Re: Preventing Unchecked_Deallocation?

[Simon Belmont <sbelmont700@gmail.com>]

On Feb 4, 9:40 am, AdaMagica <christ-usch.gr...@t-online.de> wrote:
> Don't understand your problem. However, keep in mind that UD with a
> type different from the one with which the objects were allocated is
> erroneous.

When you say erroneous, do you mean forbidden by the language (i.e. an
exception) or that it will cause undefined operation?  My concern is
that if a unit exposes an access value to other units, any of them may
use UD to delete the object at any time.  Obviously this sort of
behavior would cause the program to quickly crash due to a null
pointer, but all things being equal I would prefer a compile-time
mechanism to prevent the UD outright.  For instance:


package ud is
  function Get return not null access Integer;
end ud;

package body ud is
  type Int_Ptr is access all Integer;
  o : Int_Ptr := new Integer'(42);

  function Get return not null access Integer is
  begin
    return o;
  end Get;

end ud;


procedure test is

  type Fake_Ptr is access all Integer;

  procedure Free is new Ada.Unchecked_Deallocation (Object => Integer,
                                                    Name => Fake_Ptr);

  p : Fake_Ptr;

begin

  p := Fake_Ptr(ud.Get);  -- cast to a local type

  Free (p);  -- phuck the whole program

end test;

-sb