GNU bug report logs - #29520
peval leaves behind dangling lexical reference

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From: Mark H Weaver <mhw <at> netris.org>
To: Stefan Israelsson Tampe <stefan.itampe <at> gmail.com>
Cc: 29520 <at> debbugs.gnu.org
Subject: bug#29520: peval leaves behind dangling lexical reference
Date: Mon, 04 Dec 2017 16:10:00 -0500

Mark H Weaver <mhw <at> netris.org> writes:

> Mark H Weaver <mhw <at> netris.org> writes:
>
>> I believe the problem is most likely in 'lift-applied-lambda' in
>> peval.scm.  When transforming:
>>
>>   (lambda args (apply (lambda ...) args)) => (lambda ...)
>>
>> it does not appear to check whether 'args' is referenced within the
>> inner lambda.

It occurs to me that there's another problem with this optimization:

  scheme@(guile-user)> ,optimize (lambda (x y . z) (apply (lambda x x) x y z))
  $1 = (lambda x x)

This optimization changes the arity of the procedure.  The original
version checks that at least 2 arguments are provided, and ensures that
at least 2 arguments are passed to the inner procedure, which the code
might depend on.  The optimization effectively removes this check.

I'll look into how to fix this.

       Mark

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