Following example causes double deallocation of a sequence and crashing.

class A(list):
    def __del__(self):
        next(it)

it = iter(A())
next(it)

The same is for subclass of tuple, str, bytes and bytearray.

Proposed patch fixes this issue.

Updated patch fixes also set, dict and os.scandir() iterator.

May be sqlite3 cursor needs a fix, but it is too complicated.

TODO: After resolving issue26492 add the test for array.

Fixed test for OrderedDict. Tests for list and tuple are moved up to seq_tests.py.

Hi Serhiy,

I tried the short example you gave, but it doesn't crash. I'm getting:

Exception ignored in: <bound method A.__del__ of []>
Traceback (most recent call last):
  File "./test.py", line 5, in __del__
    next(it)
StopIteration
Exception ignored in: <bound method A.__del__ of []>
Traceback (most recent call last):
  File "./test.py", line 5, in __del__
    next(it)
StopIteration
Traceback (most recent call last):
  File "./test.py", line 8, in <module>
    next(it)
StopIteration

Am I missing something?

It crashes in debug build.

Could anyone please look at the patch? I'm not sure about organizing tests.

New changeset 905b5944119c by Serhiy Storchaka in branch '3.5':
Issue #26494: Fixed crash on iterating exhausting iterators.
https://hg.python.org/cpython/rev/905b5944119c

New changeset 73ce47d4a7b2 by Serhiy Storchaka in branch 'default':
Issue #26494: Fixed crash on iterating exhausting iterators.
https://hg.python.org/cpython/rev/73ce47d4a7b2

New changeset cff06d875678 by Serhiy Storchaka in branch '2.7':
Issue #26494: Fixed crash on iterating exhausting iterators.
https://hg.python.org/cpython/rev/cff06d875678