Re: [PATCH] virtio: Change typecasts in vring_init()

From: Michael S. Tsirkin
Date: Fri Aug 30 2019 - 10:02:42 EST


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.genci@xxxxxxxxxxx>
> ---
> 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.

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.


> --
> 2.22.0
>