assertion failures in case a module has a bad __name__ attribute

[orenmn]

BPO	31492
Nosy	@ethanfurman, @serhiy-storchaka, @orenmn
PRs	bpo-31492: Fix assertion failures in case of a module with a bad __name__ attribute #3620 [3.6] bpo-31492: Fix assertion failures in case of a module with a bad __name__ attribute. (GH-3620). #3773

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2017-09-27.06:46:43.849>
created_at = <Date 2017-09-16.18:00:45.072>
labels = ['interpreter-core', '3.7', 'type-crash']
title = 'assertion failures in case a module has a bad __name__ attribute'
updated_at = <Date 2017-09-27.06:46:43.849>
user = 'https://github.com/orenmn'

bugs.python.org fields:

activity = <Date 2017-09-27.06:46:43.849>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = True
closed_date = <Date 2017-09-27.06:46:43.849>
closer = 'serhiy.storchaka'
components = ['Interpreter Core']
creation = <Date 2017-09-16.18:00:45.072>
creator = 'Oren Milman'
dependencies = []
files = []
hgrepos = []
issue_num = 31492
keywords = ['patch']
message_count = 3.0
messages = ['302348', '302514', '303090']
nosy_count = 3.0
nosy_names = ['ethan.furman', 'serhiy.storchaka', 'Oren Milman']
pr_nums = ['3620', '3773']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'crash'
url = 'https://bugs.python.org/issue31492'
versions = ['Python 3.6', 'Python 3.7']

[orenmn]

The following code causes an assertion failure:
import os
os.__name__ = None
os.does_not_exist

this is because module_getattro() (in Objects/moduleobject.c) assumes that
__name__ is a string, and passes it to PyErr_Format(), which asserts it is a
string.

if we fixed that one (so that the code above would raise an AttributeError),
the following code would still cause an assertion failure:

import os
os.__name__ = None
from os import does_not_exist

this is because import_from() (in Python/ceval.c) also assumes that __name__
is a string, and passes it to PyUnicode_FromFormat(), which asserts it is a
string.

BTW, while we are in module_getattro(): isn't the second call to PyErr_Clear()
redundant? (Ethan, IIUC, you worked on this as part of bpo-8297 some years ago..)

[serhiy-storchaka]

New changeset 6db7033 by Serhiy Storchaka (Oren Milman) in branch 'master':
bpo-31492: Fix assertion failures in case of a module with a bad __name__ attribute. (bpo-3620)
6db7033

[serhiy-storchaka]

New changeset f0db2df by Serhiy Storchaka in branch '3.6':
[3.6] bpo-31492: Fix assertion failures in case of a module with a bad __name__ attribute. (GH-3620). (bpo-3773)
f0db2df