<!DOCTYPE html><htmllang="en"><head><metacharset="utf-8"><metaname="viewport"content="width=device-width, initial-scale=1.0"><metaname="generator"content="rustdoc"><metaname="description"content="Atomic memory orderings"><title>Ordering in atomic_polyfill - Rust</title><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../static.files/SourceSerif4-Regular-46f98efaafac5295.ttf.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../static.files/FiraSans-Regular-018c141bf0843ffd.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../static.files/FiraSans-Medium-8f9a781e4970d388.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../static.files/SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../static.files/SourceSerif4-Bold-a2c9cd1067f8b328.ttf.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../static.files/SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2"><linkrel="stylesheet"href="../static.files/normalize-76eba96aa4d2e634.css"><linkrel="stylesheet"href="../static.files/rustdoc-cb6f1f67f1bcd037.css"id="mainThemeStyle"><metaname="rustdoc-vars"data-root-path="../"data-static-root-path="../static.files/"data-current-crate="atomic_polyfill"data-themes=""data-resource-suffix=""data-rustdoc-version="1.73.0-nightly (500647fd8 2023-07-27)"data-channel="nightly"data-search-js="search-6dfdfced5eff6596.js"data-settings-js="settings-de11bff964e9d4e5.js"data-settings-css="settings-8c76f75bfb6bd192.css"data-theme-light-css="light-6d2c9675f3d09c26.css"data-theme-dark-css="dark-45ceb8f2e522f4d1.css"data-theme-ayu-css="ayu-fd19013d6ce078bf.css"><scriptsrc="../static.files/storage-db41da1a38ea3cb8.js"></script><scriptdefersrc="sidebar-items.js"></script><scriptdefersrc="../static.files/main-0795b7d26be81095.js"></script><noscript><linkrel="stylesheet"media="(prefers-color-scheme:light)"href="../static.files/light-6d2c9675f3d09c26.css"><linkrel="stylesheet"media="(prefers-color-scheme:dark)"href="../static.files/dark-45ceb8f2e522f4d1.css"><linkrel="stylesheet"href="../static.files/noscript-cffde32267a19fd6.css"></noscript><linkrel="alternate icon"type="image/png"href="../static.files/favicon-16x16-8b506e7a72182f1c.png"><linkrel="alternate icon"type="image/png"href="../static.files/favicon-32x32-422f7d1d52889060.png"><linkrel="icon"type="image/svg+xml"href="../static.files/favicon-2c020d218678b618.svg"></head><bodyclass="rustdoc enum"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><navclass="mobile-topbar"><buttonclass="sidebar-menu-toggle">☰</button><aclass="logo-container"href="../atomic_polyfill/index.html"><imgclass="rust-logo"src="../static.files/rust-logo-151179464ae7ed46.svg"alt="logo"></a><h2></h2></nav><navclass="sidebar"><aclass="logo-container"href="../atomic_polyfill/index.html"><imgclass="rust-logo"src="../static.files/rust-logo-151179464ae7ed46.svg"alt="logo"></a><h2class="location"><ahref="#">Ordering</a></h2><divclass="sidebar-elems"><section><h3><ahref="#variants">Variants</a></h3><ulclass="block"><li><ahref="#variant.AcqRel">AcqRel</a></li><li><ahref="#variant.Acquire">Acquire</a></li><li><ahref="#variant.Relaxed">Relaxed</a></li><li><ahref="#variant.Release">Release</a></li><li><ahref="#variant.SeqCst">SeqCst</a></li></ul><h3><ahref="#trait-implementations">Trait Implementations</a></h3><ulclass="block"><li><ahref="#impl-Clone-for-Ordering">Clone</a></li><li><ahref="#impl-Copy-for-Ordering">Copy</a></li><li><ahref="#impl-Debug-for-Ordering">Debug</a></li><li><ahref="#impl-Eq-for-Ordering">Eq</a></li><li><ahref="#impl-Hash-for-Ordering">Hash</a></li><li><ahref="#impl-PartialEq%3COrdering%3E-for-Ordering">PartialEq<Ordering></a></li><li><ahref="#impl-StructuralEq-for-Ordering">StructuralEq</a></li><li><ahref="#impl-StructuralPartialEq-for-Ordering">StructuralPartialEq</a></li>
<p>Memory orderings specify the way atomic operations synchronize memory.
