strtod ("nan") returns negative NaN

[Craig Howland]

On 08/15/2018 11:40 AM, Joseph Myers wrote:
> On Wed, 15 Aug 2018, Joseph Myers wrote:
>
>> On Tue, 14 Aug 2018, Craig Howland wrote:
>>
>>>       The f_QNAN value should be 0x7fc00000 regardless of byte ordering.  In
>> It would be better to use __builtin_nan ("") (and __builtin_nanf,
>> __builtin_nanl for other types) rather than using an integer
>> representation at all (of course that requires changes to other code to
>> avoid requiring an integer representation there).
I totally agree.  To add it to the record, in conjunction with this, the strtod 
implementation really should be upgraded to David Gay's more recent version, 
which is 128-bit friendly.  (I almost had this done some time ago, but didn't 
quite finish.)
> (This is not an objection to any of the present patch proposals, just an
> observation that a different approach would avoid a series of problems
> that result from trying to hardcode information about such choices of
> bit-patterns for NaNs.)
>
Also agreed.  If I had had time yesterday I might have tried it as I had briefly 
thought of it, but didn't think to get the idea out to the list, so I'm glad you 
did.