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From: jans@stalker.UUCP
Newsgroups: comp.lang.c
Subject: Re: initializing null pointers
Message-ID: <8134@tekecs.TEK.COM>
Date: Fri, 6-Feb-87 11:04:11 EST
Article-I.D.: tekecs.8134
Posted: Fri Feb  6 11:04:11 1987
Date-Received: Sun, 8-Feb-87 06:00:38 EST
References: <347@bms-at.UUCP> <7614@utzoo.UUCP>
Sender: nobody@tekecs.TEK.COM
Reply-To: jans@stalker.UUCP (Jan Steinman)
Organization: Tektronix, Inc., Wilsonville, OR
Lines: 20

In article <7614@utzoo.UUCP> henry@utzoo.UUCP (Henry Spencer) writes:
>> What about pointer arrays allocated with calloc()?  Does one have to
>> initialize all the elements in a loop to be portable...
>
>Fraid so.  What you might do, though, if you are willing to risk some small
>degree of unportability for the sake of efficiency, is first test an element
>of the array for equality to NULL...
>
>The small portability risk in this is the possibility that an all-zeros
>pointer might have magic properties (e.g. trap on any use of it).

Or that you might, by chance, have tested a pointer that had been NULL in a
previous life!

The most portable thing to do is NEVER dereference a pointer that has not been
initialized.  Some micro compilers I've used don't even initialize automatics!

:::::: Artificial   Intelligence   Machines   ---   Smalltalk   Project ::::::
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