Make <sys/select.h> self-contained, i.e. make it possible to include it

without prior <sys/types.h>.

diff --git a/m4/sys_select_h.m4 b/m4/sys_select_h.m4
index f7070fa..7fe67df 100644 (file)
--- a/m4/sys_select_h.m4
+++ b/m4/sys_select_h.m4
@@ -1,18 +1,32 @@
-# sys_select_h.m4 serial 1
-dnl Copyright (C) 2006 Free Software Foundation, Inc.
+# sys_select_h.m4 serial 2
+dnl Copyright (C) 2006-2007 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.
 
-dnl Adapted from arpa_inet.m4, written by Simon Josefsson.
-
 AC_DEFUN([gl_HEADER_SYS_SELECT],
 [
-  AC_CHECK_HEADERS_ONCE([sys/select.h])
-  if test $ac_cv_header_sys_select_h = yes; then
+  AC_CACHE_CHECK([whether <sys/select.h> is self-contained],
+    [gl_cv_header_sys_select_h_selfcontained],
+    [
+      AC_COMPILE_IFELSE([AC_LANG_PROGRAM([#include <sys/select.h>], [])],
+        [gl_cv_header_sys_select_h_selfcontained=yes],
+        [gl_cv_header_sys_select_h_selfcontained=no])
+    ])
+  if test $gl_cv_header_sys_select_h_selfcontained = yes; then
     SYS_SELECT_H=''
   else
     SYS_SELECT_H='sys/select.h'
+    AC_CHECK_HEADERS([sys/select.h])
+    gl_ABSOLUTE_HEADER([sys/select.h])
+    ABSOLUTE_SYS_SELECT_H=\"$gl_cv_absolute_sys_select_h\"
+    AC_SUBST([ABSOLUTE_SYS_SELECT_H])
+    if test $ac_cv_header_sys_select_h = yes; then
+      HAVE_SYS_SELECT_H=1
+    else
+      HAVE_SYS_SELECT_H=0
+    fi
+    AC_SUBST([HAVE_SYS_SELECT_H])
   fi
-  AC_SUBST(SYS_SELECT_H)
+  AC_SUBST([SYS_SELECT_H])
 ])