jyknight added a comment. Blah. So, the issue is that LLVM_ALIGNAS needs an integer, not a constant expression, because of MSVC limitations. Otherwise, EHCleanupScope would also specify uint64_t alignment, instead of 8. I'll just change ScopeStackAlignment to a fixed 8, to match. Repository: rL LLVM http://reviews.llvm.org/D10272