[CJefferson]

The problem is 'undefined behaviour' is far too powerful.

Why not make division by zero implementation defined. I'm happy with my compiler telling me my program will get terminated if I divide by zero, no problem. Let's even say it "may" be terminated (because maybe the division is optimised out if we don't actually need to calculate it, fine).

My problem is that UB let's compilers do all kinds of weird things, like assume if I write:

    int dividebyzero = 0;
    if(y == 0) { dividebyzero = 1; }
    z=x/y;

Then set dividebyzero to always be 0, because 'obviously' y can't be 0, because then I would invoke undefined behaviour.

Also, for two-complement, it's fairly common people want wrapping behaviour. Also, I don't think basically anyone is using C++ on non-twos complement CPUs (both gcc and clang don't support it), and even if it does run on such CPUs, why not still require a well-defined behaviour, in the same way C++ runs on 32-bit and 64-bit systems, but we don't say asking for the size of a pointer is undefined behaviour -- everyone just defines what it is on their system!