<?xml version="1.0" encoding="utf-8" standalone="yes"?><rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom"><channel><title>Windows API on kenji.blog</title><link>http://kenji.blog/zh-tw/tags/windows-api/</link><description>Recent content in Windows API on kenji.blog</description><generator>Hugo -- gohugo.io</generator><language>zh-tw</language><copyright>kenjinote</copyright><lastBuildDate>Sat, 12 Sep 2026 06:00:00 +0900</lastBuildDate><atom:link href="http://kenji.blog/zh-tw/tags/windows-api/index.xml" rel="self" type="application/rss+xml"/><item><title>使用現代C++安全且現代化地處理Windows API (Win32) 的手法</title><link>http://kenji.blog/zh-tw/p/modern-cpp-win32-api-safe-handling/</link><pubDate>Sat, 12 Sep 2026 06:00:00 +0900</pubDate><guid>http://kenji.blog/zh-tw/p/modern-cpp-win32-api-safe-handling/</guid><description>&lt;img src="http://kenji.blog/p/modern-cpp-win32-api-safe-handling/img/eyecatch.jpg" alt="Featured image of post 使用現代C++安全且現代化地處理Windows API (Win32) 的手法" />&lt;h2 id="1-簡介基於c語言的win32-api與現代c的脫節">1. 簡介：基於C語言的Win32 API與現代C++的脫節
&lt;/h2>&lt;p>作為Windows OS基礎的 &lt;strong>Windows API（通稱 Win32 API）&lt;/strong>，是從1990年代的 Windows NT 和 Windows 95 時代脈脈相傳下來的巨大C語言介面。即便是現在，在開發Windows原生應用程式時，為了存取OS的核心功能（行程管理、檔案I/O、執行緒同步、視窗控制等），最終仍必須呼叫這個Win32 API。&lt;/p>
&lt;p>然而，Win32 API純粹是為C語言所設計，並未以**現代C++（Modern C++）**所具備的高階語言功能（例外處理、基於RAII的自動資源管理、移動語意、型別安全的列舉、智慧指標等）為前提。結果，如果將原始的Win32 API直接混入C++程式碼中，就會發生以下問題：&lt;/p>
&lt;ul>
&lt;li>&lt;strong>手動的資源管理：&lt;/strong> 透過 &lt;code>CreateFile&lt;/code> 或 &lt;code>CreateEvent&lt;/code> 取得的 &lt;code>HANDLE&lt;/code>，必須確保呼叫 &lt;code>CloseHandle&lt;/code> 來釋放。&lt;/li>
&lt;li>&lt;strong>缺乏例外安全性：&lt;/strong> 當C++拋出例外時，如果沒有撰寫適當呼叫 &lt;code>CloseHandle&lt;/code> 的處理，很容易發生資源外洩 (Resource leak)。&lt;/li>
&lt;li>&lt;strong>不一致的錯誤表現：&lt;/strong> 某些API會回傳 &lt;code>BOOL&lt;/code>，失敗時需要呼叫 &lt;code>GetLastError()&lt;/code>。有些API會回傳 &lt;code>HRESULT&lt;/code>，而有些API（如GDI）則回傳 &lt;code>NULL&lt;/code>。&lt;/li>
&lt;li>&lt;strong>缺乏型別安全性：&lt;/strong> &lt;code>HANDLE&lt;/code>、&lt;code>HWND&lt;/code>、&lt;code>HDC&lt;/code> 等，展開巨集後通常不過是單純的 &lt;code>void*&lt;/code>，編譯器很難進行嚴格的型別檢查。&lt;/li>
&lt;/ul>
&lt;p>本文將極其詳細地解說如何避開這些「老舊C介面」的陷阱，並利用現代C++ (C++11/14/17/20/23) 的功能，以&lt;strong>安全（Safe）且現代化（Modern）的方式來處理Win32 API 的手法&lt;/strong>。&lt;/p>
&lt;hr>
&lt;h2 id="2-原始win32-api的危險性資源外洩與錯誤處理的陷阱">2. 原始Win32 API的危險性：資源外洩與錯誤處理的陷阱
&lt;/h2>&lt;p>首先，讓我們來看看以傳統C風格呼叫Win32 API的一般程式碼。乍看之下似乎沒有問題，但從現代C++的觀點來看，卻抱有致命的脆弱性。&lt;/p>
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&lt;pre tabindex="0" class="chroma">&lt;code class="language-cpp" data-lang="cpp">&lt;span class="line">&lt;span class="cl">&lt;span class="cp">#include&lt;/span> &lt;span class="cpf">&amp;lt;windows.h&amp;gt;&lt;/span>&lt;span class="cp">
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="cp">#include&lt;/span> &lt;span class="cpf">&amp;lt;iostream&amp;gt;&lt;/span>&lt;span class="cp">
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="cp">#include&lt;/span> &lt;span class="cpf">&amp;lt;vector&amp;gt;&lt;/span>&lt;span class="cp">
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="cp">&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="kt">void&lt;/span> &lt;span class="nf">ProcessFileLegacy&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="k">const&lt;/span> &lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">wstring&lt;/span>&lt;span class="o">&amp;amp;&lt;/span> &lt;span class="n">filename&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 1. 取得檔案控制代碼
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="n">HANDLE&lt;/span> &lt;span class="n">hFile&lt;/span> &lt;span class="o">=&lt;/span> &lt;span class="o">::&lt;/span>&lt;span class="n">CreateFileW&lt;/span>&lt;span class="p">(&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">filename&lt;/span>&lt;span class="p">.&lt;/span>&lt;span class="n">c_str&lt;/span>&lt;span class="p">(),&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">GENERIC_READ&lt;/span>&lt;span class="p">,&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">FILE_SHARE_READ&lt;/span>&lt;span class="p">,&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="nb">NULL&lt;/span>&lt;span class="p">,&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">OPEN_EXISTING&lt;/span>&lt;span class="p">,&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">FILE_ATTRIBUTE_NORMAL&lt;/span>&lt;span class="p">,&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="nb">NULL&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">);&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">if&lt;/span> &lt;span class="p">(&lt;/span>&lt;span class="n">hFile&lt;/span> &lt;span class="o">==&lt;/span> &lt;span class="n">INVALID_HANDLE_VALUE&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">cerr&lt;/span> &lt;span class="o">&amp;lt;&amp;lt;&lt;/span> &lt;span class="s">&amp;#34;Failed to open file. Error: &amp;#34;&lt;/span> &lt;span class="o">&amp;lt;&amp;lt;&lt;/span> &lt;span class="o">::&lt;/span>&lt;span class="n">GetLastError&lt;/span>&lt;span class="p">()&lt;/span> &lt;span class="o">&amp;lt;&amp;lt;&lt;/span> &lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">endl&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">return&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 2. 取得檔案大小
