Description

colesbury

opened on Oct 30, 2023

Issue body actions

Bug report

After #110764, --disable-gil builds of CPython 3.13 are (temporarily) not be compatible with the limited API or the stable ABI due to modifications to the PyObject header. For context, this was noted in the "Backwards Compatibility" section of PEP 703.

Based on feedback on the related discuss post and discussions with Gregory Smith, Guido, Petr, and Victor at the core dev sprint, I believe we can make changes to the stable ABI so that extension author can target a single stable ABI that supports CPython 3.7+ and both the default build and the --disable-gil builds of CPython 3.13+.

These changes will require a PEP. This issue is intended just to keep track of the known problem.

The rough idea is:

1. make a number of macro/inline functions (e.g., Py_SIZE, Py_TYPE, Py_SET_REFCNT, Py_REFCNT) "real" function calls in the stable ABI for CPython 3.13+
2. When targeting CPython <= 3.12, use dynamic symbol lookup (GetProcAddress on Windows) or weak symbols (on Linux/macOS) to determine at runtime if the active CPython version provides the desired functions. Otherwise, fall back to old definitions of the above functions for CPython <= 3.12.

Linked PRs

• gh-111506: Implement Py_SET_REFCNT() as opaque function in limited C API #111508
• gh-111506: Implement Py_REFCNT() as opaque function call #112747
• gh-111506: Rename _Py_SetRefcnt() to Py_SET_REFCNT() #112794
• gh-111506: Implement Py_SET_REFCNT() as inline function #112798
• gh-111506: Error if the limited API is used in free-threaded build #117762
• gh-111506: Add _Py_OPAQUE_PYOBJECT to hide PyObject layout & related API #136505

Reacted by Justin Chu and impervius

Activity

1. colesbury

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   3.13only security fixesonly security fixes

   topic-free-threading

   on Oct 30, 2023
2. corona10 commented on Oct 30, 2023

   

   corona10

   on Oct 30, 2023

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   cc @vstinner
3. vstinner

   added 2 commits that reference this issue on Oct 30, 2023

   pythongh-111506: Implement Py_SET_REFCNT() as opaque function in limi…

   485ad40

   pythongh-111506: Implement Py_SET_REFCNT() as opaque function in limi…

   67638c4
4. vstinner commented on Oct 30, 2023

   

   vstinner

   on Oct 30, 2023

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   Before creating a whole new ABI, I would like first to avoid __asm__(...); in Include/*.h, in the limited C API. Assembly code is not portable and can cause compilation issues.

   A first step for that is to implement Py_SET_REFCNT() as a function call: PR #111508.
5. vstinner

   added a commit that references this issue on Oct 30, 2023

   pythongh-111506: Implement Py_SET_REFCNT() as opaque function in limi…

   ac0c1dd
6. encukou commented on Oct 31, 2023

   

   encukou

   on Oct 31, 2023

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   These changes will require a PEP.

   Please, could we have the PEP first, then do the changes?
7. AlexWaygood

   added

   topic-C-API

   on Oct 31, 2023
8. vstinner

   added a commit that references this issue on Nov 3, 2023

   gh-111506: Implement Py_SET_REFCNT() as opaque function in limited C …

   20cfab9
9. vstinner

   added 2 commits that reference this issue on Dec 5, 2023

   pythongh-111506: Implement Py_REFCNT() as opaque function call

   d52b1e9

   pythongh-111506: Implement Py_REFCNT() as opaque function call

   4fd7ed6
10. encukou commented on Dec 5, 2023

    

    encukou

    on Dec 5, 2023

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    Please, could we have the PEP first, then do the changes?

    @colesbury, do you still plan to write the PEP? Do you need any help?
11. colesbury commented on Dec 5, 2023

    

    colesbury

    on Dec 5, 2023

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    @encukou, yes I still intend to write the PEP. It just hasn't been as a high a priority as integrating the pieces of PEP 703.
12. 35 remaining items
13. zmedico

    added 2 commits that reference this issue on Oct 27, 2025

    Support Py_GIL_DISABLED

    5a37226

    Support Py_GIL_DISABLED

    b750891
14. zmedico

    added 4 commits that reference this issue on Nov 18, 2025

    Support Py_GIL_DISABLED

    41a90cd

    Support Py_GIL_DISABLED

    fc573cc

    Support Py_GIL_DISABLED

    ebd1aa9

    Support Py_GIL_DISABLED

    2dd9a6c
15. cclauss

    added a commit that references this issue on Nov 19, 2025

    Support Py_GIL_DISABLED (#206)

    ac7cb9e
16. lpsinger

    added a commit that references this issue on Dec 4, 2025

    Fix free-threaded Python builds

    3e2b38d
17. hubot

    added a commit that references this issue on Jan 6, 2026

    wheel: Don't enable limited API when using a no-gil build

    056e79e
18. kumaraditya303 commented on Apr 5, 2026

    

    kumaraditya303

    on Apr 5, 2026

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    Closing this in favor of #146636 which implements abi3t

    Reacted by Clément Robert
19. kumaraditya303

    closed this as not plannedon Apr 5, 2026
20. msk

    added a commit that references this issue on May 11, 2026

    py-setuptools: update to 73.0.1.

    4c6f72d
21. jperkin

    added a commit that references this issue on May 14, 2026

    py-setuptools: update to 73.0.1.

    14b22b2
22. mitrlk

    added a commit that references this issue on Sep 23, 2026

    ci: pin pyvista<0.49, it cannot install on free-threaded python

    71fa29c
23. tsutsui

    added a commit that references this issue on Oct 17, 2026

    py-setuptools: update to 73.0.1.

    cbbaa05

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