[Bug libstdc++/96862] -frounding-math -std=c++2a error: '(1.29e+2 * 6.9314718055994529e-1)' is not a constant expression

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96862

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I think this is a compiler bug. The arithmetic must be valid in constexpr. It
does not have to give the same result as it would during runtime evaluation, so
I think constexpr evaluation should not be disabled by -frounding-math.