stack using linked list - c++

Question

I got "segmentation error" in my code. what is wrong? thanks in advance. p.s it's a stack using linked list.
#include <iostream>
//stack using linked list
class LinkedList {
public:
LinkedList() : head(0), tail(0) {}
~LinkedList() {
while (!empty()) pop();
delete head;
}
void pop() {
node* temp;
temp = head;
for ( ; temp->next_ != tail; temp = temp->next_) {
tail = temp;
}
delete temp;
tail->next_ = 0;
} //removes, but does not return, the top element
int top() {
return tail->value_;
} //returns, but does not remove, the top element
bool empty() {
return head == 0;
}
void push(const int& value) {
node* element = new node(value);
if (empty()) {
head = tail = element;
} else {
tail->next_ = element;
tail = element;
}
} //place a new top element
private:
class node {
public:
node(const int& input) : value_(input), next_(0) {};
int value_; //store value
node* next_; //link to the next element
};
node* head;
node* tail;
};
int main() {
LinkedList list;
list.push(1);
list.push(2);
list.push(3);
list.pop();
std::cout << list.top() << std::endl;
return 0;
}

Answer 1

This part doesn't look right
for ( ; temp->next_ != tail; temp = temp->next_) {
tail = temp;
}
because once you set tail to be the same as temp, temp->next != tail will always be true.

Answer 2

for ( ; temp->next_ != tail; temp = temp->next_) {
tail = temp;
}
The condition should have been
temp->next_ != 0

Answer 3

This method
void pop() {
node* temp;
temp = head;
for ( ; temp->next_ != tail; temp = temp->next_) {
tail = temp;
}
delete temp;
tail->next_ = 0;
} //removes, but does not return, the top element
must be like this:
void pop() {
if( head == tail )
{
delete head;
head = 0;
}
else
{
node* temp;
temp = head;
for ( ; temp->next_ != tail; temp = temp->next_) {
}
delete tail;
temp->next_ = 0;
tail = temp;
}
} //removes, but does not return, the top element

Answer 4

The problem I think is:
for ( ; temp->next_ != tail; temp = temp->next_) {
tail = temp;
}
delete temp;
tail->next_ = 0;
tail = temp should be after you find the temp that leads to tail (i.e. outside of the for loop).
Also, temp = not the tail but the one before the tail. So probably you need:
for ( ; temp->next_ != tail; temp = temp->next_) {}
delete tail;
tail = temp;
tail->next_ = 0;

Answer 5

The destructor looks buggy to me: you keep "popping" until empty() returns true, which happens when head is the null pointer. But then you can't call delete on head after the while loop is over...
I don't know if this is the issue, but I would check it.
Another humble tip: you didn't tell us where the seg fault happens... If you run your code with gdb (or if you just put a lot of "cout" in your code), you can detect the line that causes you problems.