Write a program to demonstrate that different threads in the same process can have different sets of pending signals, as returned by sigpending(). You can do this by using pthread_kill() to send different signals to two different threads that have blocked these signals, and then have each of the threads call sigpending() and display information about pending signals. (You may find the functions in Example 20-4 useful.)

Suppose that a thread creates a child using fork(). When the child terminates, is it guaranteed that the resulting SIGCHLD signal will be delivered to the thread that called fork() (as opposed to some other thread in the process)?