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

[Rémi Denis-Courmont]

	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 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.

> 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.

> 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.

> 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.

IMNSHO, the proper fix consists of disabling non-cached plugins support, 
especially for LibVLC applications other than VLC proper. That is doable, but 
not completely straightforward.

-- 
Rémi Denis-Courmont
http://www.remlab.net/