Re: [boost] shared_ptr in multithreaded environments

From: Emil Dotchevski (emil_at_[hidden])
Date: 2008-03-11 01:34:03

>  On Mar 10, 2008, at 6:27 PM, Emil Dotchevski wrote:
>  > On Mon, Mar 10, 2008 at 3:18 PM, Mathias Gaunard
>  > <mathias.gaunard_at_[hidden]> wrote:
>  >> I see that shared_ptr is quite costly in multithreaded environments
>  >> cause it would need DCAS, and thus uses a spinlock in cases where
>  >> it is
>  >> not available.
>  >
>  > If you pass shared_ptr objects by const &, the refcount doesn't need
>  > to be updated.   ... [snip]
>
>  Yes, but be careful that the lifetime of the shared_ptr object passed
>  as const & must be guaranteed to outlive the const &, otherwise you
>  have a dangling reference.

This is true, but it is also true for any object you pass by
reference. It is even true for the this pointer in a member function.
Regardless, in general, objects of user-defined types are best passed
by const reference; the same is true for shared_ptr.

-- 
Emil Dotchevski
Reverge Studios, Inc.
http://www.revergestudios.com/reblog/index.php?n=ReCode