[Bug libquadmath/114140] different results for std::fmin/std::fmax and quadmath fminq/fmaxq if one argument=signaling_NaN

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114140

--- Comment #15 from Richard Biener <rguenth at gcc dot gnu.org> ---
It's the old argument on whether isnan(NaN) should return true or false with
-ffinite-math-only.  With what we currently do "constant folding" sNaN into NaN
would be correct with -fno-signalling-nans, likewise constant folding Inf into
42.0 is "correct" for -ffinite-math-only.

You are basically invoking undefined beavior when introducing sNaN into a
program without using -fsignalling-nans.