From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Monjalon Subject: Re: [PATCH] gcc compiler option -Og warnings fix Date: Tue, 05 Apr 2016 10:23:58 +0200 Message-ID: <2122802.lhySAYkBc9@xps13> References: <1459538419-81284-1-git-send-email-keith.wiles@intel.com> <22459074.ccNYgpjxy1@xps13> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: dev@dpdk.org, "Xie, Huawei" , "yuanhan.liu@linux.intel.com" , "adrien.mazarguil@6wind.com" To: "Wiles, Keith" Return-path: Received: from mail-wm0-f52.google.com (mail-wm0-f52.google.com [74.125.82.52]) by dpdk.org (Postfix) with ESMTP id 6CD972BF8 for ; Tue, 5 Apr 2016 10:25:36 +0200 (CEST) Received: by mail-wm0-f52.google.com with SMTP id f198so21131365wme.0 for ; Tue, 05 Apr 2016 01:25:36 -0700 (PDT) In-Reply-To: List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" 2016-04-04 23:03, Wiles, Keith: > >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? > > Did you want me to make these changes or just request everyone to use -Wno-error with -Og? I was suggesting that everyone can use -Wno-error when using -Og. > If you want a new patch from me on these changes it will be > toward the weekend after I get back home from traveling. If some driver maintainers think there are some things to fix, they are free to send a patch by themselves before the end of the week. > >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? > > > > > > > Regards, > Keith > > > >