From: Robert Dewar <robert_dewar@my-deja.com>
Subject: Re: Does a null pointer always raise Constraint_Error?
Date: Wed, 13 Dec 2000 00:46:20 GMT
Date: 2000-12-13T00:46:20+00:00 [thread overview]
Message-ID: <916gsr$e6e$1@nnrp1.deja.com> (raw)
In-Reply-To: yec1yvdtmf1.fsf@king.cts.com
In article <yec1yvdtmf1.fsf@king.cts.com>,
Keith Thompson <kst@cts.com> wrote:
> Wayne Magor <none@nowhere.com> writes:
> [...]
> > I remember with one Ada compiler I wanted to make null to be
a
> > pointer to a zero-length segment so the null check would be
> > unnecessary (the hardware would do it for you).
No, that's not quite right, you can still miss things, consider
subtype n is string (1 .. 0);
type np is access n;
a, b : np;
if a.all = b.all then ...
it is a common compiler bug to translate this as
for j in n'range loop
if a.all (j) = b.all (j) ....
and the null loop causes no checks to be made :-)
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next prev parent reply other threads:[~2000-12-13 0:46 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <Pine.LNX.4.10.10011301306120.793-100000@lexis.di.fct.unl.pt>
[not found] ` <tgzoihpon4.fsf@mercury.rus.uni-stuttgart.de>
[not found] ` <9074fi$93b$1@nnrp1.deja.com>
[not found] ` <3A3253B1.AD8F32CF@ebox.tninet.se>
[not found] ` <90u1vi$uah$1@nnrp1.deja.com>
[not found] ` <90ukfm$c4p$1@nnrp1.deja.com>
2000-12-12 16:23 ` Does a null pointer always raise Constraint_Error? Wayne Magor
2000-12-12 20:27 ` Keith Thompson
2000-12-13 0:46 ` Robert Dewar [this message]
2000-12-13 8:58 ` Lutz Donnerhacke
2000-12-13 13:56 ` Ken Garlington
2000-12-13 14:25 ` Lutz Donnerhacke
2000-12-13 14:58 ` Florian Weimer
2000-12-13 15:17 ` Lutz Donnerhacke
2000-12-13 15:40 ` Robert Dewar
2000-12-13 20:07 ` Florian Weimer
2000-12-14 13:08 ` Robert Dewar
2000-12-14 14:29 ` Ken Garlington
2000-12-15 1:45 ` Robert Dewar
2000-12-13 15:37 ` Robert Dewar
2000-12-12 20:31 ` Keith Thompson
2000-12-13 19:58 ` Florian Weimer
2000-12-13 0:43 ` Robert Dewar
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