Problem: poller_t invalid behaviour on invalid sockets

On adding invalid socket (e.g. after move) there was exception thrown
but leaving modified and unconsistent internal state.
Besides that there was no possibility to remove a socket that was moved
into.

Solutions: check for socket validity (added operator bool) and changed
internal unordered_map "handlers" to operator on zmq internal pointers.

Added two test cases covering the issues.

Author: kurdybacha

tests/poller.cpp

@@ -228,4 +228,28 @@ TEST(poller, client_server)
     ASSERT_TRUE(got_pollout);
 }
 
+TEST(poller, poller_add_invalid_socket_throws)
+{
+    zmq::context_t context;
+    zmq::poller_t poller;
+    zmq::socket_t a {context, zmq::socket_type::router};
+    zmq::socket_t b {std::move (a)};
+    ASSERT_THROW (poller.add (a, ZMQ_POLLIN, zmq::poller_t::handler_t {}),
+                  zmq::error_t);
+    ASSERT_EQ (0u, poller.size ());
+}
+
+TEST(poller, poller_remove_invalid_socket_throws)
+{
+    zmq::context_t context;
+    zmq::socket_t socket {context, zmq::socket_type::router};
+    zmq::poller_t poller;
+    ASSERT_NO_THROW (poller.add (socket, ZMQ_POLLIN, zmq::poller_t::handler_t {}));
+    ASSERT_EQ (1u, poller.size ());
+    std::vector<zmq::socket_t> sockets;
+    sockets.emplace_back (std::move (socket));
+    ASSERT_THROW (poller.remove (socket), zmq::error_t);
+    ASSERT_EQ (1u, poller.size ());
+}
+
 #endif

zmq.hpp

@@ -536,6 +536,11 @@ namespace zmq
         {
             return ptr;
         }
+
+        inline operator bool() const ZMQ_NOTHROW
+        {
+            return ptr != NULL;
+        }
     private:
 
         void *ptr;
@@ -1053,10 +1058,12 @@ namespace zmq
 
         void add (zmq::socket_t &socket, short events, handler_t handler)
         {
+            if (!socket)
+                throw error_t ();
             handler_t *handler_ptr = nullptr;
             /// \todo is it sensible to allow handler to be empty? doesn't this lead to an error when the event is signalled? (perhaps it should already lead to an error in zmq_poller_add then)
             if (handler) {
-                auto emplace_res = handlers.emplace(&socket, std::move(handler));
+                auto emplace_res = handlers.emplace (socket.ptr, std::move (handler));
                 handler_ptr = &emplace_res.first->second;
             }
             if (0 == zmq_poller_add (poller_ptr, socket.ptr, handler_ptr, events)) {
@@ -1069,10 +1076,7 @@ namespace zmq
         void remove (zmq::socket_t &socket)
         {
             if (0 == zmq_poller_remove (poller_ptr, socket.ptr)) {
-                auto it = handlers.find (&socket);
-                if (it != handlers.end ()) { /// \todo this may only be false if handler was empty on add
-                    handlers.erase (it);
-                }
+                handlers.erase (socket.ptr);
                 poller_events.pop_back ();
                 return;
             }
@@ -1108,7 +1112,7 @@ namespace zmq
     private:
         void *poller_ptr;
         std::vector<zmq_poller_event_t> poller_events;
-        std::unordered_map<socket_t*, handler_t> handlers;
+        std::unordered_map<void*, handler_t> handlers;
     };  // class poller_t
 #endif //  defined(ZMQ_BUILD_DRAFT_API) && defined(ZMQ_CPP11) && defined(ZMQ_HAVE_POLLER)