[Buildroot] [PATCH] meson: bump version to 0.48.1

[Baruch Siach]

Hi Arnout,

Arnout Vandecappelle writes:
> On 20/10/2018 15:00, Arnout Vandecappelle wrote:
>> On 20/10/2018 13:57, Arnout Vandecappelle wrote:
> [snip]
>>>> Maybe host-python-setuptools are build for the wrong python version (python2 instead of python3)?
>>>  That is correct. When target python or python3 is selected, then the
>>> corresponding host python is also selected, and *all* host python packages are
>>> built for that specific python version. But if only target python is selected,
>>> then you will get host-python as well, but you can also still depend on
>>> host-python3. In that case, however, all the host python packages will be built
>>> only for python2, not for python3. Hence the breakage.
>>>
>>>  I'm surprised though that we don't see this in the autobuilders... Your patch
>>> doesn't change anything there, does it?
>> It actually does... meson 0.47.1 still had a fallback on distutils if
>> setuptools wasn't available, but 0.48.1 removed that fallback.
>
> Long discussion an the BR developer meeting, here is the conclusion. Adding
> Yegor and Asaf in Cc as python maintainers.
>
> The issue we have at the moment is that all host python packages are built for
> Python 2, not Python 3, *unless* Python 3 is selected for the target.
>
> However, *most* packages support Python 3 as well.
>
> So, the idea is to default to Python 3 for the host. In other words, all host
> packages will use Python 3 (independent of what is going on the target), except
> for the packages that work on python2 only. This step by itself is quite a bit
> of work because there are many packages that can use python2 OR python3.
>
> This leaves us with two problems.
>
> First of all, there may be python-2-only host packages that depend on some
> other host-python package that would only get built for python3. We investigated
> that, and it looks OK: there are only 4 python-2-only host packages: gdb,
> python-cheetah, python-enum34, and python-yieldfrom. The latter two are
> compatibility libraries so obviously only available on Python2. python-yieldfrom
> is not used at all. python-enum34 is only used by setools, in case it needs to
> be built for host-python2, so that should be OK. host-python-cheetah is only
> used by gr-osmosdr; bumping python-cheetah probably enables it for Python 3 so
> would solve that issue. And gdb doesn't need any other python package, just
> python itself. So all this looks fixable.
>
> The bigger problem, is when a setup.py script tries to import a module from
> some python package. The clearest one of those is python-setuptools: any python
> package that uses setuptools will import setuptools using the same host-python
> version as on the target. So when you have python2 on the target, the setup.py
> script will be run in python2, so we need host-python-setuptools for python2.
> The solution there, we think, is to add a separate host-python2-setuptools
> package that is used instead of host-python-setuptools in case the target is
> python2. Unfortunately there are quite a few others that may need the same
> treatment. Some of them, however, probably don't really need to be imported in
> the setup.py script so they can be removed as a dependency. Others, however,
> will need the same treatment. In some cases, we might be able to just build both
> python2 and python3 versions (e.g. for python-sip this should be possible).
>
> Finally, there are most likely some corner cases that we didn't think of...
>
> So it looks like this will be a pretty big migration. Therefore, for the time
> being, it may be easier to just add a host-python3-setuptools package and use
> that in meson.
>
> By the way, lirc-tools has the same problem. It adds python3
> host-python-setuptools to its dependencies, but the setuptools don't get
> imported so it just doesn't work (I think). Baruch, care to take a look at that?

I'm not that much of a Python expert so I might be missing something
here.

The python-pkg/setup.py file in the lirc-tools source tree have this:

from setuptools import setup, Extension

A build test with python3 enabled installs lirc python and binary code
under /usr/lib/python3.7/site-packages/lirc in the target.

So what is it that "doesn't work"? Please enlighten me.

Thanks,
baruch

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