# std::is_destructible, std::is_trivially_destructible, std::is_nothrow_destructible

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< cpp‎ | types

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 (possibly cv-qualified) void, a function type, or an array of unknown bound, `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) same as 1), and additionally std::remove_all_extents <T>::type is either a non-class type or a class type with a trivial destructor.

3) same as 1), but the destructor is noexcept.

`T` shall be a complete type, (possibly cv-qualified) void, or an array of unknown bound. Otherwise, the behavior is undefined.

If an instantiation of a template above depends, directly or indirectly, on an incomplete type, and that instantiation could yield a different result if that type were hypothetically completed, the behavior is undefined.

### Helper variable templates

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)

## Inherited from std::integral_constant

### Member constants

value [static] | true if `T` is destructible, false otherwise (public static member constant)

### Member functions

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

### Member types

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

### Notes

Because the C++ program terminates if a destructor throws an exception during stack unwinding (which usually cannot be predicted), all practical destructors are non-throwing even if they are not declared noexcept. All destructors found in the C++ standard library are non-throwing.

Storage occupied by trivially destructible objects may be reused without calling the destructor.

### Example

Run this code

    #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';
    }

Output:

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

### See also

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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