From: Noam Postavsky <npostavs@users.sourceforge.net>
To: Tino Calancha <tino.calancha@gmail.com>
Cc: 29799@debbugs.gnu.org, monnier@iro.umontreal.ca
Subject: bug#29799: 24.5; cl-loop guard clause missing
Date: Mon, 01 Jan 2018 16:46:30 -0500 [thread overview]
Message-ID: <874lo5tfpl.fsf@users.sourceforge.net> (raw)
In-Reply-To: <87d138beur.fsf@gmail.com> (Tino Calancha's message of "Thu, 21 Dec 2017 18:38:20 +0900")
Tino Calancha <tino.calancha@gmail.com> writes:
> (require 'cl-lib)
> (let* ((size 7)
> (arr (make-vector size 0)))
> (cl-loop for k below size
> for x = (* 2 k) and y = (1+ (elt arr k))
> collect (list k x y)))
>
>
> When you execute the form above it fails because
> the loop overrun `arr'.
A simpler example:
(require 'cl-lib)
(cl-loop for k below 3
for x = (progn (message "k = %d" k) 1)
and y = 1)
prints
k = 0
k = 1
k = 2
k = 3
in *Messages*. The expansion looks like this:
(cl-block nil
(let* ((k 0))
(let ((x nil)
(y nil))
(let* ((--cl-var-- t))
(while (< k 3)
(cl-psetq x
(if --cl-var--
(progn
(message "k = %d" k)
1)
x)
y (if --cl-var-- 1 y))
(setq k (+ k 1))
(cl-psetq x (progn
(message "k = %d" k)
1)
y 1)
(setq --cl-var-- nil))
nil))))
I don't understand why the "then" step is put at the of the loop. The
following patch (commenting out the "ands" branch) avoids doing that,
and fixes this bug. But presumably there is some reason for having this
code in the first place? I guess some more complicated example would be
needed to show why this naive fix won't work.
--- i/lisp/emacs-lisp/cl-macs.el
+++ w/lisp/emacs-lisp/cl-macs.el
@@ -1288,7 +1288,7 @@ cl--parse-loop-clause
(then (if (eq (car cl--loop-args) 'then)
(cl--pop2 cl--loop-args) start)))
(push (list var nil) loop-for-bindings)
- (if (or ands (eq (car cl--loop-args) 'and))
+ (if nil ;(or ands (eq (car cl--loop-args) 'and))
(progn
(push `(,var
(if ,(or cl--loop-first-flag
next prev parent reply other threads:[~2018-01-01 21:46 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-21 9:38 bug#29799: 24.5; cl-loop guard clause missing Tino Calancha
2018-01-01 21:46 ` Noam Postavsky [this message]
2018-01-01 22:58 ` Noam Postavsky
2018-01-03 10:34 ` Tino Calancha
2018-01-06 13:43 ` Noam Postavsky
2018-01-08 10:20 ` Tino Calancha
2019-10-28 3:59 ` dick.r.chiang
2019-11-21 23:25 ` dick.r.chiang
2019-11-22 12:55 ` Lars Ingebrigtsen
2019-11-22 13:51 ` dick.r.chiang
2019-11-22 14:53 ` Lars Ingebrigtsen
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