rb_hash_compare_by_id_p 2605 hash.c         static VALUE rb_hash_compare_by_id_p(VALUE hash);
rb_hash_compare_by_id_p 2626 hash.c             if (rb_hash_compare_by_id_p(hash)) return hash;
rb_hash_compare_by_id_p 4330 hash.c             rb_define_method(rb_cHash,"compare_by_identity?", rb_hash_compare_by_id_p, 0);