gdb.texinfo

这个是LINUX下的GDB调度工具的源码

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}
* Logging output::              How to log @value{GDBN}'s output to a file
@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:

@smallexample
@value{GDBP} @var{program}
@end smallexample

@noindent
You can also start with both an executable program and a core file
specified:

@smallexample
@value{GDBP} @var{program} @var{core}
@end smallexample

You can, instead, specify a process ID as a second argument, if you want
to debug a running process:

@smallexample
@value{GDBP} @var{program} 1234
@end smallexample

@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.
@smallexample
gdb --args gcc -O2 -c foo.c
@end smallexample
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

@smallexample
@value{GDBP} -help
@end smallexample

@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:

@smallexample
gdb -batch -nx -mapped -readnow programname
@end smallexample

@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

@smallexample
Program exited normally.
@end smallexample

@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