Restrict param type of FSM events

Previously the param type was `void*` now the type has to be specified
as template parameter of the `CFsm`.
With this commit some casts can be removed.

source/network/FSM.h

@@ -1,4 +1,4 @@
-/* Copyright (C) 2024 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -29,12 +29,13 @@ constexpr unsigned int FSM_INVALID_STATE{std::numeric_limits<unsigned int>::max(
  * The CFsmEvent objects are under the control of CFsm so
  * they are created and deleted via CFsm.
  */
+template <typename MessageType>
 class CFsmEvent
 {
 public:
-	CFsmEvent(unsigned int type, void* pParam) :
+	CFsmEvent(unsigned int type, MessageType param) :
 		m_Type{type},
-		m_Param{pParam}
+		m_Param{param}
 	{}
 
 	unsigned int GetType() const
@@ -42,14 +43,14 @@ public:
 		return m_Type;
 	}
 
-	void* GetParamRef()
+	MessageType GetParamRef()
 	{
 		return m_Param;
 	}
 
 private:
 	unsigned int m_Type; // Event type
-	void* m_Param; // Event paramater
+	MessageType m_Param; // Event paramater
 };
 
 /**
@@ -63,17 +64,17 @@ private:
  * transitions; Mealy machines are event driven where an
  * event triggers a state transition.
  */
-template <typename Context>
+template <typename Context, typename MessageType>
 class CFsm
 {
-	using Action = bool(Context* pContext, CFsmEvent* pEvent);
+	using Action = bool(Context* pContext, CFsmEvent<MessageType>* pEvent);
 
 	struct CallbackFunction
 	{
 		Action* pFunction{nullptr};
 		Context* pContext{nullptr};
 
-		bool operator()(CFsmEvent& event) const
+		bool operator()(CFsmEvent<MessageType>& event) const
 		{
 			return !pFunction || pFunction(pContext, &event);
 		}
@@ -123,7 +124,7 @@ public:
 	 * Updates the FSM and retrieves next state.
 	 * @return whether the state was changed.
 	 */
-	bool Update(unsigned int eventType, void* pEventData)
+	bool Update(unsigned int eventType, MessageType eventData)
 	{
 		if (IsFirstTime())
 			m_CurrState = m_FirstState;
@@ -133,7 +134,7 @@ public:
 		if (transitionIterator == m_Transitions.end())
 			return false;
 
-		CFsmEvent event{eventType, pEventData};
+		CFsmEvent<MessageType> event{eventType, eventData};
 
 		// Save the default state transition (actions might call SetNextState
 		// to override this)

source/network/NetClient.cpp

@@ -663,7 +663,7 @@ void CNetClient::StartGame(const JS::MutableHandleValue initAttributes, const st
 	m_Game->StartGame(initAttributes, savedState);
 }
 
-bool CNetClient::OnConnect(CNetClient* client, CFsmEvent* event)
+bool CNetClient::OnConnect(CNetClient* client, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_CONNECT_COMPLETE);
 
@@ -674,7 +674,7 @@ bool CNetClient::OnConnect(CNetClient* client, CFsmEvent* event)
 	return true;
 }
 
-bool CNetClient::OnHandshake(CNetClient* client, CFsmEvent* event)
+bool CNetClient::OnHandshake(CNetClient* client, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_SERVER_HANDSHAKE);
 	client->m_ServerHandshake = *static_cast<CSrvHandshakeMessage*>(event->GetParamRef());
@@ -685,7 +685,7 @@ bool CNetClient::OnHandshake(CNetClient* client, CFsmEvent* event)
 	return true;
 }
 
-bool CNetClient::OnHandshakeResponse(CNetClient* client, CFsmEvent* event)
+bool CNetClient::OnHandshakeResponse(CNetClient* client, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_SERVER_HANDSHAKE_RESPONSE);
 
@@ -713,7 +713,7 @@ bool CNetClient::OnHandshakeResponse(CNetClient* client, CFsmEvent* event)
 	return true;
 }
 
-bool CNetClient::OnAuthenticateRequest(CNetClient* client, CFsmEvent* event)
+bool CNetClient::OnAuthenticateRequest(CNetClient* client, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_AUTHENTICATE);
 
@@ -721,7 +721,7 @@ bool CNetClient::OnAuthenticateRequest(CNetClient* client, CFsmEvent* event)
 	return true;
 }
 
-bool CNetClient::OnAuthenticate(CNetClient* client, CFsmEvent* event)
+bool CNetClient::OnAuthenticate(CNetClient* client, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_AUTHENTICATE_RESULT);
 
@@ -742,7 +742,7 @@ bool CNetClient::OnAuthenticate(CNetClient* client, CFsmEvent* event)
 	return true;
 }
 