In its weakest <ahref="enum.Ordering.html#variant.Relaxed"title="variant atomic_polyfill::Ordering::Relaxed"><code>Ordering::Relaxed</code></a>, only the memory directly touched by the
operation is synchronized. On the other hand, a store-load pair of <ahref="enum.Ordering.html#variant.SeqCst"title="variant atomic_polyfill::Ordering::SeqCst"><code>Ordering::SeqCst</code></a>
operations synchronize other memory while additionally preserving a total order of such
operations across all threads.</p>
<p>Rust’s memory orderings are <ahref="https://en.cppreference.com/w/cpp/atomic/memory_order">the same as those of
C++20</a>.</p>
<p>For more information see the <ahref="../../../nomicon/atomics.html">nomicon</a>.</p>
</div></details><h2id="variants"class="variants small-section-header">Variants (Non-exhaustive)<ahref="#variants"class="anchor">§</a></h2><detailsclass="toggle non-exhaustive"><summaryclass="hideme"><span>This enum is marked as non-exhaustive</span></summary><divclass="docblock">Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.</div></details><divclass="variants"><sectionid="variant.Relaxed"class="variant"><ahref="#variant.Relaxed"class="anchor">§</a><h3class="code-header">Relaxed</h3></section><divclass="docblock"><p>No ordering constraints, only atomic operations.</p>
<p>Corresponds to <ahref="https://en.cppreference.com/w/cpp/atomic/memory_order#Relaxed_ordering"><code>memory_order_relaxed</code></a> in C++20.</p>
</div><sectionid="variant.Release"class="variant"><ahref="#variant.Release"class="anchor">§</a><h3class="code-header">Release</h3></section><divclass="docblock"><p>When coupled with a store, all previous operations become ordered
before any load of this value with <ahref="enum.Ordering.html#variant.Acquire"title="variant atomic_polyfill::Ordering::Acquire"><code>Acquire</code></a> (or stronger) ordering.
In particular, all previous writes become visible to all threads
that perform an <ahref="enum.Ordering.html#variant.Acquire"title="variant atomic_polyfill::Ordering::Acquire"><code>Acquire</code></a> (or stronger) load of this value.</p>
<p>Notice that using this ordering for an operation that combines loads
and stores leads to a <ahref="enum.Ordering.html#variant.Relaxed"title="variant atomic_polyfill::Ordering::Relaxed"><code>Relaxed</code></a> load operation!</p>
<p>This ordering is only applicable for operations that can perform a store.</p>
<p>Corresponds to <ahref="https://en.cppreference.com/w/cpp/atomic/memory_order#Release-Acquire_ordering"><code>memory_order_release</code></a> in C++20.</p>
</div><sectionid="variant.Acquire"class="variant"><ahref="#variant.Acquire"class="anchor">§</a><h3class="code-header">Acquire</h3></section><divclass="docblock"><p>When coupled with a load, if the loaded value was written by a store operation with
<ahref="enum.Ordering.html#variant.Release"title="variant atomic_polyfill::Ordering::Release"><code>Release</code></a> (or stronger) ordering, then all subsequent operations
become ordered after that store. In particular, all subsequent loads will see data
written before the store.</p>
<p>Notice that using this ordering for an operation that combines loads
and stores leads to a <ahref="enum.Ordering.html#variant.Relaxed"title="variant atomic_polyfill::Ordering::Relaxed"><code>Relaxed</code></a> store operation!</p>
<p>This ordering is only applicable for operations that can perform a load.</p>
<p>Corresponds to <ahref="https://en.cppreference.com/w/cpp/atomic/memory_order#Release-Acquire_ordering"><code>memory_order_acquire</code></a> in C++20.</p>
