b=3) at @dots{}
31439 The program being debugged stopped while in a function called from GDB.
31441 (@value{GDBP}) @kbd{maint print dummy-frames}
31442 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
31443 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
31444 call_lo=0x01014000 call_hi=0x01014001
31448 Takes an optional file parameter.
31450 @kindex maint print registers
31451 @kindex maint print raw-registers
31452 @kindex maint print cooked-registers
31453 @kindex maint print register-groups
31454 @item maint print registers @r{[}@var{file}@r{]}
31455 @itemx maint print raw-registers @r{[}@var{file}@r{]}
31456 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
31457 @itemx maint print register-groups @r{[}@var{file}@r{]}
31458 Print @value{GDBN}'s internal register data structures.
31460 The command @code{maint print raw-registers} includes the contents of
31461 the raw register cache; the command @code{maint print cooked-registers}
31462 includes the (cooked) value of all registers, including registers which
31463 aren't available on the target nor visible to user; and the
31464 command @code{maint print register-groups} includes the groups that each
31465 register is a member of. @xref{Registers,, Registers, gdbint,
31466 @value{GDBN} Internals}.
31468 These commands take an optional parameter, a file name to which to
31469 write the information.
31471 @kindex maint print reggroups
31472 @item maint print reggroups @r{[}@var{file}@r{]}
31473 Print @value{GDBN}'s internal register group data structures. The
31474 optional argument @var{file} tells to what file to write the
31477 The register groups info looks like this:
31480 (@value{GDBP}) @kbd{maint print reggroups}
31493 This command forces @value{GDBN} to flush its internal register cache.
31495 @kindex maint print objfiles
31496 @cindex info for known object files
31497 @item maint print objfiles
31498 Print a dump of all known object files. For each object file, this
31499 command prints its name, address in memory, and all of its psymtabs
31502 @kindex maint print section-scripts
31503 @cindex info for known .debug_gdb_scripts-loaded scripts
31504 @item maint print section-scripts [@var{regexp}]
31505 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
31506 If @var{regexp} is specified, only print scripts loaded by object files
31507 matching @var{regexp}.
31508 For each script, this command prints its name as specified in the objfile,
31509 and the full path if known.
31510 @xref{.debug_gdb_scripts section}.
31512 @kindex maint print statistics
31513 @cindex bcache statistics
31514 @item maint print statistics
31515 This command prints, for each object file in the program, various data
31516 about that object file followed by the byte cache (@dfn{bcache})
31517 statistics for the object file. The objfile data includes the number
31518 of minimal, partial, full, and stabs symbols, the number of types
31519 defined by the objfile, the number of as yet unexpanded psym tables,
31520 the number of line tables and string tables, and the amount of memory
31521 used by the various tables. The bcache statistics include the counts,
31522 sizes, and counts of duplicates of all and unique objects, max,
31523 average, and median entry size, total memory used and its overhead and
31524 savings, and various measures of the hash table size and chain
31527 @kindex maint print target-stack
31528 @cindex target stack description
31529 @item maint print target-stack
31530 A @dfn{target} is an interface between the debugger and a particular
31531 kind of file or process. Targets can be stacked in @dfn{strata},
31532 so that more than one target can potentially respond to a request.
31533 In particular, memory accesses will walk down the stack of targets
31534 until they find a target that is interested in handling that particular
31537 This command prints a short description of each layer that was pushed on
31538 the @dfn{target stack}, starting from the top layer down to the bottom one.
31540 @kindex maint print type
31541 @cindex type chain of a data type
31542 @item maint print type @var{expr}
31543 Print the type chain for a type specified by @var{expr}. The argument
31544 can be either a type name or a symbol. If it is a symbol, the type of
31545 that symbol is described. The type chain produced by this command is
31546 a recursive definition of the data type as stored in @value{GDBN}'s
31547 data structures, including its flags and contained types.
31549 @kindex maint set dwarf2 always-disassemble
31550 @kindex maint show dwarf2 always-disassemble
31551 @item maint set dwarf2 always-disassemble
31552 @item maint show dwarf2 always-disassemble
31553 Control the behavior of @code{info address} when using DWARF debugging
31556 The default is @code{off}, which means that @value{GDBN} should try to
31557 describe a variable's location in an easily readable format. When
31558 @code{on}, @value{GDBN} will instead display the DWARF location
31559 expression in an assembly-like format. Note that some locations are
31560 too complex for @value{GDBN} to describe simply; in this case you will
31561 always see the disassembly form.
31563 Here is an example of the resulting disassembly:
31566 (gdb) info addr argc
31567 Symbol "argc" is a complex DWARF expression:
31571 For more information on these expressions, see
31572 @uref{http://www.dwarfstd.org/, the DWARF standard}.
31574 @kindex maint set dwarf2 max-cache-age
31575 @kindex maint show dwarf2 max-cache-age
31576 @item maint set dwarf2 max-cache-age
31577 @itemx maint show dwarf2 max-cache-age
31578 Control the DWARF 2 compilation unit cache.
31580 @cindex DWARF 2 compilation units cache
31581 In object files with inter-compilation-unit references, such as those
31582 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
31583 reader needs to frequently refer to previously read compilation units.
31584 This setting controls how long a compilation unit will remain in the
31585 cache if it is not referenced. A higher limit means that cached
31586 compilation units will be stored in memory longer, and more total
31587 memory will be used. Setting it to zero disables caching, which will
31588 slow down @value{GDBN} startup, but reduce memory consumption.
31590 @kindex maint set profile
31591 @kindex maint show profile
31592 @cindex profiling GDB
31593 @item maint set profile
31594 @itemx maint show profile
31595 Control profiling of @value{GDBN}.
31597 Profiling will be disabled until you use the @samp{maint set profile}
31598 command to enable it. When you enable profiling, the system will begin
31599 collecting timing and execution count data; when you disable profiling or
31600 exit @value{GDBN}, the results will be written to a log file. Remember that
31601 if you use profiling, @value{GDBN} will overwrite the profiling log file
31602 (often called @file{gmon.out}). If you have a record of important profiling
31603 data in a @file{gmon.out} file, be sure to move it to a safe location.
31605 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
31606 compiled with the @samp{-pg} compiler option.
31608 @kindex maint set show-debug-regs
31609 @kindex maint show show-debug-regs
31610 @cindex hardware debug registers
31611 @item maint set show-debug-regs
31612 @itemx maint show show-debug-regs
31613 Control whether to show variables that mirror the hardware debug
31614 registers. Use @code{ON} to enable, @code{OFF} to disable. If
31615 enabled, the debug registers values are shown when @value{GDBN} inserts or
31616 removes a hardware breakpoint or watchpoint, and when the inferior
31617 triggers a hardware-assisted breakpoint or watchpoint.
31619 @kindex maint set show-all-tib
31620 @kindex maint show show-all-tib
31621 @item maint set show-all-tib
31622 @itemx maint show show-all-tib
31623 Control whether to show all non zero areas within a 1k block starting
31624 at thread local base, when using the @samp{info w32 thread-information-block}
31627 @kindex maint space
31628 @cindex memory used by commands
31630 Control whether to display memory usage for each command. If set to a
31631 nonzero value, @value{GDBN} will display how much memory each command
31632 took, following the command's own output. This can also be requested
31633 by invoking @value{GDBN} with the @option{--statistics} command-line
31634 switch (@pxref{Mode Options}).
31637 @cindex time of command execution
31639 Control whether to display the execution time for each command. If
31640 set to a nonzero value, @value{GDBN} will display how much time it
31641 took to execute each command, following the command's own output.
31642 The time is not printed for the commands that run the target, since
31643 there's no mechanism currently to compute how much time was spend
31644 by @value{GDBN} and how much time was spend by the program been debugged.
31645 it's not possibly currently
31646 This can also be requested by invoking @value{GDBN} with the
31647 @option{--statistics} command-line switch (@pxref{Mode Options}).
31649 @kindex maint translate-address
31650 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
31651 Find the symbol stored at the location specified by the address
31652 @var{addr} and an optional section name @var{section}. If found,
31653 @value{GDBN} prints the name of the closest symbol and an offset from
31654 the symbol's location to the specified address. This is similar to
31655 the @code{info address} command (@pxref{Symbols}), except that this
31656 command also allows to find symbols in other sections.
31658 If section was not specified, the section in which the symbol was found
31659 is also printed. For dynamically linked executables, the name of
31660 executable or shared library containing the symbol is printed as well.
31664 The following command is useful for non-interactive invocations of
31665 @value{GDBN}, such as in the test suite.
31668 @item set watchdog @var{nsec}
31669 @kindex set watchdog
31670 @cindex watchdog timer
31671 @cindex timeout for commands
31672 Set the maximum number of seconds @value{GDBN} will wait for the
31673 target operation to finish. If this time expires, @value{GDBN}
31674 reports and error and the command is aborted.
31676 @item show watchdog
31677 Show the current setting of the target wait timeout.
31680 @node Remote Protocol
31681 @appendix @value{GDBN} Remote Serial Protocol
31686 * Stop Reply Packets::
31687 * General Query Packets::
31688 * Architecture-Specific Protocol Details::
31689 * Tracepoint Packets::
31690 * Host I/O Packets::
31692 * Notification Packets::
31693 * Remote Non-Stop::
31694 * Packet Acknowledgment::
31696 * File-I/O Remote Protocol Extension::
31697 * Library List Format::
31698 * Memory Map Format::
31699 * Thread List Format::
31700 * Traceframe Info Format::
31706 There may be occasions when you need to know something about the
31707 protocol---for example, if there is only one serial port to your target
31708 machine, you might want your program to do something special if it
31709 recognizes a packet meant for @value{GDBN}.
31711 In the examples below, @samp{->} and @samp{<-} are used to indicate
31712 transmitted and received data, respectively.
31714 @cindex protocol, @value{GDBN} remote serial
31715 @cindex serial protocol, @value{GDBN} remote
31716 @cindex remote serial protocol
31717 All @value{GDBN} commands and responses (other than acknowledgments
31718 and notifications, see @ref{Notification Packets}) are sent as a
31719 @var{packet}. A @var{packet} is introduced with the character
31720 @samp{$}, the actual @var{packet-data}, and the terminating character
31721 @samp{#} followed by a two-digit @var{checksum}:
31724 @code{$}@var{packet-data}@code{#}@var{checksum}
31728 @cindex checksum, for @value{GDBN} remote
31730 The two-digit @var{checksum} is computed as the modulo 256 sum of all
31731 characters between the leading @samp{$} and the trailing @samp{#} (an
31732 eight bit unsigned checksum).
31734 Implementors should note that prior to @value{GDBN} 5.0 the protocol
31735 specification also included an optional two-digit @var{sequence-id}:
31738 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
31741 @cindex sequence-id, for @value{GDBN} remote
31743 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
31744 has never output @var{sequence-id}s. Stubs that handle packets added
31745 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
31747 When either the host or the target machine receives a packet, the first
31748 response expected is an acknowledgment: either @samp{+} (to indicate
31749 the package was received correctly) or @samp{-} (to request
31753 -> @code{$}@var{packet-data}@code{#}@var{checksum}
31758 The @samp{+}/@samp{-} acknowledgments can be disabled
31759 once a connection is established.
31760 @xref{Packet Acknowledgment}, for details.
31762 The host (@value{GDBN}) sends @var{command}s, and the target (the
31763 debugging stub incorporated in your program) sends a @var{response}. In
31764 the case of step and continue @var{command}s, the response is only sent
31765 when the operation has completed, and the target has again stopped all
31766 threads in all attached processes. This is the default all-stop mode
31767 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
31768 execution mode; see @ref{Remote Non-Stop}, for details.
31770 @var{packet-data} consists of a sequence of characters with the
31771 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
31774 @cindex remote protocol, field separator
31775 Fields within the packet should be separated using @samp{,} @samp{;} or
31776 @samp{:}. Except where otherwise noted all numbers are represented in
31777 @sc{hex} with leading zeros suppressed.
31779 Implementors should note that prior to @value{GDBN} 5.0, the character
31780 @samp{:} could not appear as the third character in a packet (as it
31781 would potentially conflict with the @var{sequence-id}).
31783 @cindex remote protocol, binary data
31784 @anchor{Binary Data}
31785 Binary data in most packets is encoded either as two hexadecimal
31786 digits per byte of binary data. This allowed the traditional remote
31787 protocol to work over connections which were only seven-bit clean.
31788 Some packets designed more recently assume an eight-bit clean
31789 connection, and use a more efficient encoding to send and receive
31792 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
31793 as an escape character. Any escaped byte is transmitted as the escape
31794 character followed by the original character XORed with @code{0x20}.
31795 For example, the byte @code{0x7d} would be transmitted as the two
31796 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
31797 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
31798 @samp{@}}) must always be escaped. Responses sent by the stub
31799 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
31800 is not interpreted as the start of a run-length encoded sequence
31803 Response @var{data} can be run-length encoded to save space.
31804 Run-length encoding replaces runs of identical characters with one
31805 instance of the repeated character, followed by a @samp{*} and a
31806 repeat count. The repeat count is itself sent encoded, to avoid
31807 binary characters in @var{data}: a value of @var{n} is sent as
31808 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
31809 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
31810 code 32) for a repeat count of 3. (This is because run-length
31811 encoding starts to win for counts 3 or more.) Thus, for example,
31812 @samp{0* } is a run-length encoding of ``0000'': the space character
31813 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
31816 The printable characters @samp{#} and @samp{$} or with a numeric value
31817 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
31818 seven repeats (@samp{$}) can be expanded using a repeat count of only
31819 five (@samp{"}). For example, @samp{00000000} can be encoded as
31822 The error response returned for some packets includes a two character
31823 error number. That number is not well defined.
31825 @cindex empty response, for unsupported packets
31826 For any @var{command} not supported by the stub, an empty response
31827 (@samp{$#00}) should be returned. That way it is possible to extend the
31828 protocol. A newer @value{GDBN} can tell if a packet is supported based
31831 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
31832 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
31838 The following table provides a complete list of all currently defined
31839 @var{command}s and their corresponding response @var{data}.
31840 @xref{File-I/O Remote Protocol Extension}, for details about the File
31841 I/O extension of the remote protocol.
31843 Each packet's description has a template showing the packet's overall
31844 syntax, followed by an explanation of the packet's meaning. We
31845 include spaces in some of the templates for clarity; these are not
31846 part of the packet's syntax. No @value{GDBN} packet uses spaces to
31847 separate its components. For example, a template like @samp{foo
31848 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
31849 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
31850 @var{baz}. @value{GDBN} does not transmit a space character between the
31851 @samp{foo} and the @var{bar}, or between the @var{bar} and the
31854 @cindex @var{thread-id}, in remote protocol
31855 @anchor{thread-id syntax}
31856 Several packets and replies include a @var{thread-id} field to identify
31857 a thread. Normally these are positive numbers with a target-specific
31858 interpretation, formatted as big-endian hex strings. A @var{thread-id}
31859 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
31862 In addition, the remote protocol supports a multiprocess feature in
31863 which the @var{thread-id} syntax is extended to optionally include both
31864 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
31865 The @var{pid} (process) and @var{tid} (thread) components each have the
31866 format described above: a positive number with target-specific
31867 interpretation formatted as a big-endian hex string, literal @samp{-1}
31868 to indicate all processes or threads (respectively), or @samp{0} to
31869 indicate an arbitrary process or thread. Specifying just a process, as
31870 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
31871 error to specify all processes but a specific thread, such as
31872 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
31873 for those packets and replies explicitly documented to include a process
31874 ID, rather than a @var{thread-id}.
31876 The multiprocess @var{thread-id} syntax extensions are only used if both
31877 @value{GDBN} and the stub report support for the @samp{multiprocess}
31878 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
31881 Note that all packet forms beginning with an upper- or lower-case
31882 letter, other than those described here, are reserved for future use.
31884 Here are the packet descriptions.
31889 @cindex @samp{!} packet
31890 @anchor{extended mode}
31891 Enable extended mode. In extended mode, the remote server is made
31892 persistent. The @samp{R} packet is used to restart the program being
31898 The remote target both supports and has enabled extended mode.
31902 @cindex @samp{?} packet
31903 Indicate the reason the target halted. The reply is the same as for
31904 step and continue. This packet has a special interpretation when the
31905 target is in non-stop mode; see @ref{Remote Non-Stop}.
31908 @xref{Stop Reply Packets}, for the reply specifications.
31910 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
31911 @cindex @samp{A} packet
31912 Initialized @code{argv[]} array passed into program. @var{arglen}
31913 specifies the number of bytes in the hex encoded byte stream
31914 @var{arg}. See @code{gdbserver} for more details.
31919 The arguments were set.
31925 @cindex @samp{b} packet
31926 (Don't use this packet; its behavior is not well-defined.)
31927 Change the serial line speed to @var{baud}.
31929 JTC: @emph{When does the transport layer state change? When it's
31930 received, or after the ACK is transmitted. In either case, there are
31931 problems if the command or the acknowledgment packet is dropped.}
31933 Stan: @emph{If people really wanted to add something like this, and get
31934 it working for the first time, they ought to modify ser-unix.c to send
31935 some kind of out-of-band message to a specially-setup stub and have the
31936 switch happen "in between" packets, so that from remote protocol's point
31937 of view, nothing actually happened.}
31939 @item B @var{addr},@var{mode}
31940 @cindex @samp{B} packet
31941 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
31942 breakpoint at @var{addr}.
31944 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
31945 (@pxref{insert breakpoint or watchpoint packet}).
31947 @cindex @samp{bc} packet
31950 Backward continue. Execute the target system in reverse. No parameter.
31951 @xref{Reverse Execution}, for more information.
31954 @xref{Stop Reply Packets}, for the reply specifications.
31956 @cindex @samp{bs} packet
31959 Backward single step. Execute one instruction in reverse. No parameter.
31960 @xref{Reverse Execution}, for more information.
31963 @xref{Stop Reply Packets}, for the reply specifications.
31965 @item c @r{[}@var{addr}@r{]}
31966 @cindex @samp{c} packet
31967 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
31968 resume at current address.
31971 @xref{Stop Reply Packets}, for the reply specifications.
