[Boost-bugs] [Boost C++ Libraries] #6174: packaged_task does correctly handle moving results

Subject: [Boost-bugs] [Boost C++ Libraries] #6174: packaged_task does correctly handle moving results
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2011-11-25 12:37:57

#6174: packaged_task does correctly handle moving results
-------------------------------------+--------------------------------------
 Reporter:  onlyone@…                |       Owner:  anthonyw   
     Type:  Bugs                     |      Status:  new        
Milestone:  To Be Determined         |   Component:  thread     
  Version:  Boost Development Trunk  |    Severity:  Showstopper
 Keywords:  move packaged_task       |  
-------------------------------------+--------------------------------------
 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.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/6174>
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