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="n">LARGE_INTEGER&lt;/span> &lt;span class="n">fileSize&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">if&lt;/span> &lt;span class="p">(&lt;/span>&lt;span class="o">!::&lt;/span>&lt;span class="n">GetFileSizeEx&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">hFile&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="o">&amp;amp;&lt;/span>&lt;span class="n">fileSize&lt;/span>&lt;span class="p">))&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="o">::&lt;/span>&lt;span class="n">CloseHandle&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">hFile&lt;/span>&lt;span class="p">);&lt;/span> &lt;span class="c1">// 發生錯誤時手動釋放
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="k">return&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 3. 配置記憶體與讀取
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">vector&lt;/span>&lt;span class="o">&amp;lt;&lt;/span>&lt;span class="kt">char&lt;/span>&lt;span class="o">&amp;gt;&lt;/span> &lt;span class="n">buffer&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">fileSize&lt;/span>&lt;span class="p">.&lt;/span>&lt;span class="n">QuadPart&lt;/span>&lt;span class="p">);&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">DWORD&lt;/span> &lt;span class="n">bytesRead&lt;/span> &lt;span class="o">=&lt;/span> &lt;span class="mi">0&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">if&lt;/span> &lt;span class="p">(&lt;/span>&lt;span class="o">!::&lt;/span>&lt;span class="n">ReadFile&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">hFile&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="n">buffer&lt;/span>&lt;span class="p">.&lt;/span>&lt;span class="n">data&lt;/span>&lt;span class="p">(),&lt;/span> &lt;span class="n">buffer&lt;/span>&lt;span class="p">.&lt;/span>&lt;span class="n">size&lt;/span>&lt;span class="p">(),&lt;/span> &lt;span class="o">&amp;amp;&lt;/span>&lt;span class="n">bytesRead&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="nb">NULL&lt;/span>&lt;span class="p">))&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="o">::&lt;/span>&lt;span class="n">CloseHandle&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">hFile&lt;/span>&lt;span class="p">);&lt;/span> &lt;span class="c1">// 發生錯誤時手動釋放
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="k">return&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// --- 假設這裡有會發生例外的處理 ---
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="c1">// 例：解析 buffer 內容的函數拋出了 std::runtime_error
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="c1">// ParseBuffer(buffer); // 如果拋出例外，下方的 CloseHandle 就不會被呼叫，導致外洩！
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 4. 手動釋放資源
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="o">::&lt;/span>&lt;span class="n">CloseHandle&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">hFile&lt;/span>&lt;span class="p">);&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;/code>&lt;/pre>&lt;/td>&lt;/tr>&lt;/table>
&lt;/div>
&lt;/div>&lt;h3 id="這段程式碼有什麼問題">這段程式碼有什麼問題？
&lt;/h3>&lt;ol>
&lt;li>&lt;strong>程式碼重複與繁雜：&lt;/strong> 每次提早回傳（&lt;code>return&lt;/code>）時都必須寫上 &lt;code>::CloseHandle(hFile);&lt;/code>，違反了 DRY (Don&amp;rsquo;t Repeat Yourself) 原則。&lt;/li>
&lt;li>&lt;strong>完全缺乏例外安全性 (Exception Unsafe)：&lt;/strong> 在C++中，當 &lt;code>std::vector&lt;/code> 記憶體配置失敗 (&lt;code>std::bad_alloc&lt;/code>)，或是其他函數拋出例外時，會強制退出函數。此時，末尾的 &lt;code>CloseHandle&lt;/code> 不會被執行，導致&lt;strong>檔案控制代碼永遠外洩&lt;/strong>（會引起行程結束前檔案持續被鎖定等嚴重錯誤）。&lt;/li>
&lt;/ol>
&lt;hr>
&lt;h2 id="3-例外安全與資源管理的數學模型">3. 例外安全與資源管理的數學模型
&lt;/h2>&lt;p>在這裡，讓我們以數學（機率論）的方式來建立模型，看看手動的資源管理是多麼脆弱。&lt;/p>
&lt;p>假設函數內有 $N$ 個資源獲取（或是提早回傳點、例外發生點）。在每個步驟 $i$，因發生錯誤或例外而退出函數的機率為 $P(\text{Exit}_i)$。考慮無法在所有退出路徑上手動正確寫滿清理程式碼（如 &lt;code>CloseHandle&lt;/code>）而導致資源外洩的機率。&lt;/p>
&lt;p>將因人類注意力不集中而漏寫，或因未知例外導致預期外退出的機率（每條路徑的外洩機率）設為 $p$，整個程式中發生至少一個資源外洩的機率 $P(\text{Leak})$ 可以用以下公式表示：&lt;/p>
$$ P(\text{Leak}) = 1 - (1 - p)^N $$
&lt;p>例如，當 $p = 0.05$（有5%的機率在例外處理或清理上發生失誤），且 $N = 20$（複雜的函數中有20處錯誤回傳或例外點）時：&lt;/p>
$$ P(\text{Leak}) = 1 - (1 - 0.05)^{20} \approx 1 - 0.358 = 0.642 $$
&lt;p>居然&lt;strong>有約 64.2% 的機率在某處潛藏著資源外洩的錯誤&lt;/strong>。隨著軟體規模變大、$N \to \infty$ 時，$P(\text{Leak}) \to 1$，系統必然會崩潰。&lt;/p>
&lt;p>要對抗這個數學現實的唯一合理手段，就是C++的 &lt;strong>RAII (Resource Acquisition Is Initialization)&lt;/strong>。&lt;/p>
&lt;hr>
&lt;h2 id="4-raii-resource-acquisition-is-initialization-的基礎">4. RAII (Resource Acquisition Is Initialization) 的基礎
&lt;/h2>&lt;p>RAII是由C++之父 Bjarne Stroustrup 先生提倡的概念。其原則極為簡單且強大。&lt;/p>
&lt;ol>
&lt;li>在物件的&lt;strong>建構子 (Initialization)&lt;/strong> 中進行資源的獲取 (Acquisition)。&lt;/li>
&lt;li>在物件的&lt;strong>解構子&lt;/strong>中進行資源的釋放。&lt;/li>
&lt;/ol>
&lt;p>根據C++的語言規範，當離開作用域時（無論是正常的 &lt;code>return&lt;/code>，還是因例外導致的堆疊展開），堆疊上配置的物件的解構子會被&lt;strong>確實且自動地&lt;/strong>呼叫。&lt;/p>
&lt;p>如此一來，就能在數學上將前面公式中人為失誤的機率 $p$ 降為 &lt;strong>$0$&lt;/strong>。&lt;/p>
&lt;h3 id="物件生命週期的視覺化">物件生命週期的視覺化
&lt;/h3>&lt;p>以下的循序圖展示了使用原始API的手動管理與使用RAII的自動管理在生命週期上的差異。&lt;/p>
&lt;div class="mermaid">sequenceDiagram
participant App as "C++ 應用程式"
participant Wrapper as "RAII 包裝器"
participant OS as "Windows OS (Win32)"
Note over App, OS: "原始Win32 API (手動管理)"
App->>OS: "CreateFile()"
OS-->>App: "回傳原始 HANDLE"
App->>App: "執行工作 (發生例外!)"
App--xOS: "繞過 CloseHandle()"
Note right of OS: "發生資源外洩"
Note over App, OS: "現代C++ (RAII管理)"
App->>Wrapper: "請求資源"
Wrapper->>OS: "CreateFile()"
OS-->>Wrapper: "回傳原始 HANDLE"
Wrapper-->>App: "回傳 std::unique_ptr"
App->>App: "執行工作 (發生例外!)"
