[Python-Dev] Stackless Python

[Christian Tismer]

Guido van Rossum wrote:

>>>Anything that can be supported by a pure extension module is fair
>>>game IMO.  But it was my understanding that Stackless requires
>>>changes to the VM.

As Armin has shown, it is possible to do the hard switching approach
as a pure extension module.
But that's the opposite of what I want. I want a supportive core
without the need to fiddle with C stacks.
That needs VM changes. Cheating and supplying a different VM
as an extension module is probably no option? :-)

>>>Hey, that's what Stackless already does.  Why is that approach
>>>suddenly not good enough any more?

Philip:

>>I didn't say that.  I was just suggesting that if people had
>>specific features of Stackless that they wanted to see in CPython,
>>that it would be best for them to write a PEP specifically
>>addressing the desired feature(s), rather than asking "why isn't
>>CPython stackless?"

Guido:

> I think the bar should be raised pretty high for Stackless, given the
> various objections that have been raised against it (x86-only code, no
> Jython support, arbitrary exceptions, murky semantics, to name a few).

Huh? There is support for 8 or more platforms, and I'm not addressing
the assembly parts.
It is most probably possible to implement soft-switchign in Jython.
No idea what you mean by arbitrary exceptions (I never had that)
or what's wrong with semantics. On the latter: Well, this is a pure
interface issue. I don't say that everybody must love tasklets,
there are other approaches and interfaces possible.
But they all rely on the non-recursive interpreter core, and that's
the point, IMHO.

> Together, the answer as to "why" should be pretty clean by now.

If you understand the question like "why is current Stackless
not included", that's true. I understood it more like the more
advanced question "why does Python still block itself from
lightweight threading by keping state on the C stack".

ciao - chris
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