</div><sectionid="variant.AcqRel"class="variant"><ahref="#variant.AcqRel"class="anchor">§</a><h3class="code-header">AcqRel</h3></section><divclass="docblock"><p>Has the effects of both <ahref="enum.Ordering.html#variant.Acquire"title="variant atomic_polyfill::Ordering::Acquire"><code>Acquire</code></a> and <ahref="enum.Ordering.html#variant.Release"title="variant atomic_polyfill::Ordering::Release"><code>Release</code></a> together:
For loads it uses <ahref="enum.Ordering.html#variant.Acquire"title="variant atomic_polyfill::Ordering::Acquire"><code>Acquire</code></a> ordering. For stores it uses the <ahref="enum.Ordering.html#variant.Release"title="variant atomic_polyfill::Ordering::Release"><code>Release</code></a> ordering.</p>
<p>Notice that in the case of <code>compare_and_swap</code>, it is possible that the operation ends up
not performing any store and hence it has just <ahref="enum.Ordering.html#variant.Acquire"title="variant atomic_polyfill::Ordering::Acquire"><code>Acquire</code></a> ordering. However,
<code>AcqRel</code> will never perform <ahref="enum.Ordering.html#variant.Relaxed"title="variant atomic_polyfill::Ordering::Relaxed"><code>Relaxed</code></a> accesses.</p>
<p>This ordering is only applicable for operations that combine both loads and stores.</p>
<p>Corresponds to <ahref="https://en.cppreference.com/w/cpp/atomic/memory_order#Release-Acquire_ordering"><code>memory_order_acq_rel</code></a> in C++20.</p>
</div><sectionid="variant.SeqCst"class="variant"><ahref="#variant.SeqCst"class="anchor">§</a><h3class="code-header">SeqCst</h3></section><divclass="docblock"><p>Like <ahref="enum.Ordering.html#variant.Acquire"title="variant atomic_polyfill::Ordering::Acquire"><code>Acquire</code></a>/<ahref="enum.Ordering.html#variant.Release"title="variant atomic_polyfill::Ordering::Release"><code>Release</code></a>/<ahref="enum.Ordering.html#variant.AcqRel"title="variant atomic_polyfill::Ordering::AcqRel"><code>AcqRel</code></a> (for load, store, and load-with-store
operations, respectively) with the additional guarantee that all threads see all
sequentially consistent operations in the same order.</p>
<p>Corresponds to <ahref="https://en.cppreference.com/w/cpp/atomic/memory_order#Sequentially-consistent_ordering"><code>memory_order_seq_cst</code></a> in C++20.</p>
</div></div><h2id="trait-implementations"class="small-section-header">Trait Implementations<ahref="#trait-implementations"class="anchor">§</a></h2><divid="trait-implementations-list"><detailsclass="toggle implementors-toggle"open><summary><sectionid="impl-Clone-for-Ordering"class="impl"><ahref="#impl-Clone-for-Ordering"class="anchor">§</a><h3class="code-header">impl Clone for <aclass="enum"href="enum.Ordering.html"title="enum atomic_polyfill::Ordering">Ordering</a></h3></section></summary><divclass="impl-items"><detailsclass="toggle method-toggle"open><summary><sectionid="method.clone"class="method trait-impl"><ahref="#method.clone"class="anchor">§</a><h4class="code-header">fn <aclass="fn">clone</a>(&self) -><aclass="enum"href="enum.Ordering.html"title="enum atomic_polyfill::Ordering">Ordering</a></h4></section></summary><divclass='docblock'>Returns a copy of the value. <a>Read more</a></div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.clone_from"class="method trait-impl"><ahref="#method.clone_from"class="anchor">§</a><h4class="code-header">fn <aclass="fn">clone_from</a>(&mut self, source: &Self)</h4></section></summary><divclass='docblock'>Performs copy-assignment from <code>source</code>. <a>Read more</a></div></details></div></details><detailsclass="toggle implementors-toggle"open><summary><sectionid="impl-Debug-for-Ordering"class="impl"><ahref="#impl-Debug-for-Ordering"class="anchor">§</a><h3class="code-header">impl Debug for <aclass="enum"href="enum.Ordering.html"title="enum atomic_polyfill::Ordering">Ordering</a></h3></section></summary><divclass="impl-items"><detailsclass="toggle method-toggle"open><summary><sectionid="method.fmt"class="method trait-impl"><ahref="#method.fmt"class="anchor">§</a><h4class="code-header">fn <aclass="fn">fmt</a>(&self, f: &mut Formatter<'_>) -> Result<(), Error></h4></section></summary><divclass='docblock'>Formats the value using the given formatter. <a>Read more</a></div></details></div></details><detailsclass="toggle implementors-toggle"open><summary><sectionid="impl-Hash-for-Ordering"class="impl"><ahref="#impl-Hash-for-Ordering"class="anchor">§</a><h3class="code-header">impl Hash for <aclass="enum"href="enum.Ordering.html"title="enum atomic_polyfill::Ordering">Ordering</a></h3></section></summary><divclass="impl-items"><detailsclass="toggle method-toggle"open><summary><sectionid="method.hash"class="method trait-impl"><ahref="#method.hash"class="anchor">§</a><h4class="code-header">fn <aclass="fn">hash</a><__H>(&self, state: &mut __H)<spanclass="where fmt-newline">where
__H: Hasher,</span></h4></section></summary><divclass='docblock'>Feeds this value into the given [<code>Hasher</code>]. <a>Read more</a></div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.hash_slice"class="method trait-impl"><spanclass="since rightside"title="Stable since Rust version 1.3.0">1.3.0</span><ahref="#method.hash_slice"class="anchor">§</a><h4class="code-header">fn <aclass="fn">hash_slice</a><H>(data: &[Self], state: &mut H)<spanclass="where fmt-newline">where
H: Hasher,
Self: Sized,</span></h4></section></summary><divclass='docblock'>Feeds a slice of this type into the given [<code>Hasher</code>]. <a>Read more</a></div></details></div></details><detailsclass="toggle implementors-toggle"open><summary><sectionid="impl-PartialEq%3COrdering%3E-for-Ordering"class="impl"><ahref="#impl-PartialEq%3COrdering%3E-for-Ordering"class="anchor">§</a><h3class="code-header">impl PartialEq<<aclass="enum"href="enum.Ordering.html"title="enum atomic_polyfill::Ordering">Ordering</a>> for <aclass="enum"href="enum.Ordering.html"title="enum atomic_polyfill::Ordering">Ordering</a></h3></section></summary><divclass="impl-items"><detailsclass="toggle method-toggle"open><summary><sectionid="method.eq"class="method trait-impl"><ahref="#method.eq"class="anchor">§</a><h4class="code-header">fn <aclass="fn">eq</a>(&self, other: &<aclass="enum"href="enum.Ordering.html"title="enum atomic_polyfill::Ordering">Ordering</a>) -> bool</h4></section></summary><divclass='docblock'>This method tests for <code>self</code> and <code>other</code> values to be equal, and is used
by <code>==</code>.</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.ne"class="method trait-impl"><ahref="#method.ne"class="anchor">§</a><h4class="code-header">fn <aclass="fn">ne</a>(&self, other: &Rhs) -> bool</h4></section></summary><divclass='docblock'>This method tests for <code>!=</code>. The default implementation is almost always
