> Now that C2x plans to make two's complement the only sign representation, is there any reason why signed overflow has to continue being undefined behavior?

I presume you'd want signed overflow to have the usual 2's-complement wraparound behavior.

One problem with that is that a compiler (probably) couldn't warn about overflows that are actually errors.

For example:

    int n = INT_MAX;
    /* ... */
    n++;

With integer overflow having undefined behavior, if the compiler can determine that the value of n is INT_MAX it can warn about the overflow. If it were defined to yield INT_MIN, then the compiler would have to assume that the wraparound was what the programmer intended.

A compiler could have an option to warn about detected overflow/wraparound even if it's well defined. But really, how often do you want wraparound for signed types? In the code above, is there any sense in which INT_MIN is the "right" answer for any typical problem domain?