Calling connect within extension class ctor causes set_instance_bindings error

[Naros]

Godot version

4.2

godot-cpp version

4.2

System information

Windows 11

Issue description

When calling the connect method from within a GDE class ctor, the following error is thrown:

ERROR: Condition "_instance_bindings != nullptr && _instance_bindings[0].binding != nullptr" is true.
   at: Object::set_instance_binding (core\object\object.cpp:1824)

Steps to reproduce

Create a simple GDE class and register signal listener callback in the ctor:

class MyClass : public LineEdit {
 ...
}

MyClass::MyClass() {
  connect("text_submitted", callable_mp(this, &MyClass::_on_text_submitted));
}
...

When the class is created, the error will be thrown.

Minimal reproduction project

N/A

[dsnopek]

Thanks!

I think this is a variation on issue #1039

Basically, at present, you can't pass this into any Godot APIs during the constructor, because the object isn't finished being setup at that point.

[AThousandShips]

Can you try using NOTIFICATION_POSTINITIALIZE instead as a workaround?

[Naros]

Can you try using NOTIFICATION_POSTINITIALIZE instead as a workaround?

No, because unfortunately NOTIFICATION_POSTINITIALIZE is not fired like it is in GDScript, see #1269 ; however, right now I am using NOTIFICATION_ENTER_TREE or NOTIFICATION_READY at the moment.

[bearman92]

I found a workaround that works for me

I added _init() method to Wrapped

class Wrapped() {
...
	virtual void _init() { } // <- here
	void _notification(int p_what) {}
...
}

And call at end of the Wrapped::_postinitialize

void Wrapped::_postinitialize() {
	const StringName *extension_class = _get_extension_class_name();
	if (extension_class) {
		godot::internal::gdextension_interface_object_set_instance(_owner, reinterpret_cast<GDExtensionConstStringNamePtr>(extension_class), this);
	}
	godot::internal::gdextension_interface_object_set_instance_binding(_owner, godot::internal::token, this, _get_bindings_callbacks());
	_init(); // <- here
}

And I just use _init instead of constructors.

[AThousandShips]

Generally many signals are best to connect on entering the tree, partially due to threading, see:

• Crash when connecting or disconnecting a signal from multiple threads godot#34752 (comment)

[dsnopek]

Can you try using NOTIFICATION_POSTINITIALIZE instead as a workaround?

No, because unfortunately NOTIFICATION_POSTINITIALIZE is not fired like it is in GDScript, see #1269 ; however, right now I am using NOTIFICATION_ENTER_TREE or NOTIFICATION_READY at the moment.

PR #1321 was recently merged to fix NOTIFICATION_POSTINITIALIZE. Perhaps that is now another way to work around this issue?

[Naros]

Thanks, based on the feedback, I am going to close this as it seems the agreed approach is to use a later phase during object construction than the constructor to perform signal connections.