UObject's created from python are now managed by python itself

Author: Roberto De Ioris

Source/UnrealEnginePython/Private/UEPyEngine.cpp

@@ -601,7 +601,17 @@ PyObject *py_unreal_engine_new_object(PyObject * self, PyObject * args)
 	if (!new_object)
 		return PyErr_Format(PyExc_Exception, "unable to create object");
 
-	Py_RETURN_UOBJECT(new_object);
+	ue_PyUObject *py_uobject = ue_get_python_uobject(new_object);
+	if (!py_uobject)
+	{
+		return PyErr_Format(PyExc_Exception, "unable to create python wrapper for uobject");
+	}
+	py_uobject->owned = 1;
+
+	// UObject crated explicitely from python, will be managed by python...
+	FUnrealEnginePythonHouseKeeper::Get()->TrackUObject(new_object);
+
+	return (PyObject *)py_uobject;
 }
 
 PyObject *py_unreal_engine_get_mutable_default(PyObject * self, PyObject * args)

Source/UnrealEnginePython/Private/UEPyModule.cpp

@@ -1122,6 +1122,11 @@ 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
+	if (self->owned)
+	{
+		FUnrealEnginePythonHouseKeeper::Get()->UntrackUObject(self->ue_object);
+	}
+
 	if (self->auto_rooted && (self->ue_object && self->ue_object->IsValidLowLevel() && self->ue_object->IsRooted()))
 	{
 		self->ue_object->RemoveFromRoot();
@@ -1756,6 +1761,7 @@ ue_PyUObject *ue_get_python_uobject(UObject *ue_obj)
 		ue_py_object->py_proxy = nullptr;
 		ue_py_object->auto_rooted = 0;
 		ue_py_object->py_dict = PyDict_New();
+		ue_py_object->owned = 0;
 
 		FUnrealEnginePythonHouseKeeper::Get()->RegisterPyUObject(ue_obj, ue_py_object);
 

Source/UnrealEnginePython/Public/PythonHouseKeeper.h

@@ -5,9 +5,10 @@
 #include "UObject/WeakObjectPtr.h"
 #include "Widgets/SWidget.h"
 #include "Slate/UEPySlateDelegate.h"
+#include "Runtime/CoreUObject/Public/UObject/GCObject.h"
 #include "PythonDelegate.h"
 
-class FUnrealEnginePythonHouseKeeper
+class FUnrealEnginePythonHouseKeeper : public FGCObject
 {
 
 	struct FPythonUOjectTracker
@@ -53,6 +54,11 @@ class FUnrealEnginePythonHouseKeeper
 
 public:
 
+	virtual void AddReferencedObjects(FReferenceCollector& InCollector) override
+	{
+		InCollector.AddReferencedObjects(PythonTrackedObjects);
+	}
+
 	static FUnrealEnginePythonHouseKeeper *Get()
 	{
 		static FUnrealEnginePythonHouseKeeper *Singleton;
@@ -101,6 +107,16 @@ class FUnrealEnginePythonHouseKeeper
 
 	}
 
+	void TrackUObject(UObject *Object)
+	{
+		PythonTrackedObjects.Add(Object);
+	}
+
+	void UntrackUObject(UObject *Object)
+	{
+		PythonTrackedObjects.Remove(Object);
+	}
+
 	void RegisterPyUObject(UObject *Object, ue_PyUObject *InPyUObject)
 	{
 		UObjectPyMapping.Add(Object, FPythonUOjectTracker(Object, InPyUObject));
@@ -124,7 +140,8 @@ class FUnrealEnginePythonHouseKeeper
 #if defined(UEPY_MEMORY_DEBUG)
 			UE_LOG(LogPython, Warning, TEXT("DEFREF'ing UObject at %p (refcnt: %d)"), Object, Tracker->PyUObject->ob_base.ob_refcnt);
 #endif
-			Py_DECREF((PyObject *)Tracker->PyUObject);
+			if (!Tracker->PyUObject->owned)
+				Py_DECREF((PyObject *)Tracker->PyUObject);
 			UnregisterPyUObject(Object);
 			return nullptr;
 		}
@@ -157,18 +174,19 @@ class FUnrealEnginePythonHouseKeeper
 				UE_LOG(LogPython, Error, TEXT("UObject at %p %s is in use"), Object, *Object->GetName());
 #endif
 			}
-			}
+		}
 
 		for (UObject *Object : BrokenList)
 		{
 			FPythonUOjectTracker &Tracker = UObjectPyMapping[Object];
-			Py_DECREF((PyObject *)Tracker.PyUObject);
+			if (!Tracker.PyUObject->owned)
+				Py_DECREF((PyObject *)Tracker.PyUObject);
 			UnregisterPyUObject(Object);
 		}
 
 		return Garbaged;
 
-		}
+	}
 
 
 	int32 DelegatesGC()
@@ -261,4 +279,6 @@ class FUnrealEnginePythonHouseKeeper
 
 	TArray<FPythonSWidgetDelegateTracker> PySlateDelegatesTracker;
 	TArray<TSharedRef<FPythonSlateDelegate>> PyStaticSlateDelegatesTracker;
-	};
+
+	TArray<UObject *> PythonTrackedObjects;
+};

Source/UnrealEnginePython/Public/UnrealEnginePython.h

@@ -36,14 +36,16 @@
 typedef struct
 {
 	PyObject_HEAD
-		/* Type-specific fields go here. */
-		UObject *ue_object;
+	/* Type-specific fields go here. */
+	UObject *ue_object;
 	// reference to proxy class (can be null)
 	PyObject *py_proxy;
 	// the __dict__
 	PyObject *py_dict;
 	// if true RemoveFromRoot will be called at object destruction time
 	int auto_rooted;
+	// if owned the life of the UObject is related to the life of PyObject
+	int owned;
 } ue_PyUObject;
 
 UNREALENGINEPYTHON_API void ue_py_register_magic_module(char *name, PyObject *(*)());