> 2025年4月17日 22:08，Ard Biesheuvel <a...@kernel.org> 写道：
>
> On Thu, 17 Apr 2025 at 15:12, Coly Li <i...@coly.li> wrote:
>>
>>
>>
>>> 2025年4月17日 15:10，Kees Cook <k...@kernel.org> 写道：
>>>
>>>
>>>
>>> On April 16, 2025 11:16:45 PM PDT, Ard Biesheuvel <a...@kernel.org> wrote:
>>>> On Thu, 17 Apr 2025 at 00:01, Kees Cook <k...@kernel.org> wrote:
>>>>>
>>>>> GCC 15's new -Wunterminated-string-initialization notices that the 16
>>>>> character lookup table "zero_uuid" (which is not used as a C-String)
>>>>> needs to be marked as "nonstring":
>>>>>
>>>>> drivers/md/bcache/super.c: In function 'uuid_find_empty':
>>>>> drivers/md/bcache/super.c:549:43: warning: initializer-string for array
>>>>> of 'char' truncates NUL terminator but destination lacks 'nonstring'
>>>>> attribute (17 chars into 16 available)
>>>>> [-Wunterminated-string-initialization]
>>>>> 549 | static const char zero_uuid[16] =
>>>>> "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
>>>>> |
>>>>> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>>>
>>>>> Add the annotation to silence the GCC warning.
>>>>>
>>>>> Signed-off-by: Kees Cook <k...@kernel.org>
>>>>> ---
>>>>> Cc: Coly Li <col...@kernel.org>
>>>>> Cc: Kent Overstreet <kent.overstr...@linux.dev>
>>>>> Cc: linux-bca...@vger.kernel.org
>>>>> ---
>>>>> drivers/md/bcache/super.c | 2 +-
>>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
>>>>> index e42f1400cea9..577d048170fe 100644
>>>>> --- a/drivers/md/bcache/super.c
>>>>> +++ b/drivers/md/bcache/super.c
>>>>> @@ -546,7 +546,7 @@ static struct uuid_entry *uuid_find(struct cache_set
>>>>> *c, const char *uuid)
>>>>>
>>>>> static struct uuid_entry *uuid_find_empty(struct cache_set *c)
>>>>> {
>>>>> - static const char zero_uuid[16] =
>>>>> "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
>>>>> + static const char zero_uuid[] __nonstring =
>>>>> "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
>>>>>
>>>>
>>>> Just
>>>>
>>>> static const char zero_uuid[16] = {};
>>>>
>>>> should work fine here too. No need for the initializer.
>>>
>>> 🤦 Yes. This is what I get for fixing dozens of these. I'll send a v2...
>>
>>
>> Can we do this,
>>
>> static const char zero_uuid[16] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
>> 0, 0};
>>
>> I like the explicit array element number 16, and the explicit uuid content
>> by obvious zero (‘0’) symbols. They provide redundant information.
>> Not sure whether GCC 15 complains or not.
>>
>
> Even the {} initializer is entirely redundant, given that the variable
> has static linkage, and so C guarantees that it will be zero
> initialized.
>
> Could you use NULL_GUID and be done with it?
I feel the “static” here is an optimization to avoid initializing zero_uuid
again ….
Kent,
Am I right?
Coly Li
