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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Packed array problem
Date: Sun, 06 Mar 2016 22:55:27 +0000
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Simon Wright <simon@pushface.org> writes:

> Investigating the SVD2Ada program[1], for converting an ARM System
> View Description[2] into bindings, I got this message when compiling
> against my STM32F429I runtime:
>
>    stm32f429x-rcc.ads:149:09: packing of 3-bit components not
>    supported by configuration
>
> which is the same as in this little example:
>
>      1. package Checks is
>      2.    type Uint3 is mod 8 with Size => 3;
>      3.    type Arry is array (0 .. 1) of Uint3
>                 |
>         >>> packing of 3-bit components not supported by configuration
>
>      4.    with Component_Size => 3, Size => 6;
>      5. end Checks;
>
> This code compiles perfectly happily against AdaCore's ravenscar-sfp
> runtime.

Solved. I had pragma Normalize_Scalars in package System; removed this,
now all OK.

I don't quite see why Normalize_Scalars should affect matters, since the
compiler is quite capable of generating access-3-bits code directly in
all normal cases!

Normalize_Scalars came from the Ada Bare Bones tutorial at
http://wiki.osdev.org/Ada_Bare_bones.