--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2008-04-13  Bruno Haible  <bruno@clisp.org>
+
+	* doc/posix-headers/sys_socket.texi: Document the problem on EMX.
+	* lib/sys_socket.in.h (SHUT_RD, SHUT_WR, SHUT_RDWR): Define if missing.
+	* m4/sys_socket_h.m4 (gl_HEADER_SYS_SOCKET): Replace <sys/socket.h>
+	also if it exists but lacks definitions of the SHUT_* macros.
+	* modules/sys_socket (Description): Update.
+	Reported by Elbert Pol <e.pol@chello.nl>.
+
 2008-04-13  Bruno Haible  <bruno@clisp.org>
 
 	* lib/localcharset.c (OS2): Don't redefine if already defined.

--- a/doc/posix-headers/sys_socket.texi
+++ b/doc/posix-headers/sys_socket.texi
@@ -13,6 +13,11 @@
 @item
 This header file is not self-contained on some platforms: it requires
 @code{<sys/types.h>} to be included first.
+@item
+This header file is lacking the @code{SHUT_RD}, @code{SHUT_WR},
+@code{SHUT_RDWR} macros on some platforms, despite having the @code{shutdown}
+functions:
+emx+gcc.
 @end itemize
 
 Portability problems not fixed by Gnulib:

--- a/lib/sys_socket.in.h
+++ b/lib/sys_socket.in.h
@@ -1,5 +1,6 @@
-/* Provide a sys/socket header file for systems lacking it (read: MinGW).
-   Copyright (C) 2005, 2006, 2007 Free Software Foundation, Inc.
+/* Provide a sys/socket header file for systems lacking it (read: MinGW)
+   and for systems where it is incomplete.
+   Copyright (C) 2005-2008 Free Software Foundation, Inc.
    Written by Simon Josefsson.
 
    This program is free software; you can redistribute it and/or modify
@@ -16,8 +17,9 @@
    along with this program; if not, write to the Free Software Foundation,
    Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
 
-/* This file is supposed to be used on platforms that lack <sys/socket.h>
-   and on platforms where <sys/socket.h> cannot be included standalone.
+/* This file is supposed to be used on platforms that lack <sys/socket.h>,
+   on platforms where <sys/socket.h> cannot be included standalone, and on
+   platforms where <sys/socket.h> does not provide all necessary definitions.
    It is intended to provide definitions and prototypes needed by an
    application.  */
 
@@ -37,7 +39,22 @@
 #ifndef _GL_SYS_SOCKET_H
 #define _GL_SYS_SOCKET_H
 
-#if !@HAVE_SYS_SOCKET_H@
+#if @HAVE_SYS_SOCKET_H@
+
+/* A platform that has <sys/socket.h>.  */
+
+/* For shutdown().  */
+# if !defined SHUT_RD
+#  define SHUT_RD 0
+# endif
+# if !defined SHUT_WR
+#  define SHUT_WR 1
+# endif
+# if !defined SHUT_RDWR
+#  define SHUT_RDWR 2
+# endif
+
+#else
 
 /* A platform that lacks <sys/socket.h>.
 

--- a/m4/sys_socket_h.m4
+++ b/m4/sys_socket_h.m4
@@ -1,5 +1,5 @@
-# sys_socket_h.m4 serial 4
-dnl Copyright (C) 2005, 2006, 2007 Free Software Foundation, Inc.
+# sys_socket_h.m4 serial 5
+dnl Copyright (C) 2005-2008 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
@@ -17,9 +17,28 @@
     ])
   if test $gl_cv_header_sys_socket_h_selfcontained = yes; then
     SYS_SOCKET_H=''
+    dnl If the shutdown function exists, <sys/socket.h> should define
+    dnl SHUT_RD, SHUT_WR, SHUT_RDWR.
+    AC_CHECK_FUNCS([shutdown])
+    if test $ac_cv_func_shutdown = yes; then
+      AC_CACHE_CHECK([whether <sys/socket.h> defines the SHUT_* macros],
+        [gl_cv_header_sys_socket_h_shut],
+        [
+          AC_COMPILE_IFELSE(
+            [AC_LANG_PROGRAM([[#include <sys/socket.h>]],
+               [[int a[] = { SHUT_RD, SHUT_WR, SHUT_RDWR };]])],
+            [gl_cv_header_sys_socket_h_shut=yes],
+            [gl_cv_header_sys_socket_h_shut=no])
+        ])
+      if test $gl_cv_header_sys_socket_h_shut = no; then
+        SYS_SOCKET_H='sys/socket.h'
+      fi
+    fi
   else
     SYS_SOCKET_H='sys/socket.h'
-
+  fi
+  if test -n "$SYS_SOCKET_H"; then
+    dnl Check prerequisites of the <sys/socket.h> replacement.
     gl_CHECK_NEXT_HEADERS([sys/socket.h])
     if test $ac_cv_header_sys_socket_h = yes; then
       HAVE_SYS_SOCKET_H=1

--- a/modules/sys_socket
+++ b/modules/sys_socket
@@ -1,5 +1,5 @@
 Description:
-A <sys/socket.h> for systems lacking it.
+A POSIX-like <sys/socket.h>.
 
 Files:
 lib/sys_socket.in.h