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From: Simon Wright <simon.j.wright@mac.com>
Newsgroups: comp.lang.ada
Subject: Re: Misaligned address error
Date: Fri, 07 Sep 2007 22:49:26 +0100
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Date: 2007-09-07T22:49:26+01:00
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shaunpatterson@gmail.com writes:

> i'm working with some really old legacy code that seemed to be
> working fine with gnat pro 3.16a1.  However, we decided to upgrade
> to gnat 5.

Not GNAT 6?

> Everything built fine - however, I'm getting a misaligned address
> value error at runtime:
>
> raised PROGRAM_ERROR : data_reader.2.ada:109 misaligned address
> value
>
>   Data_String : Data_Type_Array (1 .. 8) := (others => Data_Type
> (Ascii.Nul));
>   for Data_String'Alignment use 4;

>   Eight_Byte_Float : Long_Float_Type;
>   for Eight_Byte_Float'Address use Data_String'Address;  --- FAILS ON
> THIS LINE ---

I would guess that Eight_Byte_Float'Alignment needs to be 8 on your
machine? As I remember, a PowerPC has a maximum alignment requirement
of 4, an x86 8.

You could try saying

  for Data_String'Alignment use Long_Float_Type'Alignment;

if the compiler will let you. Other than that, there is an attribute
(possibly GNAT-special) which tells you the maximum alignment required
by the processor.