<!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 `OnceState` struct in crate `std`."><meta name="keywords" content="rust, rustlang, rust-lang, OnceState"><title>std::sync::OnceState - 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 struct"><!--[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><p class='location'>Struct OnceState</p><div class="sidebar-elems"><div class="block items"><a class="sidebar-title" href="#methods">Methods</a><div class="sidebar-links"><a href="#method.poisoned">poisoned</a></div><a class="sidebar-title" href="#implementations">Trait Implementations</a><div class="sidebar-links"><a href="#impl-Debug">Debug</a></div><a class="sidebar-title" href="#synthetic-implementations">Auto Trait Implementations</a><div class="sidebar-links"><a href="#impl-Send">Send</a><a href="#impl-Sync">Sync</a></div></div><p class='location'><a href='../index.html'>std</a>::<wbr><a href='index.html'>sync</a></p><script>window.sidebarCurrent = {name: 'OnceState', ty: 'struct', 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'>Struct <a href='../index.html'>std</a>::<wbr><a href='index.html'>sync</a>::<wbr><a class="struct" href=''>OnceState</a></span><span class='out-of-band'><span class='since' title='Stable since Rust version '></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/sync/once.rs.html#114-116' title='goto source code'>[src]</a></span></h1><div class="docblock type-decl"><pre class='rust struct'>pub struct OnceState { /* fields omitted */ }</pre></div><div class='stability'><div class='stab unstable'><span class=microscope>🔬</span> This is a nightly-only experimental API. (<code>once_poison </code><a href="https://github.com/rust-lang/rust/issues/33577">#33577</a>)</div></div><div class='docblock'><p>State yielded to <a href="struct.Once.html#method.call_once_force"><code>call_once_force</code></a>’s closure parameter. The state can be
used to query the poison status of the <a href="struct.Once.html"><code>Once</code></a>.</p>
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<h2 id='methods' class='small-section-header'>
Methods<a href='#methods' class='anchor'></a>
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<h3 id='impl' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl <a class="struct" href="../../std/sync/struct.OnceState.html" title="struct std::sync::OnceState">OnceState</a></code><a href='#impl' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/std/sync/once.rs.html#421-467' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.poisoned' class="method"><span id='poisoned.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.poisoned' class='fnname'>poisoned</a>(&self) -> <a class="primitive" href="../primitive.bool.html">bool</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/std/sync/once.rs.html#464-466' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='stability'><div class='stab unstable'><span class=microscope>🔬</span> This is a nightly-only experimental API. (<code>once_poison </code><a href="https://github.com/rust-lang/rust/issues/33577">#33577</a>)</div></div><div class='docblock'><p>Returns whether the associated <a href="struct.Once.html"><code>Once</code></a> was poisoned prior to the
invocation of the closure passed to <a href="struct.Once.html#method.call_once_force"><code>call_once_force</code></a>.</p>
<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
<p>A poisoned <code>Once</code>:</p>
<pre class="rust rust-example-rendered">
<span class="attribute">#![<span class="ident">feature</span>(<span class="ident">once_poison</span>)]</span>
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">sync</span>::<span class="ident">Once</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">thread</span>;
<span class="kw">static</span> <span class="ident">INIT</span>: <span class="ident">Once</span> <span class="op">=</span> <span class="ident">Once</span>::<span class="ident">new</span>();
<span class="comment">// poison the once</span>
<span class="kw">let</span> <span class="ident">handle</span> <span class="op">=</span> <span class="ident">thread</span>::<span class="ident">spawn</span>(<span class="op">||</span> {
<span class="ident">INIT</span>.<span class="ident">call_once</span>(<span class="op">||</span> <span class="macro">panic</span><span class="macro">!</span>());
});
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">handle</span>.<span class="ident">join</span>().<span class="ident">is_err</span>());
