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: <6umkbn$pv5$1@nnrp1.dejanews.com> (raw)
In-Reply-To: evans-2709981430360001@ppp23.s9.pgh.net
In article <evans-2709981430360001@ppp23.s9.pgh.net>,
evans@evans.pgh.pa.us (Arthur Evans Jr) wrote:
> In article <yec1zoyd2xa.fsf@king.cts.com>,
> Keith Thompson <kst@king.cts.com> wrote:
>
> > Nor can we assume that a ... null pointer is represented as all-bits-zero
>
> Indeed not. Some years ago I was concerned about this very issue and
> asked around (probably on cla) about it. The answers were instructive.
> Most compilers did in fact use all zeros, but some other values were
> used, including one compiler (from IBM, I think) that used the HEX
> number DEAD BEEF. I suppose it really stood out in HEX dumps.
Art, I think this memory is wrong. At least in compilers I have seen, it is
indeed common to use DEAD BEEF for uninitialized variables, but I have not
seen it used for null pointers. If someone knows a counter example, I would
be interested.
Certainly though, you are right, Null_Address can be assumed to be all
zero bits in practice, but not Null.
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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 ` dewarr
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 [this message]
1998-09-28 0:00 ` Keith Thompson
1998-09-28 0:00 ` dewarr
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
1998-09-24 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 ` dewarr
1998-09-25 0:00 ` Robert I. Eachus
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