<!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 `write` fn in crate `std`."><meta name="keywords" content="rust, rustlang, rust-lang, write"><title>std::ptr::write - 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'>ptr</a></p><script>window.sidebarCurrent = {name: 'write', 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'>ptr</a>::<wbr><a class="fn" href=''>write</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/ptr.rs.html#362-364' title='goto source code'>[src]</a></span></h1><pre class='rust fn'>pub unsafe fn write<T>(dst: <a class="primitive" href="../primitive.pointer.html">*mut T</a>, src: T)</pre><div class='docblock'><p>Overwrites a memory location with the given value without reading or dropping the old value.</p> <h1 id="safety" class="section-header"><a href="#safety">Safety</a></h1> <p>This operation is marked unsafe because it accepts a raw pointer.</p> <p>It does not drop the contents of <code>dst</code>. This is safe, but it could leak allocations or resources, so care must be taken not to overwrite an object that should be dropped.</p> <p>Additionally, it does not drop <code>src</code>. Semantically, <code>src</code> is moved into the location pointed to by <code>dst</code>.</p> <p>This is appropriate for initializing uninitialized memory, or overwriting memory that has previously been <code>read</code> from.</p> <p>The pointer must be aligned; use <code>write_unaligned</code> if that is not the case.</p> <h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1> <p>Basic usage:</p> <pre class="rust rust-example-rendered"> <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">x</span> <span class="op">=</span> <span class="number">0</span>; <span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">x</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">i32</span>; <span class="kw">let</span> <span class="ident">z</span> <span class="op">=</span> <span class="number">12</span>; <span class="kw">unsafe</span> { <span class="ident">std</span>::<span class="ident">ptr</span>::<span class="ident">write</span>(<span class="ident">y</span>, <span class="ident">z</span>); <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">std</span>::<span class="ident">ptr</span>::<span class="ident">read</span>(<span class="ident">y</span>), <span class="number">12</span>); }<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Afn%20main()%20%7B%0Alet%20mut%20x%20%3D%200%3B%0Alet%20y%20%3D%20%26mut%20x%20as%20*mut%20i32%3B%0Alet%20z%20%3D%2012%3B%0A%0Aunsafe%20%7B%0A%20%20%20%20std%3A%3Aptr%3A%3Awrite(y%2C%20z)%3B%0A%20%20%20%20assert_eq!(std%3A%3Aptr%3A%3Aread(y)%2C%2012)%3B%0A%7D%0A%7D">Run</a></pre> </div></section><section id="search" class="content hidden"></section><section class="footer"></section><aside id="help" class="hidden"><div><h1 class="hidden">Help</h1><div class="shortcuts"><h2>Keyboard Shortcuts</h2><dl><dt><kbd>?</kbd></dt><dd>Show this help dialog</dd><dt><kbd>S</kbd></dt><dd>Focus the search field</dd><dt><kbd>↑</kbd></dt><dd>Move up in search results</dd><dt><kbd>↓</kbd></dt><dd>Move down in search results</dd><dt><kbd>↹</kbd></dt><dd>Switch tab</dd><dt><kbd>⏎</kbd></dt><dd>Go to active search result</dd><dt><kbd>+</kbd></dt><dd>Expand all sections</dd><dt><kbd>-</kbd></dt><dd>Collapse all sections</dd></dl></div><div class="infos"><h2>Search Tricks</h2><p>Prefix searches with a type followed by a colon (e.g. <code>fn:</code>) to restrict the search to a given type.</p><p>Accepted types are: <code>fn</code>, <code>mod</code>, <code>struct</code>, <code>enum</code>, <code>trait</code>, <code>type</code>, <code>macro</code>, and <code>const</code>.</p><p>Search functions by type signature (e.g. <code>vec -> usize</code> or <code>* -> vec</code>)</p><p>Search multiple things at once by splitting your query with comma (e.g. <code>str,u8</code> or <code>String,struct:Vec,test</code>)</p></div></div></aside><script>window.rootPath = "../../";window.currentCrate = "std";</script><script src="../../aliases.js"></script><script src="../../main.js"></script><script defer src="../../search-index.js"></script></body></html>