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Article View: comp.std.c
Article #1810

bounds checking (was: X3J11 Pleasanton meeting summary)

#1810
From: Karl Heuer
Date: Mon, 08 Oct 1990 19:18
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In article <14049@smoke.BRL.MIL> gwyn@smoke.BRL.MIL (Doug Gwyn) writes:
>	int a[4][5];
>	a[1][7] = 0;	/* undefined behavior */
>[justification for the above]

I presume that this ruling (if upheld) also means that strictly conforming
programs may not use extensible structs via the usual overmalloc hack?

>What is missing in the standard that would be required for such punning
>to be strictly conforming is some sort of guarantee that an array of
>arrays of T is also in some contexts considered an array of T itself.

I believe X3J11 has previously stated that "objects are composed of bytes"
means that any object may be considered an array of char.  If this continues
to be true, and yet the above example is illegal, then there's a bunch of
intermediate cases that have questionable legality.  I posted an article about
this (my "proof" that extensible structs are legal) on or around 20-Dec-1989,
I think.  Anyone still have a copy?

Karl W. Z. Heuer (karl@kelp.ima.isc.com or ima!kelp!karl), The Walking Lint
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!asuvax!ncar!ico!haddock!karl
References: <13996@smoke.BRL.MIL> <1990Oct3.184359.2348@sq.sq.com> <1737:Oct803:02:5890@kramden.acf.nyu.edu> <14049@smoke.BRL.MIL>

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Path: arc1-ca.pugleaf.net!utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!asuvax!ncar!ico!haddock!karl
From: karl@haddock.ima.isc.com (Karl Heuer)
Newsgroups: comp.std.c
Subject: bounds checking (was: X3J11 Pleasanton meeting summary)
Message-ID: <18456@haddock.ima.isc.com>
Date: 8 Oct 90 19:18:21 GMT
References: <13996@smoke.BRL.MIL> <1990Oct3.184359.2348@sq.sq.com> <1737:Oct803:02:5890@kramden.acf.nyu.edu> <14049@smoke.BRL.MIL>
Reply-To: karl@kelp.ima.isc.com (Karl Heuer)
Organization: Interactive Systems, Cambridge, MA 02138-5302
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