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

Antoine Pitrou solipsis at pitrou.net
Mon May 6 11:34:22 EDT 2019

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 
> 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.



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