Hi, Boost.Thread documentation has a section regarding the creation of lazy futures. http://www.boost.org/doc/libs/1_47_0/doc/html/thread/synchronization.html#th... The code on this page runs fine, but I can't find a way to return such future. Naïve code below exits with a boost::broken_promise in unique_future::get(). boost::unique_future <int> create_future() { boost::packaged_task<int> task(calculate_the_answer_to_life_the_universe_and_everything); task.set_wait_callback(invoke_lazy_task); return task.get_future(); } int main() { assert(create_future().get()==42); } Exceptional finish is marked in packaged_task destructor. And regardless of exceptions, since set_wait_callback want something that operates on packaged_task and not on pointed task_base, the code is doomed to do an access violation. So, is there any way to return lazy futures ? Regards, Ivan