On 8/30/2019 3:02 PM, Michael S. Tsirkin wrote:
> On Tue, Aug 27, 2019 at 03:20:57PM +0000, Matej Genci wrote:
>> Compilers such as g++ 7.3 complain about assigning void* variable to
>> a non-void* variable (like struct pointers) and pointer arithmetics
>> on void*.
>>
>> Signed-off-by: Matej Genci <matej.ge...@nutanix.com>
>> ---
>> include/uapi/linux/virtio_ring.h | 9 +++++----
>> 1 file changed, 5 insertions(+), 4 deletions(-)
>>
>> diff --git a/include/uapi/linux/virtio_ring.h
>> b/include/uapi/linux/virtio_ring.h
>> index 4c4e24c291a5..2c339b9e2923 100644
>> --- a/include/uapi/linux/virtio_ring.h
>> +++ b/include/uapi/linux/virtio_ring.h
>> @@ -168,10 +168,11 @@ static inline void vring_init(struct vring *vr,
>> unsigned int num, void *p,
>> unsigned long align)
>> {
>> vr->num = num;
>> - vr->desc = p;
>> - vr->avail = p + num*sizeof(struct vring_desc);
>> - vr->used = (void *)(((uintptr_t)&vr->avail->ring[num] +
>> sizeof(__virtio16)
>> - + align-1) & ~(align - 1));
>> + vr->desc = (struct vring_desc *)p;
>> + vr->avail = (struct vring_avail *)((uintptr_t)p
>> + + num*sizeof(struct vring_desc));
>> + vr->used = (struct vring_used *)(((uintptr_t)&vr->avail->ring[num]
>> + + sizeof(__virtio16) + align-1) & ~(align - 1));
>> }
>>
>> static inline unsigned vring_size(unsigned int num, unsigned long align)
>
> I'm not really interested in building with g++, sorry.
> Centainly not if it makes code less robust by forcing
> casts where they weren't previously necessary.
Can you elaborate on how these casts make the code less robust?
They aren't necessary in C but I think being explicit can improve
readability as argued in
https://softwareengineering.stackexchange.com/a/275714
>
> However, vring_init and vring_size are legacy APIs anyway,
> so I'd be happy to add ifndefs that will allow userspace
> simply hide these functions if it does not need them.
>
I feel like my patch is a harmless way of allowing this header
to be used in C++ projects, but I'm happy to drop it in lieu of
the guards if you feel strongly about it.
Thanks.
Matej
>
>> --
>> 2.22.0
>>
