src: make ObjectWrap dtor virtual

Otherwise, subclasses of `ObjectWrap` would not be deleted
correctly by the `delete instance;` line in `FinalizeCallback()`.

(This is also just the right thing to do for classes from which
subclasses are supposed to be created.)

Author: addaleax

napi-inl.h

@@ -2806,11 +2806,10 @@ inline ObjectWrap<T>::ObjectWrap(const Napi::CallbackInfo& callbackInfo) {
   napi_value wrapper = callbackInfo.This();
   napi_status status;
   napi_ref ref;
-  T* instance = static_cast<T*>(this);
-  status = napi_wrap(env, wrapper, instance, FinalizeCallback, nullptr, &ref);
+  status = napi_wrap(env, wrapper, this, FinalizeCallback, nullptr, &ref);
   NAPI_THROW_IF_FAILED_VOID(env, status);
 
-  Reference<Object>* instanceRef = instance;
+  Reference<Object>* instanceRef = this;
   *instanceRef = Reference<Object>(env, ref);
 }
 
@@ -3338,7 +3337,7 @@ inline napi_value ObjectWrap<T>::InstanceSetterCallbackWrapper(
 
 template <typename T>
 inline void ObjectWrap<T>::FinalizeCallback(napi_env /*env*/, void* data, void* /*hint*/) {
-  T* instance = reinterpret_cast<T*>(data);
+  ObjectWrap<T>* instance = static_cast<ObjectWrap<T>*>(data);
   delete instance;
 }
 

napi.h

@@ -1569,7 +1569,7 @@ namespace Napi {
   class ObjectWrap : public Reference<Object> {
   public:
     ObjectWrap(const CallbackInfo& callbackInfo);
-    ~ObjectWrap();
+    virtual ~ObjectWrap();
 
     static T* Unwrap(Object wrapper);