Re: [boost] [smart_ptr] Some questions

From: Peter Dimov (pdimov_at_[hidden])
Date: 2008-04-11 14:38:07

Frank Mori Hess:
> On Friday 11 April 2008 12:11 pm, Peter Dimov wrote:
>> I'm still not 100% convinced that we need this functionality in 
>> shared_ptr.
>> But if we do, it seems that the proper way to add it is to make 
>> shared_ptr
>> issue an unqualified call to
>>
>>     sp_accept_owner( this, p );
>
> It does provide an alternative to making shared_from_this() callable in
> constructors.  As long as sp_accept_owner() is always run after
> enable_shared_from_this is set up (and there is no reason it can't be 
> since
> shared_ptr is fully aware of enable_shared_from_this) then it is usable as 
> a
> post constructor where shared_from_this can be used safely.  Actually, you
> don't even need enable_shared_from_this if don't need to use
> shared_from_this() outside the postconstructor, since you are passed in 
> the
> owning shared_ptr.

You're right! sp_accept_owner can indeed be used as a postconstructor.

My original idea was for it to replace sp_enable_shared_from_this entirely, 
making enable_shared_from_this non-special and fully implementable in "user 
mode". This doesn't seem to be a problem for the use case you describe 
though. The programmer would just implement sp_accept_owner for the derived 
class and call sp_accept_owner( (esft*)this ) before using shared_from_this.