detecting invalid pointers

[Joseph S. D. Yao]

In article <15495 at cup.portal.com> Kevin_P_McCarty at 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 at hadron.COM (not yet domainised??)
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