Merge pull request #900 from pijyoi/master

fix: win32 tcp_keepalive gets set even when option is -1

src/tcp.cpp

@@ -95,6 +95,7 @@ void zmq::tune_tcp_keepalives (fd_t s_, int keepalive_, int keepalive_cnt_, int
     //  Tuning TCP keep-alives if platform allows it
     //  All values = -1 means skip and leave it for OS
 #ifdef ZMQ_HAVE_WINDOWS
+    if (keepalive_ != -1) {
         tcp_keepalive keepalive_opts;
         keepalive_opts.onoff = keepalive_;
         keepalive_opts.keepalivetime = keepalive_idle_ != -1 ? keepalive_idle_ * 1000 : 7200000;
@@ -102,6 +103,7 @@ void zmq::tune_tcp_keepalives (fd_t s_, int keepalive_, int keepalive_cnt_, int
         DWORD num_bytes_returned;
         int rc = WSAIoctl(s_, SIO_KEEPALIVE_VALS, &keepalive_opts, sizeof(keepalive_opts), NULL, 0, &num_bytes_returned, NULL, NULL);
         wsa_assert (rc != SOCKET_ERROR);
+    }
 #else
 #ifdef ZMQ_HAVE_SO_KEEPALIVE
     if (keepalive_ != -1) {