Issue with dynamic C array

Question

I'm trying to make a dynamic char array, but I'm running into issues. I get segmentation fault when I try to add anything to the array.

static int arrays()
   {
    int INITIAL = 1;
    char **all_words;
    all_words = (char**)malloc(INITIAL*sizeof(*all_words));
    int currentSize = INITIAL;

    for(int i = 0; i < counter; i++){
        all_words = realloc(all_words,currentSize*sizeof(*all_words));
        strcpy(all_words[i], "hello");
        currentSize++;
    }
    for(int i = 0; i < counter; i++){
        printf("%s ", all_words[i]);
    }

}

I pretty much copied this from a guide online, so I'm not sure why it wouldn't work.

Answer 1

You've correctly allocated an array of char *, however those pointers remain uninitiaized. So when you then do this:

strcpy(all_words[i], "hello");

You're dereferencing an invalid pointer.

Each element of all_words needs to point to allocated space. This simplest way to do this is to use strdup if your system supports it instead of strcpy:

all_words[i] = strdup("hello");

Otherwise you would use malloc to allocate the space, then use strcpy

all_words[i] = malloc(sizeof("hello"));
strcpy(all_words[i], "hello");