On 12/1/2012 3:43 PM, Jonathan M Davis wrote:
Any struct which contains reference types needs them. For instance, a struct containing int[] needs to dup that array if it doesn't want to have the copy referring to the same elements as the original and therefore risk having them be mutated. Arrays with immutable elements don't have that problem, but those with mutable elements (and to some extent those with const) do have such a problem, as to structs with classes or structs which are reference types, etc. I'm surprised that you'd think that postblit constructors were only useful for implementing reference counting types. IMHO, the language would be crippled without a postblit or copy constructor for structs.
On the other hand, I'd say you have a pretty expensive design if it required you to allocate memory in order to do a copy. Making copies ought to be a cheap operation.
It's not hard to implement copy-on-write for the referenced data. In fact, with reference counting, you shouldn't need to make those dups.