Note over App, Wrapper: "因堆疊展開觸發解構子"
Wrapper->>OS: "CloseHandle()"
Note right of OS: "安全地釋放資源"&lt;/div>
&lt;hr>
&lt;h2 id="5-使用-stdunique_ptr-安全包裝-handle-的手法">5. 使用 &lt;code>std::unique_ptr&lt;/code> 安全包裝 &lt;code>HANDLE&lt;/code> 的手法
&lt;/h2>&lt;p>從 C++11 開始，標準函式庫提供了通用的 RAII 包裝器 &lt;code>std::unique_ptr&lt;/code>。這不單單用於記憶體（&lt;code>new/delete&lt;/code>）的管理，透過指定&lt;strong>自訂刪除器 (Custom Deleter)&lt;/strong>，它可以應用於任何資源的管理。&lt;/p>
&lt;p>為了用 &lt;code>std::unique_ptr&lt;/code> 來管理 Win32 的 &lt;code>HANDLE&lt;/code>，基本的刪除器可以這樣寫：&lt;/p>
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&lt;pre tabindex="0" class="chroma">&lt;code class="language-cpp" data-lang="cpp">&lt;span class="line">&lt;span class="cl">&lt;span class="cp">#include&lt;/span> &lt;span class="cpf">&amp;lt;windows.h&amp;gt;&lt;/span>&lt;span class="cp">
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="cp">#include&lt;/span> &lt;span class="cpf">&amp;lt;memory&amp;gt;&lt;/span>&lt;span class="cp">
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="cp">&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">// 供 HANDLE 使用的自訂刪除器
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span>&lt;span class="k">struct&lt;/span> &lt;span class="nc">handle_deleter&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 指定 std::unique_ptr 內部處理的指標型別
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="k">using&lt;/span> &lt;span class="n">pointer&lt;/span> &lt;span class="o">=&lt;/span> &lt;span class="n">HANDLE&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="kt">void&lt;/span> &lt;span class="nf">operator&lt;/span>&lt;span class="p">()(&lt;/span>&lt;span class="n">HANDLE&lt;/span> &lt;span class="n">handle&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="k">const&lt;/span> &lt;span class="k">noexcept&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">if&lt;/span> &lt;span class="p">(&lt;/span>&lt;span class="n">handle&lt;/span> &lt;span class="o">!=&lt;/span> &lt;span class="k">nullptr&lt;/span> &lt;span class="o">&amp;amp;&amp;amp;&lt;/span> &lt;span class="n">handle&lt;/span> &lt;span class="o">!=&lt;/span> &lt;span class="n">INVALID_HANDLE_VALUE&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="o">::&lt;/span>&lt;span class="n">CloseHandle&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">handle&lt;/span>&lt;span class="p">);&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="p">};&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">// 安全的控制代碼型別別名
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span>&lt;span class="k">using&lt;/span> &lt;span class="n">unique_handle&lt;/span> &lt;span class="o">=&lt;/span> &lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">unique_ptr&lt;/span>&lt;span class="o">&amp;lt;&lt;/span>&lt;span class="kt">void&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="n">handle_deleter&lt;/span>&lt;span class="o">&amp;gt;&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;/code>&lt;/pre>&lt;/td>&lt;/tr>&lt;/table>
&lt;/div>
&lt;/div>&lt;p>使用這個 &lt;code>unique_handle&lt;/code>，前面危險的程式碼就會重生為如下的形式：&lt;/p>
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&lt;pre tabindex="0" class="chroma">&lt;code class="language-cpp" data-lang="cpp">&lt;span class="line">&lt;span class="cl">&lt;span class="kt">void&lt;/span> &lt;span class="nf">ProcessFileModern&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="k">const&lt;/span> &lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">wstring&lt;/span>&lt;span class="o">&amp;amp;&lt;/span> &lt;span class="n">filename&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 取得後立即將所有權交給 RAII 物件
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="n">unique_handle&lt;/span> &lt;span class="n">hFile&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">CreateFileW&lt;/span>&lt;span class="p">(&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">filename&lt;/span>&lt;span class="p">.&lt;/span>&lt;span class="n">c_str&lt;/span>&lt;span class="p">(),&lt;/span> &lt;span class="n">GENERIC_READ&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="n">FILE_SHARE_READ&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="nb">NULL&lt;/span>&lt;span class="p">,&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">OPEN_EXISTING&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="n">FILE_ATTRIBUTE_NORMAL&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="nb">NULL&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">));&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 錯誤檢查 (對 INVALID_HANDLE_VALUE 的對策於後文詳述)
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="k">if&lt;/span> &lt;span class="p">(&lt;/span>&lt;span class="n">hFile&lt;/span>&lt;span class="p">.&lt;/span>&lt;span class="n">get&lt;/span>&lt;span class="p">()&lt;/span> &lt;span class="o">==&lt;/span> &lt;span class="n">INVALID_HANDLE_VALUE&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">throw&lt;/span> &lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">runtime_error&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="s">&amp;#34;Failed to open file&amp;#34;&lt;/span>&lt;span class="p">);&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">LARGE_INTEGER&lt;/span> &lt;span class="n">fileSize&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">if&lt;/span> &lt;span class="p">(&lt;/span>&lt;span class="o">!::&lt;/span>&lt;span class="n">GetFileSizeEx&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">hFile&lt;/span>&lt;span class="p">.&lt;/span>&lt;span class="n">get&lt;/span>&lt;span class="p">(),&lt;/span> &lt;span class="o">&amp;amp;&lt;/span>&lt;span class="n">fileSize&lt;/span>&lt;span class="p">))&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">throw&lt;/span> &lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">runtime_error&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="s">&amp;#34;Failed to get file size&amp;#34;&lt;/span>&lt;span class="p">);&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">vector&lt;/span>&lt;span class="o">&amp;lt;&lt;/span>&lt;span class="kt">char&lt;/span>&lt;span class="o">&amp;gt;&lt;/span> &lt;span class="n">buffer&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">fileSize&lt;/span>&lt;span class="p">.&lt;/span>&lt;span class="n">QuadPart&lt;/span>&lt;span class="p">);&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">DWORD&lt;/span> &lt;span class="n">bytesRead&lt;/span> &lt;span class="o">=&lt;/span> &lt;span class="mi">0&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">if&lt;/span> &lt;span class="p">(&lt;/span>&lt;span class="o">!::&lt;/span>&lt;span class="n">ReadFile&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">hFile&lt;/span>&lt;span class="p">.&lt;/span>&lt;span class="n">get&lt;/span>&lt;span class="p">(),&lt;/span> &lt;span class="n">buffer&lt;/span>&lt;span class="p">.&lt;/span>&lt;span class="n">data&lt;/span>&lt;span class="p">(),&lt;/span> &lt;span class="n">buffer&lt;/span>&lt;span class="p">.&lt;/span>&lt;span class="n">size&lt;/span>&lt;span class="p">(),&lt;/span> &lt;span class="o">&amp;amp;&lt;/span>&lt;span class="n">bytesRead&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="nb">NULL&lt;/span>&lt;span class="p">))&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">throw&lt;/span> &lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">runtime_error&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="s">&amp;#34;Failed to read file&amp;#34;&lt;/span>&lt;span class="p">);&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 在這裡即使發生例外或提早回傳，
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="c1">// 在離開函數的瞬間 unique_handle 的解構子都會呼叫 CloseHandle！
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span>&lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;/code>&lt;/pre>&lt;/td>&lt;/tr>&lt;/table>
