Compiler Warning (level 3) C4243
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Compiler Warning (level 3) C4243

Error Message

'conversion type' conversion exists from 'type1' to 'type2', but is inaccessible

A pointer to a derived class is converted to a pointer to a base class, but the derived class inherits the base class with private or protected access.

The following sample generates C4243:

// C4243.cpp
// compile with: /W3
// C4243 expected
struct B {
   int f() {
      return 0;

struct D : private B {};
struct E : public B {};

int main() {
   // Delete the following 2 lines to resolve.
   int (D::* d)() = (int(D::*)()) &B::f; 

   int (E::* e)() = (int(E::*)()) &B::f; // OK
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