Thread: error : pointer being freed not allocated

I have typed this code from a book after learning about classes/objects in c++.
It runs until the user enters name for player 1, but then the error
"Conquest game classes objects(491) malloc: *** error for object 0x100007280: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug"

I dont see any pointers used in this code, nor any memory allocated with "new"(which are both covered in the next chapter of the book).

Is there a problem with the code from the book, or have I made a silly mistake. I have tried going over the code looking for typing errors, but can't see any, also I tried to solve the malloc / pointer not freed problem with google searches but couldn't see how this code used them.

Code:

#include <iostream>
#include <string>
using namespace std;

//handles each nation for each player
class Nation{
public:
	int land;
	int troops;
private:
	string name;
	int food;
	int gold;
	int people;
	int farmers;
	int merchants;
	int blacksmiths;
public:
	Nation (string lName);
	Nation();
	~Nation();
	bool takeTurn();
private:
	void menu(void);
};

Nation nation1;
Nation nation2;

//sets the default nation values
Nation::Nation(string lName):
	name(lName),land(20), food(50), troops(15), gold(100), people(100),
farmers(0), merchants(0), blacksmiths(0){}

//a default constructor
Nation::Nation(){}

//takes a turn for player
bool Nation::takeTurn(){
	cout<<"It's now" <<name<< "'s turn.\n";
	people += land * 0.2;
	food += farmers - people * 0.25;
	gold += merchants * 20;
	troops += blacksmiths;
	menu();
	if (nation1.land <= 0 || nation2.land<=0) {
		return false;
	}//if
	return true;
}//bool nation

void Nation::menu(){
	while (true) {
		int input = 0;
		cout << "Food " << food<< "\nGold"<<gold
		<<"\nland "<<land<<"\nMerchants "<< merchants<<"\nTroops "
		<<troops<<"\nUnemployed "<< people<<"\n";
		cout<<"1) Buy Land.\n"
			<<"2) Hire Farmers\n"
			<<"3) Hire merchants\n"
			<<"4) Hire Weaponsmiths\n"
			<<"5) Attack!\n"
			<<"6)Take Turn\n";
		cin>>input;
		switch (input) {
			case 1://buys land
				cout << "You buy "<<gold/20<<" sections of land\n";
				land += gold/20;
				gold %=20;
				cout<< "You now have "<<gold<< "gold\n";
				
				break;
				
				case 2:
				farmers += people;
				cout<<"you hired " << people<< " farmers\n";
				people = 0;
					break;
				
				case 3:
				merchants += people;
				cout<< "You hired " << people<< "merchants\n";
				people = 0;
					break;
				
				case 4:
				blacksmiths += people;
				cout<< "You hired " << people<< "blacksmiths\n";
				people = 0;
				break;
					
				case 5:
					cout<< "the war wages into the night and all die\n";
				if (nation1.troops < nation2.troops) {
					nation2.land += 10;
					nation1.land -= 10;
				}//if
				
				else if (nation1.troops > nation2.troops){
					nation2.land -= 10;
					nation1.land += 10;
				}//else if
				
				nation1.troops = 0;
				nation2.troops = 0;
				break;
				
				case 6:
				return; //ends the turn
					break;


		}//while
		
	}//switch
}//menu






int main(){
	string tempString;
	cout<<"Welcome to the conquest\n";
	cout<<"What is your name player 1?\n";
	cin>>tempString;
	nation1 = Nation(tempString);
	
	
	cout<<"What is your name player 2?\n";
	cin>>tempString;
	nation2 = Nation(tempString);
	while (nation1.takeTurn() && nation2.takeTurn()) {
		
	}
	return 0;
}//main

I am using Xcode

I uncommented the destructor declearation in the class Nation

Code:

~Nation();

and added a destructor definition

Code:

//a default constructor
Nation::Nation(){}
Nation::~Nation(){}

compiled and ran it but got the same error after the first name input.