__attritbute __（（aligned（8）））在结构标签和结构成员上

Question

我试过以下程序：

#include<stdio.h>
typedef struct __attribute__((packed,aligned(8))) Ball {

    int  size;
    int s1;
    int s2 __attribute__((packed,aligned(16)));
    double q __attribute__((packed,aligned(16)));
} Ball_t;

Ball_t var;
int main()
{
   printf("%lu\n",sizeof(Ball_t));
   printf("%p %p %p %p\n",&var.size,&var.s1,&var.s2,&var.q);
   return 0;
}

Output-
48
0x601060 0x601064 0x601070 0x601080

我原以为输出like-sizeof结构应该是40个字节。 但是，我得到了48个字节。根据我的理解，对齐应该像这样 -

(let suppose start address of structure is 0)

typedef struct __attribute__((packed,aligned(8))) Ball {
    int  size;  // start at 0th and occupy 4 bytes
    int s1;      //start at 4th and occupy 4 bytes  + padding of 8 bytes
    int s2 __attribute__((packed,aligned(16)));  // starts at 16th byte and occupy 4 bytes +padding 12 bytes
    double q __attribute__((packed,aligned(16))); //starts at 32nd and occupy 8 bytes 
} Ball_t;

因此，总大小将是4 + 4 + 8 + 4 + 12 + 8 = 40。如果我理解错误，请澄清我。

提前致谢