I am trying to compile my code. The compiler is giving random errors about 'multiple definition':

/tmp/cctnjqVc.o:(.bss+0x0): multiple definition of 'firstname'
/tmp/ccPgFuZw.o:(.bss+0x0): first defined here
/tmp/cctnjqVc.o:(.bss+0x200): multiple definition of 'resultName[abi:cxx11]'
/tmp/ccPgFuZw.o:(.bss+0x200): first defined here

I can assure you that there is no multiple definition at all in my code. My code is in multiple files so if you want to see them all:

http://www.github.com/calmunicorn/virtualsociety

but there are two files that I think are concerned:

FileStream.h

#ifndef FILESTREAM_H
#define FILESTREAM_H
#include <fstream>
#include <string>
#include <limits>
using namespace std;
static fstream logFile;
ofstream firstname;
void log(string argument);
string firstName_read(bool boyOrGirl);
string resultName;

#endif

FileStream.cpp

#include "FileStream.h"
void log(string argument)
{
    logFile.open ("log.txt", fstream::out | fstream::app);

    logFile << argument;

    logFile.close();
}

string firstName_read (bool boyOrGirl)
{

    if (boyOrGirl == true)
         {
              firstname.open("Name/FirstName_Male.txt", fstream::in);
              firstname.close();
              return resultName;
         }
    else
         {
              firstname.open("Name/FirstName_Female.txt", fstream::in);
              firstname.close();
              return resultName;
         }
}

I'm on Arch Linux if makes any difference.

edit :

Thank you for all the answer i did everything i was told to and now it work without any problems!