Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

This is an older version of Boost and was released in 2018. The current version is 1.89.0.

static_string::max_size_n

Maximum size of the string excluding the null terminator.

static
std::size_t constexpr max_size_n = N;