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

[Wei Liu <wei.liu@kernel.org>]

On Fri, Dec 12, 2025 at 03:44:50PM +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:
> 
> include/hyperv/hvgdk_mini.h:581:25: 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 u64 gva_list[]; onto the FAM
> struct hv_tlb_flush_ex::hv_vp_set.bank_contents[], 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 related structure --no
> blank line in between.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Applied. I fixed a typo in the commit message ("inmediately" ->
"immediately").

Wei

> ---
>  include/hyperv/hvgdk_mini.h | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/include/hyperv/hvgdk_mini.h b/include/hyperv/hvgdk_mini.h
> index 04b18d0e37af..30fbbde81c5c 100644
> --- a/include/hyperv/hvgdk_mini.h
> +++ b/include/hyperv/hvgdk_mini.h
> @@ -578,9 +578,12 @@ struct hv_tlb_flush {	 /* HV_INPUT_FLUSH_VIRTUAL_ADDRESS_LIST */
>  struct hv_tlb_flush_ex {
>  	u64 address_space;
>  	u64 flags;
> -	struct hv_vpset hv_vp_set;
> -	u64 gva_list[];
> +	__TRAILING_OVERLAP(struct hv_vpset, hv_vp_set, bank_contents, __packed,
> +		u64 gva_list[];
> +	);
>  } __packed;
> +static_assert(offsetof(struct hv_tlb_flush_ex, hv_vp_set.bank_contents) ==
> +	      offsetof(struct hv_tlb_flush_ex, gva_list));
>  
>  struct ms_hyperv_tsc_page {	 /* HV_REFERENCE_TSC_PAGE */
>  	volatile u32 tsc_sequence;
> -- 
> 2.43.0
>