结构体长度的奇怪问题

代码：
struct SPackage
{
DWORD dwFlag;
BYTE byIndex;
DWORD dwID;
}; SPackage sPackage;
sPackage.dwFlag=0x28000001;
sPackage.byIndex=0xc;
sPackage.dwID=0x4f070000;
调试：
sizeof(sPackage)
12&sPackage
0x0018f4bc {dwFlag=671088641 byIndex='' dwID=1325858816 }
    dwFlag: 671088641
    byIndex: 12 ''
    dwID: 1325858816
内存：01 00 00 28 0c cc cc cc 00 00 07 4f
按理说长度应该4+1+4才对，内存里的cccc是哪来的？