sufficient, and should not be overridden without very good reason.</div></details></div></details><sectionid="impl-Copy-for-Ordering"class="impl"><ahref="#impl-Copy-for-Ordering"class="anchor">§</a><h3class="code-header">impl Copy for <aclass="enum"href="enum.Ordering.html"title="enum atomic_polyfill::Ordering">Ordering</a></h3></section><sectionid="impl-Eq-for-Ordering"class="impl"><ahref="#impl-Eq-for-Ordering"class="anchor">§</a><h3class="code-header">impl Eq for <aclass="enum"href="enum.Ordering.html"title="enum atomic_polyfill::Ordering">Ordering</a></h3></section><sectionid="impl-StructuralEq-for-Ordering"class="impl"><ahref="#impl-StructuralEq-for-Ordering"class="anchor">§</a><h3class="code-header">impl StructuralEq for <aclass="enum"href="enum.Ordering.html"title="enum atomic_polyfill::Ordering">Ordering</a></h3></section><sectionid="impl-StructuralPartialEq-for-Ordering"class="impl"><ahref="#impl-StructuralPartialEq-for-Ordering"class="anchor">§</a><h3class="code-header">impl StructuralPartialEq for <aclass="enum"href="enum.Ordering.html"title="enum atomic_polyfill::Ordering">Ordering</a></h3></section></div><h2id="synthetic-implementations"class="small-section-header">Auto Trait Implementations<ahref="#synthetic-implementations"class="anchor">§</a></h2><divid="synthetic-implementations-list"><sectionid="impl-RefUnwindSafe-for-Ordering"class="impl"><ahref="#impl-RefUnwindSafe-for-Ordering"class="anchor">§</a><h3class="code-header">impl RefUnwindSafe for <aclass="enum"href="enum.Ordering.html"title="enum atomic_polyfill::Ordering">Ordering</a></h3></section><sectionid="impl-Send-for-Ordering"class="impl"><ahref="#impl-Send-for-Ordering"class="anchor">§</a><h3class="code-header">impl Send for <aclass="enum"href="enum.Ordering.html"title="enum atomic_polyfill::Ordering">Ordering</a></h3></section><sectionid="impl-Sync-for-Ordering"class="impl"><ahref="#impl-Sync-for-Ordering"class="anchor">§</a><h3class="code-header">impl Sync for <aclass="enum"href="enum.Ordering.html"title="enum atomic_polyfill::Ordering">Ordering</a></h3></section><sectionid="impl-Unpin-for-Ordering"class="impl"><ahref="#impl-Unpin-for-Ordering"class="anchor">§</a><h3class="code-header">impl Unpin for <aclass="enum"href="enum.Ordering.html"title="enum atomic_polyfill::Ordering">Ordering</a></h3></section><sectionid="impl-UnwindSafe-for-Ordering"class="impl"><ahref="#impl-UnwindSafe-for-Ordering"class="anchor">§</a><h3class="code-header">impl UnwindSafe for <aclass="enum"href="enum.Ordering.html"title="enum atomic_polyfill::Ordering">Ordering</a></h3></section></div><h2id="blanket-implementations"class="small-section-header">Blanket Implementations<ahref="#blanket-implementations"class="anchor">§</a></h2><divid="blanket-implementations-list"><detailsclass="toggle implementors-toggle"><summary><sectionid="impl-Any-for-Ordering"class="impl"><ahref="#impl-Any-for-Ordering"class="anchor">§</a><h3class="code-header">impl<T> Any for T<spanclass="where fmt-newline">where
T: 'static + ?Sized,</span></h3></section></summary><divclass="impl-items"><detailsclass="toggle method-toggle"open><summary><sectionid="method.type_id"class="method trait-impl"><ahref="#method.type_id"class="anchor">§</a><h4class="code-header">fn <aclass="fn">type_id</a>(&self) -> TypeId</h4></section></summary><divclass='docblock'>Gets the <code>TypeId</code> of <code>self</code>. <a>Read more</a></div></details></div></details><detailsclass="toggle implementors-toggle"><summary><sectionid="impl-Borrow%3CT%3E-for-Ordering"class="impl"><ahref="#impl-Borrow%3CT%3E-for-Ordering"class="anchor">§</a><h3class="code-header">impl<T> Borrow<T> for T<spanclass="where fmt-newline">where
