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14884 lines
528 KiB
Plaintext
14884 lines
528 KiB
Plaintext
\input texinfo @c -*-texinfo-*-
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@c Copyright 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
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@c 1999, 2000, 2001
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@c 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-cfg.texi
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@c
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@settitle Debugging with @value{GDBN}
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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, @findex and @ftable,
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@c annotate.texi and gdbmi use @findex.
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@syncodeindex vr cp
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@syncodeindex fn cp
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@c !!set GDB manual's edition---not the same as GDB version!
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@set EDITION Ninth
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@c !!set GDB manual's revision date
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@set DATE December 2001
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@c THIS MANUAL REQUIRES TEXINFO 3.12 OR LATER.
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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.
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@dircategory Programming & development tools.
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@direntry
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* Gdb: (gdb). The @sc{gnu} debugger.
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@end direntry
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@ifinfo
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This file documents the @sc{gnu} debugger @value{GDBN}.
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This is the @value{EDITION} Edition, @value{DATE},
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of @cite{Debugging with @value{GDBN}: the @sc{gnu} Source-Level Debugger}
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for @value{GDBN} Version @value{GDBVN}.
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Copyright (C) 1988,1989,1990,1991,1992,1993,1994,1995,1996,1998,1999,2000,2001
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Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.1 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being ``Free Software'' and ``Free Software Needs
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Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
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and with the Back-Cover Texts as in (a) below.
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(a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
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this GNU Manual, like GNU software. Copies published by the Free
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Software Foundation raise funds for GNU development.''
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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 @sc{gnu} Source-Level Debugger
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@sp 1
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@subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
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@subtitle @value{DATE}
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@author Richard Stallman, Roland Pesch, Stan Shebs, et al.
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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\@gnu.org.)\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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}
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@end tex
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@vskip 0pt plus 1filll
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Copyright @copyright{} 1988,1989,1990,1991,1992,1993,1994,1995,1996,1998,1999,2000,2001
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Free Software Foundation, Inc.
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@sp 2
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Published by the Free Software Foundation @*
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59 Temple Place - Suite 330, @*
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Boston, MA 02111-1307 USA @*
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ISBN 1-882114-77-9 @*
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.1 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being ``Free Software'' and ``Free Software Needs
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Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
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and with the Back-Cover Texts as in (a) below.
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(a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
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this GNU Manual, like GNU software. Copies published by the Free
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Software Foundation raise funds for GNU development.''
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@end titlepage
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@page
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@ifinfo
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@node Top, Summary, (dir), (dir)
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@top Debugging with @value{GDBN}
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This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
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This is the @value{EDITION} Edition, @value{DATE}, for @value{GDBN} Version
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@value{GDBVN}.
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Copyright (C) 1988-2001 Free Software Foundation, Inc.
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@menu
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* Summary:: Summary of @value{GDBN}
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* Sample Session:: A sample @value{GDBN} session
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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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* Tracepoints:: Debugging remote targets non-intrusively
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* Overlays:: Debugging programs that use overlays
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* Languages:: Using @value{GDBN} with different languages
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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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* Configurations:: Configuration-specific information
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* Controlling GDB:: Controlling @value{GDBN}
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* Sequences:: Canned sequences of commands
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* TUI:: @value{GDBN} Text User Interface
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* Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
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* Annotations:: @value{GDBN}'s annotation interface.
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* GDB/MI:: @value{GDBN}'s Machine Interface.
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* GDB Bugs:: Reporting bugs in @value{GDBN}
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* Formatting Documentation:: How to format and print @value{GDBN} documentation
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* Command Line Editing:: Command Line Editing
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* Using History Interactively:: Using History Interactively
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* Installing GDB:: Installing GDB
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* Index:: Index
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@end menu
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@end ifinfo
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@c the replication sucks, but this avoids a texinfo 3.12 lameness
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@ifhtml
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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 @sc{gnu} symbolic debugger.
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This is the @value{EDITION} Edition, @value{DATE}, for @value{GDBN} Version
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@value{GDBVN}.
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Copyright (C) 1988-2000 Free Software Foundation, Inc.
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@menu
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* Summary:: Summary of @value{GDBN}
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* Sample Session:: A sample @value{GDBN} session
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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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* Tracepoints:: Debugging remote targets non-intrusively
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* Overlays:: Debugging programs that use overlays
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* Languages:: Using @value{GDBN} with different languages
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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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* Configurations:: Configuration-specific information
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* Controlling GDB:: Controlling @value{GDBN}
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* Sequences:: Canned sequences of commands
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* TUI:: @value{GDBN} Text User Interface
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* Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
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* Annotations:: @value{GDBN}'s annotation interface.
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* GDB/MI:: @value{GDBN}'s Machine Interface.
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* GDB Bugs:: Reporting bugs in @value{GDBN}
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* Formatting Documentation:: How to format and print @value{GDBN} documentation
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* Command Line Editing:: Command Line Editing
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* Using History Interactively:: Using History Interactively
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* Installing GDB:: Installing GDB
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* Index:: Index
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@end menu
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@end ifhtml
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@c TeX can handle the contents at the start but makeinfo 3.12 can not
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@iftex
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@contents
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@end iftex
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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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You can use @value{GDBN} to debug programs written in C and C++.
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For more information, see @ref{Support,,Supported languages}.
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For more information, see @ref{C,,C and C++}.
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@cindex Chill
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@cindex Modula-2
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Support for Modula-2 and Chill is partial. For information on Modula-2,
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see @ref{Modula-2,,Modula-2}. For information on Chill, see @ref{Chill}.
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@cindex Pascal
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Debugging Pascal programs which use sets, subranges, file variables, or
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nested functions does not currently work. @value{GDBN} does not support
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entering expressions, printing values, or similar features using Pascal
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syntax.
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@cindex Fortran
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@value{GDBN} can be used to debug programs written in Fortran, although
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it may be necessary to refer to some variables with a trailing
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underscore.
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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 @sc{gnu}
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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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@unnumberedsec Free Software Needs Free Documentation
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The biggest deficiency in the free software community today is not in
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the software---it is the lack of good free documentation that we can
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include with the free software. Many of our most important
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programs do not come with free reference manuals and free introductory
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texts. Documentation is an essential part of any software package;
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when an important free software package does not come with a free
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manual and a free tutorial, that is a major gap. We have many such
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gaps today.
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Consider Perl, for instance. The tutorial manuals that people
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normally use are non-free. How did this come about? Because the
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authors of those manuals published them with restrictive terms---no
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copying, no modification, source files not available---which exclude
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them from the free software world.
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That wasn't the first time this sort of thing happened, and it was far
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from the last. Many times we have heard a GNU user eagerly describe a
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manual that he is writing, his intended contribution to the community,
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only to learn that he had ruined everything by signing a publication
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contract to make it non-free.
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Free documentation, like free software, is a matter of freedom, not
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price. The problem with the non-free manual is not that publishers
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charge a price for printed copies---that in itself is fine. (The Free
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Software Foundation sells printed copies of manuals, too.) The
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problem is the restrictions on the use of the manual. Free manuals
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are available in source code form, and give you permission to copy and
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modify. Non-free manuals do not allow this.
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The criteria of freedom for a free manual are roughly the same as for
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free software. Redistribution (including the normal kinds of
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commercial redistribution) must be permitted, so that the manual can
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accompany every copy of the program, both on-line and on paper.
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Permission for modification of the technical content is crucial too.
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When people modify the software, adding or changing features, if they
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are conscientious they will change the manual too---so they can
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provide accurate and clear documentation for the modified program. A
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manual that leaves you no choice but to write a new manual to document
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a changed version of the program is not really available to our
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community.
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Some kinds of limits on the way modification is handled are
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acceptable. For example, requirements to preserve the original
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author's copyright notice, the distribution terms, or the list of
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authors, are ok. It is also no problem to require modified versions
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to include notice that they were modified. Even entire sections that
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may not be deleted or changed are acceptable, as long as they deal
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with nontechnical topics (like this one). These kinds of restrictions
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are acceptable because they don't obstruct the community's normal use
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of the manual.
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However, it must be possible to modify all the @emph{technical}
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content of the manual, and then distribute the result in all the usual
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media, through all the usual channels. Otherwise, the restrictions
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obstruct the use of the manual, it is not free, and we need another
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manual to replace it.
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Please spread the word about this issue. Our community continues to
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lose manuals to proprietary publishing. If we spread the word that
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free software needs free reference manuals and free tutorials, perhaps
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the next person who wants to contribute by writing documentation will
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realize, before it is too late, that only free manuals contribute to
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the free software community.
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If you are writing documentation, please insist on publishing it under
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the GNU Free Documentation License or another free documentation
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license. Remember that this decision requires your approval---you
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don't have to let the publisher decide. Some commercial publishers
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will use a free license if you insist, but they will not propose the
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option; it is up to you to raise the issue and say firmly that this is
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what you want. If the publisher you are dealing with refuses, please
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try other publishers. If you're not sure whether a proposed license
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is free, write to @email{licensing@@gnu.org}.
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You can encourage commercial publishers to sell more free, copylefted
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manuals and tutorials by buying them, and particularly by buying
|
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copies from the publishers that paid for their writing or for major
|
|
improvements. Meanwhile, try to avoid buying non-free documentation
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at all. Check the distribution terms of a manual before you buy it,
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and insist that whoever seeks your business must respect your freedom.
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Check the history of the book, and try to reward the publishers that
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have paid or pay the authors to work on it.
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The Free Software Foundation maintains a list of free documentation
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published by other publishers, at
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@url{http://www.fsf.org/doc/other-free-books.html}.
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@node Contributors
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@unnumberedsec Contributors to @value{GDBN}
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Richard Stallman was the original author of @value{GDBN}, and of many
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other @sc{gnu} programs. Many others have contributed to its
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development. This section attempts to credit major contributors. One
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of the virtues of free software is that everyone is free to contribute
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to it; with regret, we cannot actually acknowledge everyone here. The
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file @file{ChangeLog} in the @value{GDBN} distribution approximates a
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blow-by-blow 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 many labors as thankless, we
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particularly thank those who shepherded @value{GDBN} through major
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releases:
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Andrew Cagney (releases 5.0 and 5.1);
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|
Jim Blandy (release 4.18);
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|
Jason Molenda (release 4.17);
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|
Stan Shebs (release 4.14);
|
|
Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
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Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
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John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
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Jim Kingdon (releases 3.5, 3.4, and 3.3);
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and Randy Smith (releases 3.2, 3.1, and 3.0).
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Richard Stallman, assisted at various times by Peter TerMaat, Chris
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|
Hanson, and Richard Mlynarik, handled releases through 2.8.
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Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
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in @value{GDBN}, with significant additional contributions from Per
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|
Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
|
|
demangler. Early work on C@t{++} was by Peter TerMaat (who also did
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|
much general update work leading to release 3.0).
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|
@value{GDBN} 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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|
Brent Benson of Harris Computer Systems contributed DWARF2 support.
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|
Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
|
|
Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
|
|
support.
|
|
Jean-Daniel Fekete contributed Sun 386i support.
|
|
Chris Hanson improved the HP9000 support.
|
|
Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
|
|
David Johnson contributed Encore Umax support.
|
|
Jyrki Kuoppala contributed Altos 3068 support.
|
|
Jeff Law contributed HP PA and SOM support.
|
|
Keith Packard contributed NS32K support.
|
|
Doug Rabson contributed Acorn Risc Machine support.
|
|
Bob Rusk contributed Harris Nighthawk CX-UX support.
|
|
Chris Smith contributed Convex support (and Fortran debugging).
|
|
Jonathan Stone contributed Pyramid support.
|
|
Michael Tiemann contributed SPARC support.
|
|
Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
|
|
Pace Willison contributed Intel 386 support.
|
|
Jay Vosburgh contributed Symmetry support.
|
|
|
|
Andreas Schwab contributed M68K Linux support.
|
|
|
|
Rich Schaefer and Peter Schauer helped with support of SunOS shared
|
|
libraries.
|
|
|
|
Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
|
|
about several machine instruction sets.
|
|
|
|
Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
|
|
remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
|
|
contributed remote debugging modules for the i960, VxWorks, A29K UDI,
|
|
and RDI targets, respectively.
|
|
|
|
Brian Fox is the author of the readline libraries providing
|
|
command-line editing and command history.
|
|
|
|
Andrew Beers of SUNY Buffalo wrote the language-switching code, the
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|
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.
|
|
He also enhanced the command-completion support to cover C@t{++} overloaded
|
|
symbols.
|
|
|
|
Hitachi America, Ltd. sponsored the support for H8/300, H8/500, and
|
|
Super-H processors.
|
|
|
|
NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
|
|
|
|
Mitsubishi sponsored the support for D10V, D30V, and M32R/D processors.
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|
|
Toshiba sponsored the support for the TX39 Mips processor.
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|
|
|
Matsushita sponsored the support for the MN10200 and MN10300 processors.
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|
|
Fujitsu sponsored the support for SPARClite and FR30 processors.
|
|
|
|
Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
|
|
watchpoints.
|
|
|
|
Michael Snyder added support for tracepoints.
|
|
|
|
Stu Grossman wrote gdbserver.
|
|
|
|
Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
|
|
nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
|
|
|
|
The following people at the Hewlett-Packard Company contributed
|
|
support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
|
|
(narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
|
|
compiler, and the terminal user interface: Ben Krepp, Richard Title,
|
|
John Bishop, Susan Macchia, Kathy Mann, Satish Pai, India Paul, Steve
|
|
Rehrauer, and Elena Zannoni. Kim Haase provided HP-specific
|
|
information in this manual.
|
|
|
|
DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
|
|
Robert Hoehne made significant contributions to the DJGPP port.
|
|
|
|
Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
|
|
development since 1991. Cygnus engineers who have worked on @value{GDBN}
|
|
fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
|
|
Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
|
|
Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
|
|
Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
|
|
Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
|
|
addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
|
|
JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
|
|
Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
|
|
Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
|
|
Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
|
|
Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
|
|
Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
|
|
Zuhn have made contributions both large and small.
|
|
|
|
|
|
@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 @sc{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
|
|
$ @b{cd gnu/m4}
|
|
$ @b{./m4}
|
|
@b{define(foo,0000)}
|
|
|
|
@b{foo}
|
|
0000
|
|
@b{define(bar,defn(`foo'))}
|
|
|
|
@b{bar}
|
|
0000
|
|
@b{changequote(<QUOTE>,<UNQUOTE>)}
|
|
|
|
@b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
|
|
@b{baz}
|
|
@b{C-d}
|
|
m4: End of input: 0: fatal error: EOF in string
|
|
@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.
|
|
@value{GDBN} 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 @value{GDBN}; type "show warranty"
|
|
for details.
|
|
|
|
@value{GDBN} @value{GDBVN}, Copyright 1999 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 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 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
|
|
|
|
@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 are:
|
|
@itemize @bullet
|
|
@item
|
|
type @samp{@value{GDBP}} to start @value{GDBN}.
|
|
@item
|
|
type @kbd{quit} or @kbd{C-d} to exit.
|
|
@end itemize
|
|
|
|
@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}
|
|
|
|
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.
|
|
|
|
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.
|
|
|
|
The most usual way to start @value{GDBN} is with one argument,
|
|
specifying an executable program:
|
|
|
|
@example
|
|
@value{GDBP} @var{program}
|
|
@end example
|
|
|
|
@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. @value{GDBN}
|
|
will warn you if it is unable to attach or to read core dumps.
|
|
|
|
You can optionally have @code{@value{GDBP}} pass any arguments after the
|
|
executable file to the inferior using @code{--args}. This option stops
|
|
option processing.
|
|
@example
|
|
gdb --args gcc -O2 -c foo.c
|
|
@end example
|
|
This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
|
|
@code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
|
|
|
|
You can run @code{@value{GDBP}} without printing the front material, which describes
|
|
@value{GDBN}'s non-warranty, by specifying @code{-silent}:
|
|
|
|
@smallexample
|
|
@value{GDBP} -silent
|
|
@end smallexample
|
|
|
|
@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
|
|
* File Options:: Choosing files
|
|
* Mode Options:: Choosing modes
|
|
@end menu
|
|
|
|
@node File Options
|
|
@subsection Choosing files
|
|
|
|
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} (or @samp{-p} 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}/@samp{-p} option followed by that argument.)
|
|
If the second argument begins with a decimal digit, @value{GDBN} will
|
|
first attempt to attach to it as a process, and if that fails, attempt
|
|
to open it as a corefile. If you have a corefile whose name begins with
|
|
a digit, you can prevent @value{GDBN} from treating it as a pid by
|
|
prefixing it with @file{./}, eg. @file{./12345}.
|
|
|
|
If @value{GDBN} has not been configured to included core file support,
|
|
such as for most embedded targets, then it will complain about a second
|
|
argument and ignore it.
|
|
|
|
Many options have both long and short forms; both are shown in the
|
|
following list. @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.)
|
|
|
|
@c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
|
|
@c way, both those who look for -foo and --foo in the index, will find
|
|
@c it.
|
|
|
|
@table @code
|
|
@item -symbols @var{file}
|
|
@itemx -s @var{file}
|
|
@cindex @code{--symbols}
|
|
@cindex @code{-s}
|
|
Read symbol table from file @var{file}.
|
|
|
|
@item -exec @var{file}
|
|
@itemx -e @var{file}
|
|
@cindex @code{--exec}
|
|
@cindex @code{-e}
|
|
Use file @var{file} as the executable file to execute when appropriate,
|
|
and for examining pure data in conjunction with a core dump.
|
|
|
|
@item -se @var{file}
|
|
@cindex @code{--se}
|
|
Read symbol table from file @var{file} and use it as the executable
|
|
file.
|
|
|
|
@item -core @var{file}
|
|
@itemx -c @var{file}
|
|
@cindex @code{--core}
|
|
@cindex @code{-c}
|
|
Use file @var{file} as a core dump to examine.
|
|
|
|
@item -c @var{number}
|
|
@item -pid @var{number}
|
|
@itemx -p @var{number}
|
|
@cindex @code{--pid}
|
|
@cindex @code{-p}
|
|
Connect to process ID @var{number}, as with the @code{attach} command.
|
|
If there is no such process, @value{GDBN} will attempt to open a core
|
|
file named @var{number}.
|
|
|
|
@item -command @var{file}
|
|
@itemx -x @var{file}
|
|
@cindex @code{--command}
|
|
@cindex @code{-x}
|
|
Execute @value{GDBN} commands from file @var{file}. @xref{Command
|
|
Files,, Command files}.
|
|
|
|
@item -directory @var{directory}
|
|
@itemx -d @var{directory}
|
|
@cindex @code{--directory}
|
|
@cindex @code{-d}
|
|
Add @var{directory} to the path to search for source files.
|
|
|
|
@item -m
|
|
@itemx -mapped
|
|
@cindex @code{--mapped}
|
|
@cindex @code{-m}
|
|
@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 is @file{/tmp/fred.syms}.
|
|
Future @value{GDBN} debugging sessions notice the presence of this file,
|
|
and can quickly map in symbol information from it, rather than reading
|
|
the symbol table from the executable program.
|
|
|
|
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.
|
|
|
|
@item -r
|
|
@itemx -readnow
|
|
@cindex @code{--readnow}
|
|
@cindex @code{-r}
|
|
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
|
|
|
|
You typically combine the @code{-mapped} and @code{-readnow} options 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 @value{GDBN} invocation to do nothing
|
|
but build a @file{.syms} file for future use is:
|
|
|
|
@example
|
|
gdb -batch -nx -mapped -readnow programname
|
|
@end example
|
|
|
|
@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
|
|
@cindex @code{--nx}
|
|
@cindex @code{-n}
|
|
Do not execute commands found in any initialization files. Normally,
|
|
@value{GDBN} executes the commands in these files after all the command
|
|
options and arguments have been processed. @xref{Command Files,,Command
|
|
files}.
|
|
|
|
@item -quiet
|
|
@itemx -silent
|
|
@itemx -q
|
|
@cindex @code{--quiet}
|
|
@cindex @code{--silent}
|
|
@cindex @code{-q}
|
|
``Quiet''. Do not print the introductory and copyright messages. These
|
|
messages are also suppressed in batch mode.
|
|
|
|
@item -batch
|
|
@cindex @code{--batch}
|
|
Run in batch mode. Exit with status @code{0} after processing all the
|
|
command files specified with @samp{-x} (and all commands from
|
|
initialization files, if not inhibited with @samp{-n}). 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 -nowindows
|
|
@itemx -nw
|
|
@cindex @code{--nowindows}
|
|
@cindex @code{-nw}
|
|
``No windows''. If @value{GDBN} comes with a graphical user interface
|
|
(GUI) built in, then this option tells @value{GDBN} to only use the command-line
|
|
interface. If no GUI is available, this option has no effect.
|
|
|
|
@item -windows
|
|
@itemx -w
|
|
@cindex @code{--windows}
|
|
@cindex @code{-w}
|
|
If @value{GDBN} includes a GUI, then this option requires it to be
|
|
used if possible.
|
|
|
|
@item -cd @var{directory}
|
|
@cindex @code{--cd}
|
|
Run @value{GDBN} using @var{directory} as its working directory,
|
|
instead of the current directory.
|
|
|
|
@item -fullname
|
|
@itemx -f
|
|
@cindex @code{--fullname}
|
|
@cindex @code{-f}
|
|
@sc{gnu} 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.
|
|
|
|
@item -epoch
|
|
@cindex @code{--epoch}
|
|
The Epoch Emacs-@value{GDBN} interface sets this option when it runs
|
|
@value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
|
|
routines so as to allow Epoch to display values of expressions in a
|
|
separate window.
|
|
|
|
@item -annotate @var{level}
|
|
@cindex @code{--annotate}
|
|
This option sets the @dfn{annotation level} inside @value{GDBN}. Its
|
|
effect is identical to using @samp{set annotate @var{level}}
|
|
(@pxref{Annotations}).
|
|
Annotation level controls how much information does @value{GDBN} print
|
|
together with its prompt, values of expressions, source lines, and other
|
|
types of output. Level 0 is the normal, level 1 is for use when
|
|
@value{GDBN} is run as a subprocess of @sc{gnu} Emacs, level 2 is the
|
|
maximum annotation suitable for programs that control @value{GDBN}.
|
|
|
|
@item -async
|
|
@cindex @code{--async}
|
|
Use the asynchronous event loop for the command-line interface.
|
|
@value{GDBN} processes all events, such as user keyboard input, via a
|
|
special event loop. This allows @value{GDBN} to accept and process user
|
|
commands in parallel with the debugged process being
|
|
run@footnote{@value{GDBN} built with @sc{djgpp} tools for
|
|
MS-DOS/MS-Windows supports this mode of operation, but the event loop is
|
|
suspended when the debuggee runs.}, so you don't need to wait for
|
|
control to return to @value{GDBN} before you type the next command.
|
|
(@emph{Note:} as of version 5.1, the target side of the asynchronous
|
|
operation is not yet in place, so @samp{-async} does not work fully
|
|
yet.)
|
|
@c FIXME: when the target side of the event loop is done, the above NOTE
|
|
@c should be removed.
|
|
|
|
When the standard input is connected to a terminal device, @value{GDBN}
|
|
uses the asynchronous event loop by default, unless disabled by the
|
|
@samp{-noasync} option.
|
|
|
|
@item -noasync
|
|
@cindex @code{--noasync}
|
|
Disable the asynchronous event loop for the command-line interface.
|
|
|
|
@item --args
|
|
@cindex @code{--args}
|
|
Change interpretation of command line so that arguments following the
|
|
executable file are passed as command line arguments to the inferior.
|
|
This option stops option processing.
|
|
|
|
@item -baud @var{bps}
|
|
@itemx -b @var{bps}
|
|
@cindex @code{--baud}
|
|
@cindex @code{-b}
|
|
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}
|
|
@itemx -t @var{device}
|
|
@cindex @code{--tty}
|
|
@cindex @code{-t}
|
|
Run using @var{device} for your program's standard input and output.
|
|
@c FIXME: kingdon thinks there is more to -tty. Investigate.
|
|
|
|
@c resolve the situation of these eventually
|
|
@item -tui
|
|
@cindex @code{--tui}
|
|
Activate the Terminal User Interface when starting.
|
|
The Terminal User Interface manages several text windows on the terminal,
|
|
showing source, assembly, registers and @value{GDBN} command outputs
|
|
(@pxref{TUI, ,@value{GDBN} Text User Interface}).
|
|
Do not use this option if you run @value{GDBN} from Emacs
|
|
(@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
|
|
|
|
@c @item -xdb
|
|
@c @cindex @code{--xdb}
|
|
@c Run in XDB compatibility mode, allowing the use of certain XDB commands.
|
|
@c For information, see the file @file{xdb_trans.html}, which is usually
|
|
@c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
|
|
@c systems.
|
|
|
|
@item -interpreter @var{interp}
|
|
@cindex @code{--interpreter}
|
|
Use the interpreter @var{interp} for interface with the controlling
|
|
program or device. This option is meant to be set by programs which
|
|
communicate with @value{GDBN} using it as a back end.
|
|
|
|
@samp{--interpreter=mi} (or @samp{--interpreter=mi1}) causes
|
|
@value{GDBN} to use the @dfn{gdb/mi interface} (@pxref{GDB/MI, , The
|
|
@sc{gdb/mi} Interface}). The older @sc{gdb/mi} interface, included in
|
|
@value{GDBN} version 5.0 can be selected with @samp{--interpreter=mi0}.
|
|
|
|
@item -write
|
|
@cindex @code{--write}
|
|
Open the executable and core files for both reading and writing. This
|
|
is equivalent to the @samp{set write on} command inside @value{GDBN}
|
|
(@pxref{Patching}).
|
|
|
|
@item -statistics
|
|
@cindex @code{--statistics}
|
|
This option causes @value{GDBN} to print statistics about time and
|
|
memory usage after it completes each command and returns to the prompt.
|
|
|
|
@item -version
|
|
@cindex @code{--version}
|
|
This option causes @value{GDBN} to print its version number and
|
|
no-warranty blurb, and exit.
|
|
|
|
@end table
|
|
|
|
@node Quitting GDB
|
|
@section Quitting @value{GDBN}
|
|
@cindex exiting @value{GDBN}
|
|
@cindex leaving @value{GDBN}
|
|
|
|
@table @code
|
|
@kindex quit @r{[}@var{expression}@r{]}
|
|
@kindex q @r{(@code{quit})}
|
|
@item quit @r{[}@var{expression}@r{]}
|
|
@itemx q
|
|
To exit @value{GDBN}, use the @code{quit} command (abbreviated
|
|
@code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
|
|
do not supply @var{expression}, @value{GDBN} will terminate normally;
|
|
otherwise it will terminate using the result of @var{expression} as the
|
|
error code.
|
|
@end table
|
|
|
|
@cindex interrupt
|
|
An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
|
|
terminates the action of any @value{GDBN} command that is in progress and
|
|
returns 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.
|
|
|
|
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}).
|
|
|
|
@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
|
|
@kindex shell
|
|
@cindex shell escape
|
|
@item shell @var{command string}
|
|
Invoke a standard shell to execute @var{command string}.
|
|
If it exists, the environment variable @code{SHELL} determines which
|
|
shell to run. Otherwise @value{GDBN} uses the default shell
|
|
(@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
|
|
@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
|
|
@kindex make
|
|
@cindex calling make
|
|
@item make @var{make-args}
|
|
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 commands 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 @r{(repeat last command)}
|
|
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 whose 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 # @r{(a comment)}
|
|
@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}).
|
|
|
|
@cindex repeating command sequences
|
|
@kindex C-o @r{(operate-and-get-next)}
|
|
The @kbd{C-o} binding is useful for repeating a complex sequence of
|
|
commands. This command accepts the current line, like @kbd{RET}, and
|
|
then fetches the next line relative to the current line from the history
|
|
for editing.
|
|
|
|
@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} fills in the
|
|
word, and waits 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} sounds a bell. You can either supply more
|
|
characters and try again, or just press @key{TAB} a second time;
|
|
@value{GDBN} displays 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 displays 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 either by holding down a
|
|
key designated as the @key{META} shift on your keyboard (if there is
|
|
one) while typing @kbd{?}, or 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.
|
|
|
|
The most likely situation where you might need this is in typing the
|
|
name of a C@t{++} function. This is because C@t{++} 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( @kbd{M-?}
|
|
bubble(double,double) bubble(int,int)
|
|
(@value{GDBP}) b 'bubble(
|
|
@end example
|
|
|
|
In some cases, @value{GDBN} can tell that completing a name requires using
|
|
quotes. When this happens, @value{GDBN} inserts 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.
|
|
|
|
For more information about overloaded functions, see @ref{C plus plus
|
|
expressions, ,C@t{++} expressions}. You can use the command @code{set
|
|
overload-resolution off} to disable overload resolution;
|
|
see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
|
|
|
|
|
|
@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
|
|
@kindex h @r{(@code{help})}
|
|
@item help
|
|
@itemx 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:
|
|
|
|
aliases -- Aliases of other commands
|
|
breakpoints -- Making program stop at certain points
|
|
data -- Examining data
|
|
files -- Specifying and examining files
|
|
internals -- Maintenance commands
|
|
obscure -- Obscure features
|
|
running -- Running the program
|
|
stack -- Examining the stack
|
|
status -- Status inquiries
|
|
support -- Support facilities
|
|
tracepoints -- Tracing of program execution without@*
|
|
stopping the program
|
|
user-defined -- User-defined commands
|
|
|
|
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
|
|
@c the above line break eliminates huge line overfull...
|
|
|
|
@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.
|
|
info -- Generic command for showing things
|
|
about the program being debugged
|
|
show -- Generic command for showing things
|
|
about the debugger
|
|
|
|
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} displays a
|
|
short paragraph on how to use that command.
|
|
|
|
@kindex apropos
|
|
@item apropos @var{args}
|
|
The @code{apropos @var{args}} command searches through all of the @value{GDBN}
|
|
commands, and their documentation, for the regular expression specified in
|
|
@var{args}. It prints out all matches found. For example:
|
|
|
|
@smallexample
|
|
apropos reload
|
|
@end smallexample
|
|
|
|
@noindent
|
|
results in:
|
|
|
|
@smallexample
|
|
@c @group
|
|
set symbol-reloading -- Set dynamic symbol table reloading
|
|
multiple times in one run
|
|
show symbol-reloading -- Show dynamic symbol table reloading
|
|
multiple times in one run
|
|
@c @end group
|
|
@end smallexample
|
|
|
|
@kindex complete
|
|
@item complete @var{args}
|
|
The @code{complete @var{args}} command lists all the possible completions
|
|
for the beginning of a command. Use @var{args} to specify the beginning of the
|
|
command you want completed. For example:
|
|
|
|
@smallexample
|
|
complete i
|
|
@end smallexample
|
|
|
|
@noindent results in:
|
|
|
|
@smallexample
|
|
@group
|
|
if
|
|
ignore
|
|
info
|
|
inspect
|
|
@end group
|
|
@end smallexample
|
|
|
|
@noindent This is intended for use by @sc{gnu} Emacs.
|
|
@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
|
|
@kindex info
|
|
@kindex i @r{(@code{info})}
|
|
@item info
|
|
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 set
|
|
@item set
|
|
You can assign the result of an expression to an environment variable with
|
|
@code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
|
|
@code{set prompt $}.
|
|
|
|
@kindex show
|
|
@item show
|
|
In contrast to @code{info}, @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 need to determine which
|
|
version of @value{GDBN} you are running; as @value{GDBN} evolves, new
|
|
commands are introduced, and old ones may wither away. Also, many
|
|
system vendors ship variant versions of @value{GDBN}, and there are
|
|
variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
|
|
The version number is the same as the one announced when you start
|
|
@value{GDBN}.
|
|
|
|
@kindex show copying
|
|
@item show copying
|
|
Display information about permission for copying @value{GDBN}.
|
|
|
|
@kindex show warranty
|
|
@item show warranty
|
|
Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
|
|
if your version of @value{GDBN} comes with one.
|
|
|
|
@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.
|
|
|
|
You may start @value{GDBN} with its arguments, if any, in an environment
|
|
of your choice. If you are doing native debugging, you may redirect
|
|
your program's input and output, debug an already running process, or
|
|
kill a child process.
|
|
|
|
@menu
|
|
* Compilation:: Compiling for debugging
|
|
* Starting:: Starting your program
|
|
* 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
|
|
|
|
* Threads:: Debugging programs with multiple threads
|
|
* Processes:: Debugging programs with multiple processes
|
|
@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 @sc{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 shows 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} never sees 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 to us as a bug (including a test case!).
|
|
|
|
Older versions of the @sc{gnu} C compiler permitted a variant option
|
|
@w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
|
|
format; if your @sc{gnu} C compiler has this option, do not use it.
|
|
|
|
@need 2000
|
|
@node Starting
|
|
@section Starting your program
|
|
@cindex starting
|
|
@cindex running
|
|
|
|
@table @code
|
|
@kindex run
|
|
@kindex r @r{(@code{run})}
|
|
@item run
|
|
@itemx r
|
|
Use the @code{run} command to start your program under @value{GDBN}.
|
|
You must first specify the program name (except on VxWorks) 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
|
|
|
|
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 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 affect
|
|
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
|
|
|
|
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 call 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} discards its symbol
|
|
table, and reads it again. When it does this, @value{GDBN} tries to retain
|
|
your current breakpoints.
|
|
|
|
@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} uses. If you do not define @code{SHELL}, @value{GDBN} uses
|
|
the default shell (@file{/bin/sh} on Unix).
|
|
|
|
On non-Unix systems, the program is usually invoked directly by
|
|
@value{GDBN}, which emulates I/O redirection via the appropriate system
|
|
calls, and the wildcard characters are expanded by the startup code of
|
|
the program, not by the shell.
|
|
|
|
@code{run} with no arguments uses the same arguments used by the previous
|
|
@code{run}, or those set by the @code{set args} command.
|
|
|
|
@table @code
|
|
@kindex set args
|
|
@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} executes 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.
|
|
|
|
@kindex show args
|
|
@item 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
|
|
@kindex path
|
|
@item path @var{directory}
|
|
Add @var{directory} to the front of the @code{PATH} environment variable
|
|
(the search path for executables) that will be passed to your program.
|
|
The value of @code{PATH} used by @value{GDBN} does not change.
|
|
You may specify several directory names, separated by whitespace or by a
|
|
system-dependent separator character (@samp{:} on Unix, @samp{;} on
|
|
MS-DOS and MS-Windows). If @var{directory} is already in the path, it
|
|
is moved to the front, so it is 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} replaces @samp{.} in the
|
|
@var{directory} argument (with the current path) before adding
|
|
@var{directory} 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.
|
|
|
|
@kindex show paths
|
|
@item show paths
|
|
Display the list of search paths for executables (the @code{PATH}
|
|
environment variable).
|
|
|
|
@kindex show environment
|
|
@item show environment @r{[}@var{varname}@r{]}
|
|
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}.
|
|
|
|
@kindex set environment
|
|
@item set environment @var{varname} @r{[}=@var{value}@r{]}
|
|
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 the debugged 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.)
|
|
|
|
@kindex unset environment
|
|
@item unset environment @var{varname}
|
|
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:} On Unix systems, @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 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
|
|
@kindex cd
|
|
@item cd @var{directory}
|
|
Set the @value{GDBN} working directory to @var{directory}.
|
|
|
|
@kindex pwd
|
|
@item 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
|
|
@kindex info terminal
|
|
@item 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} shows your active
|
|
targets.) The command takes as argument a process ID. The usual way to
|
|
find out the process-id of a Unix process is with the @code{ps} utility,
|
|
or with the @samp{jobs -l} shell command.
|
|
|
|
@code{attach} does not repeat if you press @key{RET} a second time after
|
|
executing the command.
|
|
@end table
|
|
|
|
To use @code{attach}, your program must be running in an environment
|
|
which supports processes; for example, @code{attach} does not work for
|
|
programs on bare-board targets that lack an operating system. You must
|
|
also have permission to send the process a signal.
|
|
|
|
When you use @code{attach}, the debugger finds the program running in
|
|
the process first by looking in the current working directory, then (if
|
|
the program is not found) by using the source file search path
|
|
(@pxref{Source Path, ,Specifying source directories}). You can also use
|
|
the @code{file} command to load the program. @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
|
|
@kindex detach
|
|
@item 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} does 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, @value{GDBN} asks
|
|
for confirmation if you try to do either of these things; you can
|
|
control whether or not you need to confirm by using the @code{set
|
|
confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
|
|
messages}).
|
|
|
|
@node Kill Process
|
|
@section Killing the child process
|
|
|
|
@table @code
|
|
@kindex kill
|
|
@item 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.
|
|
|
|
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} notices that the file has changed, and
|
|
reads the symbol table again (while trying to preserve your current
|
|
breakpoint settings).
|
|
|
|
@node Threads
|
|
@section Debugging programs with multiple threads
|
|
|
|
@cindex threads of execution
|
|
@cindex multiple threads
|
|
@cindex switching threads
|
|
In some operating systems, such as HP-UX and Solaris, a single program
|
|
may have more than one @dfn{thread} of execution. The precise semantics
|
|
of threads differ from one operating system to another, but in general
|
|
the threads of a single program are akin to multiple processes---except
|
|
that they share one address space (that is, they can all examine and
|
|
modify the same variables). On the other hand, each thread has its own
|
|
registers and execution stack, and perhaps private memory.
|
|
|
|
@value{GDBN} provides these facilities for debugging multi-thread
|
|
programs:
|
|
|
|
@itemize @bullet
|
|
@item automatic notification of new threads
|
|
@item @samp{thread @var{threadno}}, a command to switch among threads
|
|
@item @samp{info threads}, a command to inquire about existing threads
|
|
@item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
|
|
a command to apply a command to a list of threads
|
|
@item thread-specific breakpoints
|
|
@end itemize
|
|
|
|
@quotation
|
|
@emph{Warning:} These facilities are not yet available on every
|
|
@value{GDBN} configuration where the operating system supports threads.
|
|
If your @value{GDBN} does not support threads, these commands have no
|
|
effect. For example, a system without thread support shows no output
|
|
from @samp{info threads}, and always rejects the @code{thread} command,
|
|
like this:
|
|
|
|
@smallexample
|
|
(@value{GDBP}) info threads
|
|
(@value{GDBP}) thread 1
|
|
Thread ID 1 not known. Use the "info threads" command to
|
|
see the IDs of currently known threads.
|
|
@end smallexample
|
|
@c FIXME to implementors: how hard would it be to say "sorry, this GDB
|
|
@c doesn't support threads"?
|
|
@end quotation
|
|
|
|
@cindex focus of debugging
|
|
@cindex current thread
|
|
The @value{GDBN} thread debugging facility allows you to observe all
|
|
threads while your program runs---but whenever @value{GDBN} takes
|
|
control, one thread in particular is always the focus of debugging.
|
|
This thread is called the @dfn{current thread}. Debugging commands show
|
|
program information from the perspective of the current thread.
|
|
|
|
@cindex @code{New} @var{systag} message
|
|
@cindex thread identifier (system)
|
|
@c FIXME-implementors!! It would be more helpful if the [New...] message
|
|
@c included GDB's numeric thread handle, so you could just go to that
|
|
@c thread without first checking `info threads'.
|
|
Whenever @value{GDBN} detects a new thread in your program, it displays
|
|
the target system's identification for the thread with a message in the
|
|
form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
|
|
whose form varies depending on the particular system. For example, on
|
|
LynxOS, you might see
|
|
|
|
@example
|
|
[New process 35 thread 27]
|
|
@end example
|
|
|
|
@noindent
|
|
when @value{GDBN} notices a new thread. In contrast, on an SGI system,
|
|
the @var{systag} is simply something like @samp{process 368}, with no
|
|
further qualifier.
|
|
|
|
@c FIXME!! (1) Does the [New...] message appear even for the very first
|
|
@c thread of a program, or does it only appear for the
|
|
@c second---i.e., when it becomes obvious we have a multithread
|
|
@c program?
|
|
@c (2) *Is* there necessarily a first thread always? Or do some
|
|
@c multithread systems permit starting a program with multiple
|
|
@c threads ab initio?
|
|
|
|
@cindex thread number
|
|
@cindex thread identifier (GDB)
|
|
For debugging purposes, @value{GDBN} associates its own thread
|
|
number---always a single integer---with each thread in your program.
|
|
|
|
@table @code
|
|
@kindex info threads
|
|
@item info threads
|
|
Display a summary of all threads currently in your
|
|
program. @value{GDBN} displays for each thread (in this order):
|
|
|
|
@enumerate
|
|
@item the thread number assigned by @value{GDBN}
|
|
|
|
@item the target system's thread identifier (@var{systag})
|
|
|
|
@item the current stack frame summary for that thread
|
|
@end enumerate
|
|
|
|
@noindent
|
|
An asterisk @samp{*} to the left of the @value{GDBN} thread number
|
|
indicates the current thread.
|
|
|
|
For example,
|
|
@end table
|
|
@c end table here to get a little more width for example
|
|
|
|
@smallexample
|
|
(@value{GDBP}) info threads
|
|
3 process 35 thread 27 0x34e5 in sigpause ()
|
|
2 process 35 thread 23 0x34e5 in sigpause ()
|
|
* 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
|
|
at threadtest.c:68
|
|
@end smallexample
|
|
|
|
On HP-UX systems:
|
|
|
|
@cindex thread number
|
|
@cindex thread identifier (GDB)
|
|
For debugging purposes, @value{GDBN} associates its own thread
|
|
number---a small integer assigned in thread-creation order---with each
|
|
thread in your program.
|
|
|
|
@cindex @code{New} @var{systag} message, on HP-UX
|
|
@cindex thread identifier (system), on HP-UX
|
|
@c FIXME-implementors!! It would be more helpful if the [New...] message
|
|
@c included GDB's numeric thread handle, so you could just go to that
|
|
@c thread without first checking `info threads'.
|
|
Whenever @value{GDBN} detects a new thread in your program, it displays
|
|
both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
|
|
form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
|
|
whose form varies depending on the particular system. For example, on
|
|
HP-UX, you see
|
|
|
|
@example
|
|
[New thread 2 (system thread 26594)]
|
|
@end example
|
|
|
|
@noindent
|
|
when @value{GDBN} notices a new thread.
|
|
|
|
@table @code
|
|
@kindex info threads
|
|
@item info threads
|
|
Display a summary of all threads currently in your
|
|
program. @value{GDBN} displays for each thread (in this order):
|
|
|
|
@enumerate
|
|
@item the thread number assigned by @value{GDBN}
|
|
|
|
@item the target system's thread identifier (@var{systag})
|
|
|
|
@item the current stack frame summary for that thread
|
|
@end enumerate
|
|
|
|
@noindent
|
|
An asterisk @samp{*} to the left of the @value{GDBN} thread number
|
|
indicates the current thread.
|
|
|
|
For example,
|
|
@end table
|
|
@c end table here to get a little more width for example
|
|
|
|
@example
|
|
(@value{GDBP}) info threads
|
|
* 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
|
|
at quicksort.c:137
|
|
2 system thread 26606 0x7b0030d8 in __ksleep () \@*
|
|
from /usr/lib/libc.2
|
|
1 system thread 27905 0x7b003498 in _brk () \@*
|
|
from /usr/lib/libc.2
|
|
@end example
|
|
|
|
@table @code
|
|
@kindex thread @var{threadno}
|
|
@item thread @var{threadno}
|
|
Make thread number @var{threadno} the current thread. The command
|
|
argument @var{threadno} is the internal @value{GDBN} thread number, as
|
|
shown in the first field of the @samp{info threads} display.
|
|
@value{GDBN} responds by displaying the system identifier of the thread
|
|
you selected, and its current stack frame summary:
|
|
|
|
@smallexample
|
|
@c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
|
|
(@value{GDBP}) thread 2
|
|
[Switching to process 35 thread 23]
|
|
0x34e5 in sigpause ()
|
|
@end smallexample
|
|
|
|
@noindent
|
|
As with the @samp{[New @dots{}]} message, the form of the text after
|
|
@samp{Switching to} depends on your system's conventions for identifying
|
|
threads.
|
|
|
|
@kindex thread apply
|
|
@item thread apply [@var{threadno}] [@var{all}] @var{args}
|
|
The @code{thread apply} command allows you to apply a command to one or
|
|
more threads. Specify the numbers of the threads that you want affected
|
|
with the command argument @var{threadno}. @var{threadno} is the internal
|
|
@value{GDBN} thread number, as shown in the first field of the @samp{info
|
|
threads} display. To apply a command to all threads, use
|
|
@code{thread apply all} @var{args}.
|
|
@end table
|
|
|
|
@cindex automatic thread selection
|
|
@cindex switching threads automatically
|
|
@cindex threads, automatic switching
|
|
Whenever @value{GDBN} stops your program, due to a breakpoint or a
|
|
signal, it automatically selects the thread where that breakpoint or
|
|
signal happened. @value{GDBN} alerts you to the context switch with a
|
|
message of the form @samp{[Switching to @var{systag}]} to identify the
|
|
thread.
|
|
|
|
@xref{Thread Stops,,Stopping and starting multi-thread programs}, for
|
|
more information about how @value{GDBN} behaves when you stop and start
|
|
programs with multiple threads.
|
|
|
|
@xref{Set Watchpoints,,Setting watchpoints}, for information about
|
|
watchpoints in programs with multiple threads.
