Add constructor initializers for ScriptEngines to remove derived classes from ScriptEngine.hpp.

Makefile

@@ -16,7 +16,7 @@ include $(RACK_DIR)/arch.mk
 DUKTAPE ?= 0
 QUICKJS ?= 1
 LUAJIT ?= 1
-PYTHON ?= 1
+PYTHON ?= 0
 
 # Entropia File System Watcher
 efsw := dep/lib/libefsw-static-release.a

src/DuktapeEngine.cpp

@@ -217,6 +217,7 @@ struct DuktapeEngine : ScriptEngine {
 };
 
 
-ScriptEngine* createDuktapeEngine() {
-	return new DuktapeEngine;
-}
+__attribute__((constructor(1000)))
+static void constructor() {
+	addScriptEngine<DuktapeEngine>("js");
+}

src/LuaJITEngine.cpp

@@ -317,6 +317,7 @@ struct LuaJITEngine : ScriptEngine {
 };
 
 
-ScriptEngine* createLuaJITEngine() {
-	return new LuaJITEngine;
-}
+__attribute__((constructor(1000)))
+static void constructor() {
+	addScriptEngine<LuaJITEngine>("lua");
+}

src/Prototype.cpp

@@ -13,6 +13,18 @@ using namespace rack;
 Plugin* pluginInstance;
 
 
+// Don't bother deleting this with a destructor.
+__attribute((init_priority(999)))
+std::map<std::string, ScriptEngineFactory*> scriptEngineFactories;
+
+ScriptEngine* createScriptEngine(std::string extension) {
+	auto it = scriptEngineFactories.find(extension);
+	if (it == scriptEngineFactories.end())
+		return NULL;
+	return it->second->createScriptEngine();
+}
+
+
 // Global warning message for script security
 bool securityRequested = false;
 bool securityAccepted = false;
@@ -253,10 +265,10 @@ struct Prototype : Module {
 		this->script = script;
 
 		// Create script engine from path extension
-		std::string ext = string::filenameExtension(string::filename(path));
-		scriptEngine = createScriptEngine(ext);
+		std::string extension = string::filenameExtension(string::filename(path));
+		scriptEngine = createScriptEngine(extension);
 		if (!scriptEngine) {
-			message = string::f("No engine for .%s extension", ext.c_str());
+			message = string::f("No engine for .%s extension", extension.c_str());
 			return;
 		}
 		scriptEngine->module = this;

src/PythonEngine.cpp

@@ -247,6 +247,7 @@ struct PythonEngine : ScriptEngine {
 };
 
 
-ScriptEngine* createPythonEngine() {
-	return new PythonEngine;
-}
+__attribute__((constructor(1000)))
+static void constructor() {
+	addScriptEngine<PythonEngine>("py");
+}

src/QuickJSEngine.cpp

@@ -327,6 +327,7 @@ struct QuickJSEngine : ScriptEngine {
 };
 
 
-ScriptEngine* createQuickJSEngine() {
-	return new QuickJSEngine();
+__attribute__((constructor(1000)))
+static void constructor() {
+  addScriptEngine<QuickJSEngine>("js");
 }

src/ScriptEngine.hpp

@@ -48,22 +48,20 @@ struct ScriptEngine {
 };
 
 
-// List of ScriptEngines
-
-// Add your createMyEngine() function here.
-ScriptEngine* createDuktapeEngine();
-ScriptEngine* createQuickJSEngine();
-ScriptEngine* createPythonEngine();
-ScriptEngine* createLuaJITEngine();
+struct ScriptEngineFactory {
+	virtual ScriptEngine* createScriptEngine() = 0;
+};
+extern std::map<std::string, ScriptEngineFactory*> scriptEngineFactories;
 
-inline ScriptEngine* createScriptEngine(std::string ext) {
-	ext = rack::string::lowercase(ext);
-	if (ext == "js")
-		return createQuickJSEngine();
-	else if (ext == "lua")
-		return createLuaJITEngine();
-	else if (ext == "py")
-		return createPythonEngine();
-	// Add your file extension check here.
-	return NULL;
+/** Called from functions with
+__attribute__((constructor(1000)))
+*/
+template<typename TScriptEngine>
+void addScriptEngine(std::string extension) {
+	struct TScriptEngineFactory : ScriptEngineFactory {
+		ScriptEngine* createScriptEngine() {
+			return new TScriptEngine;
+		}
+	};
+	scriptEngineFactories[extension] = new TScriptEngineFactory;
 }