From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 598BC2517B9; Mon, 20 Oct 2025 15:58:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760975898; cv=none; b=YzmnxFDCvyb5yeRdT+jM6DAng7PG8XJx/dTuiE6LqEIntasMU1rxJ0AacvD9susLstKDImBviY04qTuC8hw+FytAQ/qsaEZYjT2XoFT/CzTaHZg7H/DRViUFzisoqaQqkEC8m5vYipyNS1UNxGt3j4eJLT9a5Zp8saIPc6sipF8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760975898; c=relaxed/simple; bh=c1pFx8WKouJ8FJj3ToqXrSrEjMFH54BLR0ELsARARUk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=BK4kyFvlm9kUSIVB4Jg+eFCCIo2fsTSVnJ3LU9DxpVci5hRQy5WHM0TU2Zv9k7Q74Z3+INalhh+phoBsN92UdVyMBjrXpnPkKRw9ES2tb9yzg19uW2F8hDVwX+OsayvqU4q0Z5XAHg7ACF8T/G5lb+oeugFeLs1GOE+Tq+kPqs8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=VvRasipR; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="VvRasipR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1A484C4CEFE; Mon, 20 Oct 2025 15:58:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1760975897; bh=c1pFx8WKouJ8FJj3ToqXrSrEjMFH54BLR0ELsARARUk=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=VvRasipRZTsQXIgyYOKhcKTqIYGgRXodZ4d8kfXfct1ws2fA5ltN3WFtMw4RiJuzG 77YD/cXjTnqdgq/JezeOxH/HeEM1zD+CeoS+O+KaqnnwOIAvdlW1nj87aPwh6C2x4B 0MSyKwSo8+FSJETqUTV3ypgWzF1M8ah5y58979IaDkTkM+n0H/yfeZANNSZo9xX/yG acd5h6/wQCMzExGPopD48E10PfZ29vYCNiP3J+QSI8bnkQFfqglc7ygDP7oZvej7Tw CuNIjW3yNrbJceNpeZrIplXe5pFU3T0LXXlpEkltDu0uBy+htp8izJlP6a4a1/i0qK UtKk1Q8MMGsuA== Message-ID: Date: Mon, 20 Oct 2025 17:58:12 +0200 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 5.15.y 2/3] arch: back to -std=gnu89 in < v5.18 Content-Language: en-GB, fr-BE To: Greg Kroah-Hartman Cc: stable@vger.kernel.org, Sasha Levin , MPTCP Upstream , Nathan Chancellor , Ard Biesheuvel , Alexey Dobriyan , Arnd Bergmann References: <20251017-v5-15-gcc-15-v1-0-da6c065049d7@kernel.org> <20251017-v5-15-gcc-15-v1-2-da6c065049d7@kernel.org> <2025102015-alongside-kiwi-6f75@gregkh> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Greg, On 20/10/2025 15:30, Greg Kroah-Hartman wrote: > On Fri, Oct 17, 2025 at 06:24:01PM +0200, Matthieu Baerts (NGI0) wrote: >> Recent fixes have been backported to < v5.18 to fix build issues with >> GCC 5.15. They all force -std=gnu11 in the CFLAGS, "because [the kernel] >> requests the gnu11 standard via '-std=' in the main Makefile". >> >> This is true for >= 5.18 versions, but not before. This switch to >> -std=gnu11 has been done in commit e8c07082a810 ("Kbuild: move to >> -std=gnu11"). >> >> For a question of uniformity, force -std=gnu89, similar to what is done >> in the main Makefile. >> >> Note: the fixes tags below refers to upstream commits, but this fix is >> only for kernels not having commit e8c07082a810 ("Kbuild: move to >> -std=gnu11"). >> >> Fixes: 7cbb015e2d3d ("parisc: fix building with gcc-15") >> Fixes: 3b8b80e99376 ("s390: Add '-std=gnu11' to decompressor and purgatory CFLAGS") >> Fixes: b3bee1e7c3f2 ("x86/boot: Compile boot code with -std=gnu11 too") >> Fixes: ee2ab467bddf ("x86/boot: Use '-std=gnu11' to fix build with GCC 15") >> Fixes: 8ba14d9f490a ("efi: libstub: Use '-std=gnu11' to fix build with GCC 15") >> Signed-off-by: Matthieu Baerts (NGI0) >> --- >> Note: >> An alternative is to backport commit e8c07082a810 ("Kbuild: move to >> -std=gnu11"), but I guess we might not want to do that for stable, as >> it might introduce new warnings. > > I would rather do that, as that would allow us to make things align up > and be easier to support over the next two years that this kernel needs > to be alive for. How much work would that entail? Good question. I'm not an expert in this area, but I just did a quick test: I backported commit e8c07082a810 ("Kbuild: move to -std=gnu11") and its parent commit 4d94f910e79a ("Kbuild: use -Wdeclaration-after-statement"). A build with 'make allyesconfig' and GCC 5.15 looks OK to me, no warnings. But when looking a bit around, I noticed these patches have already been suggested to be backported to v5.15 in 2023, but they got removed -- except the doc update, see patch 3/3 -- because they were causing build issues with GCC 8 and 12, see: https://lore.kernel.org/a2fbbaa2-51d2-4a8c-b032-5331e72cd116@linaro.org I didn't try to reproduce the issues, but maybe we can re-add them to the v5.15 queue, and ask the CIs to test that? Note that even if we do that, the first patch will still be needed to have GCC 15 support in v5.15. Cheers, Matt -- Sponsored by the NGI0 Core fund.