I’ve just seen that in the few days between I’ve checked the Forum and posting my question a similar Thread was opened: Root-6.06.00 on Ubuntu 14.04 32 bit
But there is also no solution.
So it seems it’s a general 32bit problem…
Edit:
I’ve looked a bit around and found out, that the __int128 types are only supported on 64bit.
This means ROOT is broken on x86 32bit since this commit: github.com/root-mirror/root/com … a9bde2bcb7