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Posting-Version: version B 2.10.1 6/24/83; site decvax.UUCP
Path: utzoo!linus!security!genrad!decvax!minow
From: minow@decvax.UUCP (Martin Minow)
Newsgroups: net.bugs.4bsd
Subject: NULL pointer dereferencing and printf
Message-ID: <352@decvax.UUCP>
Date: Thu, 26-Jan-84 21:45:24 EST
Article-I.D.: decvax.352
Posted: Thu Jan 26 21:45:24 1984
Date-Received: Sat, 28-Jan-84 03:20:48 EST
References: <1590@rlgvax.UUCP>
Organization: DEC UNIX Engineering Group
Lines: 18

This discussion seems to pop up once a year -- perhaps it could
be put in net.announce and be done with.  You shouldn't dereference
NULL.

But people do -- mostly by accident.  As a slight debugging aid,
the Decus C printf (and, I think, the V6 printf) test for
printf("%s", NULL) and print "{null}".  This at least keeps
the bug from being fatal.  Vax-11 C crashes the program which
gets the bug out quicker, I suppose.

(Actually, on Vax, the first 512 bytes of the user
address space can't be referenced, so most instances
of ((struct foo *) NULL)->bar are caught, too.

Martin Minow
decvax!minow