[Python-Dev] Stable ABI or not for PyTypeObject?

[Antoine Pitrou]

On Mon, 6 May 2019 15:55:03 +0200
Jeroen Demeyer <J.Demeyer at UGent.be> wrote:
> Hello,
> 
> I have a simple question for which there doesn't seem to be a good 
> answer: is the layout of PyTypeObject considered to be part of the 
> stable ABI?
> 
> Officially, the answer is certainly "no" (see PEP 384).
> 
> However, unofficially the answer might be "yes". At least, the last time 
> that an incompatible change was made to PyTypeObject (adding tp_finalize 
> in Python 3.4, PEP 442), care was taken not to break the ABI by using 
> the Py_TPFLAGS_HAVE_FINALIZE flag.
> 
> There is some discussion about this on https://bugs.python.org/issue32388

The discussion there was more or less conclusive.  At the time it was
too late to go into 3.7 and then I (and others) forgot about it.

We should revive that PR in time for 3.8.

Regards

Antoine.