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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: CONSTRAINT ERROR? access check failed
Date: Thu, 01 Mar 2018 17:26:07 +0000
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Date: 2018-03-01T17:26:07+00:00
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Mehdi Saada <00120260a@gmail.com> writes:

> Work finished ! Thank you.
> But I would like to know why I get a warning at compile time with
> type Link (Num : LINE_NUMBER := 0; Length : NATURAL := 0) is
>       record
> 	 NEXT : access LINK := null;
> 	 Line : String (1 .. Length) := (1..Length => ' ');
>       end record;
> As if it could cause a stack overflow (was written as is). Yet I don't get at each compilation, surprisingly.

Because Length could be Natural'Last which would make Line large enough
to break the stack on any machine likely to be available to you.

Do you really need the default values? If you have defaults, then
creating an object of the type without specifying values for the
discriminants makes the discriminants changeable (by whole-record
assignment), so that sufficient space has to be reserved for the largest
possible record. Without defaults, you have to supply discriminants when
you create an object (the discriminants then can't be changed, but will
that matter?).