Question

I have a function “PrintHeader” for my project, defined in io.cpp. Even though io.h is included in my main file, I get the error

error C3861: 'PrintHeader': identifier not found.

When I copy the function for PrintHeader into my main file, I get the errors

error LNK2005: 'void _cdeci PrintHeader(void)" (?PrintHeader@@YAXXZ) already defined in io.obj.  

and

error LNK1169: one or more multiply defined symbols found.

I can understand the second error set, since I do have it defined twice, but I don’t understand why it doesn’t work when I just remove the duplicate definition. Any help is greatly appreciated.

Main file

#include "stdio.h"
#include <iostream>
#include "io.h"

void PrintHeader()
{
    cout << endl;
    cout << "Month\tPrincipal\t Interest\t  Balance" << endl;
    cout << "-----\t---------\t---------\t---------" << endl;
}
int main()
{
    cout << "Hello World\n";
    PrintHeader();
    getchar();
    return 0;
}  

io.cpp

#include <iostream>
#include <iomanip>
#include "io.h"

void PrintHeader (void)
{
    cout << endl;
    cout << "Month\tPrincipal\t Interest\t  Balance" << endl;
    cout << "-----\t---------\t---------\t---------" << endl;
}

io.h

#ifndef __IO_H__
#define __IO_H__

#include <string>
using namespace std;

void PrintHeader (void);

#endif

Answer 1

You are most likely including the wrong file in main.cpp. You can make sure it is the right file by right clicking on the include "io.h" and choosing open file.