Re: [Patch] Support building with SWIG 4 on Python 3.x

On 2019/11/15 14:04, Nathan Hartman wrote:
> On Thu, Nov 14, 2019 at 8:18 AM Jun Omae <jun66j5_at_gmail.com> wrote:
>
>> (Posting to dev list, again...)
>>
>> On Thu, Nov 14, 2019 at 1:47 AM Julian Foad <julianfoad_at_apache.org> wrote:
>>> Perhaps someone could commit this if there are no other concerns with
>>> it, and adjust INSTALL at the same time?
>>
>> Updated proposed patch, including a change of
>> subversion/bindings/swig/INSTALL.
>>
>
> Hi all,
>
> Jun, thank you for this patch.
>
> I would like to get this committed quickly if there are no objections, but
> this is not my area of expertise.
>
> Brane, do I understand correctly that you are satisfied with the results of
> your review/test?

I also tested make check-swig-py on FreeBSD, with Python 2.7/3.7 and
SWIG 2.0.0/2.0.12/3.0.9/3.0.10/3.0.12/4.0.1 combination. Of course,
combination of Python 2.7 + SWIG 4.0.1 and combination of
Python 3.7 + SWIG < 3.0.10 are blocked by .check_swig_py target :)
Other combinations are passed the test.

I considered if we can move classic style versus new style class conditional
from run time to SWIG code generation time only, but it is not just
problem in this patch only, but also in current code.
  
> In particular, the main question I have is with regards to the -modern
> option being added for SWIG 3.x .. <4 with Py3. If I understand correctly,
> this changes the way SWIG will generate accessors (properties vs
> getters/setters). Would this break any downstream code? (And if so, is that
> acceptable?)

There is no Python 3 application depending on it, because we have not yet
released SWIG Python bindings that supports Python 3.

> Also I don't fully understand the last part of the patch: is it creating
> replacements for the aforementioned getters/setters?

No, they are only helpers to create them to absorb difference how to access
attributes between combination of Python/SWIG versions. I think this is
a private part how we implement proxy objects for C data structures, and
not for expose to be used from applications.

Cheers,

-- 
Yasuhito FUTATSUKI <futatuki_at_yf.bsdclub.org>/<futatuki_at_poem.co.jp>