Fix Container sorting not working when overriding _sort_children in gdscript

Remove _sort_children from script bindings:
_sort_children is an internal method which shouldn't be exposed to scripts.

Added support for non-bound methods in MessageQueue:
So we can use deferred calls without exposing internal methods to scripts.

Added debug checks in CallableCustomMethodPointer:
Adding method pointer callables to the message queue was causing crashes
in case an object was destroyed and the same memory was allocated for
another one. The new object had a valid object id but the call was erroneous.
Release will be fixed later, along with Variant which has the same problem and
is also fixed for debug only.

core/callable_method_pointer.h

@@ -161,19 +161,35 @@ template <class T, class... P>
 class CallableCustomMethodPointer : public CallableCustomMethodPointerBase {
 	struct Data {
 		T *instance;
+#ifdef DEBUG_ENABLED
+		uint64_t object_id;
+#endif
 		void (T::*method)(P...);
 	} data;
 
 public:
-	virtual ObjectID get_object() const { return data.instance->get_instance_id(); }
+	virtual ObjectID get_object() const {
+#ifdef DEBUG_ENABLED
+		if (ObjectDB::get_instance(ObjectID(data.object_id)) == nullptr) {
+			return ObjectID();
+		}
+#endif
+		return data.instance->get_instance_id();
+	}
 
 	virtual void call(const Variant **p_arguments, int p_argcount, Variant &r_return_value, Callable::CallError &r_call_error) const {
+#ifdef DEBUG_ENABLED
+		ERR_FAIL_COND_MSG(ObjectDB::get_instance(ObjectID(data.object_id)) == nullptr, "Invalid Object id '" + uitos(data.object_id) + "', can't call method.");
+#endif
 		call_with_variant_args(data.instance, data.method, p_arguments, p_argcount, r_call_error);
 	}
 
 	CallableCustomMethodPointer(T *p_instance, void (T::*p_method)(P...)) {
 		zeromem(&data, sizeof(Data)); // Clear beforehand, may have padding bytes.
 		data.instance = p_instance;
+#ifdef DEBUG_ENABLED
+		data.object_id = p_instance->get_instance_id();
+#endif
 		data.method = p_method;
 		_setup((uint32_t *)&data, sizeof(Data));
 	}
@@ -242,20 +258,36 @@ template <class T, class R, class... P>
 class CallableCustomMethodPointerRet : public CallableCustomMethodPointerBase {
 	struct Data {
 		T *instance;
+#ifdef DEBUG_ENABLED
+		uint64_t object_id;
+#endif
 		R(T::*method)
 		(P...);
 	} data;
 
 public:
-	virtual ObjectID get_object() const { return data.instance->get_instance_id(); }
+	virtual ObjectID get_object() const {
+#ifdef DEBUG_ENABLED
+		if (ObjectDB::get_instance(ObjectID(data.object_id)) == nullptr) {
+			return ObjectID();
+		}
+#endif
+		return data.instance->get_instance_id();
+	}
 
 	virtual void call(const Variant **p_arguments, int p_argcount, Variant &r_return_value, Callable::CallError &r_call_error) const {
+#ifdef DEBUG_ENABLED
+		ERR_FAIL_COND_MSG(ObjectDB::get_instance(ObjectID(data.object_id)) == nullptr, "Invalid Object id '" + uitos(data.object_id) + "', can't call method.");
+#endif
 		call_with_variant_args_ret(data.instance, data.method, p_arguments, p_argcount, r_return_value, r_call_error);
 	}
 
 	CallableCustomMethodPointerRet(T *p_instance, R (T::*p_method)(P...)) {
 		zeromem(&data, sizeof(Data)); // Clear beforehand, may have padding bytes.
 		data.instance = p_instance;
+#ifdef DEBUG_ENABLED
+		data.object_id = p_instance->get_instance_id();
+#endif
 		data.method = p_method;
 		_setup((uint32_t *)&data, sizeof(Data));
 	}

core/message_queue.cpp

@@ -155,6 +155,21 @@ Error MessageQueue::push_callable(const Callable &p_callable, const Variant **p_
 	return OK;
 }
 
+Error MessageQueue::push_callable(const Callable &p_callable, VARIANT_ARG_DECLARE) {
+	VARIANT_ARGPTRS;
+
+	int argc = 0;
+
+	for (int i = 0; i < VARIANT_ARG_MAX; i++) {
+		if (argptr[i]->get_type() == Variant::NIL) {
+			break;
+		}
+		argc++;
+	}
+
+	return push_callable(p_callable, argptr, argc);
+}
+
 void MessageQueue::statistics() {
 	Map<StringName, int> set_count;
 	Map<int, int> notify_count;

core/message_queue.h

@@ -79,6 +79,7 @@ public:
 	Error push_notification(ObjectID p_id, int p_notification);
 	Error push_set(ObjectID p_id, const StringName &p_prop, const Variant &p_value);
 	Error push_callable(const Callable &p_callable, const Variant **p_args, int p_argcount, bool p_show_error = false);
+	Error push_callable(const Callable &p_callable, VARIANT_ARG_LIST);
 
 	Error push_call(Object *p_object, const StringName &p_method, VARIANT_ARG_LIST);
 	Error push_notification(Object *p_object, int p_notification);

scene/gui/container.cpp

@@ -140,7 +140,7 @@ void Container::queue_sort() {
 		return;
 	}
 
-	MessageQueue::get_singleton()->push_call(this, "_sort_children");
+	MessageQueue::get_singleton()->push_callable(callable_mp(this, &Container::_sort_children));
 	pending_sort = true;
 }
 
@@ -177,8 +177,6 @@ String Container::get_configuration_warning() const {
 }
 
 void Container::_bind_methods() {
-	ClassDB::bind_method(D_METHOD("_sort_children"), &Container::_sort_children);
-
 	ClassDB::bind_method(D_METHOD("queue_sort"), &Container::queue_sort);
 	ClassDB::bind_method(D_METHOD("fit_child_in_rect", "child", "rect"), &Container::fit_child_in_rect);