Hi, I want to add Allocators to the packaged_task and promise class of Boost.Thread template <class Allocator> promise(allocator_arg_t, const Allocator& a); template <class F, class Allocator> explicit packaged_task(allocator_arg_t, const Allocator& a, F&& f); I see that Boost.Container has already defined in namespace boost::container and in file boost/container/scoped_allocator.hpp the following struct allocator_arg_t { }; constexpr allocator_arg_t allocator_arg = allocator_arg_t(); template <class T, class Alloc> struct uses_allocator; I would like to shared these to all the Boost libraries. I don't think it is a good idea to make Boost.Thread depend on Boost.Container just for this. Could these declarations be included in a specific file? These declaration are included in <memory> in the C++11. What would be the best library to contain these declarations? What about a new boost/memory.hpp file? What about moving them to the boost or boost::memory namespace? Best, Vicente