linux-kernel - Re: [PATCH] kbuild: Add '-fms-extensions' to areas with dedicated CFLAGS

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Message-ID: <aQtUujos2ADVs-_O@gate>
Date: Wed, 5 Nov 2025 07:44:26 -0600
From: Segher Boessenkool <segher@...nel.crashing.org>
To: Nathan Chancellor <nathan@...nel.org>
Cc: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
        Huacai Chen <chenhuacai@...nel.org>, WANG Xuerui <kernel@...0n.name>,
        "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
        Helge Deller <deller@....de>,
        Madhavan Srinivasan <maddy@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        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>,
        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,
        Ard Biesheuvel <ardb@...nel.org>,
        Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
        Bill Wendling <morbo@...gle.com>,
        Justin Stitt <justinstitt@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        loongarch@...ts.linux.dev, linux-parisc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        linux-efi@...r.kernel.org, llvm@...ts.linux.dev,
        Christian Brauner <brauner@...nel.org>
Subject: Re: [PATCH] kbuild: Add '-fms-extensions' to areas with dedicated
 CFLAGS

Hi!

On Sat, Nov 01, 2025 at 12:35:47PM -0400, Nathan Chancellor wrote:
> There are many places within the kernel that use their own CFLAGS
> instead of the main KBUILD_CFLAGS, meaning code written with the main
> kernel's use of '-fms-extensions' in mind that may be tangentially
> included in these areas will result in "error: declaration does not
> declare anything" messages from the compiler.

Please fix such non-standard code then, instead?  The only (documented)
thing -fms-extensions does for C code is give meaning to something that
otherwise is a syntax error (and it is for a good reason!)


Segher