TO_EXTERNAL_FORMAT (LISP_STRING, vtype, C_STRING_ALLOCA, vtype_ext, Qnative);
if (NILP (value))
tt_message_arg_add (m, n, vtype_ext, NULL);
else if (STRINGP (value))
{
TO_EXTERNAL_FORMAT (LISP_STRING, vtype, C_STRING_ALLOCA, vtype_ext, Qnative);
if (NILP (value))
tt_message_arg_add (m, n, vtype_ext, NULL);
else if (STRINGP (value))
{