Let's go back again to the BOOST_NO_CXX11_HDR_INITIALIZER_LIST discussion. I believe that BOOST_NO_UNIFIED_INITIALIZATION_SYNTAX checks the compiler support of initializer_list as well. So better implementation of BOOST_NO_CXX11_HDR_INITIALIZER_LIST would be: 1. In compiler configs, don't define BOOST_NO_CXX11_HDR_INITIALIZER_LIST. 2. In stdlib configs, define BOOST_NO_CXX11_HDR_INITIALIZER_LIST if stdlib doesn't have <initializer_list>. 3. In suffix.hpp, define BOOST_NO_CXX11_HDR_INITIALIZER_LIST if BOOST_NO_UNIFIED_INITIALIZATION_SYNTAX is defined (and BOOST_NO_CXX11_HDR_INITIALIZER_LIST is not defined): #if defined(BOOST_NO_UNIFIED_INITIALIZATION_SYNTAX) && !defined(BOOST_NO_CXX11_HDR_INITIALIZER_LIST) # define BOOST_NO_CXX11_HDR_INITIALIZER_LIST #endif I also came up with another thoughts. Do we really want BOOST_NO_CXX11_HDR_INITIALIZER_LIST to check the compiler support of initializer_list? Even if BOOST_NO_CXX11_HDR_INITIALIZER_LIST checks only the existence of <initializer_list>, we can check both the compiler support and the header existence by defined(BOOST_NO_UNIFIED_INITIALIZATION_SYNTAX) || defined(BOOST_NO_CXX11_HDR_INITIALIZER_LIST) Comments? Regards, Michel