Re: On absurdity of collections 7.6.1 (11.1/3)

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On 2021-09-30 02:23, Randy Brukardt wrote:
> It's surely wrong, because you have to deallocate from the same pool as you
> allocated. And you have no way to save such a thing. There is no capability
> in Ada to use multiple pools with one access type.

You mean Unchecked_Dellocation? Maybe, then it is another language bug. 
However, the object collection schema is irrelevant for a while. The 
first problem is that Finalize is called twice.

> At best, you could directly call Allocate and Deallocate for this purpose,
> but it is impossible to use anything built-in.

Actually it is possible using a fake pool:

    type Fake_Pool is new Root_Storage_Pool with record
       Pool : access Root_Storage_Pool'Class;
    end record;

Allocate goes like this:

    procedure Allocate
              (  Pool            : in out Fake_Pool;
                 Storage_Address : out System.Address;
                 Size            : Storage_Count;
                 Alignment       : Storage_Count
              )  is
    begin
       Pool.Pool.Allocate (Storage_Address, Size, Alignment);
    end Allocate;

Then:

    Fake : Fake_Pool;
    type Ptr is access Item;
    for Ptr'Storage_Pool use Fake; -- "collection" lives here

    function New_Item
             (  Pool : in out Root_Storage_Pool'Class;
                Text : String
             )  return Item_Ptr is
       Object : Ptr;
    begin
       Fake.Pool := Pool'Unchecked_Access; -- Add mutex here
       Object := new Item (Text'Length);
       Object.Text := Text;
       return Object.all'Unchecked_Access;
    end New_Item;

Now the object is intact.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de