Re: [boost] [smart ptr] Any interest in copy-on-write pointer for C++11?

Subject: Re: [boost] [smart ptr] Any interest in copy-on-write pointer for C++11?
From: Mathias Gaunard (mathias.gaunard_at_[hidden])
Date: 2013-02-09 01:13:49

On 08/02/13 22:44, Jeffrey Yasskin wrote:

> I'm sure the WebKit project would welcome a patch demonstrating that
> flyweights are a more efficient technique for CSS matching. I don't expect
> they are because these values are built up through several mutations, and a
> hash table lookup plus a copy on each mutation sounds more expensive than
> the current copy-on-write system.

I don't pretend to know anything about what WebKit is actually doing.
I interpreted what you said to mean that they want all values that are 
equal to use the same object. In that case the logical approach is 
indeed to use a flyweight factory.

I think I just misunderstood what this was about; maybe they want to do 
partial COW on subtrees to minimize memory usage for redundant 
information, which is a whole different beast. COW on whole data 
structures is useless, but it is very useful when partial sharing is 
involved. That is not, however, the case that was presented here.