From: Eli Zaretskii <eliz@gnu.org>
Date: Fri, 27 May 2016 09:17:15 +0000 (+0300)
Subject: Fix infloop in 'number-sequence'
X-Git-Tag: emacs-25.0.95~36
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=f7ffc4b;p=emacs.git
Fix infloop in 'number-sequence'
* lisp/subr.el (number-sequence): Avoid overflow leading to an
infloop. (Bug#23627)
* test/automated/subr-tests.el (number-sequence-test): New test.
---
diff --git a/lisp/subr.el b/lisp/subr.el
index 3ac61f9a45f..43660d74377 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -484,13 +484,16 @@ of course, also replace TO with a slightly larger value
(list from)
(or inc (setq inc 1))
(when (zerop inc) (error "The increment can not be zero"))
- (let (seq (n 0) (next from))
+ (let (seq (n 0) (next from) (last from))
(if (> inc 0)
- (while (<= next to)
+ ;; The (>= next last) condition protects against integer
+ ;; overflow in computing NEXT.
+ (while (and (>= next last) (<= next to))
(setq seq (cons next seq)
n (1+ n)
+ last next
next (+ from (* n inc))))
- (while (>= next to)
+ (while (and (<= next last) (>= next to))
(setq seq (cons next seq)
n (1+ n)
next (+ from (* n inc)))))
diff --git a/test/automated/subr-tests.el b/test/automated/subr-tests.el
index 7906a207a96..ce212903c9d 100644
--- a/test/automated/subr-tests.el
+++ b/test/automated/subr-tests.el
@@ -61,6 +61,15 @@
(quote
(0 font-lock-keyword-face))))))))
+(ert-deftest number-sequence-test ()
+ (should (= (length
+ (number-sequence (1- most-positive-fixnum) most-positive-fixnum))
+ 2))
+ (should (= (length
+ (number-sequence
+ (1+ most-negative-fixnum) most-negative-fixnum -1))
+ 2)))
+
(ert-deftest string-comparison-test ()
(should (string-lessp "abc" "acb"))
(should (string-lessp "aBc" "abc"))