-bool CNetClient::OnChat(CNetClient* client, CFsmEvent* event)
+bool CNetClient::OnChat(CNetClient* client, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_CHAT);
 
@@ -756,7 +756,7 @@ bool CNetClient::OnChat(CNetClient* client, CFsmEvent* event)
 	return true;
 }
 
-bool CNetClient::OnReady(CNetClient* client, CFsmEvent* event)
+bool CNetClient::OnReady(CNetClient* client, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_READY);
 
@@ -770,7 +770,7 @@ bool CNetClient::OnReady(CNetClient* client, CFsmEvent* event)
 	return true;
 }
 
-bool CNetClient::OnGameSetup(CNetClient* client, CFsmEvent* event)
+bool CNetClient::OnGameSetup(CNetClient* client, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_GAME_SETUP);
 
@@ -783,7 +783,7 @@ bool CNetClient::OnGameSetup(CNetClient* client, CFsmEvent* event)
 	return true;
 }
 
-bool CNetClient::OnPlayerAssignment(CNetClient* client, CFsmEvent* event)
+bool CNetClient::OnPlayerAssignment(CNetClient* client, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_PLAYER_ASSIGNMENT);
 
@@ -810,7 +810,7 @@ bool CNetClient::OnPlayerAssignment(CNetClient* client, CFsmEvent* event)
 
 // This is called either when the host clicks the StartGame button or
 // if this client rejoins and finishes the download of the simstate.
-bool CNetClient::OnGameStart(CNetClient* client, CFsmEvent* event)
+bool CNetClient::OnGameStart(CNetClient* client, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_GAME_START);
 
@@ -826,7 +826,7 @@ bool CNetClient::OnGameStart(CNetClient* client, CFsmEvent* event)
 	return true;
 }
 
-bool CNetClient::OnSavedGameStart(CNetClient* client, CFsmEvent* event)
+bool CNetClient::OnSavedGameStart(CNetClient* client, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == static_cast<uint>(NMT_SAVED_GAME_START));
 	CGameSavedStartMessage* message{static_cast<CGameSavedStartMessage*>(event->GetParamRef())};
@@ -850,7 +850,7 @@ bool CNetClient::OnSavedGameStart(CNetClient* client, CFsmEvent* event)
 }
 
 
-bool CNetClient::OnJoinSyncStart(CNetClient* client, CFsmEvent* event)
+bool CNetClient::OnJoinSyncStart(CNetClient* client, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_JOIN_SYNC_START);
 
@@ -875,7 +875,7 @@ bool CNetClient::OnJoinSyncStart(CNetClient* client, CFsmEvent* event)
 	return true;
 }
 
-bool CNetClient::OnJoinSyncEndCommandBatch(CNetClient* client, CFsmEvent* event)
+bool CNetClient::OnJoinSyncEndCommandBatch(CNetClient* client, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_END_COMMAND_BATCH);
 
@@ -889,7 +889,7 @@ bool CNetClient::OnJoinSyncEndCommandBatch(CNetClient* client, CFsmEvent* event)
 	return true;
 }
 
-bool CNetClient::OnRejoined(CNetClient* client, CFsmEvent* event)
+bool CNetClient::OnRejoined(CNetClient* client, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_REJOINED);
 
@@ -902,7 +902,7 @@ bool CNetClient::OnRejoined(CNetClient* client, CFsmEvent* event)
 	return true;
 }
 
-bool CNetClient::OnKicked(CNetClient* client, CFsmEvent* event)
+bool CNetClient::OnKicked(CNetClient* client, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_KICKED);
 
@@ -916,7 +916,7 @@ bool CNetClient::OnKicked(CNetClient* client, CFsmEvent* event)
 	return true;
 }
 
-bool CNetClient::OnClientTimeout(CNetClient* client, CFsmEvent* event)
+bool CNetClient::OnClientTimeout(CNetClient* client, CFsmEvent<CNetMessage*>* event)
 {
 	// Report the timeout of some other client
 
@@ -933,7 +933,7 @@ bool CNetClient::OnClientTimeout(CNetClient* client, CFsmEvent* event)
 	return true;
 }
 
-bool CNetClient::OnClientPerformance(CNetClient* client, CFsmEvent* event)
+bool CNetClient::OnClientPerformance(CNetClient* client, CFsmEvent<CNetMessage*>* event)
 {
 	// Performance statistics for one or multiple clients
 
@@ -957,7 +957,7 @@ bool CNetClient::OnClientPerformance(CNetClient* client, CFsmEvent* event)
 	return true;
 }
 
-bool CNetClient::OnClientsLoading(CNetClient* client, CFsmEvent *event)
+bool CNetClient::OnClientsLoading(CNetClient* client, CFsmEvent<CNetMessage*> *event)
 {
 	ENSURE(event->GetType() == (uint)NMT_CLIENTS_LOADING);
 
