David Abrahams <dave <at> boost-consulting.com> writes:
on Mon Dec 03 2007, Anthony Williams <anthony_w.geo-AT-yahoo.com> wrote:
David Abrahams <dave <at> boost-consulting.com> writes:
on Mon Dec 03 2007, Anthony Williams <anthony_w.geo-AT-yahoo.com> wrote:
However, I did post a message asking for a fast-track review of it so that it could become a documented part of boost. The only response I got was "there's another implementation in the sandbox".
And that implementation is fatally flawed, I'm ashamed to say. We should be using http://opensource.adobe.com/group__move__related.html
How does that help with a movable-but-not-copyable type (such as boost::thread)?
I'm not sure, frankly; the author of that library believes all types are intrinsically both movable and copiable. Maybe for that purpose we need something else.
Can I (again) propose the simple scheme I'm using for boost::thread? In boost/thread/detail/move.hpp we (now) have boost::detail::thread_move_t<T> as the transfer type and boost::detail::thread_move(T&) as the move-from-lvalue helper boost::thread then looks like this (move-related parts only) class thread { private: thread(thread&); // no copy. Note no const thread& operator=(thread&); // no assign. Note no const public: thread(detail::thread_move_t<thread>); // move constructor thread& operator=(detail::thread_move_t<thread>); // move assignment operator detail::thread_move_t<thread>(); // allow conversion to the //transfer type detail::thread_move_t<thread> move(); // make it explicit }; If you try and construct a thread object from an rvalue then it won't bind to the (private) copy constructor, as it can't bind to a non-const reference. However, a single user-defined conversion (to detail::thread_move_t<thread>) allows it to bind to the move constructor. Likewise for assignment. It works for gcc and MSVC, but not for Borland. When the test results come through for the new test_thread_move test, we'll know which other compilers it works on, too. Anthony -- Anthony Williams Just Software Solutions Ltd - http://www.justsoftwaresolutions.co.uk Registered in England, Company Number 5478976. Registered Office: 15 Carrallack Mews, St Just, Cornwall, TR19 7UL