From: Eli Barzilay
Subject: A strange bug with ACL4.3's compiler??
Date: 
Message-ID: <skg10wzwjw.fsf@mojave.cs.cornell.edu>
I just had a strange bug popping up in a small piece of code - when I
compiled my program with safety < 3, the following comparison fails:

  (= (aref *f-labels* f) (aref *labels* s))

what it is getting is always the same result, 0 - even when I print
the two arrays just before doing this, and making sure that both
defenitely hold #(0 1 2) and that the two indices are different!

Then I discovered that wrapping this by a safety setting of 3 (since I
had a global 0 setting before) cured the bug.

Have I gone crazy?  Is there any bug in the compiler - I thought that
changing compiler settings should not change a program when it doesn't
do "bad" things...
-- 
          ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
         http://www.cs.cornell.edu/eli/meaning.html        Maze is Life!
From: Stig Hemmer
Subject: Re: A strange bug with ACL4.3's compiler??
Date: 
Message-ID: <ekvaer4bjq2.fsf@epoksy.pvv.ntnu.no>
Eli Barzilay <ยทยทยท@mojave.cs.cornell.edu> writes:
> I just had a strange bug popping up in a small piece of code - when I
> compiled my program with safety < 3, the following comparison fails:
> 
>   (= (aref *f-labels* f) (aref *labels* s))

Write the shortest possible piece of code that demonstrates the
problem.  Start from a fresh image, use DRIBBLE, execute the code.

If it still looks like a bug, report to Franz. Include the dribble.

Stig Hemmer,
Jack of a Few Trades.