(.text+0xc): undefined reference to `func()' C++

Everything is fine until I pass arguments into a function, then I get the errors "(.text+0xc): undefined reference to...", I used no header file. hier is .cpp file

#include <fstream>
#include <iostream>
#include <vector>
#include <string>
#include <ctime>

void func();
void func_2();

using namespace std;


int main(){
    func();
}

void func(string func_2txt){
cout << "Func";
func_2();
}

void func_2(){
string func_2txt = "Func_2";
func(func_2txt);
}