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<div class="identifier-type">function</div><div class="header"><debugging></div><h1 itemprop="name"><span class="namespace" title="namespace std">std::</span><span class="token">breakpoint</span><span class="cpp cpp26" title="C++26で追加">(C++26)</span></h1>
<div itemprop="articleBody"><p><div class="codehilite"><pre><span></span><code><span class="k">namespace</span><span class="w"> </span><span class="nn">std</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="nf">breakpoint</span><span class="p">()</span><span class="w"> </span><span class="k">noexcept</span><span class="p">;</span><span class="w"> </span><span class="c1">// (1) C++26</span>
<span class="p">}</span>
</code></pre></div>
</p>
<h2>概要</h2>
<p>ブレークポイントを設置する。</p>
<p>この関数は無条件のブレークポイントであり、デバッガの存在を検出できない状況でもプログラムの一時停止 (ブレーク) を試みる。</p>
<p>プログラムコードでブレークポイントを指定できると、複雑な実行時条件でプログラムを一時停止させることができる。</p>
<h2>効果</h2>
<p>標準規格としては、この関数の意味論は<a class="cpprefjp-defined-word" data-desc="処理系定義の動作。処理系によって事前に定めた動作をする" href="../../implementation-compliance.html#dfn-implementation-defined-behavior">実装定義</a>である。</p>
<p>実際の動作としては、この関数が呼び出されるとプログラムの実行が一時停止され、以下のいずれかの時点までデバッガに制御が渡される：</p>
<ul>
<li>デバッガによってプログラムが終了される、または</li>
<li>デバッガが、この関数が呼び出されなかったかのようにプログラムの実行を再開する</li>
</ul>
<h2><a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a></h2>
<p>投げない</p>
<h2>備考</h2>
<ul>
<li>実装としては、生成されるコードがプラットフォームに対して可能な限り最小になるように最適化することが期待される。例として、x86ターゲット環境ではINT3命令をひとつだけ生成することが期待される</li>
</ul>
<h2>例</h2>
<p><div class="yata" id="862fb42dd730cd979e3ee05a79ee6411fe0a8a96"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../print.html"><print></a></span>
<span class="cp">#include <a href="../debugging.html"><debugging></a></span>
<span class="cp">#include <a href="../cmath.html"><cmath></a></span>
<span class="c1">// なんらかの処理</span>
<span class="kt">double</span><span class="w"> </span><span class="nf">g</span><span class="p">(</span><span class="kt">double</span><span class="w"> </span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">b</span><span class="p">;</span>
<span class="p">}</span>
<span class="kt">double</span><span class="w"> </span><span class="nf">f</span><span class="p">(</span><span class="kt">double</span><span class="w"> </span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="n">b</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="n">ret</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">g</span><span class="p">(</span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="n">b</span><span class="p">);</span>
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n"><a href="../cmath/isnan.html">std::isnan</a></span><span class="p">(</span><span class="n">ret</span><span class="p">)</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n"><a href="../cmath/isinf.html">std::isinf</a></span><span class="p">(</span><span class="n">ret</span><span class="p">))</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">// 演算結果でNaNかinfが発生したらブレークし、</span>
<span class="w"> </span><span class="c1">// デバッガでパラメータ (ローカル変数) などを確認する</span>
<span class="w"> </span><span class="n"><span style="color:#ff0000">std::breakpoint</span></span><span class="p">();</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">ret</span><span class="p">;</span>
<span class="p">}</span>
<span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">()</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="kt">double</span><span class="w"> </span><span class="n">ret</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">f</span><span class="p">(</span><span class="mf">2.0</span><span class="p">,</span><span class="w"> </span><span class="mf">0.0</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../print/println.html">std::println</a></span><span class="p">(</span><span class="s">"{}"</span><span class="p">,</span><span class="w"> </span><span class="n">ret</span><span class="p">);</span>
<span class="p">}</span>
</code></pre></div>
</div></p>
<h3>出力例</h3>
<p><pre><code>inf
</code></pre></p>
<h2>バージョン</h2>
<h3>言語</h3>
<ul>
<li>C++26</li>
</ul>
<h3>処理系</h3>
<ul>
<li><a href="../../implementation.html#clang">Clang</a>: 19 <span aria-label="未実装" role="img" title="未実装">❌</span></li>
<li><a href="../../implementation.html#gcc">GCC</a>: 14 <span aria-label="未実装" role="img" title="未実装">❌</span></li>
<li><a href="../../implementation.html#visual_cpp">Visual C++</a>: 2022 Update 10 <span aria-label="未実装" role="img" title="未実装">❌</span></li>
</ul>
<h2>参照</h2>
<ul>
<li><a href="https://open-std.org/jtc1/sc22/wg21/docs/papers/2023/p2546r5.html" target="_blank">P2546R5 Debugging Support</a></li>
</ul></div>
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