Subject: Re: bug#64309: Python dlopen()s musl libc

From: Josselin Poiret <[email-masked]>
Date: Wed, 12 Jul 2023 10:50:40 +0200

Hi Lars,

Lars-Dominik Braun <[email-masked]> writes:

> I think the problem is bigger than usercustomize. Any custom PYTHONPATH
> also slips through and causes this issue, as well as any custom
> GUIX_PYTHONPATH, because the executable wrapper appends it (think nested
> `guix shell` invokations with different versions of a library for
> an example where this could go wrong).
>
> Guix-managed Python packages (libraries nor applications) should
> generally not pick up dependencies from random paths – only those
> from their package description, so we can keep Guix’ promise of being
> self-contained.
>
> I have experimented with customizing Python’s importing mechanism
> through a custom MetaPathFinder. It works by adding a __guix_pythonpath__
> variable to every Python package’s __init__.py file and modifying the
> module loader’s search path accordingly if such a variable exists. It
> would provide exactly that guarantee, but it’s just a PoC at this
> point – see attached file.

Woah, looks like a neat solution.  Do you think it would scale for all
our Python packages without manual intervention?  If so, this would
definitely be the way forward.

> Apart from that I don’t see a good short-term solution right now. It’s
> just how Python works.

I mostly agree with you, but for this rather common case of having also
a usercustomize it would be nice to circumvent it.  In general, I don't
think we ever want a Guix-produced Python script to load the
usercustomize, hence my suggestion.  The other case of PYTHONPATH is
also annoying but can be tamed by modifying the env variable
temporarily.

Best,
-- 
Josselin Poiret