1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html><meta http-equiv="Content-Type" content="text/html; charset=utf-8"> 3<title>void strong_swap(bool &all_good, T &a, T &b) - Boost.Outcome documentation</title> 4<link rel="stylesheet" href="../../css/boost.css" type="text/css"> 5<meta name="generator" content="Hugo 0.52 with Boostdoc theme"> 6<meta name="viewport" content="width=device-width,initial-scale=1.0"/> 7 8<link rel="icon" href="../../images/favicon.ico" type="image/ico"/> 9<body><div class="spirit-nav"> 10<a accesskey="p" href="../../reference/functions/error_from_exception.html"><img src="../../images/prev.png" alt="Prev"></a> 11 <a accesskey="u" href="../../reference/functions.html"><img src="../../images/up.png" alt="Up"></a> 12 <a accesskey="h" href="../../index.html"><img src="../../images/home.png" alt="Home"></a><a accesskey="n" href="../../reference/functions/try_throw_std_exception_from_error.html"><img src="../../images/next.png" alt="Next"></a></div><div id="content"> 13 <div class="titlepage"><div><div><h1 style="clear: both"><code>void strong_swap(bool &all_good, T &a, T &b)</code></h1></div></div></div> 14 <p>The standard <code>swap()</code> function provides the weak guarantee i.e. that no resources are lost. This ADL discovered function provides the strong guarantee instead: that if any of these operations throw an exception (i) move construct to temporary (ii) move assign <code>b</code> to <code>a</code> (iii) move assign temporary to <code>b</code>, an attempt is made to restore the exact pre-swapped state upon entry, and if that recovery too fails, then the boolean <code>all_good</code> will be false during stack unwind from the exception throw, to indicate that state has been lost.</p> 15 16<p>This function is used within <code>basic_result::</code><a href="../../reference/types/basic_result/swap.html" class="api-reference"><code>swap(basic_result &)</code></a> 17 if, and only if, either or both of <code>value_type</code> or <code>error_type</code> have a throwing move constructor or move assignment. It permits you to customise the implementation of the strong guarantee swap in Outcome with a more efficient implementation.</p> 18 19<p><em>Overridable</em>: By Argument Dependent Lookup (ADL).</p> 20 21<p><em>Requires</em>: That <code>T</code> is both move constructible and move assignable.</p> 22 23<p><em>Namespace</em>: <code>BOOST_OUTCOME_V2_NAMESPACE</code></p> 24 25<p><em>Header</em>: <code><boost/outcome/basic_result.hpp></code></p> 26 27 28 </div><p><small>Last revised: June 24, 2019 at 21:09:37 +0100</small></p> 29<hr> 30<div class="spirit-nav"> 31<a accesskey="p" href="../../reference/functions/error_from_exception.html"><img src="../../images/prev.png" alt="Prev"></a> 32 <a accesskey="u" href="../../reference/functions.html"><img src="../../images/up.png" alt="Up"></a> 33 <a accesskey="h" href="../../index.html"><img src="../../images/home.png" alt="Home"></a><a accesskey="n" href="../../reference/functions/try_throw_std_exception_from_error.html"><img src="../../images/next.png" alt="Next"></a></div></body> 34</html> 35
