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From: Brian Drummond <brian@shapes.demon.co.uk>
Newsgroups: comp.lang.ada
Subject: Re: Why is the destructor called multiple times after I declare an
 object?
Date: Mon, 11 Jan 2016 16:29:44 -0000 (UTC)
Organization: A noiseless patient Spider
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Date: 2016-01-11T16:29:44+00:00
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On Sun, 10 Jan 2016 19:18:53 -0700, Jeffrey R. Carter wrote:

> On 01/10/2016 06:37 PM, Andrew Shvets wrote:
>> 
>> Why is "Resetting values of Creat to defaults." displaying 6 times as
>> opposed to just twice?
> 
> ARM 7.6(13-17.1) apply here. Note that Init declares a local variable of
> the type, which is finalized when Init returns, and that the anonymous
> object that is the result of the call to Init is finalized after
> initialization is finished.
> This gives you 2 calls to Finalize for each variable of the type
> declared and initialized by a call to Init. Finally you have a call to
> Finalize for each variable of the type when the program ends.
> 
> http://www.adaic.org/resources/add_content/standards/12rm/html/
RM-7-6.html


Interesting. I thought you could eliminate one of those local copies 
using "extended return" in the Init function, as in:

  function Init return Creature is
  begin
    return TempCreature : Creature do 
       TempCreature.Name          :=  
Ada.Strings.Unbounded.To_Unbounded_String("dog");
       TempCreature.Legs          := 4;
       TempCreature.WeightInGrams := 3000;
       TempCreature.HeightInCm    := 40;
     end return;
  end Init;

Somehow I expected "extended return" to allocate space and "build in 
place" during the execution of the return statement. 

Is this something legal that Gnat doesn't take advantage of? Or is there 
a Gnat option I'm not aware of?

Of course instead of a default constructor, the record can be populated 
with default values, to eliminate both the "Init" call and two temporary 
objects, but the "problem" remains for the other constructor.

-- Brian