8931 lines
323 KiB
Text
8931 lines
323 KiB
Text
\input texinfo @c -*-texinfo-*-
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@c Copyright (c) 1988 1989 1990 1991 1992 1993 Free Software Foundation, Inc.
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@c
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@c %**start of header
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@c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
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@c of @set vars. However, you can override filename with makeinfo -o.
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@setfilename gdb.info
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@c
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@include gdb-config.texi
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@c
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@ifset GENERIC
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@settitle Debugging with @value{GDBN}
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@end ifset
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@ifclear GENERIC
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@settitle Debugging with @value{GDBN} (@value{TARGET})
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@end ifclear
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@setchapternewpage odd
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@c %**end of header
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@iftex
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@c @smallbook
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@c @cropmarks
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@end iftex
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@finalout
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@syncodeindex ky cp
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@c readline appendices use @vindex
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@syncodeindex vr cp
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@c ===> NOTE! <==
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@c Determine the edition number in *three* places by hand:
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@c 1. First ifinfo section 2. title page 3. top node
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@c To find the locations, search for !!set
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@c GDB CHANGELOG CONSULTED BETWEEN:
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@c Fri Oct 11 23:27:06 1991 John Gilmore (gnu at cygnus.com)
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@c Sat Dec 22 02:51:40 1990 John Gilmore (gnu at cygint)
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@c THIS MANUAL REQUIRES TEXINFO-2 macros and info-makers to format properly.
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@ifinfo
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@c This is a dir.info fragment to support semi-automated addition of
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@c manuals to an info tree. zoo@cygnus.com is developing this facility.
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@format
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START-INFO-DIR-ENTRY
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* Gdb:: The GNU debugger.
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END-INFO-DIR-ENTRY
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@end format
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@end ifinfo
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@c
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@c
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@ifinfo
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This file documents the GNU debugger @value{GDBN}.
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@c !!set edition, date, version
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This is Edition 4.09, April 1993,
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of @cite{Debugging with @value{GDBN}: the GNU Source-Level Debugger}
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for GDB Version @value{GDBVN}.
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Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993 Free Software Foundation, Inc.
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Permission is granted to make and distribute verbatim copies of
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this manual provided the copyright notice and this permission notice
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are preserved on all copies.
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@ignore
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Permission is granted to process this file through TeX and print the
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results, provided the printed document carries copying permission
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notice identical to this one except for the removal of this paragraph
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(this paragraph not being relevant to the printed manual).
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@end ignore
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Permission is granted to copy and distribute modified versions of this
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manual under the conditions for verbatim copying, provided also that the
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section entitled ``GNU General Public License'' is included exactly as
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in the original, and provided that the entire resulting derived work is
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distributed under the terms of a permission notice identical to this
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one.
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Permission is granted to copy and distribute translations of this manual
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into another language, under the above conditions for modified versions,
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except that the section entitled ``GNU General Public License'' may be
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included in a translation approved by the Free Software Foundation
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instead of in the original English.
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@end ifinfo
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@titlepage
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@title Debugging with @value{GDBN}
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@subtitle The GNU Source-Level Debugger
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@ifclear GENERIC
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@subtitle (@value{TARGET})
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@end ifclear
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@sp 1
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@c !!set edition, date, version
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@subtitle Edition 4.09, for @value{GDBN} version @value{GDBVN}
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@subtitle April 1993
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@author by Richard M. Stallman and Roland H. Pesch
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@page
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@tex
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{\parskip=0pt
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\hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@prep.ai.mit.edu.)\par
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\hfill {\it Debugging with @value{GDBN}}\par
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\hfill \TeX{}info \texinfoversion\par
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\hfill pesch\@cygnus.com\par
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}
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@end tex
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@vskip 0pt plus 1filll
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Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993 Free Software Foundation, Inc.
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Permission is granted to make and distribute verbatim copies of
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this manual provided the copyright notice and this permission notice
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are preserved on all copies.
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Permission is granted to copy and distribute modified versions of this
|
|
manual under the conditions for verbatim copying, provided also that the
|
|
section entitled ``GNU General Public License'' is included exactly as
|
|
in the original, and provided that the entire resulting derived work is
|
|
distributed under the terms of a permission notice identical to this
|
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one.
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Permission is granted to copy and distribute translations of this manual
|
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into another language, under the above conditions for modified versions,
|
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except that the section entitled ``GNU General Public License'' may be
|
|
included in a translation approved by the Free Software Foundation
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instead of in the original English.
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@end titlepage
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@page
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@ifinfo
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@node Top
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@top Debugging with @value{GDBN}
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This file describes @value{GDBN}, the GNU symbolic debugger.
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@c !!set edition, date, version
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This is Edition 4.09, April 1993, for GDB Version @value{GDBVN}.
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@menu
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* Summary:: Summary of @value{GDBN}
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@ifset NOVEL
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* New Features:: New features since GDB version 3.5
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@end ifset
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@ifclear BARETARGET
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* Sample Session:: A sample @value{GDBN} session
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@end ifclear
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* Invocation:: Getting in and out of @value{GDBN}
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* Commands:: @value{GDBN} commands
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* Running:: Running programs under @value{GDBN}
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* Stopping:: Stopping and continuing
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* Stack:: Examining the stack
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* Source:: Examining source files
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* Data:: Examining data
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@ifclear CONLY
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* Languages:: Using @value{GDBN} with different languages
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@end ifclear
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@ifset CONLY
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* C:: C language support
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@end ifset
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@c remnant makeinfo bug, blank line needed after two end-ifs?
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* Symbols:: Examining the symbol table
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* Altering:: Altering execution
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* GDB Files:: @value{GDBN} files
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* Targets:: Specifying a debugging target
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* Controlling GDB:: Controlling @value{GDBN}
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* Sequences:: Canned sequences of commands
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@ifclear DOSHOST
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* Emacs:: Using @value{GDBN} under GNU Emacs
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@end ifclear
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* GDB Bugs:: Reporting bugs in @value{GDBN}
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* Command Line Editing:: Facilities of the readline library
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* Using History Interactively::
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@ifset NOVEL
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* Renamed Commands::
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@end ifset
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|
@ifclear PRECONFIGURED
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* Formatting Documentation:: How to format and print GDB documentation
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* Installing GDB:: Installing GDB
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@end ifclear
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@ifclear AGGLOMERATION
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* Copying:: GNU GENERAL PUBLIC LICENSE
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@end ifclear
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* Index:: Index
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@end menu
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@end ifinfo
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@node Summary
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@unnumbered Summary of @value{GDBN}
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The purpose of a debugger such as @value{GDBN} is to allow you to see what is
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going on ``inside'' another program while it executes---or what another
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program was doing at the moment it crashed.
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@value{GDBN} can do four main kinds of things (plus other things in support of
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these) to help you catch bugs in the act:
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@itemize @bullet
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@item
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Start your program, specifying anything that might affect its behavior.
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@item
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Make your program stop on specified conditions.
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@item
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Examine what has happened, when your program has stopped.
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@item
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Change things in your program, so you can experiment with correcting the
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effects of one bug and go on to learn about another.
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@end itemize
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@ifclear CONLY
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You can use @value{GDBN} to debug programs written in C, C++, and Modula-2.
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Fortran support will be added when a GNU Fortran compiler is ready.
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@end ifclear
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@menu
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* Free Software:: Freely redistributable software
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* Contributors:: Contributors to GDB
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@end menu
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@node Free Software
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@unnumberedsec Free software
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@value{GDBN} is @dfn{free software}, protected by the GNU General Public License
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(GPL). The GPL gives you the freedom to copy or adapt a licensed
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program---but every person getting a copy also gets with it the
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freedom to modify that copy (which means that they must get access to
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the source code), and the freedom to distribute further copies.
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Typical software companies use copyrights to limit your freedoms; the
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Free Software Foundation uses the GPL to preserve these freedoms.
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Fundamentally, the General Public License is a license which says that
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you have these freedoms and that you cannot take these freedoms away
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from anyone else.
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@ifclear AGGLOMERATION
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For full details, @pxref{Copying, ,GNU GENERAL PUBLIC LICENSE}.
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@end ifclear
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@node Contributors
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@unnumberedsec Contributors to GDB
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Richard Stallman was the original author of GDB, and of many other GNU
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programs. Many others have contributed to its development. This
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section attempts to credit major contributors. One of the virtues of
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free software is that everyone is free to contribute to it; with
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regret, we cannot actually acknowledge everyone here. The file
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@file{ChangeLog} in the GDB distribution approximates a blow-by-blow
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account.
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Changes much prior to version 2.0 are lost in the mists of time.
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@quotation
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@emph{Plea:} Additions to this section are particularly welcome. If you
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or your friends (or enemies, to be evenhanded) have been unfairly
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omitted from this list, we would like to add your names!
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@end quotation
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So that they may not regard their long labor as thankless, we
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particularly thank those who shepherded GDB through major releases: Stu
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|
Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, 4.4), John Gilmore
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(releases 4.3, 4.2, 4.1, 4.0, and 3.9); Jim Kingdon (releases 3.5, 3.4,
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3.3); and Randy Smith (releases 3.2, 3.1, 3.0). As major maintainer of
|
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GDB for some period, each contributed significantly to the structure,
|
|
stability, and capabilities of the entire debugger.
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Richard Stallman, assisted at various times by Pete TerMaat, Chris
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|
Hanson, and Richard Mlynarik, handled releases through 2.8.
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|
@ifclear CONLY
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|
Michael Tiemann is the author of most of the GNU C++ support in GDB,
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|
with significant additional contributions from Per Bothner. James
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|
Clark wrote the GNU C++ demangler. Early work on C++ was by Peter
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|
TerMaat (who also did much general update work leading to release 3.0).
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@end ifclear
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|
GDB 4 uses the BFD subroutine library to examine multiple
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object-file formats; BFD was a joint project of David V.
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|
Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
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|
David Johnson wrote the original COFF support; Pace Willison did
|
|
the original support for encapsulated COFF.
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|
Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
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|
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.
|
|
Keith Packard contributed NS32K support. Doug Rabson contributed
|
|
Acorn Risc Machine 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
|
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support.
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|
Rich Schaefer and Peter Schauer helped with support of SunOS shared
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|
libraries.
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|
Jay Fenlason and Roland McGrath ensured that GDB and GAS agree about
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|
several machine instruction sets.
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|
Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped
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|
develop remote debugging. Intel Corporation and Wind River Systems
|
|
contributed remote debugging modules for their products.
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|
Brian Fox is the author of the readline libraries providing
|
|
command-line editing and command history.
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|
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|
Andrew Beers of SUNY Buffalo wrote the language-switching code and
|
|
the Modula-2 support, and contributed the Languages chapter of this
|
|
manual.
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|
Fred Fish wrote most of the support for Unix System Vr4.
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|
@ifclear CONLY
|
|
He also enhanced the command-completion support to cover C++ overloaded
|
|
symbols.
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|
@end ifclear
|
|
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|
Hitachi America, Ltd. sponsored the support for Hitachi microprocessors.
|
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|
|
@ifset NOVEL
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@node New Features
|
|
@unnumbered New Features since GDB Version 3.5
|
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|
@table @emph
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@item Targets
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|
Using the new command @code{target}, you can select at runtime whether
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|
you are debugging local files, local processes, standalone systems over
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|
a serial port, realtime systems over a TCP/IP connection, etc. The
|
|
command @code{load} can download programs into a remote system. Serial
|
|
stubs are available for Motorola 680x0, Intel 80386, and Sparc remote
|
|
systems; GDB also supports debugging realtime processes running under
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|
VxWorks, using SunRPC Remote Procedure Calls over TCP/IP to talk to a
|
|
debugger stub on the target system. Internally, GDB now uses a function
|
|
vector to mediate access to different targets; if you need to add your
|
|
own support for a remote protocol, this makes it much easier.
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|
@item Watchpoints
|
|
GDB now sports watchpoints as well as breakpoints. You can use a
|
|
watchpoint to stop execution whenever the value of an expression
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|
changes, without having to predict a particular place in your program
|
|
where this may happen.
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|
@item Wide Output
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|
Commands that issue wide output now insert newlines at places designed
|
|
to make the output more readable.
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|
@item Object Code Formats
|
|
GDB uses a new library called the Binary File Descriptor (BFD)
|
|
Library to permit it to switch dynamically, without reconfiguration or
|
|
recompilation, between different object-file formats. Formats currently
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|
supported are COFF, a.out, and the Intel 960 b.out; files may be read as
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|
.o files, archive libraries, or core dumps. BFD is available as a
|
|
subroutine library so that other programs may take advantage of it, and
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the other GNU binary utilities are being converted to use it.
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|
@item Configuration and Ports
|
|
Compile-time configuration (to select a particular architecture and
|
|
operating system) is much easier. The script @code{configure} now
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|
allows you to configure GDB as either a native debugger or a
|
|
cross-debugger. @xref{Installing GDB}, for details on how to
|
|
configure.
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|
@item Interaction
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|
The user interface to the GDB control variables is simpler,
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|
and is consolidated in two commands, @code{set} and @code{show}. Output
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|
lines are now broken at readable places, rather than overflowing onto
|
|
the next line. You can suppress output of machine-level addresses,
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|
displaying only source language information.
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|
@item C++
|
|
GDB now supports C++ multiple inheritance (if used with a GCC
|
|
version 2 compiler), and also has limited support for C++ exception
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handling, with the commands @code{catch} and @code{info catch}: GDB
|
|
can break when an exception is raised, before the stack is peeled back
|
|
to the exception handler's context.
|
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|
@item Modula-2
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|
GDB now has preliminary support for the GNU Modula-2 compiler, currently
|
|
under development at the State University of New York at Buffalo.
|
|
Coordinated development of both GDB and the GNU Modula-2 compiler will
|
|
continue. Other Modula-2 compilers are currently not supported, and
|
|
attempting to debug programs compiled with them will likely result in an
|
|
error as the symbol table of the executable is read in.
|
|
|
|
@item Command Rationalization
|
|
Many GDB commands have been renamed to make them easier to remember
|
|
and use. In particular, the subcommands of @code{info} and
|
|
@code{show}/@code{set} are grouped to make the former refer to the state
|
|
of your program, and the latter refer to the state of GDB itself.
|
|
@xref{Renamed Commands}, for details on what commands were renamed.
|
|
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|
@item Shared Libraries
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|
GDB 4 can debug programs and core files that use SunOS, SVR4, or IBM RS/6000
|
|
shared libraries.
|
|
|
|
@item Reference Card
|
|
GDB 4 has a reference card. @xref{Formatting Documentation,,Formatting
|
|
the Documentation}, for instructions about how to print it.
|
|
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|
@item Work in Progress
|
|
Kernel debugging for BSD and Mach systems; Tahoe and HPPA architecture
|
|
support.
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|
@end table
|
|
@end ifset
|
|
|
|
@ifclear BARETARGET
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|
@node Sample Session
|
|
@chapter A Sample @value{GDBN} Session
|
|
|
|
You can use this manual at your leisure to read all about @value{GDBN}.
|
|
However, a handful of commands are enough to get started using the
|
|
debugger. This chapter illustrates those commands.
|
|
|
|
@iftex
|
|
In this sample session, we emphasize user input like this: @b{input},
|
|
to make it easier to pick out from the surrounding output.
|
|
@end iftex
|
|
|
|
@c FIXME: this example may not be appropriate for some configs, where
|
|
@c FIXME...primary interest is in remote use.
|
|
|
|
One of the preliminary versions of GNU @code{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 @code{m4}
|
|
session, we define a macro @code{foo} which expands to @code{0000}; we
|
|
then use the @code{m4} built-in @code{defn} to define @code{bar} as the
|
|
same thing. However, when we change the open quote string to
|
|
@code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
|
|
procedure fails to define a new synonym @code{baz}:
|
|
|
|
@smallexample
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|
$ @b{cd gnu/m4}
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|
$ @b{./m4}
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|
@b{define(foo,0000)}
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|
@b{foo}
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|
0000
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|
@b{define(bar,defn(`foo'))}
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|
@b{bar}
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|
0000
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|
@b{changequote(<QUOTE>,<UNQUOTE>)}
|
|
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|
@b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
|
|
@b{baz}
|
|
@b{C-d}
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|
m4: End of input: 0: fatal error: EOF in string
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|
@end smallexample
|
|
|
|
@noindent
|
|
Let us use @value{GDBN} to try to see what is going on.
|
|
|
|
@smallexample
|
|
$ @b{@value{GDBP} m4}
|
|
@c FIXME: this falsifies the exact text played out, to permit smallbook
|
|
@c FIXME... format to come out better.
|
|
GDB is free software and you are welcome to distribute copies
|
|
of it under certain conditions; type "show copying" to see
|
|
the conditions.
|
|
There is absolutely no warranty for GDB; type "show warranty"
|
|
for details.
|
|
GDB @value{GDBVN}, Copyright 1993 Free Software Foundation, Inc...
|
|
(@value{GDBP})
|
|
@end smallexample
|
|
|
|
@noindent
|
|
@value{GDBN} reads only enough symbol data to know where to find the rest when
|
|
needed; as a result, the first prompt comes up very quickly. We now
|
|
tell @value{GDBN} to use a narrower display width than usual, so that examples
|
|
will fit in this manual.
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{set width 70}
|
|
@end smallexample
|
|
|
|
@noindent
|
|
We need to see how the @code{m4} built-in @code{changequote} works.
|
|
Having looked at the source, we know the relevant subroutine is
|
|
@code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
|
|
@code{break} command.
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{break m4_changequote}
|
|
Breakpoint 1 at 0x62f4: file builtin.c, line 879.
|
|
@end smallexample
|
|
|
|
@noindent
|
|
Using the @code{run} command, we start @code{m4} running under @value{GDBN}
|
|
control; as long as control does not reach the @code{m4_changequote}
|
|
subroutine, the program runs as usual:
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{run}
|
|
Starting program: /work/Editorial/gdb/gnu/m4/m4
|
|
@b{define(foo,0000)}
|
|
|
|
@b{foo}
|
|
0000
|
|
@end smallexample
|
|
|
|
@noindent
|
|
To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
|
|
suspends execution of @code{m4}, displaying information about the
|
|
context where it stops.
|
|
|
|
@smallexample
|
|
@b{changequote(<QUOTE>,<UNQUOTE>)}
|
|
|
|
Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
|
|
at builtin.c:879
|
|
879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
|
|
@end smallexample
|
|
|
|
@noindent
|
|
Now we use the command @code{n} (@code{next}) to advance execution to
|
|
the next line of the current function.
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{n}
|
|
882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
|
|
: nil,
|
|
@end smallexample
|
|
|
|
@noindent
|
|
@code{set_quotes} looks like a promising subroutine. We can go into it
|
|
by using the command @code{s} (@code{step}) instead of @code{next}.
|
|
@code{step} goes to the next line to be executed in @emph{any}
|
|
subroutine, so it steps into @code{set_quotes}.
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{s}
|
|
set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
|
|
at input.c:530
|
|
530 if (lquote != def_lquote)
|
|
@end smallexample
|
|
|
|
@noindent
|
|
The display that shows the subroutine where @code{m4} is now
|
|
suspended (and its arguments) is called a stack frame display. It
|
|
shows a summary of the stack. We can use the @code{backtrace}
|
|
command (which can also be spelled @code{bt}), to see where we are
|
|
in the stack as a whole: the @code{backtrace} command displays a
|
|
stack frame for each active subroutine.
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{bt}
|
|
#0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
|
|
at input.c:530
|
|
#1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
|
|
at builtin.c:882
|
|
#2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
|
|
#3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
|
|
at macro.c:71
|
|
#4 0x79dc in expand_input () at macro.c:40
|
|
#5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
|
|
@end smallexample
|
|
|
|
@noindent
|
|
We will step through a few more lines to see what happens. The first two
|
|
times, we can use @samp{s}; the next two times we use @code{n} to avoid
|
|
falling into the @code{xstrdup} subroutine.
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{s}
|
|
0x3b5c 532 if (rquote != def_rquote)
|
|
(@value{GDBP}) @b{s}
|
|
0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
|
|
def_lquote : xstrdup(lq);
|
|
(@value{GDBP}) @b{n}
|
|
536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
|
|
: xstrdup(rq);
|
|
(@value{GDBP}) @b{n}
|
|
538 len_lquote = strlen(rquote);
|
|
@end smallexample
|
|
|
|
@noindent
|
|
The last line displayed looks a little odd; we can examine the variables
|
|
@code{lquote} and @code{rquote} to see if they are in fact the new left
|
|
and right quotes we specified. We use the command @code{p}
|
|
(@code{print}) to see their values.
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{p lquote}
|
|
$1 = 0x35d40 "<QUOTE>"
|
|
(@value{GDBP}) @b{p rquote}
|
|
$2 = 0x35d50 "<UNQUOTE>"
|
|
@end smallexample
|
|
|
|
@noindent
|
|
@code{lquote} and @code{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 @code{l} (@code{list}) command.
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{l}
|
|
533 xfree(rquote);
|
|
534
|
|
535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
|
|
: xstrdup (lq);
|
|
536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
|
|
: xstrdup (rq);
|
|
537
|
|
538 len_lquote = strlen(rquote);
|
|
539 len_rquote = strlen(lquote);
|
|
540 @}
|
|
541
|
|
542 void
|
|
@end smallexample
|
|
|
|
@noindent
|
|
Let us step past the two lines that set @code{len_lquote} and
|
|
@code{len_rquote}, and then examine the values of those variables.
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{n}
|
|
539 len_rquote = strlen(lquote);
|
|
(@value{GDBP}) @b{n}
|
|
540 @}
|
|
(@value{GDBP}) @b{p len_lquote}
|
|
$3 = 9
|
|
(@value{GDBP}) @b{p len_rquote}
|
|
$4 = 7
|
|
@end smallexample
|
|
|
|
@noindent
|
|
That certainly looks wrong, assuming @code{len_lquote} and
|
|
@code{len_rquote} are meant to be the lengths of @code{lquote} and
|
|
@code{rquote} respectively. We can set them to better values using
|
|
the @code{p} command, since it can print the value of
|
|
any expression---and that expression can include subroutine calls and
|
|
assignments.
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{p len_lquote=strlen(lquote)}
|
|
$5 = 7
|
|
(@value{GDBP}) @b{p len_rquote=strlen(rquote)}
|
|
$6 = 9
|
|
@end smallexample
|
|
|
|
@noindent
|
|
Is that enough to fix the problem of using the new quotes with the
|
|
@code{m4} built-in @code{defn}? We can allow @code{m4} to continue
|
|
executing with the @code{c} (@code{continue}) command, and then try the
|
|
example that caused trouble initially:
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{c}
|
|
Continuing.
|
|
|
|
@b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
|
|
|
|
baz
|
|
0000
|
|
@end smallexample
|
|
|
|
@noindent
|
|
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 @code{m4} exit by giving it an EOF as input:
|
|
|
|
@smallexample
|
|
@b{C-d}
|
|
Program exited normally.
|
|
@end smallexample
|
|
|
|
@noindent
|
|
The message @samp{Program exited normally.} is from @value{GDBN}; it
|
|
indicates @code{m4} has finished executing. We can end our @value{GDBN}
|
|
session with the @value{GDBN} @code{quit} command.
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{quit}
|
|
@end smallexample
|
|
@end ifclear
|
|
|
|
@node Invocation
|
|
@chapter Getting In and Out of @value{GDBN}
|
|
|
|
This chapter discusses how to start @value{GDBN}, and how to get out of it.
|
|
(The essentials: type @samp{@value{GDBP}} to start GDB, and type @kbd{quit}
|
|
or @kbd{C-d} to exit.)
|
|
|
|
@menu
|
|
* Invoking GDB:: How to start @value{GDBN}
|
|
* Quitting GDB:: How to quit @value{GDBN}
|
|
* Shell Commands:: How to use shell commands inside @value{GDBN}
|
|
@end menu
|
|
|
|
@node Invoking GDB
|
|
@section Invoking @value{GDBN}
|
|
|
|
@ifset H8EXCLUSIVE
|
|
For details on starting up @value{GDBP} as a
|
|
remote debugger attached to a Hitachi microprocessor, see @ref{Hitachi
|
|
Remote,,@value{GDBN} and Hitachi Microprocessors}.
|
|
@end ifset
|
|
|
|
Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
|
|
@value{GDBN} reads commands from the terminal until you tell it to exit.
|
|
|
|
You can also run @code{@value{GDBP}} with a variety of arguments and options,
|
|
to specify more of your debugging environment at the outset.
|
|
|
|
@ifset GENERIC
|
|
The command-line options described here are designed
|
|
to cover a variety of situations; in some environments, some of these
|
|
options may effectively be unavailable.
|
|
@end ifset
|
|
|
|
The most usual way to start @value{GDBN} is with one argument,
|
|
specifying an executable program:
|
|
|
|
@example
|
|
@value{GDBP} @var{program}
|
|
@end example
|
|
|
|
@ifclear BARETARGET
|
|
@noindent
|
|
You can also start with both an executable program and a core file
|
|
specified:
|
|
|
|
@example
|
|
@value{GDBP} @var{program} @var{core}
|
|
@end example
|
|
|
|
You can, instead, specify a process ID as a second argument, if you want
|
|
to debug a running process:
|
|
|
|
@example
|
|
@value{GDBP} @var{program} 1234
|
|
@end example
|
|
|
|
@noindent
|
|
would attach @value{GDBN} to process @code{1234} (unless you also have a file
|
|
named @file{1234}; @value{GDBN} does check for a core file first).
|
|
|
|
Taking advantage of the second command-line argument requires a fairly
|
|
complete operating system; when you use @value{GDBN} as a remote debugger
|
|
attached to a bare board, there may not be any notion of ``process'',
|
|
and there is often no way to get a core dump.
|
|
@end ifclear
|
|
|
|
@noindent
|
|
You can further control how @value{GDBN} starts up by using command-line
|
|
options. @value{GDBN} itself can remind you of the options available.
|
|
|
|
@noindent
|
|
Type
|
|
|
|
@example
|
|
@value{GDBP} -help
|
|
@end example
|
|
|
|
@noindent
|
|
to display all available options and briefly describe their use
|
|
(@samp{@value{GDBP} -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
|
|
@samp{-x} option is used.
|
|
|
|
|
|
@menu
|
|
@ifclear GENERIC
|
|
@ifset REMOTESTUB
|
|
* Remote Serial:: @value{GDBN} remote serial protocol
|
|
@end ifset
|
|
@ifset I960
|
|
* i960-Nindy Remote:: @value{GDBN} with a remote i960 (Nindy)
|
|
@end ifset
|
|
@ifset AMD29K
|
|
* UDI29K Remote:: @value{GDBN} and the UDI protocol for AMD29K
|
|
* EB29K Remote:: @value{GDBN} with a remote EB29K
|
|
@end ifset
|
|
@ifset VXWORKS
|
|
* VxWorks Remote:: @value{GDBN} and VxWorks
|
|
@end ifset
|
|
@ifset ST2000
|
|
* ST2000 Remote:: @value{GDBN} with a Tandem ST2000
|
|
@end ifset
|
|
@ifset H8
|
|
* Hitachi Remote:: @value{GDBN} and Hitachi Microprocessors
|
|
@end ifset
|
|
@ifset MIPS
|
|
* MIPS Remote:: @value{GDBN} and MIPS boards
|
|
@end ifset
|
|
@ifset SIMS
|
|
* Simulator:: Simulated CPU target
|
|
@end ifset
|
|
@end ifclear
|
|
@c remnant makeinfo bug requires this blank line after *two* end-ifblahs:
|
|
|
|
* File Options:: Choosing files
|
|
* Mode Options:: Choosing modes
|
|
@end menu
|
|
|
|
@ifclear GENERIC
|
|
@include gdbinv-s.texi
|
|
@end ifclear
|
|
|
|
@node File Options
|
|
@subsection Choosing files
|
|
|
|
@ifclear BARETARGET
|
|
When @value{GDBN} 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 @samp{-se} and
|
|
@samp{-c} options respectively. (@value{GDBN} reads the first argument
|
|
that does not have an associated option flag as equivalent to the
|
|
@samp{-se} option followed by that argument; and the second argument
|
|
that does not have an associated option flag, if any, as equivalent to
|
|
the @samp{-c} option followed by that argument.)
|
|
@end ifclear
|
|
@ifset BARETARGET
|
|
When @value{GDBN} starts, it reads any argument other than options as
|
|
specifying an executable file. This is the same as if the argument was
|
|
specified by the @samp{-se} option.
|
|
@end ifset
|
|
|
|
Many options have both long and short forms; both are shown in the
|
|
following list. @value{GDBN} 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 @samp{--} rather
|
|
than @samp{-}, though we illustrate the more usual convention.)
|
|
|
|
@table @code
|
|
@item -symbols=@var{file}
|
|
@itemx -s @var{file}
|
|
Read symbol table from file @var{file}.
|
|
|
|
@item -exec=@var{file}
|
|
@itemx -e @var{file}
|
|
Use file @var{file} as the executable file to execute when
|
|
@ifset BARETARGET
|
|
appropriate.
|
|
@end ifset
|
|
@ifclear BARETARGET
|
|
appropriate, and for examining pure data in conjunction with a core
|
|
dump.
|
|
@end ifclear
|
|
|
|
@item -se=@var{file}
|
|
Read symbol table from file @var{file} and use it as the executable
|
|
file.
|
|
|
|
@ifclear BARETARGET
|
|
@item -core=@var{file}
|
|
@itemx -c @var{file}
|
|
Use file @var{file} as a core dump to examine.
|
|
@end ifclear
|
|
|
|
@item -command=@var{file}
|
|
@itemx -x @var{file}
|
|
Execute @value{GDBN} commands from file @var{file}. @xref{Command
|
|
Files,, Command files}.
|
|
|
|
@item -directory=@var{directory}
|
|
@itemx -d @var{directory}
|
|
Add @var{directory} to the path to search for source files.
|
|
|
|
@ifclear BARETARGET
|
|
@item -m
|
|
@itemx -mapped
|
|
@emph{Warning: this option depends on operating system facilities that are not
|
|
supported on all systems.}@*
|
|
If memory-mapped files are available on your system through the @code{mmap}
|
|
system call, you can use this option
|
|
to have @value{GDBN} write the symbols from your
|
|
program into a reusable file in the current directory. If the program you are debugging is
|
|
called @file{/tmp/fred}, the mapped symbol file will be @file{./fred.syms}.
|
|
Future @value{GDBN} debugging sessions will notice the presence of this file,
|
|
and will quickly map in symbol information from it, rather than reading
|
|
the symbol table from the executable program.
|
|
|
|
@c FIXME! Really host, not target?
|
|
The @file{.syms} file is specific to the host machine where @value{GDBN}
|
|
is run. It holds an exact image of the internal @value{GDBN} symbol
|
|
table. It cannot be shared across multiple host platforms.
|
|
@end ifclear
|
|
|
|
@item -r
|
|
@itemx -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.
|
|
@end table
|
|
|
|
@ifclear BARETARGET
|
|
The @code{-mapped} and @code{-readnow} options are typically combined in
|
|
order to build a @file{.syms} file that contains complete symbol
|
|
information. (@xref{Files,,Commands to specify files}, for information
|
|
on @file{.syms} files.) A simple GDB invocation to do nothing but build
|
|
a @file{.syms} file for future use is:
|
|
|
|
@example
|
|
gdb -batch -nx -mapped -readnow programname
|
|
@end example
|
|
@end ifclear
|
|
|
|
@node Mode Options
|
|
@subsection Choosing modes
|
|
|
|
You can run @value{GDBN} in various alternative modes---for example, in
|
|
batch mode or quiet mode.
|
|
|
|
@table @code
|
|
@item -nx
|
|
@itemx -n
|
|
Do not execute commands from any @file{@value{GDBINIT}} initialization files.
|
|
Normally, the commands in these files are executed after all the
|
|
command options and arguments have been processed.
|
|
@xref{Command Files,,Command files}.
|
|
|
|
@item -quiet
|
|
@itemx -q
|
|
``Quiet''. Do not print the introductory and copyright messages. These
|
|
messages are also suppressed in batch mode.
|
|
|
|
@item -batch
|
|
Run in batch mode. Exit with status @code{0} after processing all the command
|
|
files specified with @samp{-x} (and @file{@value{GDBINIT}}, if not inhibited).
|
|
Exit with nonzero status if an error occurs in executing the @value{GDBN}
|
|
commands in the command files.
|
|
|
|
Batch mode may be useful for running @value{GDBN} as a filter, for example to
|
|
download and run a program on another computer; in order to make this
|
|
more useful, the message
|
|
|
|
@example
|
|
Program exited normally.
|
|
@end example
|
|
|
|
@noindent
|
|
(which is ordinarily issued whenever a program running under @value{GDBN} control
|
|
terminates) is not issued when running in batch mode.
|
|
|
|
@item -cd=@var{directory}
|
|
Run @value{GDBN} using @var{directory} as its working directory,
|
|
instead of the current directory.
|
|
|
|
@ifset LUCID
|
|
@item -context @var{authentication}
|
|
When the Energize programming system starts up @value{GDBN}, it uses this
|
|
option to trigger an alternate mode of interaction.
|
|
@var{authentication} is a pair of numeric codes that identify @value{GDBN}
|
|
as a client in the Energize environment. Avoid this option when you run
|
|
@value{GDBN} directly from the command line. See @ref{Energize,,Using
|
|
@value{GDBN} with Energize} for more discussion of using @value{GDBN} with Energize.
|
|
@end ifset
|
|
|
|
@ifclear DOSHOST
|
|
@item -fullname
|
|
@itemx -f
|
|
Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells @value{GDBN}
|
|
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 @samp{\032} characters, followed by the file name, line number
|
|
and character position separated by colons, and a newline. The
|
|
Emacs-to-@value{GDBN} interface program uses the two @samp{\032} characters as
|
|
a signal to display the source code for the frame.
|
|
@end ifclear
|
|
|
|
@ifset SERIAL
|
|
@item -b @var{bps}
|
|
Set the line speed (baud rate or bits per second) of any serial
|
|
interface used by @value{GDBN} for remote debugging.
|
|
|
|
@item -tty=@var{device}
|
|
Run using @var{device} for your program's standard input and output.
|
|
@c FIXME: kingdon thinks there is more to -tty. Investigate.
|
|
@end ifset
|
|
@end table
|
|
|
|
@node Quitting GDB
|
|
@section Quitting @value{GDBN}
|
|
@cindex exiting @value{GDBN}
|
|
@cindex leaving @value{GDBN}
|
|
|
|
@table @code
|
|
@item quit
|
|
@kindex quit
|
|
@kindex q
|
|
To exit @value{GDBN}, use the @code{quit} command (abbreviated @code{q}), or type
|
|
an end-of-file character (usually @kbd{C-d}).
|
|
@end table
|
|
|
|
@cindex interrupt
|
|
An interrupt (often @kbd{C-c}) will not exit from @value{GDBN}, but rather
|
|
will terminate the action of any @value{GDBN} command that is in progress and
|
|
return to @value{GDBN} command level. It is safe to type the interrupt
|
|
character at any time because @value{GDBN} does not allow it to take effect
|
|
until a time when it is safe.
|
|
|
|
@ifclear BARETARGET
|
|
If you have been using @value{GDBN} to control an attached process or
|
|
device, you can release it with the @code{detach} command
|
|
(@pxref{Attach, ,Debugging an already-running process}).
|
|
@end ifclear
|
|
|
|
@node Shell Commands
|
|
@section Shell commands
|
|
|
|
If you need to execute occasional shell commands during your
|
|
debugging session, there is no need to leave or suspend @value{GDBN}; you can
|
|
just use the @code{shell} command.
|
|
|
|
@table @code
|
|
@item shell @var{command string}
|
|
@kindex shell
|
|
@cindex shell escape
|
|
Invoke a the standard shell to execute @var{command string}.
|
|
@ifclear DOSHOST
|
|
If it exists, the environment variable @code{SHELL} determines which
|
|
shell to run. Otherwise @value{GDBN} uses @code{/bin/sh}.
|
|
@end ifclear
|
|
@end table
|
|
|
|
The utility @code{make} is often needed in development environments.
|
|
You do not have to use the @code{shell} command for this purpose in
|
|
@value{GDBN}:
|
|
|
|
@table @code
|
|
@item make @var{make-args}
|
|
@kindex make
|
|
@cindex calling make
|
|
Execute the @code{make} program with the specified
|
|
arguments. This is equivalent to @samp{shell make @var{make-args}}.
|
|
@end table
|
|
|
|
@node Commands
|
|
@chapter @value{GDBN} Commands
|
|
|
|
You can abbreviate a @value{GDBN} command to the first few letters of the command
|
|
name, if that abbreviation is unambiguous; and you can repeat certain
|
|
@value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
|
|
key to get @value{GDBN} to fill out the rest of a word in a command (or to
|
|
show you the alternatives available, if there is more than one possibility).
|
|
|
|
@menu
|
|
* Command Syntax:: How to give commands to @value{GDBN}
|
|
* Completion:: Command completion
|
|
* Help:: How to ask @value{GDBN} for help
|
|
@end menu
|
|
|
|
@node Command Syntax
|
|
@section Command syntax
|
|
|
|
A @value{GDBN} 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 @code{step} accepts an argument which is the number of times to
|
|
step, as in @samp{step 5}. You can also use the @code{step} command
|
|
with no arguments. Some command names do not allow any arguments.
|
|
|
|
@cindex abbreviation
|
|
@value{GDBN} 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, @code{s} is specially defined as
|
|
equivalent to @code{step} even though there are other commands whose
|
|
names start with @code{s}. You can test abbreviations by using them as
|
|
arguments to the @code{help} command.
|
|
|
|
@cindex repeating commands
|
|
@kindex RET
|
|
A blank line as input to @value{GDBN} (typing just @key{RET}) means to
|
|
repeat the previous command. Certain commands (for example, @code{run})
|
|
will not repeat this way; these are commands for which unintentional
|
|
repetition might cause trouble and which you are unlikely to want to
|
|
repeat.
|
|
|
|
The @code{list} and @code{x} commands, when you repeat them with
|
|
@key{RET}, construct new arguments rather than repeating
|
|
exactly as typed. This permits easy scanning of source or memory.
|
|
|
|
@value{GDBN} can also use @key{RET} in another way: to partition lengthy
|
|
output, in a way similar to the common utility @code{more}
|
|
(@pxref{Screen Size,,Screen size}). Since it is easy to press one
|
|
@key{RET} too many in this situation, @value{GDBN} disables command
|
|
repetition after any command that generates this sort of display.
|
|
|
|
@kindex #
|
|
@cindex comment
|
|
Any text from a @kbd{#} to the end of the line is a comment; it does
|
|
nothing. This is useful mainly in command files (@pxref{Command
|
|
Files,,Command files}).
|
|
|
|
@node Completion
|
|
@section Command completion
|
|
|
|
@cindex completion
|
|
@cindex word completion
|
|
@value{GDBN} can fill in the rest of a word in a command for you, if there is
|
|
only one possibility; it can also show you what the valid possibilities
|
|
are for the next word in a command, at any time. This works for @value{GDBN}
|
|
commands, @value{GDBN} subcommands, and the names of symbols in your program.
|
|
|
|
Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
|
|
of a word. If there is only one possibility, @value{GDBN} will fill in the
|
|
word, and wait for you to finish the command (or press @key{RET} to
|
|
enter it). For example, if you type
|
|
|
|
@c FIXME "@key" does not distinguish its argument sufficiently to permit
|
|
@c complete accuracy in these examples; space introduced for clarity.
|
|
@c If texinfo enhancements make it unnecessary, it would be nice to
|
|
@c replace " @key" by "@key" in the following...
|
|
@example
|
|
(@value{GDBP}) info bre @key{TAB}
|
|
@end example
|
|
|
|
@noindent
|
|
@value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
|
|
the only @code{info} subcommand beginning with @samp{bre}:
|
|
|
|
@example
|
|
(@value{GDBP}) info breakpoints
|
|
@end example
|
|
|
|
@noindent
|
|
You can either press @key{RET} at this point, to run the @code{info
|
|
breakpoints} command, or backspace and enter something else, if
|
|
@samp{breakpoints} does not look like the command you expected. (If you
|
|
were sure you wanted @code{info breakpoints} in the first place, you
|
|
might as well just type @key{RET} immediately after @samp{info bre},
|
|
to exploit command abbreviations rather than command completion).
|
|
|
|
If there is more than one possibility for the next word when you press
|
|
@key{TAB}, @value{GDBN} will sound a bell. You can either supply more
|
|
characters and try again, or just press @key{TAB} a second time, and
|
|
@value{GDBN} will display all the possible completions for that word. For
|
|
example, you might want to set a breakpoint on a subroutine whose name
|
|
begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
|
|
just sounds the bell. Typing @key{TAB} again will display all the
|
|
function names in your program that begin with those characters, for
|
|
example:
|
|
|
|
@example
|
|
(@value{GDBP}) b make_ @key{TAB}
|
|
@exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
|
|
make_a_section_from_file make_environ
|
|
make_abs_section make_function_type
|
|
make_blockvector make_pointer_type
|
|
make_cleanup make_reference_type
|
|
make_command make_symbol_completion_list
|
|
(@value{GDBP}) b make_
|
|
@end example
|
|
|
|
@noindent
|
|
After displaying the available possibilities, @value{GDBN} copies your
|
|
partial input (@samp{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 @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
|
|
means @kbd{@key{META} ?}. You can type this
|
|
@ifclear DOSHOST
|
|
either by holding down a
|
|
key designated as the @key{META} shift on your keyboard (if there is
|
|
one) while typing @kbd{?}, or
|
|
@end ifclear
|
|
as @key{ESC} followed by @kbd{?}.
|
|
|
|
@cindex quotes in commands
|
|
@cindex completion of quoted strings
|
|
Sometimes the string you need, while logically a ``word'', may contain
|
|
parentheses or other characters that @value{GDBN} normally excludes from its
|
|
notion of a word. To permit word completion to work in this situation,
|
|
you may enclose words in @code{'} (single quote marks) in @value{GDBN} commands.
