Re: [boost] [type_traits] is_convertible<noncopyable,To> crashes

From: David Abrahams (dave_at_[hidden])
Date: 2006-04-13 17:43:28

"JOAQUIN LOPEZ MU?Z" <joaquin_at_[hidden]> writes:

> Hello,
>
> In a post from yesterday (see http://tinyurl.com/hzk5w),
> Alexei Alexandrov found a rather serious problem with
> is_convertible in at least MSVC 7.1 and Intel 9.0, namely
> that is_convertible<From,To> fails to compile when
>>From is non-copyable, emitting an error message like this:
>
> boost/boost/type_traits/is_convertible.hpp(254): error:
> class "XXX" has no suitable copy constructor
>       BOOST_STATIC_CONSTANT(bool, value =
> ...
>
> where XXX is the From argument. Needless to say, some
> fix for this issue would be most welcome. I'm sorry
> I cannot provide any more help than a mere report
> of the problem.

I don't think this is a solvable problem, unless there's something
hiding in the implementation of is_base_and_derived that can be
leveraged (see the comment in that header for more info -- I can't
understand what's being said there due to the use of the identifier
'C' without any introduction).  The basic problem is what's required
in the implementation of is_convertible in order to work around VC7.1
bugs (Intel Windows emulates the same bugs).

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com