updated for version 7.4.158

Problem:    Pattern containing \zs is not handled correctly by substitute().
Solution:   Change how an empty match is skipped. (Yukihiro Nakadaira)

src/eval.c

@@ -24365,7 +24365,7 @@ do_string_sub(str, pat, sub, flags)
     garray_T	ga;
     char_u	*ret;
     char_u	*save_cpo;
-    int		zero_width;
+    char_u	*zero_width = NULL;
 
     /* Make 'cpoptions' empty, so that the 'l' flag doesn't work here */
     save_cpo = p_cpo;
@@ -24382,6 +24382,19 @@ do_string_sub(str, pat, sub, flags)
 	tail = str;
 	while (vim_regexec_nl(&regmatch, str, (colnr_T)(tail - str)))
 	{
+	    /* Skip empty match except for first match. */
+	    if (regmatch.startp[0] == regmatch.endp[0])
+	    {
+		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;
+		    continue;
+		}
+		zero_width = regmatch.startp[0];
+	    }
+
 	    /*
 	     * Get some space for a temporary buffer to do the substitution
 	     * into.  It will contain:
@@ -24404,17 +24417,9 @@ do_string_sub(str, pat, sub, flags)
 	    (void)vim_regsub(&regmatch, sub, (char_u *)ga.ga_data
 					  + ga.ga_len + i, TRUE, TRUE, FALSE);
 	    ga.ga_len += i + sublen - 1;
-	    zero_width = (tail == regmatch.endp[0]
-				    || regmatch.startp[0] == regmatch.endp[0]);
 	    tail = regmatch.endp[0];
 	    if (*tail == NUL)
 		break;
-	    if (zero_width)
-	    {
-		/* avoid getting stuck on a match with an empty string */
-		*((char_u *)ga.ga_data + ga.ga_len) = *tail++;
-		++ga.ga_len;
-	    }
 	    if (!do_all)
 		break;
 	}

src/testdir/test80.in

@@ -175,6 +175,23 @@ ENDTEST
 
 TEST_9:
 
+STARTTEST
+:set magic&
+:set cpo&
+:$put =\"\n\nTEST_9:\"
+:$put ='xxx'
+:s/x/X/gc
+yyq/^TEST_10:
+ENDTEST
+
+TEST_10:
+
+STARTTEST
+:set magic&
+:set cpo&
+:$put =\"\n\nTEST_10:\"
+:let y = substitute('123', '\zs', 'a', 'g')             | $put =y
+:let y = substitute('123', '\zs.', 'a', 'g')            | $put =y
 :let y = substitute('123', '.\zs', 'a', 'g')            | $put =y
 :let y = substitute('123', '\ze', 'a', 'g')             | $put =y
 :let y = substitute('123', '\ze.', 'a', 'g')            | $put =y

src/testdir/test80.ok

@@ -115,3 +115,14 @@ N,,NZ
 c
 %
 
+
+TEST_7:
+A
+A
+B
+B
+-abab
+c-cbcbc
+
+
+TEST_8:

src/version.c

@@ -738,6 +738,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    158,
 /**/
     157,
 /**/