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From: dave@murphy.UUCP
Newsgroups: comp.lang.c
Subject: Re: Query: Implementation with non-zero NULL
Message-ID: <374@murphy.UUCP>
Date: Wed, 3-Jun-87 16:25:41 EDT
Article-I.D.: murphy.374
Posted: Wed Jun  3 16:25:41 1987
Date-Received: Sat, 6-Jun-87 04:29:45 EDT
References: <1217@batcomputer.tn.cornell.edu>
Organization: Gould CSD, Fort Lauderdale, FL
Lines: 26
Summary: statics ARE supposed to be zeroed

In article <1217@batcomputer.tn.cornell.edu>, garry@batcomputer.tn.cornell.edu (Garry Wiegand) writes:
> You should NEVER assume a not-explicitly-initialized static variable
> is given any particular value by anybody.

K&R says, on p. 198, about halfway down: "Static and external variables
which are not initialized are guaranteed to start off as 0."  The ANSI
draft that I have (admittedly an old one, July 1985) says, in section
C.5.6, p.51: "If such an object [static object] is not initialized
explicitly, it is initialized implicitly as if every scalar member were
assigned the integer constant 0."

In most virtual-memory environments, this is done by the OS zeroing out the
allocated memory for security reasons.  The only place where it might
cause problems is in zeroing out static pointers or floating types, where
the bit pattern that means zero might not be the all-zeroes pattern.
---
"Country beats the hell out of me" -- Jerry Dale McFadden

Dave Cornutt, Gould Computer Systems, Ft. Lauderdale, FL
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