自引用结构

struct node{
    int data1;
    int data2;
    struct node *ptr;
}obj,*temp;

int main()
{
     printf("n Address of variable data1 in struct is %p",&obj.data1);
     printf("n Address of variable data2 in struct is %p",&obj.data2);
}

o / p是

Address of variable data1 in struct is 0xd0c7010
Address of variable data2 in struct is 0xd0c7018

这意味着data1占用了8个字节的内存,对吧？

但是如果我有以下结构定义

struct node{
    int data1;
    int data2;
}obj,&obj.data2);
}

o / p是

Address of variable data1 in struct is 0xd0c6010
Address of variable data2 in struct is 0xd0c6014

所以data1占用4个字节的内存,这是一个整数变量,对吧？

但为什么在第一种情况下data1占用的内存空间增加了？

编辑：
?对于第一种情况,o / p是

Address of variable data1 in struct is 0x600940
Address of variable data2 in struct is 0x600944
The address of ptr is 0x600948
The size of struct is 16

对于第二种情况

Address of variable data1 in struct is 0x600910
 Address of variable data2 in struct is 0x600914
 The size of struct is 8

我在Linux上运行此代码
gcc(GCC)4.1.2

上面的代码工作正常,但下面的代码呢

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

struct node
{
  int data;
  struct node *next;
};

// This function prints contents of linked list starting from the given node
void printList(struct node *n)
{
  printf("n The memory location of n is %p ",n);
  while (n != NULL)
  {
     printf(" %d ",n->data);
     n = n->next;
     printf("n The memory location of n in while loop is %p ",n);
  }
}

int main()
{
  struct node* head = NULL;
  struct node* second = NULL;
  struct node* third = NULL;

  // allocate 3 nodes in the heap
  head  = (struct node*)malloc(sizeof(struct node));
  second = (struct node*)malloc(sizeof(struct node));
  third  = (struct node*)malloc(sizeof(struct node));

  head->data = 1; //assign data in first node
  head->next = second; // Link first node with the second node
  printf("n The memory address of head->data is %p ",&head->data);
  printf("n The memory address of head->next is %p ",&head->next);

  second->data = 2; //assign data to second node
  second->next = third;
  printf("n The memory address of second->data is %p ",&second->data);
  printf("n The memory address of second->next is %p ",&second->next);

  third->data = 3; //assign data to third node
  third->next = NULL;

  printf("n The memory address of third->data is %p ",&third->data);
  printf("n The memory address of third->next is %p ",&third->next);

  printList(head);

  getchar();
  printf("n");
  return 0;
}

O / P是

The memory address of head->data is 0x215c010
 The memory address of head->next is 0x215c018
 The memory address of second->data is 0x215c030
 The memory address of second->next is 0x215c038
 The memory address of third->data is 0x215c050
 The memory address of third->next is 0x215c058
 The memory location of n is 0x215c010  1
 The memory location of n in while loop is 0x215c030  2
 The memory location of n in while loop is 0x215c050  3
 The memory location of n in while loop is (nil)

为什么现在还有8个字节的差异？
我在与其他两个相同的环境下运行此代码.