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

[Warner Losh]

On Mon, Nov 30, 2020 at 9:56 AM Michal Meloun <meloun.michal at gmail.com>
wrote:

>
>
> 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.
>

__unused means 'don't warn me if this is unused' elsewhere in the tree.
Better to use it here.

Warner