commit https://github.com/vim/vim/commit/b9644433d2728e99fab874e5e33147ad95d23a31 Author: Bram Moolenaar <Bram@vim.org> Date: Tue Jul 19 12:33:44 2016 +0200 patch 7.4.2068 Problem: Not all arguments of trunc_string() are tested. Memory access error when running the message tests. Solution: Add another test case. (Yegappan Lakshmanan) Make it easy to run unittests with valgrind. Fix the access error.

--- a/src/message.c
+++ b/src/message.c
@@ -298,9 +298,9 @@ trunc_string(
 	{
 	    do
 		half = half - (*mb_head_off)(s, s + half - 1) - 1;
-	    while (utf_iscomposing(utf_ptr2char(s + half)) && half > 0);
+	    while (half > 0 && utf_iscomposing(utf_ptr2char(s + half)));
 	    n = ptr2cells(s + half);
-	    if (len + n > room)
+	    if (len + n > room || half == 0)
 		break;
 	    len += n;
 	    i = half;