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h=Date:From:To:Cc:Subject:References:In-Reply-To; b=h5kFVbKGgWVM4/By8YauS1zHj3ZfSM7nv7xk5g47JSYjO4uExbSJ8vU62gwc4dAjb 9QQCREwAtgUZqllgZ0AZ8AUIqgkKZFTwlNCOGAb9zpcS8ZM+lT1XkImHiYqor5wnS1 /XlH4Q1yDcsbIC2OsFk+IKqTlK9WBNa20C5VrMvxCEruIE9fHYYaJ7JmPuzX3Wtp2i 3EghSwMOFry9oSJBFg7uVX9Lsap2HZmy+EoldQIf4mz2RbBTkpKKaPMVrv4PmoLKgA g6YTizz/03AnztZfkq647HYGn7jqBBAF5k1WupLx5j698k7fx5hbgFDH/ed/3FrRFy 43v2riFR3o/4g== Date: Thu, 4 Jun 2026 18:57:24 -0700 From: Nathan Chancellor To: David Laight Cc: Linus Torvalds , Askar Safin , metze@samba.org, akpm@linux-foundation.org, axboe@kernel.dk, brauner@kernel.org, david@kernel.org, dhowells@redhat.com, hch@infradead.org, jack@suse.cz, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, miklos@szeredi.hu, netdev@vger.kernel.org, patches@lists.linux.dev, pfalcato@suse.de, viro@zeniv.linux.org.uk, willy@infradead.org Subject: Re: [PATCH 2/3] vmsplice: make vmsplice a trivial wrapper for preadv2/pwritev2 Message-ID: <20260605015724.GA520134@ax162> References: <20260603211736.755139-1-safinaskar@gmail.com> <20260604100609.6b37f500@pumpkin> <20260604183829.63c35fd9@pumpkin> <20260604223216.73468830@pumpkin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260604223216.73468830@pumpkin> X-Rspamd-Queue-Id: 2377914000A X-Stat-Signature: o73ah3gqme69nd6rdcs76rgu3furqboh X-Rspamd-Server: rspam03 X-Rspam-User: X-HE-Tag: 1780624651-525016 X-HE-Meta: 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 HZVlUNBT enHQdAil06huVpKwuSL9uZL336PR78xxVTkVP04WuLTaIbJPaq5OmRlfF0qqnYcpJrXgvbQn9L26VJ9W5wyCnPIFu93Oh4rCPbRQqdrgXrdePQJunnxZ5RssqvhHsi+FipIoX0N5hauSPRw/Vi6mnouHMHvDiWGMzwRIoUfWOmjCJfwVlfQc8s0SXcns+XgXQNttHNv3FU8dP39DdKnZXkXWItjnYqjzvHml0WjbU/Bj37TTDrtxh12QbedJhEtIAnm7sBDyb8scfiwu8YkRglIyGbqN6Dd8e8QAPPt19lxMJyVk/xZqtkw4sfbWKll1K/13p/SpNR/iH1TEbxtlmwt9KEStcd3i32o6VcmTewsGk7SlN6X3SXqGl2JlBIv0NvC/3 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Jun 04, 2026 at 10:32:16PM +0100, David Laight wrote: > Talking of broken compilers, had you noticed that: > struct foo { > int a; > char c[32]; > }; > > int b(struct foo *f) > { > return __builtin_object_size(f->c, 1); > } > returns -1 (size unknown/indefinite). > You can't use __builtin_object_size() to stop code running off the end > of anything referenced by address - even when the size is constant. That is the entire point of using '-fstrict-flex-arrays=3' in the kernel: df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3") https://godbolt.org/z/bvfrh7W58 Without it, all trailing arrays in structures are treated as flexible arrays, even those with fixed sizes. -- Cheers, Nathan