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    std::is_virtual_base_of

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    Defined in header <type_traits>
    template< class Base, class Derived > struct is_virtual_base_of;
    		 (since C++26)
    See More

    std::is_virtual_base_of is a BinaryTypeTrait.

    If Base is a virtual base class of Derived (ignoring cv-qualification), provides the member constant value equal to true. Otherwise value is false.

    If both Base and Derived are non-union class types (ignoring cv-qualification), Derived should be a complete type; otherwise the behavior is undefined.

    If the program adds specializations for std::is_virtual_base_of or std::is_virtual_base_of_v, the behavior is undefined.

    Helper variable template

    template< class Base, class Derived > constexpr bool is_virtual_base_of_v = is_virtual_base_of<Base, Derived>::value;
    		 (since C++26)
    [edit]

    Inherited from std::integral_constant

    Member constants

    value
    [static]
    		 true if Derived is derived from virtual base class Base (ignoring cv-qualification), false otherwise
    (public static member constant)

    Member functions

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

    Member types

    Type Definition
    value_type bool
    type std::integral_constant<bool, value>

    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

    Run this code
    #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

    (C++11)
    		 checks if a type is a base of the other type
    (class template) [edit]
    (C++11)(C++20)
    		 checks if a type can be converted to the other type
    (class template) [edit]
    (C++20)
    		 specifies that a type is derived from another type
    (concept) [edit]