Re: [Qemu-devel] [PATCH 1/4] configure: keep track of Python version

[Eduardo Habkost <ehabkost@redhat.com>]

On Fri, Nov 09, 2018 at 11:39:32AM -0500, Cleber Rosa wrote:
> 
> 
> On 11/9/18 10:49 AM, Eduardo Habkost wrote:
> > On Fri, Nov 09, 2018 at 10:07:07AM -0500, Cleber Rosa wrote:
> >> Some functionality is dependent on the Python version
> >> detected/configured on configure.  While it's possible to run the
> >> Python version later and check for the version, doing it once is
> >> preferable.  Also, it's a relevant information to keep in build logs,
> >> as the overall behavior of the build can be affected by it.
> >>
> >> Signed-off-by: Cleber Rosa <crosa@redhat.com>
> >> ---
> >>  configure | 6 +++++-
> >>  1 file changed, 5 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/configure b/configure
> >> index 74e313a810..67fff0290d 100755
> >> --- a/configure
> >> +++ b/configure
> >> @@ -1740,6 +1740,9 @@ if ! $python -c 'import sys; sys.exit(sys.version_info < (2,7))'; then
> >>        "Use --python=/path/to/python to specify a supported Python."
> >>  fi
> >>  
> >> +# Preserve python version since some functionality is dependent on it
> >> +python_version=$($python -V 2>&1 | sed -e 's/Python\ //')
> > 
> > What about:
> >   $($python -c 'import sys;print(sys.version)')
> > ?
> > 
> > It is very verbose, but I think that's a good thing.
> > 
> 
> Well, something like:
> 
> '3.7.1 (default, Oct 23 2018, 18:19:07) \n[GCC 8.2.1 20180801 (Red Hat
> 8.2.1-2)]'
> 
> Doesn't qualify as simply the Python *version*.  The documentation[1]
> puts it clearly: "A string containing the version number of the Python
> interpreter plus additional information on the build number and compiler
> used. This string is displayed when the interactive interpreter is started."
> 
> I can't see how the compiler used on the Python build, or the build
> date, can be significant to someone debugging the type of Python code
> that will be on QEMU.

No problem to me.

> 
> >> +
> >>  # Suppress writing compiled files
> >>  python="$python -B"
> >>  
> >> @@ -5918,7 +5921,7 @@ echo "LDFLAGS           $LDFLAGS"
> >>  echo "QEMU_LDFLAGS      $QEMU_LDFLAGS"
> >>  echo "make              $make"
> >>  echo "install           $install"
> >> -echo "python            $python"
> >> +echo "python            $python ($python_version)"
> >>  if test "$slirp" = "yes" ; then
> >>      echo "smbd              $smbd"
> >>  fi
> >> @@ -6823,6 +6826,7 @@ echo "INSTALL_DATA=$install -c -m 0644" >> $config_host_mak
> >>  echo "INSTALL_PROG=$install -c -m 0755" >> $config_host_mak
> >>  echo "INSTALL_LIB=$install -c -m 0644" >> $config_host_mak
> >>  echo "PYTHON=$python" >> $config_host_mak
> >> +echo "PYTHON_VERSION=$python_version" >> $config_host_mak
> > 
> > The output of "python -V" and "sys.version" seems to be meant for
> > humans, not software.  If we really want something to be used in
> > conditional makefile rules, I'd prefer to use sys.version_info.
> > e.g.:
> > 
> 
> "Python -V" is quite different from "sys.version".  Indeed it includes
> the "Python " prefix, but that's all, everything else is the version number.

Is this a guarantee documented somewhere?

> 
> >   python_major_version="$($python -c 'import sys;print(sys.version_info[0])')"
> >   echo "PYTHON_MAJOR_VERSION=$python_major_version"
> > 
> > 
> 
> No, I'm actually interested in the other version components, not just
> the major version.  As I tried to explain in another thread, differences
> from Python 3.0 to 3.4 are many, and from 3.4 to 3.6 and so on.

Do you have any examples in mind?  I really doubt we will need to
look at the Python minor version number inside shell scripts or
makefiles.

> 
> Then, we can either introduce "PYTHON_MAJOR_VERSION",
> "PYTHON_MINOR_VERSION", "PYTHON_RELEASE" of sorts, or just have a single
> dot separated version string.

A dot separated version string would work for me, too.  I don't
mind the format that much, because I expect the new variable to
become unnecessary in the next year.  :)

-- 
Eduardo