You can run your code in ASAN in UBSAN nowadays, it will catch many or most of issues as they happen.

But that's completely besides the point. UB on signed overflow, or really most of UB, is not unrelated to C flexibility. It is a detail of the spec related to portability and performance. IIRC it is even required to make such trivial optimizations as turning

    for (int i = 0; i < n; i++) func(a[i]);

    for (Foo *p = a, *last = a + n; p < last; p++) func(p);