-This is gdb.info, produced by makeinfo version 4.8 from ./gdb.texinfo.
+This is gdb.info, produced by makeinfo version 5.2 from gdb.texinfo.
-INFO-DIR-SECTION Software development
-START-INFO-DIR-ENTRY
-* Gdb: (gdb). The GNU debugger.
-END-INFO-DIR-ENTRY
-
- Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
-1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
-2010 2011, 2012 Free Software Foundation, Inc.
+Copyright (C) 1988-2014 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
(a) The FSF's Back-Cover Text is: "You are free to copy and modify
this GNU Manual. Buying copies from GNU Press supports the FSF in
developing GNU and promoting software freedom."
+INFO-DIR-SECTION Software development
+START-INFO-DIR-ENTRY
+* Gdb: (gdb). The GNU debugger.
+* gdbserver: (gdb) Server. The GNU debugging server.
+END-INFO-DIR-ENTRY
This file documents the GNU debugger GDB.
- This is the Tenth Edition, of `Debugging with GDB: the GNU
-Source-Level Debugger' for GDB (GDB) Version 7.5.1.
+ This is the Tenth Edition, of 'Debugging with GDB: the GNU
+Source-Level Debugger' for GDB (GDB) Version 7.8.1.
- Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
-1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
-2010 2011, 2012 Free Software Foundation, Inc.
+ Copyright (C) 1988-2014 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
This file describes GDB, the GNU symbolic debugger.
- This is the Tenth Edition, for GDB (GDB) Version 7.5.1.
+ This is the Tenth Edition, for GDB (GDB) Version 7.8.1.
- Copyright (C) 1988-2012 Free Software Foundation, Inc.
+ Copyright (C) 1988-2014 Free Software Foundation, Inc.
This edition of the GDB manual is dedicated to the memory of Fred
Fish. Fred was a long-standing contributor to GDB and to Free software
* GDB Bugs:: Reporting bugs in GDB
-
* Command Line Editing:: Command Line Editing
* Using History Interactively:: Using History Interactively
* In Memoriam:: In Memoriam
the operating system
* Trace File Format:: GDB trace file format
* Index Section Format:: .gdb_index section format
+* Man Pages:: Manual pages
* Copying:: GNU General Public License says
how you can copy and share GDB
* GNU Free Documentation License:: The license for this documentation
functions, and Python data types
\1f
-File: gdb.info, Node: Summary, Next: Sample Session, Prev: Top, Up: Top
+File: gdb.info, Node: Summary, Next: Sample Session, Up: Top
Summary of GDB
**************
correcting the effects of one bug and go on to learn about another.
You can use GDB to debug programs written in C and C++. For more
-information, see *Note Supported Languages: Supported Languages. For
-more information, see *Note C and C++: C.
+information, see *note Supported Languages: Supported Languages. For
+more information, see *note C and C++: C.
- Support for D is partial. For information on D, see *Note D: D.
+ Support for D is partial. For information on D, see *note D: D.
Support for Modula-2 is partial. For information on Modula-2, see
-*Note Modula-2: Modula-2.
+*note Modula-2: Modula-2.
Support for OpenCL C is partial. For information on OpenCL C, see
-*Note OpenCL C: OpenCL C.
+*note OpenCL C: OpenCL C.
Debugging Pascal programs which use sets, subranges, file variables,
or nested functions does not currently work. GDB does not support
entering expressions, printing values, or similar features using Pascal
syntax.
- GDB can be used to debug programs written in Fortran, although it
-may be necessary to refer to some variables with a trailing underscore.
+ GDB can be used to debug programs written in Fortran, although it may
+be necessary to refer to some variables with a trailing underscore.
GDB can be used to debug programs written in Objective-C, using
either the Apple/NeXT or the GNU Objective-C runtime.
=============
GDB is "free software", protected by the GNU General Public License
-(GPL). The GPL gives you the freedom to copy or adapt a licensed
+(GPL). The GPL gives you the freedom to copy or adapt a licensed
program--but every person getting a copy also gets with it the freedom
-to modify that copy (which means that they must get access to the
-source code), and the freedom to distribute further copies. Typical
-software companies use copyrights to limit your freedoms; the Free
-Software Foundation uses the GPL to preserve these freedoms.
+to modify that copy (which means that they must get access to the source
+code), and the freedom to distribute further copies. Typical software
+companies use copyrights to limit your freedoms; the Free Software
+Foundation uses the GPL to preserve these freedoms.
Fundamentally, the General Public License is a license which says
that you have these freedoms and that you cannot take these freedoms
Consider Perl, for instance. The tutorial manuals that people
normally use are non-free. How did this come about? Because the
authors of those manuals published them with restrictive terms--no
-copying, no modification, source files not available--which exclude
-them from the free software world.
+copying, no modification, source files not available--which exclude them
+from the free software world.
That wasn't the first time this sort of thing happened, and it was
-far from the last. Many times we have heard a GNU user eagerly
-describe a manual that he is writing, his intended contribution to the
-community, only to learn that he had ruined everything by signing a
-publication contract to make it non-free.
+far from the last. Many times we have heard a GNU user eagerly describe
+a manual that he is writing, his intended contribution to the community,
+only to learn that he had ruined everything by signing a publication
+contract to make it non-free.
Free documentation, like free software, is a matter of freedom, not
price. The problem with the non-free manual is not that publishers
modify. Non-free manuals do not allow this.
The criteria of freedom for a free manual are roughly the same as for
-free software. Redistribution (including the normal kinds of
-commercial redistribution) must be permitted, so that the manual can
-accompany every copy of the program, both on-line and on paper.
+free software. Redistribution (including the normal kinds of commercial
+redistribution) must be permitted, so that the manual can accompany
+every copy of the program, both on-line and on paper.
Permission for modification of the technical content is crucial too.
When people modify the software, adding or changing features, if they
changed version of the program is not really available to our community.
Some kinds of limits on the way modification is handled are
-acceptable. For example, requirements to preserve the original
-author's copyright notice, the distribution terms, or the list of
-authors, are ok. It is also no problem to require modified versions to
-include notice that they were modified. Even entire sections that may
-not be deleted or changed are acceptable, as long as they deal with
+acceptable. For example, requirements to preserve the original author's
+copyright notice, the distribution terms, or the list of authors, are
+ok. It is also no problem to require modified versions to include
+notice that they were modified. Even entire sections that may not be
+deleted or changed are acceptable, as long as they deal with
nontechnical topics (like this one). These kinds of restrictions are
-acceptable because they don't obstruct the community's normal use of
-the manual.
+acceptable because they don't obstruct the community's normal use of the
+manual.
- However, it must be possible to modify all the _technical_ content
-of the manual, and then distribute the result in all the usual media,
+ However, it must be possible to modify all the _technical_ content of
+the manual, and then distribute the result in all the usual media,
through all the usual channels. Otherwise, the restrictions obstruct
the use of the manual, it is not free, and we need another manual to
replace it.
Please spread the word about this issue. Our community continues to
-lose manuals to proprietary publishing. If we spread the word that
-free software needs free reference manuals and free tutorials, perhaps
-the next person who wants to contribute by writing documentation will
-realize, before it is too late, that only free manuals contribute to
-the free software community.
+lose manuals to proprietary publishing. If we spread the word that free
+software needs free reference manuals and free tutorials, perhaps the
+next person who wants to contribute by writing documentation will
+realize, before it is too late, that only free manuals contribute to the
+free software community.
If you are writing documentation, please insist on publishing it
under the GNU Free Documentation License or another free documentation
license. Remember that this decision requires your approval--you don't
-have to let the publisher decide. Some commercial publishers will use
-a free license if you insist, but they will not propose the option; it
-is up to you to raise the issue and say firmly that this is what you
-want. If the publisher you are dealing with refuses, please try other
+have to let the publisher decide. Some commercial publishers will use a
+free license if you insist, but they will not propose the option; it is
+up to you to raise the issue and say firmly that this is what you want.
+If the publisher you are dealing with refuses, please try other
publishers. If you're not sure whether a proposed license is free,
write to <licensing@gnu.org>.
The Free Software Foundation maintains a list of free documentation
published by other publishers, at
-`http://www.fsf.org/doc/other-free-books.html'.
+<http://www.fsf.org/doc/other-free-books.html>.
\1f
File: gdb.info, Node: Contributors, Prev: Free Documentation, Up: Summary
Richard Stallman was the original author of GDB, and of many other GNU
programs. Many others have contributed to its development. This
section attempts to credit major contributors. One of the virtues of
-free software is that everyone is free to contribute to it; with
-regret, we cannot actually acknowledge everyone here. The file
-`ChangeLog' in the GDB distribution approximates a blow-by-blow account.
+free software is that everyone is free to contribute to it; with regret,
+we cannot actually acknowledge everyone here. The file 'ChangeLog' in
+the GDB distribution approximates a blow-by-blow account.
Changes much prior to version 2.0 are lost in the mists of time.
So that they may not regard their many labors as thankless, we
particularly thank those who shepherded GDB through major releases:
Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0); Jim
-Blandy (release 4.18); Jason Molenda (release 4.17); Stan Shebs
-(release 4.14); Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10,
-and 4.9); Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5,
-and 4.4); John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9); Jim
-Kingdon (releases 3.5, 3.4, and 3.3); and Randy Smith (releases 3.2,
-3.1, and 3.0).
+Blandy (release 4.18); Jason Molenda (release 4.17); Stan Shebs (release
+4.14); Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
+Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
+John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9); Jim Kingdon
+(releases 3.5, 3.4, and 3.3); and Randy Smith (releases 3.2, 3.1, and
+3.0).
Richard Stallman, assisted at various times by Peter TerMaat, Chris
Hanson, and Richard Mlynarik, handled releases through 2.8.
Michael Tiemann is the author of most of the GNU C++ support in GDB,
with significant additional contributions from Per Bothner and Daniel
-Berlin. James Clark wrote the GNU C++ demangler. Early work on C++
-was by Peter TerMaat (who also did much general update work leading to
+Berlin. James Clark wrote the GNU C++ demangler. Early work on C++ was
+by Peter TerMaat (who also did much general update work leading to
release 3.0).
GDB uses the BFD subroutine library to examine multiple object-file
-formats; BFD was a joint project of David V. Henkel-Wallace, Rich
+formats; BFD was a joint project of David V. Henkel-Wallace, Rich
Pixley, Steve Chamberlain, and John Gilmore.
David Johnson wrote the original COFF support; Pace Willison did the
Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
-support. Jean-Daniel Fekete contributed Sun 386i support. Chris
-Hanson improved the HP9000 support. Noboyuki Hikichi and Tomoyuki
-Hasei contributed Sony/News OS 3 support. David Johnson contributed
-Encore Umax support. Jyrki Kuoppala contributed Altos 3068 support.
-Jeff Law contributed HP PA and SOM support. Keith Packard contributed
-NS32K support. Doug Rabson contributed Acorn Risc Machine support.
-Bob Rusk contributed Harris Nighthawk CX-UX support. Chris Smith
-contributed Convex support (and Fortran debugging). Jonathan Stone
-contributed Pyramid support. Michael Tiemann contributed SPARC support.
-Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
-Pace Willison contributed Intel 386 support. Jay Vosburgh contributed
+support. Jean-Daniel Fekete contributed Sun 386i support. Chris Hanson
+improved the HP9000 support. Noboyuki Hikichi and Tomoyuki Hasei
+contributed Sony/News OS 3 support. David Johnson contributed Encore
+Umax support. Jyrki Kuoppala contributed Altos 3068 support. Jeff Law
+contributed HP PA and SOM support. Keith Packard contributed NS32K
+support. Doug Rabson contributed Acorn Risc Machine support. Bob Rusk
+contributed Harris Nighthawk CX-UX support. Chris Smith contributed
+Convex support (and Fortran debugging). Jonathan Stone contributed
+Pyramid support. Michael Tiemann contributed SPARC support. Tim Tucker
+contributed support for the Gould NP1 and Gould Powernode. Pace
+Willison contributed Intel 386 support. Jay Vosburgh contributed
Symmetry support. Marko Mlinar contributed OpenRISC 1000 support.
Andreas Schwab contributed M68K GNU/Linux support.
Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped
develop remote debugging. Intel Corporation, Wind River Systems, AMD,
-and ARM contributed remote debugging modules for the i960, VxWorks,
-A29K UDI, and RDI targets, respectively.
+and ARM contributed remote debugging modules for the i960, VxWorks, A29K
+UDI, and RDI targets, respectively.
Brian Fox is the author of the readline libraries providing
command-line editing and command history.
Fred Fish wrote most of the support for Unix System Vr4. He also
enhanced the command-completion support to cover C++ overloaded symbols.
- Hitachi America (now Renesas America), Ltd. sponsored the support for
-H8/300, H8/500, and Super-H processors.
+ Hitachi America (now Renesas America), Ltd. sponsored the support
+for H8/300, H8/500, and Super-H processors.
NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx
processors.
The following people at the Hewlett-Packard Company contributed
support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
(narrow mode), HP's implementation of kernel threads, HP's aC++
-compiler, and the Text User Interface (nee Terminal User Interface):
-Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
-Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
-provided HP-specific information in this manual.
+compiler, and the Text User Interface (nee Terminal User Interface): Ben
+Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann, Satish
+Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase provided
+HP-specific information in this manual.
DJ Delorie ported GDB to MS-DOS, for the DJGPP project. Robert
Hoehne made significant contributions to the DJGPP port.
frame IDs, independent frame sniffers, and the sentinel frame. Mark
Kettenis implemented the DWARF 2 unwinder, Jeff Johnston the libunwind
unwinder, and Andrew Cagney the dummy, sentinel, tramp, and trad
-unwinders. The architecture-specific changes, each involving a
-complete rewrite of the architecture's frame code, were carried out by
-Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
-Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
-Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
-Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
-Weigand.
+unwinders. The architecture-specific changes, each involving a complete
+rewrite of the architecture's frame code, were carried out by Jim
+Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane Carrez,
+Randolph Chung, Orjan Friberg, Richard Henderson, Daniel Jacobowitz,
+Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei Sakamoto, Yoshinori
+Sato, Michael Snyder, Corinna Vinschen, and Ulrich Weigand.
Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
Tensilica, Inc. contributed support for Xtensa processors. Others who
1 A Sample GDB Session
**********************
-You can use this manual at your leisure to read all about GDB.
-However, a handful of commands are enough to get started using the
-debugger. This chapter illustrates those commands.
+You can use this manual at your leisure to read all about GDB. However,
+a handful of commands are enough to get started using the debugger.
+This chapter illustrates those commands.
- One of the preliminary versions of GNU `m4' (a generic macro
+ One of the preliminary versions of GNU 'm4' (a generic macro
processor) exhibits the following bug: sometimes, when we change its
quote strings from the default, the commands used to capture one macro
-definition within another stop working. In the following short `m4'
-session, we define a macro `foo' which expands to `0000'; we then use
-the `m4' built-in `defn' to define `bar' as the same thing. However,
-when we change the open quote string to `<QUOTE>' and the close quote
-string to `<UNQUOTE>', the same procedure fails to define a new synonym
-`baz':
+definition within another stop working. In the following short 'm4'
+session, we define a macro 'foo' which expands to '0000'; we then use
+the 'm4' built-in 'defn' to define 'bar' as the same thing. However,
+when we change the open quote string to '<QUOTE>' and the close quote
+string to '<UNQUOTE>', the same procedure fails to define a new synonym
+'baz':
$ cd gnu/m4
$ ./m4
foo
0000
- define(bar,defn(`foo'))
+ define(bar,defn('foo'))
bar
0000
There is absolutely no warranty for GDB; type "show warranty"
for details.
- GDB 7.5.1, Copyright 1999 Free Software Foundation, Inc...
+ GDB 7.8.1, Copyright 1999 Free Software Foundation, Inc...
(gdb)
GDB reads only enough symbol data to know where to find the rest when
(gdb) set width 70
-We need to see how the `m4' built-in `changequote' works. Having
-looked at the source, we know the relevant subroutine is
-`m4_changequote', so we set a breakpoint there with the GDB `break'
-command.
+We need to see how the 'm4' built-in 'changequote' works. Having looked
+at the source, we know the relevant subroutine is 'm4_changequote', so
+we set a breakpoint there with the GDB 'break' command.
(gdb) break m4_changequote
Breakpoint 1 at 0x62f4: file builtin.c, line 879.
-Using the `run' command, we start `m4' running under GDB control; as
-long as control does not reach the `m4_changequote' subroutine, the
+Using the 'run' command, we start 'm4' running under GDB control; as
+long as control does not reach the 'm4_changequote' subroutine, the
program runs as usual:
(gdb) run
foo
0000
-To trigger the breakpoint, we call `changequote'. GDB suspends
-execution of `m4', displaying information about the context where it
+To trigger the breakpoint, we call 'changequote'. GDB suspends
+execution of 'm4', displaying information about the context where it
stops.
changequote(<QUOTE>,<UNQUOTE>)
at builtin.c:879
879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
-Now we use the command `n' (`next') to advance execution to the next
+Now we use the command 'n' ('next') to advance execution to the next
line of the current function.
(gdb) n
882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
: nil,
-`set_quotes' looks like a promising subroutine. We can go into it by
-using the command `s' (`step') instead of `next'. `step' goes to the
+'set_quotes' looks like a promising subroutine. We can go into it by
+using the command 's' ('step') instead of 'next'. 'step' goes to the
next line to be executed in _any_ subroutine, so it steps into
-`set_quotes'.
+'set_quotes'.
(gdb) s
set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
at input.c:530
530 if (lquote != def_lquote)
-The display that shows the subroutine where `m4' is now suspended (and
+The display that shows the subroutine where 'm4' is now suspended (and
its arguments) is called a stack frame display. It shows a summary of
-the stack. We can use the `backtrace' command (which can also be
-spelled `bt'), to see where we are in the stack as a whole: the
-`backtrace' command displays a stack frame for each active subroutine.
+the stack. We can use the 'backtrace' command (which can also be
+spelled 'bt'), to see where we are in the stack as a whole: the
+'backtrace' command displays a stack frame for each active subroutine.
(gdb) bt
#0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
#5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
We step through a few more lines to see what happens. The first two
-times, we can use `s'; the next two times we use `n' to avoid falling
-into the `xstrdup' subroutine.
+times, we can use 's'; the next two times we use 'n' to avoid falling
+into the 'xstrdup' subroutine.
(gdb) s
0x3b5c 532 if (rquote != def_rquote)
538 len_lquote = strlen(rquote);
The last line displayed looks a little odd; we can examine the variables
-`lquote' and `rquote' to see if they are in fact the new left and right
-quotes we specified. We use the command `p' (`print') to see their
+'lquote' and 'rquote' to see if they are in fact the new left and right
+quotes we specified. We use the command 'p' ('print') to see their
values.
(gdb) p lquote
(gdb) p rquote
$2 = 0x35d50 "<UNQUOTE>"
-`lquote' and `rquote' are indeed the new left and right quotes. To
-look at some context, we can display ten lines of source surrounding
-the current line with the `l' (`list') command.
+'lquote' and 'rquote' are indeed the new left and right quotes. To look
+at some context, we can display ten lines of source surrounding the
+current line with the 'l' ('list') command.
(gdb) l
533 xfree(rquote);
541
542 void
-Let us step past the two lines that set `len_lquote' and `len_rquote',
+Let us step past the two lines that set 'len_lquote' and 'len_rquote',
and then examine the values of those variables.
(gdb) n
(gdb) p len_rquote
$4 = 7
-That certainly looks wrong, assuming `len_lquote' and `len_rquote' are
-meant to be the lengths of `lquote' and `rquote' respectively. We can
-set them to better values using the `p' command, since it can print the
+That certainly looks wrong, assuming 'len_lquote' and 'len_rquote' are
+meant to be the lengths of 'lquote' and 'rquote' respectively. We can
+set them to better values using the 'p' command, since it can print the
value of any expression--and that expression can include subroutine
calls and assignments.
(gdb) p len_rquote=strlen(rquote)
$6 = 9
-Is that enough to fix the problem of using the new quotes with the `m4'
-built-in `defn'? We can allow `m4' to continue executing with the `c'
-(`continue') command, and then try the example that caused trouble
+Is that enough to fix the problem of using the new quotes with the 'm4'
+built-in 'defn'? We can allow 'm4' to continue executing with the 'c'
+('continue') command, and then try the example that caused trouble
initially:
(gdb) c
Success! The new quotes now work just as well as the default ones. The
problem seems to have been just the two typos defining the wrong
-lengths. We allow `m4' exit by giving it an EOF as input:
+lengths. We allow 'm4' exit by giving it an EOF as input:
Ctrl-d
Program exited normally.
-The message `Program exited normally.' is from GDB; it indicates `m4'
-has finished executing. We can end our GDB session with the GDB `quit'
+The message 'Program exited normally.' is from GDB; it indicates 'm4'
+has finished executing. We can end our GDB session with the GDB 'quit'
command.
(gdb) quit
This chapter discusses how to start GDB, and how to get out of it. The
essentials are:
- * type `gdb' to start GDB.
-
- * type `quit' or `Ctrl-d' to exit.
+ * type 'gdb' to start GDB.
+ * type 'quit' or 'Ctrl-d' to exit.
* Menu:
2.1 Invoking GDB
================
-Invoke GDB by running the program `gdb'. Once started, GDB reads
+Invoke GDB by running the program 'gdb'. Once started, GDB reads
commands from the terminal until you tell it to exit.
- You can also run `gdb' with a variety of arguments and options, to
+ You can also run 'gdb' with a variety of arguments and options, to
specify more of your debugging environment at the outset.
The command-line options described here are designed to cover a
gdb PROGRAM 1234
-would attach GDB to process `1234' (unless you also have a file named
-`1234'; GDB does check for a core file first).
+would attach GDB to process '1234' (unless you also have a file named
+'1234'; GDB does check for a core file first).
Taking advantage of the second command-line argument requires a
fairly complete operating system; when you use GDB as a remote debugger
there is often no way to get a core dump. GDB will warn you if it is
unable to attach or to read core dumps.
- You can optionally have `gdb' pass any arguments after the
-executable file to the inferior using `--args'. This option stops
-option processing.
+ You can optionally have 'gdb' pass any arguments after the executable
+file to the inferior using '--args'. This option stops option
+processing.
gdb --args gcc -O2 -c foo.c
- This will cause `gdb' to debug `gcc', and to set `gcc''s
-command-line arguments (*note Arguments::) to `-O2 -c foo.c'.
+ This will cause 'gdb' to debug 'gcc', and to set 'gcc''s command-line
+arguments (*note Arguments::) to '-O2 -c foo.c'.
- You can run `gdb' without printing the front material, which
-describes GDB's non-warranty, by specifying `-silent':
+ You can run 'gdb' without printing the front material, which
+describes GDB's non-warranty, by specifying '--silent' (or
+'-q'/'--quiet'):
- gdb -silent
+ gdb --silent
-You can further control how GDB starts up by using command-line
-options. GDB itself can remind you of the options available.
+You can further control how GDB starts up by using command-line options.
+GDB itself can remind you of the options available.
Type
gdb -help
-to display all available options and briefly describe their use (`gdb
+to display all available options and briefly describe their use ('gdb
-h' is a shorter equivalent).
All options and command line arguments you give are processed in
-sequential order. The order makes a difference when the `-x' option is
+sequential order. The order makes a difference when the '-x' option is
used.
* Menu:
2.1.1 Choosing Files
--------------------
-When GDB starts, it reads any arguments other than options as
-specifying an executable file and core file (or process ID). This is
-the same as if the arguments were specified by the `-se' and `-c' (or
-`-p') options respectively. (GDB reads the first argument that does
-not have an associated option flag as equivalent to the `-se' option
-followed by that argument; and the second argument that does not have
-an associated option flag, if any, as equivalent to the `-c'/`-p'
-option followed by that argument.) If the second argument begins with
-a decimal digit, GDB will first attempt to attach to it as a process,
-and if that fails, attempt to open it as a corefile. If you have a
-corefile whose name begins with a digit, you can prevent GDB from
-treating it as a pid by prefixing it with `./', e.g. `./12345'.
-
- If GDB has not been configured to included core file support, such
-as for most embedded targets, then it will complain about a second
-argument and ignore it.
+When GDB starts, it reads any arguments other than options as specifying
+an executable file and core file (or process ID). This is the same as if
+the arguments were specified by the '-se' and '-c' (or '-p') options
+respectively. (GDB reads the first argument that does not have an
+associated option flag as equivalent to the '-se' option followed by
+that argument; and the second argument that does not have an associated
+option flag, if any, as equivalent to the '-c'/'-p' option followed by
+that argument.) If the second argument begins with a decimal digit, GDB
+will first attempt to attach to it as a process, and if that fails,
+attempt to open it as a corefile. If you have a corefile whose name
+begins with a digit, you can prevent GDB from treating it as a pid by
+prefixing it with './', e.g. './12345'.
+
+ If GDB has not been configured to included core file support, such as
+for most embedded targets, then it will complain about a second argument
+and ignore it.
Many options have both long and short forms; both are shown in the
following list. GDB also recognizes the long forms if you truncate
-them, so long as enough of the option is present to be unambiguous.
-(If you prefer, you can flag option arguments with `--' rather than
-`-', though we illustrate the more usual convention.)
+them, so long as enough of the option is present to be unambiguous. (If
+you prefer, you can flag option arguments with '--' rather than '-',
+though we illustrate the more usual convention.)
-`-symbols FILE'
-`-s FILE'
+'-symbols FILE'
+'-s FILE'
Read symbol table from file FILE.
-`-exec FILE'
-`-e FILE'
+'-exec FILE'
+'-e FILE'
Use file FILE as the executable file to execute when appropriate,
and for examining pure data in conjunction with a core dump.
-`-se FILE'
+'-se FILE'
Read symbol table from file FILE and use it as the executable file.
-`-core FILE'
-`-c FILE'
+'-core FILE'
+'-c FILE'
Use file FILE as a core dump to examine.
-`-pid NUMBER'
-`-p NUMBER'
- Connect to process ID NUMBER, as with the `attach' command.
+'-pid NUMBER'
+'-p NUMBER'
+ Connect to process ID NUMBER, as with the 'attach' command.
-`-command FILE'
-`-x FILE'
+'-command FILE'
+'-x FILE'
Execute commands from file FILE. The contents of this file is
- evaluated exactly as the `source' command would. *Note Command
+ evaluated exactly as the 'source' command would. *Note Command
files: Command Files.
-`-eval-command COMMAND'
-`-ex COMMAND'
+'-eval-command COMMAND'
+'-ex COMMAND'
Execute a single GDB command.
This option may be used multiple times to call multiple commands.
- It may also be interleaved with `-command' as required.
+ It may also be interleaved with '-command' as required.
gdb -ex 'target sim' -ex 'load' \
-x setbreakpoints -ex 'run' a.out
-`-init-command FILE'
-`-ix FILE'
+'-init-command FILE'
+'-ix FILE'
Execute commands from file FILE before loading the inferior (but
after loading gdbinit files). *Note Startup::.
-`-init-eval-command COMMAND'
-`-iex COMMAND'
- Execute a single GDB command before loading the inferior (but
- after loading gdbinit files). *Note Startup::.
+'-init-eval-command COMMAND'
+'-iex COMMAND'
+ Execute a single GDB command before loading the inferior (but after
+ loading gdbinit files). *Note Startup::.
-`-directory DIRECTORY'
-`-d DIRECTORY'
+'-directory DIRECTORY'
+'-d DIRECTORY'
Add DIRECTORY to the path to search for source and script files.
-`-r'
-`-readnow'
+'-r'
+'-readnow'
Read each symbol file's entire symbol table immediately, rather
than the default, which is to read it incrementally as it is
needed. This makes startup slower, but makes future operations
faster.
-
\1f
File: gdb.info, Node: Mode Options, Next: Startup, Prev: File Options, Up: Invoking GDB
2.1.2 Choosing Modes
--------------------
-You can run GDB in various alternative modes--for example, in batch
-mode or quiet mode.
-
-`-nx'
-`-n'
- Do not execute commands found in any initialization files.
- Normally, GDB executes the commands in these files after all the
- command options and arguments have been processed. *Note Command
+You can run GDB in various alternative modes--for example, in batch mode
+or quiet mode.
+
+'-nx'
+'-n'
+ Do not execute commands found in any initialization file. There
+ are three init files, loaded in the following order:
+
+ 'system.gdbinit'
+ This is the system-wide init file. Its location is specified
+ with the '--with-system-gdbinit' configure option (*note
+ System-wide configuration::). It is loaded first when GDB
+ starts, before command line options have been processed.
+ '~/.gdbinit'
+ This is the init file in your home directory. It is loaded
+ next, after 'system.gdbinit', and before command options have
+ been processed.
+ './.gdbinit'
+ This is the init file in the current directory. It is loaded
+ last, after command line options other than '-x' and '-ex'
+ have been processed. Command line options '-x' and '-ex' are
+ processed last, after './.gdbinit' has been loaded.
+
+ For further documentation on startup processing, *Note Startup::.
+ For documentation on how to write command files, *Note Command
Files: Command Files.
-`-quiet'
-`-silent'
-`-q'
+'-nh'
+ Do not execute commands found in '~/.gdbinit', the init file in
+ your home directory. *Note Startup::.
+
+'-quiet'
+'-silent'
+'-q'
"Quiet". Do not print the introductory and copyright messages.
These messages are also suppressed in batch mode.
-`-batch'
- Run in batch mode. Exit with status `0' after processing all the
- command files specified with `-x' (and all commands from
- initialization files, if not inhibited with `-n'). Exit with
+'-batch'
+ Run in batch mode. Exit with status '0' after processing all the
+ command files specified with '-x' (and all commands from
+ initialization files, if not inhibited with '-n'). Exit with
nonzero status if an error occurs in executing the GDB commands in
the command files. Batch mode also disables pagination, sets
unlimited terminal width and height *note Screen Size::, and acts
- as if `set confirm off' were in effect (*note Messages/Warnings::).
+ as if 'set confirm off' were in effect (*note Messages/Warnings::).
Batch mode may be useful for running GDB as a filter, for example
- to download and run a program on another computer; in order to
- make this more useful, the message
+ to download and run a program on another computer; in order to make
+ this more useful, the message
Program exited normally.
(which is ordinarily issued whenever a program running under GDB
control terminates) is not issued when running in batch mode.
-`-batch-silent'
- Run in batch mode exactly like `-batch', but totally silently. All
- GDB output to `stdout' is prevented (`stderr' is unaffected).
- This is much quieter than `-silent' and would be useless for an
+'-batch-silent'
+ Run in batch mode exactly like '-batch', but totally silently. All
+ GDB output to 'stdout' is prevented ('stderr' is unaffected). This
+ is much quieter than '-silent' and would be useless for an
interactive session.
- This is particularly useful when using targets that give `Loading
+ This is particularly useful when using targets that give 'Loading
section' messages, for example.
Note that targets that give their output via GDB, as opposed to
- writing directly to `stdout', will also be made silent.
+ writing directly to 'stdout', will also be made silent.
-`-return-child-result'
+'-return-child-result'
The return code from GDB will be the return code from the child
process (the process being debugged), with the following
exceptions:
* GDB exits abnormally. E.g., due to an incorrect argument or
an internal error. In this case the exit code is the same as
- it would have been without `-return-child-result'.
-
- * The user quits with an explicit value. E.g., `quit 1'.
-
+ it would have been without '-return-child-result'.
+ * The user quits with an explicit value. E.g., 'quit 1'.
* The child process never runs, or is not allowed to terminate,
in which case the exit code will be -1.
- This option is useful in conjunction with `-batch' or
- `-batch-silent', when GDB is being used as a remote program loader
+ This option is useful in conjunction with '-batch' or
+ '-batch-silent', when GDB is being used as a remote program loader
or simulator interface.
-`-nowindows'
-`-nw'
+'-nowindows'
+'-nw'
"No windows". If GDB comes with a graphical user interface (GUI)
built in, then this option tells GDB to only use the command-line
interface. If no GUI is available, this option has no effect.
-`-windows'
-`-w'
+'-windows'
+'-w'
If GDB includes a GUI, then this option requires it to be used if
possible.
-`-cd DIRECTORY'
+'-cd DIRECTORY'
Run GDB using DIRECTORY as its working directory, instead of the
current directory.
-`-data-directory DIRECTORY'
+'-data-directory DIRECTORY'
+'-D DIRECTORY'
Run GDB using DIRECTORY as its data directory. The data directory
is where GDB searches for its auxiliary files. *Note Data Files::.
-`-fullname'
-`-f'
+'-fullname'
+'-f'
GNU Emacs sets this option when it runs GDB as a subprocess. It
tells GDB to output the full file name and line number in a
- standard, recognizable fashion each time a stack frame is
- displayed (which includes each time your program stops). This
- recognizable format looks like two `\032' characters, followed by
- the file name, line number and character position separated by
- colons, and a newline. The Emacs-to-GDB interface program uses
- the two `\032' characters as a signal to display the source code
- for the frame.
-
-`-epoch'
- The Epoch Emacs-GDB interface sets this option when it runs GDB as
- a subprocess. It tells GDB to modify its print routines so as to
- allow Epoch to display values of expressions in a separate window.
-
-`-annotate LEVEL'
+ standard, recognizable fashion each time a stack frame is displayed
+ (which includes each time your program stops). This recognizable
+ format looks like two '\032' characters, followed by the file name,
+ line number and character position separated by colons, and a
+ newline. The Emacs-to-GDB interface program uses the two '\032'
+ characters as a signal to display the source code for the frame.
+
+'-annotate LEVEL'
This option sets the "annotation level" inside GDB. Its effect is
- identical to using `set annotate LEVEL' (*note Annotations::).
- The annotation LEVEL controls how much information GDB prints
- together with its prompt, values of expressions, source lines, and
- other types of output. Level 0 is the normal, level 1 is for use
- when GDB is run as a subprocess of GNU Emacs, level 3 is the
- maximum annotation suitable for programs that control GDB, and
- level 2 has been deprecated.
+ identical to using 'set annotate LEVEL' (*note Annotations::). The
+ annotation LEVEL controls how much information GDB prints together
+ with its prompt, values of expressions, source lines, and other
+ types of output. Level 0 is the normal, level 1 is for use when
+ GDB is run as a subprocess of GNU Emacs, level 3 is the maximum
+ annotation suitable for programs that control GDB, and level 2 has
+ been deprecated.
The annotation mechanism has largely been superseded by GDB/MI
(*note GDB/MI::).
-`--args'
+'--args'
Change interpretation of command line so that arguments following
the executable file are passed as command line arguments to the
inferior. This option stops option processing.
-`-baud BPS'
-`-b BPS'
+'-baud BPS'
+'-b BPS'
Set the line speed (baud rate or bits per second) of any serial
interface used by GDB for remote debugging.
-`-l TIMEOUT'
+'-l TIMEOUT'
Set the timeout (in seconds) of any communication used by GDB for
remote debugging.
-`-tty DEVICE'
-`-t DEVICE'
+'-tty DEVICE'
+'-t DEVICE'
Run using DEVICE for your program's standard input and output.
-`-tui'
+'-tui'
Activate the "Text User Interface" when starting. The Text User
Interface manages several text windows on the terminal, showing
- source, assembly, registers and GDB command outputs (*note GDB
- Text User Interface: TUI.). Do not use this option if you run GDB
- from Emacs (*note Using GDB under GNU Emacs: Emacs.).
+ source, assembly, registers and GDB command outputs (*note GDB Text
+ User Interface: TUI.). Do not use this option if you run GDB from
+ Emacs (*note Using GDB under GNU Emacs: Emacs.).
-`-interpreter INTERP'
+'-interpreter INTERP'
Use the interpreter INTERP for interface with the controlling
program or device. This option is meant to be set by programs
which communicate with GDB using it as a back end. *Note Command
Interpreters: Interpreters.
- `--interpreter=mi' (or `--interpreter=mi2') causes GDB to use the
+ '--interpreter=mi' (or '--interpreter=mi2') causes GDB to use the
"GDB/MI interface" (*note The GDB/MI Interface: GDB/MI.) included
since GDB version 6.0. The previous GDB/MI interface, included in
- GDB version 5.3 and selected with `--interpreter=mi1', is
+ GDB version 5.3 and selected with '--interpreter=mi1', is
deprecated. Earlier GDB/MI interfaces are no longer supported.
-`-write'
+'-write'
Open the executable and core files for both reading and writing.
- This is equivalent to the `set write on' command inside GDB (*note
+ This is equivalent to the 'set write on' command inside GDB (*note
Patching::).
-`-statistics'
+'-statistics'
This option causes GDB to print statistics about time and memory
usage after it completes each command and returns to the prompt.
-`-version'
+'-version'
This option causes GDB to print its version number and no-warranty
blurb, and exit.
+'-configuration'
+ This option causes GDB to print details about its build-time
+ configuration parameters, and then exit. These details can be
+ important when reporting GDB bugs (*note GDB Bugs::).
\1f
File: gdb.info, Node: Startup, Prev: Mode Options, Up: Invoking GDB
1. Sets up the command interpreter as specified by the command line
(*note interpreter: Mode Options.).
- 2. Reads the system-wide "init file" (if `--with-system-gdbinit' was
+ 2. Reads the system-wide "init file" (if '--with-system-gdbinit' was
used when building GDB; *note System-wide configuration and
- settings: System-wide configuration.) and executes all the
- commands in that file.
+ settings: System-wide configuration.) and executes all the commands
+ in that file.
- 3. Reads the init file (if any) in your home directory(1) and
- executes all the commands in that file.
+ 3. Reads the init file (if any) in your home directory(1) and executes
+ all the commands in that file.
- 4. Executes commands and command files specified by the `-iex' and
- `-ix' options in their specified order. Usually you should use the
- `-ex' and `-x' options instead, but this way you can apply
- settings before GDB init files get executed and before inferior
- gets loaded.
+ 4. Executes commands and command files specified by the '-iex' and
+ '-ix' options in their specified order. Usually you should use the
+ '-ex' and '-x' options instead, but this way you can apply settings
+ before GDB init files get executed and before inferior gets loaded.
5. Processes command line options and operands.
6. Reads and executes the commands from init file (if any) in the
- current working directory as long as `set auto-load local-gdbinit'
- is set to `on' (*note Init File in the Current Directory::). This
+ current working directory as long as 'set auto-load local-gdbinit'
+ is set to 'on' (*note Init File in the Current Directory::). This
is only done if the current directory is different from your home
- directory. Thus, you can have more than one init file, one
- generic in your home directory, and another, specific to the
- program you are debugging, in the directory where you invoke GDB.
+ directory. Thus, you can have more than one init file, one generic
+ in your home directory, and another, specific to the program you
+ are debugging, in the directory where you invoke GDB.
7. If the command line specified a program to debug, or a process to
attach to, or a core file, GDB loads any auto-loaded scripts
- provided for the program or for its loaded shared libraries.
- *Note Auto-loading::.
+ provided for the program or for its loaded shared libraries. *Note
+ Auto-loading::.
- If you wish to disable the auto-loading during startup, you must
- do something like the following:
+ If you wish to disable the auto-loading during startup, you must do
+ something like the following:
$ gdb -iex "set auto-load python-scripts off" myprogram
- Option `-ex' does not work because the auto-loading is then turned
+ Option '-ex' does not work because the auto-loading is then turned
off too late.
- 8. Executes commands and command files specified by the `-ex' and
- `-x' options in their specified order. *Note Command Files::, for
- more details about GDB command files.
+ 8. Executes commands and command files specified by the '-ex' and '-x'
+ options in their specified order. *Note Command Files::, for more
+ details about GDB command files.
9. Reads the command history recorded in the "history file". *Note
Command History::, for more details about the command history and
Init files use the same syntax as "command files" (*note Command
Files::) and are processed by GDB in the same way. The init file in
-your home directory can set options (such as `set complaints') that
-affect subsequent processing of command line options and operands.
