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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-439b3cc2e65sm6649234f8f.2.2026.03.01.14.16.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 01 Mar 2026 14:16:37 -0800 (PST) Date: Sun, 1 Mar 2026 22:16:36 +0000 From: David Laight To: Linus Torvalds Cc: "Christophe Leroy (CS GROUP)" , Thomas Gleixner , LKML , Christophe Leroy , Mathieu Desnoyers , Andrew Cooper , kernel test robot , Russell King , linux-arm-kernel@lists.infradead.org, x86@kernel.org, Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , linuxppc-dev@lists.ozlabs.org, Paul Walmsley , Palmer Dabbelt , linux-riscv@lists.infradead.org, Heiko Carstens , Christian Borntraeger , Sven Schnelle , linux-s390@vger.kernel.org, Julia Lawall , Nicolas Palix , Peter Zijlstra , Darren Hart , Davidlohr Bueso , Andre Almeida , Alexander Viro , Christian Brauner , Jan Kara , linux-fsdevel@vger.kernel.org Subject: Re: [PATCH] uaccess: Fix build of scoped user access with const pointer Message-ID: <20260301221636.0efa722c@pumpkin> In-Reply-To: References: <4e994e13b48420ef36be686458ce3512657ddb41.1772393211.git.chleroy@kernel.org> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Sun, 1 Mar 2026 12:01:08 -0800 Linus Torvalds wrote: I also added to compiler.h : +/* + * Sometimes a #define needs to declare a variable that is scoped + * to the statement that follows without having mismatched {}. + * with (int x = expression) { + * statements + * } + * is the same as: + * { + * int x = expression; + * statements + * } + * but lets it all be hidden from the call site, eg: + * frobnicate(args) { + * statements + * } + * Only a single variable can be defined, and_with() allows extra ones + * without adding an additional outer loop. + * + * The controlled scope can be terminated using break, continue or goto. + */ +#define with(declaration) \ + for (bool _with_done = false; !_with_done; _with_done = true) \ + and_with (declaration) +#define and_with(declaration) \ + for (declaration; !_with_done; _with_done = true) + So that you get: #define __scoped_user_access(mode, uptr, size, elbl) \ with (auto _tmpptr = __scoped_user_access_begin(mode, uptr, size, elbl)) \ and_with (CLASS(user_##mode##_access, scope)(_tmpptr)) \ /* Force modified pointer usage within the scope */ \ and_with (const auto uptr = _tmpptr) The next patch did: - and_with (const typeof(uptr) uptr = _tmpptr) + __diag_push() __diag_ignore_all("-Wshadow", "uptr is readonly copy") \ + and_with (const typeof(uptr) uptr = _tmpptr) \ + __diag_pop() I'll update (to use auto as above) and resend. David