struct Foo {
    packet_bufs: Vec<Vec<u8>>,
    sockaddrs: Vec<std::net::SocketAddr>,
    lengths: Vec<usize>,
}

impl Foo {
    fn doit1(&mut self, sock: &std::net::UdpSocket) -> Result<usize, std::io::Error> {
        // trying to get rid of the allocation for this Vec
        let mut iovecs: Vec<[&mut [u8]; 1]> = self.packet_bufs
            .iter_mut()
            .map(|pk| {
                let iov = &mut pk[..];
                [iov]
            })
            .collect();
        Self::doit3(sock, &mut self.sockaddrs[..], &mut self.lengths, &mut iovecs[..])
    }

    fn doit2(&mut self, sock: &std::net::UdpSocket) -> Result<usize, std::io::Error> {
        // switching the code to ArrayVec doesn't compile
        let mut iovecs: arrayvec::ArrayVec<[[&mut [u8]; 1]; 8]> = self.packet_bufs
            .iter_mut()
            .map(|pk| {
                let iov = &mut pk[..];
                [iov]
            })
            .collect();
        Self::doit3(sock, &mut self.sockaddrs[..], &mut self.lengths, &mut iovecs[..])
        //                                                                 ^^^^^^ borrowed value does not live long enough
    }
//  |     `iovecs` dropped here while still borrowed


    fn doit3<'a, 'b: 'a>(
        _sock: &'a std::net::UdpSocket,
        _sockaddrs: &'a mut [std::net::SocketAddr],
        _lengths: &mut Vec<usize>,
        _iovecs: &'b mut [[&'a mut [u8]; 1]],
    ) -> Result<usize, std::io::Error> {
        //let mut recv_headers: arrayvec::ArrayVec<[RecvMMsgHdr<'_>; 8]> = iovecs
        //    .iter_mut()
        //    .zip(sockaddrs.iter_mut())
        //    .map(|(iov, sockaddr)| {
        //        RecvMMsgHdr::new(iov, None, MsgFlags::empty(), Some(sockaddr))
        //    })
        //    .collect();
        //let size = recvmmsg(sock.as_raw_fd(), &mut recv_headers[..], MsgFlags::empty(), None)?;
        //lengths.extend(recv_headers.drain(..size).map(|hdr| hdr.msg_len()));
        //Ok(size)
        Ok(0)
    }
}