[PATCH] No extern declarations of optarg & co if getopt.h is available

[Corinna Vinschen]

On Wed, Sep 10, 2003 at 03:32:10PM -0500, Ben Lindstrom wrote:
> On Wed, 10 Sep 2003, Corinna Vinschen wrote:
> 
> > Hi,
> >
> > I have a problem with the extern declarations of optarg, optind, etc.
> >
> > We're currently moving getopt from being a statically linked function
> > to a dynamically linked function as part of the Cygwin DLL.  On Windows,
> > this requires to generate special symbols (__imp__optarg, etc.), which
> > is done by marking the exported variables in the corresponding header.
> > Instead of
> >
> >   extern char *optarg;
> >
> > getopt.h now contains
> >
> >   extern char __declspec(dllimport) *optarg;
> >
> > I'm sorry, but that's not my invention.
> >
> > Now the problem.  ssh.c, sshd.c and a lot of other files do explicitely
> > declare the opt* variables at the beginning of main(), even when a
> > getopt.h file is available.  The problem with this is, that this
> > explicit extern declaration overrides the declaration from getopt.h.
> > So instead of linking against the correct __imp__optarg symbol, the
> > linker tries to linked against the normal _optarg.
> >
> > This could be easily circumvented by either not declaring the variables
> > at all in these main() funcs, or by surrounding the declarations with
> >
> >   #ifndef HAVE_GETOPT_H
> >       extern char *optarg;
> >       ...
> >   #endif
> 
> No, I don't think that is right, and in fact it will break older
> platforms.
> 
> I think your linker/compiler is doing it wrong.  My understand of the C

It's not *my* compiler, it's gcc.  And it's not wrong but it's the way
dynamic imorting/exporting works on Windows platforms.  What I don't get
is why extern declarations are duplicated here.  Either they exist in
getopt.h or they should be declared explicitely in the source but not both. 
So I think my patch is correct.  The other way is to substitute the

  #ifndef HAVE_GETOPT_H

by

  #ifndef HAVE_CYGWIN

if you like this better.

Corinna

-- 
Corinna Vinschen
Cygwin Developer
Red Hat, Inc.