Problem: Poller event fd unspecified

Solution: Specify an invalid file descriptor for socket events

doc/zmq_poller.txt

@@ -104,11 +104,7 @@ The *zmq_poller_event_t* structure is defined as follows:
 typedef struct
 {
     void *socket;
-#if defined _WIN32
-    SOCKET fd;
-#else
-    int fd;
-#endif
+    zmq_fd_t fd;
     void *user_data;
     short events;
 } zmq_poller_event_t;
@@ -142,6 +138,9 @@ _zmq_poller_size_.
 _zmq_poller_wait_all_ returns the number of valid elements. The valid elements
 are placed in positions '0' to 'n_events - 1' in the 'events' array. All
 members of a valid element are set to valid values by _zmq_poller_wait_all_.
+For socket events 'socket' is non-null and 'fd' is an operating system
+specific value for an invalid socket (-1 or INVALID_SOCKET). For fd events
+'socket' is NULL and 'fd' is a valid file descriptor.
 The client does therefore not need to initialize the contents of the events
 array before a call to _zmq_poller_wait_all_. It is unspecified whether the
 the remaining elements of 'events' are written to by _zmq_poller_wait_all_.

src/socket_poller.cpp

@@ -403,7 +403,7 @@ void zmq::socket_poller_t::zero_trail_events (
 {
     for (int i = found_; i < n_events_; ++i) {
         events_[i].socket = NULL;
-        events_[i].fd = 0;
+        events_[i].fd = zmq::retired_fd;
         events_[i].user_data = NULL;
         events_[i].events = 0;
     }
@@ -435,7 +435,7 @@ int zmq::socket_poller_t::check_events (zmq::socket_poller_t::event_t *events_,
 
             if (it->events & events) {
                 events_[found].socket = it->socket;
-                events_[found].fd = 0;
+                events_[found].fd = zmq::retired_fd;
                 events_[found].user_data = it->user_data;
                 events_[found].events = it->events & events;
                 ++found;

src/zmq.cpp

@@ -1299,9 +1299,10 @@ int zmq_poller_wait (void *poller_, zmq_poller_event_t *event_, long timeout_)
     const int rc = zmq_poller_wait_all (poller_, event_, 1, timeout_);
 
     if (rc < 0 && event_) {
-        // TODO this is not portable... zmq_poller_event_t contains pointers,
-        // for which nullptr does not need to be represented by all-zeroes
-        memset (event_, 0, sizeof (zmq_poller_event_t));
+        event_->socket = NULL;
+        event_->fd = zmq::retired_fd;
+        event_->user_data = NULL;
+        event_->events = 0;
     }
     // wait_all returns number of events, but we return 0 for any success
     return rc >= 0 ? 0 : rc;

tests/test_poller.cpp

@@ -686,6 +686,9 @@ void test_poll_client_server ()
     TEST_ASSERT_SUCCESS_ERRNO (zmq_poller_wait (poller, &event, 500));
     TEST_ASSERT_EQUAL_PTR (server, event.socket);
     TEST_ASSERT_NULL (event.user_data);
+#ifndef _WIN32
+    TEST_ASSERT (event.fd == -1);
+#endif
     recv_string_expect_success (server, client_server_msg, 0);
 
     //  Polling on pollout
@@ -694,6 +697,9 @@ void test_poll_client_server ()
     TEST_ASSERT_SUCCESS_ERRNO (zmq_poller_wait (poller, &event, 0));
     TEST_ASSERT_EQUAL_PTR (server, event.socket);
     TEST_ASSERT_NULL (event.user_data);
+#ifndef _WIN32
+    TEST_ASSERT (event.fd == -1);
+#endif
     TEST_ASSERT_EQUAL_INT (ZMQ_POLLOUT, event.events);
 
     //  Stop polling server