linux-kernel - Re: [linux-next-20250422] Build failure: Wvla-larger-than=0 is meaningless

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Message-ID: <e8bf676e-7bf0-4896-b104-ac75e1b22d2e@linux.ibm.com>
Date: Sat, 26 Apr 2025 20:23:49 +0530
From: Venkat Rao Bagalkote <venkat88@...ux.ibm.com>
To: Kees Cook <kees@...nel.org>
Cc: Stephen Rothwell <sfr@...b.auug.org.au>, nathan@...nel.org, hch@....de,
        Madhavan Srinivasan <maddy@...ux.ibm.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux Next Mailing List <linux-next@...r.kernel.org>
Subject: Re: [linux-next-20250422] Build failure: Wvla-larger-than=0 is
 meaningless


On 26/04/25 11:20 am, Kees Cook wrote:
> On Wed, Apr 23, 2025 at 07:11:43PM +0530, Venkat Rao Bagalkote wrote:
>> I am observing linux-next build failure on IBM Power8 server.
>>
>>
>> Repo: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
>>
>> Branch: master
>>
>> GCC: 8.5.0 20210514
>>
>> ldd (GNU libc) 2.28
>>
>> Attached is the .config file.
>>
>>
>> Build errors:
>>
>>
>> [[01m^[[Kcc1:^[[m^[[K ^[[01;36m^[[Knote: ^[[m^[[K-Wvla-larger-than=0 is
>> meaningless
> Weird that it doesn't get dropped by "cc-option". I reproduced the
> issue, and this patch seems to fix it:
>
> diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
> index 70ff932fd5ec..59d3d196fe4f 100644
> --- a/scripts/Makefile.extrawarn
> +++ b/scripts/Makefile.extrawarn
> @@ -51,7 +51,7 @@ KBUILD_CFLAGS += $(call cc-disable-warning, dangling-pointer)
>   # types, so depend on GCC for now to keep stack VLAs out of the tree.
>   # https://github.com/llvm/llvm-project/issues/57098
>   # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98217
> -KBUILD_CFLAGS += $(call cc-option,-Wvla-larger-than=0)
> +KBUILD_CFLAGS += $(call cc-option,-Wvla-larger-than=1)
>   
>   # disable pointer signed / unsigned warnings in gcc 4.0
>   KBUILD_CFLAGS += -Wno-pointer-sign
>

Thanks for the fix. Applied the above patch on top of next-20250424 and 
it fixes the reported issue. Hence,


Tested-by: Venkat Rao Bagalkote <venkat88@...ux.ibm.com>


Regards,

Venkat.