Re: limited agregate and limited components default initialization

[Jere <jhb.chat@gmail.com>]

On Saturday, March 31, 2018 at 7:36:59 PM UTC-4, Jean-Claude Rostaing wrote:
> Why does a component declaration like that:
> type Item_Accessor (Item: not null access Item_type) is limited record
>       Ref: Item_access := SET(Item_Record'(Item => ITEM.all, others => <>));
>    end record;
> unconstrained subtype in component declaration
> ? ITEM is limited but IS constrained by the default initialisation
> It forced me to add the function DEFAULT_INITIALIZATION as a parameter, which I would prefer to not to. But since the result is the same, I'll drop it.
> Item (and the article it is in) is never meant to be left uninitialized.
> 
> Also, how to get rid of the problem with
> function Set (Value: in Item_type) return Smart_Pointers is
>      (Smart_Pointers'(Controlled with Node => new Accessor_type'(Data => new Item_type'(Value), Count => 1)));
> which gives :Initialization not allowed for limited types.
> So an aggregate like this is not counted as a "limited agregate" ??

I may be misunderstanding you, but if Item is a limited type with a default
discriminant, it is "unconstrained" since the ada compiler cannot know
at compile time what the actual size will be.

See:
https://gcc.gnu.org/onlinedocs/gnat_rm/The-Size-of-Discriminated-Records-with-Default-Discriminants.html