...and the definition itself feels like implementation defined. Could not find it on any standard, only note that other FE_* definitions are left for implementation specific things.
>>> maybe add this to Lua.c ? (even if not needed)
>>>
>>> fesetenv (FE_PC53_ENV);
>
> 'fesetenv' is part of C99, but where does 'FE_PC53_ENV' come from?
>
> -- Roberto