Re: [PATCH 2/3] container_of: remove useless pair of parentheses

[Vincent Mailhol <mailhol@kernel.org>]

On 15/07/2026 at 16:30, Alexey Dobriyan wrote:
> On Tue, Jul 14, 2026 at 08:18:02PM +0200, Vincent Mailhol wrote:
>> The last expression in container_of() doesn't need an extra pair of
>> parenthesis. Remove it.
>>
>> Signed-off-by: Vincent Mailhol <mailhol@kernel.org>
>> ---
>>  include/linux/container_of.h | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/include/linux/container_of.h b/include/linux/container_of.h
>> index 28500a62ab7e..68153170db32 100644
>> --- a/include/linux/container_of.h
>> +++ b/include/linux/container_of.h
>> @@ -21,7 +21,7 @@
>>  	static_assert(__same_type(*(ptr), typeof_member(type, member)) || \
>>  		      __same_type(*(ptr), void),			\
>>  		      "pointer type mismatch in container_of()");	\
>> -	((type *)(__mptr - offsetof(type, member))); })
>> +	(type *)(__mptr - offsetof(type, member)); })
> 
> container_of_const() has the same problem.

Yes. But scoped I my series to the container_of() macro only.

I don't plan to send a follow-up patch to remove the other useless
parenthesis. The things which really bothered me was the __mptr
variable which I removed in patch #3. And with that, I am done with
what I wanted to contribute in this file.

But you are welcome to do this clean-up if you feel the need for it.

> And it should parenthesize first argument to _Generic.

Do you mean like this:

	#define container_of_const(ptr, type, member)				\
		_Generic((ptr),							\
			const typeof(*(ptr)) *: ((const type *)container_of(ptr, type, member)),\
			default: ((type *)container_of(ptr, type, member))	\
		)

?

Why would parenthesis be needed here? I don't see what kind of
expression would make the current implementation unsafe.


Yours sincerely,
Vincent Mailhol