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Date:Mon Feb 5 20:52:59 1993 
Subject:Re: Re: dlocals etc. (and shallow binding) 
From:Ray Dunn 
Volume-ID:930208.01 

In refd article, sfk@otter.hpl.hp.com (Steve Knight) writes:
>Ray Dunn writes on the subject of dynamic binding and the use of
>the value of identifiers before they are assigned to:
>> Of course not!  But that's the point.  It never was written into the
>> manual, so using the "feature" is intrinsically unsafe.  At any time, a
>> kind system maintainer could have, with perfect validity, decided to
>> initialize the values of locals on function entry to "undef".
>
>Just to clarify for any puzzled readers, this feature is excellently
>documented in Poplog and is completely reliable.

Sorry if I confused anyone.  I was just replying to Aaron's:

  >>[AS]
  >>But note that this has been a dependable feature of every Pop
  >>implementation for at least 22 years. Suppose it were written into
  >>the manual, would you still object to its use?

If the truth be known, my posted response was my third or fourth attempt,
through line disconnections then a system crash over two days.  The last
version was not as lucid as the first!!

>Any system
>maintainer's doing what Ray suggests would be summarily executed [*].

That lenient, eh?

Accessing uninitialized variables is one of the more common programming
errors, and one which can cause very subtle bugs.  On balance it's probably
unfortunate that locals were never initialized by the compiler to "undef"
or whatever, as we did from day one for globals.
-- 
Ray Dunn at home        |  Beaconsfield, Quebec  |  Phone: (514) 630 3749
ray@philmtl.philips.ca  |  ray@cam.org           |  uunet!sobeco!philmtl!ray