When does a sub-class override a super-class method?

gistfile1.cpp

#include <cstdio>

void checkVTBL0andCall(void* ptr)
{
    long long* ptr_object = (long long*)ptr;
    printf("ptr_object = %llx\n", (long long)ptr_object);

    long long vptr = ptr_object[0];
    printf("vptr = %llx\n", (long long)vptr);

    long long* vtbl = (long long*)vptr;
    printf("vtbl[0] = %llx\n", (long long)vtbl[0]);

    void (*f)() = (void (*)())vtbl[0];
    f();

    return;
}

class ClassA
{
public:
    ClassA()
    {
        checkVTBL0andCall(this);
        method(); // will call ClassA::method()
    }

    virtual void method()
    {
        printf("ClassA::method()\n");
    }

    void method2()
    {
        method(); // will call ClassB::method()
    }
};

class ClassB : public ClassA
{
public:
    void method()
    {
        printf("ClassB::method()\n");
    }
};

int main()
{
    ClassA* ptr = new ClassB;
    checkVTBL0andCall(ptr);
    ptr->method2();

    return 0;
}