[PATCH] gethostname: fix build on mingw

[Eric Blake]

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>.

* lib/sys_socket.in.h (includes): Set witness when including
winsock2.h.
* lib/unistd.in.h (includes): Likewise, after hoisting <winsock2.h>
inclusion.  Don't replace anything when included by winsock2.h.
Reported by Matthias Bolte.

Signed-off-by: Eric Blake <address@hidden>
---

I think this is more robust, but would appreciate another round
of testing before I push.

 ChangeLog           |    9 +++++++++
 lib/sys_socket.in.h |    7 ++++++-
 lib/unistd.in.h     |   15 +++++++++++++--
 3 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index de054fa..2125639 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2010-03-19  Eric Blake  <address@hidden>
+
+       gethostname: fix build on mingw
+       * lib/sys_socket.in.h (includes): Set witness when including
+       winsock2.h.
+       * lib/unistd.in.h (includes): Don't replace anything when included
+       by winsock2.h.
+       Reported by Matthias Bolte.
+
 2010-02-17  Eric Blake  <address@hidden>

        manywarnings: add more warnings
diff --git a/lib/sys_socket.in.h b/lib/sys_socket.in.h
index 006a901..b34b506 100644
--- a/lib/sys_socket.in.h
+++ b/lib/sys_socket.in.h
@@ -28,7 +28,10 @@
    - On Cygwin 1.5.x we have a sequence of nested includes
      <sys/socket.h> -> <cygwin/socket.h> -> <asm/socket.h> -> <cygwin/if.h>,
      and the latter includes <sys/socket.h>.  In this situation, the functions
-     are not yet declared, therefore we cannot provide the C++ aliases.  */
+     are not yet declared, therefore we cannot provide the C++ aliases.
+   - On mingw, <sys/socket.h> -> <winsock2.h> -> <unistd.h>, and the latter
+     includes <winsock2.h>.  In this situation, functions like gethostname
+     are not yet declared, therefore we must defer.  */

 address@hidden@ @NEXT_SYS_SOCKET_H@

@@ -129,7 +132,9 @@ struct sockaddr_storage


 # if @HAVE_WINSOCK2_H@
+#  define _GL_INCLUDING_WINSOCK2_H
 #  include <winsock2.h>
+#  undef _GL_INCLUDING_WINSOCK2_H
 # endif
 # if @HAVE_WS2TCPIP_H@
 #  include <ws2tcpip.h>
diff --git a/lib/unistd.in.h b/lib/unistd.in.h
index b74484a..a57ba37 100644
--- a/lib/unistd.in.h
+++ b/lib/unistd.in.h
@@ -26,7 +26,19 @@
 # @INCLUDE_NEXT@ @NEXT_UNISTD_H@
 #endif

-#ifndef _GL_UNISTD_H
+/* On mingw, <winsock2.h> includes <unistd.h> prior to declaring
+   gethostname, but we want to replace gethostname.  We must ensure
+   that <winsock2.h> is completely included first.  */
+#if @GNULIB_GETHOSTNAME@
+/* Get all possible declarations of gethostname().  */
+# if @UNISTD_H_HAVE_WINSOCK2_H@
+#  define _GL_INCLUDING_WINSOCK2_H
+#  include <winsock2.h>
+#  undef _GL_INCLUDING_WINSOCK2_H
+# endif
+#endif
+
+#if !defined _GL_UNISTD_H && !defined _GL_INCLUDING_WINSOCK2_H
 #define _GL_UNISTD_H

 /* NetBSD 5.0 mis-defines NULL.  Also get size_t.  */
@@ -76,7 +88,6 @@
 #if @GNULIB_GETHOSTNAME@
 /* Get all possible declarations of gethostname().  */
 # if @UNISTD_H_HAVE_WINSOCK2_H@
-#  include <winsock2.h>
 #  if !defined _GL_SYS_SOCKET_H
 #   undef socket
 #   define socket               socket_used_without_including_sys_socket_h
-- 
1.6.6.1