http://sourceware.org/ml/libc-hacker/2002-11/msg00071.html

When fnmatch detects an invalid multibyte character it should fall back to
single byte matching, so that "*" has a chance to match such a string.

Andreas.

2005-04-12  Andreas Schwab  <schwab@suse.de>

	* posix/fnmatch.c (fnmatch): If conversion to wide character
	fails fall back to single byte matching.

Index: posix/fnmatch.c
===================================================================

diff -durN glibc-2.10.1.orig/posix/fnmatch.c glibc-2.10.1/posix/fnmatch.c
--- glibc-2.10.1.orig/posix/fnmatch.c	2007-07-28 22:35:00.000000000 +0200
+++ glibc-2.10.1/posix/fnmatch.c	2009-11-13 00:50:39.000000000 +0100
@@ -327,6 +327,7 @@
 # if HANDLE_MULTIBYTE
   if (__builtin_expect (MB_CUR_MAX, 1) != 1)
     {
+      const char *orig_pattern = pattern;
       mbstate_t ps;
       size_t n;
       const char *p;
@@ -382,10 +383,8 @@
 	  wstring = (wchar_t *) alloca ((n + 1) * sizeof (wchar_t));
 	  n = mbsrtowcs (wstring, &p, n + 1, &ps);
 	  if (__builtin_expect (n == (size_t) -1, 0))
-	    /* Something wrong.
-	       XXX Do we have to set `errno' to something which mbsrtows hasn't
-	       already done?  */
-	    return -1;
+	    /* Something wrong.  Fall back to single byte matching.  */
+	    goto try_singlebyte;
 	  if (p)
 	    {
 	      memset (&ps, '\0', sizeof (ps));
@@ -397,10 +396,8 @@
 	prepare_wstring:
 	  n = mbsrtowcs (NULL, &string, 0, &ps);
 	  if (__builtin_expect (n == (size_t) -1, 0))
-	    /* Something wrong.
-	       XXX Do we have to set `errno' to something which mbsrtows hasn't
-	       already done?  */
-	    return -1;
+	    /* Something wrong.  Fall back to single byte matching.  */
+	    goto try_singlebyte;
 	  wstring = (wchar_t *) alloca ((n + 1) * sizeof (wchar_t));
 	  assert (mbsinit (&ps));
 	  (void) mbsrtowcs (wstring, &string, n + 1, &ps);
@@ -408,6 +405,9 @@
 
       return internal_fnwmatch (wpattern, wstring, wstring + n,
 				flags & FNM_PERIOD, flags, NULL);
+
+    try_singlebyte:
+      pattern = orig_pattern;
     }
 # endif  /* mbstate_t and mbsrtowcs or _LIBC.  */
 
