在char指针数组中进行malloc分配时接收segfault

Question

I'm writing a simple c program that reads lines from a text file into a char **. In my main function, I create the char * array, allocate memory for it, and pass a pointer to the array to another function to populate each index in the array with a char * representing the content of each line in the text file.

For some reason related to my memory management I'm guessing, I'm receiving a segmentation fault on the third iteration of my while loop, which copies the string into the array of strings. Why is this?

My code:

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

void getRestaurants(char ***restaurantsArray) {
    FILE *restaurantsFile = fopen("./restaurants.txt", "r");
    char *restaurant = (char *)malloc(50 * sizeof(char));
    char *restaurantCopy = restaurant;

    //fopen will return null if it is unable to read the file
    if (restaurantsFile == NULL) {
    free(restaurant);
    return;
    }

    int index = 0;
    while (fgets(restaurantCopy, 50, restaurantsFile)) {
        // segfault occurs the third time the following line is executed
        *restaurantsArray[index] = (char*)malloc(50 * sizeof(char));
        strcpy(*restaurantsArray[index], restaurantCopy);
        printf("%s", restaurantCopy);
        printf("%s", *restaurantsArray[index]);
        index++;
    }

    fclose(restaurantsFile);
    free(restaurant);
}

void main() {
    char **restaurantsArray = (char **)malloc(100 * sizeof(char *));
    char **restaurantsArrayCopy = restaurantsArray;
    getRestaurants(&restaurantsArrayCopy);
}

Expected Result:

firstline
firstline
secondline
secondline
thirdline
thirdline

and so on, if the provided restaurants.txt file contains:

firstline
secondline
thirdline

Answer 1

In getRestaurants , restaurantsArray is declared as char ***Array . In the line *restaurantsArray[index] = …; , it takes restaurantsArray[index] and attempts to use it as a pointer (by applying the * operator). But restaurantsArray is merely a pointer to the restaurantsArrayCopy in main . restaurantsArrayCopy is merely a single object, not an array. It is just one char ** . In getRestaurants , using restaurantsArray[index] with anything but zero for index uses some undefined thing.

There is no need to pass &restaurantsArrayCopy from main to getRestaurants . Just pass restaurantsArray . This is a pointer to allocated space.

Then, in getRestaurants , instead of *restaurantsArray[index] = …; , use restaurantsArray[index] = …; , without the * . This will assign a value to an element in restaurantsArray , which is what you want to do. Similarly, remove the * in the strcpy and the printf .