[Python-Dev] PyIndex_Check conflicts with PEP 384

[Christian Tismer]

Hi Nate,

I just did that, and I got some follow-up work, too, which is fine
with me. Just as a note for you:

Qt not itself, but PyQt5 did that already and submitted a stable
ABI for Python 3.5 and up.

I was challenged end of last December to try that, and I succeeded
after a long struggle, because I also needed to convert all of PySide2
to using heaptypes, and that was really hard. Actually, I succeeded
yesterday, after 5 months. And now I know all the subtle things
that people need to know when converting existing types to heaptypes.

Since QtC has adopted PySide2 in 2016, including myself as a consultant,
now it is really a Qt product, and the limited API is due to my work.
It comes naturally that I also should fix the problems which showed up
during that process.

I also think to submit a paper to python.org where I document all the
subtle problems which occured during the conversion process. It looks
simple, but it really is not.

All the best -- Chris


On 01.06.18 17:18, Nathaniel Smith wrote:
> Indeed, that sounds like a pretty straightforward bug in the stable ABI.
> You should file an issue on bugs.python.org <http://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
> <mailto: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
>     <mailto:tismer at stackless.com>
>     Software Consulting          :     http://www.stackless.com/
>     Karl-Liebknecht-Str. 121     :     http://pyside.org
>     14482 Potsdam                :     GPG key -> 0xFB7BEE0E
>     phone +49 173 24 18 776  fax +49 (30) 700143-0023
> 
>     _______________________________________________
>     Python-Dev mailing list
>     Python-Dev at python.org <mailto:Python-Dev at python.org>
>     https://mail.python.org/mailman/listinfo/python-dev
>     Unsubscribe:
>     https://mail.python.org/mailman/options/python-dev/njs%40pobox.com
> 


-- 
Christian Tismer-Sperling    :^)   tismer at stackless.com
Software Consulting          :     http://www.stackless.com/
Karl-Liebknecht-Str. 121     :     http://pyside.org
14482 Potsdam                :     GPG key -> 0xFB7BEE0E
phone +49 173 24 18 776  fax +49 (30) 700143-0023

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 496 bytes
Desc: OpenPGP digital signature
URL: <http://mail.python.org/pipermail/python-dev/attachments/20180601/f55fa5ac/attachment.sig>