Re: Where are returned values stored?

[James Alan Farrell <anonymous@anonymous.com>]

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.