Don't crash with invalid argument in check-coding-systems-region

* src/coding.c (Fcheck_coding_systems_region): Don't crash if
the third arg contains something that isn't a coding system.
* test/src/coding-tests.el (coding-check-coding-systems-region):
New test.

1 files changed, 8 insertions, 0 deletions

diff --git a/test/src/coding-tests.el b/test/src/coding-tests.el
index 83a06b8179e..8d92bcdcd1a 100644
--- a/test/src/coding-tests.el
+++ b/test/src/coding-tests.el
@@ -411,6 +411,14 @@
         (should (eq (decode-coding-string s coding t) s))
         (should (eq (encode-coding-string s coding t) s))))))
 
+(ert-deftest coding-check-coding-systems-region ()
+  (should (equal (check-coding-systems-region "aå" nil '(utf-8))
+                 nil))
+  (should (equal (check-coding-systems-region "aåbγc" nil
+                                              '(utf-8 iso-latin-1 us-ascii))
+                 '((iso-latin-1 3) (us-ascii 1 3))))
+  (should-error (check-coding-systems-region "å" nil '(bad-coding-system))))
+
 ;; Local Variables:
 ;; byte-compile-warnings: (not obsolete)
 ;; End: