BUG: Template Friend Function Causes Compiler Error C2248

• The C/C++ Compiler (CL.EXE) included with: - Microsoft Visual C++, 32-bit Editions, version 5.0

SYMPTOMS

The compiler generates a compiler error C2248 as follows:

   Error C2248: 'member' : cannot access member declared in class 'class'

- If a class declares a template function as a friend function, and - If the template function definition appears after the class definition.

RESOLUTION

Do not declare a template function as a friend of a class.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. We are researching this bug and will post new information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION

The following sample demonstrates the problem and the workaround.

Sample Code

   /*
   Compile option: None
   */

   class X;

   template <class T> void AFunction(X &x, T &t);

   class X
   {
   private:

      int m_n;

   public:

      template <class T> friend void AFunction(X &x, T &t) ;
   };

   template <class T> void AFunction(X &x, T &t)
   {
      x.m_n = t; // C2248 here.
   }

   int main()
   {
      X x;
      int n;
      AFunction(x, n);

           return 0 ;
   }