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// Copyright 2013-2016 The Rust Project Developers. See the COPYRIGHT // file at the top-level directory of this distribution and at // http://rust-lang.org/COPYRIGHT. // // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms. // Private macro to get the offset of a struct field in bytes from the address of the struct. macro_rules! offset_of { ($container:path, $field:ident) => {{ // Make sure the field actually exists. This line ensures that a compile-time error is // generated if $field is accessed through a Deref impl. let $container { $field : _, .. }; // Create an (invalid) instance of the container and calculate the offset to its // field. Using a null pointer might be UB if `&(*(0 as *const T)).field` is interpreted to // be nullptr deref. let invalid: $container = ::core::mem::uninitialized(); let offset = &invalid.$field as *const _ as usize - &invalid as *const _ as usize; // Do not run destructors on the made up invalid instance. ::core::mem::forget(invalid); offset as isize }}; }