Not sure what you think the source code "says". I mean, I know what you want it to mean, but just because integer wrapping is intuitive to you doesn't imply tha

Not sure what you think the source code "says". I mean, I know what you want it to mean, but just because integer wrapping is intuitive to you doesn't imply that that is what the code means. C++ abstract machine and all. But to answer the actual question: For C++20, integer types were revisited. It is now (finally) guaranteed that signed integers are two's complement, along with a list of other changes. See http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0907r4.html http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p090... also for how the committee voted on the individual issues. Note in particular: > The main change between [P0907r0] and the subsequent revision is to maintain undefined behavior when signed integer overflow occurs, instead of defining wrapping behavior. This direction was motivated by: > - Performance concerns, whereby defining the behavior prevents optimizers from assuming that overflow never occurs; > - Implementation leeway for tools such as sanitizers; > - Data from Google suggesting that over 90% of all overflow is a bug, and defining wrapping behavior would not have solved the bug. So yes, the committee very recently revisited this specific issue, and re-affirmed that signed integer overflow should be UB.