FairMQ: Support Apple Compiler 8.0

In fact, this commit will workaround a bug with template alias compilation
from Clang 3.4 to Clang 3.8.

fairmq/EventManager.h

@@ -32,7 +32,7 @@ namespace mq
 template<typename K>
 struct Event
 {
-    using KeyType = const K;
+    using KeyType = K;
 };
 
 /**
@@ -53,16 +53,19 @@ struct Event
 class EventManager
 {
   public:
-    template<typename E, typename ...Args>
+    // Clang 3.4-3.8 has a bug and cannot properly deal with the following template alias.
-    using Callback = std::function<void(typename E::KeyType, Args...)>;
+    // Therefore, we leave them here commented out for now.
+    // template<typename E, typename ...Args>
+    // using Callback = std::function<void(typename E::KeyType, Args...)>;
+
     template<typename E, typename ...Args>
     using Signal = boost::signals2::signal<void(typename E::KeyType, Args...)>;
 
     template<typename E, typename ...Args>
-    auto Subscribe(const std::string& subscriber, Callback<E, Args...> callback) -> void
+    auto Subscribe(const std::string& subscriber, std::function<void(typename E::KeyType, Args...)> callback) -> void
     {
         const std::type_index event_type_index{typeid(E)};
-        const std::type_index callback_type_index{typeid(Callback<E, Args...>)};
+        const std::type_index callback_type_index{typeid(std::function<void(typename E::KeyType, Args...)>)};
         const auto signalsKey = std::make_pair(event_type_index, callback_type_index);
         const auto connectionsKey = std::make_pair(subscriber, signalsKey);
 
@@ -84,7 +87,7 @@ class EventManager
     auto Unsubscribe(const std::string& subscriber) -> void
     {
         const std::type_index event_type_index{typeid(E)};
-        const std::type_index callback_type_index{typeid(Callback<E, Args...>)};
+        const std::type_index callback_type_index{typeid(std::function<void(typename E::KeyType, Args...)>)};
         const auto signalsKey = std::make_pair(event_type_index, callback_type_index);
         const auto connectionsKey = std::make_pair(subscriber, signalsKey);
 
@@ -95,10 +98,10 @@ class EventManager
     }
 
     template<typename E, typename ...Args>
-    auto Emit(typename E::KeyType& key, Args... args) const -> void
+    auto Emit(typename E::KeyType key, Args... args) const -> void
     {
         const std::type_index event_type_index{typeid(E)};
-        const std::type_index callback_type_index{typeid(Callback<E, Args...>)};
+        const std::type_index callback_type_index{typeid(std::function<void(typename E::KeyType, Args...)>)};
         const auto signalsKey = std::make_pair(event_type_index, callback_type_index);
 
         (*GetSignal<E, Args...>(signalsKey))(key, std::forward<Args>(args)...);

fairmq/StateMachine.h

@@ -95,7 +95,7 @@ class StateMachine
     struct StateQueued : Event<State> {};
     auto SubscribeToStateChange(const std::string& subscriber, std::function<void(typename StateChange::KeyType newState, State lastState)> callback) -> void { fCallbacks.Subscribe<StateChange, State>(subscriber, callback); }
     auto UnsubscribeFromStateChange(const std::string& subscriber) -> void { fCallbacks.Unsubscribe<StateChange, State>(subscriber); }
-    auto SubscribeToStateQueued(const std::string& subscriber, std::function<void(typename StateChange::KeyType newState, State lastState)> callback) -> void { fCallbacks.Subscribe<StateQueued, State>(subscriber, callback); }
+    auto SubscribeToStateQueued(const std::string& subscriber, std::function<void(typename StateQueued::KeyType newState, State lastState)> callback) -> void { fCallbacks.Subscribe<StateQueued, State>(subscriber, callback); }
     auto UnsubscribeFromStateQueued(const std::string& subscriber) -> void { fCallbacks.Unsubscribe<StateQueued, State>(subscriber); }
 
     auto GetCurrentState() const -> State { std::lock_guard<std::mutex> lock{fMutex}; return fState; }

fairmq/test/event_manager/_event_manager.cxx

@@ -16,7 +16,7 @@ namespace
 using namespace std;
 using namespace fair::mq;
 
-struct TestEvent : fair::mq::Event<std::string> {};
+struct TestEvent : fair::mq::Event<const std::string&> {};
 
 TEST(EventManager, Basics)
 {
@@ -26,14 +26,14 @@ TEST(EventManager, Basics)
     int value = 0;
     string value2;
 
-    EventManager::Callback<TestEvent, int> callback{
+    std::function<void(typename TestEvent::KeyType, int)> callback{
-        [&](TestEvent::KeyType& key, int newValue){
+        [&](TestEvent::KeyType key, int newValue){
             ++call_counter;
             if (key == "test") value = newValue;
         }
     };
-    EventManager::Callback<TestEvent, string> callback2{
+    std::function<void(typename TestEvent::KeyType, string)> callback2{
-        [&](TestEvent::KeyType& key, string newValue){
+        [&](TestEvent::KeyType key, string newValue){
             ++call_counter2;
             if (key == "test") value2 = newValue;
         }