程序代码：

#include <stdio.h>
#include <malloc.h>
#include <string.h>

typedef unsigned long LCNT;
typedef unsigned long CELL;

#define DAT_SIZE 2000000000
#define CELL_SIZE (sizeof(CELL)*8)
#define MEM_SIZE (DAT_SIZE/CELL_SIZE + 1)  //Fix: MEM_SIZE 表示需要开辟的CELL数组大小 

LCNT BitSearch(CELL bitSet[], LCNT startPos);
void BitClear(CELL bitSet[], LCNT bitPos);

int main()
{
    LCNT i, primSum = 0, primCnt = 2;
    CELL *primSet = (CELL*)malloc(MEM_SIZE*sizeof(CELL));  //Fix: 开辟MEM_SIZE需要的字节数 
    
    if(primSet == NULL){
        printf("内存不足\n");
        return 1;
    }
    else{
        memset(primSet, 0xFF, MEM_SIZE*sizeof(CELL));  //Fix: 清空MEM_SIZE需要的字节数 
        primSet[0] ^= 3;  //质数从2开始，自然数[0,1]所在位清零  
    }
    
    while(primCnt < DAT_SIZE){        
        for(i=2; primCnt*i < DAT_SIZE; i++)
            BitClear(primSet, primCnt*i);
            
        primSum += primCnt;
        primCnt = BitSearch(primSet, primCnt+1);    
    }
    
    printf("The Sum is %ld\n", primSum);
    
    return 0;
}

LCNT BitSearch(CELL bitSet[], LCNT startPos)
{
    LCNT arrPos = startPos/CELL_SIZE, bitPos = startPos%CELL_SIZE;
    
    while(arrPos < MEM_SIZE){
        if(bitSet[arrPos] != 0){
            for(bitPos; bitPos < CELL_SIZE; bitPos++)
                if((bitSet[arrPos] >> bitPos)%2 == 1)
                    goto OUT; 
            bitPos = 0;
        }
        arrPos++;
    }

OUT:
    return arrPos*CELL_SIZE + bitPos;
}

void BitClear(CELL bitSet[], LCNT bitPos)
{
    bitSet[bitPos/CELL_SIZE] &= ~((LCNT)1 << bitPos%CELL_SIZE);
}