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From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Uninitialized out parameters.
Date: Wed, 6 Apr 2016 23:41:24 +0300
Organization: Tidorum Ltd
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Xref: news.eternal-september.org comp.lang.ada:30016
Date: 2016-04-06T23:41:24+03:00
List-Id: <comp.lang.ada>

On 16-04-06 14:44 , Dennis Lee Bieber wrote:
> On Wed, 6 Apr 2016 12:17:05 +0200, "G.B." <bauhaus@futureapps.invalid>
> declaimed the following:
>
>> On 06.04.16 10:19, ahlan@marriott.org wrote:
>>> On Tuesday, April 5, 2016 at 6:19:47 PM UTC+2, G.B. wrote:
>>>> On 05.04.16 14:02, ahlan@marriott.org wrote:
>>>>>      Ada.Text_IO.Put_Line ("V:" & V'img);
>>>>>
>>>>> The value zero is output, which because V is positive should be impossible.
>>>>
>>>> Addressing just this issue: the line is calling
>>>> implementation defined attribute 'IMG, which can
>>>> do as it pleases. The Ada type attribute 'Image
>>>> takes a value of type Positive'Base, which includes 0,
>>>> which is why outputting 0 is perfectly fine.
>>>>
>>>> (It's not a subtype attribute, but a type attribute,
>>>> if this makes sense.)
>>>
>>> The issue here is not whether or not 'img fails but the fact that V is returned with a value out of range.
>>
>> 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,

Then GNAT would be in violation of the Ada standard -- see RM 6.2(3/3). 
I hope and believe that is not the case...

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
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