gethostname fix for mingw (was: Re: Problem with gethostbyname)

[Ben Pfaff]

Michel reported on pspp-dev that PSPP fails to compile on mingw
due to the following error:

> In file included from
> C:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../../include/windows.h:98,
>                  from lseek.c:26:
> C:/MinGW/bin/../lib/gcc/mingw32/3.4.5/../../../../include/winsock2.h:635:
> error: conflicting types for 'gethostname'
> ./unistd.h:313: error: previous declaration of 'gethostname' was here

I can see what is going wrong:

        - The gethostname module fails to find gethostname()
          because it is in the ws2_32 library, which it doesn't
          try to link against.  Thus, it tries to replace it.

        - Thus, it adds a prototype for gethostname() to the
          replacement unistd.h.  This prototype has a length
          parameter of type size_t (per POSIX).

        - The lseek module needs unistd.h and windows.h.  The
          latter in turn includes winsock2.h, which contains the
          Windows prototype for gethostname(), which has an
          length parameter of type int (who knows why).

I think that the following change will fix the problem.  Does it
look like the right approach?  If so, I will generate a new
snapshot for Michel to test before I commit it to gnulib.

Thanks,

Ben.

commit ed8093c8eedcf44193b29155a9bbf49f83e0d3e7
Author: Ben Pfaff <address@hidden>
Date:   Wed Oct 22 21:54:23 2008 -0700

    Fix gethostname on mingw.
    * lib/unistd.in.h: Bypass bad winsock2 prototype for gethostname.
    Prevent calling gethostname on mingw without using the gethostname
    module.
    * gethostname.m4: Invoke gl_PREREQ_SYS_H_WINSOCK2 if it is
    available.
    * doc/posix-functions/gethostname.texi: Update.

diff --git a/ChangeLog b/ChangeLog
index b6c2893..e47a922 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2008-10-22  Ben Pfaff  <address@hidden>
+
+       * lib/unistd.in.h: Bypass bad winsock2 prototype for gethostname.
+       Prevent calling gethostname on mingw without using the gethostname
+       module.
+       * gethostname.m4: Invoke gl_PREREQ_SYS_H_WINSOCK2 if it is
+       available.
+       * doc/posix-functions/gethostname.texi: Update.
+
 2008-10-22  Simon Josefsson  <address@hidden>
 
        * lib/sys_socket.in.h (FD_ISSET): Fix warnings under mingw.
diff --git a/doc/posix-functions/gethostname.texi 
b/doc/posix-functions/gethostname.texi
index 9d32a8b..1ff45fd 100644
--- a/doc/posix-functions/gethostname.texi
+++ b/doc/posix-functions/gethostname.texi
@@ -9,8 +9,8 @@ Gnulib module: gethostname
 Portability problems fixed by Gnulib:
 @itemize
 @item
-This function is missing on some platforms:
-mingw.
+On mingw, this function has a prototype that differs from that
+specified by POSIX, and it is defined only in the ws2_32 library.
 @end itemize
 
 Portability problems not fixed by Gnulib:
diff --git a/lib/unistd.in.h b/lib/unistd.in.h
index bfa3d49..7a5db76 100644
--- a/lib/unistd.in.h
+++ b/lib/unistd.in.h
@@ -281,8 +281,17 @@ extern int getdtablesize (void);
    If the host name is longer than LEN, set errno = EINVAL and return -1.
    Return 0 if successful, otherwise set errno and return -1.  */
 # if address@hidden@
+#  if HAVE_WINSOCK2_H
+#   /* Bypass bad prototype for gethostname(). */
+#   include <winsock2.h>
+#   undef gethostname
+#   define gethostname rpl_gethostname
+#  endif
 extern int gethostname(char *name, size_t len);
 # endif
+#elif @UNISTD_H_HAVE_WINSOCK2_H@
+# undef gethostname
+# define gethostname 
gethostname_used_without_requesting_gnulib_module_gethostname
 #elif defined GNULIB_POSIXCHECK
 # undef gethostname
 # define gethostname(n,l) \
diff --git a/m4/gethostname.m4 b/m4/gethostname.m4
index b8c4e2a..7095ac3 100644
--- a/m4/gethostname.m4
+++ b/m4/gethostname.m4
@@ -6,6 +6,7 @@ dnl with or without modifications, as long as this notice is 
preserved.
 
 AC_DEFUN([gl_FUNC_GETHOSTNAME],
 [
+  m4_ifdef([gl_PREREQ_SYS_H_WINSOCK2], [gl_PREREQ_SYS_H_WINSOCK2])
   AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
   AC_REPLACE_FUNCS(gethostname)
   if test $ac_cv_func_gethostname = no; then

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 Say, can you work 70 hours this week?"
--Ron Mansolino