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<p class='location'>Struct Shared</p><div class="block items"><ul><li><a href="#methods">Methods</a></li><li><a href="#implementations">Trait Implementations</a></li></ul></div><p class='location'><a href='../index.html'>std</a>::<wbr><a href='index.html'>ptr</a></p><script>window.sidebarCurrent = {name: 'Shared', ty: 'struct', relpath: ''};</script><script defer src="sidebar-items.js"></script>
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<h1 class='fqn'><span class='in-band'>Struct <a href='../index.html'>std</a>::<wbr><a href='index.html'>ptr</a>::<wbr><a class="struct" href=''>Shared</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/core/ptr.rs.html#1099-1107' title='goto source code'>[src]</a></span></h1>
<pre class='rust struct'>pub struct Shared<T> <span class="where fmt-newline">where<br> T: ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>, </span> { /* fields omitted */ }</pre><div class='stability'><div class='stab unstable'><details><summary><span class=microscope>🔬</span> This is a nightly-only experimental API. (<code>shared </code><a href="https://github.com/rust-lang/rust/issues/27730">#27730</a>)</summary><p>needs an RFC to flesh out design</p>
</details></div></div><div class='docblock'><p>A wrapper around a raw <code>*mut T</code> that indicates that the possessor
of this wrapper has shared ownership of the referent. Useful for
building abstractions like <code>Rc<T></code>, <code>Arc<T></code>, or doubly-linked lists, which
internally use aliased raw pointers to manage the memory that they own.</p>
<p>This is similar to <code>Unique</code>, except that it doesn't make any aliasing
guarantees, and doesn't derive Send and Sync. Note that unlike <code>&T</code>,
Shared has no special mutability requirements. Shared may mutate data
aliased by other Shared pointers. More precise rules require Rust to
develop an actual aliasing model.</p>
<p>Unlike <code>*mut T</code>, the pointer must always be non-null, even if the pointer
is never dereferenced. This is so that enums may use this forbidden value
as a discriminant -- <code>Option<Shared<T>></code> has the same size as <code>Shared<T></code>.
However the pointer may still dangle if it isn't dereferenced.</p>
<p>Unlike <code>*mut T</code>, <code>Shared<T></code> is covariant over <code>T</code>. If this is incorrect
for your use case, you should include some PhantomData in your type to
provide invariance, such as <code>PhantomData<Cell<T>></code> or <code>PhantomData<&'a mut T></code>.
Usually this won't be necessary; covariance is correct for Rc, Arc, and LinkedList
because they provide a public API that follows the normal shared XOR mutable
rules of Rust.</p>
</div><h2 id='methods'>Methods</h2><h3 class='impl'><span class='in-band'><code>impl<T> <a class="struct" href="../../std/ptr/struct.Shared.html" title="struct std::ptr::Shared">Shared</a><T></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/ptr.rs.html#1120-1131' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.empty' class="method"><span id='empty.v' class='invisible'><code>fn <a href='#method.empty' class='fnname'>empty</a>() -> <a class="struct" href="../../std/ptr/struct.Shared.html" title="struct std::ptr::Shared">Shared</a><T></code></span></h4>
<div class='stability'><div class='stab unstable'><span class=microscope>🔬</span> This is a nightly-only experimental API. (<code>shared </code><a href="https://github.com/rust-lang/rust/issues/27730">#27730</a>)</div></div><div class='docblock'><p>Creates a new <code>Shared</code> that is dangling, but well-aligned.</p>
<p>This is useful for initializing types which lazily allocate, like
<code>Vec::new</code> does.</p>
</div></div><h3 class='impl'><span class='in-band'><code>impl<T> <a class="struct" href="../../std/ptr/struct.Shared.html" title="struct std::ptr::Shared">Shared</a><T> <span class="where fmt-newline">where<br> T: ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/ptr.rs.html#1134-1173' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.new' class="method"><span id='new.v' class='invisible'><code>unsafe fn <a href='#method.new' class='fnname'>new</a>(ptr: <a class="primitive" href="../primitive.pointer.html">*mut T</a>) -> <a class="struct" href="../../std/ptr/struct.Shared.html" title="struct std::ptr::Shared">Shared</a><T></code></span></h4>
