gdb.texinfo

这个是LINUX下的GDB调度工具的源码

Andrew Cagney (releases 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
Jim Blandy (release 4.18);
Jason Molenda (release 4.17);
Stan Shebs (release 4.14);
Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
Jim Kingdon (releases 3.5, 3.4, and 3.3);
and Randy Smith (releases 3.2, 3.1, and 3.0).

Richard Stallman, assisted at various times by Peter TerMaat, Chris
Hanson, and Richard Mlynarik, handled releases through 2.8.

Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
in @value{GDBN}, with significant additional contributions from Per
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
much general update work leading to release 3.0).

@value{GDBN} uses the BFD subroutine library to examine multiple
object-file formats; BFD was a joint project of David V.
Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.

David Johnson wrote the original COFF support; Pace Willison did
the original support for encapsulated COFF.

Brent Benson of Harris Computer Systems contributed DWARF 2 support.

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.
Marko Mlinar contributed OpenRISC 1000 support.

Andreas Schwab contributed M68K @sc{gnu}/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
Modula-2 support, and contributed the Languages chapter of this manual.

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 (now Renesas America), Ltd. sponsored the support for
H8/300, H8/500, and Super-H processors.

NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.

Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
processors.

Toshiba sponsored the support for the TX39 Mips processor.

Matsushita sponsored the support for the MN10200 and MN10300 processors.

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 Text User Interface (nee Terminal User Interface):
Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni.  Kim Haase
provided HP-specific information in this manual.

DJ Delorie ported @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.

Jim Blandy added support for preprocessor macros, while working for Red
Hat.

@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