- const char enable = (addr.empty() || addr == "*") ? 0 : 1;
- setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &enable, sizeof(enable));
+ /* This must be >= sizeof(DWORD) on Windows */
+ const int enable = (addr.empty() || addr == "*") ? 0 : 1;
+ /* This must be before bind() */
+ setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, reinterpret_cast<const char *>(&enable), sizeof(enable));