Try placing the access variable inside the protected type:

package Managed_Allocation is

  type Node is private;

  function New_Node return Node;

private
  type Node_Data is
     record
        Reference_Count : Natural := 0;
     end record;

  type Node_Data_Access is access all Node_Data;

  type Node is new Ada.Finalization.Controlled with
     record
        Node_Data_Ref : Node_Data_Access;
     end record;

  procedure Initialize (
        Object : in out Node );
  procedure Adjust (
        Object : in out Node );
  procedure Finalize (
        Object : in out Node );

end Managed_Allocation;

with Ada.Unchecked_Deallocation;

package body Managed_Allocation is

  function New_Node return Node is
    Data_Node : Node;
  begin
    Data_Node.Node_Data_Ref := new Node_Data;
    return Data_Node;
  end New_Node;

  procedure Free is
  new Ada.Unchecked_Deallocation( Node_Data, Node_Data_Access );

  procedure Initialize (
        Object : in out Node ) is
  begin
    Object .Node_Data_Ref := null;
  end Initialize;

  procedure Adjust (
        Object : in out Node ) is
  begin
    if Object .Node_Data_Ref /= null then
      Object.Node_Data_Ref.Reference_Count := Object .Node_Data_Ref.
        Reference_Count + 1;
    end if;
  end Adjust;

  procedure Finalize (
        Object : in out Node ) is
  begin
    if Object.Node_Data_Ref /= null then
      Object.Node_Data_Ref.Reference_Count := Object.Node_Data_Ref.
        Reference_Count - 1;
      if Object .Node_Data_Ref.Reference_Count = 0 then
        Free( Object .Node_Data_Ref );
        Object .Node_Data_Ref := null;
      end if;
    end if;
  end Finalize;

end Managed_Allocation;


BTW: I didn't check, but you can probably find another example of this at:
  www.adapower.com

SteveD

"Preben Randhol" <randhol+abuse@pvv.org> wrote in message
news:slrn9e2vqb.aah.randhol+abuse@kiuk0156.chembio.ntnu.no...
>
> Hi
>
> I'm wondering if it is possible to do something like this
>
>    type Data_Type is new Ada.Finalization.Controlled with
>       record
>          References: Integer := 0;
>    end record;
>
>    type Data_Access_Type is access Data_Type;
>
> [..]
>
> and then in the main program if I do something like this:
>
>    procedure main is
>
>       Pointer : Data_Access_Type := null;
>       Data : Data_Access_Type := new Data_Type;
>
>    begin
>
>       Pointer := Data;
>
>    end main;
>
> to have Data.References increases by using Adjust? I'm trying but it
> looks like it only works if I do:
>
>    Pointer : Data_Type;
>    ...
>    Pointer := Data.all;
>    ...
> otherwise Adjust is not invoked. Is it possible to get it invoked if one
> point an access type to an object? I'm trying to eliminate the problem
> of dangling pointers in a program...
>
> Thanks in advance.
>
> --
> Preben Randhol ------------------- http://www.pvv.org/~randhol/ --
>                  �For me, Ada95 puts back the joy in programming.