c++ - How constructor works in private inheritance -

i know there same question topic. i'm still confused. please explain how a's class constructor executing obj inherit a's class constructor privately.

#include <iostream> using namespace std; class a{     public:         a(){             cout << "a" << endl;         } }; class b:private a{     public:         b(){             cout << "b" << endl;         } }; int main(){     b obj;      return 0; } 

output

a b 

private inheritance means public , protected base members become private in derived class. a::a() private in b, , accessible b::b().

what b::b() can't use private constructors of a (but don't have of those):

struct { public:     a(); protected:     a(int); private:     a(int, int); };  struct derived : /* access irrelevant question */ {     derived() : a() {}      // ok     derived() : a(10) {}    // ok     derived() : a(1, 2) {}  // error, inaccessible };