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

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

Hi Markus,


Le jeu. 8 nov. 2018 09:46, Markus Armbruster <armbru@redhat.com> a écrit :

> Cleber Rosa <crosa@redhat.com> writes:
>
> > On 11/7/18 1:05 AM, Markus Armbruster wrote:
> >> Eduardo Habkost <ehabkost@redhat.com> writes:
> >>
> >>> The $(SHELLSTATUS) variable requires GNU make >= 4.2, but Travis
> >>> seems to provide an older version.  Change the existing rules to
> >>> use command output instead of exit code, to make it compatible
> >>> with older GNU make versions.
> >>>
> >>> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> >>> ---
> >>> I think that's the cause of the Travis failures.  I have
> >>> submitted a test job right now, at:
> >>>   https://travis-ci.org/ehabkost/qemu-hacks/jobs/451387962
> >>> Let's see if it fixes the issue.
> >>> ---
> >>>  tests/Makefile.include | 4 ++--
> >>>  1 file changed, 2 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/tests/Makefile.include b/tests/Makefile.include
> >>> index d2e577eabb..074eece558 100644
> >>> --- a/tests/Makefile.include
> >>> +++ b/tests/Makefile.include
> >>> @@ -913,8 +913,8 @@ TESTS_RESULTS_DIR=$(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?
>

Arch doesn't provide python2 by default, thus python points to python3.
I think what's crappy is scripts expecting python to be python2.

>