Rule Definition
Circular references between header files can lead to difficulties during the program compilation (or can even prevent the compilation).

Remediation
The best answer to this problem is to reconsider the architecture of the program. Sometimes you can use forward declarations to avoid circular references. Using pointers instead of the class allows this to be achieved more easily.

Violation Code Sample

// FILE C1.H 
#ifndef C1_H 
#define C1_H 
#include "C2.h" 
class C2;
class C1 
{ 
   public:
      C1(); 
      C2 x; 
}; 
#endif


// FILE C2.H 
#ifndef C2_H 
#define C2_H 
#include "C1.h" 
class C1;
class C2 
{ 
   public:
       C2(); 
       C1 x; 
}; 
#endif

Fixed Code Sample

// FILE C1.H 
#ifndef C1_H 
#define C1_H 
class C2;
class C1 
{ 
   public:
       C1(); 
        C2 * x; 
}; 
#endif 

// FILE C2.H 
#ifndef C2_H 
#define C2_H 
class C1;
class C2 
{ 
   public:
      C2(); 
      C1 * x; 
}; 
#endif