GNU bug report logs - #21899
let/ec continuations not distinct under compiler

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Message #14 received at 21899 <at> debbugs.gnu.org (full text, mbox):

From: Zefram <zefram <at> fysh.org>
To: Andy Wingo <wingo <at> pobox.com>, 21899 <at> debbugs.gnu.org
Subject: Re: bug#21899: let/ec continuations not distinct under compiler
Date: Fri, 24 Jun 2016 18:00:38 +0100

Andy Wingo wrote:
>  ,opt (let* ((x (list 'a))
>              (y (list 'a)))
>         (list x y))
>  ;; ->
>  (let* ((x (list 'a)) (y x)) (list x y))

Wow, that's a scary level of wrongitude.  It's specific to let* (or
equivalent nested let forms), but really easy to trigger within that:

scheme@(guile-user)> (let ((x (list 'a)) (y (list 'a))) (eq? x y))
$1 = #f
scheme@(guile-user)> (let* ((x (list 'a)) (y (list 'a))) (eq? x y))
$2 = #t
scheme@(guile-user)> (let ((x (list 'a))) (let ((y (list 'a))) (eq? x y)))
$3 = #t

-zefram

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