Re: Allocators and the requirement to raise `Storage_Error`

["Yannick Duchêne (Hibou57)" <yannick_duchene@yahoo.fr>]

Le Fri, 03 May 2013 09:31:56 +0200, egilhh <egilhovik@hotmail.com> a écrit:

> On Friday, May 3, 2013 7:35:29 AM UTC+2, Hibou57 (Yannick Duchêne) 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=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 was  
about the subtype of the allocated object, not of the returned access type.

I still wonder why there is no provision for an allocator to return `null`  
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.


-- 
“Syntactic sugar causes cancer of the semi-colons.” [1]
“Structured Programming supports the law of the excluded muddle.” [1]
[1]: Epigrams on Programming — Alan J. — P. Yale University