-Init files are not executed if you use the `-nx' option (*note Choosing
+your home directory can set options (such as 'set complaints') that
+affect subsequent processing of command line options and operands. Init
+files are not executed if you use the '-nx' option (*note Choosing
Modes: Mode Options.).
To display the list of init files loaded by gdb at startup, you can
-use `gdb --help'.
+use 'gdb --help'.
- The GDB init files are normally called `.gdbinit'. The DJGPP port
-of GDB uses the name `gdb.ini', due to the limitations of file names
-imposed by DOS filesystems. The Windows ports of GDB use the standard
-name, but if they find a `gdb.ini' file, they warn you about that and
-suggest to rename the file to the standard name.
+ The GDB init files are normally called '.gdbinit'. The DJGPP port of
+GDB uses the name 'gdb.ini', due to the limitations of file names
+imposed by DOS filesystems. The Windows port of GDB uses the standard
+name, but if it finds a 'gdb.ini' file in your home directory, it warns
+you about that and suggests to rename the file to the standard name.
---------- Footnotes ----------
(1) On DOS/Windows systems, the home directory is the one pointed to
-by the `HOME' environment variable.
+by the 'HOME' environment variable.
\1f
File: gdb.info, Node: Quitting GDB, Next: Shell Commands, Prev: Invoking GDB, Up: Invocation
2.2 Quitting GDB
================
-`quit [EXPRESSION]'
-`q'
- To exit GDB, use the `quit' command (abbreviated `q'), or type an
- end-of-file character (usually `Ctrl-d'). If you do not supply
+'quit [EXPRESSION]'
+'q'
+ To exit GDB, use the 'quit' command (abbreviated 'q'), or type an
+ end-of-file character (usually 'Ctrl-d'). If you do not supply
EXPRESSION, GDB will terminate normally; otherwise it will
terminate using the result of EXPRESSION as the error code.
- An interrupt (often `Ctrl-c') does not exit from GDB, but rather
-terminates the action of any GDB command that is in progress and
-returns to GDB command level. It is safe to type the interrupt
-character at any time because GDB does not allow it to take effect
-until a time when it is safe.
+ An interrupt (often 'Ctrl-c') does not exit from GDB, but rather
+terminates the action of any GDB command that is in progress and returns
+to GDB command level. It is safe to type the interrupt character at any
+time because GDB does not allow it to take effect until a time when it
+is safe.
If you have been using GDB to control an attached process or device,
-you can release it with the `detach' command (*note Debugging an
+you can release it with the 'detach' command (*note Debugging an
Already-running Process: Attach.).
\1f
If you need to execute occasional shell commands during your debugging
session, there is no need to leave or suspend GDB; you can just use the
-`shell' command.
+'shell' command.
-`shell COMMAND-STRING'
-`!COMMAND-STRING'
+'shell COMMAND-STRING'
+'!COMMAND-STRING'
Invoke a standard shell to execute COMMAND-STRING. Note that no
- space is needed between `!' and COMMAND-STRING. If it exists, the
- environment variable `SHELL' determines which shell to run.
- Otherwise GDB uses the default shell (`/bin/sh' on Unix systems,
- `COMMAND.COM' on MS-DOS, etc.).
+ space is needed between '!' and COMMAND-STRING. If it exists, the
+ environment variable 'SHELL' determines which shell to run.
+ Otherwise GDB uses the default shell ('/bin/sh' on Unix systems,
+ 'COMMAND.COM' on MS-DOS, etc.).
- The utility `make' is often needed in development environments. You
-do not have to use the `shell' command for this purpose in GDB:
+ The utility 'make' is often needed in development environments. You
+do not have to use the 'shell' command for this purpose in GDB:
-`make MAKE-ARGS'
- Execute the `make' program with the specified arguments. This is
- equivalent to `shell make MAKE-ARGS'.
+'make MAKE-ARGS'
+ Execute the 'make' program with the specified arguments. This is
+ equivalent to 'shell make MAKE-ARGS'.
\1f
File: gdb.info, Node: Logging Output, Prev: Shell Commands, Up: Invocation
You may want to save the output of GDB commands to a file. There are
several commands to control GDB's logging.
-`set logging on'
+'set logging on'
Enable logging.
-
-`set logging off'
- Disable logging.
-
-`set logging file FILE'
+'set logging off'
+ Disable logging.
+'set logging file FILE'
Change the name of the current logfile. The default logfile is
- `gdb.txt'.
-
-`set logging overwrite [on|off]'
- By default, GDB will append to the logfile. Set `overwrite' if
- you want `set logging on' to overwrite the logfile instead.
-
-`set logging redirect [on|off]'
+ 'gdb.txt'.
+'set logging overwrite [on|off]'
+ By default, GDB will append to the logfile. Set 'overwrite' if you
+ want 'set logging on' to overwrite the logfile instead.
+'set logging redirect [on|off]'
By default, GDB output will go to both the terminal and the
- logfile. Set `redirect' if you want output to go only to the log
- file.
-
-`show logging'
+ logfile. Set 'redirect' if you want output to go only to the log
+ file.
+'show logging'
Show the current values of the logging settings.
\1f
A GDB command is a single line of input. There is no limit on how long
it can be. It starts with a command name, which is followed by
arguments whose meaning depends on the command name. For example, the
-command `step' accepts an argument which is the number of times to
-step, as in `step 5'. You can also use the `step' command with no
-arguments. Some commands do not allow any arguments.
+command 'step' accepts an argument which is the number of times to step,
+as in 'step 5'. You can also use the 'step' command with no arguments.
+Some commands do not allow any arguments.
GDB command names may always be truncated if that abbreviation is
unambiguous. Other possible command abbreviations are listed in the
documentation for individual commands. In some cases, even ambiguous
-abbreviations are allowed; for example, `s' is specially defined as
-equivalent to `step' even though there are other commands whose names
-start with `s'. You can test abbreviations by using them as arguments
-to the `help' command.
+abbreviations are allowed; for example, 's' is specially defined as
+equivalent to 'step' even though there are other commands whose names
+start with 's'. You can test abbreviations by using them as arguments
+to the 'help' command.
A blank line as input to GDB (typing just <RET>) means to repeat the
-previous command. Certain commands (for example, `run') will not
-repeat this way; these are commands whose unintentional repetition
-might cause trouble and which you are unlikely to want to repeat.
-User-defined commands can disable this feature; see *Note dont-repeat:
-Define.
+previous command. Certain commands (for example, 'run') will not repeat
+this way; these are commands whose unintentional repetition might cause
+trouble and which you are unlikely to want to repeat. User-defined
+commands can disable this feature; see *note dont-repeat: Define.
- The `list' and `x' commands, when you repeat them with <RET>,
+ The 'list' and 'x' commands, when you repeat them with <RET>,
construct new arguments rather than repeating exactly as typed. This
permits easy scanning of source or memory.
GDB can also use <RET> in another way: to partition lengthy output,
-in a way similar to the common utility `more' (*note Screen Size:
-Screen Size.). Since it is easy to press one <RET> too many in this
-situation, GDB disables command repetition after any command that
-generates this sort of display.
+in a way similar to the common utility 'more' (*note Screen Size: Screen
+Size.). Since it is easy to press one <RET> too many in this situation,
+GDB disables command repetition after any command that generates this
+sort of display.
- Any text from a `#' to the end of the line is a comment; it does
+ Any text from a '#' to the end of the line is a comment; it does
nothing. This is useful mainly in command files (*note Command Files:
Command Files.).
- The `Ctrl-o' binding is useful for repeating a complex sequence of
+ The 'Ctrl-o' binding is useful for repeating a complex sequence of
commands. This command accepts the current line, like <RET>, and then
fetches the next line relative to the current line from the history for
editing.
(gdb) info bre <TAB>
-GDB fills in the rest of the word `breakpoints', since that is the only
-`info' subcommand beginning with `bre':
+GDB fills in the rest of the word 'breakpoints', since that is the only
+'info' subcommand beginning with 'bre':
(gdb) info breakpoints
-You can either press <RET> at this point, to run the `info breakpoints'
-command, or backspace and enter something else, if `breakpoints' does
+You can either press <RET> at this point, to run the 'info breakpoints'
+command, or backspace and enter something else, if 'breakpoints' does
not look like the command you expected. (If you were sure you wanted
-`info breakpoints' in the first place, you might as well just type
-<RET> immediately after `info bre', to exploit command abbreviations
-rather than command completion).
+'info breakpoints' in the first place, you might as well just type <RET>
+immediately after 'info bre', to exploit command abbreviations rather
+than command completion).
If there is more than one possibility for the next word when you
press <TAB>, GDB sounds a bell. You can either supply more characters
and try again, or just press <TAB> a second time; GDB displays all the
possible completions for that word. For example, you might want to set
-a breakpoint on a subroutine whose name begins with `make_', but when
-you type `b make_<TAB>' GDB just sounds the bell. Typing <TAB> again
+a breakpoint on a subroutine whose name begins with 'make_', but when
+you type 'b make_<TAB>' GDB just sounds the bell. Typing <TAB> again
displays all the function names in your program that begin with those
characters, for example:
(gdb) b make_
After displaying the available possibilities, GDB copies your partial
-input (`b make_' in the example) so you can finish the command.
+input ('b make_' in the example) so you can finish the command.
If you just want to see the list of alternatives in the first place,
-you can press `M-?' rather than pressing <TAB> twice. `M-?' means
-`<META> ?'. You can type this either by holding down a key designated
-as the <META> shift on your keyboard (if there is one) while typing
-`?', or as <ESC> followed by `?'.
+you can press 'M-?' rather than pressing <TAB> twice. 'M-?' means
+'<META> ?'. You can type this either by holding down a key designated
+as the <META> shift on your keyboard (if there is one) while typing '?',
+or as <ESC> followed by '?'.
Sometimes the string you need, while logically a "word", may contain
parentheses or other characters that GDB normally excludes from its
notion of a word. To permit word completion to work in this situation,
-you may enclose words in `'' (single quote marks) in GDB commands.
+you may enclose words in ''' (single quote marks) in GDB commands.
The most likely situation where you might need this is in typing the
-name of a C++ function. This is because C++ allows function
-overloading (multiple definitions of the same function, distinguished
-by argument type). For example, when you want to set a breakpoint you
-may need to distinguish whether you mean the version of `name' that
-takes an `int' parameter, `name(int)', or the version that takes a
-`float' parameter, `name(float)'. To use the word-completion
-facilities in this situation, type a single quote `'' at the beginning
-of the function name. This alerts GDB that it may need to consider
-more information than usual when you press <TAB> or `M-?' to request
-word completion:
+name of a C++ function. This is because C++ allows function overloading
+(multiple definitions of the same function, distinguished by argument
+type). For example, when you want to set a breakpoint you may need to
+distinguish whether you mean the version of 'name' that takes an 'int'
+parameter, 'name(int)', or the version that takes a 'float' parameter,
+'name(float)'. To use the word-completion facilities in this situation,
+type a single quote ''' at the beginning of the function name. This
+alerts GDB that it may need to consider more information than usual when
+you press <TAB> or 'M-?' to request word completion:
(gdb) b 'bubble( M-?
bubble(double,double) bubble(int,int)
have not yet started typing the argument list when you ask for
completion on an overloaded symbol.
- For more information about overloaded functions, see *Note C++
-Expressions: C Plus Plus Expressions. You can use the command `set
-overload-resolution off' to disable overload resolution; see *Note GDB
+ For more information about overloaded functions, see *note C++
+Expressions: C Plus Plus Expressions. You can use the command 'set
+overload-resolution off' to disable overload resolution; see *note GDB
Features for C++: Debugging C Plus Plus.
When completing in an expression which looks up a field in a
to_delete to_put to_write_async_safe
to_flush to_read
-This is because the `gdb_stdout' is a variable of the type `struct
+This is because the 'gdb_stdout' is a variable of the type 'struct
ui_file' that is defined in GDB sources as follows:
struct ui_file
3.3 Getting Help
================
-You can always ask GDB itself for information on its commands, using
-the command `help'.
+You can always ask GDB itself for information on its commands, using the
+command 'help'.
-`help'
-`h'
- You can use `help' (abbreviated `h') with no arguments to display
- a short list of named classes of commands:
+'help'
+'h'
+ You can use 'help' (abbreviated 'h') with no arguments to display a
+ short list of named classes of commands:
(gdb) help
List of classes of commands:
Command name abbreviations are allowed if unambiguous.
(gdb)
-`help CLASS'
+'help CLASS'
Using one of the general help classes as an argument, you can get a
list of the individual commands in that class. For example, here
- is the help display for the class `status':
+ is the help display for the class 'status':
(gdb) help status
Status inquiries.
Command name abbreviations are allowed if unambiguous.
(gdb)
-`help COMMAND'
- With a command name as `help' argument, GDB displays a short
+'help COMMAND'
+ With a command name as 'help' argument, GDB displays a short
paragraph on how to use that command.
-`apropos ARGS'
- The `apropos' command searches through all of the GDB commands,
- and their documentation, for the regular expression specified in
- ARGS. It prints out all matches found. For example:
+'apropos ARGS'
+ The 'apropos' command searches through all of the GDB commands, and
+ their documentation, for the regular expression specified in ARGS.
+ It prints out all matches found. For example:
apropos alias
del -- Delete some breakpoints or auto-display expressions
delete -- Delete some breakpoints or auto-display expressions
-`complete ARGS'
- The `complete ARGS' command lists all the possible completions for
+'complete ARGS'
+ The 'complete ARGS' command lists all the possible completions for
the beginning of a command. Use ARGS to specify the beginning of
the command you want completed. For example:
This is intended for use by GNU Emacs.
- In addition to `help', you can use the GDB commands `info' and
-`show' to inquire about the state of your program, or the state of GDB
-itself. Each command supports many topics of inquiry; this manual
-introduces each of them in the appropriate context. The listings under
-`info' and under `show' in the Command, Variable, and Function Index
-point to all the sub-commands. *Note Command and Variable Index::.
+ In addition to 'help', you can use the GDB commands 'info' and 'show'
+to inquire about the state of your program, or the state of GDB itself.
+Each command supports many topics of inquiry; this manual introduces
+each of them in the appropriate context. The listings under 'info' and
+under 'show' in the Command, Variable, and Function Index point to all
+the sub-commands. *Note Command and Variable Index::.
-`info'
- This command (abbreviated `i') is for describing the state of your
+'info'
+ This command (abbreviated 'i') is for describing the state of your
program. For example, you can show the arguments passed to a
- function with `info args', list the registers currently in use
- with `info registers', or list the breakpoints you have set with
- `info breakpoints'. You can get a complete list of the `info'
- sub-commands with `help info'.
+ function with 'info args', list the registers currently in use with
+ 'info registers', or list the breakpoints you have set with 'info
+ breakpoints'. You can get a complete list of the 'info'
+ sub-commands with 'help info'.
-`set'
+'set'
You can assign the result of an expression to an environment
- variable with `set'. For example, you can set the GDB prompt to a
- $-sign with `set prompt $'.
+ variable with 'set'. For example, you can set the GDB prompt to a
+ $-sign with 'set prompt $'.
-`show'
- In contrast to `info', `show' is for describing the state of GDB
- itself. You can change most of the things you can `show', by
- using the related command `set'; for example, you can control what
- number system is used for displays with `set radix', or simply
- inquire which is currently in use with `show radix'.
+'show'
+ In contrast to 'info', 'show' is for describing the state of GDB
+ itself. You can change most of the things you can 'show', by using
+ the related command 'set'; for example, you can control what number
+ system is used for displays with 'set radix', or simply inquire
+ which is currently in use with 'show radix'.
To display all the settable parameters and their current values,
- you can use `show' with no arguments; you may also use `info set'.
+ you can use 'show' with no arguments; you may also use 'info set'.
Both commands produce the same display.
- Here are three miscellaneous `show' subcommands, all of which are
-exceptional in lacking corresponding `set' commands:
+ Here are several miscellaneous 'show' subcommands, all of which are
+exceptional in lacking corresponding 'set' commands:
-`show version'
+'show version'
Show what version of GDB is running. You should include this
- information in GDB bug-reports. If multiple versions of GDB are
- in use at your site, you may need to determine which version of
- GDB you are running; as GDB evolves, new commands are introduced,
- and old ones may wither away. Also, many system vendors ship
- variant versions of GDB, and there are variant versions of GDB in
- GNU/Linux distributions as well. The version number is the same
- as the one announced when you start GDB.
-
-`show copying'
-`info copying'
+ information in GDB bug-reports. If multiple versions of GDB are in
+ use at your site, you may need to determine which version of GDB
+ you are running; as GDB evolves, new commands are introduced, and
+ old ones may wither away. Also, many system vendors ship variant
+ versions of GDB, and there are variant versions of GDB in GNU/Linux
+ distributions as well. The version number is the same as the one
+ announced when you start GDB.
+
+'show copying'
+'info copying'
Display information about permission for copying GDB.
-`show warranty'
-`info warranty'
+'show warranty'
+'info warranty'
Display the GNU "NO WARRANTY" statement, or a warranty, if your
version of GDB comes with one.
+'show configuration'
+ Display detailed information about the way GDB was configured when
+ it was built. This displays the optional arguments passed to the
+ 'configure' script and also configuration parameters detected
+ automatically by 'configure'. When reporting a GDB bug (*note GDB
+ Bugs::), it is important to include this information in your
+ report.
\1f
File: gdb.info, Node: Running, Next: Stopping, Prev: Commands, Up: Top
function and the correspondence between source line numbers and
addresses in the executable code.
- To request debugging information, specify the `-g' option when you
+ To request debugging information, specify the '-g' option when you
run the compiler.
Programs that are to be shipped to your customers are compiled with
-optimizations, using the `-O' compiler option. However, some compilers
-are unable to handle the `-g' and `-O' options together. Using those
+optimizations, using the '-O' compiler option. However, some compilers
+are unable to handle the '-g' and '-O' options together. Using those
compilers, you cannot generate optimized executables containing
debugging information.
- GCC, the GNU C/C++ compiler, supports `-g' with or without `-O',
+ GCC, the GNU C/C++ compiler, supports '-g' with or without '-O',
making it possible to debug optimized code. We recommend that you
-_always_ use `-g' whenever you compile a program. You may think your
+_always_ use '-g' whenever you compile a program. You may think your
program is correct, but there is no sense in pushing your luck. For
-more information, see *Note Optimized Code::.
+more information, see *note Optimized Code::.
- Older versions of the GNU C compiler permitted a variant option
-`-gg' for debugging information. GDB no longer supports this format;
-if your GNU C compiler has this option, do not use it.
+ Older versions of the GNU C compiler permitted a variant option '-gg'
+for debugging information. GDB no longer supports this format; if your
+GNU C compiler has this option, do not use it.
GDB knows about preprocessor macros and can show you their expansion
(*note Macros::). Most compilers do not include information about
-preprocessor macros in the debugging information if you specify the
-`-g' flag alone. Version 3.1 and later of GCC, the GNU C compiler,
-provides macro information if you are using the DWARF debugging format,
-and specify the option `-g3'.
+preprocessor macros in the debugging information if you specify the '-g'
+flag alone. Version 3.1 and later of GCC, the GNU C compiler, provides
+macro information if you are using the DWARF debugging format, and
+specify the option '-g3'.
*Note Options for Debugging Your Program or GCC: (gcc.info)Debugging
Options, for more information on GCC options affecting debug
4.2 Starting your Program
=========================
-`run'
-`r'
- Use the `run' command to start your program under GDB. You must
- first specify the program name (except on VxWorks) with an
- argument to GDB (*note Getting In and Out of GDB: Invocation.), or
- by using the `file' or `exec-file' command (*note Commands to
- Specify Files: Files.).
-
+'run'
+'r'
+ Use the 'run' command to start your program under GDB. You must
+ first specify the program name (except on VxWorks) with an argument
+ to GDB (*note Getting In and Out of GDB: Invocation.), or by using
+ the 'file' or 'exec-file' command (*note Commands to Specify Files:
+ Files.).
If you are running your program in an execution environment that
-supports processes, `run' creates an inferior process and makes that
-process run your program. In some environments without processes,
-`run' jumps to the start of your program. Other targets, like
-`remote', are always running. If you get an error message like this
-one:
+supports processes, 'run' creates an inferior process and makes that
+process run your program. In some environments without processes, 'run'
+jumps to the start of your program. Other targets, like 'remote', are
+always running. If you get an error message like this one:
The "remote" target does not support "run".
Try "help target" or "continue".
-then use `continue' to run your program. You may need `load' first
+then use 'continue' to run your program. You may need 'load' first
(*note load::).
The execution of a program is affected by certain information it
receives from its superior. GDB provides ways to specify this
-information, which you must do _before_ starting your program. (You
-can change it after starting your program, but such changes only affect
-your program the next time you start it.) This information may be
-divided into four categories:
+information, which you must do _before_ starting your program. (You can
+change it after starting your program, but such changes only affect your
+program the next time you start it.) This information may be divided
+into four categories:
The _arguments._
Specify the arguments to give your program as the arguments of the
- `run' command. If a shell is available on your target, the shell
+ 'run' command. If a shell is available on your target, the shell
is used to pass the arguments, so that you may use normal
conventions (such as wildcard expansion or variable substitution)
in describing the arguments. In Unix systems, you can control
- which shell is used with the `SHELL' environment variable. *Note
- Your Program's Arguments: Arguments.
+ which shell is used with the 'SHELL' environment variable. If you
+ do not define 'SHELL', GDB uses the default shell ('/bin/sh'). You
+ can disable use of any shell with the 'set startup-with-shell'
+ command (see below for details).
The _environment._
Your program normally inherits its environment from GDB, but you
- can use the GDB commands `set environment' and `unset environment'
- to change parts of the environment that affect your program.
- *Note Your Program's Environment: Environment.
+ can use the GDB commands 'set environment' and 'unset environment'
+ to change parts of the environment that affect your program. *Note
+ Your Program's Environment: Environment.
The _working directory._
Your program inherits its working directory from GDB. You can set
- the GDB working directory with the `cd' command in GDB. *Note
- Your Program's Working Directory: Working Directory.
+ the GDB working directory with the 'cd' command in GDB. *Note Your
+ Program's Working Directory: Working Directory.
The _standard input and output._
Your program normally uses the same device for standard input and
standard output as GDB is using. You can redirect input and output
- in the `run' command line, or you can use the `tty' command to set
+ in the 'run' command line, or you can use the 'tty' command to set
a different device for your program. *Note Your Program's Input
and Output: Input/Output.
another program; if you attempt this, GDB is likely to wind up
debugging the wrong program.
- When you issue the `run' command, your program begins to execute
-immediately. *Note Stopping and Continuing: Stopping, for discussion
-of how to arrange for your program to stop. Once your program has
-stopped, you may call functions in your program, using the `print' or
-`call' commands. *Note Examining Data: Data.
+ When you issue the 'run' command, your program begins to execute
+immediately. *Note Stopping and Continuing: Stopping, for discussion of
+how to arrange for your program to stop. Once your program has stopped,
+you may call functions in your program, using the 'print' or 'call'
+commands. *Note Examining Data: Data.
If the modification time of your symbol file has changed since the
-last time GDB read its symbols, GDB discards its symbol table, and
-reads it again. When it does this, GDB tries to retain your current
+last time GDB read its symbols, GDB discards its symbol table, and reads
+it again. When it does this, GDB tries to retain your current
breakpoints.
-`start'
+'start'
The name of the main procedure can vary from language to language.
- With C or C++, the main procedure name is always `main', but other
- languages such as Ada do not require a specific name for their
- main procedure. The debugger provides a convenient way to start
- the execution of the program and to stop at the beginning of the
- main procedure, depending on the language used.
+ With C or C++, the main procedure name is always 'main', but other
+ languages such as Ada do not require a specific name for their main
+ procedure. The debugger provides a convenient way to start the
+ execution of the program and to stop at the beginning of the main
+ procedure, depending on the language used.
- The `start' command does the equivalent of setting a temporary
+ The 'start' command does the equivalent of setting a temporary
breakpoint at the beginning of the main procedure and then invoking
- the `run' command.
+ the 'run' command.
Some programs contain an "elaboration" phase where some startup
- code is executed before the main procedure is called. This
- depends on the languages used to write your program. In C++, for
- instance, constructors for static and global objects are executed
- before `main' is called. It is therefore possible that the
- debugger stops before reaching the main procedure. However, the
- temporary breakpoint will remain to halt execution.
+ code is executed before the main procedure is called. This depends
+ on the languages used to write your program. In C++, for instance,
+ constructors for static and global objects are executed before
+ 'main' is called. It is therefore possible that the debugger stops
+ before reaching the main procedure. However, the temporary
+ breakpoint will remain to halt execution.
Specify the arguments to give to your program as arguments to the
- `start' command. These arguments will be given verbatim to the
- underlying `run' command. Note that the same arguments will be
+ 'start' command. These arguments will be given verbatim to the
+ underlying 'run' command. Note that the same arguments will be
reused if no argument is provided during subsequent calls to
- `start' or `run'.
+ 'start' or 'run'.
It is sometimes necessary to debug the program during elaboration.
- In these cases, using the `start' command would stop the
- execution of your program too late, as the program would have
- already completed the elaboration phase. Under these
- circumstances, insert breakpoints in your elaboration code before
- running your program.
-
-`set exec-wrapper WRAPPER'
-`show exec-wrapper'
-`unset exec-wrapper'
- When `exec-wrapper' is set, the specified wrapper is used to
- launch programs for debugging. GDB starts your program with a
- shell command of the form `exec WRAPPER PROGRAM'. Quoting is
- added to PROGRAM and its arguments, but not to WRAPPER, so you
- should add quotes if appropriate for your shell. The wrapper runs
- until it executes your program, and then GDB takes control.
-
- You can use any program that eventually calls `execve' with its
+ In these cases, using the 'start' command would stop the execution
+ of your program too late, as the program would have already
+ completed the elaboration phase. Under these circumstances, insert
+ breakpoints in your elaboration code before running your program.
+
+'set exec-wrapper WRAPPER'
+'show exec-wrapper'
+'unset exec-wrapper'
+ When 'exec-wrapper' is set, the specified wrapper is used to launch
+ programs for debugging. GDB starts your program with a shell
+ command of the form 'exec WRAPPER PROGRAM'. Quoting is added to
+ PROGRAM and its arguments, but not to WRAPPER, so you should add
+ quotes if appropriate for your shell. The wrapper runs until it
+ executes your program, and then GDB takes control.
+
+ You can use any program that eventually calls 'execve' with its
arguments as a wrapper. Several standard Unix utilities do this,
- e.g. `env' and `nohup'. Any Unix shell script ending with `exec
+ e.g. 'env' and 'nohup'. Any Unix shell script ending with 'exec
"$@"' will also work.
- For example, you can use `env' to pass an environment variable to
+ For example, you can use 'env' to pass an environment variable to
the debugged program, without setting the variable in your shell's
environment:
This command is available when debugging locally on most targets,
excluding DJGPP, Cygwin, MS Windows, and QNX Neutrino.
-`set disable-randomization'
-`set disable-randomization on'
+'set startup-with-shell'
+'set startup-with-shell on'
+'set startup-with-shell off'
+'show set startup-with-shell'
+ On Unix systems, by default, if a shell is available on your
+ target, GDB) uses it to start your program. Arguments of the 'run'
+ command are passed to the shell, which does variable substitution,
+ expands wildcard characters and performs redirection of I/O. In
+ some circumstances, it may be useful to disable such use of a
+ shell, for example, when debugging the shell itself or diagnosing
+ startup failures such as:
+
+ (gdb) run
+ Starting program: ./a.out
+ During startup program terminated with signal SIGSEGV, Segmentation fault.
+
+ which indicates the shell or the wrapper specified with
+ 'exec-wrapper' crashed, not your program. Most often, this is
+ caused by something odd in your shell's non-interactive mode
+ initialization file--such as '.cshrc' for C-shell, $'.zshenv' for
+ the Z shell, or the file specified in the 'BASH_ENV' environment
+ variable for BASH.
+
+'set auto-connect-native-target'
+'set auto-connect-native-target on'
+'set auto-connect-native-target off'
+'show auto-connect-native-target'
+
+ By default, if not connected to any target yet (e.g., with 'target
+ remote'), the 'run' command starts your program as a native process
+ under GDB, on your local machine. If you're sure you don't want to
+ debug programs on your local machine, you can tell GDB to not
+ connect to the native target automatically with the 'set
+ auto-connect-native-target off' command.
+
+ If 'on', which is the default, and if GDB is not connected to a
+ target already, the 'run' command automaticaly connects to the
+ native target, if one is available.
+
+ If 'off', and if GDB is not connected to a target already, the
+ 'run' command fails with an error:
+
+ (gdb) run
+ Don't know how to run. Try "help target".
+
+ If GDB is already connected to a target, GDB always uses it with
+ the 'run' command.
+
+ In any case, you can explicitly connect to the native target with
+ the 'target native' command. For example,
+
+ (gdb) set auto-connect-native-target off
+ (gdb) run
+ Don't know how to run. Try "help target".
+ (gdb) target native
+ (gdb) run
+ Starting program: ./a.out
+ [Inferior 1 (process 10421) exited normally]
+
+ In case you connected explicitly to the 'native' target, GDB
+ remains connected even if all inferiors exit, ready for the next
+ 'run' command. Use the 'disconnect' command to disconnect.
+
+ Examples of other commands that likewise respect the
+ 'auto-connect-native-target' setting: 'attach', 'info proc', 'info
+ os'.
+
+'set disable-randomization'
+'set disable-randomization on'
This option (enabled by default in GDB) will turn off the native
randomization of the virtual address space of the started program.
This option is useful for multiple debugging sessions to make the
(gdb) set exec-wrapper setarch `uname -m` -R
-`set disable-randomization off'
+'set disable-randomization off'
Leave the behavior of the started executable unchanged. Some bugs
rear their ugly heads only when the program is loaded at certain
addresses. If your bug disappears when you run the program under
GDB, that might be because GDB by default disables the address
randomization on platforms, such as GNU/Linux, which do that for
- stand-alone programs. Use `set disable-randomization off' to try
+ stand-alone programs. Use 'set disable-randomization off' to try
to reproduce such elusive bugs.
On targets where it is available, virtual address space
randomization protects the programs against certain kinds of
security attacks. In these cases the attacker needs to know the
exact location of a concrete executable code. Randomizing its
- location makes it impossible to inject jumps misusing a code at
- its expected addresses.
+ location makes it impossible to inject jumps misusing a code at its
+ expected addresses.
Prelinking shared libraries provides a startup performance
- advantage but it makes addresses in these libraries predictable
- for privileged processes by having just unprivileged access at the
+ advantage but it makes addresses in these libraries predictable for
+ privileged processes by having just unprivileged access at the
target system. Reading the shared library binary gives enough
information for assembling the malicious code misusing it. Still
even a prelinked shared library can get loaded at a new random
startup. Shared libraries not already prelinked are always loaded
at a randomly chosen address.
- Position independent executables (PIE) contain position
- independent code similar to the shared libraries and therefore
- such executables get loaded at a randomly chosen address upon
- startup. PIE executables always load even already prelinked
- shared libraries at a random address. You can build such
- executable using `gcc -fPIE -pie'.
+ Position independent executables (PIE) contain position independent
+ code similar to the shared libraries and therefore such executables
+ get loaded at a randomly chosen address upon startup. PIE
+ executables always load even already prelinked shared libraries at
+ a random address. You can build such executable using 'gcc -fPIE
+ -pie'.
Heap (malloc storage), stack and custom mmap areas are always
placed randomly (as long as the randomization is enabled).
-`show disable-randomization'
+'show disable-randomization'
Show the current setting of the explicit disable of the native
randomization of the virtual address space of the started program.
-
\1f
File: gdb.info, Node: Arguments, Next: Environment, Prev: Starting, Up: Running
============================
The arguments to your program can be specified by the arguments of the
-`run' command. They are passed to a shell, which expands wildcard
+'run' command. They are passed to a shell, which expands wildcard
characters and performs redirection of I/O, and thence to your program.
-Your `SHELL' environment variable (if it exists) specifies what shell
-GDB uses. If you do not define `SHELL', GDB uses the default shell
-(`/bin/sh' on Unix).
+Your 'SHELL' environment variable (if it exists) specifies what shell
+GDB uses. If you do not define 'SHELL', GDB uses the default shell
+('/bin/sh' on Unix).
On non-Unix systems, the program is usually invoked directly by GDB,
-which emulates I/O redirection via the appropriate system calls, and
-the wildcard characters are expanded by the startup code of the
-program, not by the shell.
+which emulates I/O redirection via the appropriate system calls, and the
+wildcard characters are expanded by the startup code of the program, not
+by the shell.
- `run' with no arguments uses the same arguments used by the previous
-`run', or those set by the `set args' command.
+ 'run' with no arguments uses the same arguments used by the previous
+'run', or those set by the 'set args' command.
-`set args'
- Specify the arguments to be used the next time your program is
- run. If `set args' has no arguments, `run' executes your program
- with no arguments. Once you have run your program with arguments,
- using `set args' before the next `run' is the only way to run it
- again without arguments.
+'set args'
+ Specify the arguments to be used the next time your program is run.
+ If 'set args' has no arguments, 'run' executes your program with no
+ arguments. Once you have run your program with arguments, using
+ 'set args' before the next 'run' is the only way to run it again
+ without arguments.
-`show args'
+'show args'
Show the arguments to give your program when it is started.
\1f
==============================
The "environment" consists of a set of environment variables and their
-values. Environment variables conventionally record such things as
-your user name, your home directory, your terminal type, and your search
-path for programs to run. Usually you set up environment variables with
-the shell and they are inherited by all the other programs you run.
-When debugging, it can be useful to try running your program with a
-modified environment without having to start GDB over again.
-
-`path DIRECTORY'
- Add DIRECTORY to the front of the `PATH' environment variable (the
+values. Environment variables conventionally record such things as your
+user name, your home directory, your terminal type, and your search path
+for programs to run. Usually you set up environment variables with the
+shell and they are inherited by all the other programs you run. When
+debugging, it can be useful to try running your program with a modified
+environment without having to start GDB over again.
+
+'path DIRECTORY'
+ Add DIRECTORY to the front of the 'PATH' environment variable (the
search path for executables) that will be passed to your program.
- The value of `PATH' used by GDB does not change. You may specify
+ The value of 'PATH' used by GDB does not change. You may specify
several directory names, separated by whitespace or by a
- system-dependent separator character (`:' on Unix, `;' on MS-DOS
+ system-dependent separator character (':' on Unix, ';' on MS-DOS
and MS-Windows). If DIRECTORY is already in the path, it is moved
to the front, so it is searched sooner.
- You can use the string `$cwd' to refer to whatever is the current
+ You can use the string '$cwd' to refer to whatever is the current
working directory at the time GDB searches the path. If you use
- `.' instead, it refers to the directory where you executed the
- `path' command. GDB replaces `.' in the DIRECTORY argument (with
+ '.' instead, it refers to the directory where you executed the
+ 'path' command. GDB replaces '.' in the DIRECTORY argument (with
the current path) before adding DIRECTORY to the search path.
-`show paths'
- Display the list of search paths for executables (the `PATH'
+'show paths'
+ Display the list of search paths for executables (the 'PATH'
environment variable).
-`show environment [VARNAME]'
- Print the value of environment variable VARNAME to be given to
- your program when it starts. If you do not supply VARNAME, print
- the names and values of all environment variables to be given to
- your program. You can abbreviate `environment' as `env'.
+'show environment [VARNAME]'
+ Print the value of environment variable VARNAME to be given to your
+ program when it starts. If you do not supply VARNAME, print the
+ names and values of all environment variables to be given to your
+ program. You can abbreviate 'environment' as 'env'.
-`set environment VARNAME [=VALUE]'
+'set environment VARNAME [=VALUE]'
Set environment variable VARNAME to VALUE. The value changes for
- your program only, not for GDB itself. VALUE may be any string;
- the values of environment variables are just strings, and any
- interpretation is supplied by your program itself. The VALUE
- parameter is optional; if it is eliminated, the variable is set to
- a null value.
+ your program (and the shell GDB uses to launch it), not for GDB
+ itself. The VALUE may be any string; the values of environment
+ variables are just strings, and any interpretation is supplied by
+ your program itself. The VALUE parameter is optional; if it is
+ eliminated, the variable is set to a null value.
For example, this command:
set env USER = foo
- tells the debugged program, when subsequently run, that its user
- is named `foo'. (The spaces around `=' are used for clarity here;
+ tells the debugged program, when subsequently run, that its user is
+ named 'foo'. (The spaces around '=' are used for clarity here;
they are not actually required.)
-`unset environment VARNAME'
+ Note that on Unix systems, GDB runs your program via a shell, which
+ also inherits the environment set with 'set environment'. If
+ necessary, you can avoid that by using the 'env' program as a
+ wrapper instead of using 'set environment'. *Note set
+ exec-wrapper::, for an example doing just that.
+
+'unset environment VARNAME'
Remove variable VARNAME from the environment to be passed to your
- program. This is different from `set env VARNAME ='; `unset
- environment' removes the variable from the environment, rather
- than assigning it an empty value.
+ program. This is different from 'set env VARNAME ='; 'unset
+ environment' removes the variable from the environment, rather than
+ assigning it an empty value.
_Warning:_ On Unix systems, GDB runs your program using the shell
-indicated by your `SHELL' environment variable if it exists (or
-`/bin/sh' if not). If your `SHELL' variable names a shell that runs an
-initialization file--such as `.cshrc' for C-shell, or `.bashrc' for
-BASH--any variables you set in that file affect your program. You may
-wish to move setting of environment variables to files that are only
-run when you sign on, such as `.login' or `.profile'.
+indicated by your 'SHELL' environment variable if it exists (or
+'/bin/sh' if not). If your 'SHELL' variable names a shell that runs an
+initialization file when started non-interactively--such as '.cshrc' for
+C-shell, $'.zshenv' for the Z shell, or the file specified in the
+'BASH_ENV' environment variable for BASH--any variables you set in that
+file affect your program. You may wish to move setting of environment
+variables to files that are only run when you sign on, such as '.login'
+or '.profile'.
\1f
File: gdb.info, Node: Working Directory, Next: Input/Output, Prev: Environment, Up: Running
4.5 Your Program's Working Directory
====================================
-Each time you start your program with `run', it inherits its working
+Each time you start your program with 'run', it inherits its working
directory from the current working directory of GDB. The GDB working
directory is initially whatever it inherited from its parent process
(typically the shell), but you can specify a new working directory in
-GDB with the `cd' command.
+GDB with the 'cd' command.
The GDB working directory also serves as a default for the commands
that specify files for GDB to operate on. *Note Commands to Specify
Files: Files.
-`cd DIRECTORY'
- Set the GDB working directory to DIRECTORY.
+'cd [DIRECTORY]'
+ Set the GDB working directory to DIRECTORY. If not given,
+ DIRECTORY uses ''~''.
-`pwd'
+'pwd'
Print the GDB working directory.
It is generally impossible to find the current working directory of
the process being debugged (since a program can change its directory
during its run). If you work on a system where GDB is configured with
-the `/proc' support, you can use the `info proc' command (*note SVR4
+the '/proc' support, you can use the 'info proc' command (*note SVR4
Process Information::) to find out the current working directory of the
debuggee.
your program was using and switches back to them when you continue
running your program.
-`info terminal'
+'info terminal'
Displays information recorded by GDB about the terminal modes your
program is using.
You can redirect your program's input and/or output using shell
-redirection with the `run' command. For example,
+redirection with the 'run' command. For example,
run > outfile
-starts your program, diverting its output to the file `outfile'.
+starts your program, diverting its output to the file 'outfile'.
