std::has_virtual_destructor - cppreference.com

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`template< class T > struct has_virtual_destructor;`		(since C++11)

std::has_virtual_destructor is a UnaryTypeTrait.

If T is a type with a virtual destructor, the base characteristic is std::true_type. For any other type, the base characteristic is std::false_type.

If T is an incomplete non-union class type, the behavior is undefined.

If the program adds specializations for std::has_virtual_destructor or std::has_virtual_destructor_v, the behavior is undefined.

Template parameters

Helper variable template

`template< class T > constexpr bool has_virtual_destructor_v = has_virtual_destructor<T>::value;`		(since C++17)

Inherited from std::integral_constant

Member constants

true if T has a virtual destructor, false otherwise
(public static member constant)

Member functions

	converts the object to `bool`, returns `value` (public member function)
	returns `value` (public member function)

Member types

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

Notes

If a class C has a public virtual destructor, it can be derived from, and the derived object can be safely deleted through a pointer to the base object (GotW #18). In this case, std::is_polymorphic<C>::value is true.

Example

#include <type_traits>

struct S {};
static_assert(!std::has_virtual_destructor_v<S>);

struct B { virtual ~B() {} };
static_assert(std::has_virtual_destructor_v<B>);

struct D : B { ~D() {} };
static_assert(std::has_virtual_destructor_v<D>);

int main()
{
    B* pd = new D;
    delete pd;
}

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 2015	C++11	the behavior was undefined if `T` is an incomplete union type	the base characteristic is std::false_type in this case