Compiler Error C2248 

Error Message

'member' : cannot access 'access' member declared in class 'class'

Members of a derived class cannot access private members of a base class. Objects created from a class cannot access protected or private members of that class.

See Knowledge Base article Q243351 for more information on C2248.

The following sample generates C2248:

// C2248.cpp
#include <stdio.h>
class X {
public:
   int  m_pubMemb;
   void setPrivMemb( int i ) {
      m_privMemb = i;
      printf_s("\n%d", m_privMemb);
   }
protected:
   int  m_protMemb;

private:
   int  m_privMemb;
} x;

int main() {
   x.m_pubMemb = 4;
   printf_s("\n%d", x.m_pubMemb);
   x.m_protMemb = 2;   // C2248 m_protMemb is protected
   x.m_privMemb = 3;   // C2248  m_privMemb is private
   x.setPrivMemb(0);   // OK uses public access function
}

Another conformance issue that exposes C2248 is the use of template friends and specialization. For more information, see Linker Tools Error LNK2019.

// C2248_b.cpp
template<class T>
void f(T t) {
   t.i;   // C2248
}

struct S {
private:
   int i;

public:
   S() {}
   // Delete the following line to resolve.
   friend void f(S);   // refer to the non-template function void f(S)

   // Uncomment the following line to resolve.
   // friend void f<S>(S);
};

int main() {
   S s;
   f<S>(s);
}

Another conformance issue that exposes C2248 is when you attempt to declare a friend of a class and when the class is not visible to the friend declaration in the scope of the class. In this case, grant friendship to the enclosing class to resolve the error. For more information, see Breaking Changes in the Visual C++ 2005 Compiler.

// C2248_c.cpp
// compile with: /c
class T {
   class S {
      class E {};
   };
   friend class S::E;   // C2248
};

class A {
   class S {
      class E {};
      friend class A;   // grant friendship to enclosing class
   };
   friend class S::E;   // OK
};