constexpr initializing with pointers

c++, constants, constexpr, pointers

Solution

Make them `static` to fix their addresses:

int main()
{
  constexpr int *np = nullptr; // np is a constant to int that points to null;
  static int j = 0;
  static constexpr int i = 42; // type of i is const int
  constexpr const int *p = &i; // p is a constant pointer to the const int i;
  constexpr int *p1 = &j; // p1 is a constant pointer to the int j; 
}

This is known as an address constant expression [5.19p3]:

An address constant expression is a prvalue core constant expression of pointer type that evaluates to the address of an object with static storage duration, to the address of a function, or to a null pointer value, or a prvalue core constant expression of type std::nullptr_t.

Problem

I am trying to initialize a constexpr declaration with a pointer to int which is a const object. I also try to define an object with a object that is not a const type. Code: ``` #include <iostream> int main() { constexpr int *np = nullptr; // np is a constant to int that points to null; int j = 0; constexpr int i = 42; // type of i is const int constexpr const int *p = &i; // p is a constant pointer to the const int i; constexpr int *p1 = &j; // p1 is a constant pointer to the int j; } ``` g++ log: ``` constexpr.cc:8:27: error: ‘& i’ is not a constant expression constexpr.cc:9:22: error: ‘& j’ is not a constant expression ``` I believe it is because the objects in main have no fixed addresses, thus g++ is throwing error messages back at me; how would I correct this? Without using literal types.

Original source