http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48851
--- Comment #16 from Jonathan Gray <jsg at openbsd dot org> 2011-06-30 12:18:43 UTC --- Yes, it appears to be the AIX/Interix part which is causing the problem. I removed just the OpenBSD part and it still happened and then further removed the AIX/Interix one and it was then fine. I can now build 4.6.1 with lto/plugin (with some additional patches I'll submit soon) and run the dragonegg LLVM plugin. Can you expand on why you think the header isn't suitable for c++ inclusion?