Merge pull request #83670 from raulsntos/notification-predelete-cleanup

Add `NOTIFICATION_PREDELETE_CLEANUP` notification to fix C# `Dispose()`

core/object/object.cpp

@@ -198,6 +198,7 @@ bool Object::_predelete() {
 	notification(NOTIFICATION_PREDELETE, true);
 	if (_predelete_ok) {
 		_class_name_ptr = nullptr; // Must restore, so constructors/destructors have proper class name access at each stage.
+		notification(NOTIFICATION_PREDELETE_CLEANUP, true);
 	}
 	return _predelete_ok;
 }

core/object/object.h

@@ -801,6 +801,8 @@ public:
 		NOTIFICATION_POSTINITIALIZE = 0,
 		NOTIFICATION_PREDELETE = 1,
 		NOTIFICATION_EXTENSION_RELOADED = 2,
+		// Internal notification to send after NOTIFICATION_PREDELETE, not bound to scripting.
+		NOTIFICATION_PREDELETE_CLEANUP = 3,
 	};
 
 	/* TYPE API */

modules/mono/csharp_script.cpp

@@ -1989,24 +1989,31 @@ const Variant CSharpInstance::get_rpc_config() const {
 
 void CSharpInstance::notification(int p_notification, bool p_reversed) {
 	if (p_notification == Object::NOTIFICATION_PREDELETE) {
-		// When NOTIFICATION_PREDELETE is sent, we also take the chance to call Dispose().
-		// It's safe to call Dispose() multiple times and NOTIFICATION_PREDELETE is guaranteed
+		if (base_ref_counted) {
+			// At this point, Dispose() was already called (manually or from the finalizer).
+			// The RefCounted wouldn't have reached 0 otherwise, since the managed side
+			// references it and Dispose() needs to be called to release it.
+			// However, this means C# RefCounted scripts can't receive NOTIFICATION_PREDELETE, but
+			// this is likely the case with GDScript as well: https://github.com/godotengine/godot/issues/6784
+			return;
+		}
+	} else if (p_notification == Object::NOTIFICATION_PREDELETE_CLEANUP) {
+		// When NOTIFICATION_PREDELETE_CLEANUP is sent, we also take the chance to call Dispose().
+		// It's safe to call Dispose() multiple times and NOTIFICATION_PREDELETE_CLEANUP is guaranteed
 		// to be sent at least once, which happens right before the call to the destructor.
 
 		predelete_notified = true;
 
 		if (base_ref_counted) {
-			// It's not safe to proceed if the owner derives RefCounted and the refcount reached 0.
-			// At this point, Dispose() was already called (manually or from the finalizer) so
-			// that's not a problem. The refcount wouldn't have reached 0 otherwise, since the
-			// managed side references it and Dispose() needs to be called to release it.
-			// However, this means C# RefCounted scripts can't receive NOTIFICATION_PREDELETE, but
-			// this is likely the case with GDScript as well: https://github.com/godotengine/godot/issues/6784
+			// At this point, Dispose() was already called (manually or from the finalizer).
+			// The RefCounted wouldn't have reached 0 otherwise, since the managed side
+			// references it and Dispose() needs to be called to release it.
 			return;
 		}
 
-		_call_notification(p_notification, p_reversed);
-
+		// NOTIFICATION_PREDELETE_CLEANUP is not sent to scripts.
+		// After calling Dispose() the C# instance can no longer be used,
+		// so it should be the last thing we do.
 		GDMonoCache::managed_callbacks.CSharpInstanceBridge_CallDispose(
 				gchandle.get_intptr(), /* okIfNull */ false);