g++ rejects following code.

template<class T> struct B
{
  void foo() { }
};

template <class T> struct D: B<int>,B<T>
{
  void bar() { foo(); } // call B<int>::foo()
};

int main()
{
  D<void> x;
  x.bar();
  return 0;
}

-------------------------------------------
$ gcc cc.cpp
cc.cpp: In member function 'void D<T>::bar() [with T = void]':
cc.cpp:14:   instantiated from here
cc.cpp:8: error: request for member 'foo' is ambiguous
cc.cpp:3: error: candidates are: void B<T>::foo() [with T = void]
cc.cpp:3: error:                 void B<T>::foo() [with T = int]