set_xattrs(struct archive_write_disk *a)
{
	static int warning_done = 0;

	/* If there aren't any extended attributes, then it's okay not
	 * to extract them, otherwise, issue a single warning. */
	if (archive_entry_xattr_count(a->entry) != 0 && !warning_done) {
		warning_done = 1;
		archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
		    "Cannot restore extended attributes on this system");
		return (ARCHIVE_WARN);
	}
	/* Warning was already emitted; suppress further warnings. */
	return (ARCHIVE_OK);
}