Question

What happens to a child process that dies and has no parent process to wait for it and what's bad about this?

Answer 1

What happens to the child process really depends on the program you are running.

If the parent process is terminated, then the child process is terminated, too.

Some program might inform you that the child process is going to be terminated and might prompt you to save the work or to let the whole process be executed.

Some programs might automatically save the progress and the child process could be executed when the parent process is run again.

Some programs readily terminate the child process along with the parent ones.

In all of the above cases, the actions might be or might not be logged into a log file.

All really depends on the program in question.