NULL

Defined in header <cstddef>

Defined in header <cstring>

Defined in header <cwchar>

Defined in header <ctime>

Defined in header <cstdio>

(until C++11)

Defined in header <clocale>

(since C++11)

Defined in header <cstdlib>

(since C++11)

1	`#define NULL /implementation-defined/`

The macro NULL is an implementation-defined null pointer constant, which may be.

an integral constant expression rvalue of integer type that evaluates to zero.	(until C++11)
an integral constant expression prvalue of integer type that evaluates to zero or a prvalue of type `std::nullptr_t`.	(since C++11) (until C++14)
an integer literal with value zero, or a prvalue of type `std::nullptr_t`.	(since C++14)

A null pointer constant may be implicitly converted to any pointer type; such conversion results in the null pointer value of that type. If a null pointer constant has integer type, it may be converted to a prvalue of type std::nullptr_t.

Possible implementation

#define NULL 0
//since C++11
#define NULL nullptr

Notes

In C, the macro NULL may have the type void*, but that is not allowed in C++.

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;
}

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

NULL

Possible implementation

Notes

Example

See also