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std::has_vi...l_destructor(3)  C++ Standard Libary std::has_vi...l_destructor(3)

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  ob-
     ject (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 retroac-
     tively to
	previously published C++ standards.

	   DR	 Applied to	Behavior as published		Correct behavior
	LWG 2015 C++11	    the behavior was undefined if the base  characteris-
     tic 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)

http://cppreference.com 	   2024.06.10	   std::has_vi...l_destructor(3)
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