&lt;/div>
&lt;/div>&lt;hr>
&lt;h2 id="6-深入探討解決-invalid_handle_value-與-nullptr-的問題">6. 深入探討：解決 &lt;code>INVALID_HANDLE_VALUE&lt;/code> 與 &lt;code>nullptr&lt;/code> 的問題
&lt;/h2>&lt;p>在處理 Win32 API 時，最讓 C++ 程式設計師苦惱的規格之一，就是&lt;strong>無效控制代碼的表現方式不一致&lt;/strong>。&lt;/p>
&lt;ul>
&lt;li>&lt;code>CreateEvent&lt;/code> 或 &lt;code>CreateThread&lt;/code> 等：失敗時回傳 &lt;code>NULL&lt;/code> (&lt;code>nullptr&lt;/code>)。&lt;/li>
&lt;li>&lt;code>CreateFile&lt;/code> 等：失敗時回傳 &lt;code>INVALID_HANDLE_VALUE&lt;/code> (值為 &lt;code>(HANDLE)-1&lt;/code>)。&lt;/li>
&lt;/ul>
&lt;p>標準的 &lt;code>std::unique_ptr&lt;/code> 會將內部指標為 &lt;code>nullptr&lt;/code> 的情況視為「空狀態（未擁有資源的狀態）」來特別處理。也就是說，像 &lt;code>if (ptr)&lt;/code> 這樣的布林值判定，只有在遇到 &lt;code>nullptr&lt;/code> 時才會回傳 &lt;code>false&lt;/code>。&lt;/p>
&lt;p>然而，當 &lt;code>CreateFile&lt;/code> 失敗並回傳 &lt;code>INVALID_HANDLE_VALUE&lt;/code> 時，&lt;code>std::unique_ptr&lt;/code> 會將其誤認為「有效的非NULL指標」。&lt;/p>
&lt;p>為了解決這個問題，我們可以利用 C++ &lt;code>std::unique_ptr&lt;/code> 的進階規格，定義&lt;strong>自訂指標型別&lt;/strong>。&lt;/p>
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&lt;pre tabindex="0" class="chroma">&lt;code class="language-cpp" data-lang="cpp">&lt;span class="line">&lt;span class="cl">&lt;span class="cp">#include&lt;/span> &lt;span class="cpf">&amp;lt;windows.h&amp;gt;&lt;/span>&lt;span class="cp">
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="cp">#include&lt;/span> &lt;span class="cpf">&amp;lt;memory&amp;gt;&lt;/span>&lt;span class="cp">
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="cp">&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="k">struct&lt;/span> &lt;span class="nc">win32_handle_traits&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 定義自訂指標型別
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="k">class&lt;/span> &lt;span class="nc">pointer&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">HANDLE&lt;/span> &lt;span class="n">m_handle&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">public&lt;/span>&lt;span class="o">:&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 在預設建構或代入 nullptr 時，雖可設計為以 INVALID_HANDLE_VALUE 為初始值，
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="c1">// 但為了提高泛用性，這裡將 nullptr 與 INVALID_HANDLE_VALUE 雙雙視為無效狀態。
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="n">pointer&lt;/span>&lt;span class="p">()&lt;/span> &lt;span class="k">noexcept&lt;/span> &lt;span class="o">:&lt;/span> &lt;span class="n">m_handle&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="k">nullptr&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="p">{}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">pointer&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">nullptr_t&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="k">noexcept&lt;/span> &lt;span class="o">:&lt;/span> &lt;span class="n">m_handle&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="k">nullptr&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="p">{}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">pointer&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">HANDLE&lt;/span> &lt;span class="n">h&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="k">noexcept&lt;/span> &lt;span class="o">:&lt;/span> &lt;span class="n">m_handle&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">h&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="p">{}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 覆載 operator bool，同時排除 Win32 的兩種無效值
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="k">explicit&lt;/span> &lt;span class="k">operator&lt;/span> &lt;span class="nf">bool&lt;/span>&lt;span class="p">()&lt;/span> &lt;span class="k">const&lt;/span> &lt;span class="k">noexcept&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">return&lt;/span> &lt;span class="n">m_handle&lt;/span> &lt;span class="o">!=&lt;/span> &lt;span class="k">nullptr&lt;/span> &lt;span class="o">&amp;amp;&amp;amp;&lt;/span> &lt;span class="n">m_handle&lt;/span> &lt;span class="o">!=&lt;/span> &lt;span class="n">INVALID_HANDLE_VALUE&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">operator&lt;/span> &lt;span class="nf">HANDLE&lt;/span>&lt;span class="p">()&lt;/span> &lt;span class="k">const&lt;/span> &lt;span class="k">noexcept&lt;/span> &lt;span class="p">{&lt;/span> &lt;span class="k">return&lt;/span> &lt;span class="n">m_handle&lt;/span>&lt;span class="p">;&lt;/span> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">friend&lt;/span> &lt;span class="kt">bool&lt;/span> &lt;span class="k">operator&lt;/span>&lt;span class="o">==&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">pointer&lt;/span> &lt;span class="n">a&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="n">pointer&lt;/span> &lt;span class="n">b&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="k">noexcept&lt;/span> &lt;span class="p">{&lt;/span> &lt;span class="k">return&lt;/span> &lt;span class="n">a&lt;/span>&lt;span class="p">.&lt;/span>&lt;span class="n">m_handle&lt;/span> &lt;span class="o">==&lt;/span> &lt;span class="n">b&lt;/span>&lt;span class="p">.&lt;/span>&lt;span class="n">m_handle&lt;/span>&lt;span class="p">;&lt;/span> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">friend&lt;/span> &lt;span class="kt">bool&lt;/span> &lt;span class="k">operator&lt;/span>&lt;span class="o">!=&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">pointer&lt;/span> &lt;span class="n">a&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="n">pointer&lt;/span> &lt;span class="n">b&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="k">noexcept&lt;/span> &lt;span class="p">{&lt;/span> &lt;span class="k">return&lt;/span> &lt;span class="n">a&lt;/span>&lt;span class="p">.&lt;/span>&lt;span class="n">m_handle&lt;/span> &lt;span class="o">!=&lt;/span> &lt;span class="n">b&lt;/span>&lt;span class="p">.&lt;/span>&lt;span class="n">m_handle&lt;/span>&lt;span class="p">;&lt;/span> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">};&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="kt">void&lt;/span> &lt;span class="nf">operator&lt;/span>&lt;span class="p">()(&lt;/span>&lt;span class="n">pointer&lt;/span> &lt;span class="n">p&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="k">const&lt;/span> &lt;span class="k">noexcept&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">if&lt;/span> &lt;span class="p">(&lt;/span>&lt;span class="n">p&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="p">{&lt;/span> &lt;span class="c1">// 會呼叫 operator bool
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="o">::&lt;/span>&lt;span class="n">CloseHandle&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">p&lt;/span>&lt;span class="p">);&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="p">};&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="k">using&lt;/span> &lt;span class="n">safe_win32_handle&lt;/span> &lt;span class="o">=&lt;/span> &lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">unique_ptr&lt;/span>&lt;span class="o">&amp;lt;&lt;/span>&lt;span class="kt">void&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="n">win32_handle_traits&lt;/span>&lt;span class="o">&amp;gt;&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;/code>&lt;/pre>&lt;/td>&lt;/tr>&lt;/table>
&lt;/div>
&lt;/div>&lt;p>透過這個實作，就能寫出如下直覺且安全的程式碼：&lt;/p>
&lt;div class="highlight">&lt;div class="chroma">
&lt;table class="lntable">&lt;tr>&lt;td class="lntd">
&lt;pre tabindex="0" class="chroma">&lt;code>&lt;span class="lnt">1
