Merge pull request #1891 from paddor/master

Fix return value of zmq_poller_wait when used on empty poller

src/socket_poller.cpp

@@ -393,16 +393,22 @@ int zmq::socket_poller_t::wait (zmq::socket_poller_t::event_t *event_, long time
 
 #if defined ZMQ_POLL_BASED_ON_POLL
     if (unlikely (poll_size == 0)) {
+	// We'll report an error (timed out) as if the list was non-empty and
+	// no event occured within the specified timeout. Otherwise the caller
+	// needs to check the return value AND the event to avoid using the
+	// nullified event data.
+        errno = ETIMEDOUT;
         if (timeout_ == 0)
-            return 0;
+            return -1;
 #if defined ZMQ_HAVE_WINDOWS
         Sleep (timeout_ > 0 ? timeout_ : INFINITE);
-        return 0;
+        return -1;
 #elif defined ZMQ_HAVE_ANDROID
         usleep (timeout_ * 1000);
-        return 0;
+        return -1;
 #else
-        return usleep (timeout_ * 1000);
+        usleep (timeout_ * 1000);
+        return -1;
 #endif
     }
 

src/zmq.cpp

@@ -1209,6 +1209,8 @@ int zmq_poller_wait (void *poller_, zmq_poller_event_t *event, long timeout_)
         return -1;
     }
 
+    zmq_assert (event != NULL);
+
     zmq::socket_poller_t::event_t e;
     memset (&e, 0, sizeof (e));
 

tests/test_poller.cpp

@@ -60,6 +60,14 @@ int main (void)
 
     //  Set up poller
     void* poller = zmq_poller_new ();
+    zmq_poller_event_t event;
+
+    // waiting on poller with no registered sockets should report error
+    rc = zmq_poller_wait(poller, &event, 0);
+    assert (rc == -1);
+    assert (errno == ETIMEDOUT);
+
+    // register sink
     rc = zmq_poller_add (poller, sink, sink, ZMQ_POLLIN);
     assert (rc == 0);
     
@@ -69,7 +77,6 @@ int main (void)
     assert (rc == 1);   
 
     //  We expect a message only on the sink
-    zmq_poller_event_t event;
     rc = zmq_poller_wait (poller, &event, -1);
     assert (rc == 0);
     assert (event.socket == sink);