error: invalid initialization of non-const reference of type ‘int&’ from an rvalue of type ‘int’

Question

Wrong form:

int &z = 12;

Correct form:

int y;
int &r = y;

Question:

Answer 1

12 is a compile-time constant which can not be changed unlike the data referenced by int&. What you can do is

const int& z = 12;