archive_read_support_format_xar(struct archive *_a)
{
	struct archive_read *a = (struct archive_read *)_a;
	archive_check_magic(_a, ARCHIVE_READ_MAGIC,
	    ARCHIVE_STATE_NEW, "archive_read_support_format_xar");

	archive_set_error(&a->archive, ARCHIVE_ERRNO_MISC,
	    "Xar not supported on this platform");
	return (ARCHIVE_WARN);
}

The product reads data past the end, or before the beginning, of the intended buffer.