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&lt;pre tabindex="0" class="chroma">&lt;code class="language-cpp" data-lang="cpp">&lt;span class="line">&lt;span class="cl">&lt;span class="n">safe_win32_handle&lt;/span> &lt;span class="nf">hFile&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">CreateFileW&lt;/span>&lt;span class="p">(...));&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="k">if&lt;/span> &lt;span class="p">(&lt;/span>&lt;span class="o">!&lt;/span>&lt;span class="n">hFile&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 可以在這裡同時捕捉到 nullptr 與 INVALID_HANDLE_VALUE！
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="k">throw&lt;/span> &lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">system_error&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">GetLastError&lt;/span>&lt;span class="p">(),&lt;/span> &lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">system_category&lt;/span>&lt;span class="p">(),&lt;/span> &lt;span class="s">&amp;#34;CreateFile failed&amp;#34;&lt;/span>&lt;span class="p">);&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;/code>&lt;/pre>&lt;/td>&lt;/tr>&lt;/table>
&lt;/div>
&lt;/div>&lt;hr>
&lt;h2 id="7-gdi物件hdchbitmap的進階raii管理">7. GDI物件（&lt;code>HDC&lt;/code>、&lt;code>HBITMAP&lt;/code>）的進階RAII管理
&lt;/h2>&lt;p>Win32的另一個鬼門關是 GDI (Graphics Device Interface) 的資源管理。
GDI物件（畫筆、筆刷、字型、點陣圖等）在建立後，需透過 &lt;code>SelectObject&lt;/code> 選入裝置內容 (&lt;code>HDC&lt;/code>) 中使用，使用完畢後&lt;strong>必須再次呼叫 SelectObject 恢復原本的物件，然後才能用 DeleteObject 銷毀&lt;/strong>。這種作法非常繁瑣。&lt;/p>
&lt;p>要用RAII解決這個問題，包裝器會長得像這樣：&lt;/p>
&lt;div class="highlight">&lt;div class="chroma">
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&lt;td class="lntd">
&lt;pre tabindex="0" class="chroma">&lt;code class="language-cpp" data-lang="cpp">&lt;span class="line">&lt;span class="cl">&lt;span class="c1">// 刪除 GDI 物件用的刪除器
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span>&lt;span class="k">struct&lt;/span> &lt;span class="nc">gdi_deleter&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">using&lt;/span> &lt;span class="n">pointer&lt;/span> &lt;span class="o">=&lt;/span> &lt;span class="n">HGDIOBJ&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="kt">void&lt;/span> &lt;span class="nf">operator&lt;/span>&lt;span class="p">()(&lt;/span>&lt;span class="n">HGDIOBJ&lt;/span> &lt;span class="n">obj&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="k">const&lt;/span> &lt;span class="k">noexcept&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">if&lt;/span> &lt;span class="p">(&lt;/span>&lt;span class="n">obj&lt;/span> &lt;span class="o">!=&lt;/span> &lt;span class="k">nullptr&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="o">::&lt;/span>&lt;span class="n">DeleteObject&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">obj&lt;/span>&lt;span class="p">);&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="p">};&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="k">using&lt;/span> &lt;span class="n">unique_gdi_obj&lt;/span> &lt;span class="o">=&lt;/span> &lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">unique_ptr&lt;/span>&lt;span class="o">&amp;lt;&lt;/span>&lt;span class="kt">void&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="n">gdi_deleter&lt;/span>&lt;span class="o">&amp;gt;&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">// SelectObject 的 RAII 包裝器 (離開作用域時會恢復原本的物件)
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span>&lt;span class="k">class&lt;/span> &lt;span class="nc">gdi_selector&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">HDC&lt;/span> &lt;span class="n">m_hdc&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">HGDIOBJ&lt;/span> &lt;span class="n">m_oldObj&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="k">public&lt;/span>&lt;span class="o">:&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">gdi_selector&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">HDC&lt;/span> &lt;span class="n">hdc&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="n">HGDIOBJ&lt;/span> &lt;span class="n">newObj&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="o">:&lt;/span> &lt;span class="n">m_hdc&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">hdc&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 選擇新物件，並保存舊物件
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="n">m_oldObj&lt;/span> &lt;span class="o">=&lt;/span> &lt;span class="o">::&lt;/span>&lt;span class="n">SelectObject&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">m_hdc&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="n">newObj&lt;/span>&lt;span class="p">);&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="o">~&lt;/span>&lt;span class="n">gdi_selector&lt;/span>&lt;span class="p">()&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">if&lt;/span> &lt;span class="p">(&lt;/span>&lt;span class="n">m_oldObj&lt;/span> &lt;span class="o">!=&lt;/span> &lt;span class="k">nullptr&lt;/span> &lt;span class="o">&amp;amp;&amp;amp;&lt;/span> &lt;span class="n">m_oldObj&lt;/span> &lt;span class="o">!=&lt;/span> &lt;span class="n">HGDI_ERROR&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 離開作用域時自動恢復
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="o">::&lt;/span>&lt;span class="n">SelectObject&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">m_hdc&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="n">m_oldObj&lt;/span>&lt;span class="p">);&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 禁止複製
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="n">gdi_selector&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="k">const&lt;/span> &lt;span class="n">gdi_selector&lt;/span>&lt;span class="o">&amp;amp;&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="o">=&lt;/span> &lt;span class="k">delete&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">gdi_selector&lt;/span>&lt;span class="o">&amp;amp;&lt;/span> &lt;span class="k">operator&lt;/span>&lt;span class="o">=&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="k">const&lt;/span> &lt;span class="n">gdi_selector&lt;/span>&lt;span class="o">&amp;amp;&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="o">=&lt;/span> &lt;span class="k">delete&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="p">};&lt;/span>
&lt;/span>&lt;/span>&lt;/code>&lt;/pre>&lt;/td>&lt;/tr>&lt;/table>
&lt;/div>
&lt;/div>&lt;h3 id="使用範例">使用範例
&lt;/h3>&lt;div class="highlight">&lt;div class="chroma">
&lt;table class="lntable">&lt;tr>&lt;td class="lntd">
&lt;pre tabindex="0" class="chroma">&lt;code>&lt;span class="lnt"> 1
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&lt;td class="lntd">
&lt;pre tabindex="0" class="chroma">&lt;code class="language-cpp" data-lang="cpp">&lt;span class="line">&lt;span class="cl">&lt;span class="kt">void&lt;/span> &lt;span class="nf">DrawMyGraphics&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">HDC&lt;/span> &lt;span class="n">hdc&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 建立畫筆 (RAII管理)
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="n">unique_gdi_obj&lt;/span> &lt;span class="n">hPen&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">CreatePen&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">PS_SOLID&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="mi">1&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="n">RGB&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="mi">255&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="mi">0&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="mi">0&lt;/span>&lt;span class="p">)));&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 將畫筆選入 HDC (作用域管理)
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="n">gdi_selector&lt;/span> &lt;span class="n">penSelect&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">hdc&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="n">hPen&lt;/span>&lt;span class="p">.&lt;/span>&lt;span class="n">get&lt;/span>&lt;span class="p">());&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 繪圖處理...
