Re: PreScheme exception handling

Thomas Hintz <[email protected]> writes:

> I'm attempting to use setjmp and longjmp with PreScheme to handle
> exceptions. The problem is PreScheme pulls the result of the setjmp call
> out of the if statement and instead stores its result in a variable
> which the if statement then checks. For setjmp the call needs to be in
> the if test itself or you get some wacky behavior (it would seem).
>
> So I need:
>
> if (!setjmp(buf)) {
>   handle_error
> } else {
>   code_that_calls_longjmp();
> }
>
> but PreScheme generates:
>
> v = setjmp(buf));
> if ((0 == v)) {
>   code_that_calls_longjmp();
> } else {
>   handle_error
> }
>
> Is there maybe some trick to get PreScheme to do what I want? Or is
> there a better way to do it within PreScheme?

I suspect what you're trying to do is fundamentally incompatible with a
lot of the optimizations performed by the C compiler, which assume there
can't be non-local transfer of control.

I'd start by trying to declare the setjmp be a simple C primop.  Or did
you already do that?

-- 
Regards,
Mike