Issue #21704 has been updated by akr (Akira Tanaka). rb_process_status_new is declared in the PR as follows. ``` /** * Creates a new instance of Process::Status. * * @param[in] pid The process ID. * @param[in] status The "waitpid status", as returned by waitpid(2). This is NOT the exit status/exit code, see waitpid(2). * @param[in] error Error code (if waitpid(2) returned -1). * @return VALUE An instance of Process::Status. */ VALUE rb_process_status_new(rb_pid_t pid, int status, int error); ``` I doubt about `error` argument. If waitpid(2) returns -1, waitpid is failed. Why Process::Status object is created in such situations? What does it mean? I feel the API is not well designed. ---------------------------------------- Feature #21704: Expose rb_process_status_new to C extensions https://bugs.ruby-lang.org/issues/21704#change-115580 * 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/