[raldi]

Hacking analogy: if you compile and run this program:

    main() {
      int i;
      i = i++;
    }

...the results are undefined. In theory (and the C FAQ has stated this for decades) the compiler can make a program that erases everything on your hard drive and then has the sound card start swearing at you.

But if you're being advised by an expert in the field, they'll tell you that in reality, the results aren't going to be anything like that.