xorg-server is crashing if compiled with clang
This does not happen anymore with xorg-server-1.16.3-r1 (latest unstable) and clang-3.5.0-r100.
I can't test xorg-server latest stable (1.15.2-r1) as that would mean downgrading many packages and most probably breaking my desktop.
If testing on latest stable passes, I think this bug can be safely closed.
I tried to compile 1.12 and test it through ebuild, but tests fail with a stack trace, so I guess the issue is not solved for this particular version of xorg-server.
I think backporting the patches from 1.16 (or possibly 1.15) to 1.12 would not be worth the time (unless I'm wrong and there's only one patch to apply).