[Python-Dev] frame evaluation API PEP

[Guido van Rossum]

On Mon, Jun 20, 2016 at 12:59 PM, Brett Cannon <brett at python.org> wrote:

> MRAB's response made me think of a possible approach: the co_extra field
>> could be the very last field of the PyCodeObject struct and only present if
>> a certain flag is set in co_flags. This is similar to a trick used by X11
>> (I know, it's long ago :-)
>>
>
> But that doesn't resolve your memory worry, right? For a JIT you will have
> to access the memory regardless for execution count (unless Yury's patch to
> add caching goes in, in which case it will be provided by code objects
> already).
>

If you make the code object constructor another function pointer in the
interpreter struct, you could solve this quite well IMO. An interpreter
with a JIT installed would always create code objects with the co_extra
field. But interpreters without a JIT would have have code objects without
it. This would mean the people who aren't using a JIT at all don't pay for
co_extra. The flag would still be needed so the JIT can tell when you pass
it a code object that was created before the JIT was installed (or
belonging to a different interpreter).

Would that work? Or is it important to be able to import a lot of code and
then later import+install the JIT and have it benefit the code you already
imported?

-- 
--Guido van Rossum (python.org/~guido)
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