Simple test of signed overflow UB

test_ub.cpp

#include <iostream>
#include <cstdint>
#include <limits>

int main(int argc, char **argv) {
    std::int32_t i = std::numeric_limits<int32_t>::max();
    i++;                                           // signed overflow
    if (i < 0) {
        std::cerr << "i<0 and i=" << i << "\n";    // "expected" or "safe" result   (-O1)
    } else {
        std::cerr << "i>=0 and i=" << i << "\n";   // result taking advantage of UB
    }                                              // to eliminate branch           (-O2)
}