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From: Simon Wright <simon@pogner.demon.co.uk>
Subject: Re: Initialized global data
Date: 1998/05/09
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Date: 1998-05-09T00:00:00+00:00
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stt@houdini.camb.inmet.com (Tucker Taft) writes:

> Simon Wright (simon@pogner.demon.co.uk) wrote:
> 
> : nobody@REPLAY.COM (Anonymous) writes:
> : [...]
> : > Or you can use an uninitialized "variable" (that doesn't) at a specified
> : > address:
> : > 
> : > X : T;
> : > for X'Address use A; -- Ada 83: "for X use at A;"
> 
> : I'm not sure of chapter-and-verse, but I believe that a compiler is
> : allowed to initialize X here under some circumstances; which wouldn't
> : be what you wanted!
> 
> A "pragma Import(Ada, X);" would prevent initialization.

I saw (searching the AARM for 'implicit initialization' and 'default
initialization') that a pragma Import would do the trick but I must
say it never occured to me to do this!

So, to get it straight, if I have the code below

with System;
with System.Storage_Elements;
package Foo is
  Vme_Address : constant System.Address
     := System.Storage_Elements.To_Address (16#1_000_000#);
  Vme_Items : array (0 .. 16#1_000#) of Integer;
  for Vme_Items'Address use Vme_Address;
  pragma Import (Ada, Vme_Items);
end Foo;

and I want to be quite sure that Vme_Items isn't initialized, the Ada
idiom is to include the pragma Import line?