NAME¶

std::has_virtual_destructor - std::has_virtual_destructor

Synopsis¶

Defined in header <type_traits>
template< class T > (since C++11)
struct has_virtual_destructor;

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¶

T - a type to check

Helper variable template

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

Inherited from std::integral_constant

Member constants¶

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

Member functions¶

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

// Run this code

#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 the base characteristic is
T is an incomplete union type std::false_type in this case

See also¶

is_destructible
is_trivially_destructible
is_nothrow_destructible checks if a type has a non-deleted destructor
(C++11) (class template)
(C++11)
(C++11)
is_polymorphic checks if a type is a polymorphic class type
(C++11) (class template)