lxc move_fd MACRO 관련 질문...

#define move_fd(fd)                         \
	({                                  \
		int __internal_fd__ = (fd); \
		(fd) = -EBADF;              \
		__internal_fd__;            \
	})
 
int lxc_unix_connect_type(struct sockaddr_un *addr, int type)
{
	__do_close int fd = -EBADF;
	int ret;
	ssize_t len;
 
	fd = socket(AF_UNIX, type | SOCK_CLOEXEC, 0);
	if (fd < 0)
		return syserror("Failed to open new AF_UNIX socket");
 
	if (addr->sun_path[0] == '\0')
		len = strlen(&addr->sun_path[1]);
	else
		len = strlen(&addr->sun_path[0]);
 
	ret = connect(fd, (struct sockaddr *)addr,
		      offsetof(struct sockaddr_un, sun_path) + len);
	if (ret < 0)
		return syserror("Failed to bind new AF_UNIX socket");
 
	return move_fd(fd);
}