+1 to remove SetPointerType as it is not thread safe too and can crash as the uses of info->proto use borrowed reference.

Oh, do you mean that no one use should be using it? in this case, I'll remove the use set_type instead.

Yes, you should remove the underlying C implementation as well.

Yes, you should remove the underlying C implementation as well.

I'm not entirely sure I can do it. We only communicated that the Python interface is deprecated, not the C one (even if this should not be used). cc @vstinner @encukou.

(I'm however in favor of doing it, just that I don't know if we can do it without an explicit notice)

set_type set proto for pointer type, that used in lot of places. Also, it will break external users like pyglet who implements IUnknown interface with _type_.

I don't think that the ctypes C API is considered as part of the public C API. I'm not sure if it's technically usable outside CPython.

Yes, we'll need to deprecate set_type, and its C implementation, separately; in 3.15.

Now that __pointer_type__ is in, it should be possible to replace set_type by the new API, in all use cases we're aware of. But let's give users time to report other use cases.