On 12.08.2025 00:59, Paolo Bonzini wrote:
Il lun 11 ago 2025, 21:02 John Snow <js...@redhat.com <mailto:js...@redhat.com>> ha scritto:From: "Sv. Lockal" <lockals...@gmail.com <mailto:lockals...@gmail.com>> Fix compilation with pip-25.2 due to missing distlib.versionStupid question: can we just say that, starting with 10.1, people have to install distlib to build QEMU?
There's nothing changed in this regard on the qemu side, - distlib has always been required. The change is on the python side, not on qemu. The same fix is needed for all previous qemu releases. Or to install distlib.
We're bending over backwards just because the Python developers on one hand keep shipping pip while saying that "no, pip is absolutely not special"; and on the other hand keep *not* shipping packaging and distlib while complaining that people don't use them.
This is a bit backwards, it looks like, and a bit too gross. First, pip vendors a few crate^Wlibs for internal use, but these libs had never been public, - that's why distlib is imported from pip._vendor. We used this hack in qemu to simplify bootstrap, but it was never the intended usage in pip, and hence there's no backwards compatibility break here from the pip side. Second, which is a continuation of the first, strictly speaking it is our fault that we use distlib without depending on it. And 3rd, it seems like Current Way (tm) is to use "packaging" library instead of distlib. And packaging library is shipped within pip for a decade or so already - the same way as distlib. This is why I wrote "backwards" above - by requiring distlib, we seems to work backwards, because current python way - which's been this way for years - is to use packaging, not distlib. But I'm not someone involved in python, - I don't even know python language enough to write a minimal hello,world! program :) -- so I might be misunderstanding something here. In debian, I just added a build dependency on distlib for qemu - in addition to venv, so it's definitely not a big deal. But ok. To sum it up: right now, with introduction of pip 25.2, qemu can't be built anymore without installing additional deps. So far, qemu had worked around missing python deps automatically, shipping everyhing it needs (except of the python itself) in the source tarball. We can continue to try to be friendly to the target environment and require nothing, - if we do, we have to adjust. If we require some python library to be present, we as well can just list everything we need and stop jumping through hoops entirely in mkvenv.py (and elsewhere), and just use things directly, assuming they're installed. This simplifies our bootstrap, - but I don't think this is actually necessary, bootstrap is not the most complicated thing in qemu. And whenever to embed/require distlib or to switch to packaging is an orthogonal question, - it looks like "packaging" is the way to go now, with switching other distlib usage(s) to it. But I'm definitely not the one to judge here. Either way, we're at rc3 now, and have to do some quick fix, - this fix (or similar one which prefers packaging over distlib) seems to be the best quick solution. Thanks, /mjt
