How can a derived class use a protected member of the base class?

Question

Say that a base class A defines a protected member. A derived class B uses this member.

class A
{
public:
  A(int v) : value(v) { }         


        

Answer 1

There is actually a loophole using member pointers (no casting, no copying):

void B::compare_and_print(const A& other) const
{
  auto max_value = std::max(value, other.*(&B::value));
  std::cout << "Max value: " << max_value << "\n";
}