i'd like to merge r86144 into release. it is not exactly a bugfix, but it enables double-width cas support for msvc, which is rather important for many lock-free algorithms to be lockfree with this toolchain (including some configurations of stack/queue of boost.lockfree).
I don't think the commit is correct.
1. 64-bit CAS for 32-bit x86 was already supported before. It is controlled by the BOOST_ATOMIC_X86_HAS_CMPXCHG8B macro, which is automatically defined when the compiler targets Pentium or later (may need to be enabled by a compiler switch).
2. Your change modifies 64-bit branch, which always have 64-bit atomic ops available (i.e. CAS-based path is not needed). This branch is not used by 32- bit targets.
ccing gavin, who provided the patch and asked me to merge it.