Cannot create constexpr std::vector

Question

I can create constexpr std::array:

constexpr std::array values {1,2,3,4,5};

It works fine. But I cannot create

Answer 1

For c++ version at least prior C++2a:

std::vector uses a dynamic memory allocation. Operator new can't be used in constexpr methods, thus std::vector will never be constexpr, constexpr constructor can't be declared for it. std::array doesn't use dynamic memory allocation, it is allocated in stack. It has no any problem with rules of creation constexpr objects and can be constexpr.