[Python-Dev] 'stackless' python?

[Christian Tismer]

rushing at nightmare.com wrote:

[...]

> BTW, I have actually made progress borrowing a bit of code from SCM.
> It uses the stack-copying technique, along with setjmp/longjmp.  It's
> too ugly and unportable to be a real candidate for inclusion in
> Official Python.  [i.e., if it could be made to work it should be
> considered a stopgap measure for the desperate].

I tried it and built it as a Win32 .pyd file, and it seems to
work, but...

> I haven't tested it thoroughly, but I have successfully saved and
> invoked (and reinvoked) a continuation.  Caveat: I have to turn off
> Py_DECREF in order to keep it from crashing.

Indeed, and this seems to be a problem too hard to solve
without lots of work.
Since you keep a snapshot of the current machine stack,
it contains a number of object references which have been
valid when the snapshot was taken, but many are most
probably invalid when you restart the continuation.
I guess, incref-ing all current alive objects on
the interpreter stack would be the minimum, maybe more.

A tuple of necessary references could be used as an
attribute of a Continuation object. I will look
how difficult this is.

ciao - chris


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