<div class='stability'><div class='stab unstable'><span class=microscope>🔬</span> This is a nightly-only experimental API. (<code>shared </code><a href="https://github.com/rust-lang/rust/issues/27730">#27730</a>)</div></div><div class='docblock'><p>Creates a new <code>Shared</code>.</p>
<h1 id='safety' class='section-header'><a href='#safety'>Safety</a></h1>
<p><code>ptr</code> must be non-null.</p>
</div><h4 id='method.as_ptr' class="method"><span id='as_ptr.v' class='invisible'><code>fn <a href='#method.as_ptr' class='fnname'>as_ptr</a>(self) -> <a class="primitive" href="../primitive.pointer.html">*mut T</a></code></span></h4>
<div class='stability'><div class='stab unstable'><span class=microscope>🔬</span> This is a nightly-only experimental API. (<code>shared </code><a href="https://github.com/rust-lang/rust/issues/27730">#27730</a>)</div></div><div class='docblock'><p>Acquires the underlying <code>*mut</code> pointer.</p>
</div><h4 id='method.as_ref' class="method"><span id='as_ref.v' class='invisible'><code>unsafe fn <a href='#method.as_ref' class='fnname'>as_ref</a>(&self) -> &T</code></span></h4>
<div class='stability'><div class='stab unstable'><span class=microscope>🔬</span> This is a nightly-only experimental API. (<code>shared </code><a href="https://github.com/rust-lang/rust/issues/27730">#27730</a>)</div></div><div class='docblock'><p>Dereferences the content.</p>
<p>The resulting lifetime is bound to self so this behaves "as if"
it were actually an instance of T that is getting borrowed. If a longer
(unbound) lifetime is needed, use <code>&*my_ptr.ptr()</code>.</p>
</div><h4 id='method.as_mut' class="method"><span id='as_mut.v' class='invisible'><code>unsafe fn <a href='#method.as_mut' class='fnname'>as_mut</a>(&mut self) -> &mut T</code></span></h4>
<div class='stability'><div class='stab unstable'><span class=microscope>🔬</span> This is a nightly-only experimental API. (<code>shared </code><a href="https://github.com/rust-lang/rust/issues/27730">#27730</a>)</div></div><div class='docblock'><p>Mutably dereferences the content.</p>
<p>The resulting lifetime is bound to self so this behaves "as if"
it were actually an instance of T that is getting borrowed. If a longer
(unbound) lifetime is needed, use <code>&mut *my_ptr.ptr_mut()</code>.</p>
</div><h4 id='method.as_mut_ptr' class="method"><span id='as_mut_ptr.v' class='invisible'><code>unsafe fn <a href='#method.as_mut_ptr' class='fnname'>as_mut_ptr</a>(&self) -> <a class="primitive" href="../primitive.pointer.html">*mut T</a></code></span></h4>
<div class='stability'><div class='stab deprecated'>Deprecated since 1.19<p>: renamed to <code>as_ptr</code> for ergonomics/consistency</p>
</div><div class='stab unstable'><span class=microscope>🔬</span> This is a nightly-only experimental API. (<code>shared </code><a href="https://github.com/rust-lang/rust/issues/27730">#27730</a>)</div></div><div class='docblock'><p>Acquires the underlying pointer as a <code>*mut</code> pointer.</p>
</div></div><h2 id='implementations'>Trait Implementations</h2><h3 class='impl'><span class='in-band'><code>impl<T> <a class="trait" href="../../std/fmt/trait.Pointer.html" title="trait std::fmt::Pointer">Pointer</a> for <a class="struct" href="../../std/ptr/struct.Shared.html" title="struct std::ptr::Shared">Shared</a><T> <span class="where fmt-newline">where<br> T: ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/ptr.rs.html#1189-1193' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.fmt' class="method"><span id='fmt.v' class='invisible'><code>fn <a href='../../std/fmt/trait.Pointer.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="enum" href="../../std/result/enum.Result.html" title="enum std::result::Result">Result</a><<a class="primitive" href="../primitive.tuple.html">()</a>, <a class="struct" href="../../std/fmt/struct.Error.html" title="struct std::fmt::Error">Error</a>></code></span></h4>
<div class='docblock'><p>Formats the value using the given formatter.</p>