|
|
|
|
@node Processes
|
|
@section Debugging programs with multiple processes
|
|
|
|
@cindex fork, debugging programs which call
|
|
@cindex multiple processes
|
|
@cindex processes, multiple
|
|
On most systems, @value{GDBN} has no special support for debugging
|
|
programs which create additional processes using the @code{fork}
|
|
function. When a program forks, @value{GDBN} will continue to debug the
|
|
parent process and the child process will run unimpeded. If you have
|
|
set a breakpoint in any code which the child then executes, the child
|
|
will get a @code{SIGTRAP} signal which (unless it catches the signal)
|
|
will cause it to terminate.
|
|
|
|
However, if you want to debug the child process there is a workaround
|
|
which isn't too painful. Put a call to @code{sleep} in the code which
|
|
the child process executes after the fork. It may be useful to sleep
|
|
only if a certain environment variable is set, or a certain file exists,
|
|
so that the delay need not occur when you don't want to run @value{GDBN}
|
|
on the child. While the child is sleeping, use the @code{ps} program to
|
|
get its process ID. Then tell @value{GDBN} (a new invocation of
|
|
@value{GDBN} if you are also debugging the parent process) to attach to
|
|
the child process (@pxref{Attach}). From that point on you can debug
|
|
the child process just like any other process which you attached to.
|
|
|
|
On HP-UX (11.x and later only?), @value{GDBN} provides support for
|
|
debugging programs that create additional processes using the
|
|
@code{fork} or @code{vfork} function.
|
|
|
|
By default, when a program forks, @value{GDBN} will continue to debug
|
|
the parent process and the child process will run unimpeded.
|
|
|
|
If you want to follow the child process instead of the parent process,
|
|
use the command @w{@code{set follow-fork-mode}}.
|
|
|
|
@table @code
|
|
@kindex set follow-fork-mode
|
|
@item set follow-fork-mode @var{mode}
|
|
Set the debugger response to a program call of @code{fork} or
|
|
@code{vfork}. A call to @code{fork} or @code{vfork} creates a new
|
|
process. The @var{mode} can be:
|
|
|
|
@table @code
|
|
@item parent
|
|
The original process is debugged after a fork. The child process runs
|
|
unimpeded. This is the default.
|
|
|
|
@item child
|
|
The new process is debugged after a fork. The parent process runs
|
|
unimpeded.
|
|
|
|
@item ask
|
|
The debugger will ask for one of the above choices.
|
|
@end table
|
|
|
|
@item show follow-fork-mode
|
|
Display the current debugger response to a @code{fork} or @code{vfork} call.
|
|
@end table
|
|
|
|
If you ask to debug a child process and a @code{vfork} is followed by an
|
|
@code{exec}, @value{GDBN} executes the new target up to the first
|
|
breakpoint in the new target. If you have a breakpoint set on
|
|
@code{main} in your original program, the breakpoint will also be set on
|
|
the child process's @code{main}.
|
|
|
|
When a child process is spawned by @code{vfork}, you cannot debug the
|
|
child or parent until an @code{exec} call completes.
|
|
|
|
If you issue a @code{run} command to @value{GDBN} after an @code{exec}
|
|
call executes, the new target restarts. To restart the parent process,
|
|
use the @code{file} command with the parent executable name as its
|
|
argument.
|
|
|
|
You can use the @code{catch} command to make @value{GDBN} stop whenever
|
|
a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
|
|
Catchpoints, ,Setting catchpoints}.
|
|
|
|
@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 a signal, 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
|
|
@kindex info program
|
|
@item info program
|
|
Display information about the status of your program: whether it is
|
|
running or not, what process it is, and why it stopped.
|
|
@end table
|
|
|
|
@menu
|
|
* Breakpoints:: Breakpoints, watchpoints, and catchpoints
|
|
* Continuing and Stepping:: Resuming execution
|
|
* Signals:: Signals
|
|
* Thread Stops:: Stopping and starting multi-thread programs
|
|
@end menu
|
|
|
|
@node Breakpoints
|
|
@section Breakpoints, watchpoints, and catchpoints
|
|
|
|
@cindex breakpoints
|
|
A @dfn{breakpoint} makes your program stop whenever a certain point in
|
|
the program is reached. For each breakpoint, you can add conditions to
|
|
control in finer detail whether your program stops. You can set
|
|
breakpoints with the @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.
|
|
|
|
In HP-UX, SunOS 4.x, SVR4, and Alpha OSF/1 configurations, you can set
|
|
breakpoints in shared libraries before the executable is run. There is
|
|
a minor limitation on HP-UX systems: you must wait until the executable
|
|
is run in order to set breakpoints in shared library routines that are
|
|
not called directly by the program (for example, routines that are
|
|
arguments in a @code{pthread_create} call).
|
|
|
|
@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 catchpoints
|
|
@cindex breakpoint on events
|
|
A @dfn{catchpoint} is another special breakpoint that stops your program
|
|
when a certain kind of event occurs, such as the throwing of a C@t{++}
|
|
exception or the loading of a library. As with watchpoints, you use a
|
|
different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
|
|
catchpoints}), but aside from that, you can manage a catchpoint like any
|
|
other breakpoint. (To stop when your program receives a signal, use the
|
|
@code{handle} command; see @ref{Signals, ,Signals}.)
|
|
|
|
@cindex breakpoint numbers
|
|
@cindex numbers for breakpoints
|
|
@value{GDBN} assigns a number to each breakpoint, watchpoint, or
|
|
catchpoint 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.
|
|
|
|
@cindex breakpoint ranges
|
|
@cindex ranges of breakpoints
|
|
Some @value{GDBN} commands accept a range of breakpoints on which to
|
|
operate. A breakpoint range is either a single breakpoint number, like
|
|
@samp{5}, or two such numbers, in increasing order, separated by a
|
|
hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
|
|
all breakpoint in that range are operated on.
|
|
|
|
@menu
|
|
* Set Breaks:: Setting breakpoints
|
|
* Set Watchpoints:: Setting watchpoints
|
|
* Set Catchpoints:: Setting catchpoints
|
|
* Delete Breaks:: Deleting breakpoints
|
|
* Disabling:: Disabling breakpoints
|
|
* Conditions:: Break conditions
|
|
* Break Commands:: Breakpoint command lists
|
|
* Breakpoint Menus:: Breakpoint menus
|
|
* Error in Breakpoints:: ``Cannot insert breakpoints''
|
|
@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 @r{(@code{break})}
|
|
@vindex $bpnum@r{, convenience variable}
|
|
@cindex latest breakpoint
|
|
Breakpoints are set with the @code{break} command (abbreviated
|
|
@code{b}). The debugger convenience variable @samp{$bpnum} records the
|
|
number of the breakpoint 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}.
|
|
When using source languages that permit overloading of symbols, such as
|
|
C@t{++}, @var{function} may refer to more than one possible place to break.
|
|
@xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
|
|
|
|
@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 @dfn{stack frame}.
|
|
(@xref{Frames, ,Frames}, for a description of stack frames.)
|
|
|
|
@item break @var{linenum}
|
|
Set a breakpoint at line @var{linenum} in the current source file.
|
|
The current source file is the last file whose source text was printed.
|
|
The 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 makes your program 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} stops
|
|
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.
|
|
|
|
@kindex tbreak
|
|
@item tbreak @var{args}
|
|
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 deleted after the first time your
|
|
program stops there. @xref{Disabling, ,Disabling breakpoints}.
|
|
|
|
@kindex hbreak
|
|
@item hbreak @var{args}
|
|
Set a hardware-assisted breakpoint. @var{args} are the same as for the
|
|
@code{break} command and the breakpoint is set in the same way, but the
|
|
breakpoint requires hardware support and some target hardware may not
|
|
have this support. The main purpose of this is EPROM/ROM code
|
|
debugging, so you can set a breakpoint at an instruction without
|
|
changing the instruction. This can be used with the new trap-generation
|
|
provided by SPARClite DSU and some x86-based targets. These targets
|
|
will generate traps when a program accesses some data or instruction
|
|
address that is assigned to the debug registers. However the hardware
|
|
breakpoint registers can take a limited number of breakpoints. For
|
|
example, on the DSU, only two data breakpoints can be set at a time, and
|
|
@value{GDBN} will reject this command if more than two are used. Delete
|
|
or disable unused hardware breakpoints before setting new ones
|
|
(@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
|
|
|
|
@kindex thbreak
|
|
@item thbreak @var{args}
|
|
Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
|
|
are the same as for the @code{hbreak} command and the breakpoint is set in
|
|
the same way. However, like the @code{tbreak} command,
|
|
the breakpoint is automatically deleted after the
|
|
first time your program stops there. Also, like the @code{hbreak}
|
|
command, the breakpoint requires hardware support and some target hardware
|
|
may not have this support. @xref{Disabling, ,Disabling breakpoints}.
|
|
See also @ref{Conditions, ,Break conditions}.
|
|
|
|
@kindex rbreak
|
|
@cindex regular expression
|
|
@item rbreak @var{regex}
|
|
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. You can delete them, disable them, or make
|
|
them conditional the same way as any other breakpoint.
|
|
|
|
The syntax of the regular expression is the standard one used with tools
|
|
like @file{grep}. Note that this is different from the syntax used by
|
|
shells, so for instance @code{foo*} matches all functions that include
|
|
an @code{fo} followed by zero or more @code{o}s. There is an implicit
|
|
@code{.*} leading and trailing the regular expression you supply, so to
|
|
match only functions that begin with @code{foo}, use @code{^foo}.
|
|
|
|
When debugging C@t{++} programs, @code{rbreak} is useful for setting
|
|
breakpoints on overloaded functions that are not members of any special
|
|
classes.
|
|
|
|
@kindex info breakpoints
|
|
@cindex @code{$_} and @code{info breakpoints}
|
|
@item info breakpoints @r{[}@var{n}@r{]}
|
|
@itemx info break @r{[}@var{n}@r{]}
|
|
@itemx info watchpoints @r{[}@var{n}@r{]}
|
|
Print a table of all breakpoints, watchpoints, and catchpoints set and
|
|
not deleted, with the following columns for each breakpoint:
|
|
|
|
@table @emph
|
|
@item Breakpoint Numbers
|
|
@item Type
|
|
Breakpoint, watchpoint, or catchpoint.
|
|
@item Disposition
|
|
Whether the breakpoint is marked to be disabled or deleted when hit.
|
|
@item Enabled or Disabled
|
|
Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
|
|
that are not enabled.
|
|
@item Address
|
|
Where the breakpoint is in your program, as a memory address.
|
|
@item What
|
|
Where the breakpoint is in the source for your program, as a file and
|
|
line number.
|
|
@end table
|
|
|
|
@noindent
|
|
If a breakpoint is conditional, @code{info break} shows the condition on
|
|
the line following the affected breakpoint; breakpoint commands, if any,
|
|
are listed after that.
|
|
|
|
@noindent
|
|
@code{info break} with a breakpoint
|
|
number @var{n} as argument lists only that breakpoint. The
|
|
convenience variable @code{$_} and the default examining-address for
|
|
the @code{x} command are set to the address of the last breakpoint
|
|
listed (@pxref{Memory, ,Examining memory}).
|
|
|
|
@noindent
|
|
@code{info break} displays a count of the number of times the breakpoint
|
|
has been hit. This is especially useful in conjunction with the
|
|
@code{ignore} command. You can ignore a large number of breakpoint
|
|
hits, look at the breakpoint info to see how many times the breakpoint
|
|
was hit, and then run again, ignoring one less than that number. This
|
|
will get you quickly to the last hit of that breakpoint.
|
|
@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.
|
|
|
|
@item shlib events
|
|
Shared library events.
|
|
|
|
@end table
|
|
|
|
@end table
|
|
|
|
|
|
@node Set Watchpoints
|
|
@subsection Setting watchpoints
|
|
|
|
@cindex setting watchpoints
|
|
@cindex software watchpoints
|
|
@cindex hardware 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.
|
|
|
|
Depending on your system, watchpoints may be implemented in software or
|
|
hardware. @value{GDBN} does software watchpointing by single-stepping your
|
|
program and testing the variable's value each time, which is hundreds of
|
|
times slower than normal execution. (But this may still be worth it, to
|
|
catch errors where you have no clue what part of your program is the
|
|
culprit.)
|
|
|
|
On some systems, such as HP-UX, Linux and some other x86-based targets,
|
|
@value{GDBN} includes support for
|
|
hardware watchpoints, which do not slow down the running of your
|
|
program.
|
|
|
|
@table @code
|
|
@kindex watch
|
|
@item watch @var{expr}
|
|
Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
|
|
is written into by the program and its value changes.
|
|
|
|
@kindex rwatch
|
|
@item rwatch @var{expr}
|
|
Set a watchpoint that will break when watch @var{expr} is read by the program.
|
|
|
|
@kindex awatch
|
|
@item awatch @var{expr}
|
|
Set a watchpoint that will break when @var{expr} is either read or written into
|
|
by the program.
|
|
|
|
@kindex info watchpoints
|
|
@item info watchpoints
|
|
This command prints a list of watchpoints, breakpoints, and catchpoints;
|
|
it is the same as @code{info break}.
|
|
@end table
|
|
|
|
@value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
|
|
watchpoints execute very quickly, and the debugger reports a change in
|
|
value at the exact instruction where the change occurs. If @value{GDBN}
|
|
cannot set a hardware watchpoint, it sets a software watchpoint, which
|
|
executes more slowly and reports the change in value at the next
|
|
statement, not the instruction, after the change occurs.
|
|
|
|
When you issue the @code{watch} command, @value{GDBN} reports
|
|
|
|
@example
|
|
Hardware watchpoint @var{num}: @var{expr}
|
|
@end example
|
|
|
|
@noindent
|
|
if it was able to set a hardware watchpoint.
|
|
|
|
Currently, the @code{awatch} and @code{rwatch} commands can only set
|
|
hardware watchpoints, because accesses to data that don't change the
|
|
value of the watched expression cannot be detected without examining
|
|
every instruction as it is being executed, and @value{GDBN} does not do
|
|
that currently. If @value{GDBN} finds that it is unable to set a
|
|
hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
|
|
will print a message like this:
|
|
|
|
@smallexample
|
|
Expression cannot be implemented with read/access watchpoint.
|
|
@end smallexample
|
|
|
|
Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
|
|
data type of the watched expression is wider than what a hardware
|
|
watchpoint on the target machine can handle. For example, some systems
|
|
can only watch regions that are up to 4 bytes wide; on such systems you
|
|
cannot set hardware watchpoints for an expression that yields a
|
|
double-precision floating-point number (which is typically 8 bytes
|
|
wide). As a work-around, it might be possible to break the large region
|
|
into a series of smaller ones and watch them with separate watchpoints.
|
|
|
|
If you set too many hardware watchpoints, @value{GDBN} might be unable
|
|
to insert all of them when you resume the execution of your program.
|
|
Since the precise number of active watchpoints is unknown until such
|
|
time as the program is about to be resumed, @value{GDBN} might not be
|
|
able to warn you about this when you set the watchpoints, and the
|
|
warning will be printed only when the program is resumed:
|
|
|
|
@smallexample
|
|
Hardware watchpoint @var{num}: Could not insert watchpoint
|
|
@end smallexample
|
|
|
|
@noindent
|
|
If this happens, delete or disable some of the watchpoints.
|
|
|
|
The SPARClite DSU will generate traps when a program accesses some data
|
|
or instruction address that is assigned to the debug registers. For the
|
|
data addresses, DSU facilitates the @code{watch} command. However the
|
|
hardware breakpoint registers can only take two data watchpoints, and
|
|
both watchpoints must be the same kind. For example, you can set two
|
|
watchpoints with @code{watch} commands, two with @code{rwatch} commands,
|
|
@strong{or} two with @code{awatch} commands, but you cannot set one
|
|
watchpoint with one command and the other with a different command.
|
|
@value{GDBN} will reject the command if you try to mix watchpoints.
|
|
Delete or disable unused watchpoint commands before setting new ones.
|
|
|
|
If you call a function interactively using @code{print} or @code{call},
|
|
any watchpoints you have set will be inactive until @value{GDBN} reaches another
|
|
kind of breakpoint or the call completes.
|
|
|
|
@value{GDBN} automatically deletes watchpoints that watch local
|
|
(automatic) variables, or expressions that involve such variables, when
|
|
they go out of scope, that is, when the execution leaves the block in
|
|
which these variables were defined. In particular, when the program
|
|
being debugged terminates, @emph{all} local variables go out of scope,
|
|
and so only watchpoints that watch global variables remain set. If you
|
|
rerun the program, you will need to set all such watchpoints again. One
|
|
way of doing that would be to set a code breakpoint at the entry to the
|
|
@code{main} function and when it breaks, set all the watchpoints.
|
|
|
|
@quotation
|
|
@cindex watchpoints and threads
|
|
@cindex threads and watchpoints
|
|
@emph{Warning:} In multi-thread programs, watchpoints have only limited
|
|
usefulness. With the current watchpoint implementation, @value{GDBN}
|
|
can only watch the value of an expression @emph{in a single thread}. If
|
|
you are confident that the expression can only change due to the current
|
|
thread's activity (and if you are also confident that no other thread
|
|
can become current), then you can use watchpoints as usual. However,
|
|
@value{GDBN} may not notice when a non-current thread's activity changes
|
|
the expression.
|
|
|
|
@c FIXME: this is almost identical to the previous paragraph.
|
|
@emph{HP-UX Warning:} In multi-thread programs, software watchpoints
|
|
have only limited usefulness. If @value{GDBN} creates a software
|
|
watchpoint, it can only watch the value of an expression @emph{in a
|
|
single thread}. If you are confident that the expression can only
|
|
change due to the current thread's activity (and if you are also
|
|
confident that no other thread can become current), then you can use
|
|
software watchpoints as usual. However, @value{GDBN} may not notice
|
|
when a non-current thread's activity changes the expression. (Hardware
|
|
watchpoints, in contrast, watch an expression in all threads.)
|
|
@end quotation
|
|
|
|
@node Set Catchpoints
|
|
@subsection Setting catchpoints
|
|
@cindex catchpoints, setting
|
|
@cindex exception handlers
|
|
@cindex event handling
|
|
|
|
You can use @dfn{catchpoints} to cause the debugger to stop for certain
|
|
kinds of program events, such as C@t{++} exceptions or the loading of a
|
|
shared library. Use the @code{catch} command to set a catchpoint.
|
|
|
|
@table @code
|
|
@kindex catch
|
|
@item catch @var{event}
|
|
Stop when @var{event} occurs. @var{event} can be any of the following:
|
|
@table @code
|
|
@item throw
|
|
@kindex catch throw
|
|
The throwing of a C@t{++} exception.
|
|
|
|
@item catch
|
|
@kindex catch catch
|
|
The catching of a C@t{++} exception.
|
|
|
|
@item exec
|
|
@kindex catch exec
|
|
A call to @code{exec}. This is currently only available for HP-UX.
|
|
|
|
@item fork
|
|
@kindex catch fork
|
|
A call to @code{fork}. This is currently only available for HP-UX.
|
|
|
|
@item vfork
|
|
@kindex catch vfork
|
|
A call to @code{vfork}. This is currently only available for HP-UX.
|
|
|
|
@item load
|
|
@itemx load @var{libname}
|
|
@kindex catch load
|
|
The dynamic loading of any shared library, or the loading of the library
|
|
@var{libname}. This is currently only available for HP-UX.
|
|
|
|
@item unload
|
|
@itemx unload @var{libname}
|
|
@kindex catch unload
|
|
The unloading of any dynamically loaded shared library, or the unloading
|
|
of the library @var{libname}. This is currently only available for HP-UX.
|
|
@end table
|
|
|
|
@item tcatch @var{event}
|
|
Set a catchpoint that is enabled only for one stop. The catchpoint is
|
|
automatically deleted after the first time the event is caught.
|
|
|
|
@end table
|
|
|
|
Use the @code{info break} command to list the current catchpoints.
|
|
|
|
There are currently some limitations to C@t{++} exception handling
|
|
(@code{catch throw} and @code{catch catch}) in @value{GDBN}:
|
|
|
|
@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 either to abort or to
|
|
simply continue running until it hits a breakpoint, catches a signal
|
|
that @value{GDBN} is listening for, or exits. This is the case even if
|
|
you set a catchpoint for the exception; catchpoints on exceptions are
|
|
disabled within interactive calls.
|
|
|
|
@item
|
|
You cannot raise an exception interactively.
|
|
|
|
@item
|
|
You cannot install an exception handler interactively.
|
|
@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 @sc{gnu} C@t{++}, 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.
|
|
@var{id} is the exception identifier. */
|
|
void __raise_exception (void **addr, void *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.
|
|
|
|
|
|
@node Delete Breaks
|
|
@subsection Deleting breakpoints
|
|
|
|
@cindex clearing breakpoints, watchpoints, catchpoints
|
|
@cindex deleting breakpoints, watchpoints, catchpoints
|
|
It is often necessary to eliminate a breakpoint, watchpoint, or
|
|
catchpoint 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, watchpoints, or catchpoints 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
|
|
@kindex clear
|
|
@item 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.
|
|
|
|
@cindex delete breakpoints
|
|
@kindex delete
|
|
@kindex d @r{(@code{delete})}
|
|
@item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
|
|
Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
|
|
ranges 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
|
|
|
|
@kindex disable breakpoints
|
|
@kindex enable breakpoints
|
|
Rather than deleting a breakpoint, watchpoint, or catchpoint, 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, watchpoints, and catchpoints 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, watchpoints, and
|
|
catchpoints if you do not know which numbers to use.
|
|
|
|
A breakpoint, watchpoint, or catchpoint can have any of four different
|
|
states of enablement:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
Enabled. The breakpoint stops 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 stops your program, but then becomes
|
|
disabled.
|
|
@item
|
|
Enabled for deletion. The breakpoint stops your program, but
|
|
immediately after it does so it is deleted permanently. A breakpoint
|
|
set with the @code{tbreak} command starts out in this state.
|
|
@end itemize
|
|
|
|
You can use the following commands to enable or disable breakpoints,
|
|
watchpoints, and catchpoints:
|
|
|
|
@table @code
|
|
@kindex disable breakpoints
|
|
@kindex disable
|
|
@kindex dis @r{(@code{disable})}
|
|
@item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
|
|
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}.
|
|
|
|
@kindex enable breakpoints
|
|
@kindex enable
|
|
@item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
|
|
Enable the specified breakpoints (or all defined breakpoints). They
|
|
become effective once again in stopping your program.
|
|
|
|
@item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
|
|
Enable the specified breakpoints temporarily. @value{GDBN} disables any
|
|
of these breakpoints immediately after stopping your program.
|
|
|
|
@item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
|
|
Enable the specified breakpoints to work once, then die. @value{GDBN}
|
|
deletes any of these breakpoints as soon as your program stops there.
|
|
@end table
|
|
|
|
@c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
|
|
@c confusing: tbreak is also initially enabled.
|
|
Except 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 does 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 than break
|
|
conditions 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.
|
|
|
|
You can also use the @code{if} keyword with the @code{watch} command.
|
|
The @code{catch} command does not recognize the @code{if} keyword;
|
|
@code{condition} is the only way to impose a further condition on a
|
|
catchpoint.
|
|
|
|
@table @code
|
|
@kindex condition
|
|
@item condition @var{bnum} @var{expression}
|
|
Specify @var{expression} as the break condition for breakpoint,
|
|
watchpoint, or catchpoint number @var{bnum}. After you set a condition,
|
|
breakpoint @var{bnum} stops 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. If @var{expression} uses
|
|
symbols not referenced in the context of the breakpoint, @value{GDBN}
|
|
prints an error message:
|
|
|
|
@example
|
|
No symbol "foo" in current context.
|
|
@end example
|
|
|
|
@noindent
|
|
@value{GDBN} does
|
|
not actually evaluate @var{expression} at the time the @code{condition}
|
|
command (or a command that sets a breakpoint with a condition, like
|
|
@code{break if @dots{}}) 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 does not stop the next @var{n} times
|
|
your program reaches it.
|
|
|
|
@table @code
|
|
@kindex ignore
|
|
@item ignore @var{bnum} @var{count}
|
|
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 does 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.
|
|
|
|
When you use @code{continue} to resume execution of your program from a
|
|
breakpoint, you can specify an ignore count directly as an argument to
|
|
@code{continue}, rather than using @code{ignore}. @xref{Continuing and
|
|
Stepping,,Continuing and stepping}.
|
|
|
|
If a breakpoint has a positive ignore count and a condition, the
|
|
condition is not checked. Once the ignore count reaches zero,
|
|
@value{GDBN} resumes checking the condition.
|
|
|
|
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}.
|
|
@end table
|
|
|
|
Ignore counts apply to breakpoints, watchpoints, and catchpoints.
|
|
|
|
|
|
@node Break Commands
|
|
@subsection Breakpoint command lists
|
|
|
|
@cindex breakpoint commands
|
|
You can give any breakpoint (or watchpoint or catchpoint) 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
|
|
@kindex commands
|
|
@kindex end
|
|
@item commands @r{[}@var{bnum}@r{]}
|
|
@itemx @dots{} @var{command-list} @dots{}
|
|
@itemx 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, watchpoint, or catchpoint 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
|
|
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}, @code{output}, and @code{printf} allow you to
|
|
print precisely controlled output, and 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
|
|
printf "x is %d\n",x
|
|
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
|
|
|
|
@node Breakpoint Menus
|
|
@subsection Breakpoint menus
|
|
@cindex overloading
|
|
@cindex symbol overloading
|
|
|
|
Some programming languages (notably C@t{++}) 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 is 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
|
|
@smallexample
|
|
@group
|
|
(@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 group
|
|
@end smallexample
|
|
|
|
@c @ifclear BARETARGET
|
|
@node Error in Breakpoints
|
|
@subsection ``Cannot insert breakpoints''
|
|
@c
|
|
@c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
|
|
@c
|
|
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 print an error message:
|
|
|
|
@example
|
|
Cannot insert breakpoints.
|
|
The same program may be running in another process.
|
|
@end example
|
|
|
|
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.
|
|
|
|
@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
|
|
@c @end ifclear
|
|
|
|
A similar message can be printed if you request too many active
|
|
hardware-assisted breakpoints and watchpoints:
|
|
|
|
@c FIXME: the precise wording of this message may change; the relevant
|
|
@c source change is not committed yet (Sep 3, 1999).
|
|
@smallexample
|
|
Stopped; cannot insert breakpoints.
|
|
You may have requested too many hardware breakpoints and watchpoints.
|
|
@end smallexample
|
|
|
|
@noindent
|
|
This message is printed when you attempt to resume the program, since
|
|
only then @value{GDBN} knows exactly how many hardware breakpoints and
|
|
watchpoints it needs to insert.
|
|
|
|
When this message is printed, you need to disable or remove some of the
|
|
hardware-assisted breakpoints and watchpoints, and then continue.
|
|
|
|
|
|
@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 a breakpoint or a signal. (If
|
|
it stops due to a signal, you may want to use @code{handle}, or use
|
|
@samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
|
|
|
|
@table @code
|
|
@kindex continue
|
|
@kindex c @r{(@code{continue})}
|
|
@kindex fg @r{(resume foreground execution)}
|
|
@item continue @r{[}@var{ignore-count}@r{]}
|
|
@itemx c @r{[}@var{ignore-count}@r{]}
|
|
@itemx fg @r{[}@var{ignore-count}@r{]}
|
|
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}).
|
|
|
|
The argument @var{ignore-count} is meaningful only when your program
|
|
stopped due to a breakpoint. At other times, the argument to
|
|
@code{continue} is ignored.
|
|
|
|
The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
|
|
debugged program is deemed to be the foreground program) are provided
|
|
purely for convenience, and have exactly the same behavior as
|
|
@code{continue}.
|
|
@end table
|
|
|
|
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.
|
|
|
|
A typical technique for using stepping is to set a breakpoint
|
|
(@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) 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
|
|
@kindex step
|
|
@kindex s @r{(@code{step})}
|
|
@item step
|
|
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
|
|
@c "without debugging information" is imprecise; actually "without line
|
|
@c numbers in the debugging information". (gcc -g1 has debugging info but
|
|
@c not line numbers). But it seems complex to try to make that
|
|
@c distinction here.
|
|
@emph{Warning:} If you use the @code{step} command while control is
|
|
within a function that was compiled without debugging information,
|
|
execution proceeds until control reaches a function that does have
|
|
debugging information. Likewise, it will not step into a function which
|
|
is compiled without debugging information. To step through functions
|
|
without debugging information, use the @code{stepi} command, described
|
|
below.
|
|
@end quotation
|
|
|
|
The @code{step} command only stops at the first instruction of a source
|
|
line. This prevents the multiple stops that could otherwise occur in
|
|
@code{switch} statements, @code{for} loops, etc. @code{step} continues
|
|
to stop if a function that has debugging information is called within
|
|
the line. In other words, @code{step} @emph{steps inside} any functions
|
|
called within the line.
|
|
|
|
Also, the @code{step} command only enters a function if there is line
|
|
number information for the function. Otherwise it acts like the
|
|
@code{next} command. This avoids problems when using @code{cc -gl}
|
|
on MIPS machines. Previously, @code{step} entered subroutines if there
|
|
was any debugging information about the routine.
|
|
|
|
@item step @var{count}
|
|
Continue running as in @code{step}, but do so @var{count} times. If a
|
|
breakpoint is reached, or a signal not related to stepping occurs before
|
|
@var{count} steps, stepping stops right away.
|
|
|
|
@kindex next
|
|
@kindex n @r{(@code{next})}
|
|
@item next @r{[}@var{count}@r{]}
|
|
Continue to the next source line in the current (innermost) stack frame.
|
|
This is similar to @code{step}, but function calls that appear within
|
|
the line of code are executed without stopping. Execution stops when
|
|
control reaches a different line of code at the original stack level
|
|
that was executing when you gave the @code{next} command. This command
|
|
is abbreviated @code{n}.
|
|
|
|
An argument @var{count} is a repeat count, as for @code{step}.
|
|
|
|
|
|
@c FIX ME!! Do we delete this, or is there a way it fits in with
|
|
@c the following paragraph? --- Vctoria
|
|
@c
|
|
@c @code{next} within a function that lacks debugging information acts like
|
|
@c @code{step}, but any function calls appearing within the code of the
|
|
@c function are executed without stopping.
|
|
|
|
The @code{next} command only stops at the first instruction of a
|
|
source line. This prevents multiple stops that could otherwise occur in
|
|
@code{switch} statements, @code{for} loops, etc.
|
|
|
|
@kindex set step-mode
|
|
@item set step-mode
|
|
@cindex functions without line info, and stepping
|
|
@cindex stepping into functions with no line info
|
|
@itemx set step-mode on
|
|
The @code{set step-mode on} command causes the @code{step} command to
|
|
stop at the first instruction of a function which contains no debug line
|
|
information rather than stepping over it.
|
|
|
|
This is useful in cases where you may be interested in inspecting the
|
|
machine instructions of a function which has no symbolic info and do not
|
|
want @value{GDBN} to automatically skip over this function.
|
|
|
|
@item set step-mode off
|
|
Causes the @code{step} command to step over any functions which contains no
|
|
debug information. This is the default.
|
|
|
|
@kindex finish
|
|
@item 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}).
|
|
|
|
@kindex until
|
|
@kindex u @r{(@code{until})}
|
|
@item until
|
|
@itemx 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} makes your program continue execution until it
|
|
exits the loop. In contrast, a @code{next} command at the end of a loop
|
|
simply steps back to the beginning of the loop, which forces you to step
|
|
through the next iteration.
|
|
|
|
@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}
|
|
@itemx 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.
|
|
|
|
@kindex stepi
|
|
@kindex si @r{(@code{stepi})}
|
|
@item stepi
|
|
@itemx stepi @var{arg}
|
|
@itemx 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 makes @value{GDBN} automatically display the next
|
|
instruction to be executed, each time your program stops. @xref{Auto
|
|
Display,, Automatic display}.
|
|
|
|
An argument is a repeat count, as in @code{step}.
|
|
|
|
@need 750
|
|
@kindex nexti
|
|
@kindex ni @r{(@code{nexti})}
|
|
@item nexti
|
|
@itemx nexti @var{arg}
|
|
@itemx 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
|
|
|
|
@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 character (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} (they 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 let the non-erroneous signals like
|
|
@code{SIGALRM} be silently passed to your program
|
|
(so as not to interfere with their role in the program's functioning)
|
|
but to stop your program immediately whenever an error signal happens.
|
|
You can change these settings with the @code{handle} command.
|
|
|
|
@table @code
|
|
@kindex info signals
|
|
@item info signals
|
|
@itemx info handle
|
|
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.
|
|
|
|
@code{info handle} is an alias for @code{info signals}.
|
|
|
|
@kindex handle
|
|
@item handle @var{signal} @var{keywords}@dots{}
|
|
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); a list of signal numbers of the form
|
|
@samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
|
|
known signals. 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
|
|
@itemx noignore
|
|
@value{GDBN} should allow your program to see this signal; your program
|
|
can handle the signal, or else it may terminate if the signal is fatal
|
|
and not handled. @code{pass} and @code{noignore} are synonyms.
|
|
|
|
@item nopass
|
|
@itemx ignore
|
|
@value{GDBN} should not allow your program to see this signal.
|
|
@code{nopass} and @code{ignore} are synonyms.
|
|
@end table
|
|
@c @end group
|
|
|
|
When a signal stops your program, the signal is not visible to the
|
|
program until you
|
|
continue. Your program sees 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 your
|
|
program sees that signal when you continue.
|
|
|
|
The default is set to @code{nostop}, @code{noprint}, @code{pass} for
|
|
non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
|
|
@code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
|
|
erroneous signals.
|
|
|
|
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}.
|
|
|
|
@node Thread Stops
|
|
@section Stopping and starting multi-thread programs
|
|
|
|
When your program has multiple threads (@pxref{Threads,, Debugging
|
|
programs with multiple threads}), you can choose whether to set
|
|
breakpoints on all threads, or on a particular thread.
|
|
|
|
@table @code
|
|
@cindex breakpoints and threads
|
|
@cindex thread breakpoints
|
|
@kindex break @dots{} thread @var{threadno}
|
|
@item break @var{linespec} thread @var{threadno}
|
|
@itemx break @var{linespec} thread @var{threadno} if @dots{}
|
|
@var{linespec} specifies source lines; there are several ways of
|
|
writing them, but the effect is always to specify some source line.
|
|
|
|
Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
|
|
to specify that you only want @value{GDBN} to stop the program when a
|
|
particular thread reaches this breakpoint. @var{threadno} is one of the
|
|
numeric thread identifiers assigned by @value{GDBN}, shown in the first
|
|
column of the @samp{info threads} display.
|
|
|
|
If you do not specify @samp{thread @var{threadno}} when you set a
|
|
breakpoint, the breakpoint applies to @emph{all} threads of your
|
|
program.
|
|
|
|
You can use the @code{thread} qualifier on conditional breakpoints as
|
|
well; in this case, place @samp{thread @var{threadno}} before the
|
|
breakpoint condition, like this:
|
|
|
|
@smallexample
|
|
(@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
|
|
@end smallexample
|
|
|
|
@end table
|
|
|
|
@cindex stopped threads
|
|
@cindex threads, stopped
|
|
Whenever your program stops under @value{GDBN} for any reason,
|
|
@emph{all} threads of execution stop, not just the current thread. This
|
|
allows you to examine the overall state of the program, including
|
|
switching between threads, without worrying that things may change
|
|
underfoot.
|
|
|
|
@cindex continuing threads
|
|
@cindex threads, continuing
|
|
Conversely, whenever you restart the program, @emph{all} threads start
|
|
executing. @emph{This is true even when single-stepping} with commands
|
|
like @code{step} or @code{next}.
|
|
|
|
In particular, @value{GDBN} cannot single-step all threads in lockstep.
|
|
Since thread scheduling is up to your debugging target's operating
|
|
system (not controlled by @value{GDBN}), other threads may
|
|
execute more than one statement while the current thread completes a
|
|
single step. Moreover, in general other threads stop in the middle of a
|
|
statement, rather than at a clean statement boundary, when the program
|
|
stops.
|
|
|
|
You might even find your program stopped in another thread after
|
|
continuing or even single-stepping. This happens whenever some other
|
|
thread runs into a breakpoint, a signal, or an exception before the
|
|
first thread completes whatever you requested.
|
|
|
|
On some OSes, you can lock the OS scheduler and thus allow only a single
|
|
thread to run.
|
|
|
|
@table @code
|
|
@item set scheduler-locking @var{mode}
|
|
Set the scheduler locking mode. If it is @code{off}, then there is no
|
|
locking and any thread may run at any time. If @code{on}, then only the
|
|
current thread may run when the inferior is resumed. The @code{step}
|
|
mode optimizes for single-stepping. It stops other threads from
|
|
``seizing the prompt'' by preempting the current thread while you are
|
|
stepping. Other threads will only rarely (or never) get a chance to run
|
|
when you step. They are more likely to run when you @samp{next} over a
|
|
function call, and they are completely free to run when you use commands
|
|
like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
|
|
thread hits a breakpoint during its timeslice, they will never steal the
|
|
@value{GDBN} prompt away from the thread that you are debugging.
|
|
|
|
@item show scheduler-locking
|
|
Display the current scheduler locking mode.
|
|
@end table
|
|
|
|
|
|
@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, information about the call
|
|
is generated.
|
|
That information includes the location of the call in your program,
|
|
the arguments of the call,
|
|
and the local variables of the function being called.
|
|
The information is saved in a block of data called a @dfn{stack frame}.
|
|
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. @xref{Selection, ,Selecting a frame}.
|
|
|
|
When your program stops, @value{GDBN} automatically selects the
|
|
currently executing frame and describes it briefly, similar to the
|
|
@code{frame} command (@pxref{Frame Info, ,Information about a frame}).
|
|
|
|
@menu
|
|
* Frames:: Stack frames
|
|
* Backtrace:: Backtraces
|
|
* Selection:: Selecting a frame
|
|
* Frame Info:: Information on a frame
|
|
|
|
@end menu
|
|
|
|
@node Frames
|
|
@section Stack frames
|
|
|
|
@cindex frame, definition
|
|
@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 byte 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.
|
|
|
|
@c The -fomit-frame-pointer below perennially causes hbox overflow
|
|
@c underflow problems.
|
|
@cindex frameless execution
|
|
Some compilers provide a way to compile functions so that they operate
|
|
without stack frames. (For example, the @value{GCC} option
|
|
@example
|
|
@samp{-fomit-frame-pointer}
|
|
@end example
|
|
generates 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} nevertheless regards it as though
|
|
it had a separate frame, which is numbered zero as usual, allowing
|
|
correct tracing of the function call chain. However, @value{GDBN} has
|
|
no provision for frameless functions elsewhere in the stack.
|
|
|
|
@table @code
|
|
@kindex frame@r{, command}
|
|
@cindex current stack frame
|
|
@item frame @var{args}
|
|
The @code{frame} command allows you to move from one stack frame to another,
|
|
and to print the stack frame you select. @var{args} may be either the
|
|
address of the frame or the stack frame number. Without an argument,
|
|
@code{frame} prints the current stack frame.
|
|
|
|
@kindex select-frame
|
|
@cindex selecting frame silently
|
|
@item select-frame
|
|
The @code{select-frame} command allows you to move from one stack frame
|
|
to another without printing the frame. This is the silent version of
|
|
@code{frame}.
|
|
@end table
|
|
|
|
@node Backtrace
|
|
@section Backtraces
|
|
|
|
@cindex backtraces
|
|
@cindex tracebacks
|
|
@cindex stack traces
|
|
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
|
|
@kindex backtrace
|
|
@kindex bt @r{(@code{backtrace})}
|
|
@item backtrace
|
|
@itemx 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 @r{(@code{info stack})}
|
|
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
|
|
@kindex frame@r{, selecting}
|
|
@kindex f @r{(@code{frame})}
|
|
@item frame @var{n}
|
|
@itemx f @var{n}
|
|
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.
|
|
|
|
On the SPARC architecture, @code{frame} needs two addresses to
|
|
select an arbitrary frame: a frame pointer and a stack pointer.
|
|
|
|
On the MIPS and Alpha architecture, it needs two addresses: a stack
|
|
pointer and a program counter.
|
|
|
|
On the 29k architecture, it needs three addresses: a register stack
|
|
pointer, a program counter, and a memory stack pointer.
|
|
@c note to future updaters: this is conditioned on a flag
|
|
@c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
|
|
@c as of 27 Jan 1994.
|
|
|
|
@kindex up
|
|
@item up @var{n}
|
|
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.
|
|
|
|
@kindex down
|
|
@kindex do @r{(@code{down})}
|
|
@item down @var{n}
|
|
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.
|
|
|
|
@need 1000
|
|
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
|
|
prints ten lines centered on the point of execution in the frame.
|
|
@xref{List, ,Printing source lines}.
|
|
|
|
@table @code
|
|
@kindex down-silently
|
|
@kindex up-silently
|
|
@item up-silently @var{n}
|
|
@itemx down-silently @var{n}
|
|
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}.
|
|
|
|
@kindex info frame
|
|
@kindex info f @r{(@code{info frame})}
|
|
@item info frame
|
|
@itemx info f
|
|
This command prints a verbose description of the selected stack frame,
|
|
including:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
the address of the frame
|
|
@item
|
|
the address of the next frame down (called by this frame)
|
|
@item
|
|
the address of the next frame up (caller of this frame)
|
|
@item
|
|
the language in which the source code corresponding to this frame is written
|
|
@item
|
|
the address of the frame's arguments
|
|
@item
|
|
the address of the frame's local variables
|
|
@item
|
|
the program counter saved in it (the address of execution in the caller frame)
|
|
@item
|
|
which registers were saved in the frame
|
|
@end itemize
|
|
|
|
@noindent 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. This requires the same kind of address (more than one for some
|
|
architectures) that you specify in the @code{frame} command.
|
|
@xref{Selection, ,Selecting a frame}.
|
|
|
|
@kindex info args
|
|
@item 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.
|
|
|
|
@kindex info catch
|
|
@cindex catch exceptions, list active handlers
|
|
@cindex exception handlers, how to list
|
|
@item info catch
|
|
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{Set Catchpoints, , Setting catchpoints}.
|
|
|
|
@end table
|
|
|
|
|
|
@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.
|
|
|
|
If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
|
|
prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
|
|
@value{GDBN} under @sc{gnu} Emacs}.
|
|
|
|
@menu
|
|
* List:: Printing source lines
|
|
* Search:: Searching source files
|
|
* Source Path:: Specifying source directories
|
|
* Machine Code:: Source and machine code
|
|
@end menu
|
|
|
|
@node List
|
|
@section Printing source lines
|
|
|
|
@kindex list
|
|
@kindex l @r{(@code{list})}
|
|
To print lines from a source file, use the @code{list} command
|
|
(abbreviated @code{l}). By default, ten lines are printed.
|
|
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
|
|
@kindex set listsize
|
|
@item set listsize @var{count}
|
|
Make the @code{list} command display @var{count} source lines (unless
|
|
the @code{list} argument explicitly specifies some other number).
|
|
|
|
@kindex show listsize
|
|
@item show listsize
|
|
Display the number of lines that @code{list} prints.
|
|
@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}
|
|
Specifies the line that begins the body of the function @var{function}.
|
|
For example: in C, this is the line with the open brace.
|
|
|
|
@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
|
|
|
|
@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
|
|
@kindex search
|
|
@kindex forward-search
|
|
@item forward-search @var{regexp}
|
|
@itemx search @var{regexp}
|
|
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 the
|
|
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
|
|
|
|
@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} looks in the current directory as a
|
|
last resort.
|
|
|
|
Whenever you reset or rearrange the source path, @value{GDBN} clears out
|
|
any information it has cached about where source files are found and where
|
|
each line is in the file.
|
|
|
|
@kindex directory
|
|
@kindex dir
|
|
When you start @value{GDBN}, its source path includes only @samp{cdir}
|
|
and @samp{cwd}, in that order.
|
|
To add other directories, use the @code{directory} command.
|
|
|
|
@table @code
|
|
@item directory @var{dirname} @dots{}
|
|
@item dir @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{:}
|
|
(@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
|
|
part of absolute file names) or
|
|
whitespace. You may specify a directory that is already in the source
|
|
path; this moves it forward, so @value{GDBN} searches it sooner.
|
|
|
|
@kindex cdir
|
|
@kindex cwd
|
|
@vindex $cdir@r{, convenience variable}
|
|
@vindex $cwdr@r{, convenience variable}
|
|
@cindex compilation directory
|
|
@cindex current directory
|
|
@cindex working directory
|
|
@cindex directory, current
|
|
@cindex directory, compilation
|
|
You can use the string @samp{$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. When run under @sc{gnu} Emacs
|
|
mode, the @code{info line} command causes the arrow to point to the
|
|
line specified. Also, @code{info line} prints addresses in symbolic form as
|
|
well as hex.
|
|
|
|
@table @code
|
|
@kindex info line
|
|
@item info line @var{linespec}
|
|
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}:
|
|
|
|
@c FIXME: I think this example should also show the addresses in
|
|
@c symbolic form, as they usually would be displayed.
|
|
@smallexample
|
|
(@value{GDBP}) info line m4_changequote
|
|
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{$_} and @code{info line}
|
|
@kindex x@r{(examine), and} info line
|
|
After @code{info line}, the default address for the @code{x} command
|
|
is changed to the starting address of the line, so that @samp{x/i} is
|
|
sufficient to begin examining the machine code (@pxref{Memory,
|
|
,Examining memory}). Also, this address is saved as the value of the
|
|
convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
|
|
variables}).
