patseb patseb - 6 months ago 46
C Question

Difference between LIST_HEAD_INIT and INIT_LIST_HEAD

I'm trying to understand the Linux kernel linked list API.

According to Linux Kernel Linked List I should initialize the list head by

but here (Linux Kernel Program) it's suggested to use

Here's a working code I wrote, but I'm not sure if I did it in proper way. Could someone verify that it's OK?

#include <stdio.h>
#include <stdlib.h>
#include "list.h"

typedef struct edge_attr {
int d;
struct list_head list;
} edge_attributes_t;

typedef struct edge {
int id;
edge_attributes_t *attributes;
} edge_t;

int main () {
int i;
struct list_head *pos;
edge_attributes_t *elem;
edge_t *a = (edge_t*)malloc(sizeof(edge_t));

a->id = 12;
a->attributes = (edge_attributes_t*) malloc(sizeof(edge_attributes_t));


for (i=0; i<5; ++i) {
elem = (edge_attributes_t*)malloc(sizeof(edge_attributes_t));
elem->d = i;
list_add(&elem->list, &a->attributes->list);

list_for_each(pos, &(a->attributes->list)) {
elem = list_entry(pos, edge_attributes_t, list);
printf("%d \n", elem->d);

return 0;

Answer Source

A quick LXR search shows:

#define LIST_HEAD_INIT(name) { &(name), &(name) }

static inline void INIT_LIST_HEAD(struct list_head *list)
        list->next = list;
        list->prev = list;

So INIT_LIST_HEAD gets a struct list head * and initializes it, while LIST_HEAD_INIT returns the address of the passed pointer in a suitable fashioned for use as an initializer for a list:

struct list_head lst1;
/* .... */

struct list_head lst2 = LIST_HEAD_INIT(lst2);
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