Re: [PATCH][next] net/mlx5: IPsec, Replace zero-length array with flexible-array member

On 2/18/20 10:35, Leon Romanovsky wrote:

On Mon, Feb 17, 2020 at 01:54:34PM -0600, Gustavo A. R. Silva wrote:

quoted

The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.

Also, notice that, dynamic memory allocations won't be affected by
this change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <redacted>
---
 drivers/net/ethernet/mellanox/mlx5/core/fpga/ipsec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Can you please do one patch for whole mlx5,
instead of many identical patches?

Sure thing. I can do that.

Thanks
--
Gustavo