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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Question: What's the difference between pools of pools and Ada
 2012's new subpools?
Date: Mon, 18 Feb 2013 17:24:34 -0600
Organization: Jacob Sparre Andersen Research & Innovation
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Date: 2013-02-18T17:24:34-06:00
List-Id: <comp.lang.ada>

"Simon Wright" <simon@pushface.org> wrote in message 
news:lyd2vzqi0w.fsf@pushface.org...
> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:
>
>> As Randy said the problem with pools when used for management the life
>> cycle of objects is finalization of controlled objects. If subpools
>> alleviate this problem is to be seen.
>
> What Randy said was that the _hand-written_ subpool implementations the
> ARG had seen had problems with finalizable objects. Of coaurse, in the
> end all implementations are hand-written by somebody.

Right (I think). When you create your own subpool-like mechanism, you can't 
force finalization of objects (unless you keep a list of objects in the 
subpool and free them individually, which would defeat the purpose). So most 
people's simply say that they cannot be used with controlled objects (or 
tasks or protected objects). Which is limiting.

The subpool mechanism in Ada 2012 is designed to ensure that objects are 
finalized no later than when the subpool is discarded (via 
Unchecked_Deallocate_Subpool). In that sense, it works just like 
Unchecked_Deallocation (except all at once, rather than one at a time). Of 
course, I can't know whether GNAT actually implements this correctly!

                                   Randy.