mlxsw: Replace zero-length array with flexible-array member
authorGustavo A. R. Silva <gustavo@embeddedor.com>
Tue, 18 Feb 2020 20:57:05 +0000 (14:57 -0600)
committerDavid S. Miller <davem@davemloft.net>
Thu, 20 Feb 2020 00:23:10 +0000 (16:23 -0800)
commite99f8e7f88b5239812acdaa84560e6015eb8c2d2
tree889bce8bda1fe6e70614097f29771c5f037c1d5a
parente96bd2d3b1f83170d1d5c1a99e439b39a22a5b58
mlxsw: Replace zero-length array with flexible-array member

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 <gustavo@embeddedor.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Tested-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
drivers/net/ethernet/mellanox/mlxsw/core.c
drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_keys.c
drivers/net/ethernet/mellanox/mlxsw/spectrum1_kvdl.c
drivers/net/ethernet/mellanox/mlxsw/spectrum2_kvdl.c
drivers/net/ethernet/mellanox/mlxsw/spectrum_acl.c
drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_bloom_filter.c
drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_tcam.c
drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_tcam.h
drivers/net/ethernet/mellanox/mlxsw/spectrum_kvdl.c
drivers/net/ethernet/mellanox/mlxsw/spectrum_mr.c
drivers/net/ethernet/mellanox/mlxsw/spectrum_nve.c