25 lines
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25 lines
5.5 KiB
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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="API documentation for the Rust `zeroed` fn in crate `nom`."><meta name="keywords" content="rust, rustlang, rust-lang, zeroed"><title>nom::lib::std::mem::zeroed - 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><noscript><link rel="stylesheet" href="../../../../noscript.css"></noscript><link rel="shortcut icon" href="../../../../favicon.ico"><style type="text/css">#crate-search{background-image:url("../../../../down-arrow.svg");}</style></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='../../../../nom/index.html'><div class='logo-container'><img src='../../../../rust-logo.png' alt='logo'></div></a><div class="sidebar-elems"><p class='location'><a href='../../../index.html'>nom</a>::<wbr><a href='../../index.html'>lib</a>::<wbr><a href='../index.html'>std</a>::<wbr><a href='index.html'>mem</a></p><script>window.sidebarCurrent = {name: 'zeroed', 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"><div class="search-container"><div><select id="crate-search"><option value="All crates">All crates</option></select><input class="search-input" name="search" disabled autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"></div><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='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='https://doc.rust-lang.org/nightly/src/core/mem/mod.rs.html#498-501' title='goto source code'>[src]</a></span><span class='in-band'>Function <a href='../../../index.html'>nom</a>::<wbr><a href='../../index.html'>lib</a>::<wbr><a href='../index.html'>std</a>::<wbr><a href='index.html'>mem</a>::<wbr><a class="fn" href=''>zeroed</a></span></h1><pre class='rust fn'>pub unsafe fn zeroed<T>() -> T</pre><div class='docblock'><p>Returns the value of type <code>T</code> represented by the all-zero byte-pattern.</p>
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<p>This means that, for example, the padding byte in <code>(u8, u16)</code> is not
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necessarily zeroed.</p>
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<p>There is no guarantee that an all-zero byte-pattern represents a valid value of
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some type <code>T</code>. For example, the all-zero byte-pattern is not a valid value
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for reference types (<code>&T</code> and <code>&mut T</code>). Using <code>zeroed</code> on such types
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causes immediate <a href="../../reference/behavior-considered-undefined.html">undefined behavior</a> because <a href="union.MaybeUninit.html#initialization-invariant">the Rust compiler assumes</a>
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that there always is a valid value in a variable it considers initialized.</p>
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<p>This has the same effect as <a href="union.MaybeUninit.html#method.zeroed"><code>MaybeUninit::zeroed().assume_init()</code></a>.
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It is useful for FFI sometimes, but should generally be avoided.</p>
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<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
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<p>Correct usage of this function: initializing an integer with zero.</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered">
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<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">mem</span>;
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<span class="kw">let</span> <span class="ident">x</span>: <span class="ident">i32</span> <span class="op">=</span> <span class="kw">unsafe</span> { <span class="ident">mem</span>::<span class="ident">zeroed</span>() };
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<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">0</span>, <span class="ident">x</span>);</pre></div>
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<p><em>Incorrect</em> usage of this function: initializing a reference with zero.</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered">
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<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">mem</span>;
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<span class="kw">let</span> <span class="ident">_x</span>: <span class="kw-2">&</span><span class="ident">i32</span> <span class="op">=</span> <span class="kw">unsafe</span> { <span class="ident">mem</span>::<span class="ident">zeroed</span>() }; <span class="comment">// Undefined behavior!</span></pre></div>
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