[userbinator]

I think that's another one of those "in theory, there is no difference between theory and practice; in practice, there is", sort of things.

One must keep in mind that the standard does not exist in a void, despite what the smartass language-lawyers unfortunately think/want. The standard committee simply did not decide to standardise things that they understood could vary between implementations. In fact, the standard has always said that "behaving during translation or program executed in a documented manner characteristic of the environment" is a possible outcome of UB.