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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: GNAT for MS Visual Studio
Newsgroups: comp.lang.ada
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Date: Sat, 6 Oct 2007 20:30:06 +0200
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Date: 2007-10-06T20:30:09+02:00
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On Sat, 06 Oct 2007 19:07:24 +0200, Pascal Obry wrote:

>    type Whatever is tagged record
>       ...
>    end record;
> 
> You can definitely read an object of type Whatever from multiple tasks.
> You don't have to use a protected object.
>
> You can also read the memory pointed to any access type from multiple
> tasks. You don't have to use a protected object.

AFAIK, ARM is silent about this. The most close reference is 9(8):

"In addition, tasks can communicate indirectly by reading and updating
(unprotected) shared variables, presuming the access is properly
synchronized through some other kind of task interaction."

Note: "properly synchronized." Unsynchronized reading and updating are
explicitly classified as erroneous execution in 9.10. But nothing is said
about reading and reading.

As a thought experiment (admittedly unrealistic) consider Ada tasks running
on a multi-core processor assessing at low level shared core memory (with
destructive reads).

My guess is that at least pragma Atomic_Components (Whatever); is required.

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