← 返回首页
GH-95589: Dont crash when subclassing extension classes with multiple inheritance by markshannon · Pull Request #96028 · python/cpython · GitHub
Skip to content

Navigation Menu

Toggle navigation
Sign in
Appearance settings
Search or jump to...

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Include my email address so I can be contacted
Cancel Submit feedback

Saved searches

Use saved searches to filter your results more quickly

Cancel Create saved search
Appearance settings
Resetting focus

GH-95589: Dont crash when subclassing extension classes with multiple inheritance#96028

Merged
markshannon merged 7 commits into
python:mainfrom
faster-cpython:dont-crash-multiple-inheritance
Aug 17, 2022
Merged

GH-95589: Dont crash when subclassing extension classes with multiple inheritance#96028
markshannon merged 7 commits into
python:mainfrom
faster-cpython:dont-crash-multiple-inheritance

Conversation

markshannon commented Aug 16, 2022 •
edited by bedevere-bot
Loading

Copy link
Copy Markdown
Member
  • Fixes crashes.
  • Documents change in behavior and recommends use of Py_TPFLAGS_MANAGED_DICT and Py_TPFLAGS_MANAGED_WEAKREF

mdboom reviewed Aug 16, 2022
View reviewed changes
Comment thread Doc/whatsnew/3.12.rst Outdated
:const:`Py_TPFLAGS_MANAGED_WEAKREF` instead of ``tp_dictoffset`` and
``tp_weaklistoffset``, respectively.
The use of ``tp_dictoffset`` and ``tp_weaklistoffset`` is still
supported, but will not fully support multiple inheritance

mdboom Aug 16, 2022

Copy link
Copy Markdown
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality Hide comment
Suggested change
supported, but will not fully support multiple inheritance
supported, but does not fully support multiple inheritance

I was a little surprised by the tense here, but I also may be wrong.

markshannon Aug 17, 2022

Copy link
Copy Markdown
Member Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality Hide comment

You are right.
Because this doesn't apply right now, I unthinkingly use the future tense.

Comment thread Lib/test/test_capi.py
pass
class B2(Both1, cls):
class B2(C4, cls):
pass

mdboom Aug 16, 2022

Copy link
Copy Markdown
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality Hide comment

Should we also assert that the mro of these classes looks correct?

markshannon Aug 17, 2022

Copy link
Copy Markdown
Member Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality Hide comment

This won't change the mro. That's determined by the C3 algorithm. https://en.wikipedia.org/wiki/C3_linearization

Comment thread Doc/whatsnew/3.12.rst
Classes declaring :const:`Py_TPFLAGS_MANAGED_DICT` should call
:c:func:`_PyObject_VisitManagedDict` and :c:func:`_PyObject_ClearManagedDict`
to traverse and clear their instance's dictionaries.
To clear weakrefs, call :c:func:`PyObject_ClearWeakRefs`, as before.

mdboom Aug 16, 2022

Copy link
Copy Markdown
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality Hide comment

Should the extension docs be updated to provide examples of using the new API? (Probably as a separate PR...)

markshannon Aug 17, 2022

Copy link
Copy Markdown
Member Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality Hide comment

Yes, they should. I also plan to add a new file documenting the new object layout.

markshannon merged commit b73e3b6 into python:main Aug 17, 2022
markshannon deleted the dont-crash-multiple-inheritance branch September 26, 2023 12:56
wsfulton added a commit to swig/swig that referenced this pull request Jun 11, 2025
Fix TypeError: multiple bases have instance lay-out conflict …
22d9fda
Fix when using -builtin and -DSWIG_HEAPTYPES in these tests: constructor_copy_non_const contract default_constructor director_basic minherit using_composition using_extend using_member_multiple_inherit cpp11_variadic_templates Fix required for python <= 3.11. Python 3.12 does not have the TypeError due to python/cpython#96028.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode characters
Show hidden characters
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

Reviewers

mdboom mdboom left review comments
ericsnowcurrently Awaiting requested review from ericsnowcurrently

Assignees

No one assigned

Labels

None yet

Projects

None yet

Milestone

No milestone

Development

Successfully merging this pull request may close these issues.

3 participants

Footer

© 2026 GitHub, Inc.