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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: A simple ADA puzzle (I haven't the answer)
Date: 16 Jun 2004 20:51:57 +0100
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Date: 2004-06-16T20:51:57+01:00
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"Abby" <none@no.one.it> writes:

> Thanx for your answer. Sorry if I don't show you well what my
> problem is, I try again ;) : I have the structure as in my first
> post and I can't change it, I mean, "someone" wrote that type and I
> must use it so i need to declare a variable of that "monstrous" type
> and I can't change that type in anyway.  DO you know some way to
> declare and use it without any constraint error?  Thanx again!

I wrote this little subset:
------------------------------------------------------------------------
procedure Huge is

   type Len_Type is array (Integer range <>) of Character;
   type String_Type (Len : Integer := 0) is record
      String : Len_Type (1 .. Len);
   end record;

   X : String_Type (Len => 24);
   Y : String_Type;

begin
   null;
end Huge;
------------------------------------------------------------------------

and GNAT says:

gcc -c -I/home/simon/tmp/ -g -gnatqQafoy -gnatwaL -O2 -I- /home/simon/tmp/huge.adb
huge.adb:4:09: warning: creation of "String_Type" object may raise Storage_Error
huge.adb:8:04: warning: "X" is never assigned a value
huge.adb:9:04: warning: "Y" is never assigned a value
huge.adb:9:04: warning: Storage_Error will be raised at run-time
gnatbind -aO./ -E -I- -x huge.ali
gnatlink huge.ali -o /home/simon/tmp/huge -g

So there is no problem with my declaration of X, because I've
constrained the object X.

The warning at line 4 says that there may be a problem ..

and sure enough the second warning at line 9 shows it's happened. I
don't know if it's clear from what the other people have been saying,
but the difficulty is that Y can change size at run time: so there has
to be enough space reserved for it to expand into.


All the above is fine at one level of record composition. I think the
full set you supplied are past praying for ..

-- 
Simon Wright                               100% Ada, no bugs.