<!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="Source to the Rust file `libcore/raw.rs`."> <meta name="keywords" content="rust, rustlang, rust-lang"> <title>raw.rs.html -- source</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="../../main.css" id="themeStyle"> <script src="../../storage.js"></script> <link rel="shortcut icon" href="https://doc.rust-lang.org/favicon.ico"> </head> <body class="rustdoc source"> <!--[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='../../core/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png' alt='logo' width='100'></a> </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"> </div> </form> </nav> <section id='main' class="content"><pre class="line-numbers"><span id="1"> 1</span> <span id="2"> 2</span> <span id="3"> 3</span> <span id="4"> 4</span> <span id="5"> 5</span> <span id="6"> 6</span> <span id="7"> 7</span> <span id="8"> 8</span> <span id="9"> 9</span> <span id="10">10</span> <span id="11">11</span> <span id="12">12</span> <span id="13">13</span> <span id="14">14</span> <span id="15">15</span> <span id="16">16</span> <span id="17">17</span> <span id="18">18</span> <span id="19">19</span> <span id="20">20</span> <span id="21">21</span> <span id="22">22</span> <span id="23">23</span> <span id="24">24</span> <span id="25">25</span> <span id="26">26</span> <span id="27">27</span> <span id="28">28</span> <span id="29">29</span> <span id="30">30</span> <span id="31">31</span> <span id="32">32</span> <span id="33">33</span> <span id="34">34</span> <span id="35">35</span> <span id="36">36</span> <span id="37">37</span> <span id="38">38</span> <span id="39">39</span> <span id="40">40</span> <span id="41">41</span> <span id="42">42</span> <span id="43">43</span> <span id="44">44</span> <span id="45">45</span> <span id="46">46</span> <span id="47">47</span> <span id="48">48</span> <span id="49">49</span> <span id="50">50</span> <span id="51">51</span> <span id="52">52</span> <span id="53">53</span> <span id="54">54</span> <span id="55">55</span> <span id="56">56</span> <span id="57">57</span> <span id="58">58</span> <span id="59">59</span> <span id="60">60</span> <span id="61">61</span> <span id="62">62</span> <span id="63">63</span> <span id="64">64</span> <span id="65">65</span> <span id="66">66</span> <span id="67">67</span> <span id="68">68</span> <span id="69">69</span> <span id="70">70</span> <span id="71">71</span> <span id="72">72</span> <span id="73">73</span> <span id="74">74</span> <span id="75">75</span> <span id="76">76</span> <span id="77">77</span> <span id="78">78</span> <span id="79">79</span> <span id="80">80</span> <span id="81">81</span> <span id="82">82</span> <span id="83">83</span> <span id="84">84</span> <span id="85">85</span> <span id="86">86</span> <span id="87">87</span> <span id="88">88</span> <span id="89">89</span> <span id="90">90</span> <span id="91">91</span> <span id="92">92</span> <span id="93">93</span> <span id="94">94</span> <span id="95">95</span> <span id="96">96</span> <span id="97">97</span> <span id="98">98</span> <span id="99">99</span> </pre><pre class="rust "> <span class="comment">// Copyright 2013 The Rust Project Developers. See the COPYRIGHT</span> <span class="comment">// file at the top-level directory of this distribution and at</span> <span class="comment">// http://rust-lang.org/COPYRIGHT.</span> <span class="comment">//</span> <span class="comment">// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or</span> <span class="comment">// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license</span> <span class="comment">// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your</span> <span class="comment">// option. This file may not be copied, modified, or distributed</span> <span class="comment">// except according to those terms.</span> <span class="attribute">#![<span class="ident">allow</span>(<span class="ident">missing_docs</span>)]</span> <span class="attribute">#![<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"raw"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"27751"</span>)]</span> <span class="doccomment">//! Contains struct definitions for the layout of compiler built-in types.</span> <span class="doccomment">//!</span> <span class="doccomment">//! They can be used as targets of transmutes in unsafe code for manipulating</span> <span class="doccomment">//! the raw representations directly.</span> <span class="doccomment">//!</span> <span class="doccomment">//! Their definition should always match the ABI defined in `rustc::back::abi`.</span> <span class="doccomment">/// The representation of a trait object like `&SomeTrait`.</span> <span class="doccomment">///</span> <span class="doccomment">/// This struct has the same layout as types like `&SomeTrait` and</span> <span class="doccomment">/// `Box<AnotherTrait>`. The [Trait Objects chapter of the</span> <span class="doccomment">/// Book][moreinfo] contains more details about the precise nature of</span> <span class="doccomment">/// these internals.