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itertools.groupby() can fail a C assert() #74532

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arigo mannequin opened this issue May 11, 2017 · 8 comments
Closed

itertools.groupby() can fail a C assert() #74532

arigo mannequin opened this issue May 11, 2017 · 8 comments
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@serhiy-storchaka
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3.7 (EOL) end of life extension-modules C modules in the Modules dir type-crash A hard crash of the interpreter, possibly with a core dump

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@arigo
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arigo mannequin commented May 11, 2017

BPO 30347
Nosy @arigo, @rhettinger, @serhiy-storchaka
PRs
  • bpo-30347: Fixed a crash in itertools.groupby() when use the grouper #1557
  • [3.6] bpo-30347: Stop crashes when concurrently iterate over itertools.groupby() iterators. (GH-1557) #3770
  • [2.7] bpo-30347: Stop crashes when concurrently iterate over itertools.groupby() iterators. (GH-1557). #3772
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    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 = 'https://github.com/serhiy-storchaka'
closed_at = <Date 2017-09-26.20:16:27.494>
created_at = <Date 2017-05-11.21:10:21.469>
labels = ['extension-modules', '3.7', 'type-crash']
title = 'itertools.groupby() can fail a C assert()'
updated_at = <Date 2017-09-26.20:16:27.493>
user = 'https://github.com/arigo'

    bugs.python.org fields:

    activity = <Date 2017-09-26.20:16:27.493>
actor = 'serhiy.storchaka'
assignee = 'serhiy.storchaka'
closed = True
closed_date = <Date 2017-09-26.20:16:27.494>
closer = 'serhiy.storchaka'
components = ['Extension Modules']
creation = <Date 2017-05-11.21:10:21.469>
creator = 'arigo'
dependencies = []
files = []
hgrepos = []
issue_num = 30347
keywords = ['patch']
message_count = 8.0
messages = ['293517', '293519', '293549', '293579', '302948', '303062', '303065', '303071']
nosy_count = 3.0
nosy_names = ['arigo', 'rhettinger', 'serhiy.storchaka']
pr_nums = ['1557', '3770', '3772']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'crash'
url = 'https://bugs.python.org/issue30347'
versions = ['Python 2.7', 'Python 3.6', 'Python 3.7']
    @arigo
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    arigo mannequin commented May 11, 2017

    This triggers an assert() failure on debug-mode Python (or a leak in release Python):

    from itertools import groupby

def f(n):
    print("enter:", n)
    if n == 5:
        list(b)
    print("leave:", n)
    return n != 6

for (k, b) in groupby(range(10), f):
    print(list(b))

    With current trunk we get: python: ./Modules/itertoolsmodule.c:303: _grouper_next: Assertion `gbo->currkey == NULL' failed.

    @arigo arigo mannequin added interpreter-core (Objects, Python, Grammar, and Parser dirs) 3.7 (EOL) end of life type-crash A hard crash of the interpreter, possibly with a core dump labels May 11, 2017
    @serhiy-storchaka serhiy-storchaka added extension-modules C modules in the Modules dir and removed interpreter-core (Objects, Python, Grammar, and Parser dirs) labels May 11, 2017
    @rhettinger
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    Do you have a suggested fix?

    @serhiy-storchaka
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    PR 1557 implements the simplest fix -- remove the assert and use Py_XSETREF() instead of simple assignment. Since the resulting code in _grouper_next() is identical to the code in groupby_next(), it was shared between these two functions.

    @rhettinger
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    At first glance, the suggested PR looks fine. Unless there is a rush, I would like to hold-off spend more time thinking about bpo-30346 before moving forward with this one.

    @serhiy-storchaka
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    Hmm, the sole bpo-30346 is not enough for fixing this crash. I don't know if there is a simpler fix based on bpo-30346, but since PR 1557 removes the code duplication I'm going to merge it in any case.

    @serhiy-storchaka
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    New changeset c740e4f by Serhiy Storchaka in branch 'master':
    bpo-30347: Stop crashes when concurrently iterate over itertools.groupby() iterators. (bpo-1557)
    c740e4f

    @serhiy-storchaka
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    New changeset 69b2dc8 by Serhiy Storchaka (Miss Islington (bot)) in branch '3.6':
    [3.6] bpo-30347: Stop crashes when concurrently iterate over itertools.groupby() iterators. (GH-1557) (bpo-3770)
    69b2dc8

    @serhiy-storchaka
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    New changeset d0b9dc3 by Serhiy Storchaka in branch '2.7':
    [2.7] bpo-30347: Stop crashes when concurrently iterate over itertools.groupby() iterators. (GH-1557). (bpo-3772)
    d0b9dc3

    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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