即使我的函数全部定义，也会在C 中获得不确定的引用

enum state{
state_Mmenu,    // State 0
state_settingmenu,      // State 1
state_gamemenu,     // State 2
state_savegamemenu,     // State 3
state_loadgamemenu,     // State 4;
state_Exit,         // State 5;
state_other
};
state stateMmenu();
state statesettingmenu(string, string);
state stategamemenu();
state statesavegamemenu(string, string, string, ofstream&);
state stateloadgamemenu(string, string, string, ifstream&);
state stateExit();

int main()
{
state curr=state_other;
string filename= "PlayerOne.jak";
string fname="Player";
string lname="One";
ifstream inFS;
ofstream outFS;

while(curr != state_Exit)
{
    switch(curr)
    {
        case state_Mmenu:
        curr = stateMmenu();
        break;
        case state_settingmenu:
        curr = statesettingmenu(fname, lname);
        break;
        case state_gamemenu:
        curr = stategamemenu();
        break;
        case state_savegamemenu:
        curr = statesavegamemenu(fname, lname, filename, outFS);
        break;
        case state_loadgamemenu:
        curr = stateloadgamemenu(fname, lname, filename, inFS);
        break;
        default:
            cout << "Don't Tip the Vending Machine"<<endl;
            curr = state_Mmenu;
        break;
    }
}

return 0;
 }

state statesavegamemenu(string fname, string lname, string filename, 
ofstream outFS)
{
state next=state_savegamemenu;
int choice4=0;
cout<<" -Save Game Menu-----------------"<<endl;
cout<<"1. File Name - "<<filename<<endl;
cout<<"2. Save" <<endl;
cout<<"3. Game Menu" <<endl;
cout<<"----------------------------"<<endl;
    do
{
    cout << "Choice? "<< endl;
    cin >> choice4;
    cin.clear();
    cin.ignore(10000,'n');
}while(!cin.good());
switch(choice4)
{
    case 1:
    {
        cout<<"What would you like to save this file as? ";
        cin>>filename;
        cout<<endl;
        next = state_savegamemenu;
    }
    break;
    case 2:
    {
        outFS.open(filename.c_str());
        if(!outFS.is_open())
        {
            next = state_savegamemenu;
            break;
        }
        else
        {
            outFS<<fname<<endl;
            outFS<<lname<<endl;
        }
        outFS.close();
        next = state_savegamemenu;
    }
    break;
    case 3:
        next = state_gamemenu;
    break;
    default:
    cout << "Bad Input!"<<endl;
        next = state_savegamemenu;
    break;  
}
cout <<endl;
return next;
}
state stateloadgamemenu(string fname, string lname, string filename, 
ifstream inFS)
{
state next=state_loadgamemenu;
int choice5=0;
cout<<" -Save Game Menu-----------------"<<endl;
cout<<"1. File Name - "<<filename<<endl;
cout<<"2. Load" <<endl;
cout<<"3. Main Menu" <<endl;
cout<<"----------------------------"<<endl;
string filecontent;
    do
{
    cout << "Choice? "<< endl;
    cin >> choice5;
    cin.clear();
    cin.ignore(10000,'n');
}while(!cin.good());
switch(choice5)
{
    case 1:
    {
        cout<<"What file would you like to load? ";
        cin>>filename;
        cout<<endl;
        next = state_loadgamemenu;
    }
    break;
    case 2:
    {
        inFS.open(filename.c_str());
        if(!inFS.is_open())
        {
            next = state_savegamemenu;
            break;
        }
        else
        {
            while(!inFS.eof())
            {
                inFS >> filecontent;
                if(inFS.good())
                {
                    cout << filecontent << endl; 
                }
            }
        }
        inFS.close();
        next = state_loadgamemenu;
    }
    break;
    case 3:
        next = state_Mmenu;
    break;
    default:
    cout << "Bad Input!"<<endl;
        next = state_loadgamemenu;
    break;  
}
cout <<endl;
return next;
}

我遇到的错误是对StatesaveGameMenu((和StateloAdgamemenu((的不确定的引用。对于我的知识范围，这样的链接器错误与该程序无法找到有关函数的定义有关，但是我显然已经实施了它们，所以我对为什么会发生这种情况以及任何帮助我感到非常困惑将不胜感激。