Use of Unchecked_Deallocation and pragma Controlled

[Mark Lorenzen <mark.lorenzen@ofir.dk>]

When Unchecked_Deallocation is used to reclaim the storage claimed by
an object, the pragma Controlled must be use to prevent automatic
reclamation (ie. "garbage collection") of storage which would otherwise result
in "double deallocation" of the object.

Example:

type Access_T is access T;
Pragma Controlled (Access_T);

procedure Free is new Ada.Unchecked_Deallocation(T, Access_T);

begin
  A : Access_T := new T;
  B : Access_T := A;

  ...

  Free(T);    -- OK, reclaim the storage.
end;          -- OK only if pragma Controlled has been applied.
              -- Otherwise B could be reclaimed by garbage collection,
              -- resulting in double deallocation of A.

Question: Do you guys actually use pragma Controlled even if no
current Ada compiler generates code with garbage collection?

Regards,
- Mark Lorenzen