linux/list.h

struct item
{
	list_head hdr;
	char cookie[];
};

LIST_HEAD(my_list);

item* p = malloc(sizeof(item) + strlen(str) + 1); ??
vs 
item* p = malloc(sizeof(item.hdr) + strlen(str) + 1); ??
vs
????????????????????????????????

strcpy(p->cookie, str);
list_add_tail(&p->hdr, &my_list);