From: utzoo!decvax!harpo!seismo!hao!csu-cs!silver Newsgroups: net.unix-wizards Title: Questions about nil-pointer dereferences (the "plague") Article-I.D.: csu-cs.1979 Posted: Fri Jan 14 12:37:54 1983 Received: Mon Jan 17 02:59:02 1983 We are bringing up System III on a machine that traps attempts to indirect through zero pointers. (Writing code that does this is at very least a poor practice and somewhat antisocial...) Anyway, we run into a lot of these in imported code. I understand that most (all?) DEC hardware supports "int *p = 0; i = *p;" by mapping memory to zero so *p returns zero. Questions: 1: Is there any GOOD reason for writing code that exercises this feature? 2: What if I do "int *a = 0, *b = 0; *b = 10; i = *a;"? What is the value of i? Does this mean that assigning indirect through a nil pointer is deadly to the rest of your nil pointer derefs? Any other comments? Please respond to the net if short and and of general interest, else mail me. Thanks! Alan Silverstein (harpo!seismo!hao!csu-cs!silver) HP Fort Collins Colorado