std::is_null_pointer is a UnaryTypeTrait.

Checks whether T is the type std::nullptr_t.

Provides the member constant value that is equal to true, if T is the type std::nullptr_t, const std::nullptr_t, volatile std::nullptr_t, or const volatile std::nullptr_t.

Otherwise, value is equal to false.

If the program adds specializations for std::is_null_pointer or std::is_null_pointer_v(since C++17), the behavior is undefined.

Template parameters

Helper variable template

Possible implementation

template<class T>
struct is_null_pointer : std::is_same<std::nullptr_t, std::remove_cv_t<T>> {};

Notes

std::is_pointer is false for std::nullptr_t because it is not a built-in pointer type.

In libc++, std::is_null_pointer is not available in C++11 mode.

Example

#include <type_traits>

static_assert(std::is_null_pointer_v<decltype(nullptr)>);
static_assert(!std::is_null_pointer_v<int*>);
static_assert(!std::is_pointer_v<decltype(nullptr)>);
static_assert(std::is_pointer_v<int*>);

int main()
{
}

Defect reports

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

See also