From: dewarr@my-dejanews.com
Subject: Re: null pointer representation (was: Boolean Representation)
Date: 1998/09/28
Date: 1998-09-28T00:00:00+00:00 [thread overview]
Message-ID: <6uo7p6$dk4$1@nnrp1.dejanews.com> (raw)
In-Reply-To: yecu31su3gj.fsf@king.cts.com
In article <yecu31su3gj.fsf@king.cts.com>,
Keith Thompson <kst@king.cts.com> wrote:
> dewarr@my-dejanews.com writes:
> [...]
> > Certainly though, you are right, Null_Address can be assumed to be all
> > zero bits in practice, but not Null.
>
> Why is it safe to assume that Null_Address is all zero bits?
> I'd normally expect it to have the same representation as a null
> pointer, though of course that's not guaranteed either.
>
> (In any case, since Null_Address is conveniently declared in System,
> there's no need to assume anything about how it's represented.)
What is and is not safe to assume cannot be derived only from ISO standards!
For all sorts of reasons, it is safe to assume that Null_Address is all
zero bits. If you think this is wrong, cough up a counter example :-)
Still, of course it is better never to have to depend on this assumption
if you can avoid it (the same comment applies exactly equivalently to C code)
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next prev parent reply other threads:[~1998-09-28 0:00 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
1998-09-24 0:00 Boolean Representation matthew_snyder
1998-09-24 0:00 ` dennison
1998-09-24 0:00 ` Keith Thompson
1998-09-25 0:00 ` dennison
1998-09-25 0:00 ` Keith Thompson
1998-09-26 0:00 ` Tucker Taft
1998-09-26 0:00 ` Keith Thompson
1998-09-27 0:00 ` null pointer representation (was: Boolean Representation) Arthur Evans Jr
1998-09-27 0:00 ` Keith Thompson
1998-09-28 0:00 ` dewarr
1998-09-28 0:00 ` Keith Thompson
1998-09-28 0:00 ` dewarr [this message]
1998-09-30 0:00 ` Keith Thompson
1998-10-02 0:00 ` Robert I. Eachus
1998-09-28 0:00 ` Lieven Marchand
1998-09-27 0:00 ` Boolean Representation dewarr
1998-09-27 0:00 ` dewarr
1998-09-24 0:00 ` dewarr
1998-09-24 0:00 ` Samuel T. Harris
1998-09-25 0:00 ` dewarr
1998-09-27 0:00 ` Samuel T. Harris
1998-09-28 0:00 ` dewar
1998-09-24 0:00 ` matthew_snyder
1998-09-24 0:00 ` dennison
1998-09-24 0:00 ` Tom Moran
1998-09-25 0:00 ` dewarr
1998-09-25 0:00 ` Tom Moran
1998-09-25 0:00 ` Robert I. Eachus
1998-09-25 0:00 ` dewarr
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