[PATCH] gcc compiler option -Og warnings fix

[PATCH] gcc compiler option -Og warnings fix

[Keith Wiles]

The new compiler option -Og causes a few warning on variables
being used before being set warnings. The new option allows better
debugging then -O0 without losing a lot of performance. This option
does not include -g debug symbol option.

Signed-off-by: Keith Wiles <keith.wiles@intel.com>
---
 lib/librte_eal/linuxapp/eal/eal_pci_uio.c | 2 +-
 lib/librte_lpm/rte_lpm6.c                 | 1 +
 lib/librte_vhost/vhost_rxtx.c             | 4 ++--
 3 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/lib/librte_eal/linuxapp/eal/eal_pci_uio.c b/lib/librte_eal/linuxapp/eal/eal_pci_uio.c
index 068694d..89709f8 100644
--- 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;
 	struct dirent *e;
 	DIR *dir;
 	char dirname[PATH_MAX];
diff --git a/lib/librte_lpm/rte_lpm6.c b/lib/librte_lpm/rte_lpm6.c
index 4c44cd7..36565da 100644
--- 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.
diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c
index 750821a..acf3632 100644
--- 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;
 		int err;
 
 		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;
 
 	LOG_DEBUG(VHOST_DATA, "(%"PRIu64") virtio_dev_merge_rx()\n",
 		dev->device_fh);
-- 
2.5.0

Re: [PATCH] gcc compiler option -Og warnings fix

[Thomas Monjalon]

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?

Re: [PATCH] gcc compiler option -Og warnings fix

[Yuanhan Liu]

On Mon, Apr 04, 2016 at 04:10:54PM +0200, Thomas Monjalon wrote:
> --- 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?

I agree with you that the compiler seems buggy here, I'm okay with
the fix though: it should not introduce slowdown, IMO. However, I'd
ask the opinion from Huawei: he knows this better than me.

	--yliu

Re: [PATCH] gcc compiler option -Og warnings fix

[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?

If you want a new patch from me on these changes it will be toward the weekend after I get back home from traveling.

>
>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

Re: [PATCH] gcc compiler option -Og warnings fix

[Thomas Monjalon]

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
> 
> 
> 
>