Re: Circular dependency - I think..

From: Karl Heinz Buchegger (kbuchegg_at_gascad.at)
Date: 07/26/04 

Date: Mon, 26 Jul 2004 09:48:30 +0200

ma740988 wrote:
>
> I think I'm caught up in a circular dependency problem. I'd thought
> forward declaration was the solution to my problem but I'm sadly
> mistaken (perphaps i've been in the lab toooo long today).
> The header file for FOO is composed of BAR, likewise BAR is composed
> of FOO.
> If I complile FOO.cpp, Visual Studio's first complaint (C2146 syntax
> error, missing ; before foo - the next complaint is BAR::FOO missing
> storage type) points to the instantiation of FOO in BAR's header(i.e
> the line FOO foo). Similarily if I compile BAR Visual first complaint
> (C2146 syntax error, missing ; before bar - the next complaint is
> FOO::BAR missing storage type) points to the instantiation of BAR in
> FOO's header (i.e the line BAR bar).

given

class FOO
{
  int i;
  BAR bar;
}

class BAR
{
  int j;
  FOO foo
};

Now answer a quick question:
What is the size of a FOO object. Assume sizeof(int) == 4

Well: a FOO object consists of an int, that would
be 4 bytes plus the size of an BAR object. That
would be another 4 bytes plus the size of an FOO object.
Which accounts for another 4 bytes plus the size of an BAR
object. Another 4 bytes plus the size of a FOO object.
Add another 4 bytes plus the size of an BAR object ....
(ad infinitum)

Answer: A FOO object would be of unlimited size. I'm quite
sure that your computer doesn't have that much memory. 

-- 
Karl Heinz Buchegger
kbuchegg@gascad.at

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