Re: [boost] Review Request: impl_ptr (pimpl)

Subject: Re: [boost] Review Request: impl_ptr (pimpl)
From: Vladimir Batov (Vladimir.Batov_at_[hidden])
Date: 2017-08-18 10:47:07

On 2017-08-18 19:50, Hans Dembinski wrote:
>> On 15. Aug 2017, at 02:51, Vladimir Batov via Boost 
>> <boost_at_[hidden]> wrote:
>> 
>> Given that it is policy-based I am hoping others might get interested 
>> writing additional policies within that framework such as COW or 
>> stack-based.
> 
> Can you use custom allocators for all policies?

Unfortunately no at the moment. It's been high on my TODO list... but 
given I do not use that functionality I've not had enough incentive 
implementing it. Still, I actually was reading about allocators right 
now. :-)

> If so, then the
> behavior of the behavior of the "onstack" policy could be achieved by
> using a stack-based allocator, like the one from Howard, right?

I am not sure but I'd prefer if was possible. I see that 
impl_ptr::copied and impl_ptr::onstack are essentially identical... mem. 
management aside.

> https://howardhinnant.github.io/stack_alloc.html
> 
> I think it is very elegant if one can switch to a stack-based version
> without huge code-refactoring if the performance need arises (I am
> paraphrasing your documentation).

Thank you for the link. Much appreciated. I'll most certainly read as 
it's what I've been scratching my head about for some time... Had a 
quick glance. I can be dead wrong but it does not seem (unfortunately) 
applicable to impl_ptr. It appears to be the standard allocator-usage 
pattern, i.e. I explicitly create an allocator (and memory arena) and 
then take from that arena. It's not applicable in the impl_ptr::onstack 
situation. Again, I'll have to read again.