updated for version 7.4.323

Problem:    Substitute() with zero width pattern breaks multi-byte character.
Solution:   Take multi-byte character size into account. (Yukihiro Nakadaira)

src/eval.c

@@ -24848,8 +24848,11 @@ do_string_sub(str, pat, sub, flags)
 		if (zero_width == regmatch.startp[0])
 		{
 		    /* avoid getting stuck on a match with an empty string */
-		    *((char_u *)ga.ga_data + ga.ga_len) = *tail++;
-		    ++ga.ga_len;
+		    i = MB_PTR2LEN(tail);
+		    mch_memmove((char_u *)ga.ga_data + ga.ga_len, tail,
+								   (size_t)i);
+		    ga.ga_len += i;
+		    tail += i;
 		    continue;
 		}
 		zero_width = regmatch.startp[0];

src/testdir/test69.in

@@ -179,6 +179,13 @@ ENDTEST
 byteidx
 byteidxcomp
 
+STARTTEST
+/^substitute
+:let y = substitute('１２３', '\zs', 'a', 'g')    | put =y
+ENDTEST
+
+substitute
+
 STARTTEST
 :g/^STARTTEST/.,/^ENDTEST/d
 :1;/^Results/,$wq! test.out

src/testdir/test69.ok

@@ -160,3 +160,7 @@ byteidxcomp
 [0, 1, 3, 4, -1]
 [0, 1, 2, 4, 5, -1]
 
+
+substitute
+a１a２a３a
+

src/version.c

@@ -734,6 +734,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    323,
 /**/
     322,
 /**/