Another way to specify where your program should do input and output
-is with the `tty' command. This command accepts a file name as
-argument, and causes this file to be the default for future `run'
+is with the 'tty' command. This command accepts a file name as
+argument, and causes this file to be the default for future 'run'
commands. It also resets the controlling terminal for the child
-process, for future `run' commands. For example,
+process, for future 'run' commands. For example,
tty /dev/ttyb
-directs that processes started with subsequent `run' commands default
-to do input and output on the terminal `/dev/ttyb' and have that as
-their controlling terminal.
+directs that processes started with subsequent 'run' commands default to
+do input and output on the terminal '/dev/ttyb' and have that as their
+controlling terminal.
- An explicit redirection in `run' overrides the `tty' command's
-effect on the input/output device, but not its effect on the controlling
+ An explicit redirection in 'run' overrides the 'tty' command's effect
+on the input/output device, but not its effect on the controlling
terminal.
- When you use the `tty' command or redirect input in the `run'
+ When you use the 'tty' command or redirect input in the 'run'
command, only the input _for your program_ is affected. The input for
-GDB still comes from your terminal. `tty' is an alias for `set
+GDB still comes from your terminal. 'tty' is an alias for 'set
inferior-tty'.
- You can use the `show inferior-tty' command to tell GDB to display
+ You can use the 'show inferior-tty' command to tell GDB to display
the name of the terminal that will be used for future runs of your
program.
-`set inferior-tty /dev/ttyb'
+'set inferior-tty /dev/ttyb'
Set the tty for the program being debugged to /dev/ttyb.
-`show inferior-tty'
+'show inferior-tty'
Show the current tty for the program being debugged.
\1f
4.7 Debugging an Already-running Process
========================================
-`attach PROCESS-ID'
+'attach PROCESS-ID'
This command attaches to a running process--one that was started
- outside GDB. (`info files' shows your active targets.) The
- command takes as argument a process ID. The usual way to find out
- the PROCESS-ID of a Unix process is with the `ps' utility, or with
- the `jobs -l' shell command.
+ outside GDB. ('info files' shows your active targets.) The
+ command takes as argument a process ID. The usual way to find out
+ the PROCESS-ID of a Unix process is with the 'ps' utility, or with
+ the 'jobs -l' shell command.
- `attach' does not repeat if you press <RET> a second time after
+ 'attach' does not repeat if you press <RET> a second time after
executing the command.
- To use `attach', your program must be running in an environment
-which supports processes; for example, `attach' does not work for
-programs on bare-board targets that lack an operating system. You must
-also have permission to send the process a signal.
+ To use 'attach', your program must be running in an environment which
+supports processes; for example, 'attach' does not work for programs on
+bare-board targets that lack an operating system. You must also have
+permission to send the process a signal.
- When you use `attach', the debugger finds the program running in the
+ When you use 'attach', the debugger finds the program running in the
process first by looking in the current working directory, then (if the
program is not found) by using the source file search path (*note
Specifying Source Directories: Source Path.). You can also use the
-`file' command to load the program. *Note Commands to Specify Files:
+'file' command to load the program. *Note Commands to Specify Files:
Files.
The first thing GDB does after arranging to debug the specified
process is to stop it. You can examine and modify an attached process
with all the GDB commands that are ordinarily available when you start
-processes with `run'. You can insert breakpoints; you can step and
+processes with 'run'. You can insert breakpoints; you can step and
continue; you can modify storage. If you would rather the process
-continue running, you may use the `continue' command after attaching
-GDB to the process.
+continue running, you may use the 'continue' command after attaching GDB
+to the process.
-`detach'
+'detach'
When you have finished debugging the attached process, you can use
- the `detach' command to release it from GDB control. Detaching
- the process continues its execution. After the `detach' command,
- that process and GDB become completely independent once more, and
- you are ready to `attach' another process or start one with `run'.
- `detach' does not repeat if you press <RET> again after executing
+ the 'detach' command to release it from GDB control. Detaching the
+ process continues its execution. After the 'detach' command, that
+ process and GDB become completely independent once more, and you
+ are ready to 'attach' another process or start one with 'run'.
+ 'detach' does not repeat if you press <RET> again after executing
the command.
If you exit GDB while you have an attached process, you detach that
-process. If you use the `run' command, you kill that process. By
+process. If you use the 'run' command, you kill that process. By
default, GDB asks for confirmation if you try to do either of these
things; you can control whether or not you need to confirm by using the
-`set confirm' command (*note Optional Warnings and Messages:
+'set confirm' command (*note Optional Warnings and Messages:
Messages/Warnings.).
\1f
4.8 Killing the Child Process
=============================
-`kill'
+'kill'
Kill the child process in which your program is running under GDB.
This command is useful if you wish to debug a core dump instead of a
running.
On some operating systems, a program cannot be executed outside GDB
-while you have breakpoints set on it inside GDB. You can use the
-`kill' command in this situation to permit running your program outside
-the debugger.
+while you have breakpoints set on it inside GDB. You can use the 'kill'
+command in this situation to permit running your program outside the
+debugger.
- The `kill' command is also useful if you wish to recompile and
-relink your program, since on many systems it is impossible to modify an
+ The 'kill' command is also useful if you wish to recompile and relink
+your program, since on many systems it is impossible to modify an
executable file while it is running in a process. In this case, when
-you next type `run', GDB notices that the file has changed, and reads
-the symbol table again (while trying to preserve your current
-breakpoint settings).
+you next type 'run', GDB notices that the file has changed, and reads
+the symbol table again (while trying to preserve your current breakpoint
+settings).
\1f
File: gdb.info, Node: Inferiors and Programs, Next: Threads, Prev: Kill Process, Up: Running
several inferiors running in different parts of a single address space.
Each inferior may in turn have multiple threads running in it.
- To find out what inferiors exist at any moment, use `info inferiors':
+ To find out what inferiors exist at any moment, use 'info inferiors':
-`info inferiors'
+'info inferiors'
Print a list of all inferiors currently being managed by GDB.
GDB displays for each inferior (in this order):
3. the name of the executable the inferior is running.
-
- An asterisk `*' preceding the GDB inferior number indicates the
+ An asterisk '*' preceding the GDB inferior number indicates the
current inferior.
For example,
2 process 2307 hello
* 1 process 3401 goodbye
- To switch focus between inferiors, use the `inferior' command:
+ To switch focus between inferiors, use the 'inferior' command:
-`inferior INFNO'
+'inferior INFNO'
Make inferior number INFNO the current inferior. The argument
- INFNO is the inferior number assigned by GDB, as shown in the
- first field of the `info inferiors' display.
+ INFNO is the inferior number assigned by GDB, as shown in the first
+ field of the 'info inferiors' display.
You can get multiple executables into a debugging session via the
-`add-inferior' and `clone-inferior' commands. On some systems GDB can
+'add-inferior' and 'clone-inferior' commands. On some systems GDB can
add inferiors to the debug session automatically by following calls to
-`fork' and `exec'. To remove inferiors from the debugging session use
-the `remove-inferiors' command.
+'fork' and 'exec'. To remove inferiors from the debugging session use
+the 'remove-inferiors' command.
-`add-inferior [ -copies N ] [ -exec EXECUTABLE ]'
- Adds N inferiors to be run using EXECUTABLE as the executable. N
- defaults to 1. If no executable is specified, the inferiors
- begins empty, with no program. You can still assign or change the
- program assigned to the inferior at any time by using the `file'
- command with the executable name as its argument.
+'add-inferior [ -copies N ] [ -exec EXECUTABLE ]'
+ Adds N inferiors to be run using EXECUTABLE as the executable; N
+ defaults to 1. If no executable is specified, the inferiors begins
+ empty, with no program. You can still assign or change the program
+ assigned to the inferior at any time by using the 'file' command
+ with the executable name as its argument.
-`clone-inferior [ -copies N ] [ INFNO ]'
+'clone-inferior [ -copies N ] [ INFNO ]'
Adds N inferiors ready to execute the same program as inferior
- INFNO. N defaults to 1. INFNO defaults to the number of the
+ INFNO; N defaults to 1, and INFNO defaults to the number of the
current inferior. This is a convenient command when you want to
run another instance of the inferior you are debugging.
You can now simply switch focus to inferior 2 and run it.
-`remove-inferiors INFNO...'
+'remove-inferiors INFNO...'
Removes the inferior or inferiors INFNO.... It is not possible to
remove an inferior that is running with this command. For those,
- use the `kill' or `detach' command first.
-
+ use the 'kill' or 'detach' command first.
To quit debugging one of the running inferiors that is not the
-current inferior, you can either detach from it by using the
-`detach inferior' command (allowing it to run independently), or kill it
-using the `kill inferiors' command:
+current inferior, you can either detach from it by using the 'detach inferior'
+command (allowing it to run independently), or kill it using the 'kill inferiors'
+command:
-`detach inferior INFNO...'
+'detach inferior INFNO...'
Detach from the inferior or inferiors identified by GDB inferior
number(s) INFNO.... Note that the inferior's entry still stays on
- the list of inferiors shown by `info inferiors', but its
- Description will show `<null>'.
-
-`kill inferiors INFNO...'
- Kill the inferior or inferiors identified by GDB inferior
- number(s) INFNO.... Note that the inferior's entry still stays on
- the list of inferiors shown by `info inferiors', but its
- Description will show `<null>'.
-
- After the successful completion of a command such as `detach',
-`detach inferiors', `kill' or `kill inferiors', or after a normal
-process exit, the inferior is still valid and listed with `info
+ the list of inferiors shown by 'info inferiors', but its
+ Description will show '<null>'.
+
+'kill inferiors INFNO...'
+ Kill the inferior or inferiors identified by GDB inferior number(s)
+ INFNO.... Note that the inferior's entry still stays on the list
+ of inferiors shown by 'info inferiors', but its Description will
+ show '<null>'.
+
+ After the successful completion of a command such as 'detach',
+'detach inferiors', 'kill' or 'kill inferiors', or after a normal
+process exit, the inferior is still valid and listed with 'info
inferiors', ready to be restarted.
- To be notified when inferiors are started or exit under GDB's
-control use `set print inferior-events':
+ To be notified when inferiors are started or exit under GDB's control
+use 'set print inferior-events':
-`set print inferior-events'
-`set print inferior-events on'
-`set print inferior-events off'
- The `set print inferior-events' command allows you to enable or
+'set print inferior-events'
+'set print inferior-events on'
+'set print inferior-events off'
+ The 'set print inferior-events' command allows you to enable or
disable printing of messages when GDB notices that new inferiors
have started or that inferiors have exited or have been detached.
By default, these messages will not be printed.
-`show print inferior-events'
+'show print inferior-events'
Show whether messages will be printed when GDB detects that
inferiors have started, exited or have been detached.
Many commands will work the same with multiple programs as with a
-single program: e.g., `print myglobal' will simply display the value of
-`myglobal' in the current inferior.
+single program: e.g., 'print myglobal' will simply display the value of
+'myglobal' in the current inferior.
Occasionaly, when debugging GDB itself, it may be useful to get more
info about the relationship of inferiors, programs, address spaces in a
-debug session. You can do that with the `maint info program-spaces'
+debug session. You can do that with the 'maint info program-spaces'
command.
-`maint info program-spaces'
+'maint info program-spaces'
Print a list of all program spaces currently being managed by GDB.
GDB displays for each program space (in this order):
1. the program space number assigned by GDB
- 2. the name of the executable loaded into the program space,
- with e.g., the `file' command.
-
+ 2. the name of the executable loaded into the program space, with
+ e.g., the 'file' command.
- An asterisk `*' preceding the GDB program space number indicates
+ An asterisk '*' preceding the GDB program space number indicates
the current program space.
In addition, below each program space line, GDB prints extra
Bound inferiors: ID 1 (process 21561)
* 1 hello
- Here we can see that no inferior is running the program `hello',
- while `process 21561' is running the program `goodbye'. On some
+ Here we can see that no inferior is running the program 'hello',
+ while 'process 21561' is running the program 'goodbye'. On some
targets, it is possible that multiple inferiors are bound to the
same program space. The most common example is that of debugging
- both the parent and child processes of a `vfork' call. For
+ both the parent and child processes of a 'vfork' call. For
example,
(gdb) maint info program-spaces
Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
Here, both inferior 2 and inferior 1 are running in the same
- program space as a result of inferior 1 having executed a `vfork'
+ program space as a result of inferior 1 having executed a 'vfork'
call.
\1f
GDB provides these facilities for debugging multi-thread programs:
* automatic notification of new threads
-
- * `thread THREADNO', a command to switch among threads
-
- * `info threads', a command to inquire about existing threads
-
- * `thread apply [THREADNO] [ALL] ARGS', a command to apply a command
+ * 'thread THREADNO', a command to switch among threads
+ * 'info threads', a command to inquire about existing threads
+ * 'thread apply [THREADNO] [ALL] ARGS', a command to apply a command
to a list of threads
-
* thread-specific breakpoints
-
- * `set print thread-events', which controls printing of messages on
+ * 'set print thread-events', which controls printing of messages on
thread start and exit.
-
- * `set libthread-db-search-path PATH', which lets the user specify
- which `libthread_db' to use if the default choice isn't compatible
+ * 'set libthread-db-search-path PATH', which lets the user specify
+ which 'libthread_db' to use if the default choice isn't compatible
with the program.
_Warning:_ These facilities are not yet available on every GDB
- configuration where the operating system supports threads. If
- your GDB does not support threads, these commands have no effect.
- For example, a system without thread support shows no output from
- `info threads', and always rejects the `thread' command, like this:
+ configuration where the operating system supports threads. If your
+ GDB does not support threads, these commands have no effect. For
+ example, a system without thread support shows no output from 'info
+ threads', and always rejects the 'thread' command, like this:
(gdb) info threads
(gdb) thread 1
perspective of the current thread.
Whenever GDB detects a new thread in your program, it displays the
-target system's identification for the thread with a message in the
-form `[New SYSTAG]'. SYSTAG is a thread identifier whose form varies
+target system's identification for the thread with a message in the form
+'[New SYSTAG]', where SYSTAG is a thread identifier whose form varies
depending on the particular system. For example, on GNU/Linux, you
might see
[New Thread 0x41e02940 (LWP 25582)]
when GDB notices a new thread. In contrast, on an SGI system, the
-SYSTAG is simply something like `process 368', with no further
+SYSTAG is simply something like 'process 368', with no further
qualifier.
For debugging purposes, GDB associates its own thread number--always
a single integer--with each thread in your program.
-`info threads [ID...]'
+'info threads [ID...]'
Display a summary of all threads currently in your program.
Optional argument ID... is one or more thread ids separated by
spaces, and means to print information only about the specified
2. the target system's thread identifier (SYSTAG)
3. the thread's name, if one is known. A thread can either be
- named by the user (see `thread name', below), or, in some
+ named by the user (see 'thread name', below), or, in some
cases, by the program itself.
4. the current stack frame summary for that thread
- An asterisk `*' to the left of the GDB thread number indicates the
+ An asterisk '*' to the left of the GDB thread number indicates the
current thread.
For example,
On Solaris, you can display more information about user threads with
a Solaris-specific command:
-`maint info sol-threads'
+'maint info sol-threads'
Display info on Solaris user threads.
-`thread THREADNO'
+'thread THREADNO'
Make thread number THREADNO the current thread. The command
argument THREADNO is the internal GDB thread number, as shown in
- the first field of the `info threads' display. GDB responds by
+ the first field of the 'info threads' display. GDB responds by
displaying the system identifier of the thread you selected, and
its current stack frame summary:
#0 some_function (ignore=0x0) at example.c:8
8 printf ("hello\n");
- As with the `[New ...]' message, the form of the text after
- `Switching to' depends on your system's conventions for identifying
+ As with the '[New ...]' message, the form of the text after
+ 'Switching to' depends on your system's conventions for identifying
threads.
- The debugger convenience variable `$_thread' contains the number
- of the current thread. You may find this useful in writing
- breakpoint conditional expressions, command scripts, and so forth.
- See *Note Convenience Variables: Convenience Vars, for general
- information on convenience variables.
+ The debugger convenience variable '$_thread' contains the number of
+ the current thread. You may find this useful in writing breakpoint
+ conditional expressions, command scripts, and so forth. See *Note
+ Convenience Variables: Convenience Vars, for general information on
+ convenience variables.
-`thread apply [THREADNO | all] COMMAND'
- The `thread apply' command allows you to apply the named COMMAND
- to one or more threads. Specify the numbers of the threads that
- you want affected with the command argument THREADNO. It can be a
+'thread apply [THREADNO | all] COMMAND'
+ The 'thread apply' command allows you to apply the named COMMAND to
+ one or more threads. Specify the numbers of the threads that you
+ want affected with the command argument THREADNO. It can be a
single thread number, one of the numbers shown in the first field
- of the `info threads' display; or it could be a range of thread
- numbers, as in `2-4'. To apply a command to all threads, type
- `thread apply all COMMAND'.
+ of the 'info threads' display; or it could be a range of thread
+ numbers, as in '2-4'. To apply a command to all threads, type
+ 'thread apply all COMMAND'.
-`thread name [NAME]'
+'thread name [NAME]'
This command assigns a name to the current thread. If no argument
is given, any existing user-specified name is removed. The thread
- name appears in the `info threads' display.
+ name appears in the 'info threads' display.
On some systems, such as GNU/Linux, GDB is able to determine the
- name of the thread as given by the OS. On these systems, a name
- specified with `thread name' will override the system-give name,
+ name of the thread as given by the OS. On these systems, a name
+ specified with 'thread name' will override the system-give name,
and removing the user-specified name will cause GDB to once again
display the system-specified name.
-`thread find [REGEXP]'
+'thread find [REGEXP]'
Search for and display thread ids whose name or SYSTAG matches the
supplied regular expression.
- As well as being the complement to the `thread name' command, this
+ As well as being the complement to the 'thread name' command, this
command also allows you to identify a thread by its target SYSTAG.
For instance, on GNU/Linux, the target SYSTAG is the LWP id.
Id Target Id Frame
4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
-`set print thread-events'
-`set print thread-events on'
-`set print thread-events off'
- The `set print thread-events' command allows you to enable or
+'set print thread-events'
+'set print thread-events on'
+'set print thread-events off'
+ The 'set print thread-events' command allows you to enable or
disable printing of messages when GDB notices that new threads have
started or that threads have exited. By default, these messages
will be printed if detection of these events is supported by the
target. Note that these messages cannot be disabled on all
targets.
-`show print thread-events'
+'show print thread-events'
Show whether messages will be printed when GDB detects that threads
have started and exited.
*Note Setting Watchpoints: Set Watchpoints, for information about
watchpoints in programs with multiple threads.
-`set libthread-db-search-path [PATH]'
+'set libthread-db-search-path [PATH]'
If this variable is set, PATH is a colon-separated list of
- directories GDB will use to search for `libthread_db'. If you
- omit PATH, `libthread-db-search-path' will be reset to its default
- value (`$sdir:$pdir' on GNU/Linux and Solaris systems).
- Internally, the default value comes from the
- `LIBTHREAD_DB_SEARCH_PATH' macro.
+ directories GDB will use to search for 'libthread_db'. If you omit
+ PATH, 'libthread-db-search-path' will be reset to its default value
+ ('$sdir:$pdir' on GNU/Linux and Solaris systems). Internally, the
+ default value comes from the 'LIBTHREAD_DB_SEARCH_PATH' macro.
On GNU/Linux and Solaris systems, GDB uses a "helper"
- `libthread_db' library to obtain information about threads in the
- inferior process. GDB will use `libthread-db-search-path' to find
- `libthread_db'. GDB also consults first if inferior specific
- thread debugging library loading is enabled by `set auto-load
+ 'libthread_db' library to obtain information about threads in the
+ inferior process. GDB will use 'libthread-db-search-path' to find
+ 'libthread_db'. GDB also consults first if inferior specific
+ thread debugging library loading is enabled by 'set auto-load
libthread-db' (*note libthread_db.so.1 file::).
- A special entry `$sdir' for `libthread-db-search-path' refers to
+ A special entry '$sdir' for 'libthread-db-search-path' refers to
the default system directories that are normally searched for
- loading shared libraries. The `$sdir' entry is the only kind not
- needing to be enabled by `set auto-load libthread-db' (*note
+ loading shared libraries. The '$sdir' entry is the only kind not
+ needing to be enabled by 'set auto-load libthread-db' (*note
libthread_db.so.1 file::).
- A special entry `$pdir' for `libthread-db-search-path' refers to
- the directory from which `libpthread' was loaded in the inferior
+ A special entry '$pdir' for 'libthread-db-search-path' refers to
+ the directory from which 'libpthread' was loaded in the inferior
process.
- For any `libthread_db' library GDB finds in above directories, GDB
+ For any 'libthread_db' library GDB finds in above directories, GDB
attempts to initialize it with the current inferior process. If
this initialization fails (which could happen because of a version
- mismatch between `libthread_db' and `libpthread'), GDB will unload
- `libthread_db', and continue with the next directory. If none of
- `libthread_db' libraries initialize successfully, GDB will issue a
+ mismatch between 'libthread_db' and 'libpthread'), GDB will unload
+ 'libthread_db', and continue with the next directory. If none of
+ 'libthread_db' libraries initialize successfully, GDB will issue a
warning and thread debugging will be disabled.
- Setting `libthread-db-search-path' is currently implemented only
- on some platforms.
+ Setting 'libthread-db-search-path' is currently implemented only on
+ some platforms.
-`show libthread-db-search-path'
+'show libthread-db-search-path'
Display current libthread_db search path.
-`set debug libthread-db'
-`show debug libthread-db'
- Turns on or off display of `libthread_db'-related events. Use `1'
- to enable, `0' to disable.
+'set debug libthread-db'
+'show debug libthread-db'
+ Turns on or off display of 'libthread_db'-related events. Use '1'
+ to enable, '0' to disable.
\1f
File: gdb.info, Node: Forks, Next: Checkpoint/Restart, Prev: Threads, Up: Running
4.11 Debugging Forks
====================
-On most systems, GDB has no special support for debugging programs
-which create additional processes using the `fork' function. When a
-program forks, GDB will continue to debug the parent process and the
-child process will run unimpeded. If you have set a breakpoint in any
-code which the child then executes, the child will get a `SIGTRAP'
-signal which (unless it catches the signal) will cause it to terminate.
+On most systems, GDB has no special support for debugging programs which
+create additional processes using the 'fork' function. When a program
+forks, GDB will continue to debug the parent process and the child
+process will run unimpeded. If you have set a breakpoint in any code
+which the child then executes, the child will get a 'SIGTRAP' signal
+which (unless it catches the signal) will cause it to terminate.
However, if you want to debug the child process there is a workaround
-which isn't too painful. Put a call to `sleep' in the code which the
+which isn't too painful. Put a call to 'sleep' in the code which the
child process executes after the fork. It may be useful to sleep only
if a certain environment variable is set, or a certain file exists, so
that the delay need not occur when you don't want to run GDB on the
-child. While the child is sleeping, use the `ps' program to get its
-process ID. Then tell GDB (a new invocation of GDB if you are also
+child. While the child is sleeping, use the 'ps' program to get its
+process ID. Then tell GDB (a new invocation of GDB if you are also
debugging the parent process) to attach to the child process (*note
-Attach::). From that point on you can debug the child process just
-like any other process which you attached to.
+Attach::). From that point on you can debug the child process just like
+any other process which you attached to.
On some systems, GDB provides support for debugging programs that
-create additional processes using the `fork' or `vfork' functions.
+create additional processes using the 'fork' or 'vfork' functions.
Currently, the only platforms with this feature are HP-UX (11.x and
-later only?) and GNU/Linux (kernel version 2.5.60 and later).
+later only?) and GNU/Linux (kernel version 2.5.60 and later).
By default, when a program forks, GDB will continue to debug the
parent process and the child process will run unimpeded.
If you want to follow the child process instead of the parent
-process, use the command `set follow-fork-mode'.
+process, use the command 'set follow-fork-mode'.
-`set follow-fork-mode MODE'
- Set the debugger response to a program call of `fork' or `vfork'.
- A call to `fork' or `vfork' creates a new process. The MODE
+'set follow-fork-mode MODE'
+ Set the debugger response to a program call of 'fork' or 'vfork'.
+ A call to 'fork' or 'vfork' creates a new process. The MODE
argument can be:
- `parent'
+ 'parent'
The original process is debugged after a fork. The child
process runs unimpeded. This is the default.
- `child'
+ 'child'
The new process is debugged after a fork. The parent process
runs unimpeded.
-
-`show follow-fork-mode'
- Display the current debugger response to a `fork' or `vfork' call.
+'show follow-fork-mode'
+ Display the current debugger response to a 'fork' or 'vfork' call.
On Linux, if you want to debug both the parent and child processes,
-use the command `set detach-on-fork'.
+use the command 'set detach-on-fork'.
-`set detach-on-fork MODE'
+'set detach-on-fork MODE'
Tells gdb whether to detach one of the processes after a fork, or
retain debugger control over them both.
- `on'
+ 'on'
The child process (or parent process, depending on the value
- of `follow-fork-mode') will be detached and allowed to run
+ of 'follow-fork-mode') will be detached and allowed to run
independently. This is the default.
- `off'
+ 'off'
Both processes will be held under the control of GDB. One
process (child or parent, depending on the value of
- `follow-fork-mode') is debugged as usual, while the other is
+ 'follow-fork-mode') is debugged as usual, while the other is
held suspended.
-
-`show detach-on-fork'
+'show detach-on-fork'
Show whether detach-on-fork mode is on/off.
- If you choose to set `detach-on-fork' mode off, then GDB will retain
+ If you choose to set 'detach-on-fork' mode off, then GDB will retain
control of all forked processes (including nested forks). You can list
-the forked processes under the control of GDB by using the
-`info inferiors' command, and switch from one fork to another by using
-the `inferior' command (*note Debugging Multiple Inferiors and
-Programs: Inferiors and Programs.).
+the forked processes under the control of GDB by using the 'info inferiors'
+command, and switch from one fork to another by using the 'inferior'
+command (*note Debugging Multiple Inferiors and Programs: Inferiors and
+Programs.).
To quit debugging one of the forked processes, you can either detach
-from it by using the `detach inferiors' command (allowing it to run
-independently), or kill it using the `kill inferiors' command. *Note
+from it by using the 'detach inferiors' command (allowing it to run
+independently), or kill it using the 'kill inferiors' command. *Note
Debugging Multiple Inferiors and Programs: Inferiors and Programs.
- If you ask to debug a child process and a `vfork' is followed by an
-`exec', GDB executes the new target up to the first breakpoint in the
-new target. If you have a breakpoint set on `main' in your original
-program, the breakpoint will also be set on the child process's `main'.
+ If you ask to debug a child process and a 'vfork' is followed by an
+'exec', GDB executes the new target up to the first breakpoint in the
+new target. If you have a breakpoint set on 'main' in your original
+program, the breakpoint will also be set on the child process's 'main'.
- On some systems, when a child process is spawned by `vfork', you
-cannot debug the child or parent until an `exec' call completes.
+ On some systems, when a child process is spawned by 'vfork', you
+cannot debug the child or parent until an 'exec' call completes.
- If you issue a `run' command to GDB after an `exec' call executes,
-the new target restarts. To restart the parent process, use the `file'
+ If you issue a 'run' command to GDB after an 'exec' call executes,
+the new target restarts. To restart the parent process, use the 'file'
command with the parent executable name as its argument. By default,
-after an `exec' call executes, GDB discards the symbols of the previous
-executable image. You can change this behaviour with the
-`set follow-exec-mode' command.
+after an 'exec' call executes, GDB discards the symbols of the previous
+executable image. You can change this behaviour with the 'set follow-exec-mode'
+command.
-`set follow-exec-mode MODE'
- Set debugger response to a program call of `exec'. An `exec' call
+'set follow-exec-mode MODE'
+
+ Set debugger response to a program call of 'exec'. An 'exec' call
replaces the program image of a process.
- `follow-exec-mode' can be:
+ 'follow-exec-mode' can be:
- `new'
- GDB creates a new inferior and rebinds the process to this
- new inferior. The program the process was running before the
- `exec' call can be restarted afterwards by restarting the
+ 'new'
+ GDB creates a new inferior and rebinds the process to this new
+ inferior. The program the process was running before the
+ 'exec' call can be restarted afterwards by restarting the
original inferior.
For example:
* 2 <null> prog2
1 <null> prog1
- `same'
+ 'same'
GDB keeps the process bound to the same inferior. The new
executable image replaces the previous executable loaded in
- the inferior. Restarting the inferior after the `exec' call,
- with e.g., the `run' command, restarts the executable the
- process was running after the `exec' call. This is the
+ the inferior. Restarting the inferior after the 'exec' call,
+ with e.g., the 'run' command, restarts the executable the
+ process was running after the 'exec' call. This is the
default mode.
For example:
Id Description Executable
* 1 <null> prog2
-
- You can use the `catch' command to make GDB stop whenever a `fork',
-`vfork', or `exec' call is made. *Note Setting Catchpoints: Set
+ You can use the 'catch' command to make GDB stop whenever a 'fork',
+'vfork', or 'exec' call is made. *Note Setting Catchpoints: Set
Catchpoints.
\1f
program's state, called a "checkpoint", and come back to it later.
Returning to a checkpoint effectively undoes everything that has
-happened in the program since the `checkpoint' was saved. This
-includes changes in memory, registers, and even (within some limits)
-system state. Effectively, it is like going back in time to the moment
-when the checkpoint was saved.
+happened in the program since the 'checkpoint' was saved. This includes
+changes in memory, registers, and even (within some limits) system
+state. Effectively, it is like going back in time to the moment when
+the checkpoint was saved.
Thus, if you're stepping thru a program and you think you're getting
close to the point where things go wrong, you can save a checkpoint.
This can be especially useful if it takes a lot of time or steps to
reach the point where you think the bug occurs.
- To use the `checkpoint'/`restart' method of debugging:
+ To use the 'checkpoint'/'restart' method of debugging:
-`checkpoint'
+'checkpoint'
Save a snapshot of the debugged program's current execution state.
- The `checkpoint' command takes no arguments, but each checkpoint
- is assigned a small integer id, similar to a breakpoint id.
+ The 'checkpoint' command takes no arguments, but each checkpoint is
+ assigned a small integer id, similar to a breakpoint id.
-`info checkpoints'
+'info checkpoints'
List the checkpoints that have been saved in the current debugging
session. For each checkpoint, the following information will be
listed:
- `Checkpoint ID'
-
- `Process ID'
-
- `Code Address'
-
- `Source line, or label'
+ 'Checkpoint ID'
+ 'Process ID'
+ 'Code Address'
+ 'Source line, or label'
-`restart CHECKPOINT-ID'
+'restart CHECKPOINT-ID'
Restore the program state that was saved as checkpoint number
- CHECKPOINT-ID. All program variables, registers, stack frames
- etc. will be returned to the values that they had when the
- checkpoint was saved. In essence, gdb will "wind back the clock"
- to the point in time when the checkpoint was saved.
+ CHECKPOINT-ID. All program variables, registers, stack frames etc.
+ will be returned to the values that they had when the checkpoint
+ was saved. In essence, gdb will "wind back the clock" to the point
+ in time when the checkpoint was saved.
- Note that breakpoints, GDB variables, command history etc. are
- not affected by restoring a checkpoint. In general, a checkpoint
- only restores things that reside in the program being debugged,
- not in the debugger.
+ Note that breakpoints, GDB variables, command history etc. are not
+ affected by restoring a checkpoint. In general, a checkpoint only
+ restores things that reside in the program being debugged, not in
+ the debugger.
-`delete checkpoint CHECKPOINT-ID'
+'delete checkpoint CHECKPOINT-ID'
Delete the previously-saved checkpoint identified by CHECKPOINT-ID.
-
Returning to a previously saved checkpoint will restore the user
state of the program being debugged, plus a significant subset of the
system (OS) state, including file pointers. It won't "un-write" data
previously read data can be read again.
Of course, characters that have been sent to a printer (or other
-external device) cannot be "snatched back", and characters received
-from eg. a serial device can be removed from internal program buffers,
-but they cannot be "pushed back" into the serial pipeline, ready to be
+external device) cannot be "snatched back", and characters received from
+eg. a serial device can be removed from internal program buffers, but
+they cannot be "pushed back" into the serial pipeline, ready to be
received again. Similarly, the actual contents of files that have been
changed cannot be restored (at this time).
Finally, there is one bit of internal program state that will be
different when you return to a checkpoint -- the program's process id.
-Each checkpoint will have a unique process id (or PID), and each will
-be different from the program's original PID. If your program has
-saved a local copy of its process id, this could potentially pose a
-problem.
+Each checkpoint will have a unique process id (or PID), and each will be
+different from the program's original PID. If your program has saved a
+local copy of its process id, this could potentially pose a problem.
4.12.1 A Non-obvious Benefit of Using Checkpoints
-------------------------------------------------
A checkpoint, however, is an _identical_ copy of a process.
Therefore if you create a checkpoint at (eg.) the start of main, and
simply return to that checkpoint instead of restarting the process, you
-can avoid the effects of address randomization and your symbols will
-all stay in the same place.
+can avoid the effects of address randomization and your symbols will all
+stay in the same place.
---------- Footnotes ----------
program before it terminates; or so that, if your program runs into
trouble, you can investigate and find out why.
- Inside GDB, your program may stop for any of several reasons, such
-as a signal, a breakpoint, or reaching a new line after a GDB command
-such as `step'. You may then examine and change variables, set new
+ Inside GDB, your program may stop for any of several reasons, such as
+a signal, a breakpoint, or reaching a new line after a GDB command such
+as 'step'. You may then examine and change variables, set new
breakpoints or remove old ones, and then continue execution. Usually,
the messages shown by GDB provide ample explanation of the status of
your program--but you can also explicitly request this information at
any time.
-`info program'
+'info program'
Display information about the status of your program: whether it is
running or not, what process it is, and why it stopped.
A "breakpoint" makes your program stop whenever a certain point in the
program is reached. For each breakpoint, you can add conditions to
control in finer detail whether your program stops. You can set
-breakpoints with the `break' command and its variants (*note Setting
+breakpoints with the 'break' command and its variants (*note Setting
Breakpoints: Set Breaks.), to specify the place where your program
should stop by line number, function name or exact address in the
program.
On some systems, you can set breakpoints in shared libraries before
the executable is run. There is a minor limitation on HP-UX systems:
-you must wait until the executable is run in order to set breakpoints
-in shared library routines that are not called directly by the program
-(for example, routines that are arguments in a `pthread_create' call).
+you must wait until the executable is run in order to set breakpoints in
+shared library routines that are not called directly by the program (for
+example, routines that are arguments in a 'pthread_create' call).
A "watchpoint" is a special breakpoint that stops your program when
the value of an expression changes. The expression may be a value of a
variable, or it could involve values of one or more variables combined
-by operators, such as `a + b'. This is sometimes called "data
+by operators, such as 'a + b'. This is sometimes called "data
breakpoints". You must use a different command to set watchpoints
(*note Setting Watchpoints: Set Watchpoints.), but aside from that, you
can manage a watchpoint like any other breakpoint: you enable, disable,
different command to set a catchpoint (*note Setting Catchpoints: Set
Catchpoints.), but aside from that, you can manage a catchpoint like any
other breakpoint. (To stop when your program receives a signal, use the
-`handle' command; see *Note Signals: Signals.)
+'handle' command; see *note Signals: Signals.)
GDB assigns a number to each breakpoint, watchpoint, or catchpoint
when you create it; these numbers are successive integers starting with
disabled, it has no effect on your program until you enable it again.
Some GDB commands accept a range of breakpoints on which to operate.
-A breakpoint range is either a single breakpoint number, like `5', or
+A breakpoint range is either a single breakpoint number, like '5', or
two such numbers, in increasing order, separated by a hyphen, like
-`5-7'. When a breakpoint range is given to a command, all breakpoints
+'5-7'. When a breakpoint range is given to a command, all breakpoints
in that range are operated on.
* Menu:
* Dynamic Printf:: Dynamic printf
* Save Breakpoints:: How to save breakpoints in a file
* Static Probe Points:: Listing static probe points
-* Error in Breakpoints:: ``Cannot insert breakpoints''
-* Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
+* Error in Breakpoints:: "Cannot insert breakpoints"
+* Breakpoint-related Warnings:: "Breakpoint address adjusted..."
\1f
File: gdb.info, Node: Set Breaks, Next: Set Watchpoints, Up: Breakpoints
5.1.1 Setting Breakpoints
-------------------------
-Breakpoints are set with the `break' command (abbreviated `b'). The
-debugger convenience variable `$bpnum' records the number of the
-breakpoint you've set most recently; see *Note Convenience Variables:
+Breakpoints are set with the 'break' command (abbreviated 'b'). The
+debugger convenience variable '$bpnum' records the number of the
+breakpoint you've set most recently; see *note Convenience Variables:
Convenience Vars, for a discussion of what you can do with convenience
variables.
-`break LOCATION'
+'break LOCATION'
Set a breakpoint at the given LOCATION, which can specify a
function name, a line number, or an address of an instruction.
(*Note Specify Location::, for a list of all the possible ways to
Breakpoints::) or a specific task (*note Ada Tasks::) hits that
breakpoint.
-`break'
- When called without any arguments, `break' sets a breakpoint at
- the next instruction to be executed in the selected stack frame
- (*note Examining the Stack: Stack.). In any selected frame but the
+'break'
+ When called without any arguments, 'break' sets a breakpoint at the
+ next instruction to be executed in the selected stack frame (*note
+ Examining the Stack: Stack.). In any selected frame but the
innermost, this makes your program stop as soon as control returns
- to that frame. This is similar to the effect of a `finish'
- command in the frame inside the selected frame--except that
- `finish' does not leave an active breakpoint. If you use `break'
- without an argument in the innermost frame, GDB stops the next
- time it reaches the current location; this may be useful inside
- loops.
+ to that frame. This is similar to the effect of a 'finish' command
+ in the frame inside the selected frame--except that 'finish' does
+ not leave an active breakpoint. If you use 'break' without an
+ argument in the innermost frame, GDB stops the next time it reaches
+ the current location; this may be useful inside loops.
GDB normally ignores breakpoints when it resumes execution, until
- at least one instruction has been executed. If it did not do
- this, you would be unable to proceed past a breakpoint without
- first disabling the breakpoint. This rule applies whether or not
- the breakpoint already existed when your program stopped.
+ at least one instruction has been executed. If it did not do this,
+ you would be unable to proceed past a breakpoint without first
+ disabling the breakpoint. This rule applies whether or not the
+ breakpoint already existed when your program stopped.
-`break ... if COND'
+'break ... if COND'
Set a breakpoint with condition COND; evaluate the expression COND
each time the breakpoint is reached, and stop only if the value is
- nonzero--that is, if COND evaluates as true. `...' stands for one
+ nonzero--that is, if COND evaluates as true. '...' stands for one
of the possible arguments described above (or no argument)
- specifying where to break. *Note Break Conditions: Conditions,
- for more information on breakpoint conditions.
+ specifying where to break. *Note Break Conditions: Conditions, for
+ more information on breakpoint conditions.
-`tbreak ARGS'
- Set a breakpoint enabled only for one stop. ARGS are the same as
- for the `break' command, and the breakpoint is set in the same
+'tbreak ARGS'
+ Set a breakpoint enabled only for one stop. The ARGS are the same
+ as for the 'break' command, and the breakpoint is set in the same
way, but the breakpoint is automatically deleted after the first
time your program stops there. *Note Disabling Breakpoints:
Disabling.
