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From: fedya_fedyakoff@inbox.ru
Newsgroups: comp.lang.ada
Subject: Re: Limited returns
Date: Tue, 24 Jun 2008 03:56:19 -0700 (PDT)
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Date: 2008-06-24T03:56:19-07:00
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> Even if it could, that would not make the program illegal. The compiler
> could only warn you about a possible exception propagation, which is not an
> error.

Well, I thought the compiler must warn about possible exception,
especially when there is such a possibility.

Ok, this is just my opinion, but returning to our rams - some
strangeness (an error?) is still there - consider:

--- named.ads
package Named is
   type Object is interface;

   function  name(this: Object) return String is abstract;
end Named;

--- some.ads
with Named;
with Ada.Finalization; use Ada.Finalization;
with Ada.Strings.Bounded;

package Some is
   Size : constant := 80;
   package bs is new Ada.Strings.Bounded.Generic_Bounded_Length(Size);
   use bs;

   type Object is new Controlled and Named.Object with private;

   function Create( name: String ) return Object;

   overriding procedure Initialize(this: in out Object);
   overriding procedure Finalize(this: in out Object);
   overriding procedure Adjust(this: in out Object);

   overriding function  name(this: Object) return String;

private
   type Object is new Controlled and Named.Object with
      record
         the_name: Bounded_String;
      end record;
end Some;

--- some.adb
with ada.Text_IO;
with system;

package body Some is
   package tio renames ada.Text_IO;

   function Create( name: String ) return Object is
   begin
      return O : Object do
         O.the_name := To_Bounded_String(name);
      end return;
   end Create;


   procedure Initialize(this: in out Object) is
   begin
      tio.Put_Line("Initialization " & this.name );
   end Initialize;

   procedure Finalize(this: in out Object) is
   begin
      tio.Put_Line("Finalization " & this.name);
   end Finalize;

   procedure Adjust(this: in out Object) is
   begin
      tio.Put_Line("Ajusting " & this.name);
   end Adjust;

   function name(this: Object) return String is
   begin
      return To_String(this.the_name);
   end name;

end Some;

--- factory.ads
with Named;

package Factory is
   function Create(name: String) return Named.Object'Class;
end Factory;

--- factory.adb
with Ada.Strings.Fixed; use Ada.Strings.Fixed;
with Some;

package body Factory is

   function Create(name: String) return Named.Object'Class is
   begin
   	return Some.Create(name);
   end;
end Factory;

--- boom.adb
with ada.Text_IO;
with Named; use Named;
with Factory;


procedure boom is
   package tio renames ada.Text_IO;
   aNamed: Named.Object'Class := Factory.create("Some1");
begin
   aNamed := Factory.create("Some1"); --- ***
   tio.put_line( "My name is " & aNamed.name );
   tio.Flush;
end boom;


What I can't figure out is why it's crashed at *** ? Factory creates
two fully equivalent objects of the same type!
Program's output looks very strange as well (at least for me) - why
for two initialization we have five (!!!) finalization? It drives me
crazy!

The program output is as follows:

Initialization
Ajusting Some1
Finalization Some1
Ajusting Some1
Initialization
Ajusting Some1
Finalization Some1
Finalization Some1
Finalization Some1
Finalization Some1

Execution terminated by unhandled exception
Exception name: CONSTRAINT_ERROR
Message: boom.adb:10 tag check failed
Call stack traceback locations:
0x401b69 0x401676 0x401235 0x401286 0x7c816d4d
[2008-06-24 14:51:09] process exited with status1 (elapsed time:
00.14s)