Fix setting a range of char-table slots in a singular case

* src/chartab.c (char_table_set_range): Start the loop from the
first character of the block to which FROM belongs.  (Bug#23797)

* test/src/chartab-tests.el: New test file.

2 files changed, 52 insertions, 1 deletions

diff --git a/src/chartab.c b/src/chartab.c
index 6cf8fea0b6d..fa5a8e41164 100644
--- a/src/chartab.c
+++ b/src/chartab.c
@@ -492,7 +492,7 @@ char_table_set_range (Lisp_Object table, int from, int to, Lisp_Object val)
       int lim = CHARTAB_IDX (to, 0, 0);
       int i, c;
 
-      for (i = CHARTAB_IDX (from, 0, 0), c = 0; i <= lim;
+      for (i = CHARTAB_IDX (from, 0, 0), c = i * chartab_chars[0]; i <= lim;
            i++, c += chartab_chars[0])
         {
           if (c > to)
diff --git a/test/src/chartab-tests.el b/test/src/chartab-tests.el
new file mode 100644
index 00000000000..016ddcdde61
--- /dev/null
+++ b/test/src/chartab-tests.el
@@ -0,0 +1,51 @@
+;;; chartab-tests.el --- Tests for char-tab.c
+
+;; Copyright (C) 2016 Free Software Foundation, Inc.
+
+;; Author: Eli Zaretskii <eliz@gnu.org>
+
+;; This program is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Code:
+
+(require 'ert)
+
+(defun chartab-set-and-test (rng)
+  (let ((tbl (make-char-table nil nil))
+        (from (car rng))
+        (to (cdr rng)))
+    (set-char-table-range tbl rng t)
+    (should (eq (aref tbl from) t))
+    (should (eq (aref tbl to) t))
+    (should (eq (aref tbl (/ (+ from to) 2)) t))
+    (when (< to (max-char))
+      (should-not (eq (aref tbl (1+ to)) t)))
+    (when (> from 0)
+      (should-not (eq (aref tbl (1- from)) t)))))
+
+(ert-deftest chartab-test-range-setting ()
+  (mapc (lambda (elt)
+          (chartab-set-and-test elt))
+        '((0 . 127)
+          (128 . 256)
+          (#x1000 . #x1fff)
+          (#x1001 . #x2000)
+          (#x10000 . #x20000)
+          (#x10001 . #x1ffff)
+          (#x20000 . #x30000)
+          (#xe0e00 . #xe0ef6)
+          )))
+
+(provide 'chartab-tests)
+;;; chartab-tests.el ends here