Re: [PATCH v2 0/7] Python: Drop support for Python 3.6

[Thomas Huth]

On 20/02/2023 20.56, John Snow wrote:
> On Mon, Feb 20, 2023 at 1:16 AM Thomas Huth <thuth@redhat.com> wrote:
> > On 17/02/2023 21.46, John Snow wrote:
> > > On Thu, Feb 16, 2023 at 5:58 AM Thomas Huth <thuth@redhat.com> wrote:
> > > > On 15/02/2023 20.05, Markus Armbruster wrote:
> > > > > The discussion under PATCH 6 makes me think there's a bit of confusion
> > > > > about the actual impact of dropping support for Python 3.6.  Possibly
> > > > > because it's spelled out in the commit message of PATCH 7.  Let me
> > > > > summarize it in one sentence:
> > > > >
> > > > >        *** All supported host systems continue to work ***
> > > > >
> > > > > Evidence: CI remains green.
> > > >
> > > > The CI remains green since one of the patches disabled the building of the
> > > > docs on CentOS 8. That's not how I'd describe "continue to work", at least
> > > > not in the same extend as before.
> > > >
> > > > > On some supported host systems, different packages need to be installed.
> > > > > On CentOS 8, for instance, we need to install Python 3.8.13 or 3.9.16
> > > > > instead of 3.6.8.  Let me stress again: same repository, different
> > > > > package.  No downsides I can see.
> > > > >
> > > > > The *one* exception is Sphinx on CentOS 8.  CentOS 8 does not ship a
> > > > > version of Sphinx that works with Python 3.7 or newer.  This series
> > > > > proposes to simply stop building the docs there, unless the user
> > > > > provides a suitable version of Sphinx (which is easy enough with pip).
> > > >
> > > > I think we've all understood that. The thing that you obviously did not
> > > > understood: This breaks our support statement.
> > > > I'm pretty sure that you could also build the whole QEMU suite successfully
> > > > on an ancient CentOS 7 or Ubuntu 18.04 system if you manually install a
> > > > newer version of GCC and some of the required libraries first. But that's
> > > > not how we understand our support statement.
> > > >
> > > > Sure, you can argue that you can use "pip install" to get a newer version of
> > > > Sphinx on RHEL 8 / CentOS 8 to continue building the docs there - but is
> > > > that really that much different from installing a newer version of GCC and
> > > > libraries on an ancient distro that we do not officially support anymore?
> > > > I'd say no. You also have to consider that not every build host has access
> > > > to the internet, maybe some companies only have an internal mirror of the
> > > > distro packages in their intranet (I remember some discussion about such a
> > > > case in the past) - so while you were perfectly fine to build the whole of
> > > > QEMU on a CentOS 8 there before this change, you could now not build parts
> > > > of QEMU anymore there due to the missing possibility to run "pip install"
> > > > without full internet connection.
> > >
> > > There are good points elsewhere in this thread and I am taking notes,
> > > but this critique caught my eye as something I was not specifically
> > > planning around, so I wanted to get an elaboration here if I may.
> > >
> > > Do we have a support statement for this? I find this critique somewhat
> > > surprising -- If we don't have internet, how did we get the other 20
> > > to 30 dependencies needed to build QEMU? To what extent are we
> > > *required* to preserve a build that works without internet access?
> >
> > It's not written in stone, but I saw it this way: If I have a complete
> > mirror of a distro repository in my intrAnet, I can use that mirror to set
> > up a QEMU build host system that has no access to the internet. Or maybe
> > think of a DVD image(s) with all distro packages that you use to install a
> > host without network access (and you copy the QEMU tarball there via USB
> > stick). I think it's not that uncommon to have such scenarios out there.
> >
> > For example, do you remember that SDL 1.2 discussion a some years ago? See:
> >
> >    https://www.mail-archive.com/qemu-devel@nongnu.org/msg631628.html
> >
> > It was not exactly the same situation, since those folks were even unable to
> > install a SDL2-devel package on their pre-installed hosts, though it was
> > theoretically available as an update in their distro, but I think it gives
> > an impression of what people are using and expecting out there... (and no,
> > I'm not happy with this, I'd also rather love if we could move faster in the
> > QEMU project sometimes).
> >
> >    Thomas
>
> Well, in this case I believe our support policy generally is written
> to require a fully up-to-date version of the LTS distros, e.g. we
> don't really test against "release day" 16.04, in the same way we
> don't offer support for RHEL 8.0, just the latest point release.

Yes, sure, that's what I meant with "not exactly the same situation" ... it 
was just an example of people trying to compile QEMU offline.

> I think really all we need is the ability to know a priori what we
> need to build QEMU before going offline without any last second
> surprises during configure, make, or make check. Right?

I think it should be OK with the patch that Paolo suggested for the support 
policy and maybe a note somewhere that you have to make sure to install a 
newer Sphinx with pip in case you still want to build the docs on older 
enterprise distros...

 Thomas