c - 奇怪的分段默认

Question

我要解决的问题是:统计一段C代码中关键字出现的次数。这是代码:

The problem is that I get a segmentation fault. In my code I mentioned where is the problem. Can you, please, explain me why ?

在标题中:

struct Chei
{
    char *cuv;
    int contor;
};

typedef struct Chei chei;

int ReadCode(char *a[]);
void  determine(chei *Ch, char *temp, int size);
void Frequency(chei *Ch, int nr_lines, char *a[], int size);

主要内容:

    chei tab_chei[] = {{"while", 0},{"if", 0}, {"case", 0}, {"switch",  0}};
    int size = sizeof(tab_chei)/sizeof(tab_chei[0]);
    char *Code[MaxL];
    int nr_lines;


    nr_lines = ReadCode(Code);//number of lines of text

    Frequency(tab_chei, nr_lines, Code, size);

在函数文件中:我认为读取文本没有问题(函数 ReadCode() -- 这里我使用 malloc 为每个 Code[i] 分配了内存)。我为此使用了指向 char 的指针数组。

// This functions determines if the word "temp" is a keyword, and increases
     //"contor" if it is.

void  determine(chei *Ch, char *temp, int size)
{
    int i;


    for (i = 0; i < size; ++i)
    {
        if (!strcmp(Ch[i].cuv, temp))
        {
            Ch[i].contor++;
            break;
        }
    }
}

数组“a”包含文本。

void Frequency(chei *Ch, int nr_lines, char *a[], int size)
{
    int i;
    char temp[MaxCh];
    char *token = 0;


        strcpy(temp, a[0]);//I put a[0] as a particular case
        token = strtok(temp, " ");
        determine(Ch, token, size);

        while (token != NULL)
        {

            token = strtok(NULL, " ");
            determine(ch, token, size); //here is the problem.
//I observed that if I delete this line, there is no error
//but still it isn't what I want to get
        }

        for (i = 0; i < size; ++i)
            {
                printf("\n%-10s%-4d", Ch[i].cuv, Ch[i].contor);
            }

}

Answer 1

token = strtok(NULL, " ");
determine(ch, token, size); //here is the problem.

在将 token 传递给 determine() 之前，您没有检查它。当给定空指针时，strcmp() 调用是未定义的行为。