I don't know how to link to just a specific part of the line, but the interesting bit is at the end of line 16 and the start of line 17:

    x*=02//* */2
          -1;

With C89, this is evaluated as "x *= 02 / 2 - 1", or "x *= 0".

With C99, this is evaluated as "x *= 02 / -1", or "x *= -2".