[Cfp-interest] FP_EXCEPTIONAL_TEST

[David Hough CFP]

I'm thinking of adding to the other proposals I've made, another special macro

FP_EXCEPTIONAL_TEST( compound-statement)

which returns a bit mask of the 5 standard IEEE exceptions arising in the
compound-statement, leaving the "global" IEEE flags unchanged, and disabling
any more globally-defined alternate exception handling.

This would be a shorthand for those who might want to know about all five
exceptions, or in situations where this would offer a performance advantage.
It would almost always be non-zero because of inexact exceptions.

It's equivalent to saving the flag set before, restoring it after, and
returning as the macro value the flags that arose in compound-statement.
Except for underflow, which is an interesting question: should it report
whether the underflow exception arose, or whether the underflow flag would
have been raised.     For underflow, those are not the same.