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25 lines
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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 `cfg_if` crate."><meta name="keywords" content="rust, rustlang, rust-lang, cfg_if"><title>cfg_if - 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="../light.css" id="themeStyle"><link rel="stylesheet" type="text/css" href="../dark.css" disabled ><link rel="stylesheet" type="text/css" href="../ayu.css" disabled ><script id="default-settings"></script><script src="../storage.js"></script><noscript><link rel="stylesheet" href="../noscript.css"></noscript><link rel="icon" type="image/svg+xml" href="../favicon.svg">
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<link rel="alternate icon" type="image/png" href="../favicon-32x32.png"><style type="text/css">#crate-search{background-image:url("../down-arrow.svg");}</style></head><body class="rustdoc mod"><!--[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='../cfg_if/index.html'><div class='logo-container rust-logo'><img src='../rust-logo.png' alt='logo'></div></a><p class="location">Crate cfg_if</p><div class="block version"><p>Version 1.0.0</p></div><div class="sidebar-elems"><a id="all-types" href="all.html"><p>See all cfg_if's items</p></a><div class="block items"><ul><li><a href="#macros">Macros</a></li></ul></div><p class="location"></p><script>window.sidebarCurrent = {name: "cfg_if", ty: "mod", relpath: "../"};</script></div></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!" aria-haspopup="menu"><img src="../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices" role="menu"></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><button type="button" class="help-button">?</button>
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<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 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/cfg_if/lib.rs.html#1-176" title="goto source code">[src]</a></span><span class="in-band">Crate <a class="mod" href="">cfg_if</a></span></h1><div class="docblock"><p>A macro for defining <code>#[cfg]</code> if-else statements.</p>
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<p>The macro provided by this crate, <code>cfg_if</code>, is similar to the <code>if/elif</code> C
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preprocessor macro by allowing definition of a cascade of <code>#[cfg]</code> cases,
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emitting the implementation which matches first.</p>
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<p>This allows you to conveniently provide a long list <code>#[cfg]</code>'d blocks of code
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without having to rewrite each clause multiple times.</p>
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<h1 id="example" class="section-header"><a href="#example">Example</a></h1>
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<div class="example-wrap"><pre class="rust rust-example-rendered">
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<span class="ident">cfg_if</span>::<span class="macro">cfg_if</span><span class="macro">!</span> {
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<span class="kw">if</span> <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">unix</span>)]</span> {
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<span class="kw">fn</span> <span class="ident">foo</span>() { <span class="comment">/* unix specific functionality */</span> }
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} <span class="kw">else</span> <span class="kw">if</span> <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">target_pointer_width</span> <span class="op">=</span> <span class="string">"32"</span>)]</span> {
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<span class="kw">fn</span> <span class="ident">foo</span>() { <span class="comment">/* non-unix, 32-bit functionality */</span> }
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} <span class="kw">else</span> {
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<span class="kw">fn</span> <span class="ident">foo</span>() { <span class="comment">/* fallback implementation */</span> }
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}
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}
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</pre></div>
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</div><h2 id="macros" class="section-header"><a href="#macros">Macros</a></h2>
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<table><tr class="module-item"><td><a class="macro" href="macro.cfg_if.html" title="cfg_if::cfg_if macro">cfg_if</a></td><td class="docblock-short"><p>The main macro provided by this crate. See crate documentation for more
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information.</p>
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