-ERR_lib_error_string(), ERR_func_error_string() and
-ERR_reason_error_string() return the strings, and B<NULL> if
-none is registered for the error code.
+ERR_lib_error_string() and ERR_reason_error_string() return the strings,
+and B<NULL> if none is registered for the error code.
+
+ERR_func_error_string() returns NULL.