llvm dev - Dec 2019 - Python 2 compatibility for utility scripts

At the beginning of the year, I've landed a large set of patches to support
both Python 2 and Python3 in most Python scripts. Looks like I missed some
of them :-)
At that time, backward portability with Python2 was still relevant, and I
suspect it will still be the case for a few distributions that ship Python2
by default. That being said, Even RHEL8 uses Python3 by default, so at some
point we may be able to drop the compatibility stuff.
Until then, I'd argue for maintaining compatibility as it's not a
tremendous task.

On Tue, Dec 17, 2019 at 10:54 AM James Henderson via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> I personally only use Python 3 reluctantly. I've yet to encounter a
> situation where I actually preferred Python 3. That being said, given the
> decision to retire Python 2.7 (*grumble* *grumble*), I'll probably be
> forced sometime in the new year to uninstall it by somebody in charge of
> security somewhere. I certainly don't see a personal need to have all
> scripts support Python 2, unless they are used in the build/test pipeline
> somewhere (i.e. get touched by a fresh check-all).
>
> On Tue, 17 Dec 2019 at 05:31, Fangrui Song via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> https://reviews.llvm.org/D71565 intends to update
>> llvm/utils/update_cc_test_checks.py to work with Python 2.
>>
>> In the original review, I suggested that we don't add Python 2
>> compatibility for new features because Python 2.7 is retiring and some
>> Linux distributions are even deprecating/removing Python 2 support. My
>> feeling is:
>>
>> If some utilities do not support Python 2, we should probably not
bother
>> making them Python 2 compatible. Maintaining Python 2/3 compatibility
>> may not worth the efforts. "utilities" include some command
line tools
>> under llvm/utils, which are not part of instructure like lit. What do
>> people think?
>>
>> BTW, what's the Python 3 support status of build bots? Are there
any
>> running Python 3?
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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On Tue, Dec 17, 2019 at 5:12 AM Serge Guelton <sguelton at redhat.com>
wrote:
> At the beginning of the year, I've landed a large set of patches to
> support both Python 2 and Python3 in most Python scripts. Looks like I
> missed some of them :-)
> At that time, backward portability with Python2 was still relevant, and I
> suspect it will still be the case for a few distributions that ship Python2
> by default. That being said, Even RHEL8 uses Python3 by default, so at some
> point we may be able to drop the compatibility stuff.
> Until then, I'd argue for maintaining compatibility as it's not a
> tremendous task.
>
This is my feeling as well. In yesterday's instance, I lost more time to
fixing bugs in the py3 detection logic on systems that don't have it than
it took me to make the script just run fine with both Python 2 and 3.

On macOS, I think 10.15 is the first version that ships with python3, and
that was released just 2 months ago.

>
> On Tue, Dec 17, 2019 at 10:54 AM James Henderson via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> I personally only use Python 3 reluctantly. I've yet to encounter a
>> situation where I actually preferred Python 3. That being said, given
the
>> decision to retire Python 2.7 (*grumble* *grumble*), I'll probably
be
>> forced sometime in the new year to uninstall it by somebody in charge
of
>> security somewhere. I certainly don't see a personal need to have
all
>> scripts support Python 2, unless they are used in the build/test
pipeline
>> somewhere (i.e. get touched by a fresh check-all).
>>
>> On Tue, 17 Dec 2019 at 05:31, Fangrui Song via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>>> https://reviews.llvm.org/D71565 intends to update
>>> llvm/utils/update_cc_test_checks.py to work with Python 2.
>>>
>>> In the original review, I suggested that we don't add Python 2
>>> compatibility for new features because Python 2.7 is retiring and
some
>>> Linux distributions are even deprecating/removing Python 2 support.
My
>>> feeling is:
>>>
>>> If some utilities do not support Python 2, we should probably not
bother
>>> making them Python 2 compatible. Maintaining Python 2/3
compatibility
>>> may not worth the efforts. "utilities" include some
command line tools
>>> under llvm/utils, which are not part of instructure like lit. What
do
>>> people think?
>>>
>>> BTW, what's the Python 3 support status of build bots? Are
there any
>>> running Python 3?
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>
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IMO, having non-critical utility scripts require python 3 should be allowed
now. But, not yet for any scripts which are critical to build or test the
distributed components.

If we need to spend some time to fix the test runner to allow properly
skipping tests of python3-only components when python3 isn't available,
that seems entirely worthwhile, since we only need to do that once.



On Tue, Dec 17, 2019, 7:43 AM Nico Weber via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> On Tue, Dec 17, 2019 at 5:12 AM Serge Guelton <sguelton at
redhat.com> wrote:
>
>> At the beginning of the year, I've landed a large set of patches to
>> support both Python 2 and Python3 in most Python scripts. Looks like I
>> missed some of them :-)
>> At that time, backward portability with Python2 was still relevant, and
I
>> suspect it will still be the case for a few distributions that ship
Python2
>> by default. That being said, Even RHEL8 uses Python3 by default, so at
some
>> point we may be able to drop the compatibility stuff.
>> Until then, I'd argue for maintaining compatibility as it's not
a
>> tremendous task.
>>
>
> This is my feeling as well. In yesterday's instance, I lost more time
to
> fixing bugs in the py3 detection logic on systems that don't have it
than
> it took me to make the script just run fine with both Python 2 and 3.
>
> On macOS, I think 10.15 is the first version that ships with python3, and
> that was released just 2 months ago.
>
>
>>
>> On Tue, Dec 17, 2019 at 10:54 AM James Henderson via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>>> I personally only use Python 3 reluctantly. I've yet to
encounter a
>>> situation where I actually preferred Python 3. That being said,
given the
>>> decision to retire Python 2.7 (*grumble* *grumble*), I'll
probably be
>>> forced sometime in the new year to uninstall it by somebody in
charge of
>>> security somewhere. I certainly don't see a personal need to
have all
>>> scripts support Python 2, unless they are used in the build/test
pipeline
>>> somewhere (i.e. get touched by a fresh check-all).
>>>
>>> On Tue, 17 Dec 2019 at 05:31, Fangrui Song via llvm-dev <
>>> llvm-dev at lists.llvm.org> wrote:
>>>
>>>> https://reviews.llvm.org/D71565 intends to update
>>>> llvm/utils/update_cc_test_checks.py to work with Python 2.
>>>>
>>>> In the original review, I suggested that we don't add
Python 2
>>>> compatibility for new features because Python 2.7 is retiring
and some
>>>> Linux distributions are even deprecating/removing Python 2
support. My
>>>> feeling is:
>>>>
>>>> If some utilities do not support Python 2, we should probably
not bother
>>>> making them Python 2 compatible. Maintaining Python 2/3
compatibility
>>>> may not worth the efforts. "utilities" include some
command line tools
>>>> under llvm/utils, which are not part of instructure like lit.
What do
>>>> people think?
>>>>
>>>> BTW, what's the Python 3 support status of build bots? Are
there any
>>>> running Python 3?
>>>> _______________________________________________
>>>> LLVM Developers mailing list
>>>> llvm-dev at lists.llvm.org
>>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>
>> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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