Why am I getting a segmentation fault with such the limits I have on my while loops?

Question

I'm currently working on a code that must be able to read in a line from a preexisting file line by line, separating different strings in the line with strep(). Currently, it is successfully reading and printing each line (of which there are 47 total). However, after it reads and prints the last line, it encounters a segmentation fault. To my understanding, this means that the code tries to access something that doesn't exist (ex. array element 8 in "int array[5];". I don't understand at what point it tries to access such an element.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(int argc, char *argv[]) {
        FILE *fp = fopen(argv[1], "r");
        int i = 0, j;
        char line[47][500];

        fgets(line[i], 500, fp);
        printf("%d", i);
        printf("%s\n", line[i]);
        i++;

        while (!feof(fp)) {
                while (fgets(line[i], 500, fp) != NULL && i < 47) {
                        printf("%d", i);
                        printf("%s\n", line[i]);
                        i++;
                }
        }

There is some code after this, but this is where is encounters the error.

Try stepping through the program with your favorite debugger; GDB is a bit user-unfriendly but works well. — SIGSTACKFAULT, Oct 15 '18 at 17:24
`while (!feof(fp))` [is wrong](https://stackoverflow.com/questions/5431941/why-is-while-feof-file-always-wrong). — melpomene, Oct 15 '18 at 17:38

score 0 · Accepted Answer · answered Oct 15 '18 at 17:22

0

Because fgets(line[i], 500, fp) != NULL gets evaluated before i < 47. This will write out of bounds when i = 47.

Try changing the order in your loop eval:

while (i < 47 && fgets(line[i], 500, fp) != NULL)

answered Oct 15 '18 at 17:22

Kon

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Why am I getting a segmentation fault with such the limits I have on my while loops?

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