@@ -974,7 +974,7 @@ bool CNetClient::OnClientsLoading(CNetClient* client, CFsmEvent *event)
 	return true;
 }
 
-bool CNetClient::OnClientPaused(CNetClient* client, CFsmEvent *event)
+bool CNetClient::OnClientPaused(CNetClient* client, CFsmEvent<CNetMessage*> *event)
 {
 	ENSURE(event->GetType() == (uint)NMT_CLIENT_PAUSED);
 
@@ -988,7 +988,7 @@ bool CNetClient::OnClientPaused(CNetClient* client, CFsmEvent *event)
 	return true;
 }
 
-bool CNetClient::OnLoadedGame(CNetClient* client, CFsmEvent* event)
+bool CNetClient::OnLoadedGame(CNetClient* client, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_LOADED_GAME);
 
@@ -1007,7 +1007,7 @@ bool CNetClient::OnLoadedGame(CNetClient* client, CFsmEvent* event)
 	return true;
 }
 
-bool CNetClient::OnInGame(CNetClient* client, CFsmEvent* event)
+bool CNetClient::OnInGame(CNetClient* client, CFsmEvent<CNetMessage*>* event)
 {
 	// TODO: should split each of these cases into a separate method
 
@@ -1035,7 +1035,7 @@ bool CNetClient::OnInGame(CNetClient* client, CFsmEvent* event)
 	return true;
 }
 
-bool CNetClient::OnFlare(CNetClient* client, CFsmEvent* event)
+bool CNetClient::OnFlare(CNetClient* client, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == static_cast<uint>(NMT_FLARE));
 

source/network/NetClient.h

@@ -59,7 +59,7 @@ enum
  * It provides an interface between the GUI, the network (via CNetClientSession),
  * and the game (via CGame and CNetClientTurnManager).
  */
-class CNetClient : public CFsm<CNetClient>
+class CNetClient : public CFsm<CNetClient, CNetMessage*>
 {
 	NONCOPYABLE(CNetClient);
 
@@ -281,28 +281,28 @@ private:
 	void SendAuthenticateMessage();
 
 	// Net message / FSM transition handlers
-	static bool OnConnect(CNetClient* client, CFsmEvent* event);
-	static bool OnHandshake(CNetClient* client, CFsmEvent* event);
-	static bool OnHandshakeResponse(CNetClient* client, CFsmEvent* event);
-	static bool OnAuthenticateRequest(CNetClient* client, CFsmEvent* event);
-	static bool OnAuthenticate(CNetClient* client, CFsmEvent* event);
-	static bool OnChat(CNetClient* client, CFsmEvent* event);
-	static bool OnReady(CNetClient* client, CFsmEvent* event);
-	static bool OnGameSetup(CNetClient* client, CFsmEvent* event);
-	static bool OnPlayerAssignment(CNetClient* client, CFsmEvent* event);
-	static bool OnInGame(CNetClient* client, CFsmEvent* event);
-	static bool OnGameStart(CNetClient* client, CFsmEvent* event);
-	static bool OnSavedGameStart(CNetClient* client, CFsmEvent* event);
-	static bool OnJoinSyncStart(CNetClient* client, CFsmEvent* event);
-	static bool OnJoinSyncEndCommandBatch(CNetClient* client, CFsmEvent* event);
-	static bool OnFlare(CNetClient* client, CFsmEvent* event);
-	static bool OnRejoined(CNetClient* client, CFsmEvent* event);
-	static bool OnKicked(CNetClient* client, CFsmEvent* event);
-	static bool OnClientTimeout(CNetClient* client, CFsmEvent* event);
-	static bool OnClientPerformance(CNetClient* client, CFsmEvent* event);
-	static bool OnClientsLoading(CNetClient* client, CFsmEvent* event);
-	static bool OnClientPaused(CNetClient* client, CFsmEvent* event);
-	static bool OnLoadedGame(CNetClient* client, CFsmEvent* event);
+	static bool OnConnect(CNetClient* client, CFsmEvent<CNetMessage*>* event);
+	static bool OnHandshake(CNetClient* client, CFsmEvent<CNetMessage*>* event);
+	static bool OnHandshakeResponse(CNetClient* client, CFsmEvent<CNetMessage*>* event);
+	static bool OnAuthenticateRequest(CNetClient* client, CFsmEvent<CNetMessage*>* event);
+	static bool OnAuthenticate(CNetClient* client, CFsmEvent<CNetMessage*>* event);
+	static bool OnChat(CNetClient* client, CFsmEvent<CNetMessage*>* event);
+	static bool OnReady(CNetClient* client, CFsmEvent<CNetMessage*>* event);
+	static bool OnGameSetup(CNetClient* client, CFsmEvent<CNetMessage*>* event);
+	static bool OnPlayerAssignment(CNetClient* client, CFsmEvent<CNetMessage*>* event);
+	static bool OnInGame(CNetClient* client, CFsmEvent<CNetMessage*>* event);
+	static bool OnGameStart(CNetClient* client, CFsmEvent<CNetMessage*>* event);
+	static bool OnSavedGameStart(CNetClient* client, CFsmEvent<CNetMessage*>* event);
+	static bool OnJoinSyncStart(CNetClient* client, CFsmEvent<CNetMessage*>* event);
+	static bool OnJoinSyncEndCommandBatch(CNetClient* client, CFsmEvent<CNetMessage*>* event);
+	static bool OnFlare(CNetClient* client, CFsmEvent<CNetMessage*>* event);
+	static bool OnRejoined(CNetClient* client, CFsmEvent<CNetMessage*>* event);
+	static bool OnKicked(CNetClient* client, CFsmEvent<CNetMessage*>* event);
+	static bool OnClientTimeout(CNetClient* client, CFsmEvent<CNetMessage*>* event);
+	static bool OnClientPerformance(CNetClient* client, CFsmEvent<CNetMessage*>* event);
+	static bool OnClientsLoading(CNetClient* client, CFsmEvent<CNetMessage*>* event);
+	static bool OnClientPaused(CNetClient* client, CFsmEvent<CNetMessage*>* event);
+	static bool OnLoadedGame(CNetClient* client, CFsmEvent<CNetMessage*>* event);
 
