Initialization of a structure that contains a pointer to an array

Question

I have the following structure:

typedef struct TRIE_NODE
{
    char* word;
    struct TRIE_NODE* node[26];
}TRIE_NODE;

I create a node called head, TRIE_NODE *head = NULL; , and then i try to initialize this node using the following function:

void initialize_node(TRIE_NODE *current_node)
{
    int MAX = 25;

    current_node = malloc(sizeof(TRIE_NODE));

    for(int i = 0; i < MAX; i++)
    {
        current_node->node[i] = NULL;
        if(current_node->node[i] == NULL)
            printf("\n -- \n");
    }
}

However, i get a segmentation fault whenever i try to even read current_node->node[i] . Does anyone have any idea of what's going on? Considering current_node->node is a pointer, that points to another pointer of type TRIE_NODE , shouldn't i be able to access it's values through bracket notation? (I've tried dereferencing it too, it doesn't compile)

Answer 1

You do everything correctly, except this line

current_node = malloc(sizeof(TRIE_NODE));

which modifies the local copy of current_node . The pointer in the caller remains unchanged.

To fix this problem, pass a pointer to pointer, and assign with an indirection operator:

void initialize_node(TRIE_NODE **current_node_ptr) {
    ...
    *current_node_ptr = malloc(sizeof(TRIE_NODE));
    ...
}