Remove no-longer-needed integer overflow code

* lisp/calculator.el (calculator-number-to-string):
Use truncate, not calculator-truncate, since integer
overflow cannot occur here.
* lisp/calendar/cal-persia.el (calendar-persian-year-from-absolute):
* lisp/gnus/gnus-agent.el (gnus-agent-read-article-number):
* lisp/gnus/nnmaildir.el (nnmaildir--group-maxnum)
(nnmaildir--new-number):
* lisp/scroll-bar.el (scroll-bar-scale):
* lisp/simple.el (beginning-of-buffer, end-of-buffer):
Simplify, now that integer overflow cannot occur.

7 files changed, 10 insertions, 43 deletions

diff --git a/lisp/calculator.el b/lisp/calculator.el
index eec7aff5878..281151c7c25 100644
--- a/lisp/calculator.el
+++ b/lisp/calculator.el
@@ -1054,7 +1054,7 @@ the `left' or `right' when one of the standard modes is used."
      ;; print with radix -- for binary, convert the octal number
      (let* ((fmt (if (eq calculator-output-radix 'hex) "%x" "%o"))
             (str (if calculator-2s-complement num (abs num)))
-            (str (format fmt (calculator-truncate str)))
+            (str (format fmt (truncate str)))
             (bins '((?0 "000") (?1 "001") (?2 "010") (?3 "011")
                     (?4 "100") (?5 "101") (?6 "110") (?7 "111")))
             (str (if (not (eq calculator-output-radix 'bin)) str
diff --git a/lisp/calendar/cal-persia.el b/lisp/calendar/cal-persia.el
index 897208fd2b4..59fe52a592a 100644
--- a/lisp/calendar/cal-persia.el
+++ b/lisp/calendar/cal-persia.el
@@ -100,13 +100,7 @@ Gregorian date Sunday, December 31, 1 BC."
          (d2                         ; prior days not in n2820 or n768
           (mod d1 280506))
          (n1        ; years not in n2820 or n768
-          ;; Want:
-          ;; (floor (+ (* 2820 d2) (* 2820 366)) 1029983))
-          ;; but that causes overflow, so use the following.
-          ;; Use 366 as the divisor because (2820*366 mod 1029983) is small.
-          (let ((a (floor d2 366))
-                (b (mod d2 366)))
-            (+ 1 a (floor (+ (* 2137 a) (* 2820 b) 2137) 1029983))))
+          (floor (* 2820 (+ d2 366)) 1029983))
          (year (+ (* 2820 n2820)        ; complete 2820 year cycles
                   (* 768 n768)          ; complete 768 year cycles
                   ;; Remaining years.
diff --git a/lisp/files.el b/lisp/files.el
index 70865ebcdf1..81ca948bd2d 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -4959,8 +4959,8 @@ Uses `backup-directory-alist' in the same way as
               (list (make-backup-file-name fn))
             (cons (format "%s.~%d~" basic-name (1+ high-water-mark))
                   (if (and (> number-to-delete 0)
-                           ;; Delete nothing if there is overflow
-                           ;; in the number of versions to keep.
+                           ;; Delete nothing if kept-new-versions and
+                           ;; kept-old-versions combine to an outlandish value.
                            (>= (+ kept-new-versions kept-old-versions -1) 0))
                       (mapcar (lambda (n)
                                 (format "%s.~%d~" basic-name n))
diff --git a/lisp/gnus/gnus-agent.el b/lisp/gnus/gnus-agent.el
index a09b4368893..40d0d246056 100644
--- a/lisp/gnus/gnus-agent.el
+++ b/lisp/gnus/gnus-agent.el
@@ -1909,21 +1909,8 @@ article numbers will be returned."
 (defsubst gnus-agent-read-article-number ()
   "Reads the article number at point.  Returns nil when a valid article number can not be read."
 
