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From: mlandau@diamond.bbn.com.UUCP
Newsgroups: comp.lang.c
Subject: Re: default initialization of static and extern
Message-ID: <6328@garnet.BBN.COM>
Date: Wed, 3-Jun-87 23:34:52 EDT
Article-I.D.: garnet.6328
Posted: Wed Jun  3 23:34:52 1987
Date-Received: Fri, 5-Jun-87 04:20:52 EDT
References: <158@delftcc.UUCP> <1070@viper.Lynx.MN.ORG> <1297@genrad.UUCP> <675@gargoyle.UChicago.EDU> <10314@sri-spam.istc.sri.com>
Reply-To: mlandau@Diamond.BBN.COM (Matt Landau)
Organization: BBN Laboratories, Inc., Cambridge, MA
Lines: 29
Keywords: C, NULL, portability
Summary: static data is initialized only once

In comp.lang.c (<10314@sri-spam.istc.sri.com>), robert@sri-spam.UUCP (Robert 
Allen) writes:
>	This may be a small point, but I always "assume" that static
>	variables local to a function are initialized to zero, and maintain
>	their value over time and function calls.  If this not the case,
>	how can one effectively determine what to initialize to?  If you
>	init explictly then it will be done each time you call the function,
>	so the routine isn't static.  

Nope.  Static data -- even static data that is local to a function -- is
initialized exactly once.  If you have

	int counter()
	{
	    static int value = 5;

	    return value++;
	}

then counter() will return 5 the first time it is called, 6 the next, and so
on.  The static variable "value" will NOT be reinitialized to 5 on each call.

Incidentally, the initialization of static data usually happens at compile 
time, but there is no requirement that this be the case.  (I know of one 
compiler that arranged for code to be generated to initialize all static data 
locations before calling main.)
-- 
 Matt Landau			    "Lead me not into temptation...
 mlandau@diamond.bbn.com	     		I can find it myself."