std::is_trivially_copyable
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| Заголовочный файл <type_traits>
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| template< class T > struct is_trivially_copyable; |
(начиная с C++11) | |
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
Содержание |
Унаследован от std::integral_constant
Member constants
| value [static] |
true если T is a trivially copyable type , false иначе 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. (public static константа-член) |
Member functions
| operator bool |
преобразует объект в bool, возвращает 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. (public функция-член) |
Member types
| Type
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> |
[править] Notes
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.
[править] Пример
#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'; }
Вывод:
true false false
