hi, gcc 4.6 (with -std=c++0x) has a bug in its support for unified initialization. specifically a derived class cannot initialize its base with members, if the base has no user-defined constructor: <code> struct base { int i; }; struct derived: base { explicit derived(int i): base{i} {} }; </code> therefore the configuration macro BOOST_NO_CXX11_UNIFIED_INITIALIZATION_SYNTAX should be fixed... Has this been already addressed? -- klaus triendl