Home - News ( United States | United Kingdom | Italy | Germany ) - Football scores

Showing content from http://en.cppreference.com/w/c/numeric/math/../../io/../types/NULL.html below:

NULL - cppreference.com

#define NULL /*implementation-defined*/

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

• an integer constant expression with the value ​0​
• an integer constant expression with the value ​0​ cast to the type void*

• predefined constant nullptr

A null pointer constant may be converted to any pointer type; such conversion results in the null pointer value of that type.

POSIX requires NULL to be defined as an integer constant expression with the value ​0​ cast to void*.

// C++ compatible:
#define NULL 0
// C++ incompatible:
#define NULL (10*2 - 20)
#define NULL ((void*)0)
// since C23 (compatible with C++11 and later)
#define NULL nullptr

#include <inttypes.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
 
int main(void)
{
    // any kind of pointer can be set to NULL
    int* p = NULL;
    struct S *s = NULL;
    void(*f)(int, double) = NULL;
    printf("%p %p %p\n", (void*)p, (void*)s, (void*)(long)f);
 
    // many pointer-returning functions use null pointers to indicate error
    char *ptr = malloc(0xFULL);
    if (ptr == NULL)
        printf("Out of memory");
    else
        printf("ptr = %#" PRIxPTR"\n", (uintptr_t)ptr);
    free(ptr);
}

Possible output:

(nil) (nil) (nil)
ptr = 0xc001cafe

RetroSearch is an open source project built by @garambo | Open a GitHub Issue

Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo

HTML: 3.2 | Encoding: UTF-8 | Version: 0.7.4