Re: [boost] Re: copy_on_write

From: Peter Dimov (pdimov_at_[hidden])
Date: 2005-06-01 05:58:48

Alexander Terekhov wrote:
> Maksym Motornyy wrote:
>>
>> Thanks for articles. Well, I understand that multithreaded
>> environment can be a bad place for COW optimization.
>
> That's a myth.

It depends on the interface of the class. Returning pointers and references 
into the object is bad, as is const/non-const overloading where the 
non-const version can be used for read access.

Non-const member functions of the begin()/end() variety are worse than just 
returning a single reference into the object, because you can't "copy on 
write" between the two, or they'll get out of sync.

Reference-counting immutable objects is fine, but COW can be a pain.