NULL

From Cppreference

Defines the null pointer constant, which is an integral constant expression prvalue of integer type that evaluates to zero or a prvalue of type std::nullptr_t. The null pointer constant may be converted to any pointer type; such conversion results in the null pointer value of that type. If the null pointer constant has integer type, it may be converted to a prvalue of type std::nullptr_t.

[edit] Equivalent definition

#define NULL 0

[edit] Example

#include <cstddef>
class S;
int main()
{
    int* p = NULL;
    int* p2 = static_cast<std::nullptr_t>(NULL);
    void(*f)(int) = NULL;
    int S::*mp = NULL;
    void(S::*mfp)(int) = NULL;
}

[edit] See also