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From: =?utf-8?Q?Yannick_Duch=C3=AAne_=28Hibou57?= =?utf-8?Q?=29?=
 <yannick_duchene@yahoo.fr>
Newsgroups: comp.lang.ada
Subject: Re: Allocators and the requirement to raise `Storage_Error`
Date: Fri, 03 May 2013 10:36:22 +0200
Organization: Ada @ Home
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Date: 2013-05-03T10:36:22+02:00
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Le Fri, 03 May 2013 09:31:56 +0200, egilhh <egilhovik@hotmail.com> a =C3=
=A9crit:

> On Friday, May 3, 2013 7:35:29 AM UTC+2, Hibou57 (Yannick Duch=C3=AAne=
) wrote:
>> ARM 2012 @4.8 says:
>>
>>
>>
>> http://www.ada-auth.org/standards/12rm/html/RM-4-8.html
>>
>> > For an allocator with a subtype_indication, the
>>
>> > subtype_indication shall not specify a null_exclusion
>>
>
> This Ada Issue may clear things up for you:
> http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ai05s/ai05-0104-1.txt?rev=3D=
1.4
>
> Basically, you have an access to an access, allocated with the default=
  =

> value,
> which is null for non-initialized access values.

You're right, that's obvious. I badly understand reading that part: it w=
as  =

about the subtype of the allocated object, not of the returned access ty=
pe.

I still wonder why there is no provision for an allocator to return `nul=
l`  =

instead of raising an exception, when a custom function of a constrained=
  =

subtype/type, which would provide the same functionality, does not get  =

imposed this obligation.


-- =

=E2=80=9CSyntactic sugar causes cancer of the semi-colons.=E2=80=9D [1]
=E2=80=9CStructured Programming supports the law of the excluded muddle.=
=E2=80=9D [1]
[1]: Epigrams on Programming =E2=80=94 Alan J. =E2=80=94 P. Yale Univers=
ity