Date: Thu, 18 Apr 2024 20:57:16 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Wei Hu <weh@microsoft.com> Cc: Warner Losh <imp@bsdimp.com>, "freebsd-hackers@FreeBSD.org" <freebsd-hackers@freebsd.org> Subject: Re: How to add a -W flag in local Makefile Message-ID: <ZiFe_A6takkhcyL7@kib.kiev.ua> In-Reply-To: <TYZP153MB039998D645FD84C28A9A057EBB0E2@TYZP153MB0399.APCP153.PROD.OUTLOOK.COM> References: <TYZP153MB0399580B98D5F790C0A551C3BB0E2@TYZP153MB0399.APCP153.PROD.OUTLOOK.COM> <CANCZdfoJD1gb1SVb9xiyUAPe8mWL1SZBB%2BtJ3ZOASMWxO6nmbg@mail.gmail.com> <TYZP153MB039998D645FD84C28A9A057EBB0E2@TYZP153MB0399.APCP153.PROD.OUTLOOK.COM>
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On Thu, Apr 18, 2024 at 03:27:13PM +0000, Wei Hu wrote:
> I added something like:
>
> diff --git a/sys/dev/hyperv/vmbus/vmbus_var.h b/sys/dev/hyperv/vmbus/vmbus_var.h
> index b598f782947e..6e3b7b040827 100644
> --- a/sys/dev/hyperv/vmbus/vmbus_var.h
> +++ b/sys/dev/hyperv/vmbus/vmbus_var.h
> @@ -193,4 +193,17 @@ struct hyperv_tlb_flush {
> uint64_t hv_vm_tlb_flush(pmap_t pmap, vm_offset_t addr1,
> vm_offset_t addr2, cpuset_t mask);
>
> +struct hv_vpset {
> + uint64_t format;
> + uint64_t valid_bank_mask;
> + uint64_t bank_contents[];
> +} __packed;
> +
> +struct hv_tlb_flush_ex {
> + uint64_t address_space;
> + uint64_t flags;
> + struct hv_vpset hv_vp_set;
> + uint64_t gva_list[];
> +} __packed;
> +
> #endif /* !_VMBUS_VAR_H_ */
>
> So, the struct hv_vpset is the second last member of struct hv_tlb_flush_ex. The member bank_contents[] in struct hv_vpset is of variable length. This would makes the last two members of struct hv_tlb_flush_ex both variable length. Therefore, the flag '-Wno-gnu-variable-sized-type-not-at-end' is needed, otherwise it would complain about this with errors like:
>
No, the compiler' complain is correct. The structure definition for
hv_tlb_flush_ex does not make sense: you never can access gva_list (except
for the case of bank_contents being zero-sized).
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