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From: Ludovic Brenta <ludovic@ludovic-brenta.org>
Newsgroups: comp.lang.ada
Subject: Re: Debugging Ada
Date: Wed, 21 Dec 2011 20:46:16 +0100
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Date: 2011-12-21T20:46:16+01:00
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awdorrin <awdorrin@gmail.com> writes:
> Ah, I see what you are saying. I don't think that is what is going on
> in this situation.
>
> The code I'm working with is a mix of Ada and C, and it was originally
> written under Ada83.
>
> The 'SysConfig' package is importing a C character array:
>   char g_cfg_file_names[100][128]; (up to 100 file names, 128
> characters each)
> as:
>   pragma Import( C, CFG_FILES, "g_cfg_file_names");
>
> LAN_CFG is part of an enumeration defined in the SysConfig package to
> map to the index numbers of that array.

OK, I think I understand the problem better too.  Your initial
description of the problem was:

> Then in the package's main procedure when I try to use the
> LAN_CFG_FILE, sometimes the value is corrupted.

I'm beginning to think that perhaps the elaboration order varies between
compilations.  The pragma Import (C, CFG_FILES, "g_cfg_file_names")
indicates that:

- the Ada language rules require that g_cfg_file_names is elaborated
  before LAN_CFG_FILE
- the Ada compiler cannot enforce this rule, so it simply assumes that
  the rule is followed
- the C compiler must emit code that elaborates *and* initializes
  g_cfg_file_names.  It is possible that what you see as "corrupted" is
  simply an uninitialized value.
- the binder must emit code that calls the C initialization routine
  *before* the elaboration of LAN_CFG_FILE

Maybe you should inspect the binder-generated file (b~*.adb) to see what
happens.  It is this file that does the elaboration, so it is fairly
easy to see what gets elaborated first.  Also, you can place a
breakpoint in this file, just like in any other file, before running
your program in gdb.  This might help too.

HTH

-- 
Ludovic Brenta.