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From: Brian Drummond <brian@shapes.demon.co.uk>
Newsgroups: comp.lang.ada
Subject: Re: Runtime startup code for the GNAT Runtime...and a bit of humble
 pie.
Date: Wed, 27 Mar 2013 22:58:19 +0000 (UTC)
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Date: 2013-03-27T22:58:19+00:00
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On Wed, 27 Mar 2013 14:38:23 +0000, Simon Clubley wrote:

> On 2013-03-27, Brian Drummond <brian@shapes.demon.co.uk> wrote:
>>
> Oh, sorry, I didn't mean to imply that I was seeing poor code in C as a
> result of marking the type itself as volatile, as I am not.

>> The only case of incorrect code generation seen so far has been where a
>> local procedure has been installed as an interrupt handler, and a local
>> variable (volatile) shared between it and the main.
>> Now it is unclear to me whether a local variable is even permitted to
>> be shared with an interrupt handler - or even if the handler is ever
>> permitted to be a local procedure. (

> Even if it appeared to work, I would be _very_ uncomfortable with the
> idea of a local procedure as a interrupt handler. Interrupt handlers are
> supposed to be a global, not localised, concept able to be executed at
> any time.

Agree absolutely. I have also verified that the AVR-Ada compiler 
prohibits local procedures as handlers, and intend to update the MSP 
tools accordingly.

>> However my reading of the Ravenscar profile only supports attaching
>> handlers via pragmas, in library level units - calling Ada.Interrupts.*
>> is a Program Error...
> I would need to read the Ravenscar profile in detail, but I thought the
> idea of a pragma based approach was that the vector table was defined
> during linking instead of at runtime.

Exactly.

> If so, I wonder how that would be compatible with the Atmel SAM7S setup
> I describe above. You may need to create a dummy interrupt table during
> linking and have the startup code populate the SAM7S interrupt registers
> from it.

I see no objection to copying a constant array to the actual interrupt 
registers during startup, should that be necessary.

- Brian