Undefined reference to cpp file

«Undefined reference to» Error while linking object files [duplicate]

I realize this question has been asked in a number of ways including this very comprehensive answer but I have looked at many and tried fixing my error to no avail. I am using .cpp and .c files to create a program. I compiled all files with g++, it seemed to have no more linking errors, though it gave me a bunch of C++ errors related to the C syntax. This was the command I used:

g++ -o program main.cpp /data/*.c -l[. libs] 

The main.cpp calls functions in the .c files. I then understood that one should not try to compile both .c and .cpp files with one compiler, instead to use gcc for one, g++ for the other, and thereafter to simply link the object files. So I did this (the .c files are part of a library, and already have .o files)

g++ -c main.cpp g++ -o program main.o /data/*.o -l[..libs] 

But then here I will get «undefined reference to» errors for functions called from main.cpp to the precompiled .c files, errors which I didn’t get previously. Could anyone help? Or do I maybe need to provide more information? EDIT (a more in depth excerpt of code, I’ve tried to simplify otherwise this will be impossible to read, but let me know if I still need to add stuff, I’ll try to remove unnecessary code): main.cpp :

#include "header.h" int main(int argc, char** argv)

#include "header.h" void fn1(string s1)

ANSWER: @Smeehey helped me figure out the solution, it was actually that I was still including the old headers in an .hpp file I was using. But the core solution was indeed to use the external C<>.

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Undefined Reference to [duplicate]

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++ 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 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 

#ifndef LINEARNODE_cpp #define LINEARNODE_cpp #include #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 

#ifndef LINKEDLIST_H #define LINKEDLIST_H #include #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 

#ifndef LINKEDLIST_CPP #define LINKEDLIST_CPP #include #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 //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 //ends else statement >//ends the else stamtement count--; >//ends the else statement of count == 0 return result; >//ends the remove function #endif 

#include #include"LinearNode.h" #include"LinkedList.h" using namespace std; int main()

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«undefined reference to» errors when linking static C library with C++ code

I have a test file (just for the link test) where I overload the new / delete operators with my own malloc / free library called libxmalloc.a . But I keep getting «undefined reference to» error as following when linking the static library, even I change the order of test.o and -lxmalloc . But everything works well with other C programs linking this library. I’m so confused with this issue and appreciate any clue. Error Msg:

g++ -m64 -O3 -I/usr/include/ethos -I/usr/include/nacl/x86_64 -c -o test.o test.cpp g++ -m64 -O3 -L. -o demo test.o -lxmalloc test.o: In function `operator new(unsigned long)': test.cpp:(.text+0x1): undefined reference to `malloc(unsigned long)' test.o: In function `operator delete(void*)': test.cpp:(.text+0x11): undefined reference to `free(void*)' test.o: In function `operator new[](unsigned long)': test.cpp:(.text+0x21): undefined reference to `malloc(unsigned long)' test.o: In function `operator delete[](void*)': test.cpp:(.text+0x31): undefined reference to `free(void*)' test.o: In function `main': test.cpp:(.text.startup+0xc): undefined reference to `malloc(unsigned long)' test.cpp:(.text.startup+0x19): undefined reference to `malloc(unsigned long)' test.cpp:(.text.startup+0x24): undefined reference to `free(void*)' test.cpp:(.text.startup+0x31): undefined reference to `free(void*)' collect2: ld returned 1 exit status make: *** [demo] Error 1 

#include #include void* operator new (size_t sz) < return malloc(sz); >void operator delete (void *ptr) < free(ptr); >void* operator new[] (size_t sz) < return malloc(sz); >void operator delete[] (void *ptr) < free(ptr); >int main(void)

CFLAGS += -m64 -O3 -I/usr/include/ethos -I/usr/include/nacl/x86_64 CXXFLAGS += -m64 -O3 LIBDIR += -L. LIBS += -lxmalloc all: demo demo: test.o $(CXX) $(CXXFLAGS) $(LIBDIR) -o demo test.o $(LIBS) test.o: test.cpp $(CXX) $(CFLAGS) -c -o $@ $< clean: - rm -f *.o demo 

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undefined reference to (function) c++ [duplicate]

