Implementation of nullptr in c++98

17 January 2023

Introduced in c++11, nullptr is a useful keyword, the advantage of nullptr over NULL is, that nullptr acts like a real pointer type thus it adds type safety whereas NULL acts like an integer just set to 0 in pre c++11.



const class nullptr_t { // is a const object
    // convertible to any type of null non-member pointer...
    template<class T>
    operator T*() const {
      return 0;

    // or any type of null member pointer...
    template<class C, class T>
    operator T C::*() const {
      return 0;

    // cant take address of nullptr
    void operator&() const;

} nullptr = {}; // and whose name is nullptr