std::is_virtual_base_of

Since C++26

Header: <type_traits>

std::is_virtual_base_of is a BinaryTypeTrait.

# Declarations

template< class Base, class Derived >
struct is_virtual_base_of;

(since C++26)

# Notes

std::is_virtual_base_of_v<A, B> is true even if A is a private, protected, or ambiguous base class of B.

If std::is_virtual_base_of_v<A, B> is true, then std::is_base_of_v<A, B> is also true. However, the converse is not always true because the check for virtual inheritance is more specific. In that case, std::is_virtual_base_of_v<T, T> is false even if T is a non-union class type.

# Example

#include <type_traits>
 
class A {};
class B : A {};
class C : B {};
class D : virtual A {};
class E : D {};
 
union F {};
using I = int;
 
static_assert
(
    std::is_virtual_base_of_v<A, A> != true &&
    std::is_virtual_base_of_v<A, B> != true &&
    std::is_virtual_base_of_v<A, D> == true &&
    std::is_virtual_base_of_v<D, E> != true &&
    std::is_virtual_base_of_v<F, F> != true &&
    std::is_virtual_base_of_v<I, I> != true
);
 
int main() {}

# See also