I've explained it here: https://blog.deckc.hair/2022-12-11-incorrect-bug-fix-for-24y...
In brief (cp[IPOPT_OLEN] - 1) is the delta, not (cp[IPOPT_OLEN]); according to the original code. (I don't pretend to know where the original -1 comes from).
This means that the IF-statement check is incorrect.
My end game is to get people to write
int const delta = (cp[IPOPT_OLEN] - 1);
>delta is allowed to be zero, we make no progress (as in the original bug)
It's not zero progress because the for loop increments cp every iteration.
In the original bug delta = -1.
However, my point still stands that extracting the complex expression as delta would have helped and possibly avoided the original bug.
int const delta = (cp[IPOPT_OLEN] - 1);
This sort of code is just begging to be misunderstood.
- if (cp[IPOPT_OLEN] > 0 && cp[IPOPT_OLEN] < hlen) {
+ if (cp[IPOPT_OLEN] > 0 && (cp[IPOPT_OLEN] - 1) <= hlen) {
cp[IPOPT_OLEN] refers to the option length. Your delta variable is the length of the option data. The confusing part is that in most network protocols length fields do not count the size of the length number.