[Python-ideas] PEP: Hide implementation details in the C API

[Victor Stinner]

2017-07-12 20:51 GMT+02:00 Brett Cannon <brett at python.org>:
> I also think the motivation doesn't have to be performance but simply
> cleaning up how we expose our C APIs to users as shown by the fact we have
> messed up the stable API by making it opt-out instead of opt-in.

It's hard to sell a "cleanup" to users with no carrot :-) Did someone
remind trying to sell the "Python 3 cleanup"? :-)

> Yeah, that's also what I initially thought. Use a cascading hierarchy so
> that people know they should put anything as high up as possible to minimize
> its exposure.

Yeah, maybe we can do that.

I have to make my own experiment to make sure that #include doesn't
leak symbols by mistakes and that it's still possible to use optimized
macros or functions in builtin modules.


> I think Victor has long-term plans to try and hide the struct details at a
> higher-level and so that would make macros a bad thing. But ignoring the
> specific Py_INCREF/DECREF example, switching to functions does buy us the
> ability to actually change the function implementations between Python
> versions compared to having to worry about what a macro used to do (which is
> a possibility with the stable ABI).

I think that my PEP is currently badly written :-)

In fact, the idea is just to make the stable ABI usable :-) Instead of
hiding structures *and* remove macros, my idea is just to hide
structures but still provides macros... as functions. Basically, it
will be the same API, but usable on more various implementations of
Python.

Victor