POC done

Author: dfb

Source/UnrealEnginePython/Private/UEPyModule.cpp

@@ -1181,10 +1181,12 @@ static void ue_pyobject_dealloc(ue_PyUObject *self)
 #if defined(UEPY_MEMORY_DEBUG)
 	UE_LOG(LogPython, Warning, TEXT("Destroying ue_PyUObject %p mapped to UObject %p"), self, self->ue_object);
 #endif
+    FUnrealEnginePythonHouseKeeper *housekeeper = FUnrealEnginePythonHouseKeeper::Get();
 	if (self->owned)
 	{
-		FUnrealEnginePythonHouseKeeper::Get()->UntrackUObject(self->ue_object);
+		housekeeper->UntrackUObject(self->ue_object);
 	}
+    housekeeper->UnregisterPyUObject(self->ue_object);
 
 	if (self->auto_rooted && (self->ue_object && self->ue_object->IsValidLowLevel() && self->ue_object->IsRooted()))
 	{
@@ -1868,7 +1870,10 @@ ue_PyUObject *ue_get_python_uobject(UObject *ue_obj)
 		ue_py_object->py_dict = PyDict_New();
 		ue_py_object->owned = 0;
 
-		FUnrealEnginePythonHouseKeeper::Get()->RegisterPyUObject(ue_obj, ue_py_object);
+        FUnrealEnginePythonHouseKeeper *housekeeper = FUnrealEnginePythonHouseKeeper::Get();
+        housekeeper->RegisterPyUObject(ue_obj, ue_py_object);
+        Py_INCREF(ue_py_object); // this is needed only because the following decrefs it
+        housekeeper->TrackUObject(ue_obj);
 
 #if defined(UEPY_MEMORY_DEBUG)
 		UE_LOG(LogPython, Warning, TEXT("CREATED UPyObject at %p for %p %s"), ue_py_object, ue_obj, *ue_obj->GetName());

Source/UnrealEnginePython/Public/PythonHouseKeeper.h

@@ -167,6 +167,7 @@ class FUnrealEnginePythonHouseKeeper : public FGCObject
 	{
 		uint32 Garbaged = 0;
 		TArray<UObject *> BrokenList;
+        TArray<ue_PyUObject *> needDecRef;
 		for (auto &UObjectPyItem : UObjectPyMapping)
 		{
 			UObject *Object = UObjectPyItem.Key;
@@ -182,14 +183,26 @@ class FUnrealEnginePythonHouseKeeper : public FGCObject
 				BrokenList.Add(Object);
 				Garbaged++;
 		}
+			else if (Tracker.PyUObject->ob_base.ob_refcnt == 1)
+			{	// the tracker is the only thing keeping this alive, so release the last reference
+#if defined(UEPY_MEMORY_DEBUG)
+				UE_LOG(LogPython, Warning, TEXT("Auto-decrefing UObject at %p %s"), Object, *Object->GetName());
+#endif
+                needDecRef.Add(Tracker.PyUObject);
+            }
 			else
 			{
 #if defined(UEPY_MEMORY_DEBUG)
-				UE_LOG(LogPython, Error, TEXT("UObject at %p %s is in use"), Object, *Object->GetName());
+				UE_LOG(LogPython, Error, TEXT("UObject at %p %s is in use, py ref count %d"), Object, *Object->GetName(), Tracker.PyUObject->ob_base.ob_refcnt);
 #endif
 	}
 		}
 
+        for (ue_PyUObject *py_obj : needDecRef)
+        {
+            Py_DECREF(py_obj); // on the next GC run, this object will dealloc and unregister itself
+        }
+
 		for (UObject *Object : BrokenList)
 		{
 			FPythonUOjectTracker &Tracker = UObjectPyMapping[Object];