|
|
|
|
@ifclear CONLY
|
|
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 @code{name} that takes an
|
|
@code{int} parameter, @code{name(int)}, or the version that takes a
|
|
@code{float} parameter, @code{name(float)}. To use the word-completion
|
|
facilities in this situation, type a single quote @code{'} at the
|
|
beginning of the function name. This alerts @value{GDBN} that it may need to
|
|
consider more information than usual when you press @key{TAB} or
|
|
@kbd{M-?} to request word completion:
|
|
|
|
@example
|
|
(@value{GDBP}) b 'bubble( @key{M-?}
|
|
bubble(double,double) bubble(int,int)
|
|
(@value{GDBP}) b 'bubble(
|
|
@end example
|
|
|
|
In some cases, @value{GDBN} can tell that completing a name will require
|
|
quotes. When this happens, @value{GDBN} will insert the quote for you (while
|
|
completing as much as it can) if you do not type the quote in the first
|
|
place:
|
|
|
|
@example
|
|
(@value{GDBP}) b bub @key{TAB}
|
|
@exdent @value{GDBN} alters your input line to the following, and rings a bell:
|
|
(@value{GDBP}) b 'bubble(
|
|
@end example
|
|
|
|
@noindent
|
|
In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
|
|
you have not yet started typing the argument list when you ask for
|
|
completion on an overloaded symbol.
|
|
@end ifclear
|
|
|
|
|
|
@node Help
|
|
@section Getting help
|
|
@cindex online documentation
|
|
@kindex help
|
|
|
|
You can always ask @value{GDBN} itself for information on its commands, using the
|
|
command @code{help}.
|
|
|
|
@table @code
|
|
@item help
|
|
@itemx h
|
|
@kindex h
|
|
You can use @code{help} (abbreviated @code{h}) with no arguments to
|
|
display a short list of named classes of commands:
|
|
|
|
@smallexample
|
|
(@value{GDBP}) help
|
|
List of classes of commands:
|
|
|
|
running -- Running the program
|
|
stack -- Examining the stack
|
|
data -- Examining data
|
|
breakpoints -- Making program stop at certain points
|
|
files -- Specifying and examining files
|
|
status -- Status inquiries
|
|
support -- Support facilities
|
|
user-defined -- User-defined commands
|
|
aliases -- Aliases of other commands
|
|
obscure -- Obscure features
|
|
|
|
Type "help" followed by a class name for a list of
|
|
commands in that class.
|
|
Type "help" followed by command name for full
|
|
documentation.
|
|
Command name abbreviations are allowed if unambiguous.
|
|
(@value{GDBP})
|
|
@end smallexample
|
|
|
|
@item help @var{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 @code{status}:
|
|
|
|
@smallexample
|
|
(@value{GDBP}) help status
|
|
Status inquiries.
|
|
|
|
List of commands:
|
|
|
|
@c Line break in "show" line falsifies real output, but needed
|
|
@c to fit in smallbook page size.
|
|
show -- Generic command for showing things set
|
|
with "set"
|
|
info -- Generic command for printing status
|
|
|
|
Type "help" followed by command name for full
|
|
documentation.
|
|
Command name abbreviations are allowed if unambiguous.
|
|
(@value{GDBP})
|
|
@end smallexample
|
|
|
|
@item help @var{command}
|
|
With a command name as @code{help} argument, @value{GDBN} will display a
|
|
short paragraph on how to use that command.
|
|
@end table
|
|
|
|
In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
|
|
and @code{show} to inquire about the state of your program, or the state
|
|
of @value{GDBN} itself. Each command supports many topics of inquiry; this
|
|
manual introduces each of them in the appropriate context. The listings
|
|
under @code{info} and under @code{show} in the Index point to
|
|
all the sub-commands. @xref{Index}.
|
|
|
|
@c @group
|
|
@table @code
|
|
@item info
|
|
@kindex info
|
|
@kindex i
|
|
This command (abbreviated @code{i}) is for describing the state of your
|
|
program. For example, you can list the arguments given to your program
|
|
with @code{info args}, list the registers currently in use with @code{info
|
|
registers}, or list the breakpoints you have set with @code{info breakpoints}.
|
|
You can get a complete list of the @code{info} sub-commands with
|
|
@w{@code{help info}}.
|
|
|
|
@kindex show
|
|
@item show
|
|
In contrast, @code{show} is for describing the state of @value{GDBN} itself.
|
|
You can change most of the things you can @code{show}, by using the
|
|
related command @code{set}; for example, you can control what number
|
|
system is used for displays with @code{set radix}, or simply inquire
|
|
which is currently in use with @code{show radix}.
|
|
|
|
@kindex info set
|
|
To display all the settable parameters and their current
|
|
values, you can use @code{show} with no arguments; you may also use
|
|
@code{info set}. Both commands produce the same display.
|
|
@c FIXME: "info set" violates the rule that "info" is for state of
|
|
@c FIXME...program. Ck w/ GNU: "info set" to be called something else,
|
|
@c FIXME...or change desc of rule---eg "state of prog and debugging session"?
|
|
@end table
|
|
@c @end group
|
|
|
|
Here are three miscellaneous @code{show} subcommands, all of which are
|
|
exceptional in lacking corresponding @code{set} commands:
|
|
|
|
@table @code
|
|
@kindex show version
|
|
@cindex version number
|
|
@item show version
|
|
Show what version of @value{GDBN} is running. You should include this
|
|
information in @value{GDBN} bug-reports. If multiple versions of @value{GDBN} are in
|
|
use at your site, you may occasionally want to determine which version
|
|
of @value{GDBN} you are running; as @value{GDBN} evolves, new commands are introduced,
|
|
and old ones may wither away. The version number is also announced
|
|
when you start @value{GDBN} with no arguments.
|
|
|
|
@kindex show copying
|
|
@item show copying
|
|
Display information about permission for copying @value{GDBN}.
|
|
|
|
@kindex show warranty
|
|
@item show warranty
|
|
Display the GNU ``NO WARRANTY'' statement.
|
|
@end table
|
|
|
|
@node Running
|
|
@chapter Running Programs Under @value{GDBN}
|
|
|
|
When you run a program under @value{GDBN}, you must first generate
|
|
debugging information when you compile it.
|
|
@ifclear BARETARGET
|
|
You may start it with its arguments, if any, in an environment of your
|
|
choice. You may redirect your program's input and output, debug an
|
|
already running process, or kill a child process.
|
|
@end ifclear
|
|
|
|
@menu
|
|
* Compilation:: Compiling for debugging
|
|
* Starting:: Starting your program
|
|
@ifclear BARETARGET
|
|
* Arguments:: Your program's arguments
|
|
* Environment:: Your program's environment
|
|
* Working Directory:: Your program's working directory
|
|
* Input/Output:: Your program's input and output
|
|
* Attach:: Debugging an already-running process
|
|
* Kill Process:: Killing the child process
|
|
* Process Information:: Additional process information
|
|
@end ifclear
|
|
@end menu
|
|
|
|
@node Compilation
|
|
@section Compiling for debugging
|
|
|
|
In order to debug a program effectively, you need to generate
|
|
debugging information when you compile it. This debugging information
|
|
is stored in the object file; it describes the data type of each
|
|
variable or function and the correspondence between source line numbers
|
|
and addresses in the executable code.
|
|
|
|
To request debugging information, specify the @samp{-g} option when you run
|
|
the compiler.
|
|
|
|
Many C compilers are unable to handle the @samp{-g} and @samp{-O}
|
|
options together. Using those compilers, you cannot generate optimized
|
|
executables containing debugging information.
|
|
|
|
@value{NGCC}, the GNU C compiler, supports @samp{-g} with or without
|
|
@samp{-O}, making it possible to debug optimized code. We recommend
|
|
that you @emph{always} use @samp{-g} whenever you compile a program.
|
|
You may think your program is correct, but there is no sense in pushing
|
|
your luck.
|
|
|
|
@cindex optimized code, debugging
|
|
@cindex debugging optimized code
|
|
When you debug a program compiled with @samp{-g -O}, remember that the
|
|
optimizer is rearranging your code; the debugger will show you what is
|
|
really there. Do not be too surprised when the execution path does not
|
|
exactly match your source file! An extreme example: if you define a
|
|
variable, but never use it, @value{GDBN} will never see that
|
|
variable---because the compiler optimizes it out of existence.
|
|
|
|
Some things do not work as well with @samp{-g -O} as with just
|
|
@samp{-g}, particularly on machines with instruction scheduling. If in
|
|
doubt, recompile with @samp{-g} alone, and if this fixes the problem,
|
|
please report it as a bug (including a test case!).
|
|
|
|
Older versions of the GNU C compiler permitted a variant option
|
|
@w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
|
|
format; if your GNU C compiler has this option, do not use it.
|
|
|
|
@ignore
|
|
@comment As far as I know, there are no cases in which @value{GDBN} will
|
|
@comment produce strange output in this case. (but no promises).
|
|
If your program includes archives made with the @code{ar} program, and
|
|
if the object files used as input to @code{ar} were compiled without the
|
|
@samp{-g} option and have names longer than 15 characters, @value{GDBN} will get
|
|
confused reading your program's symbol table. No error message will be
|
|
given, but @value{GDBN} may behave strangely. The reason for this problem is a
|
|
deficiency in the Unix archive file format, which cannot represent file
|
|
names longer than 15 characters.
|
|
|
|
To avoid this problem, compile the archive members with the @samp{-g}
|
|
option or use shorter file names. Alternatively, use a version of GNU
|
|
@code{ar} dated more recently than August 1989.
|
|
@end ignore
|
|
|
|
@node Starting
|
|
@section Starting your program
|
|
@cindex starting
|
|
@cindex running
|
|
|
|
@table @code
|
|
@item run
|
|
@itemx r
|
|
@kindex run
|
|
Use the @code{run} command to start your program under @value{GDBN}. You must
|
|
first specify the program name
|
|
@ifset VXWORKS
|
|
(except on VxWorks)
|
|
@end ifset
|
|
with an argument to @value{GDBN} (@pxref{Invocation, ,Getting In and
|
|
Out of @value{GDBN}}), or by using the @code{file} or @code{exec-file}
|
|
command (@pxref{Files, ,Commands to specify files}).
|
|
|
|
@end table
|
|
|
|
@ifclear BARETARGET
|
|
If you are running your program in an execution environment that
|
|
supports processes, @code{run} creates an inferior process and makes
|
|
that process run your program. (In environments without processes,
|
|
@code{run} jumps to the start of your program.)
|
|
|
|
The execution of a program is affected by certain information it
|
|
receives from its superior. @value{GDBN} provides ways to specify this
|
|
information, which you must do @emph{before} starting your program. (You
|
|
can change it after starting your program, but such changes will only affect
|
|
your program the next time you start it.) This information may be
|
|
divided into four categories:
|
|
|
|
@table @asis
|
|
@item The @emph{arguments.}
|
|
Specify the arguments to give your program as the arguments of the
|
|
@code{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 @code{SHELL} environment variable. @xref{Arguments, ,Your
|
|
program's arguments}.
|
|
|
|
@item The @emph{environment.}
|
|
Your program normally inherits its environment from @value{GDBN}, but you can
|
|
use the @value{GDBN} commands @code{set environment} and @code{unset
|
|
environment} to change parts of the environment that will be given to
|
|
your program. @xref{Environment, ,Your program's environment}.
|
|
|
|
@item The @emph{working directory.}
|
|
Your program inherits its working directory from @value{GDBN}. You can set
|
|
the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
|
|
@xref{Working Directory, ,Your program's working directory}.
|
|
|
|
@item The @emph{standard input and output.}
|
|
Your program normally uses the same device for standard input and
|
|
standard output as @value{GDBN} is using. You can redirect input and output
|
|
in the @code{run} command line, or you can use the @code{tty} command to
|
|
set a different device for your program.
|
|
@xref{Input/Output, ,Your program's input and output}.
|
|
|
|
@cindex pipes
|
|
@emph{Warning:} While input and output redirection work, you cannot use
|
|
pipes to pass the output of the program you are debugging to another
|
|
program; if you attempt this, @value{GDBN} is likely to wind up debugging the
|
|
wrong program.
|
|
@end table
|
|
@end ifclear
|
|
|
|
When you issue the @code{run} command, your program begins to execute
|
|
immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
|
|
of how to arrange for your program to stop. Once your program has
|
|
stopped, you may calls functions in your program, using the @code{print}
|
|
or @code{call} commands. @xref{Data, ,Examining Data}.
|
|
|
|
If the modification time of your symbol file has changed since the
|
|
last time @value{GDBN} read its symbols, @value{GDBN} will discard its symbol table and
|
|
re-read it. When it does this, @value{GDBN} tries to retain your current
|
|
breakpoints.
|
|
|
|
@ifclear BARETARGET
|
|
@node Arguments
|
|
@section Your program's arguments
|
|
|
|
@cindex arguments (to your program)
|
|
The arguments to your program can be specified by the arguments of the
|
|
@code{run} command. They are passed to a shell, which expands wildcard
|
|
characters and performs redirection of I/O, and thence to your program.
|
|
Your @code{SHELL} environment variable (if it exists) specifies what
|
|
shell @value{GDBN} if you do not define @code{SHELL}, @value{GDBN} uses
|
|
@code{/bin/sh}.
|
|
|
|
@code{run} with no arguments uses the same arguments used by the previous
|
|
@code{run}, or those set by the @code{set args} command.
|
|
|
|
@kindex set args
|
|
@table @code
|
|
@item set args
|
|
Specify the arguments to be used the next time your program is run. If
|
|
@code{set args} has no arguments, @code{run} will execute your program
|
|
with no arguments. Once you have run your program with arguments,
|
|
using @code{set args} before the next @code{run} is the only way to run
|
|
it again without arguments.
|
|
|
|
@item show args
|
|
@kindex show args
|
|
Show the arguments to give your program when it is started.
|
|
@end table
|
|
|
|
@node Environment
|
|
@section Your program's environment
|
|
|
|
@cindex environment (of your program)
|
|
The @dfn{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 @value{GDBN} over again.
|
|
|
|
@table @code
|
|
@item path @var{directory}
|
|
@kindex path
|
|
Add @var{directory} to the front of the @code{PATH} environment variable
|
|
(the search path for executables), for both @value{GDBN} and your program.
|
|
You may specify several directory names, separated by @samp{:} or
|
|
whitespace. If @var{directory} is already in the path, it is moved to
|
|
the front, so it will be searched sooner.
|
|
|
|
You can use the string @samp{$cwd} to refer to whatever is the current
|
|
working directory at the time @value{GDBN} searches the path. If you use
|
|
@samp{.} instead, it refers to the directory where you executed the
|
|
@code{path} command. @value{GDBN} fills in the current path where needed in
|
|
the @var{directory} argument, before adding it to the search path.
|
|
@c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
|
|
@c document that, since repeating it would be a no-op.
|
|
|
|
@item show paths
|
|
@kindex show paths
|
|
Display the list of search paths for executables (the @code{PATH}
|
|
environment variable).
|
|
|
|
@item show environment @r{[}@var{varname}@r{]}
|
|
@kindex show environment
|
|
Print the value of environment variable @var{varname} to be given to
|
|
your program when it starts. If you do not supply @var{varname},
|
|
print the names and values of all environment variables to be given to
|
|
your program. You can abbreviate @code{environment} as @code{env}.
|
|
|
|
@item set environment @var{varname} @r{[}=@r{]} @var{value}
|
|
@kindex set environment
|
|
Set environment variable @var{varname} to @var{value}. The value
|
|
changes for your program only, not for @value{GDBN} itself. @var{value} may
|
|
be any string; the values of environment variables are just strings, and
|
|
any interpretation is supplied by your program itself. The @var{value}
|
|
parameter is optional; if it is eliminated, the variable is set to a
|
|
null value.
|
|
@c "any string" here does not include leading, trailing
|
|
@c blanks. Gnu asks: does anyone care?
|
|
|
|
For example, this command:
|
|
|
|
@example
|
|
set env USER = foo
|
|
@end example
|
|
|
|
@noindent
|
|
tells a Unix program, when subsequently run, that its user is named
|
|
@samp{foo}. (The spaces around @samp{=} are used for clarity here; they
|
|
are not actually required.)
|
|
|
|
@item unset environment @var{varname}
|
|
@kindex unset environment
|
|
Remove variable @var{varname} from the environment to be passed to your
|
|
program. This is different from @samp{set env @var{varname} =};
|
|
@code{unset environment} removes the variable from the environment,
|
|
rather than assigning it an empty value.
|
|
@end table
|
|
|
|
@emph{Warning:} @value{GDBN} runs your program using the shell indicated
|
|
by your @code{SHELL} environment variable if it exists (or
|
|
@code{/bin/sh} if not). If your @code{SHELL} variable names a shell
|
|
that runs an initialization file---such as @file{.cshrc} for C-shell, or
|
|
@file{.bashrc} for BASH---any variables you set in that file will affect
|
|
your program. You may wish to move setting of environment variables to
|
|
files that are only run when you sign on, such as @file{.login} or
|
|
@file{.profile}.
|
|
|
|
@node Working Directory
|
|
@section Your program's working directory
|
|
|
|
@cindex working directory (of your program)
|
|
Each time you start your program with @code{run}, it inherits its
|
|
working directory from the current working directory of @value{GDBN}.
|
|
The @value{GDBN} working directory is initially whatever it inherited
|
|
from its parent process (typically the shell), but you can specify a new
|
|
working directory in @value{GDBN} with the @code{cd} command.
|
|
|
|
The @value{GDBN} working directory also serves as a default for the commands
|
|
that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
|
|
specify files}.
|
|
|
|
@table @code
|
|
@item cd @var{directory}
|
|
@kindex cd
|
|
Set the @value{GDBN} working directory to @var{directory}.
|
|
|
|
@item pwd
|
|
@kindex pwd
|
|
Print the @value{GDBN} working directory.
|
|
@end table
|
|
|
|
@node Input/Output
|
|
@section Your program's input and output
|
|
|
|
@cindex redirection
|
|
@cindex i/o
|
|
@cindex terminal
|
|
By default, the program you run under @value{GDBN} does input and output to
|
|
the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal to
|
|
its own terminal modes to interact with you, but it records the terminal
|
|
modes your program was using and switches back to them when you continue
|
|
running your program.
|
|
|
|
@table @code
|
|
@item info terminal
|
|
@kindex info terminal
|
|
Displays information recorded by @value{GDBN} about the terminal modes your
|
|
program is using.
|
|
@end table
|
|
|
|
You can redirect your program's input and/or output using shell
|
|
redirection with the @code{run} command. For example,
|
|
|
|
@example
|
|
run > outfile
|
|
@end example
|
|
|
|
@noindent
|
|
starts your program, diverting its output to the file @file{outfile}.
|
|
|
|
@kindex tty
|
|
@cindex controlling terminal
|
|
Another way to specify where your program should do input and output is
|
|
with the @code{tty} command. This command accepts a file name as
|
|
argument, and causes this file to be the default for future @code{run}
|
|
commands. It also resets the controlling terminal for the child
|
|
process, for future @code{run} commands. For example,
|
|
|
|
@example
|
|
tty /dev/ttyb
|
|
@end example
|
|
|
|
@noindent
|
|
directs that processes started with subsequent @code{run} commands
|
|
default to do input and output on the terminal @file{/dev/ttyb} and have
|
|
that as their controlling terminal.
|
|
|
|
An explicit redirection in @code{run} overrides the @code{tty} command's
|
|
effect on the input/output device, but not its effect on the controlling
|
|
terminal.
|
|
|
|
When you use the @code{tty} command or redirect input in the @code{run}
|
|
command, only the input @emph{for your program} is affected. The input
|
|
for @value{GDBN} still comes from your terminal.
|
|
|
|
@node Attach
|
|
@section Debugging an already-running process
|
|
@kindex attach
|
|
@cindex attach
|
|
|
|
@table @code
|
|
@item attach @var{process-id}
|
|
This command attaches to a running process---one that was started
|
|
outside @value{GDBN}. (@code{info files} will show 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 @code{ps} utility,
|
|
or with the @samp{jobs -l} shell command.
|
|
|
|
@code{attach} will not repeat if you press @key{RET} a second time after
|
|
executing the command.
|
|
@end table
|
|
|
|
To use @code{attach}, you must be debugging in an environment which
|
|
supports processes. You must also have permission to send the process a
|
|
signal, and it must have the same effective user ID as the @value{GDBN}
|
|
process.
|
|
|
|
When using @code{attach}, you should first use the @code{file} command
|
|
to specify the program running in the process and load its symbol table.
|
|
@xref{Files, ,Commands to Specify Files}.
|
|
|
|
The first thing @value{GDBN} does after arranging to debug the specified
|
|
process is to stop it. You can examine and modify an attached process
|
|
with all the @value{GDBN} commands that are ordinarily available when you start
|
|
processes with @code{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 @code{continue} command after
|
|
attaching @value{GDBN} to the process.
|
|
|
|
@table @code
|
|
@item detach
|
|
@kindex detach
|
|
When you have finished debugging the attached process, you can use the
|
|
@code{detach} command to release it from @value{GDBN} control. Detaching
|
|
the process continues its execution. After the @code{detach} command,
|
|
that process and @value{GDBN} become completely independent once more, and you
|
|
are ready to @code{attach} another process or start one with @code{run}.
|
|
@code{detach} will not repeat if you press @key{RET} again after
|
|
executing the command.
|
|
@end table
|
|
|
|
If you exit @value{GDBN} or use the @code{run} command while you have an attached
|
|
process, you kill that process. By default, you will be asked for
|
|
confirmation if you try to do either of these things; you can control
|
|
whether or not you need to confirm by using the @code{set confirm} command
|
|
(@pxref{Messages/Warnings, ,Optional warnings and messages}).
|
|
|
|
@node Kill Process
|
|
@c @group
|
|
@section Killing the child process
|
|
|
|
@table @code
|
|
@item kill
|
|
@kindex kill
|
|
Kill the child process in which your program is running under @value{GDBN}.
|
|
@end table
|
|
|
|
This command is useful if you wish to debug a core dump instead of a
|
|
running process. @value{GDBN} ignores any core dump file while your program
|
|
is running.
|
|
@c @end group
|
|
|
|
On some operating systems, a program cannot be executed outside @value{GDBN}
|
|
while you have breakpoints set on it inside @value{GDBN}. You can use the
|
|
@code{kill} command in this situation to permit running your program
|
|
outside the debugger.
|
|
|
|
The @code{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 @code{run}, @value{GDBN} will notice that the file has changed, and
|
|
will re-read the symbol table (while trying to preserve your current
|
|
breakpoint settings).
|
|
|
|
@node Process Information
|
|
@section Additional process information
|
|
|
|
@kindex /proc
|
|
@cindex process image
|
|
Some operating systems provide a facility called @samp{/proc} that can
|
|
be used to examine the image of a running process using file-system
|
|
subroutines. If @value{GDBN} is configured for an operating system with this
|
|
facility, the command @code{info proc} is available to report on several
|
|
kinds of information about the process running your program.
|
|
|
|
@table @code
|
|
@item info proc
|
|
@kindex info proc
|
|
Summarize available information about the process.
|
|
|
|
@item info proc mappings
|
|
@kindex info proc mappings
|
|
Report on the address ranges accessible in the program, with information
|
|
on whether your program may read, write, or execute each range.
|
|
|
|
@item info proc times
|
|
@kindex info proc times
|
|
Starting time, user CPU time, and system CPU time for your program and
|
|
its children.
|
|
|
|
@item info proc id
|
|
@kindex info proc id
|
|
Report on the process IDs related to your program: its own process ID,
|
|
the ID of its parent, the process group ID, and the session ID.
|
|
|
|
@item info proc status
|
|
@kindex info proc status
|
|
General information on the state of the process. If the process is
|
|
stopped, this report includes the reason for stopping, and any signal
|
|
received.
|
|
|
|
@item info proc all
|
|
Show all the above information about the process.
|
|
@end table
|
|
@end ifclear
|
|
|
|
@node Stopping
|
|
@chapter Stopping and Continuing
|
|
|
|
The principal purposes of using a debugger are so that you can stop your
|
|
program before it terminates; or so that, if your program runs into
|
|
trouble, you can investigate and find out why.
|
|
|
|
Inside @value{GDBN}, your program may stop for any of several reasons, such
|
|
as
|
|
@ifclear BARETARGET
|
|
a signal,
|
|
@end ifclear
|
|
a breakpoint, or reaching a new line after a @value{GDBN}
|
|
command such as @code{step}. You may then examine and change
|
|
variables, set new breakpoints or remove old ones, and then continue
|
|
execution. Usually, the messages shown by @value{GDBN} provide ample
|
|
explanation of the status of your program---but you can also explicitly
|
|
request this information at any time.
|
|
|
|
@table @code
|
|
@item info program
|
|
@kindex info program
|
|
Display information about the status of your program: whether it is
|
|
running or not,
|
|
@ifclear BARETARGET
|
|
what process it is,
|
|
@end ifclear
|
|
and why it stopped.
|
|
@end table
|
|
|
|
@menu
|
|
@ifclear CONLY
|
|
* Breakpoints:: Breakpoints, watchpoints, and exceptions
|
|
@end ifclear
|
|
@ifset CONLY
|
|
* Breakpoints:: Breakpoints and watchpoints
|
|
@end ifset
|
|
@c Remnant makeinfo bug requires blank line after *successful* end-if in menu:
|
|
|
|
* Continuing and Stepping:: Resuming execution
|
|
@ifset POSIX
|
|
* Signals:: Signals
|
|
@end ifset
|
|
@end menu
|
|
|
|
@c makeinfo node-defaulting requires adjacency of @node and sectioning cmds
|
|
@c ...hence distribute @node Breakpoints over two possible @if expansions.
|
|
@c
|
|
@ifclear CONLY
|
|
@node Breakpoints
|
|
@section Breakpoints, watchpoints, and exceptions
|
|
@end ifclear
|
|
@ifset CONLY
|
|
@node Breakpoints
|
|
@section Breakpoints and watchpoints
|
|
@end ifset
|
|
|
|
@cindex breakpoints
|
|
A @dfn{breakpoint} makes your program stop whenever a certain point in
|
|
the program is reached. For each breakpoint, you can add various
|
|
conditions to control in finer detail whether your program will stop.
|
|
You can set breakpoints with the @code{break} command and its variants
|
|
(@pxref{Set Breaks, ,Setting breakpoints}), to specify the place where
|
|
your program should stop by line number, function name or exact address
|
|
in the program.
|
|
@ifclear CONLY
|
|
In languages with exception handling (such as GNU C++), you can also set
|
|
breakpoints where an exception is raised (@pxref{Exception Handling,
|
|
,Breakpoints and exceptions}).
|
|
@end ifclear
|
|
|
|
@cindex watchpoints
|
|
@cindex memory tracing
|
|
@cindex breakpoint on memory address
|
|
@cindex breakpoint on variable modification
|
|
A @dfn{watchpoint} is a special breakpoint that stops your program
|
|
when the value of an expression changes. You must use a different
|
|
command to set watchpoints (@pxref{Set Watchpoints, ,Setting
|
|
watchpoints}), but aside from that, you can manage a watchpoint like
|
|
any other breakpoint: you enable, disable, and delete both breakpoints
|
|
and watchpoints using the same commands.
|
|
|
|
You can arrange to have values from your program displayed automatically
|
|
whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,
|
|
,Automatic display}.
|
|
|
|
@cindex breakpoint numbers
|
|
@cindex numbers for breakpoints
|
|
@value{GDBN} assigns a number to each breakpoint or watchpoint when you
|
|
create it; these numbers are successive integers starting with one. In
|
|
many of the commands for controlling various features of breakpoints you
|
|
use the breakpoint number to say which breakpoint you want to change.
|
|
Each breakpoint may be @dfn{enabled} or @dfn{disabled}; if disabled, it has
|
|
no effect on your program until you enable it again.
|
|
|
|
@menu
|
|
* Set Breaks:: Setting breakpoints
|
|
* Set Watchpoints:: Setting watchpoints
|
|
@ifclear CONLY
|
|
* Exception Handling:: Breakpoints and exceptions
|
|
@end ifclear
|
|
|
|
* Delete Breaks:: Deleting breakpoints
|
|
* Disabling:: Disabling breakpoints
|
|
* Conditions:: Break conditions
|
|
* Break Commands:: Breakpoint command lists
|
|
@ifclear CONLY
|
|
* Breakpoint Menus:: Breakpoint menus
|
|
@end ifclear
|
|
@ifclear BARETARGET
|
|
* Error in Breakpoints:: ``Cannot insert breakpoints''
|
|
@end ifclear
|
|
@end menu
|
|
|
|
@node Set Breaks
|
|
@subsection Setting breakpoints
|
|
|
|
@c FIXME LMB what does GDB do if no code on line of breakpt?
|
|
@c consider in particular declaration with/without initialization.
|
|
@c
|
|
@c FIXME 2 is there stuff on this already? break at fun start, already init?
|
|
|
|
@kindex break
|
|
@kindex b
|
|
@kindex $bpnum
|
|
@cindex latest breakpoint
|
|
Breakpoints are set with the @code{break} command (abbreviated
|
|
@code{b}). The debugger convenience variable @samp{$bpnum} records the
|
|
number of the beakpoint you've set most recently; see @ref{Convenience
|
|
Vars,, Convenience variables}, for a discussion of what you can do with
|
|
convenience variables.
|
|
|
|
You have several ways to say where the breakpoint should go.
|
|
|
|
@table @code
|
|
@item break @var{function}
|
|
Set a breakpoint at entry to function @var{function}.
|
|
@ifclear CONLY
|
|
When using source languages that permit overloading of symbols, such as
|
|
C++, @var{function} may refer to more than one possible place to break.
|
|
@xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
|
|
@end ifclear
|
|
|
|
@item break +@var{offset}
|
|
@itemx break -@var{offset}
|
|
Set a breakpoint some number of lines forward or back from the position
|
|
at which execution stopped in the currently selected frame.
|
|
|
|
@item break @var{linenum}
|
|
Set a breakpoint at line @var{linenum} in the current source file.
|
|
That file is the last file whose source text was printed. This
|
|
breakpoint will stop your program just before it executes any of the
|
|
code on that line.
|
|
|
|
@item break @var{filename}:@var{linenum}
|
|
Set a breakpoint at line @var{linenum} in source file @var{filename}.
|
|
|
|
@item break @var{filename}:@var{function}
|
|
Set a breakpoint at entry to function @var{function} found in file
|
|
@var{filename}. Specifying a file name as well as a function name is
|
|
superfluous except when multiple files contain similarly named
|
|
functions.
|
|
|
|
@item break *@var{address}
|
|
Set a breakpoint at address @var{address}. You can use this to set
|
|
breakpoints in parts of your program which do not have debugging
|
|
information or source files.
|
|
|
|
@item break
|
|
When called without any arguments, @code{break} sets a breakpoint at
|
|
the next instruction to be executed in the selected stack frame
|
|
(@pxref{Stack, ,Examining the Stack}). In any selected frame but the
|
|
innermost, this will cause your program to stop as soon as control
|
|
returns to that frame. This is similar to the effect of a
|
|
@code{finish} command in the frame inside the selected frame---except
|
|
that @code{finish} does not leave an active breakpoint. If you use
|
|
@code{break} without an argument in the innermost frame, @value{GDBN} will stop
|
|
the next time it reaches the current location; this may be useful
|
|
inside loops.
|
|
|
|
@value{GDBN} 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.
|
|
|
|
@item break @dots{} if @var{cond}
|
|
Set a breakpoint with condition @var{cond}; evaluate the expression
|
|
@var{cond} each time the breakpoint is reached, and stop only if the
|
|
value is nonzero---that is, if @var{cond} evaluates as true.
|
|
@samp{@dots{}} stands for one of the possible arguments described
|
|
above (or no argument) specifying where to break. @xref{Conditions,
|
|
,Break conditions}, for more information on breakpoint conditions.
|
|
|
|
@item tbreak @var{args}
|
|
@kindex tbreak
|
|
Set a breakpoint enabled only for one stop. @var{args} are the
|
|
same as for the @code{break} command, and the breakpoint is set in the same
|
|
way, but the breakpoint is automatically disabled after the first time your
|
|
program stops there. @xref{Disabling, ,Disabling breakpoints}.
|
|
|
|
@item rbreak @var{regex}
|
|
@kindex rbreak
|
|
@cindex regular expression
|
|
@c FIXME what kind of regexp?
|
|
Set breakpoints on all functions matching the regular expression
|
|
@var{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 @code{break} command. They can
|
|
be deleted, disabled, made conditional, etc., in the standard ways.
|
|
|
|
@ifclear CONLY
|
|
When debugging C++ programs, @code{rbreak} is useful for setting
|
|
breakpoints on overloaded functions that are not members of any special
|
|
classes.
|
|
@end ifclear
|
|
|
|
@kindex info breakpoints
|
|
@cindex @code{$_} and @code{info breakpoints}
|
|
@item info breakpoints @r{[}@var{n}@r{]}
|
|
@itemx info break @r{[}@var{n}@r{]}
|
|
@itemx info watchpoints @r{[}@var{n}@r{]}
|
|
Print a table of all breakpoints and watchpoints set and not
|
|
deleted, with the following columns for each breakpoint:
|
|
|
|
@table @emph
|
|
@item Breakpoint Numbers
|
|
@item Type
|
|
Breakpoint or watchpoint.
|
|
@item Disposition
|
|
Whether the breakpoint is marked to be disabled or deleted when hit.
|
|
@item Enabled or Disabled
|
|
Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
|
|
that are not enabled.
|
|
@item Address
|
|
Where the breakpoint is in your program, as a memory address
|
|
@item What
|
|
Where the breakpoint is in the source for your program, as a file and
|
|
line number.
|
|
@end table
|
|
|
|
@noindent
|
|
Breakpoint commands, if any, are listed after the line for the
|
|
corresponding breakpoint.
|
|
|
|
@noindent
|
|
@code{info break} with a breakpoint
|
|
number @var{n} as argument lists only that breakpoint. The
|
|
convenience variable @code{$_} and the default examining-address for
|
|
the @code{x} command are set to the address of the last breakpoint
|
|
listed (@pxref{Memory, ,Examining memory}).
|
|
@end table
|
|
|
|
@value{GDBN} allows you to set any number of breakpoints at the same place in
|
|
your program. There is nothing silly or meaningless about this. When
|
|
the breakpoints are conditional, this is even useful
|
|
(@pxref{Conditions, ,Break conditions}).
|
|
|
|
@cindex negative breakpoint numbers
|
|
@cindex internal @value{GDBN} breakpoints
|
|
@value{GDBN} itself sometimes sets breakpoints in your program for special
|
|
purposes, such as proper handling of @code{longjmp} (in C programs).
|
|
These internal breakpoints are assigned negative numbers, starting with
|
|
@code{-1}; @samp{info breakpoints} does not display them.
|
|
|
|
You can see these breakpoints with the @value{GDBN} maintenance command
|
|
@samp{maint info breakpoints}.
|
|
|
|
@table @code
|
|
@kindex maint info breakpoints
|
|
@item maint info breakpoints
|
|
Using the same format as @samp{info breakpoints}, display both the
|
|
breakpoints you've set explicitly, and those @value{GDBN} is using for
|
|
internal purposes. Internal breakpoints are shown with negative
|
|
breakpoint numbers. The type column identifies what kind of breakpoint
|
|
is shown:
|
|
|
|
@table @code
|
|
@item breakpoint
|
|
Normal, explicitly set breakpoint.
|
|
|
|
@item watchpoint
|
|
Normal, explicitly set watchpoint.
|
|
|
|
@item longjmp
|
|
Internal breakpoint, used to handle correctly stepping through
|
|
@code{longjmp} calls.
|
|
|
|
@item longjmp resume
|
|
Internal breakpoint at the target of a @code{longjmp}.
|
|
|
|
@item until
|
|
Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
|
|
|
|
@item finish
|
|
Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
|
|
@end table
|
|
|
|
@end table
|
|
|
|
|
|
@node Set Watchpoints
|
|
@subsection Setting watchpoints
|
|
@cindex setting watchpoints
|
|
|
|
You can use a watchpoint to stop execution whenever the value of an
|
|
expression changes, without having to predict a particular place
|
|
where this may happen.
|
|
|
|
Watchpoints currently execute two orders of magnitude more slowly than
|
|
other breakpoints, but this can well be worth it to catch errors where
|
|
you have no clue what part of your program is the culprit. Some
|
|
processors provide special hardware to support watchpoint evaluation; future
|
|
releases of @value{GDBN} will use such hardware if it is available.
|
|
|
|
@table @code
|
|
@kindex watch
|
|
@item watch @var{expr}
|
|
Set a watchpoint for an expression.
|
|
|
|
@kindex info watchpoints
|
|
@item info watchpoints
|
|
This command prints a list of watchpoints and breakpoints; it is the
|
|
same as @code{info break}.
|
|
@end table
|
|
|
|
@ifclear CONLY
|
|
@node Exception Handling
|
|
@subsection Breakpoints and exceptions
|
|
@cindex exception handlers
|
|
|
|
Some languages, such as GNU C++, implement exception handling. You can
|
|
use @value{GDBN} to examine what caused your program to raise an exception,
|
|
and to list the exceptions your program is prepared to handle at a
|
|
given point in time.
|
|
|
|
@table @code
|
|
@item catch @var{exceptions}
|
|
@kindex catch
|
|
You can set breakpoints at active exception handlers by using the
|
|
@code{catch} command. @var{exceptions} is a list of names of exceptions
|
|
to catch.
|
|
@end table
|
|
|
|
You can use @code{info catch} to list active exception handlers.
|
|
@xref{Frame Info, ,Information about a frame}.
|
|
|
|
There are currently some limitations to exception handling in @value{GDBN}.
|
|
These will be corrected in a future release.
|
|
|
|
@itemize @bullet
|
|
@item
|
|
If you call a function interactively, @value{GDBN} 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 to simply continue
|
|
running until it hits a breakpoint, catches a signal that @value{GDBN} is
|
|
listening for, or exits.
|
|
@item
|
|
You cannot raise an exception interactively.
|
|
@item
|
|
You cannot interactively install an exception handler.
|
|
@end itemize
|
|
|
|
@cindex raise exceptions
|
|
Sometimes @code{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 @emph{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.
|
|
|
|
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 @code{__raise_exception}
|
|
which has the following ANSI C interface:
|
|
|
|
@example
|
|
/* @var{addr} is where the exception identifier is stored.
|
|
ID is the exception identifier. */
|
|
void __raise_exception (void **@var{addr}, void *@var{id});
|
|
@end example
|
|
|
|
@noindent
|
|
To make the debugger catch all exceptions before any stack
|
|
unwinding takes place, set a breakpoint on @code{__raise_exception}
|
|
(@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
|
|
|
|
With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
|
|
that depends on the value of @var{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.
|
|
@end ifclear
|
|
|
|
@node Delete Breaks
|
|
@subsection Deleting breakpoints
|
|
|
|
@cindex clearing breakpoints, watchpoints
|
|
@cindex deleting breakpoints, watchpoints
|
|
It is often necessary to eliminate a breakpoint or watchpoint once it
|
|
has done its job and you no longer want your program to stop there. This
|
|
is called @dfn{deleting} the breakpoint. A breakpoint that has been
|
|
deleted no longer exists; it is forgotten.
|
|
|
|
With the @code{clear} command you can delete breakpoints according to
|
|
where they are in your program. With the @code{delete} command you can
|
|
delete individual breakpoints or watchpoints by specifying their
|
|
breakpoint numbers.
|
|
|
|
It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
|
|
automatically ignores breakpoints on the first instruction to be executed
|
|
when you continue execution without changing the execution address.
|
|
|
|
@table @code
|
|
@item clear
|
|
@kindex clear
|
|
Delete any breakpoints at the next instruction to be executed in the
|
|
selected stack frame (@pxref{Selection, ,Selecting a frame}). When
|
|
the innermost frame is selected, this is a good way to delete a
|
|
breakpoint where your program just stopped.
|
|
|
|
@item clear @var{function}
|
|
@itemx clear @var{filename}:@var{function}
|
|
Delete any breakpoints set at entry to the function @var{function}.
|
|
|
|
@item clear @var{linenum}
|
|
@itemx clear @var{filename}:@var{linenum}
|
|
Delete any breakpoints set at or within the code of the specified line.
|
|
|
|
@item delete @r{[}breakpoints@r{]} @r{[}@var{bnums}@dots{}@r{]}
|
|
@cindex delete breakpoints
|
|
@kindex delete
|
|
@kindex d
|
|
Delete the breakpoints or watchpoints of the numbers specified as
|
|
arguments. If no argument is specified, delete all breakpoints (@value{GDBN}
|
|
asks confirmation, unless you have @code{set confirm off}). You
|
|
can abbreviate this command as @code{d}.
|
|
@end table
|
|
|
|
@node Disabling
|
|
@subsection Disabling breakpoints
|
|
|
|
@cindex disabled breakpoints
|
|
@cindex enabled breakpoints
|
|
Rather than deleting a breakpoint or watchpoint, you might prefer to
|
|
@dfn{disable} it. This makes the breakpoint inoperative as if it had
|
|
been deleted, but remembers the information on the breakpoint so that
|
|
you can @dfn{enable} it again later.
|
|
|
|
You disable and enable breakpoints and watchpoints with the
|
|
@code{enable} and @code{disable} commands, optionally specifying one or
|
|
more breakpoint numbers as arguments. Use @code{info break} or
|
|
@code{info watch} to print a list of breakpoints or watchpoints if you
|
|
do not know which numbers to use.
|
|
|
|
A breakpoint or watchpoint can have any of four different states of
|
|
enablement:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
Enabled. The breakpoint will stop your program. A breakpoint set
|
|
with the @code{break} command starts out in this state.
|
|
@item
|
|
Disabled. The breakpoint has no effect on your program.
|
|
@item
|
|
Enabled once. The breakpoint will stop your program, but
|
|
when it does so it will become disabled. A breakpoint set
|
|
with the @code{tbreak} command starts out in this state.
|
|
@item
|
|
Enabled for deletion. The breakpoint will stop your program, but
|
|
immediately after it does so it will be deleted permanently.
