Thread: Found a seg fault, but can't explain why i get it

i'm having a problem with a seg fault, but i'm stumped.
i've found it, but i just do not understand why i get it.
it's in the seventh line of WordTree::insert(const string &).
i have put similar code in the third, fourth and fifth line of main()
and that code doesn't seg fault.

(don't worry, you don't have to count the lines, i have marked them with "//******" and a description)

Code:

/*** COMNDENSED TO SAVE SPACE ***/

#ifndef WORDTREE_H
#define WORDTREE_H
#include <string>
#include <iostream>
using std::cout;
using std::endl;
class WordTree
{
	typedef std::string str;
	public:
	WordTree(const str & = "");
	int search(const str &);
	int insert(const str &);
	void print(void);
	private:
	WordTree *left;
	WordTree *right;
	str key;
};
#endif

Code:

#include "WordTree.h"

using namespace std;

WordTree::WordTree(const string &src)
{
	key = src;
	left = right = 0;
}

int WordTree::insert(const string &src)
{
    if(!key.size())
    {
         key = src;
         return 1;
    }     
    
    // this seg faults    
    if(src < key){ cout << "test" << endl; }
    //*****************
    
    
    //the real code (i know i can factor this out, and it was to 
    //begin with, but i expanded it and simpified it to find the seg fault
    //...there's no need to fix or correct this code, i'm going to
    //revert to my original code. i have only posted it so no one would
    //accuse me not giving them the whole code and claim the seg fault is elsewhere.
    /*if(src < key)
    {
           if(left)
           {
                    cout << "CP 2" << endl;
                   return left->insert(src);
           }
           else{
                    cout << "CP 3" << endl;
               left = new WordTree();
                   cout << "CP 4" << endl;
               return left->insert(src);
           }
               
    }else{
              cout << "CP 2.b" << endl;
           if(right){
                    
                   return right->insert(src); 
                       cout << "CP 3.b" << endl;
           }
           else{
                    cout << "CP 4.b" << endl;
               right = new WordTree();
                   cout << "CP 5.b" << endl;
               return right->insert(src);
               
           }
               
    } */            
         
	
 return 1;
}


//not even called, but if you have extra time, i'd like someone to comment on it if there's a better way (it's untested)

int WordTree::search(const string &src)
{
	if(src == key)
		return 1;
	else
		if(src <= key)
			if(left)
				left->search(src);
			else
				return 0;
		else
			if(right)
				right->search(src);
			else
				return 0;
	return 0;
}

//called but still segfaults whether it's called or not
void WordTree::print(void)
	{
         cout << key << endl;
         if(left)
                 left -> print();
         if(right)
                 right -> print();
    }

Code:

/********* crappy test file, no need to pick it apart *****/

#include <cstdlib>
#include <iostream>

#include "WordTree.h"
#include <string>
using namespace std;

int main(int argc, char *argv[])
{
    
    WordTree wt("n");
   
    wt.print();

    //this doesn't seg fault
    string x = "n";
    string y = "p";
    cout << (x < y) << endl;
    //*********************
    
    while(x != "stop")
    {
         cin >> x;
         wt.insert(x);
    }
    wt.print();
    system("PAUSE");
    return EXIT_SUCCESS;
}