Red Black Tree - Initialization

Question

How can I correctly initialize a red black tree in C?

Structure:

typedef struct Node{
    int key;
    struct Node *left;
    struct Node *right;
    struct Node *parent;

    enum {RED, BLACK} color;
}node;

typedef struct RBtree{
    struct Node *root;
    struct Node *nil;
}rbtree;

Main Function:

int main(){
    rbtree *tree;
    init_rbtree(&tree);
}

Init Function:

void init_rbtree(rbtree **t){
    (*t)->root = NULL;

    node *n = (node*)malloc(sizeof(node));
    if(n != NULL){
        n->color = BLACK;
        (*t)->nil = n;
    }
}

The program crashes as soon as I run this code.

Answer 1

You need to allocate memory for *t before you can use it.

void init_rbtree(rbtree **t) {
    *t=malloc(sizeof(rbtree));

    if (*t==NULL) {
        //handle error
    }  
    else {
        (*t)->root = NULL;

        node *n = malloc(sizeof(node));
        if(n != NULL){
            n->color = BLACK;
            (*t)->nil = n;
        }
    }
}