[llvm-dev] [RFC] Python 2 / Python 3 status, final step(s)

Thu Dec 17 11:38:09 PST 2020

Can we delay this? I maintain two Windows buildbots, and I'm about to go on
holiday break, and I'd really rather not scramble to get them up to date:
http://lab.llvm.org:8011/#/builders/clang-x64-windows-msvc
http://lab.llvm.org:8011/#/builders/sanitizer-windows

Looking at them now, it seems you broke them five hours ago.

There is risk involved in simply installing Python 3, since it might
necessitate upgrading the buildbot worker version, which I have
successfully avoided doing for almost five years now.

This has not been a good month for Windows bots. As a long suffering
maintainer, I'm asking for a reprieve.

On Mon, Dec 14, 2020 at 10:30 PM Serge Guelton via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Hi Folks,
>
> unless someone has strong arguments against it, the transition to Python 3
> will happen *this week*, on Thursday morning, european time.
> The associated review is https://reviews.llvm.org/D93097, feel free to
> drop in.
> The impact should be low, Python3 is already picked by CMake as default,
> but a Python 2 fallback still exists, and it will be removed.
>
> **If you're a bot owner** please make sure Python3 is available on your
> system ! Now, is the time :-)
>
> On Mon, Oct 19, 2020 at 9:34 PM Jonas Devlieghere via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Sounds good. In LLDB we have a slightly different timeline for the test
>> suite (outlined in
>> http://lists.llvm.org/pipermail/lldb-dev/2020-August/016388.html) but
>> everything else aligns with the plan here. I already removed the fallback
>> to Python 2 in preparation for the 12.0 release.
>>
>> On Tue, Oct 13, 2020 at 11:49 AM David Blaikie via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>>> *thumbs up*
>>>
>>> Re: out of date buildbots: maybe stage the shebang changes in a time/way
>>> that's easy to rollback (or even intended to rollback after a small time
>>> window (few hours) off-peak) to flush out the buildbots. Then after that
>>> rollout, go over the buildbot failures and follow-up with buildbot owners
>>> to get them cleaned up before a more intended-to-stick rollout is done.
>>>
>>> On Tue, Oct 13, 2020 at 7:18 AM James Y Knight via llvm-dev <
>>> llvm-dev at lists.llvm.org> wrote:
>>>
>>>> Yay, thanks for persevering with this migration!
>>>>
>>>> On Tue, Oct 13, 2020 at 8:04 AM Serge Guelton via llvm-dev <
>>>> llvm-dev at lists.llvm.org> wrote:
>>>>
>>>>> Hi Folks,
>>>>>
>>>>> Now that LLVM 11.0.0 has been released, it's time to prepare for the
>>>>> final step
>>>>> envisionned in the previous RFC named *[RFC] Python 2 / Python 3
>>>>> status* [0],
>>>>> ie. requiring Python3.6 for LLVM 12.0.0, to be released in 2021.
>>>>> At least Fedora already only ships Python3 and we didn't have much
>>>>> bugs reported
>>>>> wrt. Python compatibility for the LLVM toolchain.
>>>>>
>>>>> Indeed, all Python scripts should now be at least compatible with both
>>>>> python2 (py2)
>>>>> and python3 (py3), some of them already are already py3 only.
>>>>>
>>>>> The build system still depends on Python in a few place, but it
>>>>> explicitly
>>>>> mentions Python3_EXECUTABLE, and the main dependency (llvm-build) is
>>>>> currently
>>>>> being removed  in D89142.
>>>>>
>>>>> The shebangs have already been harmonized in D83857: some mention
>>>>> /usr/bin/env
>>>>> python, some mention /usr/bin/env python3, and none mention python2
>>>>> anymore. It
>>>>> would be great to have all script use the same shebang, PEP394 [1]
>>>>> makes it
>>>>> (relatively) clear that in our case, explicitly requiring python3 is
>>>>> the way to
>>>>> go.
>>>>>
>>>>> So basically, next step would be to update the documentation, remove
>>>>> the Python2
>>>>> fallback in root CMakeLists.txt and update shebangs.
>>>>>
>>>>> Anyone seeing an issue with that approach? I'm still a bit worried
>>>>> about
>>>>> buildbots still running on py2 (?)
>>>>>
>>>>> Serge
>>>>>
>>>>> [0] http://lists.llvm.org/pipermail/llvm-dev/2020-January/138730.html
>>>>> [1] https://www.python.org/dev/peps/pep-0394/
>>>>>
>>>>> _______________________________________________
>>>>> LLVM Developers mailing list
>>>>> llvm-dev at lists.llvm.org
>>>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>>
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