__slist_splice_after
__slist_splice_after(__pos._M_node, __before_first._M_node,
__slist_splice_after(__pos._M_node,
__slist_splice_after(__slist_previous(&_M_head, __pos._M_node),
__slist_splice_after(__slist_previous(&_M_head, __pos._M_node),
__slist_splice_after(__slist_previous(&_M_head, __pos._M_node),
__slist_splice_after(__n1, &__x._M_head, __x._M_head._M_next);
__slist_splice_after(&__carry._M_head, &_M_head, _M_head._M_next);
__slist_splice_after(__n1, &__x._M_head, __x._M_head._M_next);
__slist_splice_after(&__carry._M_head, &_M_head, _M_head._M_next);