Obtained 23 stack frames.
/usr/games/crawl-0.23(_Z17write_stack_traceP8_IO_FILEi+0x23) [0x6ca153]: write_stack_trace(_IO_FILE*, int)
/usr/games/crawl-0.23(_Z20crash_signal_handleri+0x174) [0x6ca4a4]: crash_signal_handler(int)
/lib/x86_64-linux-gnu/libc.so.6(+0x33060) [0x7f74d75a1060]: 
/usr/games/crawl-0.23() [0x8d35b0]
/lib/x86_64-linux-gnu/libc.so.6(+0x33060) [0x7f74d75a1060]: 
/lib/x86_64-linux-gnu/libpthread.so.0(waitpid+0x18) [0x7f74d791dae8]: 
/usr/games/crawl-0.23(_Z8call_gdbP8_IO_FILE+0x1c3) [0x6ca7c3]: call_gdb(_IO_FILE*)
/usr/games/crawl-0.23(_Z13do_crash_dumpv+0x3d9) [0x6d19a9]: do_crash_dump()
/usr/games/crawl-0.23(_Z20crash_signal_handleri+0x74) [0x6ca3a4]: crash_signal_handler(int)
/lib/x86_64-linux-gnu/libc.so.6(+0x33060) [0x7f74d75a1060]: 
/lib/x86_64-linux-gnu/libpthread.so.0(raise+0xcf) [0x7f74d791df9f]: 
/usr/games/crawl-0.23() [0x6d1104]
/usr/games/crawl-0.23() [0x6d138a]
/usr/games/crawl-0.23(_ZNK9PlaceInfo15assert_validityEv+0xbc) [0xa69d6c]: PlaceInfo::assert_validity() const
/usr/games/crawl-0.23(_Z10load_level20dungeon_feature_type14load_mode_typeRK8level_id+0x1906) [0x78ed26]: load_level(dungeon_feature_type, load_mode_type, level_id const&)
/usr/games/crawl-0.23(_Z16floor_transition20dungeon_feature_typeS_8level_idbbbb+0x33d) [0xb47a6d]: floor_transition(dungeon_feature_type, dungeon_feature_type, level_id, bool, bool, bool, bool)
/usr/games/crawl-0.23(_Z11take_stairs20dungeon_feature_typebbb+0x36e) [0xb4a63e]: take_stairs(dungeon_feature_type, bool, bool, bool)
/usr/games/crawl-0.23(_ZN5Delay6handleEv+0x41) [0x6e81a1]: Delay::handle()
/usr/games/crawl-0.23(_Z12handle_delayv+0x30) [0x6e9f60]: handle_delay()
/usr/games/crawl-0.23() [0xc45d7a]
/usr/games/crawl-0.23(main+0x55d) [0x62c58d]: 
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf1) [0x7f74d758e2e1]: 
/usr/games/crawl-0.23() [0x62d3f5]