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From: brett@wjvax.UUCP (Brett Galloway)
Newsgroups: comp.lang.c
Subject: Re: union initialization
Message-ID: <881@wjvax.wjvax.UUCP>
Date: Thu, 30-Apr-87 11:49:03 EDT
Article-I.D.: wjvax.881
Posted: Thu Apr 30 11:49:03 1987
Date-Received: Sun, 3-May-87 05:56:19 EDT
References: <3290@burdvax.PRC.Unisys.COM> <1722@plus5.UUCP> <455@haddock.UUCP> <6483@mimsy.UUCP>
Reply-To: brett@wjvax.UUCP (Brett Galloway)
Organization: Watkins-Johnson Co., San Jose, Calif.
Lines: 28

In article <6483@mimsy.UUCP> chris@mimsy.UUCP (Chris Torek) writes:
>To refresh memories (in some cases) or provide background (in others),
>the problem, or symptom, is this:  Uninitialised variables that have
>static allocation (that is, globals and local static variables) are, in
>C, defined as though they were initialised to `zero' [example]
>In most existing systems, this is trivial because 0 and 0.0 and
>(char *)0 are all all-zero bit patterns, and operating systems or
>runtime startups need know only how many bits of zeros are required
>(the infamous `bss' space).  There are machines, though, in which
>not all of these are all zero bit patterns ...

This has always bugged me about C -- the requirement that uninitialized
variables be implicitly initialized to 'zero` is problematic.  Where
binary 0000...000 is not `zero' for every type, it is wasteful, increasing
the size of binaries.  It is even more wasteful for embedded applications
(on PROM) where static initialization must be done at run-time.

The problem is that MOST of the time, the fact that uninitialized statics
are initialized to 'zero` is NOT used.  It would have been better if K&R
had not imposed this requirement.  It would also have made feasible the
(I think) better solution to union and structure initialization proposed by
Karl Heuer.

Oh well ... wishful thinking.
-- 
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Brett Galloway
{pesnta,twg,ios,qubix,turtlevax,tymix,vecpyr,certes,isi}!wjvaxring ir