I've been banging my head against this one set of error messages for about 4 hours now and I can't seem to figure it out. I've not posted here before, so I apologize in advance if it's not in the right area or I've done something wrong. At any rate, the error messages I'm receiving are:

main.cpp|28|undefined reference to `LinkedSortedList::LinkedSortedList()'| main.cpp|52|undefined reference to `empPrint(LinkedSortedList&)'| main.cpp|58|undefined reference to `empSave(LinkedSortedList&, std::string)'| main.cpp|65|undefined reference to `empLoad(LinkedSortedList&, std::string)'| main.cpp|70|undefined reference to `LinkedSortedList::~LinkedSortedList()'| main.cpp|70|undefined reference to `LinkedSortedList::~LinkedSortedList()'| obj\Debug\main.o||In function `Z9empSearchR16LinkedSortedListI8EmployeeE':| main.cpp|109|undefined reference to `LinkedSortedList::getHead()'| 

#include #include #include #include #include "SortedList.h" #include "LinkedSortedList.h" #include "Employee.h" #include "LinkedNode.h" using namespace std; void newEmp(LinkedSortedList & empList); void empSearch(LinkedSortedList & empList); void empPrint(LinkedSortedList & empList); void empSave(LinkedSortedList & empList, string file); void empLoad(LinkedSortedList & empList, string file); int main() < //int empID; bool menuFinish = false; LinkedSortedListempList; char selection; while (!menuFinish) //simple menu system through cout, the selection is read in through cin //and converted to upper case for simplicity during the conditionals cout > selection; selection = toupper(selection); //menu selections are compared with their functions if (selection == 'I') newEmp(empList); else if (selection == 'E') empSearch(empList); else if (selection == 'P') empPrint(empList); else if (selection == 'S') < string fileName; cout > fileName; empSave(empList, fileName); > else if (selection == 'L') < string fileName; cout > fileName; empLoad(empList, fileName); > else if (selection == 'Q') menuFinish = true; else cout //function creates a new employee void newEmp(LinkedSortedList & empList) < string firstName; string lastName; int empID = -1; cout > firstName; cout > lastName; while (empID > 9999999 || empID < 0) < cout > empID; > //puts the employee in the db unless they're already found, then outputs an //error on the screen Employee emp(firstName, lastName, empID); bool findEmp = empList.find(emp); if (!findEmp) empList.insert(emp); else cout //function to search for an employee based on their employee ID void empSearch (LinkedSortedList & empList) < int empID; int sizeOfList = 0; bool noEmp = true; cout > empID; LinkedNode * temp = empList.getHead(); while (sizeOfList < empList.size() && noEmp) < sizeOfList++; if (empID == temp->value.getEmpID()) < cout value; noEmp = false; > temp = temp->next; > if (noEmp) cout //function used to print the first and last five employees from the db void empPrint (LinkedSortedList & empList) < if (empList.size() else < LinkedNode* temp = empList.getHead(); cout value next; > int midList = empList.size()-5; for (int i = 0; i < midList; i++) < temp = temp->next; > cout value next; > > > //function used to save the employee information from the db to a file void empSave(LinkedSortedList& empList, string fileName) < string lastName; string firstName; //int empID; ofstream output; output.open(fileName.c_str()); if (!output) < cout else < LinkedNode* temp = empList.getHead(); int i = 0; while (i < empList.size()) < output value.getLastName() << " " value.getFirstName() << " " value.getEmpID() next; > > output.close(); > //function used to load the employee information from a file to the db void empLoad(LinkedSortedList& empList, string fileName) < if (empList.size() >0) < empList.clear(); >ifstream input; input.open(fileName.c_str()); if (!input) < cout else < int empID; string firstName; string lastName; string delimiter; while(input.good()); < getline(input, delimiter, '\n'); getline(input, lastName, ' '); getline(input, firstName, ' '); input >> empID; Employee emp(lastName, firstName, empID); bool empFound = empList.find(emp); if(!empFound) < empList.insert(emp); >else cout > > 

