[Cfp-interest] exceptional macro

[Mike Cowlishaw]

> Part of the semantics of FP_EXCEPTIONAL is that it preserves 
> the previous state of the flags and traps for exceptions that 
> are mentioned, since these were anticipated, but not flags 
> and traps for exceptions that were not mentioned, since these
> were not.    

I'm a little uncomfortable with that because there may be new exceptions added
in the future (or implementation-specific, such as the 'Clamped' flag in
decNumber).  Having to specify all 'expected' exceptions could be difficult.

> What semantics would you propose for FP_EXCEPTIONS ?

My initial/gut feeling would be to preserve/restore all.  i.e., state after the
call is identical to that before the call.  That way the call is simply a test,
with no side-effects.

Mike


----- 
> > >  FE_EXCEPTIONAL( expression or compound statement, 
> > >                  exception1, exception2, ...)
> > 
> > Rather than having the multiple arguments, perhaps it could 
> > be simply
> > 
> >   FE_EXCEPTIONS( expression )
> > 
> > which returns the exceptions raised in the evaluation of the 
> > expression (or compound statement if that's allowed), ORed 
> > together.  
> > (Assuming the exceptions & subexpressions are defined to be 
> > bit-unique.)