Containers

[deadalnix]

On Wednesday, 1 September 2021 at 11:13:27 UTC, Steven 
Schveighoffer wrote:
> Isn't the reason they prohibited COW is because of the problems 
> with it?
>
> Not saying COW is terrible in all cases, just that a generic 
> container (non-specialized usage) should not be COW. If you 
> need that feature, you should have to ask for it, not have it 
> be an implementation detail.
>
> -Steve

Well I never experienced any problem with them, so did many other 
C++ users. As far as i am concerned, this was a net step backward.

That being said, the reason were due to iterator invalidation. 
There are several function in the string API that do not 
invalidate iterators, as per the C++ standard, and these function 
might end up copying the content of the string in some specific 
situations, which would invalidate iterators.

In practice, I think the main problem here is related to exposing 
the innards of the datastructure. An iterator that contains a 
reference to the container + index, rather than some kind of raw 
pointer for instance, could avoid that problem.