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macro.assert_eq_size_ptr.html
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<!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="Asserts that values pointed to are equal in size."><meta name="keywords" content="rust, rustlang, rust-lang, assert_eq_size_ptr"><title>static_assertions::assert_eq_size_ptr - 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="../light.css" id="themeStyle"><link rel="stylesheet" type="text/css" href="../dark.css" disabled ><link rel="stylesheet" type="text/css" href="../ayu.css" disabled ><script id="default-settings"></script><script src="../storage.js"></script><script src="../crates.js"></script><noscript><link rel="stylesheet" href="../noscript.css"></noscript><link rel="icon" type="image/svg+xml" href="../favicon.svg">
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<a id="settings-menu" href="../settings.html"><img src="../wheel.svg" width="18" height="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">static_assertions</a>::<wbr><a class="macro" href="">assert_eq_size_ptr</a></span><span class="out-of-band"><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/static_assertions/assert_eq_size.rs.html#76-86" title="goto source code">[src]</a></span></h1><div class="docblock type-decl hidden-by-usual-hider"><div class="example-wrap"><pre class="rust macro">
<span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">assert_eq_size_ptr</span> {
(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">x</span>:<span class="ident">expr</span>, $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">xs</span>:<span class="ident">expr</span>),<span class="op">+</span> $(,)<span class="question-mark">?</span>) <span class="op">=</span><span class="op">></span> { ... };
}</pre></div>
</div><div class="docblock"><p>Asserts that values pointed to are equal in size.</p>
<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
<p>This especially is useful for when coercing pointers between different types
and ensuring the underlying values are the same size.</p>
<div class="example-wrap"><pre class="rust rust-example-rendered">
<span class="kw">fn</span> <span class="ident">operation</span>(<span class="ident">x</span>: <span class="kw-2">&</span>(<span class="ident">u32</span>, <span class="ident">u32</span>), <span class="ident">y</span>: <span class="kw-2">&</span>[<span class="ident">u16</span>; <span class="number">4</span>]) {
<span class="macro">assert_eq_size_ptr</span><span class="macro">!</span>(<span class="ident">x</span>, <span class="ident">y</span>);
<span class="comment">// ...</span>
}</pre></div>
<p>The following example fails to compile because byte arrays of different
lengths have different sizes:</p>
<div class='information'><div class='tooltip compile_fail'>ⓘ</div></div><div class="example-wrap"><pre class="rust rust-example-rendered compile_fail">
<span class="kw">static</span> <span class="ident">BYTES</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>; <span class="number">4</span>] <span class="op">=</span> <span class="kw-2">&</span>[
<span class="comment">/* ... */</span>
];
<span class="kw">static</span> <span class="ident">TABLE</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>; <span class="number">16</span>] <span class="op">=</span> <span class="kw-2">&</span>[
<span class="comment">/* ... */</span>
];
<span class="macro">assert_eq_size_ptr</span><span class="macro">!</span>(<span class="ident">BYTES</span>, <span class="ident">TABLE</span>);</pre></div>
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