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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: How do I disable elaboration code on this
Date: Sat, 09 Apr 2011 20:19:18 +0100
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Date: 2011-04-09T20:19:18+01:00
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Ludovic Brenta <ludovic@ludovic-brenta.org> writes:

> Simon Wright <simon@pushface.org> writes on comp.lang.ada:
>> Jeffrey Carter <spam.jrcarter.not@spam.not.acm.org> writes:
>>
>>> On 04/09/2011 06:58 AM, Lucretia wrote:
>>>> The following code will not compile no matter what I do. Basically, I
>>>> want to write the startup code for Cortex-M3 in Ada with no assembly.
>>>> So, the ISR code needs to be elaboration free as it's the first bit of
>>>> code that would run on reset.
>>>
>>>>     Vector : constant Vectors :=
>>>>       (Dummy'Access,
>>>>        Dummy'Access,
>>>>        Dummy'Access,
>>>>        Dummy'Access);
>>>>     pragma Convention (C, Vector);
>>>>     for Vector'Address use Addr;
>>>
>>> I think what you need here is
>>>
>>> Vector : constant Vectors;
>>> pragma Import (Ada, Vector);
>>> for Vector'Address use Addr;
>>>
>>> since you don't want Vector to be initialized.
>>>
>>> Vector will not be initialized because you have pragma Import for it.
>>>
>>> Note that you don't need procedure Dummy.
>>
>> But the real code will have actual ISR procedures. OP is merely sparing
>> us the unnecessary detail of the real ISRs.
>
> But the vector being in Flash ROM, the Ada code needs not and indeed may
> not initialize it, so I think Jeffrey's reply is correct.  The pragma
> Import and the address clause will make the actual vectors (in ROM)
> visible to the Ada program.

That would be true if the vector was built in a separate C or ASM file,
but Luke wants to do the whole thing in Ada and then write it to
Flash. See above: "Basically, I want to write the startup code for
Cortex-M3 in Ada with no assembly."