31973 @item C @var{sig}@r{[};@var{addr}@r{]}
31974 @cindex @samp{C} packet
31975 Continue with signal @var{sig} (hex signal number). If
31976 @samp{;@var{addr}} is omitted, resume at same address.
31979 @xref{Stop Reply Packets}, for the reply specifications.
31982 @cindex @samp{d} packet
31985 Don't use this packet; instead, define a general set packet
31986 (@pxref{General Query Packets}).
31990 @cindex @samp{D} packet
31991 The first form of the packet is used to detach @value{GDBN} from the
31992 remote system. It is sent to the remote target
31993 before @value{GDBN} disconnects via the @code{detach} command.
31995 The second form, including a process ID, is used when multiprocess
31996 protocol extensions are enabled (@pxref{multiprocess extensions}), to
31997 detach only a specific process. The @var{pid} is specified as a
31998 big-endian hex string.
32008 @item F @var{RC},@var{EE},@var{CF};@var{XX}
32009 @cindex @samp{F} packet
32010 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
32011 This is part of the File-I/O protocol extension. @xref{File-I/O
32012 Remote Protocol Extension}, for the specification.
32015 @anchor{read registers packet}
32016 @cindex @samp{g} packet
32017 Read general registers.
32021 @item @var{XX@dots{}}
32022 Each byte of register data is described by two hex digits. The bytes
32023 with the register are transmitted in target byte order. The size of
32024 each register and their position within the @samp{g} packet are
32025 determined by the @value{GDBN} internal gdbarch functions
32026 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
32027 specification of several standard @samp{g} packets is specified below.
32029 When reading registers from a trace frame (@pxref{Analyze Collected
32030 Data,,Using the Collected Data}), the stub may also return a string of
32031 literal @samp{x}'s in place of the register data digits, to indicate
32032 that the corresponding register has not been collected, thus its value
32033 is unavailable. For example, for an architecture with 4 registers of
32034 4 bytes each, the following reply indicates to @value{GDBN} that
32035 registers 0 and 2 have not been collected, while registers 1 and 3
32036 have been collected, and both have zero value:
32040 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
32047 @item G @var{XX@dots{}}
32048 @cindex @samp{G} packet
32049 Write general registers. @xref{read registers packet}, for a
32050 description of the @var{XX@dots{}} data.
32060 @item H @var{c} @var{thread-id}
32061 @cindex @samp{H} packet
32062 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
32063 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
32064 should be @samp{c} for step and continue operations, @samp{g} for other
32065 operations. The thread designator @var{thread-id} has the format and
32066 interpretation described in @ref{thread-id syntax}.
32077 @c 'H': How restrictive (or permissive) is the thread model. If a
32078 @c thread is selected and stopped, are other threads allowed
32079 @c to continue to execute? As I mentioned above, I think the
32080 @c semantics of each command when a thread is selected must be
32081 @c described. For example:
32083 @c 'g': If the stub supports threads and a specific thread is
32084 @c selected, returns the register block from that thread;
32085 @c otherwise returns current registers.
32087 @c 'G' If the stub supports threads and a specific thread is
32088 @c selected, sets the registers of the register block of
32089 @c that thread; otherwise sets current registers.
32091 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
32092 @anchor{cycle step packet}
32093 @cindex @samp{i} packet
32094 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
32095 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
32096 step starting at that address.
32099 @cindex @samp{I} packet
32100 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
32104 @cindex @samp{k} packet
32107 FIXME: @emph{There is no description of how to operate when a specific
32108 thread context has been selected (i.e.@: does 'k' kill only that
32111 @item m @var{addr},@var{length}
32112 @cindex @samp{m} packet
32113 Read @var{length} bytes of memory starting at address @var{addr}.
32114 Note that @var{addr} may not be aligned to any particular boundary.
32116 The stub need not use any particular size or alignment when gathering
32117 data from memory for the response; even if @var{addr} is word-aligned
32118 and @var{length} is a multiple of the word size, the stub is free to
32119 use byte accesses, or not. For this reason, this packet may not be
32120 suitable for accessing memory-mapped I/O devices.
32121 @cindex alignment of remote memory accesses
32122 @cindex size of remote memory accesses
32123 @cindex memory, alignment and size of remote accesses
32127 @item @var{XX@dots{}}
32128 Memory contents; each byte is transmitted as a two-digit hexadecimal
32129 number. The reply may contain fewer bytes than requested if the
32130 server was able to read only part of the region of memory.
32135 @item M @var{addr},@var{length}:@var{XX@dots{}}
32136 @cindex @samp{M} packet
32137 Write @var{length} bytes of memory starting at address @var{addr}.
32138 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
32139 hexadecimal number.
32146 for an error (this includes the case where only part of the data was
32151 @cindex @samp{p} packet
32152 Read the value of register @var{n}; @var{n} is in hex.
32153 @xref{read registers packet}, for a description of how the returned
32154 register value is encoded.
32158 @item @var{XX@dots{}}
32159 the register's value
32163 Indicating an unrecognized @var{query}.
32166 @item P @var{n@dots{}}=@var{r@dots{}}
32167 @anchor{write register packet}
32168 @cindex @samp{P} packet
32169 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
32170 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
32171 digits for each byte in the register (target byte order).
32181 @item q @var{name} @var{params}@dots{}
32182 @itemx Q @var{name} @var{params}@dots{}
32183 @cindex @samp{q} packet
32184 @cindex @samp{Q} packet
32185 General query (@samp{q}) and set (@samp{Q}). These packets are
32186 described fully in @ref{General Query Packets}.
32189 @cindex @samp{r} packet
32190 Reset the entire system.
32192 Don't use this packet; use the @samp{R} packet instead.
32195 @cindex @samp{R} packet
32196 Restart the program being debugged. @var{XX}, while needed, is ignored.
32197 This packet is only available in extended mode (@pxref{extended mode}).
32199 The @samp{R} packet has no reply.
32201 @item s @r{[}@var{addr}@r{]}
32202 @cindex @samp{s} packet
32203 Single step. @var{addr} is the address at which to resume. If
32204 @var{addr} is omitted, resume at same address.
32207 @xref{Stop Reply Packets}, for the reply specifications.
32209 @item S @var{sig}@r{[};@var{addr}@r{]}
32210 @anchor{step with signal packet}
32211 @cindex @samp{S} packet
32212 Step with signal. This is analogous to the @samp{C} packet, but
32213 requests a single-step, rather than a normal resumption of execution.
32216 @xref{Stop Reply Packets}, for the reply specifications.
32218 @item t @var{addr}:@var{PP},@var{MM}
32219 @cindex @samp{t} packet
32220 Search backwards starting at address @var{addr} for a match with pattern
32221 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
32222 @var{addr} must be at least 3 digits.
32224 @item T @var{thread-id}
32225 @cindex @samp{T} packet
32226 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
32231 thread is still alive
32237 Packets starting with @samp{v} are identified by a multi-letter name,
32238 up to the first @samp{;} or @samp{?} (or the end of the packet).
32240 @item vAttach;@var{pid}
32241 @cindex @samp{vAttach} packet
32242 Attach to a new process with the specified process ID @var{pid}.
32243 The process ID is a
32244 hexadecimal integer identifying the process. In all-stop mode, all
32245 threads in the attached process are stopped; in non-stop mode, it may be
32246 attached without being stopped if that is supported by the target.
32248 @c In non-stop mode, on a successful vAttach, the stub should set the
32249 @c current thread to a thread of the newly-attached process. After
32250 @c attaching, GDB queries for the attached process's thread ID with qC.
32251 @c Also note that, from a user perspective, whether or not the
32252 @c target is stopped on attach in non-stop mode depends on whether you
32253 @c use the foreground or background version of the attach command, not
32254 @c on what vAttach does; GDB does the right thing with respect to either
32255 @c stopping or restarting threads.
32257 This packet is only available in extended mode (@pxref{extended mode}).
32263 @item @r{Any stop packet}
32264 for success in all-stop mode (@pxref{Stop Reply Packets})
32266 for success in non-stop mode (@pxref{Remote Non-Stop})
32269 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
32270 @cindex @samp{vCont} packet
32271 Resume the inferior, specifying different actions for each thread.
32272 If an action is specified with no @var{thread-id}, then it is applied to any
32273 threads that don't have a specific action specified; if no default action is
32274 specified then other threads should remain stopped in all-stop mode and
32275 in their current state in non-stop mode.
32276 Specifying multiple
32277 default actions is an error; specifying no actions is also an error.
32278 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
32280 Currently supported actions are:
32286 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
32290 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
32295 The optional argument @var{addr} normally associated with the
32296 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
32297 not supported in @samp{vCont}.
32299 The @samp{t} action is only relevant in non-stop mode
32300 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
32301 A stop reply should be generated for any affected thread not already stopped.
32302 When a thread is stopped by means of a @samp{t} action,
32303 the corresponding stop reply should indicate that the thread has stopped with
32304 signal @samp{0}, regardless of whether the target uses some other signal
32305 as an implementation detail.
32308 @xref{Stop Reply Packets}, for the reply specifications.
32311 @cindex @samp{vCont?} packet
32312 Request a list of actions supported by the @samp{vCont} packet.
32316 @item vCont@r{[};@var{action}@dots{}@r{]}
32317 The @samp{vCont} packet is supported. Each @var{action} is a supported
32318 command in the @samp{vCont} packet.
32320 The @samp{vCont} packet is not supported.
32323 @item vFile:@var{operation}:@var{parameter}@dots{}
32324 @cindex @samp{vFile} packet
32325 Perform a file operation on the target system. For details,
32326 see @ref{Host I/O Packets}.
32328 @item vFlashErase:@var{addr},@var{length}
32329 @cindex @samp{vFlashErase} packet
32330 Direct the stub to erase @var{length} bytes of flash starting at
32331 @var{addr}. The region may enclose any number of flash blocks, but
32332 its start and end must fall on block boundaries, as indicated by the
32333 flash block size appearing in the memory map (@pxref{Memory Map
32334 Format}). @value{GDBN} groups flash memory programming operations
32335 together, and sends a @samp{vFlashDone} request after each group; the
32336 stub is allowed to delay erase operation until the @samp{vFlashDone}
32337 packet is received.
32339 The stub must support @samp{vCont} if it reports support for
32340 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
32341 this case @samp{vCont} actions can be specified to apply to all threads
32342 in a process by using the @samp{p@var{pid}.-1} form of the
32353 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
32354 @cindex @samp{vFlashWrite} packet
32355 Direct the stub to write data to flash address @var{addr}. The data
32356 is passed in binary form using the same encoding as for the @samp{X}
32357 packet (@pxref{Binary Data}). The memory ranges specified by
32358 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
32359 not overlap, and must appear in order of increasing addresses
32360 (although @samp{vFlashErase} packets for higher addresses may already
32361 have been received; the ordering is guaranteed only between
32362 @samp{vFlashWrite} packets). If a packet writes to an address that was
32363 neither erased by a preceding @samp{vFlashErase} packet nor by some other
32364 target-specific method, the results are unpredictable.
32372 for vFlashWrite addressing non-flash memory
32378 @cindex @samp{vFlashDone} packet
32379 Indicate to the stub that flash programming operation is finished.
32380 The stub is permitted to delay or batch the effects of a group of
32381 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
32382 @samp{vFlashDone} packet is received. The contents of the affected
32383 regions of flash memory are unpredictable until the @samp{vFlashDone}
32384 request is completed.
32386 @item vKill;@var{pid}
32387 @cindex @samp{vKill} packet
32388 Kill the process with the specified process ID. @var{pid} is a
32389 hexadecimal integer identifying the process. This packet is used in
32390 preference to @samp{k} when multiprocess protocol extensions are
32391 supported; see @ref{multiprocess extensions}.
32401 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
32402 @cindex @samp{vRun} packet
32403 Run the program @var{filename}, passing it each @var{argument} on its
32404 command line. The file and arguments are hex-encoded strings. If
32405 @var{filename} is an empty string, the stub may use a default program
32406 (e.g.@: the last program run). The program is created in the stopped
32409 @c FIXME: What about non-stop mode?
32411 This packet is only available in extended mode (@pxref{extended mode}).
32417 @item @r{Any stop packet}
32418 for success (@pxref{Stop Reply Packets})
32422 @anchor{vStopped packet}
32423 @cindex @samp{vStopped} packet
32425 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
32426 reply and prompt for the stub to report another one.
32430 @item @r{Any stop packet}
32431 if there is another unreported stop event (@pxref{Stop Reply Packets})
32433 if there are no unreported stop events
32436 @item X @var{addr},@var{length}:@var{XX@dots{}}
32438 @cindex @samp{X} packet
32439 Write data to memory, where the data is transmitted in binary.
32440 @var{addr} is address, @var{length} is number of bytes,
32441 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
32451 @item z @var{type},@var{addr},@var{kind}
32452 @itemx Z @var{type},@var{addr},@var{kind}
32453 @anchor{insert breakpoint or watchpoint packet}
32454 @cindex @samp{z} packet
32455 @cindex @samp{Z} packets
32456 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
32457 watchpoint starting at address @var{address} of kind @var{kind}.
32459 Each breakpoint and watchpoint packet @var{type} is documented
32462 @emph{Implementation notes: A remote target shall return an empty string
32463 for an unrecognized breakpoint or watchpoint packet @var{type}. A
32464 remote target shall support either both or neither of a given
32465 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
32466 avoid potential problems with duplicate packets, the operations should
32467 be implemented in an idempotent way.}
32469 @item z0,@var{addr},@var{kind}
32470 @itemx Z0,@var{addr},@var{kind}
32471 @cindex @samp{z0} packet
32472 @cindex @samp{Z0} packet
32473 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
32474 @var{addr} of type @var{kind}.
32476 A memory breakpoint is implemented by replacing the instruction at
32477 @var{addr} with a software breakpoint or trap instruction. The
32478 @var{kind} is target-specific and typically indicates the size of
32479 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
32480 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
32481 architectures have additional meanings for @var{kind};
32482 see @ref{Architecture-Specific Protocol Details}.
32484 @emph{Implementation note: It is possible for a target to copy or move
32485 code that contains memory breakpoints (e.g., when implementing
32486 overlays). The behavior of this packet, in the presence of such a
32487 target, is not defined.}
32499 @item z1,@var{addr},@var{kind}
32500 @itemx Z1,@var{addr},@var{kind}
32501 @cindex @samp{z1} packet
32502 @cindex @samp{Z1} packet
32503 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
32504 address @var{addr}.
32506 A hardware breakpoint is implemented using a mechanism that is not
32507 dependant on being able to modify the target's memory. @var{kind}
32508 has the same meaning as in @samp{Z0} packets.
32510 @emph{Implementation note: A hardware breakpoint is not affected by code
32523 @item z2,@var{addr},@var{kind}
32524 @itemx Z2,@var{addr},@var{kind}
32525 @cindex @samp{z2} packet
32526 @cindex @samp{Z2} packet
32527 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
32528 @var{kind} is interpreted as the number of bytes to watch.
32540 @item z3,@var{addr},@var{kind}
32541 @itemx Z3,@var{addr},@var{kind}
32542 @cindex @samp{z3} packet
32543 @cindex @samp{Z3} packet
32544 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
32545 @var{kind} is interpreted as the number of bytes to watch.
32557 @item z4,@var{addr},@var{kind}
32558 @itemx Z4,@var{addr},@var{kind}
32559 @cindex @samp{z4} packet
32560 @cindex @samp{Z4} packet
32561 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
32562 @var{kind} is interpreted as the number of bytes to watch.
32576 @node Stop Reply Packets
32577 @section Stop Reply Packets
32578 @cindex stop reply packets
32580 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
32581 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
32582 receive any of the below as a reply. Except for @samp{?}
32583 and @samp{vStopped}, that reply is only returned
32584 when the target halts. In the below the exact meaning of @dfn{signal
32585 number} is defined by the header @file{include/gdb/signals.h} in the
32586 @value{GDBN} source code.
32588 As in the description of request packets, we include spaces in the
32589 reply templates for clarity; these are not part of the reply packet's
32590 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
32596 The program received signal number @var{AA} (a two-digit hexadecimal
32597 number). This is equivalent to a @samp{T} response with no
32598 @var{n}:@var{r} pairs.
32600 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
32601 @cindex @samp{T} packet reply
32602 The program received signal number @var{AA} (a two-digit hexadecimal
32603 number). This is equivalent to an @samp{S} response, except that the
32604 @samp{@var{n}:@var{r}} pairs can carry values of important registers
32605 and other information directly in the stop reply packet, reducing
32606 round-trip latency. Single-step and breakpoint traps are reported
32607 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
32611 If @var{n} is a hexadecimal number, it is a register number, and the
32612 corresponding @var{r} gives that register's value. @var{r} is a
32613 series of bytes in target byte order, with each byte given by a
32614 two-digit hex number.
32617 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
32618 the stopped thread, as specified in @ref{thread-id syntax}.
32621 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
32622 the core on which the stop event was detected.
32625 If @var{n} is a recognized @dfn{stop reason}, it describes a more
32626 specific event that stopped the target. The currently defined stop
32627 reasons are listed below. @var{aa} should be @samp{05}, the trap
32628 signal. At most one stop reason should be present.
32631 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
32632 and go on to the next; this allows us to extend the protocol in the
32636 The currently defined stop reasons are:
32642 The packet indicates a watchpoint hit, and @var{r} is the data address, in
32645 @cindex shared library events, remote reply
32647 The packet indicates that the loaded libraries have changed.
32648 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
32649 list of loaded libraries. @var{r} is ignored.
32651 @cindex replay log events, remote reply
32653 The packet indicates that the target cannot continue replaying
32654 logged execution events, because it has reached the end (or the
32655 beginning when executing backward) of the log. The value of @var{r}
32656 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
32657 for more information.
32661 @itemx W @var{AA} ; process:@var{pid}
32662 The process exited, and @var{AA} is the exit status. This is only
32663 applicable to certain targets.
32665 The second form of the response, including the process ID of the exited
32666 process, can be used only when @value{GDBN} has reported support for
32667 multiprocess protocol extensions; see @ref{multiprocess extensions}.
