Inheritance: 'A' is an inaccessible base of 'B'

Question

$ cat inheritance.cpp 
#include 

using namespace std;

class A { };
class B : private A { };

int main() {
    A* ab = new B;
}
$
$ g++ inheritance.         


        

Answer 1

private inheritance should only change how the members of class B are visible to the outside world

It does. And if

A* p = new B;

were allowed, then the inherited members of any B could be accessed from the outside world, just by making a A*. Since they're privately inherited, that access is illegal, and so is the upcast.