Leaving the behavior up to the compiler (or hardware) is not undefined behavior, that is unspecified behavior or implementation defined behavior. Undefined beh

Leaving the behavior up to the compiler (or hardware) is not undefined behavior, that is unspecified behavior or implementation defined behavior. Undefined behavior really does mean that the program does not have valid semantics. There is no proper interpretation of how the program is to behave if signed overflow happens. It's not simply that the interpretation of the program is beyond the language and left to the hardware or the operating system, it's that the program's behavior is undefined.