</span> <span class="doccomment">///</span> <span class="doccomment">/// [moreinfo]: ../../book/first-edition/trait-objects.html#representation</span> <span class="doccomment">///</span> <span class="doccomment">/// `TraitObject` is guaranteed to match layouts, but it is not the</span> <span class="doccomment">/// type of trait objects (e.g. the fields are not directly accessible</span> <span class="doccomment">/// on a `&SomeTrait`) nor does it control that layout (changing the</span> <span class="doccomment">/// definition will not change the layout of a `&SomeTrait`). It is</span> <span class="doccomment">/// only designed to be used by unsafe code that needs to manipulate</span> <span class="doccomment">/// the low-level details.</span> <span class="doccomment">///</span> <span class="doccomment">/// There is no way to refer to all trait objects generically, so the only</span> <span class="doccomment">/// way to create values of this type is with functions like</span> <span class="doccomment">/// [`std::mem::transmute`][transmute]. Similarly, the only way to create a true</span> <span class="doccomment">/// trait object from a `TraitObject` value is with `transmute`.</span> <span class="doccomment">///</span> <span class="doccomment">/// [transmute]: ../intrinsics/fn.transmute.html</span> <span class="doccomment">///</span> <span class="doccomment">/// Synthesizing a trait object with mismatched types—one where the</span> <span class="doccomment">/// vtable does not correspond to the type of the value to which the</span> <span class="doccomment">/// data pointer points—is highly likely to lead to undefined</span> <span class="doccomment">/// behavior.</span> <span class="doccomment">///</span> <span class="doccomment">/// # Examples</span> <span class="doccomment">///</span> <span class="doccomment">/// ```</span> <span class="doccomment">/// #![feature(raw)]</span> <span class="doccomment">///</span> <span class="doccomment">/// use std::{mem, raw};</span> <span class="doccomment">///</span> <span class="doccomment">/// // an example trait</span> <span class="doccomment">/// trait Foo {</span> <span class="doccomment">/// fn bar(&self) -> i32;</span> <span class="doccomment">/// }</span> <span class="doccomment">///</span> <span class="doccomment">/// impl Foo for i32 {</span> <span class="doccomment">/// fn bar(&self) -> i32 {</span> <span class="doccomment">/// *self + 1</span> <span class="doccomment">/// }</span> <span class="doccomment">/// }</span> <span class="doccomment">///</span> <span class="doccomment">/// let value: i32 = 123;</span> <span class="doccomment">///</span> <span class="doccomment">/// // let the compiler make a trait object</span> <span class="doccomment">/// let object: &Foo = &value;</span> <span class="doccomment">///</span> <span class="doccomment">/// // look at the raw representation</span> <span class="doccomment">/// let raw_object: raw::TraitObject = unsafe { mem::transmute(object) };</span> <span class="doccomment">///</span> <span class="doccomment">/// // the data pointer is the address of `value`</span> <span class="doccomment">/// assert_eq!(raw_object.data as *const i32, &value as *const _);</span> <span class="doccomment">///</span> <span class="doccomment">/// let other_value: i32 = 456;</span> <span class="doccomment">///</span> <span class="doccomment">/// // construct a new object, pointing to a different `i32`, being</span> <span class="doccomment">/// // careful to use the `i32` vtable from `object`</span> <span class="doccomment">/// let synthesized: &Foo = unsafe {</span> <span class="doccomment">/// mem::transmute(raw::TraitObject {</span> <span class="doccomment">/// data: &other_value as *const _ as *mut (),</span> <span class="doccomment">/// vtable: raw_object.vtable,</span> <span class="doccomment">/// })</span> <span class="doccomment">/// };</span> <span class="doccomment">///</span> <span class="doccomment">/// // it should work just as if we had constructed a trait object out of</span> <span class="doccomment">/// // `other_value` directly</span> <span class="doccomment">/// assert_eq!(synthesized.bar(), 457);</span> <span class="doccomment">/// ```</span> <span class="attribute">#[<span class="ident">repr</span>(<span class="ident">C</span>)]</span> <span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Copy</span>, <span class="ident">Clone</span>)]</span> <span class="attribute">#[<span class="ident">allow</span>(<span class="ident">missing_debug_implementations</span>)]</span> <span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">TraitObject</span> { <span class="kw">pub</span> <span class="ident">data</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> (), <span class="kw">pub</span> <span class="ident">vtable</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> (), } </pre> </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> </div> </div> </aside> <script> window.rootPath = "../../"; window.currentCrate = "core"; </script> <script src="../../main.js"></script> <script defer src="../../search-index.js"></script> </body> </html>