[issue30281] set stop default to -PY_SSIZE_T_MAX-1 in PySlice_Unpack

[Xiang Zhang]

Changes by Xiang Zhang :


--
resolution:  -> fixed
stage: patch review -> resolved
status: open -> closed

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[issue30281] set stop default to -PY_SSIZE_T_MAX-1 in PySlice_Unpack

[Xiang Zhang]

Xiang Zhang added the comment:


New changeset 05469fa1c05acf55bdca05db21822ecdd7f6487a by Xiang Zhang in branch 
'2.7':
bpo-30281: Fix the default value for stop in PySlice_Unpack() (#1531) (#1480)
https://github.com/python/cpython/commit/05469fa1c05acf55bdca05db21822ecdd7f6487a


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[issue30281] set stop default to -PY_SSIZE_T_MAX-1 in PySlice_Unpack

[Xiang Zhang]

Xiang Zhang added the comment:


New changeset 639e295650a51894412c9d976958792010d3bcf8 by Xiang Zhang in branch 
'3.5':
bpo-30281: Fix the default value for stop in PySlice_Unpack() (#1530) (#1480）
https://github.com/python/cpython/commit/639e295650a51894412c9d976958792010d3bcf8


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[issue30281] set stop default to -PY_SSIZE_T_MAX-1 in PySlice_Unpack

[Xiang Zhang]

Xiang Zhang added the comment:


New changeset 98b49a00d413972965044fd355be3b8482caa07c by Xiang Zhang in branch 
'3.6':
bpo-30281: Fix the default value for stop in PySlice_Unpack() (#1480) (#1529)
https://github.com/python/cpython/commit/98b49a00d413972965044fd355be3b8482caa07c


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[issue30281] set stop default to -PY_SSIZE_T_MAX-1 in PySlice_Unpack

[Xiang Zhang]

Changes by Xiang Zhang :


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pull_requests: +1630

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[issue30281] set stop default to -PY_SSIZE_T_MAX-1 in PySlice_Unpack

[Xiang Zhang]

Changes by Xiang Zhang :


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pull_requests: +1628

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[issue30281] set stop default to -PY_SSIZE_T_MAX-1 in PySlice_Unpack

[Xiang Zhang]

Changes by Xiang Zhang :


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pull_requests: +1629

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[issue30281] set stop default to -PY_SSIZE_T_MAX-1 in PySlice_Unpack

[Xiang Zhang]

Xiang Zhang added the comment:


New changeset 2ddf5a19c3a06978edff2c8ba0aaf5df3528204a by Xiang Zhang in branch 
'master':
bpo-30281: Fix the default value for stop in PySlice_Unpack() (#1480)
https://github.com/python/cpython/commit/2ddf5a19c3a06978edff2c8ba0aaf5df3528204a


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[issue30281] set stop default to -PY_SSIZE_T_MAX-1 in PySlice_Unpack

[Xiang Zhang]

Xiang Zhang added the comment:

I am okay to use PY_SSIZE_T_MIN. But if we are worried about future change of 
PY_SSIZE_T_MIN, seems we also need to change the API doc of PySlice_Unpack(). 
Although _PyEval_SliceIndex's comment says it clips value to -PY_SSIZE_T_MAX-1, 
actually it uses PyNumber_AsSize_t and clips value to PY_SSIZE_T_MIN.

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[issue30281] set stop default to -PY_SSIZE_T_MAX-1 in PySlice_Unpack

[STINNER Victor]

STINNER Victor added the comment:

Hum, integer overflows are complex issues. It deserves an unit test, maybe even 
in C written in _testcapi?

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nosy: +haypo

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[issue30281] set stop default to -PY_SSIZE_T_MAX-1 in PySlice_Unpack

[Serhiy Storchaka]

Serhiy Storchaka added the comment:

I'm not sure that -PY_SSIZE_T_MAX-1 always is representable. I would use 
PY_SSIZE_T_MIN and add a static assert (Py_BUILD_ASSERT) that PY_SSIZE_T_MIN + 
1 <= -PY_SSIZE_T_MAX. Actually currently PY_SSIZE_T_MIN is -PY_SSIZE_T_MAX-1 by 
definition, but this can be changed in future.

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nosy: +mark.dickinson

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[issue30281] set stop default to -PY_SSIZE_T_MAX-1 in PySlice_Unpack

[Xiang Zhang]

Changes by Xiang Zhang :


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pull_requests: +1579

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[issue30281] set stop default to -PY_SSIZE_T_MAX-1 in PySlice_Unpack

[Xiang Zhang]

New submission from Xiang Zhang:

The default value for stop in PySlice_Unpack should be -PY_SSIZE_T_MAX-1. 
Otherwise a sequence of length PY_SSIZE_T_MAX could get a wrong slicelength 
when doing L[::-1].

--
components: Interpreter Core
messages: 293097
nosy: serhiy.storchaka, xiang.zhang
priority: normal
severity: normal
stage: patch review
status: open
title: set stop default to -PY_SSIZE_T_MAX-1 in PySlice_Unpack
type: behavior
versions: Python 2.7, Python 3.5, Python 3.6, Python 3.7

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