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Fix incorrect function signatures in _testmultiphase (UBSan) #141553

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Fix incorrect function signatures in _testmultiphase (UBSan)#141553
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3.15bugs and security fixesextension-modulesC modules in the Modules dirtestsTests in the Lib/test dirtype-bugAn unexpected behavior, bug, or error

Description

@ashm-dev
ashm-dev
opened on Nov 14, 2025

Bug report

Bug description:

UBSan reports errors such as:

modexport_create_string 

Objects/moduleobject.c:546:13: runtime error: call to function modexport_create_string through pointer to incorrect function type 'struct _object *(*)(struct _object *, struct PyModuleDef *)' /home/shamil/oss/cpython/main/./Modules/_testmultiphase.c:1066:5: note: modexport_create_string defined here SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior Objects/moduleobject.c:546:13

Py_mod_state_free 

Objects/moduleobject.c:1101:9: runtime error: call to function modexport_smoke_free through pointer to incorrect function type 'void (*)(void *)' /home/shamil/oss/cpython/main/./Modules/_testmultiphase.c:974: note: modexport_smoke_free defined here SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior Objects/moduleobject.c:1101:9

The functions assigned to Py_mod_state_free and modexport_create_string use incorrect signatures, causing calls through mismatched function pointer types and leading to undefined behavior.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

Activity

  1. ashm-dev
    added
    type-bugAn unexpected behavior, bug, or error
    on Nov 14, 2025

  2. mohsinm-dev commented on Nov 14, 2025

    @mohsinm-dev
    mohsinm-dev
    on Nov 14, 2025
    Contributor

    @ashm-dev I was working on the same fix.

  3. ashm-dev commented on Nov 14, 2025

    @ashm-dev
    ashm-dev
    on Nov 14, 2025
    ContributorAuthor

    @mohsinm-dev I already have a fix)

  4. StanFromIreland
    added
    testsTests in the Lib/test dir
    extension-modulesC modules in the Modules dir
    on Nov 14, 2025

  5. picnixz commented on Nov 14, 2025

    @picnixz
    picnixz
    on Nov 14, 2025
    Member

    I am surprised that this was not caught when this was introduced.

  6. picnixz
    added
    3.15bugs and security fixes
    on Nov 15, 2025
  7. picnixz
    added a commit that references this issue on Nov 15, 2025

    gh-141553: Fix incorrect function signatures in `_testmultiphase` (#1…

    85f3009

  8. picnixz commented on Nov 15, 2025

    @picnixz
    picnixz
    on Nov 15, 2025
    Member

    Thanks for the report & fix!

  9. picnixz
    closed this as completedon Nov 15, 2025
  10. StanFromIreland
    added a commit that references this issue on Dec 6, 2025

    pythongh-141553: Fix incorrect function signatures in `_testmultiphas…

    90c2983
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    3.15bugs and security fixesextension-modulesC modules in the Modules dirtestsTests in the Lib/test dirtype-bugAn unexpected behavior, bug, or error

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