 	/**
 	 * Take ownership of a session object, and use it for all network communication.

source/network/NetServer.cpp

@@ -628,7 +628,7 @@ void CNetServerWorker::CheckClientConnections()
 	}
 }
 
-void CNetServerWorker::HandleMessageReceive(const CNetMessage* message, CNetServerSession* session)
+void CNetServerWorker::HandleMessageReceive(CNetMessage* message, CNetServerSession* session)
 {
 	// Handle non-FSM messages first
 	Status status = session->GetFileTransferer().HandleMessageReceive(*message);
@@ -652,7 +652,7 @@ void CNetServerWorker::HandleMessageReceive(const CNetMessage* message, CNetServ
 	}
 
 	// Update FSM
-	if (!session->Update(message->GetType(), (void*)message))
+	if (!session->Update(message->GetType(), message))
 		LOGERROR("Net server: Error running FSM update (type=%d state=%d)", (int)message->GetType(), (int)session->GetCurrState());
 }
 
@@ -904,7 +904,7 @@ void CNetServerWorker::ProcessLobbyAuth(const CStr& name, const CStr& token)
 	(*it)->SendMessage(&emptyMessage);
 }
 
-bool CNetServerWorker::OnClientHandshake(CNetServerSession* session, CFsmEvent* event)
+bool CNetServerWorker::OnClientHandshake(CNetServerSession* session, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_CLIENT_HANDSHAKE);
 
@@ -957,7 +957,7 @@ bool CNetServerWorker::OnClientHandshake(CNetServerSession* session, CFsmEvent*
 	return true;
 }
 
-bool CNetServerWorker::OnAuthenticate(CNetServerSession* session, CFsmEvent* event)
+bool CNetServerWorker::OnAuthenticate(CNetServerSession* session, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_AUTHENTICATE);
 
@@ -1177,7 +1177,7 @@ bool CNetServerWorker::OnAuthenticate(CNetServerSession* session, CFsmEvent* eve
 	return true;
 }
 
-bool CNetServerWorker::OnSimulationCommand(CNetServerSession* session, CFsmEvent* event)
+bool CNetServerWorker::OnSimulationCommand(CNetServerSession* session, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_SIMULATION_COMMAND);
 
@@ -1214,7 +1214,7 @@ bool CNetServerWorker::OnSimulationCommand(CNetServerSession* session, CFsmEvent
 	return true;
 }
 
-bool CNetServerWorker::OnFlare(CNetServerSession* session, CFsmEvent* event)
+bool CNetServerWorker::OnFlare(CNetServerSession* session, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_FLARE);
 
@@ -1226,7 +1226,7 @@ bool CNetServerWorker::OnFlare(CNetServerSession* session, CFsmEvent* event)
 	return true;
 }
 
-bool CNetServerWorker::OnSyncCheck(CNetServerSession* session, CFsmEvent* event)
+bool CNetServerWorker::OnSyncCheck(CNetServerSession* session, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_SYNC_CHECK);
 
@@ -1238,7 +1238,7 @@ bool CNetServerWorker::OnSyncCheck(CNetServerSession* session, CFsmEvent* event)
 	return true;
 }
 
