https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112449
--- Comment #10 from post+gcc at ralfj dot de --- The standard says > This annex does not require the full support for signaling NaNs specified in > IEC 60559. This annex uses the term NaN, unless explicitly qualified, to denote quiet NaNs. Where specification of signaling NaNs is not provided, the behavior of signaling NaNs is implementation-defined (either treated as an IEC 60559 quiet NaN or treated as an IEC 60559 signaling NaN). I have no idea how that allows a situation where the *output* of an operation becomes signaling -- that can't usually happen no matter whether the inputs are signaling or quiet. But that seems to be the common interpretation. Still, it seems important that `pow(1.0, 0.0/0.0)` returns `1.0` and not a NaN. That's what the `pow` docs say. So for this there must be a guarantee that `0.0/0.0` is a quiet NaN.