32668 The @var{pid} is formatted as a big-endian hex string.
32671 @itemx X @var{AA} ; process:@var{pid}
32672 The process terminated with signal @var{AA}.
32674 The second form of the response, including the process ID of the
32675 terminated process, can be used only when @value{GDBN} has reported
32676 support for multiprocess protocol extensions; see @ref{multiprocess
32677 extensions}. The @var{pid} is formatted as a big-endian hex string.
32679 @item O @var{XX}@dots{}
32680 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
32681 written as the program's console output. This can happen at any time
32682 while the program is running and the debugger should continue to wait
32683 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
32685 @item F @var{call-id},@var{parameter}@dots{}
32686 @var{call-id} is the identifier which says which host system call should
32687 be called. This is just the name of the function. Translation into the
32688 correct system call is only applicable as it's defined in @value{GDBN}.
32689 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
32692 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
32693 this very system call.
32695 The target replies with this packet when it expects @value{GDBN} to
32696 call a host system call on behalf of the target. @value{GDBN} replies
32697 with an appropriate @samp{F} packet and keeps up waiting for the next
32698 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
32699 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
32700 Protocol Extension}, for more details.
32704 @node General Query Packets
32705 @section General Query Packets
32706 @cindex remote query requests
32708 Packets starting with @samp{q} are @dfn{general query packets};
32709 packets starting with @samp{Q} are @dfn{general set packets}. General
32710 query and set packets are a semi-unified form for retrieving and
32711 sending information to and from the stub.
32713 The initial letter of a query or set packet is followed by a name
32714 indicating what sort of thing the packet applies to. For example,
32715 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
32716 definitions with the stub. These packet names follow some
32721 The name must not contain commas, colons or semicolons.
32723 Most @value{GDBN} query and set packets have a leading upper case
32726 The names of custom vendor packets should use a company prefix, in
32727 lower case, followed by a period. For example, packets designed at
32728 the Acme Corporation might begin with @samp{qacme.foo} (for querying
32729 foos) or @samp{Qacme.bar} (for setting bars).
32732 The name of a query or set packet should be separated from any
32733 parameters by a @samp{:}; the parameters themselves should be
32734 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
32735 full packet name, and check for a separator or the end of the packet,
32736 in case two packet names share a common prefix. New packets should not begin
32737 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
32738 packets predate these conventions, and have arguments without any terminator
32739 for the packet name; we suspect they are in widespread use in places that
32740 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
32741 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
32744 Like the descriptions of the other packets, each description here
32745 has a template showing the packet's overall syntax, followed by an
32746 explanation of the packet's meaning. We include spaces in some of the
32747 templates for clarity; these are not part of the packet's syntax. No
32748 @value{GDBN} packet uses spaces to separate its components.
32750 Here are the currently defined query and set packets:
32754 @item QAllow:@var{op}:@var{val}@dots{}
32755 @cindex @samp{QAllow} packet
32756 Specify which operations @value{GDBN} expects to request of the
32757 target, as a semicolon-separated list of operation name and value
32758 pairs. Possible values for @var{op} include @samp{WriteReg},
32759 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
32760 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
32761 indicating that @value{GDBN} will not request the operation, or 1,
32762 indicating that it may. (The target can then use this to set up its
32763 own internals optimally, for instance if the debugger never expects to
32764 insert breakpoints, it may not need to install its own trap handler.)
32767 @cindex current thread, remote request
32768 @cindex @samp{qC} packet
32769 Return the current thread ID.
32773 @item QC @var{thread-id}
32774 Where @var{thread-id} is a thread ID as documented in
32775 @ref{thread-id syntax}.
32776 @item @r{(anything else)}
32777 Any other reply implies the old thread ID.
32780 @item qCRC:@var{addr},@var{length}
32781 @cindex CRC of memory block, remote request
32782 @cindex @samp{qCRC} packet
32783 Compute the CRC checksum of a block of memory using CRC-32 defined in
32784 IEEE 802.3. The CRC is computed byte at a time, taking the most
32785 significant bit of each byte first. The initial pattern code
32786 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
32788 @emph{Note:} This is the same CRC used in validating separate debug
32789 files (@pxref{Separate Debug Files, , Debugging Information in Separate
32790 Files}). However the algorithm is slightly different. When validating
32791 separate debug files, the CRC is computed taking the @emph{least}
32792 significant bit of each byte first, and the final result is inverted to
32793 detect trailing zeros.
32798 An error (such as memory fault)
32799 @item C @var{crc32}
32800 The specified memory region's checksum is @var{crc32}.
32804 @itemx qsThreadInfo
32805 @cindex list active threads, remote request
32806 @cindex @samp{qfThreadInfo} packet
32807 @cindex @samp{qsThreadInfo} packet
32808 Obtain a list of all active thread IDs from the target (OS). Since there
32809 may be too many active threads to fit into one reply packet, this query
32810 works iteratively: it may require more than one query/reply sequence to
32811 obtain the entire list of threads. The first query of the sequence will
32812 be the @samp{qfThreadInfo} query; subsequent queries in the
32813 sequence will be the @samp{qsThreadInfo} query.
32815 NOTE: This packet replaces the @samp{qL} query (see below).
32819 @item m @var{thread-id}
32821 @item m @var{thread-id},@var{thread-id}@dots{}
32822 a comma-separated list of thread IDs
32824 (lower case letter @samp{L}) denotes end of list.
32827 In response to each query, the target will reply with a list of one or
32828 more thread IDs, separated by commas.
32829 @value{GDBN} will respond to each reply with a request for more thread
32830 ids (using the @samp{qs} form of the query), until the target responds
32831 with @samp{l} (lower-case ell, for @dfn{last}).
32832 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
32835 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
32836 @cindex get thread-local storage address, remote request
32837 @cindex @samp{qGetTLSAddr} packet
32838 Fetch the address associated with thread local storage specified
32839 by @var{thread-id}, @var{offset}, and @var{lm}.
32841 @var{thread-id} is the thread ID associated with the
32842 thread for which to fetch the TLS address. @xref{thread-id syntax}.
32844 @var{offset} is the (big endian, hex encoded) offset associated with the
32845 thread local variable. (This offset is obtained from the debug
32846 information associated with the variable.)
32848 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
32849 the load module associated with the thread local storage. For example,
32850 a @sc{gnu}/Linux system will pass the link map address of the shared
32851 object associated with the thread local storage under consideration.
32852 Other operating environments may choose to represent the load module
32853 differently, so the precise meaning of this parameter will vary.
32857 @item @var{XX}@dots{}
32858 Hex encoded (big endian) bytes representing the address of the thread
32859 local storage requested.
32862 An error occurred. @var{nn} are hex digits.
32865 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
32868 @item qGetTIBAddr:@var{thread-id}
32869 @cindex get thread information block address
32870 @cindex @samp{qGetTIBAddr} packet
32871 Fetch address of the Windows OS specific Thread Information Block.
32873 @var{thread-id} is the thread ID associated with the thread.
32877 @item @var{XX}@dots{}
32878 Hex encoded (big endian) bytes representing the linear address of the
32879 thread information block.
32882 An error occured. This means that either the thread was not found, or the
32883 address could not be retrieved.
32886 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
32889 @item qL @var{startflag} @var{threadcount} @var{nextthread}
32890 Obtain thread information from RTOS. Where: @var{startflag} (one hex
32891 digit) is one to indicate the first query and zero to indicate a
32892 subsequent query; @var{threadcount} (two hex digits) is the maximum
32893 number of threads the response packet can contain; and @var{nextthread}
32894 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
32895 returned in the response as @var{argthread}.
32897 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
32901 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
32902 Where: @var{count} (two hex digits) is the number of threads being
32903 returned; @var{done} (one hex digit) is zero to indicate more threads
32904 and one indicates no further threads; @var{argthreadid} (eight hex
32905 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
32906 is a sequence of thread IDs from the target. @var{threadid} (eight hex
32907 digits). See @code{remote.c:parse_threadlist_response()}.
32911 @cindex section offsets, remote request
32912 @cindex @samp{qOffsets} packet
32913 Get section offsets that the target used when relocating the downloaded
32918 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
32919 Relocate the @code{Text} section by @var{xxx} from its original address.
32920 Relocate the @code{Data} section by @var{yyy} from its original address.
32921 If the object file format provides segment information (e.g.@: @sc{elf}
32922 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
32923 segments by the supplied offsets.
32925 @emph{Note: while a @code{Bss} offset may be included in the response,
32926 @value{GDBN} ignores this and instead applies the @code{Data} offset
32927 to the @code{Bss} section.}
32929 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
32930 Relocate the first segment of the object file, which conventionally
32931 contains program code, to a starting address of @var{xxx}. If
32932 @samp{DataSeg} is specified, relocate the second segment, which
32933 conventionally contains modifiable data, to a starting address of
32934 @var{yyy}. @value{GDBN} will report an error if the object file
32935 does not contain segment information, or does not contain at least
32936 as many segments as mentioned in the reply. Extra segments are
32937 kept at fixed offsets relative to the last relocated segment.
32940 @item qP @var{mode} @var{thread-id}
32941 @cindex thread information, remote request
32942 @cindex @samp{qP} packet
32943 Returns information on @var{thread-id}. Where: @var{mode} is a hex
32944 encoded 32 bit mode; @var{thread-id} is a thread ID
32945 (@pxref{thread-id syntax}).
32947 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
32950 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
32954 @cindex non-stop mode, remote request
32955 @cindex @samp{QNonStop} packet
32957 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
32958 @xref{Remote Non-Stop}, for more information.
32963 The request succeeded.
32966 An error occurred. @var{nn} are hex digits.
32969 An empty reply indicates that @samp{QNonStop} is not supported by
32973 This packet is not probed by default; the remote stub must request it,
32974 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32975 Use of this packet is controlled by the @code{set non-stop} command;
32976 @pxref{Non-Stop Mode}.
32978 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
32979 @cindex pass signals to inferior, remote request
32980 @cindex @samp{QPassSignals} packet
32981 @anchor{QPassSignals}
32982 Each listed @var{signal} should be passed directly to the inferior process.
32983 Signals are numbered identically to continue packets and stop replies
32984 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
32985 strictly greater than the previous item. These signals do not need to stop
32986 the inferior, or be reported to @value{GDBN}. All other signals should be
32987 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
32988 combine; any earlier @samp{QPassSignals} list is completely replaced by the
32989 new list. This packet improves performance when using @samp{handle
32990 @var{signal} nostop noprint pass}.
32995 The request succeeded.
32998 An error occurred. @var{nn} are hex digits.
33001 An empty reply indicates that @samp{QPassSignals} is not supported by
33005 Use of this packet is controlled by the @code{set remote pass-signals}
33006 command (@pxref{Remote Configuration, set remote pass-signals}).
33007 This packet is not probed by default; the remote stub must request it,
33008 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33010 @item qRcmd,@var{command}
33011 @cindex execute remote command, remote request
33012 @cindex @samp{qRcmd} packet
33013 @var{command} (hex encoded) is passed to the local interpreter for
33014 execution. Invalid commands should be reported using the output
33015 string. Before the final result packet, the target may also respond
33016 with a number of intermediate @samp{O@var{output}} console output
33017 packets. @emph{Implementors should note that providing access to a
33018 stubs's interpreter may have security implications}.
33023 A command response with no output.
33025 A command response with the hex encoded output string @var{OUTPUT}.
33027 Indicate a badly formed request.
33029 An empty reply indicates that @samp{qRcmd} is not recognized.
33032 (Note that the @code{qRcmd} packet's name is separated from the
33033 command by a @samp{,}, not a @samp{:}, contrary to the naming
33034 conventions above. Please don't use this packet as a model for new
33037 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
33038 @cindex searching memory, in remote debugging
33039 @cindex @samp{qSearch:memory} packet
33040 @anchor{qSearch memory}
33041 Search @var{length} bytes at @var{address} for @var{search-pattern}.
33042 @var{address} and @var{length} are encoded in hex.
33043 @var{search-pattern} is a sequence of bytes, hex encoded.
33048 The pattern was not found.
33050 The pattern was found at @var{address}.
33052 A badly formed request or an error was encountered while searching memory.
33054 An empty reply indicates that @samp{qSearch:memory} is not recognized.
33057 @item QStartNoAckMode
33058 @cindex @samp{QStartNoAckMode} packet
33059 @anchor{QStartNoAckMode}
33060 Request that the remote stub disable the normal @samp{+}/@samp{-}
33061 protocol acknowledgments (@pxref{Packet Acknowledgment}).
33066 The stub has switched to no-acknowledgment mode.
33067 @value{GDBN} acknowledges this reponse,
33068 but neither the stub nor @value{GDBN} shall send or expect further
33069 @samp{+}/@samp{-} acknowledgments in the current connection.
33071 An empty reply indicates that the stub does not support no-acknowledgment mode.
33074 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
33075 @cindex supported packets, remote query
33076 @cindex features of the remote protocol
33077 @cindex @samp{qSupported} packet
33078 @anchor{qSupported}
33079 Tell the remote stub about features supported by @value{GDBN}, and
33080 query the stub for features it supports. This packet allows
33081 @value{GDBN} and the remote stub to take advantage of each others'
33082 features. @samp{qSupported} also consolidates multiple feature probes
33083 at startup, to improve @value{GDBN} performance---a single larger
33084 packet performs better than multiple smaller probe packets on
33085 high-latency links. Some features may enable behavior which must not
33086 be on by default, e.g.@: because it would confuse older clients or
33087 stubs. Other features may describe packets which could be
33088 automatically probed for, but are not. These features must be
33089 reported before @value{GDBN} will use them. This ``default
33090 unsupported'' behavior is not appropriate for all packets, but it
33091 helps to keep the initial connection time under control with new
33092 versions of @value{GDBN} which support increasing numbers of packets.
33096 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
33097 The stub supports or does not support each returned @var{stubfeature},
33098 depending on the form of each @var{stubfeature} (see below for the
33101 An empty reply indicates that @samp{qSupported} is not recognized,
33102 or that no features needed to be reported to @value{GDBN}.
33105 The allowed forms for each feature (either a @var{gdbfeature} in the
33106 @samp{qSupported} packet, or a @var{stubfeature} in the response)
33110 @item @var{name}=@var{value}
33111 The remote protocol feature @var{name} is supported, and associated
33112 with the specified @var{value}. The format of @var{value} depends
33113 on the feature, but it must not include a semicolon.
33115 The remote protocol feature @var{name} is supported, and does not
33116 need an associated value.
33118 The remote protocol feature @var{name} is not supported.
33120 The remote protocol feature @var{name} may be supported, and
33121 @value{GDBN} should auto-detect support in some other way when it is
33122 needed. This form will not be used for @var{gdbfeature} notifications,
33123 but may be used for @var{stubfeature} responses.
33126 Whenever the stub receives a @samp{qSupported} request, the
33127 supplied set of @value{GDBN} features should override any previous
33128 request. This allows @value{GDBN} to put the stub in a known
33129 state, even if the stub had previously been communicating with
33130 a different version of @value{GDBN}.
33132 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
33137 This feature indicates whether @value{GDBN} supports multiprocess
33138 extensions to the remote protocol. @value{GDBN} does not use such
33139 extensions unless the stub also reports that it supports them by
33140 including @samp{multiprocess+} in its @samp{qSupported} reply.
33141 @xref{multiprocess extensions}, for details.
33144 This feature indicates that @value{GDBN} supports the XML target
33145 description. If the stub sees @samp{xmlRegisters=} with target
33146 specific strings separated by a comma, it will report register
33150 This feature indicates whether @value{GDBN} supports the
33151 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
33152 instruction reply packet}).
33155 Stubs should ignore any unknown values for
33156 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
33157 packet supports receiving packets of unlimited length (earlier
33158 versions of @value{GDBN} may reject overly long responses). Additional values
33159 for @var{gdbfeature} may be defined in the future to let the stub take
33160 advantage of new features in @value{GDBN}, e.g.@: incompatible
33161 improvements in the remote protocol---the @samp{multiprocess} feature is
33162 an example of such a feature. The stub's reply should be independent
33163 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
33164 describes all the features it supports, and then the stub replies with
33165 all the features it supports.
33167 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
33168 responses, as long as each response uses one of the standard forms.
33170 Some features are flags. A stub which supports a flag feature
33171 should respond with a @samp{+} form response. Other features
33172 require values, and the stub should respond with an @samp{=}
33175 Each feature has a default value, which @value{GDBN} will use if
33176 @samp{qSupported} is not available or if the feature is not mentioned
33177 in the @samp{qSupported} response. The default values are fixed; a
33178 stub is free to omit any feature responses that match the defaults.
33180 Not all features can be probed, but for those which can, the probing
33181 mechanism is useful: in some cases, a stub's internal
33182 architecture may not allow the protocol layer to know some information
33183 about the underlying target in advance. This is especially common in
33184 stubs which may be configured for multiple targets.
33186 These are the currently defined stub features and their properties:
33188 @multitable @columnfractions 0.35 0.2 0.12 0.2
33189 @c NOTE: The first row should be @headitem, but we do not yet require
33190 @c a new enough version of Texinfo (4.7) to use @headitem.
33192 @tab Value Required
33196 @item @samp{PacketSize}
33201 @item @samp{qXfer:auxv:read}
33206 @item @samp{qXfer:features:read}
33211 @item @samp{qXfer:libraries:read}
33216 @item @samp{qXfer:memory-map:read}
33221 @item @samp{qXfer:sdata:read}
33226 @item @samp{qXfer:spu:read}
33231 @item @samp{qXfer:spu:write}
33236 @item @samp{qXfer:siginfo:read}
33241 @item @samp{qXfer:siginfo:write}
33246 @item @samp{qXfer:threads:read}
33251 @item @samp{qXfer:traceframe-info:read}
33257 @item @samp{QNonStop}
33262 @item @samp{QPassSignals}
33267 @item @samp{QStartNoAckMode}
33272 @item @samp{multiprocess}
33277 @item @samp{ConditionalTracepoints}
33282 @item @samp{ReverseContinue}
33287 @item @samp{ReverseStep}
33292 @item @samp{TracepointSource}
33297 @item @samp{QAllow}
33304 These are the currently defined stub features, in more detail:
33307 @cindex packet size, remote protocol
33308 @item PacketSize=@var{bytes}
33309 The remote stub can accept packets up to at least @var{bytes} in
33310 length. @value{GDBN} will send packets up to this size for bulk
33311 transfers, and will never send larger packets. This is a limit on the
33312 data characters in the packet, including the frame and checksum.
