C++ overload resolution

Question

Given the following example, why do I have to explicitly use the statement b->A::DoSomething() rather than just b->DoSomething()?

Shouldn't the compiler's overload resolution figure out which method I'm talking about?

I'm using Microsoft VS 2005. (Note: using virtual doesn't help in this case.)

class A
{
  public:
    int DoSomething() {return 0;};
};

class B : public A
{
  public:
    int DoSomething(int x) {return 1;};
};

int main()
{
  B* b = new B();
  b->A::DoSomething();    //Why this?
  //b->DoSomething();    //Why not this? (Gives compiler error.)
  delete b;
  return 0;
}

Answer 1

The two “overloads” aren't in the same scope. By default, the compiler only considers the smallest possible name scope until it finds a name match. Argument matching is done afterwards. In your case this means that the compiler sees B::DoSomething. It then tries to match the argument list, which fails.

One solution would be to pull down the overload from A into B's scope:

class B : public A {
public:
    using A::DoSomething;
    // …
}