std::is_destructible, std::is_trivially_destructible, std::is_nothrow_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) same as 1), but the destructor does not call any operation that is not trivial.

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.

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

[edit] 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.

[edit] 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

[edit] 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)
std::experimental::is_destructible_v (library fundamentals TS)	variable template alias of `std::is_destructible::value` (variable template)
std::experimental::is_trivially_destructible_v (library fundamentals TS)	variable template alias of `std::is_trivially_destructible::value` (variable template)
std::experimental::is_nothrow_destructible_v (library fundamentals TS)	variable template alias of `std::is_nothrow_destructible::value` (variable template)

Language
Standard library headers
Concepts
Utilities library
Strings library
Containers library
Algorithms library
Iterators library
Numerics library
Input/output library
Localizations library
Regular expressions library (C++11)
Atomic operations library (C++11)
Thread support library (C++11)
Technical Specifications

Type support (basic types, RTTI, type traits)
Dynamic memory management
Error handling
Program utilities
Variadic functions
Date and time
Function objects
initializer_list (C++11)
bitset
hash (C++11)
Relational operators
rel_ops::operator!=rel_ops::operator>rel_ops::operator<=rel_ops::operator>=
Pairs and tuples
pair
tuple (C++11)
piecewise_construct_t (C++11)
piecewise_construct (C++11)
integer_sequence (C++14)
Swap, forward and move
swap
exchange (C++14)
forward (C++11)
move (C++11)
move_if_noexcept (C++11)
Type operations
declval (C++11)
as_const (C++17)