[BLACKBOX] Exporting records / record fields question

From: [at]} <Chris>
Date: Tue, 27 Jul 2010 11:57:16 +0930

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A possible anomaly has been reported in the Oberon-07 compiler in our
Astrobe system - it is possible to export a field of a record even though
the record type itself is not exported. I couldn't find a definitive
description of this behaviour in the Oberon-07 language report so I checked
BlackBox to see how Component Pascal handles a similar situation. My
experiment shows that it is also allowed in CP.

For example, in CP I was able to write the following definitions in one
module:

MODULE M;

  TYPE
    T = RECORD (* not exported *)
      x*: INTEGER (* exported *)
    END;
 
  VAR
    v*: T;
  ...
  ...

I was then able to access the exported field in a client module like so:

  M.v.x := 99;

However, when I checked the 'interface' of module M using BlackBox I only
saw:

DEFINITION M;

  VAR
    v: T;

END M.

My questions are:

1. Can you think of any real-world scenarios where this would be useful? If
so what should the 'interface' show?

2. Can you think of any problems / side-effects associated with being able
to do this?

3. Would it be a good thing or a bad thing if a compiler reported an error
if you tried to export a field from a record if the record type itself was
not exported?

Regards,
Chris Burrows
CFB Software

Astrobe: ARM Oberon-07 Development System
http://www.astrobe.com

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Received on Tue Jul 27 2010 - 04:27:16 UTC