17 lines
4.9 KiB
HTML
17 lines
4.9 KiB
HTML
<!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 `uninitialized` fn in crate `nom`."><meta name="keywords" content="rust, rustlang, rust-lang, uninitialized"><title>nom::lib::std::mem::uninitialized - 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: 'uninitialized', 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#531-534' 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=''>uninitialized</a></span></h1><pre class='rust fn'>pub unsafe fn uninitialized<T>() -> T</pre><div class='stability'><div class='stab deprecated'>Deprecated since 1.39.0: <p>use <code>mem::MaybeUninit</code> instead</p>
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</div></div><div class='docblock'><p>Bypasses Rust's normal memory-initialization checks by pretending to
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produce a value of type <code>T</code>, while doing nothing at all.</p>
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<p><strong>This function is deprecated.</strong> Use <a href="union.MaybeUninit.html"><code>MaybeUninit<T></code></a> instead.</p>
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<p>The reason for deprecation is that the function basically cannot be used
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correctly: it has the same effect as <a href="union.MaybeUninit.html#method.uninit"><code>MaybeUninit::uninit().assume_init()</code></a>.
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As the <a href="union.MaybeUninit.html#method.assume_init"><code>assume_init</code> documentation</a> explains,
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<a href="union.MaybeUninit.html#initialization-invariant">the Rust compiler assumes</a> that values are properly initialized.
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As a consequence, calling e.g. <code>mem::uninitialized::<bool>()</code> causes immediate
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undefined behavior for returning a <code>bool</code> that is not definitely either <code>true</code>
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or <code>false</code>. Worse, truly uninitialized memory like what gets returned here
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is special in that the compiler knows that it does not have a fixed value.
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This makes it undefined behavior to have uninitialized data in a variable even
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if that variable has an integer type.
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(Notice that the rules around uninitialized integers are not finalized yet, but
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until they are, it is advisable to avoid them.)</p>
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