33313 There is no trailing NUL byte in a remote protocol packet; if the stub
33314 stores packets in a NUL-terminated format, it should allow an extra
33315 byte in its buffer for the NUL. If this stub feature is not supported,
33316 @value{GDBN} guesses based on the size of the @samp{g} packet response.
33318 @item qXfer:auxv:read
33319 The remote stub understands the @samp{qXfer:auxv:read} packet
33320 (@pxref{qXfer auxiliary vector read}).
33322 @item qXfer:features:read
33323 The remote stub understands the @samp{qXfer:features:read} packet
33324 (@pxref{qXfer target description read}).
33326 @item qXfer:libraries:read
33327 The remote stub understands the @samp{qXfer:libraries:read} packet
33328 (@pxref{qXfer library list read}).
33330 @item qXfer:memory-map:read
33331 The remote stub understands the @samp{qXfer:memory-map:read} packet
33332 (@pxref{qXfer memory map read}).
33334 @item qXfer:sdata:read
33335 The remote stub understands the @samp{qXfer:sdata:read} packet
33336 (@pxref{qXfer sdata read}).
33338 @item qXfer:spu:read
33339 The remote stub understands the @samp{qXfer:spu:read} packet
33340 (@pxref{qXfer spu read}).
33342 @item qXfer:spu:write
33343 The remote stub understands the @samp{qXfer:spu:write} packet
33344 (@pxref{qXfer spu write}).
33346 @item qXfer:siginfo:read
33347 The remote stub understands the @samp{qXfer:siginfo:read} packet
33348 (@pxref{qXfer siginfo read}).
33350 @item qXfer:siginfo:write
33351 The remote stub understands the @samp{qXfer:siginfo:write} packet
33352 (@pxref{qXfer siginfo write}).
33354 @item qXfer:threads:read
33355 The remote stub understands the @samp{qXfer:threads:read} packet
33356 (@pxref{qXfer threads read}).
33358 @item qXfer:traceframe-info:read
33359 The remote stub understands the @samp{qXfer:traceframe-info:read}
33360 packet (@pxref{qXfer traceframe info read}).
33363 The remote stub understands the @samp{QNonStop} packet
33364 (@pxref{QNonStop}).
33367 The remote stub understands the @samp{QPassSignals} packet
33368 (@pxref{QPassSignals}).
33370 @item QStartNoAckMode
33371 The remote stub understands the @samp{QStartNoAckMode} packet and
33372 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
33375 @anchor{multiprocess extensions}
33376 @cindex multiprocess extensions, in remote protocol
33377 The remote stub understands the multiprocess extensions to the remote
33378 protocol syntax. The multiprocess extensions affect the syntax of
33379 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
33380 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
33381 replies. Note that reporting this feature indicates support for the
33382 syntactic extensions only, not that the stub necessarily supports
33383 debugging of more than one process at a time. The stub must not use
33384 multiprocess extensions in packet replies unless @value{GDBN} has also
33385 indicated it supports them in its @samp{qSupported} request.
33387 @item qXfer:osdata:read
33388 The remote stub understands the @samp{qXfer:osdata:read} packet
33389 ((@pxref{qXfer osdata read}).
33391 @item ConditionalTracepoints
33392 The remote stub accepts and implements conditional expressions defined
33393 for tracepoints (@pxref{Tracepoint Conditions}).
33395 @item ReverseContinue
33396 The remote stub accepts and implements the reverse continue packet
33400 The remote stub accepts and implements the reverse step packet
33403 @item TracepointSource
33404 The remote stub understands the @samp{QTDPsrc} packet that supplies
33405 the source form of tracepoint definitions.
33408 The remote stub understands the @samp{QAllow} packet.
33410 @item StaticTracepoint
33411 @cindex static tracepoints, in remote protocol
33412 The remote stub supports static tracepoints.
33417 @cindex symbol lookup, remote request
33418 @cindex @samp{qSymbol} packet
33419 Notify the target that @value{GDBN} is prepared to serve symbol lookup
33420 requests. Accept requests from the target for the values of symbols.
33425 The target does not need to look up any (more) symbols.
33426 @item qSymbol:@var{sym_name}
33427 The target requests the value of symbol @var{sym_name} (hex encoded).
33428 @value{GDBN} may provide the value by using the
33429 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
33433 @item qSymbol:@var{sym_value}:@var{sym_name}
33434 Set the value of @var{sym_name} to @var{sym_value}.
33436 @var{sym_name} (hex encoded) is the name of a symbol whose value the
33437 target has previously requested.
33439 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
33440 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
33446 The target does not need to look up any (more) symbols.
33447 @item qSymbol:@var{sym_name}
33448 The target requests the value of a new symbol @var{sym_name} (hex
33449 encoded). @value{GDBN} will continue to supply the values of symbols
33450 (if available), until the target ceases to request them.
33455 @item QTDisconnected
33462 @xref{Tracepoint Packets}.
33464 @item qThreadExtraInfo,@var{thread-id}
33465 @cindex thread attributes info, remote request
33466 @cindex @samp{qThreadExtraInfo} packet
33467 Obtain a printable string description of a thread's attributes from
33468 the target OS. @var{thread-id} is a thread ID;
33469 see @ref{thread-id syntax}. This
33470 string may contain anything that the target OS thinks is interesting
33471 for @value{GDBN} to tell the user about the thread. The string is
33472 displayed in @value{GDBN}'s @code{info threads} display. Some
33473 examples of possible thread extra info strings are @samp{Runnable}, or
33474 @samp{Blocked on Mutex}.
33478 @item @var{XX}@dots{}
33479 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
33480 comprising the printable string containing the extra information about
33481 the thread's attributes.
33484 (Note that the @code{qThreadExtraInfo} packet's name is separated from
33485 the command by a @samp{,}, not a @samp{:}, contrary to the naming
33486 conventions above. Please don't use this packet as a model for new
33501 @xref{Tracepoint Packets}.
33503 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
33504 @cindex read special object, remote request
33505 @cindex @samp{qXfer} packet
33506 @anchor{qXfer read}
33507 Read uninterpreted bytes from the target's special data area
33508 identified by the keyword @var{object}. Request @var{length} bytes
33509 starting at @var{offset} bytes into the data. The content and
33510 encoding of @var{annex} is specific to @var{object}; it can supply
33511 additional details about what data to access.
33513 Here are the specific requests of this form defined so far. All
33514 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
33515 formats, listed below.
33518 @item qXfer:auxv:read::@var{offset},@var{length}
33519 @anchor{qXfer auxiliary vector read}
33520 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
33521 auxiliary vector}. Note @var{annex} must be empty.
33523 This packet is not probed by default; the remote stub must request it,
33524 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33526 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
33527 @anchor{qXfer target description read}
33528 Access the @dfn{target description}. @xref{Target Descriptions}. The
33529 annex specifies which XML document to access. The main description is
33530 always loaded from the @samp{target.xml} annex.
33532 This packet is not probed by default; the remote stub must request it,
33533 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33535 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
33536 @anchor{qXfer library list read}
33537 Access the target's list of loaded libraries. @xref{Library List Format}.
33538 The annex part of the generic @samp{qXfer} packet must be empty
33539 (@pxref{qXfer read}).
33541 Targets which maintain a list of libraries in the program's memory do
33542 not need to implement this packet; it is designed for platforms where
33543 the operating system manages the list of loaded libraries.
33545 This packet is not probed by default; the remote stub must request it,
33546 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33548 @item qXfer:memory-map:read::@var{offset},@var{length}
33549 @anchor{qXfer memory map read}
33550 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
33551 annex part of the generic @samp{qXfer} packet must be empty
33552 (@pxref{qXfer read}).
33554 This packet is not probed by default; the remote stub must request it,
33555 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33557 @item qXfer:sdata:read::@var{offset},@var{length}
33558 @anchor{qXfer sdata read}
33560 Read contents of the extra collected static tracepoint marker
33561 information. The annex part of the generic @samp{qXfer} packet must
33562 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
33565 This packet is not probed by default; the remote stub must request it,
33566 by supplying an appropriate @samp{qSupported} response
33567 (@pxref{qSupported}).
33569 @item qXfer:siginfo:read::@var{offset},@var{length}
33570 @anchor{qXfer siginfo read}
33571 Read contents of the extra signal information on the target
33572 system. The annex part of the generic @samp{qXfer} packet must be
33573 empty (@pxref{qXfer read}).
33575 This packet is not probed by default; the remote stub must request it,
33576 by supplying an appropriate @samp{qSupported} response
33577 (@pxref{qSupported}).
33579 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
33580 @anchor{qXfer spu read}
33581 Read contents of an @code{spufs} file on the target system. The
33582 annex specifies which file to read; it must be of the form
33583 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
33584 in the target process, and @var{name} identifes the @code{spufs} file
33585 in that context to be accessed.
33587 This packet is not probed by default; the remote stub must request it,
33588 by supplying an appropriate @samp{qSupported} response
33589 (@pxref{qSupported}).
33591 @item qXfer:threads:read::@var{offset},@var{length}
33592 @anchor{qXfer threads read}
33593 Access the list of threads on target. @xref{Thread List Format}. The
33594 annex part of the generic @samp{qXfer} packet must be empty
33595 (@pxref{qXfer read}).
33597 This packet is not probed by default; the remote stub must request it,
33598 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33600 @item qXfer:traceframe-info:read::@var{offset},@var{length}
33601 @anchor{qXfer traceframe info read}
33603 Return a description of the current traceframe's contents.
33604 @xref{Traceframe Info Format}. The annex part of the generic
33605 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
33607 This packet is not probed by default; the remote stub must request it,
33608 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33610 @item qXfer:osdata:read::@var{offset},@var{length}
33611 @anchor{qXfer osdata read}
33612 Access the target's @dfn{operating system information}.
33613 @xref{Operating System Information}.
33620 Data @var{data} (@pxref{Binary Data}) has been read from the
33621 target. There may be more data at a higher address (although
33622 it is permitted to return @samp{m} even for the last valid
33623 block of data, as long as at least one byte of data was read).
33624 @var{data} may have fewer bytes than the @var{length} in the
33628 Data @var{data} (@pxref{Binary Data}) has been read from the target.
33629 There is no more data to be read. @var{data} may have fewer bytes
33630 than the @var{length} in the request.
33633 The @var{offset} in the request is at the end of the data.
33634 There is no more data to be read.
33637 The request was malformed, or @var{annex} was invalid.
33640 The offset was invalid, or there was an error encountered reading the data.
33641 @var{nn} is a hex-encoded @code{errno} value.
33644 An empty reply indicates the @var{object} string was not recognized by
33645 the stub, or that the object does not support reading.
33648 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
33649 @cindex write data into object, remote request
33650 @anchor{qXfer write}
33651 Write uninterpreted bytes into the target's special data area
33652 identified by the keyword @var{object}, starting at @var{offset} bytes
33653 into the data. @var{data}@dots{} is the binary-encoded data
33654 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
33655 is specific to @var{object}; it can supply additional details about what data
33658 Here are the specific requests of this form defined so far. All
33659 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
33660 formats, listed below.
33663 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
33664 @anchor{qXfer siginfo write}
33665 Write @var{data} to the extra signal information on the target system.
33666 The annex part of the generic @samp{qXfer} packet must be
33667 empty (@pxref{qXfer write}).
33669 This packet is not probed by default; the remote stub must request it,
33670 by supplying an appropriate @samp{qSupported} response
33671 (@pxref{qSupported}).
33673 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
33674 @anchor{qXfer spu write}
33675 Write @var{data} to an @code{spufs} file on the target system. The
33676 annex specifies which file to write; it must be of the form
33677 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
33678 in the target process, and @var{name} identifes the @code{spufs} file
33679 in that context to be accessed.
33681 This packet is not probed by default; the remote stub must request it,
33682 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33688 @var{nn} (hex encoded) is the number of bytes written.
33689 This may be fewer bytes than supplied in the request.
33692 The request was malformed, or @var{annex} was invalid.
33695 The offset was invalid, or there was an error encountered writing the data.
33696 @var{nn} is a hex-encoded @code{errno} value.
33699 An empty reply indicates the @var{object} string was not
33700 recognized by the stub, or that the object does not support writing.
33703 @item qXfer:@var{object}:@var{operation}:@dots{}
33704 Requests of this form may be added in the future. When a stub does
33705 not recognize the @var{object} keyword, or its support for
33706 @var{object} does not recognize the @var{operation} keyword, the stub
33707 must respond with an empty packet.
33709 @item qAttached:@var{pid}
33710 @cindex query attached, remote request
33711 @cindex @samp{qAttached} packet
33712 Return an indication of whether the remote server attached to an
33713 existing process or created a new process. When the multiprocess
33714 protocol extensions are supported (@pxref{multiprocess extensions}),
33715 @var{pid} is an integer in hexadecimal format identifying the target
33716 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
33717 the query packet will be simplified as @samp{qAttached}.
33719 This query is used, for example, to know whether the remote process
33720 should be detached or killed when a @value{GDBN} session is ended with
33721 the @code{quit} command.
33726 The remote server attached to an existing process.
33728 The remote server created a new process.
33730 A badly formed request or an error was encountered.
33735 @node Architecture-Specific Protocol Details
33736 @section Architecture-Specific Protocol Details
33738 This section describes how the remote protocol is applied to specific
33739 target architectures. Also see @ref{Standard Target Features}, for
33740 details of XML target descriptions for each architecture.
33744 @subsubsection Breakpoint Kinds
33746 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
33751 16-bit Thumb mode breakpoint.
33754 32-bit Thumb mode (Thumb-2) breakpoint.
33757 32-bit ARM mode breakpoint.
33763 @subsubsection Register Packet Format
33765 The following @code{g}/@code{G} packets have previously been defined.
33766 In the below, some thirty-two bit registers are transferred as
33767 sixty-four bits. Those registers should be zero/sign extended (which?)
33768 to fill the space allocated. Register bytes are transferred in target
33769 byte order. The two nibbles within a register byte are transferred
33770 most-significant - least-significant.
33776 All registers are transferred as thirty-two bit quantities in the order:
33777 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
33778 registers; fsr; fir; fp.
33782 All registers are transferred as sixty-four bit quantities (including
33783 thirty-two bit registers such as @code{sr}). The ordering is the same
33788 @node Tracepoint Packets
33789 @section Tracepoint Packets
33790 @cindex tracepoint packets
33791 @cindex packets, tracepoint
33793 Here we describe the packets @value{GDBN} uses to implement
33794 tracepoints (@pxref{Tracepoints}).
33798 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
33799 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
33800 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
33801 the tracepoint is disabled. @var{step} is the tracepoint's step
33802 count, and @var{pass} is its pass count. If an @samp{F} is present,
33803 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
33804 the number of bytes that the target should copy elsewhere to make room
33805 for the tracepoint. If an @samp{X} is present, it introduces a
33806 tracepoint condition, which consists of a hexadecimal length, followed
33807 by a comma and hex-encoded bytes, in a manner similar to action
33808 encodings as described below. If the trailing @samp{-} is present,
33809 further @samp{QTDP} packets will follow to specify this tracepoint's
33815 The packet was understood and carried out.
33817 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
33819 The packet was not recognized.
33822 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
33823 Define actions to be taken when a tracepoint is hit. @var{n} and
33824 @var{addr} must be the same as in the initial @samp{QTDP} packet for
33825 this tracepoint. This packet may only be sent immediately after
33826 another @samp{QTDP} packet that ended with a @samp{-}. If the
33827 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
33828 specifying more actions for this tracepoint.
33830 In the series of action packets for a given tracepoint, at most one
33831 can have an @samp{S} before its first @var{action}. If such a packet
33832 is sent, it and the following packets define ``while-stepping''
33833 actions. Any prior packets define ordinary actions --- that is, those
33834 taken when the tracepoint is first hit. If no action packet has an
33835 @samp{S}, then all the packets in the series specify ordinary
33836 tracepoint actions.
33838 The @samp{@var{action}@dots{}} portion of the packet is a series of
33839 actions, concatenated without separators. Each action has one of the
33845 Collect the registers whose bits are set in @var{mask}. @var{mask} is
33846 a hexadecimal number whose @var{i}'th bit is set if register number
33847 @var{i} should be collected. (The least significant bit is numbered
33848 zero.) Note that @var{mask} may be any number of digits long; it may
33849 not fit in a 32-bit word.
33851 @item M @var{basereg},@var{offset},@var{len}
33852 Collect @var{len} bytes of memory starting at the address in register
33853 number @var{basereg}, plus @var{offset}. If @var{basereg} is
33854 @samp{-1}, then the range has a fixed address: @var{offset} is the
33855 address of the lowest byte to collect. The @var{basereg},
33856 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
33857 values (the @samp{-1} value for @var{basereg} is a special case).
33859 @item X @var{len},@var{expr}
33860 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
33861 it directs. @var{expr} is an agent expression, as described in
33862 @ref{Agent Expressions}. Each byte of the expression is encoded as a
33863 two-digit hex number in the packet; @var{len} is the number of bytes
33864 in the expression (and thus one-half the number of hex digits in the
33869 Any number of actions may be packed together in a single @samp{QTDP}
33870 packet, as long as the packet does not exceed the maximum packet
33871 length (400 bytes, for many stubs). There may be only one @samp{R}
33872 action per tracepoint, and it must precede any @samp{M} or @samp{X}
33873 actions. Any registers referred to by @samp{M} and @samp{X} actions
33874 must be collected by a preceding @samp{R} action. (The
33875 ``while-stepping'' actions are treated as if they were attached to a
33876 separate tracepoint, as far as these restrictions are concerned.)
33881 The packet was understood and carried out.
33883 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
33885 The packet was not recognized.
33888 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
33889 @cindex @samp{QTDPsrc} packet
33890 Specify a source string of tracepoint @var{n} at address @var{addr}.
33891 This is useful to get accurate reproduction of the tracepoints
33892 originally downloaded at the beginning of the trace run. @var{type}
33893 is the name of the tracepoint part, such as @samp{cond} for the
33894 tracepoint's conditional expression (see below for a list of types), while
33895 @var{bytes} is the string, encoded in hexadecimal.
