svn commit: r368187 - head/sys/dev/nvme

[Michal Meloun]

On 30.11.2020 17:02, Ian Lepore wrote:
> On Mon, 2020-11-30 at 14:51 +0000, Michal Meloun wrote:
>> Author: mmel
>> Date: Mon Nov 30 14:51:48 2020
>> New Revision: 368187
>> URL: https://svnweb.freebsd.org/changeset/base/368187
>>
>> Log:
>>    Unbreak r368167 in userland. Decorate unused arguments.
>>    
>>    Reported by:	kp, tuexen, jenkins, and many others
>>    MFC with:	r368167
>>
>> Modified:
>>    head/sys/dev/nvme/nvme.h
>>
>> Modified: head/sys/dev/nvme/nvme.h
>> =====================================================================
>> =========
>> --- head/sys/dev/nvme/nvme.h	Mon Nov 30 14:49:13 2020	(r368186)
>> +++ head/sys/dev/nvme/nvme.h	Mon Nov 30 14:51:48 2020	(r368187)
>> @@ -1728,9 +1728,15 @@ extern int nvme_use_nvd;
>>   
>>   #endif /* _KERNEL */
>>   
>> +#if _BYTE_ORDER != _LITTLE_ENDIAN
>> +#define MODIF
>> +#else
>> +#define MODIF __unused
>> +#endif
>> +
>>   /* Endianess conversion functions for NVMe structs */
>>   static inline
>> -void	nvme_completion_swapbytes(struct nvme_completion *s)
>> +void	nvme_completion_swapbytes(struct nvme_completion *s MODIF)
> 
> IMO, this is pretty ugly, it causes the brain to screech to a halt when
> you see it.  Why not just add an unconditional __unused to the
> functions?  The unused attribute is defined as marking the variable as
> "potentially unused" -- there is no penalty for having it there and
> then actually using the variable.
> 

I understand, (and I have significant tendency to agree) but I did not 
find more correct way how to do it.
Are you sure that __unused is defined as *potentially* unused?  I cannot 
find nothing about this and you known how are compiler guys creative 
with generating of new warnings...
I known that C++17 have 'maybe_unused' attribute, but relationship to 
standard '__unused' looks unclear.

In any case, I have not single problem to change this to the proposed 
style if we found that this is the optimal way.

Michal