Add GNU -bsd option from specs to new gnu.opt

In preparation for the driver only accepting options listed in .opt
files, and not other options that simply happen to match some spec,
this patch adds the -bsd option accepted by specs in gnu.h to a new
gnu.opt file.  (Other options are not added to this file because
<http://gcc.gnu.org/ml/gcc-patches/2011-01/msg02024.html> adds them to
gnu-user.opt, but this patch does not depend on that one; the two
patches could go in in either order.)

Tested building cc1 and xgcc for cross to i686-gnu.  OK to commit?

2011-01-27  Joseph Myers  <joseph@codesourcery.com>

	* config/gnu.opt: New.
	* config.gcc (*-*-gnu*): Use gnu.opt.

Ping.  This patch 
<http://gcc.gnu.org/ml/gcc-patches/2011-01/msg02072.html> is pending 
review.

Hallo!

Roland, Thomas, Samuel: Do you have any comments on this (read below)?
(Originally: <http://gcc.gnu.org/ml/gcc-patches/2011-01/msg02072.html>,
<http://gcc.gnu.org/ml/gcc-patches/2011-02/msg00206.html>)


On Fri, Jan 28, 2011 at 12:06:48AM +0000, Joseph S. Myers wrote:
> In preparation for the driver only accepting options listed in .opt
> files, and not other options that simply happen to match some spec,
> this patch adds the -bsd option accepted by specs in gnu.h to a new
> gnu.opt file.

> (Other options are not added to this file because
> <http://gcc.gnu.org/ml/gcc-patches/2011-01/msg02024.html> adds them to
> gnu-user.opt

Ack.

> Index: gcc/config.gcc
> ===================================================================
> --- gcc/config.gcc	(revision 169317)
> +++ gcc/config.gcc	(working copy)
> @@ -561,6 +561,9 @@ case ${target} in
>    case $target in
>      *linux*)
>        extra_options="$extra_options linux.opt";;
> +    *-*-gnu*)
> +      tm_defines="$tm_defines SINGLE_LIBC"
> +      extra_options="$extra_options gnu.opt";;
>      *)
>        tm_defines="$tm_defines SINGLE_LIBC";;
>    esac

This would also match k*bsd-gnu*, etc. -- which don't have a -bsd option
as far as I can tell -- I only find it in three places:

    config/gnu.h:#define CPP_SPEC "%{posix:-D_POSIX_SOURCE} %{bsd:-D_BSD_SOURCE}"
    config/gnu.h:#define LIB_SPEC "%{pthread:-lpthread} %{bsd:-lbsd-compat} %{pg|p|profile:-lc_p;:-lc}"
    config/i386/gnu.h:#define CPP_SPEC "%{pthread:-D_REENTRANT} %{posix:-D_POSIX_SOURCE} %{bsd:-D_BSD_SOURCE}"

So, I wondered what this -bsd option was actually about.  (I already
wondered months (uhm, years...) ago, but didn't look it up back then.)

This spec code was added with the original GNU/Hurd spec files commit by
Roland in 1994.  Roland, can you tell where you meant to / did use this
option (apart from a local command-line argument shortcut)?

The only place I can remotely find it referenced in core Hurd-related
source code is in glibc, and here it (that is, libbsd-compat) has been an
empty dummy library as of 1998-04-21.  [glibc]/NOTES has a description of
this in the ``Macro: _BSD_SOURCE'' section (but doesn't talk about a -bsd
option either).

There might be some third-party software that uses the -bsd option
(exclusively) for GNU/Hurd, but I don't think this is anywhere near
realistical, and if that softwares' builds failed loudly passing this
option to GCC (and be fixed afterwards), I'd consider that fine -- I
therefore propose removing this -bsd option right away instead of
spending any more time on it.


Grüße,
 Thomas

I don't think we need to support a -bsd command-line option.