incomplete multibyte character on some platforms:
AIX 5.1, OSF/1 5.1.
@item
+This function does not produce correct results in the zh_CN.GB18030 locale on
+some platforms:
+Solaris 8.
+@item
This function does not ignore the @code{pwc} argument if the string argument is
NULL on some platforms:
OSF/1 5.1.