cppreference.com - std::variant 与联合一样,如果一个变体包含某个对象类型的值 T ,则 --- T 对象表示直接在变体本身的对象表示中分配。不允许变体分配额外的(动态)内存。 对于std::any 这是不可能的。 到目前为止, std::variant 只需要为 std::variant 本身分配一个内存,并且它可以保留在堆栈上。 原文...
BSTR * pbstrVal; // VT_BYREF|VT_BSTR. }; }; 显然,VARIANT类型是一个C结构,它包含了一个类型成员vt、一些保留字节以及一个大的union类型例如,如果vt为VT_I2,那么我们可以从iVal中读出
C++17引入了variant,今天我们来学习一下C++中std::variant。...在 C++17 中引入了一个非常有用的类型 std::variant,它属于 C++ 标准库中的 variant> 头文件。...unsetunset特点unsetunset 类型安全:与传统的 C 联合体(union)不同,st...
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virtual HRESULT get_accHelpTopic( BSTR* pszHelpFile, VARIANT varChild, long* pidTopic); 參數pszHelpFile [in]BSTR 的位址,該字串會接收與指定對象相關聯之 WinHelp 檔案的完整路徑,如果有的話。varChild [in]指定要擷取的 Help 主題是否為 物件或物件的其中一個子專案。 這個參數可以是CHILDID_SELF(若...
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<unordered_map> <unordered_set> <utility> <valarray> <variant> <vector> C++ Standard Library overview C++ Standard Library containers Iterators Algorithms Allocators Function objects in the C++ Standard Library iostream programming Regular expressions (C++) File system navigation Download PDF Learn...
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