i'm currently doing a simulation of adt in c, and i'm supposed to make a binary search tree invloving strings, i'm currently starting coding but i get this error and it doesnt say where the error comes from, here's the code, can somebody help me.

tree.h

```
#ifndef tree_h
#define tree_h
#include <stdbool.h>
#include <stdlib.h>

typedef struct tree_node* node_ptr;

struct tree_node {
    char* word;
    node_ptr leftNode, rightNode;
};

node_ptr start = NULL;

void addItem(char*, int);
void display();

#endif

```

tree.c

```
#include "tree.h"
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>

void addItem(char arr[], int mode) {
    node_ptr temp, temp2;

    temp = (node_ptr)malloc(sizeof(struct tree_node));
    temp->leftNode=NULL;
    temp->rightNode=NULL;

    if(mode == 1){
        temp->word = arr;
        start = temp;
        }
    }  

void display() {
    node_ptr temp;
    temp = start;
    printf("%s", start->word);       
}

```

main.c

```
#include "tree.h"
#include <stdio.h>
#include <conio.h>

int main() {
    char word[31];

    printf("Enter Root Word: ");
    gets(word);
    addItem(word, 1);
}

```