*recv_cmd4 = sub ($$$) {
my ($sock, undef, $len) = @_;
- vec($_[1], ($len + 1) * 8, 1) = 0;
+ vec($_[1] //= '', ($len + 1) * 8, 1) = 0;
my $cmsghdr = "\0" x msg_controllen; # 10 * sizeof(int)
my $iov = pack('P'.TMPL_size_t, $_[1], $len);
my $mh = pack('PL' . # msg_name, msg_namelen (socklen_t (U32))