With a somewhat recent Git master (commit [2725a88d5e3ec362a4f866f53c26ca20f943eb49](https://gitweb.torproject.org/tor.git/shortlog/2725a88d5e3ec362a4f866f53c26ca20f943eb49)): ``` Oct 09 19:13:41.000 [info] circuit_expire_building(): Abandoning circ [redacted] (state 3:open, purpose 6) Oct 09 19:13:41.000 [info] internal (high-uptime) circ (length 4): [redacted](open) [redacted](open) [redacted](open) [redacted](open) Oct 09 19:13:41.000 [err] _circuit_mark_for_close(): Bug: circuitlist.c:1222: _circuit_mark_for_close: Assertion ocirc->rend_data failed; aborting. ``` (`CIRCUIT_PURPOSE_C_INTRODUCING == 6`) The assertion occurred in the following chunk of code, added to help fix legacy/trac#3825: ``` } else if (circ->purpose == CIRCUIT_PURPOSE_C_INTRODUCING && reason != END_STREAM_REASON_TIMEOUT) { origin_circuit_t *ocirc = TO_ORIGIN_CIRCUIT(circ); tor_assert(ocirc->build_state->chosen_exit); tor_assert(ocirc->rend_data); log_info(LD_REND, "Failed intro circ %s to %s " "(building circuit to intro point). " "Marking intro point as possibly unreachable.", safe_str_client(ocirc->rend_data->onion_address), safe_str_client(build_state_get_exit_nickname(ocirc->build_state))); rend_client_report_intro_point_failure(ocirc->build_state->chosen_exit, ocirc->rend_data, INTRO_POINT_FAILURE_UNREACHABLE); ``` But we should never have a circuit with that purpose with its `rend_data` field unset.