enumerator.c: add comment

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42706 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,6 +1,7 @@
 Tue Aug 27 16:51:21 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
-	* enumerator.c (enumerator_each): ensure argument array size is int.
+	* enumerator.c (enumerator_each): ensure that argument array size
+	  does not overflow at appending.
 
 Tue Aug 27 16:46:05 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 

enumerator.c

@@ -448,6 +448,7 @@ enumerator_each(int argc, VALUE *argv, VALUE obj)
 	VALUE args = e->args;
 	if (args) {
 #if SIZEOF_INT < SIZEOF_LONG
+	    /* check int range overflow */
 	    rb_long2int(RARRAY_LEN(args) + argc);
 #endif
 	    args = rb_ary_dup(args);