Virtual inheritance and static inheritance - mixing in C++

Question

If you have something like this:

#include 

template class A
{
public:
    void func()
    {
        T::func();
    }
};

c         


        

Answer 1

I'm not sure I understand what you're asking, but it appears you are missing the essential CRTP cast:

template
struct A {
  void func() {
    T& self = *static_cast(this);  // CRTP cast
    self.func();
  }
};

struct V : A {  // B for the case of virtual func
  virtual void func() {
    std::cout << "V::func\n";
  }
};

struct NV : A {  // B for the case of non-virtual func
  void func() {
    std::cout << "NV::func\n";
  }
};

If T does not declare its own func, this will be infinite recursion as self.func will find A::func. This is true even if a derived class of T (e.g. DV below) declares its own func but T does not.

Test with different final overrider to show dispatch works as advertised:

struct DV : V {
  virtual void func() {
    std::cout << "DV::func\n";
  }
};
struct DNV : NV {
  void func() {
    std::cout << "DNV::func\n";
  }
};

template
void call(A& a) {
  a.func();  // always calls A::func
}

int main() {
  DV dv;
  call(dv);   // uses virtual dispatch, finds DV::func
  DNV dnv;
  call(dnv);  // no virtual dispatch, finds NV::func

  return 0;
}