Re: [Boost-users] [shared_ptr] Can the custom deleter be a simplefunction?

Subject: Re: [Boost-users] [shared_ptr] Can the custom deleter be a simplefunction?
From: Peter Dimov (pdimov_at_[hidden])
Date: 2011-11-07 10:15:18

Robert Jones wrote:
> Thanks Gents - The phrasing of my question was hopelessly lax: I 
> appreciate in the
> general case why one might choose to use a functor rather than a function 
> as a callable
> object, what I didn't grasp (and there may be nothing to grasp), was why 
> this (from the
> shared_ptr docs)
>
> struct null_deleter
> {
>     void operator()(void const *) const
>     {
>     }
> };
>
> Is implemented as a functor rather than a function.

There's nothing to grasp. The only difference is that sizeof( null_deleter ) 
is 1, whereas sizeof the function would be 4 or 8, but due to alignment, 
they both will take up the same space in the actual control block, so it 
doesn't matter one bit. Using a functor here is purely coding style - the 
size difference, the fact that operator() would be inlined, the ability to 
template operator() could all have been relevant in another context.