Re: std::numeric_limits<__float128>::signaling_NaN + __float128-Type

From: John Maddock (jz.maddock_at_[hidden])
Date: 2022-02-17 17:44:46

>> Does anyone have a (non-theoretical) use case for signalling quad-precision NaN's?  And or a working test case?
>>
>> Thanks, John.
>>
> Crap, neither does snanf128, of course; hope that's it then :-)
> https://godbolt.org/z/v854oG8E5

That generates a NaN that has the same general appearance as a 
double-precision signalling NaN, but I'm unable to actually make it 
*signal*.  Unless this is supported by GCC and libquadmath, it still 
looks to me that there are no signalling NaN's for __float128?  To 
repeat myself: do you have a working test case where signalling NaN's 
actually do something useful?  Otherwise it looks to me as though 
has_signalling_NaN really should be false?

John.

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