1 files changed, 22 insertions, 2 deletions
diff --git a/src/nvim/globals.h b/src/nvim/globals.h
index 301a2c1663..f81fb43eaf 100644
--- a/src/nvim/globals.h
+++ b/src/nvim/globals.h
@@ -788,8 +788,28 @@ EXTERN int vr_lines_changed INIT(= 0);      /* #Lines changed by "gR" so far */
 /// Encoding used when 'fencs' is set to "default"
 EXTERN char_u *fenc_default INIT(= NULL);
 
-// To speed up BYTELEN() we keep a table with the byte lengths for utf-8
-EXTERN char utf8len_tab[256];
+// To speed up BYTELEN(); keep a lookup table to quickly get the length in
+// bytes of a UTF-8 character from the first byte of a UTF-8 string.  Bytes
+// which are illegal when used as the first byte have a 1.  The NUL byte has
+// length 1.
+EXTERN char utf8len_tab[256] INIT(= {
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
+  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
+  3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
+  4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 1, 1,
+});
 
 # if defined(USE_ICONV) && defined(DYNAMIC_ICONV)
 /* Pointers to functions and variables to be loaded at runtime */