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From: James.Kanze@dresdner-bank.com
Subject: Re: nested functions
Date: 1999/06/23
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In article <7k3fr2$7el@abyss.West.Sun.COM>,
  stanley@West.Sun.COM (Stanley Friesen [Contractor]) wrote:
> In article <7k0b01$nod$1@panix.com>,
> Greg Comeau <comeau@comeaucomputing.com> wrote:
> >scope is a syntactic thing.  It doesn't apply to a running program
> >in the same sense.

> True - but there is this little rule that variables of automatic
> *duration* are destroyed on exit from their scope.

On *final* exit from their scope.

> >  So, when you say the local vars do not exist when you leave the
> >scope, they will if the local function calls a different function,
> >perhaps passing or having pointers to the local vars.

> But if the destructors have been called on them, and the sotrage
> reused for some other set of automatic variables (as is allowed upon
> leaving a function), then those pointers generate undefined behavior,
> as they are pointers to variables after their destructors are called.

I'm pretty sure what Greg is talking about is nested function calls.
Consider the following:

    void
    f( int* pi )
    {
        ++ (*pi) ;
    }

    void
    g()
    {
        int                 x = 0 ;
        f( &x ) ;
        cout << x << '\n' ;
    }

You pass the address of a local variable to another function (eventually
in another compilation unit).  If C/C++ had nested functions, I would
expect to be able to do exactly the same thing with the address of the
nested function.

--
James Kanze                         mailto:
James.Kanze@dresdner-bank.com
Conseils en informatique orientie objet/
                        Beratung in objekt orientierter
Datenverarbeitung
Ziegelh|ttenweg 17a, 60598 Frankfurt, Germany  Tel. +49 (069) 63 19 86
27


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