Simplify HUGE_VAL definitions [committed]

[Joseph Myers]

On Fri, 1 Sep 2017, Zack Weinberg wrote:

> On 08/31/2017 12:53 PM, Joseph Myers wrote:
> > On Thu, 31 Aug 2017, Zack Weinberg wrote:
> >>
> >>    Otherwise use a numeric constant larger than the largest
> >>    representable finite value in any supported floating-point
> >>    format; in the normal rounding mode, ISO C requires this to be
> >>    rounded to +Infinity, if it exists, or else to the largest
> >>    representable positive value.
> 
> Hang on, is this actually true?  N1570 §6.4.4.2p3 says
> 
> # ... For decimal floating constants, and also for hexadecimal
> # floating constants when FLT_RADIX is not a power of 2, the result is
> # either the nearest representable value, or the larger or smaller
> # representable value immediately adjacent to the nearest
> # representable value, chosen in an implementation-defined manner.
> 
> which would appear to license 1e10000 to be converted to either +Inf
> or DBL_MAX regardless of rounding mode.

Annex F requires conversions of constants (with at most DECIMAL_DIG 
digits) to be to-nearest.  (TS 18661-1 adds the FENV_ROUND pragma to 
choose a different rounding mode for them and for certain operations.)

-- 
Joseph S. Myers
joseph@codesourcery.com