Thanks to Christopher Jefferson, I discovered a bug in the trunk (in fact in 1.46.0) for is_base_of in the type_traits library. is_base_of<int, int>::value should be true according to the doc: "is_base_of<Base, Base>::value is an integral constant expression that evaluates to true: a class is regarded as it's own base. However the following program prints 0 and not 1 with g++ 4.4.5 on linux: #include <boost/type_traits/is_base_of.hpp> #include <iostream> int main() { std::cout<<::boost::is_base_of<int, int>::value<<'\n'; return 0; } Using the sandbox version of is_base_of works just fine. This makes my type trait extension fail on 6 tests when using only the trunk (for the 6 comparison operators). I have a workaround for my extension which is to add "or is_same<T, U>" but it would be better if is_base_of would work correctly. Frédéric