Portability problems not fixed by Gnulib:
@itemize
@item
+This function accumulates hidden state on some platforms:
+glibc 2.8 (see @url{http://sourceware.org/bugzilla/show_bug.cgi?id=9674}).
+@item
On AIX and Windows platforms, @code{wchar_t} is a 16-bit type and therefore cannot
accommodate all Unicode characters.
@end itemize