-bool CNetServerWorker::OnEndCommandBatch(CNetServerSession* session, CFsmEvent* event)
+bool CNetServerWorker::OnEndCommandBatch(CNetServerSession* session, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_END_COMMAND_BATCH);
 
@@ -1251,7 +1251,7 @@ bool CNetServerWorker::OnEndCommandBatch(CNetServerSession* session, CFsmEvent*
 	return true;
 }
 
-bool CNetServerWorker::OnChat(CNetServerSession* session, CFsmEvent* event)
+bool CNetServerWorker::OnChat(CNetServerSession* session, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_CHAT);
 
@@ -1277,7 +1277,7 @@ bool CNetServerWorker::OnChat(CNetServerSession* session, CFsmEvent* event)
 	return true;
 }
 
-bool CNetServerWorker::OnReady(CNetServerSession* session, CFsmEvent* event)
+bool CNetServerWorker::OnReady(CNetServerSession* session, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_READY);
 
@@ -1297,7 +1297,7 @@ bool CNetServerWorker::OnReady(CNetServerSession* session, CFsmEvent* event)
 	return true;
 }
 
-bool CNetServerWorker::OnClearAllReady(CNetServerSession* session, CFsmEvent* event)
+bool CNetServerWorker::OnClearAllReady(CNetServerSession* session, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_CLEAR_ALL_READY);
 
@@ -1309,7 +1309,7 @@ bool CNetServerWorker::OnClearAllReady(CNetServerSession* session, CFsmEvent* ev
 	return true;
 }
 
-bool CNetServerWorker::OnGameSetup(CNetServerSession* session, CFsmEvent* event)
+bool CNetServerWorker::OnGameSetup(CNetServerSession* session, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_GAME_SETUP);
 
@@ -1332,7 +1332,7 @@ bool CNetServerWorker::OnGameSetup(CNetServerSession* session, CFsmEvent* event)
 	return true;
 }
 
-bool CNetServerWorker::OnAssignPlayer(CNetServerSession* session, CFsmEvent* event)
+bool CNetServerWorker::OnAssignPlayer(CNetServerSession* session, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_ASSIGN_PLAYER);
 	CNetServerWorker& server = session->GetServer();
@@ -1345,7 +1345,7 @@ bool CNetServerWorker::OnAssignPlayer(CNetServerSession* session, CFsmEvent* eve
 	return true;
 }
 
-bool CNetServerWorker::OnGameStart(CNetServerSession* session, CFsmEvent* event)
+bool CNetServerWorker::OnGameStart(CNetServerSession* session, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_GAME_START);
 	CNetServerWorker& server = session->GetServer();
@@ -1358,7 +1358,7 @@ bool CNetServerWorker::OnGameStart(CNetServerSession* session, CFsmEvent* event)
 	return true;
 }
 
-bool CNetServerWorker::OnSavedGameStart(CNetServerSession* session, CFsmEvent* event)
+bool CNetServerWorker::OnSavedGameStart(CNetServerSession* session, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == static_cast<uint>(NMT_SAVED_GAME_START));
 	CNetServerWorker& server{session->GetServer()};
@@ -1377,7 +1377,7 @@ bool CNetServerWorker::OnSavedGameStart(CNetServerSession* session, CFsmEvent* e
 	return true;
 }
 
-bool CNetServerWorker::OnLoadedGame(CNetServerSession* loadedSession, CFsmEvent* event)
+bool CNetServerWorker::OnLoadedGame(CNetServerSession* loadedSession, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_LOADED_GAME);
 
@@ -1411,7 +1411,7 @@ bool CNetServerWorker::OnLoadedGame(CNetServerSession* loadedSession, CFsmEvent*
 	return true;
 }
 
-bool CNetServerWorker::OnJoinSyncingLoadedGame(CNetServerSession* session, CFsmEvent* event)
+bool CNetServerWorker::OnJoinSyncingLoadedGame(CNetServerSession* session, CFsmEvent<CNetMessage*>* event)
 {
 	// A client rejoining an in-progress game has now finished loading the
 	// map and deserialized the initial state.
@@ -1463,7 +1463,7 @@ bool CNetServerWorker::OnJoinSyncingLoadedGame(CNetServerSession* session, CFsmE
 	return true;
 }
 
-bool CNetServerWorker::OnRejoined(CNetServerSession* session, CFsmEvent* event)
+bool CNetServerWorker::OnRejoined(CNetServerSession* session, CFsmEvent<CNetMessage*>* event)
 {
 	// A client has finished rejoining and the loading screen disappeared.
 	ENSURE(event->GetType() == (uint)NMT_REJOINED);
@@ -1487,7 +1487,7 @@ bool CNetServerWorker::OnRejoined(CNetServerSession* session, CFsmEvent* event)
 	return true;
 }
 
