First off, the manual is really excellent, thank you to everyone involved.

Section 28.6.2 Initializing the Shell sets the signal handler for SIGCHLD to SIG_IGN, but does not explain why.

As a consequence, in Section 28.6.5 Stopped and Terminated Jobs, wait_for_job always calls mark_process_status with pid=-1 and status=ECHILD, causing jobs in the first_job linked list to never get updated.

This is the correct behavior given POSIX:

> If the parent process of the calling process has set its SA_NOCLDWAIT flag or has set the action for the SIGCHLD signal to SIG_IGN:
> ...
> If a thread in the parent process of the calling process is blocked in wait(), waitpid(), or waitid(), and the parent process has no remaining child processes in the set of waited-for children, the wait(), waitid(), or waitpid() function shall fail and set errno to [ECHILD].

http://pubs.opengroup.org/onlinepubs/9699919799/

The paragraphs above the example in Section 28.6.5 Stopped and Terminated Jobs do call out installing/uninstalling the signal handler for SIGCHLD during specific times of the program's execution. However, it does not document this issue.

Potential Patches:

1. Remove the `signal (SIGCHLD, SIG_IGN);` line from Section 28.6.2 Initializing the Shell
2. Reset the signal handler for SIGCHLD back to SIG_IGN before calling waitpid in update_status and wait_for_job and use this as an opportunity to explain this behavior as an edit to the documentation in Section 28.6.5 Stopped and Terminated Jobs.