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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Uninitialized out parameters.
Date: Wed, 6 Apr 2016 15:54:44 -0500
Organization: JSA Research & Innovation
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Date: 2016-04-06T15:54:44-05:00
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"Dennis Lee Bieber" <wlfraed@ix.netcom.com> wrote in message 
news:c7t9gb1972nrm7e64hudekqvi5pmldtm17@4ax.com...
...
>>The issue is rather, I think, whether V is returned at all.
>>There would have to be an assignment within the null procedure.
>>
> Which could be a case if the compiler used copy-in/copy-out semantics
> for scalars (or just copy-out for the test sample). GNAT, if I recall, 
> uses
> reference semantics, and as out-only wouldn't be checking the initial 
> value
> on entry.

Scalars in Ada are always by-copy, so the *effect* always have to be 
copy-in/copy-out, regardless of how that's implemented. (I can't speak for 
GNAT, but Janus/Ada makes copies at the call-site if we want to/need to use 
by-reference parameter passing.)

The rules for whether an out parameter is initialized (and if so, how) are 
complicated - see 6.4.1(12-15). 6.4.1(15) most likely applies in this case 
(assuming no Default_Value aspect is involved), and that says that the value 
is uninitialized. And of course the value of an uninitialized object can be 
anything.

                                Randy.