Please check the output by valgrind as below.
==2292==
==2292== Process terminating with default action of signal 11 (SIGSEGV)
==2292== Access not within mapped region at address 0x18
==2292== at 0x4E57967: fill_default (in /usr/lib/libnetconf.so.0.0)
==2292== by 0x4E57CC4: ncdflt_default_values (in /usr/lib/libnetconf.so.0.0)
==2292== by 0x4E32764: ncds_apply_transapi (in /usr/lib/libnetconf.so.0.0)
==2292== by 0x4E36309: ncds_apply_rpc (in /usr/lib/libnetconf.so.0.0)
==2292== by 0x4E366E4: ncds_apply_rpc2all (in /usr/lib/libnetconf.so.0.0)
==2292== by 0x4019BB: handle_rpc_default_message (in /usr/lib/siara/bin/testserverd)
==2292== by 0x401D96: handle_rpc_message (in /usr/lib/siara/bin/testserverd)
==2292== by 0x401E15: run_event_loop (in /usr/lib/siara/bin/testserverd)
==2292== by 0x402380: main (in /usr/lib/siara/bin/testserverd)
==2292== If you believe this happened as a result of a stack
==2292== overflow in your program's main thread (unlikely but
==2292== possible), you can try to increase the size of the
==2292== main thread stack using the --main-stacksize= flag.
==2292== The main thread stack size used in this run was 8388608.
==2292==
==2292== Events : Ir
==2292== Collected : 649176894
==2292==
==2292== I refs: 649,176,894
Killed