binary tree segment fault in C++ - c++

Question

I'm trying to code a binary tree search/insert/print(BFS) functions.
It compiles fine, but I keep getting segment faults when I try to insert new nodes. Consequently, I could not test the print function neither. Any suggestions, lads?
I did code the functions in a separate Binarytree.cpp file, by the way.
#ifndef BINARYTREE_H
#define BINARYTREE_H
#include <iostream>
#include <vector>
using namespace std;
typedef struct Node{
int key;
struct Node* leftNode;
struct Node* rightNode;
//C++에서는 struct의 constructor 가능
Node(int _key){key = _key;};
} Node;
class BinaryTree
{
private:
static Node* rootNode;
public:
static Node* search(int searchkey){
Node* curNode = rootNode;
while (curNode){
if (searchkey == curNode->key){
break;
} else if (searchkey < curNode->key){
curNode = curNode->leftNode;
} else {
curNode = curNode->rightNode;
}
}
return curNode;
}
static bool insert(int insertkey){
Node* curNode = search(insertkey);
if (insertkey == search(insertkey)->key){
cout << "Key already exits" << endl;
return false;
}
if (!rootNode){
rootNode = new Node(insertkey);
return true;
} else {
Node* newNode = new Node(insertkey);
newNode = search(insertkey);
return true;
}
}
static void print(){
//Node* rootNode = getRoot();
vector<Node*> v;
if (rootNode == NULL){
cout << "Binary tree is empty." << endl;
return;
} else {
v.push_back(rootNode);
cout << rootNode->key << endl;
}
while (!v.empty()){
Node* temp = v.front();
v.erase(v.begin());
if (temp->leftNode){
v.push_back(temp->leftNode);
cout << temp->leftNode->key << endl;
}
if (temp->rightNode){
v.push_back(temp->rightNode);
cout << temp->rightNode->key << endl;
}
}
}
};
Node* BinaryTree::rootNode = NULL;
#endif

Answer 1

Here in insert:
Node* curNode = search(insertkey);
When you call insert the first time, curNode will be NULL. In the following condition:
if (insertkey == search(insertkey)->key){
cout << "Key already exits" << endl;
return false;
}
you are trying to deference a NULL pointer by doing search(insertkey)->key. This causes the seg fault.
Here is the output from backtrace in gdb on my machine:
Program received signal SIGSEGV, Segmentation fault.
0x00000000004009a3 in BinaryTree::insert (insertkey=1) at binarytree.h:38
38 if (insertkey == search(insertkey)->key){
(gdb) backtrace
#0 0x00000000004009a3 in BinaryTree::insert (insertkey=1) at binarytree.h:38
A quick way you can fix this is check if the return from search is NULL first, then move on to other cases.