-`hbreak ARGS'
- Set a hardware-assisted breakpoint. ARGS are the same as for the
- `break' command and the breakpoint is set in the same way, but the
- breakpoint requires hardware support and some target hardware may
- not have this support. The main purpose of this is EPROM/ROM code
- debugging, so you can set a breakpoint at an instruction without
- changing the instruction. This can be used with the new
+'hbreak ARGS'
+ Set a hardware-assisted breakpoint. The ARGS are the same as for
+ the 'break' command and the breakpoint is set in the same way, but
+ the breakpoint requires hardware support and some target hardware
+ may not have this support. The main purpose of this is EPROM/ROM
+ code debugging, so you can set a breakpoint at an instruction
+ without changing the instruction. This can be used with the new
trap-generation provided by SPARClite DSU and most x86-based
- targets. These targets will generate traps when a program
- accesses some data or instruction address that is assigned to the
- debug registers. However the hardware breakpoint registers can
- take a limited number of breakpoints. For example, on the DSU,
- only two data breakpoints can be set at a time, and GDB will
- reject this command if more than two are used. Delete or disable
- unused hardware breakpoints before setting new ones (*note
- Disabling Breakpoints: Disabling.). *Note Break Conditions:
- Conditions. For remote targets, you can restrict the number of
- hardware breakpoints GDB will use, see *Note set remote
- hardware-breakpoint-limit::.
-
-`thbreak ARGS'
- Set a hardware-assisted breakpoint enabled only for one stop. ARGS
- are the same as for the `hbreak' command and the breakpoint is set
- in the same way. However, like the `tbreak' command, the
+ targets. These targets will generate traps when a program accesses
+ some data or instruction address that is assigned to the debug
+ registers. However the hardware breakpoint registers can take a
+ limited number of breakpoints. For example, on the DSU, only two
+ data breakpoints can be set at a time, and GDB will reject this
+ command if more than two are used. Delete or disable unused
+ hardware breakpoints before setting new ones (*note Disabling
+ Breakpoints: Disabling.). *Note Break Conditions: Conditions. For
+ remote targets, you can restrict the number of hardware breakpoints
+ GDB will use, see *note set remote hardware-breakpoint-limit::.
+
+'thbreak ARGS'
+ Set a hardware-assisted breakpoint enabled only for one stop. The
+ ARGS are the same as for the 'hbreak' command and the breakpoint is
+ set in the same way. However, like the 'tbreak' command, the
breakpoint is automatically deleted after the first time your
- program stops there. Also, like the `hbreak' command, the
+ program stops there. Also, like the 'hbreak' command, the
breakpoint requires hardware support and some target hardware may
not have this support. *Note Disabling Breakpoints: Disabling.
- See also *Note Break Conditions: Conditions.
+ See also *note Break Conditions: Conditions.
-`rbreak REGEX'
+'rbreak REGEX'
Set breakpoints on all functions matching the regular expression
REGEX. This command sets an unconditional breakpoint on all
matches, printing a list of all breakpoints it set. Once these
- breakpoints are set, they are treated just like the breakpoints
- set with the `break' command. You can delete them, disable them,
- or make them conditional the same way as any other breakpoint.
+ breakpoints are set, they are treated just like the breakpoints set
+ with the 'break' command. You can delete them, disable them, or
+ make them conditional the same way as any other breakpoint.
The syntax of the regular expression is the standard one used with
- tools like `grep'. Note that this is different from the syntax
- used by shells, so for instance `foo*' matches all functions that
- include an `fo' followed by zero or more `o's. There is an
- implicit `.*' leading and trailing the regular expression you
- supply, so to match only functions that begin with `foo', use
- `^foo'.
-
- When debugging C++ programs, `rbreak' is useful for setting
+ tools like 'grep'. Note that this is different from the syntax
+ used by shells, so for instance 'foo*' matches all functions that
+ include an 'fo' followed by zero or more 'o's. There is an
+ implicit '.*' leading and trailing the regular expression you
+ supply, so to match only functions that begin with 'foo', use
+ '^foo'.
+
+ When debugging C++ programs, 'rbreak' is useful for setting
breakpoints on overloaded functions that are not members of any
special classes.
- The `rbreak' command can be used to set breakpoints in *all* the
+ The 'rbreak' command can be used to set breakpoints in *all* the
functions in a program, like this:
(gdb) rbreak .
-`rbreak FILE:REGEX'
- If `rbreak' is called with a filename qualification, it limits the
+'rbreak FILE:REGEX'
+ If 'rbreak' is called with a filename qualification, it limits the
search for functions matching the given regular expression to the
specified FILE. This can be used, for example, to set breakpoints
on every function in a given file:
The colon separating the filename qualifier from the regex may
optionally be surrounded by spaces.
-`info breakpoints [N...]'
-`info break [N...]'
+'info breakpoints [N...]'
+'info break [N...]'
Print a table of all breakpoints, watchpoints, and catchpoints set
and not deleted. Optional argument N means print information only
about the specified breakpoint(s) (or watchpoint(s) or
catchpoint(s)). For each breakpoint, following columns are
printed:
- _Breakpoint Numbers_
-
- _Type_
+ _Breakpoint Numbers_
+ _Type_
Breakpoint, watchpoint, or catchpoint.
-
- _Disposition_
+ _Disposition_
Whether the breakpoint is marked to be disabled or deleted
when hit.
-
- _Enabled or Disabled_
- Enabled breakpoints are marked with `y'. `n' marks
+ _Enabled or Disabled_
+ Enabled breakpoints are marked with 'y'. 'n' marks
breakpoints that are not enabled.
-
- _Address_
+ _Address_
Where the breakpoint is in your program, as a memory address.
- For a pending breakpoint whose address is not yet known,
- this field will contain `<PENDING>'. Such breakpoint won't
- fire until a shared library that has the symbol or line
- referred by breakpoint is loaded. See below for details. A
- breakpoint with several locations will have `<MULTIPLE>' in
- this field--see below for details.
-
- _What_
+ For a pending breakpoint whose address is not yet known, this
+ field will contain '<PENDING>'. Such breakpoint won't fire
+ until a shared library that has the symbol or line referred by
+ breakpoint is loaded. See below for details. A breakpoint
+ with several locations will have '<MULTIPLE>' in this
+ field--see below for details.
+ _What_
Where the breakpoint is in the source for your program, as a
file and line number. For a pending breakpoint, the original
string passed to the breakpoint command will be listed as it
If a breakpoint is conditional, there are two evaluation modes:
"host" and "target". If mode is "host", breakpoint condition
evaluation is done by GDB on the host's side. If it is "target",
- then the condition is evaluated by the target. The `info break'
+ then the condition is evaluated by the target. The 'info break'
command shows the condition on the line following the affected
breakpoint, together with its condition evaluation mode in between
parentheses.
loaded that allows the pending breakpoint to resolve to a valid
location.
- `info break' with a breakpoint number N as argument lists only
- that breakpoint. The convenience variable `$_' and the default
- examining-address for the `x' command are set to the address of
- the last breakpoint listed (*note Examining Memory: Memory.).
+ 'info break' with a breakpoint number N as argument lists only that
+ breakpoint. The convenience variable '$_' and the default
+ examining-address for the 'x' command are set to the address of the
+ last breakpoint listed (*note Examining Memory: Memory.).
- `info break' displays a count of the number of times the breakpoint
+ 'info break' displays a count of the number of times the breakpoint
has been hit. This is especially useful in conjunction with the
- `ignore' command. You can ignore a large number of breakpoint
+ 'ignore' command. You can ignore a large number of breakpoint
hits, look at the breakpoint info to see how many times the
- breakpoint was hit, and then run again, ignoring one less than
- that number. This will get you quickly to the last hit of that
+ breakpoint was hit, and then run again, ignoring one less than that
+ number. This will get you quickly to the last hit of that
breakpoint.
- For a breakpoints with an enable count (xref) greater than 1,
- `info break' also displays that count.
-
+ For a breakpoints with an enable count (xref) greater than 1, 'info
+ break' also displays that count.
GDB allows you to set any number of breakpoints at the same place in
your program. There is nothing silly or meaningless about this. When
* Multiple functions in the program may have the same name.
- * For a C++ constructor, the GCC compiler generates several
- instances of the function body, used in different cases.
+ * For a C++ constructor, the GCC compiler generates several instances
+ of the function body, used in different cases.
* For a C++ template function, a given line in the function can
correspond to any number of instantiations.
A breakpoint with multiple locations is displayed in the breakpoint
table using several rows--one header row, followed by one row for each
-breakpoint location. The header row has `<MULTIPLE>' in the address
+breakpoint location. The header row has '<MULTIPLE>' in the address
column. The rows for individual locations contain the actual addresses
for locations, and show the functions to which those locations belong.
The number column for a location is of the form
1.2 y 0x080486ca in void foo<double>() at t.cc:8
Each location can be individually enabled or disabled by passing
-BREAKPOINT-NUMBER.LOCATION-NUMBER as argument to the `enable' and
-`disable' commands. Note that you cannot delete the individual
+BREAKPOINT-NUMBER.LOCATION-NUMBER as argument to the 'enable' and
+'disable' commands. Note that you cannot delete the individual
locations from the list, you can only delete the entire list of
-locations that belong to their parent breakpoint (with the `delete NUM'
+locations that belong to their parent breakpoint (with the 'delete NUM'
command, where NUM is the number of the parent breakpoint, 1 in the
above example). Disabling or enabling the parent breakpoint (*note
Disabling::) affects all of the locations that belong to that
repeatedly, as the program is executed. To support this use case, GDB
updates breakpoint locations whenever any shared library is loaded or
unloaded. Typically, you would set a breakpoint in a shared library at
-the beginning of your debugging session, when the library is not
-loaded, and when the symbols from the library are not available. When
-you try to set breakpoint, GDB will ask you if you want to set a so
-called "pending breakpoint"--breakpoint whose address is not yet
-resolved.
+the beginning of your debugging session, when the library is not loaded,
+and when the symbols from the library are not available. When you try
+to set breakpoint, GDB will ask you if you want to set a so called
+"pending breakpoint"--breakpoint whose address is not yet resolved.
After the program is run, whenever a new shared library is loaded,
-GDB reevaluates all the breakpoints. When a newly loaded shared
-library contains the symbol or line referred to by some pending
-breakpoint, that breakpoint is resolved and becomes an ordinary
-breakpoint. When a library is unloaded, all breakpoints that refer to
-its symbols or source lines become pending again.
+GDB reevaluates all the breakpoints. When a newly loaded shared library
+contains the symbol or line referred to by some pending breakpoint, that
+breakpoint is resolved and becomes an ordinary breakpoint. When a
+library is unloaded, all breakpoints that refer to its symbols or source
+lines become pending again.
This logic works for breakpoints with multiple locations, too. For
example, if you have a breakpoint in a C++ template function, and a
-newly loaded shared library has an instantiation of that template, a
-new location is added to the list of locations for the breakpoint.
+newly loaded shared library has an instantiation of that template, a new
+location is added to the list of locations for the breakpoint.
Except for having unresolved address, pending breakpoints do not
differ from regular breakpoints. You can set conditions or commands,
enable and disable them and perform other breakpoint operations.
GDB provides some additional commands for controlling what happens
-when the `break' command cannot resolve breakpoint address
-specification to an address:
+when the 'break' command cannot resolve breakpoint address specification
+to an address:
-`set breakpoint pending auto'
+'set breakpoint pending auto'
This is the default behavior. When GDB cannot find the breakpoint
location, it queries you whether a pending breakpoint should be
created.
-`set breakpoint pending on'
+'set breakpoint pending on'
This indicates that an unrecognized breakpoint location should
automatically result in a pending breakpoint being created.
-`set breakpoint pending off'
+'set breakpoint pending off'
This indicates that pending breakpoints are not to be created. Any
- unrecognized breakpoint location results in an error. This
- setting does not affect any pending breakpoints previously created.
+ unrecognized breakpoint location results in an error. This setting
+ does not affect any pending breakpoints previously created.
-`show breakpoint pending'
+'show breakpoint pending'
Show the current behavior setting for creating pending breakpoints.
- The settings above only affect the `break' command and its variants.
+ The settings above only affect the 'break' command and its variants.
Once breakpoint is set, it will be automatically updated as shared
libraries are loaded and unloaded.
For some targets, GDB can automatically decide if hardware or
-software breakpoints should be used, depending on whether the
-breakpoint address is read-only or read-write. This applies to
-breakpoints set with the `break' command as well as to internal
-breakpoints set by commands like `next' and `finish'. For breakpoints
-set with `hbreak', GDB will always use hardware breakpoints.
+software breakpoints should be used, depending on whether the breakpoint
+address is read-only or read-write. This applies to breakpoints set
+with the 'break' command as well as to internal breakpoints set by
+commands like 'next' and 'finish'. For breakpoints set with 'hbreak',
+GDB will always use hardware breakpoints.
You can control this automatic behaviour with the following
commands::
-`set breakpoint auto-hw on'
+'set breakpoint auto-hw on'
This is the default behavior. When GDB sets a breakpoint, it will
try to use the target memory map to decide if software or hardware
breakpoint must be used.
-`set breakpoint auto-hw off'
- This indicates GDB should not automatically select breakpoint
- type. If the target provides a memory map, GDB will warn when
- trying to set software breakpoint at a read-only address.
+'set breakpoint auto-hw off'
+ This indicates GDB should not automatically select breakpoint type.
+ If the target provides a memory map, GDB will warn when trying to
+ set software breakpoint at a read-only address.
GDB normally implements breakpoints by replacing the program code at
-the breakpoint address with a special instruction, which, when
-executed, given control to the debugger. By default, the program code
-is so modified only when the program is resumed. As soon as the
-program stops, GDB restores the original instructions. This behaviour
-guards against leaving breakpoints inserted in the target should gdb
-abrubptly disconnect. However, with slow remote targets, inserting and
-removing breakpoint can reduce the performance. This behavior can be
-controlled with the following commands::
-
-`set breakpoint always-inserted off'
+the breakpoint address with a special instruction, which, when executed,
+given control to the debugger. By default, the program code is so
+modified only when the program is resumed. As soon as the program
+stops, GDB restores the original instructions. This behaviour guards
+against leaving breakpoints inserted in the target should gdb abrubptly
+disconnect. However, with slow remote targets, inserting and removing
+breakpoint can reduce the performance. This behavior can be controlled
+with the following commands::
+
+'set breakpoint always-inserted off'
All breakpoints, including newly added by the user, are inserted in
the target only when the target is resumed. All breakpoints are
removed from the target when it stops.
-`set breakpoint always-inserted on'
+'set breakpoint always-inserted on'
Causes all breakpoints to be inserted in the target at all times.
If the user adds a new breakpoint, or changes an existing
breakpoint, the breakpoints in the target are updated immediately.
- A breakpoint is removed from the target only when breakpoint
- itself is removed.
+ A breakpoint is removed from the target only when breakpoint itself
+ is removed.
-`set breakpoint always-inserted auto'
+'set breakpoint always-inserted auto'
This is the default mode. If GDB is controlling the inferior in
non-stop mode (*note Non-Stop Mode::), gdb behaves as if
- `breakpoint always-inserted' mode is on. If GDB is controlling
- the inferior in all-stop mode, GDB behaves as if `breakpoint
+ 'breakpoint always-inserted' mode is on. If GDB is controlling the
+ inferior in all-stop mode, GDB behaves as if 'breakpoint
always-inserted' mode is off.
GDB handles conditional breakpoints by evaluating these conditions
This feature can be controlled via the following commands:
-`set breakpoint condition-evaluation host'
+'set breakpoint condition-evaluation host'
This option commands GDB to evaluate the breakpoint conditions on
the host's side. Unconditional breakpoints are sent to the target
which in turn receives the triggers and reports them back to GDB
for condition evaluation. This is the standard evaluation mode.
-`set breakpoint condition-evaluation target'
+'set breakpoint condition-evaluation target'
This option commands GDB to download breakpoint conditions to the
- target at the moment of their insertion. The target is
- responsible for evaluating the conditional expression and reporting
- breakpoint stop events back to GDB whenever the condition is true.
- Due to limitations of target-side evaluation, some conditions
- cannot be evaluated there, e.g., conditions that depend on local
- data that is only known to the host. Examples include conditional
- expressions involving convenience variables, complex types that
- cannot be handled by the agent expression parser and expressions
- that are too long to be sent over to the target, specially when the
- target is a remote system. In these cases, the conditions will be
- evaluated by GDB.
-
-`set breakpoint condition-evaluation auto'
+ target at the moment of their insertion. The target is responsible
+ for evaluating the conditional expression and reporting breakpoint
+ stop events back to GDB whenever the condition is true. Due to
+ limitations of target-side evaluation, some conditions cannot be
+ evaluated there, e.g., conditions that depend on local data that is
+ only known to the host. Examples include conditional expressions
+ involving convenience variables, complex types that cannot be
+ handled by the agent expression parser and expressions that are too
+ long to be sent over to the target, specially when the target is a
+ remote system. In these cases, the conditions will be evaluated by
+ GDB.
+
+'set breakpoint condition-evaluation auto'
This is the default mode. If the target supports evaluating
breakpoint conditions on its end, GDB will download breakpoint
conditions to the target (limitations mentioned previously apply).
host's side.
GDB itself sometimes sets breakpoints in your program for special
-purposes, such as proper handling of `longjmp' (in C programs). These
-internal breakpoints are assigned negative numbers, starting with `-1';
-`info breakpoints' does not display them. You can see these
-breakpoints with the GDB maintenance command `maint info breakpoints'
-(*note maint info breakpoints::).
+purposes, such as proper handling of 'longjmp' (in C programs). These
+internal breakpoints are assigned negative numbers, starting with '-1';
+'info breakpoints' does not display them. You can see these breakpoints
+with the GDB maintenance command 'maint info breakpoints' (*note maint
+info breakpoints::).
\1f
File: gdb.info, Node: Set Watchpoints, Next: Set Catchpoints, Prev: Set Breaks, Up: Breakpoints
* A reference to the value of a single variable.
- * An address cast to an appropriate data type. For example, `*(int
+ * An address cast to an appropriate data type. For example, '*(int
*)0x12345678' will watch a 4-byte region at the specified address
- (assuming an `int' occupies 4 bytes).
+ (assuming an 'int' occupies 4 bytes).
- * An arbitrarily complex expression, such as `a*b + c/d'. The
+ * An arbitrarily complex expression, such as 'a*b + c/d'. The
expression can use any operators valid in the program's native
language (*note Languages::).
You can set a watchpoint on an expression even if the expression can
not be evaluated yet. For instance, you can set a watchpoint on
-`*global_ptr' before `global_ptr' is initialized. GDB will stop when
-your program sets `global_ptr' and the expression produces a valid
+'*global_ptr' before 'global_ptr' is initialized. GDB will stop when
+your program sets 'global_ptr' and the expression produces a valid
value. If the expression becomes valid in some other way than changing
-a variable (e.g. if the memory pointed to by `*global_ptr' becomes
-readable as the result of a `malloc' call), GDB may not stop until the
+a variable (e.g. if the memory pointed to by '*global_ptr' becomes
+readable as the result of a 'malloc' call), GDB may not stop until the
next time the expression changes.
Depending on your system, watchpoints may be implemented in software
x86-based targets, GDB includes support for hardware watchpoints, which
do not slow down the running of your program.
-`watch [-l|-location] EXPR [thread THREADNUM] [mask MASKVALUE]'
+'watch [-l|-location] EXPR [thread THREADNUM] [mask MASKVALUE]'
Set a watchpoint for an expression. GDB will break when the
expression EXPR is written into by the program and its value
changes. The simplest (and the most popular) use of this command
(gdb) watch foo
- If the command includes a `[thread THREADNUM]' argument, GDB
- breaks only when the thread identified by THREADNUM changes the
- value of EXPR. If any other threads change the value of EXPR, GDB
- will not break. Note that watchpoints restricted to a single
- thread in this way only work with Hardware Watchpoints.
+ If the command includes a '[thread THREADNUM]' argument, GDB breaks
+ only when the thread identified by THREADNUM changes the value of
+ EXPR. If any other threads change the value of EXPR, GDB will not
+ break. Note that watchpoints restricted to a single thread in this
+ way only work with Hardware Watchpoints.
Ordinarily a watchpoint respects the scope of variables in EXPR
- (see below). The `-location' argument tells GDB to instead watch
+ (see below). The '-location' argument tells GDB to instead watch
the memory referred to by EXPR. In this case, GDB will evaluate
EXPR, take the address of the result, and watch the memory at that
address. The type of the result is used to determine the size of
the watched memory. If the expression's result does not have an
address, then GDB will print an error.
- The `[mask MASKVALUE]' argument allows creation of masked
+ The '[mask MASKVALUE]' argument allows creation of masked
watchpoints, if the current architecture supports this feature
- (e.g., PowerPC Embedded architecture, see *Note PowerPC
- Embedded::.) A "masked watchpoint" specifies a mask in addition
- to an address to watch. The mask specifies that some bits of an
+ (e.g., PowerPC Embedded architecture, see *note PowerPC
+ Embedded::.) A "masked watchpoint" specifies a mask in addition to
+ an address to watch. The mask specifies that some bits of an
address (the bits which are reset in the mask) should be ignored
when matching the address accessed by the inferior against the
watchpoint address. Thus, a masked watchpoint watches many
addresses simultaneously--those addresses whose unmasked bits are
identical to the unmasked bits in the watchpoint address. The
- `mask' argument implies `-location'. Examples:
+ 'mask' argument implies '-location'. Examples:
(gdb) watch foo mask 0xffff00ff
(gdb) watch *0xdeadbeef mask 0xffffff00
-`rwatch [-l|-location] EXPR [thread THREADNUM] [mask MASKVALUE]'
+'rwatch [-l|-location] EXPR [thread THREADNUM] [mask MASKVALUE]'
Set a watchpoint that will break when the value of EXPR is read by
the program.
-`awatch [-l|-location] EXPR [thread THREADNUM] [mask MASKVALUE]'
+'awatch [-l|-location] EXPR [thread THREADNUM] [mask MASKVALUE]'
Set a watchpoint that will break when EXPR is either read from or
written into by the program.
-`info watchpoints [N...]'
+'info watchpoints [N...]'
This command prints a list of watchpoints, using the same format as
- `info break' (*note Set Breaks::).
+ 'info break' (*note Set Breaks::).
If you watch for a change in a numerically entered address you need
-to dereference it, as the address itself is just a constant number
-which will never change. GDB refuses to create a watchpoint that
-watches a never-changing value:
+to dereference it, as the address itself is just a constant number which
+will never change. GDB refuses to create a watchpoint that watches a
+never-changing value:
(gdb) watch 0x600850
Cannot watch constant value 0x600850.
GDB sets a "hardware watchpoint" if possible. Hardware watchpoints
execute very quickly, and the debugger reports a change in value at the
-exact instruction where the change occurs. If GDB cannot set a
-hardware watchpoint, it sets a software watchpoint, which executes more
-slowly and reports the change in value at the next _statement_, not the
+exact instruction where the change occurs. If GDB cannot set a hardware
+watchpoint, it sets a software watchpoint, which executes more slowly
+and reports the change in value at the next _statement_, not the
instruction, after the change occurs.
- You can force GDB to use only software watchpoints with the `set
+ You can force GDB to use only software watchpoints with the 'set
can-use-hw-watchpoints 0' command. With this variable set to zero, GDB
will never try to use hardware watchpoints, even if the underlying
system supports them. (Note that hardware-assisted watchpoints that
-were set _before_ setting `can-use-hw-watchpoints' to zero will still
+were set _before_ setting 'can-use-hw-watchpoints' to zero will still
use the hardware mechanism of watching expression values.)
-`set can-use-hw-watchpoints'
+'set can-use-hw-watchpoints'
Set whether or not to use hardware watchpoints.
-`show can-use-hw-watchpoints'
+'show can-use-hw-watchpoints'
Show the current mode of using hardware watchpoints.
For remote targets, you can restrict the number of hardware
-watchpoints GDB will use, see *Note set remote
+watchpoints GDB will use, see *note set remote
hardware-breakpoint-limit::.
- When you issue the `watch' command, GDB reports
+ When you issue the 'watch' command, GDB reports
Hardware watchpoint NUM: EXPR
if it was able to set a hardware watchpoint.
- Currently, the `awatch' and `rwatch' commands can only set hardware
-watchpoints, because accesses to data that don't change the value of
-the watched expression cannot be detected without examining every
-instruction as it is being executed, and GDB does not do that
-currently. If GDB finds that it is unable to set a hardware breakpoint
-with the `awatch' or `rwatch' command, it will print a message like
-this:
+ Currently, the 'awatch' and 'rwatch' commands can only set hardware
+watchpoints, because accesses to data that don't change the value of the
+watched expression cannot be detected without examining every
+instruction as it is being executed, and GDB does not do that currently.
+If GDB finds that it is unable to set a hardware breakpoint with the
+'awatch' or 'rwatch' command, it will print a message like this:
Expression cannot be implemented with read/access watchpoint.
- Sometimes, GDB cannot set a hardware watchpoint because the data
-type of the watched expression is wider than what a hardware watchpoint
-on the target machine can handle. For example, some systems can only
-watch regions that are up to 4 bytes wide; on such systems you cannot
-set hardware watchpoints for an expression that yields a
-double-precision floating-point number (which is typically 8 bytes
-wide). As a work-around, it might be possible to break the large region
-into a series of smaller ones and watch them with separate watchpoints.
+ Sometimes, GDB cannot set a hardware watchpoint because the data type
+of the watched expression is wider than what a hardware watchpoint on
+the target machine can handle. For example, some systems can only watch
+regions that are up to 4 bytes wide; on such systems you cannot set
+hardware watchpoints for an expression that yields a double-precision
+floating-point number (which is typically 8 bytes wide). As a
+work-around, it might be possible to break the large region into a
+series of smaller ones and watch them with separate watchpoints.
If you set too many hardware watchpoints, GDB might be unable to
-insert all of them when you resume the execution of your program.
-Since the precise number of active watchpoints is unknown until such
-time as the program is about to be resumed, GDB might not be able to
-warn you about this when you set the watchpoints, and the warning will
-be printed only when the program is resumed:
+insert all of them when you resume the execution of your program. Since
+the precise number of active watchpoints is unknown until such time as
+the program is about to be resumed, GDB might not be able to warn you
+about this when you set the watchpoints, and the warning will be printed
+only when the program is resumed:
Hardware watchpoint NUM: Could not insert watchpoint
That's because GDB needs to watch every variable in the expression with
separately allocated resources.
- If you call a function interactively using `print' or `call', any
-watchpoints you have set will be inactive until GDB reaches another
-kind of breakpoint or the call completes.
+ If you call a function interactively using 'print' or 'call', any
+watchpoints you have set will be inactive until GDB reaches another kind
+of breakpoint or the call completes.
GDB automatically deletes watchpoints that watch local (automatic)
variables, or expressions that involve such variables, when they go out
terminates, _all_ local variables go out of scope, and so only
watchpoints that watch global variables remain set. If you rerun the
program, you will need to set all such watchpoints again. One way of
-doing that would be to set a code breakpoint at the entry to the `main'
+doing that would be to set a code breakpoint at the entry to the 'main'
function and when it breaks, set all the watchpoints.
In multi-threaded programs, watchpoints will detect changes to the
_Warning:_ In multi-threaded programs, software watchpoints have
only limited usefulness. If GDB creates a software watchpoint, it
- can only watch the value of an expression _in a single thread_.
- If you are confident that the expression can only change due to
- the current thread's activity (and if you are also confident that
- no other thread can become current), then you can use software
+ can only watch the value of an expression _in a single thread_. If
+ you are confident that the expression can only change due to the
+ current thread's activity (and if you are also confident that no
+ other thread can become current), then you can use software
watchpoints as usual. However, GDB may not notice when a
non-current thread's activity changes the expression. (Hardware
watchpoints, in contrast, watch an expression in all threads.)
You can use "catchpoints" to cause the debugger to stop for certain
kinds of program events, such as C++ exceptions or the loading of a
-shared library. Use the `catch' command to set a catchpoint.
-
-`catch EVENT'
- Stop when EVENT occurs. EVENT can be any of the following:
- `throw'
- The throwing of a C++ exception.
-
- `catch'
- The catching of a C++ exception.
-
- `exception'
+shared library. Use the 'catch' command to set a catchpoint.
+
+'catch EVENT'
+ Stop when EVENT occurs. The EVENT can be any of the following:
+
+ 'throw [REGEXP]'
+ 'rethrow [REGEXP]'
+ 'catch [REGEXP]'
+ The throwing, re-throwing, or catching of a C++ exception.
+
+ If REGEXP is given, then only exceptions whose type matches
+ the regular expression will be caught.
+
+ The convenience variable '$_exception' is available at an
+ exception-related catchpoint, on some systems. This holds the
+ exception being thrown.
+
+ There are currently some limitations to C++ exception handling
+ in GDB:
+
+ * The support for these commands is system-dependent.
+ Currently, only systems using the 'gnu-v3' C++ ABI (*note
+ ABI::) are supported.
+
+ * The regular expression feature and the '$_exception'
+ convenience variable rely on the presence of some SDT
+ probes in 'libstdc++'. If these probes are not present,
+ then these features cannot be used. These probes were
+ first available in the GCC 4.8 release, but whether or
+ not they are available in your GCC also depends on how it
+ was built.
+
+ * The '$_exception' convenience variable is only valid at
+ the instruction at which an exception-related catchpoint
+ is set.
+
+ * When an exception-related catchpoint is hit, GDB stops at
+ a location in the system library which implements runtime
+ exception support for C++, usually 'libstdc++'. You can
+ use 'up' (*note Selection::) to get to your code.
+
+ * If you call a function interactively, GDB normally
+ returns control to you when the function has finished
+ executing. If the call raises an exception, however, the
+ call may bypass the mechanism that returns control to you
+ and cause your program either to abort or to simply
+ continue running until it hits a breakpoint, catches a
+ signal that GDB is listening for, or exits. This is the
+ case even if you set a catchpoint for the exception;
+ catchpoints on exceptions are disabled within interactive
+ calls. *Note Calling::, for information on controlling
+ this with 'set unwind-on-terminating-exception'.
+
+ * You cannot raise an exception interactively.
+
+ * You cannot install an exception handler interactively.
+
+ 'exception'
An Ada exception being raised. If an exception name is
- specified at the end of the command (eg `catch exception
+ specified at the end of the command (eg 'catch exception
Program_Error'), the debugger will stop only when this
specific exception is raised. Otherwise, the debugger stops
execution when any Ada exception is raised.
When inserting an exception catchpoint on a user-defined
exception whose name is identical to one of the exceptions
- defined by the language, the fully qualified name must be
- used as the exception name. Otherwise, GDB will assume that
- it should stop on the pre-defined exception rather than the
+ defined by the language, the fully qualified name must be used
+ as the exception name. Otherwise, GDB will assume that it
+ should stop on the pre-defined exception rather than the
user-defined one. For instance, assuming an exception called
- `Constraint_Error' is defined in package `Pck', then the
- command to use to catch such exceptions is `catch exception
+ 'Constraint_Error' is defined in package 'Pck', then the
+ command to use to catch such exceptions is 'catch exception
Pck.Constraint_Error'.
- `exception unhandled'
+ 'exception unhandled'
An exception that was raised but is not handled by the
program.
- `assert'
+ 'assert'
A failed Ada assertion.
- `exec'
- A call to `exec'. This is currently only available for HP-UX
+ 'exec'
+ A call to 'exec'. This is currently only available for HP-UX
and GNU/Linux.
- `syscall'
- `syscall [NAME | NUMBER] ...'
+ 'syscall'
+ 'syscall [NAME | NUMBER] ...'
A call to or return from a system call, a.k.a. "syscall". A
syscall is a mechanism for application programs to request a
- service from the operating system (OS) or one of the OS
- system services. GDB can catch some or all of the syscalls
- issued by the debuggee, and show the related information for
- each syscall. If no argument is specified, calls to and
- returns from all system calls will be caught.
+ service from the operating system (OS) or one of the OS system
+ services. GDB can catch some or all of the syscalls issued by
+ the debuggee, and show the related information for each
+ syscall. If no argument is specified, calls to and returns
+ from all system calls will be caught.
NAME can be any system call name that is valid for the
- underlying OS. Just what syscalls are valid depends on the
- OS. On GNU and Unix systems, you can find the full list of
- valid syscall names on `/usr/include/asm/unistd.h'.
+ underlying OS. Just what syscalls are valid depends on the OS.
+ On GNU and Unix systems, you can find the full list of valid
+ syscall names on '/usr/include/asm/unistd.h'.
Normally, GDB knows in advance which syscalls are valid for
each OS, so you can use the GDB command-line completion
number is the value passed to the OS's syscall dispatcher to
identify the requested service. When you specify the syscall
by its name, GDB uses its database of syscalls to convert the
- name into the corresponding numeric code, but using the
- number directly may be useful if GDB's database does not have
- the complete list of syscalls on your system (e.g., because
- GDB lags behind the OS upgrades).
+ name into the corresponding numeric code, but using the number
+ directly may be useful if GDB's database does not have the
+ complete list of syscalls on your system (e.g., because GDB
+ lags behind the OS upgrades).
The example below illustrates how this command works if you
don't provide arguments to it:
However, there can be situations when there is no
corresponding name in XML file for that syscall number. In
- this case, GDB prints a warning message saying that it was
- not able to find the syscall name, but the catchpoint will be
- set anyway. See the example below:
+ this case, GDB prints a warning message saying that it was not
+ able to find the syscall name, but the catchpoint will be set
+ anyway. See the example below:
(gdb) catch syscall 764
warning: The number '764' does not represent a known syscall.
Catchpoint 2 (syscall 764)
(gdb)
- If you configure GDB using the `--without-expat' option, it
+ If you configure GDB using the '--without-expat' option, it
will not be able to display syscall names. Also, if your
architecture does not have an XML file describing its system
calls, you will not be able to see the syscall names. It is
important to notice that these two features are used for
- accessing the syscall name database. In either case, you
- will see a warning like this:
+ accessing the syscall name database. In either case, you will
+ see a warning like this:
(gdb) catch syscall
warning: Could not open "syscalls/i386-linux.xml"
(gdb) catch syscall 252
Catchpoint 1 (syscall(s) 252)
- Again, in this case GDB would not be able to display
- syscall's names.
+ Again, in this case GDB would not be able to display syscall's
+ names.
- `fork'
- A call to `fork'. This is currently only available for HP-UX
+ 'fork'
+ A call to 'fork'. This is currently only available for HP-UX
and GNU/Linux.
- `vfork'
- A call to `vfork'. This is currently only available for HP-UX
+ 'vfork'
+ A call to 'vfork'. This is currently only available for HP-UX
and GNU/Linux.
- `load [regexp]'
- `unload [regexp]'
+ 'load [regexp]'
+ 'unload [regexp]'
The loading or unloading of a shared library. If REGEXP is
given, then the catchpoint will stop only if the regular
expression matches one of the affected libraries.
+ 'signal [SIGNAL... | 'all']'
+ The delivery of a signal.
-`tcatch EVENT'
- Set a catchpoint that is enabled only for one stop. The
- catchpoint is automatically deleted after the first time the event
- is caught.
-
-
- Use the `info break' command to list the current catchpoints.
-
- There are currently some limitations to C++ exception handling
-(`catch throw' and `catch catch') in GDB:
+ With no arguments, this catchpoint will catch any signal that
+ is not used internally by GDB, specifically, all signals
+ except 'SIGTRAP' and 'SIGINT'.
- * If you call a function interactively, GDB normally returns control
- to you when the function has finished executing. If the call
- raises an exception, however, the call may bypass the mechanism
- that returns control to you and cause your program either to abort
- or to simply continue running until it hits a breakpoint, catches
- a signal that GDB is listening for, or exits. This is the case
- even if you set a catchpoint for the exception; catchpoints on
- exceptions are disabled within interactive calls.
+ With the argument 'all', all signals, including those used by
+ GDB, will be caught. This argument cannot be used with other
+ signal names.
- * You cannot raise an exception interactively.
+ Otherwise, the arguments are a list of signal names as given
+ to 'handle' (*note Signals::). Only signals specified in this
+ list will be caught.
- * You cannot install an exception handler interactively.
+ One reason that 'catch signal' can be more useful than
+ 'handle' is that you can attach commands and conditions to the
+ catchpoint.
- Sometimes `catch' is not the best way to debug exception handling:
-if you need to know exactly where an exception is raised, it is better
-to stop _before_ the exception handler is called, since that way you
-can see the stack before any unwinding takes place. If you set a
-breakpoint in an exception handler instead, it may not be easy to find
-out where the exception was raised.
+ When a signal is caught by a catchpoint, the signal's 'stop'
+ and 'print' settings, as specified by 'handle', are ignored.
+ However, whether the signal is still delivered to the inferior
+ depends on the 'pass' setting; this can be changed in the
+ catchpoint's commands.
- To stop just before an exception handler is called, you need some
-knowledge of the implementation. In the case of GNU C++, exceptions are
-raised by calling a library function named `__raise_exception' which
-has the following ANSI C interface:
+'tcatch EVENT'
+ Set a catchpoint that is enabled only for one stop. The catchpoint
+ is automatically deleted after the first time the event is caught.
- /* ADDR is where the exception identifier is stored.
- ID is the exception identifier. */
- void __raise_exception (void **addr, void *id);
-
-To make the debugger catch all exceptions before any stack unwinding
-takes place, set a breakpoint on `__raise_exception' (*note
-Breakpoints; Watchpoints; and Exceptions: Breakpoints.).
-
- With a conditional breakpoint (*note Break Conditions: Conditions.)
-that depends on the value of ID, you can stop your program when a
-specific exception is raised. You can use multiple conditional
-breakpoints to stop your program when any of a number of exceptions are
-raised.
+ Use the 'info break' command to list the current catchpoints.
\1f
File: gdb.info, Node: Delete Breaks, Next: Disabling, Prev: Set Catchpoints, Up: Breakpoints
to stop there. This is called "deleting" the breakpoint. A breakpoint
that has been deleted no longer exists; it is forgotten.
- With the `clear' command you can delete breakpoints according to
-where they are in your program. With the `delete' command you can
+ With the 'clear' command you can delete breakpoints according to
+where they are in your program. With the 'delete' command you can
delete individual breakpoints, watchpoints, or catchpoints by specifying
their breakpoint numbers.
executed when you continue execution without changing the execution
address.
-`clear'
+'clear'
Delete any breakpoints at the next instruction to be executed in
the selected stack frame (*note Selecting a Frame: Selection.).
When the innermost frame is selected, this is a good way to delete
a breakpoint where your program just stopped.
-`clear LOCATION'
+'clear LOCATION'
Delete any breakpoints set at the specified LOCATION. *Note
Specify Location::, for the various forms of LOCATION; the most
useful ones are listed below:
- `clear FUNCTION'
- `clear FILENAME:FUNCTION'
+ 'clear FUNCTION'
+ 'clear FILENAME:FUNCTION'
Delete any breakpoints set at entry to the named FUNCTION.
- `clear LINENUM'
- `clear FILENAME:LINENUM'
+ 'clear LINENUM'
+ 'clear FILENAME:LINENUM'
Delete any breakpoints set at or within the code of the
specified LINENUM of the specified FILENAME.
-`delete [breakpoints] [RANGE...]'
+'delete [breakpoints] [RANGE...]'
Delete the breakpoints, watchpoints, or catchpoints of the
breakpoint ranges specified as arguments. If no argument is
specified, delete all breakpoints (GDB asks confirmation, unless
- you have `set confirm off'). You can abbreviate this command as
- `d'.
+ you have 'set confirm off'). You can abbreviate this command as
+ 'd'.
\1f
File: gdb.info, Node: Disabling, Next: Conditions, Prev: Delete Breaks, Up: Breakpoints
that you can "enable" it again later.
You disable and enable breakpoints, watchpoints, and catchpoints with
-the `enable' and `disable' commands, optionally specifying one or more
-breakpoint numbers as arguments. Use `info break' to print a list of
+the 'enable' and 'disable' commands, optionally specifying one or more
+breakpoint numbers as arguments. Use 'info break' to print a list of
all breakpoints, watchpoints, and catchpoints if you do not know which
numbers to use.
A breakpoint, watchpoint, or catchpoint can have any of several
different states of enablement:
- * Enabled. The breakpoint stops your program. A breakpoint set
- with the `break' command starts out in this state.
