new zmq_proxy is zmq_proxy_steerable to respect C API

include/zmq.h

@@ -395,7 +395,8 @@ ZMQ_EXPORT int zmq_poll (zmq_pollitem_t *items, int nitems, long timeout);
 
 /*  Built-in message proxy (3-way) */
 
-ZMQ_EXPORT int zmq_proxy (void *frontend, void *backend, void *capture, void *control);
+ZMQ_EXPORT int zmq_proxy (void *frontend, void *backend, void *capture);
+ZMQ_EXPORT int zmq_proxy_steerable (void *frontend, void *backend, void *capture, void *control);
 
 /*  Encode a binary key as printable text using ZMQ RFC 32  */
 ZMQ_EXPORT char *zmq_z85_encode (char *dest, uint8_t *data, size_t size);

src/zmq.cpp

@@ -1016,7 +1016,19 @@ int zmq_poll (zmq_pollitem_t *items_, int nitems_, long timeout_)
 
 //  The proxy functionality
 
-int zmq_proxy (void *frontend_, void *backend_, void *capture_, void *control_)
+int zmq_proxy (void *frontend_, void *backend_, void *capture_)
+{
+    if (!frontend_ || !backend_) {
+        errno = EFAULT;
+        return -1;
+    }
+    return zmq::proxy (
+        (zmq::socket_base_t*) frontend_,
+        (zmq::socket_base_t*) backend_,
+        (zmq::socket_base_t*) capture_);
+}
+
+int zmq_proxy_steerable (void *frontend_, void *backend_, void *capture_, void *control_)
 {
     if (!frontend_ || !backend_) {
         errno = EFAULT;

tests/test_proxy.cpp

@@ -149,7 +149,7 @@ server_task (void *ctx)
 		threads[thread_nbr] = zmq_threadstart (&server_worker, ctx);
 
 	// Connect backend to frontend via a proxy
-	zmq_proxy (frontend, backend, NULL, control);
+	zmq_proxy_steerable (frontend, backend, NULL, control);
 
 	for (thread_nbr = 0; thread_nbr < QT_WORKERS; thread_nbr++)
 		zmq_threadclose (threads[thread_nbr]);