+@item
+This function is missing on some platforms:
+HP-UX 11.00, IRIX 5.3, Solaris 2.6, mingw, Interix 3.5.
+@item
+This function returns WEOF for a NUL argument on some platforms:
+Cygwin 1.7.2.
+@item
+This function does not return WEOF for an EOF argument on some platforms:
+IRIX 6.5.