-
+ * Enabled. The breakpoint stops your program. A breakpoint set with
+ the 'break' command starts out in this state.
* Disabled. The breakpoint has no effect on your program.
-
* Enabled once. The breakpoint stops your program, but then becomes
disabled.
-
* Enabled for a count. The breakpoint stops your program for the
next N times, then becomes disabled.
-
* Enabled for deletion. The breakpoint stops your program, but
immediately after it does so it is deleted permanently. A
- breakpoint set with the `tbreak' command starts out in this state.
+ breakpoint set with the 'tbreak' command starts out in this state.
You can use the following commands to enable or disable breakpoints,
watchpoints, and catchpoints:
-`disable [breakpoints] [RANGE...]'
+'disable [breakpoints] [RANGE...]'
Disable the specified breakpoints--or all breakpoints, if none are
listed. A disabled breakpoint has no effect but is not forgotten.
All options such as ignore-counts, conditions and commands are
remembered in case the breakpoint is enabled again later. You may
- abbreviate `disable' as `dis'.
+ abbreviate 'disable' as 'dis'.
-`enable [breakpoints] [RANGE...]'
+'enable [breakpoints] [RANGE...]'
Enable the specified breakpoints (or all defined breakpoints).
They become effective once again in stopping your program.
-`enable [breakpoints] once RANGE...'
+'enable [breakpoints] once RANGE...'
Enable the specified breakpoints temporarily. GDB disables any of
these breakpoints immediately after stopping your program.
-`enable [breakpoints] count COUNT RANGE...'
+'enable [breakpoints] count COUNT RANGE...'
Enable the specified breakpoints temporarily. GDB records COUNT
with each of the specified breakpoints, and decrements a
breakpoint's count when it is hit. When any count reaches 0, GDB
(*note Break Conditions: Conditions.), that will be decremented to
0 before COUNT is affected.
-`enable [breakpoints] delete RANGE...'
+'enable [breakpoints] delete RANGE...'
Enable the specified breakpoints to work once, then die. GDB
deletes any of these breakpoints as soon as your program stops
- there. Breakpoints set by the `tbreak' command start out in this
+ there. Breakpoints set by the 'tbreak' command start out in this
state.
- Except for a breakpoint set with `tbreak' (*note Setting
-Breakpoints: Set Breaks.), breakpoints that you set are initially
-enabled; subsequently, they become disabled or enabled only when you
-use one of the commands above. (The command `until' can set and delete
-a breakpoint of its own, but it does not change the state of your other
-breakpoints; see *Note Continuing and Stepping: Continuing and
+ Except for a breakpoint set with 'tbreak' (*note Setting Breakpoints:
+Set Breaks.), breakpoints that you set are initially enabled;
+subsequently, they become disabled or enabled only when you use one of
+the commands above. (The command 'until' can set and delete a
+breakpoint of its own, but it does not change the state of your other
+breakpoints; see *note Continuing and Stepping: Continuing and
Stepping.)
\1f
This is the converse of using assertions for program validation; in
that situation, you want to stop when the assertion is violated--that
-is, when the condition is false. In C, if you want to test an
-assertion expressed by the condition ASSERT, you should set the
-condition `! ASSERT' on the appropriate breakpoint.
+is, when the condition is false. In C, if you want to test an assertion
+expressed by the condition ASSERT, you should set the condition '!
+ASSERT' on the appropriate breakpoint.
Conditions are also accepted for watchpoints; you may not need them,
since a watchpoint is inspecting the value of an expression anyhow--but
in your program. This can be useful, for example, to activate functions
that log program progress, or to use your own print functions to format
special data structures. The effects are completely predictable unless
-there is another enabled breakpoint at the same address. (In that
-case, GDB might see the other breakpoint first and stop your program
-without checking the condition of this one.) Note that breakpoint
-commands are usually more convenient and flexible than break conditions
-for the purpose of performing side effects when a breakpoint is reached
-(*note Breakpoint Command Lists: Break Commands.).
+there is another enabled breakpoint at the same address. (In that case,
+GDB might see the other breakpoint first and stop your program without
+checking the condition of this one.) Note that breakpoint commands are
+usually more convenient and flexible than break conditions for the
+purpose of performing side effects when a breakpoint is reached (*note
+Breakpoint Command Lists: Break Commands.).
Breakpoint conditions can also be evaluated on the target's side if
the target supports it. Instead of evaluating the conditions locally,
breakpoint trigger, even those with false conditions.
Break conditions can be specified when a breakpoint is set, by using
-`if' in the arguments to the `break' command. *Note Setting
+'if' in the arguments to the 'break' command. *Note Setting
Breakpoints: Set Breaks. They can also be changed at any time with the
-`condition' command.
+'condition' command.
- You can also use the `if' keyword with the `watch' command. The
-`catch' command does not recognize the `if' keyword; `condition' is the
+ You can also use the 'if' keyword with the 'watch' command. The
+'catch' command does not recognize the 'if' keyword; 'condition' is the
only way to impose a further condition on a catchpoint.
-`condition BNUM EXPRESSION'
+'condition BNUM EXPRESSION'
Specify EXPRESSION as the break condition for breakpoint,
watchpoint, or catchpoint number BNUM. After you set a condition,
breakpoint BNUM stops your program only if the value of EXPRESSION
- is true (nonzero, in C). When you use `condition', GDB checks
+ is true (nonzero, in C). When you use 'condition', GDB checks
EXPRESSION immediately for syntactic correctness, and to determine
whether symbols in it have referents in the context of your
breakpoint. If EXPRESSION uses symbols not referenced in the
No symbol "foo" in current context.
GDB does not actually evaluate EXPRESSION at the time the
- `condition' command (or a command that sets a breakpoint with a
- condition, like `break if ...') is given, however. *Note
+ 'condition' command (or a command that sets a breakpoint with a
+ condition, like 'break if ...') is given, however. *Note
Expressions: Expressions.
-`condition BNUM'
+'condition BNUM'
Remove the condition from breakpoint number BNUM. It becomes an
ordinary unconditional breakpoint.
A special case of a breakpoint condition is to stop only when the
breakpoint has been reached a certain number of times. This is so
-useful that there is a special way to do it, using the "ignore count"
-of the breakpoint. Every breakpoint has an ignore count, which is an
+useful that there is a special way to do it, using the "ignore count" of
+the breakpoint. Every breakpoint has an ignore count, which is an
integer. Most of the time, the ignore count is zero, and therefore has
no effect. But if your program reaches a breakpoint whose ignore count
is positive, then instead of stopping, it just decrements the ignore
N, the breakpoint does not stop the next N times your program reaches
it.
-`ignore BNUM COUNT'
+'ignore BNUM COUNT'
Set the ignore count of breakpoint number BNUM to COUNT. The next
COUNT times the breakpoint is reached, your program's execution
does not stop; other than to decrement the ignore count, GDB takes
To make the breakpoint stop the next time it is reached, specify a
count of zero.
- When you use `continue' to resume execution of your program from a
- breakpoint, you can specify an ignore count directly as an
- argument to `continue', rather than using `ignore'. *Note
- Continuing and Stepping: Continuing and Stepping.
+ When you use 'continue' to resume execution of your program from a
+ breakpoint, you can specify an ignore count directly as an argument
+ to 'continue', rather than using 'ignore'. *Note Continuing and
+ Stepping: Continuing and Stepping.
If a breakpoint has a positive ignore count and a condition, the
condition is not checked. Once the ignore count reaches zero, GDB
resumes checking the condition.
You could achieve the effect of the ignore count with a condition
- such as `$foo-- <= 0' using a debugger convenience variable that
- is decremented each time. *Note Convenience Variables:
- Convenience Vars.
+ such as '$foo-- <= 0' using a debugger convenience variable that is
+ decremented each time. *Note Convenience Variables: Convenience
+ Vars.
Ignore counts apply to breakpoints, watchpoints, and catchpoints.
example, you might want to print the values of certain expressions, or
enable other breakpoints.
-`commands [RANGE...]'
-`... COMMAND-LIST ...'
-`end'
+'commands [RANGE...]'
+'... COMMAND-LIST ...'
+'end'
Specify a list of commands for the given breakpoints. The commands
themselves appear on the following lines. Type a line containing
- just `end' to terminate the commands.
+ just 'end' to terminate the commands.
- To remove all commands from a breakpoint, type `commands' and
- follow it immediately with `end'; that is, give no commands.
+ To remove all commands from a breakpoint, type 'commands' and
+ follow it immediately with 'end'; that is, give no commands.
- With no argument, `commands' refers to the last breakpoint,
+ With no argument, 'commands' refers to the last breakpoint,
watchpoint, or catchpoint set (not to the breakpoint most recently
encountered). If the most recent breakpoints were set with a
- single command, then the `commands' will apply to all the
+ single command, then the 'commands' will apply to all the
breakpoints set by that command. This applies to breakpoints set
- by `rbreak', and also applies when a single `break' command
- creates multiple breakpoints (*note Ambiguous Expressions:
- Ambiguous Expressions.).
+ by 'rbreak', and also applies when a single 'break' command creates
+ multiple breakpoints (*note Ambiguous Expressions: Ambiguous
+ Expressions.).
Pressing <RET> as a means of repeating the last GDB command is
disabled within a COMMAND-LIST.
You can use breakpoint commands to start your program up again.
-Simply use the `continue' command, or `step', or any other command that
+Simply use the 'continue' command, or 'step', or any other command that
resumes execution.
Any other commands in the command list, after a command that resumes
execution, are ignored. This is because any time you resume execution
-(even with a simple `next' or `step'), you may encounter another
+(even with a simple 'next' or 'step'), you may encounter another
breakpoint--which could have its own command list, leading to
ambiguities about which list to execute.
- If the first command you specify in a command list is `silent', the
+ If the first command you specify in a command list is 'silent', the
usual message about stopping at a breakpoint is not printed. This may
be desirable for breakpoints that are to print a specific message and
then continue. If none of the remaining commands print anything, you
-see no sign that the breakpoint was reached. `silent' is meaningful
+see no sign that the breakpoint was reached. 'silent' is meaningful
only at the beginning of a breakpoint command list.
- The commands `echo', `output', and `printf' allow you to print
-precisely controlled output, and are often useful in silent
-breakpoints. *Note Commands for Controlled Output: Output.
+ The commands 'echo', 'output', and 'printf' allow you to print
+precisely controlled output, and are often useful in silent breakpoints.
+*Note Commands for Controlled Output: Output.
For example, here is how you could use breakpoint commands to print
-the value of `x' at entry to `foo' whenever `x' is positive.
+the value of 'x' at entry to 'foo' whenever 'x' is positive.
break foo if x>0
commands
so you can test for another. Put a breakpoint just after the erroneous
line of code, give it a condition to detect the case in which something
erroneous has been done, and give it commands to assign correct values
-to any variables that need them. End with the `continue' command so
-that your program does not stop, and start with the `silent' command so
+to any variables that need them. End with the 'continue' command so
+that your program does not stop, and start with the 'silent' command so
that no output is produced. Here is an example:
break 403
5.1.8 Dynamic Printf
--------------------
-The dynamic printf command `dprintf' combines a breakpoint with
+The dynamic printf command 'dprintf' combines a breakpoint with
formatted printing of your program's data to give you the effect of
-inserting `printf' calls into your program on-the-fly, without having
-to recompile it.
+inserting 'printf' calls into your program on-the-fly, without having to
+recompile it.
In its most basic form, the output goes to the GDB console. However,
-you can set the variable `dprintf-style' for alternate handling. For
+you can set the variable 'dprintf-style' for alternate handling. For
instance, you can ask to format the output by calling your program's
-`printf' function. This has the advantage that the characters go to
-the program's output device, so they can recorded in redirects to files
-and so forth.
+'printf' function. This has the advantage that the characters go to the
+program's output device, so they can recorded in redirects to files and
+so forth.
If you are doing remote debugging with a stub or agent, you can also
ask to have the printf handled by the remote agent. In addition to
Using the stub/agent is also more efficient, as it can do everything
without needing to communicate with GDB.
-`dprintf LOCATION,TEMPLATE,EXPRESSION[,EXPRESSION...]'
+'dprintf LOCATION,TEMPLATE,EXPRESSION[,EXPRESSION...]'
Whenever execution reaches LOCATION, print the values of one or
more EXPRESSIONS under the control of the string TEMPLATE. To
print several values, separate them with commas.
-`set dprintf-style STYLE'
+'set dprintf-style STYLE'
Set the dprintf output to be handled in one of several different
styles enumerated below. A change of style affects all existing
dynamic printfs immediately. (If you need individual control over
the print commands, simply define normal breakpoints with
explicitly-supplied command lists.)
-`gdb'
- Handle the output using the GDB `printf' command.
+'gdb'
+ Handle the output using the GDB 'printf' command.
-`call'
+'call'
Handle the output by calling a function in your program (normally
- `printf').
+ 'printf').
-`agent'
- Have the remote debugging agent (such as `gdbserver') handle the
+'agent'
+ Have the remote debugging agent (such as 'gdbserver') handle the
output itself. This style is only available for agents that
support running commands on the target.
-`set dprintf-function FUNCTION'
- Set the function to call if the dprintf style is `call'. By
- default its value is `printf'. You may set it to any expression.
- that GDB can evaluate to a function, as per the `call' command.
+'set dprintf-function FUNCTION'
+ Set the function to call if the dprintf style is 'call'. By
+ default its value is 'printf'. You may set it to any expression.
+ that GDB can evaluate to a function, as per the 'call' command.
-`set dprintf-channel CHANNEL'
- Set a "channel" for dprintf. If set to a non-empty value, GDB
- will evaluate it as an expression and pass the result as a first
- argument to the `dprintf-function', in the manner of `fprintf' and
+'set dprintf-channel CHANNEL'
+ Set a "channel" for dprintf. If set to a non-empty value, GDB will
+ evaluate it as an expression and pass the result as a first
+ argument to the 'dprintf-function', in the manner of 'fprintf' and
similar functions. Otherwise, the dprintf format string will be
- the first argument, in the manner of `printf'.
+ the first argument, in the manner of 'printf'.
- As an example, if you wanted `dprintf' output to go to a logfile
- that is a standard I/O stream assigned to the variable `mylog',
- you could do the following:
+ As an example, if you wanted 'dprintf' output to go to a logfile
+ that is a standard I/O stream assigned to the variable 'mylog', you
+ could do the following:
(gdb) set dprintf-style call
(gdb) set dprintf-function fprintf
continue
(gdb)
- Note that the `info break' displays the dynamic printf commands as
+ Note that the 'info break' displays the dynamic printf commands as
normal breakpoint commands; you can thus easily see the effect of
the variable settings.
-`set disconnected-dprintf on'
-`set disconnected-dprintf off'
- Choose whether `dprintf' commands should continue to run if GDB
- has disconnected from the target. This only applies if the
- `dprintf-style' is `agent'.
-
-`show disconnected-dprintf off'
- Show the current choice for disconnected `dprintf'.
+'set disconnected-dprintf on'
+'set disconnected-dprintf off'
+ Choose whether 'dprintf' commands should continue to run if GDB has
+ disconnected from the target. This only applies if the
+ 'dprintf-style' is 'agent'.
+'show disconnected-dprintf off'
+ Show the current choice for disconnected 'dprintf'.
GDB does not check the validity of function and channel, relying on
you to supply values that are meaningful for the contexts in which they
5.1.9 How to save breakpoints to a file
---------------------------------------
-To save breakpoint definitions to a file use the `save breakpoints'
+To save breakpoint definitions to a file use the 'save breakpoints'
command.
-`save breakpoints [FILENAME]'
+'save breakpoints [FILENAME]'
This command saves all current breakpoint definitions together with
- their commands and ignore counts, into a file `FILENAME' suitable
+ their commands and ignore counts, into a file 'FILENAME' suitable
for use in a later debugging session. This includes all types of
breakpoints (breakpoints, watchpoints, catchpoints, tracepoints).
- To read the saved breakpoint definitions, use the `source' command
+ To read the saved breakpoint definitions, use the 'source' command
(*note Command Files::). Note that watchpoints with expressions
involving local variables may fail to be recreated because it may
- not be possible to access the context where the watchpoint is
- valid anymore. Because the saved breakpoint definitions are
- simply a sequence of GDB commands that recreate the breakpoints,
- you can edit the file in your favorite editing program, and remove
- the breakpoint definitions you're not interested in, or that can
- no longer be recreated.
+ not be possible to access the context where the watchpoint is valid
+ anymore. Because the saved breakpoint definitions are simply a
+ sequence of GDB commands that recreate the breakpoints, you can
+ edit the file in your favorite editing program, and remove the
+ breakpoint definitions you're not interested in, or that can no
+ longer be recreated.
\1f
File: gdb.info, Node: Static Probe Points, Next: Error in Breakpoints, Prev: Save Breakpoints, Up: Breakpoints
--------------------------
GDB supports "SDT" probes in the code. SDT stands for Statically
-Defined Tracing, and the probes are designed to have a tiny runtime
-code and data footprint, and no dynamic relocations. They are usable
-from assembly, C and C++ languages. See
-`http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation' for
+Defined Tracing, and the probes are designed to have a tiny runtime code
+and data footprint, and no dynamic relocations. They are usable from
+assembly, C and C++ languages. See
+<http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation> for
a good reference on how the SDT probes are implemented.
- Currently, `SystemTap' (`http://sourceware.org/systemtap/') SDT
+ Currently, 'SystemTap' (<http://sourceware.org/systemtap/>) SDT
probes are supported on ELF-compatible systems. See
-`http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps' for
-more information on how to add `SystemTap' SDT probes in your
+<http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps> for
+more information on how to add 'SystemTap' SDT probes in your
applications.
Some probes have an associated semaphore variable; for instance, this
happens automatically if you defined your probe using a DTrace-style
-`.d' file. If your probe has a semaphore, GDB will automatically
-enable it when you specify a breakpoint using the `-probe-stap'
-notation. But, if you put a breakpoint at a probe's location by some
-other method (e.g., `break file:line'), then GDB will not automatically
-set the semaphore.
+'.d' file. If your probe has a semaphore, GDB will automatically enable
+it when you specify a breakpoint using the '-probe-stap' notation. But,
+if you put a breakpoint at a probe's location by some other method
+(e.g., 'break file:line'), then GDB will not automatically set the
+semaphore.
- You can examine the available static static probes using `info
+ You can examine the available static static probes using 'info
probes', with optional arguments:
-`info probes stap [PROVIDER [NAME [OBJFILE]]]'
+'info probes stap [PROVIDER [NAME [OBJFILE]]]'
If given, PROVIDER is a regular expression used to match against
provider names when selecting which probes to list. If omitted,
probes by all probes from all providers are listed.
object files (executable or shared libraries) to examine. If not
given, all object files are considered.
-`info probes all'
+'info probes all'
List the available static probes, from all types.
A probe may specify up to twelve arguments. These are available at
the point at which the probe is defined--that is, when the current PC is
at the probe's location. The arguments are available using the
convenience variables (*note Convenience Vars::)
-`$_probe_arg0'...`$_probe_arg11'. Each probe argument is an integer of
-the appropriate size; types are not preserved. The convenience
-variable `$_probe_argc' holds the number of arguments at the current
-probe point.
+'$_probe_arg0'...'$_probe_arg11'. Each probe argument is an integer of
+the appropriate size; types are not preserved. The convenience variable
+'$_probe_argc' holds the number of arguments at the current probe point.
These variables are always available, but attempts to access them at
any location other than a probe point will cause GDB to give an error
5.1.12 "Breakpoint address adjusted..."
---------------------------------------
-Some processor architectures place constraints on the addresses at
-which breakpoints may be placed. For architectures thus constrained,
-GDB will attempt to adjust the breakpoint's address to comply with the
+Some processor architectures place constraints on the addresses at which
+breakpoints may be placed. For architectures thus constrained, GDB will
+attempt to adjust the breakpoint's address to comply with the
constraints dictated by the architecture.
- One example of such an architecture is the Fujitsu FR-V. The FR-V is
+ One example of such an architecture is the Fujitsu FR-V. The FR-V is
a VLIW architecture in which a number of RISC-like instructions may be
bundled together for parallel execution. The FR-V architecture
-constrains the location of a breakpoint instruction within such a
-bundle to the instruction with the lowest address. GDB honors this
-constraint by adjusting a breakpoint's address to the first in the
-bundle.
+constrains the location of a breakpoint instruction within such a bundle
+to the instruction with the lowest address. GDB honors this constraint
+by adjusting a breakpoint's address to the first in the bundle.
It is not uncommon for optimized code to have bundles which contain
-instructions from different source statements, thus it may happen that
-a breakpoint's address will be adjusted from one source statement to
-another. Since this adjustment may significantly alter GDB's
-breakpoint related behavior from what the user expects, a warning is
-printed when the breakpoint is first set and also when the breakpoint
-is hit.
+instructions from different source statements, thus it may happen that a
+breakpoint's address will be adjusted from one source statement to
+another. Since this adjustment may significantly alter GDB's breakpoint
+related behavior from what the user expects, a warning is printed when
+the breakpoint is first set and also when the breakpoint is hit.
A warning like the one below is printed when setting a breakpoint
that's been subject to address adjustment:
warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
Such warnings are printed both for user settable and GDB's internal
-breakpoints. If you see one of these warnings, you should verify that
-a breakpoint set at the adjusted address will have the desired affect.
-If not, the breakpoint in question may be removed and other breakpoints
-may be set which will have the desired behavior. E.g., it may be
-sufficient to place the breakpoint at a later instruction. A
-conditional breakpoint may also be useful in some cases to prevent the
-breakpoint from triggering too often.
+breakpoints. If you see one of these warnings, you should verify that a
+breakpoint set at the adjusted address will have the desired affect. If
+not, the breakpoint in question may be removed and other breakpoints may
+be set which will have the desired behavior. E.g., it may be sufficient
+to place the breakpoint at a later instruction. A conditional
+breakpoint may also be useful in some cases to prevent the breakpoint
+from triggering too often.
GDB will also issue a warning when stopping at one of these adjusted
breakpoints:
completes normally. In contrast, "stepping" means executing just one
more "step" of your program, where "step" may mean either one line of
source code, or one machine instruction (depending on what particular
-command you use). Either when continuing or when stepping, your
-program may stop even sooner, due to a breakpoint or a signal. (If it
-stops due to a signal, you may want to use `handle', or use `signal 0'
-to resume execution. *Note Signals: Signals.)
-
-`continue [IGNORE-COUNT]'
-`c [IGNORE-COUNT]'
-`fg [IGNORE-COUNT]'
+command you use). Either when continuing or when stepping, your program
+may stop even sooner, due to a breakpoint or a signal. (If it stops due
+to a signal, you may want to use 'handle', or use 'signal 0' to resume
+execution. *Note Signals: Signals.)
+
+'continue [IGNORE-COUNT]'
+'c [IGNORE-COUNT]'
+'fg [IGNORE-COUNT]'
Resume program execution, at the address where your program last
stopped; any breakpoints set at that address are bypassed. The
optional argument IGNORE-COUNT allows you to specify a further
- number of times to ignore a breakpoint at this location; its
- effect is like that of `ignore' (*note Break Conditions:
- Conditions.).
+ number of times to ignore a breakpoint at this location; its effect
+ is like that of 'ignore' (*note Break Conditions: Conditions.).
The argument IGNORE-COUNT is meaningful only when your program
stopped due to a breakpoint. At other times, the argument to
- `continue' is ignored.
+ 'continue' is ignored.
- The synonyms `c' and `fg' (for "foreground", as the debugged
- program is deemed to be the foreground program) are provided
- purely for convenience, and have exactly the same behavior as
- `continue'.
+ The synonyms 'c' and 'fg' (for "foreground", as the debugged
+ program is deemed to be the foreground program) are provided purely
+ for convenience, and have exactly the same behavior as 'continue'.
- To resume execution at a different place, you can use `return'
-(*note Returning from a Function: Returning.) to go back to the calling
-function; or `jump' (*note Continuing at a Different Address: Jumping.)
+ To resume execution at a different place, you can use 'return' (*note
+Returning from a Function: Returning.) to go back to the calling
+function; or 'jump' (*note Continuing at a Different Address: Jumping.)
to go to an arbitrary location in your program.
A typical technique for using stepping is to set a breakpoint (*note
and then step through the suspect area, examining the variables that are
interesting, until you see the problem happen.
-`step'
+'step'
Continue running your program until control reaches a different
source line, then stop it and return control to GDB. This command
- is abbreviated `s'.
+ is abbreviated 's'.
- _Warning:_ If you use the `step' command while control is
+ _Warning:_ If you use the 'step' command while control is
within a function that was compiled without debugging
information, execution proceeds until control reaches a
function that does have debugging information. Likewise, it
will not step into a function which is compiled without
debugging information. To step through functions without
- debugging information, use the `stepi' command, described
+ debugging information, use the 'stepi' command, described
below.
- The `step' command only stops at the first instruction of a source
+ The 'step' command only stops at the first instruction of a source
line. This prevents the multiple stops that could otherwise occur
- in `switch' statements, `for' loops, etc. `step' continues to
- stop if a function that has debugging information is called within
- the line. In other words, `step' _steps inside_ any functions
- called within the line.
+ in 'switch' statements, 'for' loops, etc. 'step' continues to stop
+ if a function that has debugging information is called within the
+ line. In other words, 'step' _steps inside_ any functions called
+ within the line.
- Also, the `step' command only enters a function if there is line
+ Also, the 'step' command only enters a function if there is line
number information for the function. Otherwise it acts like the
- `next' command. This avoids problems when using `cc -gl' on MIPS
- machines. Previously, `step' entered subroutines if there was any
+ 'next' command. This avoids problems when using 'cc -gl' on MIPS
+ machines. Previously, 'step' entered subroutines if there was any
debugging information about the routine.
-`step COUNT'
- Continue running as in `step', but do so COUNT times. If a
+'step COUNT'
+ Continue running as in 'step', but do so COUNT times. If a
breakpoint is reached, or a signal not related to stepping occurs
before COUNT steps, stepping stops right away.
-`next [COUNT]'
+'next [COUNT]'
Continue to the next source line in the current (innermost) stack
- frame. This is similar to `step', but function calls that appear
+ frame. This is similar to 'step', but function calls that appear
within the line of code are executed without stopping. Execution
- stops when control reaches a different line of code at the
- original stack level that was executing when you gave the `next'
- command. This command is abbreviated `n'.
+ stops when control reaches a different line of code at the original
+ stack level that was executing when you gave the 'next' command.
+ This command is abbreviated 'n'.
- An argument COUNT is a repeat count, as for `step'.
+ An argument COUNT is a repeat count, as for 'step'.
- The `next' command only stops at the first instruction of a source
+ The 'next' command only stops at the first instruction of a source
line. This prevents multiple stops that could otherwise occur in
- `switch' statements, `for' loops, etc.
+ 'switch' statements, 'for' loops, etc.
-`set step-mode'
-`set step-mode on'
- The `set step-mode on' command causes the `step' command to stop
- at the first instruction of a function which contains no debug line
+'set step-mode'
+'set step-mode on'
+ The 'set step-mode on' command causes the 'step' command to stop at
+ the first instruction of a function which contains no debug line
information rather than stepping over it.
This is useful in cases where you may be interested in inspecting
the machine instructions of a function which has no symbolic info
and do not want GDB to automatically skip over this function.
-`set step-mode off'
- Causes the `step' command to step over any functions which
- contains no debug information. This is the default.
+'set step-mode off'
+ Causes the 'step' command to step over any functions which contains
+ no debug information. This is the default.
-`show step-mode'
- Show whether GDB will stop in or step over functions without
- source line debug information.
+'show step-mode'
+ Show whether GDB will stop in or step over functions without source
+ line debug information.
-`finish'
+'finish'
Continue running until just after function in the selected stack
frame returns. Print the returned value (if any). This command
- can be abbreviated as `fin'.
+ can be abbreviated as 'fin'.
- Contrast this with the `return' command (*note Returning from a
+ Contrast this with the 'return' command (*note Returning from a
Function: Returning.).
-`until'
-`u'
+'until'
+'u'
Continue running until a source line past the current line, in the
current stack frame, is reached. This command is used to avoid
single stepping through a loop more than once. It is like the
- `next' command, except that when `until' encounters a jump, it
+ 'next' command, except that when 'until' encounters a jump, it
automatically continues execution until the program counter is
greater than the address of the jump.
This means that when you reach the end of a loop after single
- stepping though it, `until' makes your program continue execution
- until it exits the loop. In contrast, a `next' command at the end
+ stepping though it, 'until' makes your program continue execution
+ until it exits the loop. In contrast, a 'next' command at the end
of a loop simply steps back to the beginning of the loop, which
forces you to step through the next iteration.
- `until' always stops your program if it attempts to exit the
+ 'until' always stops your program if it attempts to exit the
current stack frame.
- `until' may produce somewhat counterintuitive results if the order
+ 'until' may produce somewhat counterintuitive results if the order
of machine code does not match the order of the source lines. For
- example, in the following excerpt from a debugging session, the `f'
- (`frame') command shows that execution is stopped at line `206';
- yet when we use `until', we get to line `195':
+ example, in the following excerpt from a debugging session, the 'f'
+ ('frame') command shows that execution is stopped at line '206';
+ yet when we use 'until', we get to line '195':
(gdb) f
#0 main (argc=4, argv=0xf7fffae8) at m4.c:206
This happened because, for execution efficiency, the compiler had
generated code for the loop closure test at the end, rather than
- the start, of the loop--even though the test in a C `for'-loop is
- written before the body of the loop. The `until' command appeared
+ the start, of the loop--even though the test in a C 'for'-loop is
+ written before the body of the loop. The 'until' command appeared
to step back to the beginning of the loop when it advanced to this
expression; however, it has not really gone to an earlier
statement--not in terms of the actual machine code.
- `until' with no argument works by means of single instruction
- stepping, and hence is slower than `until' with an argument.
-
-`until LOCATION'
-`u LOCATION'
- Continue running your program until either the specified location
- is reached, or the current stack frame returns. LOCATION is any of
- the forms described in *Note Specify Location::. This form of the
- command uses temporary breakpoints, and hence is quicker than
- `until' without an argument. The specified location is actually
- reached only if it is in the current frame. This implies that
- `until' can be used to skip over recursive function invocations.
- For instance in the code below, if the current location is line
- `96', issuing `until 99' will execute the program up to line `99'
- in the same invocation of factorial, i.e., after the inner
- invocations have returned.
+ 'until' with no argument works by means of single instruction
+ stepping, and hence is slower than 'until' with an argument.
+
+'until LOCATION'
+'u LOCATION'
+ Continue running your program until either the specified LOCATION
+ is reached, or the current stack frame returns. The location is
+ any of the forms described in *note Specify Location::. This form
+ of the command uses temporary breakpoints, and hence is quicker
+ than 'until' without an argument. The specified location is
+ actually reached only if it is in the current frame. This implies
+ that 'until' can be used to skip over recursive function
+ invocations. For instance in the code below, if the current
+ location is line '96', issuing 'until 99' will execute the program
+ up to line '99' in the same invocation of factorial, i.e., after
+ the inner invocations have returned.
94 int factorial (int value)
95 {
99 return (value);
100 }
-`advance LOCATION'
- Continue running the program up to the given LOCATION. An
- argument is required, which should be of one of the forms
- described in *Note Specify Location::. Execution will also stop
- upon exit from the current stack frame. This command is similar
- to `until', but `advance' will not skip over recursive function
- calls, and the target location doesn't have to be in the same
- frame as the current one.
-
-`stepi'
-`stepi ARG'
-`si'
+'advance LOCATION'
+ Continue running the program up to the given LOCATION. An argument
+ is required, which should be of one of the forms described in *note
+ Specify Location::. Execution will also stop upon exit from the
+ current stack frame. This command is similar to 'until', but
+ 'advance' will not skip over recursive function calls, and the
+ target location doesn't have to be in the same frame as the current
+ one.
+
+'stepi'
+'stepi ARG'
+'si'
Execute one machine instruction, then stop and return to the
debugger.
- It is often useful to do `display/i $pc' when stepping by machine
+ It is often useful to do 'display/i $pc' when stepping by machine
instructions. This makes GDB automatically display the next
instruction to be executed, each time your program stops. *Note
Automatic Display: Auto Display.
- An argument is a repeat count, as in `step'.
+ An argument is a repeat count, as in 'step'.
-`nexti'
-`nexti ARG'
-`ni'
+'nexti'
+'nexti ARG'
+'ni'
Execute one machine instruction, but if it is a function call,
proceed until the function returns.
- An argument is a repeat count, as in `next'.
+ An argument is a repeat count, as in 'next'.
+
+ By default, and if available, GDB makes use of target-assisted "range
+stepping". In other words, whenever you use a stepping command (e.g.,
+'step', 'next'), GDB tells the target to step the corresponding range of
+instruction addresses instead of issuing multiple single-steps. This
+speeds up line stepping, particularly for remote targets. Ideally,
+there should be no reason you would want to turn range stepping off.
+However, it's possible that a bug in the debug info, a bug in the remote
+stub (for remote targets), or even a bug in GDB could make line stepping
+behave incorrectly when target-assisted range stepping is enabled. You
+can use the following command to turn off range stepping if necessary:
+
+'set range-stepping'
+'show range-stepping'
+ Control whether range stepping is enabled.
+
+ If 'on', and the target supports it, GDB tells the target to step a
+ range of addresses itself, instead of issuing multiple
+ single-steps. If 'off', GDB always issues single-steps, even if
+ range stepping is supported by the target. The default is 'on'.
\1f
File: gdb.info, Node: Skipping Over Functions and Files, Next: Signals, Prev: Continuing and Stepping, Up: Stopping
=====================================
The program you are debugging may contain some functions which are
-uninteresting to debug. The `skip' comand lets you tell GDB to skip a
+uninteresting to debug. The 'skip' comand lets you tell GDB to skip a
function or all functions in a file when stepping.
For example, consider the following C function:
104 bar(boring());
105 }
-Suppose you wish to step into the functions `foo' and `bar', but you
-are not interested in stepping through `boring'. If you run `step' at
-line 103, you'll enter `boring()', but if you run `next', you'll step
-over both `foo' and `boring'!
+Suppose you wish to step into the functions 'foo' and 'bar', but you are
+not interested in stepping through 'boring'. If you run 'step' at line
+103, you'll enter 'boring()', but if you run 'next', you'll step over
+both 'foo' and 'boring'!
- One solution is to `step' into `boring' and use the `finish' command
-to immediately exit it. But this can become tedious if `boring' is
+ One solution is to 'step' into 'boring' and use the 'finish' command
+to immediately exit it. But this can become tedious if 'boring' is
called from many places.
- A more flexible solution is to execute `skip boring'. This instructs
-GDB never to step into `boring'. Now when you execute `step' at line
-103, you'll step over `boring' and directly into `foo'.
+ A more flexible solution is to execute 'skip boring'. This instructs
+GDB never to step into 'boring'. Now when you execute 'step' at line
+103, you'll step over 'boring' and directly into 'foo'.
You can also instruct GDB to skip all functions in a file, with, for
-example, `skip file boring.c'.
+example, 'skip file boring.c'.
-`skip [LINESPEC]'
-`skip function [LINESPEC]'
+'skip [LINESPEC]'
+'skip function [LINESPEC]'
After running this command, the function named by LINESPEC or the
- function containing the line named by LINESPEC will be skipped
- over when stepping. *Note Specify Location::.
+ function containing the line named by LINESPEC will be skipped over
+ when stepping. *Note Specify Location::.
If you do not specify LINESPEC, the function you're currently
debugging will be skipped.
- (If you have a function called `file' that you want to skip, use
- `skip function file'.)
+ (If you have a function called 'file' that you want to skip, use
+ 'skip function file'.)
-`skip file [FILENAME]'
+'skip file [FILENAME]'
After running this command, any function whose source lives in
FILENAME will be skipped over when stepping.
- If you do not specify FILENAME, functions whose source lives in
- the file you're currently debugging will be skipped.
+ If you do not specify FILENAME, functions whose source lives in the
+ file you're currently debugging will be skipped.
Skips can be listed, deleted, disabled, and enabled, much like
breakpoints. These are the commands for managing your list of skips:
-`info skip [RANGE]'
+'info skip [RANGE]'
Print details about the specified skip(s). If RANGE is not
- specified, print a table with details about all functions and
- files marked for skipping. `info skip' prints the following
- information about each skip:
+ specified, print a table with details about all functions and files
+ marked for skipping. 'info skip' prints the following information
+ about each skip:
- _Identifier_
+ _Identifier_
A number identifying this skip.
-
- _Type_
- The type of this skip, either `function' or `file'.
-
- _Enabled or Disabled_
- Enabled skips are marked with `y'. Disabled skips are marked
- with `n'.
-
- _Address_
+ _Type_
+ The type of this skip, either 'function' or 'file'.
+ _Enabled or Disabled_
+ Enabled skips are marked with 'y'. Disabled skips are marked
+ with 'n'.
+ _Address_
For function skips, this column indicates the address in
memory of the function being skipped. If you've set a
function skip on a function which has not yet been loaded,
- this field will contain
`<PENDING>'. Once a shared library
- which has the function is loaded, `info skip' will show the
+ this field will contain
'<PENDING>'. Once a shared library
+ which has the function is loaded, 'info skip' will show the
function's address here.
-
- _What_
+ _What_
For file skips, this field contains the filename being
skipped. For functions skips, this field contains the
function name and its line number in the file where it is
defined.
-`skip delete [RANGE]'
+'skip delete [RANGE]'
Delete the specified skip(s). If RANGE is not specified, delete
all skips.
-`skip enable [RANGE]'
+'skip enable [RANGE]'
Enable the specified skip(s). If RANGE is not specified, enable
all skips.
-`skip disable [RANGE]'
+'skip disable [RANGE]'
Disable the specified skip(s). If RANGE is not specified, disable
all skips.
-
\1f
File: gdb.info, Node: Signals, Next: Thread Stops, Prev: Skipping Over Functions and Files, Up: Stopping
A signal is an asynchronous event that can happen in a program. The
operating system defines the possible kinds of signals, and gives each
-kind a name and a number. For example, in Unix `SIGINT' is the signal
-a program gets when you type an interrupt character (often `Ctrl-c');
-`SIGSEGV' is the signal a program gets from referencing a place in
-memory far away from all the areas in use; `SIGALRM' occurs when the
+kind a name and a number. For example, in Unix 'SIGINT' is the signal a
+program gets when you type an interrupt character (often 'Ctrl-c');
+'SIGSEGV' is the signal a program gets from referencing a place in
+memory far away from all the areas in use; 'SIGALRM' occurs when the
alarm clock timer goes off (which happens only if your program has
requested an alarm).
- Some signals, including `SIGALRM', are a normal part of the
-functioning of your program. Others, such as `SIGSEGV', indicate
+ Some signals, including 'SIGALRM', are a normal part of the
+functioning of your program. Others, such as 'SIGSEGV', indicate
errors; these signals are "fatal" (they kill your program immediately)
-if the program has not specified in advance some other way to handle
-the signal. `SIGINT' does not indicate an error in your program, but
-it is normally fatal so it can carry out the purpose of the interrupt:
-to kill the program.
+if the program has not specified in advance some other way to handle the
+signal. 'SIGINT' does not indicate an error in your program, but it is
+normally fatal so it can carry out the purpose of the interrupt: to kill
+the program.
GDB has the ability to detect any occurrence of a signal in your
program. You can tell GDB in advance what to do for each kind of
signal.
Normally, GDB is set up to let the non-erroneous signals like
-`SIGALRM' be silently passed to your program (so as not to interfere
+'SIGALRM' be silently passed to your program (so as not to interfere
with their role in the program's functioning) but to stop your program
immediately whenever an error signal happens. You can change these
-settings with the `handle' command.
+settings with the 'handle' command.