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="o">::&lt;/span>&lt;span class="n">MoveToEx&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">hdc&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="mi">0&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="mi">0&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="nb">NULL&lt;/span>&lt;span class="p">);&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="o">::&lt;/span>&lt;span class="n">LineTo&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">hdc&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="mi">100&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="mi">100&lt;/span>&lt;span class="p">);&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 離開作用域時，penSelect 的解構子會透過 SelectObject 恢復舊畫筆
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 離開函數時，hPen 的解構子會呼叫 DeleteObject
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span>&lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;/code>&lt;/pre>&lt;/td>&lt;/tr>&lt;/table>
&lt;/div>
&lt;/div>&lt;p>像這樣，生命週期呈現巢狀結構的資源管理，正是 RAII 大顯身手的領域。&lt;/p>
&lt;hr>
&lt;h2 id="8-執行緒同步物件的現代化">8. 執行緒同步物件的現代化
&lt;/h2>&lt;p>Win32 存在著 &lt;code>CRITICAL_SECTION&lt;/code> 與 &lt;code>SRWLOCK&lt;/code> 等執行緒同步基元。從例外安全的觀點來看，手動呼叫 &lt;code>EnterCriticalSection&lt;/code> / &lt;code>LeaveCriticalSection&lt;/code> 也是大忌。&lt;/p>
&lt;p>C++11的 &lt;code>std::mutex&lt;/code> 與 &lt;code>std::lock_guard&lt;/code> 雖然非常方便，但有時也會想直接使用 OS 原生的高速鎖定機制（尤其是 SRWLock 非常輕量）。
標準的 &lt;code>std::lock_guard&lt;/code> 其規格是可以接收任何具有 &lt;code>lock()&lt;/code> 與 &lt;code>unlock()&lt;/code> 成員函數的型別（類似鴨子型別 (Duck typing) 的模板規格）。我們就能利用這一點。&lt;/p>
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&lt;td class="lntd">
&lt;pre tabindex="0" class="chroma">&lt;code class="language-cpp" data-lang="cpp">&lt;span class="line">&lt;span class="cl">&lt;span class="k">class&lt;/span> &lt;span class="nc">win32_srwlock&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">SRWLOCK&lt;/span> &lt;span class="n">m_lock&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="k">public&lt;/span>&lt;span class="o">:&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">win32_srwlock&lt;/span>&lt;span class="p">()&lt;/span> &lt;span class="k">noexcept&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="o">::&lt;/span>&lt;span class="n">InitializeSRWLock&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="o">&amp;amp;&lt;/span>&lt;span class="n">m_lock&lt;/span>&lt;span class="p">);&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// std::lock_guard 要求的介面
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="kt">void&lt;/span> &lt;span class="nf">lock&lt;/span>&lt;span class="p">()&lt;/span> &lt;span class="k">noexcept&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="o">::&lt;/span>&lt;span class="n">AcquireSRWLockExclusive&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="o">&amp;amp;&lt;/span>&lt;span class="n">m_lock&lt;/span>&lt;span class="p">);&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="kt">void&lt;/span> &lt;span class="nf">unlock&lt;/span>&lt;span class="p">()&lt;/span> &lt;span class="k">noexcept&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="o">::&lt;/span>&lt;span class="n">ReleaseSRWLockExclusive&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="o">&amp;amp;&lt;/span>&lt;span class="n">m_lock&lt;/span>&lt;span class="p">);&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 禁止複製與移動
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="n">win32_srwlock&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="k">const&lt;/span> &lt;span class="n">win32_srwlock&lt;/span>&lt;span class="o">&amp;amp;&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="o">=&lt;/span> &lt;span class="k">delete&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">win32_srwlock&lt;/span>&lt;span class="o">&amp;amp;&lt;/span> &lt;span class="k">operator&lt;/span>&lt;span class="o">=&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="k">const&lt;/span> &lt;span class="n">win32_srwlock&lt;/span>&lt;span class="o">&amp;amp;&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="o">=&lt;/span> &lt;span class="k">delete&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="p">};&lt;/span>
&lt;/span>&lt;/span>&lt;/code>&lt;/pre>&lt;/td>&lt;/tr>&lt;/table>
&lt;/div>
&lt;/div>&lt;p>如此一來，就能完全以 C++ 標準函式庫的作法來處理 Win32 的鎖定。&lt;/p>
&lt;div class="highlight">&lt;div class="chroma">
&lt;table class="lntable">&lt;tr>&lt;td class="lntd">
&lt;pre tabindex="0" class="chroma">&lt;code>&lt;span class="lnt"> 1
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&lt;pre tabindex="0" class="chroma">&lt;code class="language-cpp" data-lang="cpp">&lt;span class="line">&lt;span class="cl">&lt;span class="n">win32_srwlock&lt;/span> &lt;span class="n">g_myLock&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="kt">int&lt;/span> &lt;span class="n">g_sharedData&lt;/span> &lt;span class="o">=&lt;/span> &lt;span class="mi">0&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="kt">void&lt;/span> &lt;span class="nf">UpdateData&lt;/span>&lt;span class="p">()&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 例外安全的鎖定獲取
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">lock_guard&lt;/span>&lt;span class="o">&amp;lt;&lt;/span>&lt;span class="n">win32_srwlock&lt;/span>&lt;span class="o">&amp;gt;&lt;/span> &lt;span class="n">lock&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">g_myLock&lt;/span>&lt;span class="p">);&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">g_sharedData&lt;/span>&lt;span class="o">++&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">if&lt;/span> &lt;span class="p">(&lt;/span>&lt;span class="n">g_sharedData&lt;/span> &lt;span class="o">&amp;gt;&lt;/span> &lt;span class="mi">100&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">throw&lt;/span> &lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">runtime_error&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="s">&amp;#34;Overflow&amp;#34;&lt;/span>&lt;span class="p">);&lt;/span> &lt;span class="c1">// 就算拋出例外也能安全釋放鎖！
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;/code>&lt;/pre>&lt;/td>&lt;/tr>&lt;/table>
&lt;/div>
&lt;/div>&lt;hr>
&lt;h2 id="9-與-c-標準函式庫的整合stdsystem_error-與-hresult">9. 與 C++ 標準函式庫的整合：&lt;code>std::system_error&lt;/code> 與 &lt;code>HRESULT&lt;/code>
&lt;/h2>&lt;p>Win32 的錯誤主要分為兩類：&lt;code>GetLastError()&lt;/code>（DWORD 型別），以及 COM 或 DirectX 中使用的 &lt;code>HRESULT&lt;/code>。將這些轉換為 C++ 的例外 &lt;code>std::system_error&lt;/code>，可以讓錯誤處理現代化。&lt;/p>
&lt;p>在拋出 &lt;code>GetLastError()&lt;/code> 時，於 MSVC (Visual C++) 的實作中，&lt;code>std::system_category()&lt;/code> 提供了 Win32 錯誤碼與訊息的映射。&lt;/p>
&lt;div class="highlight">&lt;div class="chroma">
&lt;table class="lntable">&lt;tr>&lt;td class="lntd">
&lt;pre tabindex="0" class="chroma">&lt;code>&lt;span class="lnt">1
&lt;/span>&lt;span class="lnt">2
