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From: shankar@hpclscu.HP.COM (Shankar Unni)
Newsgroups: comp.lang.c++
Subject: Re: initializing array of objects
Message-ID: <1000015@hpclscu.HP.COM>
Date: 21 Jun 89 01:49:55 GMT
References: <1284@cadillac.CAD.MCC.COM>
Organization: Hewlett-Packard Calif. Language Lab
Lines: 29

> bright@Data-IO.COM (Walter Bright) writes:
> In article <1284@cadillac.CAD.MCC.COM> rpj@redcloud.cad.mcc.com (Rich Johns) writes:
> >class Foo;
> >Foo** fooArray;
> >fooArray = new Foo*[100];
> >for (int i = 0; i < 100; i++) fooArray[i] = 0;
> >Is there a better way to initialize fooArray?
> 
> Try:
> 	memset(fooArray,0,100 * sizeof(fooArray[0]));
> or:
> 	fooArray = (Foo**) calloc(100,sizeof(fooArray[0]));
> Both are faster and generate less code.

And both are non-portable.

A NULL pointer does not have to have a bit-representation of all-zeroes.
Admittedly this is rare, but I do know of a couple of such machines.

"fooArray[i] = 0" initializes fooArray[i] to a NULL pointer value. 
"memset" and "calloc" initialize fooArray[*] to all-zero bits.

Try the following:

   memset (fooArray, (Foo *) 0, 100*sizeof(Foo *));

It's fast and correct.
----
Shankar Unni.