33897 @var{start} is the offset of the @var{bytes} within the overall source
33898 string, while @var{slen} is the total length of the source string.
33899 This is intended for handling source strings that are longer than will
33900 fit in a single packet.
33901 @c Add detailed example when this info is moved into a dedicated
33902 @c tracepoint descriptions section.
33904 The available string types are @samp{at} for the location,
33905 @samp{cond} for the conditional, and @samp{cmd} for an action command.
33906 @value{GDBN} sends a separate packet for each command in the action
33907 list, in the same order in which the commands are stored in the list.
33909 The target does not need to do anything with source strings except
33910 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
33913 Although this packet is optional, and @value{GDBN} will only send it
33914 if the target replies with @samp{TracepointSource} @xref{General
33915 Query Packets}, it makes both disconnected tracing and trace files
33916 much easier to use. Otherwise the user must be careful that the
33917 tracepoints in effect while looking at trace frames are identical to
33918 the ones in effect during the trace run; even a small discrepancy
33919 could cause @samp{tdump} not to work, or a particular trace frame not
33922 @item QTDV:@var{n}:@var{value}
33923 @cindex define trace state variable, remote request
33924 @cindex @samp{QTDV} packet
33925 Create a new trace state variable, number @var{n}, with an initial
33926 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
33927 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
33928 the option of not using this packet for initial values of zero; the
33929 target should simply create the trace state variables as they are
33930 mentioned in expressions.
33932 @item QTFrame:@var{n}
33933 Select the @var{n}'th tracepoint frame from the buffer, and use the
33934 register and memory contents recorded there to answer subsequent
33935 request packets from @value{GDBN}.
33937 A successful reply from the stub indicates that the stub has found the
33938 requested frame. The response is a series of parts, concatenated
33939 without separators, describing the frame we selected. Each part has
33940 one of the following forms:
33944 The selected frame is number @var{n} in the trace frame buffer;
33945 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
33946 was no frame matching the criteria in the request packet.
33949 The selected trace frame records a hit of tracepoint number @var{t};
33950 @var{t} is a hexadecimal number.
33954 @item QTFrame:pc:@var{addr}
33955 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
33956 currently selected frame whose PC is @var{addr};
33957 @var{addr} is a hexadecimal number.
33959 @item QTFrame:tdp:@var{t}
33960 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
33961 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
33962 is a hexadecimal number.
33964 @item QTFrame:range:@var{start}:@var{end}
33965 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
33966 currently selected frame whose PC is between @var{start} (inclusive)
33967 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
33970 @item QTFrame:outside:@var{start}:@var{end}
33971 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
33972 frame @emph{outside} the given range of addresses (exclusive).
33975 Begin the tracepoint experiment. Begin collecting data from
33976 tracepoint hits in the trace frame buffer. This packet supports the
33977 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
33978 instruction reply packet}).
33981 End the tracepoint experiment. Stop collecting trace frames.
33984 Clear the table of tracepoints, and empty the trace frame buffer.
33986 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
33987 Establish the given ranges of memory as ``transparent''. The stub
33988 will answer requests for these ranges from memory's current contents,
33989 if they were not collected as part of the tracepoint hit.
33991 @value{GDBN} uses this to mark read-only regions of memory, like those
33992 containing program code. Since these areas never change, they should
33993 still have the same contents they did when the tracepoint was hit, so
33994 there's no reason for the stub to refuse to provide their contents.
33996 @item QTDisconnected:@var{value}
33997 Set the choice to what to do with the tracing run when @value{GDBN}
33998 disconnects from the target. A @var{value} of 1 directs the target to
33999 continue the tracing run, while 0 tells the target to stop tracing if
34000 @value{GDBN} is no longer in the picture.
34003 Ask the stub if there is a trace experiment running right now.
34005 The reply has the form:
34009 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
34010 @var{running} is a single digit @code{1} if the trace is presently
34011 running, or @code{0} if not. It is followed by semicolon-separated
34012 optional fields that an agent may use to report additional status.
34016 If the trace is not running, the agent may report any of several
34017 explanations as one of the optional fields:
34022 No trace has been run yet.
34025 The trace was stopped by a user-originated stop command.
34028 The trace stopped because the trace buffer filled up.
34030 @item tdisconnected:0
34031 The trace stopped because @value{GDBN} disconnected from the target.
34033 @item tpasscount:@var{tpnum}
34034 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
34036 @item terror:@var{text}:@var{tpnum}
34037 The trace stopped because tracepoint @var{tpnum} had an error. The
34038 string @var{text} is available to describe the nature of the error
34039 (for instance, a divide by zero in the condition expression).
34040 @var{text} is hex encoded.
34043 The trace stopped for some other reason.
34047 Additional optional fields supply statistical and other information.
34048 Although not required, they are extremely useful for users monitoring
34049 the progress of a trace run. If a trace has stopped, and these
34050 numbers are reported, they must reflect the state of the just-stopped
34055 @item tframes:@var{n}
34056 The number of trace frames in the buffer.
34058 @item tcreated:@var{n}
34059 The total number of trace frames created during the run. This may
34060 be larger than the trace frame count, if the buffer is circular.
34062 @item tsize:@var{n}
34063 The total size of the trace buffer, in bytes.
34065 @item tfree:@var{n}
34066 The number of bytes still unused in the buffer.
34068 @item circular:@var{n}
34069 The value of the circular trace buffer flag. @code{1} means that the
34070 trace buffer is circular and old trace frames will be discarded if
34071 necessary to make room, @code{0} means that the trace buffer is linear
34074 @item disconn:@var{n}
34075 The value of the disconnected tracing flag. @code{1} means that
34076 tracing will continue after @value{GDBN} disconnects, @code{0} means
34077 that the trace run will stop.
34081 @item qTV:@var{var}
34082 @cindex trace state variable value, remote request
34083 @cindex @samp{qTV} packet
34084 Ask the stub for the value of the trace state variable number @var{var}.
34089 The value of the variable is @var{value}. This will be the current
34090 value of the variable if the user is examining a running target, or a
34091 saved value if the variable was collected in the trace frame that the
34092 user is looking at. Note that multiple requests may result in
34093 different reply values, such as when requesting values while the
34094 program is running.
34097 The value of the variable is unknown. This would occur, for example,
34098 if the user is examining a trace frame in which the requested variable
34104 These packets request data about tracepoints that are being used by
34105 the target. @value{GDBN} sends @code{qTfP} to get the first piece
34106 of data, and multiple @code{qTsP} to get additional pieces. Replies
34107 to these packets generally take the form of the @code{QTDP} packets
34108 that define tracepoints. (FIXME add detailed syntax)
34112 These packets request data about trace state variables that are on the
34113 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
34114 and multiple @code{qTsV} to get additional variables. Replies to
34115 these packets follow the syntax of the @code{QTDV} packets that define
34116 trace state variables.
34120 These packets request data about static tracepoint markers that exist
34121 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
34122 first piece of data, and multiple @code{qTsSTM} to get additional
34123 pieces. Replies to these packets take the following form:
34127 @item m @var{address}:@var{id}:@var{extra}
34129 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
34130 a comma-separated list of markers
34132 (lower case letter @samp{L}) denotes end of list.
34134 An error occurred. @var{nn} are hex digits.
34136 An empty reply indicates that the request is not supported by the
34140 @var{address} is encoded in hex.
34141 @var{id} and @var{extra} are strings encoded in hex.
34143 In response to each query, the target will reply with a list of one or
34144 more markers, separated by commas. @value{GDBN} will respond to each
34145 reply with a request for more markers (using the @samp{qs} form of the
34146 query), until the target responds with @samp{l} (lower-case ell, for
34149 @item qTSTMat:@var{address}
34150 This packets requests data about static tracepoint markers in the
34151 target program at @var{address}. Replies to this packet follow the
34152 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
34153 tracepoint markers.
34155 @item QTSave:@var{filename}
34156 This packet directs the target to save trace data to the file name
34157 @var{filename} in the target's filesystem. @var{filename} is encoded
34158 as a hex string; the interpretation of the file name (relative vs
34159 absolute, wild cards, etc) is up to the target.
34161 @item qTBuffer:@var{offset},@var{len}
34162 Return up to @var{len} bytes of the current contents of trace buffer,
34163 starting at @var{offset}. The trace buffer is treated as if it were
34164 a contiguous collection of traceframes, as per the trace file format.
34165 The reply consists as many hex-encoded bytes as the target can deliver
34166 in a packet; it is not an error to return fewer than were asked for.
34167 A reply consisting of just @code{l} indicates that no bytes are
34170 @item QTBuffer:circular:@var{value}
34171 This packet directs the target to use a circular trace buffer if
34172 @var{value} is 1, or a linear buffer if the value is 0.
34176 @subsection Relocate instruction reply packet
34177 When installing fast tracepoints in memory, the target may need to
34178 relocate the instruction currently at the tracepoint address to a
34179 different address in memory. For most instructions, a simple copy is
34180 enough, but, for example, call instructions that implicitly push the
34181 return address on the stack, and relative branches or other
34182 PC-relative instructions require offset adjustment, so that the effect
34183 of executing the instruction at a different address is the same as if
34184 it had executed in the original location.
34186 In response to several of the tracepoint packets, the target may also
34187 respond with a number of intermediate @samp{qRelocInsn} request
34188 packets before the final result packet, to have @value{GDBN} handle
34189 this relocation operation. If a packet supports this mechanism, its
34190 documentation will explicitly say so. See for example the above
34191 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
34192 format of the request is:
34195 @item qRelocInsn:@var{from};@var{to}
34197 This requests @value{GDBN} to copy instruction at address @var{from}
34198 to address @var{to}, possibly adjusted so that executing the
34199 instruction at @var{to} has the same effect as executing it at
34200 @var{from}. @value{GDBN} writes the adjusted instruction to target
34201 memory starting at @var{to}.
34206 @item qRelocInsn:@var{adjusted_size}
34207 Informs the stub the relocation is complete. @var{adjusted_size} is
34208 the length in bytes of resulting relocated instruction sequence.
34210 A badly formed request was detected, or an error was encountered while
34211 relocating the instruction.
34214 @node Host I/O Packets
34215 @section Host I/O Packets
34216 @cindex Host I/O, remote protocol
34217 @cindex file transfer, remote protocol
34219 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
34220 operations on the far side of a remote link. For example, Host I/O is
34221 used to upload and download files to a remote target with its own
34222 filesystem. Host I/O uses the same constant values and data structure
34223 layout as the target-initiated File-I/O protocol. However, the
34224 Host I/O packets are structured differently. The target-initiated
34225 protocol relies on target memory to store parameters and buffers.
34226 Host I/O requests are initiated by @value{GDBN}, and the
34227 target's memory is not involved. @xref{File-I/O Remote Protocol
34228 Extension}, for more details on the target-initiated protocol.
34230 The Host I/O request packets all encode a single operation along with
34231 its arguments. They have this format:
34235 @item vFile:@var{operation}: @var{parameter}@dots{}
34236 @var{operation} is the name of the particular request; the target
34237 should compare the entire packet name up to the second colon when checking
34238 for a supported operation. The format of @var{parameter} depends on
34239 the operation. Numbers are always passed in hexadecimal. Negative
34240 numbers have an explicit minus sign (i.e.@: two's complement is not
34241 used). Strings (e.g.@: filenames) are encoded as a series of
34242 hexadecimal bytes. The last argument to a system call may be a
34243 buffer of escaped binary data (@pxref{Binary Data}).
34247 The valid responses to Host I/O packets are:
34251 @item F @var{result} [, @var{errno}] [; @var{attachment}]
34252 @var{result} is the integer value returned by this operation, usually
34253 non-negative for success and -1 for errors. If an error has occured,
34254 @var{errno} will be included in the result. @var{errno} will have a
34255 value defined by the File-I/O protocol (@pxref{Errno Values}). For
34256 operations which return data, @var{attachment} supplies the data as a
34257 binary buffer. Binary buffers in response packets are escaped in the
34258 normal way (@pxref{Binary Data}). See the individual packet
34259 documentation for the interpretation of @var{result} and
34263 An empty response indicates that this operation is not recognized.
34267 These are the supported Host I/O operations:
34270 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
34271 Open a file at @var{pathname} and return a file descriptor for it, or
34272 return -1 if an error occurs. @var{pathname} is a string,
34273 @var{flags} is an integer indicating a mask of open flags
34274 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
34275 of mode bits to use if the file is created (@pxref{mode_t Values}).
34276 @xref{open}, for details of the open flags and mode values.
34278 @item vFile:close: @var{fd}
34279 Close the open file corresponding to @var{fd} and return 0, or
34280 -1 if an error occurs.
34282 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
34283 Read data from the open file corresponding to @var{fd}. Up to
34284 @var{count} bytes will be read from the file, starting at @var{offset}
34285 relative to the start of the file. The target may read fewer bytes;
34286 common reasons include packet size limits and an end-of-file
34287 condition. The number of bytes read is returned. Zero should only be
34288 returned for a successful read at the end of the file, or if
34289 @var{count} was zero.
34291 The data read should be returned as a binary attachment on success.
34292 If zero bytes were read, the response should include an empty binary
34293 attachment (i.e.@: a trailing semicolon). The return value is the
34294 number of target bytes read; the binary attachment may be longer if
34295 some characters were escaped.
34297 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
34298 Write @var{data} (a binary buffer) to the open file corresponding
34299 to @var{fd}. Start the write at @var{offset} from the start of the
34300 file. Unlike many @code{write} system calls, there is no
34301 separate @var{count} argument; the length of @var{data} in the
34302 packet is used. @samp{vFile:write} returns the number of bytes written,
34303 which may be shorter than the length of @var{data}, or -1 if an
34306 @item vFile:unlink: @var{pathname}
34307 Delete the file at @var{pathname} on the target. Return 0,
34308 or -1 if an error occurs. @var{pathname} is a string.
34313 @section Interrupts
34314 @cindex interrupts (remote protocol)
34316 When a program on the remote target is running, @value{GDBN} may
34317 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
34318 a @code{BREAK} followed by @code{g},
34319 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
34321 The precise meaning of @code{BREAK} is defined by the transport
34322 mechanism and may, in fact, be undefined. @value{GDBN} does not
34323 currently define a @code{BREAK} mechanism for any of the network
34324 interfaces except for TCP, in which case @value{GDBN} sends the
34325 @code{telnet} BREAK sequence.
34327 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
34328 transport mechanisms. It is represented by sending the single byte
34329 @code{0x03} without any of the usual packet overhead described in
34330 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
34331 transmitted as part of a packet, it is considered to be packet data
34332 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
34333 (@pxref{X packet}), used for binary downloads, may include an unescaped
34334 @code{0x03} as part of its packet.
34336 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
34337 When Linux kernel receives this sequence from serial port,
34338 it stops execution and connects to gdb.
34340 Stubs are not required to recognize these interrupt mechanisms and the
34341 precise meaning associated with receipt of the interrupt is
34342 implementation defined. If the target supports debugging of multiple
34343 threads and/or processes, it should attempt to interrupt all
34344 currently-executing threads and processes.
34345 If the stub is successful at interrupting the
34346 running program, it should send one of the stop
34347 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
34348 of successfully stopping the program in all-stop mode, and a stop reply
34349 for each stopped thread in non-stop mode.
34350 Interrupts received while the
34351 program is stopped are discarded.
34353 @node Notification Packets
34354 @section Notification Packets
34355 @cindex notification packets
34356 @cindex packets, notification
34358 The @value{GDBN} remote serial protocol includes @dfn{notifications},
34359 packets that require no acknowledgment. Both the GDB and the stub
34360 may send notifications (although the only notifications defined at
34361 present are sent by the stub). Notifications carry information
34362 without incurring the round-trip latency of an acknowledgment, and so
34363 are useful for low-impact communications where occasional packet loss
34366 A notification packet has the form @samp{% @var{data} #
34367 @var{checksum}}, where @var{data} is the content of the notification,
34368 and @var{checksum} is a checksum of @var{data}, computed and formatted
34369 as for ordinary @value{GDBN} packets. A notification's @var{data}
34370 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
34371 receiving a notification, the recipient sends no @samp{+} or @samp{-}
34372 to acknowledge the notification's receipt or to report its corruption.
34374 Every notification's @var{data} begins with a name, which contains no
34375 colon characters, followed by a colon character.
34377 Recipients should silently ignore corrupted notifications and
34378 notifications they do not understand. Recipients should restart
34379 timeout periods on receipt of a well-formed notification, whether or
34380 not they understand it.
34382 Senders should only send the notifications described here when this
34383 protocol description specifies that they are permitted. In the
34384 future, we may extend the protocol to permit existing notifications in
34385 new contexts; this rule helps older senders avoid confusing newer
34388 (Older versions of @value{GDBN} ignore bytes received until they see
34389 the @samp{$} byte that begins an ordinary packet, so new stubs may
34390 transmit notifications without fear of confusing older clients. There
34391 are no notifications defined for @value{GDBN} to send at the moment, but we
34392 assume that most older stubs would ignore them, as well.)
34394 The following notification packets from the stub to @value{GDBN} are
34398 @item Stop: @var{reply}
34399 Report an asynchronous stop event in non-stop mode.
34400 The @var{reply} has the form of a stop reply, as
34401 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
34402 for information on how these notifications are acknowledged by
34406 @node Remote Non-Stop
34407 @section Remote Protocol Support for Non-Stop Mode
34409 @value{GDBN}'s remote protocol supports non-stop debugging of
34410 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
34411 supports non-stop mode, it should report that to @value{GDBN} by including
34412 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
34414 @value{GDBN} typically sends a @samp{QNonStop} packet only when
34415 establishing a new connection with the stub. Entering non-stop mode
34416 does not alter the state of any currently-running threads, but targets
34417 must stop all threads in any already-attached processes when entering
34418 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
34419 probe the target state after a mode change.
34421 In non-stop mode, when an attached process encounters an event that
34422 would otherwise be reported with a stop reply, it uses the
34423 asynchronous notification mechanism (@pxref{Notification Packets}) to
34424 inform @value{GDBN}. In contrast to all-stop mode, where all threads
34425 in all processes are stopped when a stop reply is sent, in non-stop
34426 mode only the thread reporting the stop event is stopped. That is,
34427 when reporting a @samp{S} or @samp{T} response to indicate completion
34428 of a step operation, hitting a breakpoint, or a fault, only the
34429 affected thread is stopped; any other still-running threads continue
34430 to run. When reporting a @samp{W} or @samp{X} response, all running
34431 threads belonging to other attached processes continue to run.
