[dpdk-dev] [PATCH] examples/vhost: fix strict aliasing error on gcc 4.4.7

[Xie, Huawei]

On 12/8/2015 7:24 PM, De Lara Guarch, Pablo wrote:
> Fixes following error on gcc 4.4.7:
>
> make: Entering directory `/tmp/dpdk-tmp/examples/vhost'
>   CC main.o
> cc1: warnings being treated as errors
> /tmp/dpdk-tmp/examples/vhost/main.c: In function ‘new_device’:
> /tmp/dpdk-tmp/x86_64-native-linuxapp-gcc/include/rte_ring.h:740: error:
>     dereferencing pointer ‘mbuf.486’ does break strict-aliasing rules
> /tmp/dpdk-tmp/examples/vhost/main.c:1503: note: initialized from here
> ...
> /tmp/dpdk-tmp/examples/vhost/main.c:1503: note: initialized from here
> /tmp/dpdk-tmp/x86_64-native-linuxapp-gcc/include/rte_ring.h:740: error:
>     dereferencing pointer ‘({anonymous})’ does break strict-aliasing rules
> /tmp/dpdk-tmp/examples/vhost/main.c:1804: note: initialized from here
> make[1]: *** [main.o] Error 1
>
> Fixes: d19533e8 ("examples/vhost: copy old vhost example")
>
> Reported-by: Qian Xu <qian.q.xu at intel.com>
> Signed-off-by: Pablo de Lara <pablo.de.lara.guarch at intel.com>
> ---
>  examples/vhost/main.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
>
[...]
>  
> -	rte_ring_sc_dequeue(vpool->ring, (void **)&mbuf);
> +	rte_ring_sc_dequeue(vpool->ring, (void **)&obj);
> +	mbuf = (struct rte_mbuf *)obj;
Is rte_ring_sc_dequeue(vpool->ring, &obj) enough? Applied to the later
enqueue as well.
>  	if (unlikely(mbuf == NULL)) {
[...]
> -		rte_ring_sp_enqueue(vpool->ring, (void *)mbuf);
> +		rte_ring_sp_enqueue(vpool->ring, obj);
>  		return;
>  	}
>  
> @@ -1789,7 +1791,8 @@ virtio_tx_route_zcp(struct virtio_net *dev, struct rte_mbuf *m,
>  {
>  	
[...]
>  	vpool = &vpool_array[MAX_QUEUES + vmdq_rx_q];
> -	rte_ring_sc_dequeue(vpool->ring, (void **)&mbuf);
> +	rte_ring_sc_dequeue(vpool->ring, (void **)&obj);
> +	mbuf = (struct rte_mbuf *) obj;
>  	if (unlikely(mbuf == NULL)) {
>  		struct vhost_virtqueue *vq = dev->virtqueue[VIRTIO_TXQ];
>  		RTE_LOG(ERR, VHOST_DATA,