Re: [Boost-users] [smart_ptr] make_shared imposes const ref.

Subject: Re: [Boost-users] [smart_ptr] make_shared imposes const ref.
From: Igor R (boost.lists_at_[hidden])
Date: 2011-11-29 06:46:36

> Why is make_shared declared as
>
> template<typename T, typename Arg1 > shared_ptr<T> make_shared( Arg1
> const & arg1 );
>
> rather than
>
> template<typename T, typename Arg1 > shared_ptr<T> make_shared( Arg1 arg1 );
>
> since the effect is that if you have a constructor that takes
> non-const references you cannot use make_shared( ) on it.

I guess it's because your compiler doesn't support && (i.e. perfect
forwarding is impossible).
http://www.boost.org/doc/libs/1_48_0/libs/smart_ptr/make_shared.html#functions
<<The prototypes shown above are used if your compiler supports rvalue
references and variadic templates. They perfectly forward the args
parameters to the constructors of T.
Otherwise, the implementation will fall back on forwarding the
arguments to the constructors of T as const references. If you need to
pass a non-const reference to a constructor of T, you may do so by
wrapping the parameter in a call to boost::ref. >>