Re: Protecting C code from continuations

[Neil Jerram]

Gary Houston wrote:

> I wrote something a while ago that I think is relevant to this. In CVS:
>
> guile/workbook/extension/dynamic-root.text 

Thanks Gary, that's interesting.  However, it still doesn't do what I'm 
looking for, I'm afraid, because I actually want to be able to invoke a 
continuation within one C->Scheme entry point that was captured during a 
previous C->Scheme entry point.

I now think that I can achieve what I want by making all the C->Scheme 
entry points look like this:

(define last-c-continuation #f)

(define (entry-point ...)
  (call/cc (lambda (cont)
             (set! last-c-continuation cont)
             (catch #t
                    interesting-stuff
                    exception-handler)
             (last-c-continuation #f))))

Then, even if `interesting-stuff' invokes a continuation, it will jump 
into a call stack that is identical as far as the high level frames 
shown here are concerned; and the new call stack will still invoke 
last-c-continuation, thus restoring the stack for the containing C code.

Any comments on this, including whether it will or won't work?

Thanks,
     Neil