34433 Only one stop reply notification at a time may be pending; if
34434 additional stop events occur before @value{GDBN} has acknowledged the
34435 previous notification, they must be queued by the stub for later
34436 synchronous transmission in response to @samp{vStopped} packets from
34437 @value{GDBN}. Because the notification mechanism is unreliable,
34438 the stub is permitted to resend a stop reply notification
34439 if it believes @value{GDBN} may not have received it. @value{GDBN}
34440 ignores additional stop reply notifications received before it has
34441 finished processing a previous notification and the stub has completed
34442 sending any queued stop events.
34444 Otherwise, @value{GDBN} must be prepared to receive a stop reply
34445 notification at any time. Specifically, they may appear when
34446 @value{GDBN} is not otherwise reading input from the stub, or when
34447 @value{GDBN} is expecting to read a normal synchronous response or a
34448 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
34449 Notification packets are distinct from any other communication from
34450 the stub so there is no ambiguity.
34452 After receiving a stop reply notification, @value{GDBN} shall
34453 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
34454 as a regular, synchronous request to the stub. Such acknowledgment
34455 is not required to happen immediately, as @value{GDBN} is permitted to
34456 send other, unrelated packets to the stub first, which the stub should
34459 Upon receiving a @samp{vStopped} packet, if the stub has other queued
34460 stop events to report to @value{GDBN}, it shall respond by sending a
34461 normal stop reply response. @value{GDBN} shall then send another
34462 @samp{vStopped} packet to solicit further responses; again, it is
34463 permitted to send other, unrelated packets as well which the stub
34464 should process normally.
34466 If the stub receives a @samp{vStopped} packet and there are no
34467 additional stop events to report, the stub shall return an @samp{OK}
34468 response. At this point, if further stop events occur, the stub shall
34469 send a new stop reply notification, @value{GDBN} shall accept the
34470 notification, and the process shall be repeated.
34472 In non-stop mode, the target shall respond to the @samp{?} packet as
34473 follows. First, any incomplete stop reply notification/@samp{vStopped}
34474 sequence in progress is abandoned. The target must begin a new
34475 sequence reporting stop events for all stopped threads, whether or not
34476 it has previously reported those events to @value{GDBN}. The first
34477 stop reply is sent as a synchronous reply to the @samp{?} packet, and
34478 subsequent stop replies are sent as responses to @samp{vStopped} packets
34479 using the mechanism described above. The target must not send
34480 asynchronous stop reply notifications until the sequence is complete.
34481 If all threads are running when the target receives the @samp{?} packet,
34482 or if the target is not attached to any process, it shall respond
34485 @node Packet Acknowledgment
34486 @section Packet Acknowledgment
34488 @cindex acknowledgment, for @value{GDBN} remote
34489 @cindex packet acknowledgment, for @value{GDBN} remote
34490 By default, when either the host or the target machine receives a packet,
34491 the first response expected is an acknowledgment: either @samp{+} (to indicate
34492 the package was received correctly) or @samp{-} (to request retransmission).
34493 This mechanism allows the @value{GDBN} remote protocol to operate over
34494 unreliable transport mechanisms, such as a serial line.
34496 In cases where the transport mechanism is itself reliable (such as a pipe or
34497 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
34498 It may be desirable to disable them in that case to reduce communication
34499 overhead, or for other reasons. This can be accomplished by means of the
34500 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
34502 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
34503 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
34504 and response format still includes the normal checksum, as described in
34505 @ref{Overview}, but the checksum may be ignored by the receiver.
34507 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
34508 no-acknowledgment mode, it should report that to @value{GDBN}
34509 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
34510 @pxref{qSupported}.
34511 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
34512 disabled via the @code{set remote noack-packet off} command
34513 (@pxref{Remote Configuration}),
34514 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
34515 Only then may the stub actually turn off packet acknowledgments.
34516 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
34517 response, which can be safely ignored by the stub.
34519 Note that @code{set remote noack-packet} command only affects negotiation
34520 between @value{GDBN} and the stub when subsequent connections are made;
34521 it does not affect the protocol acknowledgment state for any current
34523 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
34524 new connection is established,
34525 there is also no protocol request to re-enable the acknowledgments
34526 for the current connection, once disabled.
34531 Example sequence of a target being re-started. Notice how the restart
34532 does not get any direct output:
34537 @emph{target restarts}
34540 <- @code{T001:1234123412341234}
34544 Example sequence of a target being stepped by a single instruction:
34547 -> @code{G1445@dots{}}
34552 <- @code{T001:1234123412341234}
34556 <- @code{1455@dots{}}
34560 @node File-I/O Remote Protocol Extension
34561 @section File-I/O Remote Protocol Extension
34562 @cindex File-I/O remote protocol extension
34565 * File-I/O Overview::
34566 * Protocol Basics::
34567 * The F Request Packet::
34568 * The F Reply Packet::
34569 * The Ctrl-C Message::
34571 * List of Supported Calls::
34572 * Protocol-specific Representation of Datatypes::
34574 * File-I/O Examples::
34577 @node File-I/O Overview
34578 @subsection File-I/O Overview
34579 @cindex file-i/o overview
34581 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
34582 target to use the host's file system and console I/O to perform various
34583 system calls. System calls on the target system are translated into a
34584 remote protocol packet to the host system, which then performs the needed
34585 actions and returns a response packet to the target system.
34586 This simulates file system operations even on targets that lack file systems.
34588 The protocol is defined to be independent of both the host and target systems.
34589 It uses its own internal representation of datatypes and values. Both
34590 @value{GDBN} and the target's @value{GDBN} stub are responsible for
34591 translating the system-dependent value representations into the internal
34592 protocol representations when data is transmitted.
34594 The communication is synchronous. A system call is possible only when
34595 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
34596 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
34597 the target is stopped to allow deterministic access to the target's
34598 memory. Therefore File-I/O is not interruptible by target signals. On
34599 the other hand, it is possible to interrupt File-I/O by a user interrupt
34600 (@samp{Ctrl-C}) within @value{GDBN}.
34602 The target's request to perform a host system call does not finish
34603 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
34604 after finishing the system call, the target returns to continuing the
34605 previous activity (continue, step). No additional continue or step
34606 request from @value{GDBN} is required.
34609 (@value{GDBP}) continue
34610 <- target requests 'system call X'
34611 target is stopped, @value{GDBN} executes system call
34612 -> @value{GDBN} returns result
34613 ... target continues, @value{GDBN} returns to wait for the target
34614 <- target hits breakpoint and sends a Txx packet
34617 The protocol only supports I/O on the console and to regular files on
34618 the host file system. Character or block special devices, pipes,
34619 named pipes, sockets or any other communication method on the host
34620 system are not supported by this protocol.
34622 File I/O is not supported in non-stop mode.
34624 @node Protocol Basics
34625 @subsection Protocol Basics
34626 @cindex protocol basics, file-i/o
34628 The File-I/O protocol uses the @code{F} packet as the request as well
34629 as reply packet. Since a File-I/O system call can only occur when
34630 @value{GDBN} is waiting for a response from the continuing or stepping target,
34631 the File-I/O request is a reply that @value{GDBN} has to expect as a result
34632 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
34633 This @code{F} packet contains all information needed to allow @value{GDBN}
34634 to call the appropriate host system call:
34638 A unique identifier for the requested system call.
34641 All parameters to the system call. Pointers are given as addresses
34642 in the target memory address space. Pointers to strings are given as
34643 pointer/length pair. Numerical values are given as they are.
34644 Numerical control flags are given in a protocol-specific representation.
34648 At this point, @value{GDBN} has to perform the following actions.
34652 If the parameters include pointer values to data needed as input to a
34653 system call, @value{GDBN} requests this data from the target with a
34654 standard @code{m} packet request. This additional communication has to be
34655 expected by the target implementation and is handled as any other @code{m}
34659 @value{GDBN} translates all value from protocol representation to host
34660 representation as needed. Datatypes are coerced into the host types.
34663 @value{GDBN} calls the system call.
34666 It then coerces datatypes back to protocol representation.
34669 If the system call is expected to return data in buffer space specified
34670 by pointer parameters to the call, the data is transmitted to the
34671 target using a @code{M} or @code{X} packet. This packet has to be expected
34672 by the target implementation and is handled as any other @code{M} or @code{X}
34677 Eventually @value{GDBN} replies with another @code{F} packet which contains all
34678 necessary information for the target to continue. This at least contains
34685 @code{errno}, if has been changed by the system call.
34692 After having done the needed type and value coercion, the target continues
34693 the latest continue or step action.
34695 @node The F Request Packet
34696 @subsection The @code{F} Request Packet
34697 @cindex file-i/o request packet
34698 @cindex @code{F} request packet
34700 The @code{F} request packet has the following format:
34703 @item F@var{call-id},@var{parameter@dots{}}
34705 @var{call-id} is the identifier to indicate the host system call to be called.
34706 This is just the name of the function.
34708 @var{parameter@dots{}} are the parameters to the system call.
34709 Parameters are hexadecimal integer values, either the actual values in case
34710 of scalar datatypes, pointers to target buffer space in case of compound
34711 datatypes and unspecified memory areas, or pointer/length pairs in case
34712 of string parameters. These are appended to the @var{call-id} as a
34713 comma-delimited list. All values are transmitted in ASCII
34714 string representation, pointer/length pairs separated by a slash.
34720 @node The F Reply Packet
34721 @subsection The @code{F} Reply Packet
34722 @cindex file-i/o reply packet
34723 @cindex @code{F} reply packet
34725 The @code{F} reply packet has the following format:
34729 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
34731 @var{retcode} is the return code of the system call as hexadecimal value.
34733 @var{errno} is the @code{errno} set by the call, in protocol-specific
34735 This parameter can be omitted if the call was successful.
34737 @var{Ctrl-C flag} is only sent if the user requested a break. In this
34738 case, @var{errno} must be sent as well, even if the call was successful.
34739 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
34746 or, if the call was interrupted before the host call has been performed:
34753 assuming 4 is the protocol-specific representation of @code{EINTR}.
34758 @node The Ctrl-C Message
34759 @subsection The @samp{Ctrl-C} Message
34760 @cindex ctrl-c message, in file-i/o protocol
34762 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
34763 reply packet (@pxref{The F Reply Packet}),
34764 the target should behave as if it had
34765 gotten a break message. The meaning for the target is ``system call
34766 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
34767 (as with a break message) and return to @value{GDBN} with a @code{T02}
34770 It's important for the target to know in which
34771 state the system call was interrupted. There are two possible cases:
34775 The system call hasn't been performed on the host yet.
34778 The system call on the host has been finished.
34782 These two states can be distinguished by the target by the value of the
34783 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
34784 call hasn't been performed. This is equivalent to the @code{EINTR} handling
34785 on POSIX systems. In any other case, the target may presume that the
34786 system call has been finished --- successfully or not --- and should behave
34787 as if the break message arrived right after the system call.
34789 @value{GDBN} must behave reliably. If the system call has not been called
34790 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
34791 @code{errno} in the packet. If the system call on the host has been finished
34792 before the user requests a break, the full action must be finished by
34793 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
34794 The @code{F} packet may only be sent when either nothing has happened
34795 or the full action has been completed.
34798 @subsection Console I/O
34799 @cindex console i/o as part of file-i/o
34801 By default and if not explicitly closed by the target system, the file
34802 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
34803 on the @value{GDBN} console is handled as any other file output operation
34804 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
34805 by @value{GDBN} so that after the target read request from file descriptor
34806 0 all following typing is buffered until either one of the following
34811 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
34813 system call is treated as finished.
34816 The user presses @key{RET}. This is treated as end of input with a trailing
34820 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
34821 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
34825 If the user has typed more characters than fit in the buffer given to
34826 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
34827 either another @code{read(0, @dots{})} is requested by the target, or debugging
34828 is stopped at the user's request.
34831 @node List of Supported Calls
34832 @subsection List of Supported Calls
34833 @cindex list of supported file-i/o calls
34850 @unnumberedsubsubsec open
34851 @cindex open, file-i/o system call
34856 int open(const char *pathname, int flags);
34857 int open(const char *pathname, int flags, mode_t mode);
34861 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
34864 @var{flags} is the bitwise @code{OR} of the following values:
34868 If the file does not exist it will be created. The host
34869 rules apply as far as file ownership and time stamps
34873 When used with @code{O_CREAT}, if the file already exists it is
34874 an error and open() fails.
34877 If the file already exists and the open mode allows
34878 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
34879 truncated to zero length.
34882 The file is opened in append mode.
34885 The file is opened for reading only.
34888 The file is opened for writing only.
34891 The file is opened for reading and writing.
34895 Other bits are silently ignored.
34899 @var{mode} is the bitwise @code{OR} of the following values:
34903 User has read permission.
34906 User has write permission.
34909 Group has read permission.
34912 Group has write permission.
34915 Others have read permission.
34918 Others have write permission.
34922 Other bits are silently ignored.
34925 @item Return value:
34926 @code{open} returns the new file descriptor or -1 if an error
34933 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
34936 @var{pathname} refers to a directory.
34939 The requested access is not allowed.
34942 @var{pathname} was too long.
34945 A directory component in @var{pathname} does not exist.
34948 @var{pathname} refers to a device, pipe, named pipe or socket.
34951 @var{pathname} refers to a file on a read-only filesystem and
34952 write access was requested.
34955 @var{pathname} is an invalid pointer value.
34958 No space on device to create the file.
34961 The process already has the maximum number of files open.
34964 The limit on the total number of files open on the system
34968 The call was interrupted by the user.
34974 @unnumberedsubsubsec close
34975 @cindex close, file-i/o system call
34984 @samp{Fclose,@var{fd}}
34986 @item Return value:
34987 @code{close} returns zero on success, or -1 if an error occurred.
34993 @var{fd} isn't a valid open file descriptor.
34996 The call was interrupted by the user.
35002 @unnumberedsubsubsec read
35003 @cindex read, file-i/o system call
35008 int read(int fd, void *buf, unsigned int count);
35012 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
35014 @item Return value:
35015 On success, the number of bytes read is returned.
35016 Zero indicates end of file. If count is zero, read
35017 returns zero as well. On error, -1 is returned.
35023 @var{fd} is not a valid file descriptor or is not open for
35027 @var{bufptr} is an invalid pointer value.
35030 The call was interrupted by the user.
35036 @unnumberedsubsubsec write
35037 @cindex write, file-i/o system call
35042 int write(int fd, const void *buf, unsigned int count);
35046 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
35048 @item Return value:
35049 On success, the number of bytes written are returned.
35050 Zero indicates nothing was written. On error, -1
35057 @var{fd} is not a valid file descriptor or is not open for
35061 @var{bufptr} is an invalid pointer value.
35064 An attempt was made to write a file that exceeds the
35065 host-specific maximum file size allowed.
35068 No space on device to write the data.
35071 The call was interrupted by the user.
35077 @unnumberedsubsubsec lseek
35078 @cindex lseek, file-i/o system call
35083 long lseek (int fd, long offset, int flag);
35087 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
35089 @var{flag} is one of:
35093 The offset is set to @var{offset} bytes.
35096 The offset is set to its current location plus @var{offset}
35100 The offset is set to the size of the file plus @var{offset}
35104 @item Return value:
35105 On success, the resulting unsigned offset in bytes from
35106 the beginning of the file is returned. Otherwise, a
35107 value of -1 is returned.
35113 @var{fd} is not a valid open file descriptor.
35116 @var{fd} is associated with the @value{GDBN} console.
35119 @var{flag} is not a proper value.
35122 The call was interrupted by the user.
35128 @unnumberedsubsubsec rename
35129 @cindex rename, file-i/o system call
35134 int rename(const char *oldpath, const char *newpath);
35138 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
35140 @item Return value:
35141 On success, zero is returned. On error, -1 is returned.
35147 @var{newpath} is an existing directory, but @var{oldpath} is not a
35151 @var{newpath} is a non-empty directory.
35154 @var{oldpath} or @var{newpath} is a directory that is in use by some
35158 An attempt was made to make a directory a subdirectory
35162 A component used as a directory in @var{oldpath} or new
35163 path is not a directory. Or @var{oldpath} is a directory
35164 and @var{newpath} exists but is not a directory.
35167 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
35170 No access to the file or the path of the file.
35174 @var{oldpath} or @var{newpath} was too long.
35177 A directory component in @var{oldpath} or @var{newpath} does not exist.
35180 The file is on a read-only filesystem.
35183 The device containing the file has no room for the new
35187 The call was interrupted by the user.
35193 @unnumberedsubsubsec unlink
35194 @cindex unlink, file-i/o system call
35199 int unlink(const char *pathname);
35203 @samp{Funlink,@var{pathnameptr}/@var{len}}
35205 @item Return value:
35206 On success, zero is returned. On error, -1 is returned.
35212 No access to the file or the path of the file.
35215 The system does not allow unlinking of directories.
35218 The file @var{pathname} cannot be unlinked because it's
35219 being used by another process.
35222 @var{pathnameptr} is an invalid pointer value.
35225 @var{pathname} was too long.
35228 A directory component in @var{pathname} does not exist.
35231 A component of the path is not a directory.
35234 The file is on a read-only filesystem.
35237 The call was interrupted by the user.
35243 @unnumberedsubsubsec stat/fstat
35244 @cindex fstat, file-i/o system call
35245 @cindex stat, file-i/o system call
35250 int stat(const char *pathname, struct stat *buf);
35251 int fstat(int fd, struct stat *buf);
35255 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
35256 @samp{Ffstat,@var{fd},@var{bufptr}}
35258 @item Return value:
35259 On success, zero is returned. On error, -1 is returned.
35265 @var{fd} is not a valid open file.
35268 A directory component in @var{pathname} does not exist or the
35269 path is an empty string.
35272 A component of the path is not a directory.
35275 @var{pathnameptr} is an invalid pointer value.
35278 No access to the file or the path of the file.
35281 @var{pathname} was too long.
