On Sat, Mar 11, 2017 at 9:01 PM Tim Peters <report@bugs.python.org> wrote:

>
> Elliot, I don't care if the example behaves differently.  Although someone
> else may ;-)
>
> The only things `.sort()` has ever tried to guarantee in the presence of
> mutations (of either the list or the elements) during sorting are that (a)
> the implementation won't segfault; and, (b) the list at the end is _some_
> permutation of the input list (no elements are lost or duplicated).
>
> If crazy mutation examples can provoke a segfault, that's possibly "a
> problem" - but different results really aren't (at least not to me).
>
>
That's great to hear. (Of course, one could always remove
unsafe_object_compare from the patch and keep the rest, but that would be a
real shame). I don't think segfaults are possible if the code is
pure-Python, because all the builtin/stdlib functions type-check anyway, so
you would just get an exception. Right? Of course, using the C API you
could probably provoke segfaults, but there are much easier ways to
segfault using the C API :).