Re: [boost] type_traits: more state-of-the-union

From: Peter Dimov (pdimov_at_[hidden])
Date: 2002-04-15 12:00:14

From: "David Abrahams" <david.abrahams_at_[hidden]>
>     BOOST_ELIPSIS_ARGS_DO_NOT_INVOKE_COPY_CONSTRUCTOR - for compilers
> that can resolve overloads to functions accepting elipsis arguments
> without invoking the copy constructor of the actual argument. This is
> nonconforming behavior AFAICT but most compilers seem to allow it, and
> it's what allows is_convertible<T,U> to work when T is noncopyable.

It's undefined behavior to pass a non-POD class type to an ellipsis.
(5.2.2/7.)