$ cc -Wall -O2 -o leak_tap_lock leak_tap_lock.c
built: ./leak_tap_lock
BUILD_EXIT=0
-rwxr-xr-x 1 root wheel 10584 Jul  2 17:02 leak_tap_lock
(no warnings — the prior unused-variable 'st' was removed when the
 waitpid(WNOHANG) detection replaced the kill(pid,0) check)