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

[Eduardo Habkost]

On Wed, Nov 07, 2018 at 07:05:03AM +0100, 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?

Because './configure --with-python=...' exists, and I didn't want
to break it.

Now, why do we need --with-python, and why do we need to use
$(PYTHON) when running tests?  If somebody wants to use a
different Python binary when running tests, they can already use
$PATH for that.

(That's the same argument I used for iotests a while ago:
https://www.mail-archive.com/address@hidden/msg566631.html)

> 
> If we can't: isn't this a configure problem?

It is, and I think Cleber mentioned that he planned to do it in
./configure, a while ago.  But just using the python3 binary from
$PATH would be even better.

-- 
Eduardo