NULL

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Defined in header <cstddef>
Defined in header <cstring>
Defined in header <cwchar>
Defined in header <ctime>
Defined in header <clocale>
Defined in header <cstdio>
#define NULL /*implementation-defined*/

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.

Possible implementation

#define NULL 0

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;
}

See also

nullptr	the pointer literal which specifies a null pointer value (C++11)
nullptr_t (C++11)	the type of the null pointer literal (typedef)