segfault in uv_ip4_name

lldb output

➜  mesh  lldb mesh
Current executable set to 'mesh' (x86_64).
(lldb) run
Process 41196 launched: '/Users/conrad/Work/scratch/mesh/mesh' (x86_64)
status: 0
Recv 8 bytes from 127.0.0.1
Process 41196 stopped
* thread #1: tid = 0x46d59, 0x0000000100011de2 libuv.dylib`inet_ntop4 + 33, queue = 'com.apple.main-thread, stop reason = EXC_BAD_ACCESS (code=1, address=0x4)
    frame #0: 0x0000000100011de2 libuv.dylib`inet_ntop4 + 33
libuv.dylib`inet_ntop4 + 33:
-> 0x100011de2:  movzbl (%rdi), %r9d
   0x100011de6:  movzbl 1(%rdi), %eax
   0x100011dea:  movzbl 2(%rdi), %ecx
   0x100011dee:  movzbl 3(%rdi), %edx
(lldb) bt full
error: bt [<digit>|all]
(lldb) bt
* thread #1: tid = 0x46d59, 0x0000000100011de2 libuv.dylib`inet_ntop4 + 33, queue = 'com.apple.main-thread, stop reason = EXC_BAD_ACCESS (code=1, address=0x4)
    frame #0: 0x0000000100011de2 libuv.dylib`inet_ntop4 + 33
    frame #1: 0x0000000100011c28 libuv.dylib`uv_inet_ntop + 241
    frame #2: 0x00000001000116f1 libuv.dylib`uv_ip4_name + 30
    frame #3: 0x0000000100000a94 mesh`on_read(req=0x00007fff5fbff868, nread=0, buf=uv_buf_t at 0x00007fff5fbf7468, addr=0x0000000000000000, flags=0) + 212 at mesh.c:22
    frame #4: 0x000000010001014c libuv.dylib`uv__udp_io + 520
    frame #5: 0x0000000100013188 libuv.dylib`uv__io_poll + 1354
    frame #6: 0x0000000100006325 libuv.dylib`uv_run + 259
    frame #7: 0x0000000100000d96 mesh`main(argc=1, argv=0x00007fff5fbff958) + 614 at mesh.c:63
    frame #8: 0x00007fff8eaba5fd libdyld.dylib`start + 1
    frame #9: 0x00007fff8eaba5fd libdyld.dylib`start + 1

mesh.c

#include <stdio.h>
#include <stdlib.h>
#include <uv.h>

uv_loop_t* loop;

uv_buf_t alloc_buffer(uv_handle_t *handle, size_t suggested_size) {
  return uv_buf_init(malloc(suggested_size), suggested_size);
}

void on_read(uv_udp_t *req, ssize_t nread, uv_buf_t buf, struct sockaddr *addr, unsigned flags) {
  if (nread < 0) {
    fprintf(stderr, "Read error %s\n", uv_err_name(uv_last_error(loop)));

    uv_close((uv_handle_t*) req, NULL);

    return;
  }

  char sender[17] = { 0 };

  uv_ip4_name((struct sockaddr_in*) addr, sender, 16);
  fprintf(stderr, "Recv %zu bytes from %s\n", nread, sender);

  free(buf.base);
}

void on_send(uv_udp_send_t* req, int status) {
  printf("status: %d\n", status);

  free(req->data);
}

int main(int argc, char** argv) {
  uv_udp_t fd;
  int rc;

  loop = uv_default_loop();

  rc = uv_udp_init(loop, &fd);
  if (rc != 0) {
    fprintf(stderr, "error initialising socket\n");
    return 1;
  }

  rc = uv_udp_bind(&fd, uv_ip4_addr("0.0.0.0", 5000), 0);
  if (rc != 0) {
    fprintf(stderr, "error binding socket\n");
    return 1;
  }

  rc = uv_udp_recv_start(&fd, alloc_buffer, on_read);
  if (rc != 0) {
    fprintf(stderr, "error listening on socket\n");
    return 1;
  }

  uv_udp_send_t req;
  uv_buf_t msg = uv_buf_init(malloc(8), 8);
  req.data = msg.base;
  uv_udp_send(&req, &fd, &msg, 1, uv_ip4_addr("127.0.0.1", 5000), on_send);

  return uv_run(loop, UV_RUN_DEFAULT);
}