static const in c++ class: undefined reference

Question

I have a class for local use only (i.e., its cope is only the c++ file it is defined in)

class A {
public:
    static const int MY_CONST = 5;
};

void fun( int b         


        

Answer 1

std::min's arguments are both const int&(not just int), i.e. references to int. And you can't pass a reference to A::MY_CONST because it is not defined (only declared).

Provide a definition in the .cpp file, outside the class:

class A {
public:
    static const int MY_CONST = 5; // declaration
};

const int A::MY_CONST; // definition (no value needed)