id,summary,reporter,owner,description,type,status,milestone,component,version,severity,resolution,keywords,cc
6174,packaged_task doesn't correctly handle moving results,onlyone@…,viboes,"I want to create a packaged task which wraps a function which returns an object which is movable but non-copyable. I tried:

{{{
#include <boost/thread.hpp>
struct MovableButNonCopyable {
    MovableButNonCopyable() = default;
    MovableButNonCopyable(MovableButNonCopyable const&) = delete;
    MovableButNonCopyable& operator=(MovableButNonCopyable const&) = delete;
    MovableButNonCopyable(MovableButNonCopyable&&) = default;
    MovableButNonCopyable& operator=(MovableButNonCopyable&&) = default;
};
int main()
{
    boost::packaged_task<MovableButNonCopyable>([]{return MovableButNonCopyable();});
}
}}}

This does not compile, because the instantiation of `packaged_task` results in the generation of a function that attempts to call the deleted copy constructor for `MovableButNonCopyable`.

I have determined that this is due to a bug at `future.hpp:325`, where an rvalue-to-lvalue decay is allowed to occur, which results in the incorrect function overload being used. A patch is attached which adds the required cast.
",Patches,closed,Boost 1.51.0,thread,Boost Development Trunk,Showstopper,fixed,move packaged_task,Anthony Williams viboes