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&lt;pre tabindex="0" class="chroma">&lt;code class="language-cpp" data-lang="cpp">&lt;span class="line">&lt;span class="cl">&lt;span class="kr">inline&lt;/span> &lt;span class="kt">void&lt;/span> &lt;span class="nf">throw_if_win32_error&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">BOOL&lt;/span> &lt;span class="n">result&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="k">const&lt;/span> &lt;span class="kt">char&lt;/span>&lt;span class="o">*&lt;/span> &lt;span class="n">msg&lt;/span> &lt;span class="o">=&lt;/span> &lt;span class="s">&amp;#34;Win32 API failed&amp;#34;&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">if&lt;/span> &lt;span class="p">(&lt;/span>&lt;span class="o">!&lt;/span>&lt;span class="n">result&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">DWORD&lt;/span> &lt;span class="n">err&lt;/span> &lt;span class="o">=&lt;/span> &lt;span class="o">::&lt;/span>&lt;span class="n">GetLastError&lt;/span>&lt;span class="p">();&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// std::system_category 會在內部呼叫 FormatMessage API，並產生錯誤字串
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="k">throw&lt;/span> &lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">system_error&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">err&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">system_category&lt;/span>&lt;span class="p">(),&lt;/span> &lt;span class="n">msg&lt;/span>&lt;span class="p">);&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;/code>&lt;/pre>&lt;/td>&lt;/tr>&lt;/table>
&lt;/div>
&lt;/div>&lt;p>另一方面，關於 &lt;code>HRESULT&lt;/code>，則可以建立專屬的錯誤類別，或是使用 Windows 標準的 &lt;code>_com_error&lt;/code>。&lt;/p>
&lt;hr>
&lt;h2 id="10-使用-stdexpected-c23-的現代化錯誤處理">10. 使用 &lt;code>std::expected&lt;/code> (C++23) 的現代化錯誤處理
&lt;/h2>&lt;p>從 C++23 開始，引入了相當於 Rust &lt;code>Result&lt;/code> 型別的 &lt;code>std::expected&lt;/code>。對於不喜歡例外（出於效能考量，或設計上錯誤頻發）的專案來說，這是讓 Win32 回傳值現代化的最佳手法。&lt;/p>
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&lt;pre tabindex="0" class="chroma">&lt;code class="language-cpp" data-lang="cpp">&lt;span class="line">&lt;span class="cl">&lt;span class="cp">#include&lt;/span> &lt;span class="cpf">&amp;lt;expected&amp;gt;&lt;/span>&lt;span class="cp">
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="cp">#include&lt;/span> &lt;span class="cpf">&amp;lt;string&amp;gt;&lt;/span>&lt;span class="cp">
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="cp">&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">// 成功時回傳 unique_handle，失敗時回傳 DWORD(錯誤碼)
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span>&lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">expected&lt;/span>&lt;span class="o">&amp;lt;&lt;/span>&lt;span class="n">safe_win32_handle&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="n">DWORD&lt;/span>&lt;span class="o">&amp;gt;&lt;/span> &lt;span class="n">OpenFileModern&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="k">const&lt;/span> &lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">wstring&lt;/span>&lt;span class="o">&amp;amp;&lt;/span> &lt;span class="n">path&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">safe_win32_handle&lt;/span> &lt;span class="nf">h&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">CreateFileW&lt;/span>&lt;span class="p">(&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">path&lt;/span>&lt;span class="p">.&lt;/span>&lt;span class="n">c_str&lt;/span>&lt;span class="p">(),&lt;/span> &lt;span class="n">GENERIC_READ&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="mi">0&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="k">nullptr&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="n">OPEN_EXISTING&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="mi">0&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="k">nullptr&lt;/span>&lt;span class="p">));&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">if&lt;/span> &lt;span class="p">(&lt;/span>&lt;span class="o">!&lt;/span>&lt;span class="n">h&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">return&lt;/span> &lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">unexpected&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">GetLastError&lt;/span>&lt;span class="p">());&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">return&lt;/span> &lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">move&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">h&lt;/span>&lt;span class="p">);&lt;/span> &lt;span class="c1">// 成功時使用移動語意回傳控制代碼
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span>&lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="kt">void&lt;/span> &lt;span class="nf">Usage&lt;/span>&lt;span class="p">()&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">auto&lt;/span> &lt;span class="n">result&lt;/span> &lt;span class="o">=&lt;/span> &lt;span class="n">OpenFileModern&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="sa">L&lt;/span>&lt;span class="s">&amp;#34;C:&lt;/span>&lt;span class="se">\\&lt;/span>&lt;span class="s">test.txt&amp;#34;&lt;/span>&lt;span class="p">);&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="k">if&lt;/span> &lt;span class="p">(&lt;/span>&lt;span class="n">result&lt;/span>&lt;span class="p">)&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 成功時的處理
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="n">safe_win32_handle&lt;/span>&lt;span class="o">&amp;amp;&lt;/span> &lt;span class="n">hFile&lt;/span> &lt;span class="o">=&lt;/span> &lt;span class="o">*&lt;/span>&lt;span class="n">result&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// ...
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="p">}&lt;/span> &lt;span class="k">else&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 失敗時的處理
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="n">DWORD&lt;/span> &lt;span class="n">err&lt;/span> &lt;span class="o">=&lt;/span> &lt;span class="n">result&lt;/span>&lt;span class="p">.&lt;/span>&lt;span class="n">error&lt;/span>&lt;span class="p">();&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">cerr&lt;/span> &lt;span class="o">&amp;lt;&amp;lt;&lt;/span> &lt;span class="s">&amp;#34;Error code: &amp;#34;&lt;/span> &lt;span class="o">&amp;lt;&amp;lt;&lt;/span> &lt;span class="n">err&lt;/span> &lt;span class="o">&amp;lt;&amp;lt;&lt;/span> &lt;span class="n">std&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">endl&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;/code>&lt;/pre>&lt;/td>&lt;/tr>&lt;/table>
&lt;/div>
&lt;/div>&lt;p>像這樣，透過使用 C++23，可以兼顧基於回傳值的錯誤處理與 RAII 帶來的好處。&lt;/p>
&lt;hr>
&lt;h2 id="11-microsoft的解答-1靈活運用-wil-windows-implementation-libraries">11. Microsoft的解答 (1)：靈活運用 WIL (Windows Implementation Libraries)
&lt;/h2>&lt;p>前面介紹了自製的包裝器，但其實 Microsoft 自身也非常重視這個問題，並開源釋出了針對現代 C++ 的官方 Header-only 函式庫 &lt;strong>WIL (Windows Implementation Libraries)&lt;/strong>（可於 GitHub 上取得）。&lt;/p>
&lt;p>使用 WIL 的話，前面辛苦自製的包裝器全部都有標準提供。&lt;/p>
&lt;div class="highlight">&lt;div class="chroma">
&lt;table class="lntable">&lt;tr>&lt;td class="lntd">
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&lt;/span>&lt;/code>&lt;/pre>&lt;/td>
&lt;td class="lntd">
&lt;pre tabindex="0" class="chroma">&lt;code class="language-cpp" data-lang="cpp">&lt;span class="line">&lt;span class="cl">&lt;span class="cp">#include&lt;/span> &lt;span class="cpf">&amp;lt;wil/resource.h&amp;gt;&lt;/span>&lt;span class="cp">
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="cp">#include&lt;/span> &lt;span class="cpf">&amp;lt;wil/result.h&amp;gt;&lt;/span>&lt;span class="cp">
