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From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.lang.c
Subject: Re: Query: Implementation with non-zero NULL
Message-ID: <6873@mimsy.UUCP>
Date: Mon, 1-Jun-87 21:43:03 EDT
Article-I.D.: mimsy.6873
Posted: Mon Jun  1 21:43:03 1987
Date-Received: Wed, 3-Jun-87 03:55:02 EDT
References: <158@delftcc.UUCP> <1070@viper.Lynx.MN.ORG>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 23
Keywords: C, NULL, portability

In article <1070@viper.Lynx.MN.ORG> john@viper.Lynx.MN.ORG (John
Stanley) writes:
>  If, you're refering to an initialized static, it's whatever you
>specify.  If, on the other hand, you're refering to an UN-initialized
>static pointer, the answer is a resounding "Neither!"....  An un-
>initialized variable is just that.

Wrong.  See K&R, p. 198.  Similar (but no doubt more precise)
wording can be found in H&S and in the dpANS.  Unitialised static
pointers must contain NULL, or the implementation is broken [1].
Automatic variables, including registers, that are not initialised
contain trash; the trash may be machine dependent, as on, e.g.,
4BSD Vaxen, where new stack pages are zero filled.

----
[1] Except static unions, where it may be impossible to have all
union members start off as zero or NULL, since zero and NULL may
differ (and indeed, zero and zero may differ, e.g., floating zero
versus integer zero).

-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690)
Domain:	chris@mimsy.umd.edu	Path:	seismo!mimsy!chris