...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Return a pointer to the string.
constexpr const_pointer c_str() const;
Returns a pointer to the underlying array serving as storage. The value
returned is such that the range {c_str(), c_str() + size())
is always a valid range, even if the
container is empty.
Constant.
The value returned from this function is never never a null pointer value.