Avoiding compiler optimization on a variable with minimum impact on performance

doNotOptimizeAway

/* 
  Usage example:
  int a = my_rand();
  int b = my_rand();
  int c = a + b;
  doNotOptimizeAway (c);
*/
template<class T>
inline void doNotOptimizeAway (T&& x)
{
  volatile const char* c = reinterpret_cast<const char*>(&x);

  if (c != c)
  {
    // the following should never be invoked
    putchar (*c);
  }
}