|
|
@end itemize
|
|
|
|
You can use the following commands to enable or disable breakpoints and
|
|
watchpoints:
|
|
|
|
@table @code
|
|
@item disable @r{[}breakpoints@r{]} @r{[}@var{bnums}@dots{}@r{]}
|
|
@kindex disable breakpoints
|
|
@kindex disable
|
|
@kindex dis
|
|
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
|
|
@code{disable} as @code{dis}.
|
|
|
|
@item enable @r{[}breakpoints@r{]} @r{[}@var{bnums}@dots{}@r{]}
|
|
@kindex enable breakpoints
|
|
@kindex enable
|
|
Enable the specified breakpoints (or all defined breakpoints). They
|
|
become effective once again in stopping your program.
|
|
|
|
@item enable @r{[}breakpoints@r{]} once @var{bnums}@dots{}
|
|
Enable the specified breakpoints temporarily. Each will be disabled
|
|
again the next time it stops your program.
|
|
|
|
@item enable @r{[}breakpoints@r{]} delete @var{bnums}@dots{}
|
|
Enable the specified breakpoints to work once and then die. Each of
|
|
the breakpoints will be deleted the next time it stops your program.
|
|
@end table
|
|
|
|
Save for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
|
|
,Setting breakpoints}), breakpoints that you set are initially enabled;
|
|
subsequently, they become disabled or enabled only when you use one of
|
|
the commands above. (The command @code{until} can set and delete a
|
|
breakpoint of its own, but it will not change the state of your other
|
|
breakpoints; see @ref{Continuing and Stepping, ,Continuing and
|
|
stepping}.)
|
|
|
|
@node Conditions
|
|
@subsection Break conditions
|
|
@cindex conditional breakpoints
|
|
@cindex breakpoint conditions
|
|
|
|
@c FIXME what is scope of break condition expr? Context where wanted?
|
|
@c in particular for a watchpoint?
|
|
The simplest sort of breakpoint breaks every time your program reaches a
|
|
specified place. You can also specify a @dfn{condition} for a
|
|
breakpoint. A condition is just a Boolean expression in your
|
|
programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
|
|
a condition evaluates the expression each time your program reaches it,
|
|
and your program stops only if the condition is @emph{true}.
|
|
|
|
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 @var{assert}, you should set the condition
|
|
@samp{! @var{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
|
|
it might be simpler, say, to just set a watchpoint on a variable name,
|
|
and specify a condition that tests whether the new value is an interesting
|
|
one.
|
|
|
|
Break conditions can have side effects, and may even call functions 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, @value{GDBN} 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 for the
|
|
purpose of performing side effects when a breakpoint is reached
|
|
(@pxref{Break Commands, ,Breakpoint command lists}).
|
|
|
|
Break conditions can be specified when a breakpoint is set, by using
|
|
@samp{if} in the arguments to the @code{break} command. @xref{Set
|
|
Breaks, ,Setting breakpoints}. They can also be changed at any time
|
|
with the @code{condition} command. The @code{watch} command does not
|
|
recognize the @code{if} keyword; @code{condition} is the only way to
|
|
impose a further condition on a watchpoint.
|
|
|
|
@table @code
|
|
@item condition @var{bnum} @var{expression}
|
|
@kindex condition
|
|
Specify @var{expression} as the break condition for breakpoint or
|
|
watchpoint number @var{bnum}. From now on, this breakpoint will stop
|
|
your program only if the value of @var{expression} is true (nonzero, in
|
|
C). When you use @code{condition}, @value{GDBN} checks @var{expression}
|
|
immediately for syntactic correctness, and to determine whether symbols
|
|
in it have referents in the context of your breakpoint.
|
|
@c FIXME so what does GDB do if there is no referent? Moreover, what
|
|
@c about watchpoints?
|
|
@value{GDBN} does
|
|
not actually evaluate @var{expression} at the time the @code{condition}
|
|
command is given, however. @xref{Expressions, ,Expressions}.
|
|
|
|
@item condition @var{bnum}
|
|
Remove the condition from breakpoint number @var{bnum}. It becomes
|
|
an ordinary unconditional breakpoint.
|
|
@end table
|
|
|
|
@cindex ignore count (of 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 @dfn{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 count by one and continues. As a result, if the ignore count
|
|
value is @var{n}, the breakpoint will not stop the next @var{n} times it
|
|
is reached.
|
|
|
|
@table @code
|
|
@item ignore @var{bnum} @var{count}
|
|
@kindex ignore
|
|
Set the ignore count of breakpoint number @var{bnum} to @var{count}.
|
|
The next @var{count} times the breakpoint is reached, your program's
|
|
execution will not stop; other than to decrement the ignore count, @value{GDBN}
|
|
takes no action.
|
|
|
|
To make the breakpoint stop the next time it is reached, specify
|
|
a count of zero.
|
|
|
|
@item continue @var{count}
|
|
@itemx c @var{count}
|
|
@itemx fg @var{count}
|
|
@kindex continue @var{count}
|
|
Continue execution of your program, setting the ignore count of the
|
|
breakpoint where your program stopped to @var{count} minus one.
|
|
Thus, your program will not stop at this breakpoint until the
|
|
@var{count}'th time it is reached.
|
|
|
|
An argument to this command is meaningful only when your program stopped
|
|
due to a breakpoint. At other times, the argument to @code{continue} is
|
|
ignored.
|
|
|
|
The synonym @code{fg} is provided purely for convenience, and has
|
|
exactly the same behavior as other forms of the command.
|
|
@end table
|
|
|
|
If a breakpoint has a positive ignore count and a condition, the condition
|
|
is not checked. Once the ignore count reaches zero, the condition will
|
|
be checked.
|
|
|
|
You could achieve the effect of the ignore count with a condition such
|
|
as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
|
|
is decremented each time. @xref{Convenience Vars, ,Convenience
|
|
variables}.
|
|
|
|
@node Break Commands
|
|
@subsection Breakpoint command lists
|
|
|
|
@cindex breakpoint commands
|
|
You can give any breakpoint (or watchpoint) a series of commands to
|
|
execute when your program stops due to that breakpoint. For example, you
|
|
might want to print the values of certain expressions, or enable other
|
|
breakpoints.
|
|
|
|
@table @code
|
|
@item commands @r{[}@var{bnum}@r{]}
|
|
@itemx @dots{} @var{command-list} @dots{}
|
|
@itemx end
|
|
@kindex commands
|
|
@kindex end
|
|
Specify a list of commands for breakpoint number @var{bnum}. The commands
|
|
themselves appear on the following lines. Type a line containing just
|
|
@code{end} to terminate the commands.
|
|
|
|
To remove all commands from a breakpoint, type @code{commands} and
|
|
follow it immediately with @code{end}; that is, give no commands.
|
|
|
|
With no @var{bnum} argument, @code{commands} refers to the last
|
|
breakpoint or watchpoint set (not to the breakpoint most recently
|
|
encountered).
|
|
@end table
|
|
|
|
Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
|
|
disabled within a @var{command-list}.
|
|
|
|
You can use breakpoint commands to start your program up again. Simply
|
|
use the @code{continue} command, or @code{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 @code{next} or @code{step}), you may encounter
|
|
another breakpoint---which could have its own command list, leading to
|
|
ambiguities about which list to execute.
|
|
|
|
@kindex silent
|
|
If the first command you specify in a command list is @code{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
|
|
will see no sign that the breakpoint was reached. @code{silent} is
|
|
meaningful only at the beginning of a breakpoint command list.
|
|
|
|
The commands @code{echo} and @code{output} that allow you to print
|
|
precisely controlled output are often useful in silent breakpoints.
|
|
@xref{Output, ,Commands for controlled output}.
|
|
|
|
For example, here is how you could use breakpoint commands to print the
|
|
value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
|
|
|
|
@example
|
|
break foo if x>0
|
|
commands
|
|
silent
|
|
echo x is\040
|
|
output x
|
|
echo \n
|
|
cont
|
|
end
|
|
@end example
|
|
|
|
One application for breakpoint commands is to compensate for one bug 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 @code{continue} command
|
|
so that your program does not stop, and start with the @code{silent}
|
|
command so that no output is produced. Here is an example:
|
|
|
|
@example
|
|
break 403
|
|
commands
|
|
silent
|
|
set x = y + 4
|
|
cont
|
|
end
|
|
@end example
|
|
|
|
@cindex lost output
|
|
One deficiency in the operation of automatically continuing breakpoints
|
|
under Unix appears when your program uses raw mode for the terminal.
|
|
@value{GDBN} switches back to its own terminal modes (not raw) before executing
|
|
commands, and then must switch back to raw mode when your program is
|
|
continued. This causes any pending terminal input to be lost.
|
|
@c FIXME: revisit below when GNU sys avail.
|
|
@c In the GNU system, this will be fixed by changing the behavior of
|
|
@c terminal modes.
|
|
|
|
Under Unix, you can get around this problem by writing actions into
|
|
the breakpoint condition rather than in commands. For example,
|
|
|
|
@example
|
|
condition 5 (x = y + 4), 0
|
|
@end example
|
|
|
|
@noindent
|
|
specifies a condition expression (@pxref{Expressions, ,Expressions}) that will
|
|
change @code{x} as needed, then always have the value zero so your
|
|
program will not stop. No input is lost here, because @value{GDBN} evaluates
|
|
break conditions without changing the terminal modes. When you want
|
|
to have nontrivial conditions for performing the side effects, the
|
|
operators @samp{&&}, @samp{||} and @samp{?@dots{}:} may be useful.
|
|
|
|
@ifclear CONLY
|
|
@node Breakpoint Menus
|
|
@subsection Breakpoint menus
|
|
@cindex overloading
|
|
@cindex symbol overloading
|
|
|
|
Some programming languages (notably C++) permit a single function name
|
|
to be defined several times, for application in different contexts.
|
|
This is called @dfn{overloading}. When a function name is overloaded,
|
|
@samp{break @var{function}} is not enough to tell @value{GDBN} where you want
|
|
a breakpoint. If you realize this will be a problem, you can use
|
|
something like @samp{break @var{function}(@var{types})} to specify which
|
|
particular version of the function you want. Otherwise, @value{GDBN} offers
|
|
you a menu of numbered choices for different possible breakpoints, and
|
|
waits for your selection with the prompt @samp{>}. The first two
|
|
options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
|
|
sets a breakpoint at each definition of @var{function}, and typing
|
|
@kbd{0} aborts the @code{break} command without setting any new
|
|
breakpoints.
|
|
|
|
For example, the following session excerpt shows an attempt to set a
|
|
breakpoint at the overloaded symbol @code{String::after}.
|
|
We choose three particular definitions of that function name:
|
|
|
|
@c FIXME! This is likely to change to show arg type lists, at least
|
|
@example
|
|
(@value{GDBP}) b String::after
|
|
[0] cancel
|
|
[1] all
|
|
[2] file:String.cc; line number:867
|
|
[3] file:String.cc; line number:860
|
|
[4] file:String.cc; line number:875
|
|
[5] file:String.cc; line number:853
|
|
[6] file:String.cc; line number:846
|
|
[7] file:String.cc; line number:735
|
|
> 2 4 6
|
|
Breakpoint 1 at 0xb26c: file String.cc, line 867.
|
|
Breakpoint 2 at 0xb344: file String.cc, line 875.
|
|
Breakpoint 3 at 0xafcc: file String.cc, line 846.
|
|
Multiple breakpoints were set.
|
|
Use the "delete" command to delete unwanted breakpoints.
|
|
(@value{GDBP})
|
|
@end example
|
|
@end ifclear
|
|
|
|
@ifclear BARETARGET
|
|
@node Error in Breakpoints
|
|
@subsection ``Cannot insert breakpoints''
|
|
|
|
@c FIXME: "cannot insert breakpoints" error, v unclear.
|
|
@c Q in pending mail to Gilmore. ---pesch@cygnus.com, 26mar91
|
|
@c some light may be shed by looking at instances of
|
|
@c ONE_PROCESS_WRITETEXT. But error message seems possible otherwise
|
|
@c too. pesch, 20sep91
|
|
Under some operating systems, breakpoints cannot be used in a program if
|
|
any other process is running that program. In this situation,
|
|
attempting to run or continue a program with a breakpoint causes @value{GDBN}
|
|
to stop the other process.
|
|
|
|
When this happens, you have three ways to proceed:
|
|
|
|
@enumerate
|
|
@item
|
|
Remove or disable the breakpoints, then continue.
|
|
|
|
@item
|
|
Suspend @value{GDBN}, and copy the file containing your program to a new name.
|
|
Resume @value{GDBN} and use the @code{exec-file} command to specify that @value{GDBN}
|
|
should run your program under that name. Then start your program again.
|
|
|
|
@c FIXME: RMS commented here "Show example". Maybe when someone
|
|
@c explains the first FIXME: in this section...
|
|
|
|
@item
|
|
Relink your program so that the text segment is nonsharable, using the
|
|
linker option @samp{-N}. The operating system limitation may not apply
|
|
to nonsharable executables.
|
|
@end enumerate
|
|
@end ifclear
|
|
|
|
@node Continuing and Stepping
|
|
@section Continuing and stepping
|
|
|
|
@cindex stepping
|
|
@cindex continuing
|
|
@cindex resuming execution
|
|
@dfn{Continuing} means resuming program execution until your program
|
|
completes normally. In contrast, @dfn{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
|
|
@ifset BARETARGET
|
|
a breakpoint.
|
|
@end ifset
|
|
@ifclear BARETARGET
|
|
a breakpoint or to a signal. (If due to a signal, you may want to use
|
|
@code{handle}, or use @samp{signal 0} to resume execution.
|
|
@xref{Signals, ,Signals}.)
|
|
@end ifclear
|
|
|
|
@table @code
|
|
@item continue @r{[}@var{ignore-count}@r{]}
|
|
@kindex continue
|
|
Resume program execution, at the address where your program last stopped;
|
|
any breakpoints set at that address are bypassed. The optional argument
|
|
@var{ignore-count} allows you to specify a further number of times to
|
|
ignore a breakpoint at this location; its effect is like that of
|
|
@code{ignore} (@pxref{Conditions, ,Break conditions}).
|
|
|
|
To resume execution at a different place, you can use @code{return}
|
|
(@pxref{Returning, ,Returning from a function}) to go back to the
|
|
calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
|
|
different address}) to go to an arbitrary location in your program.
|
|
@end table
|
|
|
|
A typical technique for using stepping is to set a breakpoint
|
|
@ifclear CONLY
|
|
(@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions})
|
|
@end ifclear
|
|
@ifset CONLY
|
|
(@pxref{Breakpoints, ,Breakpoints and watchpoints})
|
|
@end ifset
|
|
at the
|
|
beginning of the function or the section of your program where a
|
|
problem is believed to lie, run your program until it stops at that
|
|
breakpoint, and then step through the suspect area, examining the
|
|
variables that are interesting, until you see the problem happen.
|
|
|
|
@table @code
|
|
@item step
|
|
@kindex step
|
|
@kindex s
|
|
Continue running your program until control reaches a different source
|
|
line, then stop it and return control to @value{GDBN}. This command is
|
|
abbreviated @code{s}.
|
|
|
|
@quotation
|
|
@emph{Warning:} If you use the @code{step} command while control is
|
|
within a function that was compiled without debugging information,
|
|
execution will proceed until control reaches another function.
|
|
@end quotation
|
|
|
|
@item step @var{count}
|
|
Continue running as in @code{step}, but do so @var{count} times. If a
|
|
breakpoint is reached,
|
|
@ifclear BARETARGET
|
|
or a signal not related to stepping occurs before @var{count} steps,
|
|
@end ifclear
|
|
stepping stops right away.
|
|
|
|
@item next @r{[}@var{count}@r{]}
|
|
@kindex next
|
|
@kindex n
|
|
Continue to the next source line in the current (innermost) stack frame.
|
|
Similar to @code{step}, but any function calls appearing within the line
|
|
of code are executed without stopping. Execution stops when control
|
|
reaches a different line of code at the stack level which was executing
|
|
when the @code{next} command was given. This command is abbreviated
|
|
@code{n}.
|
|
|
|
An argument @var{count} is a repeat count, as for @code{step}.
|
|
|
|
@code{next} within a function that lacks debugging information acts like
|
|
@code{step}, but any function calls appearing within the code of the
|
|
function are executed without stopping.
|
|
|
|
@item finish
|
|
@kindex finish
|
|
Continue running until just after function in the selected stack frame
|
|
returns. Print the returned value (if any).
|
|
|
|
Contrast this with the @code{return} command (@pxref{Returning,
|
|
,Returning from a function}).
|
|
|
|
@item until
|
|
@kindex until
|
|
@item u
|
|
@kindex 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 @code{next}
|
|
command, except that when @code{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, @code{until} will cause your program to continue execution
|
|
until the loop is exited. In contrast, a @code{next} command at the end
|
|
of a loop will simply step back to the beginning of the loop, which
|
|
would force you to step through the next iteration.
|
|
|
|
@code{until} always stops your program if it attempts to exit the current
|
|
stack frame.
|
|
|
|
@code{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 @code{f}
|
|
(@code{frame}) command shows that execution is stopped at line
|
|
@code{206}; yet when we use @code{until}, we get to line @code{195}:
|
|
|
|
@example
|
|
(@value{GDBP}) f
|
|
#0 main (argc=4, argv=0xf7fffae8) at m4.c:206
|
|
206 expand_input();
|
|
(@value{GDBP}) until
|
|
195 for ( ; argc > 0; NEXTARG) @{
|
|
@end example
|
|
|
|
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 @code{for}-loop is
|
|
written before the body of the loop. The @code{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.
|
|
|
|
@code{until} with no argument works by means of single
|
|
instruction stepping, and hence is slower than @code{until} with an
|
|
argument.
|
|
|
|
@item until @var{location}
|
|
@item u @var{location}
|
|
Continue running your program until either the specified location is
|
|
reached, or the current stack frame returns. @var{location} is any of
|
|
the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
|
|
,Setting breakpoints}). This form of the command uses breakpoints,
|
|
and hence is quicker than @code{until} without an argument.
|
|
|
|
@item stepi
|
|
@itemx si
|
|
@kindex stepi
|
|
@kindex si
|
|
Execute one machine instruction, then stop and return to the debugger.
|
|
|
|
It is often useful to do @samp{display/i $pc} when stepping by machine
|
|
instructions. This will cause the next instruction to be executed to
|
|
be displayed automatically at each stop. @xref{Auto Display,
|
|
,Automatic display}.
|
|
|
|
An argument is a repeat count, as in @code{step}.
|
|
|
|
@need 750
|
|
@item nexti
|
|
@itemx ni
|
|
@kindex nexti
|
|
@kindex 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 @code{next}.
|
|
@end table
|
|
|
|
@ifset POSIX
|
|
@node Signals
|
|
@section Signals
|
|
@cindex signals
|
|
|
|
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 @code{SIGINT} is the
|
|
signal a program gets when you type an interrupt (often @kbd{C-c});
|
|
@code{SIGSEGV} is the signal a program gets from referencing a place in
|
|
memory far away from all the areas in use; @code{SIGALRM} occurs when
|
|
the alarm clock timer goes off (which happens only if your program has
|
|
requested an alarm).
|
|
|
|
@cindex fatal signals
|
|
Some signals, including @code{SIGALRM}, are a normal part of the
|
|
functioning of your program. Others, such as @code{SIGSEGV}, indicate
|
|
errors; these signals are @dfn{fatal} (kill your program immediately) if the
|
|
program has not specified in advance some other way to handle the signal.
|
|
@code{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.
|
|
|
|
@value{GDBN} has the ability to detect any occurrence of a signal in your
|
|
program. You can tell @value{GDBN} in advance what to do for each kind of
|
|
signal.
|
|
|
|
@cindex handling signals
|
|
Normally, @value{GDBN} is set up to ignore non-erroneous signals like @code{SIGALRM}
|
|
(so as not to interfere with their role in the functioning of your program)
|
|
but to stop your program immediately whenever an error signal happens.
|
|
You can change these settings with the @code{handle} command.
|
|
|
|
@table @code
|
|
@item info signals
|
|
@kindex info signals
|
|
Print a table of all the kinds of signals and how @value{GDBN} has been told to
|
|
handle each one. You can use this to see the signal numbers of all
|
|
the defined types of signals.
|
|
|
|
@item handle @var{signal} @var{keywords}@dots{}
|
|
@kindex handle
|
|
Change the way @value{GDBN} handles signal @var{signal}. @var{signal} can be the
|
|
number of a signal or its name (with or without the @samp{SIG} at the
|
|
beginning). The @var{keywords} say what change to make.
|
|
@end table
|
|
|
|
@c @group
|
|
The keywords allowed by the @code{handle} command can be abbreviated.
|
|
Their full names are:
|
|
|
|
@table @code
|
|
@item nostop
|
|
@value{GDBN} should not stop your program when this signal happens. It may
|
|
still print a message telling you that the signal has come in.
|
|
|
|
@item stop
|
|
@value{GDBN} should stop your program when this signal happens. This implies
|
|
the @code{print} keyword as well.
|
|
|
|
@item print
|
|
@value{GDBN} should print a message when this signal happens.
|
|
|
|
@item noprint
|
|
@value{GDBN} should not mention the occurrence of the signal at all. This
|
|
implies the @code{nostop} keyword as well.
|
|
|
|
@item pass
|
|
@value{GDBN} should allow your program to see this signal; your program will be
|
|
able to handle the signal, or may be terminated if the signal is fatal
|
|
and not handled.
|
|
|
|
@item nopass
|
|
@value{GDBN} should not allow your program to see this signal.
|
|
@end table
|
|
@c @end group
|
|
|
|
When a signal stops your program, the signal is not visible until you
|
|
continue. Your program will see the signal then, if @code{pass} is in
|
|
effect for the signal in question @emph{at that time}. In other words,
|
|
after @value{GDBN} reports a signal, you can use the @code{handle}
|
|
command with @code{pass} or @code{nopass} to control whether that
|
|
signal will be seen by your program when you later continue it.
|
|
|
|
You can also use the @code{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 @samp{signal 0}. @xref{Signaling, ,Giving your
|
|
program a signal}.
|
|
@end ifset
|
|
|
|
@node Stack
|
|
@chapter Examining the Stack
|
|
|
|
When your program has stopped, the first thing you need to know is where it
|
|
stopped and how it got there.
|
|
|
|
@cindex call stack
|
|
Each time your program performs a function call, the information about
|
|
where in your program the call was made from is saved in a block of data
|
|
called a @dfn{stack frame}. The frame also contains the arguments of the
|
|
call and the local variables of the function that was called. All the
|
|
stack frames are allocated in a region of memory called the @dfn{call
|
|
stack}.
|
|
|
|
When your program stops, the @value{GDBN} commands for examining the
|
|
stack allow you to see all of this information.
|
|
|
|
@cindex selected frame
|
|
One of the stack frames is @dfn{selected} by @value{GDBN} and many
|
|
@value{GDBN} commands refer implicitly to the selected frame. In
|
|
particular, whenever you ask @value{GDBN} for the value of a variable in
|
|
your program, the value is found in the selected frame. There are
|
|
special @value{GDBN} commands to select whichever frame you are
|
|
interested in.
|
|
|
|
When your program stops, @value{GDBN} automatically selects the
|
|
currently executing frame and describes it briefly as the @code{frame}
|
|
command does (@pxref{Frame Info, ,Information about a frame}).
|
|
|
|
@menu
|
|
* Frames:: Stack frames
|
|
* Backtrace:: Backtraces
|
|
* Selection:: Selecting a frame
|
|
* Frame Info:: Information on a frame
|
|
@ifset MIPS
|
|
* MIPS Stack:: MIPS machines and the function stack
|
|
@end ifset
|
|
@end menu
|
|
|
|
@node Frames
|
|
@section Stack frames
|
|
|
|
@cindex frame
|
|
@cindex stack frame
|
|
The call stack is divided up into contiguous pieces called @dfn{stack
|
|
frames}, or @dfn{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.
|
|
|
|
@cindex initial frame
|
|
@cindex outermost frame
|
|
@cindex innermost frame
|
|
When your program is started, the stack has only one frame, that of the
|
|
function @code{main}. This is called the @dfn{initial} frame or the
|
|
@dfn{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 @dfn{innermost} frame. This is the most
|
|
recently created of all the stack frames that still exist.
|
|
|
|
@cindex frame pointer
|
|
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 of those bytes whose
|
|
address serves as the address of the frame. Usually this address is kept
|
|
in a register called the @dfn{frame pointer register} while execution is
|
|
going on in that frame.
|
|
|
|
@cindex frame number
|
|
@value{GDBN} assigns numbers to all existing stack frames, starting with
|
|
zero for the innermost frame, one for the frame that called it,
|
|
and so on upward. These numbers do not really exist in your program;
|
|
they are assigned by @value{GDBN} to give you a way of designating stack
|
|
frames in @value{GDBN} commands.
|
|
|
|
@cindex frameless execution
|
|
Some compilers provide a way to compile functions so that they operate
|
|
without stack frames. (For example, the @code{@value{GCC}} option
|
|
@samp{-fomit-frame-pointer} will generate functions without a frame.)
|
|
This is occasionally done with heavily used library functions to save
|
|
the frame setup time. @value{GDBN} has limited facilities for dealing
|
|
with these function invocations. If the innermost function invocation
|
|
has no stack frame, @value{GDBN} will nevertheless regard it as though
|
|
it had a separate frame, which is numbered zero as usual, allowing
|
|
correct tracing of the function call chain. However, @value{GDBN} has
|
|
no provision for frameless functions elsewhere in the stack.
|
|
|
|
@node Backtrace
|
|
@section 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.
|
|
|
|
@table @code
|
|
@item backtrace
|
|
@itemx bt
|
|
@kindex backtrace
|
|
@kindex 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 @kbd{C-c}.
|
|
|
|
@item backtrace @var{n}
|
|
@itemx bt @var{n}
|
|
Similar, but print only the innermost @var{n} frames.
|
|
|
|
@item backtrace -@var{n}
|
|
@itemx bt -@var{n}
|
|
Similar, but print only the outermost @var{n} frames.
|
|
@end table
|
|
|
|
@kindex where
|
|
@kindex info stack
|
|
@kindex info s
|
|
The names @code{where} and @code{info stack} (abbreviated @code{info s})
|
|
are additional aliases for @code{backtrace}.
|
|
|
|
Each line in the backtrace shows the frame number and the function name.
|
|
The program counter value is also shown---unless you use @code{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
|
|
@samp{bt 3}, so it shows the innermost three frames.
|
|
|
|
@smallexample
|
|
@group
|
|
#0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
|
|
at builtin.c:993
|
|
#1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
|
|
#2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
|
|
at macro.c:71
|
|
(More stack frames follow...)
|
|
@end group
|
|
@end smallexample
|
|
|
|
@noindent
|
|
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 @code{993} of @code{builtin.c}.
|
|
|
|
@node Selection
|
|
@section Selecting a frame
|
|
|
|
Most commands for examining the stack and other data in your program work on
|
|
whichever stack frame is selected at the moment. Here are the commands for
|
|
selecting a stack frame; all of them finish by printing a brief description
|
|
of the stack frame just selected.
|
|
|
|
@table @code
|
|
@item frame @var{n}
|
|
@itemx f @var{n}
|
|
@kindex frame
|
|
@kindex f
|
|
Select frame number @var{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
|
|
@code{main}.
|
|
|
|
@item frame @var{addr}
|
|
@itemx f @var{addr}
|
|
Select the frame at address @var{addr}. This is useful mainly if the
|
|
chaining of stack frames has been damaged by a bug, making it
|
|
impossible for @value{GDBN} to assign numbers properly to all frames. In
|
|
addition, this can be useful when your program has multiple stacks and
|
|
switches between them.
|
|
|
|
@ifset SPARC
|
|
On the SPARC architecture, @code{frame} needs two addresses to
|
|
select an arbitrary frame: a frame pointer and a stack pointer.
|
|
@c note to future updaters: this is conditioned on a flag
|
|
@c FRAME_SPECIFICATION_DYADIC in the tm-*.h files, currently only used
|
|
@c by SPARC, hence the specific attribution. Generalize or list all
|
|
@c possibilities if more supported machines start doing this.
|
|
@end ifset
|
|
|
|
@item up @var{n}
|
|
@kindex up
|
|
Move @var{n} frames up the stack. For positive numbers @var{n}, this
|
|
advances toward the outermost frame, to higher frame numbers, to frames
|
|
that have existed longer. @var{n} defaults to one.
|
|
|
|
@item down @var{n}
|
|
@kindex down
|
|
@kindex do
|
|
Move @var{n} frames down the stack. For positive numbers @var{n}, this
|
|
advances toward the innermost frame, to lower frame numbers, to frames
|
|
that were created more recently. @var{n} defaults to one. You may
|
|
abbreviate @code{down} as @code{do}.
|
|
@end table
|
|
|
|
All of these commands end by printing two lines of output describing the
|
|
frame. The first line shows the frame number, the function name, the
|
|
arguments, and the source file and line number of execution in that
|
|
frame. The second line shows the text of that source line.
|
|
|
|
For example:
|
|
@smallexample
|
|
@group
|
|
(@value{GDBP}) up
|
|
#1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
|
|
at env.c:10
|
|
10 read_input_file (argv[i]);
|
|
@end group
|
|
@end smallexample
|
|
|
|
After such a printout, the @code{list} command with no arguments will
|
|
print ten lines centered on the point of execution in the frame.
|
|
@xref{List, ,Printing source lines}.
|
|
|
|
@table @code
|
|
@item up-silently @var{n}
|
|
@itemx down-silently @var{n}
|
|
@kindex down-silently
|
|
@kindex up-silently
|
|
These two commands are variants of @code{up} and @code{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 @value{GDBN} command scripts, where the output might be unnecessary and
|
|
distracting.
|
|
@end table
|
|
|
|
@node Frame Info
|
|
@section Information about a frame
|
|
|
|
There are several other commands to print information about the selected
|
|
stack frame.
|
|
|
|
@table @code
|
|
@item frame
|
|
@itemx 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 @code{f}. With an
|
|
argument, this command is used to select a stack frame.
|
|
@xref{Selection, ,Selecting a frame}.
|
|
|
|
@item info frame
|
|
@itemx info f
|
|
@kindex info frame
|
|
@kindex info f
|
|
This command prints a verbose description of the selected stack frame,
|
|
including the address of the frame, the addresses of the next frame down
|
|
(called by this frame) and the next frame up (caller of this frame), the
|
|
language that the source code corresponding to this frame was written in,
|
|
the address of the frame's arguments, the program counter saved in it
|
|
(the address of execution in the caller frame), and 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.
|
|
|
|
@item info frame @var{addr}
|
|
@itemx info f @var{addr}
|
|
Print a verbose description of the frame at address @var{addr},
|
|
without selecting that frame. The selected frame remains unchanged by
|
|
this command.
|
|
|
|
@item info args
|
|
@kindex info args
|
|
Print the arguments of the selected frame, each on a separate line.
|
|
|
|
@item info locals
|
|
@kindex 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.
|
|
|
|
@ifclear CONLY
|
|
@item info catch
|
|
@kindex info catch
|
|
@cindex catch exceptions
|
|
@cindex exception handlers
|
|
Print a list of all the exception handlers that are active in the
|
|
current stack frame at the current point of execution. To see other
|
|
exception handlers, visit the associated frame (using the @code{up},
|
|
@code{down}, or @code{frame} commands); then type @code{info catch}.
|
|
@xref{Exception Handling, ,Breakpoints and exceptions}.
|
|
@end ifclear
|
|
@end table
|
|
|
|
@ifset MIPS
|
|
@node MIPS Stack
|
|
@section MIPS machines and the function stack
|
|
|
|
@cindex stack on MIPS
|
|
@cindex MIPS stack
|
|
MIPS based computers use an unusual stack frame, which sometimes
|
|
requires @value{GDBN} to search backward in the object code to find the
|
|
beginning of a function.
|
|
|
|
@cindex response time, MIPS debugging
|
|
To improve response time (especially for embedded applications, where
|
|
@value{GDBN} may be restricted to a slow serial line for this search)
|
|
you may want to limit the size of this search, using one of these
|
|
commands:
|
|
@c FIXME! So what happens when GDB does *not* find the beginning of a
|
|
@c function?
|
|
|
|
@cindex @code{heuristic-fence-post} (MIPS)
|
|
@table @code
|
|
@item set heuristic-fence-post @var{limit}
|
|
Restrict @var{GDBN} to examining at most @var{limit} bytes in its search
|
|
for the beginning of a function. A value of @code{0} (the default)
|
|
means there is no limit.
|
|
|
|
@item show heuristic-fence-post
|
|
Display the current limit.
|
|
@end table
|
|
|
|
@noindent
|
|
These commands are available @emph{only} when @value{GDBN} is configured
|
|
for debugging programs on MIPS processors.
|
|
@end ifset
|
|
|
|
@node Source
|
|
@chapter Examining Source Files
|
|
|
|
@value{GDBN} can print parts of your program's source, since the debugging
|
|
information recorded in the program tells @value{GDBN} what source files were
|
|
used to build it. When your program stops, @value{GDBN} spontaneously prints
|
|
the line where it stopped. Likewise, when you select a stack frame
|
|
(@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
|
|
execution in that frame has stopped. You can print other portions of
|
|
source files by explicit command.
|
|
|
|
@ifclear DOSHOST
|
|
If you use @value{GDBN} through its GNU Emacs interface, you may prefer to use
|
|
Emacs facilities to view source; @pxref{Emacs, ,Using @value{GDBN} under GNU
|
|
Emacs}.
|
|
@end ifclear
|
|
|
|
@menu
|
|
* List:: Printing source lines
|
|
@ifclear DOSHOST
|
|
* Search:: Searching source files
|
|
@end ifclear
|
|
|
|
* Source Path:: Specifying source directories
|
|
* Machine Code:: Source and machine code
|
|
@end menu
|
|
|
|
@node List
|
|
@section Printing source lines
|
|
|
|
@kindex list
|
|
@kindex l
|
|
To print lines from a source file, use the @code{list} command
|
|
(abbreviated @code{l}). There are several ways to specify what part
|
|
of the file you want to print.
|
|
|
|
Here are the forms of the @code{list} command most commonly used:
|
|
|
|
@table @code
|
|
@item list @var{linenum}
|
|
Print lines centered around line number @var{linenum} in the
|
|
current source file.
|
|
|
|
@item list @var{function}
|
|
Print lines centered around the beginning of function
|
|
@var{function}.
|
|
|
|
@item list
|
|
Print more lines. If the last lines printed were printed with a
|
|
@code{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 (@pxref{Stack, ,Examining the
|
|
Stack}), this prints lines centered around that line.
|
|
|
|
@item list -
|
|
Print lines just before the lines last printed.
|
|
@end table
|
|
|
|
By default, @value{GDBN} prints ten source lines with any of these forms of
|
|
the @code{list} command. You can change this using @code{set listsize}:
|
|
|
|
@table @code
|
|
@item set listsize @var{count}
|
|
@kindex set listsize
|
|
Make the @code{list} command display @var{count} source lines (unless
|
|
the @code{list} argument explicitly specifies some other number).
|
|
|
|
@item show listsize
|
|
@kindex show listsize
|
|
Display the number of lines that @code{list} will currently display by
|
|
default.
|
|
@end table
|
|
|
|
Repeating a @code{list} command with @key{RET} discards the argument,
|
|
so it is equivalent to typing just @code{list}. This is more useful
|
|
than listing the same lines again. An exception is made for an
|
|
argument of @samp{-}; that argument is preserved in repetition so that
|
|
each repetition moves up in the source file.
|
|
|
|
@cindex linespec
|
|
In general, the @code{list} command expects you to supply zero, one or two
|
|
@dfn{linespecs}. Linespecs specify source lines; there are several ways
|
|
of writing them but the effect is always to specify some source line.
|
|
Here is a complete description of the possible arguments for @code{list}:
|
|
|
|
@table @code
|
|
@item list @var{linespec}
|
|
Print lines centered around the line specified by @var{linespec}.
|
|
|
|
@item list @var{first},@var{last}
|
|
Print lines from @var{first} to @var{last}. Both arguments are
|
|
linespecs.
|
|
|
|
@item list ,@var{last}
|
|
Print lines ending with @var{last}.
|
|
|
|
@item list @var{first},
|
|
Print lines starting with @var{first}.
|
|
|
|
@item list +
|
|
Print lines just after the lines last printed.
|
|
|
|
@item list -
|
|
Print lines just before the lines last printed.
|
|
|
|
@item list
|
|
As described in the preceding table.
|
|
@end table
|
|
|
|
Here are the ways of specifying a single source line---all the
|
|
kinds of linespec.
|
|
|
|
@table @code
|
|
@item @var{number}
|
|
Specifies line @var{number} of the current source file.
|
|
When a @code{list} command has two linespecs, this refers to
|
|
the same source file as the first linespec.
|
|
|
|
@item +@var{offset}
|
|
Specifies the line @var{offset} lines after the last line printed.
|
|
When used as the second linespec in a @code{list} command that has
|
|
two, this specifies the line @var{offset} lines down from the
|
|
first linespec.
|
|
|
|
@item -@var{offset}
|
|
Specifies the line @var{offset} lines before the last line printed.
|
|
|
|
@item @var{filename}:@var{number}
|
|
Specifies line @var{number} in the source file @var{filename}.
|
|
|
|
@item @var{function}
|
|
@c FIXME: "of the open-brace" is C-centric. When we add other langs...
|
|
Specifies the line of the open-brace that begins the body of the
|
|
function @var{function}.
|
|
|
|
@item @var{filename}:@var{function}
|
|
Specifies the line of the open-brace that begins the body of the
|
|
function @var{function} in the file @var{filename}. You only need the
|
|
file name with a function name to avoid ambiguity when there are
|
|
identically named functions in different source files.
|
|
|
|
@item *@var{address}
|
|
Specifies the line containing the program address @var{address}.
|
|
@var{address} may be any expression.
|
|
@end table
|
|
|
|
@ifclear DOSHOST
|
|
@node Search
|
|
@section Searching source files
|
|
@cindex searching
|
|
@kindex reverse-search
|
|
|
|
There are two commands for searching through the current source file for a
|
|
regular expression.
|
|
|
|
@table @code
|
|
@item forward-search @var{regexp}
|
|
@itemx search @var{regexp}
|
|
@kindex search
|
|
@kindex forward-search
|
|
The command @samp{forward-search @var{regexp}} checks each line,
|
|
starting with the one following the last line listed, for a match for
|
|
@var{regexp}. It lists the line that is found. You can use
|
|
synonym @samp{search @var{regexp}} or abbreviate the command name as
|
|
@code{fo}.
|
|
|
|
@item reverse-search @var{regexp}
|
|
The command @samp{reverse-search @var{regexp}} checks each line, starting
|
|
with the one before the last line listed and going backward, for a match
|
|
for @var{regexp}. It lists the line that is found. You can abbreviate
|
|
this command as @code{rev}.
|
|
@end table
|
|
@end ifclear
|
|
|
|
@node Source Path
|
|
@section Specifying source directories
|
|
|
|
@cindex source path
|
|
@cindex directories for source files
|
|
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. @value{GDBN} has a list of directories to search for source files;
|
|
this is called the @dfn{source path}. Each time @value{GDBN} 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. Note that
|
|
the executable search path is @emph{not} used for this purpose. Neither is
|
|
the current working directory, unless it happens to be in the source
|
|
path.
|
|
|
|
If @value{GDBN} cannot find a source file in the source path, and the object
|
|
program records a directory, @value{GDBN} tries that directory too. If the
|
|
source path is empty, and there is no record of the compilation
|
|
directory, @value{GDBN} will, as a last resort, look in the current
|
|
directory.
|
|
|
|
Whenever you reset or rearrange the source path, @value{GDBN} will clear out
|
|
any information it has cached about where source files are found, where
|
|
each line is in the file, etc.
|
|
|
|
@kindex directory
|
|
When you start @value{GDBN}, its source path is empty.
|
|
To add other directories, use the @code{directory} command.
|
|
|
|
@table @code
|
|
@item directory @var{dirname} @dots{}
|
|
Add directory @var{dirname} to the front of the source path. Several
|
|
directory names may be given to this command, separated by @samp{:} or
|
|
whitespace. You may specify a directory that is already in the source
|
|
path; this moves it forward, so it will be searched sooner.
|
|
|
|
You can use the string @samp{$cdir} to refer to the compilation
|
|
directory (if one is recorded), and @samp{$cwd} to refer to the current
|
|
working directory. @samp{$cwd} is not the same as @samp{.}---the former
|
|
tracks the current working directory as it changes during your @value{GDBN}
|
|
session, while the latter is immediately expanded to the current
|
|
directory at the time you add an entry to the source path.
|
|
|
|
@item directory
|
|
Reset the source path to empty again. This requires confirmation.
|
|
|
|
@c RET-repeat for @code{directory} is explicitly disabled, but since
|
|
@c repeating it would be a no-op we do not say that. (thanks to RMS)
|
|
|
|
@item show directories
|
|
@kindex show directories
|
|
Print the source path: show which directories it contains.
|
|
@end table
|
|
|
|
If your source path is cluttered with directories that are no longer of
|
|
interest, @value{GDBN} may sometimes cause confusion by finding the wrong
|
|
versions of source. You can correct the situation as follows:
|
|
|
|
@enumerate
|
|
@item
|
|
Use @code{directory} with no argument to reset the source path to empty.
|
|
|
|
@item
|
|
Use @code{directory} with suitable arguments to reinstall the
|
|
directories you want in the source path. You can add all the
|
|
directories in one command.
|
|
@end enumerate
|
|
|
|
@node Machine Code
|
|
@section Source and machine code
|
|
|
|
You can use the command @code{info line} to map source lines to program
|
|
addresses (and vice versa), and the command @code{disassemble} to display
|
|
a range of addresses as machine instructions.
|
|
|
|
@table @code
|
|
@item info line @var{linespec}
|
|
@kindex info line
|
|
Print the starting and ending addresses of the compiled code for
|
|
source line @var{linespec}. You can specify source lines in any of
|
|
the ways understood by the @code{list} command (@pxref{List, ,Printing
|
|
source lines}).
