An update: adding 'WSGIApplicationGroup %{GLOBAL}' to my mod_wsgi
settings, which I understand forces my test WSGI pseudo-application
to run in the context of the first Python interpreter created and not a
sub-interpreter, makes the issue go away:
list.__str__ is <slot wrapper '__str__' of 'object' objects>
I'm going to see if I can hack the example 'embedding Python' C program
to use a sub-interpreter and test the behaviour there.
- cks
> We're definitely using the system packages for mod_wsgi (and for
> Python). Ubuntu 24.04's Python is '3.12.3', and I've used lsof to verify
> that the relevant Apache process has the right Python shared library
> loaded; it is using '/usr/lib/x86_64-linux-gnu/libpython3.12.so.1.0'
> (Ubuntu package 'libpython3.12t64', also 3.12.3), and is also using the
> system mod_wsgi, '/usr/lib/apache2/modules/mod_wsgi.so-3.12'.
>
> (Ubuntu 24.04's Apache is '2.4.58', possibly plus Ubuntu patches.)
>
> As GODJonez notes, 'list' doesn't normally have a __str__ method;
> instead it usually comes from 'object'. The Ubuntu 24.04 normal python3
> binary behaves properly, with 'list.__str__' reporting:
> <slot wrapper '__str__' of 'object' objects>
>
> Within the mod_wsgi environment, 'list.__str__' is:
> <slot wrapper '__str__' of 'list' objects>
>
> (basically as expected), which as GODJonez notes explains the problem.
>
> I built the extremely simple 'embedding Python in another application'
> example from https://docs.python.org/3/extending/embedding.html and
> linked it against the same libpython3.12.so.1.0 just to check, and it
> reports that list.__str__ comes from 'object' as expected.
>
> - cks
>
> > What version of Python is Ubuntu using?
> >
> > Are you definitely using system package for mod_wsgi, or have you per
> > chance used pip to install mod_wsgi package and integrated that into your
> > Apache instead?
> >
> > Are you using a Python virtual environment?
> >
> > FWIW, I don't see issues on macOS using mod_wsgi-express and Python 3.12.
> >
> > Graham
> >
> > > On 15 Jan 2025, at 3:46 am, Chris Siebenmann
> > > <[email protected]> wrote:
> > >
> > > I've encountered what I can only describe as an extremely weird problem
> > > with method resolution order that happens only in mod_wsgi on Ubuntu
> > > 24.04, using the Ubuntu 24.04 version of mod_wsgi (with their Apache and
> > > Python 3), which appears to be an unpatched 5.0.0. The specific problem is
> > > that if you have a class that inherits from 'list,<something else>', and
> > > the second class normally supplies a __str__ method, under mod_wsgi you
> > > get list.__str__ instead. This first manifested in a Django application[*]
> > > but the minimal reproduction for us is a wsgi.py application that has:
> > >
> > > import sys
> > >
> > > class barney:
> > > def render(self):
> > > return "render() in barney"
> > > __str__ = render
> > >
> > > class fred(list, barney):
> > > pass
> > >
> > > print("fred.__str__ is", fred.__str__, file=sys.stderr)
> > >
> > > (and then the documentation example 'hello world' WSGI application()
> > > function so that mod_wsgi is happy to start this, and will produce
> > > output so that I know the whole thing is working correctly)
> > >
> > > On Ubuntu 24.04's mod_wsgi, this will report on startup:
> > > fred.__str__ is <slot wrapper '__str__' of 'list' objects>
> > >
> > > In any other environment, including Ubuntu's mod_wsgi on 20.04 and 22.04
> > > (which use earlier versions of mod_wsgi), this reports what we expect:
> > > fred.__str__ is <function barney.render at 0x782909bff2e0>
> > >
> > > (Other tests show that the 'barney' class is one of fred's parents and
> > > other attributes are being inherited from it, even though its __str__
> > > isn't being used.)
> > >
> > > The actual fred.__mro__ appears to be the same between environments,
> > > listing 'fred', 'list', 'barney', and 'object' in that order.
> > >
> > > I'm running this test wsgi.py with a very simple WSGI configuration
> > > in Apache:
> > > WSGIScriptAlias /accounts /<test location>/wsgi.py
> > > WSGIDaemonProcess accounts user=<...> group=<...>
> > > WSGIProcessGroup accounts
> > >
> > > Does anyone have any idea what might be going on and either how to fix
> > > it or how to debug it?
> > >
> > > Thanks in advance. Please let me know if I can provide more information
> > > that would be helpful.
> > >
> > > - cks
> > > [*: The specific symptom we saw was that empty django.form.util.ErrorList
> > > instances using default rendering in templates would render as
> > > '[]' instead of blank. This was traced to them using list.__str__
> > > for rendering instead of their custom rendering, which is set up in
> > > the same way that 'class barney' is in this example.
> > > ]
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