kdelibs-4.1.2-r1 does not set KDEDIRS anymore. kdelibs-3.5.9 is still setting KDEDIRS as it was removed in kde-libs-3.5.10 only and KDEDIRS is still used by kde-4.1 if declared. This happens to strange failures like crashes in kmail-4.1 trying to use khtml styles from kde 3.5 which are incompatible. Reproducible: Always Steps to Reproduce: 1.install/update kde-base/kdelibs-4.1.2-r1 2.stay on kde-3.5.9 in first slot 3.start kmail in kde4 4.check /etc/profiles.env Actual Results: Applications like kmail crash in KDE4
since KDEDIRS is not set anymore in kde-3.5.10 this bug should be fixed if kde-4.1 becomes stable before kde-3.5.10 what I do not believe to happen :) Lowered severity.
You might want to look at the bugs from tracker #239356 . I think this one here is a duplicate of one of them or at least related.
tracker #239356 = bug #239356
Yes, they are related but now the environment KDEDIRS is not set even if the useflag kdeprefix is set. In this moment KDE4 applications find depending files in the path of KDE 3.5. Actually updating kdelibs-4.1.2 to the revision dump -r1 makes the "masked" KDE4 installation unusable if "kdeprefix" is used and the stable kde-3.5.9 is installed also. But I know that this behavior must be accepted if testing packages are used :)
fixed with the new kde3 eclasses