C++

參考

<type_traits>

類模板
<type_traits>

std::is_trivially_copyable

template <class T> struct is_trivially_copyable;
Is trivially copyable

Trait class that identifies whether T is a trivially copyable type.

A trivially copyable type is a type whose storage is contiguous (and thus its copy implies a trivial memory block copy, as if performed with memcpy), either cv-qualified or not. This is true for scalar types, trivially copyable classes and arrays of any such types.

A trivially copyable class is a class (defined with類, structor聯合體定義）
  • uses the implicitly defined copy and move constructors, copy and move assignments, and destructor.
  • 沒有虛成員。
  • its base class and non-static data members (if any) are themselves also trivially copyable types.

This class inherits from integral_constant as being either true_type or false_type, depending on whetherTis a trivially copyable type.

模板引數

T
一個完整型別，或者void(possible cv-qualified), or an array of unknown bound of a complete element type.

成員型別

Inherited from integral_constant
成員型別定義
value_typebool
型別true_type 或 false_type

成員常量

Inherited from integral_constant
成員常量定義
值是trueorfalse

成員函式

Inherited from integral_constant
operator bool
Returns value (public member function)

示例

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// is_trivially_copiable example
#include <iostream>
#include <type_traits>

struct A { int i; };

struct B {
  int i,j;
  B (const B& x) : i(x.i), j(1) {};  // copy ctor
};

int main() {
  std::cout << std::boolalpha;
  std::cout << "is_trivially_copyable:" << std::endl;
  std::cout << "int: " << std::is_trivially_copyable<int>::value << std::endl;
  std::cout << "A: " << std::is_trivially_copyable<A>::value << std::endl;
  std::cout << "B: " << std::is_trivially_copyable<B>::value << std::endl;
  return 0;
}

輸出
is_trivially_copyable:
int: true
A: true
B: false


另見

is_trivial
是否為平凡型別 （類模板）
is_trivially_constructible
是否可平凡構造 （類模板）
is_trivially_copy_constructible
是否可平凡複製構造 （類模板）
is_trivially_copy_assignable
是否可平凡複製賦值 （類模板）