|
|
|
|
@table @code
|
|
@kindex disassemble
|
|
@cindex assembly instructions
|
|
@cindex instructions, assembly
|
|
@cindex machine instructions
|
|
@cindex listing machine instructions
|
|
@item disassemble
|
|
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; @value{GDBN} dumps the function
|
|
surrounding this value. Two arguments specify a range of addresses
|
|
(first inclusive, second exclusive) to dump.
|
|
@end table
|
|
|
|
The following example shows the disassembly of a range of addresses of
|
|
HP PA-RISC 2.0 code:
|
|
|
|
@smallexample
|
|
(@value{GDBP}) disas 0x32c4 0x32e4
|
|
Dump of assembler code from 0x32c4 to 0x32e4:
|
|
0x32c4 <main+204>: addil 0,dp
|
|
0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
|
|
0x32cc <main+212>: ldil 0x3000,r31
|
|
0x32d0 <main+216>: ble 0x3f8(sr4,r31)
|
|
0x32d4 <main+220>: ldo 0(r31),rp
|
|
0x32d8 <main+224>: addil -0x800,dp
|
|
0x32dc <main+228>: ldo 0x588(r1),r26
|
|
0x32e0 <main+232>: ldil 0x3000,r31
|
|
End of assembler dump.
|
|
@end smallexample
|
|
|
|
Some architectures have more than one commonly-used set of instruction
|
|
mnemonics or other syntax.
|
|
|
|
@table @code
|
|
@kindex set disassembly-flavor
|
|
@cindex assembly instructions
|
|
@cindex instructions, assembly
|
|
@cindex machine instructions
|
|
@cindex listing machine instructions
|
|
@cindex Intel disassembly flavor
|
|
@cindex AT&T disassembly flavor
|
|
@item set disassembly-flavor @var{instruction-set}
|
|
Select the instruction set to use when disassembling the
|
|
program via the @code{disassemble} or @code{x/i} commands.
|
|
|
|
Currently this command is only defined for the Intel x86 family. You
|
|
can set @var{instruction-set} to either @code{intel} or @code{att}.
|
|
The default is @code{att}, the AT&T flavor used by default by Unix
|
|
assemblers for x86-based targets.
|
|
@end table
|
|
|
|
|
|
@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}. 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}).
|
|
|
|
@table @code
|
|
@item print @var{expr}
|
|
@itemx print /@var{f} @var{expr}
|
|
@var{expr} is an expression (in the source language). By default the
|
|
value of @var{expr} 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; see @ref{Output Formats,,Output
|
|
formats}.
|
|
|
|
@item print
|
|
@itemx print /@var{f}
|
|
If you omit @var{expr}, @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 or a class 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
|
|
* Floating Point Hardware:: Floating point hardware
|
|
* Memory Region Attributes:: Memory region attributes
|
|
@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.
|
|
|
|
@value{GDBN} supports array constants in expressions input by
|
|
the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
|
|
you can use the command @code{print @{1, 2, 3@}} to build up an array in
|
|
memory that is @code{malloc}ed in the target program.
|
|
|
|
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 in order to examine a structure
|
|
at that address in memory.
|
|
@c FIXME: casts supported---Mod2 true?
|
|
|
|
@value{GDBN} supports these operators, in addition to those common
|
|
to 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}.
|
|
|
|
@cindex @{@var{type}@}
|
|
@cindex type casting memory
|
|
@cindex memory, viewing as typed object
|
|
@cindex casts, to view memory
|
|
@item @{@var{type}@} @var{addr}
|
|
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 be either:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
global (or file-static)
|
|
@end itemize
|
|
|
|
@noindent or
|
|
|
|
@itemize @bullet
|
|
@item
|
|
visible according to the scope rules of the
|
|
programming language from the point of execution in that frame
|
|
@end itemize
|
|
|
|
@noindent 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, context for variables/functions
|
|
@iftex
|
|
@c info cannot cope with a :: index entry, but why deprive hard copy readers?
|
|
@cindex @code{::}, context for variables/functions
|
|
@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
|
|
|
|
@cindex C@t{++} scope resolution
|
|
This use of @samp{::} is very rarely in conflict with the very similar
|
|
use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
|
|
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
|
|
|
|
@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.
|
|
|
|
This may also happen when the compiler does significant optimizations.
|
|
To be sure of always seeing accurate values, turn off all optimization
|
|
when compiling.
|
|
|
|
@cindex ``No symbol "foo" in current context''
|
|
Another possible effect of compiler optimizations is to optimize
|
|
unused variables out of existence, or assign variables to registers (as
|
|
opposed to memory addresses). Depending on the support for such cases
|
|
offered by the debug info format used by the compiler, @value{GDBN}
|
|
might not be able to display values for such local variables. If that
|
|
happens, @value{GDBN} will print a message like this:
|
|
|
|
@example
|
|
No symbol "foo" in current context.
|
|
@end example
|
|
|
|
To solve such problems, either recompile without optimizations, or use a
|
|
different debug info format, if the compiler supports several such
|
|
formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler usually
|
|
supports the @samp{-gstabs} option. @samp{-gstabs} produces debug info
|
|
in a format that is superior to formats such as COFF. You may be able
|
|
to use DWARF2 (@samp{-gdwarf-2}), which is also an effective form for
|
|
debug info. See @ref{Debugging Options,,Options for Debugging Your
|
|
Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}, for more
|
|
information.
|
|
|
|
|
|
@node Arrays
|
|
@section Artificial arrays
|
|
|
|
@cindex artificial array
|
|
@kindex @@@r{, referencing memory as an array}
|
|
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
|
|
and be an individual object. The right operand should be the desired length
|
|
of the array. The result is an array value whose elements are all of
|
|
the type of the left argument. The first element is actually the left
|
|
argument; the second element comes from bytes of memory immediately
|
|
following those that hold the first element, and so on. Here is an
|
|
example. If a program says
|
|
|
|
@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.
|
|
|
|
Another way to create an artificial array is to use a cast.
|
|
This re-interprets a value as if it were an array.
|
|
The value need not be in memory:
|
|
@example
|
|
(@value{GDBP}) p/x (short[2])0x12345678
|
|
$1 = @{0x1234, 0x5678@}
|
|
@end example
|
|
|
|
As a convenience, if you leave the array length out (as in
|
|
@samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
|
|
the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
|
|
@example
|
|
(@value{GDBP}) p/x (short[])0x12345678
|
|
$2 = @{0x1234, 0x5678@}
|
|
@end example
|
|
|
|
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'';
|
|
see @ref{Memory,,Examining memory}.}
|
|
|
|
@item a
|
|
@cindex unknown address, locating
|
|
@cindex locate address
|
|
Print as an address, both absolute in hexadecimal and as an offset from
|
|
the nearest preceding symbol. You can use this format used to discover
|
|
where (in what function) an unknown address is located:
|
|
|
|
@example
|
|
(@value{GDBP}) p/a 0x54320
|
|
$3 = 0x54320 <_initialize_vx+396>
|
|
@end example
|
|
|
|
@noindent
|
|
The command @code{info symbol 0x54320} yields similar results.
|
|
@xref{Symbols, info symbol}.
|
|
|
|
@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 @r{(examine memory)}
|
|
@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},
|
|
@samp{s} (null-terminated string), or @samp{i} (machine instruction).
|
|
The default is @samp{x} (hexadecimal) initially.
|
|
The default changes each time you use 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, ,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 works. The output
|
|
specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
|
|
(However, the count @var{n} must come first; @samp{wx4} does 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; see @ref{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} prints 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
|
|
@kindex display
|
|
@item display @var{expr}
|
|
Add the expression @var{expr} to the list of expressions to display
|
|
each time your program stops. @xref{Expressions, ,Expressions}.
|
|
|
|
@code{display} does not repeat if you press @key{RET} again after using it.
|
|
|
|
@item display/@var{fmt} @var{expr}
|
|
For @var{fmt} specifying only a display format and not a size or
|
|
count, add the expression @var{expr} to the auto-display list but
|
|
arrange 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, ,Registers}).
|
|
|
|
@table @code
|
|
@kindex delete display
|
|
@kindex undisplay
|
|
@item undisplay @var{dnums}@dots{}
|
|
@itemx delete display @var{dnums}@dots{}
|
|
Remove item numbers @var{dnums} from the list of expressions to display.
|
|
|
|
@code{undisplay} does not repeat if you press @key{RET} after using it.
|
|
(Otherwise you would just get the error @samp{No display number @dots{}}.)
|
|
|
|
@kindex disable display
|
|
@item disable display @var{dnums}@dots{}
|
|
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.
|
|
|
|
@kindex enable display
|
|
@item enable display @var{dnums}@dots{}
|
|
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.
|
|
|
|
@kindex info display
|
|
@item 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}, @value{GDBN} displays this argument while your program
|
|
continues to stop inside that function. When it stops elsewhere---where
|
|
there is no variable @code{last_char}---the display is disabled
|
|
automatically. 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
|
|
@kindex set print address
|
|
@item set print address
|
|
@itemx set print address on
|
|
@value{GDBN} prints 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 @code{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}:
|
|
|
|
@smallexample
|
|
@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 smallexample
|
|
|
|
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.
|
|
|
|
@kindex show print address
|
|
@item show print address
|
|
Show whether or not addresses are to be printed.
|
|
@end table
|
|
|
|
When @value{GDBN} prints a symbolic address, it normally prints the
|
|
closest earlier symbol plus an offset. If that symbol does not uniquely
|
|
identify the address (for example, it is a name whose scope is a single
|
|
source file), you may need to clarify. One way to do this is with
|
|
@code{info line}, for example @samp{info line *0x4537}. Alternately,
|
|
you can set @value{GDBN} to print the source file and line number when
|
|
it prints a symbolic address:
|
|
|
|
@table @code
|
|
@kindex set print symbol-filename
|
|
@item set print symbol-filename on
|
|
Tell @value{GDBN} to print the source file name and line number of a
|
|
symbol in the symbolic form of an address.
|
|
|
|
@item set print symbol-filename off
|
|
Do not print source file name and line number of a symbol. This is the
|
|
default.
|
|
|
|
@kindex show print symbol-filename
|
|
@item show print symbol-filename
|
|
Show whether or not @value{GDBN} will print the source file name and
|
|
line number of a symbol in the symbolic form of an address.
|
|
@end table
|
|
|
|
Another situation where it is helpful to show symbol filenames and line
|
|
numbers is when disassembling code; @value{GDBN} shows you the line
|
|
number and source file that corresponds to each instruction.
|
|
|
|
Also, you may wish to see the symbolic form only if the address being
|
|
printed is reasonably close to the closest earlier symbol:
|
|
|
|
@table @code
|
|
@kindex set print max-symbolic-offset
|
|
@item set print max-symbolic-offset @var{max-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{max-offset}. The default is 0, which tells @value{GDBN}
|
|
to always print the symbolic form of an address if any symbol precedes it.
|
|
|
|
@kindex show print max-symbolic-offset
|
|
@item show print max-symbolic-offset
|
|
Ask how large the maximum offset is that @value{GDBN} prints in a
|
|
symbolic address.
|
|
@end table
|
|
|
|
@cindex wild pointer, interpreting
|
|
@cindex pointer, finding referent
|
|
If you have a pointer and you are not sure where it points, try
|
|
@samp{set print symbol-filename on}. Then you can determine the name
|
|
and source file location of the variable where it points, using
|
|
@samp{p/a @var{pointer}}. This interprets the address in symbolic form.
|
|
For example, here @value{GDBN} shows that a variable @code{ptt} points
|
|
at another variable @code{t}, defined in @file{hi2.c}:
|
|
|
|
@example
|
|
(@value{GDBP}) set print symbol-filename on
|
|
(@value{GDBP}) p/a ptt
|
|
$4 = 0xe008 <t in hi2.c>
|
|
@end example
|
|
|
|
@quotation
|
|
@emph{Warning:} For pointers that point to a local variable, @samp{p/a}
|
|
does not show the symbol name and filename of the referent, even with
|
|
the appropriate @code{set print} options turned on.
|
|
@end quotation
|
|
|
|
Other settings control how different kinds of objects are printed:
|
|
|
|
@table @code
|
|
@kindex set print array
|
|
@item set print array
|
|
@itemx set print array on
|
|
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.
|
|
|
|
@kindex show print array
|
|
@item show print array
|
|
Show whether compressed or pretty format is selected for displaying
|
|
arrays.
|
|
|
|
@kindex set print elements
|
|
@item set print elements @var{number-of-elements}
|
|
Set a limit on how many elements of an array @value{GDBN} will print.
|
|
If @value{GDBN} is printing a large array, it stops 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.
|
|
When @value{GDBN} starts, this limit is set to 200.
|
|
Setting @var{number-of-elements} to zero means that the printing is unlimited.
|
|
|
|
@kindex show print elements
|
|
@item show print elements
|
|
Display the number of elements of a large array that @value{GDBN} will print.
|
|
If the number is 0, then the printing is unlimited.
|
|
|
|
@kindex set print null-stop
|
|
@item set print null-stop
|
|
Cause @value{GDBN} to stop printing the characters of an array when the first
|
|
@sc{null} is encountered. This is useful when large arrays actually
|
|
contain only short strings.
|
|
The default is off.
|
|
|
|
@kindex set print pretty
|
|
@item set print pretty on
|
|
Cause @value{GDBN} to print structures in an indented format with one member
|
|
per line, like this:
|
|
|
|
@smallexample
|
|
@group
|
|
$1 = @{
|
|
next = 0x0,
|
|
flags = @{
|
|
sweet = 1,
|
|
sour = 1
|
|
@},
|
|
meat = 0x54 "Pork"
|
|
@}
|
|
@end group
|
|
@end smallexample
|
|
|
|
@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.
|
|
|
|
@kindex show print pretty
|
|
@item show print pretty
|
|
Show which format @value{GDBN} is using to print structures.
|
|
|
|
@kindex set print sevenbit-strings
|
|
@item set print sevenbit-strings on
|
|
Print using only seven-bit characters; if this option is set,
|
|
@value{GDBN} displays any eight-bit characters (in strings or
|
|
character values) using the notation @code{\}@var{nnn}. This setting is
|
|
best if you are working in English (@sc{ascii}) and you use the
|
|
high-order bit of characters as a marker or ``meta'' bit.
|
|
|
|
@item set print sevenbit-strings off
|
|
Print full eight-bit characters. This allows the use of more
|
|
international character sets, and is the default.
|
|
|
|
@kindex show print sevenbit-strings
|
|
@item show print sevenbit-strings
|
|
Show whether or not @value{GDBN} is printing only seven-bit characters.
|
|
|
|
@kindex set print union
|
|
@item set print union on
|
|
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.
|
|
|
|
@kindex show print union
|
|
@item 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
|
|
@end table
|
|
|
|
@need 1000
|
|
@noindent
|
|
These settings are of interest when debugging C@t{++} programs:
|
|
|
|
@table @code
|
|
@cindex demangling
|
|
@kindex set print demangle
|
|
@item set print demangle
|
|
@itemx set print demangle on
|
|
Print C@t{++} 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 on.
|
|
|
|
@kindex show print demangle
|
|
@item show print demangle
|
|
Show whether C@t{++} names are printed in mangled or demangled form.
|
|
|
|
@kindex set print asm-demangle
|
|
@item set print asm-demangle
|
|
@itemx set print asm-demangle on
|
|
Print C@t{++} names in their source form rather than their mangled form, even
|
|
in assembler code printouts such as instruction disassemblies.
|
|
The default is off.
|
|
|
|
@kindex show print asm-demangle
|
|
@item show print asm-demangle
|
|
Show whether C@t{++} names in assembly listings are printed in mangled
|
|
or demangled form.
|
|
|
|
@kindex set demangle-style
|
|
@cindex C@t{++} symbol decoding style
|
|
@cindex symbol decoding style, C@t{++}
|
|
@item set demangle-style @var{style}
|
|
Choose among several encoding schemes used by different compilers to
|
|
represent C@t{++} 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 @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
|
|
This is the default.
|
|
|
|
@item hp
|
|
Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
|
|
|
|
@item lucid
|
|
Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
|
|
|
|
@item arm
|
|
Decode using the algorithm in the @cite{C@t{++} 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
|
|
If you omit @var{style}, you will see a list of possible formats.
|
|
|
|
@kindex show demangle-style
|
|
@item show demangle-style
|
|
Display the encoding style currently in use for decoding C@t{++} symbols.
|
|
|
|
@kindex set print object
|
|
@item set print object
|
|
@itemx set print object on
|
|
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.
|
|
|
|
@kindex show print object
|
|
@item show print object
|
|
Show whether actual, or declared, object types are displayed.
|
|
|
|
@kindex set print static-members
|
|
@item set print static-members
|
|
@itemx set print static-members on
|
|
Print static members when displaying a C@t{++} object. The default is on.
|
|
|
|
@item set print static-members off
|
|
Do not print static members when displaying a C@t{++} object.
|
|
|
|
@kindex show print static-members
|
|
@item show print static-members
|
|
Show whether C@t{++} static members are printed, or not.
|
|
|
|
@c These don't work with HP ANSI C++ yet.
|
|
@kindex set print vtbl
|
|
@item set print vtbl
|
|
@itemx set print vtbl on
|
|
Pretty print C@t{++} virtual function tables. The default is off.
|
|
(The @code{vtbl} commands do not work on programs compiled with the HP
|
|
ANSI C@t{++} compiler (@code{aCC}).)
|
|
|
|
@item set print vtbl off
|
|
Do not pretty print C@t{++} virtual function tables.
|
|
|
|
@kindex show print vtbl
|
|
@item show print vtbl
|
|
Show whether C@t{++} virtual function tables are pretty printed, or not.
|
|
@end table
|
|
|
|
@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}. This allows you to 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{$$}
|
|
@cindex history number
|
|
The values printed are given @dfn{history numbers} by which you can
|
|
refer to them. These are successive integers starting with one.
|
|
@code{print} shows you the history number assigned to a value by
|
|
printing @samp{$@var{num} = } before the value; here @var{num} is the
|
|
history number.
|
|
|
|
To refer to any previous value, use @samp{$} followed by the value's
|
|
history number. The way @code{print} labels its output is designed to
|
|
remind you of this. Just @code{$} refers to the most recent value in
|
|
the history, and @code{$$} 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, @code{show values +} 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, ,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
|
|
@kindex show convenience
|
|
@item show convenience
|
|
Print a list of convenience variables used so far, and their values.
|
|
Abbreviated @code{show conv}.
|
|
@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
|
|
@end example
|
|
|
|
@noindent
|
|
Repeat that command by typing @key{RET}.
|
|
|
|
Some convenience variables are created automatically by @value{GDBN} and given
|
|
values likely to be useful.
|
|
|
|
@table @code
|
|
@vindex $_@r{, convenience variable}
|
|
@item $_
|
|
The variable @code{$_} 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{$__}.
|
|
|
|
@vindex $__@r{, convenience variable}
|
|
@item $__
|
|
The variable @code{$__} 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.
|
|
|
|
@item $_exitcode
|
|
@vindex $_exitcode@r{, convenience variable}
|
|
The variable @code{$_exitcode} is automatically set to the exit code when
|
|
the program being debugged terminates.
|
|
@end table
|
|
|
|
On HP-UX systems, if you refer to a function or variable name that
|
|
begins with a dollar sign, @value{GDBN} searches for a user or system
|
|
name first, before it searches for a convenience variable.
|
|
|
|
@node Registers
|
|
@section Registers
|
|
|
|
@cindex registers
|
|
You can refer to machine register contents, in expressions, as variables
|
|
with names starting with @samp{$}. The names of registers are different
|
|
for each machine; use @code{info registers} to see the names used on
|
|
your machine.
|
|
|
|
@table @code
|
|
@kindex info registers
|
|
@item info registers
|
|
Print the names and values of all registers except floating-point
|
|
registers (in the selected stack frame).
|
|
|
|
@kindex info all-registers
|
|
@cindex floating point registers
|
|
@item info all-registers
|
|
Print the names and values of all registers, including floating-point
|
|
registers.
|
|
|
|
@item info registers @var{regname} @dots{}
|
|
Print the @dfn{relativized} value of each specified register @var{regname}.
|
|
As discussed in detail below, register values are normally relative to
|
|
the selected stack frame. @var{regname} may be any register name valid on
|
|
the machine you are using, with or without the initial @samp{$}.
|
|
@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};
|
|
see @ref{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{$ps}; and on x86-based machines @code{$ps}
|
|
is an alias for the @sc{eflags} register.
|
|
|
|
@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 makes no difference.
|
|
|
|
@node Floating Point Hardware
|
|
@section Floating point hardware
|
|
@cindex floating point
|
|
|
|
Depending on the configuration, @value{GDBN} may be able to give
|
|
you more information about the status of the floating point hardware.
|
|
|
|
@table @code
|
|
@kindex info float
|
|
@item info float
|
|
Display hardware-dependent information about the floating
|
|
point unit. The exact contents and layout vary depending on the
|
|
floating point chip. Currently, @samp{info float} is supported on
|
|
the ARM and x86 machines.
|
|
@end table
|
|
|
|
@node Memory Region Attributes
|
|
@section Memory Region Attributes
|
|
@cindex memory region attributes
|
|
|
|
@dfn{Memory region attributes} allow you to describe special handling
|
|
required by regions of your target's memory. @value{GDBN} uses attributes
|
|
to determine whether to allow certain types of memory accesses; whether to
|
|
use specific width accesses; and whether to cache target memory.
|
|
|
|
Defined memory regions can be individually enabled and disabled. When a
|
|
memory region is disabled, @value{GDBN} uses the default attributes when
|
|
accessing memory in that region. Similarly, if no memory regions have
|
|
been defined, @value{GDBN} uses the default attributes when accessing
|
|
all memory.
|
|
|
|
When a memory region is defined, it is given a number to identify it;
|
|
to enable, disable, or remove a memory region, you specify that number.
|
|
|
|
@table @code
|
|
@kindex mem
|
|
@item mem @var{address1} @var{address1} @var{attributes}@dots{}
|
|
Define memory region bounded by @var{address1} and @var{address2}
|
|
with attributes @var{attributes}@dots{}.
|
|
|
|
@kindex delete mem
|
|
@item delete mem @var{nums}@dots{}
|
|
Remove memory region numbers @var{nums}.
|
|
|
|
@kindex disable mem
|
|
@item disable mem @var{nums}@dots{}
|
|
Disable memory region numbers @var{nums}.
|
|
A disabled memory region is not forgotten.
|
|
It may be enabled again later.
|
|
|
|
@kindex enable mem
|
|
@item enable mem @var{nums}@dots{}
|
|
Enable memory region numbers @var{nums}.
|
|
|
|
@kindex info mem
|
|
@item info mem
|
|
Print a table of all defined memory regions, with the following columns
|
|
for each region.
|
|
|
|
@table @emph
|
|
@item Memory Region Number
|
|
@item Enabled or Disabled.
|
|
Enabled memory regions are marked with @samp{y}.
|
|
Disabled memory regions are marked with @samp{n}.
|
|
|
|
@item Lo Address
|
|
The address defining the inclusive lower bound of the memory region.
|
|
|
|
@item Hi Address
|
|
The address defining the exclusive upper bound of the memory region.
|
|
|
|
@item Attributes
|
|
The list of attributes set for this memory region.
|
|
@end table
|
|
@end table
|
|
|
|
|
|
@subsection Attributes
|
|
|
|
@subsubsection Memory Access Mode
|
|
The access mode attributes set whether @value{GDBN} may make read or
|
|
write accesses to a memory region.
|
|
|
|
While these attributes prevent @value{GDBN} from performing invalid
|
|
memory accesses, they do nothing to prevent the target system, I/O DMA,
|
|
etc. from accessing memory.
|
|
|
|
@table @code
|
|
@item ro
|
|
Memory is read only.
|
|
@item wo
|
|
Memory is write only.
|
|
@item rw
|
|
Memory is read/write (default).
|
|
@end table
|
|
|
|
@subsubsection Memory Access Size
|
|
The acccess size attributes tells @value{GDBN} to use specific sized
|
|
accesses in the memory region. Often memory mapped device registers
|
|
require specific sized accesses. If no access size attribute is
|
|
specified, @value{GDBN} may use accesses of any size.
|
|
|
|
@table @code
|
|
@item 8
|
|
Use 8 bit memory accesses.
|
|
@item 16
|
|
Use 16 bit memory accesses.
|
|
@item 32
|
|
Use 32 bit memory accesses.
|
|
@item 64
|
|
Use 64 bit memory accesses.
|
|
@end table
|
|
|
|
@c @subsubsection Hardware/Software Breakpoints
|
|
@c The hardware/software breakpoint attributes set whether @value{GDBN}
|
|
@c will use hardware or software breakpoints for the internal breakpoints
|
|
@c used by the step, next, finish, until, etc. commands.
|
|
@c
|
|
@c @table @code
|
|
@c @item hwbreak
|
|
@c Always use hardware breakpoints
|
|
@c @item swbreak (default)
|
|
@c @end table
|
|
|
|
@subsubsection Data Cache
|
|
The data cache attributes set whether @value{GDBN} will cache target
|
|
memory. While this generally improves performance by reducing debug
|
|
protocol overhead, it can lead to incorrect results because @value{GDBN}
|
|
does not know about volatile variables or memory mapped device
|
|
registers.
|
|
|
|
@table @code
|
|
@item cache
|
|
Enable @value{GDBN} to cache target memory.
|
|
@item nocache (default)
|
|
Disable @value{GDBN} from caching target memory.
|
|
@end table
|
|
|
|
@c @subsubsection Memory Write Verification
|
|
@c The memory write verification attributes set whether @value{GDBN}
|
|
@c will re-reads data after each write to verify the write was successful.
|
|
@c
|
|
@c @table @code
|
|
@c @item verify
|
|
@c @item noverify (default)
|
|
@c @end table
|
|
|
|
@node Tracepoints
|
|
@chapter Tracepoints
|
|
@c This chapter is based on the documentation written by Michael
|
|
@c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
|
|
|
|
@cindex tracepoints
|
|
In some applications, it is not feasible for the debugger to interrupt
|
|
the program's execution long enough for the developer to learn
|
|
anything helpful about its behavior. If the program's correctness
|
|
depends on its real-time behavior, delays introduced by a debugger
|
|
might cause the program to change its behavior drastically, or perhaps
|
|
fail, even when the code itself is correct. It is useful to be able
|
|
to observe the program's behavior without interrupting it.
|
|
|
|
Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
|
|
specify locations in the program, called @dfn{tracepoints}, and
|
|
arbitrary expressions to evaluate when those tracepoints are reached.
|
|
Later, using the @code{tfind} command, you can examine the values
|
|
those expressions had when the program hit the tracepoints. The
|
|
expressions may also denote objects in memory---structures or arrays,
|
|
for example---whose values @value{GDBN} should record; while visiting
|
|
a particular tracepoint, you may inspect those objects as if they were
|
|
in memory at that moment. However, because @value{GDBN} records these
|
|
values without interacting with you, it can do so quickly and
|
|
unobtrusively, hopefully not disturbing the program's behavior.
|
|
|
|
The tracepoint facility is currently available only for remote
|
|
targets. @xref{Targets}. In addition, your remote target must know how
|
|
to collect trace data. This functionality is implemented in the remote
|
|
stub; however, none of the stubs distributed with @value{GDBN} support
|
|
tracepoints as of this writing.
|
|
|
|
This chapter describes the tracepoint commands and features.
|
|
|
|
@menu
|
|
* Set Tracepoints::
|
|
* Analyze Collected Data::
|
|
* Tracepoint Variables::
|
|
@end menu
|
|
|
|
@node Set Tracepoints
|
|
@section Commands to Set Tracepoints
|
|
|
|
Before running such a @dfn{trace experiment}, an arbitrary number of
|
|
tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
|
|
tracepoint has a number assigned to it by @value{GDBN}. Like with
|
|
breakpoints, tracepoint numbers are successive integers starting from
|
|
one. Many of the commands associated with tracepoints take the
|
|
tracepoint number as their argument, to identify which tracepoint to
|
|
work on.
|
|
|
|
For each tracepoint, you can specify, in advance, some arbitrary set
|
|
of data that you want the target to collect in the trace buffer when
|
|
it hits that tracepoint. The collected data can include registers,
|
|
local variables, or global data. Later, you can use @value{GDBN}
|
|
commands to examine the values these data had at the time the
|
|
tracepoint was hit.
|
|
|
|
This section describes commands to set tracepoints and associated
|
|
conditions and actions.
|
|
|
|
@menu
|
|
* Create and Delete Tracepoints::
|
|
* Enable and Disable Tracepoints::
|
|
* Tracepoint Passcounts::
|
|
* Tracepoint Actions::
|
|
* Listing Tracepoints::
|
|
* Starting and Stopping Trace Experiment::
|
|
@end menu
|
|
|
|
@node Create and Delete Tracepoints
|
|
@subsection Create and Delete Tracepoints
|
|
|
|
@table @code
|
|
@cindex set tracepoint
|
|
@kindex trace
|
|
@item trace
|
|
The @code{trace} command is very similar to the @code{break} command.
|
|
Its argument can be a source line, a function name, or an address in
|
|
the target program. @xref{Set Breaks}. The @code{trace} command
|
|
defines a tracepoint, which is a point in the target program where the
|
|
debugger will briefly stop, collect some data, and then allow the
|
|
program to continue. Setting a tracepoint or changing its commands
|
|
doesn't take effect until the next @code{tstart} command; thus, you
|
|
cannot change the tracepoint attributes once a trace experiment is
|
|
running.
|
|
|
|
Here are some examples of using the @code{trace} command:
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{trace foo.c:121} // a source file and line number
|
|
|
|
(@value{GDBP}) @b{trace +2} // 2 lines forward
|
|
|
|
(@value{GDBP}) @b{trace my_function} // first source line of function
|
|
|
|
(@value{GDBP}) @b{trace *my_function} // EXACT start address of function
|
|
|
|
(@value{GDBP}) @b{trace *0x2117c4} // an address
|
|
@end smallexample
|
|
|
|
@noindent
|
|
You can abbreviate @code{trace} as @code{tr}.
|
|
|
|
@vindex $tpnum
|
|
@cindex last tracepoint number
|
|
@cindex recent tracepoint number
|
|
@cindex tracepoint number
|
|
The convenience variable @code{$tpnum} records the tracepoint number
|
|
of the most recently set tracepoint.
|
|
|
|
@kindex delete tracepoint
|
|
@cindex tracepoint deletion
|
|
@item delete tracepoint @r{[}@var{num}@r{]}
|
|
Permanently delete one or more tracepoints. With no argument, the
|
|
default is to delete all tracepoints.
|
|
|
|
Examples:
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
|
|
|
|
(@value{GDBP}) @b{delete trace} // remove all tracepoints
|
|
@end smallexample
|
|
|
|
@noindent
|
|
You can abbreviate this command as @code{del tr}.
|
|
@end table
|
|
|
|
@node Enable and Disable Tracepoints
|
|
@subsection Enable and Disable Tracepoints
|
|
|
|
@table @code
|
|
@kindex disable tracepoint
|
|
@item disable tracepoint @r{[}@var{num}@r{]}
|
|
Disable tracepoint @var{num}, or all tracepoints if no argument
|
|
@var{num} is given. A disabled tracepoint will have no effect during
|
|
the next trace experiment, but it is not forgotten. You can re-enable
|
|
a disabled tracepoint using the @code{enable tracepoint} command.
|
|
|
|
@kindex enable tracepoint
|
|
@item enable tracepoint @r{[}@var{num}@r{]}
|
|
Enable tracepoint @var{num}, or all tracepoints. The enabled
|
|
tracepoints will become effective the next time a trace experiment is
|
|
run.
|
|
@end table
|
|
|
|
@node Tracepoint Passcounts
|
|
@subsection Tracepoint Passcounts
|
|
|
|
@table @code
|
|
@kindex passcount
|
|
@cindex tracepoint pass count
|
|
@item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
|
|
Set the @dfn{passcount} of a tracepoint. The passcount is a way to
|
|
automatically stop a trace experiment. If a tracepoint's passcount is
|
|
@var{n}, then the trace experiment will be automatically stopped on
|
|
the @var{n}'th time that tracepoint is hit. If the tracepoint number
|
|
@var{num} is not specified, the @code{passcount} command sets the
|
|
passcount of the most recently defined tracepoint. If no passcount is
|
|
given, the trace experiment will run until stopped explicitly by the
|
|
user.
|
|
|
|
Examples:
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of tracepoint 2
|
|
|
|
(@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
|
|
// most recently defined tracepoint.
|
|
(@value{GDBP}) @b{trace foo}
|
|
(@value{GDBP}) @b{pass 3}
|
|
(@value{GDBP}) @b{trace bar}
|
|
(@value{GDBP}) @b{pass 2}
|
|
(@value{GDBP}) @b{trace baz}
|
|
(@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
|
|
// executed 3 times OR when bar has
|
|
// been executed 2 times
|
|
// OR when baz has been executed 1 time.
|
|
@end smallexample
|
|
@end table
|
|
|
|
@node Tracepoint Actions
|
|
@subsection Tracepoint Action Lists
|
|
|
|
@table @code
|
|
@kindex actions
|
|
@cindex tracepoint actions
|
|
@item actions @r{[}@var{num}@r{]}
|
|
This command will prompt for a list of actions to be taken when the
|
|
tracepoint is hit. If the tracepoint number @var{num} is not
|
|
specified, this command sets the actions for the one that was most
|
|
recently defined (so that you can define a tracepoint and then say
|
|
@code{actions} without bothering about its number). You specify the
|
|
actions themselves on the following lines, one action at a time, and
|
|
terminate the actions list with a line containing just @code{end}. So
|
|
far, the only defined actions are @code{collect} and
|
|
@code{while-stepping}.
|
|
|
|
@cindex remove actions from a tracepoint
|
|
To remove all actions from a tracepoint, type @samp{actions @var{num}}
|
|
and follow it immediately with @samp{end}.
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{collect @var{data}} // collect some data
|
|
|
|
(@value{GDBP}) @b{while-stepping 5} // single-step 5 times and collect data
|
|
|
|
(@value{GDBP}) @b{end} // signals the end of actions.
|
|
@end smallexample
|
|
|
|
In the following example, the action list begins with @code{collect}
|
|
commands indicating the things to be collected when the tracepoint is
|
|
hit. Then, in order to single-step and collect additional data
|
|
following the tracepoint, a @code{while-stepping} command is used,
|
|
followed by the list of things to be collected while stepping. The
|
|
@code{while-stepping} command is terminated by its own separate
|
|
@code{end} command. Lastly, the action list is terminated by an
|
|
@code{end} command.
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{trace foo}
|
|
(@value{GDBP}) @b{actions}
|
|
Enter actions for tracepoint 1, one per line:
|
|
> collect bar,baz
|
|
> collect $regs
|
|
> while-stepping 12
|
|
> collect $fp, $sp
|
|
> end
|
|
end
|
|
@end smallexample
|
|
|
|
@kindex collect @r{(tracepoints)}
|
|
@item collect @var{expr1}, @var{expr2}, @dots{}
|
|
Collect values of the given expressions when the tracepoint is hit.
|
|
This command accepts a comma-separated list of any valid expressions.
|
|
In addition to global, static, or local variables, the following
|
|
special arguments are supported:
|
|
|
|
@table @code
|
|
@item $regs
|
|
collect all registers
|
|
|
|
@item $args
|
|
collect all function arguments
|
|
|
|
@item $locals
|
|
collect all local variables.
|
|
@end table
|
|
|
|
You can give several consecutive @code{collect} commands, each one
|
|
with a single argument, or one @code{collect} command with several
|
|
arguments separated by commas: the effect is the same.
|
|
|
|
The command @code{info scope} (@pxref{Symbols, info scope}) is
|
|
particularly useful for figuring out what data to collect.
|
|
|
|
@kindex while-stepping @r{(tracepoints)}
|
|
@item while-stepping @var{n}
|
|
Perform @var{n} single-step traces after the tracepoint, collecting
|
|
new data at each step. The @code{while-stepping} command is
|
|
followed by the list of what to collect while stepping (followed by
|
|
its own @code{end} command):
|
|
|
|
@smallexample
|
|
> while-stepping 12
|
|
> collect $regs, myglobal
|
|
> end
|
|
>
|
|
@end smallexample
|
|
|
|
@noindent
|
|
You may abbreviate @code{while-stepping} as @code{ws} or
|
|
@code{stepping}.
|
|
@end table
|
|
|
|
@node Listing Tracepoints
|
|
@subsection Listing Tracepoints
|
|
|
|
@table @code
|
|
@kindex info tracepoints
|
|
@cindex information about tracepoints
|
|
@item info tracepoints @r{[}@var{num}@r{]}
|
|
Display information the tracepoint @var{num}. If you don't specify a
|
|
tracepoint number displays information about all the tracepoints
|
|
defined so far. For each tracepoint, the following information is
|
|
shown:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
its number
|
|
@item
|
|
whether it is enabled or disabled
|
|
@item
|
|
its address
|
|
@item
|
|
its passcount as given by the @code{passcount @var{n}} command
|
|
@item
|
|
its step count as given by the @code{while-stepping @var{n}} command
|
|
@item
|
|
where in the source files is the tracepoint set
|
|
@item
|
|
its action list as given by the @code{actions} command
|
|
@end itemize
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{info trace}
|
|
Num Enb Address PassC StepC What
|
|
1 y 0x002117c4 0 0 <gdb_asm>
|
|
2 y 0x0020dc64 0 0 in gdb_test at gdb_test.c:375
|
|
3 y 0x0020b1f4 0 0 in collect_data at ../foo.c:1741
|
|
(@value{GDBP})
|
|
@end smallexample
|
|
|
|
@noindent
|
|
This command can be abbreviated @code{info tp}.
|
|
@end table
|
|
|
|
@node Starting and Stopping Trace Experiment
|
|
@subsection Starting and Stopping Trace Experiment
|
|
|
|
@table @code
|
|
@kindex tstart
|
|
@cindex start a new trace experiment
|
|
@cindex collected data discarded
|
|
@item tstart
|
|
This command takes no arguments. It starts the trace experiment, and
|
|
begins collecting data. This has the side effect of discarding all
|
|
the data collected in the trace buffer during the previous trace
|
|
experiment.
|
|
|
|
@kindex tstop
|
|
@cindex stop a running trace experiment
|
|
@item tstop
|
|
This command takes no arguments. It ends the trace experiment, and
|
|
stops collecting data.
|
|
|
|
@strong{Note:} a trace experiment and data collection may stop
|
|
automatically if any tracepoint's passcount is reached
|
|
(@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
|
|
|
|
@kindex tstatus
|
|
@cindex status of trace data collection
|
|
@cindex trace experiment, status of
|
|
@item tstatus
|
|
This command displays the status of the current trace data
|
|
collection.
|
|
@end table
|
|
|
|
Here is an example of the commands we described so far:
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{trace gdb_c_test}
|
|
(@value{GDBP}) @b{actions}
|
|
Enter actions for tracepoint #1, one per line.
|
|
> collect $regs,$locals,$args
|
|
> while-stepping 11
|
|
> collect $regs
|
|
> end
|
|
> end
|
|
(@value{GDBP}) @b{tstart}
|
|
[time passes @dots{}]
|
|
(@value{GDBP}) @b{tstop}
|
|
@end smallexample
|
|
|
|
|
|
@node Analyze Collected Data
|
|
@section Using the collected data
|
|
|
|
After the tracepoint experiment ends, you use @value{GDBN} commands
|
|
for examining the trace data. The basic idea is that each tracepoint
|
|
collects a trace @dfn{snapshot} every time it is hit and another
|
|
snapshot every time it single-steps. All these snapshots are
|
|
consecutively numbered from zero and go into a buffer, and you can
|
|
examine them later. The way you examine them is to @dfn{focus} on a
|
|
specific trace snapshot. When the remote stub is focused on a trace
|
|
snapshot, it will respond to all @value{GDBN} requests for memory and
|
|
registers by reading from the buffer which belongs to that snapshot,
|
|
rather than from @emph{real} memory or registers of the program being
|
|
debugged. This means that @strong{all} @value{GDBN} commands
|
|
(@code{print}, @code{info registers}, @code{backtrace}, etc.) will
|
|
behave as if we were currently debugging the program state as it was
|
|
when the tracepoint occurred. Any requests for data that are not in
|
|
the buffer will fail.
|
|
|
|
@menu
|
|
* tfind:: How to select a trace snapshot
|
|
* tdump:: How to display all data for a snapshot
|
|
* save-tracepoints:: How to save tracepoints for a future run
|
|
@end menu
|
|
|
|
@node tfind
|
|
@subsection @code{tfind @var{n}}
|
|
|
|
@kindex tfind
|
|
@cindex select trace snapshot
|
|
@cindex find trace snapshot
|
|
The basic command for selecting a trace snapshot from the buffer is
|
|
@code{tfind @var{n}}, which finds trace snapshot number @var{n},
|
|
counting from zero. If no argument @var{n} is given, the next
|
|
snapshot is selected.
|
|
|
|
Here are the various forms of using the @code{tfind} command.
|
|
|
|
@table @code
|
|
@item tfind start
|
|
Find the first snapshot in the buffer. This is a synonym for
|
|
@code{tfind 0} (since 0 is the number of the first snapshot).
|
|
|
|
@item tfind none
|
|
Stop debugging trace snapshots, resume @emph{live} debugging.
|
|
|
|
@item tfind end
|
|
Same as @samp{tfind none}.
|
|
|
|
@item tfind
|
|
No argument means find the next trace snapshot.
|
|
|
|
@item tfind -
|
|
Find the previous trace snapshot before the current one. This permits
|
|
retracing earlier steps.
|
|
|
|
@item tfind tracepoint @var{num}
|
|
Find the next snapshot associated with tracepoint @var{num}. Search
|
|
proceeds forward from the last examined trace snapshot. If no
|
|
argument @var{num} is given, it means find the next snapshot collected
|
|
for the same tracepoint as the current snapshot.
|
|
|
|
@item tfind pc @var{addr}
|
|
Find the next snapshot associated with the value @var{addr} of the
|
|
program counter. Search proceeds forward from the last examined trace
|
|
snapshot. If no argument @var{addr} is given, it means find the next
|
|
snapshot with the same value of PC as the current snapshot.
|
|
|
|
@item tfind outside @var{addr1}, @var{addr2}
|
|
Find the next snapshot whose PC is outside the given range of
|
|
addresses.
|
|
|
|
@item tfind range @var{addr1}, @var{addr2}
|
|
Find the next snapshot whose PC is between @var{addr1} and
|
|
@var{addr2}. @c FIXME: Is the range inclusive or exclusive?
|
|
|
|
@item tfind line @r{[}@var{file}:@r{]}@var{n}
|
|
Find the next snapshot associated with the source line @var{n}. If
|
|
the optional argument @var{file} is given, refer to line @var{n} in
|
|
that source file. Search proceeds forward from the last examined
|
|
trace snapshot. If no argument @var{n} is given, it means find the
|
|
next line other than the one currently being examined; thus saying
|
|
@code{tfind line} repeatedly can appear to have the same effect as
|
|
stepping from line to line in a @emph{live} debugging session.
|
|
@end table
|
|
|
|
The default arguments for the @code{tfind} commands are specifically
|
|
designed to make it easy to scan through the trace buffer. For
|
|
instance, @code{tfind} with no argument selects the next trace
|
|
snapshot, and @code{tfind -} with no argument selects the previous
|
|
trace snapshot. So, by giving one @code{tfind} command, and then
|
|
simply hitting @key{RET} repeatedly you can examine all the trace
|
|
snapshots in order. Or, by saying @code{tfind -} and then hitting
|
|
@key{RET} repeatedly you can examine the snapshots in reverse order.
|
|
The @code{tfind line} command with no argument selects the snapshot
|
|
for the next source line executed. The @code{tfind pc} command with
|
|
no argument selects the next snapshot with the same program counter
|
|
(PC) as the current frame. The @code{tfind tracepoint} command with
|
|
no argument selects the next trace snapshot collected by the same
|
|
tracepoint as the current one.
|
|
|
|
In addition to letting you scan through the trace buffer manually,
|
|
these commands make it easy to construct @value{GDBN} scripts that
|
|
scan through the trace buffer and print out whatever collected data
|
|
you are interested in. Thus, if we want to examine the PC, FP, and SP
|
|
registers from each trace frame in the buffer, we can say this:
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{tfind start}
|
|
(@value{GDBP}) @b{while ($trace_frame != -1)}
|
|
> printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
|
|
$trace_frame, $pc, $sp, $fp
|
|
> tfind
|
|
> end
|
|
|
|
Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
|
|
Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
|
|
Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
|
|
Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
|
|
Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
|
|
Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
|
|
Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
|
|
Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
|
|
Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
|
|
Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
|
|
Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
|
|
@end smallexample
|
|
|
|
Or, if we want to examine the variable @code{X} at each source line in
|
|
the buffer:
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{tfind start}
|
|
(@value{GDBP}) @b{while ($trace_frame != -1)}
|
|
> printf "Frame %d, X == %d\n", $trace_frame, X
|
|
> tfind line
|
|
> end
|
|
|
|
Frame 0, X = 1
|
|
Frame 7, X = 2
|
|
Frame 13, X = 255
|
|
@end smallexample
|
|
|
|
@node tdump
|
|
@subsection @code{tdump}
|
|
@kindex tdump
|
|
@cindex dump all data collected at tracepoint
|
|
@cindex tracepoint data, display
|
|
|
|
This command takes no arguments. It prints all the data collected at
|
|
the current trace snapshot.
