#include <iostream>
 
namespace CHECK  // namespace to let "operator ==" not become global
{
  typedef char no[7];
  template<typename T> no& operator == (const T&, const T&);
 
  template <typename T>
  struct opEqualExists // *(T*)(0) can be replaced by *new T[1] also
  {
    enum { value = (sizeof(*(T*)(0) == *(T*)(0)) != sizeof(no)) };
  };
}
 
#pragma pack(1)
struct A 
{ 
	int x;
	short y;
	char z;
 
	A& operator == (A const &);
};
#pragma pack()
 
int main() {
	std::cout << "sizeof(A) = " << sizeof(A) << std::endl;
    std::cout<< "operator ==() :  exists?  " << CHECK::opEqualExists<A>::value<<std::endl;
}

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