T: ?Sized,</span></h3></section></summary><divclass="impl-items"><detailsclass="toggle method-toggle"open><summary><sectionid="method.borrow"class="method trait-impl"><ahref="#method.borrow"class="anchor">§</a><h4class="code-header">fn <aclass="fn">borrow</a>(&self) ->&T</h4></section></summary><divclass='docblock'>Immutably borrows from an owned value. <a>Read more</a></div></details></div></details><detailsclass="toggle implementors-toggle"><summary><sectionid="impl-BorrowMut%3CT%3E-for-Ordering"class="impl"><ahref="#impl-BorrowMut%3CT%3E-for-Ordering"class="anchor">§</a><h3class="code-header">impl<T> BorrowMut<T> for T<spanclass="where fmt-newline">where
T: ?Sized,</span></h3></section></summary><divclass="impl-items"><detailsclass="toggle method-toggle"open><summary><sectionid="method.borrow_mut"class="method trait-impl"><ahref="#method.borrow_mut"class="anchor">§</a><h4class="code-header">fn <aclass="fn">borrow_mut</a>(&mut self) ->&mut T</h4></section></summary><divclass='docblock'>Mutably borrows from an owned value. <a>Read more</a></div></details></div></details><detailsclass="toggle implementors-toggle"><summary><sectionid="impl-From%3CT%3E-for-Ordering"class="impl"><ahref="#impl-From%3CT%3E-for-Ordering"class="anchor">§</a><h3class="code-header">impl<T> From<T> for T</h3></section></summary><divclass="impl-items"><detailsclass="toggle method-toggle"open><summary><sectionid="method.from"class="method trait-impl"><ahref="#method.from"class="anchor">§</a><h4class="code-header">fn <aclass="fn">from</a>(t: T) -> T</h4></section></summary><divclass="docblock"><p>Returns the argument unchanged.</p>
</div></details></div></details><detailsclass="toggle implementors-toggle"><summary><sectionid="impl-Into%3CU%3E-for-Ordering"class="impl"><ahref="#impl-Into%3CU%3E-for-Ordering"class="anchor">§</a><h3class="code-header">impl<T, U> Into<U> for T<spanclass="where fmt-newline">where
U: Into<T>,</span></h3></section></summary><divclass="impl-items"><detailsclass="toggle"open><summary><sectionid="associatedtype.Error"class="associatedtype trait-impl"><ahref="#associatedtype.Error"class="anchor">§</a><h4class="code-header">type <aclass="associatedtype">Error</a> = Infallible</h4></section></summary><divclass='docblock'>The type returned in the event of a conversion error.</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.try_from"class="method trait-impl"><ahref="#method.try_from"class="anchor">§</a><h4class="code-header">fn <aclass="fn">try_from</a>(value: U) -> Result<T, <T as TryFrom<U>>::Error></h4></section></summary><divclass='docblock'>Performs the conversion.</div></details></div></details><detailsclass="toggle implementors-toggle"><summary><sectionid="impl-TryInto%3CU%3E-for-Ordering"class="impl"><ahref="#impl-TryInto%3CU%3E-for-Ordering"class="anchor">§</a><h3class="code-header">impl<T, U> TryInto<U> for T<spanclass="where fmt-newline">where
U: TryFrom<T>,</span></h3></section></summary><divclass="impl-items"><detailsclass="toggle"open><summary><sectionid="associatedtype.Error-1"class="associatedtype trait-impl"><ahref="#associatedtype.Error-1"class="anchor">§</a><h4class="code-header">type <aclass="associatedtype">Error</a> = <U as TryFrom<T>>::Error</h4></section></summary><divclass='docblock'>The type returned in the event of a conversion error.</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.try_into"class="method trait-impl"><ahref="#method.try_into"class="anchor">§</a><h4class="code-header">fn <aclass="fn">try_into</a>(self) -> Result<U, <U as TryFrom<T>>::Error></h4></section></summary><divclass='docblock'>Performs the conversion.</div></details></div></details></div></section></div></main></body></html>
