On Tue, Feb 21, 2023, 6:03 AM Paolo Bonzini <pbonz...@redhat.com> wrote:
> On 2/21/23 02:24, John Snow wrote:
> > At the moment, we look for just "python3" and "python", which is good
> > enough almost all of the time. But ... if you are on a platform that
> > uses an older Python by default and only offers a newer Python as an
> > option, you'll have to specify --python=/usr/bin/foo every time.
> >
> > As a courtesy, we can make a cursory attempt to locate a suitable Python
> > binary ourselves, looking for the remaining well-known binaries. This
> > also has the added benefit of making configure "just work" more often
> > on various BSD distributions that do not have the concept of a
> > "platform default python".
> >
> > This configure loop will prefer, in order:
> >
> > 1. Whatever is specified in $PYTHON
> > 2. python3
> > 3. python (Which is usually 2.x, but might be 3.x on some platforms.)
> > 4. python3.11 down through python3.6
> >
> > Notes:
> >
> > - Python virtual environments provide binaries for "python3", "python",
> > and whichever version you used to create the venv,
> > e.g. "python3.8". If configure is invoked from inside of a venv, this
> > configure loop will not "break out" of that venv unless that venv is
> > created using an explicitly non-suitable version of Python that we
> > cannot use.
> >
> > - In the event that no suitable python is found, the first python found
> > is the version used to generate the human-readable error message.
> >
> > - The error message isn't printed right away to allow later
> > configuration code to pick up an explicitly configured python.
> >
> > Signed-off-by: John Snow <js...@redhat.com>
> > ---
> > configure | 34 ++++++++++++++++++++++++++--------
> > 1 file changed, 26 insertions(+), 8 deletions(-)
> >
> > diff --git a/configure b/configure
> > index cf6db3d5518..6abf5a72078 100755
> > --- a/configure
> > +++ b/configure
> > @@ -592,20 +592,40 @@ esac
> >
> > : ${make=${MAKE-make}}
> >
> > -# We prefer python 3.x. A bare 'python' is traditionally
> > -# python 2.x, but some distros have it as python 3.x, so
> > -# we check that too
> > +
> > +check_py_version() {
> > + # We require python >= 3.6.
> > + # NB: a True python conditional creates a non-zero return code
> (Failure)
> > + "$1" -c 'import sys; sys.exit(sys.version_info < (3,6))'
> > +}
> > +
> > python=
> > +first_python=
> > explicit_python=no
> > -for binary in "${PYTHON-python3}" python
> > +# Check for $PYTHON, python3, python, then explicitly-versioned
> interpreters.
> > +for binary in "${PYTHON-python3}" ${PYTHON:+python3} python \
> > + python3.11 python3.10 python3.9 \
> > + python3.8 python3.7 python3.6
>
> I think if PYTHON is set we shouldn't look at anything else.
>
> Paolo
>
PYTHON is one we made up, right?
> > do
> > if has "$binary"
> > then
> > python=$(command -v "$binary")
> > - break
> > + if test -z "$first_python"; then
> > + first_python=$python
> > + fi
> > + if check_py_version "$python"; then
> > + # This one is good.
> > + first_python=
> > + break
> > + fi
> > fi
> > done
> >
> > +# If first_python is set, we didn't find a suitable binary.
> > +# Use this one for possible future error messages.
> > +if test -n "$first_python"; then
> > + python="$first_python"
> > +fi
> >
> > # Check for ancillary tools used in testing
> > genisoimage=
> > @@ -1037,9 +1057,7 @@ then
> > error_exit "GNU make ($make) not found"
> > fi
> >
> > -# Note that if the Python conditional here evaluates True we will exit
> > -# with status 1 which is a shell 'false' value.
> > -if ! $python -c 'import sys; sys.exit(sys.version_info < (3,6))'; then
> > +if ! check_py_version "$python"; then
> > error_exit "Cannot use '$python', Python >= 3.6 is required." \
> > "Use --python=/path/to/python to specify a supported Python."
> > fi
>
>