-  ;; It is unfortunate but the read function quietly overflows
-  ;; integer.  As a result, I have to use string operations to test
-  ;; for overflow BEFORE calling read.
   (when (looking-at "[0-9]+\t")
-    (let ((len (- (match-end 0) (match-beginning 0))))
-      (cond ((< len 9)
-             (read (current-buffer)))
-            ((= len 9)
-             ;; Many 9 digit base-10 numbers can be represented in a 27-bit int
-             ;; Back convert from int to string to ensure that this is one of them.
-             (let* ((str1 (buffer-substring (match-beginning 0) (1- (match-end 0))))
-                    (num (read (current-buffer)))
-                    (str2 (int-to-string num)))
-               (when (equal str1 str2)
-                 num)))))))
+    (read (current-buffer))))
 
 (defsubst gnus-agent-copy-nov-line (article)
   "Copy the indicated ARTICLE from the overview buffer to the nntp server buffer."
diff --git a/lisp/gnus/nnmaildir.el b/lisp/gnus/nnmaildir.el
index 3becee35112..246f52c8d2b 100644
--- a/lisp/gnus/nnmaildir.el
+++ b/lisp/gnus/nnmaildir.el
@@ -322,8 +322,6 @@ This variable is set by `nnmaildir-request-article'.")
         (setq ino-opened (file-attribute-inode-number attr)
               nlink (file-attribute-link-number attr)
               number-linked (+ number-opened nlink))
-        (if (or (< nlink 1) (< number-linked nlink))
-            (signal 'error '("Arithmetic overflow")))
         (setq attr (file-attributes
                     (concat dir (number-to-string number-linked))))
         (or attr (throw 'return (1- number-linked)))
@@ -395,9 +393,7 @@ This variable is set by `nnmaildir-request-article'.")
         (let* ((attr (file-attributes path-open))
                (nlink (file-attribute-link-number attr)))
           (setq ino-open (file-attribute-inode-number attr)
-                number-link (+ number-open nlink))
-          (if (or (< nlink 1) (< number-link nlink))
-              (signal 'error '("Arithmetic overflow"))))
+                number-link (+ number-open nlink)))
         (if (= number-link previous-number-link)
             ;; We've already tried this number, in the previous loop iteration,
             ;; and failed.
diff --git a/lisp/scroll-bar.el b/lisp/scroll-bar.el
index dc0df7ab3fe..61fa754e390 100644
--- a/lisp/scroll-bar.el
+++ b/lisp/scroll-bar.el
@@ -49,9 +49,7 @@ from a scroll bar event, then (scroll-bar-scale SCROLL-BAR-POS
 \(buffer-size)) is the position in the current buffer corresponding to
 that scroll bar position."
   ;; We multiply before we divide to maintain precision.
-  ;; We use floating point because the product of a large buffer size
-  ;; with a large scroll bar portion can easily overflow a lisp int.
-  (truncate (/ (* (float (car num-denom)) whole) (cdr num-denom))))
+  (truncate (* (car num-denom) whole) (cdr num-denom)))
 
 (defun scroll-bar-columns (side)
   "Return the width, measured in columns, of the vertical scrollbar on SIDE.
diff --git a/lisp/simple.el b/lisp/simple.el
index 00265ece71e..e33709e8ad4 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -1037,12 +1037,8 @@ is supplied, or Transient Mark mode is enabled and the mark is active."
       (push-mark))
   (let ((size (- (point-max) (point-min))))
     (goto-char (if (and arg (not (consp arg)))
-                   (+ (point-min)
-                      (if (> size 10000)
-                          ;; Avoid overflow for large buffer sizes!
-                          (* (prefix-numeric-value arg)
-                             (/ size 10))
-                        (/ (+ 10 (* size (prefix-numeric-value arg))) 10)))
+                   (+ (point-min) 1
+                      (/ (* size (prefix-numeric-value arg)) 10))
                  (point-min))))
   (if (and arg (not (consp arg))) (forward-line 1)))
 
@@ -1060,11 +1056,7 @@ is supplied, or Transient Mark mode is enabled and the mark is active."
   (let ((size (- (point-max) (point-min))))
     (goto-char (if (and arg (not (consp arg)))
                    (- (point-max)
-                      (if (> size 10000)
-                          ;; Avoid overflow for large buffer sizes!
-                          (* (prefix-numeric-value arg)
-                             (/ size 10))
-                        (/ (* size (prefix-numeric-value arg)) 10)))
+                      (/ (* size (prefix-numeric-value arg)) 10))
                  (point-max))))
   ;; If we went to a place in the middle of the buffer,
   ;; adjust it to the beginning of a line.