build: FAILED conformance/interfaces/fork/18-1: build: FAILED: Compiler output: conformance/interfaces/fork/18-1.c:108:18: error: variable has incomplete type 'struct sigevent' struct sigevent se; ^ conformance/interfaces/fork/18-1.c:108:9: note: forward declaration of 'struct sigevent' struct sigevent se; ^ conformance/interfaces/fork/18-1.c:118:20: error: use of undeclared identifier 'SIGEV_THREAD' se.sigev_notify = SIGEV_THREAD; ^ conformance/interfaces/fork/18-1.c:124:8: warning: implicit declaration of function 'timer_create' is invalid in C99 [-Wimplicit-function-declaration] ret = timer_create( CLOCK_REALTIME, &se, &tmr ); ^ conformance/interfaces/fork/18-1.c:140:8: warning: implicit declaration of function 'timer_settime' is invalid in C99 [-Wimplicit-function-declaration] ret = timer_settime( tmr, 0, &it, NULL ); ^ 2 warnings and 2 errors generated.