-`info signals'
-`info handle'
- Print a table of all the kinds of signals and how GDB has been
- told to handle each one. You can use this to see the signal
- numbers of all the defined types of signals.
+'info signals'
+'info handle'
+ Print a table of all the kinds of signals and how GDB has been told
+ to handle each one. You can use this to see the signal numbers of
+ all the defined types of signals.
-`info signals SIG'
+'info signals SIG'
Similar, but print information only about the specified signal
number.
- `info handle' is an alias for `info signals'.
+ 'info handle' is an alias for 'info signals'.
+
+'catch signal [SIGNAL... | 'all']'
+ Set a catchpoint for the indicated signals. *Note Set
+ Catchpoints::, for details about this command.
-`handle SIGNAL [KEYWORDS...]'
- Change the way GDB handles signal SIGNAL. SIGNAL can be the
- number of a signal or its name (with or without the `SIG' at the
- beginning); a list of signal numbers of the form `LOW-HIGH'; or
- the word `all', meaning all the known signals. Optional arguments
+'handle SIGNAL [KEYWORDS...]'
+ Change the way GDB handles signal SIGNAL. The SIGNAL can be the
+ number of a signal or its name (with or without the 'SIG' at the
+ beginning); a list of signal numbers of the form 'LOW-HIGH'; or the
+ word 'all', meaning all the known signals. Optional arguments
KEYWORDS, described below, say what change to make.
- The keywords allowed by the `handle' command can be abbreviated.
+ The keywords allowed by the 'handle' command can be abbreviated.
Their full names are:
-`nostop'
+'nostop'
GDB should not stop your program when this signal happens. It may
still print a message telling you that the signal has come in.
-`stop'
+'stop'
GDB should stop your program when this signal happens. This
- implies the `print' keyword as well.
+ implies the 'print' keyword as well.
-`print'
+'print'
GDB should print a message when this signal happens.
-`noprint'
+'noprint'
GDB should not mention the occurrence of the signal at all. This
- implies the `nostop' keyword as well.
+ implies the 'nostop' keyword as well.
-`pass'
-`noignore'
+'pass'
+'noignore'
GDB should allow your program to see this signal; your program can
handle the signal, or else it may terminate if the signal is fatal
- and not handled. `pass' and `noignore' are synonyms.
+ and not handled. 'pass' and 'noignore' are synonyms.
-`nopass'
-`ignore'
- GDB should not allow your program to see this signal. `nopass'
- and `ignore' are synonyms.
+'nopass'
+'ignore'
+ GDB should not allow your program to see this signal. 'nopass' and
+ 'ignore' are synonyms.
When a signal stops your program, the signal is not visible to the
program until you continue. Your program sees the signal then, if
-`pass' is in effect for the signal in question _at that time_. In
-other words, after GDB reports a signal, you can use the `handle'
-command with `pass' or `nopass' to control whether your program sees
-that signal when you continue.
+'pass' is in effect for the signal in question _at that time_. In other
+words, after GDB reports a signal, you can use the 'handle' command with
+'pass' or 'nopass' to control whether your program sees that signal when
+you continue.
- The default is set to `nostop', `noprint', `pass' for non-erroneous
-signals such as `SIGALRM', `SIGWINCH' and `SIGCHLD', and to `stop',
-`print', `pass' for the erroneous signals.
+ The default is set to 'nostop', 'noprint', 'pass' for non-erroneous
+signals such as 'SIGALRM', 'SIGWINCH' and 'SIGCHLD', and to 'stop',
+'print', 'pass' for the erroneous signals.
- You can also use the `signal' command to prevent your program from
+ You can also use the 'signal' command to prevent your program from
seeing a signal, or cause it to see a signal it normally would not see,
or to give it any signal at any time. For example, if your program
stopped due to some sort of memory reference error, you might store
correct values into the erroneous variables and continue, hoping to see
more execution; but your program would probably terminate immediately as
a result of the fatal signal once it saw the signal. To prevent this,
-you can continue with `signal 0'. *Note Giving your Program a Signal:
+you can continue with 'signal 0'. *Note Giving your Program a Signal:
Signaling.
On some targets, GDB can inspect extra signal information associated
with the intercepted signal, before it is actually delivered to the
-program being debugged. This information is exported by the
-convenience variable `$_siginfo', and consists of data that is passed
-by the kernel to the signal handler at the time of the receipt of a
-signal. The data type of the information itself is target dependent.
-You can see the data type using the `ptype $_siginfo' command. On Unix
-systems, it typically corresponds to the standard `siginfo_t' type, as
-defined in the `signal.h' system header.
+program being debugged. This information is exported by the convenience
+variable '$_siginfo', and consists of data that is passed by the kernel
+to the signal handler at the time of the receipt of a signal. The data
+type of the information itself is target dependent. You can see the
+data type using the 'ptype $_siginfo' command. On Unix systems, it
+typically corresponds to the standard 'siginfo_t' type, as defined in
+the 'signal.h' system header.
Here's an example, on a GNU/Linux system, printing the stray
referenced address that raised a segmentation fault.
(gdb) p $_siginfo._sifields._sigfault.si_addr
$1 = (void *) 0x7ffff7ff7000
- Depending on target support, `$_siginfo' may also be writable.
+ Depending on target support, '$_siginfo' may also be writable.
\1f
File: gdb.info, Node: Thread Stops, Prev: Signals, Up: Stopping
Programs with Multiple Threads: Threads.). There are two modes of
controlling execution of your program within the debugger. In the
default mode, referred to as "all-stop mode", when any thread in your
-program stops (for example, at a breakpoint or while being stepped),
-all other threads in the program are also stopped by GDB. On some
-targets, GDB also supports "non-stop mode", in which other threads can
-continue to run freely while you examine the stopped thread in the
-debugger.
+program stops (for example, at a breakpoint or while being stepped), all
+other threads in the program are also stopped by GDB. On some targets,
+GDB also supports "non-stop mode", in which other threads can continue
+to run freely while you examine the stopped thread in the debugger.
* Menu:
Conversely, whenever you restart the program, _all_ threads start
executing. _This is true even when single-stepping_ with commands like
-`step' or `next'.
+'step' or 'next'.
- In particular, GDB cannot single-step all threads in lockstep.
-Since thread scheduling is up to your debugging target's operating
-system (not controlled by GDB), other threads may execute more than one
-statement while the current thread completes a single step. Moreover,
-in general other threads stop in the middle of a statement, rather than
-at a clean statement boundary, when the program stops.
+ In particular, GDB cannot single-step all threads in lockstep. Since
+thread scheduling is up to your debugging target's operating system (not
+controlled by GDB), other threads may execute more than one statement
+while the current thread completes a single step. Moreover, in general
+other threads stop in the middle of a statement, rather than at a clean
+statement boundary, when the program stops.
You might even find your program stopped in another thread after
continuing or even single-stepping. This happens whenever some other
Whenever GDB stops your program, due to a breakpoint or a signal, it
automatically selects the thread where that breakpoint or signal
happened. GDB alerts you to the context switch with a message such as
-`[Switching to Thread N]' to identify the thread.
+'[Switching to Thread N]' to identify the thread.
- On some OSes, you can modify GDB's default behavior by locking the
-OS scheduler to allow only a single thread to run.
+ On some OSes, you can modify GDB's default behavior by locking the OS
+scheduler to allow only a single thread to run.
-`set scheduler-locking MODE'
- Set the scheduler locking mode. If it is `off', then there is no
- locking and any thread may run at any time. If `on', then only the
- current thread may run when the inferior is resumed. The `step'
+'set scheduler-locking MODE'
+ Set the scheduler locking mode. If it is 'off', then there is no
+ locking and any thread may run at any time. If 'on', then only the
+ current thread may run when the inferior is resumed. The 'step'
mode optimizes for single-stepping; it prevents other threads from
preempting the current thread while you are stepping, so that the
focus of debugging does not change unexpectedly. Other threads
- only rarely (or never) get a chance to run when you step. They
- are more likely to run when you `next' over a function call, and
- they are completely free to run when you use commands like
- `continue', `until', or `finish'. However, unless another thread
- hits a breakpoint during its timeslice, GDB does not change the
- current thread away from the thread that you are debugging.
-
-`show scheduler-locking'
+ only rarely (or never) get a chance to run when you step. They are
+ more likely to run when you 'next' over a function call, and they
+ are completely free to run when you use commands like 'continue',
+ 'until', or 'finish'. However, unless another thread hits a
+ breakpoint during its timeslice, GDB does not change the current
+ thread away from the thread that you are debugging.
+
+'show scheduler-locking'
Display the current scheduler locking mode.
By default, when you issue one of the execution commands such as
-`continue', `next' or `step', GDB allows only threads of the current
-inferior to run. For example, if GDB is attached to two inferiors,
-each with two threads, the `continue' command resumes only the two
-threads of the current inferior. This is useful, for example, when you
-debug a program that forks and you want to hold the parent stopped (so
-that, for instance, it doesn't run to exit), while you debug the child.
-In other situations, you may not be interested in inspecting the
-current state of any of the processes GDB is attached to, and you may
-want to resume them all until some breakpoint is hit. In the latter
-case, you can instruct GDB to allow all threads of all the inferiors to
-run with the `set schedule-multiple' command.
-
-`set schedule-multiple'
+'continue', 'next' or 'step', GDB allows only threads of the current
+inferior to run. For example, if GDB is attached to two inferiors, each
+with two threads, the 'continue' command resumes only the two threads of
+the current inferior. This is useful, for example, when you debug a
+program that forks and you want to hold the parent stopped (so that, for
+instance, it doesn't run to exit), while you debug the child. In other
+situations, you may not be interested in inspecting the current state of
+any of the processes GDB is attached to, and you may want to resume them
+all until some breakpoint is hit. In the latter case, you can instruct
+GDB to allow all threads of all the inferiors to run with the 'set schedule-multiple'
+command.
+
+'set schedule-multiple'
Set the mode for allowing threads of multiple processes to be
- resumed when an execution command is issued. When `on', all
- threads of all processes are allowed to run. When `off', only the
- threads of the current process are resumed. The default is `off'.
- The `scheduler-locking' mode takes precedence when set to `on',
- or while you are stepping and set to `step'.
+ resumed when an execution command is issued. When 'on', all
+ threads of all processes are allowed to run. When 'off', only the
+ threads of the current process are resumed. The default is 'off'.
+ The 'scheduler-locking' mode takes precedence when set to 'on', or
+ while you are stepping and set to 'step'.
-`show schedule-multiple'
+'show schedule-multiple'
Display the current mode for resuming the execution of threads of
multiple processes.
For some multi-threaded targets, GDB supports an optional mode of
operation in which you can examine stopped program threads in the
-debugger while other threads continue to execute freely. This
-minimizes intrusion when debugging live systems, such as programs where
-some threads have real-time constraints or must continue to respond to
+debugger while other threads continue to execute freely. This minimizes
+intrusion when debugging live systems, such as programs where some
+threads have real-time constraints or must continue to respond to
external events. This is referred to as "non-stop" mode.
In non-stop mode, when a thread stops to report a debugging event,
_only_ that thread is stopped; GDB does not stop other threads as well,
in contrast to the all-stop mode behavior. Additionally, execution
-commands such as `continue' and `step' apply by default only to the
+commands such as 'continue' and 'step' apply by default only to the
current thread in non-stop mode, rather than all threads as in all-stop
mode. This allows you to control threads explicitly in ways that are
not possible in all-stop mode -- for example, stepping one thread while
To enter non-stop mode, use this sequence of commands before you run
or attach to your program:
- # Enable the async interface.
- set target-async 1
-
# If using the CLI, pagination breaks non-stop.
set pagination off
You can use these commands to manipulate the non-stop mode setting:
-`set non-stop on'
+'set non-stop on'
Enable selection of non-stop mode.
-
-`set non-stop off'
- Disable selection of non-stop mode.
-
-`show non-stop'
+'set non-stop off'
+ Disable selection of non-stop mode.
+'show non-stop'
Show the current non-stop enablement setting.
Note these commands only reflect whether non-stop mode is enabled,
not whether the currently-executing program is being run in non-stop
-mode. In particular, the `set non-stop' preference is only consulted
+mode. In particular, the 'set non-stop' preference is only consulted
when GDB starts or connects to the target program, and it is generally
not possible to switch modes once debugging has started. Furthermore,
since not all targets support non-stop mode, even when you have enabled
non-stop mode, GDB may still fall back to all-stop operation by default.
In non-stop mode, all execution commands apply only to the current
-thread by default. That is, `continue' only continues one thread. To
-continue all threads, issue `continue -a' or `c -a'.
+thread by default. That is, 'continue' only continues one thread. To
+continue all threads, issue 'continue -a' or 'c -a'.
You can use GDB's background execution commands (*note Background
-Execution::) to run some threads in the background while you continue
-to examine or step others from GDB. The MI execution commands (*note
+Execution::) to run some threads in the background while you continue to
+examine or step others from GDB. The MI execution commands (*note
GDB/MI Program Execution::) are always executed asynchronously in
non-stop mode.
- Suspending execution is done with the `interrupt' command when
-running in the background, or `Ctrl-c' during foreground execution. In
+ Suspending execution is done with the 'interrupt' command when
+running in the background, or 'Ctrl-c' during foreground execution. In
all-stop mode, this stops the whole process; but in non-stop mode the
interrupt applies only to the current thread. To stop the whole
-program, use `interrupt -a'.
+program, use 'interrupt -a'.
- Other execution commands do not currently support the `-a' option.
+ Other execution commands do not currently support the '-a' option.
In non-stop mode, when a thread stops, GDB doesn't automatically make
that thread current, as it does in all-stop mode. This is because the
-thread stop notifications are asynchronous with respect to GDB's
-command interpreter, and it would be confusing if GDB unexpectedly
-changed to a different thread just as you entered a command to operate
-on the previously current thread.
+thread stop notifications are asynchronous with respect to GDB's command
+interpreter, and it would be confusing if GDB unexpectedly changed to a
+different thread just as you entered a command to operate on the
+previously current thread.
\1f
File: gdb.info, Node: Background Execution, Next: Thread-Specific Breakpoints, Prev: Non-Stop Mode, Up: Thread Stops
5.5.3 Background Execution
--------------------------
-GDB's execution commands have two variants: the normal foreground
+GDB's execution commands have two variants: the normal foreground
(synchronous) behavior, and a background (asynchronous) behavior. In
foreground execution, GDB waits for the program to report that some
thread has stopped before prompting for another command. In background
execution, GDB immediately gives a command prompt so that you can issue
other commands while your program runs.
- You need to explicitly enable asynchronous mode before you can use
-background execution commands. You can use these commands to
-manipulate the asynchronous mode setting:
-
-`set target-async on'
- Enable asynchronous mode.
-
-`set target-async off'
- Disable asynchronous mode.
-
-`show target-async'
- Show the current target-async setting.
-
- If the target doesn't support async mode, GDB issues an error
-message if you attempt to use the background execution commands.
+ If the target doesn't support async mode, GDB issues an error message
+if you attempt to use the background execution commands.
- To specify background execution, add a `&' to the command. For
-example, the background form of the `continue' command is `continue&',
-or just `c&'. The execution commands that accept background execution
+ To specify background execution, add a '&' to the command. For
+example, the background form of the 'continue' command is 'continue&',
+or just 'c&'. The execution commands that accept background execution
are:
-`run'
+'run'
*Note Starting your Program: Starting.
-`attach'
+'attach'
*Note Debugging an Already-running Process: Attach.
-`step'
+'step'
*Note step: Continuing and Stepping.
-`stepi'
+'stepi'
*Note stepi: Continuing and Stepping.
-`next'
+'next'
*Note next: Continuing and Stepping.
-`nexti'
+'nexti'
*Note nexti: Continuing and Stepping.
-`continue'
+'continue'
*Note continue: Continuing and Stepping.
-`finish'
+'finish'
*Note finish: Continuing and Stepping.
-`until'
+'until'
*Note until: Continuing and Stepping.
-
Background execution is especially useful in conjunction with
-non-stop mode for debugging programs with multiple threads; see *Note
-Non-Stop Mode::. However, you can also use these commands in the
-normal all-stop mode with the restriction that you cannot issue another
-execution command until the previous one finishes. Examples of
-commands that are valid in all-stop mode while the program is running
-include `help' and `info break'.
+non-stop mode for debugging programs with multiple threads; see *note
+Non-Stop Mode::. However, you can also use these commands in the normal
+all-stop mode with the restriction that you cannot issue another
+execution command until the previous one finishes. Examples of commands
+that are valid in all-stop mode while the program is running include
+'help' and 'info break'.
You can interrupt your program while it is running in the background
-by using the `interrupt' command.
+by using the 'interrupt' command.
+
+'interrupt'
+'interrupt -a'
-`interrupt'
-`interrupt -a'
Suspend execution of the running program. In all-stop mode,
- `interrupt' stops the whole process, but in non-stop mode, it stops
+ 'interrupt' stops the whole process, but in non-stop mode, it stops
only the current thread. To stop the whole program in non-stop
- mode, use `interrupt -a'.
+ mode, use 'interrupt -a'.
\1f
File: gdb.info, Node: Thread-Specific Breakpoints, Next: Interrupted System Calls, Prev: Background Execution, Up: Thread Stops
Multiple Threads: Threads.), you can choose whether to set breakpoints
on all threads, or on a particular thread.
-`break LINESPEC thread THREADNO'
-`break LINESPEC thread THREADNO if ...'
+'break LINESPEC thread THREADNO'
+'break LINESPEC thread THREADNO if ...'
LINESPEC specifies source lines; there are several ways of writing
them (*note Specify Location::), but the effect is always to
specify some source line.
- Use the qualifier `thread THREADNO' with a breakpoint command to
+ Use the qualifier 'thread THREADNO' with a breakpoint command to
specify that you only want GDB to stop the program when a
- particular thread reaches this breakpoint. THREADNO is one of the
- numeric thread identifiers assigned by GDB, shown in the first
- column of the `info threads' display.
+ particular thread reaches this breakpoint. The THREADNO specifier
+ is one of the numeric thread identifiers assigned by GDB, shown in
+ the first column of the 'info threads' display.
- If you do not specify `thread THREADNO' when you set a breakpoint,
+ If you do not specify 'thread THREADNO' when you set a breakpoint,
the breakpoint applies to _all_ threads of your program.
- You can use the `thread' qualifier on conditional breakpoints as
- well; in this case, place `thread THREADNO' before or after the
+ You can use the 'thread' qualifier on conditional breakpoints as
+ well; in this case, place 'thread THREADNO' before or after the
breakpoint condition, like this:
(gdb) break frik.c:13 thread 28 if bartab > lim
+ Thread-specific breakpoints are automatically deleted when GDB
+detects the corresponding thread is no longer in the thread list. For
+example:
+
+ (gdb) c
+ Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
+
+ There are several ways for a thread to disappear, such as a regular
+thread exit, but also when you detach from the process with the 'detach'
+command (*note Debugging an Already-running Process: Attach.), or if GDB
+loses the remote connection (*note Remote Debugging::), etc. Note that
+with some targets, GDB is only able to detect a thread has exited when
+the user explictly asks for the thread list with the 'info threads'
+command.
\1f
File: gdb.info, Node: Interrupted System Calls, Next: Observer Mode, Prev: Thread-Specific Breakpoints, Up: Thread Stops
sleep (10);
- The call to `sleep' will return early if a different thread stops at
+ The call to 'sleep' will return early if a different thread stops at
a breakpoint or for some other reason.
Instead, write this:
unslept = sleep (unslept);
A system call is allowed to return early, so the system is still
-conforming to its specification. But GDB does cause your
-multi-threaded program to behave differently than it would without GDB.
+conforming to its specification. But GDB does cause your multi-threaded
+program to behave differently than it would without GDB.
Also, GDB uses internal breakpoints in the thread library to monitor
certain events such as thread creation and thread destruction. When
writing memory, inserting breakpoints, etc. These operate at a low
level, intercepting operations from all commands.
- When all of these are set to `off', then GDB is said to be "observer
-mode". As a convenience, the variable `observer' can be set to disable
+ When all of these are set to 'off', then GDB is said to be "observer
+mode". As a convenience, the variable 'observer' can be set to disable
these, plus enable non-stop mode.
Note that GDB will not prevent you from making nonsensical
-combinations of these settings. For instance, if you have enabled
-`may-insert-breakpoints' but disabled `may-write-memory', then
+combinations of these settings. For instance, if you have enabled
+'may-insert-breakpoints' but disabled 'may-write-memory', then
breakpoints that work by writing trap instructions into the code stream
will still not be able to be placed.
-`set observer on'
-`set observer off'
- When set to `on', this disables all the permission variables below
- (except for `insert-fast-tracepoints'), plus enables non-stop
- debugging. Setting this to `off' switches back to normal
+'set observer on'
+'set observer off'
+ When set to 'on', this disables all the permission variables below
+ (except for 'insert-fast-tracepoints'), plus enables non-stop
+ debugging. Setting this to 'off' switches back to normal
debugging, though remaining in non-stop mode.
-`show observer'
+'show observer'
Show whether observer mode is on or off.
-`set may-write-registers on'
-`set may-write-registers off'
+'set may-write-registers on'
+'set may-write-registers off'
This controls whether GDB will attempt to alter the values of
- registers, such as with assignment expressions in `print', or the
- `jump' command. It defaults to `on'.
+ registers, such as with assignment expressions in 'print', or the
+ 'jump' command. It defaults to 'on'.
-`show may-write-registers'
+'show may-write-registers'
Show the current permission to write registers.
-`set may-write-memory on'
-`set may-write-memory off'
+'set may-write-memory on'
+'set may-write-memory off'
This controls whether GDB will attempt to alter the contents of
- memory, such as with assignment expressions in `print'. It
- defaults to `on'.
+ memory, such as with assignment expressions in 'print'. It
+ defaults to 'on'.
-`show may-write-memory'
+'show may-write-memory'
Show the current permission to write memory.
-`set may-insert-breakpoints on'
-`set may-insert-breakpoints off'
- This controls whether GDB will attempt to insert breakpoints.
- This affects all breakpoints, including internal breakpoints
- defined by GDB. It defaults to `on'.
+'set may-insert-breakpoints on'
+'set may-insert-breakpoints off'
+ This controls whether GDB will attempt to insert breakpoints. This
+ affects all breakpoints, including internal breakpoints defined by
+ GDB. It defaults to 'on'.
-`show may-insert-breakpoints'
+'show may-insert-breakpoints'
Show the current permission to insert breakpoints.
-`set may-insert-tracepoints on'
-`set may-insert-tracepoints off'
+'set may-insert-tracepoints on'
+'set may-insert-tracepoints off'
This controls whether GDB will attempt to insert (regular)
tracepoints at the beginning of a tracing experiment. It affects
- only non-fast tracepoints, fast tracepoints being under the
- control of `may-insert-fast-tracepoints'. It defaults to `on'.
+ only non-fast tracepoints, fast tracepoints being under the control
+ of 'may-insert-fast-tracepoints'. It defaults to 'on'.
-`show may-insert-tracepoints'
+'show may-insert-tracepoints'
Show the current permission to insert tracepoints.
-`set may-insert-fast-tracepoints on'
-`set may-insert-fast-tracepoints off'
+'set may-insert-fast-tracepoints on'
+'set may-insert-fast-tracepoints off'
This controls whether GDB will attempt to insert fast tracepoints
at the beginning of a tracing experiment. It affects only fast
- tracepoints, regular (non-fast) tracepoints being under the
- control of `may-insert-tracepoints'. It defaults to `on'.
+ tracepoints, regular (non-fast) tracepoints being under the control
+ of 'may-insert-tracepoints'. It defaults to 'on'.
-`show may-insert-fast-tracepoints'
+'show may-insert-fast-tracepoints'
Show the current permission to insert fast tracepoints.
-`set may-interrupt on'
-`set may-interrupt off'
- This controls whether GDB will attempt to interrupt or stop
- program execution. When this variable is `off', the `interrupt'
- command will have no effect, nor will `Ctrl-c'. It defaults to
- `on'.
+'set may-interrupt on'
+'set may-interrupt off'
+ This controls whether GDB will attempt to interrupt or stop program
+ execution. When this variable is 'off', the 'interrupt' command
+ will have no effect, nor will 'Ctrl-c'. It defaults to 'on'.
-`show may-interrupt'
+'show may-interrupt'
Show the current permission to interrupt or stop the program.
-
\1f
File: gdb.info, Node: Reverse Execution, Next: Process Record and Replay, Prev: Stopping, Up: Top
A target environment that supports reverse execution should be able
to "undo" the changes in machine state that have taken place as the
-program was executing normally. Variables, registers etc. should
-revert to their previous values. Obviously this requires a great deal
-of sophistication on the part of the target environment; not all target
+program was executing normally. Variables, registers etc. should revert
+to their previous values. Obviously this requires a great deal of
+sophistication on the part of the target environment; not all target
environments can support reverse execution.
When a program is executed in reverse, the instructions that have
If you are debugging in a target environment that supports reverse
execution, GDB provides the following commands.
-`reverse-continue [IGNORE-COUNT]'
-`rc [IGNORE-COUNT]'
+'reverse-continue [IGNORE-COUNT]'
+'rc [IGNORE-COUNT]'
Beginning at the point where your program last stopped, start
executing in reverse. Reverse execution will stop for breakpoints
and synchronous exceptions (signals), just like normal execution.
Behavior of asynchronous signals depends on the target environment.
-`reverse-step [COUNT]'
+'reverse-step [COUNT]'
Run the program backward until control reaches the start of a
different source line; then stop it, and return control to GDB.
- Like the `step' command, `reverse-step' will only stop at the
+ Like the 'step' command, 'reverse-step' will only stop at the
beginning of a source line. It "un-executes" the previously
executed source line. If the previous source line included calls
- to debuggable functions, `reverse-step' will step (backward) into
+ to debuggable functions, 'reverse-step' will step (backward) into
the called function, stopping at the beginning of the _last_
statement in the called function (typically a return statement).
- Also, as with the `step' command, if non-debuggable functions are
- called, `reverse-step' will run thru them backward without
+ Also, as with the 'step' command, if non-debuggable functions are
+ called, 'reverse-step' will run thru them backward without
stopping.
-`reverse-stepi [COUNT]'
+'reverse-stepi [COUNT]'
Reverse-execute one machine instruction. Note that the instruction
to be reverse-executed is _not_ the one pointed to by the program
counter, but the instruction executed prior to that one. For
- instance, if the last instruction was a jump, `reverse-stepi' will
+ instance, if the last instruction was a jump, 'reverse-stepi' will
take you back from the destination of the jump to the jump
instruction itself.
-`reverse-next [COUNT]'
+'reverse-next [COUNT]'
Run backward to the beginning of the previous line executed in the
current (innermost) stack frame. If the line contains function
calls, they will be "un-executed" without stopping. Starting from
- the first line of a function, `reverse-next' will take you back to
- the caller of that function, _before_ the function was called,
- just as the normal `next' command would take you from the last
- line of a function back to its return to its caller (2).
+ the first line of a function, 'reverse-next' will take you back to
+ the caller of that function, _before_ the function was called, just
+ as the normal 'next' command would take you from the last line of a
+ function back to its return to its caller (2).
-`reverse-nexti [COUNT]'
- Like `nexti', `reverse-nexti' executes a single instruction in
+'reverse-nexti [COUNT]'
+ Like 'nexti', 'reverse-nexti' executes a single instruction in
reverse, except that called functions are "un-executed" atomically.
That is, if the previously executed instruction was a return from
- another function, `reverse-nexti' will continue to execute in
+ another function, 'reverse-nexti' will continue to execute in
reverse until the call to that function (from the current stack
frame) is reached.
-`reverse-finish'
- Just as the `finish' command takes you to the point where the
- current function returns, `reverse-finish' takes you to the point
+'reverse-finish'
+ Just as the 'finish' command takes you to the point where the
+ current function returns, 'reverse-finish' takes you to the point
where it was called. Instead of ending up at the end of the
current function invocation, you end up at the beginning.
-`set exec-direction'
+'set exec-direction'
Set the direction of target execution.
-
-`set exec-direction reverse'
+'set exec-direction reverse'
GDB will perform all execution commands in reverse, until the
exec-direction mode is changed to "forward". Affected commands
- include `step, stepi, next, nexti, continue, and finish'. The
- `return' command cannot be used in reverse mode.
-
-`set exec-direction forward'
+ include 'step, stepi, next, nexti, continue, and finish'. The
+ 'return' command cannot be used in reverse mode.
+'set exec-direction forward'
GDB will perform all execution commands in the normal fashion.
This is the default.
other words, reverse execution on platforms that don't support it
directly can only be done in the replay mode.
- When debugging in the reverse direction, GDB will work in replay
-mode as long as the execution log includes the record for the previous
+ When debugging in the reverse direction, GDB will work in replay mode
+as long as the execution log includes the record for the previous
instruction; otherwise, it will work in record mode, if the platform
supports reverse execution, or stop if not.
For architecture environments that support process record and replay,
GDB provides the following commands:
-`target record'
+'record METHOD'
This command starts the process record and replay target. The
- process record and replay target can only debug a process that is
- already running. Therefore, you need first to start the process
- with the `run' or `start' commands, and then start the recording
- with the `target record' command.
+ recording method can be specified as parameter. Without a
+ parameter the command uses the 'full' recording method. The
+ following recording methods are available:
+
+ 'full'
+ Full record/replay recording using GDB's software record and
+ replay implementation. This method allows replaying and
+ reverse execution.
+
+ 'btrace'
+ Hardware-supported instruction recording. This method does
+ not record data. Further, the data is collected in a ring
+ buffer so old data will be overwritten when the buffer is
+ full. It allows limited replay and reverse execution.
- Both `record' and `rec' are aliases of `target record'.
+ This recording method may not be available on all processors.
+
+ The process record and replay target can only debug a process that
+ is already running. Therefore, you need first to start the process
+ with the 'run' or 'start' commands, and then start the recording
+ with the 'record METHOD' command.
+
+ Both 'record METHOD' and 'rec METHOD' are aliases of 'target
+ record-METHOD'.
Displaced stepping (*note displaced stepping: Maintenance
- Commands.) will be automatically disabled when process record and
+ Commands.) will be automatically disabled when process record and
replay target is started. That's because the process record and
replay target doesn't support displaced stepping.
If the inferior is in the non-stop mode (*note Non-Stop Mode::) or
in the asynchronous execution mode (*note Background Execution::),
- the process record and replay target cannot be started because it
- doesn't support these two modes.
+ not all recording methods are available. The 'full' recording
+ method does not support these two modes.
-`record stop'
+'record stop'
Stop the process record and replay target. When process record and
replay target stops, the entire execution log will be deleted and
- the inferior will either be terminated, or will remain in its
- final state.
+ the inferior will either be terminated, or will remain in its final
+ state.
When you stop the process record and replay target in record mode
(at the end of the execution log), the inferior will be stopped at
the next instruction that would have been recorded. In other
words, if you record for a while and then stop recording, the
- inferior process will be left in the same state as if the
- recording never happened.
+ inferior process will be left in the same state as if the recording
+ never happened.
On the other hand, if the process record and replay target is
stopped while in replay mode (that is, not at the end of the
execution log, but at some earlier point), the inferior process
will become "live" at that earlier state, and it will then be
- possible to continue the usual "live" debugging of the process
- from that state.
+ possible to continue the usual "live" debugging of the process from
+ that state.
When the inferior process exits, or GDB detaches from it, process
record and replay target will automatically stop itself.
-`record save FILENAME'
- Save the execution log to a file `FILENAME'. Default filename is
- `gdb_record.PROCESS_ID', where PROCESS_ID is the process ID of the
+'record goto'
+ Go to a specific location in the execution log. There are several
+ ways to specify the location to go to:
+
+ 'record goto begin'
+ 'record goto start'
+ Go to the beginning of the execution log.
+
+ 'record goto end'
+ Go to the end of the execution log.
+
+ 'record goto N'
+ Go to instruction number N in the execution log.
+
+'record save FILENAME'
+ Save the execution log to a file 'FILENAME'. Default filename is
+ 'gdb_record.PROCESS_ID', where PROCESS_ID is the process ID of the
inferior.
-`record restore FILENAME'
- Restore the execution log from a file `FILENAME'. File must have
- been created with `record save'.
+ This command may not be available for all recording methods.
+
+'record restore FILENAME'
+ Restore the execution log from a file 'FILENAME'. File must have
+ been created with 'record save'.
-`set record insn-number-max LIMIT'
- Set the limit of instructions to be recorded. Default value is
- 200000.
+'set record full insn-number-max LIMIT'
+'set record full insn-number-max unlimited'
+ Set the limit of instructions to be recorded for the 'full'
+ recording method. Default value is 200000.
If LIMIT is a positive number, then GDB will start deleting
instructions from the log once the number of the record
keep the number of recorded instructions at the limit. (Since
deleting recorded instructions loses information, GDB lets you
control what happens when the limit is reached, by means of the
- `stop-at-limit' option, described below.)
+ 'stop-at-limit' option, described below.)
- If LIMIT is zero, GDB will never delete recorded instructions from
- the execution log. The number of recorded instructions is
- unlimited in this case.
+ If LIMIT is 'unlimited' or zero, GDB will never delete recorded
+ instructions from the execution log. The number of recorded
+ instructions is limited only by the available memory.
-`show record insn-number-max'
- Show the limit of instructions to be recorded.
+'show record full insn-number-max'
+ Show the limit of instructions to be recorded with the 'full'
+ recording method.
-`set record stop-at-limit'
- Control the behavior when the number of recorded instructions
- reaches the limit. If ON (the default), GDB will stop when the
- limit is reached for the first time and ask you whether you want
- to stop the inferior or continue running it and recording the
- execution log. If you decide to continue recording, each new
- recorded instruction will cause the oldest one to be deleted.
+'set record full stop-at-limit'
+ Control the behavior of the 'full' recording method when the number
+ of recorded instructions reaches the limit. If ON (the default),
+ GDB will stop when the limit is reached for the first time and ask
+ you whether you want to stop the inferior or continue running it
+ and recording the execution log. If you decide to continue
+ recording, each new recorded instruction will cause the oldest one
+ to be deleted.
If this option is OFF, GDB will automatically delete the oldest
record to make room for each new one, without asking.
-`show record stop-at-limit'
- Show the current setting of `stop-at-limit'.
+'show record full stop-at-limit'
+ Show the current setting of 'stop-at-limit'.
-`set record memory-query'
+'set record full memory-query'
Control the behavior when GDB is unable to record memory changes
- caused by an instruction. If ON, GDB will query whether to stop
- the inferior in that case.
+ caused by an instruction for the 'full' recording method. If ON,
+ GDB will query whether to stop the inferior in that case.
If this option is OFF (the default), GDB will automatically ignore
- the effect of such instructions on memory. Later, when GDB
- replays this execution log, it will mark the log of this
- instruction as not accessible, and it will not affect the replay
- results.
-
-`show record memory-query'
- Show the current setting of `memory-query'.
-
-`info record'
- Show various statistics about the state of process record and its
- in-memory execution log buffer, including:
-
- * Whether in record mode or replay mode.
-
- * Lowest recorded instruction number (counting from when the
- current execution log started recording instructions).
-
- * Highest recorded instruction number.
-
- * Current instruction about to be replayed (if in replay mode).
-
- * Number of instructions contained in the execution log.
-
- * Maximum number of instructions that may be contained in the
- execution log.
-
-`record delete'
+ the effect of such instructions on memory. Later, when GDB replays
+ this execution log, it will mark the log of this instruction as not
+ accessible, and it will not affect the replay results.
+
+'show record full memory-query'
+ Show the current setting of 'memory-query'.
+
+ The 'btrace' record target does not trace data. As a convenience,
+ when replaying, GDB reads read-only memory off the live program
+ directly, assuming that the addresses of the read-only areas don't
+ change. This for example makes it possible to disassemble code
+ while replaying, but not to print variables. In some cases, being
+ able to inspect variables might be useful. You can use the
+ following command for that:
+
+'set record btrace replay-memory-access'
+ Control the behavior of the 'btrace' recording method when
+ accessing memory during replay. If 'read-only' (the default), GDB
+ will only allow accesses to read-only memory. If 'read-write', GDB
+ will allow accesses to read-only and to read-write memory. Beware
+ that the accessed memory corresponds to the live target and not
+ necessarily to the current replay position.
+
+'show record btrace replay-memory-access'
+ Show the current setting of 'replay-memory-access'.
+
+'info record'
+ Show various statistics about the recording depending on the
+ recording method:
+
+ 'full'
+ For the 'full' recording method, it shows the state of process
+ record and its in-memory execution log buffer, including:
+
+ * Whether in record mode or replay mode.
+ * Lowest recorded instruction number (counting from when
+ the current execution log started recording
+ instructions).
+ * Highest recorded instruction number.
+ * Current instruction about to be replayed (if in replay
+ mode).
+ * Number of instructions contained in the execution log.
+ * Maximum number of instructions that may be contained in
+ the execution log.
+
+ 'btrace'
+ For the 'btrace' recording method, it shows the number of
+ instructions that have been recorded and the number of blocks
+ of sequential control-flow that is formed by the recorded
+ instructions.
+
+'record delete'
When record target runs in replay mode ("in the past"), delete the
subsequent execution log and begin to record a new execution log
- starting from the current address. This means you will abandon
- the previously recorded "future" and begin recording a new
- "future".
+ starting from the current address. This means you will abandon the
+ previously recorded "future" and begin recording a new "future".
+
+'record instruction-history'
+ Disassembles instructions from the recorded execution log. By
+ default, ten instructions are disassembled. This can be changed
+ using the 'set record instruction-history-size' command.
+ Instructions are printed in execution order. There are several
+ ways to specify what part of the execution log to disassemble:
+
+ 'record instruction-history INSN'
+ Disassembles ten instructions starting from instruction number
+ INSN.
+
+ 'record instruction-history INSN, +/-N'
+ Disassembles N instructions around instruction number INSN.
+ If N is preceded with '+', disassembles N instructions after
+ instruction number INSN. If N is preceded with '-',
+ disassembles N instructions before instruction number INSN.
+
+ 'record instruction-history'
+ Disassembles ten more instructions after the last disassembly.
+
+ 'record instruction-history -'
+ Disassembles ten more instructions before the last
+ disassembly.
+
+ 'record instruction-history BEGIN END'
+ Disassembles instructions beginning with instruction number
+ BEGIN until instruction number END. The instruction number
+ END is included.
+
+ This command may not be available for all recording methods.
+
+'set record instruction-history-size SIZE'
+'set record instruction-history-size unlimited'
+ Define how many instructions to disassemble in the 'record
+ instruction-history' command. The default value is 10. A SIZE of
+ 'unlimited' means unlimited instructions.
+
+'show record instruction-history-size'
+ Show how many instructions to disassemble in the 'record
+ instruction-history' command.
+
+'record function-call-history'
+ Prints the execution history at function granularity. It prints
+ one line for each sequence of instructions that belong to the same
+ function giving the name of that function, the source lines for
+ this instruction sequence (if the '/l' modifier is specified), and
+ the instructions numbers that form the sequence (if the '/i'
+ modifier is specified). The function names are indented to reflect
+ the call stack depth if the '/c' modifier is specified. The '/l',
+ '/i', and '/c' modifiers can be given together.
+
+ (gdb) list 1, 10
+ 1 void foo (void)
+ 2 {
+ 3 }
+ 4
+ 5 void bar (void)
+ 6 {
+ 7 ...
+ 8 foo ();
+ 9 ...
+ 10 }
+ (gdb) record function-call-history /ilc
+ 1 bar inst 1,4 at foo.c:6,8
+ 2 foo inst 5,10 at foo.c:2,3
+ 3 bar inst 11,13 at foo.c:9,10
+
+ By default, ten lines are printed. This can be changed using the
+ 'set record function-call-history-size' command. Functions are
+ printed in execution order. There are several ways to specify what
+ to print:
+
+ 'record function-call-history FUNC'
+ Prints ten functions starting from function number FUNC.
