Documentation about Py_Finalize(): Freeing objects

[albertz]

BPO	23291
Nosy	@vstinner, @albertz, @iritkatriel

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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assignee = None
closed_at = None
created_at = <Date 2015-01-21.17:53:44.943>
labels = ['interpreter-core', '3.11', '3.9', '3.10', 'docs']
title = 'Documentation about Py_Finalize(): Freeing objects'
updated_at = <Date 2022-01-28.19:43:34.720>
user = 'https://github.com/albertz'

bugs.python.org fields:

activity = <Date 2022-01-28.19:43:34.720>
actor = 'iritkatriel'
assignee = 'docs@python'
closed = False
closed_date = None
closer = None
components = ['Documentation', 'Interpreter Core']
creation = <Date 2015-01-21.17:53:44.943>
creator = 'Albert.Zeyer'
dependencies = []
files = []
hgrepos = []
issue_num = 23291
keywords = []
message_count = 1.0
messages = ['234441']
nosy_count = 4.0
nosy_names = ['vstinner', 'docs@python', 'Albert.Zeyer', 'iritkatriel']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue23291'
versions = ['Python 3.9', 'Python 3.10', 'Python 3.11']

[albertz]

The documentation about Py_Finalize() about freeing objects is not exactly clear.

Esp., when I have called Py_INCREF somewhere, those objects will always have ob_refcnt > 0 unless I call Py_DECREF somewhere, what about these objects? Will they be freed in Py_Finalize() or not? If not, what can I do? I guess calling Py_DECREF after Py_Finalize() is not allowed.

I studied the Py_Finalize() code but I'm not exactly sure. It looks like such objects would not get freed (unless some implicit magic is happening somewhere). The comment about the last commented-out PyGC_Collect() call is also insightful and somewhat unsatisfying.

Maybe PyObject_Free() still works, although that would not free any further referenced objects, I guess. Also, I'm not exactly sure about the pymalloc arenas.

With pymalloc, maybe we could just free all pymalloc arenas and it would free all memory allocated by Python objects? Of course, that would not call any advanced tp_dealloc functions which might be important to be called, but we would never ever call those anyway anymore, or would we (how?)?
So, maybe it would be good to do that?

[kumaraditya303]

Py_Finalize is used to free up interpreter internal data, it has nothing to do with user references. See https://docs.python.org/3/c-api/refcounting.html for docs on refcounting.