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{trace 444}
|
|
(@value{GDBP}) @b{actions}
|
|
Enter actions for tracepoint #2, one per line:
|
|
> collect $regs, $locals, $args, gdb_long_test
|
|
> end
|
|
|
|
(@value{GDBP}) @b{tstart}
|
|
|
|
(@value{GDBP}) @b{tfind line 444}
|
|
#0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
|
|
at gdb_test.c:444
|
|
444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
|
|
|
|
(@value{GDBP}) @b{tdump}
|
|
Data collected at tracepoint 2, trace frame 1:
|
|
d0 0xc4aa0085 -995491707
|
|
d1 0x18 24
|
|
d2 0x80 128
|
|
d3 0x33 51
|
|
d4 0x71aea3d 119204413
|
|
d5 0x22 34
|
|
d6 0xe0 224
|
|
d7 0x380035 3670069
|
|
a0 0x19e24a 1696330
|
|
a1 0x3000668 50333288
|
|
a2 0x100 256
|
|
a3 0x322000 3284992
|
|
a4 0x3000698 50333336
|
|
a5 0x1ad3cc 1758156
|
|
fp 0x30bf3c 0x30bf3c
|
|
sp 0x30bf34 0x30bf34
|
|
ps 0x0 0
|
|
pc 0x20b2c8 0x20b2c8
|
|
fpcontrol 0x0 0
|
|
fpstatus 0x0 0
|
|
fpiaddr 0x0 0
|
|
p = 0x20e5b4 "gdb-test"
|
|
p1 = (void *) 0x11
|
|
p2 = (void *) 0x22
|
|
p3 = (void *) 0x33
|
|
p4 = (void *) 0x44
|
|
p5 = (void *) 0x55
|
|
p6 = (void *) 0x66
|
|
gdb_long_test = 17 '\021'
|
|
|
|
(@value{GDBP})
|
|
@end smallexample
|
|
|
|
@node save-tracepoints
|
|
@subsection @code{save-tracepoints @var{filename}}
|
|
@kindex save-tracepoints
|
|
@cindex save tracepoints for future sessions
|
|
|
|
This command saves all current tracepoint definitions together with
|
|
their actions and passcounts, into a file @file{@var{filename}}
|
|
suitable for use in a later debugging session. To read the saved
|
|
tracepoint definitions, use the @code{source} command (@pxref{Command
|
|
Files}).
|
|
|
|
@node Tracepoint Variables
|
|
@section Convenience Variables for Tracepoints
|
|
@cindex tracepoint variables
|
|
@cindex convenience variables for tracepoints
|
|
|
|
@table @code
|
|
@vindex $trace_frame
|
|
@item (int) $trace_frame
|
|
The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
|
|
snapshot is selected.
|
|
|
|
@vindex $tracepoint
|
|
@item (int) $tracepoint
|
|
The tracepoint for the current trace snapshot.
|
|
|
|
@vindex $trace_line
|
|
@item (int) $trace_line
|
|
The line number for the current trace snapshot.
|
|
|
|
@vindex $trace_file
|
|
@item (char []) $trace_file
|
|
The source file for the current trace snapshot.
|
|
|
|
@vindex $trace_func
|
|
@item (char []) $trace_func
|
|
The name of the function containing @code{$tracepoint}.
|
|
@end table
|
|
|
|
Note: @code{$trace_file} is not suitable for use in @code{printf},
|
|
use @code{output} instead.
|
|
|
|
Here's a simple example of using these convenience variables for
|
|
stepping through all the trace snapshots and printing some of their
|
|
data.
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{tfind start}
|
|
|
|
(@value{GDBP}) @b{while $trace_frame != -1}
|
|
> output $trace_file
|
|
> printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
|
|
> tfind
|
|
> end
|
|
@end smallexample
|
|
|
|
@node Overlays
|
|
@chapter Debugging Programs That Use Overlays
|
|
@cindex overlays
|
|
|
|
If your program is too large to fit completely in your target system's
|
|
memory, you can sometimes use @dfn{overlays} to work around this
|
|
problem. @value{GDBN} provides some support for debugging programs that
|
|
use overlays.
|
|
|
|
@menu
|
|
* How Overlays Work:: A general explanation of overlays.
|
|
* Overlay Commands:: Managing overlays in @value{GDBN}.
|
|
* Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
|
|
mapped by asking the inferior.
|
|
* Overlay Sample Program:: A sample program using overlays.
|
|
@end menu
|
|
|
|
@node How Overlays Work
|
|
@section How Overlays Work
|
|
@cindex mapped overlays
|
|
@cindex unmapped overlays
|
|
@cindex load address, overlay's
|
|
@cindex mapped address
|
|
@cindex overlay area
|
|
|
|
Suppose you have a computer whose instruction address space is only 64
|
|
kilobytes long, but which has much more memory which can be accessed by
|
|
other means: special instructions, segment registers, or memory
|
|
management hardware, for example. Suppose further that you want to
|
|
adapt a program which is larger than 64 kilobytes to run on this system.
|
|
|
|
One solution is to identify modules of your program which are relatively
|
|
independent, and need not call each other directly; call these modules
|
|
@dfn{overlays}. Separate the overlays from the main program, and place
|
|
their machine code in the larger memory. Place your main program in
|
|
instruction memory, but leave at least enough space there to hold the
|
|
largest overlay as well.
|
|
|
|
Now, to call a function located in an overlay, you must first copy that
|
|
overlay's machine code from the large memory into the space set aside
|
|
for it in the instruction memory, and then jump to its entry point
|
|
there.
|
|
|
|
@example
|
|
@group
|
|
Data Instruction Larger
|
|
Address Space Address Space Address Space
|
|
+-----------+ +-----------+ +-----------+
|
|
| | | | | |
|
|
+-----------+ +-----------+ +-----------+<-- overlay 1
|
|
| program | | main | | | load address
|
|
| variables | | program | | overlay 1 |
|
|
| and heap | | | ,---| |
|
|
+-----------+ | | | | |
|
|
| | +-----------+ | +-----------+
|
|
+-----------+ | | | | |
|
|
mapped --->+-----------+ / +-----------+<-- overlay 2
|
|
address | overlay | <-' | overlay 2 | load address
|
|
| area | <-----| |
|
|
| | <---. +-----------+
|
|
| | | | |
|
|
+-----------+ | | |
|
|
| | | +-----------+<-- overlay 3
|
|
+-----------+ `--| | load address
|
|
| overlay 3 |
|
|
| |
|
|
+-----------+
|
|
| |
|
|
+-----------+
|
|
|
|
To map an overlay, copy its code from the larger address space
|
|
to the instruction address space. Since the overlays shown here
|
|
all use the same mapped address, only one may be mapped at a time.
|
|
@end group
|
|
@end example
|
|
|
|
This diagram shows a system with separate data and instruction address
|
|
spaces. For a system with a single address space for data and
|
|
instructions, the diagram would be similar, except that the program
|
|
variables and heap would share an address space with the main program
|
|
and the overlay area.
|
|
|
|
An overlay loaded into instruction memory and ready for use is called a
|
|
@dfn{mapped} overlay; its @dfn{mapped address} is its address in the
|
|
instruction memory. An overlay not present (or only partially present)
|
|
in instruction memory is called @dfn{unmapped}; its @dfn{load address}
|
|
is its address in the larger memory. The mapped address is also called
|
|
the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
|
|
called the @dfn{load memory address}, or @dfn{LMA}.
|
|
|
|
Unfortunately, overlays are not a completely transparent way to adapt a
|
|
program to limited instruction memory. They introduce a new set of
|
|
global constraints you must keep in mind as you design your program:
|
|
|
|
@itemize @bullet
|
|
|
|
@item
|
|
Before calling or returning to a function in an overlay, your program
|
|
must make sure that overlay is actually mapped. Otherwise, the call or
|
|
return will transfer control to the right address, but in the wrong
|
|
overlay, and your program will probably crash.
|
|
|
|
@item
|
|
If the process of mapping an overlay is expensive on your system, you
|
|
will need to choose your overlays carefully to minimize their effect on
|
|
your program's performance.
|
|
|
|
@item
|
|
The executable file you load onto your system must contain each
|
|
overlay's instructions, appearing at the overlay's load address, not its
|
|
mapped address. However, each overlay's instructions must be relocated
|
|
and its symbols defined as if the overlay were at its mapped address.
|
|
You can use GNU linker scripts to specify different load and relocation
|
|
addresses for pieces of your program; see @ref{Overlay Description,,,
|
|
ld.info, Using ld: the GNU linker}.
|
|
|
|
@item
|
|
The procedure for loading executable files onto your system must be able
|
|
to load their contents into the larger address space as well as the
|
|
instruction and data spaces.
|
|
|
|
@end itemize
|
|
|
|
The overlay system described above is rather simple, and could be
|
|
improved in many ways:
|
|
|
|
@itemize @bullet
|
|
|
|
@item
|
|
If your system has suitable bank switch registers or memory management
|
|
hardware, you could use those facilities to make an overlay's load area
|
|
contents simply appear at their mapped address in instruction space.
|
|
This would probably be faster than copying the overlay to its mapped
|
|
area in the usual way.
|
|
|
|
@item
|
|
If your overlays are small enough, you could set aside more than one
|
|
overlay area, and have more than one overlay mapped at a time.
|
|
|
|
@item
|
|
You can use overlays to manage data, as well as instructions. In
|
|
general, data overlays are even less transparent to your design than
|
|
code overlays: whereas code overlays only require care when you call or
|
|
return to functions, data overlays require care every time you access
|
|
the data. Also, if you change the contents of a data overlay, you
|
|
must copy its contents back out to its load address before you can copy a
|
|
different data overlay into the same mapped area.
|
|
|
|
@end itemize
|
|
|
|
|
|
@node Overlay Commands
|
|
@section Overlay Commands
|
|
|
|
To use @value{GDBN}'s overlay support, each overlay in your program must
|
|
correspond to a separate section of the executable file. The section's
|
|
virtual memory address and load memory address must be the overlay's
|
|
mapped and load addresses. Identifying overlays with sections allows
|
|
@value{GDBN} to determine the appropriate address of a function or
|
|
variable, depending on whether the overlay is mapped or not.
|
|
|
|
@value{GDBN}'s overlay commands all start with the word @code{overlay};
|
|
you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
|
|
|
|
@table @code
|
|
@item overlay off
|
|
@kindex overlay off
|
|
Disable @value{GDBN}'s overlay support. When overlay support is
|
|
disabled, @value{GDBN} assumes that all functions and variables are
|
|
always present at their mapped addresses. By default, @value{GDBN}'s
|
|
overlay support is disabled.
|
|
|
|
@item overlay manual
|
|
@kindex overlay manual
|
|
@cindex manual overlay debugging
|
|
Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
|
|
relies on you to tell it which overlays are mapped, and which are not,
|
|
using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
|
|
commands described below.
|
|
|
|
@item overlay map-overlay @var{overlay}
|
|
@itemx overlay map @var{overlay}
|
|
@kindex overlay map-overlay
|
|
@cindex map an overlay
|
|
Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
|
|
be the name of the object file section containing the overlay. When an
|
|
overlay is mapped, @value{GDBN} assumes it can find the overlay's
|
|
functions and variables at their mapped addresses. @value{GDBN} assumes
|
|
that any other overlays whose mapped ranges overlap that of
|
|
@var{overlay} are now unmapped.
|
|
|
|
@item overlay unmap-overlay @var{overlay}
|
|
@itemx overlay unmap @var{overlay}
|
|
@kindex overlay unmap-overlay
|
|
@cindex unmap an overlay
|
|
Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
|
|
must be the name of the object file section containing the overlay.
|
|
When an overlay is unmapped, @value{GDBN} assumes it can find the
|
|
overlay's functions and variables at their load addresses.
|
|
|
|
@item overlay auto
|
|
@kindex overlay auto
|
|
Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
|
|
consults a data structure the overlay manager maintains in the inferior
|
|
to see which overlays are mapped. For details, see @ref{Automatic
|
|
Overlay Debugging}.
|
|
|
|
@item overlay load-target
|
|
@itemx overlay load
|
|
@kindex overlay load-target
|
|
@cindex reloading the overlay table
|
|
Re-read the overlay table from the inferior. Normally, @value{GDBN}
|
|
re-reads the table @value{GDBN} automatically each time the inferior
|
|
stops, so this command should only be necessary if you have changed the
|
|
overlay mapping yourself using @value{GDBN}. This command is only
|
|
useful when using automatic overlay debugging.
|
|
|
|
@item overlay list-overlays
|
|
@itemx overlay list
|
|
@cindex listing mapped overlays
|
|
Display a list of the overlays currently mapped, along with their mapped
|
|
addresses, load addresses, and sizes.
|
|
|
|
@end table
|
|
|
|
Normally, when @value{GDBN} prints a code address, it includes the name
|
|
of the function the address falls in:
|
|
|
|
@example
|
|
(gdb) print main
|
|
$3 = @{int ()@} 0x11a0 <main>
|
|
@end example
|
|
@noindent
|
|
When overlay debugging is enabled, @value{GDBN} recognizes code in
|
|
unmapped overlays, and prints the names of unmapped functions with
|
|
asterisks around them. For example, if @code{foo} is a function in an
|
|
unmapped overlay, @value{GDBN} prints it this way:
|
|
|
|
@example
|
|
(gdb) overlay list
|
|
No sections are mapped.
|
|
(gdb) print foo
|
|
$5 = @{int (int)@} 0x100000 <*foo*>
|
|
@end example
|
|
@noindent
|
|
When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
|
|
name normally:
|
|
|
|
@example
|
|
(gdb) overlay list
|
|
Section .ov.foo.text, loaded at 0x100000 - 0x100034,
|
|
mapped at 0x1016 - 0x104a
|
|
(gdb) print foo
|
|
$6 = @{int (int)@} 0x1016 <foo>
|
|
@end example
|
|
|
|
When overlay debugging is enabled, @value{GDBN} can find the correct
|
|
address for functions and variables in an overlay, whether or not the
|
|
overlay is mapped. This allows most @value{GDBN} commands, like
|
|
@code{break} and @code{disassemble}, to work normally, even on unmapped
|
|
code. However, @value{GDBN}'s breakpoint support has some limitations:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
@cindex breakpoints in overlays
|
|
@cindex overlays, setting breakpoints in
|
|
You can set breakpoints in functions in unmapped overlays, as long as
|
|
@value{GDBN} can write to the overlay at its load address.
|
|
@item
|
|
@value{GDBN} can not set hardware or simulator-based breakpoints in
|
|
unmapped overlays. However, if you set a breakpoint at the end of your
|
|
overlay manager (and tell @value{GDBN} which overlays are now mapped, if
|
|
you are using manual overlay management), @value{GDBN} will re-set its
|
|
breakpoints properly.
|
|
@end itemize
|
|
|
|
|
|
@node Automatic Overlay Debugging
|
|
@section Automatic Overlay Debugging
|
|
@cindex automatic overlay debugging
|
|
|
|
@value{GDBN} can automatically track which overlays are mapped and which
|
|
are not, given some simple co-operation from the overlay manager in the
|
|
inferior. If you enable automatic overlay debugging with the
|
|
@code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
|
|
looks in the inferior's memory for certain variables describing the
|
|
current state of the overlays.
|
|
|
|
Here are the variables your overlay manager must define to support
|
|
@value{GDBN}'s automatic overlay debugging:
|
|
|
|
@table @asis
|
|
|
|
@item @code{_ovly_table}:
|
|
This variable must be an array of the following structures:
|
|
|
|
@example
|
|
struct
|
|
@{
|
|
/* The overlay's mapped address. */
|
|
unsigned long vma;
|
|
|
|
/* The size of the overlay, in bytes. */
|
|
unsigned long size;
|
|
|
|
/* The overlay's load address. */
|
|
unsigned long lma;
|
|
|
|
/* Non-zero if the overlay is currently mapped;
|
|
zero otherwise. */
|
|
unsigned long mapped;
|
|
@}
|
|
@end example
|
|
|
|
@item @code{_novlys}:
|
|
This variable must be a four-byte signed integer, holding the total
|
|
number of elements in @code{_ovly_table}.
|
|
|
|
@end table
|
|
|
|
To decide whether a particular overlay is mapped or not, @value{GDBN}
|
|
looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
|
|
@code{lma} members equal the VMA and LMA of the overlay's section in the
|
|
executable file. When @value{GDBN} finds a matching entry, it consults
|
|
the entry's @code{mapped} member to determine whether the overlay is
|
|
currently mapped.
|
|
|
|
|
|
@node Overlay Sample Program
|
|
@section Overlay Sample Program
|
|
@cindex overlay example program
|
|
|
|
When linking a program which uses overlays, you must place the overlays
|
|
at their load addresses, while relocating them to run at their mapped
|
|
addresses. To do this, you must write a linker script (@pxref{Overlay
|
|
Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
|
|
since linker scripts are specific to a particular host system, target
|
|
architecture, and target memory layout, this manual cannot provide
|
|
portable sample code demonstrating @value{GDBN}'s overlay support.
|
|
|
|
However, the @value{GDBN} source distribution does contain an overlaid
|
|
program, with linker scripts for a few systems, as part of its test
|
|
suite. The program consists of the following files from
|
|
@file{gdb/testsuite/gdb.base}:
|
|
|
|
@table @file
|
|
@item overlays.c
|
|
The main program file.
|
|
@item ovlymgr.c
|
|
A simple overlay manager, used by @file{overlays.c}.
|
|
@item foo.c
|
|
@itemx bar.c
|
|
@itemx baz.c
|
|
@itemx grbx.c
|
|
Overlay modules, loaded and used by @file{overlays.c}.
|
|
@item d10v.ld
|
|
@itemx m32r.ld
|
|
Linker scripts for linking the test program on the @code{d10v-elf}
|
|
and @code{m32r-elf} targets.
|
|
@end table
|
|
|
|
You can build the test program using the @code{d10v-elf} GCC
|
|
cross-compiler like this:
|
|
|
|
@example
|
|
$ d10v-elf-gcc -g -c overlays.c
|
|
$ d10v-elf-gcc -g -c ovlymgr.c
|
|
$ d10v-elf-gcc -g -c foo.c
|
|
$ d10v-elf-gcc -g -c bar.c
|
|
$ d10v-elf-gcc -g -c baz.c
|
|
$ d10v-elf-gcc -g -c grbx.c
|
|
$ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
|
|
baz.o grbx.o -Wl,-Td10v.ld -o overlays
|
|
@end example
|
|
|
|
The build process is identical for any other architecture, except that
|
|
you must substitute the appropriate compiler and linker script for the
|
|
target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
|
|
|
|
|
|
@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 appear as
|
|
@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 is called the @dfn{working
|
|
language}.
|
|
|
|
@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. The working language is
|
|
used to determine how expressions you type are interpreted, how values
|
|
are printed, etc.
|
|
|
|
In addition to the working language, every source file that
|
|
@value{GDBN} knows about has its own working language. For some object
|
|
file formats, the compiler might indicate which language a particular
|
|
source file is in. However, most of the time @value{GDBN} infers the
|
|
language from the name of the file. The language of a source file
|
|
controls whether C@t{++} names are demangled---this way @code{backtrace} can
|
|
show each frame appropriately for its own language. There is no way to
|
|
set the language of a source file from within @value{GDBN}, but you can
|
|
set the language associated with a filename extension. @xref{Show, ,
|
|
Displaying the language}.
|
|
|
|
This is most commonly a problem when you use a program, such
|
|
as @code{cfront} or @code{f2c}, that generates C but is written in
|
|
another language. In that case, make the
|
|
program use @code{#line} directives in its C output; that way
|
|
@value{GDBN} will know the correct language of the source code of the original
|
|
program, and will display that source code, not the generated C code.
|
|
|
|
@menu
|
|
* Filenames:: Filename extensions and languages.
|
|
* Manually:: Setting the working language manually
|
|
* Automatically:: Having @value{GDBN} infer the source language
|
|
@end menu
|
|
|
|
@node Filenames
|
|
@subsection List of filename extensions and languages
|
|
|
|
If a source file name ends in one of the following extensions, then
|
|
@value{GDBN} infers that its language is the one indicated.
|
|
|
|
@table @file
|
|
|
|
@item .c
|
|
C source file
|
|
|
|
@item .C
|
|
@itemx .cc
|
|
@itemx .cp
|
|
@itemx .cpp
|
|
@itemx .cxx
|
|
@itemx .c++
|
|
C@t{++} source file
|
|
|
|
@item .f
|
|
@itemx .F
|
|
Fortran source file
|
|
|
|
@item .ch
|
|
@itemx .c186
|
|
@itemx .c286
|
|
CHILL source file
|
|
|
|
@item .mod
|
|
Modula-2 source file
|
|
|
|
@item .s
|
|
@itemx .S
|
|
Assembler source file. This actually behaves almost like C, but
|
|
@value{GDBN} does not skip over function prologues when stepping.
|
|
@end table
|
|
|
|
In addition, you may set the language associated with a filename
|
|
extension. @xref{Show, , Displaying the language}.
|
|
|
|
@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}.
|
|
|
|
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 working language. That is, 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 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@r{, show the source language}
|
|
@kindex info source@r{, show the source language}
|
|
@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
|
|
Display the source language for this frame. This language becomes the
|
|
working language if you use an identifier from this frame.
|
|
@xref{Frame Info, ,Information about a frame}, to identify the other
|
|
information listed here.
|
|
|
|
@item info source
|
|
Display the source language of this source file.
|
|
@xref{Symbols, ,Examining the Symbol Table}, to identify the other
|
|
information listed here.
|
|
@end table
|
|
|
|
In unusual circumstances, you may have source files with extensions
|
|
not in the standard list. You can then set the extension associated
|
|
with a language explicitly:
|
|
|
|
@kindex set extension-language
|
|
@kindex info extensions
|
|
@table @code
|
|
@item set extension-language @var{.ext} @var{language}
|
|
Set source files with extension @var{.ext} to be assumed to be in
|
|
the source language @var{language}.
|
|
|
|
@item info extensions
|
|
List all the filename extensions and the associated languages.
|
|
@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} does 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,
|
|
|
|
@smallexample
|
|
1 + 2 @result{} 3
|
|
@exdent but
|
|
@error{} 1 + 2.3
|
|
@end smallexample
|
|
|
|
The second example fails because the @code{CARDINAL} 1 is not
|
|
type-compatible with the @code{REAL} 2.3.
|
|
|
|
For the 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 to 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 if you turn type checking off, there may be other reasons
|
|
related to type that 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@r{, type}
|
|
@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 type checking 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@r{, range}
|
|
@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 and range checking is on,
|
|
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} supports C, C@t{++}, Fortran, Java, Chill, assembly, and Modula-2.
|
|
@c This is false ...
|
|
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 supported
|
|
language.
|
|
|
|
The following sections detail to what degree each source language 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 accepts, 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@t{++}
|
|
* Modula-2:: Modula-2
|
|
* Chill:: Chill
|
|
@end menu
|
|
|
|
@node C
|
|
@subsection C and C@t{++}
|
|
|
|
@cindex C and C@t{++}
|
|
@cindex expressions in C or C@t{++}
|
|
|
|
Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
|
|
to both languages. Whenever this is the case, we discuss those languages
|
|
together.
|
|
|
|
@cindex C@t{++}
|
|
@cindex @code{g++}, @sc{gnu} C@t{++} compiler
|
|
@cindex @sc{gnu} C@t{++}
|
|
The C@t{++} debugging facilities are jointly implemented by the C@t{++}
|
|
compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
|
|
effectively, you must compile your C@t{++} programs with a supported
|
|
C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
|
|
compiler (@code{aCC}).
|
|
|
|
For best results when using @sc{gnu} C@t{++}, use the stabs debugging
|
|
format. You can select that format explicitly with the @code{g++}
|
|
command-line options @samp{-gstabs} or @samp{-gstabs+}. See
|
|
@ref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
|
|
CC, gcc.info, Using @sc{gnu} CC}, for more information.
|
|
|
|
@menu
|
|
* C Operators:: C and C@t{++} operators
|
|
* C Constants:: C and C@t{++} constants
|
|
* C plus plus expressions:: C@t{++} expressions
|
|
* C Defaults:: Default settings for C and C@t{++}
|
|
* C Checks:: C and C@t{++} type and range checks
|
|
* Debugging C:: @value{GDBN} and C
|
|
* Debugging C plus plus:: @value{GDBN} features for C@t{++}
|
|
@end menu
|
|
|
|
@node C Operators
|
|
@subsubsection C and C@t{++} operators
|
|
|
|
@cindex C and C@t{++} 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 C and C@t{++}, the following definitions hold:
|
|
|
|
@itemize @bullet
|
|
|
|
@item
|
|
@emph{Integral types} include @code{int} with any of its storage-class
|
|
specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
|
|
|
|
@item
|
|
@emph{Floating-point types} include @code{float}, @code{double}, and
|
|
@code{long double} (if supported by the target platform).
|
|
|
|
@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 precedence.
|
|
@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{++}.
|
|
|
|
For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
|
|
allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
|
|
(or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
|
|
where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
|
|
stored.
|
|
|
|
@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 .*@r{, }->*
|
|
Dereferences of pointers to members.
|
|
|
|
@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{->}.
|
|
|
|
@item ::
|
|
C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
|
|
and @code{class} types.
|
|
|
|
@item ::
|
|
Doubled colons also represent the @value{GDBN} scope operator
|
|
(@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
|
|
above.
|
|
@end table
|
|
|
|
If an operator is redefined in the user code, @value{GDBN} usually
|
|
attempts to invoke the redefined version instead of using the operator's
|
|
predefined meaning.
|
|
|
|
@menu
|
|
* C Constants::
|
|
@end menu
|
|
|
|
@node C Constants
|
|
@subsubsection C and C@t{++} constants
|
|
|
|
@cindex C and C@t{++} constants
|
|
|
|
@value{GDBN} allows you to express the constants of C and C@t{++} in the
|
|
following ways:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
Integer constants are a sequence of digits. Octal constants are
|
|
specified by a leading @samp{0} (i.e. 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.
|
|
A floating-point constant may also end with a letter @samp{f} or
|
|
@samp{F}, specifying that the constant should be treated as being of
|
|
the @code{float} (as opposed to the default @code{double}) type; or with
|
|
a letter @samp{l} or @samp{L}, which specifies a @code{long double}
|
|
constant.
|
|
|
|
@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{"}). Any valid character constant (as described
|
|
above) may appear. Double quotes within the string must be preceded by
|
|
a backslash, so for instance @samp{"a\"b'c"} is a string of five
|
|
characters.
|
|
|
|
@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
|
|
|
|
@menu
|
|
* C plus plus expressions::
|
|
* C Defaults::
|
|
* C Checks::
|
|
|
|
* Debugging C::
|
|
@end menu
|
|
|
|
@node C plus plus expressions
|
|
@subsubsection C@t{++} expressions
|
|
|
|
@cindex expressions in C@t{++}
|
|
@value{GDBN} expression handling can interpret most C@t{++} expressions.
|
|
|
|
@cindex C@t{++} support, not in @sc{coff}
|
|
@cindex @sc{coff} versus C@t{++}
|
|
@cindex C@t{++} and object formats
|
|
@cindex object formats and C@t{++}
|
|
@cindex a.out and C@t{++}
|
|
@cindex @sc{ecoff} and C@t{++}
|
|
@cindex @sc{xcoff} and C@t{++}
|
|
@cindex @sc{elf}/stabs and C@t{++}
|
|
@cindex @sc{elf}/@sc{dwarf} and C@t{++}
|
|
@c FIXME!! GDB may eventually be able to debug C++ using DWARF; check
|
|
@c periodically whether this has happened...
|
|
@quotation
|
|
@emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
|
|
proper compiler. Typically, C@t{++} debugging depends on the use of
|
|
additional debugging information in the symbol table, and thus requires
|
|
special support. In particular, if your compiler generates a.out, MIPS
|
|
@sc{ecoff}, RS/6000 @sc{xcoff}, or @sc{elf} with stabs extensions to the
|
|
symbol table, these facilities are all available. (With @sc{gnu} CC,
|
|
you can use the @samp{-gstabs} option to request stabs debugging
|
|
extensions explicitly.) Where the object code format is standard
|
|
@sc{coff} or @sc{dwarf} in @sc{elf}, on the other hand, most of the C@t{++}
|
|
support in @value{GDBN} does @emph{not} work.
|
|
@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
|
|
|
|
@vindex this@r{, inside C@t{++} member functions}
|
|
@cindex namespace in C@t{++}
|
|
@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@t{++}.
|
|
|
|
@cindex call overloaded functions
|
|
@cindex overloaded functions, calling
|
|
@cindex type conversions in C@t{++}
|
|
@item
|
|
You can call overloaded functions; @value{GDBN} resolves the function
|
|
call to the right definition, with some restrictions. @value{GDBN} does not
|
|
perform overload resolution involving user-defined type conversions,
|
|
calls to constructors, or instantiations of templates that do not exist
|
|
in the program. It also cannot handle ellipsis argument lists or
|
|
default arguments.
|
|
|
|
It does perform integral conversions and promotions, floating-point
|
|
promotions, arithmetic conversions, pointer conversions, conversions of
|
|
class objects to base classes, and standard conversions such as those of
|
|
functions or arrays to pointers; it requires an exact match on the
|
|
number of function arguments.
|
|
|
|
Overload resolution is always performed, unless you have specified
|
|
@code{set overload-resolution off}. @xref{Debugging C plus plus,
|
|
,@value{GDBN} features for C@t{++}}.
|
|
|
|
You must specify @code{set overload-resolution off} in order to use an
|
|
explicit function signature to call an overloaded function, as in
|
|
@smallexample
|
|
p 'foo(char,int)'('x', 13)
|
|
@end smallexample
|
|
|
|
The @value{GDBN} command-completion facility can simplify this;
|
|
see @ref{Completion, ,Command completion}.
|
|
|
|
@cindex reference declarations
|
|
@item
|
|
@value{GDBN} understands variables declared as C@t{++} references; you can use
|
|
them in expressions just as you do in C@t{++} 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@t{++} 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@t{++}
|
|
debugging (@pxref{Variables, ,Program variables}).
|
|
@end enumerate
|
|
|
|
In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
|
|
calling virtual functions correctly, printing out virtual bases of
|
|
objects, calling functions in a base subobject, casting objects, and
|
|
invoking user-defined operators.
|
|
|
|
@node C Defaults
|
|
@subsubsection C and C@t{++} defaults
|
|
|
|
@cindex C and C@t{++} 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@t{++}. This happens regardless of whether you or @value{GDBN}
|
|
selects the working language.
|
|
|
|
If you allow @value{GDBN} to set the language automatically, it
|
|
recognizes source files whose names end with @file{.c}, @file{.C}, or
|
|
@file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
|
|
these files, it sets the working language to C or C@t{++}.
|
|
@xref{Automatically, ,Having @value{GDBN} infer the source language},
|
|
for further details.
|
|
|
|
@c Type checking is (a) primarily motivated by Modula-2, and (b)
|
|
@c unimplemented. If (b) changes, it might make sense to let this node
|
|
@c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
|
|
|
|
@node C Checks
|
|
@subsubsection C and C@t{++} type and range checks
|
|
|
|
@cindex C and C@t{++} checks
|
|
|
|
By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
|
|
is not used. However, if you turn type checking on, @value{GDBN}
|
|
considers two variables type equivalent if:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
The two variables are structured and have the same structure, union, or
|
|
enumerated tag.
|
|
|
|
@item
|
|
The 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.
|
|
|
|
@node Debugging C
|
|
@subsubsection @value{GDBN} and C
|
|
|
|
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} or @code{class} is also printed. Otherwise, it
|
|
appears as @samp{@{...@}}.
|
|
|
|
The @code{@@} operator aids in the debugging of dynamic arrays, formed
|
|
with pointers and a memory allocation function. @xref{Expressions,
|
|
,Expressions}.
|
|
|
|
@menu
|
|
* Debugging C plus plus::
|
|
@end menu
|
|
|
|
@node Debugging C plus plus
|
|
@subsubsection @value{GDBN} features for C@t{++}
|
|
|
|
@cindex commands for C@t{++}
|
|
|
|
Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
|
|
designed specifically for use with C@t{++}. 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@t{++}
|
|
@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@t{++} exception handling
|
|
@item catch throw
|
|
@itemx catch catch
|
|
Debug C@t{++} exception handling using these commands. @xref{Set
|
|
Catchpoints, , Setting catchpoints}.
|
|
|
|
@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@t{++} symbol display
|
|
@item set print demangle
|
|
@itemx show print demangle
|
|
@itemx set print asm-demangle
|
|
@itemx show print asm-demangle
|
|
Control whether C@t{++} symbols display in their source form, both when
|
|
displaying code as C@t{++} 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}.
|
|
(The @code{vtbl} commands do not work on programs compiled with the HP
|
|
ANSI C@t{++} compiler (@code{aCC}).)
|
|
|
|
@kindex set overload-resolution
|
|
@cindex overloaded functions, overload resolution
|
|
@item set overload-resolution on
|
|
Enable overload resolution for C@t{++} expression evaluation. The default
|
|
is on. For overloaded functions, @value{GDBN} evaluates the arguments
|
|
and searches for a function whose signature matches the argument types,
|
|
using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
|
|
expressions}, for details). If it cannot find a match, it emits a
|
|
message.
|
|
|
|
@item set overload-resolution off
|
|
Disable overload resolution for C@t{++} expression evaluation. For
|
|
overloaded functions that are not class member functions, @value{GDBN}
|
|
chooses the first function of the specified name that it finds in the
|
|
symbol table, whether or not its arguments are of the correct type. For
|
|
overloaded functions that are class member functions, @value{GDBN}
|
|
searches for a function whose signature @emph{exactly} matches the
|
|
argument types.
|
|
|
|
@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@t{++}: 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, @value{GDBN} support
|
|
|
|
The extensions made to @value{GDBN} to support Modula-2 only support
|
|
output from the @sc{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 is most likely
|
|
to give 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 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 conjunction. 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}
|
|
treats 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
|
|
|
|
|
|
@node Built-In Func/Proc
|
|
@subsubsection Built-in functions and procedures
|
|
@cindex Modula-2 built-ins
|
|
|
|
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} by one. 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} by one. 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 @sc{ascii} value (on machines supporting the
|
|
@sc{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} treats 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 @sc{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@t{++} 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} sets 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} prints 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
|
|
@sc{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
|
|
@cindex @code{.}, Modula-2 scope operator
|
|
@cindex colon, doubled as scope operator
|
|
@ifinfo
|
|
@vindex colon-colon@r{, in Modula-2}
|
|
@c Info cannot handle :: but TeX can.
|
|
@end ifinfo
|
|
@iftex
|
|
@vindex ::@r{, in Modula-2}
|
|
@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} searches 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@t{++}: @samp{vtbl}, @samp{demangle},
|
|
@samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
|
|
apply to C@t{++}, 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
|
|
with 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@t{++}. However, because an
|
|
address can be specified by an integral constant, the construct
|
|
@samp{@{@var{type}@}@var{adrexp}} is still useful.
|
|
|
|
@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.
|
|
|
|
@node Chill
|
|
@subsection Chill
|
|
|
|
The extensions made to @value{GDBN} to support Chill only support output
|
|
from the @sc{gnu} Chill compiler. Other Chill compilers are not currently
|
|
supported, and attempting to debug executables produced by them is most
|
|
likely to give an error as @value{GDBN} reads in the executable's symbol
|
|
table.
|
|
|
|
@c This used to say "... following Chill related topics ...", but since
|
|
@c menus are not shown in the printed manual, it would look awkward.
|
|
This section covers the Chill related topics and the features
|
|
of @value{GDBN} which support these topics.
|
|
|
|
@menu
|
|
* How modes are displayed:: How modes are displayed
|
|
* Locations:: Locations and their accesses
|
|
* Values and their Operations:: Values and their Operations
|
|
* Chill type and range checks::
|
|
* Chill defaults::
|
|
@end menu
|
|
|
|
@node How modes are displayed
|
|
@subsubsection How modes are displayed
|
|
|
|
The Chill Datatype- (Mode) support of @value{GDBN} is directly related
|
|
with the functionality of the @sc{gnu} Chill compiler, and therefore deviates
|
|
slightly from the standard specification of the Chill language. The
|
|
provided modes are:
|
|
|
|
@c FIXME: this @table's contents effectively disable @code by using @r
|
|
@c on every @item. So why does it need @code?
|
|
@table @code
|
|
@item @r{@emph{Discrete modes:}}
|
|
@itemize @bullet
|
|
@item
|
|
@emph{Integer Modes} which are predefined by @code{BYTE, UBYTE, INT,
|
|
UINT, LONG, ULONG},
|
|
@item
|
|
@emph{Boolean Mode} which is predefined by @code{BOOL},
|
|
@item
|
|
@emph{Character Mode} which is predefined by @code{CHAR},
|
|
@item
|
|
@emph{Set Mode} which is displayed by the keyword @code{SET}.
|
|
@smallexample
|
|
(@value{GDBP}) ptype x
|
|
type = SET (karli = 10, susi = 20, fritzi = 100)
|
|
@end smallexample
|
|
If the type is an unnumbered set the set element values are omitted.
|
|
@item
|
|
@emph{Range Mode} which is displayed by
|
|
@smallexample
|
|
@code{type = <basemode>(<lower bound> : <upper bound>)}
|
|
@end smallexample
|
|
where @code{<lower bound>, <upper bound>} can be of any discrete literal
|
|
expression (e.g. set element names).
|
|
@end itemize
|
|
|
|
@item @r{@emph{Powerset Mode:}}
|
|
A Powerset Mode is displayed by the keyword @code{POWERSET} followed by
|
|
the member mode of the powerset. The member mode can be any discrete mode.
|
|
@smallexample
|
|
(@value{GDBP}) ptype x
|
|
type = POWERSET SET (egon, hugo, otto)
|
|
@end smallexample
|
|
|
|
@item @r{@emph{Reference Modes:}}
|
|
@itemize @bullet
|
|
@item
|
|
@emph{Bound Reference Mode} which is displayed by the keyword @code{REF}
|
|
followed by the mode name to which the reference is bound.
|
|
@item
|
|
@emph{Free Reference Mode} which is displayed by the keyword @code{PTR}.
|
|
@end itemize
|
|
|
|
@item @r{@emph{Procedure mode}}
|
|
The procedure mode is displayed by @code{type = PROC(<parameter list>)
|
|
<return mode> EXCEPTIONS (<exception list>)}. The @code{<parameter
|
|
list>} is a list of the parameter modes. @code{<return mode>} indicates
|
|
the mode of the result of the procedure if any. The exceptionlist lists
|
|
all possible exceptions which can be raised by the procedure.
|
|
|
|
@ignore
|
|
@item @r{@emph{Instance mode}}
|
|
The instance mode is represented by a structure, which has a static
|
|
type, and is therefore not really of interest.
|
|
@end ignore
|
|
|
|
@item @r{@emph{Synchronization Modes:}}
|
|
@itemize @bullet
|
|
@item
|
|
@emph{Event Mode} which is displayed by
|
|
@smallexample
|
|
@code{EVENT (<event length>)}
|
|
@end smallexample
|
|
where @code{(<event length>)} is optional.
|
|
@item
|
|
@emph{Buffer Mode} which is displayed by
|
|
@smallexample
|
|
@code{BUFFER (<buffer length>)<buffer element mode>}
|
|
@end smallexample
|
|
where @code{(<buffer length>)} is optional.
|
|
@end itemize
|
|
|
|
@item @r{@emph{Timing Modes:}}
|
|
@itemize @bullet
|
|
@item
|
|
@emph{Duration Mode} which is predefined by @code{DURATION}
|
|
@item
|
|
@emph{Absolute Time Mode} which is predefined by @code{TIME}
|
|
@end itemize
|
|
|
|
@item @r{@emph{Real Modes:}}
|
|
Real Modes are predefined with @code{REAL} and @code{LONG_REAL}.
|
|
|
|
@item @r{@emph{String Modes:}}
|
|
@itemize @bullet
|
|
@item
|
|
@emph{Character String Mode} which is displayed by
|
|
@smallexample
|
|
@code{CHARS(<string length>)}
|
|
@end smallexample
|
|
followed by the keyword @code{VARYING} if the String Mode is a varying
|
|
mode
|
|
@item
|
|
@emph{Bit String Mode} which is displayed by
|
|
@smallexample
|
|
@code{BOOLS(<string
|
|
length>)}
|
|
@end smallexample
|
|
@end itemize
|
|
|
|
@item @r{@emph{Array Mode:}}
|
|
The Array Mode is displayed by the keyword @code{ARRAY(<range>)}
|
|
followed by the element mode (which may in turn be an array mode).
|
|
@smallexample
|
|
(@value{GDBP}) ptype x
|
|
type = ARRAY (1:42)
|
|
ARRAY (1:20)
|
|
SET (karli = 10, susi = 20, fritzi = 100)
|
|
@end smallexample
|
|
|
|
@item @r{@emph{Structure Mode}}
|
|
The Structure mode is displayed by the keyword @code{STRUCT(<field
|
|
list>)}. The @code{<field list>} consists of names and modes of fields
|
|
of the structure. Variant structures have the keyword @code{CASE <field>
|
|
OF <variant fields> ESAC} in their field list. Since the current version
|
|
of the GNU Chill compiler doesn't implement tag processing (no runtime
|
|
checks of variant fields, and therefore no debugging info), the output
|
|
always displays all variant fields.
|
|
@smallexample
|
|
(@value{GDBP}) ptype str
|
|
type = STRUCT (
|
|
as x,
|
|
bs x,
|
|
CASE bs OF
|
|
(karli):
|
|
cs a
|
|
(ott):
|
|
ds x
|
|
ESAC
|
|
)
|
|
@end smallexample
|
|
@end table
|
|
|
|
@node Locations
|
|
@subsubsection Locations and their accesses
|
|
|
|
A location in Chill is an object which can contain values.
|
|
|
|
A value of a location is generally accessed by the (declared) name of
|
|
the location. The output conforms to the specification of values in
|
|
Chill programs. How values are specified
|
|
is the topic of the next section, @ref{Values and their Operations}.
|
|
|
|
The pseudo-location @code{RESULT} (or @code{result}) can be used to
|
|
display or change the result of a currently-active procedure:
|
|
|
|
@smallexample
|
|
set result := EXPR
|
|
@end smallexample
|
|
|
|
@noindent
|
|
This does the same as the Chill action @code{RESULT EXPR} (which
|
|
is not available in @value{GDBN}).
|
|
|
|
Values of reference mode locations are printed by @code{PTR(<hex
|
|
value>)} in case of a free reference mode, and by @code{(REF <reference
|
|
mode>) (<hex-value>)} in case of a bound reference. @code{<hex value>}
|
|
represents the address where the reference points to. To access the
|
|
value of the location referenced by the pointer, use the dereference
|
|
operator @samp{->}.
|
|
|
|
Values of procedure mode locations are displayed by
|
|
@smallexample
|
|
@code{@{ PROC
|
|
(<argument modes> ) <return mode> @} <address> <name of procedure
|
|
location>}
|
|
@end smallexample
|
|
@code{<argument modes>} is a list of modes according to the parameter
|
|
specification of the procedure and @code{<address>} shows the address of
|
|
the entry point.
|
|
|
|
@ignore
|
|
Locations of instance modes are displayed just like a structure with two
|
|
fields specifying the @emph{process type} and the @emph{copy number} of
|
|
the investigated instance location@footnote{This comes from the current
|
|
implementation of instances. They are implemented as a structure (no
|
|
na). The output should be something like @code{[<name of the process>;
|
|
<instance number>]}.}. The field names are @code{__proc_type} and
|
|
@code{__proc_copy}.
|
|
|
|
Locations of synchronization modes are displayed like a structure with
|
|
the field name @code{__event_data} in case of a event mode location, and
|
|
like a structure with the field @code{__buffer_data} in case of a buffer
|
|
mode location (refer to previous paragraph).
|
|
|
|
Structure Mode locations are printed by @code{[.<field name>: <value>,
|
|
...]}. The @code{<field name>} corresponds to the structure mode
|
|
definition and the layout of @code{<value>} varies depending of the mode
|
|
of the field. If the investigated structure mode location is of variant
|
|
structure mode, the variant parts of the structure are enclosed in curled
|
|
braces (@samp{@{@}}). Fields enclosed by @samp{@{,@}} are residing
|
|
on the same memory location and represent the current values of the
|
|
memory location in their specific modes. Since no tag processing is done
|
|
all variants are displayed. A variant field is printed by
|
|
@code{(<variant name>) = .<field name>: <value>}. (who implements the
|
|
stuff ???)
|
|
@smallexample
|
|
(@value{GDBP}) print str1 $4 = [.as: 0, .bs: karli, .<TAG>: { (karli) =
|
|
[.cs: []], (susi) = [.ds: susi]}]
|
|
@end smallexample
|
|
@end ignore
|
|
|
|
Substructures of string mode-, array mode- or structure mode-values
|
|
(e.g. array slices, fields of structure locations) are accessed using
|
|
certain operations which are described in the next section, @ref{Values
|
|
and their Operations}.
|
|
|
|
A location value may be interpreted as having a different mode using the
|
|
location conversion. This mode conversion is written as @code{<mode
|
|
name>(<location>)}. The user has to consider that the sizes of the modes
|
|
have to be equal otherwise an error occurs. Furthermore, no range
|
|
checking of the location against the destination mode is performed, and
|
|
therefore the result can be quite confusing.
