David Abrahams wrote:
Hi Ion,
are you familiar with http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2009/n2855.html ?
Until the committee decides exactly how to handle it and compilers catch up with the feature they add, we need a workaround for that problem, both for C++03 and C++0x. The simplest approach requires a trait called has_nothrow_move<T> which can be used to SFINAE-out pair's move constructor unless its members all have a nonthrowing move constructor. It would be reasonable to say
template <class T> struct has_nothrow_move : has_move_constructor {};
as a default, since move constructors shouldn't throw. But still, we need an implementation of has_move_constructor. Obviously, that will require compiler support to be optimal, but in the meantime it can be specialized.
What if we say template <class T> struct move_is_nothrow : mpl::true_type {}; and have it defined whether there actually is a move constructor or not? Would that work? Or would it interact badly with copy-only types? Sebastian