I just wanted to make people away of a suggested patch to value_initialized, explicitly adding the default constructor, copy constructor and operator=, given in https://svn.boost.org/trac/boost/ticket/4213 . The default constructor is necessary for clang and comeau (in strict mode) to allow const value_initialized values without an explicit value. I believe this is correct behaviour, but other compilers are more lack. I believe this patch is small and should work fine, but I know that this has been a very sensitive bit of code in the past, prone to kicking up minor compiler problems. My preferred option would be to try submitting this patch to trunk and see if any tester kicks up a fuss. If any do, then I am happy to introduce some macros.