Path: utzoo!attcan!uunet!mcvax!dik
From: dik@cwi.nl (Dik T. Winter)
Newsgroups: comp.lang.c
Subject: Re: no noalias not negligible
Message-ID: <7552@boring.cwi.nl>
Date: 24 May 88 00:45:53 GMT
References: <54080@sun.uucp> <1988May21.030207.25063@light.uucp> <4152@haddock.ISC.COM>
Organization: CWI, Amsterdam
Lines: 17

In article <1988May21.030207.25063@light.uucp> bvs@light.UUCP (Bakul Shah) writes:
 >In article <54080@sun.uucp> dgh%dgh@Sun.COM (David Hough) writes:
 >>Anyway there is no portable way in draft ANSI C to say "this pointers are
 >>guaranteed to have no aliases".
 >
 >How about adding a test before the for loop?  Something like:
 >#define overlap(x,y,n)    (!(x + n <= y || y + n <= x))
 >	if (overlap(dx, dy, n))
 >		return complain("overlapping arrays\n");
 >
Note however that in many cases it is much more difficult to ascertain
overlap (i.e. 2 columns of matrices).  And there are cases where it
is just as difficult as the operations themselves.
-- 
dik t. winter, cwi, amsterdam, nederland
INTERNET   : dik@cwi.nl
BITNET/EARN: dik@mcvax