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From: cjkywt@hotmail.com (Sergey)
Newsgroups: comp.lang.ada
Subject: Re: Unchecked deallocation question
Date: 26 Nov 2004 10:20:01 -0800
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Date: 2004-11-26T10:20:01-08:00
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"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message news:<hzl9ywp1t6xh$.6ob5swxlfy6e.dlg@40tude.net>...
> On Fri, 26 Nov 2004 00:24:15 +0100, Adrien Plisson wrote:
> 
> > Martin Krischik wrote:
> >> You should carefully thing if you really need it. Unlike C/C++ the following
> >> is actually valid:
> >> 
> >> declare
> >>     It : Root'Class := Derived'(...);
> >> begin
> >>     ...
> >> end;
> > 
> > mmmm, i don't think there is any problem doing this in C++:
> > 
> > class Root;
> > class Derived : public Root;
> > 
> > Root &It = Derived( ... );
> > 
> > it just uses a reference type which is almost the same as ada access 
> > type but you cannot assign null to it and cannot dereference it.
> 
> Right, the difference appears when Derived is created by a factory:
> 
> declare
>    It : Root'Class := Create (...);
> begin
> 
> Here Create returns Root'Class, so the actual type is unknown until
> run-time. In C++ this is only possible using heap and pointers. In Ada It
> will be indeed allocated on the stack.

Nyet! You're wrong here. The example posted by Adrien is perfectly
right.

const Root &It = Derived( ... );

Derived gets allocated from the stack... But what you'll do with
constant the constant refence is another story...