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早期freebsd实现

     Invalid configuration `i786v': machine `i786v' not recognized

`config.sub' is also distributed in the GDB source directory
(`gdb-4.7', for version 4.7).


`configure' Options
====================

   Here is a summary of the `configure' options and arguments that are
most often useful for building GDB.  `configure' also has several other
options not listed here.  *note : (configure.info)What Configure Does,
for a full explanation of `configure'.

     configure [--help]
               [--prefix=DIR]
               [--srcdir=PATH]
               [--norecursion] [--rm]
               [--target=TARGET] HOST

You may introduce options with a single `-' rather than `--' if you
prefer; but you may abbreviate option names if you use `--'.

`--help'
     Display a quick summary of how to invoke `configure'.

`-prefix=DIR'
     Configure the source to install programs and files under directory
     `DIR'.

`--srcdir=PATH'
     *Warning: using this option requires GNU `make', or another `make'
     that implements the `VPATH' feature.*
     Use this option to make configurations in directories separate
     from the GDB source directories.  Among other things, you can use
     this to build (or maintain) several configurations simultaneously,
     in separate directories.  `configure' writes configuration
     specific files in the current directory, but arranges for them to
     use the source in the directory PATH.  `configure' will create
     directories under the working directory in parallel to the source
     directories below PATH.

`--norecursion'
     Configure only the directory level where `configure' is executed;
     do not propagate configuration to subdirectories.

`--rm'
     Remove the configuration that the other arguments specify.

`--target=TARGET'
     Configure GDB for cross-debugging programs running on the specified
     TARGET.  Without this option, GDB is configured to debug programs
     that run on the same machine (HOST) as GDB itself.

     There is no convenient way to generate a list of all available
     targets.

`HOST ...'
     Configure GDB to run on the specified HOST.

     There is no convenient way to generate a list of all available
     hosts.

`configure' accepts other options, for compatibility with configuring
other GNU tools recursively; but these are the only options that affect
GDB or its supporting libraries.



Languages other than C
=======================

GDB provides some support for debugging C++ progams.  Partial Modula-2
support is now in GDB.  GDB should work with FORTRAN programs.  (If you
have problems, please send a bug report; you may have to refer to some
FORTRAN variables with a trailing underscore).  I am not aware of
anyone who is working on getting gdb to use the syntax of any other
language.  Pascal programs which use sets, subranges, file variables,
or nested functions will not currently work.


Kernel debugging
=================

I have't done this myself so I can't really offer any advice.
Remote debugging over serial lines works fine, but the kernel debugging
code in here has not been tested in years.  Van Jacobson has
better kernel debugging, but the UC lawyers won't let FSF have it.


Remote debugging
=================

The files m68k-stub.c, i386-stub.c, and sparc-stub.c are examples of
remote stubs to be used with remote.c.  They are designed to run
standalone on a 68k, 386, or SPARC cpu and communicate properly with
the remote.c stub over a serial line.

The file rem-multi.shar contains a general stub that can probably
run on various different flavors of unix to allow debugging over a
serial line from one machine to another.

Some working remote interfaces for talking to existing ROM monitors
are:
	remote-eb.c	 AMD 29000 "EBMON"
	remote-hms.c	 Hitachi Micro Systems H8/300 monitor
	remote-nindy.c   Intel 960 "Nindy"
	remote-adapt.c	 AMD 29000 "Adapt"
	remote-mm.c	 AMD 29000 "minimon"

Remote-vx.c and the vx-share subdirectory contain a remote interface for the
VxWorks realtime kernel, which communicates over TCP using the Sun
RPC library.  This would be a useful starting point for other remote-
via-ethernet back ends.


Reporting Bugs
===============

The correct address for reporting bugs found in gdb is
"[e-mail]".  Please email all bugs to that address.
Please include the GDB version number (e.g. gdb-4.7), and how
you configured it (e.g. "sun4" or "mach386 host, i586-intel-synopsys
target").

Known bugs:

  * If you run with a watchpoint enabled, breakpoints will become
    erratic and might not stop the program.  Disabling or deleting the
    watchpoint will fix the problem.

  * Under Ultrix 4.2 (DECstation-3100), we have seen problems with backtraces
    after interrupting the inferior out of a read().  The problem is caused by
    ptrace() returning an incorrect value for register 30.  As far as we can
    tell, this is a kernel problem.  Any help with this would be greatly
    appreciated.

  * The IBM RS6000 (running AIX 3.1) has problems doing backtraces when stopped
    inside of library routines.  It also reports incorrect values for arguments
    of functions under some circumstances.

  * Most SPARC versions of GDB report incorrect values of struct arguments to
    functions.

GDB can produce warnings about symbols that it does not understand.  By
default, these warnings are disabled.  You can enable them by executing
`set complaint 10' (which you can put in your ~/.gdbinit if you like).
I recommend doing this if you are working on a compiler, assembler,
linker, or gdb, since it will point out problems that you may be able
to fix.  Warnings produced during symbol reading indicate some mismatch
between the object file and GDB's symbol reading code.  In many cases,
it's a mismatch between the specs for the object file format, and what
the compiler actually outputs or the debugger actually understands.

If you port gdb to a new machine, please send the required changes to
[e-mail].  There's lots of information about doing your
own port in the file gdb-4.7/gdb/doc/gdbint.texinfo, which you can
print out, or read with `info' (see the Makefile.in there).  If your
changes are more than a few lines, obtain and send in a copyright
assignment from [e-mail], as described in the section
`Writing Code for GDB' below.


