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Date: Wed, 19 Mar 2008 23:17:46 +0100
From: Georg Bauhaus <rm.tsoh.plus-bug.bauhaus@maps.futureapps.de>
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Subject: Re: Prohibiting dynamic allocation for the given type
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Date: 2008-03-19T23:17:48+01:00
List-Id: <comp.lang.ada>

Maciej Sobczak wrote:
> On 19 Mar, 04:06, gp...@axonx.com wrote:
> 
>> Ada is high level language
> 
> That does not matter.
> Ada is a high level language, but still provides two ways to create an
> object:
> 
> X : Type;
> Y : Type_Ptr := new Type;
> 
> If these two methods are available, then apparently there is a
> difference between them and this difference is not in *where* objects
> are created, but *how long* they are allowed to live.
> 
> The high-level part of Ada can hide the "where" part, but not "how
> long".

(Somehow a posting of today is only visible through Google,
but not via the news server, apologies if this a repeated
remark.)

Using Ada 2005, you can have some of the "how long" control.
Deriving in nested scopes will limit the objects to that
scope. This includes heap objects. For example, you cannot
use pointers to Parent'Class to refer to objects of inner
scope types.

package body News10 is

   use Ada;

   procedure Scope is
      type T is new Finalization.Controlled with null record;
      type T_Ptr is access all T;

      overriding
      procedure Finalize(Object: in out T) is
         -- just show what is going on
      begin
         Text_IO.Put_Line("Finalized");
      end Finalize;

      X: T_Ptr;
   begin
      Text_IO.Put_Line("Enter");
      X := new T;
      pragma Inspection_Point(X);
      Text_IO.Put_Line("Exit");
   end Scope;

end News10;

with News10;
procedure Test_News10 is
begin
   loop
      News10.Scope;
      delay 2.0;
   end loop;
end;