--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2007-01-12  Eric Blake  <ebb9@byu.net>
+
+	Provide a robust <wchar.h>.  Further simplifications are now
+	possible in other modules, but not included here.
+	* modules/wchar: New module.
+	* m4/wchar.m4: New file.
+	* lib/wchar_.h: Likewise.
+	* modules/mbchar (Depends-on): Depend on wchar, as the first use
+	of the new module.
+	* MODULES.html.sh (Extended multibyte and wide character utilities):
+	New section.
+
 2007-01-12  Paul Eggert  <eggert@cs.ucla.edu>
 
 	* lib/xreadlink.c (SYMLINK_MAX) [!defined SYMLINK_MAX]: Define

--- a/MODULES.html.sh
+++ b/MODULES.html.sh
@@ -1844,6 +1844,16 @@
   func_module strtoumax
   func_end_table
 
+  element="Extended multibyte and wide character utilities <wchar.h>"
+  element=`printf "%s" "$element" | sed -e "$sed_lt" -e "$sed_gt"`
+  func_section_wrap isoc_sup_wchar
+  func_wrap H3
+  func_echo "$element"
+
+  func_begin_table
+  func_module wchar
+  func_end_table
+
   element="Wide character classification and mapping utilities <wctype.h>"
   element=`printf "%s" "$element" | sed -e "$sed_lt" -e "$sed_gt"`
   func_section_wrap isoc_sup_wctype

new file mode 100644
--- /dev/null
+++ b/lib/wchar_.h
@@ -0,0 +1,42 @@
+/* A substitute for ISO C99 <wchar.h>, for platforms that have issues.
+
+   Copyright (C) 2007 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+/* Written by Eric Blake.  */
+
+/*
+ * ISO C 99 <wchar.h> for platforms that have issues.
+ * <http://www.opengroup.org/susv3xbd/wchar.h.html>
+ *
+ * For now, this just ensures proper prerequisite inclusion order.
+ */
+
+#ifndef _GL_WCHAR_H
+#define _GL_WCHAR_H
+
+/* Tru64 with Desktop Toolkit C has a bug: <stdio.h> must be included before
+   <wchar.h>.
+   BSD/OS 4.0.1 has a bug: <stddef.h>, <stdio.h> and <time.h> must be
+   included before <wchar.h>.  */
+#include <stddef.h>
+#include <stdio.h>
+#include <time.h>
+
+/* Include the original <wchar.h>.  */
+#include @ABSOLUTE_WCHAR_H@
+
+#endif /* _GL_WCHAR_H */

new file mode 100644
--- /dev/null
+++ b/m4/wchar.m4
@@ -0,0 +1,29 @@
+dnl A placeholder for ISO C99 <wchar.h>, for platforms that have issues.
+
+dnl Copyright (C) 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 Written by Eric Blake.
+
+# wchar.m4 serial 1
+
+AC_DEFUN([gl_WCHAR_H],
+[
+  AC_CACHE_CHECK([whether <wchar.h> is standalone],
+    [gl_cv_header_wchar_h_standalone],
+    [AC_COMPILE_IFELSE([[#include <wchar.h>
+wchar_t w;]],
+      [gl_cv_header_wchar_h_standalone=yes],
+      [gl_cv_header_wchar_h_standalone=no])])
+  if test $gl_cv_header_wchar_h_standalone = yes; then
+    WCHAR_H=
+  else
+    gl_ABSOLUTE_HEADER([wchar.h])
+    ABSOLUTE_WCHAR_H=\"$gl_cv_absolute_wchar_h\"
+    WCHAR_H=wchar.h
+  fi
+  AC_SUBST([ABSOLUTE_WCHAR_H])
+  AC_SUBST([WCHAR_H])
+])

--- a/modules/mbchar
+++ b/modules/mbchar
@@ -8,6 +8,7 @@
 
 Depends-on:
 stdbool
+wchar
 wctype
 wcwidth
 

new file mode 100644
--- /dev/null
+++ b/modules/wchar
@@ -0,0 +1,35 @@
+Description:
+A <wchar.h> that works around platform issues.
+
+Files:
+lib/wchar_.h
+m4/wchar.m4
+
+Depends-on:
+absolute-header
+
+configure.ac:
+gl_WCHAR_H
+
+Makefile.am:
+BUILT_SOURCES += $(WCHAR_H)
+
+# We need the following in order to create <wchar.h> when the system
+# version does not work standalone.
+wchar.h: wchar_.h
+	rm -f $@-t $@
+	{ echo '/* DO NOT EDIT! GENERATED AUTOMATICALLY! */'; \
+	  sed -e 's|@''ABSOLUTE_WCHAR_H''@|$(ABSOLUTE_WCHAR_H)|g' \
+	    < $(srcdir)/wchar_.h; \
+	} > $@-t
+	mv $@-t $@
+MOSTLYCLEANFILES += wchar.h wchar.h-t
+
+Include:
+#include <wchar.h>
+
+License:
+LGPL
+
+Maintainer:
+all