trap 'echo xxx' 1 2 3 15
read x
is not interrupted by ^C (due to restartable read syscall) and must be
interrupted per POSIX
Worse case:
read -t 5 x
hangs forever after ^C pressed (supposed to timeout after 5 secs)
Fixed by adding siginterrupt(signo, 1) after catch handler installed
2) Do not reinstall sighandler immediately after it is called,
BSD do it for us