使用 atoi() 时出现分段错误

Question

I'm getting a segmentation fault (core dumped) error when I try to run my program. I pass this into the command line./stats 1 2 50 100 argv[3] is the number of samples, and argv[4], argv[5] are the lower and upper bounds of the sample. I'm going through it slowly to see where I get errors and I think I get seg fault when I try to assigned these to int variables

int main(int argc, char *argv[])
{
    for (int i = 1; i < argc; i ++)
    {
        if (is_valid_int(argv[i]) == 1)
        {
            continue;
        }
        else
        {
            printf("%s is not a valid integer\n", argv[i]);
            exit(0);
        }
    }

    int size = atoi(argv[3]);
    int lower = atoi(argv[4]);
    int upper = atoi(argv[5]);
    printf("%d%d%d", size, lower, upper);

    generate_population(size, lower, upper);
    return 0;
}

int *generate_population(int size, int lower, int upper)
{
    int *my_array=(int*)malloc(size * sizeof(int));

    for (int i = 0; i < size; i++)
    {
        my_array[i] = (rand() % (upper - lower + 1)) + lower;
    }

    for (int j = 0; j < size; j++)
    {
        printf("%d", my_array[0]);
    }
    
    return 0;
}

It does not print the values after I assign them. I tried commenting out call of generate_population() and I still get the error.

Answer 1

When you run ./stats 1 2 50 100 argv will be [0: "./stats", 1: "1", 2: "2", 3: "50", 4: "100"] . So there is no argv[5] , it will be NULL on most os. The fix is:

int size = atoi(argv[2]);
int lower = atoi(argv[3]);
int upper = atoi(argv[4]);

Also you should check argc in case the user does not provide enough arguments.