Misleading documentation about weakrefs

[pitrou]

BPO	14933
Nosy	@tim-one, @freddrake, @ncoghlan, @pitrou

^{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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GitHub fields:

assignee = None
closed_at = <Date 2012-06-15.17:16:14.039>
created_at = <Date 2012-05-28.13:17:39.225>
labels = ['type-bug', 'docs']
title = 'Misleading documentation about weakrefs'
updated_at = <Date 2012-06-15.17:16:14.038>
user = 'https://github.com/pitrou'

bugs.python.org fields:

activity = <Date 2012-06-15.17:16:14.038>
actor = 'pitrou'
assignee = 'docs@python'
closed = True
closed_date = <Date 2012-06-15.17:16:14.039>
closer = 'pitrou'
components = ['Documentation']
creation = <Date 2012-05-28.13:17:39.225>
creator = 'pitrou'
dependencies = []
files = []
hgrepos = []
issue_num = 14933
keywords = []
message_count = 2.0
messages = ['161780', '162922']
nosy_count = 7.0
nosy_names = ['tim.peters', 'fdrake', 'ncoghlan', 'pitrou', 'docs@python', 'python-dev', 'sbt']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue14933'
versions = ['Python 2.7', 'Python 3.2', 'Python 3.3']

[pitrou]

In http://docs.python.org/dev/extending/newtypes.html?highlight=pyobject_clearweakrefs#weak-reference-support, you can read:

“The only further addition is that the destructor needs to call the weak reference manager to clear any weak references. This should be done before any other parts of the destruction have occurred”

I don't believe there is any need to clear weakrefs before starting with other parts of the destruction. Weakref callbacks cannot access the original object, by construction (else they never get called).

Actually, if a weakref callback can rely on some resources having been released (say, a file descriptor), it is better to clear the weakrefs *after* other parts of the destruction.

This seems to be a by-product of the erroneous doc committed in SVN r16381, part of which was removed in r18223.

[python-dev]

New changeset 69177ff1a643 by Antoine Pitrou in branch '3.2':
Issue bpo-14933: fix misleading doc about weakref support in extension types.
http://hg.python.org/cpython/rev/69177ff1a643

New changeset b17c8005e08a by Antoine Pitrou in branch 'default':
Issue bpo-14933: fix misleading doc about weakref support in extension types.
http://hg.python.org/cpython/rev/b17c8005e08a

New changeset 0ac1f90954dc by Antoine Pitrou in branch '2.7':
Issue bpo-14933: fix misleading doc about weakref support in extension types.
http://hg.python.org/cpython/rev/0ac1f90954dc