35284 The call was interrupted by the user.
35290 @unnumberedsubsubsec gettimeofday
35291 @cindex gettimeofday, file-i/o system call
35296 int gettimeofday(struct timeval *tv, void *tz);
35300 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
35302 @item Return value:
35303 On success, 0 is returned, -1 otherwise.
35309 @var{tz} is a non-NULL pointer.
35312 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
35318 @unnumberedsubsubsec isatty
35319 @cindex isatty, file-i/o system call
35324 int isatty(int fd);
35328 @samp{Fisatty,@var{fd}}
35330 @item Return value:
35331 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
35337 The call was interrupted by the user.
35342 Note that the @code{isatty} call is treated as a special case: it returns
35343 1 to the target if the file descriptor is attached
35344 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
35345 would require implementing @code{ioctl} and would be more complex than
35350 @unnumberedsubsubsec system
35351 @cindex system, file-i/o system call
35356 int system(const char *command);
35360 @samp{Fsystem,@var{commandptr}/@var{len}}
35362 @item Return value:
35363 If @var{len} is zero, the return value indicates whether a shell is
35364 available. A zero return value indicates a shell is not available.
35365 For non-zero @var{len}, the value returned is -1 on error and the
35366 return status of the command otherwise. Only the exit status of the
35367 command is returned, which is extracted from the host's @code{system}
35368 return value by calling @code{WEXITSTATUS(retval)}. In case
35369 @file{/bin/sh} could not be executed, 127 is returned.
35375 The call was interrupted by the user.
35380 @value{GDBN} takes over the full task of calling the necessary host calls
35381 to perform the @code{system} call. The return value of @code{system} on
35382 the host is simplified before it's returned
35383 to the target. Any termination signal information from the child process
35384 is discarded, and the return value consists
35385 entirely of the exit status of the called command.
35387 Due to security concerns, the @code{system} call is by default refused
35388 by @value{GDBN}. The user has to allow this call explicitly with the
35389 @code{set remote system-call-allowed 1} command.
35392 @item set remote system-call-allowed
35393 @kindex set remote system-call-allowed
35394 Control whether to allow the @code{system} calls in the File I/O
35395 protocol for the remote target. The default is zero (disabled).
35397 @item show remote system-call-allowed
35398 @kindex show remote system-call-allowed
35399 Show whether the @code{system} calls are allowed in the File I/O
35403 @node Protocol-specific Representation of Datatypes
35404 @subsection Protocol-specific Representation of Datatypes
35405 @cindex protocol-specific representation of datatypes, in file-i/o protocol
35408 * Integral Datatypes::
35410 * Memory Transfer::
35415 @node Integral Datatypes
35416 @unnumberedsubsubsec Integral Datatypes
35417 @cindex integral datatypes, in file-i/o protocol
35419 The integral datatypes used in the system calls are @code{int},
35420 @code{unsigned int}, @code{long}, @code{unsigned long},
35421 @code{mode_t}, and @code{time_t}.
35423 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
35424 implemented as 32 bit values in this protocol.
35426 @code{long} and @code{unsigned long} are implemented as 64 bit types.
35428 @xref{Limits}, for corresponding MIN and MAX values (similar to those
35429 in @file{limits.h}) to allow range checking on host and target.
35431 @code{time_t} datatypes are defined as seconds since the Epoch.
35433 All integral datatypes transferred as part of a memory read or write of a
35434 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
35437 @node Pointer Values
35438 @unnumberedsubsubsec Pointer Values
35439 @cindex pointer values, in file-i/o protocol
35441 Pointers to target data are transmitted as they are. An exception
35442 is made for pointers to buffers for which the length isn't
35443 transmitted as part of the function call, namely strings. Strings
35444 are transmitted as a pointer/length pair, both as hex values, e.g.@:
35451 which is a pointer to data of length 18 bytes at position 0x1aaf.
35452 The length is defined as the full string length in bytes, including
35453 the trailing null byte. For example, the string @code{"hello world"}
35454 at address 0x123456 is transmitted as
35460 @node Memory Transfer
35461 @unnumberedsubsubsec Memory Transfer
35462 @cindex memory transfer, in file-i/o protocol
35464 Structured data which is transferred using a memory read or write (for
35465 example, a @code{struct stat}) is expected to be in a protocol-specific format
35466 with all scalar multibyte datatypes being big endian. Translation to
35467 this representation needs to be done both by the target before the @code{F}
35468 packet is sent, and by @value{GDBN} before
35469 it transfers memory to the target. Transferred pointers to structured
35470 data should point to the already-coerced data at any time.
35474 @unnumberedsubsubsec struct stat
35475 @cindex struct stat, in file-i/o protocol
35477 The buffer of type @code{struct stat} used by the target and @value{GDBN}
35478 is defined as follows:
35482 unsigned int st_dev; /* device */
35483 unsigned int st_ino; /* inode */
35484 mode_t st_mode; /* protection */
35485 unsigned int st_nlink; /* number of hard links */
35486 unsigned int st_uid; /* user ID of owner */
35487 unsigned int st_gid; /* group ID of owner */
35488 unsigned int st_rdev; /* device type (if inode device) */
35489 unsigned long st_size; /* total size, in bytes */
35490 unsigned long st_blksize; /* blocksize for filesystem I/O */
35491 unsigned long st_blocks; /* number of blocks allocated */
35492 time_t st_atime; /* time of last access */
35493 time_t st_mtime; /* time of last modification */
35494 time_t st_ctime; /* time of last change */
35498 The integral datatypes conform to the definitions given in the
35499 appropriate section (see @ref{Integral Datatypes}, for details) so this
35500 structure is of size 64 bytes.
35502 The values of several fields have a restricted meaning and/or
35508 A value of 0 represents a file, 1 the console.
35511 No valid meaning for the target. Transmitted unchanged.
35514 Valid mode bits are described in @ref{Constants}. Any other
35515 bits have currently no meaning for the target.
35520 No valid meaning for the target. Transmitted unchanged.
35525 These values have a host and file system dependent
35526 accuracy. Especially on Windows hosts, the file system may not
35527 support exact timing values.
35530 The target gets a @code{struct stat} of the above representation and is
35531 responsible for coercing it to the target representation before
35534 Note that due to size differences between the host, target, and protocol
35535 representations of @code{struct stat} members, these members could eventually
35536 get truncated on the target.
35538 @node struct timeval
35539 @unnumberedsubsubsec struct timeval
35540 @cindex struct timeval, in file-i/o protocol
35542 The buffer of type @code{struct timeval} used by the File-I/O protocol
35543 is defined as follows:
35547 time_t tv_sec; /* second */
35548 long tv_usec; /* microsecond */
35552 The integral datatypes conform to the definitions given in the
35553 appropriate section (see @ref{Integral Datatypes}, for details) so this
35554 structure is of size 8 bytes.
35557 @subsection Constants
35558 @cindex constants, in file-i/o protocol
35560 The following values are used for the constants inside of the
35561 protocol. @value{GDBN} and target are responsible for translating these
35562 values before and after the call as needed.
35573 @unnumberedsubsubsec Open Flags
35574 @cindex open flags, in file-i/o protocol
35576 All values are given in hexadecimal representation.
35588 @node mode_t Values
35589 @unnumberedsubsubsec mode_t Values
35590 @cindex mode_t values, in file-i/o protocol
35592 All values are given in octal representation.
35609 @unnumberedsubsubsec Errno Values
35610 @cindex errno values, in file-i/o protocol
35612 All values are given in decimal representation.
35637 @code{EUNKNOWN} is used as a fallback error value if a host system returns
35638 any error value not in the list of supported error numbers.
35641 @unnumberedsubsubsec Lseek Flags
35642 @cindex lseek flags, in file-i/o protocol
35651 @unnumberedsubsubsec Limits
35652 @cindex limits, in file-i/o protocol
35654 All values are given in decimal representation.
35657 INT_MIN -2147483648
35659 UINT_MAX 4294967295
35660 LONG_MIN -9223372036854775808
35661 LONG_MAX 9223372036854775807
35662 ULONG_MAX 18446744073709551615
35665 @node File-I/O Examples
35666 @subsection File-I/O Examples
35667 @cindex file-i/o examples
35669 Example sequence of a write call, file descriptor 3, buffer is at target
35670 address 0x1234, 6 bytes should be written:
35673 <- @code{Fwrite,3,1234,6}
35674 @emph{request memory read from target}
35677 @emph{return "6 bytes written"}
35681 Example sequence of a read call, file descriptor 3, buffer is at target
35682 address 0x1234, 6 bytes should be read:
35685 <- @code{Fread,3,1234,6}
35686 @emph{request memory write to target}
35687 -> @code{X1234,6:XXXXXX}
35688 @emph{return "6 bytes read"}
35692 Example sequence of a read call, call fails on the host due to invalid
35693 file descriptor (@code{EBADF}):
35696 <- @code{Fread,3,1234,6}
35700 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
35704 <- @code{Fread,3,1234,6}
35709 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
35713 <- @code{Fread,3,1234,6}
35714 -> @code{X1234,6:XXXXXX}
35718 @node Library List Format
35719 @section Library List Format
35720 @cindex library list format, remote protocol
35722 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
35723 same process as your application to manage libraries. In this case,
35724 @value{GDBN} can use the loader's symbol table and normal memory
35725 operations to maintain a list of shared libraries. On other
35726 platforms, the operating system manages loaded libraries.
35727 @value{GDBN} can not retrieve the list of currently loaded libraries
35728 through memory operations, so it uses the @samp{qXfer:libraries:read}
35729 packet (@pxref{qXfer library list read}) instead. The remote stub
35730 queries the target's operating system and reports which libraries
35733 The @samp{qXfer:libraries:read} packet returns an XML document which
35734 lists loaded libraries and their offsets. Each library has an
35735 associated name and one or more segment or section base addresses,
35736 which report where the library was loaded in memory.
35738 For the common case of libraries that are fully linked binaries, the
35739 library should have a list of segments. If the target supports
35740 dynamic linking of a relocatable object file, its library XML element
35741 should instead include a list of allocated sections. The segment or
35742 section bases are start addresses, not relocation offsets; they do not
35743 depend on the library's link-time base addresses.
35745 @value{GDBN} must be linked with the Expat library to support XML
35746 library lists. @xref{Expat}.
35748 A simple memory map, with one loaded library relocated by a single
35749 offset, looks like this:
35753 <library name="/lib/libc.so.6">
35754 <segment address="0x10000000"/>
35759 Another simple memory map, with one loaded library with three
35760 allocated sections (.text, .data, .bss), looks like this:
35764 <library name="sharedlib.o">
35765 <section address="0x10000000"/>
35766 <section address="0x20000000"/>
35767 <section address="0x30000000"/>
35772 The format of a library list is described by this DTD:
35775 <!-- library-list: Root element with versioning -->
35776 <!ELEMENT library-list (library)*>
35777 <!ATTLIST library-list version CDATA #FIXED "1.0">
35778 <!ELEMENT library (segment*, section*)>
35779 <!ATTLIST library name CDATA #REQUIRED>
35780 <!ELEMENT segment EMPTY>
35781 <!ATTLIST segment address CDATA #REQUIRED>
35782 <!ELEMENT section EMPTY>
35783 <!ATTLIST section address CDATA #REQUIRED>
35786 In addition, segments and section descriptors cannot be mixed within a
35787 single library element, and you must supply at least one segment or
35788 section for each library.
35790 @node Memory Map Format
35791 @section Memory Map Format
35792 @cindex memory map format
35794 To be able to write into flash memory, @value{GDBN} needs to obtain a
35795 memory map from the target. This section describes the format of the
35798 The memory map is obtained using the @samp{qXfer:memory-map:read}
35799 (@pxref{qXfer memory map read}) packet and is an XML document that
35800 lists memory regions.
35802 @value{GDBN} must be linked with the Expat library to support XML
35803 memory maps. @xref{Expat}.
35805 The top-level structure of the document is shown below:
35808 <?xml version="1.0"?>
35809 <!DOCTYPE memory-map
35810 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
35811 "http://sourceware.org/gdb/gdb-memory-map.dtd">
35817 Each region can be either:
35822 A region of RAM starting at @var{addr} and extending for @var{length}
35826 <memory type="ram" start="@var{addr}" length="@var{length}"/>
35831 A region of read-only memory:
35834 <memory type="rom" start="@var{addr}" length="@var{length}"/>
35839 A region of flash memory, with erasure blocks @var{blocksize}
35843 <memory type="flash" start="@var{addr}" length="@var{length}">
35844 <property name="blocksize">@var{blocksize}</property>
35850 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
35851 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
35852 packets to write to addresses in such ranges.
35854 The formal DTD for memory map format is given below:
35857 <!-- ................................................... -->
35858 <!-- Memory Map XML DTD ................................ -->
35859 <!-- File: memory-map.dtd .............................. -->
35860 <!-- .................................... .............. -->
35861 <!-- memory-map.dtd -->
35862 <!-- memory-map: Root element with versioning -->
35863 <!ELEMENT memory-map (memory | property)>
35864 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
35865 <!ELEMENT memory (property)>
35866 <!-- memory: Specifies a memory region,
35867 and its type, or device. -->
35868 <!ATTLIST memory type CDATA #REQUIRED
35869 start CDATA #REQUIRED
35870 length CDATA #REQUIRED
35871 device CDATA #IMPLIED>
35872 <!-- property: Generic attribute tag -->
35873 <!ELEMENT property (#PCDATA | property)*>
35874 <!ATTLIST property name CDATA #REQUIRED>
35877 @node Thread List Format
35878 @section Thread List Format
35879 @cindex thread list format
35881 To efficiently update the list of threads and their attributes,
35882 @value{GDBN} issues the @samp{qXfer:threads:read} packet
35883 (@pxref{qXfer threads read}) and obtains the XML document with
35884 the following structure:
35887 <?xml version="1.0"?>
35889 <thread id="id" core="0">
35890 ... description ...
35895 Each @samp{thread} element must have the @samp{id} attribute that
35896 identifies the thread (@pxref{thread-id syntax}). The
35897 @samp{core} attribute, if present, specifies which processor core
35898 the thread was last executing on. The content of the of @samp{thread}
35899 element is interpreted as human-readable auxilliary information.
35901 @node Traceframe Info Format
35902 @section Traceframe Info Format
35903 @cindex traceframe info format
35905 To be able to know which objects in the inferior can be examined when
35906 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
35907 memory ranges, registers and trace state variables that have been
35908 collected in a traceframe.
35910 This list is obtained using the @samp{qXfer:traceframe-info:read}
35911 (@pxref{qXfer traceframe info read}) packet and is an XML document.
35913 @value{GDBN} must be linked with the Expat library to support XML
35914 traceframe info discovery. @xref{Expat}.
35916 The top-level structure of the document is shown below:
35919 <?xml version="1.0"?>
35920 <!DOCTYPE traceframe-info
35921 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
35922 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
35928 Each traceframe block can be either:
35933 A region of collected memory starting at @var{addr} and extending for
35934 @var{length} bytes from there:
35937 <memory start="@var{addr}" length="@var{length}"/>
35942 The formal DTD for the traceframe info format is given below:
35945 <!ELEMENT traceframe-info (memory)* >
35946 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
35948 <!ELEMENT memory EMPTY>
35949 <!ATTLIST memory start CDATA #REQUIRED
35950 length CDATA #REQUIRED>
35953 @include agentexpr.texi
35955 @node Trace File Format
35956 @appendix Trace File Format
35957 @cindex trace file format
35959 The trace file comes in three parts: a header, a textual description
35960 section, and a trace frame section with binary data.
35962 The header has the form @code{\x7fTRACE0\n}. The first byte is
35963 @code{0x7f} so as to indicate that the file contains binary data,
35964 while the @code{0} is a version number that may have different values
35967 The description section consists of multiple lines of @sc{ascii} text
35968 separated by newline characters (@code{0xa}). The lines may include a
35969 variety of optional descriptive or context-setting information, such
35970 as tracepoint definitions or register set size. @value{GDBN} will
35971 ignore any line that it does not recognize. An empty line marks the end
35974 @c FIXME add some specific types of data
35976 The trace frame section consists of a number of consecutive frames.
35977 Each frame begins with a two-byte tracepoint number, followed by a
35978 four-byte size giving the amount of data in the frame. The data in
35979 the frame consists of a number of blocks, each introduced by a
35980 character indicating its type (at least register, memory, and trace
35981 state variable). The data in this section is raw binary, not a
35982 hexadecimal or other encoding; its endianness matches the target's
35985 @c FIXME bi-arch may require endianness/arch info in description section
35988 @item R @var{bytes}
35989 Register block. The number and ordering of bytes matches that of a
35990 @code{g} packet in the remote protocol. Note that these are the
35991 actual bytes, in target order and @value{GDBN} register order, not a
35992 hexadecimal encoding.
35994 @item M @var{address} @var{length} @var{bytes}...
35995 Memory block. This is a contiguous block of memory, at the 8-byte
35996 address @var{address}, with a 2-byte length @var{length}, followed by
35997 @var{length} bytes.
35999 @item V @var{number} @var{value}
36000 Trace state variable block. This records the 8-byte signed value
36001 @var{value} of trace state variable numbered @var{number}.
36005 Future enhancements of the trace file format may include additional types
36008 @node Target Descriptions
36009 @appendix Target Descriptions
36010 @cindex target descriptions
36012 @strong{Warning:} target descriptions are still under active development,
36013 and the contents and format may change between @value{GDBN} releases.
36014 The format is expected to stabilize in the future.
36016 One of the challenges of using @value{GDBN} to debug embedded systems
36017 is that there are so many minor variants of each processor
36018 architecture in use. It is common practice for vendors to start with
36019 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
36020 and then make changes to adapt it to a particular market niche. Some
36021 architectures have hundreds of variants, available from dozens of
36022 vendors. This leads to a number of problems:
36026 With so many different customized processors, it is difficult for
36027 the @value{GDBN} maintainers to keep up with the changes.
36029 Since individual variants may have short lifetimes or limited
36030 audiences, it may not be worthwhile to carry information about every
36031 variant in the @value{GDBN} source tree.
