JuniorTheoryCommon

What happens when you build and run this program?

C++

#include <iostream>

int main() {
    unsigned i = 2;
    while (i >= 0) {
        std::cout << i << '\n';
        --i;
    }
}

It prints 2, 1, 0, then the largest unsigned value, and never stops

Expecting the loop to stop at -1: an unsigned value is never negative, so --i at 0 gives the largest unsigned value and i >= 0 stays true.
Expecting undefined behavior: only signed overflow is undefined; unsigned arithmetic wraps around by definition, so the loop keeps printing.

How would you rewrite this countdown so it prints 2, 1, 0 and stops, keeping i unsigned?
Which warning flags make GCC and Clang report that i >= 0 is always true here?

JuniorTheoryCommon

C++

#include <iostream>

int main() {
    unsigned i = 2;
    while (i >= 0) {
        std::cout << i << '\n';
        --i;
    }
}

It prints 2, 1, 0, then the largest unsigned value, and never stops

Expecting the loop to stop at -1: an unsigned value is never negative, so --i at 0 gives the largest unsigned value and i >= 0 stays true.
Expecting undefined behavior: only signed overflow is undefined; unsigned arithmetic wraps around by definition, so the loop keeps printing.

How would you rewrite this countdown so it prints 2, 1, 0 and stops, keeping i unsigned?
Which warning flags make GCC and Clang report that i >= 0 is always true here?