|
|
|
|
@smallexample
|
|
(@value{GDBP}) print int (s(3 up 4)) XXX TO be filled in !! XXX
|
|
@end smallexample
|
|
|
|
@node Values and their Operations
|
|
@subsubsection Values and their Operations
|
|
|
|
Values are used to alter locations, to investigate complex structures in
|
|
more detail or to filter relevant information out of a large amount of
|
|
data. There are several (mode dependent) operations defined which enable
|
|
such investigations. These operations are not only applicable to
|
|
constant values but also to locations, which can become quite useful
|
|
when debugging complex structures. During parsing the command line
|
|
(e.g. evaluating an expression) @value{GDBN} treats location names as
|
|
the values behind these locations.
|
|
|
|
This section describes how values have to be specified and which
|
|
operations are legal to be used with such values.
|
|
|
|
@table @code
|
|
@item Literal Values
|
|
Literal values are specified in the same manner as in @sc{gnu} Chill programs.
|
|
For detailed specification refer to the @sc{gnu} Chill implementation Manual
|
|
chapter 1.5.
|
|
@c FIXME: if the Chill Manual is a Texinfo documents, the above should
|
|
@c be converted to a @ref.
|
|
|
|
@ignore
|
|
@itemize @bullet
|
|
@item
|
|
@emph{Integer Literals} are specified in the same manner as in Chill
|
|
programs (refer to the Chill Standard z200/88 chpt 5.2.4.2)
|
|
@item
|
|
@emph{Boolean Literals} are defined by @code{TRUE} and @code{FALSE}.
|
|
@item
|
|
@emph{Character Literals} are defined by @code{'<character>'}. (e.g.
|
|
@code{'M'})
|
|
@item
|
|
@emph{Set Literals} are defined by a name which was specified in a set
|
|
mode. The value delivered by a Set Literal is the set value. This is
|
|
comparable to an enumeration in C/C@t{++} language.
|
|
@item
|
|
@emph{Emptiness Literal} is predefined by @code{NULL}. The value of the
|
|
emptiness literal delivers either the empty reference value, the empty
|
|
procedure value or the empty instance value.
|
|
|
|
@item
|
|
@emph{Character String Literals} are defined by a sequence of characters
|
|
enclosed in single- or double quotes. If a single- or double quote has
|
|
to be part of the string literal it has to be stuffed (specified twice).
|
|
@item
|
|
@emph{Bitstring Literals} are specified in the same manner as in Chill
|
|
programs (refer z200/88 chpt 5.2.4.8).
|
|
@item
|
|
@emph{Floating point literals} are specified in the same manner as in
|
|
(gnu-)Chill programs (refer @sc{gnu} Chill implementation Manual chapter 1.5).
|
|
@end itemize
|
|
@end ignore
|
|
|
|
@item Tuple Values
|
|
A tuple is specified by @code{<mode name>[<tuple>]}, where @code{<mode
|
|
name>} can be omitted if the mode of the tuple is unambiguous. This
|
|
unambiguity is derived from the context of a evaluated expression.
|
|
@code{<tuple>} can be one of the following:
|
|
|
|
@itemize @bullet
|
|
@item @emph{Powerset Tuple}
|
|
@item @emph{Array Tuple}
|
|
@item @emph{Structure Tuple}
|
|
Powerset tuples, array tuples and structure tuples are specified in the
|
|
same manner as in Chill programs refer to z200/88 chpt 5.2.5.
|
|
@end itemize
|
|
|
|
@item String Element Value
|
|
A string element value is specified by
|
|
@smallexample
|
|
@code{<string value>(<index>)}
|
|
@end smallexample
|
|
where @code{<index>} is a integer expression. It delivers a character
|
|
value which is equivalent to the character indexed by @code{<index>} in
|
|
the string.
|
|
|
|
@item String Slice Value
|
|
A string slice value is specified by @code{<string value>(<slice
|
|
spec>)}, where @code{<slice spec>} can be either a range of integer
|
|
expressions or specified by @code{<start expr> up <size>}.
|
|
@code{<size>} denotes the number of elements which the slice contains.
|
|
The delivered value is a string value, which is part of the specified
|
|
string.
|
|
|
|
@item Array Element Values
|
|
An array element value is specified by @code{<array value>(<expr>)} and
|
|
delivers a array element value of the mode of the specified array.
|
|
|
|
@item Array Slice Values
|
|
An array slice is specified by @code{<array value>(<slice spec>)}, where
|
|
@code{<slice spec>} can be either a range specified by expressions or by
|
|
@code{<start expr> up <size>}. @code{<size>} denotes the number of
|
|
arrayelements the slice contains. The delivered value is an array value
|
|
which is part of the specified array.
|
|
|
|
@item Structure Field Values
|
|
A structure field value is derived by @code{<structure value>.<field
|
|
name>}, where @code{<field name>} indicates the name of a field specified
|
|
in the mode definition of the structure. The mode of the delivered value
|
|
corresponds to this mode definition in the structure definition.
|
|
|
|
@item Procedure Call Value
|
|
The procedure call value is derived from the return value of the
|
|
procedure@footnote{If a procedure call is used for instance in an
|
|
expression, then this procedure is called with all its side
|
|
effects. This can lead to confusing results if used carelessly.}.
|
|
|
|
Values of duration mode locations are represented by @code{ULONG} literals.
|
|
|
|
Values of time mode locations appear as
|
|
@smallexample
|
|
@code{TIME(<secs>:<nsecs>)}
|
|
@end smallexample
|
|
|
|
|
|
@ignore
|
|
This is not implemented yet:
|
|
@item Built-in Value
|
|
@noindent
|
|
The following built in functions are provided:
|
|
|
|
@table @code
|
|
@item @code{ADDR()}
|
|
@item @code{NUM()}
|
|
@item @code{PRED()}
|
|
@item @code{SUCC()}
|
|
@item @code{ABS()}
|
|
@item @code{CARD()}
|
|
@item @code{MAX()}
|
|
@item @code{MIN()}
|
|
@item @code{SIZE()}
|
|
@item @code{UPPER()}
|
|
@item @code{LOWER()}
|
|
@item @code{LENGTH()}
|
|
@item @code{SIN()}
|
|
@item @code{COS()}
|
|
@item @code{TAN()}
|
|
@item @code{ARCSIN()}
|
|
@item @code{ARCCOS()}
|
|
@item @code{ARCTAN()}
|
|
@item @code{EXP()}
|
|
@item @code{LN()}
|
|
@item @code{LOG()}
|
|
@item @code{SQRT()}
|
|
@end table
|
|
|
|
For a detailed description refer to the GNU Chill implementation manual
|
|
chapter 1.6.
|
|
@end ignore
|
|
|
|
@item Zero-adic Operator Value
|
|
The zero-adic operator value is derived from the instance value for the
|
|
current active process.
|
|
|
|
@item Expression Values
|
|
The value delivered by an expression is the result of the evaluation of
|
|
the specified expression. If there are error conditions (mode
|
|
incompatibility, etc.) the evaluation of expressions is aborted with a
|
|
corresponding error message. Expressions may be parenthesised which
|
|
causes the evaluation of this expression before any other expression
|
|
which uses the result of the parenthesised expression. The following
|
|
operators are supported by @value{GDBN}:
|
|
|
|
@table @code
|
|
@item @code{OR, ORIF, XOR}
|
|
@itemx @code{AND, ANDIF}
|
|
@itemx @code{NOT}
|
|
Logical operators defined over operands of boolean mode.
|
|
|
|
@item @code{=, /=}
|
|
Equality and inequality operators defined over all modes.
|
|
|
|
@item @code{>, >=}
|
|
@itemx @code{<, <=}
|
|
Relational operators defined over predefined modes.
|
|
|
|
@item @code{+, -}
|
|
@itemx @code{*, /, MOD, REM}
|
|
Arithmetic operators defined over predefined modes.
|
|
|
|
@item @code{-}
|
|
Change sign operator.
|
|
|
|
@item @code{//}
|
|
String concatenation operator.
|
|
|
|
@item @code{()}
|
|
String repetition operator.
|
|
|
|
@item @code{->}
|
|
Referenced location operator which can be used either to take the
|
|
address of a location (@code{->loc}), or to dereference a reference
|
|
location (@code{loc->}).
|
|
|
|
@item @code{OR, XOR}
|
|
@itemx @code{AND}
|
|
@itemx @code{NOT}
|
|
Powerset and bitstring operators.
|
|
|
|
@item @code{>, >=}
|
|
@itemx @code{<, <=}
|
|
Powerset inclusion operators.
|
|
|
|
@item @code{IN}
|
|
Membership operator.
|
|
@end table
|
|
@end table
|
|
|
|
@node Chill type and range checks
|
|
@subsubsection Chill type and range checks
|
|
|
|
@value{GDBN} considers two Chill variables mode equivalent if the sizes
|
|
of the two modes are equal. This rule applies recursively to more
|
|
complex datatypes which means that complex modes are treated
|
|
equivalent if all element modes (which also can be complex modes like
|
|
structures, arrays, etc.) have the same size.
|
|
|
|
Range checking is done on all mathematical operations, assignment, array
|
|
index bounds and all built in procedures.
|
|
|
|
Strong type checks are forced using the @value{GDBN} command @code{set
|
|
check strong}. This enforces strong type and range checks on all
|
|
operations where Chill constructs are used (expressions, built in
|
|
functions, etc.) in respect to the semantics as defined in the z.200
|
|
language specification.
|
|
|
|
All checks can be disabled by the @value{GDBN} command @code{set check
|
|
off}.
|
|
|
|
@ignore
|
|
@c Deviations from the Chill Standard Z200/88
|
|
see last paragraph ?
|
|
@end ignore
|
|
|
|
@node Chill defaults
|
|
@subsubsection Chill defaults
|
|
|
|
If type and range checking are set automatically by @value{GDBN}, they
|
|
both default to @code{on} whenever the working language changes to
|
|
Chill. 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{.ch} sets the
|
|
working language to Chill. @xref{Automatically, ,Having @value{GDBN} set
|
|
the language automatically}, for further details.
|
|
|
|
@node Symbols
|
|
@chapter Examining the Symbol Table
|
|
|
|
The commands described in this chapter 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}).
|
|
|
|
@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
|
|
@kindex info address
|
|
@cindex address of a symbol
|
|
@item info address @var{symbol}
|
|
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 variable, and for a stack local variable prints
|
|
the exact address of the current instantiation of the variable.
|
|
|
|
@kindex info symbol
|
|
@cindex symbol from address
|
|
@item info symbol @var{addr}
|
|
Print the name of a symbol which is stored at the address @var{addr}.
|
|
If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
|
|
nearest symbol and an offset from it:
|
|
|
|
@example
|
|
(@value{GDBP}) info symbol 0x54320
|
|
_initialize_vx + 396 in section .text
|
|
@end example
|
|
|
|
@noindent
|
|
This is the opposite of the @code{info address} command. You can use
|
|
it to find out the name of a variable or a function given its address.
|
|
|
|
@kindex whatis
|
|
@item whatis @var{expr}
|
|
Print the data type of expression @var{expr}. @var{expr} 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.
|
|
|
|
@kindex ptype
|
|
@item ptype @var{typename}
|
|
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{class
|
|
@var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
|
|
@var{union-tag}} or @samp{enum @var{enum-tag}}.
|
|
|
|
@item ptype @var{expr}
|
|
@itemx ptype
|
|
Print a description of the type of expression @var{expr}. @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{$}, the last value in the value history.
|
|
|
|
@kindex info types
|
|
@item info types @var{regexp}
|
|
@itemx info types
|
|
Print a brief description of all types whose names match @var{regexp}
|
|
(or all types in your program, if you supply no argument). Each
|
|
complete typename is matched as though it were a complete line; thus,
|
|
@samp{i type value} gives information on all types in your program whose
|
|
names include the string @code{value}, but @samp{i type ^value$} 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.
|
|
|
|
@kindex info scope
|
|
@cindex local variables
|
|
@item info scope @var{addr}
|
|
List all the variables local to a particular scope. This command
|
|
accepts a location---a function name, a source line, or an address
|
|
preceded by a @samp{*}, and prints all the variables local to the
|
|
scope defined by that location. For example:
|
|
|
|
@smallexample
|
|
(@value{GDBP}) @b{info scope command_line_handler}
|
|
Scope for command_line_handler:
|
|
Symbol rl is an argument at stack/frame offset 8, length 4.
|
|
Symbol linebuffer is in static storage at address 0x150a18, length 4.
|
|
Symbol linelength is in static storage at address 0x150a1c, length 4.
|
|
Symbol p is a local variable in register $esi, length 4.
|
|
Symbol p1 is a local variable in register $ebx, length 4.
|
|
Symbol nline is a local variable in register $edx, length 4.
|
|
Symbol repeat is a local variable at frame offset -8, length 4.
|
|
@end smallexample
|
|
|
|
@noindent
|
|
This command is especially useful for determining what data to collect
|
|
during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
|
|
collect}.
|
|
|
|
@kindex info source
|
|
@item 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.
|
|
|
|
@kindex info sources
|
|
@item 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.
|
|
|
|
@kindex info functions
|
|
@item 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}. If a function name contains characters
|
|
that conflict with the regular expression language (eg.
|
|
@samp{operator*()}), they may be quoted with a backslash.
|
|
|
|
@kindex info variables
|
|
@item 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.
|
|
@kindex info methods
|
|
@item info methods
|
|
@itemx info methods @var{regexp}
|
|
The @code{info methods} command permits the user to examine all defined
|
|
methods within C@t{++} program, or (with the @var{regexp} argument) a
|
|
specific set of methods found in the various C@t{++} classes. Many
|
|
C@t{++} 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
|
|
|
|
@cindex reloading symbols
|
|
Some systems allow individual object files that make up your program to
|
|
be replaced without stopping and restarting your program. For example,
|
|
in VxWorks you can simply recompile a defective object file and keep on
|
|
running. 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 encountering object files of the
|
|
same name more than once. This is the default state; if you are not
|
|
running on a system that permits automatic relinking of 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.
|
|
|
|
@kindex show symbol-reloading
|
|
@item show symbol-reloading
|
|
Show the current @code{on} or @code{off} setting.
|
|
@end table
|
|
|
|
@kindex set opaque-type-resolution
|
|
@item set opaque-type-resolution on
|
|
Tell @value{GDBN} to resolve opaque types. An opaque type is a type
|
|
declared as a pointer to a @code{struct}, @code{class}, or
|
|
@code{union}---for example, @code{struct MyType *}---that is used in one
|
|
source file although the full declaration of @code{struct MyType} is in
|
|
another source file. The default is on.
|
|
|
|
A change in the setting of this subcommand will not take effect until
|
|
the next time symbols for a file are loaded.
|
|
|
|
@item set opaque-type-resolution off
|
|
Tell @value{GDBN} not to resolve opaque types. In this case, the type
|
|
is printed as follows:
|
|
@smallexample
|
|
@{<no data fields>@}
|
|
@end smallexample
|
|
|
|
@kindex show opaque-type-resolution
|
|
@item show opaque-type-resolution
|
|
Show whether opaque types are resolved or not.
|
|
|
|
@kindex maint print symbols
|
|
@cindex symbol dump
|
|
@kindex maint print psymbols
|
|
@cindex partial symbol dump
|
|
@item maint print symbols @var{filename}
|
|
@itemx maint print psymbols @var{filename}
|
|
@itemx maint print msymbols @var{filename}
|
|
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.
|
|
@xref{Files, ,Commands to specify files}, for a discussion of how
|
|
@value{GDBN} reads symbols (in the description of @code{symbol-file}).
|
|
@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, give your program a signal, restart it at a different
|
|
address, or even return prematurely from a function.
|
|
|
|
@menu
|
|
* Assignment:: Assignment to variables
|
|
* Jumping:: Continuing at a different address
|
|
* Signaling:: Giving your program a signal
|
|
* 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).
|
|
@xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
|
|
information on operators in supported languages.
|
|
|
|
@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
|
|
|
|
Because the @code{set} command has many subcommands that can conflict
|
|
with the names of program variables, it is a good idea to use the
|
|
@code{set variable} command instead of just @code{set}. For example, if
|
|
your program has a variable @code{g}, you run into problems if you try
|
|
to set a new value with just @samp{set g=4}, because @value{GDBN} has
|
|
the command @code{set gnutarget}, abbreviated @code{set g}:
|
|
|
|
@example
|
|
@group
|
|
(@value{GDBP}) whatis g
|
|
type = double
|
|
(@value{GDBP}) p g
|
|
$1 = 1
|
|
(@value{GDBP}) set g=4
|
|
(@value{GDBP}) p g
|
|
$2 = 1
|
|
(@value{GDBP}) r
|
|
The program being debugged has been started already.
|
|
Start it from the beginning? (y or n) y
|
|
Starting program: /home/smith/cc_progs/a.out
|
|
"/home/smith/cc_progs/a.out": can't open to read symbols:
|
|
Invalid bfd target.
|
|
(@value{GDBP}) show g
|
|
The current BFD target is "=4".
|
|
@end group
|
|
@end example
|
|
|
|
@noindent
|
|
The program variable @code{g} did not change, and you silently set the
|
|
@code{gnutarget} to an invalid value. In order to set the variable
|
|
@code{g}, use
|
|
|
|
@example
|
|
(@value{GDBP}) set var g=4
|
|
@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 /doc@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
|
|
@kindex jump
|
|
@item jump @var{linespec}
|
|
Resume execution at line @var{linespec}. Execution stops again
|
|
immediately if there is a breakpoint there. @xref{List, ,Printing
|
|
source lines}, for a description of the different forms of
|
|
@var{linespec}. It is common practice to use the @code{tbreak} command
|
|
in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
|
|
breakpoints}.
|
|
|
|
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
|
|
|
|
@c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
|
|
On many systems, you can get much the same effect as the @code{jump}
|
|
command by storing a new value into the register @code{$pc}. The
|
|
difference is that this does not start your program running; it only
|
|
changes the address of where it @emph{will} run when you continue. For
|
|
example,
|
|
|
|
@example
|
|
set $pc = 0x485
|
|
@end example
|
|
|
|
@noindent
|
|
makes the next @code{continue} command or stepping command 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.
|
|
|
|
@c @group
|
|
@node Signaling
|
|
@section Giving your program a signal
|
|
|
|
@table @code
|
|
@kindex signal
|
|
@item signal @var{signal}
|
|
Resume execution where your program stopped, but immediately give it the
|
|
signal @var{signal}. @var{signal} can be the name or the number of a
|
|
signal. For example, on many systems @code{signal 2} and @code{signal
|
|
SIGINT} are both ways of sending an interrupt signal.
|
|
|
|
Alternatively, if @var{signal} 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
|
|
|
|
Invoking the @code{signal} command is not the same as invoking the
|
|
@code{kill} utility from the shell. Sending a signal with @code{kill}
|
|
causes @value{GDBN} to decide what to do with the signal depending on
|
|
the signal handling tables (@pxref{Signals}). The @code{signal} command
|
|
passes the signal directly to your program.
|
|
|
|
|
|
@node Returning
|
|
@section Returning from a function
|
|
|
|
@table @code
|
|
@cindex returning from a function
|
|
@kindex return
|
|
@item return
|
|
@itemx return @var{expression}
|
|
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. If the result is not void, it
|
|
is printed and saved in the value history.
|
|
|
|
For the A29K, a user-controlled variable @code{call_scratch_address},
|
|
specifies the location of a scratch area to be used when @value{GDBN}
|
|
calls a function in the target. This is necessary because the usual
|
|
method of putting the scratch area on the stack does not work in systems
|
|
that have separate instruction and data spaces.
|
|
|
|
@node Patching
|
|
@section Patching programs
|
|
|
|
@cindex patching binaries
|
|
@cindex writing into executables
|
|
@cindex writing into corefiles
|
|
|
|
By default, @value{GDBN} opens the file containing your program's
|
|
executable code (or the corefile) 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
|
|
@kindex set write
|
|
@item set write on
|
|
@itemx set write off
|
|
If you specify @samp{set write on}, @value{GDBN} opens executable and
|
|
core files for both reading and writing; if you specify @samp{set write
|
|
off} (the default), @value{GDBN} opens them read-only.
|
|
|
|
If you have already loaded a file, you must load it again (using the
|
|
@code{exec-file} or @code{core-file} command) after changing @code{set
|
|
write}, for your new setting to take effect.
|
|
|
|
@item show write
|
|
@kindex show write
|
|
Display whether executable files and core files are 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. To debug a core dump of a previous run, you must also tell
|
|
@value{GDBN} the name of the core dump file.
|
|
|
|
@menu
|
|
* Files:: Commands to specify files
|
|
* Symbol Errors:: Errors reading symbol files
|
|
@end menu
|
|
|
|
@node Files
|
|
@section Commands to specify files
|
|
|
|
@cindex symbol table
|
|
@cindex core dump file
|
|
|
|
You may want to specify executable and core dump file names. The usual
|
|
way to do this is at start-up time, using the arguments to
|
|
@value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
|
|
Out of @value{GDBN}}).
|
|
|
|
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
|
|
@cindex executable file
|
|
@kindex file
|
|
@item file @var{filename}
|
|
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 file named
|
|
@file{@var{filename}.syms} may hold symbol table information for
|
|
@var{filename}. If so, @value{GDBN} maps in the symbol table from
|
|
@file{@var{filename}.syms}, starting up more quickly. See the
|
|
descriptions of the file 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}, described below),
|
|
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.
|
|
|
|
@kindex exec-file
|
|
@item exec-file @r{[} @var{filename} @r{]}
|
|
Specify that the program to be run (but not the symbol table) is found
|
|
in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
|
|
if necessary to locate your program. Omitting @var{filename} means to
|
|
discard information on the executable file.
|
|
|
|
@kindex symbol-file
|
|
@item symbol-file @r{[} @var{filename} @r{]}
|
|
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} does not repeat if you press @key{RET} again after
|
|
executing it once.
|
|
|
|
When @value{GDBN} is configured for a particular environment, it
|
|
understands debugging information in whatever format is the standard
|
|
generated for that environment; you may use either a @sc{gnu} compiler, or
|
|
other compilers that adhere to the local conventions.
|
|
Best results are usually obtained from @sc{gnu} compilers; for example,
|
|
using @code{@value{GCC}} you can generate debugging information for
|
|
optimized code.
|
|
|
|
For most kinds of object files, with the exception of old SVR3 systems
|
|
using COFF, 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. Note that ``stabs-in-COFF''
|
|
still does the two-stage strategy, since the debug info is actually
|
|
in stabs format.
|
|
|
|
@kindex readnow
|
|
@cindex reading symbols immediately
|
|
@cindex symbols, reading immediately
|
|
@kindex mapped
|
|
@cindex memory-mapped symbol file
|
|
@cindex saving symbol table
|
|
@item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
|
|
@itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
|
|
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.
|
|
|
|
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 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} always attempts 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.
|
|
|
|
@kindex core
|
|
@kindex core-file
|
|
@item core-file @r{[} @var{filename} @r{]}
|
|
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}).
|
|
|
|
@kindex add-symbol-file
|
|
@cindex dynamic linking
|
|
@item add-symbol-file @var{filename} @var{address}
|
|
@itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
|
|
@itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
|
|
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. You can additionally specify an arbitrary number
|
|
of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
|
|
section name and base address for that section. You can specify any
|
|
@var{address} as an expression.
|
|
|
|
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 without any arguments.
|
|
|
|
@cindex relocatable object files, reading symbols from
|
|
@cindex object files, relocatable, reading symbols from
|
|
@cindex reading symbols from relocatable object files
|
|
@cindex symbols, reading from relocatable object files
|
|
@cindex @file{.o} files, reading symbols from
|
|
Although @var{filename} is typically a shared library file, an
|
|
executable file, or some other object file which has been fully
|
|
relocated for loading into a process, you can also load symbolic
|
|
information from relocatable @file{.o} files, as long as:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
the file's symbolic information refers only to linker symbols defined in
|
|
that file, not to symbols defined by other object files,
|
|
@item
|
|
every section the file's symbolic information refers to has actually
|
|
been loaded into the inferior, as it appears in the file, and
|
|
@item
|
|
you can determine the address at which every section was loaded, and
|
|
provide these to the @code{add-symbol-file} command.
|
|
@end itemize
|
|
|
|
@noindent
|
|
Some embedded operating systems, like Sun Chorus and VxWorks, can load
|
|
relocatable files into an already running program; such systems
|
|
typically make the requirements above easy to meet. However, it's
|
|
important to recognize that many native systems use complex link
|
|
procedures (@code{.linkonce} section factoring and C++ constructor table
|
|
assembly, for example) that make the requirements difficult to meet. In
|
|
general, one cannot assume that using @code{add-symbol-file} to read a
|
|
relocatable object file's symbolic information will have the same effect
|
|
as linking the relocatable object file into the program in the normal
|
|
way.
|
|
|
|
@code{add-symbol-file} does 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}.
|
|
|
|
@kindex add-shared-symbol-file
|
|
@item add-shared-symbol-file
|
|
The @code{add-shared-symbol-file} command can be used only under Harris' CXUX
|
|
operating system for the Motorola 88k. @value{GDBN} automatically looks for
|
|
shared libraries, however if @value{GDBN} does not find yours, you can run
|
|
@code{add-shared-symbol-file}. It takes no arguments.
|
|
|
|
@kindex section
|
|
@item section
|
|
The @code{section} command changes the base address of section SECTION of
|
|
the exec file to ADDR. This can be used if the exec file does not contain
|
|
section addresses, (such as in the a.out format), or when the addresses
|
|
specified in the file itself are wrong. Each section must be changed
|
|
separately. The @code{info files} command, described below, lists all
|
|
the sections and their addresses.
|
|
|
|
@kindex info files
|
|
@kindex info target
|
|
@item info files
|
|
@itemx info target
|
|
@code{info files} and @code{info target} are synonymous; both print the
|
|
current target (@pxref{Targets, ,Specifying a Debugging Target}),
|
|
including the names of the executable and core dump files currently in
|
|
use by @value{GDBN}, and the files from which symbols were loaded. The
|
|
command @code{help target} lists all possible targets rather than
|
|
current ones.
|
|
|
|
@kindex maint info sections
|
|
@item maint info sections
|
|
Another command that can give you extra information about program sections
|
|
is @code{maint info sections}. In addition to the section information
|
|
displayed by @code{info files}, this command displays the flags and file
|
|
offset of each section in the executable and core dump files. In addition,
|
|
@code{maint info sections} provides the following command options (which
|
|
may be arbitrarily combined):
|
|
|
|
@table @code
|
|
@item ALLOBJ
|
|
Display sections for all loaded object files, including shared libraries.
|
|
@item @var{sections}
|
|
Display info only for named @var{sections}.
|
|
@item @var{section-flags}
|
|
Display info only for sections for which @var{section-flags} are true.
|
|
The section flags that @value{GDBN} currently knows about are:
|
|
@table @code
|
|
@item ALLOC
|
|
Section will have space allocated in the process when loaded.
|
|
Set for all sections except those containing debug information.
|
|
@item LOAD
|
|
Section will be loaded from the file into the child process memory.
|
|
Set for pre-initialized code and data, clear for @code{.bss} sections.
|
|
@item RELOC
|
|
Section needs to be relocated before loading.
|
|
@item READONLY
|
|
Section cannot be modified by the child process.
|
|
@item CODE
|
|
Section contains executable code only.
|
|
@item DATA
|
|
Section contains data only (no executable code).
|
|
@item ROM
|
|
Section will reside in ROM.
|
|
@item CONSTRUCTOR
|
|
Section contains data for constructor/destructor lists.
|
|
@item HAS_CONTENTS
|
|
Section is not empty.
|
|
@item NEVER_LOAD
|
|
An instruction to the linker to not output the section.
|
|
@item COFF_SHARED_LIBRARY
|
|
A notification to the linker that the section contains
|
|
COFF shared library information.
|
|
@item IS_COMMON
|
|
Section contains common symbols.
|
|
@end table
|
|
@end table
|
|
@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 file
|
|
name and remembers it that way.
|
|
|
|
@cindex shared libraries
|
|
@value{GDBN} supports HP-UX, SunOS, SVr4, Irix 5, 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} does not understand
|
|
references to a function in a shared library, however---unless you are
|
|
debugging a core file).
|
|
|
|
On HP-UX, if the program loads a library explicitly, @value{GDBN}
|
|
automatically loads the symbols at the time of the @code{shl_load} call.
|
|
|
|
@c FIXME: some @value{GDBN} release may permit some refs to undef
|
|
@c FIXME...symbols---eg in a break cmd---assuming they are from a shared
|
|
@c FIXME...lib; check this from time to time when updating manual
|
|
|
|
There are times, however, when you may wish to not automatically load
|
|
symbol definitions from shared libraries, such as when they are
|
|
particularly large or there are many of them.
|
|
|
|
To control the automatic loading of shared library symbols, use the
|
|
commands:
|
|
|
|
@table @code
|
|
@kindex set auto-solib-add
|
|
@item set auto-solib-add @var{mode}
|
|
If @var{mode} is @code{on}, symbols from all shared object libraries
|
|
will be loaded automatically when the inferior begins execution, you
|
|
attach to an independently started inferior, or when the dynamic linker
|
|
informs @value{GDBN} that a new library has been loaded. If @var{mode}
|
|
is @code{off}, symbols must be loaded manually, using the
|
|
@code{sharedlibrary} command. The default value is @code{on}.
|
|
|
|
@kindex show auto-solib-add
|
|
@item show auto-solib-add
|
|
Display the current autoloading mode.
|
|
@end table
|
|
|
|
To explicitly load shared library symbols, use the @code{sharedlibrary}
|
|
command:
|
|
|
|
@table @code
|
|
@kindex info sharedlibrary
|
|
@kindex info share
|
|
@item info share
|
|
@itemx info sharedlibrary
|
|
Print the names of the shared libraries which are currently loaded.
|
|
|
|
@kindex sharedlibrary
|
|
@kindex share
|
|
@item sharedlibrary @var{regex}
|
|
@itemx share @var{regex}
|
|
Load shared object library symbols for files matching a
|
|
Unix regular expression.
|
|
As with files loaded automatically, it only loads 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
|
|
|
|
On some systems, such as HP-UX systems, @value{GDBN} supports
|
|
autoloading shared library symbols until a limiting threshold size is
|
|
reached. This provides the benefit of allowing autoloading to remain on
|
|
by default, but avoids autoloading excessively large shared libraries,
|
|
up to a threshold that is initially set, but which you can modify if you
|
|
wish.
|
|
|
|
Beyond that threshold, symbols from shared libraries must be explicitly
|
|
loaded. To load these symbols, use the command @code{sharedlibrary
|
|
@var{filename}}. The base address of the shared library is determined
|
|
automatically by @value{GDBN} and need not be specified.
|
|
|
|
To display or set the threshold, use the commands:
|
|
|
|
@table @code
|
|
@kindex set auto-solib-limit
|
|
@item set auto-solib-limit @var{threshold}
|
|
Set the autoloading size threshold, in an integral number of megabytes.
|
|
If @var{threshold} is nonzero and shared library autoloading is enabled,
|
|
symbols from all shared object libraries will be loaded until the total
|
|
size of the loaded shared library symbols exceeds this threshold.
|
|
Otherwise, symbols must be loaded manually, using the
|
|
@code{sharedlibrary} command. The default threshold is 100 (i.e. 100
|
|
Mb).
|
|
|
|
@kindex show auto-solib-limit
|
|
@item show auto-solib-limit
|
|
Display the current autoloading size threshold, in megabytes.
|
|
@end table
|
|
|
|
@node Symbol Errors
|
|
@section Errors reading symbol files
|
|
|
|
While reading a symbol file, @value{GDBN} occasionally encounters 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, include:
|
|
|
|
@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 has 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
|
|
uncomprehended information, in hexadecimal.
|
|
|
|
@value{GDBN} circumvents the error by ignoring this symbol information.
|
|
This usually allows you to debug your program, though certain symbols
|
|
are not 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 a struct or class.
|
|
|
|
@item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
|
|
The symbol information for a C@t{++} member function is missing some
|
|
information that recent versions of the compiler should have output for
|
|
it.
|
|
|
|
@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.
|
|
|
|
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 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
|
|
* Byte Order:: Choosing target byte order
|
|
* Remote:: Remote debugging
|
|
* KOD:: Kernel Object Display
|
|
|
|
@end menu
|
|
|
|
@node Active Targets
|
|
@section Active targets
|
|
|
|
@cindex stacking targets
|
|
@cindex active targets
|
|
@cindex multiple targets
|
|
|
|
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 uses 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.)
|
|
|
|
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 active core file or executable file target are obscured while the
|
|
process target is active.
|
|
|
|
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}).
|
|
|
|
@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 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.
|
|
|
|
The @code{target} command does not repeat if you press @key{RET} again
|
|
after executing the command.
|
|
|
|
@kindex help target
|
|
@item 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.
|
|
|
|
@kindex set gnutarget
|
|
@item set gnutarget @var{args}
|
|
@value{GDBN} uses its own library BFD to read your files. @value{GDBN}
|
|
knows whether it is reading an @dfn{executable},
|
|
a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
|
|
with the @code{set gnutarget} command. Unlike most @code{target} commands,
|
|
with @code{gnutarget} the @code{target} refers to a program, not a machine.
|
|
|
|
@quotation
|
|
@emph{Warning:} To specify a file format with @code{set gnutarget},
|
|
you must know the actual BFD name.
|
|
@end quotation
|
|
|
|
@noindent
|
|
@xref{Files, , Commands to specify files}.
|
|
|
|
@kindex show gnutarget
|
|
@item show gnutarget
|
|
Use the @code{show gnutarget} command to display what file format
|
|
@code{gnutarget} is set to read. If you have not set @code{gnutarget},
|
|
@value{GDBN} will determine the file format for each file automatically,
|
|
and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
|
|
@end table
|
|
|
|
Here are some common targets (available, or not, depending on the GDB
|
|
configuration):
|
|
|
|
@table @code
|
|
@kindex target exec
|
|
@item target exec @var{program}
|
|
An executable file. @samp{target exec @var{program}} is the same as
|
|
@samp{exec-file @var{program}}.
|
|
|
|
@kindex target core
|
|
@item target core @var{filename}
|
|
A core dump file. @samp{target core @var{filename}} is the same as
|
|
@samp{core-file @var{filename}}.
|
|
|
|
@kindex target remote
|
|
@item target remote @var{dev}
|
|
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}. @code{target remote}
|
|
supports the @code{load} command. This is only useful if you have
|
|
some other way of getting the stub to the target system, and you can put
|
|
it somewhere in memory where it won't get clobbered by the download.
|
|
|
|
@kindex target sim
|
|
@item target sim
|
|
Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
|
|
In general,
|
|
@example
|
|
target sim
|
|
load
|
|
run
|
|
@end example
|
|
@noindent
|
|
works; however, you cannot assume that a specific memory map, device
|
|
drivers, or even basic I/O is available, although some simulators do
|
|
provide these. For info about any processor-specific simulator details,
|
|
see the appropriate section in @ref{Embedded Processors, ,Embedded
|
|
Processors}.
|
|
|
|
@end table
|
|
|
|
Some configurations may include these targets as well:
|
|
|
|
@table @code
|
|
|
|
@kindex target nrom
|
|
@item target nrom @var{dev}
|
|
NetROM ROM emulator. This target only supports downloading.
|
|
|
|
@end table
|
|
|
|
Different targets are available on different configurations of @value{GDBN};
|
|
your configuration may have more or fewer targets.
|
|
|
|
Many remote targets require you to download the executable's code
|
|
once you've successfully established a connection.
|
|
|
|
@table @code
|
|
|
|
@kindex load @var{filename}
|
|
@item load @var{filename}
|
|
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{}}''
|
|
|
|
The file is loaded at whatever address is specified in the executable.
|
|
For some object file formats, you can specify the load address when you
|
|
link the program; for other formats, like a.out, the object file format
|
|
specifies a fixed address.
|
|
@c FIXME! This would be a good place for an xref to the GNU linker doc.
|
|
|
|
@code{load} does not repeat if you press @key{RET} again after using it.
|
|
@end table
|
|
|
|
@node Byte Order
|
|
@section Choosing target byte order
|
|
|
|
@cindex choosing target byte order
|
|
@cindex target byte order
|
|
|
|
Some types of processors, such as the MIPS, PowerPC, and Hitachi SH,
|
|
offer the ability to run either big-endian or little-endian byte
|
|
orders. Usually the executable or symbol will include a bit to
|
|
designate the endian-ness, and you will not need to worry about
|
|
which to use. However, you may still find it useful to adjust
|
|
@value{GDBN}'s idea of processor endian-ness manually.
|
|
|
|
@table @code
|
|
@kindex set endian big
|
|
@item set endian big
|
|
Instruct @value{GDBN} to assume the target is big-endian.
|
|
|
|
@kindex set endian little
|
|
@item set endian little
|
|
Instruct @value{GDBN} to assume the target is little-endian.
|
|
|
|
@kindex set endian auto
|
|
@item set endian auto
|
|
Instruct @value{GDBN} to use the byte order associated with the
|
|
executable.
|
|
|
|
@item show endian
|
|
Display @value{GDBN}'s current idea of the target byte order.
|
|
|
|
@end table
|
|
|
|
Note that these commands merely adjust interpretation of symbolic
|
|
data on the host, and that they have absolutely no effect on the
|
|
target system.
|
|
|
|
@node Remote
|
|
@section Remote debugging
|
|
@cindex remote debugging
|
|
|
|
If you are trying to debug a program running on a machine that cannot run
|
|
@value{GDBN} 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 @value{GDBN} have special serial or TCP/IP interfaces
|
|
to make this work with particular debugging targets. In addition,
|
|
@value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
|
|
but not specific to any particular target system) which you can use if you
|
|
write the remote stubs---the code that runs on the remote system to
|
|
communicate with @value{GDBN}.
|
|
|
|
Other remote targets may be available in your
|
|
configuration of @value{GDBN}; use @code{help target} to list them.
|
|
|
|
@menu
|
|
* Remote Serial:: @value{GDBN} remote serial protocol
|
|
@end menu
|
|
|
|
@node Remote Serial
|
|
@subsection The @value{GDBN} remote serial protocol
|
|
|
|
@cindex remote serial debugging, overview
|
|
To debug a program running on another machine (the debugging
|
|
@dfn{target} machine), you must first arrange for all the usual
|
|
prerequisites for the program to run by itself. For example, for a C
|
|
program, you need:
|
|
|
|
@enumerate
|
|
@item
|
|
A startup routine to set up the C runtime environment; these usually
|
|
have a name like @file{crt0}. The startup routine may be supplied by
|
|
your hardware supplier, or you may have to write your own.
|
|
|
|
@item
|
|
A C subroutine library to support your program's
|
|
subroutine calls, notably managing input and output.
|
|
|
|
@item
|
|
A way of getting your program to the other machine---for example, a
|
|
download program. These are often supplied by the hardware
|
|
manufacturer, but you may have to write your own from hardware
|
|
documentation.
|
|
@end enumerate
|
|
|
|
The next step is to arrange for your program to use a serial port to
|
|
communicate with the machine where @value{GDBN} is running (the @dfn{host}
|
|
machine). In general terms, the scheme looks like this:
|
|
|
|
@table @emph
|
|
@item On the host,
|
|
@value{GDBN} already understands how to use this protocol; when everything
|
|
else is set up, you can simply use the @samp{target remote} command
|
|
(@pxref{Targets,,Specifying a Debugging Target}).
|
|
|
|
@item On the target,
|
|
you must link with your program a few special-purpose subroutines that
|
|
implement the @value{GDBN} remote serial protocol. The file containing these
|
|
subroutines is called a @dfn{debugging stub}.
|
|
|
|
On certain remote targets, you can use an auxiliary program
|
|
@code{gdbserver} instead of linking a stub into your program.
|
|
@xref{Server,,Using the @code{gdbserver} program}, for details.
|
|
@end table
|
|
|
|
The debugging stub is specific to the architecture of the remote
|
|
machine; for example, use @file{sparc-stub.c} to debug programs on
|
|
@sc{sparc} boards.
|
|
|
|
@cindex remote serial stub list
|
|
These working remote stubs are distributed with @value{GDBN}:
|
|
|
|
@table @code
|
|
|
|
@item i386-stub.c
|
|
@cindex @file{i386-stub.c}
|
|
@cindex Intel
|
|
@cindex i386
|
|
For Intel 386 and compatible architectures.
|
|
|
|
@item m68k-stub.c
|
|
@cindex @file{m68k-stub.c}
|
|
@cindex Motorola 680x0
|
|
@cindex m680x0
|
|
For Motorola 680x0 architectures.
|
|
|
|
@item sh-stub.c
|
|
@cindex @file{sh-stub.c}
|
|
@cindex Hitachi
|
|
@cindex SH
|
|
For Hitachi SH architectures.
|
|
|
|
@item sparc-stub.c
|
|
@cindex @file{sparc-stub.c}
|
|
@cindex Sparc
|
|
For @sc{sparc} architectures.
|
|
|
|
@item sparcl-stub.c
|
|
@cindex @file{sparcl-stub.c}
|
|
@cindex Fujitsu
|
|
@cindex SparcLite
|
|
For Fujitsu @sc{sparclite} architectures.
|
|
|
|
@end table
|
|
|
|
The @file{README} file in the @value{GDBN} distribution may list other
|
|
recently added stubs.
|
|
|
|
@menu
|
|
* Stub Contents:: What the stub can do for you
|
|
* Bootstrapping:: What you must do for the stub
|
|
* Debug Session:: Putting it all together
|
|
* Protocol:: Definition of the communication protocol
|
|
* Server:: Using the `gdbserver' program
|
|
* NetWare:: Using the `gdbserve.nlm' program
|
|
@end menu
|
|
|
|
@node Stub Contents
|
|
@subsubsection What the stub can do for you
|
|
|
|
@cindex remote serial stub
|
|
The debugging stub for your architecture supplies these three
|
|
subroutines:
|
|
|
|
@table @code
|
|
@item set_debug_traps
|
|
@kindex set_debug_traps
|
|
@cindex remote serial stub, initialization
|
|
This routine arranges for @code{handle_exception} to run when your
|
|
program stops. You must call this subroutine explicitly near the
|
|
beginning of your program.
|
|
|
|
@item handle_exception
|
|
@kindex handle_exception
|
|
@cindex remote serial stub, main routine
|
|
This is the central workhorse, but your program never calls it
|
|
explicitly---the setup code arranges for @code{handle_exception} to
|
|
run when a trap is triggered.
|
|
|
|
@code{handle_exception} takes control when your program stops during
|
|
execution (for example, on a breakpoint), and mediates communications
|
|
with @value{GDBN} on the host machine. This is where the communications
|
|
protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
|
|
representative on the target machine. It begins by sending summary
|
|
information on the state of your program, then continues to execute,
|
|
retrieving and transmitting any information @value{GDBN} needs, until you
|
|
execute a @value{GDBN} command that makes your program resume; at that point,
|
|
@code{handle_exception} returns control to your own code on the target
|
|
machine.
|
|
|
|
@item breakpoint
|
|
@cindex @code{breakpoint} subroutine, remote
|
|
Use this auxiliary subroutine to make your program contain a
|
|
breakpoint. Depending on the particular situation, this may be the only
|
|
way for @value{GDBN} to get control. For instance, if your target
|
|
machine has some sort of interrupt button, you won't need to call this;
|
|
pressing the interrupt button transfers control to
|
|
@code{handle_exception}---in effect, to @value{GDBN}. On some machines,
|
|
simply receiving characters on the serial port may also trigger a trap;
|
|
again, in that situation, you don't need to call @code{breakpoint} from
|
|
your own program---simply running @samp{target remote} from the host
|
|
@value{GDBN} session gets control.
|
|
|
|
Call @code{breakpoint} if none of these is true, or if you simply want
|
|
to make certain your program stops at a predetermined point for the
|
|
start of your debugging session.
|
|
@end table
|
|
|
|
@node Bootstrapping
|
|
@subsubsection What you must do for the stub
|
|
|
|
@cindex remote stub, support routines
|
|
The debugging stubs that come with @value{GDBN} are set up for a particular
|
|
chip architecture, but they have no information about the rest of your
|
|
debugging target machine.
|
|
|
|
First of all you need to tell the stub how to communicate with the
|
|
serial port.
|
|
|
|
@table @code
|
|
@item int getDebugChar()
|
|
@kindex getDebugChar
|
|
Write this subroutine to read a single character from the serial port.
|
|
It may be identical to @code{getchar} for your target system; a
|
|
different name is used to allow you to distinguish the two if you wish.
|
|
|
|
@item void putDebugChar(int)
|
|
@kindex putDebugChar
|
|
Write this subroutine to write a single character to the serial port.
|
|
It may be identical to @code{putchar} for your target system; a
|
|
different name is used to allow you to distinguish the two if you wish.
|
|
@end table
|
|
|
|
@cindex control C, and remote debugging
|
|
@cindex interrupting remote targets
|
|
If you want @value{GDBN} to be able to stop your program while it is
|
|
running, you need to use an interrupt-driven serial driver, and arrange
|
|
for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
|
|
character). That is the character which @value{GDBN} uses to tell the
|
|
remote system to stop.
|
|
|
|
Getting the debugging target to return the proper status to @value{GDBN}
|
|
probably requires changes to the standard stub; one quick and dirty way
|
|
is to just execute a breakpoint instruction (the ``dirty'' part is that
|
|
@value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
|
|
|
|
Other routines you need to supply are:
|
|
|
|
@table @code
|
|
@item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
|
|
@kindex exceptionHandler
|
|
Write this function to install @var{exception_address} in the exception
|
|
handling tables. You need to do this because the stub does not have any
|
|
way of knowing what the exception handling tables on your target system
|
|
are like (for example, the processor's table might be in @sc{rom},
|
|
containing entries which point to a table in @sc{ram}).
