#define INT_MIN (-1<<(sizeof(int)*8-1))

int main()
{
  int a, b, neg;
  
  // this should not overflow, even not for a=INT_MIN
  b=a-a;
  
  // this should also not overflow as long as pos<0
  if(neg<0)
    b=neg-INT_MIN;
  
  int x, y, z;

  x = INT_MIN+1;
  y = INT_MIN;
  z = x-y; // neither
}
