[Bug libstdc++/110860] std::format("{:f}",2e304) invokes undefined behaviour

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110860

--- Comment #13 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Oh dear, I should stop trying to do so many things at once. I did consider
using __v < some_constant because we only need that code for large values, not
for 0 and not for anything less than 1. We could maybe use
numeric_limits<Fp>::digits10 or something like that.

Your approach looks good though. I'm not sure if frexpf and frexpl are
universally supported on all targets we care about, but maybe they're present
on all targets where our std::to_chars is enabled.