Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!usc!elroy.jpl.nasa.gov!decwrl!infopiz!lupine!rfg
From: rfg@NCD.COM (Ron Guilmette)
Newsgroups: comp.lang.c++
Subject: Re: Smart pointers and stupid people (was: garbage collection...)
Message-ID: <4186@lupine.NCD.COM>
Date: 2 Mar 91 18:35:28 GMT
References: <3945@lupine.NCD.COM> <49285@apple.Apple.COM> <27C19834.162A@tct.uucp>
Organization: Network Computing Devices, Inc., Mt. View, CA
Lines: 41

In article <27C19834.162A@tct.uucp> chip@tct.uucp (Chip Salzenberg) writes:
+According to ksand@Apple.COM (Kent Sandvik):
+>Anyway, I have not checked ARM and the ANSI specs/drafts, but I would 
+>be highly surprised if the standards lock the underlying object
+>memory handling scheme to a plain non-moveable version only.
+
+Prepare for a big surprise, then: They _do_ require unmoving objects.
+A pointer value derived at the beginning of a program had better
+compare equal to the same pointer value derived at any later time in
+the same program...

I think that there may have been some misunderstanding regarding the true
meaning of my statement to the effect that C++ objects don't move.

When I said that C++ objects don't move, I meant that they do not move
just like memory locations themselves do not move.  Sure, you can copy
the *contents* of one location to another, but I have yet to see any
program on any computer which caused a little mechanical arm to whiz
around inside the machine pulling DRAMS out of sockets and them plugging
them into different sockets.  (It sure would be entertaining to see such
a machine, or such a program however.  Perhaps that would be the ultimate
in "hardware assisted relocation". :-)

Likewise, given some C++ code like:

		{
		    SOME_TYPE some_object;

		    //...
		    //...
		}

I think that it is fairly clear that `some_object' resides in one (and only
one) place throughout its lifetime.  That's true even if you copy its
*contents* into some other object.

-- 

// Ron Guilmette  -  C++ Entomologist
// Internet: rfg@ncd.com      uucp: ...uunet!lupine!rfg
// Motto:  If it sticks, force it.  If it breaks, it needed replacing anyway.