> Sure, and that's basically what I was wondering about with respect to "can't define it" being shorthand for something else

Eh, I'd say it's still the same thing; can't define a sanitizer for it if what you define isn't a sanitizer. Depends on a specific definition of "sanitizer" though.

> At least making your own isn't horrendously difficult.

In C++ perhaps, but impossible in C. (and there are still some funky edge-cases where multiplying two `uint16_t`s can overflow due to implicit promotion to signed int; C's _BitInt solves at least that)

Clang does actually have experimental support for these - https://clang.llvm.org/docs/OverflowBehaviorTypes.html