--- a/src/window.c
+++ b/src/window.c
@@ -6816,6 +6816,87 @@ frame_check_width(frame_T *topfrp, int w
     return TRUE;
 }
 
+#if defined(FEAT_SYN_HL) || defined(PROTO)
+/*
+ * Simple int comparison function for use with qsort()
+ */
+    static int
+int_cmp(const void *a, const void *b)
+{
+    return *(const int *)a - *(const int *)b;
+}
+
+/*
+ * Handle setting 'colorcolumn' or 'textwidth' in window "wp".
+ * Returns error message, NULL if it's OK.
+ */
+    char *
+check_colorcolumn(win_T *wp)
+{
+    char_u	*s;
+    int		col;
+    int		count = 0;
+    int		color_cols[256];
+    int		i;
+    int		j = 0;
+
+    if (wp->w_buffer == NULL)
+	return NULL;  // buffer was closed
+
+    for (s = wp->w_p_cc; *s != NUL && count < 255;)
+    {
+	if (*s == '-' || *s == '+')
+	{
+	    // -N and +N: add to 'textwidth'
+	    col = (*s == '-') ? -1 : 1;
+	    ++s;
+	    if (!VIM_ISDIGIT(*s))
+		return e_invarg;
+	    col = col * getdigits(&s);
+	    if (wp->w_buffer->b_p_tw == 0)
+		goto skip;  // 'textwidth' not set, skip this item
+	    col += wp->w_buffer->b_p_tw;
+	    if (col < 0)
+		goto skip;
+	}
+	else if (VIM_ISDIGIT(*s))
+	    col = getdigits(&s);
+	else
+	    return e_invarg;
+	color_cols[count++] = col - 1;  // 1-based to 0-based
+skip:
+	if (*s == NUL)
+	    break;
+	if (*s != ',')
+	    return e_invarg;
+	if (*++s == NUL)
+	    return e_invarg;  // illegal trailing comma as in "set cc=80,"
+    }
+
+    vim_free(wp->w_p_cc_cols);
+    if (count == 0)
+	wp->w_p_cc_cols = NULL;
+    else
+    {
+	wp->w_p_cc_cols = ALLOC_MULT(int, count + 1);
+	if (wp->w_p_cc_cols != NULL)
+	{
+	    // sort the columns for faster usage on screen redraw inside
+	    // win_line()
+	    qsort(color_cols, count, sizeof(int), int_cmp);
+
+	    for (i = 0; i < count; ++i)
+		// skip duplicates
+		if (j == 0 || wp->w_p_cc_cols[j - 1] != color_cols[i])
+		    wp->w_p_cc_cols[j++] = color_cols[i];
+	    wp->w_p_cc_cols[j] = -1;  // end marker
+	}
+    }
+
+    return NULL;  // no error
+}
+#endif
+
 #if defined(FEAT_EVAL) || defined(PROTO)
     int
 win_getid(typval_T *argvars)