Why does my program crash?

[gemmotipul173]

Hello all,

I'm having some trouble getting my program to run. I don't get any errors when I try to run it. It just crashes.

Anyway, I've got a class with public and private functions each with their own assigned task. I have a feeling that the problem is somewhere in the setScore function but I'm not sure. Any ideas as to why this might be happening?

Thanks!

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

// Student class declaration
class Student
{
	private:
		string name;
		int id;
		int *test;
		int num;
		void makeArray();
	public:
		Student();
		Student(int n);
		Student(string nm, int i, int n);
		void setName(string nm);
		void setID(int i);
		void setScore(int i, int s);
		string getName() const;
		int getID() const;
		void showScore();
		void display();
		~Student();			
};

//************************************************** 
// FUNCTION DEFINITION                             *  
//**************************************************
void Student::makeArray()
{
	int size = Student::num;
	int *studentArray;
	studentArray = new int[num];
	Student::test = studentArray;

	test = 0;
}

//************************************************** 
// FUNCTION DEFINITION                             *  
//**************************************************
Student::Student()
{
	setName("NONE");
	setID(10);
	Student::num = 3;
	makeArray();

}

//************************************************** 
// FUNCTION DEFINITION                             *  
//**************************************************
Student::Student(int n)
{
	setName("None");
	setID(10);
	if(n > 0){
		Student::num = n;
	}else{
		Student::num = 3;
	}
	makeArray();
}

//************************************************** 
// FUNCTION DEFINITION                             *  
//**************************************************
Student::Student(string nm, int i, int n)
{
	setName(nm);
	setID(i);
	if(n > 0)
	{
		Student::num = n;
	}
	else
	{
		Student::num = 3;
	}
	makeArray();
}

//************************************************** 
// FUNCTION DEFINITION                             *  
//**************************************************
void Student::setName(string nm)
{
	Student::name = nm;
}

//************************************************** 
// FUNCTION DEFINITION                             *  
//**************************************************
void Student::setID(int i)
{
	if(i >= 10 && i <= 99)
	{
		Student::id = i;
	}
	else
	{
		Student::id = 10;
		cout << "Invalid.  Can not set id to " << i << " for " << getName() << endl;
	}
}

//************************************************** 
// FUNCTION DEFINITION                             *  
//**************************************************
void Student::setScore(int i, int s)
{
	if(i < Student::num)
	{
		if(s >= 0 && s <= 100)
		{
			test[i] = s;
		}
		else
		{
			cout << "Invalid.  Can not set test " << i << " to " << s << " for " << getName() << endl;
		}
	}
	else
	{
		cout << "Invalid.  Can not set test " << i << " to " << s << " for " << getName() << endl;
	}
}

//************************************************** 
// FUNCTION DEFINITION                             *  
//**************************************************
string Student::getName() const
{
	return Student::name;
}

//************************************************** 
// FUNCTION DEFINITION                             *  
//**************************************************
int Student::getID() const
{
	return Student::id;
}

//************************************************** 
// FUNCTION DEFINITION                             *  
//**************************************************
void Student::showScore()
{
	for(int count = 0; count < Student::num; count++)
	{
		cout << "Test " << count << "had a score of " << test[count] << endl;
	}
}

//************************************************** 
// FUNCTION DEFINITION                             *  
//**************************************************
void Student::display()
{
	cout << "The Name: " << getName();
	cout << "The ID: " << getID();
	showScore();
	cout << endl;
	cout << endl;
}

//************************************************** 
// FUNCTION DEFINITION                             *  
//**************************************************
Student::~Student()
{
	free(test);
}

int main()
{
	Student a;
	Student b(4);
	Student c("Joe", 40, 5);

	cout << "Calling the set functions";

	a.setName("Tom");
	a.setID(200);
	a.setID(20);
	a.setScore(0, 75);
	a.setScore(1, 85);
	a.setScore(2, 95);

	b.setName("John");
	b.setID(30);
	b.setScore(0, 70);
	b.setScore(1, 80);
	b.setScore(2, 90);
	b.setScore(3, 100);

	c.setScore(0, 90);
	c.setScore(1, 91);
	c.setScore(2, 92);
	c.setScore(3, 93);
	c.setScore(4, 94);
	c.setScore(5, 95);
	c.setScore(4, 105);
	c.setScore(5, 105);

	a.display();
	b.display();
	c.display();

	system("pause");
	return 0;
}

[ne555]

> I don't get any errors when I try to run it. It just crashes.
Unless the crash is intended, I'll say that's an error.

$ gdb a.out

Program received signal SIGSEGV, Segmentation fault.
0x00000000004010fb in Student::setScore (this=0x7fffffffe250, i=0, s=75) at foo.cpp:121
121                             test[i] = s;

(gdb) p test
$1 = (int *) 0x0

[gemmotipul173]

Does that mean that i is outside the acceptable range of indexes? How would I fix this problem?

[ne555]

Keep reading, `test' is NULL.

void Student::makeArray()
{
	int size = Student::num;
	int *studentArray;
	studentArray = new int[num];
	Student::test = studentArray;

	test = 0; //¿?
}

By the way, you must deallocate with delete[] if you allocate with new[]