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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: High-Integrity OO and controlled types
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Date: Mon, 2 May 2011 09:59:33 +0200
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Date: 2011-05-02T09:59:33+02:00
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On Sun, 01 May 2011 17:29:10 -0400, Robert A Duff wrote:

> Maciej Sobczak <see.my.homepage@gmail.com> writes:
> 
>> "Controlled types are not supported since they require extensive run-
>> time support."

A prejudice

>> This is surprising to me. I don't see anything in controlled types
>> that would require "extensive run-time support".
> 
> Most of the "extensive run-time support" comes from heap-allocated
> objects containing controlled parts.
> 
> If you say (for example, perhaps in a nested scope):
> 
>     type A is access T'Class;
>     type T2 is new T with ...;
>     X : A := new T2'(...);
[...]
> Finalization also needs to deal with partially-initialized objects,
> and finalize exactly those subcomponents that were successfully
> initialized.
>
> That's all "extensive run-time support".

No, that is an extensive run-time support of dynamically allocated
controlled objects. Any dynamically allocated object requires run-time
support (e.g. heap), which can be considered extensive.

Regarding Finalization, that is not "support", it is a part of the type's
semantics. In this sense the ADD instruction is a run-time support of
Integer type, and thus the whole program's code is "support" of itself. 

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de