Problem: waiting on an empty poller with infinite timeout waits forever

Solution: return EFAULT when such an operation is attempted

src/socket_poller.cpp

@@ -400,6 +400,11 @@ int zmq::socket_poller_t::rebuild ()
 
 int zmq::socket_poller_t::wait (zmq::socket_poller_t::event_t *events_, int n_events_, long timeout_)
 {
+    if (items.empty () && timeout_ < 0) {
+        errno = EFAULT;
+        return -1;
+    }
+
     if (need_rebuild)
         if (rebuild () == -1)
             return -1;

tests/test_poller.cpp

@@ -180,20 +180,16 @@ void test_wait_corner_cases (void *ctx)
     int rc = zmq_poller_wait(poller, &event, 0);
     assert (rc == -1 && errno == ETIMEDOUT);
 
-    //  TODO this can never return, and should yield an error
-#if 0
+    //  this can never return since no socket was registered, and should yield an error
     rc = zmq_poller_wait(poller, &event, -1);
-    assert (rc == 0);
-#endif
+    assert (rc == -1 && errno == EFAULT);
 
     rc = zmq_poller_wait_all (poller, &event, 0, 0);
     assert (rc == -1 && errno == ETIMEDOUT);
 
-    //  TODO this can never return, and should yield an error
-#if 0
+    //  this can never return since no socket was registered, and should yield an error
     rc = zmq_poller_wait_all (poller, &event, 0, -1);
-    assert (rc == 0);
-#endif
+    assert (rc == -1 && errno == EFAULT);
 
     rc = zmq_poller_destroy (&poller);
     assert (rc == 0);