+
+ 'record function-call-history FUNC, +/-N'
+ Prints N functions around function number FUNC. If N is
+ preceded with '+', prints N functions after function number
+ FUNC. If N is preceded with '-', prints N functions before
+ function number FUNC.
+
+ 'record function-call-history'
+ Prints ten more functions after the last ten-line print.
+
+ 'record function-call-history -'
+ Prints ten more functions before the last ten-line print.
+
+ 'record function-call-history BEGIN END'
+ Prints functions beginning with function number BEGIN until
+ function number END. The function number END is included.
+
+ This command may not be available for all recording methods.
+
+'set record function-call-history-size SIZE'
+'set record function-call-history-size unlimited'
+ Define how many lines to print in the 'record
+ function-call-history' command. The default value is 10. A size
+ of 'unlimited' means unlimited lines.
+
+'show record function-call-history-size'
+ Show how many lines to print in the 'record function-call-history'
+ command.
\1f
File: gdb.info, Node: Stack, Next: Source, Prev: Process Record and Replay, Up: Top
8 Examining the Stack
*********************
-When your program has stopped, the first thing you need to know is
-where it stopped and how it got there.
+When your program has stopped, the first thing you need to know is where
+it stopped and how it got there.
Each time your program performs a function call, information about
the call is generated. That information includes the location of the
-call in your program, the arguments of the call, and the local
-variables of the function being called. The information is saved in a
-block of data called a "stack frame". The stack frames are allocated
-in a region of memory called the "call stack".
+call in your program, the arguments of the call, and the local variables
+of the function being called. The information is saved in a block of
+data called a "stack frame". The stack frames are allocated in a region
+of memory called the "call stack".
When your program stops, the GDB commands for examining the stack
allow you to see all of this information.
One of the stack frames is "selected" by GDB and many GDB commands
-refer implicitly to the selected frame. In particular, whenever you
-ask GDB for the value of a variable in your program, the value is found
-in the selected frame. There are special GDB commands to select
-whichever frame you are interested in. *Note Selecting a Frame:
-Selection.
+refer implicitly to the selected frame. In particular, whenever you ask
+GDB for the value of a variable in your program, the value is found in
+the selected frame. There are special GDB commands to select whichever
+frame you are interested in. *Note Selecting a Frame: Selection.
When your program stops, GDB automatically selects the currently
-executing frame and describes it briefly, similar to the `frame'
-command (*note Information about a Frame: Frame Info.).
+executing frame and describes it briefly, similar to the 'frame' command
+(*note Information about a Frame: Frame Info.).
* Menu:
* Frames:: Stack frames
* Backtrace:: Backtraces
+* Frame Filter Management:: Managing frame filters
* Selection:: Selecting a frame
* Frame Info:: Information on a frame
The call stack is divided up into contiguous pieces called "stack
frames", or "frames" for short; each frame is the data associated with
-one call to one function. The frame contains the arguments given to
-the function, the function's local variables, and the address at which
-the function is executing.
+one call to one function. The frame contains the arguments given to the
+function, the function's local variables, and the address at which the
+function is executing.
When your program is started, the stack has only one frame, that of
-the function `main'. This is called the "initial" frame or the
-"outermost" frame. Each time a function is called, a new frame is
-made. Each time a function returns, the frame for that function
-invocation is eliminated. If a function is recursive, there can be
-many frames for the same function. The frame for the function in which
-execution is actually occurring is called the "innermost" frame. This
-is the most recently created of all the stack frames that still exist.
+the function 'main'. This is called the "initial" frame or the
+"outermost" frame. Each time a function is called, a new frame is made.
+Each time a function returns, the frame for that function invocation is
+eliminated. If a function is recursive, there can be many frames for
+the same function. The frame for the function in which execution is
+actually occurring is called the "innermost" frame. This is the most
+recently created of all the stack frames that still exist.
Inside your program, stack frames are identified by their addresses.
-A stack frame consists of many bytes, each of which has its own
-address; each kind of computer has a convention for choosing one byte
-whose address serves as the address of the frame. Usually this address
-is kept in a register called the "frame pointer register" (*note $fp:
+A stack frame consists of many bytes, each of which has its own address;
+each kind of computer has a convention for choosing one byte whose
+address serves as the address of the frame. Usually this address is
+kept in a register called the "frame pointer register" (*note $fp:
Registers.) while execution is going on in that frame.
GDB assigns numbers to all existing stack frames, starting with zero
Some compilers provide a way to compile functions so that they
operate without stack frames. (For example, the GCC option
- `-fomit-frame-pointer'
- generates functions without a frame.) This is occasionally done
-with heavily used library functions to save the frame setup time. GDB
-has limited facilities for dealing with these function invocations. If
-the innermost function invocation has no stack frame, GDB nevertheless
+ '-fomit-frame-pointer'
+ generates functions without a frame.) This is occasionally done with
+heavily used library functions to save the frame setup time. GDB has
+limited facilities for dealing with these function invocations. If the
+innermost function invocation has no stack frame, GDB nevertheless
regards it as though it had a separate frame, which is numbered zero as
usual, allowing correct tracing of the function call chain. However,
GDB has no provision for frameless functions elsewhere in the stack.
-`frame ARGS'
- The `frame' command allows you to move from one stack frame to
- another, and to print the stack frame you select. ARGS may be
- either the address of the frame or the stack frame number.
- Without an argument, `frame' prints the current stack frame.
+'frame [FRAMESPEC]'
+ The 'frame' command allows you to move from one stack frame to
+ another, and to print the stack frame you select. The FRAMESPEC
+ may be either the address of the frame or the stack frame number.
+ Without an argument, 'frame' prints the current stack frame.
-`select-frame'
- The `select-frame' command allows you to move from one stack frame
+'select-frame'
+ The 'select-frame' command allows you to move from one stack frame
to another without printing the frame. This is the silent version
- of `frame'.
+ of 'frame'.
\1f
-File: gdb.info, Node: Backtrace, Next: Selection, Prev: Frames, Up: Stack
+File: gdb.info, Node: Backtrace, Next: Frame Filter Management, Prev: Frames, Up: Stack
8.2 Backtraces
==============
A backtrace is a summary of how your program got where it is. It shows
one line per frame, for many frames, starting with the currently
-executing frame (frame zero), followed by its caller (frame one), and
-on up the stack.
+executing frame (frame zero), followed by its caller (frame one), and on
+up the stack.
-`backtrace'
-`bt'
+'backtrace'
+'bt'
Print a backtrace of the entire stack: one line per frame for all
frames in the stack.
You can stop the backtrace at any time by typing the system
- interrupt character, normally `Ctrl-c'.
+ interrupt character, normally 'Ctrl-c'.
-`backtrace N'
-`bt N'
+'backtrace N'
+'bt N'
Similar, but print only the innermost N frames.
-`backtrace -N'
-`bt -N'
+'backtrace -N'
+'bt -N'
Similar, but print only the outermost N frames.
-`backtrace full'
-`bt full'
-`bt full N'
-`bt full -N'
- Print the values of the local variables also. N specifies the
- number of frames to print, as described above.
-
- The names `where' and `info stack' (abbreviated `info s') are
-additional aliases for `backtrace'.
+'backtrace full'
+'bt full'
+'bt full N'
+'bt full -N'
+ Print the values of the local variables also. As described above,
+ N specifies the number of frames to print.
+
+'backtrace no-filters'
+'bt no-filters'
+'bt no-filters N'
+'bt no-filters -N'
+'bt no-filters full'
+'bt no-filters full N'
+'bt no-filters full -N'
+ Do not run Python frame filters on this backtrace. *Note Frame
+ Filter API::, for more information. Additionally use *note disable
+ frame-filter all:: to turn off all frame filters. This is only
+ relevant when GDB has been configured with 'Python' support.
+
+ The names 'where' and 'info stack' (abbreviated 'info s') are
+additional aliases for 'backtrace'.
In a multi-threaded program, GDB by default shows the backtrace only
for the current thread. To display the backtrace for several or all of
-the threads, use the command `thread apply' (*note thread apply:
-Threads.). For example, if you type `thread apply all backtrace', GDB
+the threads, use the command 'thread apply' (*note thread apply:
+Threads.). For example, if you type 'thread apply all backtrace', GDB
will display the backtrace for all the threads; this is handy when you
debug a core dump of a multi-threaded program.
Each line in the backtrace shows the frame number and the function
-name. The program counter value is also shown--unless you use `set
+name. The program counter value is also shown--unless you use 'set
print address off'. The backtrace also shows the source file name and
line number, as well as the arguments to the function. The program
counter value is omitted if it is at the beginning of the code for that
line number.
- Here is an example of a backtrace. It was made with the command `bt
+ Here is an example of a backtrace. It was made with the command 'bt
3', so it shows the innermost three frames.
#0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
The display for frame zero does not begin with a program counter value,
indicating that your program has stopped at the beginning of the code
-for line `993' of `builtin.c'.
+for line '993' of 'builtin.c'.
-The value of parameter `data' in frame 1 has been replaced by `...'.
-By default, GDB prints the value of a parameter only if it is a scalar
-(integer, pointer, enumeration, etc). See command `set print
-frame-arguments' in *Note Print Settings:: for more details on how to
+The value of parameter 'data' in frame 1 has been replaced by '...'. By
+default, GDB prints the value of a parameter only if it is a scalar
+(integer, pointer, enumeration, etc). See command 'set print
+frame-arguments' in *note Print Settings:: for more details on how to
configure the way function parameter values are printed.
If your program was compiled with optimizations, some compilers will
-optimize away arguments passed to functions if those arguments are
-never used after the call. Such optimizations generate code that
-passes arguments through registers, but doesn't store those arguments
-in the stack frame. GDB has no way of displaying such arguments in
-stack frames other than the innermost one. Here's what such a
-backtrace might look like:
+optimize away arguments passed to functions if those arguments are never
+used after the call. Such optimizations generate code that passes
+arguments through registers, but doesn't store those arguments in the
+stack frame. GDB has no way of displaying such arguments in stack
+frames other than the innermost one. Here's what such a backtrace might
+look like:
#0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
at builtin.c:993
(More stack frames follow...)
The values of arguments that were not saved in their stack frames are
-shown as `<optimized out>'.
+shown as '<optimized out>'.
If you need to display the values of such optimized-out arguments,
either deduce that from other variables whose values depend on the one
Most programs have a standard user entry point--a place where system
libraries and startup code transition into user code. For C this is
-`main'(1). When GDB finds the entry function in a backtrace it will
+'main'(1). When GDB finds the entry function in a backtrace it will
terminate the backtrace, to avoid tracing into highly system-specific
(and generally uninteresting) code.
If you need to examine the startup code, or limit the number of
levels in a backtrace, you can change this behavior:
-`set backtrace past-main'
-`set backtrace past-main on'
+'set backtrace past-main'
+'set backtrace past-main on'
Backtraces will continue past the user entry point.
-`set backtrace past-main off'
+'set backtrace past-main off'
Backtraces will stop when they encounter the user entry point.
This is the default.
-`show backtrace past-main'
+'show backtrace past-main'
Display the current user entry point backtrace policy.
-`set backtrace past-entry'
-`set backtrace past-entry on'
+'set backtrace past-entry'
+'set backtrace past-entry on'
Backtraces will continue past the internal entry point of an
application. This entry point is encoded by the linker when the
application is built, and is likely before the user entry point
- `main' (or equivalent) is called.
+ 'main' (or equivalent) is called.
-`set backtrace past-entry off'
+'set backtrace past-entry off'
Backtraces will stop when they encounter the internal entry point
of an application. This is the default.
-`show backtrace past-entry'
+'show backtrace past-entry'
Display the current internal entry point backtrace policy.
-`set backtrace limit N'
-`set backtrace limit 0'
- Limit the backtrace to N levels. A value of zero means unlimited.
+'set backtrace limit N'
+'set backtrace limit 0'
+'set backtrace limit unlimited'
+ Limit the backtrace to N levels. A value of 'unlimited' or zero
+ means unlimited levels.
-`show backtrace limit'
+'show backtrace limit'
Display the current limit on backtrace levels.
+ You can control how file names are displayed.
+
+'set filename-display'
+'set filename-display relative'
+ Display file names relative to the compilation directory. This is
+ the default.
+
+'set filename-display basename'
+ Display only basename of a filename.
+
+'set filename-display absolute'
+ Display an absolute filename.
+
+'show filename-display'
+ Show the current way to display filenames.
+
---------- Footnotes ----------
(1) Note that embedded programs (the so-called "free-standing"
-environment) are not required to have a `main' function as the entry
+environment) are not required to have a 'main' function as the entry
point. They could even have multiple entry points.
\1f
-File: gdb.info, Node: Selection, Next: Frame Info, Prev: Backtrace, Up: Stack
+File: gdb.info, Node: Frame Filter Management, Next: Selection, Prev: Backtrace, Up: Stack
+
+8.3 Management of Frame Filters.
+================================
+
+Frame filters are Python based utilities to manage and decorate the
+output of frames. *Note Frame Filter API::, for further information.
+
+ Managing frame filters is performed by several commands available
+within GDB, detailed here.
+
+'info frame-filter'
+ Print a list of installed frame filters from all dictionaries,
+ showing their name, priority and enabled status.
+
+'disable frame-filter FILTER-DICTIONARY FILTER-NAME'
+ Disable a frame filter in the dictionary matching FILTER-DICTIONARY
+ and FILTER-NAME. The FILTER-DICTIONARY may be 'all', 'global',
+ 'progspace', or the name of the object file where the frame filter
+ dictionary resides. When 'all' is specified, all frame filters
+ across all dictionaries are disabled. The FILTER-NAME is the name
+ of the frame filter and is used when 'all' is not the option for
+ FILTER-DICTIONARY. A disabled frame-filter is not deleted, it may
+ be enabled again later.
+
+'enable frame-filter FILTER-DICTIONARY FILTER-NAME'
+ Enable a frame filter in the dictionary matching FILTER-DICTIONARY
+ and FILTER-NAME. The FILTER-DICTIONARY may be 'all', 'global',
+ 'progspace' or the name of the object file where the frame filter
+ dictionary resides. When 'all' is specified, all frame filters
+ across all dictionaries are enabled. The FILTER-NAME is the name
+ of the frame filter and is used when 'all' is not the option for
+ FILTER-DICTIONARY.
+
+ Example:
+
+ (gdb) info frame-filter
+
+ global frame-filters:
+ Priority Enabled Name
+ 1000 No PrimaryFunctionFilter
+ 100 Yes Reverse
+
+ progspace /build/test frame-filters:
+ Priority Enabled Name
+ 100 Yes ProgspaceFilter
+
+ objfile /build/test frame-filters:
+ Priority Enabled Name
+ 999 Yes BuildProgra Filter
+
+ (gdb) disable frame-filter /build/test BuildProgramFilter
+ (gdb) info frame-filter
+
+ global frame-filters:
+ Priority Enabled Name
+ 1000 No PrimaryFunctionFilter
+ 100 Yes Reverse
+
+ progspace /build/test frame-filters:
+ Priority Enabled Name
+ 100 Yes ProgspaceFilter
+
+ objfile /build/test frame-filters:
+ Priority Enabled Name
+ 999 No BuildProgramFilter
+
+ (gdb) enable frame-filter global PrimaryFunctionFilter
+ (gdb) info frame-filter
+
+ global frame-filters:
+ Priority Enabled Name
+ 1000 Yes PrimaryFunctionFilter
+ 100 Yes Reverse
+
+ progspace /build/test frame-filters:
+ Priority Enabled Name
+ 100 Yes ProgspaceFilter
+
+ objfile /build/test frame-filters:
+ Priority Enabled Name
+ 999 No BuildProgramFilter
+
+'set frame-filter priority FILTER-DICTIONARY FILTER-NAME PRIORITY'
+ Set the PRIORITY of a frame filter in the dictionary matching
+ FILTER-DICTIONARY, and the frame filter name matching FILTER-NAME.
+ The FILTER-DICTIONARY may be 'global', 'progspace' or the name of
+ the object file where the frame filter dictionary resides. The
+ PRIORITY is an integer.
+
+'show frame-filter priority FILTER-DICTIONARY FILTER-NAME'
+ Show the PRIORITY of a frame filter in the dictionary matching
+ FILTER-DICTIONARY, and the frame filter name matching FILTER-NAME.
+ The FILTER-DICTIONARY may be 'global', 'progspace' or the name of
+ the object file where the frame filter dictionary resides.
+
+ Example:
+
+ (gdb) info frame-filter
+
+ global frame-filters:
+ Priority Enabled Name
+ 1000 Yes PrimaryFunctionFilter
+ 100 Yes Reverse
+
+ progspace /build/test frame-filters:
+ Priority Enabled Name
+ 100 Yes ProgspaceFilter
+
+ objfile /build/test frame-filters:
+ Priority Enabled Name
+ 999 No BuildProgramFilter
+
+ (gdb) set frame-filter priority global Reverse 50
+ (gdb) info frame-filter
+
+ global frame-filters:
+ Priority Enabled Name
+ 1000 Yes PrimaryFunctionFilter
+ 50 Yes Reverse
+
+ progspace /build/test frame-filters:
+ Priority Enabled Name
+ 100 Yes ProgspaceFilter
+
+ objfile /build/test frame-filters:
+ Priority Enabled Name
+ 999 No BuildProgramFilter
+
+\1f
+File: gdb.info, Node: Selection, Next: Frame Info, Prev: Frame Filter Management, Up: Stack
-8.3 Selecting a Frame
+8.4 Selecting a Frame
=====================
Most commands for examining the stack and other data in your program
commands for selecting a stack frame; all of them finish by printing a
brief description of the stack frame just selected.
-`frame N'
-`f N'
+'frame N'
+'f N'
Select frame number N. Recall that frame zero is the innermost
(currently executing) frame, frame one is the frame that called the
innermost one, and so on. The highest-numbered frame is the one
- for `main'.
+ for 'main'.
-`frame ADDR'
-`f ADDR'
+'frame ADDR'
+'f ADDR'
Select the frame at address ADDR. This is useful mainly if the
chaining of stack frames has been damaged by a bug, making it
impossible for GDB to assign numbers properly to all frames. In
addition, this can be useful when your program has multiple stacks
and switches between them.
- On the SPARC architecture, `frame' needs two addresses to select
- an arbitrary frame: a frame pointer and a stack pointer.
+ On the SPARC architecture, 'frame' needs two addresses to select an
+ arbitrary frame: a frame pointer and a stack pointer.
On the MIPS and Alpha architecture, it needs two addresses: a stack
pointer and a program counter.
On the 29k architecture, it needs three addresses: a register stack
pointer, a program counter, and a memory stack pointer.
-`up N'
- Move N frames up the stack. For positive numbers N, this advances
- toward the outermost frame, to higher frame numbers, to frames
- that have existed longer. N defaults to one.
+'up N'
+ Move N frames up the stack; N defaults to 1. For positive numbers
+ N, this advances toward the outermost frame, to higher frame
+ numbers, to frames that have existed longer.
-`down N'
- Move N frames down the stack. For positive numbers N, this
- advances toward the innermost frame, to lower frame numbers, to
- frames that were created more recently. N defaults to one. You
- may abbreviate `down' as `do'.
+'down N'
+ Move N frames down the stack; N defaults to 1. For positive
+ numbers N, this advances toward the innermost frame, to lower frame
+ numbers, to frames that were created more recently. You may
+ abbreviate 'down' as 'do'.
All of these commands end by printing two lines of output describing
the frame. The first line shows the frame number, the function name,
at env.c:10
10 read_input_file (argv[i]);
- After such a printout, the `list' command with no arguments prints
-ten lines centered on the point of execution in the frame. You can
-also edit the program at the point of execution with your favorite
-editing program by typing `edit'. *Note Printing Source Lines: List,
-for details.
+ After such a printout, the 'list' command with no arguments prints
+ten lines centered on the point of execution in the frame. You can also
+edit the program at the point of execution with your favorite editing
+program by typing 'edit'. *Note Printing Source Lines: List, for
+details.
-`up-silently N'
-`down-silently N'
- These two commands are variants of `up' and `down', respectively;
+'up-silently N'
+'down-silently N'
+ These two commands are variants of 'up' and 'down', respectively;
they differ in that they do their work silently, without causing
display of the new frame. They are intended primarily for use in
GDB command scripts, where the output might be unnecessary and
\1f
File: gdb.info, Node: Frame Info, Prev: Selection, Up: Stack
-8.4 Information About a Frame
+8.5 Information About a Frame
=============================
There are several other commands to print information about the selected
stack frame.
-`frame'
-`f'
+'frame'
+'f'
When used without any argument, this command does not change which
frame is selected, but prints a brief description of the currently
- selected stack frame. It can be abbreviated `f'. With an
+ selected stack frame. It can be abbreviated 'f'. With an
argument, this command is used to select a stack frame. *Note
Selecting a Frame: Selection.
-`info frame'
-`info f'
+'info frame'
+'info f'
This command prints a verbose description of the selected stack
frame, including:
* the address of the frame
-
* the address of the next frame down (called by this frame)
-
* the address of the next frame up (caller of this frame)
-
* the language in which the source code corresponding to this
frame is written
-
* the address of the frame's arguments
-
* the address of the frame's local variables
-
* the program counter saved in it (the address of execution in
the caller frame)
-
* which registers were saved in the frame
The verbose description is useful when something has gone wrong
that has made the stack format fail to fit the usual conventions.
-`info frame ADDR'
-`info f ADDR'
+'info frame ADDR'
+'info f ADDR'
Print a verbose description of the frame at address ADDR, without
selecting that frame. The selected frame remains unchanged by this
- command. This requires the same kind of address (more than one
- for some architectures) that you specify in the `frame' command.
- *Note Selecting a Frame: Selection.
+ command. This requires the same kind of address (more than one for
+ some architectures) that you specify in the 'frame' command. *Note
+ Selecting a Frame: Selection.
-`info args'
+'info args'
Print the arguments of the selected frame, each on a separate line.
-`info locals'
+'info locals'
Print the local variables of the selected frame, each on a separate
line. These are all variables (declared either static or
automatic) accessible at the point of execution of the selected
frame.
-
\1f
File: gdb.info, Node: Source, Next: Data, Prev: Stack, Up: Top
GDB can print parts of your program's source, since the debugging
information recorded in the program tells GDB what source files were
-used to build it. When your program stops, GDB spontaneously prints
-the line where it stopped. Likewise, when you select a stack frame
-(*note Selecting a Frame: Selection.), GDB prints the line where
-execution in that frame has stopped. You can print other portions of
-source files by explicit command.
+used to build it. When your program stops, GDB spontaneously prints the
+line where it stopped. Likewise, when you select a stack frame (*note
+Selecting a Frame: Selection.), GDB prints the line where execution in
+that frame has stopped. You can print other portions of source files by
+explicit command.
- If you use GDB through its GNU Emacs interface, you may prefer to
-use Emacs facilities to view source; see *Note Using GDB under GNU
-Emacs: Emacs.
+ If you use GDB through its GNU Emacs interface, you may prefer to use
+Emacs facilities to view source; see *note Using GDB under GNU Emacs:
+Emacs.
* Menu:
9.1 Printing Source Lines
=========================
-To print lines from a source file, use the `list' command (abbreviated
-`l'). By default, ten lines are printed. There are several ways to
-specify what part of the file you want to print; see *Note Specify
+To print lines from a source file, use the 'list' command (abbreviated
+'l'). By default, ten lines are printed. There are several ways to
+specify what part of the file you want to print; see *note Specify
Location::, for the full list.
- Here are the forms of the `list' command most commonly used:
+ Here are the forms of the 'list' command most commonly used:
-`list LINENUM'
+'list LINENUM'
Print lines centered around line number LINENUM in the current
source file.
-`list FUNCTION'
+'list FUNCTION'
Print lines centered around the beginning of function FUNCTION.
-`list'
+'list'
Print more lines. If the last lines printed were printed with a
- `list' command, this prints lines following the last lines
- printed; however, if the last line printed was a solitary line
- printed as part of displaying a stack frame (*note Examining the
- Stack: Stack.), this prints lines centered around that line.
+ 'list' command, this prints lines following the last lines printed;
+ however, if the last line printed was a solitary line printed as
+ part of displaying a stack frame (*note Examining the Stack:
+ Stack.), this prints lines centered around that line.
-`list -'
+'list -'
Print lines just before the lines last printed.
By default, GDB prints ten source lines with any of these forms of
-the `list' command. You can change this using `set listsize':
+the 'list' command. You can change this using 'set listsize':
-`set listsize COUNT'
- Make the `list' command display COUNT source lines (unless the
- `list' argument explicitly specifies some other number).
+'set listsize COUNT'
+'set listsize unlimited'
+ Make the 'list' command display COUNT source lines (unless the
+ 'list' argument explicitly specifies some other number). Setting
+ COUNT to 'unlimited' or 0 means there's no limit.
-`show listsize'
- Display the number of lines that `list' prints.
+'show listsize'
+ Display the number of lines that 'list' prints.
- Repeating a `list' command with <RET> discards the argument, so it
-is equivalent to typing just `list'. This is more useful than listing
-the same lines again. An exception is made for an argument of `-';
-that argument is preserved in repetition so that each repetition moves
-up in the source file.
+ Repeating a 'list' command with <RET> discards the argument, so it is
+equivalent to typing just 'list'. This is more useful than listing the
+same lines again. An exception is made for an argument of '-'; that
+argument is preserved in repetition so that each repetition moves up in
+the source file.
- In general, the `list' command expects you to supply zero, one or two
+ In general, the 'list' command expects you to supply zero, one or two
"linespecs". Linespecs specify source lines; there are several ways of
writing them (*note Specify Location::), but the effect is always to
specify some source line.
- Here is a complete description of the possible arguments for `list':
+ Here is a complete description of the possible arguments for 'list':
-`list LINESPEC'
+'list LINESPEC'
Print lines centered around the line specified by LINESPEC.
-`list FIRST,LAST'
+'list FIRST,LAST'
Print lines from FIRST to LAST. Both arguments are linespecs.
- When a `list' command has two linespecs, and the source file of
- the second linespec is omitted, this refers to the same source
- file as the first linespec.
+ When a 'list' command has two linespecs, and the source file of the
+ second linespec is omitted, this refers to the same source file as
+ the first linespec.
-`list ,LAST'
+'list ,LAST'
Print lines ending with LAST.
-`list FIRST,'
+'list FIRST,'
Print lines starting with FIRST.
-`list +'
+'list +'
Print lines just after the lines last printed.
-`list -'
+'list -'
Print lines just before the lines last printed.
-`list'
+'list'
As described in the preceding table.
\1f
Here are all the different ways of specifying a code location that
GDB understands:
-`LINENUM'
+'LINENUM'
Specifies the line number LINENUM of the current source file.
-`-OFFSET'
-`+OFFSET'
- Specifies the line OFFSET lines before or after the "current
- line". For the `list' command, the current line is the last one
- printed; for the breakpoint commands, this is the line at which
- execution stopped in the currently selected "stack frame" (*note
- Frames: Frames, for a description of stack frames.) When used as
- the second of the two linespecs in a `list' command, this
- specifies the line OFFSET lines up or down from the first linespec.
-
-`FILENAME:LINENUM'
+'-OFFSET'
+'+OFFSET'
+ Specifies the line OFFSET lines before or after the "current line".
+ For the 'list' command, the current line is the last one printed;
+ for the breakpoint commands, this is the line at which execution
+ stopped in the currently selected "stack frame" (*note Frames:
+ Frames, for a description of stack frames.) When used as the
+ second of the two linespecs in a 'list' command, this specifies the
+ line OFFSET lines up or down from the first linespec.
+
+'FILENAME:LINENUM'
Specifies the line LINENUM in the source file FILENAME. If
FILENAME is a relative file name, then it will match any source
file name with the same trailing components. For example, if
- FILENAME is `gcc/expr.c', then it will match source file name of
- `/build/trunk/gcc/expr.c', but not `/build/trunk/libcpp/expr.c' or
- `/build/trunk/gcc/x-expr.c'.
+ FILENAME is 'gcc/expr.c', then it will match source file name of
+ '/build/trunk/gcc/expr.c', but not '/build/trunk/libcpp/expr.c' or
+ '/build/trunk/gcc/x-expr.c'.
-`FUNCTION'
+'FUNCTION'
Specifies the line that begins the body of the function FUNCTION.
For example, in C, this is the line with the open brace.
-`FUNCTION:LABEL'
+'FUNCTION:LABEL'
Specifies the line where LABEL appears in FUNCTION.
-`FILENAME:FUNCTION'
- Specifies the line that begins the body of the function FUNCTION
- in the file FILENAME. You only need the file name with a function
+'FILENAME:FUNCTION'
+ Specifies the line that begins the body of the function FUNCTION in
+ the file FILENAME. You only need the file name with a function
name to avoid ambiguity when there are identically named functions
in different source files.
-`LABEL'
+'LABEL'
Specifies the line at which the label named LABEL appears. GDB
searches for the label in the function corresponding to the
currently selected stack frame. If there is no current selected
stack frame (for instance, if the inferior is not running), then
GDB will not search for a label.
-`*ADDRESS'
- Specifies the program address ADDRESS. For line-oriented
- commands, such as `list' and `edit', this specifies a source line
- that contains ADDRESS. For `break' and other breakpoint oriented
+'*ADDRESS'
+ Specifies the program address ADDRESS. For line-oriented commands,
+ such as 'list' and 'edit', this specifies a source line that
+ contains ADDRESS. For 'break' and other breakpoint oriented
commands, this can be used to set breakpoints in parts of your
program which do not have debugging information or source files.
frequently happen during debugging. Here are the various forms of
ADDRESS:
- `EXPRESSION'
+ 'EXPRESSION'
Any expression valid in the current working language.
- `FUNCADDR'
+ 'FUNCADDR'
An address of a function or procedure derived from its name.
In C, C++, Java, Objective-C, Fortran, minimal, and assembly,
this is simply the function's name FUNCTION (and actually a
special case of a valid expression). In Pascal and Modula-2,
- this is `&FUNCTION'. In Ada, this is `FUNCTION'Address'
+ this is '&FUNCTION'. In Ada, this is 'FUNCTION'Address'
(although the Pascal form also works).
This form specifies the address of the function's first
instruction, before the stack frame and arguments have been
set up.
- `'FILENAME'::FUNCADDR'
+ ''FILENAME'::FUNCADDR'
Like FUNCADDR above, but also specifies the name of the source
file explicitly. This is useful if the name of the function
does not specify the function unambiguously, e.g., if there
- are several functions with identical names in different
- source files.
+ are several functions with identical names in different source
+ files.
-`-pstap|-probe-stap [OBJFILE:[PROVIDER:]]NAME'
- The GNU/Linux tool `SystemTap' provides a way for applications to
+'-pstap|-probe-stap [OBJFILE:[PROVIDER:]]NAME'
+ The GNU/Linux tool 'SystemTap' provides a way for applications to
embed static probes. *Note Static Probe Points::, for more
information on finding and using static probes. This form of
linespec specifies the location of such a static probe.
- If OBJFILE is given, only probes coming from that shared library
- or executable matching OBJFILE as a regular expression are
- considered. If PROVIDER is given, then only probes from that
- provider are considered. If several probes match the spec, GDB
- will insert a breakpoint at each one of those probes.
-
+ If OBJFILE is given, only probes coming from that shared library or
+ executable matching OBJFILE as a regular expression are considered.
+ If PROVIDER is given, then only probes from that provider are
+ considered. If several probes match the spec, GDB will insert a
+ breakpoint at each one of those probes.
\1f
File: gdb.info, Node: Edit, Next: Search, Prev: Specify Location, Up: Source
9.3 Editing Source Files
========================
-To edit the lines in a source file, use the `edit' command. The
-editing program of your choice is invoked with the current line set to
-the active line in the program. Alternatively, there are several ways
-to specify what part of the file you want to print if you want to see
-other parts of the program:
+To edit the lines in a source file, use the 'edit' command. The editing
+program of your choice is invoked with the current line set to the
+active line in the program. Alternatively, there are several ways to
+specify what part of the file you want to print if you want to see other
+parts of the program:
-`edit LOCATION'
- Edit the source file specified by `location'. Editing starts at
+'edit LOCATION'
+ Edit the source file specified by 'location'. Editing starts at
that LOCATION, e.g., at the specified source line of the specified
file. *Note Specify Location::, for all the possible forms of the
- LOCATION argument; here are the forms of the `edit' command most
+ LOCATION argument; here are the forms of the 'edit' command most
commonly used:
- `edit NUMBER'
+ 'edit NUMBER'
Edit the current source file with NUMBER as the active line
number.
- `edit FUNCTION'
+ 'edit FUNCTION'
Edit the file containing FUNCTION at the beginning of its
definition.
-
9.3.1 Choosing your Editor
--------------------------
-You can customize GDB to use any editor you want (1). By default, it
-is `/bin/ex', but you can change this by setting the environment
-variable `EDITOR' before using GDB. For example, to configure GDB to
-use the `vi' editor, you could use these commands with the `sh' shell:
+You can customize GDB to use any editor you want (1). By default, it is
+'/bin/ex', but you can change this by setting the environment variable
+'EDITOR' before using GDB. For example, to configure GDB to use the
+'vi' editor, you could use these commands with the 'sh' shell:
EDITOR=/usr/bin/vi
export EDITOR
gdb ...
- or in the `csh' shell,
+ or in the 'csh' shell,
setenv EDITOR /usr/bin/vi
gdb ...
---------- Footnotes ----------
- (1) The only restriction is that your editor (say `ex'), recognizes
+ (1) The only restriction is that your editor (say 'ex'), recognizes
the following command-line syntax:
ex +NUMBER file
The optional numeric value +NUMBER specifies the number of the line
9.4 Searching Source Files
==========================
-There are two commands for searching through the current source file
-for a regular expression.
+There are two commands for searching through the current source file for
+a regular expression.
-`forward-search REGEXP'
-`search REGEXP'
- The command `forward-search REGEXP' checks each line, starting
- with the one following the last line listed, for a match for
- REGEXP. It lists the line that is found. You can use the synonym
- `search REGEXP' or abbreviate the command name as `fo'.
+'forward-search REGEXP'
+'search REGEXP'
+ The command 'forward-search REGEXP' checks each line, starting with
+ the one following the last line listed, for a match for REGEXP. It
+ lists the line that is found. You can use the synonym 'search
+ REGEXP' or abbreviate the command name as 'fo'.
-`reverse-search REGEXP'
- The command `reverse-search REGEXP' checks each line, starting
- with the one before the last line listed and going backward, for a
- match for REGEXP. It lists the line that is found. You can
- abbreviate this command as `rev'.
+'reverse-search REGEXP'
+ The command 'reverse-search REGEXP' checks each line, starting with
+ the one before the last line listed and going backward, for a match
+ for REGEXP. It lists the line that is found. You can abbreviate
+ this command as 'rev'.
\1f
File: gdb.info, Node: Source Path, Next: Machine Code, Prev: Search, Up: Source
Executable programs sometimes do not record the directories of the
source files from which they were compiled, just the names. Even when
-they do, the directories could be moved between the compilation and
-your debugging session. GDB has a list of directories to search for
-source files; this is called the "source path". Each time GDB wants a
-source file, it tries all the directories in the list, in the order
-they are present in the list, until it finds a file with the desired
-name.
+they do, the directories could be moved between the compilation and your
+debugging session. GDB has a list of directories to search for source
+files; this is called the "source path". Each time GDB wants a source
+file, it tries all the directories in the list, in the order they are
+present in the list, until it finds a file with the desired name.
For example, suppose an executable references the file
-`/usr/src/foo-1.0/lib/foo.c', and our source path is `/mnt/cross'. The
+'/usr/src/foo-1.0/lib/foo.c', and our source path is '/mnt/cross'. The
file is first looked up literally; if this fails,
-`/mnt/cross/usr/src/foo-1.0/lib/foo.c' is tried; if this fails,
-`/mnt/cross/foo.c' is opened; if this fails, an error message is
+'/mnt/cross/usr/src/foo-1.0/lib/foo.c' is tried; if this fails,
+'/mnt/cross/foo.c' is opened; if this fails, an error message is
printed. GDB does not look up the parts of the source file name, such
-as `/mnt/cross/src/foo-1.0/lib/foo.c'. Likewise, the subdirectories of
-the source path are not searched: if the source path is `/mnt/cross',
-and the binary refers to `foo.c', GDB would not find it under
-`/mnt/cross/usr/src/foo-1.0/lib'.
+as '/mnt/cross/src/foo-1.0/lib/foo.c'. Likewise, the subdirectories of
+the source path are not searched: if the source path is '/mnt/cross',
+and the binary refers to 'foo.c', GDB would not find it under
+'/mnt/cross/usr/src/foo-1.0/lib'.
Plain file names, relative file names with leading directories, file
names containing dots, etc. are all treated as described above; for
-instance, if the source path is `/mnt/cross', and the source file is
-recorded as `../lib/foo.c', GDB would first try `../lib/foo.c', then
-`/mnt/cross/../lib/foo.c', and after that--`/mnt/cross/foo.c'.
+instance, if the source path is '/mnt/cross', and the source file is
+recorded as '../lib/foo.c', GDB would first try '../lib/foo.c', then
+'/mnt/cross/../lib/foo.c', and after that--'/mnt/cross/foo.c'.
Note that the executable search path is _not_ used to locate the
source files.
information it has cached about where source files are found and where
each line is in the file.
- When you start GDB, its source path includes only `cdir' and `cwd',
-in that order. To add other directories, use the `directory' command.
+ When you start GDB, its source path includes only 'cdir' and 'cwd',
+in that order. To add other directories, use the 'directory' command.
The search path is used to find both program source files and GDB
-script files (read using the `-command' option and `source' command).
+script files (read using the '-command' option and 'source' command).
In addition to the source path, GDB provides a set of commands that
manage a list of source path substitution rules. A "substitution rule"
debug information in case the sources were moved to a different
directory between compilation and debugging. A rule is made of two
strings, the first specifying what needs to be rewritten in the path,
-and the second specifying how it should be rewritten. In *Note set
+and the second specifying how it should be rewritten. In *note set
substitute-path::, we name these two parts FROM and TO respectively.
-GDB does a simple string replacement of FROM with TO at the start of
-the directory part of the source file name, and uses that result
-instead of the original file name to look up the sources.
-
- Using the previous example, suppose the `foo-1.0' tree has been
-moved from `/usr/src' to `/mnt/cross', then you can tell GDB to replace
-`/usr/src' in all source path names with `/mnt/cross'. The first
-lookup will then be `/mnt/cross/foo-1.0/lib/foo.c' in place of the
-original location of `/usr/src/foo-1.0/lib/foo.c'. To define a source
-path substitution rule, use the `set substitute-path' command (*note
-set substitute-path::).
+GDB does a simple string replacement of FROM with TO at the start of the
+directory part of the source file name, and uses that result instead of
+the original file name to look up the sources.
+
+ Using the previous example, suppose the 'foo-1.0' tree has been moved
+from '/usr/src' to '/mnt/cross', then you can tell GDB to replace
+'/usr/src' in all source path names with '/mnt/cross'. The first lookup
+will then be '/mnt/cross/foo-1.0/lib/foo.c' in place of the original
+location of '/usr/src/foo-1.0/lib/foo.c'. To define a source path
+substitution rule, use the 'set substitute-path' command (*note set
+substitute-path::).
To avoid unexpected substitution results, a rule is applied only if
the FROM part of the directory name ends at a directory separator. For
-instance, a rule substituting `/usr/source' into `/mnt/cross' will be
-applied to `/usr/source/foo-1.0' but not to `/usr/sourceware/foo-2.0'.
+instance, a rule substituting '/usr/source' into '/mnt/cross' will be
+applied to '/usr/source/foo-1.0' but not to '/usr/sourceware/foo-2.0'.
