Re: [boost] Movable but not copyable bug?

Subject: Re: [boost] Movable but not copyable bug?
From: Ion Gaztañaga (igaztanaga_at_[hidden])
Date: 2014-08-26 02:42:10

El 26/08/2014 1:18, Peter Dimov escribió:
> Mostafa wrote:
>> Then why is it that in C++03 with g++ 4.8.2 the code sample compiles
>> if the copy ctor for Bar is not explicitly defined?
>
> C++03 12.8/5:
>
> The implicitly-declared copy constructor for a class X will have the form
> X::X(const X&)
> if
> — each direct or virtual base class B of X has a copy constructor whose
> first parameter is of type const
> B& or const volatile B&, and
> — for all the nonstatic data members of X that are of a class type M (or
> array thereof), each such class type
> has a copy constructor whose first parameter is of type const M& or
> const volatile M&.107)
> Otherwise, the implicitly declared copy constructor will have the form
> X::X(X&)
>
> My guess is that Boost.Move declares Foo's copy constructor to take
> Foo&. This causes Bar's implicit copy constructor to take Bar&, which
> doesn't match rvalues.

Right. From boost/move/core.hpp:

    #define BOOST_MOVABLE_BUT_NOT_COPYABLE(TYPE)\
       BOOST_MOVE_IMPL_NO_COPY_CTOR_OR_ASSIGN(TYPE)\
       public:\
       operator ::boost::rv<TYPE>&() \
       {  return *static_cast< ::boost::rv<TYPE>* >(this);  }\
       operator const ::boost::rv<TYPE>&() const \
       {  return *static_cast<const ::boost::rv<TYPE>* >(this);  }\
       private:\
    //

and

#if defined(BOOST_NO_CXX11_DELETED_FUNCTIONS)
    #define BOOST_MOVE_IMPL_NO_COPY_CTOR_OR_ASSIGN(TYPE) \
       private:\
       TYPE(TYPE &);\
       TYPE& operator=(TYPE &);\
       public:\
       typedef int boost_move_no_copy_constructor_or_assign; \
       private:\
    //
#else
    #define BOOST_MOVE_IMPL_NO_COPY_CTOR_OR_ASSIGN(TYPE) \
       public:\
       TYPE(TYPE const &) = delete;\
       TYPE& operator=(TYPE const &) = delete;\
       public:\
       typedef int boost_move_no_copy_constructor_or_assign; \
       private:\
    //
#endif   //BOOST_NO_CXX11_DELETED_FUNCTIONS

Best,

Ion