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bpo-28737: Document when tp_dealloc should call PyObject_GC_UnTrack() (GH-29246)

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Objects that support garbage collection ("container" objects) should
call PyObject_GC_UnTrack() from their destructors before clearing any
fields which may point to other "container" objects.
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Sam Gross 2021-10-27 15:15:13 -04:00 • committed by GitHub
parent 4776b07d17
commit 35e1ff38ee
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3 changed files with 33 additions and 9 deletions
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Doc/c-api/gcsupport.rst
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@ -33,6 +33,14 @@ Constructors for container types must conform to two rules:
#. Once all the fields which may contain references to other containers are
initialized, it must call :c:func:`PyObject_GC_Track`.
Similarly, the deallocator for the object must conform to a similar pair of
rules:
#. Before fields which refer to other containers are invalidated,
:c:func:`PyObject_GC_UnTrack` must be called.
#. The object's memory must be deallocated using :c:func:`PyObject_GC_Del`.
.. warning::
If a type adds the Py_TPFLAGS_HAVE_GC, then it *must* implement at least
a :c:member:`~PyTypeObject.tp_traverse` handler or explicitly use one
@ -100,14 +108,6 @@ Constructors for container types must conform to two rules:
.. versionadded:: 3.9
Similarly, the deallocator for the object must conform to a similar pair of
rules:
#. Before fields which refer to other containers are invalidated,
:c:func:`PyObject_GC_UnTrack` must be called.
#. The object's memory must be deallocated using :c:func:`PyObject_GC_Del`.
.. c:function:: void PyObject_GC_Del(void *op)