|
|
@end table
|
|
|
|
For example, we can use @code{info line} to discover the location of
|
|
the object code for the first line of function
|
|
@code{m4_changequote}:
|
|
|
|
@smallexample
|
|
(@value{GDBP}) info line m4_changecom
|
|
Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
|
|
@end smallexample
|
|
|
|
@noindent
|
|
We can also inquire (using @code{*@var{addr}} as the form for
|
|
@var{linespec}) what source line covers a particular address:
|
|
@smallexample
|
|
(@value{GDBP}) info line *0x63ff
|
|
Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
|
|
@end smallexample
|
|
|
|
@cindex @code{$_} and @code{info line}
|
|
After @code{info line}, the default address for the @code{x} command
|
|
is changed to the starting address of the line, so that @samp{x/i} is
|
|
sufficient to begin examining the machine code (@pxref{Memory,
|
|
,Examining memory}). Also, this address is saved as the value of the
|
|
convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
|
|
variables}).
|
|
|
|
@table @code
|
|
@kindex disassemble
|
|
@item disassemble
|
|
@cindex assembly instructions
|
|
@cindex instructions, assembly
|
|
@cindex machine instructions
|
|
@cindex listing machine instructions
|
|
This specialized command dumps a range of memory as machine
|
|
instructions. 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; the function surrounding this value
|
|
will be dumped. Two arguments specify a range of addresses (first
|
|
inclusive, second exclusive) to dump.
|
|
@end table
|
|
|
|
@ifclear H8EXCLUSIVE
|
|
We can use @code{disassemble} to inspect the object code
|
|
range shown in the last @code{info line} example (the example
|
|
shows SPARC machine instructions):
|
|
|
|
|
|
@smallexample
|
|
(@value{GDBP}) disas 0x63e4 0x6404
|
|
Dump of assembler code from 0x63e4 to 0x6404:
|
|
0x63e4 <builtin_init+5340>: ble 0x63f8 <builtin_init+5360>
|
|
0x63e8 <builtin_init+5344>: sethi %hi(0x4c00), %o0
|
|
0x63ec <builtin_init+5348>: ld [%i1+4], %o0
|
|
0x63f0 <builtin_init+5352>: b 0x63fc <builtin_init+5364>
|
|
0x63f4 <builtin_init+5356>: ld [%o0+4], %o0
|
|
0x63f8 <builtin_init+5360>: or %o0, 0x1a4, %o0
|
|
0x63fc <builtin_init+5364>: call 0x9288 <path_search>
|
|
0x6400 <builtin_init+5368>: nop
|
|
End of assembler dump.
|
|
@end smallexample
|
|
@end ifclear
|
|
|
|
@ifset H8EXCLUSIVE
|
|
For example, here is the beginning of the output for the
|
|
disassembly of a function @code{fact}:
|
|
|
|
|
|
@smallexample
|
|
(@value{GDBP}) disas fact
|
|
Dump of assembler code for function fact:
|
|
to 0x808c:
|
|
0x802c <fact>: 6d f2 mov.w r2,@@-r7
|
|
0x802e <fact+2>: 6d f3 mov.w r3,@@-r7
|
|
0x8030 <fact+4>: 6d f6 mov.w r6,@@-r7
|
|
0x8032 <fact+6>: 0d 76 mov.w r7,r6
|
|
0x8034 <fact+8>: 6f 70 00 08 mov.w @@(0x8,r7),r0
|
|
0x8038 <fact+12> 19 11 sub.w r1,r1
|
|
.
|
|
.
|
|
.
|
|
@end smallexample
|
|
@end ifset
|
|
|
|
@node Data
|
|
@chapter Examining Data
|
|
|
|
@cindex printing data
|
|
@cindex examining data
|
|
@kindex print
|
|
@kindex inspect
|
|
@c "inspect" is not quite a synonym if you are using Epoch, which we do not
|
|
@c document because it is nonstandard... Under Epoch it displays in a
|
|
@c different window or something like that.
|
|
The usual way to examine data in your program is with the @code{print}
|
|
command (abbreviated @code{p}), or its synonym @code{inspect}.
|
|
@ifclear CONLY
|
|
It evaluates and prints the value of an expression of the language your
|
|
program is written in (@pxref{Languages, ,Using @value{GDBN} with Different
|
|
Languages}).
|
|
@end ifclear
|
|
|
|
@table @code
|
|
@item print @var{exp}
|
|
@itemx print /@var{f} @var{exp}
|
|
@var{exp} is an expression (in the source language). By default the
|
|
value of @var{exp} is printed in a format appropriate to its data type;
|
|
you can choose a different format by specifying @samp{/@var{f}}, where
|
|
@var{f} is a letter specifying the format; @pxref{Output Formats,,Output
|
|
formats}.
|
|
|
|
@item print
|
|
@itemx print /@var{f}
|
|
If you omit @var{exp}, @value{GDBN} displays the last value again (from the
|
|
@dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
|
|
conveniently inspect the same value in an alternative format.
|
|
@end table
|
|
|
|
A more low-level way of examining data is with the @code{x} command.
|
|
It examines data in memory at a specified address and prints it in a
|
|
specified format. @xref{Memory, ,Examining memory}.
|
|
|
|
If you are interested in information about types, or about how the fields
|
|
of a struct
|
|
@ifclear CONLY
|
|
or class
|
|
@end ifclear
|
|
are declared, use the @code{ptype @var{exp}}
|
|
command rather than @code{print}. @xref{Symbols, ,Examining the Symbol Table}.
|
|
|
|
@menu
|
|
* Expressions:: Expressions
|
|
* Variables:: Program variables
|
|
* Arrays:: Artificial arrays
|
|
* Output Formats:: Output formats
|
|
* Memory:: Examining memory
|
|
* Auto Display:: Automatic display
|
|
* Print Settings:: Print settings
|
|
* Value History:: Value history
|
|
* Convenience Vars:: Convenience variables
|
|
* Registers:: Registers
|
|
@ifclear HAVE-FLOAT
|
|
* Floating Point Hardware:: Floating point hardware
|
|
@end ifclear
|
|
@end menu
|
|
|
|
@node Expressions
|
|
@section Expressions
|
|
|
|
@cindex expressions
|
|
@code{print} and many other @value{GDBN} 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
|
|
@value{GDBN}. This includes conditional expressions, function calls, casts
|
|
and string constants. It unfortunately does not include symbols defined
|
|
by preprocessor @code{#define} commands.
|
|
|
|
@ifclear CONLY
|
|
Because C is so widespread, most of the expressions shown in examples in
|
|
this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
|
|
Languages}, for information on how to use expressions in other
|
|
languages.
|
|
|
|
In this section, we discuss operators that you can use in @value{GDBN}
|
|
expressions regardless of your programming language.
|
|
|
|
Casts are supported in all languages, not just in C, because it is so
|
|
useful to cast a number into a pointer so as to examine a structure
|
|
at that address in memory.
|
|
@c FIXME: casts supported---Mod2 true?
|
|
@end ifclear
|
|
|
|
@value{GDBN} supports these operators in addition to those of programming
|
|
languages:
|
|
|
|
@table @code
|
|
@item @@
|
|
@samp{@@} is a binary operator for treating parts of memory as arrays.
|
|
@xref{Arrays, ,Artificial arrays}, for more information.
|
|
|
|
@item ::
|
|
@samp{::} allows you to specify a variable in terms of the file or
|
|
function where it is defined. @xref{Variables, ,Program variables}.
|
|
|
|
@item @{@var{type}@} @var{addr}
|
|
@cindex @{@var{type}@}
|
|
@cindex type casting memory
|
|
@cindex memory, viewing as typed object
|
|
@cindex casts, to view memory
|
|
Refers to an object of type @var{type} stored at address @var{addr} in
|
|
memory. @var{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 @var{addr}.
|
|
@end table
|
|
|
|
@node Variables
|
|
@section 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
|
|
(@pxref{Selection, ,Selecting a frame}); they must either be global
|
|
(or static) or be visible according to the scope rules of the
|
|
programming language from the point of execution in that frame. This
|
|
means that in the function
|
|
|
|
@example
|
|
foo (a)
|
|
int a;
|
|
@{
|
|
bar (a);
|
|
@{
|
|
int b = test ();
|
|
bar (b);
|
|
@}
|
|
@}
|
|
@end example
|
|
|
|
@noindent
|
|
you can examine and use the variable @code{a} whenever your program is
|
|
executing within the function @code{foo}, but you can only use or
|
|
examine the variable @code{b} while your program is executing inside
|
|
the block where @code{b} is declared.
|
|
|
|
@cindex variable name conflict
|
|
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,
|
|
using the colon-colon notation:
|
|
|
|
@cindex colon-colon
|
|
@iftex
|
|
@c info cannot cope with a :: index entry, but why deprive hard copy readers?
|
|
@kindex ::
|
|
@end iftex
|
|
@example
|
|
@var{file}::@var{variable}
|
|
@var{function}::@var{variable}
|
|
@end example
|
|
|
|
@noindent
|
|
Here @var{file} or @var{function} is the name of the context for the
|
|
static @var{variable}. In the case of file names, you can use quotes to
|
|
make sure @value{GDBN} parses the file name as a single word---for example,
|
|
to print a global value of @code{x} defined in @file{f2.c}:
|
|
|
|
@example
|
|
(@value{GDBP}) p 'f2.c'::x
|
|
@end example
|
|
|
|
@ifclear CONLY
|
|
@cindex C++ scope resolution
|
|
This use of @samp{::} is very rarely in conflict with the very similar
|
|
use of the same notation in C++. @value{GDBN} also supports use of the C++
|
|
scope resolution operator in @value{GDBN} expressions.
|
|
@c FIXME: Um, so what happens in one of those rare cases where it's in
|
|
@c conflict?? --mew
|
|
@end ifclear
|
|
|
|
@cindex wrong values
|
|
@cindex variable values, wrong
|
|
@quotation
|
|
@emph{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.
|
|
@end quotation
|
|
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.
|
|
|
|
@node Arrays
|
|
@section Artificial arrays
|
|
|
|
@cindex artificial array
|
|
@kindex @@
|
|
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
|
|
@dfn{artificial array}, using the binary operator @samp{@@}. The left
|
|
operand of @samp{@@} should be the first element of the desired array,
|
|
as 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
|
|
|
|
@example
|
|
int *array = (int *) malloc (len * sizeof (int));
|
|
@end example
|
|
|
|
@noindent
|
|
you can print the contents of @code{array} with
|
|
|
|
@example
|
|
p *array@@len
|
|
@end example
|
|
|
|
The left operand of @samp{@@} must reside in memory. Array values made
|
|
with @samp{@@} 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
|
|
(@pxref{Value History, ,Value history}), after printing one out.)
|
|
|
|
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 (@pxref{Convenience Vars, ,Convenience
|
|
variables}) as a counter in an expression that prints the first
|
|
interesting value, and then repeat that expression via @key{RET}. For
|
|
instance, suppose you have an array @code{dtab} of pointers to
|
|
structures, and you are interested in the values of a field @code{fv}
|
|
in each structure. Here is an example of what you might type:
|
|
|
|
@example
|
|
set $i = 0
|
|
p dtab[$i++]->fv
|
|
@key{RET}
|
|
@key{RET}
|
|
@dots{}
|
|
@end example
|
|
|
|
@node Output Formats
|
|
@section Output formats
|
|
|
|
@cindex formatted output
|
|
@cindex output formats
|
|
By default, @value{GDBN} 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 @dfn{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
|
|
@code{print} command with a slash and a format letter. The format
|
|
letters supported are:
|
|
|
|
@table @code
|
|
@item x
|
|
Regard the bits of the value as an integer, and print the integer in
|
|
hexadecimal.
|
|
|
|
@item d
|
|
Print as integer in signed decimal.
|
|
|
|
@item u
|
|
Print as integer in unsigned decimal.
|
|
|
|
@item o
|
|
Print as integer in octal.
|
|
|
|
@item t
|
|
Print as integer in binary. The letter @samp{t} stands for ``two''.
|
|
@footnote{@samp{b} cannot be used because these format letters are also
|
|
used with the @code{x} command, where @samp{b} stands for ``byte'';
|
|
@pxref{Memory,,Examining memory}.}
|
|
|
|
@item a
|
|
Print as an address, both absolute in hex and as an offset from the
|
|
nearest preceding symbol. This format can be used to discover where (in
|
|
what function) an unknown address is located:
|
|
|
|
@example
|
|
(@value{GDBP}) p/a 0x54320
|
|
$3 = 0x54320 <_initialize_vx+396>
|
|
@end example
|
|
|
|
@item c
|
|
Regard as an integer and print it as a character constant.
|
|
|
|
@item f
|
|
Regard the bits of the value as a floating point number and print
|
|
using typical floating point syntax.
|
|
@end table
|
|
|
|
For example, to print the program counter in hex (@pxref{Registers}), type
|
|
|
|
@example
|
|
p/x $pc
|
|
@end example
|
|
|
|
@noindent
|
|
Note that no space is required before the slash; this is because command
|
|
names in @value{GDBN} cannot contain a slash.
|
|
|
|
To reprint the last value in the value history with a different format,
|
|
you can use the @code{print} command with just a format and no
|
|
expression. For example, @samp{p/x} reprints the last value in hex.
|
|
|
|
@node Memory
|
|
@section Examining memory
|
|
|
|
You can use the command @code{x} (for ``examine'') to examine memory in
|
|
any of several formats, independently of your program's data types.
|
|
|
|
@cindex examining memory
|
|
@table @code
|
|
@kindex x
|
|
@item x/@var{nfu} @var{addr}
|
|
@itemx x @var{addr}
|
|
@itemx x
|
|
Use the @code{x} command to examine memory.
|
|
@end table
|
|
|
|
@var{n}, @var{f}, and @var{u} are all optional parameters that specify how
|
|
much memory to display and how to format it; @var{addr} is an
|
|
expression giving the address where you want to start displaying memory.
|
|
If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
|
|
Several commands set convenient defaults for @var{addr}.
|
|
|
|
@table @r
|
|
@item @var{n}, the repeat count
|
|
The repeat count is a decimal integer; the default is 1. It specifies
|
|
how much memory (counting by units @var{u}) to display.
|
|
@c This really is **decimal**; unaffected by 'set radix' as of GDB
|
|
@c 4.1.2.
|
|
|
|
@item @var{f}, the display format
|
|
The display format is one of the formats used by @code{print},
|
|
or @samp{s} (null-terminated string) or @samp{i} (machine instruction).
|
|
The default is @samp{x} (hexadecimal) initially, or the format from the
|
|
last time you used either @code{x} or @code{print}.
|
|
|
|
@item @var{u}, the unit size
|
|
The unit size is any of
|
|
|
|
@table @code
|
|
@item b
|
|
Bytes.
|
|
@item h
|
|
Halfwords (two bytes).
|
|
@item w
|
|
Words (four bytes). This is the initial default.
|
|
@item g
|
|
Giant words (eight bytes).
|
|
@end table
|
|
|
|
Each time you specify a unit size with @code{x}, that size becomes the
|
|
default unit the next time you use @code{x}. (For the @samp{s} and
|
|
@samp{i} formats, the unit size is ignored and is normally not written.)
|
|
|
|
@item @var{addr}, starting display address
|
|
@var{addr} is the address where you want @value{GDBN} 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.
|
|
@xref{Expressions, ,Expressions}, for more information on expressions. The default for
|
|
@var{addr} is usually just after the last address examined---but several
|
|
other commands also set the default address: @code{info breakpoints} (to
|
|
the address of the last breakpoint listed), @code{info line} (to the
|
|
starting address of a line), and @code{print} (if you use it to display
|
|
a value from memory).
|
|
@end table
|
|
|
|
For example, @samp{x/3uh 0x54320} is a request to display three halfwords
|
|
(@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
|
|
starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
|
|
words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
|
|
@pxref{Registers}) in hexadecimal (@samp{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 will work. The output
|
|
specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
|
|
(However, the count @var{n} must come first; @samp{wx4} will not work.)
|
|
|
|
Even though the unit size @var{u} is ignored for the formats @samp{s}
|
|
and @samp{i}, you might still want to use a count @var{n}; for example,
|
|
@samp{3i} specifies that you want to see three machine instructions,
|
|
including any operands. The command @code{disassemble} gives an
|
|
alternative way of inspecting machine instructions; @pxref{Machine
|
|
Code,,Source and machine code}.
|
|
|
|
All the defaults for the arguments to @code{x} are designed to make it
|
|
easy to continue scanning memory with minimal specifications each time
|
|
you use @code{x}. For example, after you have inspected three machine
|
|
instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
|
|
with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
|
|
the repeat count @var{n} is used again; the other arguments default as
|
|
for successive uses of @code{x}.
|
|
|
|
@cindex @code{$_}, @code{$__}, and value history
|
|
The addresses and contents printed by the @code{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, @value{GDBN} makes these values available for
|
|
subsequent use in expressions as values of the convenience variables
|
|
@code{$_} and @code{$__}. After an @code{x} command, the last address
|
|
examined is available for use in expressions in the convenience variable
|
|
@code{$_}. The contents of that address, as examined, are available in
|
|
the convenience variable @code{$__}.
|
|
|
|
If the @code{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.
|
|
|
|
@node Auto Display
|
|
@section Automatic display
|
|
@cindex automatic display
|
|
@cindex display of expressions
|
|
|
|
If you find that you want to print the value of an expression frequently
|
|
(to see how it changes), you might want to add it to the @dfn{automatic
|
|
display list} so that @value{GDBN} will print its value each time your program stops.
|
|
Each expression added to the list is given a number to identify it;
|
|
to remove an expression from the list, you specify that number.
|
|
The automatic display looks like this:
|
|
|
|
@example
|
|
2: foo = 38
|
|
3: bar[5] = (struct hack *) 0x3804
|
|
@end example
|
|
|
|
@noindent
|
|
This display shows item numbers, expressions and their current values. As with
|
|
displays you request manually using @code{x} or @code{print}, you can
|
|
specify the output format you prefer; in fact, @code{display} decides
|
|
whether to use @code{print} or @code{x} depending on how elaborate your
|
|
format specification is---it uses @code{x} if you specify a unit size,
|
|
or one of the two formats (@samp{i} and @samp{s}) that are only
|
|
supported by @code{x}; otherwise it uses @code{print}.
|
|
|
|
@table @code
|
|
@item display @var{exp}
|
|
@kindex display
|
|
Add the expression @var{exp} to the list of expressions to display
|
|
each time your program stops. @xref{Expressions, ,Expressions}.
|
|
|
|
@code{display} will not repeat if you press @key{RET} again after using it.
|
|
|
|
@item display/@var{fmt} @var{exp}
|
|
For @var{fmt} specifying only a display format and not a size or
|
|
count, add the expression @var{exp} to the auto-display list but
|
|
arranges to display it each time in the specified format @var{fmt}.
|
|
@xref{Output Formats,,Output formats}.
|
|
|
|
@item display/@var{fmt} @var{addr}
|
|
For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
|
|
number of units, add the expression @var{addr} as a memory address to
|
|
be examined each time your program stops. Examining means in effect
|
|
doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
|
|
@end table
|
|
|
|
For example, @samp{display/i $pc} can be helpful, to see the machine
|
|
instruction about to be executed each time execution stops (@samp{$pc}
|
|
is a common name for the program counter; @pxref{Registers}).
|
|
|
|
@table @code
|
|
@item undisplay @var{dnums}@dots{}
|
|
@itemx delete display @var{dnums}@dots{}
|
|
@kindex delete display
|
|
@kindex undisplay
|
|
Remove item numbers @var{dnums} from the list of expressions to display.
|
|
|
|
@code{undisplay} will not repeat if you press @key{RET} after using it.
|
|
(Otherwise you would just get the error @samp{No display number @dots{}}.)
|
|
|
|
@item disable display @var{dnums}@dots{}
|
|
@kindex disable display
|
|
Disable the display of item numbers @var{dnums}. A disabled display
|
|
item is not printed automatically, but is not forgotten. It may be
|
|
enabled again later.
|
|
|
|
@item enable display @var{dnums}@dots{}
|
|
@kindex enable display
|
|
Enable display of item numbers @var{dnums}. It becomes effective once
|
|
again in auto display of its expression, until you specify otherwise.
|
|
|
|
@item display
|
|
Display the current values of the expressions on the list, just as is
|
|
done when your program stops.
|
|
|
|
@item info display
|
|
@kindex info display
|
|
Print the list of expressions previously set up to display
|
|
automatically, each one with its item number, but without showing the
|
|
values. This includes disabled expressions, which are marked as such.
|
|
It also includes expressions which would not be displayed right now
|
|
because they refer to automatic variables not currently available.
|
|
@end table
|
|
|
|
If a display expression refers to local variables, then it does not make
|
|
sense outside the lexical context for which it was set up. Such an
|
|
expression is disabled when execution enters a context where one of its
|
|
variables is not defined. For example, if you give the command
|
|
@code{display last_char} while inside a function with an argument
|
|
@code{last_char}, then this argument will be displayed while your program
|
|
continues to stop inside that function. When it stops elsewhere---where
|
|
there is no variable @code{last_char}---display is disabled. The next time
|
|
your program stops where @code{last_char} is meaningful, you can enable the
|
|
display expression once again.
|
|
|
|
@node Print Settings
|
|
@section Print settings
|
|
|
|
@cindex format options
|
|
@cindex print settings
|
|
@value{GDBN} provides the following ways to control how arrays, structures,
|
|
and symbols are printed.
|
|
|
|
@noindent
|
|
These settings are useful for debugging programs in any language:
|
|
|
|
@table @code
|
|
@item set print address
|
|
@item set print address on
|
|
@kindex set print address
|
|
@value{GDBN} will print memory addresses showing the location of stack
|
|
traces, structure values, pointer values, breakpoints, and so forth,
|
|
even when it also displays the contents of those addresses. The default
|
|
is on. For example, this is what a stack frame display looks like, with
|
|
@code{set print address on}:
|
|
|
|
@smallexample
|
|
@group
|
|
(@value{GDBP}) f
|
|
#0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
|
|
at input.c:530
|
|
530 if (lquote != def_lquote)
|
|
@end group
|
|
@end smallexample
|
|
|
|
@item set print address off
|
|
Do not print addresses when displaying their contents. For example,
|
|
this is the same stack frame displayed with @code{set print address off}:
|
|
|
|
@example
|
|
@group
|
|
(@value{GDBP}) set print addr off
|
|
(@value{GDBP}) f
|
|
#0 set_quotes (lq="<<", rq=">>") at input.c:530
|
|
530 if (lquote != def_lquote)
|
|
@end group
|
|
@end example
|
|
|
|
You can use @samp{set print address off} to eliminate all machine
|
|
dependent displays from the @value{GDBN} interface. For example, with
|
|
@code{print address off}, you should get the same text for backtraces on
|
|
all machines---whether or not they involve pointer arguments.
|
|
|
|
@item show print address
|
|
@kindex show print address
|
|
Show whether or not addresses are to be printed.
|
|
|
|
@item set print array
|
|
@itemx set print array on
|
|
@kindex set print array
|
|
@value{GDBN} will pretty-print arrays. This format is more convenient to read,
|
|
but uses more space. The default is off.
|
|
|
|
@item set print array off
|
|
Return to compressed format for arrays.
|
|
|
|
@item show print array
|
|
@kindex show print array
|
|
Show whether compressed or pretty format is selected for displaying
|
|
arrays.
|
|
|
|
@item set print elements @var{number-of-elements}
|
|
@kindex set print elements
|
|
If @value{GDBN} is printing a large array, it will stop printing after it has
|
|
printed the number of elements set by the @code{set print elements} command.
|
|
This limit also applies to the display of strings.
|
|
|
|
@item show print elements
|
|
@kindex show print elements
|
|
Display the number of elements of a large array that @value{GDBN} will print
|
|
before losing patience.
|
|
|
|
@item set print pretty on
|
|
@kindex set print pretty
|
|
Cause @value{GDBN} to print structures in an indented format with one member per
|
|
line, like this:
|
|
|
|
@example
|
|
@group
|
|
$1 = @{
|
|
next = 0x0,
|
|
flags = @{
|
|
sweet = 1,
|
|
sour = 1
|
|
@},
|
|
meat = 0x54 "Pork"
|
|
@}
|
|
@end group
|
|
@end example
|
|
|
|
@item set print pretty off
|
|
Cause @value{GDBN} to print structures in a compact format, like this:
|
|
|
|
@smallexample
|
|
@group
|
|
$1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
|
|
meat = 0x54 "Pork"@}
|
|
@end group
|
|
@end smallexample
|
|
|
|
@noindent
|
|
This is the default format.
|
|
|
|
@item show print pretty
|
|
@kindex show print pretty
|
|
Show which format @value{GDBN} will use to print structures.
|
|
|
|
@item set print sevenbit-strings on
|
|
@kindex set print sevenbit-strings
|
|
Print using only seven-bit characters; if this option is set,
|
|
@value{GDBN} will display any eight-bit characters (in strings or character
|
|
values) using the notation @code{\}@var{nnn}. For example, @kbd{M-a} is
|
|
displayed as @code{\341}.
|
|
|
|
@item set print sevenbit-strings off
|
|
Print using either seven-bit or eight-bit characters, as required. This
|
|
is the default.
|
|
|
|
@item show print sevenbit-strings
|
|
@kindex show print sevenbit-strings
|
|
Show whether or not @value{GDBN} will print only seven-bit characters.
|
|
|
|
@item set print union on
|
|
@kindex set print union
|
|
Tell @value{GDBN} to print unions which are contained in structures. This is the
|
|
default setting.
|
|
|
|
@item set print union off
|
|
Tell @value{GDBN} not to print unions which are contained in structures.
|
|
|
|
@item show print union
|
|
@kindex show print union
|
|
Ask @value{GDBN} whether or not it will print unions which are contained in
|
|
structures.
|
|
|
|
For example, given the declarations
|
|
|
|
@smallexample
|
|
typedef enum @{Tree, Bug@} Species;
|
|
typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
|
|
typedef enum @{Caterpillar, Cocoon, Butterfly@}
|
|
Bug_forms;
|
|
|
|
struct thing @{
|
|
Species it;
|
|
union @{
|
|
Tree_forms tree;
|
|
Bug_forms bug;
|
|
@} form;
|
|
@};
|
|
|
|
struct thing foo = @{Tree, @{Acorn@}@};
|
|
@end smallexample
|
|
|
|
@noindent
|
|
with @code{set print union on} in effect @samp{p foo} would print
|
|
|
|
@smallexample
|
|
$1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
|
|
@end smallexample
|
|
|
|
@noindent
|
|
and with @code{set print union off} in effect it would print
|
|
|
|
@smallexample
|
|
$1 = @{it = Tree, form = @{...@}@}
|
|
@end smallexample
|
|
|
|
@item set print max-symbolic-offset @var{maxoff}
|
|
@kindex set print max-symbolic-offset
|
|
Tell @value{GDBN} to only display the symbolic form of an address if the
|
|
offset between the closest earlier symbol and the address is less than
|
|
@var{maxoff}. The default is 0, which means to always print the
|
|
symbolic form of an address, if any symbol precedes it.
|
|
|
|
@item show print max-symbolic-offset
|
|
@kindex show print max-symbolic-offset
|
|
Ask how large the maximum offset is that @value{GDBN} will print in a
|
|
symbolic address.
|
|
|
|
@item set print symbol-filename on
|
|
@kindex set print symbol-filename
|
|
Tell @value{GDBN} to print the source filename and linenumber of a symbol
|
|
in the symbolic form of an address.
|
|
|
|
@item set print symbol-filename off
|
|
Do not print source filename and linenumber of a symbol. This is the default.
|
|
|
|
@item show print symbol-filename
|
|
@kindex show print symbol-filename
|
|
Show whether or not @value{GDBN} will print the source filename and linenumber
|
|
of a symbol in the symbolic form of an address.
|
|
|
|
@end table
|
|
|
|
@ifclear CONLY
|
|
@noindent
|
|
These settings are of interest when debugging C++ programs:
|
|
|
|
@table @code
|
|
@item set print demangle
|
|
@itemx set print demangle on
|
|
@kindex set print demangle
|
|
Print C++ names in their source form rather than in the encoded
|
|
(``mangled'') form passed to the assembler and linker for type-safe
|
|
linkage. The default is @samp{on}.
|
|
|
|
@item show print demangle
|
|
@kindex show print demangle
|
|
Show whether C++ names will be printed in mangled or demangled form.
|
|
|
|
@item set print asm-demangle
|
|
@itemx set print asm-demangle on
|
|
@kindex set print asm-demangle
|
|
Print C++ names in their source form rather than their mangled form, even
|
|
in assembler code printouts such as instruction disassemblies.
|
|
The default is off.
|
|
|
|
@item show print asm-demangle
|
|
@kindex show print asm-demangle
|
|
Show whether C++ names in assembly listings will be printed in mangled
|
|
or demangled form.
|
|
|
|
@item set demangle-style @var{style}
|
|
@kindex set demangle-style
|
|
@cindex C++ symbol decoding style
|
|
@cindex symbol decoding style, C++
|
|
Choose among several encoding schemes used by different compilers to
|
|
represent C++ names. The choices for @var{style} are currently:
|
|
|
|
@table @code
|
|
@item auto
|
|
Allow @value{GDBN} to choose a decoding style by inspecting your program.
|
|
|
|
@item gnu
|
|
Decode based on the GNU C++ compiler (@code{g++}) encoding algorithm.
|
|
|
|
@item lucid
|
|
Decode based on the Lucid C++ compiler (@code{lcc}) encoding algorithm.
|
|
|
|
@item arm
|
|
Decode using the algorithm in the @cite{C++ Annotated Reference Manual}.
|
|
@strong{Warning:} this setting alone is not sufficient to allow
|
|
debugging @code{cfront}-generated executables. @value{GDBN} would
|
|
require further enhancement to permit that.
|
|
@end table
|
|
|
|
@item show demangle-style
|
|
@kindex show demangle-style
|
|
Display the encoding style currently in use for decoding C++ symbols.
|
|
|
|
@item set print object
|
|
@itemx set print object on
|
|
@kindex set print object
|
|
When displaying a pointer to an object, identify the @emph{actual}
|
|
(derived) type of the object rather than the @emph{declared} type, using
|
|
the virtual function table.
|
|
|
|
@item set print object off
|
|
Display only the declared type of objects, without reference to the
|
|
virtual function table. This is the default setting.
|
|
|
|
@item show print object
|
|
@kindex show print object
|
|
Show whether actual, or declared, object types will be displayed.
|
|
|
|
@item set print vtbl
|
|
@itemx set print vtbl on
|
|
@kindex set print vtbl
|
|
Pretty print C++ virtual function tables. The default is off.
|
|
|
|
@item set print vtbl off
|
|
Do not pretty print C++ virtual function tables.
|
|
|
|
@item show print vtbl
|
|
@kindex show print vtbl
|
|
Show whether C++ virtual function tables are pretty printed, or not.
|
|
@end table
|
|
@end ifclear
|
|
|
|
@node Value History
|
|
@section Value history
|
|
|
|
@cindex value history
|
|
Values printed by the @code{print} command are saved in the @value{GDBN} @dfn{value
|
|
history} so that you can refer to them in other expressions. Values are
|
|
kept until the symbol table is re-read or discarded (for example with
|
|
the @code{file} or @code{symbol-file} commands). When the symbol table
|
|
changes, the value history is discarded, since the values may contain
|
|
pointers back to the types defined in the symbol table.
|
|
|
|
@cindex @code{$}
|
|
@cindex @code{$$}
|
|
@cindex history number
|
|
The values printed are given @dfn{history numbers} for you to refer to them
|
|
by. These are successive integers starting with one. @code{print} shows you
|
|
the history number assigned to a value by printing @samp{$@var{num} = }
|
|
before the value; here @var{num} is the history number.
|
|
|
|
To refer to any previous value, use @samp{$} followed by the value's
|
|
history number. The way @code{print} labels its output is designed to
|
|
remind you of this. Just @code{$} refers to the most recent value in
|
|
the history, and @code{$$} refers to the value before that.
|
|
@code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
|
|
is the value just prior to @code{$$}, @code{$$1} is equivalent to
|
|
@code{$$}, and @code{$$0} is equivalent to @code{$}.
|
|
|
|
For example, suppose you have just printed a pointer to a structure and
|
|
want to see the contents of the structure. It suffices to type
|
|
|
|
@example
|
|
p *$
|
|
@end example
|
|
|
|
If you have a chain of structures where the component @code{next} points
|
|
to the next one, you can print the contents of the next one with this:
|
|
|
|
@example
|
|
p *$.next
|
|
@end example
|
|
|
|
@noindent
|
|
You can print successive links in the chain by repeating this
|
|
command---which you can do by just typing @key{RET}.
|
|
|
|
Note that the history records values, not expressions. If the value of
|
|
@code{x} is 4 and you type these commands:
|
|
|
|
@example
|
|
print x
|
|
set x=5
|
|
@end example
|
|
|
|
@noindent
|
|
then the value recorded in the value history by the @code{print} command
|
|
remains 4 even though the value of @code{x} has changed.
|
|
|
|
@table @code
|
|
@kindex show values
|
|
@item show values
|
|
Print the last ten values in the value history, with their item numbers.
|
|
This is like @samp{p@ $$9} repeated ten times, except that @code{show
|
|
values} does not change the history.
|
|
|
|
@item show values @var{n}
|
|
Print ten history values centered on history item number @var{n}.
|
|
|
|
@item show values +
|
|
Print ten history values just after the values last printed. If no more
|
|
values are available, produces no display.
|
|
@end table
|
|
|
|
Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
|
|
same effect as @samp{show values +}.
|
|
|
|
@node Convenience Vars
|
|
@section Convenience variables
|
|
|
|
@cindex convenience variables
|
|
@value{GDBN} provides @dfn{convenience variables} that you can use within
|
|
@value{GDBN} to hold on to a value and refer to it later. These variables
|
|
exist entirely within @value{GDBN}; they are not part of your program, and
|
|
setting a convenience variable has no direct effect on further execution
|
|
of your program. That is why you can use them freely.
|
|
|
|
Convenience variables are prefixed with @samp{$}. Any name preceded by
|
|
@samp{$} can be used for a convenience variable, unless it is one of
|
|
the predefined machine-specific register names (@pxref{Registers}).
|
|
(Value history references, in contrast, are @emph{numbers} preceded
|
|
by @samp{$}. @xref{Value History, ,Value history}.)
|
|
|
|
You can save a value in a convenience variable with an assignment
|
|
expression, just as you would set a variable in your program.
|
|
For example:
|
|
|
|
@example
|
|
set $foo = *object_ptr
|
|
@end example
|
|
|
|
@noindent
|
|
would save in @code{$foo} the value contained in the object pointed to by
|
|
@code{object_ptr}.
|
|
|
|
Using a convenience variable for the first time creates it; but its value
|
|
is @code{void} until you assign a new value. You can alter the value with
|
|
another assignment at any time.
|
|
|
|
Convenience variables have no fixed types. You can assign a convenience
|
|
variable any type of value, including structures and arrays, even if
|
|
that variable already has a value of a different type. The convenience
|
|
variable, when used as an expression, has the type of its current value.
|
|
|
|
@table @code
|
|
@item show convenience
|
|
@kindex show convenience
|
|
Print a list of convenience variables used so far, and their values.
|
|
Abbreviated @code{show con}.
|
|
@end table
|
|
|
|
One of the ways to use a convenience variable is as a counter to be
|
|
incremented or a pointer to be advanced. For example, to print
|
|
a field from successive elements of an array of structures:
|
|
|
|
@example
|
|
set $i = 0
|
|
print bar[$i++]->contents
|
|
@i{@dots{} repeat that command by typing @key{RET}.}
|
|
@end example
|
|
|
|
Some convenience variables are created automatically by @value{GDBN} and given
|
|
values likely to be useful.
|
|
|
|
@table @code
|
|
@item $_
|
|
@kindex $_
|
|
The variable @code{$_} is automatically set by the @code{x} command to
|
|
the last address examined (@pxref{Memory, ,Examining memory}). Other
|
|
commands which provide a default address for @code{x} to examine also
|
|
set @code{$_} to that address; these commands include @code{info line}
|
|
and @code{info breakpoint}. The type of @code{$_} is @code{void *}
|
|
except when set by the @code{x} command, in which case it is a pointer
|
|
to the type of @code{$__}.
|
|
|
|
@item $__
|
|
@kindex $__
|
|
The variable @code{$__} is automatically set by the @code{x} command
|
|
to the value found in the last address examined. Its type is chosen
|
|
to match the format in which the data was printed.
|
|
@end table
|
|
|
|
@node Registers
|
|
@section Registers
|
|
|
|
@cindex registers
|
|
You can refer to machine register contents, in expressions, as variables
|
|
with names starting with @samp{$}. The names of registers are different
|
|
for each machine; use @code{info registers} to see the names used on
|
|
your machine.
|
|
|
|
@table @code
|
|
@item info registers
|
|
@kindex info registers
|
|
Print the names and values of all registers except floating-point
|
|
registers (in the selected stack frame).
|
|
|
|
@item info all-registers
|
|
@kindex info all-registers
|
|
@cindex floating point registers
|
|
Print the names and values of all registers, including floating-point
|
|
registers.
|
|
|
|
@item info registers @var{regname} @dots{}
|
|
Print the relativized value of each specified register @var{regname}.
|
|
@var{regname} may be any register name valid on the machine you are using, with
|
|
or without the initial @samp{$}.
|
|
@end table
|
|
|
|
@value{GDBN} has four ``standard'' register names that are available (in
|
|
expressions) on most machines---whenever they do not conflict with an
|
|
architecture's canonical mnemonics for registers. The register names
|
|
@code{$pc} and @code{$sp} are used for the program counter register and
|
|
the stack pointer. @code{$fp} is used for a register that contains a
|
|
pointer to the current stack frame, and @code{$ps} is used for a
|
|
register that contains the processor status. For example,
|
|
you could print the program counter in hex with
|
|
|
|
@example
|
|
p/x $pc
|
|
@end example
|
|
|
|
@noindent
|
|
or print the instruction to be executed next with
|
|
|
|
@example
|
|
x/i $pc
|
|
@end example
|
|
|
|
@noindent
|
|
or add four to the stack pointer@footnote{This is a way of removing
|
|
one word from the stack, on machines where stacks grow downward in
|
|
memory (most machines, nowadays). This assumes that the innermost
|
|
stack frame is selected; setting @code{$sp} is not allowed when other
|
|
stack frames are selected. To pop entire frames off the stack,
|
|
regardless of machine architecture, use @code{return};
|
|
@pxref{Returning, ,Returning from a function}.} with
|
|
|
|
@example
|
|
set $sp += 4
|
|
@end example
|
|
|
|
Whenever possible, these four standard register names are available on
|
|
your machine even though the machine has different canonical mnemonics,
|
|
so long as there is no conflict. The @code{info registers} command
|
|
shows the canonical names. For example, on the SPARC, @code{info
|
|
registers} displays the processor status register as @code{$psr} but you
|
|
can also refer to it as @code{$ps}.
|
|
|
|
@value{GDBN} always considers the contents of an ordinary register as an
|
|
integer when the register is examined in this way. Some machines have
|
|
special registers which can hold nothing but floating point; these
|
|
registers are considered to have floating point values. There is no way
|
|
to refer to the contents of an ordinary register as floating point value
|
|
(although you can @emph{print} it as a floating point value with
|
|
@samp{print/f $@var{regname}}).
|
|
|
|
Some registers have distinct ``raw'' and ``virtual'' data formats. This
|
|
means that the data format in which the register contents are saved by
|
|
the operating system is not the same one that your program normally
|
|
sees. For example, the registers of the 68881 floating point
|
|
coprocessor are always saved in ``extended'' (raw) format, but all C
|
|
programs expect to work with ``double'' (virtual) format. In such
|
|
cases, @value{GDBN} normally works with the virtual format only (the format that
|
|
makes sense for your program), but the @code{info registers} command
|
|
prints the data in both formats.
|
|
|
|
Normally, register values are relative to the selected stack frame
|
|
(@pxref{Selection, ,Selecting a frame}). This means that you get the
|
|
value that the register would contain if all stack frames farther in
|
|
were exited and their saved registers restored. In order to see the
|
|
true contents of hardware registers, you must select the innermost
|
|
frame (with @samp{frame 0}).
|
|
|
|
However, @value{GDBN} must deduce where registers are saved, from the machine
|
|
code generated by your compiler. If some registers are not saved, or if
|
|
@value{GDBN} is unable to locate the saved registers, the selected stack
|
|
frame will make no difference.
|
|
|
|
@ifset AMD29K
|
|
@table @code
|
|
@item set rstack_high_address @var{address}
|
|
@kindex set rstack_high_address
|
|
@cindex AMD 29K register stack
|
|
@cindex register stack, AMD29K
|
|
On AMD 29000 family processors, registers are saved in a separate
|
|
``register stack''. There is no way for @value{GDBN} to determine the extent
|
|
of this stack. Normally, @value{GDBN} just assumes that the stack is ``large
|
|
enough''. This may result in @value{GDBN} referencing memory locations that
|
|
do not exist. If necessary, you can get around this problem by
|
|
specifying the ending address of the register stack with the @code{set
|
|
rstack_high_address} command. The argument should be an address, which
|
|
you will probably want to precede with @samp{0x} to specify in
|
|
hexadecimal.
|
|
|
|
@item show rstack_high_address
|
|
@kindex show rstack_high_address
|
|
Display the current limit of the register stack, on AMD 29000 family
|
|
processors.
|
|
@end table
|
|
@end ifset
|
|
|
|
@ifclear HAVE-FLOAT
|
|
@node Floating Point Hardware
|
|
@section Floating point hardware
|
|
@cindex floating point
|
|
|
|
@c FIXME! Really host, not target?
|
|
Depending on the host machine architecture, @value{GDBN} may be able to give
|
|
you more information about the status of the floating point hardware.
|
|
|
|
@table @code
|
|
@item info float
|
|
@kindex info float
|
|
Display hardware-dependent information about the floating
|
|
point unit. The exact contents and layout vary depending on the
|
|
floating point chip; on some platforms, @samp{info float} is not
|
|
available at all.
