attachment set

Thu, 13 Jun 2013 09:51:02 GMT

attachment → boost-move-1.53.diff

Extending boost/move by macro BOOST_RV_REF_WRAPPER() for safer usage. Patch has been created against Boost 1.53

version, type changed

Thu, 13 Jun 2013 10:04:56 GMT

version Boost 1.52.0 → Boost 1.53.0
type Feature Requests → Patches

Hi, I locally solved the problem in Boost 1.53. May changes are attached as "boost-move-1.53.diff". To be sure we are talking about the same problem, let me explain, which problem I see. Let's assume the following use case:

  class Movable
  {
    private:
      BOOST_MOVABLE_BUT_NOT_COPYABLE(Movable);
    public:
      Movable() : mNrMoves(0)
      { }
      Movable(BOOST_RV_REF(Movable) other)
      : mNrMoves(other.mNrMoves + 1)
      {
        other.mNrMoves = 0;
      }
      unsigned mNrMoves;
  };
  struct MovableUser
  {
    Movable m;
    MovableUser(BOOST_RV_REF_WRAPPER(Movable) mi)
    : m(boost::move(mi))
    { }
  };

If I use this implementation, pre-C++11 compiler users might use it with bad surprising behaviour:

  Movable m;
  MovableUser mu(m); // this silently compile wit pre-C++11 compiler, C++11 compiler correctly fails because of missing boost::move()

My fix just added a wrapper class for boost::rv and an accompanying macro BOOST_RV_REF_WRAPPER(). If You change Movable(BOOST_RV_REF(Movable) other) to Movable(BOOST_RV_REF_WRAPPER(Movable) other), then the example above also fails with pre-C++11 compiler enforcing the usage of boost::move():

  Movable m;
  MovableUser mu(boost::move(m)); // now correct

I hope, that helps. Please consider to add this patch or a similar solution to new releases.

status changed; resolution set

Ion Gaztañaga — Thu, 30 Jun 2016 11:39:38 GMT

status new → closed
resolution → wontfix

Closing old bugs, this feature was not generally requested by users so closing as WONTFIX.

Boost C++ Libraries: Ticket #7418: Copyable and explicitly movable classes

attachment set

version, type changed

status changed; resolution set