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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-488fb75c695sm134995895e9.14.2026.04.22.06.22.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Apr 2026 06:22:54 -0700 (PDT) Date: Wed, 22 Apr 2026 14:22:52 +0100 From: David Laight To: Miguel Ojeda Cc: Arnd Bergmann , Marco Elver , kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, Miguel Ojeda , Dmitry Vyukov , Nathan Chancellor , llvm@lists.linux.dev Subject: Re: [PATCH 1/2] Compiler Attributes: Add __access macro Message-ID: <20260422142252.2e2c927c@pumpkin> In-Reply-To: References: <20260421190351.1976329-1-elver@google.com> <63e461c3-2d8e-47c0-9901-34b53e53f22b@app.fastmail.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Wed, 22 Apr 2026 12:25:26 +0200 Miguel Ojeda wrote: > On Tue, Apr 21, 2026 at 9:30=E2=80=AFPM Arnd Bergmann wro= te: > > > > gcc-10 knows the 'access' attribute, but not the 'none' variant: > > > > echo 'int f(void *p) __attribute__((access(none, 1)));' | /home/arnd/cr= oss/arm64/gcc-10.5.0-nolibc/aarch64-linux/bin/aarch64-linux-gcc -xc - -o /= dev/null -c > > :1:1: error: attribute 'access' invalid mode 'none'; expected on= e of 'read_only', 'read_write', or 'write_only' =20 >=20 > Which is exactly the one we use in #2, indeed. >=20 > That makes sense, thanks! >=20 > We should still change the number here, because `__has_attribute` will > pass even with GCC 10, i.e. since someone using `none` without a gate > in Kconfig or elsewhere may not realize the mistake. >=20 > So we should probably add a comment that the access mode `none` is > only available in GCC 11 -- especially so if we add the docs David > suggests, because otherwise it seems like it is supported. Especially since the gcc docs make it pretty impossible to find out when anything was added. Trial and error on godbolt shouldn't really be needed. (and I missed that the size/count is the argument number as well). David >=20 > Cheers, > Miguel >=20