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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: [No_Elaboration_Code] GNAT still generating rep_to_pos, why?
Date: 03 Jan 2004 11:53:03 +0000
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Date: 2004-01-03T11:53:03+00:00
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"Luke A. Guest" <laguest@n_o_p_o_r_k_a_n_d_h_a_m.abyss2.demon.co.uk> writes:

> This is my code:
> 
>   type T_SPB is
>     record
>       ...
>     end record;
> 
>   type T_SPB_PTR is access T_SPB;
> 
>   SP_Block : T_SPB;
>   for SP_Block'Address use System'To_Address(16#80001000#);
>   -- Tell the compiler that this record is defined elsewhere.
>   -- Stops the compiler from producing a warning.
>   pragma Import(Ada, SP_Block);

Not sure whether this will help ..

   with System.Storage_Elements;

   package Luke is

      type P is access Integer;
      pragma Suppress_Initialization (P);

      type R is record
         The_P : P;
      end record;
      pragma Suppress_Initialization (R);

      V : R;
      for V'Address use System.Storage_Elements.To_Address (16#80001000#);
   --     pragma Import (Ada, V);

   end Luke;

I found Suppress_Initialization at
http://gcc.gnu.org/onlinedocs/gnat_rm/Implementation-Defined-Pragmas.html#Implementation%20Defined%20Pragmas
but I don't know whether it is officially supported by ACT for the
future (I tried it with 3.15p and 5.01a, the latter is closer to the
GCC version).

The key was to apply the pragma to type P.

I've managed to get myself confused about which combination of
options/compiler produced which effect, but I get the impression that
there is a difference between 3.15p and 5.01a here ..

I'm not familiar with System'To_Address .. neater than the
Storage_Elements version, but more difficult to grep for in the
source!

-- 
Simon Wright                               100% Ada, no bugs.