[boost] [utility/value_init] boost::value_initialized<T> direct-initialized?

Subject: [boost] [utility/value_init] boost::value_initialized<T> direct-initialized?
From: Niels Dekker - address until 2010-10-10 (niels_address_until_2010-10-10_at_[hidden])
Date: 2010-03-30 16:25:52

Can anybody please have a look at the following feature request by 
Edward Diener? https://svn.boost.org/trac/boost/ticket/3472 He proposed 
to add an explicit constructor, value_initialized(T const&), to 
boost::value_initialized<T>. This constructor would copy the value of 
its argument to the object held by value_initialized<T>.

When such a constructor would be added, an object held by 
value_initialized<T> might no longer be value-initialized. Instead it 
might be direct-initialized. Does anybody have any moral (?) objections 
against the idea that value_initialized<T> might hold a 
non-value-initialized object?

Personally I think it would be useful to allow the wrapped object to be 
direct-initialized. But I do think there's a small risk that the new 
explicit constructor might cause ambiguities in legacy user code. 
Therefor I suggested adding an extra "tag" parameter to the new 
constructor, of a new type, boost::direct_initialized_t:

   struct direct_initialized_t { };
   value_initialized(T const&, direct_initialized_t)

Does anyone else also think that's a good idea? Or does anyone prefer 
the explicit value_initialized(T const&) constructor originally proposed 
by Edward?

See also the thread starting at:
"Re: [boost] Transfer of Maintenance Rights (utility/value_init)"
http://lists.boost.org/Archives/boost/2010/03/164125.php

Kind regards,

   Niels
-- 
Niels Dekker
http://www.xs4all.nl/~nd/dekkerware
Scientific programmer at LKEB, Leiden University Medical Center