Re: Replacement for SCM_SETJMPBUF?

[Gary Houston]

> From: Maciej Stachowiak <address@hidden>
> Date: Sat, 15 Sep 2001 14:53:41 -0700
> 
> Actually, I do not understand why call-with-dynamic-root unwinds the
> wind handlers at all. On a practical level, I have not seen a case
> where this behavior is useful on a practical level, and on a
> theoretical level, this code does not really leave the dynamic extent
> of the calling function since it will in fact return to it, so
> unwinding the wind handlers here seems counter-intuitive.

That seems reasonable.  Mikael's suggestion that threads start with a
new dynamic context doesn't seem relevant, since threads get a new
dynamic root, unlike the munging of the current root done by
call-with-dynamic-root.

> So rather than seeing a function like this added to Guile, I'd rather
> see the unwinding behavior removed from call-with-dynamic-root, and
> better yet, see a nice function for invoking callbacks that has all
> the desirable properties but does not require filling out structs or
> writing awkward C functions.

I think the cwdr procedure in root.c is almost what you want.  Since
scm_apply_with_dynamic_root seems obsolete, cwdr could take a thunk
instead of a1/args.  Then rename and export.