Ah, ça aide vachement :
Core was generated by `/usr/bin/unbound -d -p'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x00007404a8942976 in ?? () from /usr/lib/libevent-2.1.so.7
(gdb) where
#0 0x00007404a8942976 in ?? () from /usr/lib/libevent-2.1.so.7
#1 0x00007404a894a344 in event_base_loop () from /usr/lib/libevent-2.1.so.7
...
#7 0x00007404a8039d4c in __libc_start_main () from /usr/lib/libc.so.6
#8 0x0000597888960375 in ?? ()
(gdb)