#ifndef _LinkedSortedList_ #define _LinkedSortedList_ #include "Employee.h" #include "LinkedSortedList.h" #include "SortedList.h" #include "LinkedNode.h" #include #include #include using namespace std; //default constructor //sets head to null and makes the size of the list 0 template LinkedSortedList::LinkedSortedList() < head = NULL; listSize = 0; >//destructor, clears list THEN deletes the head so memory leaks are //stopped template LinkedSortedList::~LinkedSortedList() < clear(); delete head; >//clears the list, freeing memory and stopping leaks and resets the //list size template void LinkedSortedList::clear() < LinkedNode*indexPtr = head; while (head != NULL) < head = head->next; delete indexPtr; indexPtr = head; > listSize = 0; > //finds a search value in the list. if it finds it then it returns true, //otherwise it returns false template bool LinkedSortedList::find(Elem searchValue) const < LinkedNode* indexPtr = head; while (indexPtr != NULL) < if (indexPtr->value == searchValue) < return true; >indexPtr = indexPtr->next; > return false; > //gets and DELETES first value in the list - if it finds nothing then //return false, otherwise true template bool LinkedSortedList::getFirst(Elem &returnValue) < LinkedNode* indexPtr = head; if (indexPtr == NULL) return false; else < head = head->next; returnValue = indexPtr->value; delete indexPtr; listSize--; return true; > returnValue = indexPtr->value; > //prints the list to cout or prints a warning if the list contains //no values template void LinkedSortedList::print() const < if (head == NULL) < cout else < LinkedNode* indexPtr = head; while (indexPtr != NULL) < cout value next; > > > //returns the size of the list to the caller template int LinkedSortedList::size() const < return listSize; >//inserts a value into the list where it should go, if the list is empty it will //say there are no existing nodes template bool LinkedSortedList::insert(Elem newValue) < LinkedNode* indexPtr = head; LinkedNode* newNode; //newNode->value = newValue; try < newNode = new LinkedNode(newValue); > catch(exception e) < cout//checks to see if the list is empty, if it is then it makes the newNode //the head if (head == NULL) < cout value /*looks to see if the value of the newNode is less than or equal to the index, if it is then it sets the point of the newNode equal to the head then makes the head the newNode and increments the listSize by one to keep track of the size of the list and returns true*/ else if (newNode->value value) < newNode->next = head; head = newNode; listSize++; return true; > /*if the newNode value is greater than the index, then:*/ else < while(indexPtr->next != NULL && newNode->value > indexPtr->next->value) < indexPtr = indexPtr->next; > if (indexPtr->next == NULL) < indexPtr->next = newNode; listSize++; return true; > else < newNode->next = indexPtr->next; indexPtr->next = newNode; listSize++; return true; > > > //added for project 2 to return the head of the LL template LinkedNode* LinkedSortedList::getHead() < return head; >#endif 

#ifndef _Employee_ #define _Employee_ #include "Employee.h" #include "LinkedSortedList.h" #include #include #include using namespace std; //blank default constructor Employee::Employee() < >//constructor that takes 3 parameters and sets them Employee::Employee(string lastName, string firstName, int eID) < this->lastName = lastName; this->firstName = firstName; this->empID = eID; > //blank deconstructor Employee::~Employee() < >//overloaded equality operator bool Employee::operator==(Employee &nextEmployee) < if (this->empID == nextEmployee.empID) return true; else return false; > //overloaded less than or equal to operator bool Employee::operator empID //overloaded greater than or equal to operator bool Employee::operator >= (Employee &nextEmployee) < if (this->empID >= nextEmployee.empID) return true; else return false; > //overloaded less than operator bool Employee::operator < (Employee &nextEmployee) < if (this->empID < nextEmployee.empID) return true; else return false; >//overloaded greater than operator bool Employee::operator > (Employee &nextEmployee) < if (this->empID > nextEmployee.empID) return true; else return false; > // overloaded output stream operator ostream& operator <<(ostream& os, const Employee empl) < os << "Last: " << empl.lastName << endl; os << "First: " << empl.firstName << endl; os << "Employee ID: " << empl.empID << endl; return os; >#endif 

#ifndef _LinkedSortedListClass_ #define _LinkedSortedListClass_ #include "SortedList.h" #include "LinkedNode.h" #include #include #include //using namespace std; template class LinkedSortedList : public SortedList < Elem >< public: LinkedSortedList(); ~LinkedSortedList(); virtual void clear(); virtual bool insert(Elem newValue); virtual bool getFirst(Elem &returnValue); virtual void print() const; virtual bool find(Elem searchValue) const; virtual int size() const; LinkedNode* getHead(); //added for project 2 private: LinkedNode* head; int listSize; >; #endif 

#ifndef _EmployeeClass_ #define _EmployeeClass_ #include #include #include using namespace std; class Employee < public: Employee(); ~Employee(); Employee(string, string, int); bool operator == (Employee& nextEmployee); bool operator = (Employee &nextEmployee); bool operator < (Employee &nextEmployee); bool operator >(Employee &nextEmployee); friend ostream& operator <<(ostream& os, const Employee empl); string getLastName()string getFirstName() int getEmpID() private: string lastName; string firstName; int empID; >; #endif 

I'm just not seeing the problem here, I've spoken to my TA, the helproom staff and other students. I haven't heard back from the prof yet, but I doubt I'll hear from her this weekend anyway. Thank you VERY much for any insight you can provide. I need some tylenol. -Josh

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