On 19 September 2015 at 08:31, François Dumont wrote: > On 16/09/2015 22:29, Jonathan Wakely wrote: >> No, because it is undefined to compare iterators that belong to >> different containers, or to compare pointers that point to different >> arrays. >> > > (Written before Christopher reply:) > > At least program will compile only if iterator is coming from a vector > of the same type. So behavior is undefined only if user pass an invalid > iterator which is exactly what this check tries to detect, isn't it > paradoxical ? If this undefined behavior results in the program abortion > this is what should happen anyway. If it doesn't abort then the program > will definitely not behaves as expected so this check doesn't make > anything worst, no ?
The problem is that undefined behaviour can "travel backwards in time". It's not as simple as saying that if the invalid check happens _then_ undefined behaviour happens afterwards. However, Google seem to find these checks useful, and you and Chris are in favour, so let's keep them.
