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Showing content from https://cplusplus.com/reference/type_traits/has_virtual_destructor/ below:

class template

<type_traits>

std::has_virtual_destructor

template <class T> struct has_virtual_destructor;

Has virtual destructor

Trait class that identifies whether T has a virtual destructor.

Only the classes (declared with class, struct or union) that have a destructor explicitly declared as such (or that inherit from a class that does) have a virtual destructor.

has_virtual_destructor inherits from integral_constant as being either true_type or false_type, depending on whether T's destructor is trivial.

Template parameters

T

A complete type, or void (possible cv-qualified), or an array of unknown bound of a complete element type.

A type.
If a class type, it shall be a complete type or a union (for unions, this trait is always false).

Member types Inherited from integral_constant:

Member constants Inherited from integral_constant:
member constant definition value either true or false
Member functions Inherited from integral_constant:

operator bool: Returns value (public member function)

Example

// has_virtual_destructor example
#include <iostream>
#include <type_traits>

struct A { };
struct B { virtual ~B(){} };
struct C : B { };

int main() {
  std::cout << std::boolalpha;
  std::cout << "has_virtual_destructor:" << std::endl;
  std::cout << "int: " << std::has_virtual_destructor<int>::value << std::endl;
  std::cout << "A: " << std::has_virtual_destructor<A>::value << std::endl;
  std::cout << "B: " << std::has_virtual_destructor<B>::value << std::endl;
  std::cout << "C: " << std::has_virtual_destructor<C>::value << std::endl;
  return 0;
}

Output:

has_virtual_destructor:
int: false
A: false
B: true
C: true