大家帮我看段程序（关于左移操作符）

zxq230104

#include "stdafx.h"

typedef unsigned short uint16;
typedef unsigned int uint32;
typedef unsigned long long uint64;

#define RecordGetOff(rec) \
( \
        (uint64) (((rec)->off_hi << 32) | ((uint32) (rec)->off_lo)) \
)

#define BlockIdGetBlockNumber(blockId) \
( \
        (uint32) (((blockId)->bi_hi << 16) | ((uint16) (blockId)->bi_lo)) \
)

typedef struct BlockIdData
{
        uint16                bi_hi;
        uint16                bi_lo;
} BlockIdData;

typedef struct XLogRecOff
{
        uint32                off_hi;
        uint32                off_lo;
} XLogRecOff;

int _tmain(int argc, _TCHAR* argv[])
{
        BlockIdData test;
        test.bi_hi = 2;
        test.bi_lo = 3;

        XLogRecOff test1;
        test1.off_hi = 2;
        test1.off_lo = 3;

        printf("%u\n", BlockIdGetBlockNumber(&test));
        printf("%llu\n", RecordGetOff(&test1));
        return 0;
}

会报c:\documents and settings\administrator\my documents\visual studio 2005\projects\test\test\test.cpp(43) : warning C4293: “<<”: Shift 计数为负或过大，其行为未定义

结果为
131075
3

为什么对于16位的这样的操作是对的，而对于32位的同样操作就不行了？谢谢大家

hellio

对32位数移位32结果是未定义，16位的移位大概是转成32位处理了吧