Description

assignee = None
closed_at = None
created_at = <Date 2017-10-13.10:54:20.321>
labels = ['extension-modules', '3.10', '3.9', 'type-crash', '3.11']
title = 'assertion failures and a crash when using an uninitialized struct.Struct object'
updated_at = <Date 2021-10-19.10:22:17.196>
user = 'https://github.com/orenmn'

activity = <Date 2021-10-19.10:22:17.196>
actor = 'iritkatriel'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Extension Modules']
creation = <Date 2017-10-13.10:54:20.321>
creator = 'Oren Milman'
dependencies = []
files = []
hgrepos = []
issue_num = 31779
keywords = ['patch']
message_count = 3.0
messages = ['304328', '325462', '404285']
nosy_count = 7.0
nosy_names = ['mark.dickinson', 'meador.inge', 'berker.peksag', 'serhiy.storchaka', 'Oren Milman', 'izbyshev', 'iritkatriel']
pr_nums = ['3984']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'crash'
url = 'https://bugs.python.org/issue31779'
versions = ['Python 3.9', 'Python 3.10', 'Python 3.11']

Activity

1. orenmn commented on Oct 13, 2017

   

   orenmnmannequin

   on Oct 13, 2017

   MannequinAuthor

   More actions

   The following code causes an assertion failure:
   import _struct
   struct_obj = _struct.Struct.__new__(_struct.Struct)
   struct_obj.iter_unpack(b'foo')

   This is because Struct_iter_unpack() (in Modules/_struct.c) assumes that
   Struct.init() was called, and so it does assert(self->s_codes != NULL);.

   The same happens in (almost) every method of Struct, and in s_get_format(), so
   in all them, too, we would get an assertion failure in case of an uninitialized
   Struct object.
   The exception is sizeof(), which doesn't have an assert, and simply
   crashes while trying to iterate over self->s_codes.

   I would open a PR to fix this soon.
2. orenmn

   added

   3.7 (EOL)end of lifeend of life

   extension-modulesC modules in the Modules dirC modules in the Modules dir

   type-crashA hard crash of the interpreter, possibly with a core dumpA hard crash of the interpreter, possibly with a core dump

   on Oct 13, 2017
3. izbyshev commented on Sep 15, 2018

   

   izbyshevmannequin

   on Sep 15, 2018

   Mannequin

   More actions

   What are the drawbacks of moving all code from __init__ to __new__, at least in master branch (3.8)? IMO it's much more robust than playing whack-a-mole both with ref/memleaks caused by repeated calls to __init__ and absence of initialization checks in all methods.
4. izbyshev

   added

   3.8 (EOL)end of lifeend of life

   on Sep 15, 2018
5. iritkatriel commented on Oct 19, 2021

   

   iritkatriel

   on Oct 19, 2021

   Member

   More actions

   Reproduced on 3.11.
6. iritkatriel

   added

   3.9 (EOL)end of lifeend of life

   3.10 (EOL)end of lifeend of life

   3.11only security fixesonly security fixes

   and removed

   3.7 (EOL)end of lifeend of life

   3.8 (EOL)end of lifeend of life

   on Oct 19, 2021
7. ezio-melotti

   transferred this issue fromon Apr 10, 2022
8. kumaraditya303

   added

   3.12only security fixesonly security fixes

   and removed

   3.9 (EOL)end of lifeend of life

   on Jul 3, 2022
9. kumaraditya303

   self-assigned this

   on Jul 3, 2022
10. mdickinson

    closed this as completedin #94532on Sep 25, 2022
11. mdickinson

    added a commit that references this issue on Sep 25, 2022

    GH-78724: Initialize struct.Struct in __new__ (GH-94532)

    c8c0afc
12. mdickinson commented on Nov 26, 2023

    

    mdickinson

    on Nov 26, 2023

    Member

    More actions

    Re-opening: the original fix for this issue has been reverted, since it broke code for users in the wild who were subclassing struct.Struct.
13. mdickinson

    reopened this on Nov 26, 2023
14. kumaraditya303

    removed their assignment

    on Jul 8, 2025
15. kumaraditya303

    closed this as a duplicateof _struct.Struct: calling functions without calling __init__ results in SystemError #78724 on Jul 8, 2025
16. skirpichev

    added a commit that references this issue on Feb 28, 2026

    pythonGH-78724: Initialize struct.Struct in __new__ (pythonGH-94532)

    be9d0d8
17. serhiy-storchaka

    added this to Struct, memoryview and array issues 🏗️on Jul 13, 2026
18. github-project-automation

    moved this to Todo in Struct, memoryview and array issues 🏗️on Jul 13, 2026
19. github-project-automation

    moved this from Todo to Done in Struct, memoryview and array issues 🏗️on Jul 13, 2026

Issue actions