std::is_trivially_copyable
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| Defined in header <type_traits>
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| template< class T > struct is_trivially_copyable; |
（C++11 起） | |
If T is a trivially copyable type, provides the member constant value equal true. For any other type, value is false.
The only trivially copyable types are scalar types, trivially copyable classes, and arrays of such types/classes (possibly cv-qualified).
A trivially copyable class is a class that
1. Has no non-trivial copy constructors (this also requires no virtual functions or virtual bases)
2. Has no non-trivial move constructors
3. Has no non-trivial copy assignment operators
4. Has no non-trivial move assignment operators
5. Has a trivial destructor
目錄 |
Inherited from std::integral_constant
Member constants
| value [靜態的] </ SPAN></div></div>
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true如果 T is a trivially copyable type ，false其他方式 Original: true if T is a trivially copyable type , false otherwise The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. （公共靜態成員常量） |
Member functions
| operator bool |
轉換的對象bool，返回 value Original: converts the object to bool, returns value The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. （公共成員函數） |
Member types
| 類型
Original: Type The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
Definition |
value_type
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bool
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type
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std::integral_constant<bool, value> |
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[编辑] 注釋
Objects of trivially-copyable types are the only C++ objects that may be safely copied with std::memcpy or serialized to/from binary files with std::ofstream::write()/std::ifstream::read(). In general, a trivially copyable type is any type for which the underlying bytes can be copied to an array of char or unsigned char and into a new object of the same type, and the resulting object would have the same value as the original.
[编辑] 為例
#include <iostream> #include <type_traits> struct A { int m; }; struct B { B(const B&) {} }; struct C { virtual void foo(); }; int main() { std::cout << std::boolalpha; std::cout << std::is_trivially_copyable<A>::value << '\n'; std::cout << std::is_trivially_copyable<B>::value << '\n'; std::cout << std::is_trivially_copyable<C>::value << '\n'; }
Output:
true false false
