Refine documentation of libm exceptions goals [committed]

[Joseph Myers]

On Wed, 18 Feb 2015, Szabolcs Nagy wrote:

> this is an interesting issue because iso c annex f forbids the
> omission of underflow right now, which is hard to achive unless
> libm checks <= DBL_MIN instead of the sensible < DBL_MIN and
> raises spurious underflow for a lot of exact (or non-tiny) DBL_MIN
> results (which is allowed by the standard)

I don't believe it forbids computing an imprecise result that happens to 
be (exactly) DBL_MIN or more, and so doesn't underflow.

-- 
Joseph S. Myers
joseph@codesourcery.com