Article View: comp.std.c
Article #673Re: Out-of-bounds pointers
From: Doug Gwyn
Date: Fri, 06 Oct 1989 19:09
Date: Fri, 06 Oct 1989 19:09
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In article <12570028@hpclwjm.HP.COM> walter@hpclwjm.HP.COM (Walter Murray) writes: -the wording of 3.3.6 might be misleading: "Unless both the pointer -operand and the result point to elements of the same array object, -or the pointer operand points one past the last element of an array -object and the result points to an element of the same array object, -the behavior is undefined if the result is used as an operand of -the unary * operator." Doesn't this imply rather strongly that it -IS legal to compute an invalid address, as long as it isn't -dereferenced? Not the way I read it in context, and certainly not the way it was intended. There are a lot of constraints on pointer arithmetic in the same paragraph; the cited sentence is merely one more constraint. It IS undefined behavior if you try to access some place outside the actual array. There are many other ways to obtain undefined behavior during pointer arithmetic itself.
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Path: arc1-ca.pugleaf.net!utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!uflorida!haven!ncifcrf!nlm-mcs!adm!smoke!gwyn From: gwyn@smoke.BRL.MIL (Doug Gwyn) Newsgroups: comp.std.c Subject: Re: Out-of-bounds pointers Message-ID: <11230@smoke.BRL.MIL> Date: 6 Oct 89 19:09:03 GMT References: <1009@mtxinu.UUCP> <12570028@hpclwjm.HP.COM> Reply-To: gwyn@brl.arpa (Doug Gwyn) Organization: Ballistic Research Lab (BRL), APG, MD. Lines: 16