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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-439b037213dsm40479475e9.40.2025.02.22.00.41.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 22 Feb 2025 00:41:13 -0800 (PST) Date: Sat, 22 Feb 2025 08:41:12 +0000 From: David Laight To: Willy Tarreau Cc: Linus Torvalds , Jan Engelhardt , "H. Peter Anvin" , Greg KH , Boqun Feng , Miguel Ojeda , Christoph Hellwig , rust-for-linux , David Airlie , linux-kernel@vger.kernel.org, ksummit@lists.linux.dev Subject: Re: C aggregate passing (Rust kernel policy) Message-ID: <20250222084112.23eb2856@pumpkin> In-Reply-To: <20250222063730.GB11482@1wt.eu> References: <2025021954-flaccid-pucker-f7d9@gregkh> <2nn05osp-9538-11n6-5650-p87s31pnnqn0@vanv.qr> <2025022052-ferment-vice-a30b@gregkh> <9B01858A-7EBD-4570-AC51-3F66B2B1E868@zytor.com> <20250221183437.1e2b5b94@pumpkin> <20250221214501.11b76aa8@pumpkin> <20250222063210.GA11482@1wt.eu> <20250222063730.GB11482@1wt.eu> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: ksummit@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Sat, 22 Feb 2025 07:37:30 +0100 Willy Tarreau wrote: ... > Update: I found in my code a comment suggesting that it works when using > -freg-struct (which is in fact -freg-struct-return) which works both on > i386 and ARM. The problem is that you need it to be an __attribute__(()) so it can be per-function without breaking ABI. > I just didn't remember about this and couldn't find it when > looking at gcc docs. I can never find anything in there either. And then I wish they say when it was introduced. David