|
|
@var{exception_number} is the exception number which should be changed;
|
|
its meaning is architecture-dependent (for example, different numbers
|
|
might represent divide by zero, misaligned access, etc). When this
|
|
exception occurs, control should be transferred directly to
|
|
@var{exception_address}, and the processor state (stack, registers,
|
|
and so on) should be just as it is when a processor exception occurs. So if
|
|
you want to use a jump instruction to reach @var{exception_address}, it
|
|
should be a simple jump, not a jump to subroutine.
|
|
|
|
For the 386, @var{exception_address} should be installed as an interrupt
|
|
gate so that interrupts are masked while the handler runs. The gate
|
|
should be at privilege level 0 (the most privileged level). The
|
|
@sc{sparc} and 68k stubs are able to mask interrupts themselves without
|
|
help from @code{exceptionHandler}.
|
|
|
|
@item void flush_i_cache()
|
|
@kindex flush_i_cache
|
|
On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
|
|
instruction cache, if any, on your target machine. If there is no
|
|
instruction cache, this subroutine may be a no-op.
|
|
|
|
On target machines that have instruction caches, @value{GDBN} requires this
|
|
function to make certain that the state of your program is stable.
|
|
@end table
|
|
|
|
@noindent
|
|
You must also make sure this library routine is available:
|
|
|
|
@table @code
|
|
@item void *memset(void *, int, int)
|
|
@kindex memset
|
|
This is the standard library function @code{memset} that sets an area of
|
|
memory to a known value. If you have one of the free versions of
|
|
@code{libc.a}, @code{memset} can be found there; otherwise, you must
|
|
either obtain it from your hardware manufacturer, or write your own.
|
|
@end table
|
|
|
|
If you do not use the GNU C compiler, you may need other standard
|
|
library subroutines as well; this varies from one stub to another,
|
|
but in general the stubs are likely to use any of the common library
|
|
subroutines which @code{@value{GCC}} generates as inline code.
|
|
|
|
|
|
@node Debug Session
|
|
@subsubsection Putting it all together
|
|
|
|
@cindex remote serial debugging summary
|
|
In summary, when your program is ready to debug, you must follow these
|
|
steps.
|
|
|
|
@enumerate
|
|
@item
|
|
Make sure you have defined the supporting low-level routines
|
|
(@pxref{Bootstrapping,,What you must do for the stub}):
|
|
@display
|
|
@code{getDebugChar}, @code{putDebugChar},
|
|
@code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
|
|
@end display
|
|
|
|
@item
|
|
Insert these lines near the top of your program:
|
|
|
|
@example
|
|
set_debug_traps();
|
|
breakpoint();
|
|
@end example
|
|
|
|
@item
|
|
For the 680x0 stub only, you need to provide a variable called
|
|
@code{exceptionHook}. Normally you just use:
|
|
|
|
@example
|
|
void (*exceptionHook)() = 0;
|
|
@end example
|
|
|
|
@noindent
|
|
but if before calling @code{set_debug_traps}, you set it to point to a
|
|
function in your program, that function is called when
|
|
@code{@value{GDBN}} continues after stopping on a trap (for example, bus
|
|
error). The function indicated by @code{exceptionHook} is called with
|
|
one parameter: an @code{int} which is the exception number.
|
|
|
|
@item
|
|
Compile and link together: your program, the @value{GDBN} debugging stub for
|
|
your target architecture, and the supporting subroutines.
|
|
|
|
@item
|
|
Make sure you have a serial connection between your target machine and
|
|
the @value{GDBN} host, and identify the serial port on the host.
|
|
|
|
@item
|
|
@c The "remote" target now provides a `load' command, so we should
|
|
@c document that. FIXME.
|
|
Download your program to your target machine (or get it there by
|
|
whatever means the manufacturer provides), and start it.
|
|
|
|
@item
|
|
To start remote debugging, run @value{GDBN} on the host machine, and specify
|
|
as an executable file the program that is running in the remote machine.
|
|
This tells @value{GDBN} how to find your program's symbols and the contents
|
|
of its pure text.
|
|
|
|
@item
|
|
@cindex serial line, @code{target remote}
|
|
Establish communication using the @code{target remote} command.
|
|
Its argument specifies how to communicate with the target
|
|
machine---either via a devicename attached to a direct serial line, or a
|
|
TCP port (usually to a terminal server which in turn has a serial line
|
|
to the target). For example, to use a serial line connected to the
|
|
device named @file{/dev/ttyb}:
|
|
|
|
@example
|
|
target remote /dev/ttyb
|
|
@end example
|
|
|
|
@cindex TCP port, @code{target remote}
|
|
To use a TCP connection, use an argument of the form
|
|
@code{@var{host}:port}. For example, to connect to port 2828 on a
|
|
terminal server named @code{manyfarms}:
|
|
|
|
@example
|
|
target remote manyfarms:2828
|
|
@end example
|
|
|
|
If your remote target is actually running on the same machine as
|
|
your debugger session (e.g.@: a simulator of your target running on
|
|
the same host), you can omit the hostname. For example, to connect
|
|
to port 1234 on your local machine:
|
|
|
|
@example
|
|
target remote :1234
|
|
@end example
|
|
@noindent
|
|
|
|
Note that the colon is still required here.
|
|
@end enumerate
|
|
|
|
Now you can use all the usual commands to examine and change data and to
|
|
step and continue the remote program.
|
|
|
|
To resume the remote program and stop debugging it, use the @code{detach}
|
|
command.
|
|
|
|
@cindex interrupting remote programs
|
|
@cindex remote programs, interrupting
|
|
Whenever @value{GDBN} is waiting for the remote program, if you type the
|
|
interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
|
|
program. This may or may not succeed, depending in part on the hardware
|
|
and the serial drivers the remote system uses. If you type the
|
|
interrupt character once again, @value{GDBN} displays this prompt:
|
|
|
|
@example
|
|
Interrupted while waiting for the program.
|
|
Give up (and stop debugging it)? (y or n)
|
|
@end example
|
|
|
|
If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
|
|
(If you decide you want to try again later, you can use @samp{target
|
|
remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
|
|
goes back to waiting.
|
|
|
|
@node Protocol
|
|
@subsubsection Communication protocol
|
|
|
|
@cindex debugging stub, example
|
|
@cindex remote stub, example
|
|
@cindex stub example, remote debugging
|
|
The stub files provided with @value{GDBN} implement the target side of the
|
|
communication protocol, and the @value{GDBN} side is implemented in the
|
|
@value{GDBN} source file @file{remote.c}. Normally, you can simply allow
|
|
these subroutines to communicate, and ignore the details. (If you're
|
|
implementing your own stub file, you can still ignore the details: start
|
|
with one of the existing stub files. @file{sparc-stub.c} is the best
|
|
organized, and therefore the easiest to read.)
|
|
|
|
However, there may be occasions when you need to know something about
|
|
the protocol---for example, if there is only one serial port to your
|
|
target machine, you might want your program to do something special if
|
|
it recognizes a packet meant for @value{GDBN}.
|
|
|
|
In the examples below, @samp{<-} and @samp{->} are used to indicate
|
|
transmitted and received data respectfully.
|
|
|
|
@cindex protocol, @value{GDBN} remote serial
|
|
@cindex serial protocol, @value{GDBN} remote
|
|
@cindex remote serial protocol
|
|
All @value{GDBN} commands and responses (other than acknowledgments) are
|
|
sent as a @var{packet}. A @var{packet} is introduced with the character
|
|
@samp{$}, the actual @var{packet-data}, and the terminating character
|
|
@samp{#} followed by a two-digit @var{checksum}:
|
|
|
|
@example
|
|
@code{$}@var{packet-data}@code{#}@var{checksum}
|
|
@end example
|
|
@noindent
|
|
|
|
@cindex checksum, for @value{GDBN} remote
|
|
@noindent
|
|
The two-digit @var{checksum} is computed as the modulo 256 sum of all
|
|
characters between the leading @samp{$} and the trailing @samp{#} (an
|
|
eight bit unsigned checksum).
|
|
|
|
Implementors should note that prior to @value{GDBN} 5.0 the protocol
|
|
specification also included an optional two-digit @var{sequence-id}:
|
|
|
|
@example
|
|
@code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
|
|
@end example
|
|
|
|
@cindex sequence-id, for @value{GDBN} remote
|
|
@noindent
|
|
That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
|
|
has never output @var{sequence-id}s. Stubs that handle packets added
|
|
since @value{GDBN} 5.0 must not accept @var{sequence-id}.
|
|
|
|
@cindex acknowledgment, for @value{GDBN} remote
|
|
When either the host or the target machine receives a packet, the first
|
|
response expected is an acknowledgment: either @samp{+} (to indicate
|
|
the package was received correctly) or @samp{-} (to request
|
|
retransmission):
|
|
|
|
@example
|
|
<- @code{$}@var{packet-data}@code{#}@var{checksum}
|
|
-> @code{+}
|
|
@end example
|
|
@noindent
|
|
|
|
The host (@value{GDBN}) sends @var{command}s, and the target (the
|
|
debugging stub incorporated in your program) sends a @var{response}. In
|
|
the case of step and continue @var{command}s, the response is only sent
|
|
when the operation has completed (the target has again stopped).
|
|
|
|
@var{packet-data} consists of a sequence of characters with the
|
|
exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
|
|
exceptions).
|
|
|
|
Fields within the packet should be separated using @samp{,} @samp{;} or
|
|
@samp{:}. Except where otherwise noted all numbers are represented in
|
|
HEX with leading zeros suppressed.
|
|
|
|
Implementors should note that prior to @value{GDBN} 5.0, the character
|
|
@samp{:} could not appear as the third character in a packet (as it
|
|
would potentially conflict with the @var{sequence-id}).
|
|
|
|
Response @var{data} can be run-length encoded to save space. A @samp{*}
|
|
means that the next character is an @sc{ascii} encoding giving a repeat count
|
|
which stands for that many repetitions of the character preceding the
|
|
@samp{*}. The encoding is @code{n+29}, yielding a printable character
|
|
where @code{n >=3} (which is where rle starts to win). The printable
|
|
characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
|
|
value greater than 126 should not be used.
|
|
|
|
Some remote systems have used a different run-length encoding mechanism
|
|
loosely refered to as the cisco encoding. Following the @samp{*}
|
|
character are two hex digits that indicate the size of the packet.
|
|
|
|
So:
|
|
@example
|
|
"@code{0* }"
|
|
@end example
|
|
@noindent
|
|
means the same as "0000".
|
|
|
|
The error response returned for some packets includes a two character
|
|
error number. That number is not well defined.
|
|
|
|
For any @var{command} not supported by the stub, an empty response
|
|
(@samp{$#00}) should be returned. That way it is possible to extend the
|
|
protocol. A newer @value{GDBN} can tell if a packet is supported based
|
|
on that response.
|
|
|
|
A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
|
|
@samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
|
|
optional.
|
|
|
|
Below is a complete list of all currently defined @var{command}s and
|
|
their corresponding response @var{data}:
|
|
@page
|
|
@multitable @columnfractions .30 .30 .40
|
|
@item Packet
|
|
@tab Request
|
|
@tab Description
|
|
|
|
@item extended mode
|
|
@tab @code{!}
|
|
@tab
|
|
Enable extended mode. In extended mode, the remote server is made
|
|
persistent. The @samp{R} packet is used to restart the program being
|
|
debugged.
|
|
@item
|
|
@tab reply @samp{OK}
|
|
@tab
|
|
The remote target both supports and has enabled extended mode.
|
|
|
|
@item last signal
|
|
@tab @code{?}
|
|
@tab
|
|
Indicate the reason the target halted. The reply is the same as for step
|
|
and continue.
|
|
@item
|
|
@tab reply
|
|
@tab see below
|
|
|
|
|
|
@item reserved
|
|
@tab @code{a}
|
|
@tab Reserved for future use
|
|
|
|
@item set program arguments @strong{(reserved)}
|
|
@tab @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,...}
|
|
@tab
|
|
@item
|
|
@tab
|
|
@tab
|
|
Initialized @samp{argv[]} array passed into program. @var{arglen}
|
|
specifies the number of bytes in the hex encoded byte stream @var{arg}.
|
|
See @file{gdbserver} for more details.
|
|
@item
|
|
@tab reply @code{OK}
|
|
@item
|
|
@tab reply @code{E}@var{NN}
|
|
|
|
@item set baud @strong{(deprecated)}
|
|
@tab @code{b}@var{baud}
|
|
@tab
|
|
Change the serial line speed to @var{baud}. JTC: @emph{When does the
|
|
transport layer state change? When it's received, or after the ACK is
|
|
transmitted. In either case, there are problems if the command or the
|
|
acknowledgment packet is dropped.} Stan: @emph{If people really wanted
|
|
to add something like this, and get it working for the first time, they
|
|
ought to modify ser-unix.c to send some kind of out-of-band message to a
|
|
specially-setup stub and have the switch happen "in between" packets, so
|
|
that from remote protocol's point of view, nothing actually
|
|
happened.}
|
|
|
|
@item set breakpoint @strong{(deprecated)}
|
|
@tab @code{B}@var{addr},@var{mode}
|
|
@tab
|
|
Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
|
|
breakpoint at @var{addr}. @emph{This has been replaced by the @samp{Z} and
|
|
@samp{z} packets.}
|
|
|
|
@item continue
|
|
@tab @code{c}@var{addr}
|
|
@tab
|
|
@var{addr} is address to resume. If @var{addr} is omitted, resume at
|
|
current address.
|
|
@item
|
|
@tab reply
|
|
@tab see below
|
|
|
|
@item continue with signal
|
|
@tab @code{C}@var{sig}@code{;}@var{addr}
|
|
@tab
|
|
Continue with signal @var{sig} (hex signal number). If
|
|
@code{;}@var{addr} is omitted, resume at same address.
|
|
@item
|
|
@tab reply
|
|
@tab see below
|
|
|
|
@item toggle debug @strong{(deprecated)}
|
|
@tab @code{d}
|
|
@tab
|
|
toggle debug flag.
|
|
|
|
@item detach
|
|
@tab @code{D}
|
|
@tab
|
|
Detach @value{GDBN} from the remote system. Sent to the remote target before
|
|
@value{GDBN} disconnects.
|
|
@item
|
|
@tab reply @emph{no response}
|
|
@tab
|
|
@value{GDBN} does not check for any response after sending this packet.
|
|
|
|
@item reserved
|
|
@tab @code{e}
|
|
@tab Reserved for future use
|
|
|
|
@item reserved
|
|
@tab @code{E}
|
|
@tab Reserved for future use
|
|
|
|
@item reserved
|
|
@tab @code{f}
|
|
@tab Reserved for future use
|
|
|
|
@item reserved
|
|
@tab @code{F}
|
|
@tab Reserved for future use
|
|
|
|
@item read registers
|
|
@tab @code{g}
|
|
@tab Read general registers.
|
|
@item
|
|
@tab reply @var{XX...}
|
|
@tab
|
|
Each byte of register data is described by two hex digits. The bytes
|
|
with the register are transmitted in target byte order. The size of
|
|
each register and their position within the @samp{g} @var{packet} are
|
|
determined by the @value{GDBN} internal macros @var{REGISTER_RAW_SIZE} and
|
|
@var{REGISTER_NAME} macros. The specification of several standard
|
|
@code{g} packets is specified below.
|
|
@item
|
|
@tab @code{E}@var{NN}
|
|
@tab for an error.
|
|
|
|
@item write regs
|
|
@tab @code{G}@var{XX...}
|
|
@tab
|
|
See @samp{g} for a description of the @var{XX...} data.
|
|
@item
|
|
@tab reply @code{OK}
|
|
@tab for success
|
|
@item
|
|
@tab reply @code{E}@var{NN}
|
|
@tab for an error
|
|
|
|
@item reserved
|
|
@tab @code{h}
|
|
@tab Reserved for future use
|
|
|
|
@item set thread
|
|
@tab @code{H}@var{c}@var{t...}
|
|
@tab
|
|
Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
|
|
@samp{G}, et.al.). @var{c} = @samp{c} for thread used in step and
|
|
continue; @var{t...} can be -1 for all threads. @var{c} = @samp{g} for
|
|
thread used in other operations. If zero, pick a thread, any thread.
|
|
@item
|
|
@tab reply @code{OK}
|
|
@tab for success
|
|
@item
|
|
@tab reply @code{E}@var{NN}
|
|
@tab for an error
|
|
|
|
@c FIXME: JTC:
|
|
@c 'H': How restrictive (or permissive) is the thread model. If a
|
|
@c thread is selected and stopped, are other threads allowed
|
|
@c to continue to execute? As I mentioned above, I think the
|
|
@c semantics of each command when a thread is selected must be
|
|
@c described. For example:
|
|
@c
|
|
@c 'g': If the stub supports threads and a specific thread is
|
|
@c selected, returns the register block from that thread;
|
|
@c otherwise returns current registers.
|
|
@c
|
|
@c 'G' If the stub supports threads and a specific thread is
|
|
@c selected, sets the registers of the register block of
|
|
@c that thread; otherwise sets current registers.
|
|
|
|
@item cycle step @strong{(draft)}
|
|
@tab @code{i}@var{addr}@code{,}@var{nnn}
|
|
@tab
|
|
Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
|
|
present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
|
|
step starting at that address.
|
|
|
|
@item signal then cycle step @strong{(reserved)}
|
|
@tab @code{I}
|
|
@tab
|
|
See @samp{i} and @samp{S} for likely syntax and semantics.
|
|
|
|
@item reserved
|
|
@tab @code{j}
|
|
@tab Reserved for future use
|
|
|
|
@item reserved
|
|
@tab @code{J}
|
|
@tab Reserved for future use
|
|
|
|
@item kill request
|
|
@tab @code{k}
|
|
@tab
|
|
FIXME: @emph{There is no description of how operate when a specific
|
|
thread context has been selected (ie. does 'k' kill only that thread?)}.
|
|
|
|
@item reserved
|
|
@tab @code{l}
|
|
@tab Reserved for future use
|
|
|
|
@item reserved
|
|
@tab @code{L}
|
|
@tab Reserved for future use
|
|
|
|
@item read memory
|
|
@tab @code{m}@var{addr}@code{,}@var{length}
|
|
@tab
|
|
Read @var{length} bytes of memory starting at address @var{addr}.
|
|
Neither @value{GDBN} nor the stub assume that sized memory transfers are assumed
|
|
using word alligned accesses. FIXME: @emph{A word aligned memory
|
|
transfer mechanism is needed.}
|
|
@item
|
|
@tab reply @var{XX...}
|
|
@tab
|
|
@var{XX...} is mem contents. Can be fewer bytes than requested if able
|
|
to read only part of the data. Neither @value{GDBN} nor the stub assume that
|
|
sized memory transfers are assumed using word alligned accesses. FIXME:
|
|
@emph{A word aligned memory transfer mechanism is needed.}
|
|
@item
|
|
@tab reply @code{E}@var{NN}
|
|
@tab @var{NN} is errno
|
|
|
|
@item write mem
|
|
@tab @code{M}@var{addr},@var{length}@code{:}@var{XX...}
|
|
@tab
|
|
Write @var{length} bytes of memory starting at address @var{addr}.
|
|
@var{XX...} is the data.
|
|
@item
|
|
@tab reply @code{OK}
|
|
@tab for success
|
|
@item
|
|
@tab reply @code{E}@var{NN}
|
|
@tab
|
|
for an error (this includes the case where only part of the data was
|
|
written).
|
|
|
|
@item reserved
|
|
@tab @code{n}
|
|
@tab Reserved for future use
|
|
|
|
@item reserved
|
|
@tab @code{N}
|
|
@tab Reserved for future use
|
|
|
|
@item reserved
|
|
@tab @code{o}
|
|
@tab Reserved for future use
|
|
|
|
@item reserved
|
|
@tab @code{O}
|
|
@tab Reserved for future use
|
|
|
|
@item read reg @strong{(reserved)}
|
|
@tab @code{p}@var{n...}
|
|
@tab
|
|
See write register.
|
|
@item
|
|
@tab return @var{r....}
|
|
@tab The hex encoded value of the register in target byte order.
|
|
|
|
@item write reg
|
|
@tab @code{P}@var{n...}@code{=}@var{r...}
|
|
@tab
|
|
Write register @var{n...} with value @var{r...}, which contains two hex
|
|
digits for each byte in the register (target byte order).
|
|
@item
|
|
@tab reply @code{OK}
|
|
@tab for success
|
|
@item
|
|
@tab reply @code{E}@var{NN}
|
|
@tab for an error
|
|
|
|
@item general query
|
|
@tab @code{q}@var{query}
|
|
@tab
|
|
Request info about @var{query}. In general @value{GDBN} queries
|
|
have a leading upper case letter. Custom vendor queries should use a
|
|
company prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may
|
|
optionally be followed by a @samp{,} or @samp{;} separated list. Stubs
|
|
must ensure that they match the full @var{query} name.
|
|
@item
|
|
@tab reply @code{XX...}
|
|
@tab Hex encoded data from query. The reply can not be empty.
|
|
@item
|
|
@tab reply @code{E}@var{NN}
|
|
@tab error reply
|
|
@item
|
|
@tab reply @samp{}
|
|
@tab Indicating an unrecognized @var{query}.
|
|
|
|
@item general set
|
|
@tab @code{Q}@var{var}@code{=}@var{val}
|
|
@tab
|
|
Set value of @var{var} to @var{val}. See @samp{q} for a discussing of
|
|
naming conventions.
|
|
|
|
@item reset @strong{(deprecated)}
|
|
@tab @code{r}
|
|
@tab
|
|
Reset the entire system.
|
|
|
|
@item remote restart
|
|
@tab @code{R}@var{XX}
|
|
@tab
|
|
Restart the program being debugged. @var{XX}, while needed, is ignored.
|
|
This packet is only available in extended mode.
|
|
@item
|
|
@tab
|
|
no reply
|
|
@tab
|
|
The @samp{R} packet has no reply.
|
|
|
|
@item step
|
|
@tab @code{s}@var{addr}
|
|
@tab
|
|
@var{addr} is address to resume. If @var{addr} is omitted, resume at
|
|
same address.
|
|
@item
|
|
@tab reply
|
|
@tab see below
|
|
|
|
@item step with signal
|
|
@tab @code{S}@var{sig}@code{;}@var{addr}
|
|
@tab
|
|
Like @samp{C} but step not continue.
|
|
@item
|
|
@tab reply
|
|
@tab see below
|
|
|
|
@item search
|
|
@tab @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM}
|
|
@tab
|
|
Search backwards starting at address @var{addr} for a match with pattern
|
|
@var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4
|
|
bytes. @var{addr} must be at least 3 digits.
|
|
|
|
@item thread alive
|
|
@tab @code{T}@var{XX}
|
|
@tab Find out if the thread XX is alive.
|
|
@item
|
|
@tab reply @code{OK}
|
|
@tab thread is still alive
|
|
@item
|
|
@tab reply @code{E}@var{NN}
|
|
@tab thread is dead
|
|
|
|
@item reserved
|
|
@tab @code{u}
|
|
@tab Reserved for future use
|
|
|
|
@item reserved
|
|
@tab @code{U}
|
|
@tab Reserved for future use
|
|
|
|
@item reserved
|
|
@tab @code{v}
|
|
@tab Reserved for future use
|
|
|
|
@item reserved
|
|
@tab @code{V}
|
|
@tab Reserved for future use
|
|
|
|
@item reserved
|
|
@tab @code{w}
|
|
@tab Reserved for future use
|
|
|
|
@item reserved
|
|
@tab @code{W}
|
|
@tab Reserved for future use
|
|
|
|
@item reserved
|
|
@tab @code{x}
|
|
@tab Reserved for future use
|
|
|
|
@item write mem (binary)
|
|
@tab @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX...}
|
|
@tab
|
|
@var{addr} is address, @var{length} is number of bytes, @var{XX...} is
|
|
binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
|
|
escaped using @code{0x7d}.
|
|
@item
|
|
@tab reply @code{OK}
|
|
@tab for success
|
|
@item
|
|
@tab reply @code{E}@var{NN}
|
|
@tab for an error
|
|
|
|
@item reserved
|
|
@tab @code{y}
|
|
@tab Reserved for future use
|
|
|
|
@item reserved
|
|
@tab @code{Y}
|
|
@tab Reserved for future use
|
|
|
|
@item remove break or watchpoint @strong{(draft)}
|
|
@tab @code{z}@var{t}@code{,}@var{addr}@code{,}@var{length}
|
|
@tab
|
|
See @samp{Z}.
|
|
|
|
@item insert break or watchpoint @strong{(draft)}
|
|
@tab @code{Z}@var{t}@code{,}@var{addr}@code{,}@var{length}
|
|
@tab
|
|
@var{t} is type: @samp{0} - software breakpoint, @samp{1} - hardware
|
|
breakpoint, @samp{2} - write watchpoint, @samp{3} - read watchpoint,
|
|
@samp{4} - access watchpoint; @var{addr} is address; @var{length} is in
|
|
bytes. For a software breakpoint, @var{length} specifies the size of
|
|
the instruction to be patched. For hardware breakpoints and watchpoints
|
|
@var{length} specifies the memory region to be monitored. To avoid
|
|
potential problems with duplicate packets, the operations should be
|
|
implemented in an idempotent way.
|
|
@item
|
|
@tab reply @code{E}@var{NN}
|
|
@tab for an error
|
|
@item
|
|
@tab reply @code{OK}
|
|
@tab for success
|
|
@item
|
|
@tab @samp{}
|
|
@tab If not supported.
|
|
|
|
@item reserved
|
|
@tab <other>
|
|
@tab Reserved for future use
|
|
|
|
@end multitable
|
|
|
|
The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
|
|
receive any of the below as a reply. In the case of the @samp{C},
|
|
@samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
|
|
when the target halts. In the below the exact meaning of @samp{signal
|
|
number} is poorly defined. In general one of the UNIX signal numbering
|
|
conventions is used.
|
|
|
|
@multitable @columnfractions .4 .6
|
|
|
|
@item @code{S}@var{AA}
|
|
@tab @var{AA} is the signal number
|
|
|
|
@item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
|
|
@tab
|
|
@var{AA} = two hex digit signal number; @var{n...} = register number
|
|
(hex), @var{r...} = target byte ordered register contents, size defined
|
|
by @code{REGISTER_RAW_SIZE}; @var{n...} = @samp{thread}, @var{r...} =
|
|
thread process ID, this is a hex integer; @var{n...} = other string not
|
|
starting with valid hex digit. @value{GDBN} should ignore this
|
|
@var{n...}, @var{r...} pair and go on to the next. This way we can
|
|
extend the protocol.
|
|
|
|
@item @code{W}@var{AA}
|
|
@tab
|
|
The process exited, and @var{AA} is the exit status. This is only
|
|
applicable for certains sorts of targets.
|
|
|
|
@item @code{X}@var{AA}
|
|
@tab
|
|
The process terminated with signal @var{AA}.
|
|
|
|
@item @code{N}@var{AA}@code{;}@var{t...}@code{;}@var{d...}@code{;}@var{b...} @strong{(obsolete)}
|
|
@tab
|
|
@var{AA} = signal number; @var{t...} = address of symbol "_start";
|
|
@var{d...} = base of data section; @var{b...} = base of bss section.
|
|
@emph{Note: only used by Cisco Systems targets. The difference between
|
|
this reply and the "qOffsets" query is that the 'N' packet may arrive
|
|
spontaneously whereas the 'qOffsets' is a query initiated by the host
|
|
debugger.}
|
|
|
|
@item @code{O}@var{XX...}
|
|
@tab
|
|
@var{XX...} is hex encoding of @sc{ascii} data. This can happen at any time
|
|
while the program is running and the debugger should continue to wait
|
|
for 'W', 'T', etc.
|
|
|
|
@end multitable
|
|
|
|
The following set and query packets have already been defined.
|
|
|
|
@multitable @columnfractions .2 .2 .6
|
|
|
|
@item current thread
|
|
@tab @code{q}@code{C}
|
|
@tab Return the current thread id.
|
|
@item
|
|
@tab reply @code{QC}@var{pid}
|
|
@tab
|
|
Where @var{pid} is a HEX encoded 16 bit process id.
|
|
@item
|
|
@tab reply *
|
|
@tab Any other reply implies the old pid.
|
|
|
|
@item all thread ids
|
|
@tab @code{q}@code{fThreadInfo}
|
|
@item
|
|
@tab @code{q}@code{sThreadInfo}
|
|
@tab
|
|
Obtain a list of active thread ids from the target (OS). Since there
|
|
may be too many active threads to fit into one reply packet, this query
|
|
works iteratively: it may require more than one query/reply sequence to
|
|
obtain the entire list of threads. The first query of the sequence will
|
|
be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
|
|
sequence will be the @code{qs}@code{ThreadInfo} query.
|
|
@item
|
|
@tab
|
|
@tab NOTE: replaces the @code{qL} query (see below).
|
|
@item
|
|
@tab reply @code{m}@var{<id>}
|
|
@tab A single thread id
|
|
@item
|
|
@tab reply @code{m}@var{<id>},@var{<id>...}
|
|
@tab a comma-separated list of thread ids
|
|
@item
|
|
@tab reply @code{l}
|
|
@tab (lower case 'el') denotes end of list.
|
|
@item
|
|
@tab
|
|
@tab
|
|
In response to each query, the target will reply with a list of one
|
|
or more thread ids, in big-endian hex, separated by commas. GDB will
|
|
respond to each reply with a request for more thread ids (using the
|
|
@code{qs} form of the query), until the target responds with @code{l}
|
|
(lower-case el, for @code{'last'}).
|
|
|
|
@item extra thread info
|
|
@tab @code{q}@code{ThreadExtraInfo}@code{,}@var{id}
|
|
@tab
|
|
@item
|
|
@tab
|
|
@tab
|
|
Where @var{<id>} is a thread-id in big-endian hex.
|
|
Obtain a printable string description of a thread's attributes from
|
|
the target OS. This string may contain anything that the target OS
|
|
thinks is interesting for @value{GDBN} to tell the user about the thread.
|
|
The string is displayed in @value{GDBN}'s @samp{info threads} display.
|
|
Some examples of possible thread extra info strings are "Runnable", or
|
|
"Blocked on Mutex".
|
|
@item
|
|
@tab reply @var{XX...}
|
|
@tab
|
|
Where @var{XX...} is a hex encoding of @sc{ascii} data, comprising the
|
|
printable string containing the extra information about the thread's
|
|
attributes.
|
|
|
|
@item query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
|
|
@tab @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread}
|
|
@tab
|
|
@item
|
|
@tab
|
|
@tab
|
|
Obtain thread information from RTOS. Where: @var{startflag} (one hex
|
|
digit) is one to indicate the first query and zero to indicate a
|
|
subsequent query; @var{threadcount} (two hex digits) is the maximum
|
|
number of threads the response packet can contain; and @var{nextthread}
|
|
(eight hex digits), for subsequent queries (@var{startflag} is zero), is
|
|
returned in the response as @var{argthread}.
|
|
@item
|
|
@tab
|
|
@tab NOTE: this query is replaced by the @code{q}@code{fThreadInfo}
|
|
query (see above).
|
|
@item
|
|
@tab reply @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread...}
|
|
@tab
|
|
@item
|
|
@tab
|
|
@tab
|
|
Where: @var{count} (two hex digits) is the number of threads being
|
|
returned; @var{done} (one hex digit) is zero to indicate more threads
|
|
and one indicates no further threads; @var{argthreadid} (eight hex
|
|
digits) is @var{nextthread} from the request packet; @var{thread...} is
|
|
a sequence of thread IDs from the target. @var{threadid} (eight hex
|
|
digits). See @code{remote.c:parse_threadlist_response()}.
|
|
|
|
@item compute CRC of memory block
|
|
@tab @code{q}@code{CRC:}@var{addr}@code{,}@var{length}
|
|
@tab
|
|
@item
|
|
@tab reply @code{E}@var{NN}
|
|
@tab An error (such as memory fault)
|
|
@item
|
|
@tab reply @code{C}@var{CRC32}
|
|
@tab A 32 bit cyclic redundancy check of the specified memory region.
|
|
|
|
@item query sect offs
|
|
@tab @code{q}@code{Offsets}
|
|
@tab
|
|
Get section offsets that the target used when re-locating the downloaded
|
|
image. @emph{Note: while a @code{Bss} offset is included in the
|
|
response, @value{GDBN} ignores this and instead applies the @code{Data}
|
|
offset to the @code{Bss} section.}
|
|
@item
|
|
@tab reply @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
|
|
|
|
@item thread info request
|
|
@tab @code{q}@code{P}@var{mode}@var{threadid}
|
|
@tab
|
|
@item
|
|
@tab
|
|
@tab
|
|
Returns information on @var{threadid}. Where: @var{mode} is a hex
|
|
encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
|
|
@item
|
|
@tab reply *
|
|
@tab
|
|
See @code{remote.c:remote_unpack_thread_info_response()}.
|
|
|
|
@item remote command
|
|
@tab @code{q}@code{Rcmd,}@var{COMMAND}
|
|
@tab
|
|
@item
|
|
@tab
|
|
@tab
|
|
@var{COMMAND} (hex encoded) is passed to the local interpreter for
|
|
execution. Invalid commands should be reported using the output string.
|
|
Before the final result packet, the target may also respond with a
|
|
number of intermediate @code{O}@var{OUTPUT} console output
|
|
packets. @emph{Implementors should note that providing access to a
|
|
stubs's interpreter may have security implications}.
|
|
@item
|
|
@tab reply @code{OK}
|
|
@tab
|
|
A command response with no output.
|
|
@item
|
|
@tab reply @var{OUTPUT}
|
|
@tab
|
|
A command response with the hex encoded output string @var{OUTPUT}.
|
|
@item
|
|
@tab reply @code{E}@var{NN}
|
|
@tab
|
|
Indicate a badly formed request.
|
|
|
|
@item
|
|
@tab reply @samp{}
|
|
@tab
|
|
When @samp{q}@samp{Rcmd} is not recognized.
|
|
|
|
@item symbol lookup
|
|
@tab @code{qSymbol::}
|
|
@tab
|
|
Notify the target that @value{GDBN} is prepared to serve symbol lookup
|
|
requests. Accept requests from the target for the values of symbols.
|
|
@item
|
|
@tab
|
|
@tab
|
|
@item
|
|
@tab reply @code{OK}
|
|
@tab
|
|
The target does not need to look up any (more) symbols.
|
|
@item
|
|
@tab reply @code{qSymbol:}@var{sym_name}
|
|
@tab
|
|
The target requests the value of symbol @var{sym_name} (hex encoded).
|
|
@value{GDBN} may provide the value by using the
|
|
@code{qSymbol:}@var{sym_value}:@var{sym_name}
|
|
message, described below.
|
|
|
|
@item symbol value
|
|
@tab @code{qSymbol:}@var{sym_value}:@var{sym_name}
|
|
@tab
|
|
Set the value of SYM_NAME to SYM_VALUE.
|
|
@item
|
|
@tab
|
|
@tab
|
|
@var{sym_name} (hex encoded) is the name of a symbol whose value
|
|
the target has previously requested.
|
|
@item
|
|
@tab
|
|
@tab
|
|
@var{sym_value} (hex) is the value for symbol @var{sym_name}.
|
|
If @value{GDBN} cannot supply a value for @var{sym_name}, then this
|
|
field will be empty.
|
|
@item
|
|
@tab reply @code{OK}
|
|
@tab
|
|
The target does not need to look up any (more) symbols.
|
|
@item
|
|
@tab reply @code{qSymbol:}@var{sym_name}
|
|
@tab
|
|
The target requests the value of a new symbol @var{sym_name} (hex encoded).
|
|
@value{GDBN} will continue to supply the values of symbols (if available),
|
|
until the target ceases to request them.
|
|
|
|
@end multitable
|
|
|
|
The following @samp{g}/@samp{G} packets have previously been defined.
|
|
In the below, some thirty-two bit registers are transferred as sixty-four
|
|
bits. Those registers should be zero/sign extended (which?) to fill the
|
|
space allocated. Register bytes are transfered in target byte order.
|
|
The two nibbles within a register byte are transfered most-significant -
|
|
least-significant.
|
|
|
|
@multitable @columnfractions .5 .5
|
|
|
|
@item MIPS32
|
|
@tab
|
|
All registers are transfered as thirty-two bit quantities in the order:
|
|
32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
|
|
registers; fsr; fir; fp.
|
|
|
|
@item MIPS64
|
|
@tab
|
|
All registers are transfered as sixty-four bit quantities (including
|
|
thirty-two bit registers such as @code{sr}). The ordering is the same
|
|
as @code{MIPS32}.
|
|
|
|
@end multitable
|
|
|
|
Example sequence of a target being re-started. Notice how the restart
|
|
does not get any direct output:
|
|
|
|
@example
|
|
<- @code{R00}
|
|
-> @code{+}
|
|
@emph{target restarts}
|
|
<- @code{?}
|
|
-> @code{+}
|
|
-> @code{T001:1234123412341234}
|
|
<- @code{+}
|
|
@end example
|
|
|
|
Example sequence of a target being stepped by a single instruction:
|
|
|
|
@example
|
|
<- @code{G1445...}
|
|
-> @code{+}
|
|
<- @code{s}
|
|
-> @code{+}
|
|
@emph{time passes}
|
|
-> @code{T001:1234123412341234}
|
|
<- @code{+}
|
|
<- @code{g}
|
|
-> @code{+}
|
|
-> @code{1455...}
|
|
<- @code{+}
|
|
@end example
|
|
|
|
@node Server
|
|
@subsubsection Using the @code{gdbserver} program
|
|
|
|
@kindex gdbserver
|
|
@cindex remote connection without stubs
|
|
@code{gdbserver} is a control program for Unix-like systems, which
|
|
allows you to connect your program with a remote @value{GDBN} via
|
|
@code{target remote}---but without linking in the usual debugging stub.
|
|
|
|
@code{gdbserver} is not a complete replacement for the debugging stubs,
|
|
because it requires essentially the same operating-system facilities
|
|
that @value{GDBN} itself does. In fact, a system that can run
|
|
@code{gdbserver} to connect to a remote @value{GDBN} could also run
|
|
@value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
|
|
because it is a much smaller program than @value{GDBN} itself. It is
|
|
also easier to port than all of @value{GDBN}, so you may be able to get
|
|
started more quickly on a new system by using @code{gdbserver}.
|
|
Finally, if you develop code for real-time systems, you may find that
|
|
the tradeoffs involved in real-time operation make it more convenient to
|
|
do as much development work as possible on another system, for example
|
|
by cross-compiling. You can use @code{gdbserver} to make a similar
|
|
choice for debugging.
|
|
|
|
@value{GDBN} and @code{gdbserver} communicate via either a serial line
|
|
or a TCP connection, using the standard @value{GDBN} remote serial
|
|
protocol.
|
|
|
|
@table @emph
|
|
@item On the target machine,
|
|
you need to have a copy of the program you want to debug.
|
|
@code{gdbserver} does not need your program's symbol table, so you can
|
|
strip the program if necessary to save space. @value{GDBN} on the host
|
|
system does all the symbol handling.
|
|
|
|
To use the server, you must tell it how to communicate with @value{GDBN};
|
|
the name of your program; and the arguments for your program. The
|
|
syntax is:
|
|
|
|
@smallexample
|
|
target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
|
|
@end smallexample
|
|
|
|
@var{comm} is either a device name (to use a serial line) or a TCP
|
|
hostname and portnumber. For example, to debug Emacs with the argument
|
|
@samp{foo.txt} and communicate with @value{GDBN} over the serial port
|
|
@file{/dev/com1}:
|
|
|
|
@smallexample
|
|
target> gdbserver /dev/com1 emacs foo.txt
|
|
@end smallexample
|
|
|
|
@code{gdbserver} waits passively for the host @value{GDBN} to communicate
|
|
with it.
|
|
|
|
To use a TCP connection instead of a serial line:
|
|
|
|
@smallexample
|
|
target> gdbserver host:2345 emacs foo.txt
|
|
@end smallexample
|
|
|
|
The only difference from the previous example is the first argument,
|
|
specifying that you are communicating with the host @value{GDBN} via
|
|
TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
|
|
expect a TCP connection from machine @samp{host} to local TCP port 2345.
|
|
(Currently, the @samp{host} part is ignored.) You can choose any number
|
|
you want for the port number as long as it does not conflict with any
|
|
TCP ports already in use on the target system (for example, @code{23} is
|
|
reserved for @code{telnet}).@footnote{If you choose a port number that
|
|
conflicts with another service, @code{gdbserver} prints an error message
|
|
and exits.} You must use the same port number with the host @value{GDBN}
|
|
@code{target remote} command.
|
|
|
|
@item On the @value{GDBN} host machine,
|
|
you need an unstripped copy of your program, since @value{GDBN} needs
|
|
symbols and debugging information. Start up @value{GDBN} as usual,
|
|
using the name of the local copy of your program as the first argument.
|
|
(You may also need the @w{@samp{--baud}} option if the serial line is
|
|
running at anything other than 9600@dmn{bps}.) After that, use @code{target
|
|
remote} to establish communications with @code{gdbserver}. Its argument
|
|
is either a device name (usually a serial device, like
|
|
@file{/dev/ttyb}), or a TCP port descriptor in the form
|
|
@code{@var{host}:@var{PORT}}. For example:
|
|
|
|
@smallexample
|
|
(@value{GDBP}) target remote /dev/ttyb
|
|
@end smallexample
|
|
|
|
@noindent
|
|
communicates with the server via serial line @file{/dev/ttyb}, and
|
|
|
|
@smallexample
|
|
(@value{GDBP}) target remote the-target:2345
|
|
@end smallexample
|
|
|
|
@noindent
|
|
communicates via a TCP connection to port 2345 on host @w{@file{the-target}}.
|
|
For TCP connections, you must start up @code{gdbserver} prior to using
|
|
the @code{target remote} command. Otherwise you may get an error whose
|
|
text depends on the host system, but which usually looks something like
|
|
@samp{Connection refused}.
|
|
@end table
|
|
|
|
@node NetWare
|
|
@subsubsection Using the @code{gdbserve.nlm} program
|
|
|
|
@kindex gdbserve.nlm
|
|
@code{gdbserve.nlm} is a control program for NetWare systems, which
|
|
allows you to connect your program with a remote @value{GDBN} via
|
|
@code{target remote}.
|
|
|
|
@value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
|
|
using the standard @value{GDBN} remote serial protocol.
|
|
|
|
@table @emph
|
|
@item On the target machine,
|
|
you need to have a copy of the program you want to debug.
|
|
@code{gdbserve.nlm} does not need your program's symbol table, so you
|
|
can strip the program if necessary to save space. @value{GDBN} on the
|
|
host system does all the symbol handling.
|
|
|
|
To use the server, you must tell it how to communicate with
|
|
@value{GDBN}; the name of your program; and the arguments for your
|
|
program. The syntax is:
|
|
|
|
@smallexample
|
|
load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
|
|
[ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
|
|
@end smallexample
|
|
|
|
@var{board} and @var{port} specify the serial line; @var{baud} specifies
|
|
the baud rate used by the connection. @var{port} and @var{node} default
|
|
to 0, @var{baud} defaults to 9600@dmn{bps}.
|
|
|
|
For example, to debug Emacs with the argument @samp{foo.txt}and
|
|
communicate with @value{GDBN} over serial port number 2 or board 1
|
|
using a 19200@dmn{bps} connection:
|
|
|
|
@smallexample
|
|
load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
|
|
@end smallexample
|
|
|
|
@item On the @value{GDBN} host machine,
|
|
you need an unstripped copy of your program, since @value{GDBN} needs
|
|
symbols and debugging information. Start up @value{GDBN} as usual,
|
|
using the name of the local copy of your program as the first argument.
|
|
(You may also need the @w{@samp{--baud}} option if the serial line is
|
|
running at anything other than 9600@dmn{bps}. After that, use @code{target
|
|
remote} to establish communications with @code{gdbserve.nlm}. Its
|
|
argument is a device name (usually a serial device, like
|
|
@file{/dev/ttyb}). For example:
|
|
|
|
@smallexample
|
|
(@value{GDBP}) target remote /dev/ttyb
|
|
@end smallexample
|
|
|
|
@noindent
|
|
communications with the server via serial line @file{/dev/ttyb}.
|
|
@end table
|
|
|
|
@node KOD
|
|
@section Kernel Object Display
|
|
|
|
@cindex kernel object display
|
|
@cindex kernel object
|
|
@cindex KOD
|
|
|
|
Some targets support kernel object display. Using this facility,
|
|
@value{GDBN} communicates specially with the underlying operating system
|
|
and can display information about operating system-level objects such as
|
|
mutexes and other synchronization objects. Exactly which objects can be
|
|
displayed is determined on a per-OS basis.
|
|
|
|
Use the @code{set os} command to set the operating system. This tells
|
|
@value{GDBN} which kernel object display module to initialize:
|
|
|
|
@example
|
|
(@value{GDBP}) set os cisco
|
|
@end example
|
|
|
|
If @code{set os} succeeds, @value{GDBN} will display some information
|
|
about the operating system, and will create a new @code{info} command
|
|
which can be used to query the target. The @code{info} command is named
|
|
after the operating system:
|
|
|
|
@example
|
|
(@value{GDBP}) info cisco
|
|
List of Cisco Kernel Objects
|
|
Object Description
|
|
any Any and all objects
|
|
@end example
|
|
|
|
Further subcommands can be used to query about particular objects known
|
|
by the kernel.
