Re: strtod ("nan") returns negative NaN

Corinna Vinschen <[email protected]> Thu, 16 Aug 2018 11:56:21 +0200

Newsgroups	gmane.comp.lib.newlib
Message-ID	<[email protected]>

On Aug 16 10:22, Masamichi Hosoda wrote:
> > On Aug 15 11:51, Craig Howland wrote:
> >> 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.
> > 
> > Sounds like a nice followup patch...?
> 
> Here's patch v4.
> It uses {nan|nanl} ("") instead of the integer representations of NaN.
> It also removes the unused definitions of them.

Still looks good on Cygwin.  I'll push this tomorrow, unless somebody
objects.


Thanks,
Corinna

-- 
Corinna Vinschen
Cygwin Maintainer
Red Hat

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