> tp_flags type is long, not int.

Oh, I misunderstood what MvL wrote, sorry. I missed PyType_Spec structure.

Here is an updated and more complete patch. I changed the return code of PyType_GetFlags(), instead of changing PyType_HasFeature() macro.

> OTOH, a number of the flags are not considered part of the API at all (unfortunately, they aren't explicitly excluded, either). Before we make such a change, we should really declare what flags are meant to be by an extension module, and what flags are implementation details only to be used by the object runtime itself.

Can't we decide that later? (in other issue?)