|
|
|
|
There is currently no way to determine whether a given operating system
|
|
is supported other than to try it.
|
|
|
|
|
|
@node Configurations
|
|
@chapter Configuration-Specific Information
|
|
|
|
While nearly all @value{GDBN} commands are available for all native and
|
|
cross versions of the debugger, there are some exceptions. This chapter
|
|
describes things that are only available in certain configurations.
|
|
|
|
There are three major categories of configurations: native
|
|
configurations, where the host and target are the same, embedded
|
|
operating system configurations, which are usually the same for several
|
|
different processor architectures, and bare embedded processors, which
|
|
are quite different from each other.
|
|
|
|
@menu
|
|
* Native::
|
|
* Embedded OS::
|
|
* Embedded Processors::
|
|
* Architectures::
|
|
@end menu
|
|
|
|
@node Native
|
|
@section Native
|
|
|
|
This section describes details specific to particular native
|
|
configurations.
|
|
|
|
@menu
|
|
* HP-UX:: HP-UX
|
|
* SVR4 Process Information:: SVR4 process information
|
|
* DJGPP Native:: Features specific to the DJGPP port
|
|
@end menu
|
|
|
|
@node HP-UX
|
|
@subsection HP-UX
|
|
|
|
On HP-UX systems, if you refer to a function or variable name that
|
|
begins with a dollar sign, @value{GDBN} searches for a user or system
|
|
name first, before it searches for a convenience variable.
|
|
|
|
@node SVR4 Process Information
|
|
@subsection SVR4 process information
|
|
|
|
@kindex /proc
|
|
@cindex process image
|
|
|
|
Many versions of SVR4 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.
|
|
@code{info proc} works only on SVR4 systems that include the
|
|
@code{procfs} code. This includes OSF/1 (Digital Unix), Solaris, Irix,
|
|
and Unixware, but not HP-UX or Linux, for example.
|
|
|
|
@table @code
|
|
@kindex info proc
|
|
@item info proc
|
|
Summarize available information about the process.
|
|
|
|
@kindex info proc mappings
|
|
@item 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.
|
|
@ignore
|
|
@comment These sub-options of 'info proc' were not included when
|
|
@comment procfs.c was re-written. Keep their descriptions around
|
|
@comment against the day when someone finds the time to put them back in.
|
|
@kindex info proc times
|
|
@item info proc times
|
|
Starting time, user CPU time, and system CPU time for your program and
|
|
its children.
|
|
|
|
@kindex info proc id
|
|
@item 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.
|
|
|
|
@kindex info proc status
|
|
@item 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 ignore
|
|
@end table
|
|
|
|
@node DJGPP Native
|
|
@subsection Features for Debugging @sc{djgpp} Programs
|
|
@cindex @sc{djgpp} debugging
|
|
@cindex native @sc{djgpp} debugging
|
|
@cindex MS-DOS-specific commands
|
|
|
|
@sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
|
|
MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
|
|
that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
|
|
top of real-mode DOS systems and their emulations.
|
|
|
|
@value{GDBN} supports native debugging of @sc{djgpp} programs, and
|
|
defines a few commands specific to the @sc{djgpp} port. This
|
|
subsection describes those commands.
|
|
|
|
@table @code
|
|
@kindex info dos
|
|
@item info dos
|
|
This is a prefix of @sc{djgpp}-specific commands which print
|
|
information about the target system and important OS structures.
|
|
|
|
@kindex sysinfo
|
|
@cindex MS-DOS system info
|
|
@cindex free memory information (MS-DOS)
|
|
@item info dos sysinfo
|
|
This command displays assorted information about the underlying
|
|
platform: the CPU type and features, the OS version and flavor, the
|
|
DPMI version, and the available conventional and DPMI memory.
|
|
|
|
@cindex GDT
|
|
@cindex LDT
|
|
@cindex IDT
|
|
@cindex segment descriptor tables
|
|
@cindex descriptor tables display
|
|
@item info dos gdt
|
|
@itemx info dos ldt
|
|
@itemx info dos idt
|
|
These 3 commands display entries from, respectively, Global, Local,
|
|
and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
|
|
tables are data structures which store a descriptor for each segment
|
|
that is currently in use. The segment's selector is an index into a
|
|
descriptor table; the table entry for that index holds the
|
|
descriptor's base address and limit, and its attributes and access
|
|
rights.
|
|
|
|
A typical @sc{djgpp} program uses 3 segments: a code segment, a data
|
|
segment (used for both data and the stack), and a DOS segment (which
|
|
allows access to DOS/BIOS data structures and absolute addresses in
|
|
conventional memory). However, the DPMI host will usually define
|
|
additional segments in order to support the DPMI environment.
|
|
|
|
@cindex garbled pointers
|
|
These commands allow to display entries from the descriptor tables.
|
|
Without an argument, all entries from the specified table are
|
|
displayed. An argument, which should be an integer expression, means
|
|
display a single entry whose index is given by the argument. For
|
|
example, here's a convenient way to display information about the
|
|
debugged program's data segment:
|
|
|
|
@smallexample
|
|
(@value{GDBP}) info dos ldt $ds
|
|
0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)
|
|
@end smallexample
|
|
|
|
@noindent
|
|
This comes in handy when you want to see whether a pointer is outside
|
|
the data segment's limit (i.e.@: @dfn{garbled}).
|
|
|
|
@cindex page tables display (MS-DOS)
|
|
@item info dos pde
|
|
@itemx info dos pte
|
|
These two commands display entries from, respectively, the Page
|
|
Directory and the Page Tables. Page Directories and Page Tables are
|
|
data structures which control how virtual memory addresses are mapped
|
|
into physical addresses. A Page Table includes an entry for every
|
|
page of memory that is mapped into the program's address space; there
|
|
may be several Page Tables, each one holding up to 4096 entries. A
|
|
Page Directory has up to 4096 entries, one each for every Page Table
|
|
that is currently in use.
|
|
|
|
Without an argument, @kbd{info dos pde} displays the entire Page
|
|
Directory, and @kbd{info dos pte} displays all the entries in all of
|
|
the Page Tables. An argument, an integer expression, given to the
|
|
@kbd{info dos pde} command means display only that entry from the Page
|
|
Directory table. An argument given to the @kbd{info dos pte} command
|
|
means display entries from a single Page Table, the one pointed to by
|
|
the specified entry in the Page Directory.
|
|
|
|
These commands are useful when your program uses @dfn{DMA} (Direct
|
|
Memory Access), which needs physical addresses to program the DMA
|
|
controller.
|
|
|
|
These commands are supported only with some DPMI servers.
|
|
|
|
@cindex physical address from linear address
|
|
@item info dos address-pte
|
|
This command displays the Page Table entry for a specified linear
|
|
address. The argument linear address should already have the
|
|
appropriate segment's base address added to it, because this command
|
|
accepts addresses which may belong to @emph{any} segment. For
|
|
example, here's how to display the Page Table entry for the page where
|
|
the variable @code{i} is stored:
|
|
|
|
@smallexample
|
|
(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i
|
|
Page Table entry for address 0x11a00d30:
|
|
Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30
|
|
@end smallexample
|
|
|
|
@noindent
|
|
This says that @code{i} is stored at offset @code{0xd30} from the page
|
|
whose physical base address is @code{0x02698000}, and prints all the
|
|
attributes of that page.
|
|
|
|
Note that you must cast the addresses of variables to a @code{char *},
|
|
since otherwise the value of @code{__djgpp_base_address}, the base
|
|
address of all variables and functions in a @sc{djgpp} program, will
|
|
be added using the rules of C pointer arithmetics: if @code{i} is
|
|
declared an @code{int}, @value{GDBN} will add 4 times the value of
|
|
@code{__djgpp_base_address} to the address of @code{i}.
|
|
|
|
Here's another example, it displays the Page Table entry for the
|
|
transfer buffer:
|
|
|
|
@smallexample
|
|
(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)
|
|
Page Table entry for address 0x29110:
|
|
Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110
|
|
@end smallexample
|
|
|
|
@noindent
|
|
(The @code{+ 3} offset is because the transfer buffer's address is the
|
|
3rd member of the @code{_go32_info_block} structure.) The output of
|
|
this command clearly shows that addresses in conventional memory are
|
|
mapped 1:1, i.e.@: the physical and linear addresses are identical.
|
|
|
|
This command is supported only with some DPMI servers.
|
|
@end table
|
|
|
|
@node Embedded OS
|
|
@section Embedded Operating Systems
|
|
|
|
This section describes configurations involving the debugging of
|
|
embedded operating systems that are available for several different
|
|
architectures.
|
|
|
|
@menu
|
|
* VxWorks:: Using @value{GDBN} with VxWorks
|
|
@end menu
|
|
|
|
@value{GDBN} includes the ability to debug programs running on
|
|
various real-time operating systems.
|
|
|
|
@node VxWorks
|
|
@subsection Using @value{GDBN} with VxWorks
|
|
|
|
@cindex VxWorks
|
|
|
|
@table @code
|
|
|
|
@kindex target vxworks
|
|
@item target vxworks @var{machinename}
|
|
A VxWorks system, attached via TCP/IP. The argument @var{machinename}
|
|
is the target system's machine name or IP address.
|
|
|
|
@end table
|
|
|
|
On VxWorks, @code{load} links @var{filename} dynamically on the
|
|
current target system as well as adding its symbols in @value{GDBN}.
|
|
|
|
@value{GDBN} enables developers to spawn and debug tasks running on networked
|
|
VxWorks targets from a Unix host. Already-running tasks spawned from
|
|
the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
|
|
both the Unix host and on the VxWorks target. The program
|
|
@code{@value{GDBP}} is installed and executed on the Unix host. (It may be
|
|
installed with the name @code{vxgdb}, to distinguish it from a
|
|
@value{GDBN} for debugging programs on the host itself.)
|
|
|
|
@table @code
|
|
@item VxWorks-timeout @var{args}
|
|
@kindex vxworks-timeout
|
|
All VxWorks-based targets now support the option @code{vxworks-timeout}.
|
|
This option is set by the user, and @var{args} represents the number of
|
|
seconds @value{GDBN} waits for responses to rpc's. You might use this if
|
|
your VxWorks target is a slow software simulator or is on the far side
|
|
of a thin network line.
|
|
@end table
|
|
|
|
The following information on connecting to VxWorks was current when
|
|
this manual was produced; newer releases of VxWorks may use revised
|
|
procedures.
|
|
|
|
@kindex INCLUDE_RDB
|
|
To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
|
|
to include the remote debugging interface routines in the VxWorks
|
|
library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
|
|
VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
|
|
kernel. The resulting kernel contains @file{rdb.a}, and spawns the
|
|
source debugging task @code{tRdbTask} when VxWorks is booted. For more
|
|
information on configuring and remaking VxWorks, see the manufacturer's
|
|
manual.
|
|
@c VxWorks, see the @cite{VxWorks Programmer's Guide}.
|
|
|
|
Once you have included @file{rdb.a} in your VxWorks system image and set
|
|
your Unix execution search path to find @value{GDBN}, you are ready to
|
|
run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
|
|
@code{vxgdb}, depending on your installation).
|
|
|
|
@value{GDBN} comes up showing the prompt:
|
|
|
|
@example
|
|
(vxgdb)
|
|
@end example
|
|
|
|
@menu
|
|
* VxWorks Connection:: Connecting to VxWorks
|
|
* VxWorks Download:: VxWorks download
|
|
* VxWorks Attach:: Running tasks
|
|
@end menu
|
|
|
|
@node VxWorks Connection
|
|
@subsubsection Connecting to VxWorks
|
|
|
|
The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
|
|
network. To connect to a target whose host name is ``@code{tt}'', type:
|
|
|
|
@example
|
|
(vxgdb) target vxworks tt
|
|
@end example
|
|
|
|
@need 750
|
|
@value{GDBN} displays messages like these:
|
|
|
|
@smallexample
|
|
Attaching remote machine across net...
|
|
Connected to tt.
|
|
@end smallexample
|
|
|
|
@need 1000
|
|
@value{GDBN} then attempts to read the symbol tables of any object modules
|
|
loaded into the VxWorks target since it was last booted. @value{GDBN} locates
|
|
these files by searching the directories listed in the command search
|
|
path (@pxref{Environment, ,Your program's environment}); if it fails
|
|
to find an object file, it displays a message such as:
|
|
|
|
@example
|
|
prog.o: No such file or directory.
|
|
@end example
|
|
|
|
When this happens, add the appropriate directory to the search path with
|
|
the @value{GDBN} command @code{path}, and execute the @code{target}
|
|
command again.
|
|
|
|
@node VxWorks Download
|
|
@subsubsection VxWorks download
|
|
|
|
@cindex download to VxWorks
|
|
If you have connected to the VxWorks target and you want to debug an
|
|
object that has not yet been loaded, you can use the @value{GDBN}
|
|
@code{load} command to download a file from Unix to VxWorks
|
|
incrementally. The object file given as an argument to the @code{load}
|
|
command is actually opened twice: first by the VxWorks target in order
|
|
to download the code, then by @value{GDBN} in order to read the symbol
|
|
table. This can lead to problems if the current working directories on
|
|
the two systems differ. If both systems have NFS mounted the same
|
|
filesystems, you can avoid these problems by using absolute paths.
|
|
Otherwise, it is simplest to set the working directory on both systems
|
|
to the directory in which the object file resides, and then to reference
|
|
the file by its name, without any path. For instance, a program
|
|
@file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
|
|
and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
|
|
program, type this on VxWorks:
|
|
|
|
@example
|
|
-> cd "@var{vxpath}/vw/demo/rdb"
|
|
@end example
|
|
|
|
@noindent
|
|
Then, in @value{GDBN}, type:
|
|
|
|
@example
|
|
(vxgdb) cd @var{hostpath}/vw/demo/rdb
|
|
(vxgdb) load prog.o
|
|
@end example
|
|
|
|
@value{GDBN} displays a response similar to this:
|
|
|
|
@smallexample
|
|
Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
|
|
@end smallexample
|
|
|
|
You can also use the @code{load} command to reload an object module
|
|
after editing and recompiling the corresponding source file. Note that
|
|
this makes @value{GDBN} delete all currently-defined breakpoints,
|
|
auto-displays, and convenience variables, and to clear the value
|
|
history. (This is necessary in order to preserve the integrity of
|
|
debugger's data structures that reference the target system's symbol
|
|
table.)
|
|
|
|
@node VxWorks Attach
|
|
@subsubsection Running tasks
|
|
|
|
@cindex running VxWorks tasks
|
|
You can also attach to an existing task using the @code{attach} command as
|
|
follows:
|
|
|
|
@example
|
|
(vxgdb) attach @var{task}
|
|
@end example
|
|
|
|
@noindent
|
|
where @var{task} is the VxWorks hexadecimal task ID. The task can be running
|
|
or suspended when you attach to it. Running tasks are suspended at
|
|
the time of attachment.
|
|
|
|
@node Embedded Processors
|
|
@section Embedded Processors
|
|
|
|
This section goes into details specific to particular embedded
|
|
configurations.
|
|
|
|
@menu
|
|
* A29K Embedded:: AMD A29K Embedded
|
|
* ARM:: ARM
|
|
* H8/300:: Hitachi H8/300
|
|
* H8/500:: Hitachi H8/500
|
|
* i960:: Intel i960
|
|
* M32R/D:: Mitsubishi M32R/D
|
|
* M68K:: Motorola M68K
|
|
* M88K:: Motorola M88K
|
|
* MIPS Embedded:: MIPS Embedded
|
|
* PA:: HP PA Embedded
|
|
* PowerPC: PowerPC
|
|
* SH:: Hitachi SH
|
|
* Sparclet:: Tsqware Sparclet
|
|
* Sparclite:: Fujitsu Sparclite
|
|
* ST2000:: Tandem ST2000
|
|
* Z8000:: Zilog Z8000
|
|
@end menu
|
|
|
|
@node A29K Embedded
|
|
@subsection AMD A29K Embedded
|
|
|
|
@menu
|
|
* A29K UDI::
|
|
* A29K EB29K::
|
|
* Comms (EB29K):: Communications setup
|
|
* gdb-EB29K:: EB29K cross-debugging
|
|
* Remote Log:: Remote log
|
|
@end menu
|
|
|
|
@table @code
|
|
|
|
@kindex target adapt
|
|
@item target adapt @var{dev}
|
|
Adapt monitor for A29K.
|
|
|
|
@kindex target amd-eb
|
|
@item target amd-eb @var{dev} @var{speed} @var{PROG}
|
|
@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{A29K EB29K, ,EBMON protocol for AMD29K}.
|
|
|
|
@end table
|
|
|
|
@node A29K UDI
|
|
@subsubsection A29K UDI
|
|
|
|
@cindex UDI
|
|
@cindex AMD29K via UDI
|
|
|
|
@value{GDBN} supports AMD's UDI (``Universal Debugger Interface'')
|
|
protocol for debugging the a29k processor family. To use this
|
|
configuration with AMD targets running the MiniMON monitor, you need the
|
|
program @code{MONTIP}, available from AMD at no charge. You can also
|
|
use @value{GDBN} with the UDI-conformant a29k simulator program
|
|
@code{ISSTIP}, also available from AMD.
|
|
|
|
@table @code
|
|
@item target udi @var{keyword}
|
|
@kindex udi
|
|
Select the UDI interface to a remote a29k board or simulator, where
|
|
@var{keyword} is an entry in the AMD configuration file @file{udi_soc}.
|
|
This file contains keyword entries which specify parameters used to
|
|
connect to a29k targets. If the @file{udi_soc} file is not in your
|
|
working directory, you must set the environment variable @samp{UDICONF}
|
|
to its pathname.
|
|
@end table
|
|
|
|
@node A29K EB29K
|
|
@subsubsection EBMON protocol for AMD29K
|
|
|
|
@cindex EB29K board
|
|
@cindex running 29K programs
|
|
|
|
AMD distributes a 29K development board meant to fit in a PC, together
|
|
with a DOS-hosted monitor program called @code{EBMON}. As a shorthand
|
|
term, this development system is called the ``EB29K''. To use
|
|
@value{GDBN} from a Unix system to run programs on the EB29K board, you
|
|
must first connect a serial cable between the PC (which hosts the EB29K
|
|
board) and a serial port on the Unix system. In the following, we
|
|
assume you've hooked the cable between the PC's @file{COM1} port and
|
|
@file{/dev/ttya} on the Unix system.
|
|
|
|
@node Comms (EB29K)
|
|
@subsubsection Communications setup
|
|
|
|
The next step is to set up the PC's port, by doing something like this
|
|
in DOS on the PC:
|
|
|
|
@example
|
|
C:\> MODE com1:9600,n,8,1,none
|
|
@end example
|
|
|
|
@noindent
|
|
This example---run on an MS DOS 4.0 system---sets the PC port to 9600
|
|
bps, no parity, eight data bits, one stop bit, and no ``retry'' action;
|
|
you must match the communications parameters when establishing the Unix
|
|
end of the connection as well.
|
|
@c FIXME: Who knows what this "no retry action" crud from the DOS manual may
|
|
@c mean? It's optional; leave it out? ---doc@cygnus.com, 25feb91
|
|
@c
|
|
@c It's optional, but it's unwise to omit it: who knows what is the
|
|
@c default value set when the DOS machines boots? "No retry" means that
|
|
@c the DOS serial device driver won't retry the operation if it fails;
|
|
@c I understand that this is needed because the GDB serial protocol
|
|
@c handles any errors and retransmissions itself. ---Eli Zaretskii, 3sep99
|
|
|
|
To give control of the PC to the Unix side of the serial line, type
|
|
the following at the DOS console:
|
|
|
|
@example
|
|
C:\> CTTY com1
|
|
@end example
|
|
|
|
@noindent
|
|
(Later, if you wish to return control to the DOS console, you can use
|
|
the command @code{CTTY con}---but you must send it over the device that
|
|
had control, in our example over the @file{COM1} serial line.)
|
|
|
|
From the Unix host, use a communications program such as @code{tip} or
|
|
@code{cu} to communicate with the PC; for example,
|
|
|
|
@example
|
|
cu -s 9600 -l /dev/ttya
|
|
@end example
|
|
|
|
@noindent
|
|
The @code{cu} options shown specify, respectively, the linespeed and the
|
|
serial port to use. If you use @code{tip} instead, your command line
|
|
may look something like the following:
|
|
|
|
@example
|
|
tip -9600 /dev/ttya
|
|
@end example
|
|
|
|
@noindent
|
|
Your system may require a different name where we show
|
|
@file{/dev/ttya} as the argument to @code{tip}. The communications
|
|
parameters, including which port to use, are associated with the
|
|
@code{tip} argument in the ``remote'' descriptions file---normally the
|
|
system table @file{/etc/remote}.
|
|
@c FIXME: What if anything needs doing to match the "n,8,1,none" part of
|
|
@c the DOS side's comms setup? cu can support -o (odd
|
|
@c parity), -e (even parity)---apparently no settings for no parity or
|
|
@c for character size. Taken from stty maybe...? John points out tip
|
|
@c can set these as internal variables, eg ~s parity=none; man stty
|
|
@c suggests that it *might* work to stty these options with stdin or
|
|
@c stdout redirected... ---doc@cygnus.com, 25feb91
|
|
@c
|
|
@c There's nothing to be done for the "none" part of the DOS MODE
|
|
@c command. The rest of the parameters should be matched by the
|
|
@c baudrate, bits, and parity used by the Unix side. ---Eli Zaretskii, 3Sep99
|
|
|
|
@kindex EBMON
|
|
Using the @code{tip} or @code{cu} connection, change the DOS working
|
|
directory to the directory containing a copy of your 29K program, then
|
|
start the PC program @code{EBMON} (an EB29K control program supplied
|
|
with your board by AMD). You should see an initial display from
|
|
@code{EBMON} similar to the one that follows, ending with the
|
|
@code{EBMON} prompt @samp{#}---
|
|
|
|
@example
|
|
C:\> G:
|
|
|
|
G:\> CD \usr\joe\work29k
|
|
|
|
G:\USR\JOE\WORK29K> EBMON
|
|
Am29000 PC Coprocessor Board Monitor, version 3.0-18
|
|
Copyright 1990 Advanced Micro Devices, Inc.
|
|
Written by Gibbons and Associates, Inc.
|
|
|
|
Enter '?' or 'H' for help
|
|
|
|
PC Coprocessor Type = EB29K
|
|
I/O Base = 0x208
|
|
Memory Base = 0xd0000
|
|
|
|
Data Memory Size = 2048KB
|
|
Available I-RAM Range = 0x8000 to 0x1fffff
|
|
Available D-RAM Range = 0x80002000 to 0x801fffff
|
|
|
|
PageSize = 0x400
|
|
Register Stack Size = 0x800
|
|
Memory Stack Size = 0x1800
|
|
|
|
CPU PRL = 0x3
|
|
Am29027 Available = No
|
|
Byte Write Available = Yes
|
|
|
|
# ~.
|
|
@end example
|
|
|
|
Then exit the @code{cu} or @code{tip} program (done in the example by
|
|
typing @code{~.} at the @code{EBMON} prompt). @code{EBMON} keeps
|
|
running, ready for @value{GDBN} to take over.
|
|
|
|
For this example, we've assumed what is probably the most convenient
|
|
way to make sure the same 29K program is on both the PC and the Unix
|
|
system: a PC/NFS connection that establishes ``drive @file{G:}'' on the
|
|
PC as a file system on the Unix host. If you do not have PC/NFS or
|
|
something similar connecting the two systems, you must arrange some
|
|
other way---perhaps floppy-disk transfer---of getting the 29K program
|
|
from the Unix system to the PC; @value{GDBN} does @emph{not} download it over the
|
|
serial line.
|
|
|
|
@node gdb-EB29K
|
|
@subsubsection EB29K cross-debugging
|
|
|
|
Finally, @code{cd} to the directory containing an image of your 29K
|
|
program on the Unix system, and start @value{GDBN}---specifying as argument the
|
|
name of your 29K program:
|
|
|
|
@example
|
|
cd /usr/joe/work29k
|
|
@value{GDBP} myfoo
|
|
@end example
|
|
|
|
@need 500
|
|
Now you can use the @code{target} command:
|
|
|
|
@example
|
|
target amd-eb /dev/ttya 9600 MYFOO
|
|
@c FIXME: test above 'target amd-eb' as spelled, with caps! caps are meant to
|
|
@c emphasize that this is the name as seen by DOS (since I think DOS is
|
|
@c single-minded about case of letters). ---doc@cygnus.com, 25feb91
|
|
@end example
|
|
|
|
@noindent
|
|
In this example, we've assumed your program is in a file called
|
|
@file{myfoo}. Note that the filename given as the last argument to
|
|
@code{target amd-eb} should be the name of the program as it appears to DOS.
|
|
In our example this is simply @code{MYFOO}, but in general it can include
|
|
a DOS path, and depending on your transfer mechanism may not resemble
|
|
the name on the Unix side.
|
|
|
|
At this point, you can set any breakpoints you wish; when you are ready
|
|
to see your program run on the 29K board, use the @value{GDBN} command
|
|
@code{run}.
|
|
|
|
To stop debugging the remote program, use the @value{GDBN} @code{detach}
|
|
command.
|
|
|
|
To return control of the PC to its console, use @code{tip} or @code{cu}
|
|
once again, after your @value{GDBN} session has concluded, to attach to
|
|
@code{EBMON}. You can then type the command @code{q} to shut down
|
|
@code{EBMON}, returning control to the DOS command-line interpreter.
|
|
Type @kbd{CTTY con} to return command input to the main DOS console,
|
|
and type @kbd{~.} to leave @code{tip} or @code{cu}.
|
|
|
|
@node Remote Log
|
|
@subsubsection Remote log
|
|
@cindex @file{eb.log}, a log file for EB29K
|
|
@cindex log file for EB29K
|
|
|
|
The @code{target amd-eb} command creates a file @file{eb.log} in the
|
|
current working directory, to help debug problems with the connection.
|
|
@file{eb.log} records all the output from @code{EBMON}, including echoes
|
|
of the commands sent to it. Running @samp{tail -f} on this file in
|
|
another window often helps to understand trouble with @code{EBMON}, or
|
|
unexpected events on the PC side of the connection.
|
|
|
|
@node ARM
|
|
@subsection ARM
|
|
|
|
@table @code
|
|
|
|
@kindex target rdi
|
|
@item target rdi @var{dev}
|
|
ARM Angel monitor, via RDI library interface to ADP protocol. You may
|
|
use this target to communicate with both boards running the Angel
|
|
monitor, or with the EmbeddedICE JTAG debug device.
|
|
|
|
@kindex target rdp
|
|
@item target rdp @var{dev}
|
|
ARM Demon monitor.
|
|
|
|
@end table
|
|
|
|
@node H8/300
|
|
@subsection Hitachi H8/300
|
|
|
|
@table @code
|
|
|
|
@kindex target hms@r{, with H8/300}
|
|
@item target hms @var{dev}
|
|
A Hitachi SH, H8/300, or H8/500 board, attached via serial line to your host.
|
|
Use special commands @code{device} and @code{speed} to control the serial
|
|
line and the communications speed used.
|
|
|
|
@kindex target e7000@r{, with H8/300}
|
|
@item target e7000 @var{dev}
|
|
E7000 emulator for Hitachi H8 and SH.
|
|
|
|
@kindex target sh3@r{, with H8/300}
|
|
@kindex target sh3e@r{, with H8/300}
|
|
@item target sh3 @var{dev}
|
|
@itemx target sh3e @var{dev}
|
|
Hitachi SH-3 and SH-3E target systems.
|
|
|
|
@end table
|
|
|
|
@cindex download to H8/300 or H8/500
|
|
@cindex H8/300 or H8/500 download
|
|
@cindex download to Hitachi SH
|
|
@cindex Hitachi SH download
|
|
When you select remote debugging to a Hitachi SH, H8/300, or H8/500
|
|
board, 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).
|
|
|
|
@value{GDBN} needs to know these things to talk to your
|
|
Hitachi SH, H8/300, or H8/500:
|
|
|
|
@enumerate
|
|
@item
|
|
that you want to use @samp{target hms}, the remote debugging interface
|
|
for Hitachi microprocessors, or @samp{target e7000}, the in-circuit
|
|
emulator for the Hitachi SH and the Hitachi 300H. (@samp{target hms} is
|
|
the default when @value{GDBN} is configured specifically for the Hitachi SH,
|
|
H8/300, or H8/500.)
|
|
|
|
@item
|
|
what serial device connects your host to your Hitachi board (the first
|
|
serial device available on your host is the default).
|
|
|
|
@item
|
|
what speed to use over the serial device.
|
|
@end enumerate
|
|
|
|
@menu
|
|
* Hitachi Boards:: Connecting to Hitachi boards.
|
|
* Hitachi ICE:: Using the E7000 In-Circuit Emulator.
|
|
* Hitachi Special:: Special @value{GDBN} commands for Hitachi micros.
|
|
@end menu
|
|
|
|
@node Hitachi Boards
|
|
@subsubsection Connecting to Hitachi boards
|
|
|
|
@c only for Unix hosts
|
|
@kindex device
|
|
@cindex serial device, Hitachi micros
|
|
Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
|
|
need to explicitly set the serial device. The default @var{port} is the
|
|
first available port on your host. This is only necessary on Unix
|
|
hosts, where it is typically something like @file{/dev/ttya}.
|
|
|
|
@kindex speed
|
|
@cindex serial line speed, Hitachi micros
|
|
@code{@value{GDBN}} has another special command to set the communications
|
|
speed: @samp{speed @var{bps}}. This command also is only used from Unix
|
|
hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
|
|
the DOS @code{mode} command (for instance,
|
|
@w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
|
|
|
|
The @samp{device} and @samp{speed} commands are available only when you
|
|
use a Unix host to debug your Hitachi microprocessor programs. If you
|
|
use a DOS host,
|
|
@value{GDBN} depends on an auxiliary terminate-and-stay-resident program
|
|
called @code{asynctsr} to communicate with the development board
|
|
through a PC serial port. You must also use the DOS @code{mode} command
|
|
to set up the serial port on the DOS side.
|
|
|
|
The following sample session illustrates the steps needed to start a
|
|
program under @value{GDBN} control on an H8/300. The example uses a
|
|
sample H8/300 program called @file{t.x}. The procedure is the same for
|
|
the Hitachi SH and the H8/500.
|
|
|
|
First hook up your development board. In this example, we use a
|
|
board attached to serial port @code{COM2}; if you use a different serial
|
|
port, substitute its name in the argument of the @code{mode} command.
|
|
When you call @code{asynctsr}, the auxiliary comms program used by the
|
|
debugger, you give it just the numeric part of the serial port's name;
|
|
for example, @samp{asyncstr 2} below runs @code{asyncstr} on
|
|
@code{COM2}.
|
|
|
|
@example
|
|
C:\H8300\TEST> asynctsr 2
|
|
C:\H8300\TEST> mode com2:9600,n,8,1,p
|
|
|
|
Resident portion of MODE loaded
|
|
|
|
COM2: 9600, n, 8, 1, p
|
|
|
|
@end example
|
|
|
|
@quotation
|
|
@emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
|
|
@code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
|
|
disable it, or even boot without it, to use @code{asynctsr} to control
|
|
your development board.
|
|
@end quotation
|
|
|
|
@kindex target hms@r{, and serial protocol}
|
|
Now that serial communications are set up, and the development board is
|
|
connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with
|
|
the name of your program as the argument. @code{@value{GDBN}} prompts
|
|
you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
|
|
commands to begin your debugging session: @samp{target hms} to specify
|
|
cross-debugging to the Hitachi board, and the @code{load} command to
|
|
download your program to the board. @code{load} displays the names of
|
|
the program's sections, and a @samp{*} for each 2K of data downloaded.
|
|
(If you want to refresh @value{GDBN} data on symbols or on the
|
|
executable file without downloading, use the @value{GDBN} commands
|
|
@code{file} or @code{symbol-file}. These commands, and @code{load}
|
|
itself, are described in @ref{Files,,Commands to specify files}.)
|
|
|
|
@smallexample
|
|
(eg-C:\H8300\TEST) @value{GDBP} t.x
|
|
@value{GDBN} 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 @value{GDBN}; type "show warranty"
|
|
for details.
|
|
@value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
|
|
(@value{GDBP}) target hms
|
|
Connected to remote H8/300 HMS system.
|
|
(@value{GDBP}) load t.x
|
|
.text : 0x8000 .. 0xabde ***********
|
|
.data : 0xabde .. 0xad30 *
|
|
.stack : 0xf000 .. 0xf014 *
|
|
@end smallexample
|
|
|
|
At this point, you're ready to run or debug your program. From here on,
|
|
you can use all the usual @value{GDBN} commands. The @code{break} command
|
|
sets breakpoints; the @code{run} command starts your program;
|
|
@code{print} or @code{x} display data; the @code{continue} command
|
|
resumes execution after stopping at a breakpoint. You can use the
|
|
@code{help} command at any time to find out more about @value{GDBN} commands.
|
|
|
|
Remember, however, that @emph{operating system} facilities aren't
|
|
available on your development board; for example, if your program hangs,
|
|
you can't send an interrupt---but you can press the @sc{reset} switch!
|
|
|
|
Use the @sc{reset} button on the development board
|
|
@itemize @bullet
|
|
@item
|
|
to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
|
|
no way to pass an interrupt signal to the development board); and
|
|
|
|
@item
|
|
to return to the @value{GDBN} command prompt after your program finishes
|
|
normally. The communications protocol provides no other way for @value{GDBN}
|
|
to detect program completion.
|
|
@end itemize
|
|
|
|
In either case, @value{GDBN} sees the effect of a @sc{reset} on the
|
|
development board as a ``normal exit'' of your program.
|
|
|
|
@node Hitachi ICE
|
|
@subsubsection Using the E7000 in-circuit emulator
|
|
|
|
@kindex target e7000@r{, with Hitachi ICE}
|
|
You can use the E7000 in-circuit emulator to develop code for either the
|
|
Hitachi SH or the H8/300H. Use one of these forms of the @samp{target
|
|
e7000} command to connect @value{GDBN} to your E7000:
|
|
|
|
@table @code
|
|
@item target e7000 @var{port} @var{speed}
|
|
Use this form if your E7000 is connected to a serial port. The
|
|
@var{port} argument identifies what serial port to use (for example,
|
|
@samp{com2}). The third argument is the line speed in bits per second
|
|
(for example, @samp{9600}).
|
|
|
|
@item target e7000 @var{hostname}
|
|
If your E7000 is installed as a host on a TCP/IP network, you can just
|
|
specify its hostname; @value{GDBN} uses @code{telnet} to connect.
|
|
@end table
|
|
|
|
@node Hitachi Special
|
|
@subsubsection Special @value{GDBN} commands for Hitachi micros
|
|
|
|
Some @value{GDBN} commands are available only for the H8/300:
|
|
|
|
@table @code
|
|
|
|
@kindex set machine
|
|
@kindex show machine
|
|
@item set machine h8300
|
|
@itemx set machine h8300h
|
|
Condition @value{GDBN} for one of the two variants of the H8/300
|
|
architecture with @samp{set machine}. You can use @samp{show machine}
|
|
to check which variant is currently in effect.
|
|
|
|
@end table
|
|
|
|
@node H8/500
|
|
@subsection H8/500
|
|
|
|
@table @code
|
|
|
|
@kindex set memory @var{mod}
|
|
@cindex memory models, H8/500
|
|
@item set memory @var{mod}
|
|
@itemx show memory
|
|
Specify which H8/500 memory model (@var{mod}) you are using with
|
|
@samp{set memory}; check which memory model is in effect with @samp{show
|
|
memory}. The accepted values for @var{mod} are @code{small},
|
|
@code{big}, @code{medium}, and @code{compact}.
|
|
|
|
@end table
|
|
|
|
@node i960
|
|
@subsection Intel i960
|
|
|
|
@table @code
|
|
|
|
@kindex target mon960
|
|
@item target mon960 @var{dev}
|
|
MON960 monitor for Intel i960.
|
|
|
|
@kindex target nindy
|
|
@item target nindy @var{devicename}
|
|
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}.
|
|
|
|
@end table
|
|
|
|
@cindex Nindy
|
|
@cindex i960
|
|
@dfn{Nindy} is a ROM Monitor program for Intel 960 target systems. When
|
|
@value{GDBN} is configured to control a remote Intel 960 using Nindy, you can
|
|
tell @value{GDBN} how to connect to the 960 in several ways:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
Through command line options specifying serial port, version of the
|
|
Nindy protocol, and communications speed;
|
|
|
|
@item
|
|
By responding to a prompt on startup;
|
|
|
|
@item
|
|
By using the @code{target} command at any point during your @value{GDBN}
|
|
session. @xref{Target Commands, ,Commands for managing targets}.
|
|
|
|
@end itemize
|
|
|
|
@cindex download to Nindy-960
|
|
With the Nindy interface to an Intel 960 board, @code{load}
|
|
downloads @var{filename} to the 960 as well as adding its symbols in
|
|
@value{GDBN}.
|
|
|
|
@menu
|
|
* Nindy Startup:: Startup with Nindy
|
|
* Nindy Options:: Options for Nindy
|
|
* Nindy Reset:: Nindy reset command
|
|
@end menu
|
|
|
|
@node Nindy Startup
|
|
@subsubsection Startup with Nindy
|
|
|
|
If you simply start @code{@value{GDBP}} without using any command-line
|
|
options, you are prompted for what serial port to use, @emph{before} you
|
|
reach the ordinary @value{GDBN} prompt:
|
|
|
|
@example
|
|
Attach /dev/ttyNN -- specify NN, or "quit" to quit:
|
|
@end example
|
|
|
|
@noindent
|
|
Respond to the prompt with whatever suffix (after @samp{/dev/tty})
|
|
identifies the serial port you want to use. You can, if you choose,
|
|
simply start up with no Nindy connection by responding to the prompt
|
|
with an empty line. If you do this and later wish to attach to Nindy,
|
|
use @code{target} (@pxref{Target Commands, ,Commands for managing targets}).
|
|
|
|
@node Nindy Options
|
|
@subsubsection Options for Nindy
|
|
|
|
These are the startup options for beginning your @value{GDBN} session with a
|
|
Nindy-960 board attached:
|
|
|
|
@table @code
|
|
@item -r @var{port}
|
|
Specify the serial port name of a serial interface to be used to connect
|
|
to the target system. This option is only available when @value{GDBN} is
|
|
configured for the Intel 960 target architecture. You may specify
|
|
@var{port} as any of: a full pathname (e.g. @samp{-r /dev/ttya}), a
|
|
device name in @file{/dev} (e.g. @samp{-r ttya}), or simply the unique
|
|
suffix for a specific @code{tty} (e.g. @samp{-r a}).
|
|
|
|
@item -O
|
|
(An uppercase letter ``O'', not a zero.) Specify that @value{GDBN} should use
|
|
the ``old'' Nindy monitor protocol to connect to the target system.
|
|
This option is only available when @value{GDBN} is configured for the Intel 960
|
|
target architecture.
|
|
|
|
@quotation
|
|
@emph{Warning:} if you specify @samp{-O}, but are actually trying to
|
|
connect to a target system that expects the newer protocol, the connection
|
|
fails, appearing to be a speed mismatch. @value{GDBN} repeatedly
|
|
attempts to reconnect at several different line speeds. You can abort
|
|
this process with an interrupt.
|
|
@end quotation
|
|
|
|
@item -brk
|
|
Specify that @value{GDBN} should first send a @code{BREAK} signal to the target
|
|
system, in an attempt to reset it, before connecting to a Nindy target.
|
|
|
|
@quotation
|
|
@emph{Warning:} Many target systems do not have the hardware that this
|
|
requires; it only works with a few boards.
|
|
@end quotation
|
|
@end table
|
|
|
|
The standard @samp{-b} option controls the line speed used on the serial
|
|
port.
|
|
|
|
@c @group
|
|
@node Nindy Reset
|
|
@subsubsection Nindy reset command
|
|
|
|
@table @code
|
|
@item reset
|
|
@kindex reset
|
|
For a Nindy target, this command sends a ``break'' to the remote target
|
|
system; this is only useful if the target has been equipped with a
|
|
circuit to perform a hard reset (or some other interesting action) when
|
|
a break is detected.
|
|
@end table
|
|
@c @end group
|
|
|
|
@node M32R/D
|
|
@subsection Mitsubishi M32R/D
|
|
|
|
@table @code
|
|
|
|
@kindex target m32r
|
|
@item target m32r @var{dev}
|
|
Mitsubishi M32R/D ROM monitor.
|
|
|
|
@end table
|
|
|
|
@node M68K
|
|
@subsection M68k
|
|
|
|
The Motorola m68k configuration includes ColdFire support, and
|
|
target command for the following ROM monitors.
|
|
|
|
@table @code
|
|
|
|
@kindex target abug
|
|
@item target abug @var{dev}
|
|
ABug ROM monitor for M68K.
|
|
|
|
@kindex target cpu32bug
|
|
@item target cpu32bug @var{dev}
|
|
CPU32BUG monitor, running on a CPU32 (M68K) board.
|
|
|
|
@kindex target dbug
|
|
@item target dbug @var{dev}
|
|
dBUG ROM monitor for Motorola ColdFire.
|
|
|
|
@kindex target est
|
|
@item target est @var{dev}
|
|
EST-300 ICE monitor, running on a CPU32 (M68K) board.
|
|
|
|
@kindex target rom68k
|
|
@item target rom68k @var{dev}
|
|
ROM 68K monitor, running on an M68K IDP board.
|
|
|
|
@end table
|
|
|
|
If @value{GDBN} is configured with @code{m68*-ericsson-*}, it will
|
|
instead have only a single special target command:
|
|
|
|
@table @code
|
|
|
|
@kindex target es1800
|
|
@item target es1800 @var{dev}
|
|
ES-1800 emulator for M68K.
|
|
|
|
@end table
|
|
|
|
[context?]
|
|
|
|
@table @code
|
|
|
|
@kindex target rombug
|
|
@item target rombug @var{dev}
|
|
ROMBUG ROM monitor for OS/9000.
|
|
|
|
@end table
|
|
|
|
@node M88K
|
|
@subsection M88K
|
|
|
|
@table @code
|
|
|
|
@kindex target bug
|
|
@item target bug @var{dev}
|
|
BUG monitor, running on a MVME187 (m88k) board.
|
|
|
|
@end table
|
|
|
|
@node MIPS Embedded
|
|
@subsection MIPS Embedded
|
|
|
|
@cindex MIPS boards
|
|
@value{GDBN} can use the MIPS remote debugging protocol to talk to a
|
|
MIPS board attached to a serial line. This is available when
|
|
you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
|
|
|
|
@need 1000
|
|
Use these @value{GDBN} commands to specify the connection to your target board:
|
|
|
|
@table @code
|
|
@item target mips @var{port}
|
|
@kindex target mips @var{port}
|
|
To run a program on the board, start up @code{@value{GDBP}} with the
|
|
name of your program as the argument. To connect to the board, use the
|
|
command @samp{target mips @var{port}}, where @var{port} is the name of
|
|
the serial port connected to the board. If the program has not already
|
|
been downloaded to the board, you may use the @code{load} command to
|
|
download it. You can then use all the usual @value{GDBN} commands.
|
|
|
|
For example, this sequence connects to the target board through a serial
|
|
port, and loads and runs a program called @var{prog} through the
|
|
debugger:
|
|
|
|
@example
|
|
host$ @value{GDBP} @var{prog}
|
|
@value{GDBN} is free software and @dots{}
|
|
(@value{GDBP}) target mips /dev/ttyb
|
|
(@value{GDBP}) load @var{prog}
|
|
(@value{GDBP}) run
|
|
@end example
|
|
|
|
@item target mips @var{hostname}:@var{portnumber}
|
|
On some @value{GDBN} host configurations, you can specify a TCP
|
|
connection (for instance, to a serial line managed by a terminal
|
|
concentrator) instead of a serial port, using the syntax
|
|
@samp{@var{hostname}:@var{portnumber}}.
|
|
|
|
@item target pmon @var{port}
|
|
@kindex target pmon @var{port}
|
|
PMON ROM monitor.
|
|
|
|
@item target ddb @var{port}
|
|
@kindex target ddb @var{port}
|
|
NEC's DDB variant of PMON for Vr4300.
|
|
|
|
@item target lsi @var{port}
|
|
@kindex target lsi @var{port}
|
|
LSI variant of PMON.
|
|
|
|
@kindex target r3900
|
|
@item target r3900 @var{dev}
|
|
Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
|
|
|
|
@kindex target array
|
|
@item target array @var{dev}
|
|
Array Tech LSI33K RAID controller board.
|
|
|
|
@end table
|
|
|
|
|
|
@noindent
|
|
@value{GDBN} also supports these special commands for MIPS targets:
|
|
|
|
@table @code
|
|
@item set processor @var{args}
|
|
@itemx show processor
|
|
@kindex set processor @var{args}
|
|
@kindex show processor
|
|
Use the @code{set processor} command to set the type of MIPS
|
|
processor when you want to access processor-type-specific registers.
|
|
For example, @code{set processor @var{r3041}} tells @value{GDBN}
|
|
to use the CPU registers appropriate for the 3041 chip.
|
|
Use the @code{show processor} command to see what MIPS processor @value{GDBN}
|
|
is using. Use the @code{info reg} command to see what registers
|
|
@value{GDBN} is using.
