Re: [PATCH v2 07/10] selftests/nolibc: avoid unused arguments warnings

[Thomas Weißschuh]

Aug 1, 2023 12:15:27 Zhangjin Wu <falcon@xxxxxxxxxxx>:

> Hi, Thomas
>
>> On 2023-08-01 10:07:28+0200, Willy Tarreau wrote:
>>> On Tue, Aug 01, 2023 at 07:30:14AM +0200, Thomas Weißschuh wrote:
>>>> This warnings will be enabled later so avoid triggering it.
>>>>
>>>> Signed-off-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx>
>>>> ---
>>>> tools/testing/selftests/nolibc/nolibc-test.c | 3 ++-
>>>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
>>>> index 53a3773c7790..cb17cccd0bc7 100644
>>>> --- a/tools/testing/selftests/nolibc/nolibc-test.c
>>>> +++ b/tools/testing/selftests/nolibc/nolibc-test.c
>>>> @@ -1089,7 +1089,8 @@ static int smash_stack(void)
>>>>     return 1;
>>>> }
>>>>
>>>> -static int run_protection(int min, int max)
>>>> +static int run_protection(int __attribute__((unused)) min,
>>>> +             int __attribute__((unused)) max)
>>>
>>> This one is used to silence -Wunused-parameter I guess.
>>
>> Yep.
>>
>>> It's one of
>>> the rare warnings that I find totally useless in field, because it's
>>> simply against the principle of using function pointers with different
>>> functions having the same interface but different implementations. As
>>> your code evolves you end up with unused on absolutely *all* of the
>>> arguments of *all* such functions, which makes them a real pain to add
>>> and tends to encourage poor practices such as excessive code reuse just
>>> by laziness or boredom. BTW it's one of those that are already disabled
>>> in the kernel and we could very well do the same here.
>>
>> It's indeed unfortunate.
>>
>> As long as we don't have too many of them I would prefer to keep the
>> explicit annotations. While they are ugly we then can still reap the
>> positive aspects of the warning.
>>
>> This is where -std=c89 bites us. With extensions (or C2X) we could also
>> just leave off the argument name to mark it as unused:
>>     run_protection(int, int)
>
> what about further simply ignore the arguments like we did for main(void)?

That doesn't work because it is stored as a function pointer in the testcases array.
And these members all take the two parameters.