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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Memory Access
Date: Tue, 08 Nov 2011 18:33:02 +0000
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Date: 2011-11-08T18:33:02+00:00
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awdorrin <awdorrin@gmail.com> writes:

> I think I have myself rather confused at the moment with all of
> this...
>
> Reviewing the code more - I now have a different understanding of what
> Dev_Table is meant to be.
>
> I think that Dev_Table is supposed to be an array of
> Dev_Table_Ptr_Type (an array of pointer addresses) that point to the
> Dev_Table_Type array of Config_Type records.

Yuo said:
   The original code has the following statements:

   type Dev_Table_Type is array (Device_Num_Type range <>) of Config_Type;
   type Dev_Table_Ptr_Type is access Dev_Table_Type;
   Dev_Table := Dev_Table_Ptr_Type;
   Bounds_Ptr : Global_Types.Int_Ptr_Type;

which looks pretty clear to me! If that's what the original compiler
worked with, then .... oh. It can't possibly be what the original
compiler worked with; just look at

   Dev_Table := Dev_Table_Ptr_Type;

.... perhaps the '=' is a typo?

Assuming it is, then Dev_Table is a pointer to an array of Config_Types.

> Stepping through the code with GDB has shed some light, although not a
> solution to my problem, quite yet.
>
> The problem I'm running into is a SegFault when the code tries to
> assign a value read from the data file.
>
>   Dev_Table(Dev_Num).Dev_Name := Current_Dev_Name;
>
> GDB cannot resolve what Dev_Table(Dev_Num) is - I'm thinking because
> it and Ada isn't seeing Dev_Table as an array of pointers.

GDB doesn't always understand things completely.

Dev_Table(Dev_Num) is an implicit dereference of the pointer Dev_Table,
which desgnates the Dev_Num'th element of the array or Config_Types; and
.Dev_Name is the record component of that element. It could have been
written

   Dev_Table.all(Dev_Num).Dev_Name := Current_Dev_Name;

In passing, I see someone with a C background was responsible for the
naming conventions. Why Dev_Name? just Name would have done
perfectly. Oh well, the least of your worries, I'm sure!