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From: "Xenos" <dont.spam.me@spamhate.com>
Newsgroups: comp.lang.ada
Subject: Re: Zero length Objects
Date: Thu, 1 Jul 2004 11:03:14 -0400
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Date: 2004-07-01T11:03:14-04:00
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"Nick Roberts" <nick.roberts@acm.org> wrote in message
news:2kimpdF2orakU1@uni-berlin.de...

> To my mind, a significant problem remains. If we declared something like:
>
>       CWhatever mem_a[1000000];
>
> somewhere in a template class, where CWhatever was a template parameter,
and
> then instantiated the class with CEmpty replacing CWhatever, we would get
a
> mem_a in the instance that took up a whopping amount of memory to store
> absolutely nada! Yuk.
>
> PS: Please forgive any minor mistakes, I'm not a C++ expert.
>
> -- 
> Nick Roberts
>
>

But C++ does compensate for this somewhat.  Empty base classes (used for
traits and the like) will not take any space in derived classes.  For
example:

class Empty {};

class Derived : public Empty {
   char a;
};

Derived D[1000000];

Here, Empty is not increase the size of D at all.

DrX