Fix so that C++ destructors can be called again when wrapper objects are garbage collected.

Author: jdduncan

jones-ndb/impl/include/common/JsWrapper.h

@@ -90,14 +90,42 @@ inline void check_class_id(const char *a, const char *b) {
 #define CHECK_CLASS_ID(env, PTR)
 #endif
 
-///*  Delete a native C++ object when the Garbage Collector reclaims its
-//    JavaScript handle.
-//*/
-//template<typename PTR>
-//void onGcReclaim(const WeakCallbackData<Object, PTR> data) {
-//  PTR ptr = data.GetParameter();
-//  if(ptr) delete ptr;
-//}
+/*  Delete a native C++ object when the Garbage Collector reclaims its
+    JavaScript handle.
+    The GcReclaimer holds the pointer to be deleted, its classname for
+    debugging output, and the weak JS reference (which should be Reset).
+*/
+template<typename CPP_OBJECT> class GcReclaimer;  // forward declaration
+
+template<typename CPP_OBJECT>
+void onGcReclaim(const WeakCallbackData<Value, GcReclaimer<CPP_OBJECT> > & data) {
+  GcReclaimer<CPP_OBJECT> * reclaimer = data.GetParameter();
+  reclaimer->reclaim();
+  delete reclaimer;
+}
+
+template<typename CPP_OBJECT> class GcReclaimer {
+public:
+  GcReclaimer(const char * cls, CPP_OBJECT * p) : classname(cls), ptr(p)   { }
+
+  void SetWeakReference(Isolate *isolate, Handle<Value> obj) {
+    notifier.Reset(isolate, obj);
+    notifier.MarkIndependent();
+    notifier.SetWeak(this, onGcReclaim<CPP_OBJECT>);
+  }
+
+  void reclaim() {
+    delete ptr;
+    DEBUG_PRINT_DETAIL("GC Reclaim %s %p", classname, ptr);
+    notifier.Reset();
+  }
+
+private:
+  const char * classname;
+  CPP_OBJECT * ptr;
+  Persistent<Value> notifier;
+};
+
 
 /*****************************************************************
  An Envelope is a simple structure providing some safety 
@@ -190,14 +218,11 @@ class Envelope {
    (if you hold a const pointer to something, you probably don't own its
    memory allocation).
    ******************************************************************/
-  template<typename PTR> 
-  void freeFromGC(PTR ptr, Handle<Value> obj) {
+  template<typename P>
+  void freeFromGC(P * ptr, Handle<Value> obj) {
     if(ptr) {
-      Persistent<Object> notifier;
-      notifier.Reset(isolate, obj->ToObject());
-      notifier.MarkIndependent();
-//      TODO: Figure this out
-//      notifier.SetWeak((void *) ptr, onGcReclaim<PTR>);
+      GcReclaimer<P> * reclaimer = new GcReclaimer<P>(classname, ptr);
+      reclaimer->SetWeakReference(isolate, obj);
     }
   }
 };

jones-ndb/impl/include/ndb/ColumnProxy.h

@@ -50,6 +50,11 @@ inline ColumnProxy::ColumnProxy() :
   jsValue(), blobBuffer(), isNull(false), isLoaded(false), isDirty(false)
 {}
 
+inline ColumnProxy::~ColumnProxy() {
+  jsValue.Reset();
+  blobBuffer.Reset();
+}
+
 inline void ColumnProxy::setHandler(const ColumnHandler *h) {
   handler = h;
 }

jones-ndb/impl/src/ndb/Record_wrapper.cpp

@@ -40,7 +40,7 @@ V8WrapperFn getColumnOffset_wrapper,
 
 class RecordEnvelopeClass : public Envelope {
 public:
-  RecordEnvelopeClass() : Envelope("Record") {
+  RecordEnvelopeClass() : Envelope("const Record") {
     addMethod("getColumnOffset", getColumnOffset_wrapper);
     addMethod("getBufferSize", getBufferSize_wrapper);
     addMethod("setNull", setNull_wrapper);
@@ -57,7 +57,6 @@ RecordEnvelopeClass RecordEnvelope;
 *****/
 Local<Value> Record_Wrapper(const Record *rec) {
   Local<Value> js_record = RecordEnvelope.wrap(rec);
-  RecordEnvelope.freeFromGC(rec, js_record);
   return js_record;
 }