From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00
	autolearn=unavailable autolearn_force=no version=3.4.4
X-Received: by 2002:ac8:c86:: with SMTP id n6mr25293623qti.345.1567362846014;
        Sun, 01 Sep 2019 11:34:06 -0700 (PDT)
X-Received: by 2002:a05:6830:1db2:: with SMTP id
 z18mr21938883oti.110.1567362845639;
 Sun, 01 Sep 2019 11:34:05 -0700 (PDT)
Path: 
 eternal-september.org!reader01.eternal-september.org!feeder.eternal-september.org!news.mixmin.net!proxad.net!feeder1-2.proxad.net!209.85.160.216.MISMATCH!o24no281484qtl.0!news-out.google.com!d29ni294qtg.1!nntp.google.com!o24no281477qtl.0!postnews.google.com!glegroupsg2000goo.googlegroups.com!not-for-mail
Newsgroups: comp.lang.ada
Date: Sun, 1 Sep 2019 11:34:05 -0700 (PDT)
In-Reply-To: <a2264c91-67b6-4846-a415-e4428dcdfaa2@googlegroups.com>
Complaints-To: groups-abuse@google.com
Injection-Info: glegroupsg2000goo.googlegroups.com; posting-host=76.77.182.20;
 posting-account=W2gdXQoAAADxIuhBWhPFjUps3wUp4RhQ
NNTP-Posting-Host: 76.77.182.20
References: <f5528641-7f77-4754-8f2a-ac5f66e53a36@googlegroups.com>
 <a2264c91-67b6-4846-a415-e4428dcdfaa2@googlegroups.com>
User-Agent: G2/1.0
MIME-Version: 1.0
Message-ID: <a72343a2-1a48-42a2-b125-4b123c94d28d@googlegroups.com>
Subject: Re: Question about finalization of local object returned from the
 function
From: Stephen Leake <stephen_leake@stephe-leake.org>
Injection-Date: Sun, 01 Sep 2019 18:34:06 +0000
Content-Type: text/plain; charset="UTF-8"
Xref: reader01.eternal-september.org comp.lang.ada:57095
Date: 2019-09-01T11:34:05-07:00
List-Id: <comp.lang.ada>

On Wednesday, August 28, 2019 at 6:45:16 PM UTC-7, Brad Moore wrote:
> On Wednesday, August 28, 2019 at 4:36:38 PM UTC-6, darkestkhan wrote:
> > Given a function returning controlled type:
> > 
> > function Bar return T is
> >   Foo : T;
> > begin
> >   ...
> >   return Foo;
> > end Bar;
> > 
> > would Foo be finalized upon end of the function?
> > 
> 
> Yes Foo is finalized upon end of the function, but not before copying the
> object to a temporary result object which is returned to the caller. The temporary is finalized also after being assigned to the result object.
> In other words, the expected result is returned to the caller, and the Foo object on the stack is also properly finalized.
> 

However, the compiler is free to optimize away any of these steps, as long as the net effect is preserved.

To expand on Brad's comment about the extended return statement, consider:

function Bar return T is
begin
   return Foo : T do
      ...
   end return;
end Bar;

then 'Foo' is actually the object that the client has declared/allocated. For example:

declare
   A : T := Bar;
begin
...

"Foo" is actually "A", so no temporary objects are required. 

I don't think Limited_Controlled is required for this to happen; ARM 6.5 (24/3) mentions "built in place", but not Limited_Controlled. Also ARM 7.6 (17.1/3) gives the conditions where "built in place" is required.

-- Stephe