36033 When @value{GDBN} does support the architecture of the embedded system
36034 at hand, the task of finding the correct architecture name to give the
36035 @command{set architecture} command can be error-prone.
36038 To address these problems, the @value{GDBN} remote protocol allows a
36039 target system to not only identify itself to @value{GDBN}, but to
36040 actually describe its own features. This lets @value{GDBN} support
36041 processor variants it has never seen before --- to the extent that the
36042 descriptions are accurate, and that @value{GDBN} understands them.
36044 @value{GDBN} must be linked with the Expat library to support XML
36045 target descriptions. @xref{Expat}.
36048 * Retrieving Descriptions:: How descriptions are fetched from a target.
36049 * Target Description Format:: The contents of a target description.
36050 * Predefined Target Types:: Standard types available for target
36052 * Standard Target Features:: Features @value{GDBN} knows about.
36055 @node Retrieving Descriptions
36056 @section Retrieving Descriptions
36058 Target descriptions can be read from the target automatically, or
36059 specified by the user manually. The default behavior is to read the
36060 description from the target. @value{GDBN} retrieves it via the remote
36061 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
36062 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
36063 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
36064 XML document, of the form described in @ref{Target Description
36067 Alternatively, you can specify a file to read for the target description.
36068 If a file is set, the target will not be queried. The commands to
36069 specify a file are:
36072 @cindex set tdesc filename
36073 @item set tdesc filename @var{path}
36074 Read the target description from @var{path}.
36076 @cindex unset tdesc filename
36077 @item unset tdesc filename
36078 Do not read the XML target description from a file. @value{GDBN}
36079 will use the description supplied by the current target.
36081 @cindex show tdesc filename
36082 @item show tdesc filename
36083 Show the filename to read for a target description, if any.
36087 @node Target Description Format
36088 @section Target Description Format
36089 @cindex target descriptions, XML format
36091 A target description annex is an @uref{http://www.w3.org/XML/, XML}
36092 document which complies with the Document Type Definition provided in
36093 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
36094 means you can use generally available tools like @command{xmllint} to
36095 check that your feature descriptions are well-formed and valid.
36096 However, to help people unfamiliar with XML write descriptions for
36097 their targets, we also describe the grammar here.
36099 Target descriptions can identify the architecture of the remote target
36100 and (for some architectures) provide information about custom register
36101 sets. They can also identify the OS ABI of the remote target.
36102 @value{GDBN} can use this information to autoconfigure for your
36103 target, or to warn you if you connect to an unsupported target.
36105 Here is a simple target description:
36108 <target version="1.0">
36109 <architecture>i386:x86-64</architecture>
36114 This minimal description only says that the target uses
36115 the x86-64 architecture.
36117 A target description has the following overall form, with [ ] marking
36118 optional elements and @dots{} marking repeatable elements. The elements
36119 are explained further below.
36122 <?xml version="1.0"?>
36123 <!DOCTYPE target SYSTEM "gdb-target.dtd">
36124 <target version="1.0">
36125 @r{[}@var{architecture}@r{]}
36126 @r{[}@var{osabi}@r{]}
36127 @r{[}@var{compatible}@r{]}
36128 @r{[}@var{feature}@dots{}@r{]}
36133 The description is generally insensitive to whitespace and line
36134 breaks, under the usual common-sense rules. The XML version
36135 declaration and document type declaration can generally be omitted
36136 (@value{GDBN} does not require them), but specifying them may be
36137 useful for XML validation tools. The @samp{version} attribute for
36138 @samp{<target>} may also be omitted, but we recommend
36139 including it; if future versions of @value{GDBN} use an incompatible
36140 revision of @file{gdb-target.dtd}, they will detect and report
36141 the version mismatch.
36143 @subsection Inclusion
36144 @cindex target descriptions, inclusion
36147 @cindex <xi:include>
36150 It can sometimes be valuable to split a target description up into
36151 several different annexes, either for organizational purposes, or to
36152 share files between different possible target descriptions. You can
36153 divide a description into multiple files by replacing any element of
36154 the target description with an inclusion directive of the form:
36157 <xi:include href="@var{document}"/>
36161 When @value{GDBN} encounters an element of this form, it will retrieve
36162 the named XML @var{document}, and replace the inclusion directive with
36163 the contents of that document. If the current description was read
36164 using @samp{qXfer}, then so will be the included document;
36165 @var{document} will be interpreted as the name of an annex. If the
36166 current description was read from a file, @value{GDBN} will look for
36167 @var{document} as a file in the same directory where it found the
36168 original description.
36170 @subsection Architecture
36171 @cindex <architecture>
36173 An @samp{<architecture>} element has this form:
36176 <architecture>@var{arch}</architecture>
36179 @var{arch} is one of the architectures from the set accepted by
36180 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
36183 @cindex @code{<osabi>}
36185 This optional field was introduced in @value{GDBN} version 7.0.
36186 Previous versions of @value{GDBN} ignore it.
36188 An @samp{<osabi>} element has this form:
36191 <osabi>@var{abi-name}</osabi>
36194 @var{abi-name} is an OS ABI name from the same selection accepted by
36195 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
36197 @subsection Compatible Architecture
36198 @cindex @code{<compatible>}
36200 This optional field was introduced in @value{GDBN} version 7.0.
36201 Previous versions of @value{GDBN} ignore it.
36203 A @samp{<compatible>} element has this form:
36206 <compatible>@var{arch}</compatible>
36209 @var{arch} is one of the architectures from the set accepted by
36210 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
36212 A @samp{<compatible>} element is used to specify that the target
36213 is able to run binaries in some other than the main target architecture
36214 given by the @samp{<architecture>} element. For example, on the
36215 Cell Broadband Engine, the main architecture is @code{powerpc:common}
36216 or @code{powerpc:common64}, but the system is able to run binaries
36217 in the @code{spu} architecture as well. The way to describe this
36218 capability with @samp{<compatible>} is as follows:
36221 <architecture>powerpc:common</architecture>
36222 <compatible>spu</compatible>
36225 @subsection Features
36228 Each @samp{<feature>} describes some logical portion of the target
36229 system. Features are currently used to describe available CPU
36230 registers and the types of their contents. A @samp{<feature>} element
36234 <feature name="@var{name}">
36235 @r{[}@var{type}@dots{}@r{]}
36241 Each feature's name should be unique within the description. The name
36242 of a feature does not matter unless @value{GDBN} has some special
36243 knowledge of the contents of that feature; if it does, the feature
36244 should have its standard name. @xref{Standard Target Features}.
36248 Any register's value is a collection of bits which @value{GDBN} must
36249 interpret. The default interpretation is a two's complement integer,
36250 but other types can be requested by name in the register description.
36251 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
36252 Target Types}), and the description can define additional composite types.
36254 Each type element must have an @samp{id} attribute, which gives
36255 a unique (within the containing @samp{<feature>}) name to the type.
36256 Types must be defined before they are used.
36259 Some targets offer vector registers, which can be treated as arrays
36260 of scalar elements. These types are written as @samp{<vector>} elements,
36261 specifying the array element type, @var{type}, and the number of elements,
36265 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
36269 If a register's value is usefully viewed in multiple ways, define it
36270 with a union type containing the useful representations. The
36271 @samp{<union>} element contains one or more @samp{<field>} elements,
36272 each of which has a @var{name} and a @var{type}:
36275 <union id="@var{id}">
36276 <field name="@var{name}" type="@var{type}"/>
36282 If a register's value is composed from several separate values, define
36283 it with a structure type. There are two forms of the @samp{<struct>}
36284 element; a @samp{<struct>} element must either contain only bitfields
36285 or contain no bitfields. If the structure contains only bitfields,
36286 its total size in bytes must be specified, each bitfield must have an
36287 explicit start and end, and bitfields are automatically assigned an
36288 integer type. The field's @var{start} should be less than or
36289 equal to its @var{end}, and zero represents the least significant bit.
36292 <struct id="@var{id}" size="@var{size}">
36293 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
36298 If the structure contains no bitfields, then each field has an
36299 explicit type, and no implicit padding is added.
36302 <struct id="@var{id}">
36303 <field name="@var{name}" type="@var{type}"/>
36309 If a register's value is a series of single-bit flags, define it with
36310 a flags type. The @samp{<flags>} element has an explicit @var{size}
36311 and contains one or more @samp{<field>} elements. Each field has a
36312 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
36316 <flags id="@var{id}" size="@var{size}">
36317 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
36322 @subsection Registers
36325 Each register is represented as an element with this form:
36328 <reg name="@var{name}"
36329 bitsize="@var{size}"
36330 @r{[}regnum="@var{num}"@r{]}
36331 @r{[}save-restore="@var{save-restore}"@r{]}
36332 @r{[}type="@var{type}"@r{]}
36333 @r{[}group="@var{group}"@r{]}/>
36337 The components are as follows:
36342 The register's name; it must be unique within the target description.
36345 The register's size, in bits.
36348 The register's number. If omitted, a register's number is one greater
36349 than that of the previous register (either in the current feature or in
36350 a preceeding feature); the first register in the target description
36351 defaults to zero. This register number is used to read or write
36352 the register; e.g.@: it is used in the remote @code{p} and @code{P}
36353 packets, and registers appear in the @code{g} and @code{G} packets
36354 in order of increasing register number.
36357 Whether the register should be preserved across inferior function
36358 calls; this must be either @code{yes} or @code{no}. The default is
36359 @code{yes}, which is appropriate for most registers except for
36360 some system control registers; this is not related to the target's
36364 The type of the register. @var{type} may be a predefined type, a type
36365 defined in the current feature, or one of the special types @code{int}
36366 and @code{float}. @code{int} is an integer type of the correct size
36367 for @var{bitsize}, and @code{float} is a floating point type (in the
36368 architecture's normal floating point format) of the correct size for
36369 @var{bitsize}. The default is @code{int}.
36372 The register group to which this register belongs. @var{group} must
36373 be either @code{general}, @code{float}, or @code{vector}. If no
36374 @var{group} is specified, @value{GDBN} will not display the register
36375 in @code{info registers}.
36379 @node Predefined Target Types
36380 @section Predefined Target Types
36381 @cindex target descriptions, predefined types
36383 Type definitions in the self-description can build up composite types
36384 from basic building blocks, but can not define fundamental types. Instead,
36385 standard identifiers are provided by @value{GDBN} for the fundamental
36386 types. The currently supported types are:
36395 Signed integer types holding the specified number of bits.
36402 Unsigned integer types holding the specified number of bits.
36406 Pointers to unspecified code and data. The program counter and
36407 any dedicated return address register may be marked as code
36408 pointers; printing a code pointer converts it into a symbolic
36409 address. The stack pointer and any dedicated address registers
36410 may be marked as data pointers.
36413 Single precision IEEE floating point.
36416 Double precision IEEE floating point.
36419 The 12-byte extended precision format used by ARM FPA registers.
36422 The 10-byte extended precision format used by x87 registers.
36425 32bit @sc{eflags} register used by x86.
36428 32bit @sc{mxcsr} register used by x86.
36432 @node Standard Target Features
36433 @section Standard Target Features
36434 @cindex target descriptions, standard features
36436 A target description must contain either no registers or all the
36437 target's registers. If the description contains no registers, then
36438 @value{GDBN} will assume a default register layout, selected based on
36439 the architecture. If the description contains any registers, the
36440 default layout will not be used; the standard registers must be
36441 described in the target description, in such a way that @value{GDBN}
36442 can recognize them.
36444 This is accomplished by giving specific names to feature elements
36445 which contain standard registers. @value{GDBN} will look for features
36446 with those names and verify that they contain the expected registers;
36447 if any known feature is missing required registers, or if any required
36448 feature is missing, @value{GDBN} will reject the target
36449 description. You can add additional registers to any of the
36450 standard features --- @value{GDBN} will display them just as if
36451 they were added to an unrecognized feature.
36453 This section lists the known features and their expected contents.
36454 Sample XML documents for these features are included in the
36455 @value{GDBN} source tree, in the directory @file{gdb/features}.
36457 Names recognized by @value{GDBN} should include the name of the
36458 company or organization which selected the name, and the overall
36459 architecture to which the feature applies; so e.g.@: the feature
36460 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
36462 The names of registers are not case sensitive for the purpose
36463 of recognizing standard features, but @value{GDBN} will only display
36464 registers using the capitalization used in the description.
36471 * PowerPC Features::
36476 @subsection ARM Features
36477 @cindex target descriptions, ARM features
36479 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
36481 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
36482 @samp{lr}, @samp{pc}, and @samp{cpsr}.
36484 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
36485 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
36486 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
36489 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
36490 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
36492 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
36493 it should contain at least registers @samp{wR0} through @samp{wR15} and
36494 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
36495 @samp{wCSSF}, and @samp{wCASF} registers are optional.
36497 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
36498 should contain at least registers @samp{d0} through @samp{d15}. If
36499 they are present, @samp{d16} through @samp{d31} should also be included.
36500 @value{GDBN} will synthesize the single-precision registers from
36501 halves of the double-precision registers.
36503 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
36504 need to contain registers; it instructs @value{GDBN} to display the
36505 VFP double-precision registers as vectors and to synthesize the
36506 quad-precision registers from pairs of double-precision registers.
36507 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
36508 be present and include 32 double-precision registers.
36510 @node i386 Features
36511 @subsection i386 Features
36512 @cindex target descriptions, i386 features
36514 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
36515 targets. It should describe the following registers:
36519 @samp{eax} through @samp{edi} plus @samp{eip} for i386
36521 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
36523 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
36524 @samp{fs}, @samp{gs}
36526 @samp{st0} through @samp{st7}
36528 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
36529 @samp{foseg}, @samp{fooff} and @samp{fop}
36532 The register sets may be different, depending on the target.
36534 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
36535 describe registers:
36539 @samp{xmm0} through @samp{xmm7} for i386
36541 @samp{xmm0} through @samp{xmm15} for amd64
36546 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
36547 @samp{org.gnu.gdb.i386.sse} feature. It should
36548 describe the upper 128 bits of @sc{ymm} registers:
36552 @samp{ymm0h} through @samp{ymm7h} for i386
36554 @samp{ymm0h} through @samp{ymm15h} for amd64
36557 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
36558 describe a single register, @samp{orig_eax}.
36560 @node MIPS Features
36561 @subsection MIPS Features
36562 @cindex target descriptions, MIPS features
36564 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
36565 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
36566 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
36569 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
36570 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
36571 registers. They may be 32-bit or 64-bit depending on the target.
36573 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
36574 it may be optional in a future version of @value{GDBN}. It should
36575 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
36576 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
36578 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
36579 contain a single register, @samp{restart}, which is used by the
36580 Linux kernel to control restartable syscalls.
36582 @node M68K Features
36583 @subsection M68K Features
36584 @cindex target descriptions, M68K features
36587 @item @samp{org.gnu.gdb.m68k.core}
36588 @itemx @samp{org.gnu.gdb.coldfire.core}
36589 @itemx @samp{org.gnu.gdb.fido.core}
36590 One of those features must be always present.
36591 The feature that is present determines which flavor of m68k is
36592 used. The feature that is present should contain registers
36593 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
36594 @samp{sp}, @samp{ps} and @samp{pc}.
36596 @item @samp{org.gnu.gdb.coldfire.fp}
36597 This feature is optional. If present, it should contain registers
36598 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
36602 @node PowerPC Features
36603 @subsection PowerPC Features
36604 @cindex target descriptions, PowerPC features
36606 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
36607 targets. It should contain registers @samp{r0} through @samp{r31},
36608 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
36609 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
36611 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
36612 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
36614 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
36615 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
36618 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
36619 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
36620 will combine these registers with the floating point registers
36621 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
36622 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
36623 through @samp{vs63}, the set of vector registers for POWER7.
36625 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
36626 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
36627 @samp{spefscr}. SPE targets should provide 32-bit registers in
36628 @samp{org.gnu.gdb.power.core} and provide the upper halves in
36629 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
36630 these to present registers @samp{ev0} through @samp{ev31} to the
36633 @node Operating System Information
36634 @appendix Operating System Information
36635 @cindex operating system information
36641 Users of @value{GDBN} often wish to obtain information about the state of
36642 the operating system running on the target---for example the list of
36643 processes, or the list of open files. This section describes the
36644 mechanism that makes it possible. This mechanism is similar to the
36645 target features mechanism (@pxref{Target Descriptions}), but focuses
36646 on a different aspect of target.
36648 Operating system information is retrived from the target via the
36649 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
36650 read}). The object name in the request should be @samp{osdata}, and
36651 the @var{annex} identifies the data to be fetched.
36654 @appendixsection Process list
36655 @cindex operating system information, process list
36657 When requesting the process list, the @var{annex} field in the
36658 @samp{qXfer} request should be @samp{processes}. The returned data is
36659 an XML document. The formal syntax of this document is defined in
36660 @file{gdb/features/osdata.dtd}.
36662 An example document is:
36665 <?xml version="1.0"?>
36666 <!DOCTYPE target SYSTEM "osdata.dtd">
36667 <osdata type="processes">
36669 <column name="pid">1</column>
36670 <column name="user">root</column>
36671 <column name="command">/sbin/init</column>
36672 <column name="cores">1,2,3</column>
36677 Each item should include a column whose name is @samp{pid}. The value
36678 of that column should identify the process on the target. The
36679 @samp{user} and @samp{command} columns are optional, and will be
36680 displayed by @value{GDBN}. The @samp{cores} column, if present,
36681 should contain a comma-separated list of cores that this process
36682 is running on. Target may provide additional columns,
36683 which @value{GDBN} currently ignores.
36687 @node GNU Free Documentation License
36688 @appendix GNU Free Documentation License
36697 % I think something like @colophon should be in texinfo. In the
36699 \long\def\colophon{\hbox to0pt{}\vfill
36700 \centerline{The body of this manual is set in}
36701 \centerline{\fontname\tenrm,}
36702 \centerline{with headings in {\bf\fontname\tenbf}}
36703 \centerline{and examples in {\tt\fontname\tentt}.}
36704 \centerline{{\it\fontname\tenit\/},}
36705 \centerline{{\bf\fontname\tenbf}, and}
36706 \centerline{{\sl\fontname\tensl\/}}
36707 \centerline{are used for emphasis.}\vfill}
36709 % Blame: doc@cygnus.com, 1991.