[PATCH] Bluetooth: btusb: Use DECLARE_FLEX_ARRAY() for memdump segment data

[PATCH] Bluetooth: btusb: Use DECLARE_FLEX_ARRAY() for memdump segment data

[Hex Lindqvist]

struct qhci_vse_memdump declares segdata as a zero-length array in a
union. Zero-length arrays are deprecated [1], so use DECLARE_FLEX_ARRAY()
instead.

No functional change: segdata is only used with offsetof(). With debug
info stripped, btusb.o is byte-for-byte identical before and after,
built with GCC 16 and Clang 21 on x86_64 and GCC 16 on arm64, with
UBSAN_BOUNDS and FORTIFY_SOURCE enabled.

An AI assistant helped find and check this change and drafted this
message.

Link: https://docs.kernel.org/process/deprecated.html#zero-length-and-one-element-arrays [1]
Signed-off-by: Hex Lindqvist <hex@freenixos.com>
---
 drivers/bluetooth/btusb_qcom.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/bluetooth/btusb_qcom.c b/drivers/bluetooth/btusb_qcom.c
index cc4cfcde2afa..97be9078e045 100644
--- a/drivers/bluetooth/btusb_qcom.c
+++ b/drivers/bluetooth/btusb_qcom.c
@@ -533,7 +533,7 @@ struct qhci_vse_memdump {
 	__le16 seqno;
 	u8     subsys;
 	union {
-		u8 segdata[0];
+		DECLARE_FLEX_ARRAY(u8, segdata);
 		struct {
 			__le32 dump_size;
 			u8 first_segdata[];

base-commit: ebdfe8561b5496b7eafedccd13a000a7261bc52b
-- 
2.56.0

Re: [PATCH] Bluetooth: btusb: Use DECLARE_FLEX_ARRAY() for memdump segment data

[Paul Menzel]

Dear Hex,


Thank you for your patch.

Am 08.11.26 um 05:20 schrieb Hex Lindqvist:
> struct qhci_vse_memdump declares segdata as a zero-length array in a
> union. Zero-length arrays are deprecated [1], so use DECLARE_FLEX_ARRAY()
> instead.
> 
> No functional change: segdata is only used with offsetof(). With debug
> info stripped, btusb.o is byte-for-byte identical before and after,
> built with GCC 16 and Clang 21 on x86_64 and GCC 16 on arm64, with
> UBSAN_BOUNDS and FORTIFY_SOURCE enabled.
> 
> An AI assistant helped find and check this change and drafted this
> message.
> 
> Link: https://docs.kernel.org/process/deprecated.html#zero-length-and-one-element-arrays [1]
> Signed-off-by: Hex Lindqvist <hex@freenixos.com>
> ---
>   drivers/bluetooth/btusb_qcom.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/bluetooth/btusb_qcom.c b/drivers/bluetooth/btusb_qcom.c
> index cc4cfcde2afa..97be9078e045 100644
> --- a/drivers/bluetooth/btusb_qcom.c
> +++ b/drivers/bluetooth/btusb_qcom.c
> @@ -533,7 +533,7 @@ struct qhci_vse_memdump {
>   	__le16 seqno;
>   	u8     subsys;
>   	union {
> -		u8 segdata[0];
> +		DECLARE_FLEX_ARRAY(u8, segdata);
>   		struct {
>   			__le32 dump_size;
>   			u8 first_segdata[];

Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de>


Kind regards,

Paul