> Does that stay true once the GIL turns back on? In the current nogil implementation, AFAICS, it seems the GIL can't be turned back on so there is no answer y

> Does that stay true once the GIL turns back on? In the current nogil implementation, AFAICS, it seems the GIL can't be turned back on so there is no answer yet. Theoretically, you could have a one-off operation which fixes all objects when the GIL is turned on. However, there's no way to get all objects in Python. gc.get_objects() only returns tracked objects, and there is no way to list untracked objects. It seems, three fields are exposed on every CPython object in the stable ABI, any change which affects their offsets will break the stable ABI. https://github.com/capi-workgroup/problems/issues/4#issuecomment-1540917809 https://github.com/capi-workgroup/problems/issues/4#issuecom... > I'm not following why this affects ABI compatibility, sorry. True, PyType_FromSpec can set tp_alloc to a wrapper function which papers over the difference in what the "allocfunc" should initialise the memory to. Re performance - merging the change is the only way people will actually start targeting nogil.