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From: Wojtek Narczynski <wojtek@power.com.pl>
Newsgroups: comp.lang.ada
Subject: Re: Is this a bug?
Date: Fri, 24 Sep 2004 14:37:05 +0200
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Date: 2004-09-24T14:37:05+02:00
List-Id: <comp.lang.ada>

Hello,

> If so, then "renames" isn't quite as simple as I thought. It is more
> like a "hard link" then a "symbolic link". i.e. it links to the object
> rather then the name of the object. Interesting.

Ada rename is not like C #define. Big thanks to the makers of Ada for this.

It is more apparent what's going on in my code if you move the elaboration
time initialization of Current_Hook to execution time:

is
   Current_Hook : Bucket_Access_Access;
   --  Current : Bucket_Access renames Current_Hook.all;
   --  XXX Uncommented and used causes null pointer dereference
begin
   Current_Hook  := Queue.Anchor'Unchecked_Access;

This yields immediate failure.

Another example is:

procedure Test_Rename is
   Arr : array (1..3) of Integer := (1,2);
   Ind : Positive := Arr'First;
   Curr : Integer renames Arr (Ind);
begin
   Put_Line (Curr);
   Ind := Arr'Last;
   Put_Line (Curr);
end;

This will print 1 twice.

Those #defines are one of the main reasons why C code so hard
to read and debug, so I prefer to do some more typing.

Regards,
Wojtek