Function mpi::ffi::MPI_Comm_create_keyval

pub unsafe extern fn MPI_Comm_create_keyval(comm_copy_attr_fn: MPI_Comm_copy_attr_function,
                                            comm_delete_attr_fn: MPI_Comm_delete_attr_function,
                                            comm_keyval: *mut c_int,
                                            extra_state: *mut c_void)
                                            -> c_int