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_ctypes\cfield.c identical subexpressions in Z_set #70032

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ariccio mannequin opened this issue Dec 12, 2015 · 5 comments
Closed

_ctypes\cfield.c identical subexpressions in Z_set #70032

ariccio mannequin opened this issue Dec 12, 2015 · 5 comments
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topic-ctypes type-feature A feature request or enhancement

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@ariccio
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Mannequin

ariccio mannequin commented Dec 12, 2015

BPO 25845
Nosy @amauryfa, @abalkin, @meadori, @vadmium, @ariccio

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 2015-12-12.07:38:51.973>
created_at = <Date 2015-12-12.04:50:49.417>
labels = ['ctypes', 'type-feature']
title = '_ctypes\\cfield.c identical subexpressions in Z_set'
updated_at = <Date 2015-12-12.07:38:51.929>
user = 'https://github.com/ariccio'

bugs.python.org fields:

activity = <Date 2015-12-12.07:38:51.929>
actor = 'martin.panter'
assignee = 'none'
closed = True
closed_date = <Date 2015-12-12.07:38:51.973>
closer = 'martin.panter'
components = ['ctypes']
creation = <Date 2015-12-12.04:50:49.417>
creator = 'Alexander Riccio'
dependencies = []
files = []
hgrepos = []
issue_num = 25845
keywords = []
message_count = 5.0
messages = ['256256', '256261', '256262', '256269', '256271']
nosy_count = 7.0
nosy_names = ['amaury.forgeotdarc', 'belopolsky', 'meador.inge', 'python-dev', 'martin.panter', 'random832', 'Alexander Riccio']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue25845'
versions = ['Python 3.5', 'Python 3.6']
@ariccio
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ariccio mannequin commented Dec 12, 2015

I found this while writing up a separate bug (CPython doesn't use static analysis!).

In _ctypes/cfield.c, Z_set has a bug of some sort:

    if (PyLong_Check(value) || PyLong_Check(value)) {

See: https://hg.python.org/cpython/file/tip/Modules/_ctypes/cfield.c#l1378

...which has been there for at least 5 years: https://hg.python.org/cpython/rev/cab14be0ada1

I'm not sure what the original programmer meant - it's been around forever & I don't know what was there before it - but PyLong_Check(value) is evaluated twice. Which doesn't really make sense.

Compiling with /analyze found this quite easily:

c:\pythondev\repo\modules\_ctypes\cfield.c(1378): warning C6287: Redundant code: the left and right sub-expressions are identical.

There's a similar issue in P_set, at line 1486.

@ariccio ariccio mannequin added the topic-ctypes label Dec 12, 2015
@random832
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random832 mannequin commented Dec 12, 2015

Looks like a result of searching and replacing PyInt with PyLong - the diff can be found here, if anyone cares. https://hg.python.org/cpython-fullhistory/rev/f324631462a2.

Oddly, there was _another, older_ revision that fixed this correctly: https://hg.python.org/cpython-fullhistory/rev/003d35215ef2 - looks like there was a bad merge somewhere along the line.

@random832
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random832 mannequin commented Dec 12, 2015

Sorry, my mistake, I was looking at z_set instead of Z_set. The earlier fix had left Z_set out for some reason. Anyway, just some historical interest anyway.

@python-dev
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python-dev mannequin commented Dec 12, 2015

New changeset 26859a7e385c by Martin Panter in branch '3.5':
Issue bpo-25845: Drop redundant checks leftover from int to long conversion
https://hg.python.org/cpython/rev/26859a7e385c

New changeset 9be59ad8af80 by Martin Panter in branch 'default':
Issue bpo-25845: Merge PyLong_Check() cleanup from 3.5
https://hg.python.org/cpython/rev/9be59ad8af80

@vadmium
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vadmium commented Dec 12, 2015

History is good for understanding how things became the way they are. :) Thanks Alexander and Random!

@vadmium vadmium closed this as completed Dec 12, 2015
@vadmium vadmium added the type-feature A feature request or enhancement label Dec 12, 2015
@ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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