https://github.com/python/cpython/commit/238a1ca713f6259ee00e1d5e3cf8cb6abe126007 commit: 238a1ca713f6259ee00e1d5e3cf8cb6abe126007 branch: 3.13 author: Miss Islington (bot) <[email protected]> committer: kumaraditya303 <[email protected]> date: 2025-08-26T23:43:42+05:30 summary:
[3.13] gh-137740: Clarify `__del__` invocation mechanism in reference counting (GH-137741) (#138112) gh-137740: Clarify `__del__` invocation mechanism in reference counting (GH-137741) (cherry picked from commit 90b932e65080008dfd974b2e03c3068dbb72b95d) Co-authored-by: Robin Narsingh Ranabhat <[email protected]> Co-authored-by: Kumar Aditya <[email protected]> files: M Doc/extending/extending.rst diff --git a/Doc/extending/extending.rst b/Doc/extending/extending.rst index 17c6fb224265ca..f9b65643dfe888 100644 --- a/Doc/extending/extending.rst +++ b/Doc/extending/extending.rst @@ -1084,7 +1084,14 @@ references to all its items, so when item 1 is replaced, it has to dispose of the original item 1. Now let's suppose the original item 1 was an instance of a user-defined class, and let's further suppose that the class defined a :meth:`!__del__` method. If this class instance has a reference count of 1, -disposing of it will call its :meth:`!__del__` method. +disposing of it will call its :meth:`!__del__` method. Internally, +:c:func:`PyList_SetItem` calls :c:func:`Py_DECREF` on the replaced item, +which invokes replaced item's corresponding +:c:member:`~PyTypeObject.tp_dealloc` function. During +deallocation, :c:member:`~PyTypeObject.tp_dealloc` calls +:c:member:`~PyTypeObject.tp_finalize`, which is mapped to the +:meth:`!__del__` method for class instances (see :pep:`442`). This entire +sequence happens synchronously within the :c:func:`PyList_SetItem` call. Since it is written in Python, the :meth:`!__del__` method can execute arbitrary Python code. Could it perhaps do something to invalidate the reference to _______________________________________________ Python-checkins mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3//lists/python-checkins.python.org Member address: [email protected]
