--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/m4/double-slash-root.m4	Sun Aug 16 17:16:49 2009 +0000
@@ -0,0 +1,38 @@
+# double-slash-root.m4 serial 3   -*- Autoconf -*-
+dnl Copyright (C) 2006, 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.
+
+AC_DEFUN([gl_DOUBLE_SLASH_ROOT],
+[
+  AC_REQUIRE([AC_CANONICAL_HOST])
+  AC_CACHE_CHECK([whether // is distinct from /], [gl_cv_double_slash_root],
+    [ if test x"$cross_compiling" = xyes ; then
+	# When cross-compiling, there is no way to tell whether // is special
+	# short of a list of hosts.  However, the only known hosts to date
+	# that have a distinct // are Apollo DomainOS (too old to port to),
+	# Cygwin, and z/OS.  If anyone knows of another system for which // has
+	# special semantics and is distinct from /, please report it to
+	# <bug-gnulib@gnu.org>.
+	case $host in
+	  *-cygwin | i370-ibm-openedition)
+	    gl_cv_double_slash_root=yes ;;
+	  *)
+	    # Be optimistic and assume that / and // are the same when we
+	    # don't know.
+	    gl_cv_double_slash_root='unknown, assuming no' ;;
+	esac
+      else
+	set x `ls -di / // 2>/dev/null`
+	if test "$[2]" = "$[4]" && wc //dev/null >/dev/null 2>&1; then
+	  gl_cv_double_slash_root=no
+	else
+	  gl_cv_double_slash_root=yes
+	fi
+      fi])
+  if test "$gl_cv_double_slash_root" = yes; then
+    AC_DEFINE([DOUBLE_SLASH_IS_DISTINCT_ROOT], 1,
+      [Define to 1 if // is a file system root distinct from /.])
+  fi
+])