</div></div><h3 class='impl'><span class='in-band'><code>impl<T, U> <a class="trait" href="../../std/ops/trait.CoerceUnsized.html" title="trait std::ops::CoerceUnsized">CoerceUnsized</a><<a class="struct" href="../../std/ptr/struct.Shared.html" title="struct std::ptr::Shared">Shared</a><U>> for <a class="struct" href="../../std/ptr/struct.Shared.html" title="struct std::ptr::Shared">Shared</a><T> <span class="where fmt-newline">where<br> T: <a class="trait" href="../../std/marker/trait.Unsize.html" title="trait std::marker::Unsize">Unsize</a><U> + ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>,<br> U: ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/ptr.rs.html#1186' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'></div><h3 class='impl'><span class='in-band'><code>impl<T> !<a class="trait" href="../../std/marker/trait.Send.html" title="trait std::marker::Send">Send</a> for <a class="struct" href="../../std/ptr/struct.Shared.html" title="struct std::ptr::Shared">Shared</a><T> <span class="where fmt-newline">where<br> T: ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/ptr.rs.html#1112' title='goto source code'>[src]</a></span></h3>
<div class='docblock'><p><code>Shared</code> pointers are not <code>Send</code> because the data they reference may be aliased.</p>
</div><div class='impl-items'></div><h3 class='impl'><span class='in-band'><code>impl<T> !<a class="trait" href="../../std/marker/trait.Sync.html" title="trait std::marker::Sync">Sync</a> for <a class="struct" href="../../std/ptr/struct.Shared.html" title="struct std::ptr::Shared">Shared</a><T> <span class="where fmt-newline">where<br> T: ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/ptr.rs.html#1117' title='goto source code'>[src]</a></span></h3>
<div class='docblock'><p><code>Shared</code> pointers are not <code>Sync</code> because the data they reference may be aliased.</p>
</div><div class='impl-items'></div><h3 class='impl'><span class='in-band'><code>impl<T> <a class="trait" href="../../std/clone/trait.Clone.html" title="trait std::clone::Clone">Clone</a> for <a class="struct" href="../../std/ptr/struct.Shared.html" title="struct std::ptr::Shared">Shared</a><T> <span class="where fmt-newline">where<br> T: ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/ptr.rs.html#1176-1180' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'><h4 id='method.clone' class="method"><span id='clone.v' class='invisible'><code>fn <a href='../../std/clone/trait.Clone.html#tymethod.clone' class='fnname'>clone</a>(&self) -> <a class="struct" href="../../std/ptr/struct.Shared.html" title="struct std::ptr::Shared">Shared</a><T></code></span></h4>
<div class='docblock'><p>Returns a copy of the value. <a href="../../std/clone/trait.Clone.html#tymethod.clone">Read more</a></p>
</div><h4 id='method.clone_from' class="method"><span id='clone_from.v' class='invisible'><code>fn <a href='../../std/clone/trait.Clone.html#method.clone_from' class='fnname'>clone_from</a>(&mut self, source: &Self)</code><div class='since' title='Stable since Rust version 1.0.0'>1.0.0</div></span></h4>
<div class='docblock'><p>Performs copy-assignment from <code>source</code>. <a href="../../std/clone/trait.Clone.html#method.clone_from">Read more</a></p>
</div></div><h3 class='impl'><span class='in-band'><code>impl<T> <a class="trait" href="../../std/marker/trait.Copy.html" title="trait std::marker::Copy">Copy</a> for <a class="struct" href="../../std/ptr/struct.Shared.html" title="struct std::ptr::Shared">Shared</a><T> <span class="where fmt-newline">where<br> T: ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>, </span></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/core/ptr.rs.html#1183' title='goto source code'>[src]</a></span></h3>
<div class='impl-items'></div><h3 class='impl'><span class='in-band'><code>impl<T: <a class="trait" href="../../std/panic/trait.RefUnwindSafe.html" title="trait std::panic::RefUnwindSafe">RefUnwindSafe</a> + ?<a class="trait" href="../../std/marker/trait.Sized.html" title="trait std::marker::Sized">Sized</a>> <a class="trait" href="../../std/panic/trait.UnwindSafe.html" title="trait std::panic::UnwindSafe">UnwindSafe</a> for <a class="struct" href="../../std/ptr/struct.Shared.html" title="struct std::ptr::Shared">Shared</a><T></code></span><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/std/panic.rs.html#203' title='goto source code'>[src]</a></span></h3>
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