结构体 字节对齐的练习

    
        struct S1
        {
              char c1;
              double d;
              char c2;
              char c3;
        };
        struct S2
        {
              char c1;
              char c2;
              char c3;
              double d;
        };
        struct S3
        {
              char c1;
              S1 s;
              char c2;
              char c3;
        };        

        #pragma pack(1)
        struct S1
        {
              char c1;
              double d;
              char c2;
              char c3;
        };
        #pragma pack()
        struct S3
        {
              char c1;
              S1 s;
              char c2;
              char c3;
        };

    
        #pragma pack(4)
        struct S1
        {
              char c1;
              double d;
              char c2;
              char c3;
        };
        #pragma pack()
        struct S3
        {
              char c1;
              S1 s;
              char c2;
              char c3;
        };

        struct S1
        {
              char c1;
              double d;
              char c2;
              char c3;
        };
        #pragma pack(1)
        struct S3
        {
              char c1;
              S1 s;
              char c2;
              char c3;
        };
        #pragma pack()