When I compile my code for a linked list, I get a bunch of undefined reference errors. The code is below. I have been compiling with both of these statements:
g++ test.cpp as well as
g++ LinearNode.h LinearNode.cpp LinkedList.h LinkedList.cpp test.cpp I really do not understand why I am getting these errors because I am really rusty on classes in C++. I could really use some help.
LinearNode.h:
#ifndef LINEARNODE_H #define LINEARNODE_H #include<iostream> using namespace std; class LinearNode { public: //Constructor for the LinearNode class that takes no arguments LinearNode(); //Constructor for the LinearNode class that takes the element as an argument LinearNode(int el); //returns the next node in the set. LinearNode* getNext(); //returns the previous node in the set LinearNode* getPrevious(); //sets the next element in the set void setNext(LinearNode* node); //sets the previous element in the set void setPrevious(LinearNode* node); //sets the element of the node void setElement(int el); //gets the element of the node int getElement(); private: LinearNode* next; LinearNode* previous; int element; };//ends the LinearNode class #endif LinearNode.cpp:
#ifndef LINEARNODE_cpp #define LINEARNODE_cpp #include<iostream> #include"LinearNode.h" using namespace std; //Constructor for LinearNode, sets next and element to initialized states LinearNode::LinearNode() { next = NULL; element = 0; }//ends LinearNode default constructor //Constructor for LinearNode takes an element as argument. LinearNode::LinearNode(int el) { next = NULL; previous = NULL; element = 0; }//ends LinearNode constructor //returns the next element in the structure LinearNode* LinearNode::getNext() { return next; }//ends getNext function //returns previous element in structure LinearNode* LinearNode::getPrevious() { return previous; }//ends getPrevious function //sets the next variable for the node void LinearNode::setNext(LinearNode* node) { next = node; }//ends the setNext function //sets previous for the node void LinearNode::setPrevious(LinearNode* node) { previous = node; }//ends the setPrevious function //returns element of the node int LinearNode::getElement() { return element; }//ends the getelement function //sets the element of the node void LinearNode::setElement(int el) { element = el; }//ends the setElement function #endif LinkedList.h:
#ifndef LINKEDLIST_H #define LINKEDLIST_H #include<iostream> #include"LinearNode.h" using namespace std; class LinkedList { public: LinkedList(); void add(int element); int removie (int element); private: int count; LinearNode *contents; };//ends the class linked list #endif LinkedList.cpp:
#ifndef LINKEDLIST_CPP #define LINKEDLIST_CPP #include<iostream> #include"LinearNode.h" #include"LinkedList.h" using namespace std; //linkedlist constructor for an empty linked list LinkedList::LinkedList() { count = 0; contents = NULL; }//ends the constructor //adds an element to the front of the linked list void LinkedList::add(int element) { int found = 0, current = 0; while( (found == 0) && (current !=count) ) { if (contents.getElement() == element) found = 1; else { contents = contents.getNext(); current++; }//ends the else statement }//ends the while loop if (found == 0) { LinearNode node = new LinearNode(element); node.setNext(contents); contents.setPrevious(node); count++; }//ends the found == 0 if statment }//ends the add function //this function removes one element from the linked list. int LinearNode::remove(int element) { int found = 0; if (count == 0) cout << "The list is empty" << endl; else { if (contents.getElement() == element) { result = contents.getElement(); contents = contents.getNext(); }//ends the contents.getElement() == element else { previous = contents; current = contents.getNext(); for (int index = 0; ( (index < count) && (found == 0) )index++) if (current.getElement() = element) found = 1; else { previous = current; current = current.getNext(); }//ends the else statement if (found == 0) cout << "The element is not in the list" << endl; else { result = current.getElement(); previous.setNext(current.getNext()); }//ends else statement }//ends the else stamtement count--; }//ends the else statement of count == 0 return result; }//ends the remove function #endif test.cpp:
#include<iostream> #include"LinearNode.h" #include"LinkedList.h" using namespace std; int main() { LinearNode node1, node2, node3, move; LinkedList list; node1.setElement(1); node2.setElement(2); node3.setElement(3); } 6 Answers
- Usually headers guards are for header files (i.e.,
.h) not for source files ( i.e.,.cpp). - Include the necessary standard headers and namespaces in source files.
LinearNode.h:
#ifndef LINEARNODE_H #define LINEARNODE_H class LinearNode { // ..... }; #endif LinearNode.cpp:
#include "LinearNode.h" #include <iostream> using namespace std; // And now the definitions LinkedList.h:
#ifndef LINKEDLIST_H #define LINKEDLIST_H class LinearNode; // Forward Declaration class LinkedList { // ... }; #endif LinkedList.cpp
#include "LinearNode.h" #include "LinkedList.h" #include <iostream> using namespace std; // Definitions test.cpp is source file is fine. Note that header files are never compiled. Assuming all the files are in a single folder -
g++ LinearNode.cpp LinkedList.cpp test.cpp -o exe.out I was getting this error because my cpp files was not added in the CMakeLists.txt file
g++ test.cpp LinearNode.cpp LinkedList.cpp -o test I had this issue when I forgot to add the new .h/.c file I created to the meson recipe so this is just a friendly reminder.
Another way to get this error is by accidentally writing the definition of something in an anonymous namespace:
foo.h:
namespace foo { void bar(); } foo.cc:
namespace foo { namespace { // wrong void bar() { cout << "hello"; }; } } other.cc file:
#include "foo.h" void baz() { foo::bar(); } Try to remove the constructor and destructors, it's working for me....
