Copy Constructor for not dynamic allocation

Question

According to definition : When an object of this class is copied, the pointer member is copied, but not the pointed buffer, resulting in two objects pointing to the same so we use copy constructor.
But in following class there is no copy constructor but it Works! why? Why i dont need to deep copying?

class Human
{
private:
    int* aValue;

public:
    Human(int* param)
    {
        aValue=param;
    }

    void ShowInfos()
    {
        cout<<"Human's info:"<<*aValue<<endl;
    }
};

void JustAFunction(Human m)
{
    m.ShowInfos();
}

int main()
{
    int age = 10;
    Human aHuman(&age);
    aHuman.ShowInfos();
    JustAFunction(aHuman);
    return 0;
}

output:

Human's info : 10
Human's info : 10

Answer 1

A copy constructor is useful when your class owns resources. In your case, it doesn't - it neither creates nor deletes aValue itself.

If you did do that though, say:

Human()
{
    aValue=new int;
}

and properly cleaned up the memory:

~Human()
{
    delete aValue;
}

then you'd run into issues, because Human a; and Human b(a); would have the members aValue point to the same location, and the when they go out of scope, the same memory is released, resulting in a double delete.