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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43ea8d2bc7fsm32322305e9.0.2025.04.02.15.01.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Apr 2025 15:01:27 -0700 (PDT) Date: Wed, 2 Apr 2025 23:01:25 +0100 From: David Laight To: Leo Yan Cc: Ian Rogers , Yury Norov , Rasmus Villemoes , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Adrian Hunter , Kan Liang , Thomas Gleixner , Darren Hart , Davidlohr Bueso , =?UTF-8?B?QW5kcsOp?= Almeida , John Garry , Will Deacon , James Clark , Mike Leach , Leo Yan , Yicong Yang , Jonathan Cameron , Nathan Chancellor , Bill Wendling , Justin Stitt , Josh Poimboeuf , Al Viro , Kyle Meyer , Ben Gainey , Athira Rajeev , Kajol Jain , Aditya Gupta , Eder Zulian , Dapeng Mi , Kuan-Wei Chiu , He Zhe , Dirk Gouders , Brian Geffon , Ravi Bangoria , Howard Chu , Charlie Jenkins , Colin Ian King , Dominique Martinet , Jann Horn , Masahiro Yamada , Arnd Bergmann , Yang Jihong , Dmitry Vyukov , Andi Kleen , Graham Woodward , Ilkka Koskinen , Anshuman Khandual , Zhongqiu Han , Hao Ge , Tengda Wu , Gabriele Monaco , Chun-Tse Shao , Casey Chen , "Dr. David Alan Gilbert" , Li Huafei , "Steinar H. Gunderson" , Levi Yun , Weilin Wang , Thomas Falcon , Thomas Richter , Andrew Kreimer , Krzysztof =?UTF-8?B?xYFvcGF0b3dza2k=?= , Christophe Leroy , Jean-Philippe Romain , Junhao He , "Masami Hiramatsu (Google)" , Xu Yang , Steve Clevenger , Zixian Cai , Stephen Brennan , Yujie Liu , linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-arm-kernel@lists.infradead.org, llvm@lists.linux.dev Subject: Re: [PATCH v1 09/48] perf tests: Silence -Wshorten-64-to-32 warnings Message-ID: <20250402230125.366ac21c@pumpkin> In-Reply-To: <20250402163807.GP115840@e132581.arm.com> References: <20250401182347.3422199-1-irogers@google.com> <20250401182347.3422199-10-irogers@google.com> <20250402143541.GM115840@e132581.arm.com> <20250402163807.GP115840@e132581.arm.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 2 Apr 2025 17:38:07 +0100 Leo Yan wrote: > Hi Ian, ... > If we use casts just to silence warnings, we also lose the opportunity > to improve code quality. The changes in this series that fix type > mismatches are good, but I think the use of casts is not particularly > helpful - we're simply switching from implicit compiler casts to > explicit ones. It is certainly my experience (a lot of years) that casts between integers of different sizes just make code harder to read and possibly even more buggy. If the compiler really knew the valid range of the value (rather than just the type) then perhaps a warning that significant bits were being discarded might be more reasonable. But even then you don't want anything for code like: hi_32 = val_64 >> 32; lo_32 = val_64; David