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<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Calculates the offset of the specified field from the start of the named struct."><title>offset_of in memoffset - Rust</title><script>if(window.location.protocol!=="file:")document.head.insertAdjacentHTML("beforeend","SourceSerif4-Regular-6b053e98.ttf.woff2,FiraSans-Regular-0fe48ade.woff2,FiraSans-Medium-e1aa3f0a.woff2,SourceCodePro-Regular-8badfe75.ttf.woff2,SourceCodePro-Semibold-aa29a496.ttf.woff2".split(",").map(f=>`<link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/${f}">`).join(""))</script><link rel="stylesheet" href="../static.files/normalize-9960930a.css"><link rel="stylesheet" href="../static.files/rustdoc-46132b98.css"><meta name="rustdoc-vars" data-root-path="../" data-static-root-path="../static.files/" data-current-crate="memoffset" data-themes="" data-resource-suffix="" data-rustdoc-version="1.85.1 (4eb161250 2025-03-15)" data-channel="1.85.1" data-search-js="search-75f5ac3e.js" data-settings-js="settings-0f613d39.js" ><script src="../static.files/storage-59e33391.js"></script><script defer src="sidebar-items.js"></script><script defer src="../static.files/main-5f194d8c.js"></script><noscript><link rel="stylesheet" href="../static.files/noscript-893ab5e7.css"></noscript><link rel="alternate icon" type="image/png" href="../static.files/favicon-32x32-6580c154.png"><link rel="icon" type="image/svg+xml" href="../static.files/favicon-044be391.svg"></head><body class="rustdoc macro"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle" title="show sidebar"></button></nav><nav class="sidebar"><div class="sidebar-crate"><h2><a href="../memoffset/index.html">memoffset</a><span class="version">0.9.1</span></h2></div><div class="sidebar-elems"><section id="rustdoc-toc"><h2 class="location"><a href="#">offset_<wbr>of</a></h2><h3><a href="#">Sections</a></h3><ul class="block top-toc"><li><a href="#examples" title="Examples">Examples</a></li><li><a href="#notes" title="Notes">Notes</a></li></ul></section><div id="rustdoc-modnav"><h2 class="in-crate"><a href="index.html">In crate memoffset</a></h2></div></div></nav><div class="sidebar-resizer"></div><main><div class="width-limiter"><rustdoc-search></rustdoc-search><section id="main-content" class="content"><div class="main-heading"><span class="rustdoc-breadcrumbs"><a href="index.html">memoffset</a></span><h1>Macro <span class="macro">offset_of</span><button id="copy-path" title="Copy item path to clipboard">Copy item path</button></h1><rustdoc-toolbar></rustdoc-toolbar><span class="sub-heading"><a class="src" href="../src/memoffset/offset_of.rs.html#119-125">Source</a> </span></div><pre class="rust item-decl"><code>macro_rules! offset_of {
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($parent:path, $field:tt) => { ... };
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}</code></pre><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Calculates the offset of the specified field from the start of the named struct.</p>
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<h3 id="examples"><a class="doc-anchor" href="#examples">§</a>Examples</h3>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>memoffset::offset_of;
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<span class="attr">#[repr(C, packed)]
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</span><span class="kw">struct </span>Foo {
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a: u32,
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b: u64,
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c: [u8; <span class="number">5</span>]
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}
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<span class="macro">assert_eq!</span>(<span class="macro">offset_of!</span>(Foo, a), <span class="number">0</span>);
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<span class="macro">assert_eq!</span>(<span class="macro">offset_of!</span>(Foo, b), <span class="number">4</span>);</code></pre></div>
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<h3 id="notes"><a class="doc-anchor" href="#notes">§</a>Notes</h3>
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<p>Rust’s ABI is unstable, and <a href="https://doc.rust-lang.org/reference/type-layout.html">type layout can be changed with each
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compilation</a>.</p>
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<p>Using <code>offset_of!</code> with a <code>repr(Rust)</code> struct will return the correct offset of the
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specified <code>field</code> for a particular compilation, but the exact value may change
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based on the compiler version, concrete struct type, time of day, or rustc’s mood.</p>
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<p>As a result, the value should not be retained and used between different compilations.</p>
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</div></details></section></div></main></body></html> |