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AJvYcCX1dwgN9Gko/B5FdrCz/huF4Pu5+pDZIsdVyv/tPnkOgonYmmjJB/8hDOEQ9CMFR5eEQQcLOLm7102/Org=@vger.kernel.org X-Gm-Message-State: AOJu0YxxPCA8ODOIxUrr1Ro+M7rHkWgtyzROinW0EuSA3jjjmjnQUPkq ev9sx1wxsY5IZRMZXyo1/lXK8e/+ZdNKJPSnQeP8we9sXBRFpLikztlUucaTTsY9XJsActR7U4q FDNTLEqFfHtlogg== X-Google-Smtp-Source: AGHT+IHuEh0PHsblUmRpudvQyFJnWydTJl4ycn67zlZjeRLQa0PjIHRx7xRfnVI+/QHeDLPzSmmHSLuK5qL4i40= X-Received: from wmbeq6.prod.google.com ([2002:a05:600c:8486:b0:43e:9aac:5a49]) (user=aliceryhl job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:a08e:b0:43c:eeee:b706 with SMTP id 5b1f17b1804b1-43f3a9aa66dmr110937825e9.24.1744639477678; Mon, 14 Apr 2025 07:04:37 -0700 (PDT) Date: Mon, 14 Apr 2025 14:04:35 +0000 In-Reply-To: <20250412-b4-container-of-type-check-v2-1-f3cc9934c160@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250412-b4-container-of-type-check-v2-1-f3cc9934c160@gmail.com> Message-ID: Subject: Re: [PATCH v2] rust: check type of `$ptr` in `container_of!` From: Alice Ryhl To: Tamir Duberstein Cc: Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , "=?utf-8?B?QmrDtnJu?= Roy Baron" , Benno Lossin , Andreas Hindborg , Trevor Gross , Danilo Krummrich , rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" On Sat, Apr 12, 2025 at 02:16:08PM -0400, Tamir Duberstein wrote: > + ($field_ptr:expr, $Container:ty, $($fields:tt)*) => {{ > + let offset: usize = ::core::mem::offset_of!($Container, $($fields)*); > + let container_ptr = $field_ptr.byte_sub(offset).cast::<$Container>(); > + if false { > + let field_ptr = ::core::ptr::addr_of!((*container_ptr).$($fields)*).cast_mut(); > + [$field_ptr, field_ptr]; // typeof(`$ptr_to_field`) == typeof(`$Container.$($fields)*`) This evaluates $field_ptr twice. The `if false` avoids bad stuff if the expression has side-effects, but still seems sub-optimal. Alice