int main ( void )
{
  int x = 2;
  int y = 0;
  int z = 0;

  //...

  switch ( x )
  {
    case 1:
      if ( 0 == y )
      {
        case 2:   //违背1
          z = 1;
          break;
      }
      z = 2;
      break;
    default:
      break;
  }

  return ( 0 );
}