<span class="ident">INIT</span>.<span class="ident">call_once_force</span>(<span class="op">|</span><span class="ident">state</span><span class="op">|</span> {
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">state</span>.<span class="ident">poisoned</span>());
});<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0A%23!%5Bfeature(once_poison)%5D%0A%0Afn%20main()%20%7B%0Ause%20std%3A%3Async%3A%3AOnce%3B%0Ause%20std%3A%3Athread%3B%0A%0Astatic%20INIT%3A%20Once%20%3D%20Once%3A%3Anew()%3B%0A%0A%2F%2F%20poison%20the%20once%0Alet%20handle%20%3D%20thread%3A%3Aspawn(%7C%7C%20%7B%0A%20%20%20%20INIT.call_once(%7C%7C%20panic!())%3B%0A%7D)%3B%0Aassert!(handle.join().is_err())%3B%0A%0AINIT.call_once_force(%7Cstate%7C%20%7B%0A%20%20%20%20assert!(state.poisoned())%3B%0A%7D)%3B%0A%7D&version=nightly">Run</a></pre>
<p>An unpoisoned <code>Once</code>:</p>
<pre class="rust rust-example-rendered">
<span class="attribute">#![<span class="ident">feature</span>(<span class="ident">once_poison</span>)]</span>
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">sync</span>::<span class="ident">Once</span>;
<span class="kw">static</span> <span class="ident">INIT</span>: <span class="ident">Once</span> <span class="op">=</span> <span class="ident">Once</span>::<span class="ident">new</span>();
<span class="ident">INIT</span>.<span class="ident">call_once_force</span>(<span class="op">|</span><span class="ident">state</span><span class="op">|</span> {
<span class="macro">assert</span><span class="macro">!</span>(<span class="op">!</span><span class="ident">state</span>.<span class="ident">poisoned</span>());
});<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=%23!%5Ballow(unused)%5D%0A%23!%5Bfeature(once_poison)%5D%0A%0Afn%20main()%20%7B%0Ause%20std%3A%3Async%3A%3AOnce%3B%0A%0Astatic%20INIT%3A%20Once%20%3D%20Once%3A%3Anew()%3B%0A%0AINIT.call_once_force(%7Cstate%7C%20%7B%0A%20%20%20%20assert!(!state.poisoned())%3B%0A%7D)%3B%0A%7D&version=nightly">Run</a></pre>
</div></div>
<h2 id='implementations' class='small-section-header'>
Trait Implementations<a href='#implementations' class='anchor'></a>
</h2>
<div id='implementations-list'><h3 id='impl-Debug' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl <a class="trait" href="../../std/fmt/trait.Debug.html" title="trait std::fmt::Debug">Debug</a> for <a class="struct" href="../../std/sync/struct.OnceState.html" title="struct std::sync::OnceState">OnceState</a></code><a href='#impl-Debug' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/std/sync/once.rs.html#113' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.fmt' class="method"><span id='fmt.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../std/fmt/trait.Debug.html#tymethod.fmt' class='fnname'>fmt</a>(&self, f: &mut <a class="struct" href="../../std/fmt/struct.Formatter.html" title="struct std::fmt::Formatter">Formatter</a>) -> <a class="type" href="../../std/fmt/type.Result.html" title="type std::fmt::Result">Result</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/std/sync/once.rs.html#113' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Formats the value using the given formatter. <a href="../../std/fmt/trait.Debug.html#tymethod.fmt">Read more</a></p>
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Auto Trait Implementations<a href='#synthetic-implementations' class='anchor'></a>
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<h3 id='impl-Send' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl <a class="trait" href="../../std/marker/trait.Send.html" title="trait std::marker::Send">Send</a> for <a class="struct" href="../../std/sync/struct.OnceState.html" title="struct std::sync::OnceState">OnceState</a></code><a href='#impl-Send' class='anchor'></a></span></td><td><span class='out-of-band'></span></td></tr></tbody></table></h3><div class='impl-items'></div><h3 id='impl-Sync' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl <a class="trait" href="../../std/marker/trait.Sync.html" title="trait std::marker::Sync">Sync</a> for <a class="struct" href="../../std/sync/struct.OnceState.html" title="struct std::sync::OnceState">OnceState</a></code><a href='#impl-Sync' class='anchor'></a></span></td><td><span class='out-of-band'></span></td></tr></tbody></table></h3><div class='impl-items'></div></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>
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