std::has_virtual_destructor - cppreference.com (original) (raw)

| | | | | ----------------------------------------------------- | | ------------- | | 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.

Contents

• 1 Template parameters
• 2 Helper variable template
• 3 Inherited from std::integral_constant
  • 3.1 Member constants
  • 3.2 Member functions
  • 3.3 Member types
  • 3.4 Notes
  • 3.5 Example
  • 3.6 Defect reports
  • 3.7 See also

[edit] Template parameters

[edit] 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

[edit] 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.

[edit] Example

#include   struct S {}; static_assert(!std::has_virtual_destructor_v);   struct B { virtual ~B() {} }; static_assert(std::has_virtual_destructor_v);   struct D : B { ~D() {} }; static_assert(std::has_virtual_destructor_v);   int main() { B* pd = new D; delete pd; }

[edit] Defect reports

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

[edit] See also