NULL

 

C

Language

Standard Library

Type support

Dynamic memory management

Error handling

Program utilities

Date and time utilities

Strings library

Algorithms

Numerics

Input/output support

Localization support

Thread support (C11)

Atomic operations (C11)

 

Type support

size_t

ptrdiff_t

NULL

max_align_t (since C11)

offsetof

Numeric limits

 

Defined in header <stddef.h>
Defined in header <string.h>
Defined in header <wchar.h>
Defined in header <time.h>
Defined in header <locale.h>
Defined in header <stdio.h>
#define NULL /*implementation-defined*/

Expands into implementation-defined null-pointer constant.

Example

Run this code

#include <stdlib.h>
 
struct S;
void(*f)() = NULL;
 
int main(void)
{    
    char *ptr = malloc(sizeof(char)*10);
    if (ptr == NULL) exit(EXIT_FAILURE);
    free(ptr);
    ptr = NULL;
 
    int* p = NULL;
    struct S *s = NULL;
 
    return EXIT_SUCCESS;
}

Possible output:

(none)

See also

C++ documentation for NULL