Do not allow out-of-range character position in Fcompare_strings.

* src/fns.c (validate_subarray): Add prototype.
(Fcompare_substring): Use validate_subarray to check ranges.
Adjust comment to mention that the semantics was changed.  Also see
http://lists.gnu.org/archive/html/emacs-devel/2014-06/msg00447.html.
* lisp/files.el (dir-locals-find-file, file-relative-name):
* lisp/info.el (Info-complete-menu-item):
* lisp/minibuffer.el (completion-table-subvert): Prefer string-prefix-p
to compare-strings to avoid out-of-range errors.
* lisp/subr.el (string-prefix-p): Adjust to match strict range
checking in compare-strings.
* test/automated/fns-tests.el (fns-tests-compare-string): New test.

1 files changed, 31 insertions, 0 deletions

diff --git a/test/automated/fns-tests.el b/test/automated/fns-tests.el
index 21a9e4536af..461995b602e 100644
--- a/test/automated/fns-tests.el
+++ b/test/automated/fns-tests.el
@@ -69,3 +69,34 @@
     (nreverse A)
     (should (equal [nil nil nil nil nil t t t t t] (vconcat A)))
     (should (equal [t t t t t nil nil nil nil nil] (vconcat (nreverse A))))))
+
+(ert-deftest fns-tests-compare-strings ()
+  (should-error (compare-strings))
+  (should-error (compare-strings "xyzzy" "xyzzy"))
+  (should-error (compare-strings "xyzzy" 0 10 "zyxxy" 0 5))
+  (should-error (compare-strings "xyzzy" 0 5 "zyxxy" -1 2))
+  (should-error (compare-strings "xyzzy" 'foo nil "zyxxy" 0 1))
+  (should-error (compare-strings "xyzzy" 0 'foo "zyxxy" 2 3))
+  (should-error (compare-strings "xyzzy" 0 2 "zyxxy" 'foo 3))
+  (should-error (compare-strings "xyzzy" nil 3 "zyxxy" 4 'foo))
+  (should (compare-strings "" nil nil "" nil nil))
+  (should (compare-strings "" 0 0 "" 0 0))
+  (should (compare-strings "test" nil nil "test" nil nil))
+  (should (compare-strings "test" nil nil "test" nil nil t))
+  (should (compare-strings "test" nil nil "test" nil nil nil))
+  (should (compare-strings "Test" nil nil "test" nil nil t))
+  (should (= (compare-strings "Test" nil nil "test" nil nil) -1))
+  (should (= (compare-strings "Test" nil nil "test" nil nil) -1))
+  (should (= (compare-strings "test" nil nil "Test" nil nil) 1))
+  (should (= (compare-strings "foobaz" nil nil "barbaz" nil nil) 1))
+  (should (= (compare-strings "barbaz" nil nil "foobar" nil nil) -1))
+  (should (= (compare-strings "foobaz" nil nil "farbaz" nil nil) 2))
+  (should (= (compare-strings "farbaz" nil nil "foobar" nil nil) -2))
+  (should (compare-strings "abcxyz" 0 2 "abcprq" 0 2))
+  (should (compare-strings "abcxyz" 0 -3 "abcprq" 0 -3))
+  (should (= (compare-strings "abcxyz" 0 6 "abcprq" 0 6) 4))
+  (should (= (compare-strings "abcprq" 0 6 "abcxyz" 0 6) -4))
+  (should (compare-strings "xyzzy" -3 4 "azza" -3 3))
+  (should (compare-strings "こんにちはｺﾝﾆﾁﾊ" nil nil "こんにちはｺﾝﾆﾁﾊ" nil nil))
+  (should (= (compare-strings "んにちはｺﾝﾆﾁﾊこ" nil nil "こんにちはｺﾝﾆﾁﾊ" nil nil) 1))
+  (should (= (compare-strings "こんにちはｺﾝﾆﾁﾊ" nil nil "んにちはｺﾝﾆﾁﾊこ" nil nil) -1)))