[Python-Dev] Handling support for newer OS features at run time

[Trent Nelson]

On Tue, Nov 27, 2012 at 03:09:12PM -0800, Matthias Klose wrote:
> Am 27.11.2012 23:49, schrieb Trent Nelson:
> >     I don't think we've currently got the ability to do this, right?
> >     Is there a precedent set anywhere else?  I suspect it's not as
> >     much of an issue on *NIX platforms as you'll typically compile
> >     from source.  Windows, not so much.
> > 
> >     Thoughts?  A single binary that dynamically loads applicable
> >     modules seems cleaner but will obviously take more work.  Other
> >     approach would be to start distributing multiple versions of
> >     Python based on the underlying Windows version.  Not the nicest
> >     approach.
> 
> Usually I have to build a python package on a build daemon running the
> kernel of the latest stable (or latest stable long term support)
> release.  Thus if a configure test checks the current kernel, then you
> may get an unexpected answer and a missing feature. It is somehow
> different that I already build different binaries (per release), but
> the hard-coding of kernel features during configure time looks like
> the same issue. Currently working around it by patching configure to
> remove the test and hard-code it for a particular build. Another
> solution maybe would to have something like --enable-kernel=<version>
> (as found in glibc), and hope that you can deduce the features from
> the kernel version.

    Hmmm.  How often do Linux kernel versions expose new features that
    we can make use of in Python?  i.e. do you run into this problem
    often?  Can you cite some recent examples?

    I'm not sure how much could be shared between Windows and Linux with
    what you've just described.  With Windows, specifically with regards
    to providing dynamic select.poll() support, I was thinking of having
    multiple modules:

        Python33\
            DLLs\
                select.pyd
                select_win6.pyd
                select_win7.pyd
                select_win8.pyd

    And Python would automatically import the appropriate one.  I don't
    think this would be that useful on Linux -- as you say, the decision
    is typically made at ./configure time.

        Trent.