为什么该过程处理被阻止的信号？

Consider the following program:

考虑以下程序:

void handler(int signum){
    printf("handling %d\n", signum);
}

int main() {
    signal(SIGINT, handler);
    sigset_t *ss;
    sigemptyset(ss);
    sigaddset(ss, SIGINT);
    sigprocmask(SIG_BLOCK, ss, NULL);
    for(;;);
    return 0;
}
voi