Re: Legit Warnings or not

[Anh Vo <anhvofrcaus@gmail.com>]

On Jul 20, 4:16 pm, 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:  If 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 := (Size => 1_000_000, Name => Something)").
>
> > Is this warnings legitimate? If yes, why line 8 is OK. Otherwise,
> > should it be a bug?
>
> It's not a bug.  An object of type Warned_Person might need huge amounts
> of memory, so Storage_Error might well be raised.  It'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:
>
>    subtype Name_Length is Natural range 0..1000;
>
>    type Not_Warned_Person (Size : Name_Length := 0) is
>       record
>          Name : String (1 .. Size);
>       end record;

Good suggestion. Again, thanks.

Anh Vo