severity 639658 important retitle 639658 [kfreebsd] waitpid from a thread does not work for child processes created by other threads reassign 639658 kfreebsd-8, kfreebsd-9, eglibc --
As you can see, the main thread delegates the waitpid call to a sub-thread. But both threads are still part of the same process, so waitpid should not fail. Debian GNU/kFreeBSD: ./debian-kfreebsd-amd64:~# ./forkthread PID: 719 waitpid: No child processes
It is known limitation of our current linuxthreads based pthread implementation. It cannot be solved easily :-(
The fix probably will be mainly in eglibc part. Petr