xorg-server is crashing if compiled with clang see http://llvm.org/bugs/show_bug.cgi?id=13439
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).