Re: GNAT GPL 2013 bug?

[Adam Beneschan <adambeneschan@aol.com>]

On Friday, August 9, 2013 11:51:34 PM UTC-7, Dmitry A. Kazakov wrote:
> On Fri, 09 Aug 2013 16:04:02 -0400, Robert A Duff wrote:

> I can "dispatch" on null anyway:
> 
>    type T is tagged null record;
>    procedure P (X : T) is null;
>    procedure R (X : access T'Class);
> 
>    procedure R (X : access T'Class) is
>    begin
>      X.P;
>    end R;

But I could write

   procedure R (X : access T'Class) is
   begin
      if X = null then
         -- take some special default action
      else
         X.P;
      end if;
   end R;

The point is that when a caller calls R, the above procedure is simply called.  So it will work to call it with a null parameter; the code in R may later run into a Constraint_Error or not, depending on how it's written, but there's no problem calling R.  But when P is called, the dispatching occurs *at* *that* *point*, before any code in any of the P procedures is executed; if the parameter is null, the dispatch cannot work.

I'm really not clear at all on what point you're trying to make.

                             -- Adam