Problem: Missing swap functions

Solution: Implement for socket_t, context_t, message_t and poller_t
Additionally remove dependency on <functional> by refactoring poller_t
and remove unused <unordered_map> include.

tests/context.cpp

@@ -1,6 +1,11 @@
 #include <catch.hpp>
 #include <zmq.hpp>
 
+#if (__cplusplus >= 201703L)
+static_assert(std::is_nothrow_swappable<zmq::context_t>::value,
+              "context_t should be nothrow swappable");
+#endif
+
 TEST_CASE("context construct default and destroy", "[context]")
 {
     zmq::context_t context;
@@ -12,3 +17,13 @@ TEST_CASE("context create, close and destroy", "[context]")
     context.close();
     CHECK(NULL == (void *) context);
 }
+
+#ifdef ZMQ_CPP11
+TEST_CASE("context swap", "[context]")
+{
+    zmq::context_t context1;
+    zmq::context_t context2;
+    using std::swap;
+    swap(context1, context2);
+}
+#endif

tests/message.cpp

@@ -8,6 +8,10 @@ static_assert(!std::is_copy_constructible<zmq::message_t>::value,
 static_assert(!std::is_copy_assignable<zmq::message_t>::value,
               "message_t should not be copy-assignable");
 #endif
+#if (__cplusplus >= 201703L)
+static_assert(std::is_nothrow_swappable<zmq::message_t>::value,
+              "message_t should be nothrow swappable");
+#endif
 
 TEST_CASE("message default constructed", "[message]")
 {
@@ -15,6 +19,22 @@ TEST_CASE("message default constructed", "[message]")
     CHECK(0u == message.size());
 }
 
+#ifdef ZMQ_CPP11
+TEST_CASE("message swap", "[message]")
+{
+    const std::string data = "foo";
+    zmq::message_t message1;
+    zmq::message_t message2(data.data(), data.size());
+    using std::swap;
+    swap(message1, message2);
+    CHECK(message1.size() == data.size());
+    CHECK(message2.size() == 0);
+    swap(message1, message2);
+    CHECK(message1.size() == 0);
+    CHECK(message2.size() == data.size());
+}
+#endif
+
 namespace {
 const char *const data = "Hi";
 }

tests/monitor.cpp

@@ -4,6 +4,7 @@
 #include <thread>
 #include <mutex>
 #include <condition_variable>
+#include <functional>
 
 class mock_monitor_t : public zmq::monitor_t
 {

tests/poller.cpp

@@ -5,6 +5,11 @@
 #include <array>
 #include <memory>
 
+#if (__cplusplus >= 201703L)
+static_assert(std::is_nothrow_swappable<zmq::poller_t<>>::value,
+              "poller_t should be nothrow swappable");
+#endif
+
 TEST_CASE("poller create destroy", "[poller]")
 {
     zmq::poller_t<> poller;
@@ -28,6 +33,14 @@ TEST_CASE("poller move assign empty", "[poller]")
     b = std::move(a);
 }
 
+TEST_CASE("poller swap", "[poller]")
+{
+    zmq::poller_t<> a;
+    zmq::poller_t<> b;
+    using std::swap;
+    swap(a, b);
+}
+
 TEST_CASE("poller move construct non empty", "[poller]")
 {
     zmq::context_t context;

tests/socket.cpp

@@ -4,6 +4,11 @@
 #include <future>
 #endif
 
+#if (__cplusplus >= 201703L)
+static_assert(std::is_nothrow_swappable<zmq::socket_t>::value,
+              "socket_t should be nothrow swappable");
+#endif
+
 TEST_CASE("socket create destroy", "[socket]")
 {
     zmq::context_t context;
@@ -16,6 +21,15 @@ TEST_CASE("socket create by enum and destroy", "[socket]")
     zmq::context_t context;
     zmq::socket_t socket(context, zmq::socket_type::router);
 }
+
+TEST_CASE("socket swap", "[socket]")
+{
+    zmq::context_t context;
+    zmq::socket_t socket1(context, zmq::socket_type::router);
+    zmq::socket_t socket2(context, zmq::socket_type::dealer);
+    using std::swap;
+    swap(socket1, socket2);
+}
 #endif
 
 TEST_CASE("socket sends and receives const buffer", "[socket]")