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Re: Multiarch file overlap summary and proposal (was: Summary: dpkg shared / reference counted files and version match)

Russ Allbery writes ("Multiarch file overlap summary and proposal (was: Summary: dpkg shared / reference counted files and version match)"):
> There's been a lot of discussion of this, but it seems to have been fairly
> inconclusive.  We need to decide what we're doing, if anything, for wheezy
> fairly soon, so I think we need to try to drive this discussion to some
> concrete conclusions.


> If this is comprehensive, then I propose the following path forward, which
> is a mix of the various solutions that have been discussed:

Thanks for this summary and analysis.  I agree with your conclusions.

> Does this seem comprehensive to everyone?  Am I missing any cases?

I think you have covered all of the cases that have been brought up on
this list, which I think are all of the important and frequent cases.

Thinking about other corner cases can be deferred for now because we
can put off converting affected packages until wheezy+1, or if we
really want to convert we can very probably add a "common" package.
So let us press on.

> * The binNMU process is changed to add the binNMU changelog entry to an
>   arch-qualified file (changelog.Debian.arch, probably).  We need to
>   figure out what this means if the package being binNMU'd has a
>   /usr/share/doc/<package> symlink to another package, though; it's not
>   obvious what to do here.

If we always put the binNMU changelog file in
then in the symlink case we can put it file in 
and everything will work (apart from the fact that some minority of
changelog-reading tools will need to be taught to look at the new path).

> Please note that this is a bunch of work.  I think the Lintian work is a
> good idea regardless, and it can start independently.  I think the same is
> true of the binNMU changelog work, since this will address some
> long-standing issues with changelog handling in some situations, including
> resolving just how we're supposed to handle /usr/share/doc symlinks.  But
> even with those aside, this is a lot of stuff that we need to agree on,
> and in some cases implement, in a fairly short timeline if this is going
> to make wheezy.

Yes.  The work that absolutely needs to be done ASAP seems to be:
 - put the refcounting back in dpkg
 - lintian support for arch-qualified overrides
 - update the binNMU machinery to write the new changelog file instead

Things that should be done but are not on the critical paths:
 - transpose the restrictions on use of refcounting into policy
   (for now they can go in a text file in dpkg-dev, or even just
   a reference to your email)
 - update changelog-reading tools to look for binNMU changelogs too

Things which we can do at our leisure:
 - convert individual libraries
 - think about whether to always arch-qualify the whole changelog
 - think other refcounting corner cases (see my comments above)

> 5. Data files that vary by architecture.  This includes big-endian
>    vs. little-endian issues.  These are simply incompatible with
>    multiarch as currently designed, and incompatible with the obvious
>    variations that I can think of, and will have to either be moved
>    into arch-qualified directories (with corresponding patches to the
>    paths from which the libraries load the data) or these packages
>    can't be made multiarch.

Yes.  Of these, arch-qualifying the path seem to be to be obviously
the right answer.  Of course eg if the data files just come in big-
and little-endian, you can qualify the path with only the endianness
and use refcounting to allow the equal-endianness packages to share.


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