GNU bug report logs - #9769
Misplaced tail call optimization

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: ludo <at> gnu.org (Ludovic Courtès)
To: bug-guile <at> gnu.org
Subject: Misplaced tail call optimization
Date: Sun, 16 Oct 2011 22:29:00 +0200

(This is a copy of <http://savannah.gnu.org/bugs/?34300>, so it doesn't
get lost.  :-))

Consider this example:

  (define bar
    (lambda ()
      (let ((fail (lambda () 'fail)))
        (let loop ((a (iota 3)))
          (if (pair? a)
              (loop (cdr a))
              (fail)))
        (pk 'done))))

This function should return 'done but it instead returns 'fail, because both
the call to `loop' and the call to `fail' are compiled as if they were tail
calls.

To reproduce the test, turn partial evaluation off---otherwise the call to
`fail' is inlined and the problem doesn't show up.

Ludo'.

Message #8 received at 9769 <at> debbugs.gnu.org (full text, mbox):

From: Andy Wingo <wingo <at> pobox.com>
To: ludo <at> gnu.org (Ludovic Courtès)
Cc: 9769 <at> debbugs.gnu.org
Subject: Re: bug#9769: Misplaced tail call optimization
Date: Mon, 17 Oct 2011 10:33:12 +0200

The title of this bug isn't quite right.  It's not that Guile is
intentionally treating the call to fail as a tail call; it's some
bug in the way that "labels allocated" procedures in compile-glil.scm
are called.

Andy
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Message #13 received at 9769-done <at> debbugs.gnu.org (full text, mbox):

From: Andy Wingo <wingo <at> pobox.com>
To: ludo <at> gnu.org (Ludovic Courtès)
Cc: 9769-done <at> debbugs.gnu.org
Subject: Re: bug#9769: Misplaced tail call optimization
Date: Thu, 20 Oct 2011 23:51:20 +0200

Fixed in git.  Thanks for the report!

commit aa9c19858872a135ea959066fff26f86527a1bd0
Author: Andy Wingo <wingo <at> pobox.com>
Date:   Thu Oct 20 23:50:05 2011 +0200

    fix misallocation of some <fix> procedures
    
    * module/language/tree-il/analyze.scm (analyze-lexicals): When stepping
      into a non-tail form, we know that labels allocation will be invalid,
      so use an empty labels set.  Fixes http://debbugs.gnu.org/9769.
    
    * test-suite/tests/tree-il.test ("labels allocation"): Add a test.

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