|
|
@end table
|
|
@c FIXME: this is a cop-out. Try to get examples, explanations. Only
|
|
@c FIXME...supported currently on arm's and 386's. Mark properly with
|
|
@c FIXME... m4 macros to isolate general statements from hardware-dep,
|
|
@c FIXME... at that point.
|
|
@end ifclear
|
|
|
|
@ifclear CONLY
|
|
@node Languages
|
|
@chapter Using @value{GDBN} with Different Languages
|
|
@cindex languages
|
|
|
|
Although programming languages generally have common aspects, they are
|
|
rarely expressed in the same manner. For instance, in ANSI C,
|
|
dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
|
|
Modula-2, it is accomplished by @code{p^}. Values can also be
|
|
represented (and displayed) differently. Hex numbers in C are written
|
|
like @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
|
|
|
|
@cindex working language
|
|
Language-specific information is built into @value{GDBN} for some languages,
|
|
allowing you to express operations like the above in your program's
|
|
native language, and allowing @value{GDBN} to output values in a manner
|
|
consistent with the syntax of your program's native language. The
|
|
language you use to build expressions, called the @dfn{working
|
|
language}, can be selected manually, or @value{GDBN} can set it
|
|
automatically.
|
|
|
|
@menu
|
|
* Setting:: Switching between source languages
|
|
* Show:: Displaying the language
|
|
* Checks:: Type and range checks
|
|
* Support:: Supported languages
|
|
@end menu
|
|
|
|
@node Setting
|
|
@section Switching between source languages
|
|
|
|
There are two ways to control the working language---either have @value{GDBN}
|
|
set it automatically, or select it manually yourself. You can use the
|
|
@code{set language} command for either purpose. On startup, @value{GDBN}
|
|
defaults to setting the language automatically.
|
|
|
|
@menu
|
|
* Manually:: Setting the working language manually
|
|
* Automatically:: Having @value{GDBN} infer the source language
|
|
@end menu
|
|
|
|
@node Manually
|
|
@subsection Setting the working language
|
|
|
|
If you allow @value{GDBN} to set the language automatically,
|
|
expressions are interpreted the same way in your debugging session and
|
|
your program.
|
|
|
|
@kindex set language
|
|
If you wish, you may set the language manually. To do this, issue the
|
|
command @samp{set language @var{lang}}, where @var{lang} is the name of
|
|
a language, such as @code{c} or @code{modula-2}. For a list of the supported
|
|
languages, type @samp{set language}.
|
|
@c FIXME: rms: eventually this command should be "help set language".
|
|
|
|
Setting the language manually prevents @value{GDBN} from updating the working
|
|
language automatically. This can lead to confusion if you try
|
|
to debug a program when the working language is not the same as the
|
|
source language, when an expression is acceptable to both
|
|
languages---but means different things. For instance, if the current
|
|
source file were written in C, and @value{GDBN} was parsing Modula-2, a
|
|
command such as:
|
|
|
|
@example
|
|
print a = b + c
|
|
@end example
|
|
|
|
@noindent
|
|
might not have the effect you intended. In C, this means to add
|
|
@code{b} and @code{c} and place the result in @code{a}. The result
|
|
printed would be the value of @code{a}. In Modula-2, this means to compare
|
|
@code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
|
|
|
|
@node Automatically
|
|
@subsection Having @value{GDBN} infer the source language
|
|
|
|
To have @value{GDBN} set the working language automatically, use @samp{set
|
|
language local} or @samp{set language auto}. @value{GDBN} then infers the
|
|
language that a program was written in by looking at the name of its
|
|
source files, and examining their extensions:
|
|
|
|
@table @file
|
|
@item *.mod
|
|
Modula-2 source file
|
|
|
|
@item *.c
|
|
C source file
|
|
|
|
@item *.C
|
|
@itemx *.cc
|
|
C++ source file
|
|
@end table
|
|
|
|
This information is recorded for each function or procedure in a source
|
|
file. When your program stops in a frame (usually by encountering a
|
|
breakpoint), @value{GDBN} sets the working language to the language recorded
|
|
for the function in that frame. If the language for a frame is unknown
|
|
(that is, if the function or block corresponding to the frame was
|
|
defined in a source file that does not have a recognized extension), the
|
|
current working language is not changed, and @value{GDBN} issues a warning.
|
|
|
|
This may not seem necessary for most programs, which are written
|
|
entirely in one source language. However, program modules and libraries
|
|
written in one source language can be used by a main program written in
|
|
a different source language. Using @samp{set language auto} in this
|
|
case frees you from having to set the working language manually.
|
|
|
|
@node Show
|
|
@section Displaying the language
|
|
|
|
The following commands will help you find out which language is the
|
|
working language, and also what language source files were written in.
|
|
|
|
@kindex show language
|
|
@kindex info frame
|
|
@kindex info source
|
|
@table @code
|
|
@item show language
|
|
Display the current working language. This is the
|
|
language you can use with commands such as @code{print} to
|
|
build and compute expressions that may involve variables in your program.
|
|
|
|
@item info frame
|
|
Among the other information listed here (@pxref{Frame Info, ,Information
|
|
about a frame}) is the source language for this frame. This is the
|
|
language that will become the working language if you ever use an
|
|
identifier that is in this frame.
|
|
|
|
@item info source
|
|
Among the other information listed here (@pxref{Symbols, ,Examining the
|
|
Symbol Table}) is the source language of this source file.
|
|
@end table
|
|
|
|
@node Checks
|
|
@section Type and range checking
|
|
|
|
@quotation
|
|
@emph{Warning:} In this release, the @value{GDBN} commands for type and range
|
|
checking are included, but they do not yet have any effect. This
|
|
section documents the intended facilities.
|
|
@end quotation
|
|
@c FIXME remove warning when type/range code added
|
|
|
|
Some languages are designed to guard you against making seemingly common
|
|
errors through a series of compile- and run-time checks. These include
|
|
checking the type of arguments to functions and operators, and making
|
|
sure mathematical overflows are caught at run time. Checks such as
|
|
these help to ensure a program's correctness once it has been compiled
|
|
by eliminating type mismatches, and providing active checks for range
|
|
errors when your program is running.
|
|
|
|
@value{GDBN} can check for conditions like the above if you wish.
|
|
Although @value{GDBN} will not check the statements in your program, it
|
|
can check expressions entered directly into @value{GDBN} for evaluation via
|
|
the @code{print} command, for example. As with the working language,
|
|
@value{GDBN} can also decide whether or not to check automatically based on
|
|
your program's source language. @xref{Support, ,Supported languages},
|
|
for the default settings of supported languages.
|
|
|
|
@menu
|
|
* Type Checking:: An overview of type checking
|
|
* Range Checking:: An overview of range checking
|
|
@end menu
|
|
|
|
@cindex type checking
|
|
@cindex checks, type
|
|
@node Type Checking
|
|
@subsection An overview of type checking
|
|
|
|
Some languages, such as Modula-2, are strongly typed, meaning that the
|
|
arguments to operators and functions have to be of the correct type,
|
|
otherwise an error occurs. These checks prevent type mismatch
|
|
errors from ever causing any run-time problems. For example,
|
|
|
|
@example
|
|
1 + 2 @result{} 3
|
|
@exdent but
|
|
@error{} 1 + 2.3
|
|
@end example
|
|
|
|
The second example fails because the @code{CARDINAL} 1 is not
|
|
type-compatible with the @code{REAL} 2.3.
|
|
|
|
For expressions you use in @value{GDBN} commands, you can tell the @value{GDBN}
|
|
type checker to skip checking; to treat any mismatches as errors and
|
|
abandon the expression; or only issue warnings when type mismatches
|
|
occur, but evaluate the expression anyway. When you choose the last of
|
|
these, @value{GDBN} evaluates expressions like the second example above, but
|
|
also issues a warning.
|
|
|
|
Even though you may turn type checking off, other type-based reasons may
|
|
prevent @value{GDBN} from evaluating an expression. For instance, @value{GDBN} does not
|
|
know how to add an @code{int} and a @code{struct foo}. These particular
|
|
type errors have nothing to do with the language in use, and usually
|
|
arise from expressions, such as the one described above, which make
|
|
little sense to evaluate anyway.
|
|
|
|
Each language defines to what degree it is strict about type. For
|
|
instance, both Modula-2 and C require the arguments to arithmetical
|
|
operators to be numbers. In C, enumerated types and pointers can be
|
|
represented as numbers, so that they are valid arguments to mathematical
|
|
operators. @xref{Support, ,Supported languages}, for further
|
|
details on specific languages.
|
|
|
|
@value{GDBN} provides some additional commands for controlling the type checker:
|
|
|
|
@kindex set check
|
|
@kindex set check type
|
|
@kindex show check type
|
|
@table @code
|
|
@item set check type auto
|
|
Set type checking on or off based on the current working language.
|
|
@xref{Support, ,Supported languages}, for the default settings for
|
|
each language.
|
|
|
|
@item set check type on
|
|
@itemx set check type off
|
|
Set type checking on or off, overriding the default setting for the
|
|
current working language. Issue a warning if the setting does not
|
|
match the language default. If any type mismatches occur in
|
|
evaluating an expression while typechecking is on, @value{GDBN} prints a
|
|
message and aborts evaluation of the expression.
|
|
|
|
@item set check type warn
|
|
Cause the type checker to issue warnings, but to always attempt to
|
|
evaluate the expression. Evaluating the expression may still
|
|
be impossible for other reasons. For example, @value{GDBN} cannot add
|
|
numbers and structures.
|
|
|
|
@item show type
|
|
Show the current setting of the type checker, and whether or not @value{GDBN} is
|
|
setting it automatically.
|
|
@end table
|
|
|
|
@cindex range checking
|
|
@cindex checks, range
|
|
@node Range Checking
|
|
@subsection An overview of range checking
|
|
|
|
In some languages (such as Modula-2), it is an error to exceed the
|
|
bounds of a type; this is enforced with run-time checks. Such range
|
|
checking is meant to ensure program correctness by making sure
|
|
computations do not overflow, or indices on an array element access do
|
|
not exceed the bounds of the array.
|
|
|
|
For expressions you use in @value{GDBN} commands, you can tell
|
|
@value{GDBN} to treat range errors in one of three ways: ignore them,
|
|
always treat them as errors and abandon the expression, or issue
|
|
warnings but evaluate the expression anyway.
|
|
|
|
A range error can result from numerical overflow, from exceeding an
|
|
array index bound, or when you type a constant that is not a member
|
|
of any type. Some languages, however, do not treat overflows as an
|
|
error. In many implementations of C, mathematical overflow causes the
|
|
result to ``wrap around'' to lower values---for example, if @var{m} is
|
|
the largest integer value, and @var{s} is the smallest, then
|
|
|
|
@example
|
|
@var{m} + 1 @result{} @var{s}
|
|
@end example
|
|
|
|
This, too, is specific to individual languages, and in some cases
|
|
specific to individual compilers or machines. @xref{Support, ,
|
|
Supported languages}, for further details on specific languages.
|
|
|
|
@value{GDBN} provides some additional commands for controlling the range checker:
|
|
|
|
@kindex set check
|
|
@kindex set check range
|
|
@kindex show check range
|
|
@table @code
|
|
@item set check range auto
|
|
Set range checking on or off based on the current working language.
|
|
@xref{Support, ,Supported languages}, for the default settings for
|
|
each language.
|
|
|
|
@item set check range on
|
|
@itemx set check range off
|
|
Set range checking on or off, overriding the default setting for the
|
|
current working language. A warning is issued if the setting does not
|
|
match the language default. If a range error occurs, then a message
|
|
is printed and evaluation of the expression is aborted.
|
|
|
|
@item set check range warn
|
|
Output messages when the @value{GDBN} range checker detects a range error,
|
|
but attempt to evaluate the expression anyway. Evaluating the
|
|
expression may still be impossible for other reasons, such as accessing
|
|
memory that the process does not own (a typical example from many UNIX
|
|
systems).
|
|
|
|
@item show range
|
|
Show the current setting of the range checker, and whether or not it is
|
|
being set automatically by @value{GDBN}.
|
|
@end table
|
|
|
|
@node Support
|
|
@section Supported languages
|
|
|
|
@value{GDBN} 4 supports C, C++, and Modula-2. Some @value{GDBN}
|
|
features may be used in expressions regardless of the language you
|
|
use: the @value{GDBN} @code{@@} and @code{::} operators, and the
|
|
@samp{@{type@}addr} construct (@pxref{Expressions, ,Expressions}) can be
|
|
used with the constructs of any of the supported languages.
|
|
|
|
The following sections detail to what degree each of these
|
|
source languages is supported by @value{GDBN}. These sections are
|
|
not meant to be language tutorials or references, but serve only as a
|
|
reference guide to what the @value{GDBN} expression parser will accept, and
|
|
what input and output formats should look like for different languages.
|
|
There are many good books written on each of these languages; please
|
|
look to these for a language reference or tutorial.
|
|
|
|
@menu
|
|
* C:: C and C++
|
|
* Modula-2:: Modula-2
|
|
@end menu
|
|
|
|
@node C
|
|
@subsection C and C++
|
|
@cindex C and C++
|
|
@cindex expressions in C or C++
|
|
|
|
Since C and C++ are so closely related, many features of @value{GDBN} apply
|
|
to both languages. Whenever this is the case, we discuss both languages
|
|
together.
|
|
|
|
@cindex C++
|
|
@kindex g++
|
|
@cindex GNU C++
|
|
The C++ debugging facilities are jointly implemented by the GNU C++
|
|
compiler and @value{GDBN}. Therefore, to debug your C++ code effectively,
|
|
you must compile your C++ programs with the GNU C++ compiler,
|
|
@code{g++}.
|
|
@end ifclear
|
|
@ifset CONLY
|
|
@node C
|
|
@chapter C Language Support
|
|
@cindex C language
|
|
@cindex expressions in C
|
|
|
|
Information specific to the C language is built into @value{GDBN} so that you
|
|
can use C expressions while degugging. This also permits @value{GDBN} to
|
|
output values in a manner consistent with C conventions.
|
|
|
|
@menu
|
|
* C Operators:: C operators
|
|
* C Constants:: C constants
|
|
* Debugging C:: @value{GDBN} and C
|
|
@end menu
|
|
@end ifset
|
|
@ifclear CONLY
|
|
@menu
|
|
* C Operators:: C and C++ operators
|
|
* C Constants:: C and C++ constants
|
|
* Cplus expressions:: C++ expressions
|
|
* C Defaults:: Default settings for C and C++
|
|
* C Checks:: C and C++ type and range checks
|
|
* Debugging C:: @value{GDBN} and C
|
|
* Debugging C plus plus:: Special features for C++
|
|
@end menu
|
|
@end ifclear
|
|
|
|
@ifclear CONLY
|
|
@cindex C and C++ operators
|
|
@node C Operators
|
|
@subsubsection C and C++ operators
|
|
@end ifclear
|
|
@ifset CONLY
|
|
@cindex C operators
|
|
@node C Operators
|
|
@section C operators
|
|
@end ifset
|
|
|
|
Operators must be defined on values of specific types. For instance,
|
|
@code{+} is defined on numbers, but not on structures. Operators are
|
|
often defined on groups of types.
|
|
|
|
@ifclear CONLY
|
|
For the purposes of C and C++, the following definitions hold:
|
|
@end ifclear
|
|
|
|
@itemize @bullet
|
|
@item
|
|
@emph{Integral types} include @code{int} with any of its storage-class
|
|
specifiers; @code{char}; and @code{enum}.
|
|
|
|
@item
|
|
@emph{Floating-point types} include @code{float} and @code{double}.
|
|
|
|
@item
|
|
@emph{Pointer types} include all types defined as @code{(@var{type}
|
|
*)}.
|
|
|
|
@item
|
|
@emph{Scalar types} include all of the above.
|
|
@end itemize
|
|
|
|
@noindent
|
|
The following operators are supported. They are listed here
|
|
in order of increasing precedence:
|
|
|
|
@table @code
|
|
@item ,
|
|
The comma or sequencing operator. Expressions in a comma-separated list
|
|
are evaluated from left to right, with the result of the entire
|
|
expression being the last expression evaluated.
|
|
|
|
@item =
|
|
Assignment. The value of an assignment expression is the value
|
|
assigned. Defined on scalar types.
|
|
|
|
@item @var{op}=
|
|
Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
|
|
and translated to @w{@code{@var{a} = @var{a op b}}}.
|
|
@w{@code{@var{op}=}} and @code{=} have the same precendence.
|
|
@var{op} is any one of the operators @code{|}, @code{^}, @code{&},
|
|
@code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
|
|
|
|
@item ?:
|
|
The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
|
|
of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
|
|
integral type.
|
|
|
|
@item ||
|
|
Logical @sc{or}. Defined on integral types.
|
|
|
|
@item &&
|
|
Logical @sc{and}. Defined on integral types.
|
|
|
|
@item |
|
|
Bitwise @sc{or}. Defined on integral types.
|
|
|
|
@item ^
|
|
Bitwise exclusive-@sc{or}. Defined on integral types.
|
|
|
|
@item &
|
|
Bitwise @sc{and}. Defined on integral types.
|
|
|
|
@item ==@r{, }!=
|
|
Equality and inequality. Defined on scalar types. The value of these
|
|
expressions is 0 for false and non-zero for true.
|
|
|
|
@item <@r{, }>@r{, }<=@r{, }>=
|
|
Less than, greater than, less than or equal, greater than or equal.
|
|
Defined on scalar types. The value of these expressions is 0 for false
|
|
and non-zero for true.
|
|
|
|
@item <<@r{, }>>
|
|
left shift, and right shift. Defined on integral types.
|
|
|
|
@item @@
|
|
The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
|
|
|
|
@item +@r{, }-
|
|
Addition and subtraction. Defined on integral types, floating-point types and
|
|
pointer types.
|
|
|
|
@item *@r{, }/@r{, }%
|
|
Multiplication, division, and modulus. Multiplication and division are
|
|
defined on integral and floating-point types. Modulus is defined on
|
|
integral types.
|
|
|
|
@item ++@r{, }--
|
|
Increment and decrement. When appearing before a variable, the
|
|
operation is performed before the variable is used in an expression;
|
|
when appearing after it, the variable's value is used before the
|
|
operation takes place.
|
|
|
|
@item *
|
|
Pointer dereferencing. Defined on pointer types. Same precedence as
|
|
@code{++}.
|
|
|
|
@item &
|
|
Address operator. Defined on variables. Same precedence as @code{++}.
|
|
|
|
@ifclear CONLY
|
|
For debugging C++, @value{GDBN} implements a use of @samp{&} beyond what is
|
|
allowed in the C++ language itself: you can use @samp{&(&@var{ref})}
|
|
(or, if you prefer, simply @samp{&&@var{ref}} to examine the address
|
|
where a C++ reference variable (declared with @samp{&@var{ref}}) is
|
|
stored.
|
|
@end ifclear
|
|
|
|
@item -
|
|
Negative. Defined on integral and floating-point types. Same
|
|
precedence as @code{++}.
|
|
|
|
@item !
|
|
Logical negation. Defined on integral types. Same precedence as
|
|
@code{++}.
|
|
|
|
@item ~
|
|
Bitwise complement operator. Defined on integral types. Same precedence as
|
|
@code{++}.
|
|
|
|
|
|
@item .@r{, }->
|
|
Structure member, and pointer-to-structure member. For convenience,
|
|
@value{GDBN} regards the two as equivalent, choosing whether to dereference a
|
|
pointer based on the stored type information.
|
|
Defined on @code{struct} and @code{union} data.
|
|
|
|
@item []
|
|
Array indexing. @code{@var{a}[@var{i}]} is defined as
|
|
@code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
|
|
|
|
@item ()
|
|
Function parameter list. Same precedence as @code{->}.
|
|
|
|
@ifclear CONLY
|
|
@item ::
|
|
C++ scope resolution operator. Defined on
|
|
@code{struct}, @code{union}, and @code{class} types.
|
|
@end ifclear
|
|
|
|
@item ::
|
|
Doubled colons
|
|
@ifclear CONLY
|
|
also
|
|
@end ifclear
|
|
represent the @value{GDBN} scope operator (@pxref{Expressions,
|
|
,Expressions}).
|
|
@ifclear CONLY
|
|
Same precedence as @code{::}, above.
|
|
@end ifclear
|
|
@end table
|
|
|
|
@ifclear CONLY
|
|
@cindex C and C++ constants
|
|
@node C Constants
|
|
@subsubsection C and C++ constants
|
|
|
|
@value{GDBN} allows you to express the constants of C and C++ in the
|
|
following ways:
|
|
@end ifclear
|
|
@ifset CONLY
|
|
@cindex C constants
|
|
@node C Constants
|
|
@section C constants
|
|
|
|
@value{GDBN} allows you to express the constants of C in the
|
|
following ways:
|
|
@end ifset
|
|
|
|
@itemize @bullet
|
|
@item
|
|
Integer constants are a sequence of digits. Octal constants are
|
|
specified by a leading @samp{0} (ie. zero), and hexadecimal constants by
|
|
a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
|
|
@samp{l}, specifying that the constant should be treated as a
|
|
@code{long} value.
|
|
|
|
@item
|
|
Floating point constants are a sequence of digits, followed by a decimal
|
|
point, followed by a sequence of digits, and optionally followed by an
|
|
exponent. An exponent is of the form:
|
|
@samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
|
|
sequence of digits. The @samp{+} is optional for positive exponents.
|
|
|
|
@item
|
|
Enumerated constants consist of enumerated identifiers, or their
|
|
integral equivalents.
|
|
|
|
@item
|
|
Character constants are a single character surrounded by single quotes
|
|
(@code{'}), or a number---the ordinal value of the corresponding character
|
|
(usually its @sc{ASCII} value). Within quotes, the single character may
|
|
be represented by a letter or by @dfn{escape sequences}, which are of
|
|
the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
|
|
of the character's ordinal value; or of the form @samp{\@var{x}}, where
|
|
@samp{@var{x}} is a predefined special character---for example,
|
|
@samp{\n} for newline.
|
|
|
|
@item
|
|
String constants are a sequence of character constants surrounded
|
|
by double quotes (@code{"}).
|
|
|
|
@item
|
|
Pointer constants are an integral value. You can also write pointers
|
|
to constants using the C operator @samp{&}.
|
|
|
|
@item
|
|
Array constants are comma-separated lists surrounded by braces @samp{@{}
|
|
and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
|
|
integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
|
|
and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
|
|
@end itemize
|
|
|
|
@ifclear CONLY
|
|
@node Cplus expressions
|
|
@subsubsection C++ expressions
|
|
|
|
@cindex expressions in C++
|
|
@value{GDBN} expression handling has a number of extensions to
|
|
interpret a significant subset of C++ expressions.
|
|
|
|
@cindex C++ support, not in @sc{coff}
|
|
@cindex @sc{coff} versus C++
|
|
@cindex C++ and object formats
|
|
@cindex object formats and C++
|
|
@cindex a.out and C++
|
|
@cindex @sc{ecoff} and C++
|
|
@cindex @sc{xcoff} and C++
|
|
@cindex @sc{elf}/stabs and C++
|
|
@cindex @sc{elf}/@sc{dwarf} and C++
|
|
@quotation
|
|
@emph{Warning:} Most of these extensions depend on the use of additional
|
|
debugging information in the symbol table, and thus require a rich,
|
|
extendable object code format. In particular, if your system uses
|
|
a.out, MIPS @sc{ecoff}, RS/6000 @sc{xcoff}, or Sun @sc{elf} with stabs
|
|
extensions to the symbol table, these facilities are all available.
|
|
Where the object code format is standard @sc{coff}, on the other hand,
|
|
most of the C++ support in @value{GDBN} will @emph{not} work, nor can it.
|
|
For the standard SVr4 debugging format, @sc{dwarf} in @sc{elf}, the
|
|
standard is still evolving, so the C++ support in @value{GDBN} is still
|
|
fragile; when this debugging format stabilizes, however, C++ support
|
|
will also be available on systems that use it.
|
|
@end quotation
|
|
|
|
@enumerate
|
|
|
|
@cindex member functions
|
|
@item
|
|
Member function calls are allowed; you can use expressions like
|
|
|
|
@example
|
|
count = aml->GetOriginal(x, y)
|
|
@end example
|
|
|
|
@kindex this
|
|
@cindex namespace in C++
|
|
@item
|
|
While a member function is active (in the selected stack frame), your
|
|
expressions have the same namespace available as the member function;
|
|
that is, @value{GDBN} allows implicit references to the class instance
|
|
pointer @code{this} following the same rules as C++.
|
|
|
|
@cindex call overloaded functions
|
|
@cindex type conversions in C++
|
|
@item
|
|
You can call overloaded functions; @value{GDBN} will resolve the function
|
|
call to the right definition, with one restriction---you must use
|
|
arguments of the type required by the function that you want to call.
|
|
@value{GDBN} will not perform conversions requiring constructors or
|
|
user-defined type operators.
|
|
|
|
@cindex reference declarations
|
|
@item
|
|
@value{GDBN} understands variables declared as C++ references; you can use them in
|
|
expressions just as you do in C++ source---they are automatically
|
|
dereferenced.
|
|
|
|
In the parameter list shown when @value{GDBN} displays a frame, the values of
|
|
reference variables are not displayed (unlike other variables); this
|
|
avoids clutter, since references are often used for large structures.
|
|
The @emph{address} of a reference variable is always shown, unless
|
|
you have specified @samp{set print address off}.
|
|
|
|
@item
|
|
@value{GDBN} supports the C++ name resolution operator @code{::}---your
|
|
expressions can use it just as expressions in your program do. Since
|
|
one scope may be defined in another, you can use @code{::} repeatedly if
|
|
necessary, for example in an expression like
|
|
@samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
|
|
resolving name scope by reference to source files, in both C and C++
|
|
debugging (@pxref{Variables, ,Program variables}).
|
|
@end enumerate
|
|
|
|
@node C Defaults
|
|
@subsubsection C and C++ defaults
|
|
@cindex C and C++ defaults
|
|
|
|
If you allow @value{GDBN} to set type and range checking automatically, they
|
|
both default to @code{off} whenever the working language changes to
|
|
C or C++. This happens regardless of whether you, or @value{GDBN},
|
|
selected the working language.
|
|
|
|
If you allow @value{GDBN} to set the language automatically, it sets the
|
|
working language to C or C++ on entering code compiled from a source file
|
|
whose name ends with @file{.c}, @file{.C}, or @file{.cc}.
|
|
@xref{Automatically, ,Having @value{GDBN} infer the source language}, for
|
|
further details.
|
|
|
|
@node C Checks
|
|
@subsubsection C and C++ type and range checks
|
|
@cindex C and C++ checks
|
|
|
|
By default, when @value{GDBN} parses C or C++ expressions, type checking
|
|
is not used. However, if you turn type checking on, @value{GDBN} will
|
|
consider two variables type equivalent if:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
The two variables are structured and have the same structure, union, or
|
|
enumerated tag.
|
|
|
|
@item
|
|
Two two variables have the same type name, or types that have been
|
|
declared equivalent through @code{typedef}.
|
|
|
|
@ignore
|
|
@c leaving this out because neither J Gilmore nor R Pesch understand it.
|
|
@c FIXME--beers?
|
|
@item
|
|
The two @code{struct}, @code{union}, or @code{enum} variables are
|
|
declared in the same declaration. (Note: this may not be true for all C
|
|
compilers.)
|
|
@end ignore
|
|
@end itemize
|
|
|
|
Range checking, if turned on, is done on mathematical operations. Array
|
|
indices are not checked, since they are often used to index a pointer
|
|
that is not itself an array.
|
|
@end ifclear
|
|
|
|
@ifclear CONLY
|
|
@node Debugging C
|
|
@subsubsection @value{GDBN} and C
|
|
@end ifclear
|
|
@ifset CONLY
|
|
@node Debugging C
|
|
@section @value{GDBN} and C
|
|
@end ifset
|
|
|
|
The @code{set print union} and @code{show print union} commands apply to
|
|
the @code{union} type. When set to @samp{on}, any @code{union} that is
|
|
inside a @code{struct}
|
|
@ifclear CONLY
|
|
or @code{class}
|
|
@end ifclear
|
|
will also be printed.
|
|
Otherwise, it will appear as @samp{@{...@}}.
|
|
|
|
The @code{@@} operator aids in the debugging of dynamic arrays, formed
|
|
with pointers and a memory allocation function. @xref{Expressions,
|
|
,Expressions}.
|
|
|
|
@ifclear CONLY
|
|
@node Debugging C plus plus
|
|
@subsubsection @value{GDBN} features for C++
|
|
|
|
@cindex commands for C++
|
|
Some @value{GDBN} commands are particularly useful with C++, and some are
|
|
designed specifically for use with C++. Here is a summary:
|
|
|
|
@table @code
|
|
@cindex break in overloaded functions
|
|
@item @r{breakpoint menus}
|
|
When you want a breakpoint in a function whose name is overloaded,
|
|
@value{GDBN} breakpoint menus help you specify which function definition
|
|
you want. @xref{Breakpoint Menus,,Breakpoint menus}.
|
|
|
|
@cindex overloading in C++
|
|
@item rbreak @var{regex}
|
|
Setting breakpoints using regular expressions is helpful for setting
|
|
breakpoints on overloaded functions that are not members of any special
|
|
classes.
|
|
@xref{Set Breaks, ,Setting breakpoints}.
|
|
|
|
@cindex C++ exception handling
|
|
@item catch @var{exceptions}
|
|
@itemx info catch
|
|
Debug C++ exception handling using these commands. @xref{Exception
|
|
Handling, ,Breakpoints and exceptions}.
|
|
|
|
@cindex inheritance
|
|
@item ptype @var{typename}
|
|
Print inheritance relationships as well as other information for type
|
|
@var{typename}.
|
|
@xref{Symbols, ,Examining the Symbol Table}.
|
|
|
|
@cindex C++ symbol display
|
|
@item set print demangle
|
|
@itemx show print demangle
|
|
@itemx set print asm-demangle
|
|
@itemx show print asm-demangle
|
|
Control whether C++ symbols display in their source form, both when
|
|
displaying code as C++ source and when displaying disassemblies.
|
|
@xref{Print Settings, ,Print settings}.
|
|
|
|
@item set print object
|
|
@itemx show print object
|
|
Choose whether to print derived (actual) or declared types of objects.
|
|
@xref{Print Settings, ,Print settings}.
|
|
|
|
@item set print vtbl
|
|
@itemx show print vtbl
|
|
Control the format for printing virtual function tables.
|
|
@xref{Print Settings, ,Print settings}.
|
|
|
|
@item @r{Overloaded symbol names}
|
|
You can specify a particular definition of an overloaded symbol, using
|
|
the same notation that is used to declare such symbols in C++: type
|
|
@code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
|
|
also use the @value{GDBN} command-line word completion facilities to list the
|
|
available choices, or to finish the type list for you.
|
|
@xref{Completion,, Command completion}, for details on how to do this.
|
|
@end table
|
|
|
|
@node Modula-2
|
|
@subsection Modula-2
|
|
@cindex Modula-2
|
|
|
|
The extensions made to @value{GDBN} to support Modula-2 only support
|
|
output from the GNU Modula-2 compiler (which is currently being
|
|
developed). Other Modula-2 compilers are not currently supported, and
|
|
attempting to debug executables produced by them will most likely
|
|
result in an error as @value{GDBN} reads in the executable's symbol
|
|
table.
|
|
|
|
@cindex expressions in Modula-2
|
|
@menu
|
|
* M2 Operators:: Built-in operators
|
|
* Built-In Func/Proc:: Built-in functions and procedures
|
|
* M2 Constants:: Modula-2 constants
|
|
* M2 Defaults:: Default settings for Modula-2
|
|
* Deviations:: Deviations from standard Modula-2
|
|
* M2 Checks:: Modula-2 type and range checks
|
|
* M2 Scope:: The scope operators @code{::} and @code{.}
|
|
* GDB/M2:: @value{GDBN} and Modula-2
|
|
@end menu
|
|
|
|
@node M2 Operators
|
|
@subsubsection Operators
|
|
@cindex Modula-2 operators
|
|
|
|
Operators must be defined on values of specific types. For instance,
|
|
@code{+} is defined on numbers, but not on structures. Operators are
|
|
often defined on groups of types. For the purposes of Modula-2, the
|
|
following definitions hold:
|
|
|
|
@itemize @bullet
|
|
|
|
@item
|
|
@emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
|
|
their subranges.
|
|
|
|
@item
|
|
@emph{Character types} consist of @code{CHAR} and its subranges.
|
|
|
|
@item
|
|
@emph{Floating-point types} consist of @code{REAL}.
|
|
|
|
@item
|
|
@emph{Pointer types} consist of anything declared as @code{POINTER TO
|
|
@var{type}}.
|
|
|
|
@item
|
|
@emph{Scalar types} consist of all of the above.
|
|
|
|
@item
|
|
@emph{Set types} consist of @code{SET} and @code{BITSET} types.
|
|
|
|
@item
|
|
@emph{Boolean types} consist of @code{BOOLEAN}.
|
|
@end itemize
|
|
|
|
@noindent
|
|
The following operators are supported, and appear in order of
|
|
increasing precedence:
|
|
|
|
@table @code
|
|
@item ,
|
|
Function argument or array index separator.
|
|
|
|
@item :=
|
|
Assignment. The value of @var{var} @code{:=} @var{value} is
|
|
@var{value}.
|
|
|
|
@item <@r{, }>
|
|
Less than, greater than on integral, floating-point, or enumerated
|
|
types.
|
|
|
|
@item <=@r{, }>=
|
|
Less than, greater than, less than or equal to, greater than or equal to
|
|
on integral, floating-point and enumerated types, or set inclusion on
|
|
set types. Same precedence as @code{<}.
|
|
|
|
@item =@r{, }<>@r{, }#
|
|
Equality and two ways of expressing inequality, valid on scalar types.
|
|
Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
|
|
available for inequality, since @code{#} conflicts with the script
|
|
comment character.
|
|
|
|
@item IN
|
|
Set membership. Defined on set types and the types of their members.
|
|
Same precedence as @code{<}.
|
|
|
|
@item OR
|
|
Boolean disjunction. Defined on boolean types.
|
|
|
|
@item AND@r{, }&
|
|
Boolean conjuction. Defined on boolean types.
|
|
|
|
@item @@
|
|
The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
|
|
|
|
@item +@r{, }-
|
|
Addition and subtraction on integral and floating-point types, or union
|
|
and difference on set types.
|
|
|
|
@item *
|
|
Multiplication on integral and floating-point types, or set intersection
|
|
on set types.
|
|
|
|
@item /
|
|
Division on floating-point types, or symmetric set difference on set
|
|
types. Same precedence as @code{*}.
|
|
|
|
@item DIV@r{, }MOD
|
|
Integer division and remainder. Defined on integral types. Same
|
|
precedence as @code{*}.
|
|
|
|
@item -
|
|
Negative. Defined on @code{INTEGER} and @code{REAL} data.
|
|
|
|
@item ^
|
|
Pointer dereferencing. Defined on pointer types.
|
|
|
|
@item NOT
|
|
Boolean negation. Defined on boolean types. Same precedence as
|
|
@code{^}.
|
|
|
|
@item .
|
|
@code{RECORD} field selector. Defined on @code{RECORD} data. Same
|
|
precedence as @code{^}.
|
|
|
|
@item []
|
|
Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
|
|
|
|
@item ()
|
|
Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
|
|
as @code{^}.
|
|
|
|
@item ::@r{, }.
|
|
@value{GDBN} and Modula-2 scope operators.
|
|
@end table
|
|
|
|
@quotation
|
|
@emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
|
|
will treat the use of the operator @code{IN}, or the use of operators
|
|
@code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
|
|
@code{<=}, and @code{>=} on sets as an error.
|
|
@end quotation
|
|
|
|
@cindex Modula-2 built-ins
|
|
@node Built-In Func/Proc
|
|
@subsubsection Built-in functions and procedures
|
|
|
|
Modula-2 also makes available several built-in procedures and functions.
|
|
In describing these, the following metavariables are used:
|
|
|
|
@table @var
|
|
|
|
@item a
|
|
represents an @code{ARRAY} variable.
|
|
|
|
@item c
|
|
represents a @code{CHAR} constant or variable.
|
|
|
|
@item i
|
|
represents a variable or constant of integral type.
|
|
|
|
@item m
|
|
represents an identifier that belongs to a set. Generally used in the
|
|
same function with the metavariable @var{s}. The type of @var{s} should
|
|
be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}.
|
|
|
|
@item n
|
|
represents a variable or constant of integral or floating-point type.
|
|
|
|
@item r
|
|
represents a variable or constant of floating-point type.
|
|
|
|
@item t
|
|
represents a type.
|
|
|
|
@item v
|
|
represents a variable.
|
|
|
|
@item x
|
|
represents a variable or constant of one of many types. See the
|
|
explanation of the function for details.
|
|
@end table
|
|
|
|
All Modula-2 built-in procedures also return a result, described below.
|
|
|
|
@table @code
|
|
@item ABS(@var{n})
|
|
Returns the absolute value of @var{n}.
|
|
|
|
@item CAP(@var{c})
|
|
If @var{c} is a lower case letter, it returns its upper case
|
|
equivalent, otherwise it returns its argument
|
|
|
|
@item CHR(@var{i})
|
|
Returns the character whose ordinal value is @var{i}.
|
|
|
|
@item DEC(@var{v})
|
|
Decrements the value in the variable @var{v}. Returns the new value.
|
|
|
|
@item DEC(@var{v},@var{i})
|
|
Decrements the value in the variable @var{v} by @var{i}. Returns the
|
|
new value.
|
|
|
|
@item EXCL(@var{m},@var{s})
|
|
Removes the element @var{m} from the set @var{s}. Returns the new
|
|
set.
|
|
|
|
@item FLOAT(@var{i})
|
|
Returns the floating point equivalent of the integer @var{i}.
|
|
|
|
@item HIGH(@var{a})
|
|
Returns the index of the last member of @var{a}.
|
|
|
|
@item INC(@var{v})
|
|
Increments the value in the variable @var{v}. Returns the new value.
|
|
|
|
@item INC(@var{v},@var{i})
|
|
Increments the value in the variable @var{v} by @var{i}. Returns the
|
|
new value.
|
|
|
|
@item INCL(@var{m},@var{s})
|
|
Adds the element @var{m} to the set @var{s} if it is not already
|
|
there. Returns the new set.
|
|
|
|
@item MAX(@var{t})
|
|
Returns the maximum value of the type @var{t}.
|
|
|
|
@item MIN(@var{t})
|
|
Returns the minimum value of the type @var{t}.
|
|
|
|
@item ODD(@var{i})
|
|
Returns boolean TRUE if @var{i} is an odd number.
|
|
|
|
@item ORD(@var{x})
|
|
Returns the ordinal value of its argument. For example, the ordinal
|
|
value of a character is its ASCII value (on machines supporting the
|
|
ASCII character set). @var{x} must be of an ordered type, which include
|
|
integral, character and enumerated types.
|
|
|
|
@item SIZE(@var{x})
|
|
Returns the size of its argument. @var{x} can be a variable or a type.
|
|
|
|
@item TRUNC(@var{r})
|
|
Returns the integral part of @var{r}.
|
|
|
|
@item VAL(@var{t},@var{i})
|
|
Returns the member of the type @var{t} whose ordinal value is @var{i}.
|
|
@end table
|
|
|
|
@quotation
|
|
@emph{Warning:} Sets and their operations are not yet supported, so
|
|
@value{GDBN} will treat the use of procedures @code{INCL} and @code{EXCL} as
|
|
an error.
|
|
@end quotation
|
|
|
|
@cindex Modula-2 constants
|
|
@node M2 Constants
|
|
@subsubsection Constants
|
|
|
|
@value{GDBN} allows you to express the constants of Modula-2 in the following
|
|
ways:
|
|
|
|
@itemize @bullet
|
|
|
|
@item
|
|
Integer constants are simply a sequence of digits. When used in an
|
|
expression, a constant is interpreted to be type-compatible with the
|
|
rest of the expression. Hexadecimal integers are specified by a
|
|
trailing @samp{H}, and octal integers by a trailing @samp{B}.
|
|
|
|
@item
|
|
Floating point constants appear as a sequence of digits, followed by a
|
|
decimal point and another sequence of digits. An optional exponent can
|
|
then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
|
|
@samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
|
|
digits of the floating point constant must be valid decimal (base 10)
|
|
digits.
|
|
|
|
@item
|
|
Character constants consist of a single character enclosed by a pair of
|
|
like quotes, either single (@code{'}) or double (@code{"}). They may
|
|
also be expressed by their ordinal value (their ASCII value, usually)
|
|
followed by a @samp{C}.
|
|
|
|
@item
|
|
String constants consist of a sequence of characters enclosed by a
|
|
pair of like quotes, either single (@code{'}) or double (@code{"}).
|
|
Escape sequences in the style of C are also allowed. @xref{C
|
|
Constants, ,C and C++ constants}, for a brief explanation of escape
|
|
sequences.
|
|
|
|
@item
|
|
Enumerated constants consist of an enumerated identifier.
|
|
|
|
@item
|
|
Boolean constants consist of the identifiers @code{TRUE} and
|
|
@code{FALSE}.
|
|
|
|
@item
|
|
Pointer constants consist of integral values only.
|
|
|
|
@item
|
|
Set constants are not yet supported.
|
|
@end itemize
|
|
|
|
@node M2 Defaults
|
|
@subsubsection Modula-2 defaults
|
|
@cindex Modula-2 defaults
|
|
|
|
If type and range checking are set automatically by @value{GDBN}, they
|
|
both default to @code{on} whenever the working language changes to
|
|
Modula-2. This happens regardless of whether you, or @value{GDBN},
|
|
selected the working language.
|
|
|
|
If you allow @value{GDBN} to set the language automatically, then entering
|
|
code compiled from a file whose name ends with @file{.mod} will set the
|
|
working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
|
|
the language automatically}, for further details.
|
|
|
|
@node Deviations
|
|
@subsubsection Deviations from standard Modula-2
|
|
@cindex Modula-2, deviations from
|
|
|
|
A few changes have been made to make Modula-2 programs easier to debug.
