add an option to check if the socket is thread safe

include/zmq.h

@@ -322,6 +322,7 @@ ZMQ_EXPORT uint32_t zmq_msg_get_routing_id(zmq_msg_t *msg);
 #define ZMQ_XPUB_VERBOSE_UNSUBSCRIBE 78
 #define ZMQ_CONNECT_TIMEOUT 79
 #define ZMQ_TCP_RETRANSMIT_TIMEOUT 80
+#define ZMQ_THREAD_SAFE 81
 
 /*  Message options                                                           */
 #define ZMQ_MORE 1

src/socket_base.cpp

@@ -423,6 +423,19 @@ int zmq::socket_base_t::getsockopt (int option_, void *optval_,
         return 0;
     }
 
+    if (option_ == ZMQ_THREAD_SAFE) {
+        if (*optvallen_ < sizeof (int)) {
+            errno = EINVAL;
+            EXIT_MUTEX();
+            return -1;
+        }
+        memset(optval_, 0, *optvallen_);
+        *((int*) optval_) = thread_safe	? 1 : 0;
+        *optvallen_ = sizeof (int);
+        EXIT_MUTEX();
+        return 0;
+    }  
+
     int rc = options.getsockopt (option_, optval_, optvallen_);
     EXIT_MUTEX();
     return rc;

tests/test_thread_safe.cpp

@@ -41,6 +41,13 @@ int main (void)
     void *client = zmq_socket (ctx, ZMQ_CLIENT);
     void *client2 = zmq_socket (ctx, ZMQ_CLIENT);
 
+    int thread_safe;
+    size_t size = sizeof(int);
+
+    zmq_getsockopt (client, ZMQ_THREAD_SAFE, &thread_safe, &size);
+
+    assert (thread_safe == 1);
+
     int rc;
 
     rc = zmq_bind (client, "tcp://127.0.0.1:5560");