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From: Victor Porton <porton@narod.ru>
Newsgroups: comp.lang.ada
Subject: GNAT 4.9 - missing optimization feature?
Date: Wed, 06 Aug 2014 01:55:01 +0300
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Date: 2014-08-06T01:55:01+03:00
List-Id: <comp.lang.ada>

The below program, compiled with GNAT 4.9, calls Adjust two times when 
copying a T1 object.

But it does the same operations with a T2 object without calling Adjust.

So calling Adjust on a T1 object is here redundant and can be optimized away 
for greater performance. If I recall correctly, Ada Reference Manual allows 
this kind of optimization.

So GNAT is not as good as I expected, isn't it?

with Ada.Finalization;
with Ada.Text_IO;

procedure Main is

   type T1 is new Ada.Finalization.Controlled with null record;
   type T2 is new Ada.Finalization.Limited_Controlled with null record;
   
   overriding procedure Adjust(Object: in out T1) is
   begin
      Ada.Text_IO.Put_Line("Adjust");
   end;

   function F return T1 is
   begin
      return (Ada.Finalization.Controlled with null record);
   end;
   
   function F return T2 is
   begin
      return (Ada.Finalization.Limited_Controlled with null record);
   end;
   
   X: T1 := F;
   Y: T2 := F;

begin
   null;
end;

-- 
Victor Porton - http://portonvictor.org