C lacks safe primitives or non-error-prone ways to build abstractions to refer to business objects. There are no safe string references, let along ways to safely manipulate strings. Want to iterate over or index into a result set? You can try to remember to put bounds checks into every API function.

But even with explicit bounds checks, C has an ace up its sleeve.

    int cost_of_nth_item(int n) {
        if (n < 0 || n >= num_items)
            return -1;  // error handling
        …
    }

Safe, right? Not so fast, because if the caller has a code path that forgets to initialize the argument, it’s UB.