unresolved externals Error in C++ Project

Question

I wrote my project using a simple editor and I compile them by using Microsoft vc++ compiler through command line interface, I am getting the following error:

/out:Main.exe Main.obj

Main.obj : error LNK2019: unresolved external symbol "public: void __thiscall Ac count::debit(int)" (?debit@Account@@QAEXH@Z) referenced in function _main

Main.obj : error LNK2019: unresolved external symbol "public: int __thiscall Acc ount::getBalance(void)" (?getBalance@Account@@QAEHXZ) referenced in function _main

Main.obj : error LNK2019: unresolved external symbol "public: __thiscall Account ::Account(int)" (??0Account@@QAE@H@Z) referenced in function _main Main.exe : fatal error LNK1120: 3 unresolved externals

Here is the code:

//File : Account.h
class Account{
    public:
        Account( int );
        void credit( int );
        void debit( int );
        int getBalance();
    private:
        int balance;
};

//File:Account.cpp

#include<iostream>
using std::cout;
using std::endl;

#include "Account.h"

Account::Account( int initialbalance ){
    balance = 0;

    if( initialbalance > 0 )
        balance = initialbalance;

    if ( initialbalance < 0 )
        cout<<"Initial Balance is empty\n"<<endl;
}

void Account::credit( int amount ){
        balance = balance + amount;
}

void Account::debit( int amount ){
        if( amount <= balance )
            balance = balance - amount;
        else
            cout<<"Debit amount exceed balance amount\n"<<endl;
}

int Account::getBalance(){
        return balance;
}

//File : Main.cpp
#include<iostream>
using std::cout;
using std::endl;
using std::cin;

#include "Account.h"

int main(){
    Account obj(50);

    cout<<"Account balance Rs. "<<obj.getBalance()<<"\n"<<endl;
    int withdraw;

    cout<<"Withdrawal amount for your account\n"<<endl;
    cin>>withdraw;

    cout<<"Withdrawing ....."<<endl;
    obj.debit( withdraw );

    cout<<"Final account balance : "<<obj.getBalance()<<endl;


    return 0;
}

I have first compiled Account.cpp by using "cl /LD Account.cpp" , then when i try to compile "Main.cpp" I get these error , to be specific I want to know how to use a compiled .dll or .obj file in my client code that uses these compiled files when their source code is not available .

Thanks in advance.

I actually never compiler with the command line in VC++, but you would have to include the account.h/cpp into the compilation. from what I see you're only compiling the main.cpp, and that's not compiling and linking automatically account.cpp — Marius Bancila

Messa Messa · Accepted Answer · 2011-05-16T10:16:07

It looks you are creating Main.exe just from Main.obj; you should link also Account.obj.

unresolved externals Error in C++ Project

4 Answers