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Re: [Gcl-devel] New random tester failures

From: Paul F. Dietz
Subject: Re: [Gcl-devel] New random tester failures
Date: Tue, 30 Nov 2004 07:52:00 -0600
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.2) Gecko/20040803

Camm Maguire wrote:

Thanks again, Paul as always!  OK, try it again now please.  Have made
use of the side-effect flag in the optimizer to push intermediary
values to the C stack.

Ok, this appears to be working now.

I've checked in the updated random tester, along with a bug fix in
the pruner.  I'm seeing one kind of failure now, related to
side effects in INCF/DECF forms.  Section 5.1.3 requires
that expressions like

    (incf x (setf x y))

perform the setf *before* retrieving the value from x to be
incremented (so x ends up = to (+ y y).)  gcl is doing this
differently in the compiler and the interpreter.

Many other lisps get this wrong in both compile and eval;
I added tests for this to incf.lsp and decf.lsp the other
day after gcl showed I had missed testing this possibility.

Since I can change the failure rate by tweaking various
parameters in the random form generator, it might be
interesting to try increasing the failure rate via
a genetic algorithm, or perhaps just setting those
parameters randomly before each iteration.


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