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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-442cd33103dsm12361095e9.10.2025.05.07.13.46.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 07 May 2025 13:46:17 -0700 (PDT) Date: Wed, 7 May 2025 21:46:16 +0100 From: David Laight To: WangYuli Cc: Matthew Wilcox , akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, yuzhao@google.com, stevensd@chromium.org, kaleshsingh@google.com, zhanjun@uniontech.com, niecheng1@uniontech.com, guanwentao@uniontech.com Subject: Re: [PATCH] mm: vmscan: Avoid signedness error for GCC 5.4 Message-ID: <20250507214616.4d91620e@pumpkin> In-Reply-To: References: <85050791B887DC13+20250506160238.799984-1-wangyuli@uniontech.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@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, 7 May 2025 10:55:31 +0800 WangYuli wrote: > Hi Matthew Wilcox and Andrew Morton, > > On 2025/5/7 00:22, Matthew Wilcox wrote: > > 1. This has nothing to do with the compiler version; the type-checking > > is built into min(). > > Thank you for pointing that out! My previous statement was incorrect. > > The error is actually from the __types_ok check within the > __careful_cmp_once macro failing, which triggered BUILD_BUG_ON. > > But then, why do newer compilers compile this without error? Is it > perhaps because they consider 4U - 1 to be signed? No, statically_true(tier >= 0) is true even though 'tier' is signed because the compiler has inlined the function and followed the domain of 'tier' from the assignments and loops. David