[Python-Dev] Are undocumented functions part of the stable ABI?

[Jeroen Demeyer]

On 2018-04-10 13:49, Nick Coghlan wrote:
> If it's only a semantic level change in the way the macro gets
> expanded, then whether or not it needs an ABI version guard gets
> judged on a case-by-case basis, and in this particular case, my view
> would be that developers should be able to write extensions using the
> stable ABI that accept function subclasses on 3.8+, without having to
> *require* the use of 3.8+ to import their module.

I don't really get this paragraph, but in any case I decided to *not* 
change PyCFunction_Check in PEP 575. It doesn't seem worth the trouble 
as this macro is probably not often used anyway. Also, it's hard to 
guess what it should be replaced with: why would extensions be calling 
PyCFunction_Check()?