Path: utzoo!mnetor!uunet!mcvax!ukc!mupsy!liv-cs!sqkeith
From: sqkeith@csvax.liv.ac.uk
Newsgroups: comp.lang.pascal
Subject: Re:  Global variables
Message-ID: <277@csvax.liv.ac.uk>
Date: 13 Apr 88 19:32:34 GMT
References: <12654@brl-adm.ARPA> <529@taux01.UUCP> <4770@aw.sei.cmu.edu>
Lines: 30
Organisation: Computer Science CSVAX (VAX1), Liverpool University


In article <4770@aw.sei.cmu.edu>, firth@sei.cmu.edu (Robert Firth) writes:
>
> I don't think that's right.  For example, in Pascal, an explicit
> pointer (^Thing) cannot point anywhere except into the heap, ie
> at an object created by NEW.  It cannot alias any global variable.
> 
> That leaves only VAR parameters as potential aliases.  Even here,
> a VAR parameter of one type (VAR p: ThingA) cannot alias a global
> variable of any other type (VAR g: ThingB).

Ah, but most Pascal compilers encourage filthy habits such as

  var p : ^integer; x : integer;
  begin
    p := @x;
    { or p := address(x); in VAX/VMS pascal }

Admitedly, one doesn't have to use this and decent compilers such as VAX/VMS
Pascal invent an extra layer of type compatibility rules insisting that
x be declared as a [volatile] integer.

		Keith

PS. I can't kick the above habit - I'm a part-time systems programmer!

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