std::is_trivially_destructible

Defined in header <type_traits>
template< class T > struct is_destructible;	(1)	(since C++11)
template< class T > struct is_trivially_destructible;	(2)	(since C++11)
template< class T > struct is_nothrow_destructible;	(3)	(since C++11)

1) If an imaginary struct containing a member object of type T has a non-deleted destructor, provides the member constant value equal true. For any other type, value is false.	(until C++14)
1) If T is a reference type, provides the member constant value equal true. If T is an incomplete type (including void) or a function type, value equals false. If T is an object type, then, for the type U equal std::remove_all_extents<T>::type, if the expression std::declval<U&>().~U() is well-formed in unevaluated context, value equals true. Otherwise, value equals false.	(since C++14)

2%29与1%29相同，但析构函数不调用任何不平凡的操作。

3%29和1%29相同，但破坏者除外。

T为完整类型，%28可能是cv-合格%29void，或者一系列未知的界限。否则，行为就没有定义。

辅助变量模板

template< class T > inline constexpr bool is_destructible_v = is_destructible<T>::value;		(since C++17)
template< class T > inline constexpr bool is_trivially_destructible_v = is_trivially_destructible<T>::value;		(since C++17)
template< class T > inline constexpr bool is_nothrow_destructible_v = is_nothrow_destructible<T>::value;		(since C++17)

继承自STD：积分[医]常量

成员常数

value static	true if T is destructible, false otherwise (public static member constant)

成员函数

operator bool	converts the object to bool, returns value (public member function)
operator() (C++14)	returns value (public member function)

成员类型

Type	Definition
value_type	bool
type	std::integral_constant<bool, value>

注记

由于C++程序在堆栈展开过程中抛出异常(通常无法预测为%29)，则所有实际的析构函数都不会抛出，即使它们没有声明为no。在C++标准库中找到的所有析构函数都是不抛出的。

可销毁物品占用的存储器可重复使用而不打电话给破坏者。

例

二次

#include <iostream>
#include <string>
#include <type_traits>
struct Foo {
   std::string str;
   ~Foo() noexcept {};
};
struct Bar {
    ~Bar() = default;
};
int main() {
    std::cout << std::boolalpha
              << "std::string is destructible? "
              << std::is_destructible<std::string>::value << '\n'
              << "Foo is nothrow destructible? "
              << std::is_nothrow_destructible<Foo>::value << '\n'
              << "Bar is trivally destructible? "
              << std::is_trivially_destructible<Bar>::value << '\n';
}

二次

产出：

二次

std::string is destructible? true
Foo is nothrow destructible? true
Bar is trivally destructible? true

二次

另见

is_constructibleis_trivially_constructibleis_nothrow_constructible (C++11)(C++11)(C++11)	checks if a type has a constructor for specific arguments (class template)
has_virtual_destructor (C++11)	checks if a type has a virtual destructor (class template)

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最后更新于：2017-12-18