|
|
|
|
@item set mipsfpu double
|
|
@itemx set mipsfpu single
|
|
@itemx set mipsfpu none
|
|
@itemx show mipsfpu
|
|
@kindex set mipsfpu
|
|
@kindex show mipsfpu
|
|
@cindex MIPS remote floating point
|
|
@cindex floating point, MIPS remote
|
|
If your target board does not support the MIPS floating point
|
|
coprocessor, you should use the command @samp{set mipsfpu none} (if you
|
|
need this, you may wish to put the command in your @value{GDBN} init
|
|
file). This tells @value{GDBN} how to find the return value of
|
|
functions which return floating point values. It also allows
|
|
@value{GDBN} to avoid saving the floating point registers when calling
|
|
functions on the board. If you are using a floating point coprocessor
|
|
with only single precision floating point support, as on the @sc{r4650}
|
|
processor, use the command @samp{set mipsfpu single}. The default
|
|
double precision floating point coprocessor may be selected using
|
|
@samp{set mipsfpu double}.
|
|
|
|
In previous versions the only choices were double precision or no
|
|
floating point, so @samp{set mipsfpu on} will select double precision
|
|
and @samp{set mipsfpu off} will select no floating point.
|
|
|
|
As usual, you can inquire about the @code{mipsfpu} variable with
|
|
@samp{show mipsfpu}.
|
|
|
|
@item set remotedebug @var{n}
|
|
@itemx show remotedebug
|
|
@kindex set remotedebug@r{, MIPS protocol}
|
|
@kindex show remotedebug@r{, MIPS protocol}
|
|
@cindex @code{remotedebug}, MIPS protocol
|
|
@cindex MIPS @code{remotedebug} protocol
|
|
@c FIXME! For this to be useful, you must know something about the MIPS
|
|
@c FIXME...protocol. Where is it described?
|
|
You can see some debugging information about communications with the board
|
|
by setting the @code{remotedebug} variable. If you set it to @code{1} using
|
|
@samp{set remotedebug 1}, every packet is displayed. If you set it
|
|
to @code{2}, every character is displayed. You can check the current value
|
|
at any time with the command @samp{show remotedebug}.
|
|
|
|
@item set timeout @var{seconds}
|
|
@itemx set retransmit-timeout @var{seconds}
|
|
@itemx show timeout
|
|
@itemx show retransmit-timeout
|
|
@cindex @code{timeout}, MIPS protocol
|
|
@cindex @code{retransmit-timeout}, MIPS protocol
|
|
@kindex set timeout
|
|
@kindex show timeout
|
|
@kindex set retransmit-timeout
|
|
@kindex show retransmit-timeout
|
|
You can control the timeout used while waiting for a packet, in the MIPS
|
|
remote protocol, with the @code{set timeout @var{seconds}} command. The
|
|
default is 5 seconds. Similarly, you can control the timeout used while
|
|
waiting for an acknowledgement of a packet with the @code{set
|
|
retransmit-timeout @var{seconds}} command. The default is 3 seconds.
|
|
You can inspect both values with @code{show timeout} and @code{show
|
|
retransmit-timeout}. (These commands are @emph{only} available when
|
|
@value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
|
|
|
|
The timeout set by @code{set timeout} does not apply when @value{GDBN}
|
|
is waiting for your program to stop. In that case, @value{GDBN} waits
|
|
forever because it has no way of knowing how long the program is going
|
|
to run before stopping.
|
|
@end table
|
|
|
|
@node PowerPC
|
|
@subsection PowerPC
|
|
|
|
@table @code
|
|
|
|
@kindex target dink32
|
|
@item target dink32 @var{dev}
|
|
DINK32 ROM monitor.
|
|
|
|
@kindex target ppcbug
|
|
@item target ppcbug @var{dev}
|
|
@kindex target ppcbug1
|
|
@item target ppcbug1 @var{dev}
|
|
PPCBUG ROM monitor for PowerPC.
|
|
|
|
@kindex target sds
|
|
@item target sds @var{dev}
|
|
SDS monitor, running on a PowerPC board (such as Motorola's ADS).
|
|
|
|
@end table
|
|
|
|
@node PA
|
|
@subsection HP PA Embedded
|
|
|
|
@table @code
|
|
|
|
@kindex target op50n
|
|
@item target op50n @var{dev}
|
|
OP50N monitor, running on an OKI HPPA board.
|
|
|
|
@kindex target w89k
|
|
@item target w89k @var{dev}
|
|
W89K monitor, running on a Winbond HPPA board.
|
|
|
|
@end table
|
|
|
|
@node SH
|
|
@subsection Hitachi SH
|
|
|
|
@table @code
|
|
|
|
@kindex target hms@r{, with Hitachi SH}
|
|
@item target hms @var{dev}
|
|
A Hitachi SH board attached via serial line to your host. Use special
|
|
commands @code{device} and @code{speed} to control the serial line and
|
|
the communications speed used.
|
|
|
|
@kindex target e7000@r{, with Hitachi SH}
|
|
@item target e7000 @var{dev}
|
|
E7000 emulator for Hitachi SH.
|
|
|
|
@kindex target sh3@r{, with SH}
|
|
@kindex target sh3e@r{, with SH}
|
|
@item target sh3 @var{dev}
|
|
@item target sh3e @var{dev}
|
|
Hitachi SH-3 and SH-3E target systems.
|
|
|
|
@end table
|
|
|
|
@node Sparclet
|
|
@subsection Tsqware Sparclet
|
|
|
|
@cindex Sparclet
|
|
|
|
@value{GDBN} enables developers to debug tasks running on
|
|
Sparclet targets from a Unix host.
|
|
@value{GDBN} uses code that runs on
|
|
both the Unix host and on the Sparclet target. The program
|
|
@code{@value{GDBP}} is installed and executed on the Unix host.
|
|
|
|
@table @code
|
|
@item remotetimeout @var{args}
|
|
@kindex remotetimeout
|
|
@value{GDBN} supports the option @code{remotetimeout}.
|
|
This option is set by the user, and @var{args} represents the number of
|
|
seconds @value{GDBN} waits for responses.
|
|
@end table
|
|
|
|
@cindex compiling, on Sparclet
|
|
When compiling for debugging, include the options @samp{-g} to get debug
|
|
information and @samp{-Ttext} to relocate the program to where you wish to
|
|
load it on the target. You may also want to add the options @samp{-n} or
|
|
@samp{-N} in order to reduce the size of the sections. Example:
|
|
|
|
@example
|
|
sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
|
|
@end example
|
|
|
|
You can use @code{objdump} to verify that the addresses are what you intended:
|
|
|
|
@example
|
|
sparclet-aout-objdump --headers --syms prog
|
|
@end example
|
|
|
|
@cindex running, on Sparclet
|
|
Once you have set
|
|
your Unix execution search path to find @value{GDBN}, you are ready to
|
|
run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
|
|
(or @code{sparclet-aout-gdb}, depending on your installation).
|
|
|
|
@value{GDBN} comes up showing the prompt:
|
|
|
|
@example
|
|
(gdbslet)
|
|
@end example
|
|
|
|
@menu
|
|
* Sparclet File:: Setting the file to debug
|
|
* Sparclet Connection:: Connecting to Sparclet
|
|
* Sparclet Download:: Sparclet download
|
|
* Sparclet Execution:: Running and debugging
|
|
@end menu
|
|
|
|
@node Sparclet File
|
|
@subsubsection Setting file to debug
|
|
|
|
The @value{GDBN} command @code{file} lets you choose with program to debug.
|
|
|
|
@example
|
|
(gdbslet) file prog
|
|
@end example
|
|
|
|
@need 1000
|
|
@value{GDBN} then attempts to read the symbol table of @file{prog}.
|
|
@value{GDBN} locates
|
|
the file by searching the directories listed in the command search
|
|
path.
|
|
If the file was compiled with debug information (option "-g"), source
|
|
files will be searched as well.
|
|
@value{GDBN} locates
|
|
the source files by searching the directories listed in the directory search
|
|
path (@pxref{Environment, ,Your program's environment}).
|
|
If it fails
|
|
to find a file, it displays a message such as:
|
|
|
|
@example
|
|
prog: No such file or directory.
|
|
@end example
|
|
|
|
When this happens, add the appropriate directories to the search paths with
|
|
the @value{GDBN} commands @code{path} and @code{dir}, and execute the
|
|
@code{target} command again.
|
|
|
|
@node Sparclet Connection
|
|
@subsubsection Connecting to Sparclet
|
|
|
|
The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
|
|
To connect to a target on serial port ``@code{ttya}'', type:
|
|
|
|
@example
|
|
(gdbslet) target sparclet /dev/ttya
|
|
Remote target sparclet connected to /dev/ttya
|
|
main () at ../prog.c:3
|
|
@end example
|
|
|
|
@need 750
|
|
@value{GDBN} displays messages like these:
|
|
|
|
@example
|
|
Connected to ttya.
|
|
@end example
|
|
|
|
@node Sparclet Download
|
|
@subsubsection Sparclet download
|
|
|
|
@cindex download to Sparclet
|
|
Once connected to the Sparclet target,
|
|
you can use the @value{GDBN}
|
|
@code{load} command to download the file from the host to the target.
|
|
The file name and load offset should be given as arguments to the @code{load}
|
|
command.
|
|
Since the file format is aout, the program must be loaded to the starting
|
|
address. You can use @code{objdump} to find out what this value is. The load
|
|
offset is an offset which is added to the VMA (virtual memory address)
|
|
of each of the file's sections.
|
|
For instance, if the program
|
|
@file{prog} was linked to text address 0x1201000, with data at 0x12010160
|
|
and bss at 0x12010170, in @value{GDBN}, type:
|
|
|
|
@example
|
|
(gdbslet) load prog 0x12010000
|
|
Loading section .text, size 0xdb0 vma 0x12010000
|
|
@end example
|
|
|
|
If the code is loaded at a different address then what the program was linked
|
|
to, you may need to use the @code{section} and @code{add-symbol-file} commands
|
|
to tell @value{GDBN} where to map the symbol table.
|
|
|
|
@node Sparclet Execution
|
|
@subsubsection Running and debugging
|
|
|
|
@cindex running and debugging Sparclet programs
|
|
You can now begin debugging the task using @value{GDBN}'s execution control
|
|
commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
|
|
manual for the list of commands.
|
|
|
|
@example
|
|
(gdbslet) b main
|
|
Breakpoint 1 at 0x12010000: file prog.c, line 3.
|
|
(gdbslet) run
|
|
Starting program: prog
|
|
Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
|
|
3 char *symarg = 0;
|
|
(gdbslet) step
|
|
4 char *execarg = "hello!";
|
|
(gdbslet)
|
|
@end example
|
|
|
|
@node Sparclite
|
|
@subsection Fujitsu Sparclite
|
|
|
|
@table @code
|
|
|
|
@kindex target sparclite
|
|
@item target sparclite @var{dev}
|
|
Fujitsu sparclite boards, used only for the purpose of loading.
|
|
You must use an additional command to debug the program.
|
|
For example: target remote @var{dev} using @value{GDBN} standard
|
|
remote protocol.
|
|
|
|
@end table
|
|
|
|
@node ST2000
|
|
@subsection Tandem ST2000
|
|
|
|
@value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
|
|
STDBUG protocol.
|
|
|
|
To connect your ST2000 to the host system, see the manufacturer's
|
|
manual. Once the ST2000 is physically attached, you can run:
|
|
|
|
@example
|
|
target st2000 @var{dev} @var{speed}
|
|
@end example
|
|
|
|
@noindent
|
|
to establish it as your debugging environment. @var{dev} is normally
|
|
the name of a serial device, such as @file{/dev/ttya}, connected to the
|
|
ST2000 via a serial line. You can instead specify @var{dev} as a TCP
|
|
connection (for example, to a serial line attached via a terminal
|
|
concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
|
|
|
|
The @code{load} and @code{attach} commands are @emph{not} defined for
|
|
this target; you must load your program into the ST2000 as you normally
|
|
would for standalone operation. @value{GDBN} reads debugging information
|
|
(such as symbols) from a separate, debugging version of the program
|
|
available on your host computer.
|
|
@c FIXME!! This is terribly vague; what little content is here is
|
|
@c basically hearsay.
|
|
|
|
@cindex ST2000 auxiliary commands
|
|
These auxiliary @value{GDBN} commands are available to help you with the ST2000
|
|
environment:
|
|
|
|
@table @code
|
|
@item st2000 @var{command}
|
|
@kindex st2000 @var{cmd}
|
|
@cindex STDBUG commands (ST2000)
|
|
@cindex commands to STDBUG (ST2000)
|
|
Send a @var{command} to the STDBUG monitor. See the manufacturer's
|
|
manual for available commands.
|
|
|
|
@item connect
|
|
@cindex connect (to STDBUG)
|
|
Connect the controlling terminal to the STDBUG command monitor. When
|
|
you are done interacting with STDBUG, typing either of two character
|
|
sequences gets you back to the @value{GDBN} command prompt:
|
|
@kbd{@key{RET}~.} (Return, followed by tilde and period) or
|
|
@kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
|
|
@end table
|
|
|
|
@node Z8000
|
|
@subsection Zilog Z8000
|
|
|
|
@cindex Z8000
|
|
@cindex simulator, Z8000
|
|
@cindex Zilog Z8000 simulator
|
|
|
|
When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
|
|
a Z8000 simulator.
|
|
|
|
For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
|
|
unsegmented variant of the Z8000 architecture) or the Z8001 (the
|
|
segmented variant). The simulator recognizes which architecture is
|
|
appropriate by inspecting the object code.
|
|
|
|
@table @code
|
|
@item target sim @var{args}
|
|
@kindex sim
|
|
@kindex target sim@r{, with Z8000}
|
|
Debug programs on a simulated CPU. If the simulator supports setup
|
|
options, specify them via @var{args}.
|
|
@end table
|
|
|
|
@noindent
|
|
After specifying this target, you can debug programs for the simulated
|
|
CPU in the same style as programs for your host computer; use the
|
|
@code{file} command to load a new program image, the @code{run} command
|
|
to run your program, and so on.
|
|
|
|
As well as making available all the usual machine registers
|
|
(@pxref{Registers, ,Registers}), the Z8000 simulator provides three
|
|
additional items of information as specially named registers:
|
|
|
|
@table @code
|
|
|
|
@item cycles
|
|
Counts clock-ticks in the simulator.
|
|
|
|
@item insts
|
|
Counts instructions run in the simulator.
|
|
|
|
@item time
|
|
Execution time in 60ths of a second.
|
|
|
|
@end table
|
|
|
|
You can refer to these values in @value{GDBN} expressions with the usual
|
|
conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
|
|
conditional breakpoint that suspends only after at least 5000
|
|
simulated clock ticks.
|
|
|
|
@node Architectures
|
|
@section Architectures
|
|
|
|
This section describes characteristics of architectures that affect
|
|
all uses of @value{GDBN} with the architecture, both native and cross.
|
|
|
|
@menu
|
|
* A29K::
|
|
* Alpha::
|
|
* MIPS::
|
|
@end menu
|
|
|
|
@node A29K
|
|
@subsection A29K
|
|
|
|
@table @code
|
|
|
|
@kindex set rstack_high_address
|
|
@cindex AMD 29K register stack
|
|
@cindex register stack, AMD29K
|
|
@item set rstack_high_address @var{address}
|
|
On AMD 29000 family processors, registers are saved in a separate
|
|
@dfn{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 probably want to precede with @samp{0x} to specify in
|
|
hexadecimal.
|
|
|
|
@kindex show rstack_high_address
|
|
@item show rstack_high_address
|
|
Display the current limit of the register stack, on AMD 29000 family
|
|
processors.
|
|
|
|
@end table
|
|
|
|
@node Alpha
|
|
@subsection Alpha
|
|
|
|
See the following section.
|
|
|
|
@node MIPS
|
|
@subsection MIPS
|
|
|
|
@cindex stack on Alpha
|
|
@cindex stack on MIPS
|
|
@cindex Alpha stack
|
|
@cindex MIPS stack
|
|
Alpha- and 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:
|
|
|
|
@table @code
|
|
@cindex @code{heuristic-fence-post} (Alpha, MIPS)
|
|
@item set heuristic-fence-post @var{limit}
|
|
Restrict @value{GDBN} to examining at most @var{limit} bytes in its
|
|
search for the beginning of a function. A value of @var{0} (the
|
|
default) means there is no limit. However, except for @var{0}, the
|
|
larger the limit the more bytes @code{heuristic-fence-post} must search
|
|
and therefore the longer it takes to run.
|
|
|
|
@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 Alpha or MIPS processors.
|
|
|
|
|
|
@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, see @ref{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
|
|
* Debugging Output:: Optional messages about internal happenings
|
|
@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.
|
|
|
|
@emph{Note:} @code{set prompt} does not add a space for you after the
|
|
prompt you set. This allows you to set a prompt which ends in a space
|
|
or a prompt that does not.
|
|
|
|
@table @code
|
|
@kindex set prompt
|
|
@item set prompt @var{newprompt}
|
|
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
|
|
@sc{gnu} library provides consistent behavior for programs which provide a
|
|
command line interface to the user. Advantages are @sc{gnu} Emacs-style
|
|
or @dfn{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
|
|
@kindex GDBHISTFILE
|
|
@item set history filename @var{fname}
|
|
Set the name of the @value{GDBN} command history file to @var{fname}.
|
|
This is the file where @value{GDBN} reads an initial command history
|
|
list, and where it writes the command history from this session when it
|
|
exits. You can access this list 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} (@file{./_gdb_history} on MS-DOS) 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} keeps 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 do 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 @sc{gnu} 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 shows
|
|
@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 terminal
|
|
driver software. For example, on Unix @value{GDBN} uses 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
|
|
@kindex set height
|
|
@kindex set width
|
|
@kindex show width
|
|
@kindex show height
|
|
@item set height @var{lpp}
|
|
@itemx show height
|
|
@itemx set width @var{cpl}
|
|
@itemx show width
|
|
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} does 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.
|
|
|
|
Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
|
|
from wrapping its output.
|
|
@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 input-radix
|
|
@item set input-radix @var{base}
|
|
Set the default base for numeric input. Supported choices
|
|
for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
|
|
specified either unambiguously or using the current default radix; for
|
|
example, any of
|
|
|
|
@smallexample
|
|
set radix 012
|
|
set radix 10.
|
|
set radix 0xa
|
|
@end smallexample
|
|
|
|
@noindent
|
|
sets the base to decimal. On the other hand, @samp{set radix 10}
|
|
leaves the radix unchanged no matter what it was.
|
|
|
|
@kindex set output-radix
|
|
@item set output-radix @var{base}
|
|
Set the default base for numeric display. Supported choices
|
|
for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
|
|
specified either unambiguously or using the current default radix.
|
|
|
|
@kindex show input-radix
|
|
@item show input-radix
|
|
Display the current default base for numeric input.
|
|
|
|
@kindex show output-radix
|
|
@item show output-radix
|
|
Display the current default base for numeric 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. This makes @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).
|
|
|
|
@kindex show confirm
|
|
@item show confirm
|
|
Displays state of confirmation requests.
|
|
|
|
@end table
|
|
|
|
@node Debugging Output
|
|
@section Optional messages about internal happenings
|
|
@table @code
|
|
@kindex set debug arch
|
|
@item set debug arch
|
|
Turns on or off display of gdbarch debugging info. The default is off
|
|
@kindex show debug arch
|
|
@item show debug arch
|
|
Displays the current state of displaying gdbarch debugging info.
|
|
@kindex set debug event
|
|
@item set debug event
|
|
Turns on or off display of @value{GDBN} event debugging info. The
|
|
default is off.
|
|
@kindex show debug event
|
|
@item show debug event
|
|
Displays the current state of displaying @value{GDBN} event debugging
|
|
info.
|
|
@kindex set debug expression
|
|
@item set debug expression
|
|
Turns on or off display of @value{GDBN} expression debugging info. The
|
|
default is off.
|
|
@kindex show debug expression
|
|
@item show debug expression
|
|
Displays the current state of displaying @value{GDBN} expression
|
|
debugging info.
|
|
@kindex set debug overload
|
|
@item set debug overload
|
|
Turns on or off display of @value{GDBN} C@t{++} overload debugging
|
|
info. This includes info such as ranking of functions, etc. The default
|
|
is off.
|
|
@kindex show debug overload
|
|
@item show debug overload
|
|
Displays the current state of displaying @value{GDBN} C@t{++} overload
|
|
debugging info.
|
|
@kindex set debug remote
|
|
@cindex packets, reporting on stdout
|
|
@cindex serial connections, debugging
|
|
@item set debug remote
|
|
Turns on or off display of reports on all packets sent back and forth across
|
|
the serial line to the remote machine. The info is printed on the
|
|
@value{GDBN} standard output stream. The default is off.
|
|
@kindex show debug remote
|
|
@item show debug remote
|
|
Displays the state of display of remote packets.
|
|
@kindex set debug serial
|
|
@item set debug serial
|
|
Turns on or off display of @value{GDBN} serial debugging info. The
|
|
default is off.
|
|
@kindex show debug serial
|
|
@item show debug serial
|
|
Displays the current state of displaying @value{GDBN} serial debugging
|
|
info.
|
|
@kindex set debug target
|
|
@item set debug target
|
|
Turns on or off display of @value{GDBN} target debugging info. This info
|
|
includes what is going on at the target level of GDB, as it happens. The
|
|
default is off.
|
|
@kindex show debug target
|
|
@item show debug target
|
|
Displays the current state of displaying @value{GDBN} target debugging
|
|
info.
|
|
@kindex set debug varobj
|
|
@item set debug varobj
|
|
Turns on or off display of @value{GDBN} variable object debugging
|
|
info. The default is off.
|
|
@kindex show debug varobj
|
|
@item show debug varobj
|
|
Displays the current state of displaying @value{GDBN} variable object
|
|
debugging info.
|
|
@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. User commands may accept up to 10 arguments
|
|
separated by whitespace. Arguments are accessed within the user command
|
|
via @var{$arg0@dots{}$arg9}. A trivial example:
|
|
|
|
@smallexample
|
|
define adder
|
|
print $arg0 + $arg1 + $arg2
|
|
@end smallexample
|
|
|
|
@noindent
|
|
To execute the command use:
|
|
|
|
@smallexample
|
|
adder 1 2 3
|
|
@end smallexample
|
|
|
|
@noindent
|
|
This defines the command @code{adder}, which prints the sum of
|
|
its three arguments. Note the arguments are text substitutions, so they may
|
|
reference variables, use complex expressions, or even perform inferior
|
|
functions calls.
|
|
|
|
@table @code
|
|
|
|
@kindex define
|
|
@item define @var{commandname}
|
|
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}.
|
|
|
|
@kindex if
|
|
@kindex else
|
|
@item if
|
|
Takes a single argument, which is an expression to evaluate.
|
|
It is followed by a series of commands that are executed
|
|
only if the expression is true (nonzero).
|
|
There can then optionally be a line @code{else}, followed
|
|
by a series of commands that are only executed if the expression
|
|
was false. The end of the list is marked by a line containing @code{end}.
|
|
|
|
@kindex while
|
|
@item while
|
|
The syntax is similar to @code{if}: the command takes a single argument,
|
|
which is an expression to evaluate, and must be followed by the commands to
|
|
execute, one per line, terminated by an @code{end}.
|
|
The commands are executed repeatedly as long as the expression
|
|
evaluates to true.
|
|
|
|
@kindex document
|
|
@item document @var{commandname}
|
|
Document the user-defined command @var{commandname}, so that it can be
|
|
accessed by @code{help}. 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} displays the documentation you have written.
|
|
|
|
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.
|
|
|
|
@kindex help user-defined
|
|
@item help user-defined
|
|
List all user-defined commands, with the first line of the documentation
|
|
(if any) for each.
|
|
|
|
@kindex show user
|
|
@item show user
|
|
@itemx show user @var{commandname}
|
|
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
|
|
|
|
When user-defined commands are executed, the
|
|
commands of the definition are not printed. An error in any command
|
|
stops execution of the user-defined command.
|
|
|
|
If used interactively, commands that would ask for confirmation 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 hooks
|
|
@cindex hooks, for commands
|
|
@cindex hooks, pre-command
|
|
|
|
@kindex hook
|
|
@kindex hook-
|
|
You may define @dfn{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.
|
|
|
|
@cindex hooks, post-command
|
|
@kindex hookpost
|
|
@kindex hookpost-
|
|
A hook may also be defined which is run after the command you executed.
|
|
Whenever you run the command @samp{foo}, if the user-defined command
|
|
@samp{hookpost-foo} exists, it is executed (with no arguments) after
|
|
that command. Post-execution hooks may exist simultaneously with
|
|
pre-execution hooks, for the same command.
|
|
|
|
It is valid for a hook to call the command which it hooks. If this
|
|
occurs, the hook is not re-executed, thereby avoiding infinte recursion.
|
|
|
|
@c It would be nice if hookpost could be passed a parameter indicating
|
|
@c if the command it hooks executed properly or not. FIXME!
|
|
|
|
@kindex stop@r{, a pseudo-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.
|
|
|
|
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
|
|
|
|
As a further example, to hook at the begining and end of the @code{echo}
|
|
command, and to add extra text to the beginning and end of the message,
|
|
you could define:
|
|
|
|
@example
|
|
define hook-echo
|
|
echo <<<---
|
|
end
|
|
|
|
define hookpost-echo
|
|
echo --->>>\n
|
|
end
|
|
|
|
(@value{GDBP}) echo Hello World
|
|
<<<---Hello World--->>>
|
|
(@value{GDBP})
|
|
|
|
@end example
|
|
|
|
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
|
|
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{.gdbinit}
|
|
@cindex @file{gdb.ini}
|
|
When you start @value{GDBN}, it automatically executes commands from its
|
|
@dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
|
|
port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
|
|
limitations of file names imposed by DOS filesystems.}.
|
|
During startup, @value{GDBN} does the following:
|
|
|
|
@enumerate
|
|
@item
|
|
Reads the init file (if any) in your home directory@footnote{On
|
|
DOS/Windows systems, the home directory is the one pointed to by the
|
|
@code{HOME} environment variable.}.
|
|
|
|
@item
|
|
Processes command line options and operands.
|
|
|
|
@item
|
|
Reads the init file (if any) in the current working directory.
|
|
|
|
@item
|
|
Reads command files specified by the @samp{-x} option.
|
|
@end enumerate
|
|
|
|
The init file in your home directory can set options (such as @samp{set
|
|
complaints}) that affect subsequent processing of command line options
|
|
and operands. Init files are not executed if you use the @samp{-nx}
|
|
option (@pxref{Mode Options, ,Choosing modes}).
|
|
|
|
@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 @value{GDBN} 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:
|
|
|
|
@cindex @file{.vxgdbinit}
|
|
@itemize @bullet
|
|
@item
|
|
VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
|
|
|
|
@cindex @file{.os68gdbinit}
|
|
@item
|
|
OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
|
|
|
|
@cindex @file{.esgdbinit}
|
|
@item
|
|
ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
|
|
@end itemize
|
|
|
|
You can also request the execution of a command file with the
|
|
@code{source} command:
|
|
|
|
@table @code
|
|
@kindex source
|
|
@item source @var{filename}
|
|
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.
|
|
|
|
@value{GDBN} also accepts command input from standard input. In this
|
|
mode, normal output goes to standard output and error output goes to
|
|
standard error. Errors in a command file supplied on standard input do
|
|
not terminate execution of the command file --- execution continues with
|
|
the next command.
|
|
|
|
@example
|
|
gdb < cmds > log 2>&1
|
|
@end example
|
|
|
|
(The syntax above will vary depending on the shell used.) This example
|
|
will execute commands from the file @file{cmds}. All output and errors
|
|
would be directed to @file{log}.
|
|
|
|
@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
|
|
@kindex echo
|
|
@item echo @var{text}
|
|
@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 is 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
|
|
|
|
@kindex output
|
|
@item output @var{expression}
|
|
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.
|
|
|
|
@kindex printf
|
|
@item printf @var{string}, @var{expressions}@dots{}
|
|
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 the C
|
|
subroutine
|
|
@c FIXME: the above implies that at least all ANSI C formats are
|
|
@c supported, but it isn't true: %E and %G don't work (or so it seems).
|
|
@c Either this is a bug, or the manual should document what formats are
|
|
@c supported.
|
|
|
|
@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
|
|
|
|
@node TUI
|
|
@chapter @value{GDBN} Text User Interface
|
|
@cindex TUI
|
|
|
|
@menu
|
|
* TUI Overview:: TUI overview
|
|
* TUI Keys:: TUI key bindings
|
|
* TUI Commands:: TUI specific commands
|
|
* TUI Configuration:: TUI configuration variables
|
|
@end menu
|
|
|
|
The @value{GDBN} Text User Interface, TUI in short,
|
|
is a terminal interface which uses the @code{curses} library
|
|
to show the source file, the assembly output, the program registers
|
|
and @value{GDBN} commands in separate text windows.
|
|
The TUI is available only when @value{GDBN} is configured
|
|
with the @code{--enable-tui} configure option (@pxref{Configure Options}).
|
|
|
|
@node TUI Overview
|
|
@section TUI overview
|
|
|
|
The TUI has two display modes that can be switched while
|
|
@value{GDBN} runs:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
A curses (or TUI) mode in which it displays several text
|
|
windows on the terminal.
|
|
|
|
@item
|
|
A standard mode which corresponds to the @value{GDBN} configured without
|
|
the TUI.
|
|
@end itemize
|
|
|
|
In the TUI mode, @value{GDBN} can display several text window
|
|
on the terminal:
|
|
|
|
@table @emph
|
|
@item command
|
|
This window is the @value{GDBN} command window with the @value{GDBN}
|
|
prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
|
|
managed using readline but through the TUI. The @emph{command}
|
|
window is always visible.
|
|
|
|
@item source
|
|
The source window shows the source file of the program. The current
|
|
line as well as active breakpoints are displayed in this window.
|
|
The current program position is shown with the @samp{>} marker and
|
|
active breakpoints are shown with @samp{*} markers.
|
|
|
|
@item assembly
|
|
The assembly window shows the disassembly output of the program.
|
|
|
|
@item register
|
|
This window shows the processor registers. It detects when
|
|
a register is changed and when this is the case, registers that have
|
|
changed are highlighted.
|
|
|
|
@end table
|
|
|
|
The source, assembly and register windows are attached to the thread
|
|
and the frame position. They are updated when the current thread
|
|
changes, when the frame changes or when the program counter changes.
|
|
These three windows are arranged by the TUI according to several
|
|
layouts. The layout defines which of these three windows are visible.
|
|
The following layouts are available:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
source
|
|
|
|
@item
|
|
assembly
|
|
|
|
@item
|
|
source and assembly
|
|
|
|
@item
|
|
source and registers
|
|
|
|
@item
|
|
assembly and registers
|
|
|
|
@end itemize
|
|
|
|
@node TUI Keys
|
|
@section TUI Key Bindings
|
|
@cindex TUI key bindings
|
|
|
|
The TUI installs several key bindings in the readline keymaps
|
|
(@pxref{Command Line Editing}).
|
|
They allow to leave or enter in the TUI mode or they operate
|
|
directly on the TUI layout and windows. The following key bindings
|
|
are installed for both TUI mode and the @value{GDBN} standard mode.
|
|
|
|
@table @kbd
|
|
@kindex C-x C-a
|
|
@item C-x C-a
|
|
@kindex C-x a
|
|
@itemx C-x a
|
|
@kindex C-x A
|
|
@itemx C-x A
|
|
Enter or leave the TUI mode. When the TUI mode is left,
|
|
the curses window management is left and @value{GDBN} operates using
|
|
its standard mode writing on the terminal directly. When the TUI
|
|
mode is entered, the control is given back to the curses windows.
|
|
The screen is then refreshed.
|
|
|
|
@kindex C-x 1
|
|
@item C-x 1
|
|
Use a TUI layout with only one window. The layout will
|
|
either be @samp{source} or @samp{assembly}. When the TUI mode
|
|
is not active, it will switch to the TUI mode.
|
|
|
|
Think of this key binding as the Emacs @kbd{C-x 1} binding.
|
|
|
|
@kindex C-x 2
|
|
@item C-x 2
|
|
Use a TUI layout with at least two windows. When the current
|
|
layout shows already two windows, a next layout with two windows is used.
|
|
When a new layout is chosen, one window will always be common to the
|
|
previous layout and the new one.
|
|
|
|
Think of it as the Emacs @kbd{C-x 2} binding.
|
|
|
|
@end table
|
|
|
|
The following key bindings are handled only by the TUI mode:
|
|
|
|
@table @key
|
|
@kindex PgUp
|
|
@item PgUp
|
|
Scroll the active window one page up.
|
|
|
|
@kindex PgDn
|
|
@item PgDn
|
|
Scroll the active window one page down.
|
|
|
|
@kindex Up
|
|
@item Up
|
|
Scroll the active window one line up.
|
|
|
|
@kindex Down
|
|
@item Down
|
|
Scroll the active window one line down.
|
|
|
|
@kindex Left
|
|
@item Left
|
|
Scroll the active window one column left.
|
|
|
|
@kindex Right
|
|
@item Right
|
|
Scroll the active window one column right.
|
|
|
|
@kindex C-L
|
|
@item C-L
|
|
Refresh the screen.
|
|
|
|
@end table
|
|
|
|
In the TUI mode, the arrow keys are used by the active window
|
|
for scrolling. This means they are not available for readline. It is
|
|
necessary to use other readline key bindings such as @key{C-p}, @key{C-n},
|
|
@key{C-b} and @key{C-f}.
|
|
|
|
@node TUI Commands
|
|
@section TUI specific commands
|
|
@cindex TUI commands
|
|
|
|
The TUI has specific commands to control the text windows.
|
|
These commands are always available, that is they do not depend on
|
|
the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
|
|
is in the standard mode, using these commands will automatically switch
|
|
in the TUI mode.
|
|
|
|
@table @code
|
|
@item layout next
|
|
@kindex layout next
|
|
Display the next layout.
|
|
|
|
@item layout prev
|
|
@kindex layout prev
|
|
Display the previous layout.
|
|
|
|
@item layout src
|
|
@kindex layout src
|
|
Display the source window only.
|
|
|
|
@item layout asm
|
|
@kindex layout asm
|
|
Display the assembly window only.
|
|
|
|
@item layout split
|
|
@kindex layout split
|
|
Display the source and assembly window.
|
|
|
|
@item layout regs
|
|
@kindex layout regs
|
|
Display the register window together with the source or assembly window.
|
|
|
|
@item focus next | prev | src | asm | regs | split
|
|
@kindex focus
|
|
Set the focus to the named window.
|
|
This command allows to change the active window so that scrolling keys
|
|
can be affected to another window.
|
|
|
|
@item refresh
|
|
@kindex refresh
|
|
Refresh the screen. This is similar to using @key{C-L} key.
|
|
|
|
@item update
|
|
@kindex update
|
|
Update the source window and the current execution point.
|
|
|
|
@item winheight @var{name} +@var{count}
|
|
@itemx winheight @var{name} -@var{count}
|
|
@kindex winheight
|
|
Change the height of the window @var{name} by @var{count}
|
|
lines. Positive counts increase the height, while negative counts
|
|
decrease it.
|
|
|
|
@end table
|
|
|
|
@node TUI Configuration
|
|
@section TUI configuration variables
|
|
@cindex TUI configuration variables
|
|
|
|
The TUI has several configuration variables that control the
|
|
appearance of windows on the terminal.
|
|
|
|
@table @code
|
|
@item set tui border-kind @var{kind}
|
|
@kindex set tui border-kind
|
|
Select the border appearance for the source, assembly and register windows.
|
|
The possible values are the following:
|
|
@table @code
|
|
@item space
|
|
Use a space character to draw the border.
|
|
|
|
@item ascii
|
|
Use ascii characters + - and | to draw the border.
|
|
|
|
@item acs
|
|
Use the Alternate Character Set to draw the border. The border is
|
|
drawn using character line graphics if the terminal supports them.
|
|
|
|
@end table
|
|
|
|
@item set tui active-border-mode @var{mode}
|
|
@kindex set tui active-border-mode
|
|
Select the attributes to display the border of the active window.
|
|
The possible values are @code{normal}, @code{standout}, @code{reverse},
|
|
@code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
|
|
|
|
@item set tui border-mode @var{mode}
|
|
@kindex set tui border-mode
|
|
Select the attributes to display the border of other windows.
|
|
The @var{mode} can be one of the following:
|
|
@table @code
|
|
@item normal
|
|
Use normal attributes to display the border.
|
|
|
|
@item standout
|
|
Use standout mode.
|
|
|
|
@item reverse
|
|
Use reverse video mode.
|
|
|
|
@item half
|
|
Use half bright mode.
|
|
|
|
@item half-standout
|
|
Use half bright and standout mode.
|
|
|
|
@item bold
|
|
Use extra bright or bold mode.
|
|
|
|
@item bold-standout
|
|
Use extra bright or bold and standout mode.
|
|
|
|
@end table
|
|
|
|
@end table
|
|
|
|
@node Emacs
|
|
@chapter Using @value{GDBN} under @sc{gnu} Emacs
|
|
|
|
@cindex Emacs
|
|
@cindex @sc{gnu} Emacs
|
|
A special interface allows you to use @sc{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.
|
|
@c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
|
|
|
|
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 have no reason to use them from Emacs.
|
|
|
|
@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 does 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 proceeds 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 an absolute file 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{M-:} or @kbd{ESC :}, or typed in the @code{*scratch*} buffer, or
|
|
in your @file{.emacs} file) makes 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 @sc{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 &} indicates that you
|
|
wish special formatting, and also acts 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 recreates
|
|
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 cease
|
|
to correspond properly with the code.
|
|
|
|
@c The following dropped because Epoch is nonstandard. Reactivate
|
|
@c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
|
|
@ignore
|
|
@kindex Emacs Epoch environment
|
|
@kindex Epoch
|
|
@kindex inspect
|
|
|
|
Version 18 of @sc{gnu} 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
|
|
|
|
@include annotate.texi
|
|
@include gdbmi.texinfo
|
|
|
|
@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
|
|
@cindex fatal signal
|
|
@cindex debugger crash
|
|
@cindex crash of debugger
|
|
@item
|
|
If the debugger gets a fatal signal, for any input whatever, that is a
|
|
@value{GDBN} bug. Reliable debuggers never crash.
|
|
|
|
@cindex error on valid input
|
|
@item
|
|
If @value{GDBN} produces an error message for valid input, that is a
|
|
bug. (Note that if you're cross debugging, the problem may also be
|
|
somewhere in the connection to the target.)
|
|
|
|
@cindex invalid input
|
|
@item
|
|
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 @sc{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 @sc{gnu} Emacs
|
|
distribution.
|
|
@c should add a web page ref...
|
|
|
|
In any event, we also recommend that you send bug reports for
|
|
@value{GDBN} to this addresses:
|
|
|
|
@example
|
|
bug-gdb@@gnu.org
|
|
@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
|
|
@sc{gnu} Debugger Bugs
|
|
Free Software Foundation Inc.
|
|
59 Temple Place - Suite 330
|
|
Boston, MA 02111-1307
|
|
USA
|
|
@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. It may be that the bug has been reported previously, but neither
|
|
you nor we can know that unless your bug report is complete and
|
|
self-contained.
|
|
|
|
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}--2.8.1''.
|
|
|
|
@item
|
|
What compiler (and its version) was used to compile the program you are
|
|
debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
|
|
C Compiler''. For GCC, you can say @code{gcc --version} to get this
|
|
information; for other compilers, see the documentation for those
|
|
compilers.
|
|
|
|
@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. 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, and so on.
|
|
|
|
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.texinfo
|
|
@c Use -I with makeinfo to point to the appropriate directory,
|
|
@c environment var TEXINPUTS with TeX.
|
|
@include rluser.texinfo
|
|
@include inc-hist.texinfo
|
|
|
|
|
|
@node Formatting Documentation
|
|
@appendix Formatting Documentation
|
|
|
|
@cindex @value{GDBN} reference card
|
|
@cindex reference card
|
|
The @value{GDBN} 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 @value{GDBN} reference card is designed to print in @dfn{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 @value{GDBN} 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.
|
|
|
|
@value{GDBN} 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-@value{GDBVN}/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 @sc{gnu}
|
|
Emacs or the standalone @code{info} program, available as part of the
|
|
@sc{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
|
|
@value{GDBN} 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 either read or
|
|
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 type:
|
|
|
|
@example
|
|
make gdb.dvi
|
|
@end example
|
|
|
|
Then give @file{gdb.dvi} to your @sc{dvi} printing program.
|
|
|
|
@node Installing GDB
|
|
@appendix Installing @value{GDBN}
|
|
@cindex configuring @value{GDBN}
|
|
@cindex installation
|
|
|
|
@value{GDBN} comes with a @code{configure} script that automates the process
|
|
of preparing @value{GDBN} 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 @value{GDBN} 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 @value{GDBN} distribution includes all the source code you need for
|
|
@value{GDBN} in a single directory, whose name is usually composed by
|
|
appending the version number to @samp{gdb}.
|
|
|
|
For example, the @value{GDBN} 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 @value{GDBN} and all its supporting libraries
|
|
|
|
@item gdb-@value{GDBVN}/gdb
|
|
the source specific to @value{GDBN} itself
|
|
|
|
@item gdb-@value{GDBVN}/bfd
|
|
source for the Binary File Descriptor library
|
|
|
|
@item gdb-@value{GDBVN}/include
|
|
@sc{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 @sc{gnu} command-line interface
|
|
|
|
@item gdb-@value{GDBVN}/glob
|
|
source for the @sc{gnu} filename pattern-matching subroutine
|
|
|
|
@item gdb-@value{GDBVN}/mmalloc
|
|
source for the @sc{gnu} memory-mapped malloc package
|
|
@end table
|
|
|
|
The simplest way to configure and build @value{GDBN} 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 @value{GDBN} 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 @value{GDBN} will run.
|
|
(You can often leave off @var{host}; @code{configure} tries to guess the
|
|
correct value by examining your system.)
|
|
|
|
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.
|
|
|
|
@need 750
|
|
@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 @value{GDBN} 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 @value{GDBN} uses the shell to start your program---some systems refuse to
|
|
let @value{GDBN} debug child processes whose programs are not readable.
|
|
|
|
@menu
|
|
* Separate Objdir:: Compiling @value{GDBN} 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 @value{GDBN} in another directory
|
|
|
|
If you want to run @value{GDBN} 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 (@sc{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 is assumed.)
|
|
|
|
For example, with version @value{GDBVN}, you can build @value{GDBN} 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 @value{GDBN} itself in
|
|
@file{gdb-sun4/gdb}.
|
|
|
|
One popular reason to build several @value{GDBN} configurations in separate
|
|
directories is to configure @value{GDBN} for cross-compiling (where
|
|
@value{GDBN} runs on one machine---the @dfn{host}---while debugging
|
|
programs that run on another machine---the @dfn{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{dirname}/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 @value{GDBN} 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 i386-linux
|
|
i386-pc-linux-gnu
|
|
% sh config.sub alpha-linux
|
|
alpha-unknown-linux-gnu
|
|
% sh config.sub hp9k700
|
|
hppa1.1-hp-hpux
|
|
% sh config.sub sun4
|
|
sparc-sun-sunos4.1.1
|
|
% sh config.sub sun3
|
|
m68k-sun-sunos4.1.1
|
|
% sh config.sub i986v
|
|
Invalid configuration `i986v': machine `i986v' not recognized
|
|
@end smallexample
|
|
|
|
@noindent
|
|
@code{config.sub} is also distributed in the @value{GDBN} 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}.
|
|
|
|
@example
|
|
configure @r{[}--help@r{]}
|
|
@r{[}--prefix=@var{dir}@r{]}
|
|
@r{[}--exec-prefix=@var{dir}@r{]}
|
|
@r{[}--srcdir=@var{dirname}@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 --exec-prefix=@var{dir}
|
|
Configure the source to install programs under directory
|
|
@file{@var{dir}}.
|
|
|
|
@c avoid splitting the warning from the explanation:
|
|
@need 2000
|
|
@item --srcdir=@var{dirname}
|
|
@strong{Warning: using this option requires @sc{gnu} @code{make}, or another
|
|
@code{make} that implements the @code{VPATH} feature.}@*
|
|
Use this option to make configurations in directories separate from the
|
|
@value{GDBN} 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{dirname}. @code{configure} creates directories under
|
|
the working directory in parallel to the source directories below
|
|
@var{dirname}.
|
|
|
|
@item --norecursion
|
|
Configure only the directory level where @code{configure} is executed; do not
|
|
propagate configuration to subdirectories.
|
|
|
|
@item --target=@var{target}
|
|
Configure @value{GDBN} for cross-debugging programs running on the specified
|
|
@var{target}. Without this option, @value{GDBN} is configured to debug
|
|
programs that run on the same machine (@var{host}) as @value{GDBN} itself.
|
|
|
|
There is no convenient way to generate a list of all available targets.
|
|
|
|
@item @var{host} @dots{}
|
|
Configure @value{GDBN} to run on the specified @var{host}.
|
|
|
|
There is no convenient way to generate a list of all available hosts.
|
|
@end table
|
|
|
|
There are many other options available as well, but they are generally
|
|
needed for special purposes only.
|
|
|
|
@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: doc@cygnus.com, 1991.
|
|
@end tex
|
|
|
|
@c TeX can handle the contents at the start but makeinfo 3.12 can not
|
|
@ifinfo
|
|
@contents
|
|
@end ifinfo
|
|
@ifhtml
|
|
@contents
|
|
@end ifhtml
|
|
|
|
@bye
|