Virtual function does not overrides to latest inheriting object - c++

Question

I have 3 classes: A, B, C. B inherits from A, and C inherits from B (so C is grandchild of A).
Every object has function talk() that displays text, in A and B it's virtual.
Let have outside function call(A &a), that takes object A by reference, and calls function talk().
Sending object C to the function, it uses talk() from B instead of C, even that at B talk() is virtual.
Why it is so? How to make it call version from C?
#include <iostream>
using namespace std;
class A {
public:
virtual void talk() = 0;
virtual void say() = 0;
};
class B : public A {
public:
virtual void talk() // Why C does not overrides this?
{ cout << "hello\n"; }
};
class C : public B {
public:
void talk (int a) // It should override B.talk();
{ cout << "bye\n";}
virtual void say() { cout << "my name\n"; }
};
void call(A &a) {
a.talk(); // Why does it call virtual talk() from B rather than from C?
a.say(); // This was found so it knows about object C
}
int main() {
C c;
call(c);
system("PAUSE");
return 0;
}
I'd expect that call(A &a) takes the furthest inheritance version if every class between has virtual talk()

Answer 1

In your example, C.talk(int) doesn't override B.talk() because C.talk takes an int as a parameter, so it's an entirely different function.
You can add override after a function declaration to get the compiler to check if it actually overrides anything:
class C : public B {
public:
// Here, the compiler complains because there's no talk(int) method
// That it can override
void talk (int a) override;
{ cout << "bye\n";}
virtual void say() { cout << "my name\n"; }
};