[Python-Dev] PyIndex_Check conflicts with PEP 384

[Nathaniel Smith]

Indeed, that sounds like a pretty straightforward bug in the stable ABI.
You should file an issue on bugs.python.org so it doesn't get lost (and if
it's the main new stable ABI break in 3.7 then you should probably mark
that bug as a release blocker so that Ned notices it).

Unfortunately, very few people use the stable ABI currently, so it's easy
for things like this to get missed. Hopefully it Qt starts using it then
that will help us shake these things out... But it also means we need your
help to catch these kinds of issues :-). Thanks!

On Fri, Jun 1, 2018, 06:51 Christian Tismer <tismer at stackless.com> wrote:

> Hi friends,
>
> when implementing the limited API for PySide2, I recognized
> a little bug where a function was replaced by a macro.
>
> 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.
> """
>
> Without notice, this function was replaced by a macro a while
> ago, which reads
>
> #define PyIndex_Check(obj) \
>    ((obj)->ob_type->tp_as_number != NULL && \
>     (obj)->ob_type->tp_as_number->nb_index != NULL)
>
> This contradicts PEP 384, because there is no way for non-heaptype
> types to access the nb_index field.
>
> If nobody objects, I would like to submit a patch that adds the
> function back when the limited API is active.
> I think to fix that before Python 3.7 is out.
>
> Ciao -- Chris
>
> --
> Christian Tismer-Sperling    :^)   tismer at stackless.com
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