Re: [boost] auto_vector - vector with auto_ptr semantics

From: Howard Hinnant (hinnant_at_[hidden])
Date: 2002-02-04 19:08:14

On Monday, February 4, 2002, at 06:25  PM, Rainer Deyke wrote:

> What about return-by-move?  I see two possibilities:
>
> 1. Use the same syntax:
>
>   T f()
>   {
>     T a;
>     return std::move(a);
>   }
>
>   T b(f());
>
> This requires special compiler support to prevent 'a' from being
> destroyed before 'b' is constructed.
>
> 2. Let the compiler handle it automatically:
>
>   T f()
>   {
>     T a;
>     return a;
>   }
>
>   T b(f());
>
> Here the compiler realizes that 'a' will be destroyed immediately
> after 'b' is constructed, so it uses the movement constructor instead
> of the copy constructor if both are available.

Actually I believe the standard already allows return value optimization 
to make:

T b(f());

work as desired.  But here's another possibility in case your compiler 
is weak in this area:

T b(std::move(f()));

(assuming we can get the move from temporary worked out)

-Howard