Segmentation fault 11 in C on mac

Question

I am unable to read the data from the file created. This is a very simple code and I simply cannot understand why it is not working. I have just shifted to mac and installed the developer command line tools.

My code is :

int main()
{
    FILE *fp;
    int lines = 0;
    char *data;
    data = (char *)malloc(1000);
    data = NULL;

    fp = fopen("1.txt", "r");
    while (fgets(data, 1000, fp) != NULL)
    {
        printf("%s\n", data);
        lines++;
    }
    printf("Lines = %d\n", lines);
    free(data);
    fclose(fp);
    return 0;
}

Hint2: Read [the man-page for `fgets`](http://man7.org/linux/man-pages/man3/fgetc.3.html) too. Also, [Don't cast the result of malloc (and friends)](http://stackoverflow.com/q/605845). Let's omit the talk about `fopen` and `malloc` not always succeeding. — Deduplicator, Sep 28 '14 at 20:35
It is not working because you did not debug it, as @OliverCharlesworth says. If you are not willing/able to debug code, you should not write it because you don't have the required skills. — Martin James, Sep 29 '14 at 00:08

score 1 · Answer 1 · answered Sep 28 '14 at 20:34

You allocate space for data and then promptly leak it.

char *data;
data = (char *)malloc(1000);
data = NULL;

You then use fgets() with a NULL pointer, which causes undefined behavior.

fgets(data, 1000, fp)

Perhaps you should remove this line of code?

data = NULL;

Segmentation fault 11 in C on mac

1 Answers1