Issue #21704 has been updated by ioquatix (Samuel Williams). @akr
Why Process::Status object is created in such situations?
Because `Process::Status` represents either "the result of waitpid" or "errno of waitpid" and is used to transfer this information until it's finally consumed by the end user, e.g. as an instance of `Process::Status` or raising an error as per `Process.wait` etc. IOW, it captures the full fidelity result of `waitpid`. Technically, it might be preferential to write something like: ``` Process.wait -> Process::Status.new or raise ``` But due to the internal design, it's not that simple. And things like the scheduler still need to pass both "status" and "errno" back to the caller, and when I say "errno", I don't actually mean the global errno, as `errno` could be passed back via epoll, kqueue or io_uring data structures. I'm not strongly in favour of this API but we probably need something like it (accepts both the result of waitpid as well as the "errno"). ---------------------------------------- Feature #21704: Expose rb_process_status_new to C extensions https://bugs.ruby-lang.org/issues/21704#change-116925 * Author: noteflakes (Sharon Rosner) * Status: Open ---------------------------------------- A fiber scheduler implementation with a hook for `#process_wait` needs to return a `Process::Status` object, but currently it is not possible for a C extension to directly create an instance of `Process::Status`. The technique currently used in various fiber scheduler implementations is to use `pidfd_open`, poll for fd readiness, then call `Process::Status.wait`, which creates the instance. On recent Linux kernels (6.7 or newer), `io_uring_prep_waitid` can be used to directly wait for process termination, which provides us with the pid and status of the terminated child process, but there's no way to directly create an instance of `Process::Status`, required for implementing the `#process_wait` hook. Exposing the internal `rb_process_status_new` function would allow such an implementation. Using `io_uring_prep_waitid` would also lead to better compatibility of fiber schedulers with calls to `Process.wait(0)` or `Process.wait(-1)`, as those cannot be done using `pidfd_open`. The associated PR is here: https://github.com/ruby/ruby/pull/15213 An working fiber scheduler implementation of `process_wait` using `io_uring_prep_waitid` has been submitted here: https://github.com/socketry/io-event/pull/154 -- https://bugs.ruby-lang.org/