<!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="API documentation for the Rust `size_of_val` fn in crate `std`."><meta name="keywords" content="rust, rustlang, rust-lang, size_of_val"><title>std::mem::size_of_val - Rust</title><link rel="stylesheet" type="text/css" href="../../normalize.css"><link rel="stylesheet" type="text/css" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../../dark.css"><link rel="stylesheet" type="text/css" href="../../light.css" id="themeStyle"><script src="../../storage.js"></script><link rel="shortcut icon" href="https://doc.rust-lang.org/favicon.ico"></head><body class="rustdoc fn"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">☰</div><a href='../../std/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo' width='100'></a><div class="sidebar-elems"><p class='location'><a href='../index.html'>std</a>::<wbr><a href='index.html'>mem</a></p><script>window.sidebarCurrent = {name: 'size_of_val', ty: 'fn', relpath: ''};</script><script defer src="sidebar-items.js"></script></div></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../../theme.js"></script><nav class="sub"><form class="search-form js-only"><div class="search-container"><input class="search-input" name="search" autocomplete="off" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><a id="settings-menu" href="../../settings.html"><img src="../../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><h1 class='fqn'><span class='in-band'>Function <a href='../index.html'>std</a>::<wbr><a href='index.html'>mem</a>::<wbr><a class="fn" href=''>size_of_val</a></span><span class='out-of-band'><span class='since' title='Stable since Rust version 1.0.0'>1.0.0</span><span id='render-detail'><a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class='inner'>−</span>]</a></span><a class='srclink' href='../../src/core/mem.rs.html#343-345' title='goto source code'>[src]</a></span></h1><pre class='rust fn'>pub fn size_of_val<T>(val: <a class="primitive" href="../primitive.reference.html">&</a>T) -> <a class="primitive" href="../primitive.usize.html">usize</a> <span class="where fmt-newline">where<br> T: ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>, </span></pre><div class='docblock'><p>Returns the size of the pointed-to value in bytes.</p>
<p>This is usually the same as <code>size_of::<T>()</code>. However, when <code>T</code> <em>has</em> no
statically known size, e.g. a slice <a href="../../std/primitive.slice.html"><code>[T]</code></a> or a <a href="../../book/first-edition/trait-objects.html">trait object</a>,
then <code>size_of_val</code> can be used to get the dynamically-known size.</p>
<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">mem</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">4</span>, <span class="ident">mem</span>::<span class="ident">size_of_val</span>(<span class="kw-2">&</span><span class="number">5i32</span>));
<span class="kw">let</span> <span class="ident">x</span>: [<span class="ident">u8</span>; <span class="number">13</span>] <span class="op">=</span> [<span class="number">0</span>; <span class="number">13</span>];
<span class="kw">let</span> <span class="ident">y</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>] <span class="op">=</span> <span class="kw-2">&</span><span class="ident">x</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">13</span>, <span class="ident">mem</span>::<span class="ident">size_of_val</span>(<span class="ident">y</span>));<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Ause%20std%3A%3Amem%3B%0A%0Aassert_eq!(4%2C%20mem%3A%3Asize_of_val(%265i32))%3B%0A%0Alet%20x%3A%20%5Bu8%3B%2013%5D%20%3D%20%5B0%3B%2013%5D%3B%0Alet%20y%3A%20%26%5Bu8%5D%20%3D%20%26x%3B%0Aassert_eq!(13%2C%20mem%3A%3Asize_of_val(y))%3B%0A%7D">Run</a></pre>
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