New submission from Edward Yang <ezyang@mit.edu>: The fact that the error indicator may be set during tp_dealloc is somewhat well known (https://github.com/posborne/dbus-python/blob/fef4bccfc535c6c2819e3f15384600d...) but it's not documented in the official manual. We should document it. A simple suggested patch: diff --git a/Doc/c-api/typeobj.rst b/Doc/c-api/typeobj.rst index b17fb22b69..e7c9b13646 100644 --- a/Doc/c-api/typeobj.rst +++ b/Doc/c-api/typeobj.rst @@ -668,6 +668,20 @@ and :c:type:`PyType_Type` effectively act as defaults.) :c:func:`PyObject_GC_Del` if the instance was allocated using :c:func:`PyObject_GC_New` or :c:func:`PyObject_GC_NewVar`. + If you may call functions that may set the error indicator, you must + use :c:func:`PyErr_Fetch` and :c:func:`PyErr_Restore` to ensure you + don't clobber a preexisting error indicator (the deallocation could + have occurred while processing a different error): + + .. code-block:: c + + static void foo_dealloc(foo_object *self) { + PyObject *et, *ev, *etb; + PyErr_Fetch(&et, &ev, &etb); + ... + PyErr_Restore(et, ev, etb); + } + Finally, if the type is heap allocated (:const:`Py_TPFLAGS_HEAPTYPE`), the deallocator should decrement the reference count for its type object after calling the type deallocator. In order to avoid dangling pointers, the ---------- assignee: docs@python components: Documentation messages: 401854 nosy: docs@python, ezyang priority: normal severity: normal status: open title: tp_dealloc docs should mention error indicator may be set type: enhancement versions: Python 3.11 _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue45210> _______________________________________