waitpid and warn_unused_result

[Eric Blake]

Any objections to making the gnulib <sys/wait.h> apply the gcc 
warn_unused_result attribute to waitpid(), even though glibc does not 
(yet) do likewise?  After all, if you fail to check for failures on this 
syscall (particularly EINTR failures, where you should normally repeat 
the waitpid() call), you can end up leaking unreaped child processes, 
which is a rather nasty resource leak to debug.

I ask this because Coverity was complaining about a couple places where 
libvirt was calling waitpid() and ignoring the return value.

--
Eric Blake   address@hidden    +1-801-349-2682
Libvirt virtualization library http://libvirt.org