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="cp">&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="kt">void&lt;/span> &lt;span class="nf">ProcessWithWIL&lt;/span>&lt;span class="p">()&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// wil::unique_handle 已同時對應 INVALID_HANDLE_VALUE 與 NULL
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="n">wil&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">unique_handle&lt;/span> &lt;span class="n">hFile&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// THROW_IF_WIN32_BOOL_FALSE 巨集可自動化錯誤檢查與例外拋出
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="n">THROW_IF_WIN32_BOOL_FALSE&lt;/span>&lt;span class="p">(&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="o">::&lt;/span>&lt;span class="n">CreateFileW&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="sa">L&lt;/span>&lt;span class="s">&amp;#34;test.txt&amp;#34;&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="n">GENERIC_READ&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="mi">0&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="k">nullptr&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="n">OPEN_EXISTING&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="mi">0&lt;/span>&lt;span class="p">,&lt;/span> &lt;span class="k">nullptr&lt;/span>&lt;span class="p">),&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">hFile&lt;/span>&lt;span class="p">.&lt;/span>&lt;span class="n">put&lt;/span>&lt;span class="p">()&lt;/span> &lt;span class="c1">// WIL 特有的接收輸出指標用輔助函數
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="p">);&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 像是 wil::unique_cotaskmem_string 等，記憶體管理的包裝器也很齊全
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span>&lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;/code>&lt;/pre>&lt;/td>&lt;/tr>&lt;/table>
&lt;/div>
&lt;/div>&lt;p>WIL 的精髓在於名為 &lt;code>wil::unique_any&lt;/code> 的強大模板，它不僅是檔案控制代碼，還能用寥寥數行定義出登錄碼機碼、GDI 物件、本機記憶體等各種 Win32 資源的 RAII 包裝器。&lt;/p>
&lt;hr>
&lt;h2 id="12-microsoft的解答-2透過-cwinrt-抽象化-com">12. Microsoft的解答 (2)：透過 C++/WinRT 抽象化 COM
&lt;/h2>&lt;p>許多的 Win32 API（尤其是 Shell 的擴充或是 DirectX 等），是透過基於 C 語言的 COM (Component Object Model) 介面來提供的。
進一步將傳統的 &lt;code>CComPtr&lt;/code> (ATL) 與 &lt;code>ComPtr&lt;/code> (WRL) 演進，目前 Microsoft 官方推薦的就是 &lt;strong>C++/WinRT&lt;/strong>。&lt;/p>
&lt;p>C++/WinRT 不僅能處理 Windows 執行階段 (WinRT)，對於傳統的 COM 物件也能處理得極為聰明。&lt;/p>
&lt;div class="highlight">&lt;div class="chroma">
&lt;table class="lntable">&lt;tr>&lt;td class="lntd">
&lt;pre tabindex="0" class="chroma">&lt;code>&lt;span class="lnt"> 1
&lt;/span>&lt;span class="lnt"> 2
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&lt;td class="lntd">
&lt;pre tabindex="0" class="chroma">&lt;code class="language-cpp" data-lang="cpp">&lt;span class="line">&lt;span class="cl">&lt;span class="cp">#include&lt;/span> &lt;span class="cpf">&amp;lt;winrt/base.h&amp;gt;&lt;/span>&lt;span class="cp">
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="cp">&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="kt">void&lt;/span> &lt;span class="nf">ComExample&lt;/span>&lt;span class="p">()&lt;/span> &lt;span class="p">{&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// COM 的初始化 (RAII化)
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="n">winrt&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">init_apartment&lt;/span>&lt;span class="p">();&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 將繼承 IUnknown 的 COM 介面用 winrt::com_ptr 安全地管理
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span> &lt;span class="n">winrt&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">com_ptr&lt;/span>&lt;span class="o">&amp;lt;&lt;/span>&lt;span class="n">IDXGIFactory&lt;/span>&lt;span class="o">&amp;gt;&lt;/span> &lt;span class="n">factory&lt;/span>&lt;span class="p">;&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="n">winrt&lt;/span>&lt;span class="o">::&lt;/span>&lt;span class="n">check_hresult&lt;/span>&lt;span class="p">(&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="o">::&lt;/span>&lt;span class="n">CreateDXGIFactory&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">__uuidof&lt;/span>&lt;span class="p">(&lt;/span>&lt;span class="n">IDXGIFactory&lt;/span>&lt;span class="p">),&lt;/span> &lt;span class="n">factory&lt;/span>&lt;span class="p">.&lt;/span>&lt;span class="n">put_void&lt;/span>&lt;span class="p">())&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="p">);&lt;/span>
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">
&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl"> &lt;span class="c1">// 完全不需要手動呼叫 AddRef 或 Release
&lt;/span>&lt;/span>&lt;/span>&lt;span class="line">&lt;span class="cl">&lt;span class="c1">&lt;/span>&lt;span class="p">}&lt;/span>
&lt;/span>&lt;/span>&lt;/code>&lt;/pre>&lt;/td>&lt;/tr>&lt;/table>
&lt;/div>
&lt;/div>&lt;hr>
&lt;h2 id="13-架構與生命週期的視覺化">13. 架構與生命週期的視覺化
&lt;/h2>&lt;p>讓我們來整理現代 Windows C++ 應用程式開發中的分層結構。&lt;/p>
&lt;div class="mermaid">graph TD
A["現代 C++ 應用程式邏輯"] --> B["C++ 標準函式庫 (std::unique_ptr, std::mutex, std::expected)"]
A --> C["Windows Implementation Libraries (WIL)"]
A --> D["C++/WinRT"]
C --> E["原始 Win32 API (C 介面)"]
D --> F["COM 介面"]
F --> E
B --> E
E --> G["Windows 核心 (ntoskrnl.exe) / 子系統"]
style A fill:#4CAF50,stroke:#388E3C,stroke-width:2px,color:#fff
style G fill:#2196F3,stroke:#1976D2,stroke-width:2px,color:#fff&lt;/div>
&lt;p>應用程式邏輯絕不應該直接接觸原始的 Win32 API（第 E 層）。務必建立透過標準函式庫、WIL 或 C++/WinRT 任一抽象層進行存取的架構，如此一來記憶體安全性將會飛躍性地提升。&lt;/p>
&lt;hr>
&lt;h2 id="14-零成本抽象化的效能分析">14. 零成本抽象化的效能分析
&lt;/h2>&lt;p>「使用 RAII 包裝器或智慧指標，運作起來會不會比原始 C 語言 API 還要慢？」或許有人會有這樣的疑問。
在這裡，讓我們看看效能成本的數學公式模型。&lt;/p>
&lt;p>執行時間 $T_{\text{total}}$ 可以分解如下：&lt;/p>
$$ T_{\text{total}} = T_{\text{syscall}} + T_{\text{wrapper}} + T_{\text{cleanup}} $$
&lt;ul>
&lt;li>$T_{\text{syscall}}$：Win32 API 內部轉換到核心模式及實際處理所花費的時間。通常為毫秒至微秒等級。&lt;/li>
&lt;li>$T_{\text{wrapper}}$：建構 &lt;code>std::unique_ptr&lt;/code> 或 WIL 包裝器類別所花費的時間。&lt;/li>
&lt;li>$T_{\text{cleanup}}$：呼叫解構子所花費的時間。&lt;/li>
&lt;/ul>
&lt;p>C++ 的編譯器（MSVC、Clang、GCC）在行內化 (Inlining) 的最佳化上極為優異。&lt;code>std::unique_ptr&lt;/code> 的建構子與解構子、覆載的 &lt;code>operator*&lt;/code> 或 &lt;code>operator bool&lt;/code> 全部都會被 &lt;code>inline&lt;/code> 展開，編譯成與直接操作記憶體上的原始指標完全相同的機器碼。&lt;/p>
&lt;p>也就是說，&lt;strong>$T_{\text{wrapper}} \approx 0$&lt;/strong>。這正是 C++ 最大哲學 &lt;strong>Zero-cost Abstraction (零成本抽象化)&lt;/strong> 的證明。即便獲得了安全性，執行時的額外負擔 (Overhead) 依然如字面所說的是零。&lt;/p>
&lt;hr>
&lt;h2 id="15-總結安全的-windows-程式設計之未來">15. 總結：安全的 Windows 程式設計之未來
&lt;/h2>&lt;p>Win32 API 基於歷史原因，是個以 C 語言典範設計的古老美好遺產。然而，作為呼叫方的 C++ 持續在進化，如今已能寫出極為安全且具表現力的程式碼。&lt;/p>
&lt;p>回顧本文解說的重點：&lt;/p>
&lt;ol>
&lt;li>&lt;strong>絕不手動撰寫 &lt;code>CloseHandle&lt;/code> 或 &lt;code>DeleteObject&lt;/code>。&lt;/strong> 將一切都封裝在 &lt;code>std::unique_ptr&lt;/code> 等 RAII 容器中。&lt;/li>
&lt;li>&lt;strong>理解 &lt;code>INVALID_HANDLE_VALUE&lt;/code> 的陷阱。&lt;/strong> 實作專屬的自訂刪除器・自訂指標特性 (Pointer Traits)，或使用 WIL 的 &lt;code>wil::unique_handle&lt;/code>。&lt;/li>
&lt;li>&lt;strong>現代化錯誤處理。&lt;/strong> 將 &lt;code>GetLastError()&lt;/code> 或 &lt;code>HRESULT&lt;/code> 作為 &lt;code>std::system_error&lt;/code> 例外拋出，或使用 C++23 的 &lt;code>std::expected&lt;/code> 進行型別安全的處理。&lt;/li>
&lt;li>&lt;strong>站在巨人的肩膀上。&lt;/strong> 積極採用 Microsoft 官方的 WIL 與 C++/WinRT，避免重新發明輪子。&lt;/li>
&lt;/ol>
&lt;p>在現代的 C++ 開發中，帶著赤裸裸的原始指標或控制代碼到處跑，就像是不繫安全帶在高速公路上行駛一樣。請充分運用 C++ 提供的強大型別系統與 RAII，享受安全又堅固的 Windows 應用程式開發吧。&lt;/p></description></item></channel></rss>