On Fri, May 11, 2018 at 03:03:09PM +0300, Alexander Monakov wrote: > On Fri, 11 May 2018, Segher Boessenkool wrote: > > > In general such address-based comparisons steps are invalid; they lack > > > anti-reflexivity. So comparators are not actually allowed to do that. > > > > I don't know what you mean here? Every comparator is required to be > > *reflexive*! Subtracting two pointers to elements of the same array gives > > a perfectly fine total order as far as I see (it is the same as the > > difference between the array indices of those elements). > > I meant "anti-commutativity"; sorry about the mixup. Such strategy does not > give a valid total order because the order changes while in-progress sorting > reorders elements:
Ah. Right. C11 7.22.5/4. Sorry for being dense, I'll drink more coffee. Segher
