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From: lutz@iks-jena.de (Lutz Donnerhacke)
Newsgroups: comp.lang.ada
Subject: Re: Does a null pointer always raise Constraint_Error?
Date: 13 Dec 2000 14:25:42 GMT
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Date: 2000-12-13T14:25:42+00:00
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* Ken Garlington wrote:
>"Lutz Donnerhacke" <lutz@iks-jena.de> wrote in message
>: * Robert Dewar wrote:
>: [access to empty arrays represent as Null (System.Address)]
>: >   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 :-)
>:
>: I do not see the bug.
>
>Probably explains why it's so common...
>
>(I'm guessing it might have something to do with the case where a or b are
>null. Presumably, no exception would be raised if the compiler generated
>this kind of code, due to n'range causing the body of the loop to be
>skipped altogether?)

Possible, but irrelevant IMHO. Two empty arrays of the same component type
are equal per definition.


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