<!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 `thread_local` macro in crate `std`."><meta name="keywords" content="rust, rustlang, rust-lang, thread_local"><title>std::thread_local - 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 macro"><!--[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></p><script>window.sidebarCurrent = {name: 'thread_local', ty: 'macro', 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'>Macro <a href='index.html'>std</a>::<wbr><a class="macro" href=''>thread_local</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/std/thread/local.rs.html#142-156' title='goto source code'>[src]</a></span></h1><div class="docblock type-decl"><pre class="rust macro">
<span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">thread_local</span> {
() <span class="op">=></span> { ... };
($(<span class="attribute">#[<span class="macro-nonterminal">$</span><span class="macro-nonterminal">attr</span>:<span class="ident">meta</span>]</span>)<span class="op">*</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">vis</span>:<span class="ident">vis</span> <span class="kw">static</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">name</span>:<span class="ident">ident</span>: <span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span>:<span class="ident">ty</span> <span class="op">=</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">init</span>:<span class="ident">expr</span>; $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">rest</span>:<span class="ident">tt</span>)<span class="kw-2">*</span>) <span class="op">=></span> { ... };
($(<span class="attribute">#[<span class="macro-nonterminal">$</span><span class="macro-nonterminal">attr</span>:<span class="ident">meta</span>]</span>)<span class="op">*</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">vis</span>:<span class="ident">vis</span> <span class="kw">static</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">name</span>:<span class="ident">ident</span>: <span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span>:<span class="ident">ty</span> <span class="op">=</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">init</span>:<span class="ident">expr</span>) <span class="op">=></span> { ... };
}</pre>
</div><div class='docblock'><p>Declare a new thread local storage key of type <a href="../std/thread/struct.LocalKey.html"><code>std::thread::LocalKey</code></a>.</p>
<h1 id="syntax" class="section-header"><a href="#syntax">Syntax</a></h1>
<p>The macro wraps any number of static declarations and makes them thread local.
Publicity and attributes for each static are allowed. Example:</p>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">cell</span>::<span class="ident">RefCell</span>;
<span class="macro">thread_local</span><span class="macro">!</span> {
<span class="kw">pub</span> <span class="kw">static</span> <span class="ident">FOO</span>: <span class="ident">RefCell</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="ident">RefCell</span>::<span class="ident">new</span>(<span class="number">1</span>);
<span class="attribute">#[<span class="ident">allow</span>(<span class="ident">unused</span>)]</span>
<span class="kw">static</span> <span class="ident">BAR</span>: <span class="ident">RefCell</span><span class="op"><</span><span class="ident">f32</span><span class="op">></span> <span class="op">=</span> <span class="ident">RefCell</span>::<span class="ident">new</span>(<span class="number">1.0</span>);
}<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0Ause%20std%3A%3Acell%3A%3ARefCell%3B%0Athread_local!%20%7B%0A%20%20%20%20pub%20static%20FOO%3A%20RefCell%3Cu32%3E%20%3D%20RefCell%3A%3Anew(1)%3B%0A%0A%20%20%20%20%23%5Ballow(unused)%5D%0A%20%20%20%20static%20BAR%3A%20RefCell%3Cf32%3E%20%3D%20RefCell%3A%3Anew(1.0)%3B%0A%7D%0Afn%20main()%20%7B%7D">Run</a></pre>
<p>See <a href="../std/thread/struct.LocalKey.html">LocalKey documentation</a> for more
information.</p>
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