--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2011-02-13  Bruno Haible  <bruno@clisp.org>
+
+	mbsinit: Work around mingw bug.
+	* m4/mbsinit.m4 (gl_FUNC_MBSINIT): Replace mbsinit also on mingw.
+	* lib/mbsinit.c (mbsinit): Provide an alternate definition for native
+	Windows.
+	* doc/posix-functions/mbsinit.texi: Mention the mingw bug.
+
 2011-02-13  Bruno Haible  <bruno@clisp.org>
 
 	mbsinit: Don't crash for a NULL argument.

--- a/doc/posix-functions/mbsinit.texi
+++ b/doc/posix-functions/mbsinit.texi
@@ -11,6 +11,9 @@
 @item
 This function is missing on some platforms:
 HP-UX 11.00, IRIX 6.5, Solaris 2.6, Interix 3.5.
+@item
+This function always returns 1, even in multibyte locales, on some platforms:
+mingw.
 @end itemize
 
 Portability problems not fixed by Gnulib:

--- a/lib/mbsinit.c
+++ b/lib/mbsinit.c
@@ -22,6 +22,18 @@
 
 #include "verify.h"
 
+#if (defined _WIN32 || defined __WIN32__) && !defined __CYGWIN__
+
+/* On native Windows, 'mbstate_t' is defined as 'int'.  */
+
+int
+mbsinit (const mbstate_t *ps)
+{
+  return ps == NULL || *ps == 0;
+}
+
+#else
+
 /* Platforms that lack mbsinit() also lack mbrlen(), mbrtowc(), mbsrtowcs()
    and wcrtomb(), wcsrtombs().
    We assume that
@@ -45,3 +57,5 @@
 
   return pstate == NULL || pstate[0] == 0;
 }
+
+#endif

--- a/m4/mbsinit.m4
+++ b/m4/mbsinit.m4
@@ -1,4 +1,4 @@
-# mbsinit.m4 serial 4
+# mbsinit.m4 serial 5
 dnl Copyright (C) 2008, 2010-2011 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -7,6 +7,7 @@
 AC_DEFUN([gl_FUNC_MBSINIT],
 [
   AC_REQUIRE([gl_WCHAR_H_DEFAULTS])
+  AC_REQUIRE([AC_CANONICAL_HOST])
 
   AC_REQUIRE([AC_TYPE_MBSTATE_T])
   gl_MBSTATE_T_BROKEN
@@ -17,6 +18,13 @@
   else
     if test $REPLACE_MBSTATE_T = 1; then
       REPLACE_MBSINIT=1
+    else
+      dnl On mingw, mbsinit() always returns 1, which is inappropriate for
+      dnl states produced by mbrtowc() for an incomplete multibyte character
+      dnl in multibyte locales.
+      case "$host_os" in
+        mingw*) REPLACE_MBSINIT=1 ;;
+      esac
     fi
   fi
   if test $HAVE_MBSINIT = 0 || test $REPLACE_MBSINIT = 1; then