c - 段错误难题

Question

所以我很好奇为什么下面的代码段会出现段错误。在我看来它是正确的。

int * addCoins(char *val){
    const char *deli = ",";
    char *ptr =NULL;

    char *denomination = strtok_r(val, deli, &ptr);
    char *count = strtok_r(NULL, deli, &ptr);
    int deno = atoi(denomination);
    int cnt = atoi(count);
    int *k;
    k = malloc(sizeof(*k)*2);
    k[0] = deno;
    k[1] =cnt;

    return k;
}

调用 main 中的 addCoins 函数。我不认为问题出在这里，但老实说，我对这个问题有点不知所措。

char* fileNameCoin = argv[2];
FILE *fileCoin;
fileCoin = fopen(fileNameCoin, "r+");
char bufCoin[256];
int i = 0;
//vmNode->next = NULL;
int *j;
while (fgets(bufCoin, sizeof bufCoin, fileCoin) != NULL) {
    j = addCoins(bufCoin);
    int deno = j[0];
    switch(deno){
    case 5:
        Coins[i].denom = j[0];
        Coins[i].count = j[1];
        break;
    case 10:
        Coins[i].denom = j[0];
        Coins[i].count = j[1];
        break;
    case 20:
        Coins[i].denom = j[0];
        Coins[i].count = j[1];
        break;
    case 50:
        Coins[i].denom = j[0];
        Coins[i].count = j[1];
        break;
    case 100:
        Coins[i].denom = j[0];
        Coins[i].count = j[1];
        break;
    case 200:
        Coins[i].denom = j[0];
        Coins[i].count = j[1];
        break;
    case 500:
        Coins[i].denom = j[0];
        Coins[i].count = j[1];
        break;
    case 1000:
        Coins[i].denom = j[0];
        Coins[i].count = j[1];
        break;
    default:
        break;

    }

    i++;
}

下面是文件的定义

1000,3

500,4

200,20

100,30

50,5

20,3

10,40

5,20

其中第一个数字是以美分表示的面额，第二列是所述面额的数字。

这些是类型定义:

    /* The different denominations of coins available */
    enum denomination
    {
        FIVE_CENTS, TEN_CENTS, TWENTY_CENTS, FIFTY_CENTS, ONE_DOLLAR,
        TWO_DOLLARS, FIVE_DOLLARS, TEN_DOLLARS
    };

    /* Each coin in the coins array will have a denomination (20 cents,
     * 50 cents, etc) and a count - how many of that coin do we have on hand
     */
    struct coin
    {
        enum denomination denom;
        unsigned count;
    };

Answer 1

strtok() 的第二个参数/strtok_r()通过预期 0 来描述一组 分隔符-终止数组 char s，那是一个C-“字符串”。

来自 strtok() / strtok_r() 's man-page :

The delim argument specifies a set of bytes that delimit the tokens in the parsed string.

所以它的用法应该是:

const char deli[2] = {',', '\0'};
...
char * denomination = strtok_r(val, deli, &ptr);

或更直接:

const char deli[] = ",";
...
char * denomination = strtok_r(val, deli, &ptr);

或者只是删除 deli 的定义并做:

char * denomination = strtok_r(val, ";", &ptr);

---

代码还应检查是否调用了 strtok_t()返回 NULL在将结果传递给 atoi() 之前, 因为后者如果被喂食 NULL 将会惨败.