Making UB Detectable
Warning discipline, checked arithmetic, and volatile as an observation tool — the habits before sanitizers.
Warnings are UB radar
-Wall -Wextra catches a large share of the classic UB (uninitialized use, format mismatches, shifts). Promote them to errors in CI. A warning you ignore trains you to ignore warnings.
Checked arithmetic at trust boundaries
Where untrusted sizes meet arithmetic, check before it happens:
if (n > SIZE_MAX / sizeof *buf) return ENOMEM; /* before the multiply */
buf = malloc(n * sizeof *buf);
Wraparound-safe idioms (unsigned modular arithmetic) are legitimate tools when the domain genuinely wraps — hash sums, counters. The skill is choosing deliberately, not by accident.
volatile is a porthole, not a fix
Marking a variable volatile forces every read and write to actually happen — it defeats dead-store elimination and makes timing/order experiments honest. It does NOT make data races defined, does not provide atomicity, and is not a synchronization primitive. Race-free code needs atomics or locks (modules 19-20).