Listing 4 mundo.cpp after including headers

//
//  mundo.cpp
//
//  HERE is referenced by both .h files
//
#define HERE 1

//
//  hither.h
//
#if HERE != 0
   static int hither = 0;
#endif
//
//  yon.h
//
#if HERE != 0;
   extern int yon;
#else
   int yon = 0;
#endif

void main()
   {
   }

//End of File