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([187.120.154.251]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-72fe6a1a78asm8699082b3a.164.2025.02.03.09.56.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 03 Feb 2025 09:56:06 -0800 (PST) From: Guilherme Giacomo Simoes To: aliceryhl@google.com Cc: a.hindborg@kernel.org, alex.gaynor@gmail.com, benno.lossin@proton.me, bjorn3_gh@protonmail.com, boqun.feng@gmail.com, gary@garyguo.net, linux-kernel@vger.kernel.org, longman@redhat.com, mingo@redhat.com, ojeda@kernel.org, peterz@infradead.org, rust-for-linux@vger.kernel.org, tmgross@umich.edu, trintaeoitogc@gmail.com, will@kernel.org Subject: Re: [PATCH] rust: sync: lock: Add Lock::get_mut() Date: Mon, 3 Feb 2025 14:55:43 -0300 Message-Id: <20250203175543.241946-1-trintaeoitogc@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Alice Ryhl wrotes: > I maintain my objection that this function cannot be correctly called. > Yes, if you use dubious unsafe code, you can call it, but we shouldn't > do that. > > At best, you could change this method to take `self: Pin<&mut Self>`. Yes you is right, we should avoid unsafe code. But how the `self: Pin<&mut Self` help us here? The unsafe code at the get_mut() call place, is because of `get_unchecked_mut`. You probably already know, but this is unsafe because you need guarantee that the value is not move in memory. The `get_unchecked_mut` return a &mut T, (in this case return a &mut Example), and we need a reference to Example for access `d` field. since we have access for `d` , we can get get_mut() without pinned `d`. We need a way for get `Example.d` without `get_unchecked_mut`. Thanks, Guilherme