Binary Tree in c -> crashes at depth of more than 7

Question

1. I have made a simple binary tree structure in c.
2. In main(), a tree is CREATED, PRINTED and DELETED (to test if everything is in order).
3. It works fine to the depth of 7 nodes but if i set the depth to 8 or more it crashes.
4. I've tried many things but the result is always the same, I seem to be missing some basic concept.

5. All comments appreciated.

   #include<stdio.h>
   #include<stdlib.h>
   
   typedef struct tree tree;
   
   struct tree{
       int depth;
       int data;
       tree *up;
       tree *left;
       tree *right;
   };
   
   void printTree(tree *node){
       if(node){
           for(int i = 0; i < node->depth; ++i) printf("\t");
           printf("%d: ", node->depth);
           printf("%d\n", node->data);
           printTree(node->left);
           printTree(node->right);
       }
   }
   
   void fillTree0(tree *node){
       if(node->depth < 8){ //depth of 8
           //deklaration
           node->left = new tree;
           node->right = new tree;
           //set up
           node->left->up = node;
           node->right->up = node;
           //set depth
           node->left->depth = node->depth +1;
           node->right->depth = node->depth +1;
           //set data 0
           node->left->data = 0;
           node->right->data = 0;
           //recursion
           fillTree0(node->left);
           fillTree0(node->right);
       }
   }
   
   void freeTree(tree *node){
   
       if(node->left) freeTree(node->left);
       if(node->right) freeTree(node->right);
   
       delete(node->left); node->left = NULL;
       delete(node->right); node->right = NULL;
   
   }
   
   
   int main(void){
   
       tree *root;
       root = new tree;
   
       root->depth = 0;
       root->data = 0;
       fillTree0(root);
   
       printTree(root);
   
       freeTree(root);
   
       return 0;
   
   }
   

Answer 1

Short answer: Add a constructor to tree. tree(){ up=left=right=0; }

The pointers are not initialized to be 0 (null, nullptr) by default.

The problem does not come form the magic 7 or 8 as you described.

Answer 2

You have to initialize your nodes pointers left and right to NULL:

    node->left = new tree;
    node->left->left = NULL ;
    node->left->right = NULL ;

    node->right = new tree;
    node->right->left = NULL ;
    node->right->right = NULL ;

Because your print function:

void printTree(tree *node){
    if(node){ //<-- this is equal to if( node != NULL)

relies on invalid pointers left and right to be NULL, if they are not you will access unallocated memory and cause segfault.