> Ideally a constexpr string object using constexpr operator new could do that,
> but such a thing does not exist in C++ yet and definitely did not for C++11 or
> C++14.
>
> The best you can get until is to benefit from the Small String Optimisation.

What is the size threshold at which SSO kicks in? Is it implementation
defined? Is there a way to figure out if a string has been "SSO-ed" ?

The largest string in my case is 18 (lowest is 4). Wonder if SSO will
be applicable here.