On Tue, Oct 28, 2025 at 05:23:12PM +0000, Simon Horman wrote:

On Mon, Oct 27, 2025 at 10:38:56AM +0530, Ankit Khushwaha wrote:

quoted

Some network selftests defined variable-sized types defined at the end of
struct causing -Wgnu-variable-sized-type-not-at-end warning.

warning:
timestamping.c:285:18: warning: field 'cm' with variable sized type 
'struct cmsghdr' not at the end of a struct or class is a GNU 
extension [-Wgnu-variable-sized-type-not-at-end]
  285 |                 struct cmsghdr cm;
      |                                ^

ipsec.c:835:5: warning: field 'u' with variable sized type 'union 
(unnamed union at ipsec.c:831:3)' not at the end of a struct or class 
is a GNU extension [-Wgnu-variable-sized-type-not-at-end]
  835 |                 } u;
      |                   ^

This patch move these field at the end of struct to fix these warnings.

Signed-off-by: Ankit Khushwaha <redacted>

Hi Ankit,

I don't believe this change is correct.

I think that the intention of the code is the char arrays (buf and control)
provide the buffer space for the variable-length trailing field
of the preceding structure. Where we basically have a header followed
by data. But your patch would place the before the header.

Hi Simon,
So if buf and control providing the buffer space, then i think it is
better to suppress `-Wgnu-variable-sized-type-not-at-end` warning 
within this block of code.

	#pragma GCC diagnostic push
	#pragma GCC diagnostic ignored "-Wgnu-variable-sized-type-not-at-end"

	struct {
		union {
			struct xfrm_algo        alg;
			struct xfrm_algo_aead   aead;
			struct xfrm_algo_auth   auth;
		} u;
		char buf[XFRM_ALGO_KEY_BUF_SIZE];
	} alg = {};

	#pragma GCC diagnostic pop

I think this would be fine.

Thanks
-- Ankit