|
|
This is done primarily via loosening its type strictness:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
Unlike in standard Modula-2, pointer constants can be formed by
|
|
integers. This allows you to modify pointer variables during
|
|
debugging. (In standard Modula-2, the actual address contained in a
|
|
pointer variable is hidden from you; it can only be modified
|
|
through direct assignment to another pointer variable or expression that
|
|
returned a pointer.)
|
|
|
|
@item
|
|
C escape sequences can be used in strings and characters to represent
|
|
non-printable characters. @value{GDBN} will print out strings with these
|
|
escape sequences embedded. Single non-printable characters are
|
|
printed using the @samp{CHR(@var{nnn})} format.
|
|
|
|
@item
|
|
The assignment operator (@code{:=}) returns the value of its right-hand
|
|
argument.
|
|
|
|
@item
|
|
All built-in procedures both modify @emph{and} return their argument.
|
|
@end itemize
|
|
|
|
@node M2 Checks
|
|
@subsubsection Modula-2 type and range checks
|
|
@cindex Modula-2 checks
|
|
|
|
@quotation
|
|
@emph{Warning:} in this release, @value{GDBN} does not yet perform type or
|
|
range checking.
|
|
@end quotation
|
|
@c FIXME remove warning when type/range checks added
|
|
|
|
@value{GDBN} considers two Modula-2 variables type equivalent if:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
They are of types that have been declared equivalent via a @code{TYPE
|
|
@var{t1} = @var{t2}} statement
|
|
|
|
@item
|
|
They have been declared on the same line. (Note: This is true of the
|
|
GNU Modula-2 compiler, but it may not be true of other compilers.)
|
|
@end itemize
|
|
|
|
As long as type checking is enabled, any attempt to combine variables
|
|
whose types are not equivalent is an error.
|
|
|
|
Range checking is done on all mathematical operations, assignment, array
|
|
index bounds, and all built-in functions and procedures.
|
|
|
|
@node M2 Scope
|
|
@subsubsection The scope operators @code{::} and @code{.}
|
|
@cindex scope
|
|
@kindex .
|
|
@cindex colon, doubled as scope operator
|
|
@ifinfo
|
|
@kindex colon-colon
|
|
@c Info cannot handle :: but TeX can.
|
|
@end ifinfo
|
|
@iftex
|
|
@kindex ::
|
|
@end iftex
|
|
|
|
There are a few subtle differences between the Modula-2 scope operator
|
|
(@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
|
|
similar syntax:
|
|
|
|
@example
|
|
|
|
@var{module} . @var{id}
|
|
@var{scope} :: @var{id}
|
|
@end example
|
|
|
|
@noindent
|
|
where @var{scope} is the name of a module or a procedure,
|
|
@var{module} the name of a module, and @var{id} is any declared
|
|
identifier within your program, except another module.
|
|
|
|
Using the @code{::} operator makes @value{GDBN} search the scope
|
|
specified by @var{scope} for the identifier @var{id}. If it is not
|
|
found in the specified scope, then @value{GDBN} will search all scopes
|
|
enclosing the one specified by @var{scope}.
|
|
|
|
Using the @code{.} operator makes @value{GDBN} search the current scope for
|
|
the identifier specified by @var{id} that was imported from the
|
|
definition module specified by @var{module}. With this operator, it is
|
|
an error if the identifier @var{id} was not imported from definition
|
|
module @var{module}, or if @var{id} is not an identifier in
|
|
@var{module}.
|
|
|
|
@node GDB/M2
|
|
@subsubsection @value{GDBN} and Modula-2
|
|
|
|
Some @value{GDBN} commands have little use when debugging Modula-2 programs.
|
|
Five subcommands of @code{set print} and @code{show print} apply
|
|
specifically to C and C++: @samp{vtbl}, @samp{demangle},
|
|
@samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
|
|
apply to C++, and the last to the C @code{union} type, which has no direct
|
|
analogue in Modula-2.
|
|
|
|
The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
|
|
while using any language, is not useful with Modula-2. Its
|
|
intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
|
|
created in Modula-2 as they can in C or C++. However, because an
|
|
address can be specified by an integral constant, the construct
|
|
@samp{@{@var{type}@}@var{adrexp}} is still useful. (@pxref{Expressions, ,Expressions})
|
|
|
|
@cindex @code{#} in Modula-2
|
|
In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
|
|
interpreted as the beginning of a comment. Use @code{<>} instead.
|
|
|
|
@end ifclear
|
|
|
|
@node Symbols
|
|
@chapter Examining the Symbol Table
|
|
|
|
The commands described in this section allow you to inquire about the
|
|
symbols (names of variables, functions and types) defined in your
|
|
program. This information is inherent in the text of your program and
|
|
does not change as your program executes. @value{GDBN} finds it in your
|
|
program's symbol table, in the file indicated when you started @value{GDBN}
|
|
(@pxref{File Options, ,Choosing files}), or by one of the
|
|
file-management commands (@pxref{Files, ,Commands to specify files}).
|
|
|
|
@c FIXME! This might be intentionally specific to C and C++; if so, move
|
|
@c to someplace in C section of lang chapter.
|
|
@cindex symbol names
|
|
@cindex names of symbols
|
|
@cindex quoting names
|
|
Occasionally, you may need to refer to symbols that contain unusual
|
|
characters, which @value{GDBN} ordinarily treats as word delimiters. The
|
|
most frequent case is in referring to static variables in other
|
|
source files (@pxref{Variables,,Program variables}). File names
|
|
are recorded in object files as debugging symbols, but @value{GDBN} would
|
|
ordinarily parse a typical file name, like @file{foo.c}, as the three words
|
|
@samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
|
|
@samp{foo.c} as a single symbol, enclose it in single quotes; for example,
|
|
|
|
@example
|
|
p 'foo.c'::x
|
|
@end example
|
|
|
|
@noindent
|
|
looks up the value of @code{x} in the scope of the file @file{foo.c}.
|
|
|
|
@table @code
|
|
@item info address @var{symbol}
|
|
@kindex info address
|
|
Describe where the data for @var{symbol} is stored. For a register
|
|
variable, this says which register it is kept in. For a non-register
|
|
local variable, this prints the stack-frame offset at which the variable
|
|
is always stored.
|
|
|
|
Note the contrast with @samp{print &@var{symbol}}, which does not work
|
|
at all for a register variables, and for a stack local variable prints
|
|
the exact address of the current instantiation of the variable.
|
|
|
|
@item whatis @var{exp}
|
|
@kindex whatis
|
|
Print the data type of expression @var{exp}. @var{exp} is not
|
|
actually evaluated, and any side-effecting operations (such as
|
|
assignments or function calls) inside it do not take place.
|
|
@xref{Expressions, ,Expressions}.
|
|
|
|
@item whatis
|
|
Print the data type of @code{$}, the last value in the value history.
|
|
|
|
@item ptype @var{typename}
|
|
@kindex ptype
|
|
Print a description of data type @var{typename}. @var{typename} may be
|
|
the name of a type, or for C code it may have the form
|
|
@samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
|
|
@samp{enum @var{enum-tag}}.
|
|
|
|
@item ptype @var{exp}
|
|
@itemx ptype
|
|
Print a description of the type of expression @var{exp}. @code{ptype}
|
|
differs from @code{whatis} by printing a detailed description, instead
|
|
of just the name of the type.
|
|
|
|
For example, for this variable declaration:
|
|
|
|
@example
|
|
struct complex @{double real; double imag;@} v;
|
|
@end example
|
|
|
|
@noindent
|
|
the two commands give this output:
|
|
|
|
@example
|
|
@group
|
|
(@value{GDBP}) whatis v
|
|
type = struct complex
|
|
(@value{GDBP}) ptype v
|
|
type = struct complex @{
|
|
double real;
|
|
double imag;
|
|
@}
|
|
@end group
|
|
@end example
|
|
|
|
@noindent
|
|
As with @code{whatis}, using @code{ptype} without an argument refers to
|
|
the type of @code{$}, the last value in the value history.
|
|
|
|
@item info types @var{regexp}
|
|
@itemx info types
|
|
@kindex info types
|
|
Print a brief description of all types whose name matches @var{regexp}
|
|
(or all types in your program, if you supply no argument). Each
|
|
complete typename is matched as though it were a complete line; thus,
|
|
@samp{i type value} gives information on all types in your program whose
|
|
name includes the string @code{value}, but @samp{i type ^value$} gives
|
|
information only on types whose complete name is @code{value}.
|
|
|
|
This command differs from @code{ptype} in two ways: first, like
|
|
@code{whatis}, it does not print a detailed description; second, it
|
|
lists all source files where a type is defined.
|
|
|
|
@item info source
|
|
@kindex info source
|
|
Show the name of the current source file---that is, the source file for
|
|
the function containing the current point of execution---and the language
|
|
it was written in.
|
|
|
|
@item info sources
|
|
@kindex info sources
|
|
Print the names of all source files in your program for which there is
|
|
debugging information, organized into two lists: files whose symbols
|
|
have already been read, and files whose symbols will be read when needed.
|
|
|
|
@item info functions
|
|
@kindex info functions
|
|
Print the names and data types of all defined functions.
|
|
|
|
@item info functions @var{regexp}
|
|
Print the names and data types of all defined functions
|
|
whose names contain a match for regular expression @var{regexp}.
|
|
Thus, @samp{info fun step} finds all functions whose names
|
|
include @code{step}; @samp{info fun ^step} finds those whose names
|
|
start with @code{step}.
|
|
|
|
@item info variables
|
|
@kindex info variables
|
|
Print the names and data types of all variables that are declared
|
|
outside of functions (i.e., excluding local variables).
|
|
|
|
@item info variables @var{regexp}
|
|
Print the names and data types of all variables (except for local
|
|
variables) whose names contain a match for regular expression
|
|
@var{regexp}.
|
|
|
|
@ignore
|
|
This was never implemented.
|
|
@item info methods
|
|
@itemx info methods @var{regexp}
|
|
@kindex info methods
|
|
The @code{info methods} command permits the user to examine all defined
|
|
methods within C++ program, or (with the @var{regexp} argument) a
|
|
specific set of methods found in the various C++ classes. Many
|
|
C++ classes provide a large number of methods. Thus, the output
|
|
from the @code{ptype} command can be overwhelming and hard to use. The
|
|
@code{info-methods} command filters the methods, printing only those
|
|
which match the regular-expression @var{regexp}.
|
|
@end ignore
|
|
|
|
@item maint print symbols @var{filename}
|
|
@itemx maint print psymbols @var{filename}
|
|
@itemx maint print msymbols @var{filename}
|
|
@kindex maint print symbols
|
|
@cindex symbol dump
|
|
@kindex maint print psymbols
|
|
@cindex partial symbol dump
|
|
Write a dump of debugging symbol data into the file @var{filename}.
|
|
These commands are used to debug the @value{GDBN} symbol-reading code. Only
|
|
symbols with debugging data are included. If you use @samp{maint print
|
|
symbols}, @value{GDBN} includes all the symbols for which it has already
|
|
collected full details: that is, @var{filename} reflects symbols for
|
|
only those files whose symbols @value{GDBN} has read. You can use the
|
|
command @code{info sources} to find out which files these are. If you
|
|
use @samp{maint print psymbols} instead, the dump shows information about
|
|
symbols that @value{GDBN} only knows partially---that is, symbols defined in
|
|
files that @value{GDBN} has skimmed, but not yet read completely. Finally,
|
|
@samp{maint print msymbols} dumps just the minimal symbol information
|
|
required for each object file from which @value{GDBN} has read some symbols.
|
|
The description of @code{symbol-file} explains how @value{GDBN} reads
|
|
symbols; both @code{info source} and @code{symbol-file} are described in
|
|
@ref{Files, ,Commands to specify files}.
|
|
@end table
|
|
|
|
@node Altering
|
|
@chapter Altering Execution
|
|
|
|
Once you think you have found an error in your program, you might want to
|
|
find out for certain whether correcting the apparent error would lead to
|
|
correct results in the rest of the run. You can find the answer by
|
|
experiment, using the @value{GDBN} features for altering execution of the
|
|
program.
|
|
|
|
For example, you can store new values into variables or memory
|
|
locations,
|
|
@ifclear BARETARGET
|
|
give your program a signal, restart it
|
|
@end ifclear
|
|
@ifset BARETARGET
|
|
restart your program
|
|
@end ifset
|
|
at a different address, or even return prematurely from a function to
|
|
its caller.
|
|
|
|
@menu
|
|
* Assignment:: Assignment to variables
|
|
* Jumping:: Continuing at a different address
|
|
@ifclear BARETARGET
|
|
* Signaling:: Giving your program a signal
|
|
@end ifclear
|
|
|
|
* Returning:: Returning from a function
|
|
* Calling:: Calling your program's functions
|
|
* Patching:: Patching your program
|
|
@end menu
|
|
|
|
@node Assignment
|
|
@section Assignment to variables
|
|
|
|
@cindex assignment
|
|
@cindex setting variables
|
|
To alter the value of a variable, evaluate an assignment expression.
|
|
@xref{Expressions, ,Expressions}. For example,
|
|
|
|
@example
|
|
print x=4
|
|
@end example
|
|
|
|
@noindent
|
|
stores the value 4 into the variable @code{x}, and then prints the
|
|
value of the assignment expression (which is 4).
|
|
@ifclear CONLY
|
|
@xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
|
|
information on operators in supported languages.
|
|
@end ifclear
|
|
|
|
@kindex set variable
|
|
@cindex variables, setting
|
|
If you are not interested in seeing the value of the assignment, use the
|
|
@code{set} command instead of the @code{print} command. @code{set} is
|
|
really the same as @code{print} except that the expression's value is
|
|
not printed and is not put in the value history (@pxref{Value History,
|
|
,Value history}). The expression is evaluated only for its effects.
|
|
|
|
If the beginning of the argument string of the @code{set} command
|
|
appears identical to a @code{set} subcommand, use the @code{set
|
|
variable} command instead of just @code{set}. This command is identical
|
|
to @code{set} except for its lack of subcommands. For example, if
|
|
your program has a variable @code{width}, you get
|
|
an error if you try to set a new value with just @samp{set width=13},
|
|
because @value{GDBN} has the command @code{set width}:
|
|
|
|
@example
|
|
(@value{GDBP}) whatis width
|
|
type = double
|
|
(@value{GDBP}) p width
|
|
$4 = 13
|
|
(@value{GDBP}) set width=47
|
|
Invalid syntax in expression.
|
|
@end example
|
|
|
|
@noindent
|
|
The invalid expression, of course, is @samp{=47}. In
|
|
order to actually set the program's variable @code{width}, use
|
|
|
|
@example
|
|
(@value{GDBP}) set var width=47
|
|
@end example
|
|
|
|
@value{GDBN} allows more implicit conversions in assignments than C; you can
|
|
freely store an integer value into a pointer variable or vice versa,
|
|
and you can convert any structure to any other structure that is the
|
|
same length or shorter.
|
|
@comment FIXME: how do structs align/pad in these conversions?
|
|
@comment /pesch@cygnus.com 18dec1990
|
|
|
|
To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
|
|
construct to generate a value of specified type at a specified address
|
|
(@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
|
|
to memory location @code{0x83040} as an integer (which implies a certain size
|
|
and representation in memory), and
|
|
|
|
@example
|
|
set @{int@}0x83040 = 4
|
|
@end example
|
|
|
|
@noindent
|
|
stores the value 4 into that memory location.
|
|
|
|
@node Jumping
|
|
@section Continuing at a different address
|
|
|
|
Ordinarily, when you continue your program, you do so at the place where
|
|
it stopped, with the @code{continue} command. You can instead continue at
|
|
an address of your own choosing, with the following commands:
|
|
|
|
@table @code
|
|
@item jump @var{linespec}
|
|
@kindex jump
|
|
Resume execution at line @var{linespec}. Execution will stop
|
|
immediately if there is a breakpoint there. @xref{List, ,Printing
|
|
source lines}, for a description of the different forms of
|
|
@var{linespec}.
|
|
|
|
The @code{jump} command does not change the current stack frame, or
|
|
the stack pointer, or the contents of any memory location or any
|
|
register other than the program counter. If line @var{linespec} is in
|
|
a different function from the one currently executing, the results may
|
|
be bizarre if the two functions expect different patterns of arguments or
|
|
of local variables. For this reason, the @code{jump} command requests
|
|
confirmation if the specified line is not in the function currently
|
|
executing. However, even bizarre results are predictable if you are
|
|
well acquainted with the machine-language code of your program.
|
|
|
|
@item jump *@var{address}
|
|
Resume execution at the instruction at address @var{address}.
|
|
@end table
|
|
|
|
You can get much the same effect as the @code{jump} command by storing a
|
|
new value into the register @code{$pc}. The difference is that this
|
|
does not start your program running; it only changes the address where it
|
|
@emph{will} run when it is continued. For example,
|
|
|
|
@example
|
|
set $pc = 0x485
|
|
@end example
|
|
|
|
@noindent
|
|
causes the next @code{continue} command or stepping command to execute at
|
|
address @code{0x485}, rather than at the address where your program stopped.
|
|
@xref{Continuing and Stepping, ,Continuing and stepping}.
|
|
|
|
The most common occasion to use the @code{jump} command is to back up,
|
|
perhaps with more breakpoints set, over a portion of a program that has
|
|
already executed, in order to examine its execution in more detail.
|
|
|
|
@ifclear BARETARGET
|
|
@c @group
|
|
@node Signaling
|
|
@section Giving your program a signal
|
|
|
|
@table @code
|
|
@item signal @var{signalnum}
|
|
@kindex signal
|
|
Resume execution where your program stopped, but give it immediately the
|
|
signal number @var{signalnum}.
|
|
|
|
Alternatively, if @var{signalnum} is zero, continue execution without
|
|
giving a signal. This is useful when your program stopped on account of
|
|
a signal and would ordinary see the signal when resumed with the
|
|
@code{continue} command; @samp{signal 0} causes it to resume without a
|
|
signal.
|
|
|
|
@code{signal} does not repeat when you press @key{RET} a second time
|
|
after executing the command.
|
|
@end table
|
|
@c @end group
|
|
@end ifclear
|
|
|
|
@node Returning
|
|
@section Returning from a function
|
|
|
|
@table @code
|
|
@item return
|
|
@itemx return @var{expression}
|
|
@cindex returning from a function
|
|
@kindex return
|
|
You can cancel execution of a function call with the @code{return}
|
|
command. If you give an
|
|
@var{expression} argument, its value is used as the function's return
|
|
value.
|
|
@end table
|
|
|
|
When you use @code{return}, @value{GDBN} discards the selected stack frame
|
|
(and all frames within it). You can think of this as making the
|
|
discarded frame return prematurely. If you wish to specify a value to
|
|
be returned, give that value as the argument to @code{return}.
|
|
|
|
This pops the selected stack frame (@pxref{Selection, ,Selecting a
|
|
frame}), and any other frames inside of it, leaving its caller as the
|
|
innermost remaining frame. That frame becomes selected. The
|
|
specified value is stored in the registers used for returning values
|
|
of functions.
|
|
|
|
The @code{return} command does not resume execution; it leaves the
|
|
program stopped in the state that would exist if the function had just
|
|
returned. In contrast, the @code{finish} command (@pxref{Continuing
|
|
and Stepping, ,Continuing and stepping}) resumes execution until the
|
|
selected stack frame returns naturally.
|
|
|
|
@node Calling
|
|
@section Calling program functions
|
|
|
|
@cindex calling functions
|
|
@kindex call
|
|
@table @code
|
|
@item call @var{expr}
|
|
Evaluate the expression @var{expr} without displaying @code{void}
|
|
returned values.
|
|
@end table
|
|
|
|
You can use this variant of the @code{print} command if you want to
|
|
execute a function from your program, but without cluttering the output
|
|
with @code{void} returned values. The result is printed and saved in
|
|
the value history, if it is not void.
|
|
|
|
@node Patching
|
|
@section Patching programs
|
|
@cindex patching binaries
|
|
@cindex writing into executables
|
|
@ifclear BARETARGET
|
|
@cindex writing into corefiles
|
|
@end ifclear
|
|
|
|
By default, @value{GDBN} opens the file containing your program's executable
|
|
code
|
|
@ifclear BARETARGET
|
|
(or the corefile)
|
|
@end ifclear
|
|
read-only. This prevents accidental alterations
|
|
to machine code; but it also prevents you from intentionally patching
|
|
your program's binary.
|
|
|
|
If you'd like to be able to patch the binary, you can specify that
|
|
explicitly with the @code{set write} command. For example, you might
|
|
want to turn on internal debugging flags, or even to make emergency
|
|
repairs.
|
|
|
|
@table @code
|
|
@item set write on
|
|
@itemx set write off
|
|
@kindex set write
|
|
If you specify @samp{set write on}, @value{GDBN} will open executable
|
|
@ifclear BARETARGET
|
|
and core
|
|
@end ifclear
|
|
files for both reading and writing; if you specify @samp{set write
|
|
off} (the default), @value{GDBN} will open them read-only.
|
|
|
|
If you have already loaded a file, you must load it again (using the
|
|
@code{exec-file}
|
|
@ifclear BARETARGET
|
|
or @code{core-file}
|
|
@end ifclear
|
|
command) after changing @code{set write}, for your new setting to take
|
|
effect.
|
|
|
|
@item show write
|
|
@kindex show write
|
|
Display whether executable files
|
|
@ifclear BARETARGET
|
|
and core files
|
|
@end ifclear
|
|
will be opened for writing as well as reading.
|
|
@end table
|
|
|
|
@node GDB Files
|
|
@chapter @value{GDBN} Files
|
|
|
|
@value{GDBN} needs to know the file name of the program to be debugged, both in
|
|
order to read its symbol table and in order to start your program.
|
|
@ifclear BARETARGET
|
|
To debug a core dump of a previous run, you must also tell @value{GDBN}
|
|
the name of the core dump file.
|
|
@end ifclear
|
|
|
|
@menu
|
|
* Files:: Commands to specify files
|
|
* Symbol Errors:: Errors reading symbol files
|
|
@end menu
|
|
|
|
@node Files
|
|
@section Commands to specify files
|
|
@cindex symbol table
|
|
|
|
@ifclear BARETARGET
|
|
@cindex core dump file
|
|
The usual way to specify executable and core dump file names is with
|
|
the command arguments given when you start @value{GDBN} (@pxref{Invocation,
|
|
,Getting In and Out of @value{GDBN}}.
|
|
@end ifclear
|
|
@ifset BARETARGET
|
|
The usual way to specify an executable file name is with
|
|
the command argument given when you start @value{GDBN}, (@pxref{Invocation,
|
|
,Getting In and Out of @value{GDBN}}.
|
|
@end ifset
|
|
|
|
Occasionally it is necessary to change to a different file during a
|
|
@value{GDBN} session. Or you may run @value{GDBN} and forget to specify
|
|
a file you want to use. In these situations the @value{GDBN} commands
|
|
to specify new files are useful.
|
|
|
|
@table @code
|
|
@item file @var{filename}
|
|
@cindex executable file
|
|
@kindex file
|
|
Use @var{filename} as the program to be debugged. It is read for its
|
|
symbols and for the contents of pure memory. It is also the program
|
|
executed when you use the @code{run} command. If you do not specify a
|
|
directory and the file is not found in the @value{GDBN} working directory, @value{GDBN}
|
|
uses the environment variable @code{PATH} as a list of directories to
|
|
search, just as the shell does when looking for a program to run. You
|
|
can change the value of this variable, for both @value{GDBN} and your program,
|
|
using the @code{path} command.
|
|
|
|
On systems with memory-mapped files, an auxiliary symbol table file
|
|
@file{@var{filename}.syms} may be available for @var{filename}. If it
|
|
is, @value{GDBN} will map in the symbol table from
|
|
@file{@var{filename}.syms}, starting up more quickly. See the
|
|
descriptions of the options @samp{-mapped} and @samp{-readnow} (available
|
|
on the command line, and with the commands @code{file}, @code{symbol-file},
|
|
or @code{add-symbol-file}), for more information.
|
|
|
|
@item file
|
|
@code{file} with no argument makes @value{GDBN} discard any information it
|
|
has on both executable file and the symbol table.
|
|
|
|
@item exec-file @r{[} @var{filename} @r{]}
|
|
@kindex exec-file
|
|
Specify that the program to be run (but not the symbol table) is found
|
|
in @var{filename}. @value{GDBN} will search the environment variable @code{PATH}
|
|
if necessary to locate your program. Omitting @var{filename} means to
|
|
discard information on the executable file.
|
|
|
|
@item symbol-file @r{[} @var{filename} @r{]}
|
|
@kindex symbol-file
|
|
Read symbol table information from file @var{filename}. @code{PATH} is
|
|
searched when necessary. Use the @code{file} command to get both symbol
|
|
table and program to run from the same file.
|
|
|
|
@code{symbol-file} with no argument clears out @value{GDBN} information on your
|
|
program's symbol table.
|
|
|
|
The @code{symbol-file} command causes @value{GDBN} to forget the contents of its
|
|
convenience variables, the value history, and all breakpoints and
|
|
auto-display expressions. This is because they may contain pointers to
|
|
the internal data recording symbols and data types, which are part of
|
|
the old symbol table data being discarded inside @value{GDBN}.
|
|
|
|
@code{symbol-file} will not repeat if you press @key{RET} again after
|
|
executing it once.
|
|
|
|
When @value{GDBN} is configured for a particular environment, it will
|
|
understand debugging information in whatever format is the standard
|
|
generated for that environment; you may use either a GNU compiler, or
|
|
other compilers that adhere to the local conventions. Best results are
|
|
usually obtained from GNU compilers; for example, using @code{@value{GCC}}
|
|
you can generate debugging information for optimized code.
|
|
|
|
On some kinds of object files, the @code{symbol-file} command does not
|
|
normally read the symbol table in full right away. Instead, it scans
|
|
the symbol table quickly to find which source files and which symbols
|
|
are present. The details are read later, one source file at a time,
|
|
as they are needed.
|
|
|
|
The purpose of this two-stage reading strategy is to make @value{GDBN} start up
|
|
faster. For the most part, it is invisible except for occasional
|
|
pauses while the symbol table details for a particular source file are
|
|
being read. (The @code{set verbose} command can turn these pauses
|
|
into messages if desired. @xref{Messages/Warnings, ,Optional warnings
|
|
and messages}.)
|
|
|
|
We have not implemented the two-stage strategy for COFF yet. When the
|
|
symbol table is stored in COFF format, @code{symbol-file} reads the
|
|
symbol table data in full right away.
|
|
|
|
@item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
|
|
@itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
|
|
@kindex readnow
|
|
@cindex reading symbols immediately
|
|
@cindex symbols, reading immediately
|
|
@kindex mapped
|
|
@cindex memory-mapped symbol file
|
|
@cindex saving symbol table
|
|
You can override the @value{GDBN} two-stage strategy for reading symbol
|
|
tables by using the @samp{-readnow} option with any of the commands that
|
|
load symbol table information, if you want to be sure @value{GDBN} has the
|
|
entire symbol table available.
|
|
|
|
@ifclear BARETARGET
|
|
If memory-mapped files are available on your system through the
|
|
@code{mmap} system call, you can use another option, @samp{-mapped}, to
|
|
cause @value{GDBN} to write the symbols for your program into a reusable
|
|
file. Future @value{GDBN} debugging sessions will map in symbol information
|
|
from this auxiliary symbol file (if the program has not changed), rather
|
|
than spending time reading the symbol table from the executable
|
|
program. Using the @samp{-mapped} option has the same effect as
|
|
starting @value{GDBN} with the @samp{-mapped} command-line option.
|
|
|
|
You can use both options together, to make sure the auxiliary symbol
|
|
file has all the symbol information for your program.
|
|
|
|
The auxiliary symbol file for a program called @var{myprog} is called
|
|
@samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
|
|
than the corresponding executable), @value{GDBN} will always attempt to use
|
|
it when you debug @var{myprog}; no special options or commands are
|
|
needed.
|
|
|
|
The @file{.syms} file is specific to the host machine where you run
|
|
@value{GDBN}. It holds an exact image of the internal @value{GDBN}
|
|
symbol table. It cannot be shared across multiple host platforms.
|
|
|
|
@c FIXME: for now no mention of directories, since this seems to be in
|
|
@c flux. 13mar1992 status is that in theory GDB would look either in
|
|
@c current dir or in same dir as myprog; but issues like competing
|
|
@c GDB's, or clutter in system dirs, mean that in practice right now
|
|
@c only current dir is used. FFish says maybe a special GDB hierarchy
|
|
@c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
|
|
@c files.
|
|
|
|
@item core-file @r{[} @var{filename} @r{]}
|
|
@kindex core
|
|
@kindex core-file
|
|
Specify the whereabouts of a core dump file to be used as the ``contents
|
|
of memory''. Traditionally, core files contain only some parts of the
|
|
address space of the process that generated them; @value{GDBN} can access the
|
|
executable file itself for other parts.
|
|
|
|
@code{core-file} with no argument specifies that no core file is
|
|
to be used.
|
|
|
|
Note that the core file is ignored when your program is actually running
|
|
under @value{GDBN}. So, if you have been running your program and you wish to
|
|
debug a core file instead, you must kill the subprocess in which the
|
|
program is running. To do this, use the @code{kill} command
|
|
(@pxref{Kill Process, ,Killing the child process}).
|
|
@end ifclear
|
|
|
|
@item load @var{filename}
|
|
@kindex load
|
|
@ifset GENERIC
|
|
Depending on what remote debugging facilities are configured into
|
|
@value{GDBN}, the @code{load} command may be available. Where it exists, it
|
|
is meant to make @var{filename} (an executable) available for debugging
|
|
on the remote system---by downloading, or dynamic linking, for example.
|
|
@code{load} also records the @var{filename} symbol table in @value{GDBN}, like
|
|
the @code{add-symbol-file} command.
|
|
|
|
If your @value{GDBN} does not have a @code{load} command, attempting to
|
|
execute it gets the error message ``@code{You can't do that when your
|
|
target is @dots{}}''
|
|
@end ifset
|
|
|
|
@ifset VXWORKS
|
|
On VxWorks, @code{load} will dynamically link @var{filename} on the
|
|
current target system as well as adding its symbols in @value{GDBN}.
|
|
@end ifset
|
|
|
|
@ifset I960
|
|
@cindex download to Nindy-960
|
|
With the Nindy interface to an Intel 960 board, @code{load} will
|
|
download @var{filename} to the 960 as well as adding its symbols in
|
|
@value{GDBN}.
|
|
@end ifset
|
|
|
|
@ifset H8
|
|
@cindex download to H8/300 or H8/500
|
|
@cindex H8/300 or H8/500 download
|
|
@c start-sanitize-Hitachi-SH
|
|
@cindex download to Hitachi SH
|
|
@cindex Hitachi SH download
|
|
@c end-sanitize-Hitachi-SH
|
|
When you select remote debugging to a Hitachi
|
|
@c start-sanitize-Hitachi-SH
|
|
SH,
|
|
@c end-sanitize-Hitachi-SH
|
|
H8/300, or H8/500 board
|
|
(@pxref{Hitachi Remote,,@value{GDBN} and Hitachi Microprocessors}),
|
|
the @code{load} command downloads your program to the Hitachi board and also
|
|
opens it as the current executable target for @value{GDBN} on your host
|
|
(like the @code{file} command).
|
|
@end ifset
|
|
|
|
@code{load} will not repeat if you press @key{RET} again after using it.
|
|
|
|
@ifclear BARETARGET
|
|
@item add-symbol-file @var{filename} @var{address}
|
|
@itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
|
|
@kindex add-symbol-file
|
|
@cindex dynamic linking
|
|
The @code{add-symbol-file} command reads additional symbol table information
|
|
from the file @var{filename}. You would use this command when @var{filename}
|
|
has been dynamically loaded (by some other means) into the program that
|
|
is running. @var{address} should be the memory address at which the
|
|
file has been loaded; @value{GDBN} cannot figure this out for itself.
|
|
|
|
The symbol table of the file @var{filename} is added to the symbol table
|
|
originally read with the @code{symbol-file} command. You can use the
|
|
@code{add-symbol-file} command any number of times; the new symbol data thus
|
|
read keeps adding to the old. To discard all old symbol data instead,
|
|
use the @code{symbol-file} command.
|
|
|
|
@code{add-symbol-file} will not repeat if you press @key{RET} after using it.
|
|
|
|
You can use the @samp{-mapped} and @samp{-readnow} options just as with
|
|
the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
|
|
table information for @var{filename}.
|
|
@end ifclear
|
|
|
|
@item info files
|
|
@itemx info target
|
|
@kindex info files
|
|
@kindex info target
|
|
@code{info files} and @code{info target} are synonymous; both print
|
|
the current target (@pxref{Targets, ,Specifying a Debugging Target}),
|
|
including the
|
|
@ifclear BARETARGET
|
|
names of the executable and core dump files
|
|
@end ifclear
|
|
@ifset BARETARGET
|
|
name of the executable file
|
|
@end ifset
|
|
currently in use by @value{GDBN}, and the files from which symbols were
|
|
loaded. The command @code{help targets} lists all possible targets
|
|
rather than current ones.
|
|
@end table
|
|
|
|
All file-specifying commands allow both absolute and relative file names
|
|
as arguments. @value{GDBN} always converts the file name to an absolute path
|
|
name and remembers it that way.
|
|
|
|
@ifclear BARETARGET
|
|
@cindex shared libraries
|
|
@value{GDBN} supports SunOS, SVR4, and IBM RS/6000 shared libraries.
|
|
@value{GDBN} automatically loads symbol definitions from shared libraries
|
|
when you use the @code{run} command, or when you examine a core file.
|
|
(Before you issue the @code{run} command, @value{GDBN} will not understand
|
|
references to a function in a shared library, however---unless you are
|
|
debugging a core file).
|
|
@c FIXME: next @value{GDBN} release should permit some refs to undef
|
|
@c FIXME...symbols---eg in a break cmd---assuming they are from a shared lib
|
|
|
|
@table @code
|
|
@item info share
|
|
@itemx info sharedlibrary
|
|
@kindex info sharedlibrary
|
|
@kindex info share
|
|
Print the names of the shared libraries which are currently loaded.
|
|
|
|
@item sharedlibrary @var{regex}
|
|
@itemx share @var{regex}
|
|
@kindex sharedlibrary
|
|
@kindex share
|
|
This is an obsolescent command; you can use it to explicitly
|
|
load shared object library symbols for files matching a UNIX regular
|
|
expression, but as with files loaded automatically, it will only load
|
|
shared libraries required by your program for a core file or after
|
|
typing @code{run}. If @var{regex} is omitted all shared libraries
|
|
required by your program are loaded.
|
|
@end table
|
|
@end ifclear
|
|
|
|
@node Symbol Errors
|
|
@section Errors reading symbol files
|
|
|
|
While reading a symbol file, @value{GDBN} will occasionally encounter problems,
|
|
such as symbol types it does not recognize, or known bugs in compiler
|
|
output. By default, @value{GDBN} does not notify you of such problems, since
|
|
they are relatively common and primarily of interest to people
|
|
debugging compilers. If you are interested in seeing information
|
|
about ill-constructed symbol tables, you can either ask @value{GDBN} to print
|
|
only one message about each such type of problem, no matter how many
|
|
times the problem occurs; or you can ask @value{GDBN} to print more messages,
|
|
to see how many times the problems occur, with the @code{set
|
|
complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
|
|
messages}).
|
|
|
|
The messages currently printed, and their meanings, are:
|
|
|
|
@table @code
|
|
@item inner block not inside outer block in @var{symbol}
|
|
|
|
The symbol information shows where symbol scopes begin and end
|
|
(such as at the start of a function or a block of statements). This
|
|
error indicates that an inner scope block is not fully contained
|
|
in its outer scope blocks.
|
|
|
|
@value{GDBN} circumvents the problem by treating the inner block as if it had
|
|
the same scope as the outer block. In the error message, @var{symbol}
|
|
may be shown as ``@code{(don't know)}'' if the outer block is not a
|
|
function.
|
|
|
|
@item block at @var{address} out of order
|
|
|
|
The symbol information for symbol scope blocks should occur in
|
|
order of increasing addresses. This error indicates that it does not
|
|
do so.
|
|
|
|
@value{GDBN} does not circumvent this problem, and will have trouble
|
|
locating symbols in the source file whose symbols it is reading. (You
|
|
can often determine what source file is affected by specifying
|
|
@code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
|
|
messages}.)
|
|
|
|
@item bad block start address patched
|
|
|
|
The symbol information for a symbol scope block has a start address
|
|
smaller than the address of the preceding source line. This is known
|
|
to occur in the SunOS 4.1.1 (and earlier) C compiler.
|
|
|
|
@value{GDBN} circumvents the problem by treating the symbol scope block as
|
|
starting on the previous source line.
|
|
|
|
@item bad string table offset in symbol @var{n}
|
|
|
|
@cindex foo
|
|
Symbol number @var{n} contains a pointer into the string table which is
|
|
larger than the size of the string table.
|
|
|
|
@value{GDBN} circumvents the problem by considering the symbol to have the
|
|
name @code{foo}, which may cause other problems if many symbols end up
|
|
with this name.
|
|
|
|
@item unknown symbol type @code{0x@var{nn}}
|
|
|
|
The symbol information contains new data types that @value{GDBN} does not yet
|
|
know how to read. @code{0x@var{nn}} is the symbol type of the misunderstood
|
|
information, in hexadecimal.
|
|
|
|
@value{GDBN} circumvents the error by ignoring this symbol information. This
|
|
will usually allow your program to be debugged, though certain symbols
|
|
will not be accessible. If you encounter such a problem and feel like
|
|
debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint on
|
|
@code{complain}, then go up to the function @code{read_dbx_symtab} and
|
|
examine @code{*bufp} to see the symbol.
|
|
|
|
@item stub type has NULL name
|
|
@value{GDBN} could not find the full definition for
|
|
@ifclear CONLY
|
|
a struct or class.
|
|
@end ifclear
|
|
@ifset CONLY
|
|
a struct.
|
|
@end ifset
|
|
|
|
@ifclear CONLY
|
|
@item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
|
|
|
|
The symbol information for a C++ member function is missing some
|
|
information that recent versions of the compiler should have output
|
|
for it.
|
|
@end ifclear
|
|
|
|
@item info mismatch between compiler and debugger
|
|
|
|
@value{GDBN} could not parse a type specification output by the compiler.
|
|
@end table
|
|
|
|
@node Targets
|
|
@chapter Specifying a Debugging Target
|
|
@cindex debugging target
|
|
@kindex target
|
|
|
|
A @dfn{target} is the execution environment occupied by your program.
|
|
@ifclear BARETARGET
|
|
Often, @value{GDBN} runs in the same host environment as your program; in
|
|
that case, the debugging target is specified as a side effect when you
|
|
use the @code{file} or @code{core} commands. When you need more
|
|
flexibility---for example, running @value{GDBN} on a physically separate
|
|
host, or controlling a standalone system over a serial port or a
|
|
realtime system over a TCP/IP connection---you
|
|
@end ifclear
|
|
@ifset BARETARGET
|
|
You
|
|
@end ifset
|
|
can use the @code{target} command to specify one of the target types
|
|
configured for @value{GDBN} (@pxref{Target Commands, ,Commands for managing
|
|
targets}).
|
|
|
|
@menu
|
|
* Active Targets:: Active targets
|
|
* Target Commands:: Commands for managing targets
|
|
* Remote:: Remote debugging
|
|
@end menu
|
|
|
|
@node Active Targets
|
|
@section Active targets
|
|
@cindex stacking targets
|
|
@cindex active targets
|
|
@cindex multiple targets
|
|
|
|
@ifclear BARETARGET
|
|
There are three classes of targets: processes, core files, and
|
|
executable files. @value{GDBN} can work concurrently on up to three active
|
|
targets, one in each class. This allows you to (for example) start a
|
|
process and inspect its activity without abandoning your work on a core
|
|
file.
|
|
|
|
For example, if you execute @samp{gdb a.out}, then the executable file
|
|
@code{a.out} is the only active target. If you designate a core file as
|
|
well---presumably from a prior run that crashed and coredumped---then
|
|
@value{GDBN} has two active targets and will use them in tandem, looking
|
|
first in the corefile target, then in the executable file, to satisfy
|
|
requests for memory addresses. (Typically, these two classes of target
|
|
are complementary, since core files contain only a program's
|
|
read-write memory---variables and so on---plus machine status, while
|
|
executable files contain only the program text and initialized data.)
|
|
@end ifclear
|
|
|
|
When you type @code{run}, your executable file becomes an active process
|
|
target as well. When a process target is active, all @value{GDBN} commands
|
|
requesting memory addresses refer to that target; addresses in an
|
|
@ifclear BARETARGET
|
|
active core file or
|
|
@end ifclear
|
|
executable file target are obscured while the process
|
|
target is active.
|
|
|
|
@ifset BARETARGET
|
|
Use the @code{exec-file} command to select a
|
|
new executable target (@pxref{Files, ,Commands to specify
|
|
files}).
|
|
@end ifset
|
|
@ifclear BARETARGET
|
|
Use the @code{core-file} and @code{exec-file} commands to select a
|
|
new core file or executable target (@pxref{Files, ,Commands to specify
|
|
files}). To specify as a target a process that is already running, use
|
|
the @code{attach} command (@pxref{Attach, ,Debugging an
|
|
already-running process}).
|
|
@end ifclear
|
|
|
|
@node Target Commands
|
|
@section Commands for managing targets
|
|
|
|
@table @code
|
|
@item target @var{type} @var{parameters}
|
|
Connects the @value{GDBN} host environment to a target
|
|
@ifset BARETARGET
|
|
machine.
|
|
@end ifset
|
|
@ifclear BARETARGET
|
|
machine or process. A target is typically a protocol for talking to
|
|
debugging facilities. You use the argument @var{type} to specify the
|
|
type or protocol of the target machine.
|
|
|
|
Further @var{parameters} are interpreted by the target protocol, but
|
|
typically include things like device names or host names to connect
|
|
with, process numbers, and baud rates.
