[PATCH] net/mlx5: fix uninitialized warning

[PATCH] net/mlx5: fix uninitialized warning

[Stephen Hemminger]

Gcc-16 detects use of uninitialized variable.
./drivers/net/mlx5/linux/mlx5_ethdev_os.c: In function ‘mlx5_link_update’:
../drivers/net/mlx5/linux/mlx5_ethdev_os.c:539:15: warning: ‘*(long unsigned int *)((char *)&dev_link + offsetof(struct rte_eth_link, <U38c0>))’ may be used uninitialized [-Wmaybe-uninitialized]
  539 |         ret = !!memcmp(&dev->data->dev_link, &dev_link,
      |               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  540 |                        sizeof(struct rte_eth_link));
      |                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../drivers/net/mlx5/linux/mlx5_ethdev_os.c:515:29: note: ‘*(long unsigned int *)((char *)&dev_link + offsetof(struct rte_eth_link, <U38c0>))’ was declared here
  515 |         struct rte_eth_link dev_link;
      |

If the retry loop exits the code would do memcmp against unintialized
stack value. Resolve by intializing to zero.

Fixes: 1256805dd54d ("net/mlx5: move Linux-specific functions")
Cc: stable@dpdk.org

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 drivers/net/mlx5/linux/mlx5_ethdev_os.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/mlx5/linux/mlx5_ethdev_os.c b/drivers/net/mlx5/linux/mlx5_ethdev_os.c
index 4d8fbed188..d4a544e1a6 100644
--- a/drivers/net/mlx5/linux/mlx5_ethdev_os.c
+++ b/drivers/net/mlx5/linux/mlx5_ethdev_os.c
@@ -512,7 +512,7 @@ int
 mlx5_link_update(struct rte_eth_dev *dev, int wait_to_complete)
 {
 	int ret;
-	struct rte_eth_link dev_link;
+	struct rte_eth_link dev_link = { };
 	time_t start_time = time(NULL);
 	int retry = MLX5_GET_LINK_STATUS_RETRY_COUNT;
 
-- 
2.51.0

Re: [PATCH] net/mlx5: fix uninitialized warning

[Stephen Hemminger]

On Thu, 13 Nov 2025 08:33:01 -0800
Stephen Hemminger <stephen@networkplumber.org> wrote:

> Gcc-16 detects use of uninitialized variable.
> ./drivers/net/mlx5/linux/mlx5_ethdev_os.c: In function ‘mlx5_link_update’:
> ../drivers/net/mlx5/linux/mlx5_ethdev_os.c:539:15: warning: ‘*(long unsigned int *)((char *)&dev_link + offsetof(struct rte_eth_link, <U38c0>))’ may be used uninitialized [-Wmaybe-uninitialized]
>   539 |         ret = !!memcmp(&dev->data->dev_link, &dev_link,
>       |               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   540 |                        sizeof(struct rte_eth_link));
>       |                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ../drivers/net/mlx5/linux/mlx5_ethdev_os.c:515:29: note: ‘*(long unsigned int *)((char *)&dev_link + offsetof(struct rte_eth_link, <U38c0>))’ was declared here
>   515 |         struct rte_eth_link dev_link;
>       |
> 
> If the retry loop exits the code would do memcmp against unintialized
> stack value. Resolve by intializing to zero.
> 
> Fixes: 1256805dd54d ("net/mlx5: move Linux-specific functions")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> ---

The build fails with clang because of the (annoying) use of pedantic in this driver.
I will let mlx5 maintainers fix it then.

../drivers/net/mlx5/linux/mlx5_ethdev_os.c:515:33: error: use of GNU empty initializer extension [-Werror,-Wgnu-empty-initializer]
        struct rte_eth_link dev_link = { };