one or more multiply defined symbols found

[Fewgod]

Hey I'm creating a text based game and I'm getting really confused when I tried to separate the functions in different cpp files so I can clear my main.cpp file.
the errors I'm having right now are:
Error LNK1169 one or more multiply defined symbols found
Error LNK2005 "int playerchoice" (?playerchoice@@3HA) already defined in main.obj
Error LNK2005 "class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > name" (?name@@3V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@A) already defined in main.obj

Here is the code

main.cpp

#include <Mission1.h>
#include "functions.h"

using namespace std;

int player()				// Setting The Player Info
{
	cout << "Enter Name: ";
	cin >> name;
	cout << "Choose a Dragon Slayer Magic: " << endl;
	cout << "1: Fire Dragon Slayer Magic" << endl;
	cout << "2: Shadow Dragon Slayer Magic" << endl;
	cout << "3: Iron Dragon Slayer Magic" << endl;
	cout << "4: Lightning Dragon Slayer Magic" << endl;
	cout << "5: Sky Dragon Slayer Magic" << endl;
	cout << "Selection: ";
	cin >> playerchoice;
	return playerchoice;
}

void FireDragonSlayerMagic()		// FIRE DRAGON SLAYER MAGIC
{
	cout << "1: Fire Dragon's Roar" << endl;
	cout << "2: Fire Dragon's Claw" << endl;
	cout << "3: Fire Dragon's Iron Fist" << endl;
	cout << "4: Fire Dragon's Wing Attack" << endl;
}

void ShadowDragonSlayerMagic()			//SHADOW DRAGON SLAYER MAGIC
{	
	cout << "1: Shadow Dragon's Roar" << endl;
	cout << "2: Shadow Dragon's Slash" << endl;
	cout << "3: Shadow Dragon's Crushing Fang" << endl;
	cout << "4: Shadow Dragon's Waxwing Flash" << endl;
}

void IronDragonSlayerMagic()			//IRON DRAGON SLAYER MAGIC
{
	cout << "1: Iron Dragon's Roar" << endl;
	cout << "2: Iron Dragon's Club" << endl;
	cout << "3: Iron Dragon's Sword" << endl;
	cout << "4: Iron Dragon's Scales" << endl;
}

void LightningDragonSlayerMagic()		//LIGHTNING DRAGON SLAYER MAGIC
{
	cout << "1: Lightning Dragon's Roar" << endl;
	cout << "2: Raging Bolt" << endl;
	cout << "3: Lightning Dragon's Iron Fist" << endl;
	cout << "4: Lightning Dragon's Heavenward Halberd" << endl;
}

void SkyDragonSlayerMagic()		//SKY DRAGON SLAYER MAGIC
{
	cout << "1: Sky Dragon's Roar" << endl;
	cout << "2: Sky Dragon's Healing Spell" << endl;
	cout << "3: Sky Dragon's Wing Attack" << endl;
	cout << "4: Vernier" << endl;
}


int main()					// Main Function
{
	player();
	system("cls");
	cout << "Welcome to Fairy Tail " << name << endl;
	cout << endl;
	Start();
	system("pause");
	return 0;
}


void Start()				//Start of the game
{
	cout << "Master Makarov is calling you in the Fairy Tail house" << endl;
	cout << endl;
	cout << "1 - Go to Fairy Tail house" << endl;
	cout << "2 - Explore Fiore" << endl;
	cout << "Selection: ";
	cin >> choice;
	switch (choice)
	{
	case 1:
		GuildHouse();
		break;
	case 2:
		ExploreFiore();
		break;
	default:
		break;
	}
}

void GuildHouse()			// Fairy Tail's Guild House Stages
{
	system("cls");
	Mission1Start();
	cout << "1 - Missions Table\n";
	cout << "Selection: ";
	cin >> choice;
	switch (choice)
	{
	case 1: MissionsBoard();
		break;
	default:
		break;
	}
}

void GuildHouseStage2()
{
	system("cls");
	cout << "1 - Missions Table\n";
	cout << "Selection: ";
	cin >> choice;
	switch (choice)
	{
	case 1: MissionsBoard();
		break;
	default:
		break;
	}
}

						//Exploring Fiore
void ExploreFiore()
{
	system("cls");
	int rndsel = 1+rand() % 4;
	switch (rndsel)
	{
	case 1:
		AngryErza();
		break;
	case 2:
		MeetNatsu();
		break;
	case 3:
		MeetGray();
		break;
	case 4:
		MeetLucy();
	default:
		break;
	}
	cout << "1: Keep Exploring" << endl;
	cout << "2: Go Back" << endl;
	cin >> choice;
	switch (choice)
	{
	case 1:
		ExploreFiore();
		break;
	case 2:
		system("cls");
		Start();
		break;
	default:
		break;
	}
}
							// Angry Erza
	void AngryErza()
	{
		cout << "A sword almost hits you." << endl;
		cout << "Then you see that Erza is chasing Natsu and Gray for eating her cake, again" << endl;
	}

