Re: Limited_Controlled types as 'out' arguments

[Lutz Donnerhacke <lutz@iks-jena.de>]

* Dmitry A Kazakov wrote:
> On Thu, 31 Jul 2003 10:54:44 +0000 (UTC), Lutz Donnerhacke
>>   procedure Set(o1, o2 : out Test; i : Test) is
>>   begin
>>      Debug("Setting from", i.a);
>>      Debug("Setting o1  ", o1.a);
>>      Debug("Setting o2  ", o2.a);
>>      Finalize(o1);
>>      Finalize(o2);
>>      
>>      o1.a := new Character'(global);
>>      Debug("Setting to1 ", o1.a);
>>      global := Character'Succ(global);
>>
>>      o2.a := new Character'(i.a.all);
>>      Debug("Setting to2 ", o2.a);
>>   end Set;
> 
> Sort of, if you are calling Finalize from a normal subprogram! (:-))
> As for error, you call Set (a, a, b); which finalizes a twice! It is a
> language design fault that a destructor can be called explicitly. Your
> example shows why.

Changing the "Finalize" calls to "Free" causes the same effect.
So the main point is: How to manage resources correctly?

   procedure Set(o1, o2 : out Test; i : Test) is
   begin
      Debug("Setting from", i.a);
      if o1'Address /= o2'Address then
         Debug("Setting o1  ", o1.a);
         Free(o1.a);

         o1.a := new Character'(global);
         Debug("Setting to1 ", o1.a);
         global := Character'Succ(global);
      end if;

      Debug("Setting o2  ", o2.a);
      Free(o2.a);
      o2.a := new Character'(i.a.all);
      Debug("Setting to2 ", o2.a);
   end Set;

GNA!