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=ham
	autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,984d3d7860d7c8c
X-Google-Attributes: gid103376,public
From: James Alan Farrell <anonymous@anonymous.com>
Newsgroups: comp.lang.ada
Subject: Re: Where are returned values stored?
Date: Thu, 27 May 2004 16:24:06 -0400
Message-ID: <fgjcb0pnsbdcaadc3j365f3ld13m42aaf8@4ax.com>
References: <75s9b0pgo91ctvlm5op2rcql82t9ip4me2@4ax.com>
 <mailman.10.1085650792.391.comp.lang.ada@ada-france.org>
 <1dptc.49822$tb4.1731604@news20.bellglobal.com>
X-Newsreader: Forte Free Agent 2.0/32.652
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
NNTP-Posting-Host: fw.grammatech.com
X-Trace: newsfeed.slurp.net 1085689514 209.4.89.67 (27 May 2004 15:25:14
 -0500)
X-Original-NNTP-Posting-Host: 209.4.89.67
Path: 
 controlnews3.google.com!news1.google.com!news.glorb.com!cyclone1.gnilink.net!gnilink.net!peer01.cox.net!cox.net!newsfeed.slurp.net!not-for-mail
Xref: controlnews3.google.com comp.lang.ada:886
Date: 2004-05-27T16:24:06-04:00
List-Id: <comp.lang.ada>

Interesting to consider this with a recursive procedure, but yes, it
should work.

JAF

On Thu, 27 May 2004 13:05:06 -0400, "Warren W. Gay VE3WWG"
<ve3wwg@cogeco.ca> wrote:

>
>Conceptually, there is _no_ reason a compiler _must_ copy a
>return value. Consider a function like:
>
>function Foo return String is
>   I : Integer := 23;
>   S : String(1..3) := "Bar";
>   X : Natural := 0;
>begin
>   ...
>   return S;
>end;
>
>To return S, all the compiler needs to do is to extend the
>caller's stack frame to claim all the storage up to and
>including S (I and S assuming sequential assignment), at
>the point when Foo returns (return effectively does
>reclaim the storage used for X however).
>
>Then the calling code can reference S as if it were a
>local variable.  The space used for I is
>wasted at this point, but temporarily, who cares?
>
>Once the compiler knows that the caller's use of the returned
>value S is no longer required, the stack frame can be shrunk
>back to the original size that it had prior to calling Foo.
>
>Is this done? Is it done by GNAT? I have no idea, but I
>suspect that this is done in some places, some of the time,
>by some compilers. Perhaps, someone in this group
>can confirm/debunk this idea.