And because the substitution is applied only at the beginning of the
directory name, this rule will not be applied to
-`/root/usr/source/baz.c' either.
+'/root/usr/source/baz.c' either.
- In many cases, you can achieve the same result using the `directory'
-command. However, `set substitute-path' can be more efficient in the
+ In many cases, you can achieve the same result using the 'directory'
+command. However, 'set substitute-path' can be more efficient in the
case where the sources are organized in a complex tree with multiple
-subdirectories. With the `directory' command, you need to add each
+subdirectories. With the 'directory' command, you need to add each
subdirectory of your project. If you moved the entire tree while
-preserving its internal organization, then `set substitute-path' allows
+preserving its internal organization, then 'set substitute-path' allows
you to direct the debugger to all the sources with one single command.
- `set substitute-path' is also more than just a shortcut command.
-The source path is only used if the file at the original location no
-longer exists. On the other hand, `set substitute-path' modifies the
-debugger behavior to look at the rewritten location instead. So, if
-for any reason a source file that is not relevant to your executable is
-located at the original location, a substitution rule is the only
-method available to point GDB at the new location.
+ 'set substitute-path' is also more than just a shortcut command. The
+source path is only used if the file at the original location no longer
+exists. On the other hand, 'set substitute-path' modifies the debugger
+behavior to look at the rewritten location instead. So, if for any
+reason a source file that is not relevant to your executable is located
+at the original location, a substitution rule is the only method
+available to point GDB at the new location.
You can configure a default source path substitution rule by
-configuring GDB with the `--with-relocated-sources=DIR' option. The DIR
+configuring GDB with the '--with-relocated-sources=DIR' option. The DIR
should be the name of a directory under GDB's configured prefix (set
-with `--prefix' or `--exec-prefix'), and directory names in debug
+with '--prefix' or '--exec-prefix'), and directory names in debug
information under DIR will be adjusted automatically if the installed
GDB is moved to a new location. This is useful if GDB, libraries or
executables with debug information and corresponding source code are
being moved together.
-`directory DIRNAME ...'
-
-`dir DIRNAME ...'
+'directory DIRNAME ...'
+'dir DIRNAME ...'
Add directory DIRNAME to the front of the source path. Several
- directory names may be given to this command, separated by `:'
- (`;' on MS-DOS and MS-Windows, where `:' usually appears as part
- of absolute file names) or whitespace. You may specify a
- directory that is already in the source path; this moves it
- forward, so GDB searches it sooner.
-
- You can use the string `$cdir' to refer to the compilation
- directory (if one is recorded), and `$cwd' to refer to the current
- working directory. `$cwd' is not the same as `.'--the former
+ directory names may be given to this command, separated by ':' (';'
+ on MS-DOS and MS-Windows, where ':' usually appears as part of
+ absolute file names) or whitespace. You may specify a directory
+ that is already in the source path; this moves it forward, so GDB
+ searches it sooner.
+
+ You can use the string '$cdir' to refer to the compilation
+ directory (if one is recorded), and '$cwd' to refer to the current
+ working directory. '$cwd' is not the same as '.'--the former
tracks the current working directory as it changes during your GDB
session, while the latter is immediately expanded to the current
directory at the time you add an entry to the source path.
-`directory'
- Reset the source path to its default value (`$cdir:$cwd' on Unix
+'directory'
+ Reset the source path to its default value ('$cdir:$cwd' on Unix
systems). This requires confirmation.
-`set directories PATH-LIST'
- Set the source path to PATH-LIST. `$cdir:$cwd' are added if
+'set directories PATH-LIST'
+ Set the source path to PATH-LIST. '$cdir:$cwd' are added if
missing.
-`show directories'
+'show directories'
Print the source path: show which directories it contains.
-`set substitute-path FROM TO'
+'set substitute-path FROM TO'
Define a source path substitution rule, and add it at the end of
the current list of existing substitution rules. If a rule with
the same FROM was already defined, then the old rule is also
deleted.
- For example, if the file `/foo/bar/baz.c' was moved to
- `/mnt/cross/baz.c', then the command
+ For example, if the file '/foo/bar/baz.c' was moved to
+ '/mnt/cross/baz.c', then the command
(gdb) set substitute-path /usr/src /mnt/cross
- will tell GDB to replace `/usr/src' with `/mnt/cross', which will
- allow GDB to find the file `baz.c' even though it was moved.
+ will tell GDB to replace '/usr/src' with '/mnt/cross', which will
+ allow GDB to find the file 'baz.c' even though it was moved.
In the case when more than one substitution rule have been defined,
the rules are evaluated one by one in the order where they have
(gdb) set substitute-path /usr/src/include /mnt/include
(gdb) set substitute-path /usr/src /mnt/src
- GDB would then rewrite `/usr/src/include/defs.h' into
- `/mnt/include/defs.h' by using the first rule. However, it would
- use the second rule to rewrite `/usr/src/lib/foo.c' into
- `/mnt/src/lib/foo.c'.
+ GDB would then rewrite '/usr/src/include/defs.h' into
+ '/mnt/include/defs.h' by using the first rule. However, it would
+ use the second rule to rewrite '/usr/src/lib/foo.c' into
+ '/mnt/src/lib/foo.c'.
-`unset substitute-path [path]'
+'unset substitute-path [path]'
If a path is specified, search the current list of substitution
- rules for a rule that would rewrite that path. Delete that rule
- if found. A warning is emitted by the debugger if no rule could
- be found.
+ rules for a rule that would rewrite that path. Delete that rule if
+ found. A warning is emitted by the debugger if no rule could be
+ found.
If no path is specified, then all substitution rules are deleted.
-`show substitute-path [path]'
+'show substitute-path [path]'
If a path is specified, then print the source path substitution
rule which would rewrite that path, if any.
If no path is specified, then print all existing source path
substitution rules.
-
If your source path is cluttered with directories that are no longer
of interest, GDB may sometimes cause confusion by finding the wrong
versions of source. You can correct the situation as follows:
- 1. Use `directory' with no argument to reset the source path to its
+ 1. Use 'directory' with no argument to reset the source path to its
default value.
- 2. Use `directory' with suitable arguments to reinstall the
+ 2. Use 'directory' with suitable arguments to reinstall the
directories you want in the source path. You can add all the
directories in one command.
9.6 Source and Machine Code
===========================
-You can use the command `info line' to map source lines to program
-addresses (and vice versa), and the command `disassemble' to display a
+You can use the command 'info line' to map source lines to program
+addresses (and vice versa), and the command 'disassemble' to display a
range of addresses as machine instructions. You can use the command
-`set disassemble-next-line' to set whether to disassemble next source
-line when execution stops. When run under GNU Emacs mode, the `info
+'set disassemble-next-line' to set whether to disassemble next source
+line when execution stops. When run under GNU Emacs mode, the 'info
line' command causes the arrow to point to the line specified. Also,
-`info line' prints addresses in symbolic form as well as hex.
+'info line' prints addresses in symbolic form as well as hex.
-`info line LINESPEC'
+'info line LINESPEC'
Print the starting and ending addresses of the compiled code for
source line LINESPEC. You can specify source lines in any of the
- ways documented in *Note Specify Location::.
+ ways documented in *note Specify Location::.
- For example, we can use `info line' to discover the location of the
-object code for the first line of function `m4_changequote':
+ For example, we can use 'info line' to discover the location of the
+object code for the first line of function 'm4_changequote':
(gdb) info line m4_changequote
Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
-We can also inquire (using `*ADDR' as the form for LINESPEC) what
-source line covers a particular address:
+We can also inquire (using '*ADDR' as the form for LINESPEC) what source
+line covers a particular address:
(gdb) info line *0x63ff
Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
- After `info line', the default address for the `x' command is
-changed to the starting address of the line, so that `x/i' is
-sufficient to begin examining the machine code (*note Examining Memory:
-Memory.). Also, this address is saved as the value of the convenience
-variable `$_' (*note Convenience Variables: Convenience Vars.).
+ After 'info line', the default address for the 'x' command is changed
+to the starting address of the line, so that 'x/i' is sufficient to
+begin examining the machine code (*note Examining Memory: Memory.).
+Also, this address is saved as the value of the convenience variable
+'$_' (*note Convenience Variables: Convenience Vars.).
-`disassemble'
-`disassemble /m'
-`disassemble /r'
+'disassemble'
+'disassemble /m'
+'disassemble /r'
This specialized command dumps a range of memory as machine
instructions. It can also print mixed source+disassembly by
- specifying the `/m' modifier and print the raw instructions in hex
- as well as in symbolic form by specifying the `/r'. The default
- memory range is the function surrounding the program counter of
- the selected frame. A single argument to this command is a
- program counter value; GDB dumps the function surrounding this
- value. When two arguments are given, they should be separated by
- a comma, possibly surrounded by whitespace. The arguments specify
- a range of addresses to dump, in one of two forms:
-
- `START,END'
+ specifying the '/m' modifier and print the raw instructions in hex
+ as well as in symbolic form by specifying the '/r'. The default
+ memory range is the function surrounding the program counter of the
+ selected frame. A single argument to this command is a program
+ counter value; GDB dumps the function surrounding this value. When
+ two arguments are given, they should be separated by a comma,
+ possibly surrounded by whitespace. The arguments specify a range
+ of addresses to dump, in one of two forms:
+
+ 'START,END'
the addresses from START (inclusive) to END (exclusive)
-
- `START,+LENGTH'
- the addresses from START (inclusive) to `START+LENGTH'
+ 'START,+LENGTH'
+ the addresses from START (inclusive) to 'START+LENGTH'
(exclusive).
When 2 arguments are specified, the name of the function is also
range).
The argument(s) can be any expression yielding a numeric value,
- such as `0x32c4', `&main+10' or `$pc - 8'.
+ such as '0x32c4', '&main+10' or '$pc - 8'.
If the range of memory being disassembled contains current program
- counter, the instruction at that location is shown with a `=>'
+ counter, the instruction at that location is shown with a '=>'
marker.
The following example shows the disassembly of a range of addresses
0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
End of assembler dump.
+ Addresses cannot be specified as a linespec (*note Specify
+Location::). So, for example, if you want to disassemble function 'bar'
+in file 'foo.c', you must type 'disassemble 'foo.c'::bar' and not
+'disassemble foo.c:bar'.
+
Some architectures have more than one commonly-used set of
instruction mnemonics or other syntax.
location of the relocation table. On some architectures, GDB might be
able to resolve these to actual function names.
-`set disassembly-flavor INSTRUCTION-SET'
+'set disassembly-flavor INSTRUCTION-SET'
Select the instruction set to use when disassembling the program
- via the `disassemble' or `x/i' commands.
+ via the 'disassemble' or 'x/i' commands.
Currently this command is only defined for the Intel x86 family.
- You can set INSTRUCTION-SET to either `intel' or `att'. The
- default is `att', the AT&T flavor used by default by Unix
+ You can set INSTRUCTION-SET to either 'intel' or 'att'. The
+ default is 'att', the AT&T flavor used by default by Unix
assemblers for x86-based targets.
-`show disassembly-flavor'
+'show disassembly-flavor'
Show the current setting of the disassembly flavor.
-`set disassemble-next-line'
-`show disassemble-next-line'
- Control whether or not GDB will disassemble the next source line
- or instruction when execution stops. If ON, GDB will display
+'set disassemble-next-line'
+'show disassemble-next-line'
+ Control whether or not GDB will disassemble the next source line or
+ instruction when execution stops. If ON, GDB will display
disassembly of the next source line when execution of the program
being debugged stops. This is _in addition_ to displaying the
- source line itself, which GDB always does if possible. If the
- next source line cannot be displayed for some reason (e.g., if GDB
+ source line itself, which GDB always does if possible. If the next
+ source line cannot be displayed for some reason (e.g., if GDB
cannot find the source file, or there's no line info in the debug
info), GDB will display disassembly of the next _instruction_
- instead of showing the next source line. If AUTO, GDB will
- display disassembly of next instruction only if the source line
- cannot be displayed. This setting causes GDB to display some
- feedback when you step through a function with no line info or
- whose source file is unavailable. The default is OFF, which means
- never display the disassembly of the next line or instruction.
+ instead of showing the next source line. If AUTO, GDB will display
+ disassembly of next instruction only if the source line cannot be
+ displayed. This setting causes GDB to display some feedback when
+ you step through a function with no line info or whose source file
+ is unavailable. The default is OFF, which means never display the
+ disassembly of the next line or instruction.
\1f
File: gdb.info, Node: Data, Next: Optimized Code, Prev: Source, Up: Top
10 Examining Data
*****************
-The usual way to examine data in your program is with the `print'
-command (abbreviated `p'), or its synonym `inspect'. It evaluates and
+The usual way to examine data in your program is with the 'print'
+command (abbreviated 'p'), or its synonym 'inspect'. It evaluates and
prints the value of an expression of the language your program is
written in (*note Using GDB with Different Languages: Languages.). It
-may also print the expression using a Python-based pretty-printer
-(*note Pretty Printing::).
+may also print the expression using a Python-based pretty-printer (*note
+Pretty Printing::).
-`print EXPR'
-`print /F EXPR'
+'print EXPR'
+'print /F EXPR'
EXPR is an expression (in the source language). By default the
value of EXPR is printed in a format appropriate to its data type;
- you can choose a different format by specifying `/F', where F is a
- letter specifying the format; see *Note Output Formats: Output
+ you can choose a different format by specifying '/F', where F is a
+ letter specifying the format; see *note Output Formats: Output
Formats.
-`print'
-`print /F'
+'print'
+'print /F'
If you omit EXPR, GDB displays the last value again (from the
- "value history"; *note Value History: Value History.). This
- allows you to conveniently inspect the same value in an
- alternative format.
+ "value history"; *note Value History: Value History.). This allows
+ you to conveniently inspect the same value in an alternative
+ format.
- A more low-level way of examining data is with the `x' command. It
+ A more low-level way of examining data is with the 'x' command. It
examines data in memory at a specified address and prints it in a
specified format. *Note Examining Memory: Memory.
If you are interested in information about types, or about how the
-fields of a struct or a class are declared, use the `ptype EXP' command
-rather than `print'. *Note Examining the Symbol Table: Symbols.
+fields of a struct or a class are declared, use the 'ptype EXP' command
+rather than 'print'. *Note Examining the Symbol Table: Symbols.
Another way of examining values of expressions and type information
-is through the Python extension command `explore' (available only if
-the GDB build is configured with `--with-python'). It offers an
-interactive way to start at the highest level (or, the most abstract
-level) of the data type of an expression (or, the data type itself) and
-explore all the way down to leaf scalar values/fields embedded in the
-higher level data types.
-
-`explore ARG'
+is through the Python extension command 'explore' (available only if the
+GDB build is configured with '--with-python'). It offers an interactive
+way to start at the highest level (or, the most abstract level) of the
+data type of an expression (or, the data type itself) and explore all
+the way down to leaf scalar values/fields embedded in the higher level
+data types.
+
+'explore ARG'
ARG is either an expression (in the source language), or a type
visible in the current context of the program being debugged.
- The working of the `explore' command can be illustrated with an
-example. If a data type `struct ComplexStruct' is defined in your C
+ The working of the 'explore' command can be illustrated with an
+example. If a data type 'struct ComplexStruct' is defined in your C
program as
struct SimpleStruct
struct SimpleStruct ss = { 10, 1.11 };
struct ComplexStruct cs = { &ss, { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 } };
-then, the value of the variable `cs' can be explored using the
-`explore' command as follows.
+then, the value of the variable 'cs' can be explored using the 'explore'
+command as follows.
(gdb) explore cs
The value of `cs' is a struct/class of type `struct ComplexStruct' with
Enter the field number of choice:
-Since the fields of `cs' are not scalar values, you are being prompted
+Since the fields of 'cs' are not scalar values, you are being prompted
to chose the field you want to explore. Let's say you choose the field
-`ss_p' by entering `0'. Then, since this field is a pointer, you will
+'ss_p' by entering '0'. Then, since this field is a pointer, you will
be asked if it is pointing to a single value. From the declaration of
-`cs' above, it is indeed pointing to a single value, hence you enter
-`y'. If you enter `n', then you will be asked if it were pointing to
-an array of values, in which case this field will be explored as if it
-were an array.
+'cs' above, it is indeed pointing to a single value, hence you enter
+'y'. If you enter 'n', then you will be asked if it were pointing to an
+array of values, in which case this field will be explored as if it were
+an array.
`cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
Continue exploring it as a pointer to a single value [y/n]: y
Press enter to return to parent value:
-If the field `arr' of `cs' was chosen for exploration by entering `1'
+If the field 'arr' of 'cs' was chosen for exploration by entering '1'
earlier, then since it is as array, you will be prompted to enter the
index of the element in the array that you want to explore.
return key to return to the enclosing data structure (the higher level
data structure).
- Similar to exploring values, you can use the `explore' command to
+ Similar to exploring values, you can use the 'explore' command to
explore types. Instead of specifying a value (which is typically a
variable name or an expression valid in the current context of the
program being debugged), you specify a type name. If you consider the
-same example as above, your can explore the type `struct ComplexStruct'
-by passing the argument `struct ComplexStruct' to the `explore' command.
+same example as above, your can explore the type 'struct ComplexStruct'
+by passing the argument 'struct ComplexStruct' to the 'explore' command.
(gdb) explore struct ComplexStruct
By responding to the prompts appropriately in the subsequent interactive
-session, you can explore the type `struct ComplexStruct' in a manner
-similar to how the value `cs' was explored in the above example.
+session, you can explore the type 'struct ComplexStruct' in a manner
+similar to how the value 'cs' was explored in the above example.
- The `explore' command also has two sub-commands, `explore value' and
-`explore type'. The former sub-command is a way to explicitly specify
+ The 'explore' command also has two sub-commands, 'explore value' and
+'explore type'. The former sub-command is a way to explicitly specify
that value exploration of the argument is being invoked, while the
latter is a way to explicitly specify that type exploration of the
argument is being invoked.
-`explore value EXPR'
- This sub-command of `explore' explores the value of the expression
+'explore value EXPR'
+ This sub-command of 'explore' explores the value of the expression
EXPR (if EXPR is an expression valid in the current context of the
- program being debugged). The behavior of this command is
- identical to that of the behavior of the `explore' command being
- passed the argument EXPR.
-
-`explore type ARG'
- This sub-command of `explore' explores the type of ARG (if ARG is
- a type visible in the current context of program being debugged),
- or the type of the value/expression ARG (if ARG is an expression
- valid in the current context of the program being debugged). If
- ARG is a type, then the behavior of this command is identical to
- that of the `explore' command being passed the argument ARG. If
- ARG is an expression, then the behavior of this command will be
- identical to that of the `explore' command being passed the type
- of ARG as the argument.
+ program being debugged). The behavior of this command is identical
+ to that of the behavior of the 'explore' command being passed the
+ argument EXPR.
+
+'explore type ARG'
+ This sub-command of 'explore' explores the type of ARG (if ARG is a
+ type visible in the current context of program being debugged), or
+ the type of the value/expression ARG (if ARG is an expression valid
+ in the current context of the program being debugged). If ARG is a
+ type, then the behavior of this command is identical to that of the
+ 'explore' command being passed the argument ARG. If ARG is an
+ expression, then the behavior of this command will be identical to
+ that of the 'explore' command being passed the type of ARG as the
+ argument.
* Menu:
* Pretty Printing:: Python pretty printing
* Value History:: Value history
* Convenience Vars:: Convenience variables
+* Convenience Funs:: Convenience functions
* Registers:: Registers
* Floating Point Hardware:: Floating point hardware
* Vector Unit:: Vector Unit
* Core File Generation:: Cause a program dump its core
* Character Sets:: Debugging programs that use a different
character set than GDB does
-* Caching Remote Data:: Data caching for remote targets
+* Caching Target Data:: Data caching for targets
* Searching Memory:: Searching memory for a sequence of bytes
\1f
10.1 Expressions
================
-`print' and many other GDB commands accept an expression and compute
-its value. Any kind of constant, variable or operator defined by the
+'print' and many other GDB commands accept an expression and compute its
+value. Any kind of constant, variable or operator defined by the
programming language you are using is valid in an expression in GDB.
-This includes conditional expressions, function calls, casts, and
-string constants. It also includes preprocessor macros, if you
-compiled your program to include this information; see *Note
-Compilation::.
+This includes conditional expressions, function calls, casts, and string
+constants. It also includes preprocessor macros, if you compiled your
+program to include this information; see *note Compilation::.
GDB supports array constants in expressions input by the user. The
syntax is {ELEMENT, ELEMENT...}. For example, you can use the command
-`print {1, 2, 3}' to create an array of three integers. If you pass an
+'print {1, 2, 3}' to create an array of three integers. If you pass an
array to a function or assign it to a program variable, GDB copies the
-array to memory that is `malloc'ed in the target program.
+array to memory that is 'malloc'ed in the target program.
- Because C is so widespread, most of the expressions shown in
-examples in this manual are in C. *Note Using GDB with Different
-Languages: Languages, for information on how to use expressions in other
-languages.
+ Because C is so widespread, most of the expressions shown in examples
+in this manual are in C. *Note Using GDB with Different Languages:
+Languages, for information on how to use expressions in other languages.
In this section, we discuss operators that you can use in GDB
expressions regardless of your programming language.
GDB supports these operators, in addition to those common to
programming languages:
-`@'
- `@' is a binary operator for treating parts of memory as arrays.
+'@'
+ '@' is a binary operator for treating parts of memory as arrays.
*Note Artificial Arrays: Arrays, for more information.
-`::'
- `::' allows you to specify a variable in terms of the file or
+'::'
+ '::' allows you to specify a variable in terms of the file or
function where it is defined. *Note Program Variables: Variables.
-`{TYPE} ADDR'
+'{TYPE} ADDR'
Refers to an object of type TYPE stored at address ADDR in memory.
- ADDR may be any expression whose value is an integer or pointer
- (but parentheses are required around binary operators, just as in
- a cast). This construct is allowed regardless of what kind of
- data is normally supposed to reside at ADDR.
+ The address ADDR may be any expression whose value is an integer or
+ pointer (but parentheses are required around binary operators, just
+ as in a cast). This construct is allowed regardless of what kind
+ of data is normally supposed to reside at ADDR.
\1f
File: gdb.info, Node: Ambiguous Expressions, Next: Variables, Prev: Expressions, Up: Data
In some cases and depending on the language, it is possible to adjust
the expression to remove the ambiguity. For instance in C++, you can
-specify the signature of the function you want to break on, as in
-`break FUNCTION(TYPES)'. In Ada, using the fully qualified name of
-your function often makes the expression unambiguous as well.
+specify the signature of the function you want to break on, as in 'break
+FUNCTION(TYPES)'. In Ada, using the fully qualified name of your
+function often makes the expression unambiguous as well.
When an ambiguity that needs to be resolved is detected, the debugger
has the capability to display a menu of numbered choices for each
-possibility, and then waits for the selection with the prompt `>'. The
-first option is always `[0] cancel', and typing `0 <RET>' aborts the
-current command. If the command in which the expression was used
-allows more than one choice to be selected, the next option in the menu
-is `[1] all', and typing `1 <RET>' selects all possible choices.
+possibility, and then waits for the selection with the prompt '>'. The
+first option is always '[0] cancel', and typing '0 <RET>' aborts the
+current command. If the command in which the expression was used allows
+more than one choice to be selected, the next option in the menu is '[1]
+all', and typing '1 <RET>' selects all possible choices.
For example, the following session excerpt shows an attempt to set a
-breakpoint at the overloaded symbol `String::after'. We choose three
+breakpoint at the overloaded symbol 'String::after'. We choose three
particular definitions of that function name:
(gdb) b String::after
breakpoints.
(gdb)
-`set multiple-symbols MODE'
+'set multiple-symbols MODE'
+
This option allows you to adjust the debugger behavior when an
expression is ambiguous.
- By default, MODE is set to `all'. If the command with which the
+ By default, MODE is set to 'all'. If the command with which the
expression is used allows more than one choice, then GDB
automatically selects all possible choices. For instance,
inserting a breakpoint on a function using an ambiguous name
results in a breakpoint inserted on each possible match. However,
- if a unique choice must be made, then GDB uses the menu to help
- you disambiguate the expression. For instance, printing the
- address of an overloaded function will result in the use of the
- menu.
+ if a unique choice must be made, then GDB uses the menu to help you
+ disambiguate the expression. For instance, printing the address of
+ an overloaded function will result in the use of the menu.
- When MODE is set to `ask', the debugger always uses the menu when
+ When MODE is set to 'ask', the debugger always uses the menu when
an ambiguity is detected.
- Finally, when MODE is set to `cancel', the debugger reports an
+ Finally, when MODE is set to 'cancel', the debugger reports an
error due to the ambiguity and the command is aborted.
-`show multiple-symbols'
- Show the current value of the `multiple-symbols' setting.
-
-\1f
-File: gdb.info, Node: Variables, Next: Arrays, Prev: Ambiguous Expressions, Up: Data
-
-10.3 Program Variables
-======================
-
-The most common kind of expression to use is the name of a variable in
-your program.
-
- Variables in expressions are understood in the selected stack frame
-(*note Selecting a Frame: Selection.); they must be either:
-
- * global (or file-static)
-
-or
-
- * visible according to the scope rules of the programming language
- from the point of execution in that frame
-
-This means that in the function
-
- foo (a)
- int a;
- {
- bar (a);
- {
- int b = test ();
- bar (b);
- }
- }
-
-you can examine and use the variable `a' whenever your program is
-executing within the function `foo', but you can only use or examine
-the variable `b' while your program is executing inside the block where
-`b' is declared.
-
- There is an exception: you can refer to a variable or function whose
-scope is a single source file even if the current execution point is not
-in this file. But it is possible to have more than one such variable or
-function with the same name (in different source files). If that
-happens, referring to that name has unpredictable effects. If you wish,
-you can specify a static variable in a particular function or file by
-using the colon-colon (`::') notation:
-
- FILE::VARIABLE
- FUNCTION::VARIABLE
-
-Here FILE or FUNCTION is the name of the context for the static
-VARIABLE. In the case of file names, you can use quotes to make sure
-GDB parses the file name as a single word--for example, to print a
-global value of `x' defined in `f2.c':
-
- (gdb) p 'f2.c'::x
-
- The `::' notation is normally used for referring to static
-variables, since you typically disambiguate uses of local variables in
-functions by selecting the appropriate frame and using the simple name
-of the variable. However, you may also use this notation to refer to
-local variables in frames enclosing the selected frame:
-
- void
- foo (int a)
- {
- if (a < 10)
- bar (a);
- else
- process (a); /* Stop here */
- }
-
- int
- bar (int a)
- {
- foo (a + 5);
- }
-
-For example, if there is a breakpoint at the commented line, here is
-what you might see when the program stops after executing the call
-`bar(0)':
-
- (gdb) p a
- $1 = 10
- (gdb) p bar::a
- $2 = 5
- (gdb) up 2
- #2 0x080483d0 in foo (a=5) at foobar.c:12
- (gdb) p a
- $3 = 5
- (gdb) p bar::a
- $4 = 0
-
- These uses of `::' are very rarely in conflict with the very similar
-use of the same notation in C++. GDB also supports use of the C++
-scope resolution operator in GDB expressions.
-
- _Warning:_ Occasionally, a local variable may appear to have the
- wrong value at certain points in a function--just after entry to a
- new scope, and just before exit.
- You may see this problem when you are stepping by machine
-instructions. This is because, on most machines, it takes more than
-one instruction to set up a stack frame (including local variable
-definitions); if you are stepping by machine instructions, variables
-may appear to have the wrong values until the stack frame is completely
-built. On exit, it usually also takes more than one machine
-instruction to destroy a stack frame; after you begin stepping through
-that group of instructions, local variable definitions may be gone.
-
- This may also happen when the compiler does significant
-optimizations. To be sure of always seeing accurate values, turn off
-all optimization when compiling.
-
- Another possible effect of compiler optimizations is to optimize
-unused variables out of existence, or assign variables to registers (as
-opposed to memory addresses). Depending on the support for such cases
-offered by the debug info format used by the compiler, GDB might not be
-able to display values for such local variables. If that happens, GDB
-will print a message like this:
-
- No symbol "foo" in current context.
-
- To solve such problems, either recompile without optimizations, or
-use a different debug info format, if the compiler supports several such
-formats. *Note Compilation::, for more information on choosing compiler
-options. *Note C and C++: C, for more information about debug info
-formats that are best suited to C++ programs.
-
- If you ask to print an object whose contents are unknown to GDB,
-e.g., because its data type is not completely specified by the debug
-information, GDB will say `<incomplete type>'. *Note incomplete type:
-Symbols, for more about this.
-
- If you append `@entry' string to a function parameter name you get
-its value at the time the function got called. If the value is not
-available an error message is printed. Entry values are available only
-with some compilers. Entry values are normally also printed at the
-function parameter list according to *Note set print entry-values::.
-
- Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
- 29 i++;
- (gdb) next
- 30 e (i);
- (gdb) print i
- $1 = 31
- (gdb) print i@entry
- $2 = 30
-
- Strings are identified as arrays of `char' values without specified
-signedness. Arrays of either `signed char' or `unsigned char' get
-printed as arrays of 1 byte sized integers. `-fsigned-char' or
-`-funsigned-char' GCC options have no effect as GDB defines literal
-string type `"char"' as `char' without a sign. For program code
-
- char var0[] = "A";
- signed char var1[] = "A";
-
- You get during debugging
- (gdb) print var0
- $1 = "A"
- (gdb) print var1
- $2 = {65 'A', 0 '\0'}
-
-\1f
-File: gdb.info, Node: Arrays, Next: Output Formats, Prev: Variables, Up: Data
-
-10.4 Artificial Arrays
-======================
-
-It is often useful to print out several successive objects of the same
-type in memory; a section of an array, or an array of dynamically
-determined size for which only a pointer exists in the program.
-
- You can do this by referring to a contiguous span of memory as an
-"artificial array", using the binary operator `@'. The left operand of
-`@' should be the first element of the desired array and be an
-individual object. The right operand should be the desired length of
-the array. The result is an array value whose elements are all of the
-type of the left argument. The first element is actually the left
-argument; the second element comes from bytes of memory immediately
-following those that hold the first element, and so on. Here is an
-example. If a program says
-
- int *array = (int *) malloc (len * sizeof (int));
-
-you can print the contents of `array' with
-
- p *array@len
-
- The left operand of `@' must reside in memory. Array values made
-with `@' in this way behave just like other arrays in terms of
-subscripting, and are coerced to pointers when used in expressions.
-Artificial arrays most often appear in expressions via the value history
-(*note Value History: Value History.), after printing one out.
-
- Another way to create an artificial array is to use a cast. This
-re-interprets a value as if it were an array. The value need not be in
-memory:
- (gdb) p/x (short[2])0x12345678
- $1 = {0x1234, 0x5678}
-
- As a convenience, if you leave the array length out (as in
-`(TYPE[])VALUE') GDB calculates the size to fill the value (as
-`sizeof(VALUE)/sizeof(TYPE)':
- (gdb) p/x (short[])0x12345678
- $2 = {0x1234, 0x5678}
-
- Sometimes the artificial array mechanism is not quite enough; in
-moderately complex data structures, the elements of interest may not
-actually be adjacent--for example, if you are interested in the values
-of pointers in an array. One useful work-around in this situation is
-to use a convenience variable (*note Convenience Variables: Convenience
-Vars.) as a counter in an expression that prints the first interesting
-value, and then repeat that expression via <RET>. For instance,
-suppose you have an array `dtab' of pointers to structures, and you are
-interested in the values of a field `fv' in each structure. Here is an
-example of what you might type:
-
- set $i = 0
- p dtab[$i++]->fv
- <RET>
- <RET>
- ...
-
-\1f
-File: gdb.info, Node: Output Formats, Next: Memory, Prev: Arrays, Up: Data
-
-10.5 Output Formats
-===================
-
-By default, GDB prints a value according to its data type. Sometimes
-this is not what you want. For example, you might want to print a
-number in hex, or a pointer in decimal. Or you might want to view data
-in memory at a certain address as a character string or as an
-instruction. To do these things, specify an "output format" when you
-print a value.
-
- The simplest use of output formats is to say how to print a value
-already computed. This is done by starting the arguments of the
-`print' command with a slash and a format letter. The format letters
-supported are:
-
-`x'
- Regard the bits of the value as an integer, and print the integer
- in hexadecimal.
-
-`d'
- Print as integer in signed decimal.
-
-`u'
- Print as integer in unsigned decimal.
-
-`o'
- Print as integer in octal.
-
-`t'
- Print as integer in binary. The letter `t' stands for "two". (1)
-
-`a'
- Print as an address, both absolute in hexadecimal and as an offset
- from the nearest preceding symbol. You can use this format used
- to discover where (in what function) an unknown address is located:
-
- (gdb) p/a 0x54320
- $3 = 0x54320 <_initialize_vx+396>
-
- The command `info symbol 0x54320' yields similar results. *Note
- info symbol: Symbols.
-
-`c'
- Regard as an integer and print it as a character constant. This
- prints both the numerical value and its character representation.
- The character representation is replaced with the octal escape
- `\nnn' for characters outside the 7-bit ASCII range.
-
- Without this format, GDB displays `char', `unsigned char', and
- `signed char' data as character constants. Single-byte members of
- vectors are displayed as integer data.
-
-`f'
- Regard the bits of the value as a floating point number and print
- using typical floating point syntax.
-
-`s'
- Regard as a string, if possible. With this format, pointers to
- single-byte data are displayed as null-terminated strings and
- arrays of single-byte data are displayed as fixed-length strings.
- Other values are displayed in their natural types.
-
- Without this format, GDB displays pointers to and arrays of
- `char', `unsigned char', and `signed char' as strings.
- Single-byte members of a vector are displayed as an integer array.
-
-`r'
- Print using the `raw' formatting. By default, GDB will use a
- Python-based pretty-printer, if one is available (*note Pretty
- Printing::). This typically results in a higher-level display of
- the value's contents. The `r' format bypasses any Python
- pretty-printer which might exist.
-
- For example, to print the program counter in hex (*note
-Registers::), type
-
- p/x $pc
-
-Note that no space is required before the slash; this is because command
-names in GDB cannot contain a slash.
-
- To reprint the last value in the value history with a different
-format, you can use the `print' command with just a format and no
-expression. For example, `p/x' reprints the last value in hex.
-
- ---------- Footnotes ----------
-
- (1) `b' cannot be used because these format letters are also used
-with the `x' command, where `b' stands for "byte"; see *Note Examining
-Memory: Memory.
-
-\1f
-File: gdb.info, Node: Memory, Next: Auto Display, Prev: Output Formats, Up: Data
-
-10.6 Examining Memory
-=====================
-
-You can use the command `x' (for "examine") to examine memory in any of
-several formats, independently of your program's data types.
-
-`x/NFU ADDR'
-`x ADDR'
-`x'
- Use the `x' command to examine memory.
-
- N, F, and U are all optional parameters that specify how much memory
-to display and how to format it; ADDR is an expression giving the
-address where you want to start displaying memory. If you use defaults
-for NFU, you need not type the slash `/'. Several commands set
-convenient defaults for ADDR.
-
-N, the repeat count
- The repeat count is a decimal integer; the default is 1. It
- specifies how much memory (counting by units U) to display.
-
-F, the display format
- The display format is one of the formats used by `print' (`x',
- `d', `u', `o', `t', `a', `c', `f', `s'), and in addition `i' (for
- machine instructions). The default is `x' (hexadecimal)
- initially. The default changes each time you use either `x' or
- `print'.
-
-U, the unit size
- The unit size is any of
-
- `b'
- Bytes.
-
- `h'
- Halfwords (two bytes).
-
- `w'
- Words (four bytes). This is the initial default.
-
- `g'
- Giant words (eight bytes).
-
- Each time you specify a unit size with `x', that size becomes the
- default unit the next time you use `x'. For the `i' format, the
- unit size is ignored and is normally not written. For the `s'
- format, the unit size defaults to `b', unless it is explicitly
- given. Use `x /hs' to display 16-bit char strings and `x /ws' to
- display 32-bit strings. The next use of `x /s' will again display
- 8-bit strings. Note that the results depend on the programming
- language of the current compilation unit. If the language is C,
- the `s' modifier will use the UTF-16 encoding while `w' will use
- UTF-32. The encoding is set by the programming language and cannot
- be altered.
-
-ADDR, starting display address
- ADDR is the address where you want GDB to begin displaying memory.
- The expression need not have a pointer value (though it may); it
- is always interpreted as an integer address of a byte of memory.
- *Note Expressions: Expressions, for more information on
- expressions. The default for ADDR is usually just after the last
- address examined--but several other commands also set the default
- address: `info breakpoints' (to the address of the last breakpoint
- listed), `info line' (to the starting address of a line), and
- `print' (if you use it to display a value from memory).
-
- For example, `x/3uh 0x54320' is a request to display three halfwords
-(`h') of memory, formatted as unsigned decimal integers (`u'), starting
-at address `0x54320'. `x/4xw $sp' prints the four words (`w') of
-memory above the stack pointer (here, `$sp'; *note Registers:
-Registers.) in hexadecimal (`x').
-
- Since the letters indicating unit sizes are all distinct from the
-letters specifying output formats, you do not have to remember whether
-unit size or format comes first; either order works. The output
-specifications `4xw' and `4wx' mean exactly the same thing. (However,
-the count N must come first; `wx4' does not work.)
-
- Even though the unit size U is ignored for the formats `s' and `i',
-you might still want to use a count N; for example, `3i' specifies that
-you want to see three machine instructions, including any operands.
-For convenience, especially when used with the `display' command, the
-`i' format also prints branch delay slot instructions, if any, beyond
-the count specified, which immediately follow the last instruction that
-is within the count. The command `disassemble' gives an alternative
-way of inspecting machine instructions; see *Note Source and Machine
-Code: Machine Code.
-
- All the defaults for the arguments to `x' are designed to make it
-easy to continue scanning memory with minimal specifications each time
-you use `x'. For example, after you have inspected three machine
-instructions with `x/3i ADDR', you can inspect the next seven with just
-`x/7'. If you use <RET> to repeat the `x' command, the repeat count N
-is used again; the other arguments default as for successive uses of
-`x'.
-
- When examining machine instructions, the instruction at current
-program counter is shown with a `=>' marker. For example:
-
- (gdb) x/5i $pc-6
- 0x804837f <main+11>: mov %esp,%ebp
- 0x8048381 <main+13>: push %ecx
- 0x8048382 <main+14>: sub $0x4,%esp
- => 0x8048385 <main+17>: movl $0x8048460,(%esp)
- 0x804838c <main+24>: call 0x80482d4 <puts@plt>
-
- The addresses and contents printed by the `x' command are not saved
-in the value history because there is often too much of them and they
-would get in the way. Instead, GDB makes these values available for
-subsequent use in expressions as values of the convenience variables
-`$_' and `$__'. After an `x' command, the last address examined is
-available for use in expressions in the convenience variable `$_'. The
-contents of that address, as examined, are available in the convenience
-variable `$__'.
-
- If the `x' command has a repeat count, the address and contents saved
-are from the last memory unit printed; this is not the same as the last
-address printed if several units were printed on the last line of
-output.
-
- When you are debugging a program running on a remote target machine
-(*note Remote Debugging::), you may wish to verify the program's image
-in the remote machine's memory against the executable file you
-downloaded to the target. The `compare-sections' command is provided
-for such situations.
-
-`compare-sections [SECTION-NAME]'
- Compare the data of a loadable section SECTION-NAME in the
- executable file of the program being debugged with the same
- section in the remote machine's memory, and report any mismatches.
- With no arguments, compares all loadable sections. This command's
- availability depends on the target's support for the `"qCRC"'
- remote request.
+'show multiple-symbols'
+ Show the current value of the 'multiple-symbols' setting.
projects / platform / upstream / gdb.git / blobdiff