linux-kernel - Re: [PATCH v2 01/10] kbuild: don't enable CC_CAN_LINK if the dummy program generates warnings

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Message-ID: <20251114042741.GA3582402@ax162>
Date: Thu, 13 Nov 2025 21:27:41 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Cc: Nicolas Schier <nicolas.schier@...ux.dev>,
	Nicolas Schier <nsc@...nel.org>, Paul Walmsley <pjw@...nel.org>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>, Alexandre Ghiti <alex@...ti.fr>,
	Heiko Carstens <hca@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Alexander Gordeev <agordeev@...ux.ibm.com>,
	Christian Borntraeger <borntraeger@...ux.ibm.com>,
	Sven Schnelle <svens@...ux.ibm.com>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	"David S. Miller" <davem@...emloft.net>,
	Andreas Larsson <andreas@...sler.com>, linux-kbuild@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Masahiro Yamada <masahiroy@...nel.org>,
	linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-mips@...r.kernel.org,
	sparclinux@...r.kernel.org
Subject: Re: [PATCH v2 01/10] kbuild: don't enable CC_CAN_LINK if the dummy
 program generates warnings

On Tue, Oct 14, 2025 at 03:05:16PM +0200, Thomas Weißschuh wrote:
> It is possible that the kernel toolchain generates warnings when used
> together with the system toolchain. This happens for example when the
> older kernel toolchain does not handle new versions of sframe debug
> information. While these warnings where ignored during the evaluation
> of CC_CAN_LINK, together with CONFIG_WERROR the actual userprog build
> will later fail.
> 
> Example warning:
> 
> .../x86_64-linux/13.2.0/../../../../x86_64-linux/bin/ld:
> error in /lib/../lib64/crt1.o(.sframe); no .sframe will be created
> collect2: error: ld returned 1 exit status
> 
> Make sure that the very simple example program does not generate
> warnings already to avoid breaking the userprog compilations.
> 
> Fixes: ec4a3992bc0b ("kbuild: respect CONFIG_WERROR for linker and assembler")
> Fixes: 3f0ff4cc6ffb ("kbuild: respect CONFIG_WERROR for userprogs")
> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>

Reviewed-by: Nathan Chancellor <nathan@...nel.org>

While this makes sense as a way to immediately fix the problem and align
cc-can-link.sh with the other test functions like cc-option and like, it
is rather unfortunate that this particular warning causes an error since
the rest of the userprogs infrastructure does not care about SFrame...
I wonder if there is a way to avoid it since I think this warning does
not point to a fundamental problem.

> ---
>  scripts/cc-can-link.sh | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/scripts/cc-can-link.sh b/scripts/cc-can-link.sh
> index 6efcead3198989d2ab2ab6772c72d8bb61c89c4e..e67fd8d7b6841e53341045b28dc5196cc1327cbe 100755
> --- a/scripts/cc-can-link.sh
> +++ b/scripts/cc-can-link.sh
> @@ -1,7 +1,7 @@
>  #!/bin/sh
>  # SPDX-License-Identifier: GPL-2.0
>  
> -cat << "END" | $@ -x c - -o /dev/null >/dev/null 2>&1
> +cat << "END" | $@ -Werror -Wl,--fatal-warnings -x c - -o /dev/null >/dev/null 2>&1
>  #include <stdio.h>
>  int main(void)
>  {
> 
> -- 
> 2.51.0
>