extending wait4(2) or waitid(2) linux syscall

[Florian Weimer]

* Dave Martin:

> The traditional way would be install a handler for SIGCHLD and
> do a sigsuspend()/pselect()/ppoll().  Then when the suspend() returns,
> you pump the status of any children with wait*(..., WNOHANG).
>
> Does that not work for you for some reason?

Changing signal handlers is not what a library should do because they
are process-global (not even thread-specific).

Thanks,
Florian