2016-04-01 14:20, Keith Wiles: > The new compiler option -Og causes a few warning on variables > being used before being set warnings.
Sometimes the compiler is wrong. It seems this option makes it even wronger. Why not use -Wno-error with -Og? More details below: > lib/librte_eal/linuxapp/eal/eal_pci_uio.c | 2 +- > lib/librte_lpm/rte_lpm6.c | 1 + > lib/librte_vhost/vhost_rxtx.c | 4 ++-- There are also some warnings in mlx drivers, solved with patch below: --- a/drivers/net/mlx4/mlx4.c +++ b/drivers/net/mlx4/mlx4.c @@ -5415,7 +5415,7 @@ mlx4_pci_devinit(struct rte_pci_driver *pci_drv, struct rte_pci_device *pci_dev) int err = 0; struct ibv_context *attr_ctx = NULL; struct ibv_device_attr device_attr; - unsigned int vf; + unsigned int vf = 0; int idx; int i; --- a/drivers/net/mlx5/mlx5.c +++ b/drivers/net/mlx5/mlx5.c @@ -260,8 +260,8 @@ mlx5_pci_devinit(struct rte_pci_driver *pci_drv, struct rte_pci_device *pci_dev) int err = 0; struct ibv_context *attr_ctx = NULL; struct ibv_device_attr device_attr; - unsigned int vf; - unsigned int mps; + unsigned int vf = 0; + unsigned int mps = 0; int idx; int i; > --- a/lib/librte_eal/linuxapp/eal/eal_pci_uio.c > +++ b/lib/librte_eal/linuxapp/eal/eal_pci_uio.c > @@ -152,7 +152,7 @@ pci_get_uio_dev(struct rte_pci_device *dev, char *dstbuf, > unsigned int buflen, int create) > { > struct rte_pci_addr *loc = &dev->addr; > - unsigned int uio_num; > + unsigned int uio_num = 0; This one is OK to fix. > --- a/lib/librte_lpm/rte_lpm6.c > +++ b/lib/librte_lpm/rte_lpm6.c > @@ -381,6 +381,7 @@ add_step(struct rte_lpm6 *lpm, struct rte_lpm6_tbl_entry > *tbl, > int8_t bitshift; > uint8_t bits_covered; > > + *tbl_next = NULL; > /* > * Calculate index to the table based on the number and position > * of the bytes being inspected in this step. It would be more logical to set this variable in the right condition branch: --- a/lib/librte_lpm/rte_lpm6.c +++ b/lib/librte_lpm/rte_lpm6.c @@ -429,6 +429,7 @@ add_step(struct rte_lpm6 *lpm, struct rte_lpm6_tbl_entry *tbl, } } + *tbl_next = NULL; return 0; } > --- a/lib/librte_vhost/vhost_rxtx.c > +++ b/lib/librte_vhost/vhost_rxtx.c > @@ -295,7 +295,7 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id, > for (i = 0; i < count; i++) { > uint16_t desc_idx = desc_indexes[i]; > uint16_t used_idx = (res_start_idx + i) & (vq->size - 1); > - uint32_t copied; > + uint32_t copied = 0; This variable is not used if copy_mbuf_to_desc fails, so it is always initialised before being used. We can workaround the silly compiler while avoiding a performance hit by resetting the variable only in the error case of copy_mbuf_to_desc: --- a/lib/librte_vhost/vhost_rxtx.c +++ b/lib/librte_vhost/vhost_rxtx.c @@ -147,8 +147,10 @@ copy_mbuf_to_desc(struct virtio_net *dev, struct vhost_virtqueue *vq, struct virtio_net_hdr_mrg_rxbuf virtio_hdr = {{0, 0, 0, 0, 0, 0}, 0}; desc = &vq->desc[desc_idx]; - if (unlikely(desc->len < vq->vhost_hlen)) + if (unlikely(desc->len < vq->vhost_hlen)) { + *copied = 0; return -1; + } > err = copy_mbuf_to_desc(dev, vq, pkts[i], desc_idx, &copied); > @@ -531,7 +531,7 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t > queue_id, > { > struct vhost_virtqueue *vq; > uint32_t pkt_idx = 0, nr_used = 0; > - uint16_t start, end; > + uint16_t start = 0, end = 0; I don't understand this one because the variables are not used if reserve_avail_buf_mergeable fails. I don't see any smart workaround. Huawei, Yuanhan, can we expect a little slowdown with this change?