-bool CNetServerWorker::OnKickPlayer(CNetServerSession* session, CFsmEvent* event)
+bool CNetServerWorker::OnKickPlayer(CNetServerSession* session, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_KICKED);
 
@@ -1501,7 +1501,7 @@ bool CNetServerWorker::OnKickPlayer(CNetServerSession* session, CFsmEvent* event
 	return true;
 }
 
-bool CNetServerWorker::OnDisconnect(CNetServerSession* session, CFsmEvent* event)
+bool CNetServerWorker::OnDisconnect(CNetServerSession* session, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_CONNECTION_LOST);
 
@@ -1512,7 +1512,7 @@ bool CNetServerWorker::OnDisconnect(CNetServerSession* session, CFsmEvent* event
 	return true;
 }
 
-bool CNetServerWorker::OnClientPaused(CNetServerSession* session, CFsmEvent* event)
+bool CNetServerWorker::OnClientPaused(CNetServerSession* session, CFsmEvent<CNetMessage*>* event)
 {
 	ENSURE(event->GetType() == (uint)NMT_CLIENT_PAUSED);
 

source/network/NetServer.h

@@ -35,7 +35,7 @@
 
 class CNetServerSession;
 class CNetServerTurnManager;
-class CFsmEvent;
+template <typename MessageType> class CFsmEvent;
 class CPlayerAssignmentMessage;
 class CNetStatsTable;
 class CSimulationMessage;
@@ -298,25 +298,25 @@ private:
 	void OnUserJoin(CNetServerSession* session);
 	void OnUserLeave(CNetServerSession* session);
 
-	static bool OnClientHandshake(CNetServerSession* session, CFsmEvent* event);
-	static bool OnAuthenticate(CNetServerSession* session, CFsmEvent* event);
-	static bool OnSimulationCommand(CNetServerSession* session, CFsmEvent* event);
-	static bool OnFlare(CNetServerSession* session, CFsmEvent* event);
-	static bool OnSyncCheck(CNetServerSession* session, CFsmEvent* event);
-	static bool OnEndCommandBatch(CNetServerSession* session, CFsmEvent* event);
-	static bool OnChat(CNetServerSession* session, CFsmEvent* event);
-	static bool OnReady(CNetServerSession* session, CFsmEvent* event);
-	static bool OnClearAllReady(CNetServerSession* session, CFsmEvent* event);
-	static bool OnGameSetup(CNetServerSession* session, CFsmEvent* event);
-	static bool OnAssignPlayer(CNetServerSession* session, CFsmEvent* event);
-	static bool OnGameStart(CNetServerSession* session, CFsmEvent* event);
-	static bool OnSavedGameStart(CNetServerSession* session, CFsmEvent* event);
-	static bool OnLoadedGame(CNetServerSession* session, CFsmEvent* event);
-	static bool OnJoinSyncingLoadedGame(CNetServerSession* session, CFsmEvent* event);
-	static bool OnRejoined(CNetServerSession* session, CFsmEvent* event);
-	static bool OnKickPlayer(CNetServerSession* session, CFsmEvent* event);
-	static bool OnDisconnect(CNetServerSession* session, CFsmEvent* event);
-	static bool OnClientPaused(CNetServerSession* session, CFsmEvent* event);
+	static bool OnClientHandshake(CNetServerSession* session, CFsmEvent<CNetMessage*>* event);
+	static bool OnAuthenticate(CNetServerSession* session, CFsmEvent<CNetMessage*>* event);
+	static bool OnSimulationCommand(CNetServerSession* session, CFsmEvent<CNetMessage*>* event);
+	static bool OnFlare(CNetServerSession* session, CFsmEvent<CNetMessage*>* event);
+	static bool OnSyncCheck(CNetServerSession* session, CFsmEvent<CNetMessage*>* event);
+	static bool OnEndCommandBatch(CNetServerSession* session, CFsmEvent<CNetMessage*>* event);
+	static bool OnChat(CNetServerSession* session, CFsmEvent<CNetMessage*>* event);
+	static bool OnReady(CNetServerSession* session, CFsmEvent<CNetMessage*>* event);
+	static bool OnClearAllReady(CNetServerSession* session, CFsmEvent<CNetMessage*>* event);
+	static bool OnGameSetup(CNetServerSession* session, CFsmEvent<CNetMessage*>* event);
+	static bool OnAssignPlayer(CNetServerSession* session, CFsmEvent<CNetMessage*>* event);
+	static bool OnGameStart(CNetServerSession* session, CFsmEvent<CNetMessage*>* event);
+	static bool OnSavedGameStart(CNetServerSession* session, CFsmEvent<CNetMessage*>* event);
+	static bool OnLoadedGame(CNetServerSession* session, CFsmEvent<CNetMessage*>* event);
+	static bool OnJoinSyncingLoadedGame(CNetServerSession* session, CFsmEvent<CNetMessage*>* event);
+	static bool OnRejoined(CNetServerSession* session, CFsmEvent<CNetMessage*>* event);
+	static bool OnKickPlayer(CNetServerSession* session, CFsmEvent<CNetMessage*>* event);
+	static bool OnDisconnect(CNetServerSession* session, CFsmEvent<CNetMessage*>* event);
+	static bool OnClientPaused(CNetServerSession* session, CFsmEvent<CNetMessage*>* event);
 
