The funny thing is, the implementation isn't faulty either. Not on any real machine, at least. You don't have enough address space to hold an array large enough to trigger the overflow.
In Java for example, an "int" is 32 bits, even on 64 bits machines/VMs ... where the address space can reach 16.3 million terabytes.
So this little bug can byte, but only if you're manipulating large datasets in memory. And then it's easily discoverable, on top of managed languages anyway (since the index used on an array can't be negative).
if (a[i] < a[j])