http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55043
--- Comment #15 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-10-24
15:40:28 UTC ---
(In reply to comment #14)
> I think it is implementable (I have done something similar to ensure that my
> optional<T> realizes the same effect), but the costs are not small:
>
> 1) It will prevent the incomplete type support
Ouch... but not required by the standard.
> 2) The implementation changes are not small (my guess)
Apart from the changes to allocator_traits and defining CopyInsertable etc.
(which I think isn't so hard, I can do that tonight) IIUC it would require
changing every container so that e.g.
vector<T,A>::vector(const vector&)
becomes
template<typename U>
vector<T,A>::vector(const vector<U,A>&)
with constraints is_same<T,U> and CopyInsertable<A,T>, because we can't
constrain that constructor if it's not a template
Is that even allowed under the as-if rule?
Do we really want to go there?
Is there some other way to make examples like this compile?
#include <vector>
struct M
{
M() = default;
M(M&&) = default;
M& operator=(M&&) = default;
};
typedef std::vector<M> S;
static_assert( !std::is_copy_constructible<S>::value,
"not CopyConstructible" );
