conversion from derived * to base * exists but is inaccessible

Question

Why does the follwing code produce this error even though c is a struct and has a public inheritance by default??

struct c 
{
protected:
    int i;
public:
    c         


        

Answer 1

You need:

class d : public c

class inheritance is private by default.

When you privately inherit from a class or a struct, you explicitly say, among other things, that direct conversion from a derived type to a base type isn't possible.