std::bind()-ing a base protected member function from a derived class's member function

Question

I want to bind() to my base class\'s version of a function from the derived class. The function is marked protected in the base. When I do so, the code compiles

Answer 1

This has nothing to do with bind. Because of the piece of the Standard @rhalbersma already quoted, the expression &Base::foo is illegal in a non-friended member of Derived, in every context.

But if your intent was to do something equivalent to calling Base::foo();, you have a bigger issue: pointers to member functions always invoke a virtual override.

#include 

class B {
public:
    virtual void f() { std::cout << "B::f" << std::endl; }
};

class D : public B {
public:
    virtual void f() { std::cout << "D::f" << std::endl; }
};

int main() {
    D d;
    d.B::f();   // Prints B::f

    void (B::*ptr)() = &B::f;
    (d.*ptr)(); // Prints D::f!
}