Question

我正在尝试动态分配一个结构数组但是每当我运行程序时我都会得到：a.out（6487,0x7fff7ecb8300）malloc： *对象0x7fff6f670000的错误：指针是realloc＆＃39; d是没有分配 * 在malloc_error_break中设置断点以进行调试

struct node {
    char course[25];
    char category[20];
    char prereq[50];
    char notes[50];
};



int main(int argc, char* argv[])
{
    FILE *fp;
    char *filename = argv[1];
    char *token;

    char buffer[100];
    char *del = ",\n";
    int num = 5, i = 0, j =0, count = 0;
    struct node *d = malloc(num * sizeof(struct node));
    char** complete = malloc(num * sizeof(char*));
    printf("%s\n", filename);


    if( (fp = fopen(filename, "r")) == NULL )
    {
        printf("unable to open %s\n", filename);
        exit(1);
    }
    while(fgets(buffer, sizeof(buffer), fp) != NULL)
    {

        if(count == num)
        {
            num = num + 5;
            struct node *d = realloc(d, sizeof(d)*num);
            printf("Reallocating\n");
        }  
        token = strtok(buffer, del);

        if(strncmp(token, "#", 1) != 0)
        {   

            strcpy(d[count].course, token);
            printf("%s\n", d[count].course);
            strcpy(d[count].category, strtok(NULL, del));
            printf("%s\n", d[count].category);
            strcpy(d[count].prereq, strtok(NULL, del));
            printf("%s\n", d[count].prereq);
            strcpy(d[count].notes, strtok(NULL, del));
            printf("%s\n", d[count].notes);
            count++;
        }


    }

Answer 1

struct node *d = realloc(d, sizeof(d)*num);

您声明了一个新的d变量，它隐藏了前一个变量，并将其未初始化的值提供给realloc。

你需要这样做：

struct node *newD = realloc(d, num * sizeof *d);
if(!newD) {
    // Allocation failure, do something about it and break out
} /* else */
d = newD;

另请注意，我更正了sizeof，它测量了指针的大小，而不是指针的大小。

Answer 2

在：

struct node *d = realloc(d, sizeof(d)*num);

声明一个新的变量d，其初始值未确定，并将其传递给realloc。将其更改为：

struct node *tmp = realloc(d, sizeof(*d)*num);
if(!tmp)
    ; // handle error
d = tmp;

没有分配重新分配的指针

2 个答案: