I have a simple doubly linked list for a class I am in and I keep getting a seg fault on my last line of code, no matter what i make it. I can put a bunch of random couts and it will print them all then on the last one seg fault, all my test functions are working how they should too. Any idea what would cause a seg fault? only things in the class are what my prof says are the typical functions... The big 3, popBack/front, pushback/front and a few others that already work as they should... Only thing i can think of is the destructor causing a seg fault. the destructor just calls my popback function which the code for is below...could this be the problem? any help is appreciated.

void Dll11List::popBack(){
	Dll11Node* nodeptr;
		cerr<<"\nList is Empty";
	if(_first->_fore == NULL){
		delete _last;
		_first = NULL;
		_last = NULL;
		nodeptr = _last->_back;
		delete _last;
		_last = nodeptr;

Recommended Answers

All 6 Replies

DllllNode* temporaryTail = _last;

    _last = _last->_back;

    delete temporaryTail;

I tried these changes and its still giving me a seg fault on the last line of code. maybe thats not the problem. What else could cause a seg fault on the last line of code no matter what that line of code is?

What else could cause a seg fault on the last line of code no matter what that line of code is?

Corrupted memory that only manifests in the destructor is a good start.

Think of the case of a list with 2 elements. Once you've deleted the last one, where does _first->_fore point to?
BTW, same applies to _last->_fore in a general case.

well thats what i was thinking, but the destructor calls a function called delAll0() which simply calls the popback function which the code for is above, its supposed to delete the last node. i have a loop as well that says while(!isEmpty) then just called the popBack function. can you see anything wrong with the popBack function?

I am just really confused on this because the way my prof does things ive never done them this way before...I am assuming my function is mostly right since that is what my prof gave us in class for the popBack function but I just dont see how to fix it. any help is great.

Be a part of the DaniWeb community

We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, learning, and sharing knowledge.