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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43b7a27aa85sm35486045e9.28.2025.02.27.14.18.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Feb 2025 14:18:03 -0800 (PST) Date: Thu, 27 Feb 2025 22:18:01 +0000 From: David Laight To: Kent Overstreet Cc: Ralf Jung , Ventura Jack , Miguel Ojeda , Gary Guo , torvalds@linux-foundation.org, airlied@gmail.com, boqun.feng@gmail.com, ej@inai.de, gregkh@linuxfoundation.org, hch@infradead.org, hpa@zytor.com, ksummit@lists.linux.dev, linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org Subject: Re: C aggregate passing (Rust kernel policy) Message-ID: <20250227221801.63371d19@pumpkin> In-Reply-To: References: <780ff858-4f8e-424f-b40c-b9634407dce3@ralfj.de> <7edf8624-c9a0-4d8d-a09e-2eac55dc6fc5@ralfj.de> <651a087b-2311-4f70-a2d3-6d2136d0e849@ralfj.de> 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 Thu, 27 Feb 2025 15:22:20 -0500 Kent Overstreet wrote: > On Thu, Feb 27, 2025 at 08:45:09PM +0100, Ralf Jung wrote: > > Hi, > > > > > > > If C was willing to break code as much as Rust, it would be easier to > > > > > clean up C. > > > > > > > > Is that true? Gcc updates do break code. > > > > > > Surely not as much as Rust, right? From what I hear from users > > > of Rust and of C, some Rust developers complain about > > > Rust breaking a lot and being unstable, while I instead > > > hear complaints about C and C++ being unwilling to break > > > compatibility. > > > > Stable Rust code hardly ever breaks on a compiler update. I don't know which > > users you are talking about here, and it's hard to reply anything concrete > > to such a vague claim that you are making here. I also "hear" lots of > > things, but we shouldn't treat hear-say as facts. > > *Nightly* Rust features do break regularly, but nobody has any right to > > complain about that -- nightly Rust is the playground for experimenting with > > features that we know are no ready yet. > > It's also less important to avoid ever breaking working code than it was > 20 years ago: more of the code we care about is open source, everyone is > using source control, and with so much code on crates.io it's now > possible to check what the potential impact would be. Do you really want to change something that would break the linux kernel? Even a compile-time breakage would be a PITA. And the kernel is small by comparison with some other projects. Look at all the problems because python-3 was incompatible with python-2. You have to maintain compatibility. Now there are some things in C (like functions 'falling of the bottom without returning a value') that could sensibly be changed from warnings to errors, but you can't decide to fix the priority of the bitwise &. David > > This is a good thing as long as it's done judiciously, to evolve the > language towards stronger semantics and fix safety issues in the > cleanest way when found.