							//Meet Natsu
void MeetNatsu()
{
	cout << "Natsu: Hey " << name << "! How are you doing?" << endl;
	cout << name << ": Nothing much, just walking around the city." << endl;
	cout << "What about you, Natsu?" << endl;
	cout << "Natsu: Just going into Lucy's house again." << endl;
	cout << name << ": Oh good! See you later then." << endl;
	cout << "Natsu: Yeah! See you later " << name << "." << endl;
}

							//Meet Gray
void MeetGray()
{
	cout << name << ": Hey Gray! You are naked, again?" << endl;
	cout << "Gray: Ah Crap!! Didn't realise it." << endl;
	cout << name << ": Yeah, like always." << endl;
	cout << name << ": Just watch out to not take off your underwear." << endl;
	cout << "Gray: Ah Yeah!! It happenes from time to time." << endl;
	cout << name << "," << "Gray: *laughs*" << endl;
}

							//Meet Lucy
void MeetLucy()
{
	cout << name << ": Hey, Lucy!" << endl;
	cout << "Lucy: Oh hey, " << name << "! What brings you here?" << endl;
	cout << name << ": Nothing. Just walking around." << endl;
	cout << name << ": What about you? I see you are holding a book." << endl;
	cout << "Lucy: Yeah I'm heading to the library to take it back and get a new one." << endl;
	cout << name << ": Alright. See you later Lucy." << endl;
	cout << "Lucy: See ya!" << endl;
}


void MissionsBoard()			// Missions Board
{
	system("cls");
	cout << "1 - Easy: Catch a thief" << endl;
	cout << "Selection: ";
	cin >> choice;
	switch (choice)
	{
	case 1:
		Mission1();
		break;
	default:
		break;
	}
}


void Mission1Complete()
{
	system("cls");
	cout << "Makarov: Great Job " << name << ". Atleast you didn't destroy the city :D!" << endl;
	GuildHouseStage2();
}

void Mission2()
{
	cout << "done" << endl;
}

Mission1.cpp

#include "Mission1.h"
#include "functions.h"

Mission1::Mission1()
{
	system("cls");
	cout << "The thief uses speed magic and you have to catch him before he escapes." << endl;
	cout << endl;
	switch (playerchoice)
	{
	case 1:
		cout << "You striked him down with your Fire Dragon's Roar" << endl;
		break;
	case 2:
		cout << "You striked him down with your Shadow Dragon's Roar" << endl;
		break;
	case 3:
		cout << "You striked him down with your Iron Dragon's Roar" << endl;
		break;
	case 4:
		cout << "You striked him down with your Lightning Dragon's Roar" << endl;
		break;
	case 5:
		cout << "You striked him down with your Wind Dragon's Roar" << endl;
	default:
		break;
	}
	cout << endl;
	cin.ignore();
	cout << "Press Enter to Continue";
	cin.get();
}

Mission1Start::Mission1Start()
{
	cout << "das" << endl;
}

functions.h

#ifndef FUNCTIONS_H
#define FUNCTIONS_H

#endif // !FUNCTIONS_H

#include <iostream>
#include <string>
#include <stdlib.h>
#include <ctime>

using namespace std;

//Functions

//Dragon Slayer Magics

void FireDragonSlayerMagic();
void ShadowDragonSlayerMagic();
void IronDragonSlayerMagic();
void LightningDragonSlayerMagic();
void SkyDragonSlayerMagic();

/*Starting Funcs*/
void Start();

/*Exploring Fiore Funcs*/
void ExploreFiore();
void AngryErza();
void MeetNatsu();
void MeetGray();
void MeetLucy();

/*GuildHouse Funcs*/
void GuildHouse();
void GuildHouseStage2();
void MissionsBoard();

/*Mission 1 Funcs*/

/*Mission 1 Funcs*/
void Mission2();

//Variables

string name;
int choice;
int playerchoice;

Mission1.h

#pragma once

class Mission1
{
public:
	/*Mission 1 Funcs*/
	Mission1();
};

class Mission1Start
{
public:
	Mission1Start();
};

[Repeater]

The file functions.h defines a global variable: int playerchoice;

The source file main.cpp includes the file functions.h, so when compiled (and turned into an object file) the source file main.cpp defines a global variable: int playerchoice;

The source fileMission1 includes the file functions.h, so when compiled (and turned into an object file) the source file Mission1 defines a global variable: int playerchoice;

When the linker joins together the two object files, it finds that both of them are trying to create a global variable with the same name. This is bad. Don't have two global variables with the same name.

[Peter87]

The problem is that you have defined the variables in a header file so they are getting defined multiple times, once for each .cpp file that includes the header file.


If you are using a modern compiler you can solve this problem by making the variables inline.

// functions.h
inline string name;
inline int choice;
inline int playerchoice;

Otherwise you can declare them as extern in the header ...

// functions.h
extern string name;
extern int choice;
extern int playerchoice;

... and then define them as normal in a source file.

// functions.cpp
string name;
int choice;
int playerchoice;

Another alternative is of course to not use global variables in the first place.

[Fewgod]

Thanks alot to both of you!
I fixed my error and now the code looks much better.