Xref: utzoo comp.std.c:884 comp.lang.c:16905
Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!purdue!haven!decuac!hadron!jsdy
From: jsdy@hadron.UUCP (Joseph S. D. Yao)
Newsgroups: comp.std.c,comp.lang.c
Subject: Re: detecting invalid pointers
Message-ID: <842@hadron.UUCP>
Date: 10 Mar 89 16:07:04 GMT
References: <15495@cup.portal.com>
Reply-To: jsdy@hadron.UUCP (Joseph S. D. Yao)
Distribution: usa
Organization: Hadron, Inc., Fairfax, VA
Lines: 23

In article <15495@cup.portal.com> Kevin_P_McCarty@cup.portal.com writes:
>Is there any guaranteed way to detect an out of range pointer,
>i.e., one which is supposed to point into an array but might not?
>     int  x[TABLESIZE];
>     int  *p;

How about something on the order of:
	if (q != (int *) NULL &&
	    (i = q - x) >= 0 && i < TABLESIZE &&
	    q == &x[i]) {
		...
	}

I don't really think that the first comparison against NULL is nece-
ssary, but feel free to contradict.  (I know I couldn't stop ya.)

	Joe Yao		jsdy@hadron.COM (not yet domainised??)
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