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From: pascal.obry@der.edfgdf.fr (Pascal Obry)
Subject: Re: Uninitialized "out" parameters
Date: 1996/07/19
Message-ID: <4sne1p$9vj@cf01>#1/1
X-Deja-AN: 169635965
references: <31EEACDA.64880EEB@sage.inel.gov> <4smh9i$gp5@krusty.irvine.com>
organization: EDF - DER
newsgroups: comp.lang.ada
Date: 1996-07-19T00:00:00+00:00
List-Id: <comp.lang.ada>


adam@irvine.com (Adam Beneschan) wrote:

>Paul Whittington <paul@sage.inel.gov> writes:
> >In the following Ada program, should either the compiler or the run-time
> >get some kind of error because the out parameter is not initialized?
> >
> >procedure Testit is
> >
> >  procedure SubP (op : out Integer) is
> >  begin
> >    op := op+1;
> >  end SubP;
> >
> >  I : Integer;
> >
> >begin
> >  SubP (I);
> >end Testit;

>Well, you can't read an "out" parameter at all, so it's illegal to use
>"op" in the right-hand side of your assignment.  So the compiler
>should give you an error.  Also, in Ada83, you'll get an error because
>I needs to be declared before the code for SubP appears.

This is wrong for Ada(95).

In Ada you can read out parameter, and this program is then not valid.
It's behavior is unknown.

>If you change op to an "in out" parameter, you'll be reading an
>uninitialized variable, but typically neither the compiler nor the
>runtime will complain.

>                                -- Adam

Pascal.


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