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gh-110812: Isolating Extension Modules HOWTO: List GC-related gotchas #111504

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Merged
encukou merged 6 commits into from
Nov 16, 2023
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gh-110812: Isolating Extension Modules HOWTO: List GC-related gotchas #111504

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3dbeb2c
Isolating Extension Modules HOWTO: List GC-related gotchas
encukou Oct 23, 2023
dc6b990
Merge branch 'main' into howto-clarifications
hugovk Oct 31, 2023
b6c5ae8
Mention PyObject_GC_UnTrack and PyObject_GC_New
encukou Oct 31, 2023
78e0f84
Stronger language for overriding tp_free
encukou Oct 31, 2023
2a4568a
Copy-pastable examples for avoiding PyObject_New
encukou Nov 3, 2023
0b01d78
Update Doc/howto/isolating-extensions.rst
encukou Nov 13, 2023
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17 changes: 14 additions & 3 deletions Doc/howto/isolating-extensions.rst
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Expand Up @@ -438,9 +438,20 @@ GC-tracked objects need to be allocated using GC-aware functions.

If you use use :c:func:`PyObject_New` or :c:func:`PyObject_NewVar`:

- Get and call type's :c:member:`~PyTypeObject.tp_alloc` slot , if possible.
- If not possible (e.g. inside a custom ``tp_alloc``),
call :c:func:`PyObject_GC_New` or :c:func:`PyObject_GC_NewVar`.
- Get and call type's :c:member:`~PyTypeObject.tp_alloc` slot, if possible.
That is, replace ``TYPE *o = PyObject_New(TYPE, typeobj)`` by::

TYPE *o = typeobj->tp_alloc(typeobj, 0);

Replace ``o = PyObject_NewVar(TYPE, typeobj, size)`` with the same,
but use size instead of the 0.

- If the above is not possible (e.g. inside a custom ``tp_alloc``),
call :c:func:`PyObject_GC_New` or :c:func:`PyObject_GC_NewVar`::

TYPE *o = PyObject_GC_New(TYPE, typeobj);

TYPE *o = PyObject_GC_NewVar(TYPE, typeobj, size);


Module State Access from Classes
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