Re: [Qemu-block] [Qemu-devel] [PATCH] tests: Fix Python 3 detection on older GNU make versions

[Cleber Rosa]

On 11/8/18 3:45 AM, Markus Armbruster wrote:
> Cleber Rosa <address@hidden> writes:
> 
>> On 11/7/18 1:05 AM, Markus Armbruster wrote:
>>> Eduardo Habkost <address@hidden> writes:
>>>
>>>> The $(SHELLSTATUS) variable requires GNU make >= 4.2, but Travis
>>>> seems to provide an older version.  Change the existing rules to
>>>> use command output instead of exit code, to make it compatible
>>>> with older GNU make versions.
>>>>
>>>> Signed-off-by: Eduardo Habkost <address@hidden>
>>>> ---
>>>> I think that's the cause of the Travis failures.  I have
>>>> submitted a test job right now, at:
>>>>   https://travis-ci.org/ehabkost/qemu-hacks/jobs/451387962
>>>> Let's see if it fixes the issue.
>>>> ---
>>>>  tests/Makefile.include | 4 ++--
>>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/tests/Makefile.include b/tests/Makefile.include
>>>> index d2e577eabb..074eece558 100644
>>>> --- a/tests/Makefile.include
>>>> +++ b/tests/Makefile.include
>>>> @@ -913,8 +913,8 @@ TESTS_RESULTS_DIR=$(BUILD_DIR)/tests/results
>>>>  # information please refer to "avocado --help".
>>>>  AVOCADO_SHOW=none
>>>>  
>>>> -$(shell $(PYTHON) -c 'import sys; assert sys.version_info >= (3,0)' 
>>>> >/dev/null 2>&1)
>>>> -ifeq ($(.SHELLSTATUS),0)
>>>> +PYTHON3 = $(shell $(PYTHON) -c 'import sys; print(1 if sys.version_info 
>>>> >= (3, 0) else 0)')
>>>> +ifeq ($(PYTHON3), 1)
>>>>  $(TESTS_VENV_DIR): $(TESTS_VENV_REQ)
>>>>    $(call quiet-command, \
>>>>              $(PYTHON) -m venv --system-site-packages $@, \
>>>
>>> PEP 394 recommends software distributions install Python 3 into the
>>> default path as python3, and users use that instead of python, except
>>> for programs that are source compatible with both 2 and 3.  So, is
>>> finding out whether python is a Python 3 really appropriate?  Why can't
>>> we just use python3 and be done with it?
>>>
>>
>> I mentioned that before, when you pointed out the issue you fix here,
>> that configure may be the best place to get the Python version (not only
>> the major version) and make it available elsewhere.  Even if not used
>> for other purposes, it is IMO important information to show on the
>> resulting "configure" output.
>>
>> I'm sending patches to do that in a few.
>>
>>> If we can't: isn't this a configure problem?
>>>
>>
>> I believe adhering to PEP394 is a good thing, but even that document
>> recognizes that the real world is not a perfect place: "however, end
>> users should be aware that python refers to python3 on at least Arch
>> Linux".  And it only covers *nix systems, so if we hope to care for
>> non-*nix systems, we have to check the Python version manually.
>>
>> So, I guess the safest approach from QEMU's side is to check for the
>> version indeed.
> 
> If somebody can point to a system people still use where python3 doesn't
> get you a Python 3, but python does, catering for such (crappy) systems
> in configure makes sense.  Until then, it's a waste of brain waves and
> configure run time.
> 
> PEP 394 mentions Arch Linux.  It's been seven years.  What's the most
> recent version of Arch Linux that's still crappy in this regard?
> 

I'm not taking the mission of looking for those odd distros, I agree
it's not productive.  My point is that the Python version is an
important thing to keep track of, specially with the advent of running
Python dependent tests on environments we don't fully control.

Supposing the Python version is captured and tracked by configure, then
the "python" binary name becomes a non-issue.

- Cleber.