Virtual methods on a virtual base class

Question

Something that has been confusing me about virtual base class inheritance... Given the following classes:

class A
{
  virtual void foo() = 0;
}
class B : virtual A
{
  void foo() { /* do X */ }
}
class C : virtual A
{
  void foo() { /* do Y */ }
}
class D : B, C
{
}

Will this compile? If so, what would be the result of the following code:

D d;
A* a = &d;
a->foo();

Answer 1

It should not compile, the function foo will be ambiguous. Since A::foo() is pure virtual function, the ambiguity has to be resolved.