Messages in this thread | | | From | Arnd Bergmann <> | Date | Mon, 7 Aug 2017 22:20:58 +0200 | Subject | Re: [PATCH v06 33/36] uapi linux/fsmap.h: use __kernel_size_t instead of size_t |
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On Mon, Aug 7, 2017 at 6:45 PM, Darrick J. Wong <darrick.wong@oracle.com> wrote: > On Mon, Aug 07, 2017 at 06:01:43PM +0200, Arnd Bergmann wrote: >> On Mon, Aug 7, 2017 at 5:54 PM, Darrick J. Wong <darrick.wong@oracle.com> wrote: >> > On Sun, Aug 06, 2017 at 06:44:24PM +0200, Mikko Rapeli wrote: >> >> Either way works, but including a system header from a kernel header >> requires an additional "#ifndef __KERNEL__" check, so I think Miko's >> variant is a little nicer. >> >> Generally speaking, you also want to avoid including system headers >> indirectly from kernel headers, as POSIX requires that including one >> system header should not indirectly make symbols from other system >> headers visible. I think this is not a problem here though, as no system >> header should include linux/fsmap.h. > > Sorry, I guess I was a little unclear about what I was asking -- I was > wondering why can't the userspace program include sys/types.h prior to > linux/fsmap.h? I wasn't proposing including C library headers in kernel > headers. > > I think the patch author is pushing towards kernel headers never relying > on /anything/ in the system headers.
Right, and I think that is a good thing to have, because it allows us to do better compile-time testing of the exported kernel headers.
> For data structures being > exchanged with the kernel I agree, but the fsmap_sizeof result is never > passed to or received from the kernel; it exists purely for malloc > convenience.
Would you prefer making fsmap_sizeof a macro? That would also make it possible to do static checking on the header without having to resort to odd types.
Arnd
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