#include <stdio.h>

typedef struct dlNode {
    const struct dlNode* next, *prev;
    void* datum;
} dlNode;

const static dlNode tail;

const static dlNode head={
    .next=&tail,
    .prev=NULL,
    .datum=NULL
};

const static dlNode tail={
    .next=NULL,
    .prev=&head,
    .datum=NULL
};

int main(void) {
    printf("head = %p\n", (void*)&head);
    printf("tail = %p\n", (void*)&tail);
    printf("head.next = %p\n", (void*)head.next);
    printf("tail.prev = %p\n", (void*)tail.prev);
    return 0;
}