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GeezerVison is showing github.com — gh-161694: Check for integer overflow in _PyObject_VAR_SIZE() by vstinner · Pull Request #161911 · python/cpython

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@vstinner

@vstinner vstinner commented Nov 12, 2026 •
edited by bedevere-app Bot
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Check also for integer overflow in _PyType_AllocNoTrack().

Remove redundant (and incomplete) integer overflow from tuple_alloc() and _PyTuple_Resize().

  • Issue: [C API] Add PyTupleWriter API #161694

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@vstinner
pythongh-161694: Check for integer overflow in _PyObject_VAR_SIZE()
1cd073f 
Check also for integer overflow in _PyType_AllocNoTrack().

Remove redundant (and incomplete) integer overflow from tuple_alloc()
and _PyTuple_Resize().
@vstinner
vstinner requested a review from markshannon as a code owner November 12, 2026 20:41
@bedevere-app bedevere-app Bot added the type-feature A feature request or enhancement label Nov 12, 2026
@bedevere-app bedevere-app Bot mentioned this pull request Nov 12, 2026
[C API] Add PyTupleWriter API #161694
Open
@bedevere-app bedevere-app Bot added the awaiting core review label Nov 12, 2026
@vstinner vstinner removed the type-feature A feature request or enhancement label Nov 12, 2026
@vstinner

vstinner commented Nov 12, 2026

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I wrote a first PR #161908 to detect integer overflow in PyObject_GC_NewVar() and PyObject_GC_Resize().

Then I searched for _PyObject_VAR_SIZE in PyPI top 15,000 projects (at 2026-09-17) and I found 7 projects using _PyObject_VAR_SIZE():

  • cython (3.3.0)
  • jpype1 (1.7.1)
  • nuitka (4.2.1)
  • numpy (2.5.3)
  • orjson (3.12.0)
  • pywinpty (3.0.5)
  • recordclass (0.24.1)

So instead of changing PyObject_GC_NewVar() and PyObject_GC_Resize(), I wrote this PR which is more generic to change _PyObject_VAR_SIZE(). It fixes PyObject_GC_NewVar() and PyObject_GC_Resize(), but also all projects calling directly _PyObject_VAR_SIZE().
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@vstinner vstinner mentioned this pull request Nov 12, 2026
gh-161694: Check for integer overflow in PyObject_GC_Resize() #161908
Closed
vstinner added 2 commits November 12, 2026 21:59
@vstinner
Fix NEWS entry
bad2045
@vstinner
Check also overflow on nitems+1 in _PyType_AllocNoTrack()
5998a8d 
In debug mode, check also that nitems >= 0 in _PyType_AllocNoTrack()
and _PyObject_GC_Resize().
@bedevere-app bedevere-app Bot added the type-feature A feature request or enhancement label Nov 12, 2026
vstinner added 2 commits November 12, 2026 22:01
@vstinner
Fix test_cext
3b6abf7 
Fix compiler warning:

    Include/cpython/objimpl.h:31:5: error: ISO C90 forbids mixed
    declarations and code [-Werror=declaration-after-statement]
@vstinner
Micro-optimize
e9f6280 
Don't compute nitems * itemsize if tp_itemsize is zero.
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@markshannon markshannon Awaiting requested review from markshannon markshannon is a code owner

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@vstinner
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