 	/**
 	 * Checks if all clients have finished loading.
@@ -328,7 +328,7 @@ private:
 
 	void ConstructPlayerAssignmentMessage(CPlayerAssignmentMessage& message);
 
-	void HandleMessageReceive(const CNetMessage* message, CNetServerSession* session);
+	void HandleMessageReceive(CNetMessage* message, CNetServerSession* session);
 
 	/**
 	 * Send a network warning if the connection to a client is being lost or has bad latency.

source/network/NetSession.h

@@ -1,4 +1,4 @@
-/* Copyright (C) 2024 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -154,7 +154,7 @@ private:
  * Thread-safety:
  * - This is constructed and used by CNetServerWorker in the network server thread.
  */
-class CNetServerSession : public CFsm<CNetServerSession>, public INetSession
+class CNetServerSession : public CFsm<CNetServerSession, CNetMessage*>, public INetSession
 {
 	NONCOPYABLE(CNetServerSession);
 

source/network/tests/test_FSM.h

@@ -1,4 +1,4 @@
-/* Copyright (C) 2024 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -20,6 +20,7 @@
 #include "network/FSM.h"
 
 #include <array>
+#include <variant>
 
 class TestFSM : public CxxTest::TestSuite
 {
@@ -29,15 +30,15 @@ class TestFSM : public CxxTest::TestSuite
 	};
 
 	template<size_t N>
-	static bool IncrementGlobal(FSMGlobalState* state, CFsmEvent*)
+	static bool IncrementGlobal(FSMGlobalState* state, CFsmEvent<std::monostate>*)
 	{
 		++std::get<N>(state->occurCount);
 		return true;
 	}
 
-	static bool IncrementParam(FSMGlobalState*, CFsmEvent* event)
+	static bool IncrementParam(FSMGlobalState*, CFsmEvent<std::size_t&>* event)
 	{
-		++*reinterpret_cast<size_t*>(event->GetParamRef());
+		++event->GetParamRef();
 		return true;
 	}
 
@@ -60,7 +61,7 @@ public:
 	void test_global()
 	{
 		FSMGlobalState globalState;
-		CFsm<FSMGlobalState> FSMObject;
+		CFsm<FSMGlobalState, std::monostate> FSMObject;
 
 		/*
 		Corresponding pseudocode
@@ -96,27 +97,27 @@ public:
 
 		FSMObject.SetFirstState(static_cast<unsigned int>(State::ZERO));
 
-		TS_ASSERT(FSMObject.Update(static_cast<unsigned int>(Instruction::TO_ONE), nullptr));
+		TS_ASSERT(FSMObject.Update(static_cast<unsigned int>(Instruction::TO_ONE), {}));
 		TS_ASSERT_EQUALS(std::get<1>(globalState.occurCount), 1);
 		TS_ASSERT_EQUALS(FSMObject.GetCurrState(), static_cast<unsigned int>(State::ONE));
 
-		TS_ASSERT(FSMObject.Update(static_cast<unsigned int>(Instruction::TO_TWO), nullptr));
-		TS_ASSERT(FSMObject.Update(static_cast<unsigned int>(Instruction::TO_ZERO), nullptr));
-		TS_ASSERT(FSMObject.Update(static_cast<unsigned int>(Instruction::TO_ONE), nullptr));
-		TS_ASSERT(FSMObject.Update(static_cast<unsigned int>(Instruction::TO_ZERO), nullptr));
-		TS_ASSERT(FSMObject.Update(static_cast<unsigned int>(Instruction::TO_ONE), nullptr));
-		TS_ASSERT(FSMObject.Update(static_cast<unsigned int>(Instruction::TO_ZERO), nullptr));
+		TS_ASSERT(FSMObject.Update(static_cast<unsigned int>(Instruction::TO_TWO), {}));
+		TS_ASSERT(FSMObject.Update(static_cast<unsigned int>(Instruction::TO_ZERO), {}));
+		TS_ASSERT(FSMObject.Update(static_cast<unsigned int>(Instruction::TO_ONE), {}));
+		TS_ASSERT(FSMObject.Update(static_cast<unsigned int>(Instruction::TO_ZERO), {}));
+		TS_ASSERT(FSMObject.Update(static_cast<unsigned int>(Instruction::TO_ONE), {}));
+		TS_ASSERT(FSMObject.Update(static_cast<unsigned int>(Instruction::TO_ZERO), {}));
 		TS_ASSERT_EQUALS(std::get<0>(globalState.occurCount), 3);
 		TS_ASSERT_EQUALS(std::get<1>(globalState.occurCount), 3);
 		TS_ASSERT_EQUALS(std::get<2>(globalState.occurCount), 1);
 
