enum ICMP_TIME_EXCEEDED_CODE
{
 ICMP_TTL_EXCEEDED_CODE   = 0,
 ICMP_FRAGMENT_EXCEEDED_CODE  = 1,
 TOTAL_TIME_EXCEEDED_CODES  = 2
#if __DCC__
};
#else
} _pack;
#endif
和

typedef _struct SERVICE_TYPE_BIT_STRUCTURE
{
#if (_BYTE_ORDER == _LITTLE_ENDIAN)
 unsigned char   unused:2;
 unsigned char   high_reliability:1;
 unsigned char   high_throughput:1;
 unsigned char   low_delay:1;
 unsigned char   precedence:3;
#else
 unsigned char   precedence:3;
 unsigned char   low_delay:1;
 unsigned char   high_throughput:1;
 unsigned char  high_reliability:1;
 unsigned char  unused:2;
#endif
} _pack SERVICE_TYPE_BIT_STRUCTURE;

请问这个到底是什么意思？应该如何在前面定义才可以让他们编译通过？谢谢

-------------------------------------------------------------------------------------------------------------------------------------------------------------------

-------------------------------------------------------------------------------------------------------------------------------------------------------------------

-------------------------------------------------------------------------------------------------------------------------------------------------------------------