Compilers have taken advantage of undefined behavior in signed overflow for many years now. So unless you use an very ancient compiler, your code is buggy. You

Compilers have taken advantage of undefined behavior in signed overflow for many years now. So unless you use an very ancient compiler, your code is buggy. You are just lucky if it "appears" to work. What happens is that adding signed integer will appear to work most of the time... except not always. For example, your compiler may detect that 2 numbers A and B are positive (they may come from constants, or there was a previous 'if' that checked that they are positive) and when you multiply `A * B` your compiler will assume that the result is also positive because multiplying 2 positive numbers is always positive if we assume that overflow are not allowed. So if you do `if (`A * B < 0)` the compiler can and probably will remove it entirely (dead code) when turning optimizations on. Here it seems quite obvious but there can be many other less obvious ways in which the optimizer will break your code if you rely on undefined behavior. Don't rely on UB in your code. About embedded project never upgrading compiler, this is just wrong in general anyway. In your case, use uint16_t rather than in16_t if you want defined behavior when wrapping with 16 bits.