 		// Some transitions do not exist.
-		TS_ASSERT(!FSMObject.Update(static_cast<unsigned int>(Instruction::TO_ZERO), nullptr));
-		TS_ASSERT(!FSMObject.Update(static_cast<unsigned int>(Instruction::TO_TWO), nullptr));
-		TS_ASSERT(FSMObject.Update(static_cast<unsigned int>(Instruction::TO_ONE), nullptr));
-		TS_ASSERT(!FSMObject.Update(static_cast<unsigned int>(Instruction::TO_ONE), nullptr));
-		TS_ASSERT(FSMObject.Update(static_cast<unsigned int>(Instruction::TO_TWO), nullptr));
-		TS_ASSERT(!FSMObject.Update(static_cast<unsigned int>(Instruction::TO_TWO), nullptr));
+		TS_ASSERT(!FSMObject.Update(static_cast<unsigned int>(Instruction::TO_ZERO), {}));
+		TS_ASSERT(!FSMObject.Update(static_cast<unsigned int>(Instruction::TO_TWO), {}));
+		TS_ASSERT(FSMObject.Update(static_cast<unsigned int>(Instruction::TO_ONE), {}));
+		TS_ASSERT(!FSMObject.Update(static_cast<unsigned int>(Instruction::TO_ONE), {}));
+		TS_ASSERT(FSMObject.Update(static_cast<unsigned int>(Instruction::TO_TWO), {}));
+		TS_ASSERT(!FSMObject.Update(static_cast<unsigned int>(Instruction::TO_TWO), {}));
 		TS_ASSERT_EQUALS(std::get<0>(globalState.occurCount), 3);
 		TS_ASSERT_EQUALS(std::get<1>(globalState.occurCount), 4);
 		TS_ASSERT_EQUALS(std::get<2>(globalState.occurCount), 2);
@@ -125,7 +126,7 @@ public:
 	void test_param()
 	{
 		FSMGlobalState globalState;
-		CFsm<FSMGlobalState> FSMObject;
+		CFsm<FSMGlobalState, std::size_t&> FSMObject;
 
 		// Equal to the FSM in test_global.
 		FSMObject.AddTransition(static_cast<unsigned int>(State::ZERO),
@@ -145,17 +146,17 @@ public:
 
 		// Some transitions do not exist.
 		TS_ASSERT(!FSMObject.Update(static_cast<unsigned int>(Instruction::TO_ZERO),
-			static_cast<void*>(&std::get<0>(globalState.occurCount))));
+			std::get<0>(globalState.occurCount)));
 		TS_ASSERT(!FSMObject.Update(static_cast<unsigned int>(Instruction::TO_TWO),
-			static_cast<void*>(&std::get<2>(globalState.occurCount))));
+			std::get<2>(globalState.occurCount)));
 		TS_ASSERT(FSMObject.Update(static_cast<unsigned int>(Instruction::TO_ONE),
-			static_cast<void*>(&std::get<1>(globalState.occurCount))));
+			std::get<1>(globalState.occurCount)));
 		TS_ASSERT(!FSMObject.Update(static_cast<unsigned int>(Instruction::TO_ONE),
-			static_cast<void*>(&std::get<1>(globalState.occurCount))));
+			std::get<1>(globalState.occurCount)));
 		TS_ASSERT(FSMObject.Update(static_cast<unsigned int>(Instruction::TO_TWO),
-			static_cast<void*>(&std::get<2>(globalState.occurCount))));
+			std::get<2>(globalState.occurCount)));
 		TS_ASSERT(!FSMObject.Update(static_cast<unsigned int>(Instruction::TO_TWO),
-			static_cast<void*>(&std::get<2>(globalState.occurCount))));
+			std::get<2>(globalState.occurCount)));
 		TS_ASSERT_EQUALS(std::get<0>(globalState.occurCount), 0);
 		TS_ASSERT_EQUALS(std::get<1>(globalState.occurCount), 1);
 		TS_ASSERT_EQUALS(std::get<2>(globalState.occurCount), 1);