PyIndex_Check conflicts with PEP 384

[ctismer]

BPO	33738
Nosy	@pitrou, @vstinner, @larryhastings, @ned-deily, @ericsnowcurrently, @serhiy-storchaka, @ctismer
PRs	bpo-33738: Fix macros which contradict PEP 384 #7477 bpo-33738: Fix macros which contradict PEP 384 #7585 bpo-33818: PyExceptionClass_Name() will now return "const char *". #7581 Clean up after bpo-33738. #7627

^{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 2020-06-22.09:12:20.637>
created_at = <Date 2018-06-01.17:14:58.908>
labels = ['extension-modules', 'build', '3.8']
title = 'PyIndex_Check conflicts with PEP 384'
updated_at = <Date 2020-06-22.09:12:20.636>
user = 'https://github.com/ctismer'

bugs.python.org fields:

activity = <Date 2020-06-22.09:12:20.636>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2020-06-22.09:12:20.637>
closer = 'vstinner'
components = ['Extension Modules']
creation = <Date 2018-06-01.17:14:58.908>
creator = 'Christian.Tismer'
dependencies = []
files = []
hgrepos = []
issue_num = 33738
keywords = ['patch']
message_count = 26.0
messages = ['318436', '318449', '318458', '318461', '318462', '318465', '318516', '318908', '318909', '318910', '318925', '318951', '318952', '319018', '319073', '319169', '319174', '319197', '319207', '319217', '319256', '319259', '319297', '319301', '372048', '372057']
nosy_count = 7.0
nosy_names = ['pitrou', 'vstinner', 'larry', 'ned.deily', 'eric.snow', 'serhiy.storchaka', 'Christian.Tismer']
pr_nums = ['7477', '7585', '7581', '7627']
priority = 'critical'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'compile error'
url = 'https://bugs.python.org/issue33738'
versions = ['Python 3.8']

[ctismer]

The file number.rst on python 3.6 says

"""
.. c:function:: int PyIndex_Check(PyObject *o)

Returns 1 if o is an index integer (has the nb_index slot of the
tp_as_number structure filled in), and 0 otherwise.
"""

But in reality, this is a macro:

"""
#define PyIndex_Check(obj) \
   ((obj)->ob_type->tp_as_number != NULL && \
    (obj)->ob_type->tp_as_number->nb_index != NULL)
"""

But such a macro does not work with the limited API, since
non-heaptypes cannot use PyType_GetSlot.

The patch is trivial: Define the function instead of the macro
when Py_LIMITED_API is set.

I also think the documentation makes more sense when it is correct.

[ned-deily]

This is not a security issue so a change would not be applicable to the 3.4 or 3.5 branches, currently in security-fix-only mode.

[serhiy-storchaka]

Seems PyIter_Check and PySequence_ITEM have the same problem. And maybe more.

[ctismer]

Ok, I tried to submit a patch (not yet successful),
but as it stands, there are more locations in the code where
this will show up with similar problems.

Should I take care of these all as much as I can,
or is it better to leave it to one of you?

Whatever you prefer is ok. I just want the problem to disappear
in 3.7, because I hate to break the API any longer.

Cheers - Chris

[serhiy-storchaka]

Would be nice if you fix as much similar as you can with a single PR.

For performance it makes sense to keep macros if the limited API is not used.

[ctismer]

Yes, sure, I will submit a patch that tries to reach as much
as possible locations that have a similar problem. Of course,
the code will only be turned into functions for the PEP context.

Takes a day because I need to re-learn a bit how to do this :-)
(last patch was 2010, I think... )

-- related personal note - does someone know what happened to Martin?

[pitrou]

related personal note - does someone know what happened to Martin?

I don't think anything bad happened. He still seems to be teaching:
http://www.beuth-hochschule.de/people/detail/1398/

[ned-deily]

Christian, any progress on this? 3.7.0rc1 is planned to be tagged in 4 days, on Monday 2018-06-11. Do you think you will be able to provide a PR before then?

[ctismer]

Hi Ned,

we had a delivery date yesterday for PySide.
The PR is almost ready and will go out today.

Ciao - Chris

On 07.06.18 09:43, Ned Deily wrote:

Ned Deily <nad@python.org> added the comment:

Christian, any progress on this? 3.7.0rc1 is planned to be tagged in 4 days, on Monday 2018-06-11. Do you think you will be able to provide a PR before then?

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Python tracker <report@bugs.python.org>
<https://bugs.python.org/issue33738\>

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[ned-deily]

Thanks, Christian!