[Python-Dev] C API changes

[Armin Rigo]

Hi Steve,

On 30/11/2018, Steve Dower <steve.dower at python.org> wrote:
> On 29Nov2018 2206, Armin Rigo wrote:
>> On Thu, 29 Nov 2018 at 18:19, Steve Dower <steve.dower at python.org> wrote:
>>> quo. We continue to not be able to change CPython internals at all,
>>> since that will break people using option B.
>>
>> No?  That will only break users if they only have an option-B
>> ``foo.cpython-318m-x86_64-linux-gnu.so``, no option-A .so and no
>> source code, and want to run it elsewhere than CPython 3.18.  That's
>> the same as today.  If you want option-B .so for N versions of
>> CPython, recompile the source code N times.
>>
>> Just to be clear, if done correctly there should be no need for
>> #ifdefs in the source code of the extension module.
>
> The problem is that if option B remains as compatible as it is today, we
> can't make option A faster enough to be attractive. The marketing pitch
> for this looks like: "rewrite all your existing code to be slower but
> works with PyPy, or don't rewrite your existing code and it'll be
> fastest with CPython and won't break in the future". This is status quo
> (where option A today is something like CFFI or Cython), and we can
> already see how many people have made the switch (FWIW, I totally prefer
> Cython over pure C for my own projects :) ).
>
> My proposed marketing pitch is: "rewrite your existing code to be
> forward-compatible today and faster in the future without more work, or
> be prepared to rewrite/update your source code for each CPython release
> to remain compatible with the low level API".
> (...)

Discussing marketing pitches on python-dev is not one of my favorite
past-times, so I'll excuse myself out of this conversation.  Instead,
I might try to implement the basics, check out the performance on
CPython and on PyPy, and seek out interest---I'm thinking about
Cython, for example, which might relatively easily be adapted to
generate that kind of code.  This might be a solution for the poor
performance of Cython on PyPy...  If everything works out, maybe I'll
come back here at some point, with the argument "the CPython C API is
blocking CPython from evolution more and more?  Here's one possible
path forward."


A bientôt,

Armin.