libscript: Add template for creating new script objects

peter-b · peter-b · commit dbbdb07fed58 · 2017-04-28T12:50:52.000+01:00
Prevent strict aliasing violations when constructing new script
modules and instances.
diff --git a/libscript/src/script-instance.cpp b/libscript/src/script-instance.cpp
@@ -59,7 +59,7 @@ MCScriptCreateInstanceOfModule(MCScriptModuleRef p_module,
     
     // Attempt to create a script object.
     if (t_success)
-        t_success = MCScriptCreateObject(kMCScriptObjectKindInstance, sizeof(MCScriptInstance), (MCScriptObject*&)t_instance);
+        t_success = MCScriptCreateObject(kMCScriptObjectKindInstance, t_instance);
 
     // Now associate the script object with the module (so the 'slots' field make sense).
     if (t_success)
diff --git a/libscript/src/script-module.cpp b/libscript/src/script-module.cpp
@@ -409,7 +409,7 @@ bool MCScriptCreateModuleFromStream(MCStreamRef stream, MCScriptModuleRef& r_mod
     
     // If this fails then we've run out of memory (oh well - not much to be done!).
     MCScriptModule *t_module;
-    if (!MCScriptCreateObject(kMCScriptObjectKindModule, sizeof(MCScriptModule), (MCScriptObject*&)t_module))
+    if (!MCScriptCreateObject(kMCScriptObjectKindModule, t_module))
         return false;
     
     // If the unpickling fails, there's nothing we can do.
diff --git a/libscript/src/script-private.h b/libscript/src/script-private.h
@@ -70,6 +70,16 @@ struct MCScriptObject
 bool MCScriptCreateObject(MCScriptObjectKind kind, size_t size, MCScriptObject*& r_object);
 void MCScriptDestroyObject(MCScriptObject *object);
 
+template <typename ScriptObjectType>
+bool MCScriptCreateObject(MCScriptObjectKind kind, ScriptObjectType*& r_object)
+{
+    MCScriptObject* t_new = nullptr;
+    if (!MCScriptCreateObject(kind, sizeof(ScriptObjectType), t_new))
+        return false;
+    r_object = reinterpret_cast<ScriptObjectType*>(t_new);
+    return true;
+}
+
 MCScriptObject *MCScriptRetainObject(MCScriptObject *object);
 void MCScriptReleaseObject(MCScriptObject *object);
 uint32_t MCScriptGetRetainCountOfObject(MCScriptObject *object);
