Re: [PATCH] virtio: fix "warning: ‘queue’ may be used uninitialized"

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Apr 05, 2016 at 09:34:24AM -0400, Jeff Mahoney wrote:
> On 4/5/16 4:04 AM, Michael S. Tsirkin wrote:
> > On Mon, Apr 04, 2016 at 02:14:19PM -0400, Jeff Mahoney wrote:
> >> This fixes the following warning:
> >> drivers/virtio/virtio_ring.c:1032:5: warning: ‘queue’ may be used
> >> uninitialized in this function
> >>
> >> The conditions that govern when queue is set aren't apparent to gcc.
> >>
> >> Setting queue = NULL clears the warning.
> >>
> >> Signed-off-by: Jeff Mahoney <jeffm@suse.com>
> > 
> > Which gcc version produces this warning?
> > I do not seem to see it with gcc 5.3.1.
> 
> gcc version 4.8.5 (SUSE Linux)

Looks like a minor compiler bug then, fixed since.
I don't think we need to worry about that this.

> > Also - use uninitialized_var then?
> 
> If it were a fast path, sure, but otherwise the use of uninitialized_var
> just makes similar issues harder to debug if the code changes.
> 
> -Jeff

Same does = NULL though. It's not like things will work with queue ==
NULL, so it'll still crash if it's not inited properly.

> >> ---
> >>
> >>  drivers/virtio/virtio_ring.c |    2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> --- a/drivers/virtio/virtio_ring.c
> >> +++ b/drivers/virtio/virtio_ring.c
> >> @@ -1006,7 +1006,7 @@ struct virtqueue *vring_create_virtqueue
> >>  	const char *name)
> >>  {
> >>  	struct virtqueue *vq;
> >> -	void *queue;
> >> +	void *queue = NULL;
> >>  	dma_addr_t dma_addr;
> >>  	size_t queue_size_in_bytes;
> >>  	struct vring vring;
> >>
> >> -- 
> >> Jeff Mahoney
> >> SUSE Labs
> > 
> 
> 
> -- 
> Jeff Mahoney
> SUSE Labs
> 



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