[PATCH][next] KEYS: Avoid -Wflex-array-member-not-at-end warning

[PATCH][next] KEYS: Avoid -Wflex-array-member-not-at-end warning

[Gustavo A. R. Silva]

-Wflex-array-member-not-at-end was introduced in GCC-14, and we are
getting ready to enable it, globally.

Use the new TRAILING_OVERLAP() helper to fix the following warning:

crypto/asymmetric_keys/restrict.c:20:34: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]

This helper creates a union between a flexible-array member (FAM) and a
set of MEMBERS that would otherwise follow it.

This overlays the trailing MEMBER unsigned char data[10]; onto the FAM
struct asymmetric_key_id::data[], while keeping the FAM and the start
of MEMBER aligned.

The static_assert() ensures this alignment remains, and it's
intentionally placed inmediately after the corresponding structures --no
blank line in between.

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 crypto/asymmetric_keys/restrict.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/crypto/asymmetric_keys/restrict.c b/crypto/asymmetric_keys/restrict.c
index afcd4d101ac5..86292965f493 100644
--- a/crypto/asymmetric_keys/restrict.c
+++ b/crypto/asymmetric_keys/restrict.c
@@ -17,9 +17,12 @@ static struct asymmetric_key_id *ca_keyid;
 
 #ifndef MODULE
 static struct {
-	struct asymmetric_key_id id;
-	unsigned char data[10];
+	/* Must be last as it ends in a flexible-array member. */
+	TRAILING_OVERLAP(struct asymmetric_key_id, id, data,
+		unsigned char data[10];
+	);
 } cakey;
+static_assert(offsetof(typeof(cakey), id.data) == offsetof(typeof(cakey), data));
 
 static int __init ca_keys_setup(char *str)
 {
-- 
2.43.0

Re: [PATCH][next] KEYS: Avoid -Wflex-array-member-not-at-end warning

[Ignat Korchagin]

On Mon, Nov 10, 2025 at 10:46 AM Gustavo A. R. Silva
<gustavoars@kernel.org> wrote:
>
> -Wflex-array-member-not-at-end was introduced in GCC-14, and we are
> getting ready to enable it, globally.
>
> Use the new TRAILING_OVERLAP() helper to fix the following warning:
>
> crypto/asymmetric_keys/restrict.c:20:34: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
>
> This helper creates a union between a flexible-array member (FAM) and a
> set of MEMBERS that would otherwise follow it.
>
> This overlays the trailing MEMBER unsigned char data[10]; onto the FAM
> struct asymmetric_key_id::data[], while keeping the FAM and the start
> of MEMBER aligned.
>
> The static_assert() ensures this alignment remains, and it's
> intentionally placed inmediately after the corresponding structures --no
> blank line in between.
>
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Reviewed-by: Ignat Korchagin <ignat@cloudflare.com>

> ---
>  crypto/asymmetric_keys/restrict.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/crypto/asymmetric_keys/restrict.c b/crypto/asymmetric_keys/restrict.c
> index afcd4d101ac5..86292965f493 100644
> --- a/crypto/asymmetric_keys/restrict.c
> +++ b/crypto/asymmetric_keys/restrict.c
> @@ -17,9 +17,12 @@ static struct asymmetric_key_id *ca_keyid;
>
>  #ifndef MODULE
>  static struct {
> -       struct asymmetric_key_id id;
> -       unsigned char data[10];
> +       /* Must be last as it ends in a flexible-array member. */
> +       TRAILING_OVERLAP(struct asymmetric_key_id, id, data,
> +               unsigned char data[10];
> +       );
>  } cakey;
> +static_assert(offsetof(typeof(cakey), id.data) == offsetof(typeof(cakey), data));

The whole thing looks a bit convoluted to me just to declare a
fixed-sized static buffer and call sizeof() in one place in the code.
But I couldn't come up with a better refactor not introducing
potential alignment side-effects. So LGTM.

>  static int __init ca_keys_setup(char *str)
>  {
> --
> 2.43.0
>

Re: [PATCH][next] KEYS: Avoid -Wflex-array-member-not-at-end warning

[Herbert Xu]

On Mon, Nov 10, 2025 at 07:46:45PM +0900, Gustavo A. R. Silva wrote:
> -Wflex-array-member-not-at-end was introduced in GCC-14, and we are
> getting ready to enable it, globally.
> 
> Use the new TRAILING_OVERLAP() helper to fix the following warning:
> 
> crypto/asymmetric_keys/restrict.c:20:34: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> 
> This helper creates a union between a flexible-array member (FAM) and a
> set of MEMBERS that would otherwise follow it.
> 
> This overlays the trailing MEMBER unsigned char data[10]; onto the FAM
> struct asymmetric_key_id::data[], while keeping the FAM and the start
> of MEMBER aligned.
> 
> The static_assert() ensures this alignment remains, and it's
> intentionally placed inmediately after the corresponding structures --no
> blank line in between.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> ---
>  crypto/asymmetric_keys/restrict.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt