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Date: Tue, 20 Apr 2021 10:18:23 -0700 (PDT)
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Subject: Re: 'address on a subprogram parameter
From: Vincent Marciante <vincent.marciante@l3harris.com>
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Xref: reader02.eternal-september.org comp.lang.ada:61863
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On Tuesday, April 20, 2021 at 12:35:07 PM UTC-4, J-P. Rosen wrote:
> Le 20/04/2021 =C3=A0 17:10, Vincent Marciante a =C3=A9crit :=20
> > I think that I used to know this but currently am not sure:=20
> >=20
> > Assuming the a value is passed by reference, is 'Address of a parameter=
=20
> > always the address of the object that is passed as in:=20
> >=20
> > ...=20
> >=20
> > type Big_Record is ...=20
> >=20
> > Object : Big_Record;=20
> >=20
> > procedure Proc (Param : in out Big_Record) is=20
> > begin=20
> > if Param'Address /=3D Object'Address then=20
> > raise Constraint_Error;=20
> > end if;=20
> > end;=20
> >=20
> > begin=20
> > Proc(Object);=20
> > ...=20
> >
> As usual, the real question is "why do you need that?"=20
>=20
> If you want to check whether a parameter IS a certain variable, use=20
> Param'Has_Same_Storage(Object). If you want to check whether variables=20
> have a part in common, use Param'Overlaps_Storage (Object).=20
> See 13.3 (73.1/3 .. 73.10/3)=20
>=20
>=20
> --=20
> J-P. Rosen=20
> Adalog=20
> 2 rue du Docteur Lombard, 92441 Issy-les-Moulineaux CEDEX=20
> Tel: +33 1 45 29 21 52=20
> https://www.adalog.fr

I actually do not want to test that: I just wrote that as an attempt to
make explicit want I was asking and what I did not expect (exception).
I am really working with old code where I am moving some logic out=20
from within a package body that contains the "address'd" variable to
an unassociated package that defines the "Big_Record" type and I
wanted to be sure that passing it as a parameter would (always) have
the same behavior with the variable being passed as a parameter.