Re: [boost] [move][container] Review Request (new versions of Boost.Move and Boost.Container in sandbox and vault)

Subject: Re: [boost] [move][container] Review Request (new versions of Boost.Move and Boost.Container in sandbox and vault)
From: Jeffrey Hellrung (jhellrung_at_[hidden])
Date: 2009-08-27 02:12:19

Ion,

With your current move-emulation approach, it looks like functions like 
vector::push_back could actually capture genuine rvalues, similar to how 
operator= does, via BOOST_COPY_ASSIGN_REF( T ) for movable types T (and 
using const T& for nonmovable types).  For example:

template< class T >
T factory() { ... }

template< class T, ... >
struct vector
{
     ...
     typedef boost::mpl::if_<
         boost::is_movable<T>,
         BOOST_COPY_ASSIGN_REF( T ),
         const T&
     >::type const_lvalue_reference_type;
     ...
     push_back(const_lvalue_reference_type value);
     push_back(BOOST_RV_REF( T ) value);
};

...

vector<T> v;
v.push_back(factory()); // should call rvalue push_back, right?

AFAIK, if you use push_back(const T&) for movable types (as is 
standard), then that overload would be preferred in the absence of true 
rvalue references.

What do you think?

- Jeff