This is with r67651 and related to #4569, #4509 and possibly #4580.

>>> from array import array
>>> a = array('i', range(16))
>>> m = memoryview(a)
>>> a.extend(array('i', range(48)))
>>> m[:] = array('i', range(64))
Segmentation fault

>>> from array import array
>>> a = array('b', range(16))
>>> m = memoryview(a)
>>> a.extend(array('b', range(48)))
>>> m[:] = array('b', range(64))
Segmentation fault