Function swap

uspace/lib/cpp/include/__bits/string/string.hpp:1871–1876

    template<class Char, class Traits, class Allocator>
    void swap(basic_string<Char, Traits, Allocator>& lhs,
              basic_string<Char, Traits, Allocator>& rhs)
        noexcept(noexcept(lhs.swap(rhs)))
    {
        lhs.swap(rhs);
    }

    /**
     * 21.5, numeric conversions: