Bug#755154: vlc cache gen should happen at runtime, not buildtime

[Harald Sitter]

On Thu, Aug 21, 2014 at 11:22 PM, Rémi Denis-Courmont <remi at remlab.net> wrote:
>         Hello,
>
> Le vendredi 18 juillet 2014, 12:52:32 Harald Sitter a écrit :
>> since vlc plugins are spread across multiple packages the plugin cache
>> generated at buildtime is almost always wrong
>
> As long as Debian does not ship any unofficial native VLC plugin, the build-time
> cache will not lack any entry.

Which could of course change today or tomorrow or the day after.

>> which makes vlc load all plugins at runtime
>
> No. VLC only loads plugins that are absent or mismatched in the cache. As long
> as the cache contains a superset of what is actually installed, VLC will not
> attempt to load anything unnecessary.

Peculiar that it does explode then. Because clearly it doesn't like the cache.

>> which in turn can result in runtime symbol clashes
>
> That is one good reason to generate the cache at build time, where any problem
> can be detected early on. Crashing during dpkg postinst script is much worse.

|| true?

I fail to see how exactly the additions could make the maintainer
scripts fail to be honest, other than having a broken cache-gen which
surely is the sign of a much deeper problem that should not have
gotten beyond build time to begin with.

>> when it loads the qt4 gui in a qt5 libvlc application for example.
>
> That will happen only if Qt4 is not in the plugins cache. If you install the
> plugins cache from a build with Qt4, it should be in.

Maybe I am missing something, but the package is only built once (and
that build is with Qt4), is it not?

>> attached you should fine a patch which resolves this problem by
>> a) not installing the buildtime cache
>> b) fully implementing trigger capability by having postinst refresh the
>> cache c) have prerm drop the runtime cache so the dirs can be cleaned up
>> properly by dpkg
>
> I am afraid this will create more problems than it will solve. With this
> patch, there is a very real possibility that the package installation will
> fail.

|| true solves everything

HS