Thread: Error LNK2019 and Fatal error LNK1120: 1 unresolved externals

Hello,

I've been trying to find a solution to this problem, but none of them have worked so far. I know which line of code is causing the error, but not how to stop it.

I google searched for a solution, and tryed a bunch of things, such as making sure my program was a 32console application, and I was calling the header file correctly, as well as trying to find what it was that wasn't linking, but I don't have a lot of experiance, and whatever I'm missing, I can't seem to find it.


Error Message:

1>------ Build started: Project: annoting, Configuration: Debug Win32 ------
1>Main.obj : error LNK2019: unresolved external symbol "int __cdecl Equation(char)" (?Equation@@YAHD@Z) referenced in function _main
1>C:\Users\User\Documents\Visual Studio 2010\Projects\annoting\Debug\annoting.exe : fatal error LNK1120: 1 unresolved externals
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

main.cpp

Code:

 
#include <iostream>
#include <string>
#include <conio.h>
#include <time.h>
#include "functions.h"
using namespace std;
typedef struct node{
 int num1, num2;
 int data;
 node *next;
};

int Equation(char oper);
int main(){
 int enemies=30, age, result, guess, score=0;
 string username;
 char mode;
 node *head=NULL;
 node *temp;
 temp=(node*)malloc(sizeof(node));
 cout<<"Please enter your first name: \t";
 cin>>username;
 cout<<"Please enter your age: \t";
 cin>>age;
 mode =1;
 int i=enemies;
 while(i>0){
  temp->data=Equation(mode);//This is the line I have to take out inorder for the code to compile.
  temp->next=head;
  head=temp;
  i--;
 }
 
 cin>>guess;
 temp=temp->next;
 result=temp->data;
 if(guess==result){
  enemies=enemies-1;
  score=score+1;
  cout<<"\nThere are "<<enemies<<" enemies left!\n\tYour score is "<<score<<"!\n";
 }
 else{
  cout<<"\nThe correct answer was "<<result<<"\n";
 }
 _getch();
 return 0;
}

Functions.cpp

Code:

 
#include <iostream>
#include <string>
#include <time.h>
#include <conio.h>
#include "functions.h"
using namespace std;
 
int demon::Equation(char oper){
 int int_1, int_2, result;
   srand(time(NULL));
   int_1=1+rand()%5;
   int_2=1+rand()%5;
   if(oper='1'){
    result = int_1+int_2;
    cout<<int_1<<"+"<<int_2<<"=\t";
   }
   else{
    result = int_1-int_2;
    cout<<int_1<<"-"<<int_2<<"=\t";
   }
   return result;
}

functions.h

Code:

#ifndef Guy_H_
#define Guy_H_
#include <iostream>
#include <string>
#include <conio.h>
#include <time.h>
using namespace std;

class Guy{
 protected:
  bool live;
 public:
  int distance;
};
class demon: public Guy{
 private:
  int answer;
  char oper;
 public:
  int Equation(char oper);
};
#endif

I am running Microsoft Visual Studios 2010 Express

Any ideas of what might be causing the problem would help. Thank you.

You've only implemented
int demon::Equation(char oper)

Not
::Equation(char oper)

What are your demon and Guy classes for?

Delete your classes and just implement

Code:

int Equation(char oper){
  // your code
}

Okay. That worked.

However, what is the method to using funtions in inheritance classes? I don't get any errors when I use them in regular classes, but for some reason when I use them in an iheritance class I get a whole bunch of errors and I can't seem to figure out how to fix them properly.

The most common thing I saw when searching for a solution looks pretty much the same as

Code:

ElementType ClassName::FunctionName(){
}

But, if I try to call it in my main function it can never find the function.

Are you supposed to use some linked list? If so, there is std::list.
Also, you have a habit of placing all your variables at the beginning of the function. Don't do that. Instead, declare them near first use. This is C++, after all.
Don't use malloc in C++ unless you have a good reason. However, at this stage of your career, you don't, so don't do it.
Also, all new must be matched with a delete (like malloc must be matched with free). Or you could just use a smart pointer. Google it. [Hint: std::shared_ptr, std::unique_ptr, std::weak_ptr]