Question

I posted a question recently:
Initialization of Static Class members.

Now please check this code:

#include<iostream>
class A
{
    static int obj_s;
public: 
    A()
    {
        obj_s++;
        std::cout << A::obj_s << "\nObject(s) Created\n";
    }
};

int A::obj_s = 0;

int main()
{
}

Even though one has not created any object of Class A, making the member obj_s hold a value 0 – wouldn’t it need memory since its getting defined?

Answer 1

Obviously, it takes memory. And int A::obj_s=0 is exactly what it does: it defines the variable along with it’s memory. In fact, when we say we defined a variable X, that means we define a memory of sizeof(X), and that memory region we label as X.

---

More about static members:

A::obj_s is a static member of the class A. And static members exist without any instance. They’re not part of instances of A.

§9.4.2/3 and 7 from the Standard,

once the static data member has been
defined, it exists even if no objects
of its class have been created.

Static data members are initialized
and destroyed exactly like non-local
objects (3.6.2, 3.6.3).

Read my complete answer here:

Do static members of a class occupy memory if no object of that class is created?