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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: On absurdity of collections 7.6.1 (11.1/3)
Date: Fri, 1 Oct 2021 09:57:46 +0200
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On 2021-10-01 03:40, Randy Brukardt wrote:
> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message
> news:sj5127$1bbu$1@gioia.aioe.org...
>> On 2021-09-30 20:23, G.B. wrote:
>>> On 29.09.21 11:09, Dmitry A. Kazakov wrote:
>>>> For Ada programmers who wonder what it is,
>>> What's the reasoning behind run-time selection of storage pools?
>>
>> It happens quite frequently. Here is an example without controlled
>> objects, just an illustration of a dynamically selected storage pool.
>>
>> Consider a JSON parser. It is be an Ada object with a buffer inside which
>> size is a discriminant. On top of the buffer sits an arena pool. The parts
>> of the parsed JSON object are allocated in the arena. After parsing the
>> result can be used until the next parsing that will sweep the arena, no
>> Unchecked_Deallocate.
>>
>> In this case the collection rule will have no effect since JSON objects do
>> not require controlled components (or tasks, yet another thing killed by
>> the collection).
> 
> To implement an arena pool, you need to use the subpool mechanism (which
> does properly handle finalization when you "sweep the pool" as you put it).
> Each "arena" is a separate subpool, and you can dump the entire subpool with
> Unchecked_Deallocate_Subpool.

Not in this case, where all pool is arena. Allocate takes memory from 
the object's buffer.

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