Fix string-to-multibyte overlong sequence bug

* src/character.h (MULTIBYTE_LENGTH, MULTIBYTE_LENGTH_NO_CHECK):
Remove, replacing with ...
(multibyte_length): ... this new function.  All callers changed.
The new function rejects overlong multibyte forms.
* test/src/buffer-tests.el (buffer-multibyte-overlong-sequences):
New test.

1 files changed, 14 insertions, 0 deletions

diff --git a/test/src/buffer-tests.el b/test/src/buffer-tests.el
index 1c356698f66..6e87cb94897 100644
--- a/test/src/buffer-tests.el
+++ b/test/src/buffer-tests.el
@@ -1313,4 +1313,18 @@ with parameters from the *Messages* buffer modification."
         (ovshould nonempty-eob-end 4 5)
         (ovshould empty-eob        5 5)))))
 
+(ert-deftest buffer-multibyte-overlong-sequences ()
+  (dolist (uni '("\xE0\x80\x80"
+                 "\xF0\x80\x80\x80"
+                 "\xF8\x8F\xBF\xBF\x80"))
+    (let ((multi (string-to-multibyte uni)))
+      (should
+       (string-equal
+        multi
+        (with-temp-buffer
+          (set-buffer-multibyte nil)
+          (insert uni)
+          (set-buffer-multibyte t)
+          (buffer-string)))))))
+
 ;;; buffer-tests.el ends here