pub unsafe extern "C" fn sk_find(
    sk: *const _STACK,
    out_index: *mut usize,
    p: *const c_void,
    call_cmp_func: Option<unsafe extern "C" fn(arg1: stack_cmp_func, arg2: *mut *const c_void, arg3: *mut *const c_void) -> c_int>
) -> c_int