SetTimer() now uses setitimer() to sending SIGALRM every ` UnitTimeoutSec/2 + 1` s Set UnitTimeoutSec with the `-timeout=` option "POSIX.1-2008 marks getitimer() and setitimer() obsolete" and also has some issues regarding accuracy of the timers under load . See https://linux.die.net/man/2/setitimer. I propose using timer_create() and sigaction() ,See http://man7.org/linux/man-pages/man2/timer_create.2.html # test result on my x86_64 linux `make check-fuzzer` 
See http://llvm.org/docs/LibFuzzer.html