X Windows versus GDB
=====================

xgdb is obsolete.  We are not doing any development or support of it.

There is an "xxgdb", which shows more promise, which was posted to
comp.sources.x.

For those intersted in auto display of source and the availability of
an editor while debugging I suggest trying gdb-mode in gnu-emacs
(Try typing M-x gdb RETURN).  Comments on this mode are welcome.


Writing Code for GDB
=====================

Documentation about GDB's internals is in the subdirectory doc, as
`gdbint.texinfo'.  In particular, there is a `cookbook' there on how
to port GDB to a new machine.  You can read it by hand, print it
by using TeX and texinfo, or process it into an `info' file for use
with Emacs' info mode or the standalone `info' program.

We appreciate having users contribute code that is of general use, but
for it to be included in future GDB releases it must be cleanly
written.  We do not want to include changes that will needlessly make
future maintainance difficult.  It is not much harder to do things
right, and in the long term it is worth it to the GNU project, and
probably to you individually as well.

If you make substantial changes, you'll have to file a copyright
assignment with the Free Software Foundation before we can produce a
release that includes your changes.  Send mail requesting the copyright
assignment to [e-mail].  Do this early, like before the
changes actually work, or even before you start them, because a manager
or lawyer on your end will probably make this a slow process.

Please code according to the GNU coding standards.  If you do not have
a copy, you can request one by sending mail to [e-mail].

Please try to avoid making machine-specific changes to
machine-independent files.  If this is unavoidable, put a hook in the
machine-independent file which calls a (possibly) machine-dependent
macro (for example, the IGNORE_SYMBOL macro can be used for any
symbols which need to be ignored on a specific machine.  Calling
IGNORE_SYMBOL in dbxread.c is a lot cleaner than a maze of #if
defined's).  The machine-independent code should do whatever "most"
machines want if the macro is not defined in param.h.  Using #if
defined can sometimes be OK (e.g. SET_STACK_LIMIT_HUGE) but should be
conditionalized on a specific feature of an operating system (set in
tm.h or xm.h) rather than something like #if defined(vax) or #if
defined(SYSV).  If you use an #ifdef on some symbol that is defined
in a header file (e.g. #ifdef TIOCSETP), *please* make sure that you
have #include'd the relevant header file in that module!

There is a list of all known `feature-test macros' in gdbint.texinfo.
Each such macro should be defined (or left undefined) in a host-dependent,
target-dependent, or native-dependent include file.  Not all of the
macros are cleanly separated this way, yet.  As you make changes, move
the code toward cleanliness.

It is better to replace entire routines which may be system-specific,
rather than put in a whole bunch of hooks which are probably not going
to be helpful for any purpose other than your changes.  For example,
if you want to modify dbxread.c to deal with DBX debugging symbols
which are in COFF files rather than BSD a.out files, do something
along the lines of a macro GET_NEXT_SYMBOL, which could have
different definitions for COFF and a.out, rather than trying to put
the necessary changes throughout all the code in dbxread.c that
currently assumes BSD format.

When generalizing GDB along a particular interface, please use an
attribute-struct rather than inserting tests or switch statements
everywhere.  For example, GDB has been generalized to handle multiple
kinds of remote interfaces -- not by #ifdef's everywhere, but by
defining the "target_ops" structure and having a current target (as
well as a stack of targets below it, for memory references).  Whenever
something needs to be done that depends on which remote interface we
are using, a flag in the current target_ops structure is tested (e.g.
`target_has_stack'), or a function is called through a pointer in the
current target_ops structure.  In this way, when a new remote interface
is added, only one module needs to be touched -- the one that actually
implements the new remote interface.  Other examples of
attribute-structs are BFD access to multiple kinds of object file
formats, or GDB's access to multiple source languages.

Please avoid duplicating code.  For example, in GDB 3.x all the stuff
in infptrace.c was duplicated in *-dep.c, and so changing something
was very painful.  In GDB 4.x, these have all been consolidated
into infptrace.c.  infptrace.c can deal with variations between
systems the same way any system-independent file would (hooks, #if
defined, etc.), and machines which are radically different don't need
to use infptrace.c at all.  The same was true of core_file_command
and exec_file_command.


Debugging gdb with itself
==========================

If gdb is limping on your machine, this is the preferred way to get it
fully functional.  Be warned that in some ancient Unix systems, like
Ultrix 4.0, a program can't be running in one process while it is being
debugged in another.  Rather than doing "./gdb ./gdb", which works on
Suns and such, you can copy gdb to gdb2 and then do "./gdb ./gdb2".

When you run gdb in the gdb source directory, it will read a ".gdbinit"
file that sets up some simple things to make debugging gdb easier.  The
"info" command, when executed without a subcommand in a gdb being
debugged by gdb, will pop you back up to the top level gdb.  See
.gdbinit for details.

I strongly recommend printing out the reference card and using it.
Send reference-card suggestions to [e-mail], just like bugs.

If you use emacs, you will probably want to do a "make TAGS" after you
configure your distribution; this will put the machine dependent
routines for your local machine where they will be accessed first by a
M-period.

Also, make sure that you've either compiled gdb with your local cc, or
have run `fixincludes' if you are compiling with gcc.

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