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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: 'address on a subprogram parameter
Date: Tue, 20 Apr 2021 14:25:22 -0500
Organization: JSA Research & Innovation
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"Vincent Marciante" <vincent.marciante@l3harris.com> wrote in message 
news:13f272e5-14a3-45cb-abf2-3d9f5a98f715n@googlegroups.com...
On Tuesday, April 20, 2021 at 12:35:07 PM UTC-4, J-P. Rosen wrote:
> Le 20/04/2021 à 17:10, Vincent Marciante a écrit :
> > I think that I used to know this but currently am not sure:
> >
> > Assuming the a value is passed by reference,

You can only assume that for by-reference types (see RM 6.3(4-9)).

Your example just used an unspecified record type. For any old record type 
(not in that list), the parameter passing mechanism is unspecified. Which 
means a compiler can pass by copy if it wants (it *probably* will pass by 
reference, but that's not the same as being required to do so). And if it 
does, your assumption doesn't hold.

For instance, for a small record like:
    type Screen_Position is
       X, Y : System.Byte; -- A Janus/Adaism, but I think you get the point.
    end record;
it might make more sense to pass by copy (especially if registers are used 
in the usual calling convention).

                    Randy.