Re: about coroutines

[Marius Vollmer]

Keith Wright <address@hidden> writes:

> > From: Marius Vollmer <address@hidden>
> > 
> > Ok, here is what I've found.
> > 
> > It's a real conservative GC bug, and it's impossible to fix (without
> > going to a precise GC or non-copying continuations) since it is all
> > over the place.  The continuations stick in a stack slot that is not
> > associated with any variable, it's just debris from a previous
> > function call (specifically, from building the lexical environment of
> > call-with-current-continuation).
> 
> I'm not quite understanding.  Are things that have been popped off
> the stack getting included in the copied continuation stack, or
> is the stack getting pushed without being initialized?  (Or
> are those both wrong?)

I don't know.  The continuation is referenced from a cons cell that
was passed as an argument to a function.  After that particular piece
of code (eval.c:2906), the stack slot that I was watching contained
the reference to the cons cell, and it didn't get cleared before the
stack was copied.  When I cleared that stack slot manually, another
references popped up in a different stack slot.

> > One-shot continuations should make for a nice SRFI, actually.
> 
> Ouch.  I don't think so.

Hmm, well, scratch the part about "we could even avoid...", I was
thinking too fast there.  But in general, why don't you think so?