nfp: Use static_assert() to check struct sizes

[PATCH][next] nfp: Use static_assert() to check struct sizes

Posted by Gustavo A. R. Silva 1 year, 6 months ago

Commit d88cabfd9abc ("nfp: Avoid -Wflex-array-member-not-at-end
warnings") introduced tagged `struct nfp_dump_tl_hdr`. We want
to ensure that when new members need to be added to the flexible
structure, they are always included within this tagged struct.

So, we use `static_assert()` to ensure that the memory layout for
both the flexible structure and the tagged struct is the same after
any changes.

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c b/drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c
index 2dd37557185e..7276e44a21d0 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c
+++ b/drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c
@@ -41,6 +41,8 @@ struct nfp_dump_tl {
 	);
 	char data[];
 };
+static_assert(offsetof(struct nfp_dump_tl, data) == sizeof(struct nfp_dump_tl_hdr),
+	      "struct member likely outside of struct_group_tagged()");
 
 /* NFP CPP parameters */
 struct nfp_dumpspec_cpp_isl_id {
-- 
2.34.1

Re: [PATCH][next] nfp: Use static_assert() to check struct sizes

Posted by Simon Horman 1 year, 5 months ago

On Thu, Aug 08, 2024 at 04:08:35PM -0600, Gustavo A. R. Silva wrote:
> Commit d88cabfd9abc ("nfp: Avoid -Wflex-array-member-not-at-end
> warnings") introduced tagged `struct nfp_dump_tl_hdr`. We want
> to ensure that when new members need to be added to the flexible
> structure, they are always included within this tagged struct.
> 
> So, we use `static_assert()` to ensure that the memory layout for
> both the flexible structure and the tagged struct is the same after
> any changes.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Reviewed-by: Simon Horman <horms@kernel.org>