dinamic object reclamation

["Anisimkov" <anisimkov@yahoo.com>]

I wrote the test program about it.
-----------------------------
with text_io; use text_io;
procedure alloc is

  dummy : character;

  procedure act (i : integer)
  is
      type block is array (1 .. 1024) of integer;
      type block_ptr is access all block;
      ptr : block_ptr;
  begin
      ptr := new block;
      ptr (ptr'LAst) := i;
      put (integer'image(I));
  end;

begin
  for i in 1..20000 loop
    act (i);
    get_immediate(dummy);
  end loop;
end;
--------------------
The question is:
Is memory allocated by
      ptr := new block;
have to be freed automatically after leaving of procedure act ?
Am I have to use Ada.Unchecked_Deallocation for free memory ?
I'm acking becouse there is a memory leak without Unchecked_Deallocation
when program compiled in the GNAT 3.13.
Is it bug or regular behavior ?