Linker error LNK2001

Question

When I try to create an object I get a LNK2001 error in Visual Studio, it's a problem with the constructor I think since changing the constructor changes the error.

Customer bob("Bob", "25 Bob Lane", "01bob82", "M", "bob/bob/bob");

This line gives this error:

Error   1   error LNK2001: unresolved external symbol "public: __thiscall
Customer::Customer(class std::basic_string<char,struct std::char_traits<char>,class
std::allocator<char> >,class std::basic_string<char,struct std::char_traits<char>,class
std::allocator<char> >,class std::basic_string<char,struct std::char_traits<char>,class 
std::allocator<char> >,class std::basic_string<char,struct std::char_traits<char>,class
std::allocator<char> >,class std::basic_string<char,struct std::char_traits<char>,class
std::allocator<char> >)" (??0Customer@@QAE@V?$basic_string@DU?$char_traits@D@std@@V?
$allocator@D@2@@std@@0000@Z)    D:\Dropbox\Work\C++\C++ Assignment\C++ 
Assignment\driver.obj

Customer class that contains the constructor:

#pragma once
#include "l_list.h"
#include "Account.h"
#include <string>

using namespace std;

class Customer
{
private:
    l_list<Account> accounts;
    string name;
    string address;
    string telNo;
    string sex;
    string dob;

public:
    Customer(string name, string address, string telNo, string sex, string dob)
    {
        Customer::name = name;
        Customer::address = address;
        Customer::telNo = telNo;
        Customer::sex = sex;
        Customer::dob = dob;
    }

    void createAccount()
    {
        cout << "What type of account?";

    }

};

This usually means that your are including the wrong version of the header file or linking with wrong version of the runtime library. Your INCLUDE and LIB pathes should point to the same SDK version. — Flot2011
It's a linker error. So, looks like your project does not include Customer.cpp. Or you're using class Customer via old (or wrong) library. — qehgt

StahlRat StahlRat · Accepted Answer · 2012-11-30T01:22:27

If you have linking error then syntactically your code is OK otherwise you'll get compiler errors.

What you should check(or add) is path in Dependencies property of the project that uses Customer class. In VS you can find it "Project Properties->Configuration Properties->Linker->Input->Additional Dependencies". Seems that linker can't find the external library with Customer implementation. You can successfully compile your project cause all #include are correct but you fail on the stage of linking just because of dependencies.

Linker error LNK2001

4 Answers