pub unsafe extern "C" fn ffi_prep_closure( arg1: *mut ffi_closure, arg2: *mut ffi_cif, fun: Option<unsafe extern "C" fn(arg1: *mut ffi_cif, arg2: *mut c_void, arg3: *mut *mut c_void, arg4: *mut c_void)>, user_data: *mut c_void) -> ffi_status