std::is_abstract - cppreference.com

template< class T >
struct is_abstract;

std::is_abstract is a UnaryTypeTrait.

If T is an abstract class (that is, a non-union class that declares or inherits at least one pure virtual function), provides the member constant value equal to true. For any other type, value is false.

If T is an incomplete non-union class type, the behavior is undefined.

If the program adds specializations for std::is_abstract or std::is_abstract_v, the behavior is undefined.

Template parameters

Helper variable template

template< class T >
constexpr bool is_abstract_v = is_abstract<T>::value;

Example

#include <iostream>
#include <type_traits>

struct A { int m; };
static_assert(std::is_abstract_v<A> == false);

struct B { virtual void foo(); };
static_assert(std::is_abstract_v<B> == false);

struct C { virtual void foo() = 0; };
static_assert(std::is_abstract_v<C> == true);

struct D : C {};
static_assert(std::is_abstract_v<D> == true);

int main() {}

Defect reports

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

See also