(gdb) bt
#0  libtorrent::udp_tracker_connection::name_lookup (this=0xb518df80,
    error=@0xb6c08d50, i=
        {<boost::iterator_facade<asio::ip::basic_resolver_iterator<asio::ip::tcp >,const asio::ip::basic_resolver_entry<asio::ip::tcp>,boost::forward_traversal_t ag,const asio::ip::basic_resolver_entry<asio::ip::tcp>&,ptrdiff_t>> = {<No data fields>}, values_ = {px = 0x87dd298, pn = {pi_ = 0x86d2a20}}, iter_ = {_M_curren t = 0x87c4210}}) at ../asio/datagram_socket_service.hpp:151
#1  0xb7e78cf1 in asio::asio_handler_invoke<asio::detail::binder2<boost::_bi::bi nd_t<void, boost::_mfi::mf2<void, libtorrent::udp_tracker_connection, asio::erro r const&, asio::ip::basic_resolver_iterator<asio::ip::tcp> >, boost::_bi::list3< boost::_bi::value<boost::intrusive_ptr<libtorrent::udp_tracker_connection> >, bo ost::arg<1>, boost::arg<2> > >, asio::error, asio::ip::basic_resolver_iterator<a sio::ip::tcp> > > (function=
          {handler_ = {f_ = {f_ = {__pfn = 0xb7e6b7c0 <libtorrent::udp_tracker_c onnection::name_lookup(asio::error const&, asio::ip::basic_resolver_iterator<asi o::ip::tcp>)>, __delta = 0}}, l_ = {a1_ = {t_ = {p_ = 0xb518df80}}, a2_ = {<No d ata fields>}, a3_ = {<No data fields>}}}, arg1_ = {<> = {<No data fields>}, code _ = 0, what_ = {ptr = 0x0}}, arg2_ = {<boost::iterator_facade<asio::ip::basic_re solver_iterator<asio::ip::tcp>,const asio::ip::basic_resolver_entry<asio::ip::tc p>,boost::forward_traversal_tag,const asio::ip::basic_resolver_entry<asio::ip::t cp>&,ptrdiff_t>> = {<No data fields>}, values_ = {px = 0x87dd298, pn = {pi_ = 0x 86d2a20}}, iter_ = {_M_current = 0x87c4210}}})
    at udp_tracker_connection.cpp:104
---Type <return> to continue, or q <return> to quit---
#2  0xb7e78f78 in asio::detail::task_io_service<asio::detail::epoll_reactor<false> >::handler_wrapper<asio::detail::binder2<boost::_bi::bind_t<void, boost::_mfi::mf2<void, libtorrent::udp_tracker_connection, asio::error const&, asio::ip::basic_resolver_iterator<asio::ip::tcp> >, boost::_bi::list3<boost::_bi::value<boost::intrusive_ptr<libtorrent::udp_tracker_connection> >, boost::arg<1>, boost::arg<2> > >, asio::error, asio::ip::basic_resolver_iterator<asio::ip::tcp> > >::do_call (base=0x86d2a20) at /usr/include/boost/intrusive_ptr.hpp:83
#3  0xb7dd0cdb in asio::detail::task_io_service<asio::detail::epoll_reactor<false> >::run (this=0x81c9b68) at ../asio/detail/task_io_service.hpp:347
#4  0xb7dbe7f1 in libtorrent::detail::session_impl::operator() (this=0x82443ec)
    at ../asio/impl/io_service.ipp:35
#5  0xb7dde14d in boost::detail::function::void_function_obj_invoker0<libtorrent::detail::session_impl, void>::invoke (function_obj_ptr=
      {obj_ptr = 0x84157b4, const_obj_ptr = 0x84157b4, func_ptr = 0x84157b4, data = "&#65533;"}) at /usr/include/boost/function/function_template.hpp:136
#6  0xb7efd6e9 in boost::function0<void, std::allocator<boost::function_base> >::operator() () from /usr/lib/libboost_thread-mt.so.1.33.1
#7  0xb7efcc2d in boost::thread_group::join_all ()
   from /usr/lib/libboost_thread-mt.so.1.33.1
#8  0xb728a604 in __pthread_initialize_minimal () from /lib/libpthread.so.0
#9  0xb7126e6e in clone () from /lib/libc.so.6