one more attempt to fix the previous win32 problem

src/socket_base.cpp

@@ -350,19 +350,22 @@ int zmq::socket_base_t::recv (::zmq_msg_t *msg_, int flags_)
     if (rc == 0)
         return 0;
 
+    //  If we don't have the message, restore the original cause of the problem.
+    errno = err;
+
     //  If the message cannot be fetched immediately, there are two scenarios.
     //  For non-blocking recv, commands are processed in case there's a revive
     //  command already waiting int a command pipe. If it's not, return EAGAIN.
-    //  In blocking scenario, commands are processed over and over again until
-    //  we are able to fetch a message.
     if (flags_ & ZMQ_NOBLOCK) {
         if (errno != EAGAIN)
             return -1;
         app_thread->process_commands (false, false);
-        rc = xrecv (msg_, flags_);
         ticks = 0;
+        return xrecv (msg_, flags_);
     }
-    else  {
+
+    //  In blocking scenario, commands are processed over and over again until
+    //  we are able to fetch a message.
     while (rc != 0) {
         if (errno != EAGAIN)
             return -1;
@@ -370,10 +373,7 @@ int zmq::socket_base_t::recv (::zmq_msg_t *msg_, int flags_)
         rc = xrecv (msg_, flags_);
         ticks = 0;
     }
-    }
-
-    errno = err;
-    return rc;
+    return 0;
 }
 
 int zmq::socket_base_t::close ()