|
|
@end ifclear
|
|
|
|
The @code{target} command will not repeat if you press @key{RET} again
|
|
after executing the command.
|
|
|
|
@item help target
|
|
@kindex help target
|
|
Displays the names of all targets available. To display targets
|
|
currently selected, use either @code{info target} or @code{info files}
|
|
(@pxref{Files, ,Commands to specify files}).
|
|
|
|
@item help target @var{name}
|
|
Describe a particular target, including any parameters necessary to
|
|
select it.
|
|
@end table
|
|
|
|
Here are some common targets (available, or not, depending on the GDB
|
|
configuration):
|
|
|
|
@table @code
|
|
@item target exec @var{program}
|
|
@kindex target exec
|
|
An executable file. @samp{target exec @var{program}} is the same as
|
|
@samp{exec-file @var{program}}.
|
|
|
|
@ifclear BARETARGET
|
|
@item target core @var{filename}
|
|
@kindex target core
|
|
A core dump file. @samp{target core @var{filename}} is the same as
|
|
@samp{core-file @var{filename}}.
|
|
@end ifclear
|
|
|
|
@ifset REMOTESTUB
|
|
@item target remote @var{dev}
|
|
@kindex target remote
|
|
Remote serial target in GDB-specific protocol. The argument @var{dev}
|
|
specifies what serial device to use for the connection (e.g.
|
|
@file{/dev/ttya}). @xref{Remote, ,Remote debugging}.
|
|
@end ifset
|
|
|
|
@ifset SIMS
|
|
@item target sim
|
|
@kindex target sim
|
|
CPU simulator. @xref{Simulator,,Simulated CPU Target}.
|
|
@end ifset
|
|
|
|
@ifset AMD29K
|
|
@item target udi @var{keyword}
|
|
@kindex target udi
|
|
Remote AMD29K target, using the AMD UDI protocol. The @var{keyword}
|
|
argument specifies which 29K board or simulator to use. @xref{UDI29K
|
|
Remote,,@value{GDBN} and the UDI protocol for AMD29K}.
|
|
|
|
@item target amd-eb @var{dev} @var{speed} @var{PROG}
|
|
@kindex target amd-eb
|
|
@cindex AMD EB29K
|
|
Remote PC-resident AMD EB29K board, attached over serial lines.
|
|
@var{dev} is the serial device, as for @code{target remote};
|
|
@var{speed} allows you to specify the linespeed; and @var{PROG} is the
|
|
name of the program to be debugged, as it appears to DOS on the PC.
|
|
@xref{EB29K Remote, ,@value{GDBN} with a remote EB29K}.
|
|
|
|
@end ifset
|
|
@ifset H8
|
|
@item target hms
|
|
@kindex target hms
|
|
A Hitachi
|
|
@c start-sanitize-Hitachi-SH
|
|
SH,
|
|
@c end-sanitize-Hitachi-SH
|
|
H8/300, or H8/500 board, attached via serial line to your host.
|
|
@ifclear H8EXCLUSIVE
|
|
@c Unix only, not currently of interest for H8-only manual
|
|
Use special commands @code{device} and @code{speed} to control the serial
|
|
line and the communications speed used.
|
|
@end ifclear
|
|
@xref{Hitachi Remote,,@value{GDBN} and Hitachi Microprocessors}.
|
|
|
|
@end ifset
|
|
@ifset I960
|
|
@item target nindy @var{devicename}
|
|
@kindex target nindy
|
|
An Intel 960 board controlled by a Nindy Monitor. @var{devicename} is
|
|
the name of the serial device to use for the connection, e.g.
|
|
@file{/dev/ttya}. @xref{i960-Nindy Remote, ,@value{GDBN} with a remote i960 (Nindy)}.
|
|
|
|
@end ifset
|
|
@ifset ST2000
|
|
@item target st2000 @var{dev} @var{speed}
|
|
@kindex target st2000
|
|
A Tandem ST2000 phone switch, running Tandem's STDBUG protocol. @var{dev}
|
|
is the name of the device attached to the ST2000 serial line;
|
|
@var{speed} is the communication line speed. The arguments are not used
|
|
if @value{GDBN} is configured to connect to the ST2000 using TCP or Telnet.
|
|
@xref{ST2000 Remote,,@value{GDBN} with a Tandem ST2000}.
|
|
|
|
@end ifset
|
|
@ifset VXWORKS
|
|
@item target vxworks @var{machinename}
|
|
@kindex target vxworks
|
|
A VxWorks system, attached via TCP/IP. The argument @var{machinename}
|
|
is the target system's machine name or IP address.
|
|
@xref{VxWorks Remote, ,@value{GDBN} and VxWorks}.
|
|
@end ifset
|
|
@end table
|
|
|
|
@ifset GENERIC
|
|
Different targets are available on different configurations of @value{GDBN}; your
|
|
configuration may have more or fewer targets.
|
|
@end ifset
|
|
|
|
@node Remote
|
|
@section Remote debugging
|
|
@cindex remote debugging
|
|
|
|
If you are trying to debug a program running on a machine that cannot run
|
|
GDB in the usual way, it is often useful to use remote debugging. For
|
|
example, you might use remote debugging on an operating system kernel, or on
|
|
a small system which does not have a general purpose operating system
|
|
powerful enough to run a full-featured debugger.
|
|
|
|
Some configurations of GDB have special serial or TCP/IP interfaces
|
|
to make this work with particular debugging targets. In addition,
|
|
GDB comes with a generic serial protocol (specific to GDB, but
|
|
not specific to any particular target system) which you can use if you
|
|
write the remote stubs---the code that will run on the remote system to
|
|
communicate with GDB.
|
|
|
|
Other remote targets may be available in your
|
|
configuration of GDB; use @code{help targets} to list them.
|
|
|
|
@ifset GENERIC
|
|
@c Text on starting up GDB in various specific cases; it goes up front
|
|
@c in manuals configured for any of those particular situations, here
|
|
@c otherwise.
|
|
@menu
|
|
@ifset REMOTESTUB
|
|
* Remote Serial:: @value{GDBN} remote serial protocol
|
|
@end ifset
|
|
@ifset I960
|
|
* i960-Nindy Remote:: @value{GDBN} with a remote i960 (Nindy)
|
|
@end ifset
|
|
@ifset AMD29K
|
|
* UDI29K Remote:: @value{GDBN} and the UDI protocol for AMD29K
|
|
* EB29K Remote:: @value{GDBN} with a remote EB29K
|
|
@end ifset
|
|
@ifset VXWORKS
|
|
* VxWorks Remote:: @value{GDBN} and VxWorks
|
|
@end ifset
|
|
@ifset ST2000
|
|
* ST2000 Remote:: @value{GDBN} with a Tandem ST2000
|
|
@end ifset
|
|
@ifset H8
|
|
* Hitachi Remote:: @value{GDBN} and Hitachi Microprocessors
|
|
@end ifset
|
|
@ifset MIPS
|
|
* MIPS Remote:: @value{GDBN} and MIPS boards
|
|
@end ifset
|
|
@ifset SIMS
|
|
* Simulator:: Simulated CPU target
|
|
@end ifset
|
|
@end menu
|
|
|
|
@include gdbinv-s.texi
|
|
@end ifset
|
|
|
|
@node Controlling GDB
|
|
@chapter Controlling @value{GDBN}
|
|
|
|
You can alter the way @value{GDBN} interacts with you by using
|
|
the @code{set} command. For commands controlling how @value{GDBN} displays
|
|
data, @pxref{Print Settings, ,Print settings}; other settings are described here.
|
|
|
|
@menu
|
|
* Prompt:: Prompt
|
|
* Editing:: Command editing
|
|
* History:: Command history
|
|
* Screen Size:: Screen size
|
|
* Numbers:: Numbers
|
|
* Messages/Warnings:: Optional warnings and messages
|
|
@end menu
|
|
|
|
@node Prompt
|
|
@section Prompt
|
|
@cindex prompt
|
|
|
|
@value{GDBN} indicates its readiness to read a command by printing a string
|
|
called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
|
|
can change the prompt string with the @code{set prompt} command. For
|
|
instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
|
|
the prompt in one of the @value{GDBN} sessions so that you can always tell which
|
|
one you are talking to.
|
|
|
|
@table @code
|
|
@item set prompt @var{newprompt}
|
|
@kindex set prompt
|
|
Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
|
|
@kindex show prompt
|
|
@item show prompt
|
|
Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
|
|
@end table
|
|
|
|
@node Editing
|
|
@section Command editing
|
|
@cindex readline
|
|
@cindex command line editing
|
|
|
|
@value{GDBN} reads its input commands via the @dfn{readline} interface. This
|
|
GNU library provides consistent behavior for programs which provide a
|
|
command line interface to the user. Advantages are @code{emacs}-style
|
|
or @code{vi}-style inline editing of commands, @code{csh}-like history
|
|
substitution, and a storage and recall of command history across
|
|
debugging sessions.
|
|
|
|
You may control the behavior of command line editing in @value{GDBN} with the
|
|
command @code{set}.
|
|
|
|
@table @code
|
|
@kindex set editing
|
|
@cindex editing
|
|
@item set editing
|
|
@itemx set editing on
|
|
Enable command line editing (enabled by default).
|
|
|
|
@item set editing off
|
|
Disable command line editing.
|
|
|
|
@kindex show editing
|
|
@item show editing
|
|
Show whether command line editing is enabled.
|
|
@end table
|
|
|
|
@node History
|
|
@section Command history
|
|
|
|
@value{GDBN} can keep track of the commands you type during your
|
|
debugging sessions, so that you can be certain of precisely what
|
|
happened. Use these commands to manage the @value{GDBN} command
|
|
history facility.
|
|
|
|
@table @code
|
|
@cindex history substitution
|
|
@cindex history file
|
|
@kindex set history filename
|
|
@item set history filename @var{fname}
|
|
Set the name of the @value{GDBN} command history file to @var{fname}. This is
|
|
the file from which @value{GDBN} will read an initial command history
|
|
list or to which it will write this list when it exits. This list is
|
|
accessed through history expansion or through the history
|
|
command editing characters listed below. This file defaults to the
|
|
value of the environment variable @code{GDBHISTFILE}, or to
|
|
@file{./.gdb_history} if this variable is not set.
|
|
|
|
@cindex history save
|
|
@kindex set history save
|
|
@item set history save
|
|
@itemx set history save on
|
|
Record command history in a file, whose name may be specified with the
|
|
@code{set history filename} command. By default, this option is disabled.
|
|
|
|
@item set history save off
|
|
Stop recording command history in a file.
|
|
|
|
@cindex history size
|
|
@kindex set history size
|
|
@item set history size @var{size}
|
|
Set the number of commands which @value{GDBN} will keep in its history list.
|
|
This defaults to the value of the environment variable
|
|
@code{HISTSIZE}, or to 256 if this variable is not set.
|
|
@end table
|
|
|
|
@cindex history expansion
|
|
History expansion assigns special meaning to the character @kbd{!}.
|
|
@ifset have-readline-appendices
|
|
@xref{Event Designators}.
|
|
@end ifset
|
|
|
|
Since @kbd{!} is also the logical not operator in C, history expansion
|
|
is off by default. If you decide to enable history expansion with the
|
|
@code{set history expansion on} command, you may sometimes need to
|
|
follow @kbd{!} (when it is used as logical not, in an expression) with
|
|
a space or a tab to prevent it from being expanded. The readline
|
|
history facilities will not attempt substitution on the strings
|
|
@kbd{!=} and @kbd{!(}, even when history expansion is enabled.
|
|
|
|
The commands to control history expansion are:
|
|
|
|
@table @code
|
|
|
|
@kindex set history expansion
|
|
@item set history expansion on
|
|
@itemx set history expansion
|
|
Enable history expansion. History expansion is off by default.
|
|
|
|
@item set history expansion off
|
|
Disable history expansion.
|
|
|
|
The readline code comes with more complete documentation of
|
|
editing and history expansion features. Users unfamiliar with @code{emacs}
|
|
or @code{vi} may wish to read it.
|
|
@ifset have-readline-appendices
|
|
@xref{Command Line Editing}.
|
|
@end ifset
|
|
|
|
@c @group
|
|
@kindex show history
|
|
@item show history
|
|
@itemx show history filename
|
|
@itemx show history save
|
|
@itemx show history size
|
|
@itemx show history expansion
|
|
These commands display the state of the @value{GDBN} history parameters.
|
|
@code{show history} by itself displays all four states.
|
|
@c @end group
|
|
@end table
|
|
|
|
@table @code
|
|
@kindex show commands
|
|
@item show commands
|
|
Display the last ten commands in the command history.
|
|
|
|
@item show commands @var{n}
|
|
Print ten commands centered on command number @var{n}.
|
|
|
|
@item show commands +
|
|
Print ten commands just after the commands last printed.
|
|
@end table
|
|
|
|
@node Screen Size
|
|
@section Screen size
|
|
@cindex size of screen
|
|
@cindex pauses in output
|
|
|
|
Certain commands to @value{GDBN} may produce large amounts of
|
|
information output to the screen. To help you read all of it,
|
|
@value{GDBN} pauses and asks you for input at the end of each page of
|
|
output. Type @key{RET} when you want to continue the output, or @kbd{q}
|
|
to discard the remaining output. Also, the screen width setting
|
|
determines when to wrap lines of output. Depending on what is being
|
|
printed, @value{GDBN} tries to break the line at a readable place,
|
|
rather than simply letting it overflow onto the following line.
|
|
|
|
Normally @value{GDBN} knows the size of the screen from the termcap data base
|
|
together with the value of the @code{TERM} environment variable and the
|
|
@code{stty rows} and @code{stty cols} settings. If this is not correct,
|
|
you can override it with the @code{set height} and @code{set
|
|
width} commands:
|
|
|
|
@table @code
|
|
@item set height @var{lpp}
|
|
@itemx show height
|
|
@itemx set width @var{cpl}
|
|
@itemx show width
|
|
@kindex set height
|
|
@kindex set width
|
|
@kindex show width
|
|
@kindex show height
|
|
These @code{set} commands specify a screen height of @var{lpp} lines and
|
|
a screen width of @var{cpl} characters. The associated @code{show}
|
|
commands display the current settings.
|
|
|
|
If you specify a height of zero lines, @value{GDBN} will not pause during output
|
|
no matter how long the output is. This is useful if output is to a file
|
|
or to an editor buffer.
|
|
@end table
|
|
|
|
@node Numbers
|
|
@section Numbers
|
|
@cindex number representation
|
|
@cindex entering numbers
|
|
|
|
You can always enter numbers in octal, decimal, or hexadecimal in @value{GDBN} by
|
|
the usual conventions: octal numbers begin with @samp{0}, decimal
|
|
numbers end with @samp{.}, and hexadecimal numbers begin with @samp{0x}.
|
|
Numbers that begin with none of these are, by default, entered in base
|
|
10; likewise, the default display for numbers---when no particular
|
|
format is specified---is base 10. You can change the default base for
|
|
both input and output with the @code{set radix} command.
|
|
|
|
@table @code
|
|
@kindex set radix
|
|
@item set radix @var{base}
|
|
Set the default base for numeric input and display. Supported choices
|
|
for @var{base} are decimal 2, 8, 10, 16. @var{base} must itself be
|
|
specified either unambiguously or using the current default radix; for
|
|
example, any of
|
|
|
|
@example
|
|
set radix 1010
|
|
set radix 012
|
|
set radix 10.
|
|
set radix 0xa
|
|
@end example
|
|
|
|
@noindent
|
|
will set the base to decimal. On the other hand, @samp{set radix 10}
|
|
will leave the radix unchanged no matter what it was.
|
|
|
|
@kindex show radix
|
|
@item show radix
|
|
Display the current default base for numeric input and display.
|
|
@end table
|
|
|
|
@node Messages/Warnings
|
|
@section Optional warnings and messages
|
|
|
|
By default, @value{GDBN} is silent about its inner workings. If you are running
|
|
on a slow machine, you may want to use the @code{set verbose} command.
|
|
It will make @value{GDBN} tell you when it does a lengthy internal operation, so
|
|
you will not think it has crashed.
|
|
|
|
Currently, the messages controlled by @code{set verbose} are those
|
|
which announce that the symbol table for a source file is being read;
|
|
see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
|
|
|
|
@table @code
|
|
@kindex set verbose
|
|
@item set verbose on
|
|
Enables @value{GDBN} output of certain informational messages.
|
|
|
|
@item set verbose off
|
|
Disables @value{GDBN} output of certain informational messages.
|
|
|
|
@kindex show verbose
|
|
@item show verbose
|
|
Displays whether @code{set verbose} is on or off.
|
|
@end table
|
|
|
|
By default, if @value{GDBN} encounters bugs in the symbol table of an object
|
|
file, it is silent; but if you are debugging a compiler, you may find
|
|
this information useful (@pxref{Symbol Errors, ,Errors reading symbol files}).
|
|
|
|
@table @code
|
|
@kindex set complaints
|
|
@item set complaints @var{limit}
|
|
Permits @value{GDBN} to output @var{limit} complaints about each type of unusual
|
|
symbols before becoming silent about the problem. Set @var{limit} to
|
|
zero to suppress all complaints; set it to a large number to prevent
|
|
complaints from being suppressed.
|
|
|
|
@kindex show complaints
|
|
@item show complaints
|
|
Displays how many symbol complaints @value{GDBN} is permitted to produce.
|
|
@end table
|
|
|
|
By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
|
|
lot of stupid questions to confirm certain commands. For example, if
|
|
you try to run a program which is already running:
|
|
|
|
@example
|
|
(@value{GDBP}) run
|
|
The program being debugged has been started already.
|
|
Start it from the beginning? (y or n)
|
|
@end example
|
|
|
|
If you are willing to unflinchingly face the consequences of your own
|
|
commands, you can disable this ``feature'':
|
|
|
|
@table @code
|
|
@kindex set confirm
|
|
@cindex flinching
|
|
@cindex confirmation
|
|
@cindex stupid questions
|
|
@item set confirm off
|
|
Disables confirmation requests.
|
|
|
|
@item set confirm on
|
|
Enables confirmation requests (the default).
|
|
|
|
@item show confirm
|
|
@kindex show confirm
|
|
Displays state of confirmation requests.
|
|
@end table
|
|
|
|
@c FIXME this does not really belong here. But where *does* it belong?
|
|
@cindex reloading symbols
|
|
Some systems allow individual object files that make up your program to
|
|
be replaced without stopping and restarting your program.
|
|
@ifset VXWORKS
|
|
For example, in VxWorks you can simply recompile a defective object file
|
|
and keep on running.
|
|
@end ifset
|
|
If you are running on one of these systems, you can allow @value{GDBN} to
|
|
reload the symbols for automatically relinked modules:
|
|
|
|
@table @code
|
|
@kindex set symbol-reloading
|
|
@item set symbol-reloading on
|
|
Replace symbol definitions for the corresponding source file when an
|
|
object file with a particular name is seen again.
|
|
|
|
@item set symbol-reloading off
|
|
Do not replace symbol definitions when re-encountering object files of
|
|
the same name. This is the default state; if you are not running on a
|
|
system that permits automatically relinking modules, you should leave
|
|
@code{symbol-reloading} off, since otherwise @value{GDBN} may discard symbols
|
|
when linking large programs, that may contain several modules (from
|
|
different directories or libraries) with the same name.
|
|
|
|
@item show symbol-reloading
|
|
Show the current @code{on} or @code{off} setting.
|
|
@end table
|
|
|
|
@node Sequences
|
|
@chapter Canned Sequences of Commands
|
|
|
|
Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
|
|
command lists}), @value{GDBN} provides two ways to store sequences of commands
|
|
for execution as a unit: user-defined commands and command files.
|
|
|
|
@menu
|
|
* Define:: User-defined commands
|
|
* Hooks:: User-defined command hooks
|
|
* Command Files:: Command files
|
|
* Output:: Commands for controlled output
|
|
@end menu
|
|
|
|
@node Define
|
|
@section User-defined commands
|
|
|
|
@cindex user-defined command
|
|
A @dfn{user-defined command} is a sequence of @value{GDBN} commands to which you
|
|
assign a new name as a command. This is done with the @code{define}
|
|
command.
|
|
|
|
@table @code
|
|
@item define @var{commandname}
|
|
@kindex define
|
|
Define a command named @var{commandname}. If there is already a command
|
|
by that name, you are asked to confirm that you want to redefine it.
|
|
|
|
The definition of the command is made up of other @value{GDBN} command lines,
|
|
which are given following the @code{define} command. The end of these
|
|
commands is marked by a line containing @code{end}.
|
|
|
|
@item document @var{commandname}
|
|
@kindex document
|
|
Give documentation to the user-defined command @var{commandname}. The
|
|
command @var{commandname} must already be defined. This command reads
|
|
lines of documentation just as @code{define} reads the lines of the
|
|
command definition, ending with @code{end}. After the @code{document}
|
|
command is finished, @code{help} on command @var{commandname} will print
|
|
the documentation you have specified.
|
|
|
|
You may use the @code{document} command again to change the
|
|
documentation of a command. Redefining the command with @code{define}
|
|
does not change the documentation.
|
|
|
|
@item help user-defined
|
|
@kindex help user-defined
|
|
List all user-defined commands, with the first line of the documentation
|
|
(if any) for each.
|
|
|
|
@item show user
|
|
@itemx show user @var{commandname}
|
|
@kindex show user
|
|
Display the @value{GDBN} commands used to define @var{commandname} (but not its
|
|
documentation). If no @var{commandname} is given, display the
|
|
definitions for all user-defined commands.
|
|
@end table
|
|
|
|
User-defined commands do not take arguments. When they are executed, the
|
|
commands of the definition are not printed. An error in any command
|
|
stops execution of the user-defined command.
|
|
|
|
Commands that would ask for confirmation if used interactively proceed
|
|
without asking when used inside a user-defined command. Many @value{GDBN} commands
|
|
that normally print messages to say what they are doing omit the messages
|
|
when used in a user-defined command.
|
|
|
|
@node Hooks
|
|
@section User-defined command hooks
|
|
@cindex command files
|
|
|
|
You may define @emph{hooks}, which are a special kind of user-defined
|
|
command. Whenever you run the command @samp{foo}, if the user-defined
|
|
command @samp{hook-foo} exists, it is executed (with no arguments)
|
|
before that command.
|
|
|
|
In addition, a pseudo-command, @samp{stop} exists. Defining
|
|
(@samp{hook-stop}) makes the associated commands execute every time
|
|
execution stops in your program: before breakpoint commands are run,
|
|
displays are printed, or the stack frame is printed.
|
|
|
|
@ifclear BARETARGET
|
|
For example, to ignore @code{SIGALRM} signals while
|
|
single-stepping, but treat them normally during normal execution,
|
|
you could define:
|
|
|
|
@example
|
|
define hook-stop
|
|
handle SIGALRM nopass
|
|
end
|
|
|
|
define hook-run
|
|
handle SIGALRM pass
|
|
end
|
|
|
|
define hook-continue
|
|
handle SIGLARM pass
|
|
end
|
|
@end example
|
|
@end ifclear
|
|
|
|
You can define a hook for any single-word command in @value{GDBN}, but
|
|
not for command aliases; you should define a hook for the basic command
|
|
name, e.g. @code{backtrace} rather than @code{bt}.
|
|
@c FIXME! So how does Joe User discover whether a command is an alias
|
|
@c or not?
|
|
If an error occurs during the execution of your hook, execution of
|
|
@value{GDBN} commands stops and @value{GDBN} issues a prompt
|
|
(before the command that you actually typed had a chance to run).
|
|
|
|
If you try to define a hook which does not match any known command, you
|
|
will get a warning from the @code{define} command.
|
|
|
|
@node Command Files
|
|
@section Command files
|
|
|
|
@cindex command files
|
|
A command file for @value{GDBN} is a file of lines that are @value{GDBN} commands. Comments
|
|
(lines starting with @kbd{#}) may also be included. An empty line in a
|
|
command file does nothing; it does not mean to repeat the last command, as
|
|
it would from the terminal.
|
|
|
|
@cindex init file
|
|
@cindex @file{@value{GDBINIT}}
|
|
When you start @value{GDBN}, it automatically executes commands from its
|
|
@dfn{init files}. These are files named @file{@value{GDBINIT}}. @value{GDBN} reads
|
|
the init file (if any) in your home directory and then the init file
|
|
(if any) in the current working directory. (The init files are not
|
|
executed if you use the @samp{-nx} option; @pxref{Mode Options,
|
|
,Choosing modes}.)
|
|
|
|
@ifset GENERIC
|
|
@cindex init file name
|
|
On some configurations of @value{GDBN}, the init file is known by a
|
|
different name (these are typically environments where a specialized
|
|
form of GDB may need to coexist with other forms, hence a different name
|
|
for the specialized version's init file). These are the environments
|
|
with special init file names:
|
|
|
|
@itemize @bullet
|
|
@kindex .vxgdbinit
|
|
@item
|
|
VxWorks (Wind River Systems real-time OS): @samp{.vxgdbinit}
|
|
|
|
@kindex .os68gdbinit
|
|
@item
|
|
OS68K (Enea Data Systems real-time OS): @samp{.os68gdbinit}
|
|
|
|
@kindex .esgdbinit
|
|
@item
|
|
ES-1800 (Ericsson Telecom AB M68000 emulator): @samp{.esgdbinit}
|
|
@end itemize
|
|
@end ifset
|
|
|
|
You can also request the execution of a command file with the
|
|
@code{source} command:
|
|
|
|
@table @code
|
|
@item source @var{filename}
|
|
@kindex source
|
|
Execute the command file @var{filename}.
|
|
@end table
|
|
|
|
The lines in a command file are executed sequentially. They are not
|
|
printed as they are executed. An error in any command terminates execution
|
|
of the command file.
|
|
|
|
Commands that would ask for confirmation if used interactively proceed
|
|
without asking when used in a command file. Many @value{GDBN} commands that
|
|
normally print messages to say what they are doing omit the messages
|
|
when called from command files.
|
|
|
|
@node Output
|
|
@section Commands for controlled output
|
|
|
|
During the execution of a command file or a user-defined command, normal
|
|
@value{GDBN} output is suppressed; the only output that appears is what is
|
|
explicitly printed by the commands in the definition. This section
|
|
describes three commands useful for generating exactly the output you
|
|
want.
|
|
|
|
@table @code
|
|
@item echo @var{text}
|
|
@kindex echo
|
|
@c I do not consider backslash-space a standard C escape sequence
|
|
@c because it is not in ANSI.
|
|
Print @var{text}. Nonprinting characters can be included in
|
|
@var{text} using C escape sequences, such as @samp{\n} to print a
|
|
newline. @strong{No newline will be printed unless you specify one.}
|
|
In addition to the standard C escape sequences, a backslash followed
|
|
by a space stands for a space. This is useful for displaying a
|
|
string with spaces at the beginning or the end, since leading and
|
|
trailing spaces are otherwise trimmed from all arguments.
|
|
To print @samp{@w{ }and foo =@w{ }}, use the command
|
|
@samp{echo \@w{ }and foo = \@w{ }}.
|
|
|
|
A backslash at the end of @var{text} can be used, as in C, to continue
|
|
the command onto subsequent lines. For example,
|
|
|
|
@example
|
|
echo This is some text\n\
|
|
which is continued\n\
|
|
onto several lines.\n
|
|
@end example
|
|
|
|
produces the same output as
|
|
|
|
@example
|
|
echo This is some text\n
|
|
echo which is continued\n
|
|
echo onto several lines.\n
|
|
@end example
|
|
|
|
@item output @var{expression}
|
|
@kindex output
|
|
Print the value of @var{expression} and nothing but that value: no
|
|
newlines, no @samp{$@var{nn} = }. The value is not entered in the
|
|
value history either. @xref{Expressions, ,Expressions}, for more information on
|
|
expressions.
|
|
|
|
@item output/@var{fmt} @var{expression}
|
|
Print the value of @var{expression} in format @var{fmt}. You can use
|
|
the same formats as for @code{print}. @xref{Output Formats,,Output
|
|
formats}, for more information.
|
|
|
|
@item printf @var{string}, @var{expressions}@dots{}
|
|
@kindex printf
|
|
Print the values of the @var{expressions} under the control of
|
|
@var{string}. The @var{expressions} are separated by commas and may
|
|
be either numbers or pointers. Their values are printed as specified
|
|
by @var{string}, exactly as if your program were to execute
|
|
|
|
@example
|
|
printf (@var{string}, @var{expressions}@dots{});
|
|
@end example
|
|
|
|
For example, you can print two values in hex like this:
|
|
|
|
@smallexample
|
|
printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
|
|
@end smallexample
|
|
|
|
The only backslash-escape sequences that you can use in the format
|
|
string are the simple ones that consist of backslash followed by a
|
|
letter.
|
|
@end table
|
|
|
|
@ifclear DOSHOST
|
|
@node Emacs
|
|
@chapter Using @value{GDBN} under GNU Emacs
|
|
|
|
@cindex emacs
|
|
A special interface allows you to use GNU Emacs to view (and
|
|
edit) the source files for the program you are debugging with
|
|
@value{GDBN}.
|
|
|
|
To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
|
|
executable file you want to debug as an argument. This command starts
|
|
@value{GDBN} as a subprocess of Emacs, with input and output through a newly
|
|
created Emacs buffer.
|
|
|
|
Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
|
|
things:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
All ``terminal'' input and output goes through the Emacs buffer.
|
|
@end itemize
|
|
|
|
This applies both to @value{GDBN} commands and their output, and to the input
|
|
and output done by the program you are debugging.
|
|
|
|
This is useful because it means that you can copy the text of previous
|
|
commands and input them again; you can even use parts of the output
|
|
in this way.
|
|
|
|
All the facilities of Emacs' Shell mode are available for interacting
|
|
with your program. In particular, you can send signals the usual
|
|
way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
|
|
stop.
|
|
|
|
@itemize @bullet
|
|
@item
|
|
@value{GDBN} displays source code through Emacs.
|
|
@end itemize
|
|
|
|
Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
|
|
source file for that frame and puts an arrow (@samp{=>}) at the
|
|
left margin of the current line. Emacs uses a separate buffer for
|
|
source display, and splits the screen to show both your @value{GDBN} session
|
|
and the source.
|
|
|
|
Explicit @value{GDBN} @code{list} or search commands still produce output as
|
|
usual, but you probably will have no reason to use them.
|
|
|
|
@quotation
|
|
@emph{Warning:} If the directory where your program resides is not your
|
|
current directory, it can be easy to confuse Emacs about the location of
|
|
the source files, in which case the auxiliary display buffer will not
|
|
appear to show your source. @value{GDBN} can find programs by searching your
|
|
environment's @code{PATH} variable, so the @value{GDBN} input and output
|
|
session will proceed normally; but Emacs does not get enough information
|
|
back from @value{GDBN} to locate the source files in this situation. To
|
|
avoid this problem, either start @value{GDBN} mode from the directory where
|
|
your program resides, or specify a full path name when prompted for the
|
|
@kbd{M-x gdb} argument.
|
|
|
|
A similar confusion can result if you use the @value{GDBN} @code{file} command to
|
|
switch to debugging a program in some other location, from an existing
|
|
@value{GDBN} buffer in Emacs.
|
|
@end quotation
|
|
|
|
By default, @kbd{M-x gdb} calls the program called @file{gdb}. If
|
|
you need to call @value{GDBN} by a different name (for example, if you keep
|
|
several configurations around, with different names) you can set the
|
|
Emacs variable @code{gdb-command-name}; for example,
|
|
|
|
@example
|
|
(setq gdb-command-name "mygdb")
|
|
@end example
|
|
|
|
@noindent
|
|
(preceded by @kbd{ESC ESC}, or typed in the @code{*scratch*} buffer, or
|
|
in your @file{.emacs} file) will make Emacs call the program named
|
|
``@code{mygdb}'' instead.
|
|
|
|
In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
|
|
addition to the standard Shell mode commands:
|
|
|
|
@table @kbd
|
|
@item C-h m
|
|
Describe the features of Emacs' @value{GDBN} Mode.
|
|
|
|
@item M-s
|
|
Execute to another source line, like the @value{GDBN} @code{step} command; also
|
|
update the display window to show the current file and location.
|
|
|
|
@item M-n
|
|
Execute to next source line in this function, skipping all function
|
|
calls, like the @value{GDBN} @code{next} command. Then update the display window
|
|
to show the current file and location.
|
|
|
|
@item M-i
|
|
Execute one instruction, like the @value{GDBN} @code{stepi} command; update
|
|
display window accordingly.
|
|
|
|
@item M-x gdb-nexti
|
|
Execute to next instruction, using the @value{GDBN} @code{nexti} command; update
|
|
display window accordingly.
|
|
|
|
@item C-c C-f
|
|
Execute until exit from the selected stack frame, like the @value{GDBN}
|
|
@code{finish} command.
|
|
|
|
@item M-c
|
|
Continue execution of your program, like the @value{GDBN} @code{continue}
|
|
command.
|
|
|
|
@emph{Warning:} In Emacs v19, this command is @kbd{C-c C-p}.
|
|
|
|
@item M-u
|
|
Go up the number of frames indicated by the numeric argument
|
|
(@pxref{Arguments, , Numeric Arguments, emacs, The GNU Emacs Manual}),
|
|
like the @value{GDBN} @code{up} command.
|
|
|
|
@emph{Warning:} In Emacs v19, this command is @kbd{C-c C-u}.
|
|
|
|
@item M-d
|
|
Go down the number of frames indicated by the numeric argument, like the
|
|
@value{GDBN} @code{down} command.
|
|
|
|
@emph{Warning:} In Emacs v19, this command is @kbd{C-c C-d}.
|
|
|
|
@item C-x &
|
|
Read the number where the cursor is positioned, and insert it at the end
|
|
of the @value{GDBN} I/O buffer. For example, if you wish to disassemble code
|
|
around an address that was displayed earlier, type @kbd{disassemble};
|
|
then move the cursor to the address display, and pick up the
|
|
argument for @code{disassemble} by typing @kbd{C-x &}.
|
|
|
|
You can customize this further by defining elements of the list
|
|
@code{gdb-print-command}; once it is defined, you can format or
|
|
otherwise process numbers picked up by @kbd{C-x &} before they are
|
|
inserted. A numeric argument to @kbd{C-x &} will both indicate that you
|
|
wish special formatting, and act as an index to pick an element of the
|
|
list. If the list element is a string, the number to be inserted is
|
|
formatted using the Emacs function @code{format}; otherwise the number
|
|
is passed as an argument to the corresponding list element.
|
|
@end table
|
|
|
|
In any source file, the Emacs command @kbd{C-x SPC} (@code{gdb-break})
|
|
tells @value{GDBN} to set a breakpoint on the source line point is on.
|
|
|
|
If you accidentally delete the source-display buffer, an easy way to get
|
|
it back is to type the command @code{f} in the @value{GDBN} buffer, to
|
|
request a frame display; when you run under Emacs, this will recreate
|
|
the source buffer if necessary to show you the context of the current
|
|
frame.
|
|
|
|
The source files displayed in Emacs are in ordinary Emacs buffers
|
|
which are visiting the source files in the usual way. You can edit
|
|
the files with these buffers if you wish; but keep in mind that @value{GDBN}
|
|
communicates with Emacs in terms of line numbers. If you add or
|
|
delete lines from the text, the line numbers that @value{GDBN} knows will cease
|
|
to correspond properly with the code.
|
|
|
|
@c The following dropped because Epoch is nonstandard. Reactivate
|
|
@c if/when v19 does something similar. ---pesch@cygnus.com 19dec1990
|
|
@ignore
|
|
@kindex emacs epoch environment
|
|
@kindex epoch
|
|
@kindex inspect
|
|
|
|
Version 18 of Emacs has a built-in window system called the @code{epoch}
|
|
environment. Users of this environment can use a new command,
|
|
@code{inspect} which performs identically to @code{print} except that
|
|
each value is printed in its own window.
|
|
@end ignore
|
|
@end ifclear
|
|
|
|
@ifset LUCID
|
|
@node Energize
|
|
@chapter Using @value{GDBN} with Energize
|
|
|
|
@cindex Energize
|
|
The Energize Programming System is an integrated development environment
|
|
that includes a point-and-click interface to many programming tools.
|
|
When you use @value{GDBN} in this environment, you can use the standard
|
|
Energize graphical interface to drive @value{GDBN}; you can also, if you
|
|
choose, type @value{GDBN} commands as usual in a debugging window. Even if
|
|
you use the graphical interface, the debugging window (which uses Emacs,
|
|
and resembles the standard Emacs interface to @value{GDBN}) displays the
|
|
equivalent commands, so that the history of your debugging session is
|
|
properly reflected.
|
|
|
|
When Energize starts up a @value{GDBN} session, it uses one of the
|
|
command-line options @samp{-energize} or @samp{-cadillac} (``cadillac''
|
|
is the name of the communications protocol used by the Energize system).
|
|
This option makes @value{GDBN} run as one of the tools in the Energize Tool
|
|
Set: it sends all output to the Energize kernel, and accept input from
|
|
it as well.
|
|
|
|
See the user manual for the Energize Programming System for
|
|
information on how to use the Energize graphical interface and the other
|
|
development tools that Energize integrates with @value{GDBN}.
|
|
|
|
@end ifset
|
|
|
|
@node GDB Bugs
|
|
@chapter Reporting Bugs in @value{GDBN}
|
|
@cindex bugs in @value{GDBN}
|
|
@cindex reporting bugs in @value{GDBN}
|
|
|
|
Your bug reports play an essential role in making @value{GDBN} reliable.
|
|
|
|
Reporting a bug may help you by bringing a solution to your problem, or it
|
|
may not. But in any case the principal function of a bug report is to help
|
|
the entire community by making the next version of @value{GDBN} work better. Bug
|
|
reports are your contribution to the maintenance of @value{GDBN}.
|
|
|
|
In order for a bug report to serve its purpose, you must include the
|
|
information that enables us to fix the bug.
|
|
|
|
@menu
|
|
* Bug Criteria:: Have you found a bug?
|
|
* Bug Reporting:: How to report bugs
|
|
@end menu
|
|
|
|
@node Bug Criteria
|
|
@section Have you found a bug?
|
|
@cindex bug criteria
|
|
|
|
If you are not sure whether you have found a bug, here are some guidelines:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
@cindex fatal signal
|
|
@cindex debugger crash
|
|
@cindex crash of debugger
|
|
If the debugger gets a fatal signal, for any input whatever, that is a
|
|
@value{GDBN} bug. Reliable debuggers never crash.
|
|
|
|
@item
|
|
@cindex error on valid input
|
|
If @value{GDBN} produces an error message for valid input, that is a bug.
|
|
|
|
@item
|
|
@cindex invalid input
|
|
If @value{GDBN} does not produce an error message for invalid input,
|
|
that is a bug. However, you should note that your idea of
|
|
``invalid input'' might be our idea of ``an extension'' or ``support
|
|
for traditional practice''.
|
|
|
|
@item
|
|
If you are an experienced user of debugging tools, your suggestions
|
|
for improvement of @value{GDBN} are welcome in any case.
|
|
@end itemize
|
|
|
|
@node Bug Reporting
|
|
@section How to report bugs
|
|
@cindex bug reports
|
|
@cindex @value{GDBN} bugs, reporting
|
|
|
|
A number of companies and individuals offer support for GNU products.
|
|
If you obtained @value{GDBN} from a support organization, we recommend you
|
|
contact that organization first.
|
|
|
|
You can find contact information for many support companies and
|
|
individuals in the file @file{etc/SERVICE} in the GNU Emacs
|
|
distribution.
|
|
|
|
In any event, we also recommend that you send bug reports for @value{GDBN} to one
|
|
of these addresses:
|
|
|
|
@example
|
|
bug-gdb@@prep.ai.mit.edu
|
|
@{ucbvax|mit-eddie|uunet@}!prep.ai.mit.edu!bug-gdb
|
|
@end example
|
|
|
|
@strong{Do not send bug reports to @samp{info-gdb}, or to
|
|
@samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do not want to
|
|
receive bug reports. Those that do, have arranged to receive @samp{bug-gdb}.
|
|
|
|
The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
|
|
serves as a repeater. The mailing list and the newsgroup carry exactly
|
|
the same messages. Often people think of posting bug reports to the
|
|
newsgroup instead of mailing them. This appears to work, but it has one
|
|
problem which can be crucial: a newsgroup posting often lacks a mail
|
|
path back to the sender. Thus, if we need to ask for more information,
|
|
we may be unable to reach you. For this reason, it is better to send
|
|
bug reports to the mailing list.
|
|
|
|
As a last resort, send bug reports on paper to:
|
|
|
|
@example
|
|
GNU Debugger Bugs
|
|
Free Software Foundation
|
|
545 Tech Square
|
|
Cambridge, MA 02139
|
|
@end example
|
|
|
|
The fundamental principle of reporting bugs usefully is this:
|
|
@strong{report all the facts}. If you are not sure whether to state a
|
|
fact or leave it out, state it!
|
|
|
|
Often people omit facts because they think they know what causes the
|
|
problem and assume that some details do not matter. Thus, you might
|
|
assume that the name of the variable you use in an example does not matter.
|
|
Well, probably it does not, but one cannot be sure. Perhaps the bug is a
|
|
stray memory reference which happens to fetch from the location where that
|
|
name is stored in memory; perhaps, if the name were different, the contents
|
|
of that location would fool the debugger into doing the right thing despite
|
|
the bug. Play it safe and give a specific, complete example. That is the
|
|
easiest thing for you to do, and the most helpful.
|
|
|
|
Keep in mind that the purpose of a bug report is to enable us to fix
|
|
the bug if it is new to us. It is not as important as what happens if
|
|
the bug is already known. Therefore, always write your bug reports on
|
|
the assumption that the bug has not been reported previously.
|
|
|
|
Sometimes people give a few sketchy facts and ask, ``Does this ring a
|
|
bell?'' Those bug reports are useless, and we urge everyone to
|
|
@emph{refuse to respond to them} except to chide the sender to report
|
|
bugs properly.
|
|
|
|
To enable us to fix the bug, you should include all these things:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
The version of @value{GDBN}. @value{GDBN} announces it if you start with no
|
|
arguments; you can also print it at any time using @code{show version}.
