gcc-you can use this code to learn something about gcc, and inquire further into linux,

				extern "C" void abort (void);								static union { 				  int x1; 				  long x2; 				  short x3;				  long x4;				};								static union {				  union {				    union {				      int z;				    };				  };				  union {				    union {				      double d;				      int i;				    };				  };				};												int main()				{				  z = 3;				  if (i != 3)				    abort ();				  d = 2.5;				}