sigpending
doesn't tell you whether a signal is blocked. It tells you whether a signal is waiting to be delivered. (i.e., the signal is blocked and one has been sent.)
Also, blocked doesn't meean that the signal won't be delivered; it means that the signal won't be delivered now. So you can send the signal, and it will be delivered as soon as the signal is unblocked; probably after the call to sigprocmask(SIGUNBLOCKED...)
but before the call to printf
, so you'll probably see the signal received message before you see the "unblocking" message.