Path: utzoo!attcan!uunet!husc6!uwvax!rutgers!bellcore!tness7!tness1!sugar!ficc!peter
From: peter@ficc.uu.net (Peter da Silva)
Newsgroups: comp.lang.c
Subject: Re: "Numerical Recipes in C" is nonportable code
Message-ID: <1450@ficc.uu.net>
Date: 9 Sep 88 21:42:49 GMT
References: <664@lindy.Stanford.EDU> <6758@megaron.arizona.edu> <718@gtx.com> <13454@mimsy.UUCP>
Organization: SCADA
Lines: 27

In article <13454@mimsy.UUCP>, chris@mimsy.UUCP (Chris Torek) writes:
> -In article <640@drilex.UUCP> dricej@drilex.UUCP (Craig Jackson) writes
   about Burroughs putting protection in the compiler...

> In article <1429@ficc.uu.net> peter@ficc.uu.net (Peter da Silva) writes:
> -What's to stop you from doing the following:
> -
> -	Generate code in an array.
> -	Jump to the beginning of the array. *

Chris Torek noted:

> Whenever the compiler is forced to generate `iffy' code, it also generates
> tests such as tags to make sure that you do not do something like this.

So what's to stop me from writing out a load module and subverting
the protection mechanism, as I noted in my (deleted) footnote? I would
think that the perversions necessary to make 'C' safe to run on this machine
would make it sufficiently useless that a little thing like calculating
a pointer to a position before the beginning of an array is a minor
detail...

That is to say, yes... this construct is non-portable. But only to machines
you would have severe problems porting to in the first place.
-- 
Peter da Silva  `-_-'  Ferranti International Controls Corporation.
"Have you hugged  U  your wolf today?"            peter@ficc.uu.net