// N4606 Committee Draft, Standard for Programming Language C++
// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/n4606.pdf 
#define msg "p272.cpp(128) 11.2 Accessibility of base classes and base class members [class.access.base]"

#include <iostream>


class B { /* ... */ };
class D1 : private B { /* ... */ };
class D2 : public B { /* ... */ };
class D3 : B { /* ... */ }; // B private by default
struct D4 : public B { /* ... */ };
struct D5 : private B { /* ... */ };
struct D6 : B { /* ... */ }; // B public by default
class D7 : protected B { /* ... */ };
struct D8 : protected B { /* ... */ };

class B2 {
public:
int mi; // non-static member
static int si; // static member
};
class D9 : private B2 {
};
class DD : public D9 {
void f();
};
void DD::f() {
mi = 3; // error: mi is private in D9
si = 3; // error: si is private in D9
::B2 b;
b.mi = 3; // OK ( b.mi is different from this->mi)
b.si = 3; // OK ( b.si is different from this->si)
::B2::si = 3; // OK
::B2* bp1 = this; // error: B2 is a private base class
::B2* bp2 = (::B2*)this; // OK with cast
bp2->mi = 3; // OK: access through a pointer to B2.
}

class B3 {
public:
int m;
};
class S: private B3 {
friend class N;
};
class N: private S {
void f() {
B3* p = this; // OK because class S satisfies the fourth condition
// above: B3 is a base class of N accessible in f() because
// B3 is an accessible base class of S and S is an accessible
// base class of N.
}
};

class B4;
class A4 {
private:
int i;
friend void f(B4*);
};
class B4 : public A4 { };
void f(B4* p) {
p->i = 1; // OK: B4* can be implicitly converted to A4*,
// and f has access to i in A4
}


int main(){
  std::cout<< msg << std::endl;
  return EXIT_SUCCESS;
}

$ ./cppgl17.sh p272
$ clang++ p272.cpp
p272.cpp:29:1: error: cannot cast 'DD' to its private base class 'B2'
mi = 3; // error: mi is private in D9
^
p272.cpp:23:12: note: declared private here
class D9 : private B2 {
           ^~~~~~~~~~
p272.cpp:29:1: error: 'mi' is a private member of 'B2'
mi = 3; // error: mi is private in D9
^
p272.cpp:23:12: note: constrained by private inheritance here
class D9 : private B2 {
           ^~~~~~~~~~
p272.cpp:20:5: note: member is declared here
int mi; // non-static member
    ^
p272.cpp:30:1: error: 'si' is a private member of 'B2'
si = 3; // error: si is private in D9
^
p272.cpp:23:12: note: constrained by private inheritance here
class D9 : private B2 {
           ^~~~~~~~~~
p272.cpp:21:12: note: member is declared here
static int si; // static member
           ^
p272.cpp:35:13: error: cannot cast 'DD' to its private base class '::B2'
::B2* bp1 = this; // error: B2 is a private base class
            ^
p272.cpp:23:12: note: declared private here
class D9 : private B2 {
           ^~~~~~~~~~
4 errors generated.

$ g++-7 p272.cpp
p272.cpp: In member function 'void DD::f()':
p272.cpp:29:1: error: 'int B2::mi' is inaccessible within this context
 mi = 3; // error: mi is private in D9
 ^~
p272.cpp:20:5: note: declared here
 int mi; // non-static member
     ^~
p272.cpp:30:1: error: 'int B2::si' is inaccessible within this context
 si = 3; // error: si is private in D9
 ^~
p272.cpp:21:12: note: declared here
 static int si; // static member
            ^~
p272.cpp:30:1: error: 'int B2::si' is inaccessible within this context
 si = 3; // error: si is private in D9
 ^~
p272.cpp:21:12: note: declared here
 static int si; // static member
            ^~
p272.cpp:35:13: error: 'B2' is an inaccessible base of 'DD'
 ::B2* bp1 = this; // error: B2 is a private base class
             ^~~~