为什么VC编译pragma pack(show)显示8?
我在32位下编译一个helloworld程序，工程设置都是默认。代码里面加入一句:
#pragma pack(show)
竟然打印8.

应该是4才对啊，32位下按照4个自己的倍数对齐，就像我下面这个程序:

C/C++ code

#pragma pack (show) struct ss{      short s;      int i;      int ii; }; int main(void) {      ss obj[2];      printf("%d,%d\n",sizeof(size_t),sizeof(ss));      printf("%p,%p\n",&obj[0],&obj[1]);      return 0; } 

这里sizeof(ss)=12，且obj[0]和obj[1]地址相差12.
为什么MSDN上面写:
n(optional)
Specifies the value, in bytes, to be used for packing. The default value for n is 8. Valid values are 1, 2, 4, 8, and 16. The alignment of a member will be on a boundary that is either a multiple of n or a multiple of the size of the member, whichever is smaller.

n can be used with push or pop for setting a particular stack value, or alone for setting the current value used by the compiler.


[解决办法]
上面这句话已经写得很清楚了:

The alignment of a member will be on a boundary that is either a multiple of n or a multiple of the size of the member, whichever is smaller.

pack=min(n,max(成员的大小))