|
|
|
|
Without this, we will not know whether there is any point in looking for
|
|
the bug in the current version of @value{GDBN}.
|
|
|
|
@item
|
|
The type of machine you are using, and the operating system name and
|
|
version number.
|
|
|
|
@item
|
|
What compiler (and its version) was used to compile @value{GDBN}---e.g.
|
|
``@value{GCC}--2.0''.
|
|
|
|
@item
|
|
What compiler (and its version) was used to compile the program you
|
|
are debugging---e.g. ``@value{GCC}--2.0''.
|
|
|
|
@item
|
|
The command arguments you gave the compiler to compile your example and
|
|
observe the bug. For example, did you use @samp{-O}? To guarantee
|
|
you will not omit something important, list them all. A copy of the
|
|
Makefile (or the output from make) is sufficient.
|
|
|
|
If we were to try to guess the arguments, we would probably guess wrong
|
|
and then we might not encounter the bug.
|
|
|
|
@item
|
|
A complete input script, and all necessary source files, that will
|
|
reproduce the bug.
|
|
|
|
@item
|
|
A description of what behavior you observe that you believe is
|
|
incorrect. For example, ``It gets a fatal signal.''
|
|
|
|
Of course, if the bug is that @value{GDBN} gets a fatal signal, then we will
|
|
certainly notice it. But if the bug is incorrect output, we might not
|
|
notice unless it is glaringly wrong. We are human, after all. You
|
|
might as well not give us a chance to make a mistake.
|
|
|
|
Even if the problem you experience is a fatal signal, you should still
|
|
say so explicitly. Suppose something strange is going on, such as,
|
|
your copy of @value{GDBN} is out of synch, or you have encountered a
|
|
bug in the C library on your system. (This has happened!) Your copy
|
|
might crash and ours would not. If you told us to expect a crash,
|
|
then when ours fails to crash, we would know that the bug was not
|
|
happening for us. If you had not told us to expect a crash, then we
|
|
would not be able to draw any conclusion from our observations.
|
|
|
|
@item
|
|
If you wish to suggest changes to the @value{GDBN} source, send us context
|
|
diffs. If you even discuss something in the @value{GDBN} source, refer to
|
|
it by context, not by line number.
|
|
|
|
The line numbers in our development sources will not match those in your
|
|
sources. Your line numbers would convey no useful information to us.
|
|
@end itemize
|
|
|
|
Here are some things that are not necessary:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
A description of the envelope of the bug.
|
|
|
|
Often people who encounter a bug spend a lot of time investigating
|
|
which changes to the input file will make the bug go away and which
|
|
changes will not affect it.
|
|
|
|
This is often time consuming and not very useful, because the way we
|
|
will find the bug is by running a single example under the debugger
|
|
with breakpoints, not by pure deduction from a series of examples.
|
|
We recommend that you save your time for something else.
|
|
|
|
Of course, if you can find a simpler example to report @emph{instead}
|
|
of the original one, that is a convenience for us. Errors in the
|
|
output will be easier to spot, running under the debugger will take
|
|
less time, etc.
|
|
|
|
However, simplification is not vital; if you do not want to do this,
|
|
report the bug anyway and send us the entire test case you used.
|
|
|
|
@item
|
|
A patch for the bug.
|
|
|
|
A patch for the bug does help us if it is a good one. But do not omit
|
|
the necessary information, such as the test case, on the assumption that
|
|
a patch is all we need. We might see problems with your patch and decide
|
|
to fix the problem another way, or we might not understand it at all.
|
|
|
|
Sometimes with a program as complicated as @value{GDBN} it is very hard to
|
|
construct an example that will make the program follow a certain path
|
|
through the code. If you do not send us the example, we will not be able
|
|
to construct one, so we will not be able to verify that the bug is fixed.
|
|
|
|
And if we cannot understand what bug you are trying to fix, or why your
|
|
patch should be an improvement, we will not install it. A test case will
|
|
help us to understand.
|
|
|
|
@item
|
|
A guess about what the bug is or what it depends on.
|
|
|
|
Such guesses are usually wrong. Even we cannot guess right about such
|
|
things without first using the debugger to find the facts.
|
|
@end itemize
|
|
|
|
@c The readline documentation is distributed with the readline code
|
|
@c and consists of the two following files:
|
|
@c rluser.texinfo
|
|
@c inc-hist.texi
|
|
@c Use -I with makeinfo to point to the appropriate directory,
|
|
@c environment var TEXINPUTS with TeX.
|
|
@include rluser.texinfo
|
|
@include inc-hist.texi
|
|
|
|
@ifset NOVEL
|
|
@node Renamed Commands
|
|
@appendix Renamed Commands
|
|
|
|
The following commands were renamed in GDB 4, in order to make the
|
|
command set as a whole more consistent and easier to use and remember:
|
|
|
|
@kindex add-syms
|
|
@kindex delete environment
|
|
@kindex info copying
|
|
@kindex info convenience
|
|
@kindex info directories
|
|
@kindex info editing
|
|
@kindex info history
|
|
@kindex info targets
|
|
@kindex info values
|
|
@kindex info version
|
|
@kindex info warranty
|
|
@kindex set addressprint
|
|
@kindex set arrayprint
|
|
@kindex set prettyprint
|
|
@kindex set screen-height
|
|
@kindex set screen-width
|
|
@kindex set unionprint
|
|
@kindex set vtblprint
|
|
@kindex set demangle
|
|
@kindex set asm-demangle
|
|
@kindex set sevenbit-strings
|
|
@kindex set array-max
|
|
@kindex set caution
|
|
@kindex set history write
|
|
@kindex show addressprint
|
|
@kindex show arrayprint
|
|
@kindex show prettyprint
|
|
@kindex show screen-height
|
|
@kindex show screen-width
|
|
@kindex show unionprint
|
|
@kindex show vtblprint
|
|
@kindex show demangle
|
|
@kindex show asm-demangle
|
|
@kindex show sevenbit-strings
|
|
@kindex show array-max
|
|
@kindex show caution
|
|
@kindex show history write
|
|
@kindex unset
|
|
|
|
@c TEXI2ROFF-KILL
|
|
@ifinfo
|
|
@c END TEXI2ROFF-KILL
|
|
@example
|
|
OLD COMMAND NEW COMMAND
|
|
@c TEXI2ROFF-KILL
|
|
--------------- -------------------------------
|
|
@c END TEXI2ROFF-KILL
|
|
add-syms add-symbol-file
|
|
delete environment unset environment
|
|
info convenience show convenience
|
|
info copying show copying
|
|
info directories show directories
|
|
info editing show commands
|
|
info history show values
|
|
info targets help target
|
|
info values show values
|
|
info version show version
|
|
info warranty show warranty
|
|
set/show addressprint set/show print address
|
|
set/show array-max set/show print elements
|
|
set/show arrayprint set/show print array
|
|
set/show asm-demangle set/show print asm-demangle
|
|
set/show caution set/show confirm
|
|
set/show demangle set/show print demangle
|
|
set/show history write set/show history save
|
|
set/show prettyprint set/show print pretty
|
|
set/show screen-height set/show height
|
|
set/show screen-width set/show width
|
|
set/show sevenbit-strings set/show print sevenbit-strings
|
|
set/show unionprint set/show print union
|
|
set/show vtblprint set/show print vtbl
|
|
|
|
unset [No longer an alias for delete]
|
|
@end example
|
|
@c TEXI2ROFF-KILL
|
|
@end ifinfo
|
|
|
|
@tex
|
|
\vskip \parskip\vskip \baselineskip
|
|
\halign{\tt #\hfil &\qquad#&\tt #\hfil\cr
|
|
{\bf Old Command} &&{\bf New Command}\cr
|
|
add-syms &&add-symbol-file\cr
|
|
delete environment &&unset environment\cr
|
|
info convenience &&show convenience\cr
|
|
info copying &&show copying\cr
|
|
info directories &&show directories \cr
|
|
info editing &&show commands\cr
|
|
info history &&show values\cr
|
|
info targets &&help target\cr
|
|
info values &&show values\cr
|
|
info version &&show version\cr
|
|
info warranty &&show warranty\cr
|
|
set{\rm / }show addressprint &&set{\rm / }show print address\cr
|
|
set{\rm / }show array-max &&set{\rm / }show print elements\cr
|
|
set{\rm / }show arrayprint &&set{\rm / }show print array\cr
|
|
set{\rm / }show asm-demangle &&set{\rm / }show print asm-demangle\cr
|
|
set{\rm / }show caution &&set{\rm / }show confirm\cr
|
|
set{\rm / }show demangle &&set{\rm / }show print demangle\cr
|
|
set{\rm / }show history write &&set{\rm / }show history save\cr
|
|
set{\rm / }show prettyprint &&set{\rm / }show print pretty\cr
|
|
set{\rm / }show screen-height &&set{\rm / }show height\cr
|
|
set{\rm / }show screen-width &&set{\rm / }show width\cr
|
|
set{\rm / }show sevenbit-strings &&set{\rm / }show print sevenbit-strings\cr
|
|
set{\rm / }show unionprint &&set{\rm / }show print union\cr
|
|
set{\rm / }show vtblprint &&set{\rm / }show print vtbl\cr
|
|
\cr
|
|
unset &&\rm(No longer an alias for delete)\cr
|
|
}
|
|
@end tex
|
|
@c END TEXI2ROFF-KILL
|
|
@end ifset
|
|
|
|
@ifclear PRECONFIGURED
|
|
@node Formatting Documentation
|
|
@appendix Formatting Documentation
|
|
|
|
@cindex GDB reference card
|
|
@cindex reference card
|
|
The GDB 4 release includes an already-formatted reference card, ready
|
|
for printing with PostScript or GhostScript, in the @file{gdb}
|
|
subdirectory of the main source directory@footnote{In
|
|
@file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
|
|
release.}. If you can use PostScript or GhostScript with your printer,
|
|
you can print the reference card immediately with @file{refcard.ps}.
|
|
|
|
The release also includes the source for the reference card. You
|
|
can format it, using @TeX{}, by typing:
|
|
|
|
@example
|
|
make refcard.dvi
|
|
@end example
|
|
|
|
The GDB reference card is designed to print in landscape mode on US
|
|
``letter'' size paper; that is, on a sheet 11 inches wide by 8.5 inches
|
|
high. You will need to specify this form of printing as an option to
|
|
your @sc{dvi} output program.
|
|
|
|
@cindex documentation
|
|
|
|
All the documentation for GDB comes as part of the machine-readable
|
|
distribution. The documentation is written in Texinfo format, which is
|
|
a documentation system that uses a single source file to produce both
|
|
on-line information and a printed manual. You can use one of the Info
|
|
formatting commands to create the on-line version of the documentation
|
|
and @TeX{} (or @code{texi2roff}) to typeset the printed version.
|
|
|
|
GDB includes an already formatted copy of the on-line Info version of
|
|
this manual in the @file{gdb} subdirectory. The main Info file is
|
|
@file{gdb-@var{version-number}/gdb/gdb.info}, and it refers to
|
|
subordinate files matching @samp{gdb.info*} in the same directory. If
|
|
necessary, you can print out these files, or read them with any editor;
|
|
but they are easier to read using the @code{info} subsystem in GNU Emacs
|
|
or the standalone @code{info} program, available as part of the GNU
|
|
Texinfo distribution.
|
|
|
|
If you want to format these Info files yourself, you need one of the
|
|
Info formatting programs, such as @code{texinfo-format-buffer} or
|
|
@code{makeinfo}.
|
|
|
|
If you have @code{makeinfo} installed, and are in the top level GDB
|
|
source directory (@file{gdb-@value{GDBVN}}, in the case of version @value{GDBVN}), you can
|
|
make the Info file by typing:
|
|
|
|
@example
|
|
cd gdb
|
|
make gdb.info
|
|
@end example
|
|
|
|
If you want to typeset and print copies of this manual, you need @TeX{},
|
|
a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
|
|
Texinfo definitions file.
|
|
|
|
@TeX{} is a typesetting program; it does not print files directly, but
|
|
produces output files called @sc{dvi} files. To print a typeset
|
|
document, you need a program to print @sc{dvi} files. If your system
|
|
has @TeX{} installed, chances are it has such a program. The precise
|
|
command to use depends on your system; @kbd{lpr -d} is common; another
|
|
(for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
|
|
require a file name without any extension or a @samp{.dvi} extension.
|
|
|
|
@TeX{} also requires a macro definitions file called
|
|
@file{texinfo.tex}. This file tells @TeX{} how to typeset a document
|
|
written in Texinfo format. On its own, @TeX{} cannot read, much less
|
|
typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
|
|
and is located in the @file{gdb-@var{version-number}/texinfo}
|
|
directory.
|
|
|
|
If you have @TeX{} and a @sc{dvi} printer program installed, you can
|
|
typeset and print this manual. First switch to the the @file{gdb}
|
|
subdirectory of the main source directory (for example, to
|
|
@file{gdb-@value{GDBVN}/gdb}) and then type:
|
|
|
|
@example
|
|
make gdb.dvi
|
|
@end example
|
|
|
|
@node Installing GDB
|
|
@appendix Installing GDB
|
|
@cindex configuring GDB
|
|
@cindex installation
|
|
|
|
GDB comes with a @code{configure} script that automates the process
|
|
of preparing GDB for installation; you can then use @code{make} to
|
|
build the @code{gdb} program.
|
|
@iftex
|
|
@c irrelevant in info file; it's as current as the code it lives with.
|
|
@footnote{If you have a more recent version of GDB than @value{GDBVN},
|
|
look at the @file{README} file in the sources; we may have improved the
|
|
installation procedures since publishing this manual.}
|
|
@end iftex
|
|
|
|
The GDB distribution includes all the source code you need for GDB in
|
|
a single directory, whose name is usually composed by appending the
|
|
version number to @samp{gdb}.
|
|
|
|
For example, the GDB version @value{GDBVN} distribution is in the
|
|
@file{gdb-@value{GDBVN}} directory. That directory contains:
|
|
|
|
@table @code
|
|
@item gdb-@value{GDBVN}/configure @r{(and supporting files)}
|
|
script for configuring GDB and all its supporting libraries.
|
|
|
|
@item gdb-@value{GDBVN}/gdb
|
|
the source specific to GDB itself
|
|
|
|
@item gdb-@value{GDBVN}/bfd
|
|
source for the Binary File Descriptor library
|
|
|
|
@item gdb-@value{GDBVN}/include
|
|
GNU include files
|
|
|
|
@item gdb-@value{GDBVN}/libiberty
|
|
source for the @samp{-liberty} free software library
|
|
|
|
@item gdb-@value{GDBVN}/opcodes
|
|
source for the library of opcode tables and disassemblers
|
|
|
|
@item gdb-@value{GDBVN}/readline
|
|
source for the GNU command-line interface
|
|
|
|
@item gdb-@value{GDBVN}/glob
|
|
source for the GNU filename pattern-matching subroutine
|
|
|
|
@item gdb-@value{GDBVN}/mmalloc
|
|
source for the GNU memory-mapped malloc package
|
|
@end table
|
|
|
|
The simplest way to configure and build GDB is to run @code{configure}
|
|
from the @file{gdb-@var{version-number}} source directory, which in
|
|
this example is the @file{gdb-@value{GDBVN}} directory.
|
|
|
|
First switch to the @file{gdb-@var{version-number}} source directory
|
|
if you are not already in it; then run @code{configure}. Pass the
|
|
identifier for the platform on which GDB will run as an
|
|
argument.
|
|
|
|
For example:
|
|
|
|
@example
|
|
cd gdb-@value{GDBVN}
|
|
./configure @var{host}
|
|
make
|
|
@end example
|
|
|
|
@noindent
|
|
where @var{host} is an identifier such as @samp{sun4} or
|
|
@samp{decstation}, that identifies the platform where GDB will run.
|
|
|
|
Running @samp{configure @var{host}} and then running @code{make} builds the
|
|
@file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
|
|
libraries, then @code{gdb} itself. The configured source files, and the
|
|
binaries, are left in the corresponding source directories.
|
|
|
|
@code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
|
|
system does not recognize this automatically when you run a different
|
|
shell, you may need to run @code{sh} on it explicitly:
|
|
|
|
@example
|
|
sh configure @var{host}
|
|
@end example
|
|
|
|
If you run @code{configure} from a directory that contains source
|
|
directories for multiple libraries or programs, such as the
|
|
@file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
|
|
creates configuration files for every directory level underneath (unless
|
|
you tell it not to, with the @samp{--norecursion} option).
|
|
|
|
You can run the @code{configure} script from any of the
|
|
subordinate directories in the GDB distribution, if you only want to
|
|
configure that subdirectory; but be sure to specify a path to it.
|
|
|
|
For example, with version @value{GDBVN}, type the following to configure only
|
|
the @code{bfd} subdirectory:
|
|
|
|
@example
|
|
@group
|
|
cd gdb-@value{GDBVN}/bfd
|
|
../configure @var{host}
|
|
@end group
|
|
@end example
|
|
|
|
You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
|
|
However, you should make sure that the shell on your path (named by
|
|
the @samp{SHELL} environment variable) is publicly readable. Remember
|
|
that GDB uses the shell to start your program---some systems refuse to
|
|
let GDB debug child processes whose programs are not readable.
|
|
|
|
@menu
|
|
* Separate Objdir:: Compiling GDB in another directory
|
|
* Config Names:: Specifying names for hosts and targets
|
|
* configure Options:: Summary of options for configure
|
|
@end menu
|
|
|
|
@node Separate Objdir
|
|
@section Compiling GDB in another directory
|
|
|
|
If you want to run GDB versions for several host or target machines,
|
|
you need a different @code{gdb} compiled for each combination of
|
|
host and target. @code{configure} is designed to make this easy by
|
|
allowing you to generate each configuration in a separate subdirectory,
|
|
rather than in the source directory. If your @code{make} program
|
|
handles the @samp{VPATH} feature (GNU @code{make} does), running
|
|
@code{make} in each of these directories builds the @code{gdb}
|
|
program specified there.
|
|
|
|
To build @code{gdb} in a separate directory, run @code{configure}
|
|
with the @samp{--srcdir} option to specify where to find the source.
|
|
(You also need to specify a path to find @code{configure}
|
|
itself from your working directory. If the path to @code{configure}
|
|
would be the same as the argument to @samp{--srcdir}, you can leave out
|
|
the @samp{--srcdir} option; it will be assumed.)
|
|
|
|
For example, with version @value{GDBVN}, you can build GDB in a separate
|
|
directory for a Sun 4 like this:
|
|
|
|
@example
|
|
@group
|
|
cd gdb-@value{GDBVN}
|
|
mkdir ../gdb-sun4
|
|
cd ../gdb-sun4
|
|
../gdb-@value{GDBVN}/configure sun4
|
|
make
|
|
@end group
|
|
@end example
|
|
|
|
When @code{configure} builds a configuration using a remote source
|
|
directory, it creates a tree for the binaries with the same structure
|
|
(and using the same names) as the tree under the source directory. In
|
|
the example, you'd find the Sun 4 library @file{libiberty.a} in the
|
|
directory @file{gdb-sun4/libiberty}, and GDB itself in
|
|
@file{gdb-sun4/gdb}.
|
|
|
|
One popular reason to build several GDB configurations in separate
|
|
directories is to configure GDB for cross-compiling (where GDB
|
|
runs on one machine---the host---while debugging programs that run on
|
|
another machine---the target). You specify a cross-debugging target by
|
|
giving the @samp{--target=@var{target}} option to @code{configure}.
|
|
|
|
When you run @code{make} to build a program or library, you must run
|
|
it in a configured directory---whatever directory you were in when you
|
|
called @code{configure} (or one of its subdirectories).
|
|
|
|
The @code{Makefile} that @code{configure} generates in each source
|
|
directory also runs recursively. If you type @code{make} in a source
|
|
directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
|
|
directory configured with @samp{--srcdir=@var{path}/gdb-@value{GDBVN}}), you
|
|
will build all the required libraries, and then build GDB.
|
|
|
|
When you have multiple hosts or targets configured in separate
|
|
directories, you can run @code{make} on them in parallel (for example,
|
|
if they are NFS-mounted on each of the hosts); they will not interfere
|
|
with each other.
|
|
|
|
@node Config Names
|
|
@section Specifying names for hosts and targets
|
|
|
|
The specifications used for hosts and targets in the @code{configure}
|
|
script are based on a three-part naming scheme, but some short predefined
|
|
aliases are also supported. The full naming scheme encodes three pieces
|
|
of information in the following pattern:
|
|
|
|
@example
|
|
@var{architecture}-@var{vendor}-@var{os}
|
|
@end example
|
|
|
|
For example, you can use the alias @code{sun4} as a @var{host} argument,
|
|
or as the value for @var{target} in a @code{--target=@var{target}}
|
|
option. The equivalent full name is @samp{sparc-sun-sunos4}.
|
|
|
|
The @code{configure} script accompanying GDB does not provide
|
|
any query facility to list all supported host and target names or
|
|
aliases. @code{configure} calls the Bourne shell script
|
|
@code{config.sub} to map abbreviations to full names; you can read the
|
|
script, if you wish, or you can use it to test your guesses on
|
|
abbreviations---for example:
|
|
|
|
@smallexample
|
|
% sh config.sub sun4
|
|
sparc-sun-sunos411
|
|
% sh config.sub sun3
|
|
m68k-sun-sunos411
|
|
% sh config.sub decstation
|
|
mips-dec-ultrix42
|
|
% sh config.sub hp300bsd
|
|
m68k-hp-bsd
|
|
% sh config.sub i386v
|
|
i386-unknown-sysv
|
|
% sh config.sub i786v
|
|
Invalid configuration `i786v': machine `i786v' not recognized
|
|
@end smallexample
|
|
|
|
@noindent
|
|
@code{config.sub} is also distributed in the GDB source
|
|
directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
|
|
|
|
@node configure Options
|
|
@section @code{configure} options
|
|
|
|
Here is a summary of the @code{configure} options and arguments that
|
|
are most often useful for building @value{GDBN}. @code{configure} also has
|
|
several other options not listed here. @inforef{What Configure
|
|
Does,,configure.info}, for a full explanation of @code{configure}.
|
|
@c FIXME: Would this be more, or less, useful as an xref (ref to printed
|
|
@c manual in the printed manual, ref to info file only from the info file)?
|
|
|
|
@example
|
|
configure @r{[}--help@r{]}
|
|
@r{[}--prefix=@var{dir}@r{]}
|
|
@r{[}--srcdir=@var{path}@r{]}
|
|
@r{[}--norecursion@r{]} @r{[}--rm@r{]}
|
|
@r{[}--target=@var{target}@r{]} @var{host}
|
|
@end example
|
|
|
|
@noindent
|
|
You may introduce options with a single @samp{-} rather than
|
|
@samp{--} if you prefer; but you may abbreviate option names if you use
|
|
@samp{--}.
|
|
|
|
@table @code
|
|
@item --help
|
|
Display a quick summary of how to invoke @code{configure}.
|
|
|
|
@item -prefix=@var{dir}
|
|
Configure the source to install programs and files under directory
|
|
@file{@var{dir}}.
|
|
|
|
@item --srcdir=@var{path}
|
|
@strong{Warning: using this option requires GNU @code{make}, or another
|
|
@code{make} that implements the @code{VPATH} feature.}@*
|
|
Use this option to make configurations in directories separate from the
|
|
GDB source directories. Among other things, you can use this to
|
|
build (or maintain) several configurations simultaneously, in separate
|
|
directories. @code{configure} writes configuration specific files in
|
|
the current directory, but arranges for them to use the source in the
|
|
directory @var{path}. @code{configure} will create directories under
|
|
the working directory in parallel to the source directories below
|
|
@var{path}.
|
|
|
|
@item --norecursion
|
|
Configure only the directory level where @code{configure} is executed; do not
|
|
propagate configuration to subdirectories.
|
|
|
|
@item --rm
|
|
Remove the configuration that the other arguments specify.
|
|
|
|
@c This does not work (yet if ever). FIXME.
|
|
@c @item --parse=@var{lang} @dots{}
|
|
@c Configure the GDB expression parser to parse the listed languages.
|
|
@c @samp{all} configures GDB for all supported languages. To get a
|
|
@c list of all supported languages, omit the argument. Without this
|
|
@c option, GDB is configured to parse all supported languages.
|
|
|
|
@item --target=@var{target}
|
|
Configure GDB for cross-debugging programs running on the specified
|
|
@var{target}. Without this option, GDB is configured to debug
|
|
programs that run on the same machine (@var{host}) as GDB itself.
|
|
|
|
There is no convenient way to generate a list of all available targets.
|
|
|
|
@item @var{host} @dots{}
|
|
Configure GDB to run on the specified @var{host}.
|
|
|
|
There is no convenient way to generate a list of all available hosts.
|
|
@end table
|
|
|
|
@noindent
|
|
@code{configure} accepts other options, for compatibility with
|
|
configuring other GNU tools recursively; but these are the only
|
|
options that affect GDB or its supporting libraries.
|
|
@end ifclear
|
|
|
|
@ifclear AGGLOMERATION
|
|
@node Copying
|
|
@unnumbered GNU GENERAL PUBLIC LICENSE
|
|
@center Version 2, June 1991
|
|
|
|
@display
|
|
Copyright @copyright{} 1989, 1991 Free Software Foundation, Inc.
|
|
675 Mass Ave, Cambridge, MA 02139, USA
|
|
|
|
Everyone is permitted to copy and distribute verbatim copies
|
|
of this license document, but changing it is not allowed.
|
|
@end display
|
|
|
|
@unnumberedsec Preamble
|
|
|
|
The licenses for most software are designed to take away your
|
|
freedom to share and change it. By contrast, the GNU General Public
|
|
License is intended to guarantee your freedom to share and change free
|
|
software---to make sure the software is free for all its users. This
|
|
General Public License applies to most of the Free Software
|
|
Foundation's software and to any other program whose authors commit to
|
|
using it. (Some other Free Software Foundation software is covered by
|
|
the GNU Library General Public License instead.) You can apply it to
|
|
your programs, too.
|
|
|
|
When we speak of free software, we are referring to freedom, not
|
|
price. Our General Public Licenses are designed to make sure that you
|
|
have the freedom to distribute copies of free software (and charge for
|
|
this service if you wish), that you receive source code or can get it
|
|
if you want it, that you can change the software or use pieces of it
|
|
in new free programs; and that you know you can do these things.
|
|
|
|
To protect your rights, we need to make restrictions that forbid
|
|
anyone to deny you these rights or to ask you to surrender the rights.
|
|
These restrictions translate to certain responsibilities for you if you
|
|
distribute copies of the software, or if you modify it.
|
|
|
|
For example, if you distribute copies of such a program, whether
|
|
gratis or for a fee, you must give the recipients all the rights that
|
|
you have. You must make sure that they, too, receive or can get the
|
|
source code. And you must show them these terms so they know their
|
|
rights.
|
|
|
|
We protect your rights with two steps: (1) copyright the software, and
|
|
(2) offer you this license which gives you legal permission to copy,
|
|
distribute and/or modify the software.
|
|
|
|
Also, for each author's protection and ours, we want to make certain
|
|
that everyone understands that there is no warranty for this free
|
|
software. If the software is modified by someone else and passed on, we
|
|
want its recipients to know that what they have is not the original, so
|
|
that any problems introduced by others will not reflect on the original
|
|
authors' reputations.
|
|
|
|
Finally, any free program is threatened constantly by software
|
|
patents. We wish to avoid the danger that redistributors of a free
|
|
program will individually obtain patent licenses, in effect making the
|
|
program proprietary. To prevent this, we have made it clear that any
|
|
patent must be licensed for everyone's free use or not licensed at all.
|
|
|
|
The precise terms and conditions for copying, distribution and
|
|
modification follow.
|
|
|
|
@iftex
|
|
@unnumberedsec TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
|
|
@end iftex
|
|
@ifinfo
|
|
@center TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
|
|
@end ifinfo
|
|
|
|
@enumerate
|
|
@item
|
|
This License applies to any program or other work which contains
|
|
a notice placed by the copyright holder saying it may be distributed
|
|
under the terms of this General Public License. The ``Program'', below,
|
|
refers to any such program or work, and a ``work based on the Program''
|
|
means either the Program or any derivative work under copyright law:
|
|
that is to say, a work containing the Program or a portion of it,
|
|
either verbatim or with modifications and/or translated into another
|
|
language. (Hereinafter, translation is included without limitation in
|
|
the term ``modification''.) Each licensee is addressed as ``you''.
|
|
|
|
Activities other than copying, distribution and modification are not
|
|
covered by this License; they are outside its scope. The act of
|
|
running the Program is not restricted, and the output from the Program
|
|
is covered only if its contents constitute a work based on the
|
|
Program (independent of having been made by running the Program).
|
|
Whether that is true depends on what the Program does.
|
|
|
|
@item
|
|
You may copy and distribute verbatim copies of the Program's
|
|
source code as you receive it, in any medium, provided that you
|
|
conspicuously and appropriately publish on each copy an appropriate
|
|
copyright notice and disclaimer of warranty; keep intact all the
|
|
notices that refer to this License and to the absence of any warranty;
|
|
and give any other recipients of the Program a copy of this License
|
|
along with the Program.
|
|
|
|
You may charge a fee for the physical act of transferring a copy, and
|
|
you may at your option offer warranty protection in exchange for a fee.
|
|
|
|
@item
|
|
You may modify your copy or copies of the Program or any portion
|
|
of it, thus forming a work based on the Program, and copy and
|
|
distribute such modifications or work under the terms of Section 1
|
|
above, provided that you also meet all of these conditions:
|
|
|
|
@enumerate a
|
|
@item
|
|
You must cause the modified files to carry prominent notices
|
|
stating that you changed the files and the date of any change.
|
|
|
|
@item
|
|
You must cause any work that you distribute or publish, that in
|
|
whole or in part contains or is derived from the Program or any
|
|
part thereof, to be licensed as a whole at no charge to all third
|
|
parties under the terms of this License.
|
|
|
|
@item
|
|
If the modified program normally reads commands interactively
|
|
when run, you must cause it, when started running for such
|
|
interactive use in the most ordinary way, to print or display an
|
|
announcement including an appropriate copyright notice and a
|
|
notice that there is no warranty (or else, saying that you provide
|
|
a warranty) and that users may redistribute the program under
|
|
these conditions, and telling the user how to view a copy of this
|
|
License. (Exception: if the Program itself is interactive but
|
|
does not normally print such an announcement, your work based on
|
|
the Program is not required to print an announcement.)
|
|
@end enumerate
|
|
|
|
These requirements apply to the modified work as a whole. If
|
|
identifiable sections of that work are not derived from the Program,
|
|
and can be reasonably considered independent and separate works in
|
|
themselves, then this License, and its terms, do not apply to those
|
|
sections when you distribute them as separate works. But when you
|
|
distribute the same sections as part of a whole which is a work based
|
|
on the Program, the distribution of the whole must be on the terms of
|
|
this License, whose permissions for other licensees extend to the
|
|
entire whole, and thus to each and every part regardless of who wrote it.
|
|
|
|
Thus, it is not the intent of this section to claim rights or contest
|
|
your rights to work written entirely by you; rather, the intent is to
|
|
exercise the right to control the distribution of derivative or
|
|
collective works based on the Program.
|
|
|
|
In addition, mere aggregation of another work not based on the Program
|
|
with the Program (or with a work based on the Program) on a volume of
|
|
a storage or distribution medium does not bring the other work under
|
|
the scope of this License.
|
|
|
|
@item
|
|
You may copy and distribute the Program (or a work based on it,
|
|
under Section 2) in object code or executable form under the terms of
|
|
Sections 1 and 2 above provided that you also do one of the following:
|
|
|
|
@enumerate a
|
|
@item
|
|
Accompany it with the complete corresponding machine-readable
|
|
source code, which must be distributed under the terms of Sections
|
|
1 and 2 above on a medium customarily used for software interchange; or,
|
|
|
|
@item
|
|
Accompany it with a written offer, valid for at least three
|
|
years, to give any third party, for a charge no more than your
|
|
cost of physically performing source distribution, a complete
|
|
machine-readable copy of the corresponding source code, to be
|
|
distributed under the terms of Sections 1 and 2 above on a medium
|
|
customarily used for software interchange; or,
|
|
|
|
@item
|
|
Accompany it with the information you received as to the offer
|
|
to distribute corresponding source code. (This alternative is
|
|
allowed only for noncommercial distribution and only if you
|
|
received the program in object code or executable form with such
|
|
an offer, in accord with Subsection b above.)
|
|
@end enumerate
|
|
|
|
The source code for a work means the preferred form of the work for
|
|
making modifications to it. For an executable work, complete source
|
|
code means all the source code for all modules it contains, plus any
|
|
associated interface definition files, plus the scripts used to
|
|
control compilation and installation of the executable. However, as a
|
|
special exception, the source code distributed need not include
|
|
anything that is normally distributed (in either source or binary
|
|
form) with the major components (compiler, kernel, and so on) of the
|
|
operating system on which the executable runs, unless that component
|
|
itself accompanies the executable.
|
|
|
|
If distribution of executable or object code is made by offering
|
|
access to copy from a designated place, then offering equivalent
|
|
access to copy the source code from the same place counts as
|
|
distribution of the source code, even though third parties are not
|
|
compelled to copy the source along with the object code.
|
|
|
|
@item
|
|
You may not copy, modify, sublicense, or distribute the Program
|
|
except as expressly provided under this License. Any attempt
|
|
otherwise to copy, modify, sublicense or distribute the Program is
|
|
void, and will automatically terminate your rights under this License.
|
|
However, parties who have received copies, or rights, from you under
|
|
this License will not have their licenses terminated so long as such
|
|
parties remain in full compliance.
|
|
|
|
@item
|
|
You are not required to accept this License, since you have not
|
|
signed it. However, nothing else grants you permission to modify or
|
|
distribute the Program or its derivative works. These actions are
|
|
prohibited by law if you do not accept this License. Therefore, by
|
|
modifying or distributing the Program (or any work based on the
|
|
Program), you indicate your acceptance of this License to do so, and
|
|
all its terms and conditions for copying, distributing or modifying
|
|
the Program or works based on it.
|
|
|
|
@item
|
|
Each time you redistribute the Program (or any work based on the
|
|
Program), the recipient automatically receives a license from the
|
|
original licensor to copy, distribute or modify the Program subject to
|
|
these terms and conditions. You may not impose any further
|
|
restrictions on the recipients' exercise of the rights granted herein.
|
|
You are not responsible for enforcing compliance by third parties to
|
|
this License.
|
|
|
|
@item
|
|
If, as a consequence of a court judgment or allegation of patent
|
|
infringement or for any other reason (not limited to patent issues),
|
|
conditions are imposed on you (whether by court order, agreement or
|
|
otherwise) that contradict the conditions of this License, they do not
|
|
excuse you from the conditions of this License. If you cannot
|
|
distribute so as to satisfy simultaneously your obligations under this
|
|
License and any other pertinent obligations, then as a consequence you
|
|
may not distribute the Program at all. For example, if a patent
|
|
license would not permit royalty-free redistribution of the Program by
|
|
all those who receive copies directly or indirectly through you, then
|
|
the only way you could satisfy both it and this License would be to
|
|
refrain entirely from distribution of the Program.
|
|
|
|
If any portion of this section is held invalid or unenforceable under
|
|
any particular circumstance, the balance of the section is intended to
|
|
apply and the section as a whole is intended to apply in other
|
|
circumstances.
|
|
|
|
It is not the purpose of this section to induce you to infringe any
|
|
patents or other property right claims or to contest validity of any
|
|
such claims; this section has the sole purpose of protecting the
|
|
integrity of the free software distribution system, which is
|
|
implemented by public license practices. Many people have made
|
|
generous contributions to the wide range of software distributed
|
|
through that system in reliance on consistent application of that
|
|
system; it is up to the author/donor to decide if he or she is willing
|
|
to distribute software through any other system and a licensee cannot
|
|
impose that choice.
|
|
|
|
This section is intended to make thoroughly clear what is believed to
|
|
be a consequence of the rest of this License.
|
|
|
|
@item
|
|
If the distribution and/or use of the Program is restricted in
|
|
certain countries either by patents or by copyrighted interfaces, the
|
|
original copyright holder who places the Program under this License
|
|
may add an explicit geographical distribution limitation excluding
|
|
those countries, so that distribution is permitted only in or among
|
|
countries not thus excluded. In such case, this License incorporates
|
|
the limitation as if written in the body of this License.
|
|
|
|
@item
|
|
The Free Software Foundation may publish revised and/or new versions
|
|
of the General Public License from time to time. Such new versions will
|
|
be similar in spirit to the present version, but may differ in detail to
|
|
address new problems or concerns.
|
|
|
|
Each version is given a distinguishing version number. If the Program
|
|
specifies a version number of this License which applies to it and ``any
|
|
later version'', you have the option of following the terms and conditions
|
|
either of that version or of any later version published by the Free
|
|
Software Foundation. If the Program does not specify a version number of
|
|
this License, you may choose any version ever published by the Free Software
|
|
Foundation.
|
|
|
|
@item
|
|
If you wish to incorporate parts of the Program into other free
|
|
programs whose distribution conditions are different, write to the author
|
|
to ask for permission. For software which is copyrighted by the Free
|
|
Software Foundation, write to the Free Software Foundation; we sometimes
|
|
make exceptions for this. Our decision will be guided by the two goals
|
|
of preserving the free status of all derivatives of our free software and
|
|
of promoting the sharing and reuse of software generally.
|
|
|
|
@iftex
|
|
@heading NO WARRANTY
|
|
@end iftex
|
|
@ifinfo
|
|
@center NO WARRANTY
|
|
@end ifinfo
|
|
|
|
@item
|
|
BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
|
|
FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN
|
|
OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
|
|
PROVIDE THE PROGRAM ``AS IS'' WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
|
|
OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
|
|
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS
|
|
TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE
|
|
PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
|
|
REPAIR OR CORRECTION.
|
|
|
|
@item
|
|
IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
|
|
WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
|
|
REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
|
|
INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
|
|
OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED
|
|
TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY
|
|
YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
|
|
PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
|
|
POSSIBILITY OF SUCH DAMAGES.
|
|
@end enumerate
|
|
|
|
@iftex
|
|
@heading END OF TERMS AND CONDITIONS
|
|
@end iftex
|
|
@ifinfo
|
|
@center END OF TERMS AND CONDITIONS
|
|
@end ifinfo
|
|
|
|
@page
|
|
@unnumberedsec Applying These Terms to Your New Programs
|
|
|
|
If you develop a new program, and you want it to be of the greatest
|
|
possible use to the public, the best way to achieve this is to make it
|
|
free software which everyone can redistribute and change under these terms.
|
|
|
|
To do so, attach the following notices to the program. It is safest
|
|
to attach them to the start of each source file to most effectively
|
|
convey the exclusion of warranty; and each file should have at least
|
|
the ``copyright'' line and a pointer to where the full notice is found.
|
|
|
|
@smallexample
|
|
@var{one line to give the program's name and an idea of what it does.}
|
|
Copyright (C) 19@var{yy} @var{name of author}
|
|
|
|
This program is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU General Public License
|
|
as published by the Free Software Foundation; either version 2
|
|
of the License, or (at your option) any later version.
|
|
|
|
This program is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
GNU General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with this program; if not, write to the
|
|
Free Software Foundation, Inc., 675 Mass Ave,
|
|
Cambridge, MA 02139, USA.
|
|
@end smallexample
|
|
|
|
Also add information on how to contact you by electronic and paper mail.
|
|
|
|
If the program is interactive, make it output a short notice like this
|
|
when it starts in an interactive mode:
|
|
|
|
@smallexample
|
|
Gnomovision version 69, Copyright (C) 19@var{yy} @var{name of author}
|
|
Gnomovision comes with ABSOLUTELY NO WARRANTY; for details
|
|
type `show w'. This is free software, and you are welcome
|
|
to redistribute it under certain conditions; type `show c'
|
|
for details.
|
|
@end smallexample
|
|
|
|
The hypothetical commands @samp{show w} and @samp{show c} should show
|
|
the appropriate parts of the General Public License. Of course, the
|
|
commands you use may be called something other than @samp{show w} and
|
|
@samp{show c}; they could even be mouse-clicks or menu items---whatever
|
|
suits your program.
|
|
|
|
You should also get your employer (if you work as a programmer) or your
|
|
school, if any, to sign a ``copyright disclaimer'' for the program, if
|
|
necessary. Here is a sample; alter the names:
|
|
|
|
@example
|
|
Yoyodyne, Inc., hereby disclaims all copyright
|
|
interest in the program `Gnomovision'
|
|
(which makes passes at compilers) written
|
|
by James Hacker.
|
|
|
|
@var{signature of Ty Coon}, 1 April 1989
|
|
Ty Coon, President of Vice
|
|
@end example
|
|
|
|
This General Public License does not permit incorporating your program into
|
|
proprietary programs. If your program is a subroutine library, you may
|
|
consider it more useful to permit linking proprietary applications with the
|
|
library. If this is what you want to do, use the GNU Library General
|
|
Public License instead of this License.
|
|
@end ifclear
|
|
|
|
@node Index
|
|
@unnumbered Index
|
|
|
|
@printindex cp
|
|
|
|
@tex
|
|
% I think something like @colophon should be in texinfo. In the
|
|
% meantime:
|
|
\long\def\colophon{\hbox to0pt{}\vfill
|
|
\centerline{The body of this manual is set in}
|
|
\centerline{\fontname\tenrm,}
|
|
\centerline{with headings in {\bf\fontname\tenbf}}
|
|
\centerline{and examples in {\tt\fontname\tentt}.}
|
|
\centerline{{\it\fontname\tenit\/},}
|
|
\centerline{{\bf\fontname\tenbf}, and}
|
|
\centerline{{\sl\fontname\tensl\/}}
|
|
\centerline{are used for emphasis.}\vfill}
|
|
\page\colophon
|
|
% Blame: pesch@cygnus.com, 1991.
|
|
@end tex
|
|
|
|
@contents
|
|
@bye
|