Compiler Error C2051

case expression not constant

Case expressions must be integer constants.

The following sample generates C2051:

// C2051.cpp
class X {};

int main() {
   static X x;
   int i = 0;

   switch (i) {
      case x:   // C2051 use constant expression to resolve error
         break;
      default:
         break;
   }
}

Possible resolution:

// C2051b.cpp
class X {};

int main() {
   static X x;
   int i = 0;

   switch (i) {
      case 1:
         break;
      default:
         break;
   }
}