Re: [PATCH] gethostname: fix build on mingw

[Eric Blake]

On 03/21/2010 01:45 PM, Matthias Bolte wrote:
> 2010/3/20 Eric Blake <address@hidden>:
>> Since commit 4e86671a, gethostname failed to compile on mingw.
>> Gnulib's sys/socket.h includes winsock2.h, which then includes
>> unistd.h prior to declaring gethostname.  Therefore, unistd.h
>> cannot replace gethostname until winsock2.h is complete, also
>> fixing things if a .c includes <unistd.h> (or even <winsock2.h>)
>> prior to <sys/socket.h>.
>>
> 
> If I apply the attached diff on top of this patch the problem is
> fixed. It compiles without errors, I can include <unistd.h> before
> <sys/socket.h> and I can include <winsock2.h> before <sys/socket.h> as
> long as the <winsock2.h> include is wrapped in #define/#undef
> _GL_INCLUDING_WINSOCK2_H.
> 
> The important part is
> 
> -# if @UNISTD_H_HAVE_WINSOCK2_H@
> +# if @UNISTD_H_HAVE_WINSOCK2_H@ && !defined _GL_INCLUDING_WINSOCK2_H
> 
> This stops the <winsock2.h>-includes-<unistd.h>-case from undefining
> _GL_INCLUDING_WINSOCK2_H too early.

Well, we're getting closer.  But I'd really like to avoid making all
clients of <winsock2.h> make an adjustment; it seems like it should
still be possible to make _just_ <unistd.h> have the smarts necessary.
Here's some pseudocode I'm currently thinking about (patch to come up
later...)

#if [_WINSOCK2_H and !witness]
/* Someone has included <winsock2.h> prior to <unistd.h> - let it run to
completion, without declaring any of our overrides; to be portable, the
user will have to later include <unistd.h> if they plan on using
gethostname.  */
# include_next <unistd.h>
# define witness
#else
/* Normal invocation */
# if !defined _GL_UNISTD_H
# include_next <unistd.h>

/* Include everything that declares something that we might want to
override */
# define _GL_INCLUDING_WINSOCK2_H
# include <winsock2.h>
# undef _GL_INCLUDING_WINSOCK2_H

/* Split include guard.  */
# if !defined _GL_UNISTD_H && !defined _GL_INCLUDING_WINSOCK2_H
#  define _GL_UNISTD_H
/* Declare our overrides. */
# endif /* _GL_UNISTD_H/_GL_INCLUDING_WINSOCK2_H */
# endif /* _GL_UNISTD_H */
#endif /*_WINSOCK2_H */

-- 
Eric Blake   address@hidden    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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