May 19, 2012

revdep-rebuild doesn't detect qt-core's dependency on

It's a known issue, bug #413541. The end result is weird, because revdep-rebuild tells you that everything is fine, yet some apps display errors (they still launch though):

Unable to load library icui18n "Cannot load library icui18n: ( cannot open shared object file: No such file or directory)"

The workaround is to re-emerge qt-core (more packages might be affected).

If you wonder what's the root cause, it's using dlopen (in this case in qt-core) instead of linking directly (e.g. ELF DT_NEEDED entry) with given library.

In binary-only world, using dlopen may make sense sometimes. Package names, versions, and library SONAMEs vary between distros, so it's difficult to create a single package that works with multiple distros. It may be easier to dlopen the needed libraries (sometimes even trying different SONAMEs), and fail gracefully in case they are missing (e.g. just disable some optional functionality).

That's what Qt is doing here. However, in Open Source world, where software is packaged by distributions, the above case should be handled by linking directly (DT_NEEDED), allowing tools like revdep-rebuild to detect the breakage.

Other distributions are hitting this problem too, see e.g. and