[PATCH][next] io_uring: replace zero-length array with flexible-array member

[PATCH][next] io_uring: replace zero-length array with flexible-array member

[Gustavo A. R. Silva]

There is a regular need in the kernel to provide a way to declare
having a dynamically sized set of trailing elements in a structure.
Kernel code should always use “flexible array members”[1] for these
cases. The older style of one-element or zero-length arrays should
no longer be used[2].

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.16/process/deprecated.html#zero-length-and-one-element-arrays

Link: https://github.com/KSPP/linux/issues/78
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 include/uapi/linux/io_uring.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 09e7c3b13d2d..65345848be2f 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -492,7 +492,7 @@ struct io_uring_probe {
 	__u8 ops_len;	/* length of ops[] array below */
 	__u16 resv;
 	__u32 resv2[3];
-	struct io_uring_probe_op ops[0];
+	struct io_uring_probe_op ops[];
 };
 
 struct io_uring_restriction {
-- 
2.27.0

Re: [PATCH][next] io_uring: replace zero-length array with flexible-array member

[Jens Axboe]

On 6/28/22 1:33 PM, Gustavo A. R. Silva wrote:
> There is a regular need in the kernel to provide a way to declare
> having a dynamically sized set of trailing elements in a structure.
> Kernel code should always use ?flexible array members?[1] for these
> cases. The older style of one-element or zero-length arrays should
> no longer be used[2].
> 
> [1] https://en.wikipedia.org/wiki/Flexible_array_member
> [2] https://www.kernel.org/doc/html/v5.16/process/deprecated.html#zero-length-and-one-element-arrays

Thanks for sending this separately. As mentioned out-of-band, we already
have it like this in the io_uring.h header in liburing.

Applied for 5.20.

-- 
Jens Axboe