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From: Anh Vo <anhvofrcaus@gmail.com>
Newsgroups: comp.lang.ada
Subject: Re: Legit Warnings or not
Date: Thu, 21 Jul 2011 11:43:23 -0700 (PDT)
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Date: 2011-07-21T11:43:23-07:00
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On Jul 20, 4:16=A0pm, Robert A Duff <bobd...@shell01.TheWorld.com>
wrote:
> Anh Vo <anhvofrc...@gmail.com> writes:
>
> > The code segment above triggers a warnings message 'creation of
> > "Warned_Person" object may raise Storage_Error' at line 3 as marked.
> > However, no warnings is issued at line 8. The difference between them
> > is default discriminant. I am using GNAT-GPL-2011.
>
> There's a confusing rule in Ada: =A0If it has defaults, there can be
> unconstrained objects of that type (and also constrained ones).
> If it doesn't have defaults, then all objects must be constrained.
>
> So if you say "X : Warned_Person;", GNAT will allocate space for
> billions of characters (not just 10) because you might assign
> a bigger one (like "X :=3D (Size =3D> 1_000_000, Name =3D> Something)").
>
> > Is this warnings legitimate? If yes, why line 8 is OK. Otherwise,
> > should it be a bug?
>
> It's not a bug. =A0An object of type Warned_Person might need huge amount=
s
> of memory, so Storage_Error might well be raised. =A0It's illegal to say
> "X : Acceptable_Person;", so that one doesn't get a warning.

I got it now. Thanks.

> If you want unconstrained objects, use a reasonably-small size, like:
>
> =A0 =A0subtype Name_Length is Natural range 0..1000;
>
> =A0 =A0type Not_Warned_Person (Size : Name_Length :=3D 0) is
> =A0 =A0 =A0 record
> =A0 =A0 =A0 =A0 =A0Name : String (1 .. Size);
> =A0 =A0 =A0 end record;

Good suggestion. Again, thanks.

Anh Vo