How to make child process die after parent exits?

Question

Suppose I have a process which spawns exactly one child process. Now when the parent process exits for whatever reason (normally or abnormally, by kill, ^C, assert failure o

Answer 1

As other people have pointed out, relying on the parent pid to become 1 when the parent exits is non-portable. Instead of waiting for a specific parent process ID, just wait for the ID to change:

pit_t pid = getpid();
switch (fork())
{
    case -1:
    {
        abort(); /* or whatever... */
    }
    default:
    {
        /* parent */
        exit(0);
    }
    case 0:
    {
        /* child */
        /* ... */
    }
}

/* Wait for parent to exit */
while (getppid() != pid)
    ;

Add a micro-sleep as desired if you don't want to poll at full speed.

This option seems simpler to me than using a pipe or relying on signals.