C++ overloaded << operation only prints memory address of LinkedList - c++

Question

I am trying to make a Linked List Container LLC and overload the << operator as a friend. It seems like no mater what I do it either prints the memory address or throws a segmentation fault. I dont totally understand c++ yet so it is probably something obvious.
in LLC.cpp
ostream& operator<<(ostream& os, const LLC* list){
Node *curr = list.first;
for(curr; curr != NULL; curr= curr -> next){
os << curr -> data << "\n";
}
return os;
}
int main(int argc, char *argv[]){
string arr [] = {"a","b","c","d","e","f"};
LLC* link = new LLC(arr);
cout<<"testing: ";
cout<<(link);
}
in LLC.h
struct Node {
std::string data;
Node *next;
};
class LLC {
private:
Node *first;
Node *last;
public:
int main(int argc, char *argv[]);
LLC(){
first=NULL;
last=NULL;
}
friend std::ostream& operator<<(std::ostream& os, const LLC*);

Answer 1

std::ostream already has an operator<< that takes a pointer (via void*) as input. That is why you get hex output. Your operator<< overload should be taking in the LLC object by const reference, not by const pointer, to avoid ambiguities.
You did not post enough code to demonstrate the segfault error, but I suspect it is because you are not managing your node instances correctly inside the list, so when your operator<< tries to access them, it encounters a bad pointer along the way and crashes.
Try something more like this:
LLC.h
#ifndef LLCH
#define LLCH
#include <iostream>
#include <string>
struct Node {
std::string data;
Node *next;
Node(const std::string& d);
};
class LLC {
private:
Node *first;
Node *last;
public:
LLC();
template<size_t N>
LLC(std::string (&arr)[N])
: first(NULL), last(NULL) {
for(size_t i = 0; i < N; ++i) {
addToBack(arr[i]);
}
}
// other constructors, destructor, etc...
void addToBack(const std::string &s);
// other methods ...
friend std::ostream& operator<<(std::ostream& os, const LLC& list);
// other operators ...
};
#endif
LLC.cpp
#include "LLC.h"
Node::Node(const std::string& d)
: data(d), next(NULL) {
}
LLC::LLC()
: first(NULL), last(NULL) {
}
// other constructors, destructor, etc...
void LLC::addToBack(const std::string &s) {
Node *n = new Node(s);
if (!first) first = n;
if (last) last->next = n;
last = n;
}
// other methods ...
std::ostream& operator<<(std::ostream& os, const LLC& list) {
for(Node *curr = list.first; curr != NULL; curr = curr->next) {
os << curr->data << "\n";
}
return os;
}
// other operators ...
Main.cpp
#include <iostream>
#include <string>
#include "LLC.h"
int main(int argc, char *argv[]) {
std::string arr[] = {"a", "b", "c", "d", "e", "f"};
LLC* link = new LLC(arr);
cout << "testing: " << *link;
delete link;
/* or simply:
LLC link(arr);
cout << "testing: " << link;
*/
return 0;
}