Re: Validity of renamed objects?

["J-P. Rosen" <rosen@adalog.fr>]

Le 01/04/2014 15:04, Jacob Sparre Andersen a écrit :
> I've been reading section 8.5.1 in the LRM, and I can't figure out when
> the compiler is supposed to check the validity of a renamed object.
> 
> An example:
> 
> procedure Renaming_1 is
>    Object  : String (1 .. 9) := "dead beef";
>    Index   : Natural := 0;
>    Renamed : Character renames Object (Index);
> begin
>    Index := (Object'First + Object'Last) / 2;
>    if Renamed /= ' ' then
>       raise Program_Error
>         with "Expected Renamed to match the changed value of Index.";
>    end if;
> end Renaming_1;
> 
> 1) Should I get a Constraint_Error when Renamed is declared?
Yes
> 2) What will the value of Renamed be after Index has been changed?
> 

Assuming Index is 1 (in order to avoid Constraint_Error), Renamed is
unchanged.

The principle is that when you elaborate the renaming declaration, you
evaluate the renamed object, and from then on the renaming identifier
designates that object. It's not a macro!


-- 
J-P. Rosen
Adalog
2 rue du Docteur Lombard, 92441 Issy-les-Moulineaux CEDEX
Tel: +33 1 45 29 21 52, Fax: +33 1 45 29 25 00
http://www.adalog.fr