Default __sizeof__ is wrong for var-sized objects

[pitrou]

BPO	23629
Nosy	@pitrou, @skrah, @serhiy-storchaka
Files	sizeof_var_obj.patch

^{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 2015-03-10.21:41:45.251>
created_at = <Date 2015-03-10.15:44:19.227>
labels = ['interpreter-core', 'type-bug']
title = 'Default __sizeof__ is wrong for var-sized objects'
updated_at = <Date 2015-03-10.21:41:45.250>
user = 'https://github.com/pitrou'

bugs.python.org fields:

activity = <Date 2015-03-10.21:41:45.250>
actor = 'pitrou'
assignee = 'none'
closed = True
closed_date = <Date 2015-03-10.21:41:45.251>
closer = 'pitrou'
components = ['Interpreter Core']
creation = <Date 2015-03-10.15:44:19.227>
creator = 'pitrou'
dependencies = []
files = ['38422']
hgrepos = []
issue_num = 23629
keywords = ['patch']
message_count = 6.0
messages = ['237776', '237783', '237799', '237811', '237812', '237813']
nosy_count = 4.0
nosy_names = ['pitrou', 'skrah', 'python-dev', 'serhiy.storchaka']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue23629'
versions = ['Python 2.7', 'Python 3.4', 'Python 3.5']

[pitrou]

In the stdlib, this only appears with the memoryview object, but third-party types can be affected. Attaching patch.

[serhiy-storchaka]

Good catch! How it worked before?

Now we can remove __sizeof__ implementations for tuples and bytes.

Could you please add sizeof test for PyStructSequence types?

[serhiy-storchaka]

Ah, tests for PyStructSequence types already exist (tests for sys.flags and sys.float_info).

The patch LGTM.

[python-dev]

New changeset f9afa4f87570 by Antoine Pitrou in branch '3.4':
Issue bpo-23629: Fix the default __sizeof__ implementation for variable-sized objects.
https://hg.python.org/cpython/rev/f9afa4f87570

New changeset 9994e0172a0c by Antoine Pitrou in branch 'default':
Issue bpo-23629: Fix the default __sizeof__ implementation for variable-sized objects.
https://hg.python.org/cpython/rev/9994e0172a0c

[python-dev]

New changeset dbd48b22b477 by Antoine Pitrou in branch '2.7':
Issue bpo-23629: Fix the default __sizeof__ implementation for variable-sized objects.
https://hg.python.org/cpython/rev/dbd48b22b477

[pitrou]

Good, committed.