Writing templete class Liste get problems - c++

Question

My teacher asked to write a templete class List(just like in the STL)
My code compile but it will crash but I CAN`T find why, can anyone try to help me?
I think maybe there is problem with the constructor with two parameters?
-----Main.cpp------
#include "Liste.h"
#include <iostream>
int main()
{
Liste<int> l ;
int x = 5 ;
int y = 6 ;
int z = 7 ;
l.insert_first(y) ;
l.insert_first(x) ;
l.insert_last(z) ;
std::cout << l << std::endl ;
}
-----Liste.h------
#pragma once
#include <stdio.h>
#include <iostream>
#include "NoeudListe.h"
template <class T> class Liste
{
private:
NoeudListe<T>* tete;
NoeudListe<T>* fin;
public:
Liste()
{
tete = new NoeudListe<T>(NULL,fin,NULL); //<-----I think the problem lies here beacause the val can`t be NULL? But I tried 0, still not work...
fin = new NoeudListe<T>(tete,NULL,NULL);
}
void insert_after (T& val, NoeudListe<T>* location)
{
NoeudListe<T>* local = new NoeudListe<T>(location,location->getNext(),val);
(*(location->getNext())).setPrev(local);
location->setNext(local);
}
void insert_first(T& val)
{
insert_after (val, tete);
}
void insert_last(T& val)
{
insert_after (val, fin->getPrev());
}
friend std::ostream& operator << (std::ostream& os,const Liste<T>& location)
{
NoeudListe<T>* local=(location.tete)->getNext();
while( local->getVal() != NULL )
{
os<< local->getVal() << "\n";
local=local->getNext();
}
return os;
}
};
-----NoeudListe.h------
#pragma once
template <class T> class NoeudListe
{
private:
NoeudListe* prev;
NoeudListe* next;
T val;
public:
NoeudListe(NoeudListe* p, NoeudListe* n, const T& v)
{
prev = p;
next = n;
val = v;
}
void setNext(NoeudListe* n){ next = n;}
void setPrev(NoeudListe* p){ prev = p;}
void setVal(const T& v){ val = v;}
NoeudListe* getNext(){ return next;}
NoeudListe* getPrev(){ return prev;}
T getVal(){ return val;}
};

Answer 1

friend std::ostream& operator << (std::ostream& os,const Liste<T>& location)
{
NoeudListe<T>* local=(location.tete)->getNext();
while( local->getVal() != NULL )
{
os<< local->getVal() << "\n";
local=local->getNext();
}
return os;
}
You don't test here if local is NULL (why are you testing if local->getVal() is NULL ?), so you will get a segfault here.