Compiler Error C2247

 

The latest version of this topic can be found at Compiler Error C2247.

identifier' not accessible because 'class' uses 'specifier' to inherit from 'class'

identifier is inherited from a class declared with private or protected access.

The following sample generates C2247:

// C2247.cpp  
class A {  
public:  
   int i;  
};  
class B : private A {};    // B inherits a private A  
class C : public B {} c;   // so even though C's B is public  
int j = c.i;               // C2247, i not accessible  

This error can also be generated as a result of compiler conformance work that was done for Visual Studio .NET 2003: access control with protected members. A protected member (n) can only be accessed through a member function of a class (B) that inherits from the class (A) of which it (n) is a member.

For code that is valid in both the Visual Studio .NET 2003 and Visual Studio .NET versions of Visual C++, declare the member to be a friend of the type. Public inheritance could also be used.

// C2247b.cpp  
// compile with: /c  
// C2247 expected  
class A {  
public:  
   void f();  
   int n;  
};  
  
class B: protected A {  
   // Uncomment the following line to resolve.  
   // friend void A::f();  
};  
  
void A::f() {  
   B b;  
   b.n;  
}  

C2247 can also be generated as a result of compiler conformance work that was done for Visual Studio .NET 2003: private base classes now inaccessible. A class (A) that is a private base class to a type (B) should not be accessible to a type (C) that uses B as a base class.

For code that is valid in both the Visual Studio .NET 2003 and Visual Studio .NET versions of Visual C++, use the scope operator.

// C2247c.cpp  
// compile with: /c  
struct A {};  
  
struct B: private A {};  
  
struct C : B {  
   void f() {  
      A *p1 = (A*) this;   // C2247  
      // try the following line instead  
      // ::A *p2 = (::A*) this;  
   }  
};