Segmentation fault

[ybq5Djzh]

How are segmentation faults fixed? I'm not understanding what to do!

#include <iostream>
#include <cstdio>
#include <cstring>
#include "Student_Class.h"
using namespace std;

void treeInsert (student *& root, char key[])
{
	char item[50];
	strcpy (item, root -> getName ());
	if (root == NULL)
	{
		root = new student (key);
	}
	else if (key < item)
	{
		treeInsert (root -> left, key);
	}
	else if (key > item)
	{
		treeInsert (root -> right, key);
	}
}

bool treeContains (student *root, char key[])
{
	char item[50];
	strcpy (item, root -> getName());
	if (root == NULL)
	{
		return false;
	}
	else if (key == item)
	{
		return true;
	}
	else if (key < item)
	{
		return treeContains (root -> left, key);
	}
	else if (key > item)
	{
		return treeContains (root -> right, key);
	}
}

void treeList (student *root)
{
	char item[50];
	strcpy (item, root -> getName ());
	if (root != NULL)
	{
		treeList (root -> left);
		cout << item << endl;
		treeList (root -> right);
	}
}

int main()
{
	student *s; //Pointer to the Student object
	FILE *stud; //File pointer
	int i, j, k; //Loop variables
	char lineStr[1000]; //To store text of each line
	char temp[100]; //To store each value for a variable before pushing it to the tree
	char out[100]; //To fix last value errors
	stud = fopen ("Random.txt", "r");
	s = NULL;
	while (!feof (stud))
	{
		fgets (lineStr, 1000, stud);
		i = 0;
		j = 0;
		for (k = 0; temp[k] != '\0'; k++)
		{
			temp[k] = ' ';
		}
		while (lineStr[i] != ',')
		{
			temp[j++] = lineStr[i++];
		}
		temp[j] = '\0';
		if (treeContains (s, temp))
		{
			cout << "Duplicate\n";
			continue;
		}
		if (strcmp (temp, out) == 0)
		{
			continue;
		}
		treeInsert (s, temp);
		strcpy (out, temp);
	}
	treeList (s);
	return 0;
}

the Student_Class.h file

//CS101 Course Project, Autumn Semester, Lab Group 542
//File Student_Class.h

class student
{
	private:
		char name[50];
		char rollNo[10];
		int mobile;
		char email[40];
		int hostel;
		int roomNo;
		char dept[3]; //Just a 2 letter dept code e.g. CS for Computer Science, CL for Chemical etc., one extra null
		int dobDate; //DOB - Date
		int dobMonth; //DOB - Month
		int dobYear; //DOB - Year
		int courseProg; //Type of programme e.g. 4 year B. Tech., 5 year B. Tech. + M. Tech. Dual Degree, 2 year M. Sc. Refer Course_Prog.txt for the codes
		int semOfStudy; //1st semester, 2nd semester etc.
		int yearOfJoin; //Which year the student joins
		int noOfCourses; //Number of courses the student has taken
		char course[10][6]; //5 letter course code e.g. MA105, CS101; one extra null
		int marks[10]; //Marks attained in each course
		char grade[10][3]; // AA, AB etc., one extra null
		int maxCredit[10]; //Credits alloted for each course
		float spi[10];
		float cpi;
		float attendance[10]; //Percentage of attendance in each course. Hence, float.
		char password[20]; //Max length of password is 20 characters

	public:
		student *left;
		student *right;

		void setName (char nm[])
		{
			strcpy (name, nm);
		}

		char* getName ()
		{
			return name;
		}

		void setRollNo (char roll[])
		{
			strcpy (rollNo, roll);
		}

		void getRollNo (char roll[])
		{
			strcpy (roll, rollNo);
		}

		void setMobile (int mob)
		{
			mobile = mob;
		}

		int getMobile ()
		{
			return mobile;
		}

		void setEmail (char mail[])
		{
			strcpy (email, mail);
		}

		void getEmail (char mail[])
		{
			strcpy (mail, email);
		}

		void setHostel (int host)
		{
			hostel = host;
		}

		int getHostel ()
		{
			return hostel;
		}

		void setRoomNo (int room)
		{
			roomNo = room;
		}

		int getRoomNo ()
		{
			return roomNo;
		}

		void setDept (char dep[])
		{
			strcpy (dept, dep);
		}

		void getDept (char dep[])
		{
			strcpy (dep, dept);
		}

		void setDobDate (int ddate)
		{
			dobDate = ddate;
		}

		int getDobDate ()
		{
			return dobDate;
		}

		void setDobMonth (int dmonth)
		{
			dobMonth = dmonth;
		}

		int getDobMonth ()
		{
			return dobMonth;
		}

		void setDobYear (int dyear)
		{
			dobYear = dyear;
		}

		int getDobYear ()
		{
			return dobYear;
		}

		void setCourseProg (int prog)
		{
			courseProg = prog;
		}

		int getCourseProg ()
		{
			return courseProg;
		}

		void setSemOfStudy (int sem)
		{
			semOfStudy = sem;
		}

		int getSemOfStudy ()
		{
			return semOfStudy;
		}
		
		void setYearOfJoin (int year)
		{
			yearOfJoin = year;
		}
        
		int getYearOfJoin ()
		{
			return yearOfJoin;
		}

		void setNoOfCourses (int num)
		{
			noOfCourses = num;
		}

		int getNoOfCourses ()
		{
			return noOfCourses;
		}

		void setCourse (char crse[][6])
		{
			int i, j;
			for (i = 0; i < noOfCourses; i++)
			{
				strcpy (course[i], crse[i]);
			}
		}

		void getCourse (char crse[][6])
		{
			int i, j;
			for (i = 0; i < noOfCourses; i++)
			{
				strcpy (crse[i], course[i]);
			}
		}

		void setMarks (int mrks[])
		{
			int i;
			for (i = 0; i < noOfCourses; i++)
			{
				marks[i] = mrks[i];
			}
		}

		void getMarks (int mrks[])
		{
			int i;
			for (i = 0; i < noOfCourses; i++)
			{
				mrks[i] = marks[i];
			}
		}

		void setGrade (char grd[][3])
		{
			int i;
			for (i = 0; i < noOfCourses; i++)
			{
				strcpy (grade[i], grd[i]);
			}
		}

		void getGrade (char grd[][3])
		{
			int i;
			for (i = 0; i < noOfCourses; i++)
			{
				strcpy (grd[i], grade[i]);
			}
		}

		void setMaxCredit (int crdt[])
		{
			int i;
			for (i = 0; i < noOfCourses; i++)
			{
				maxCredit[i] = crdt[i];
			}
		}

		void getMaxCredit (int crdt[])
		{
			int i;
			for (i = 0; i < noOfCourses; i++)
			{
				crdt[i] = maxCredit[i];
			}
		}
		
		void setSpi (float subjSpi[])
		{
			int i;
			for (i = 0; i < noOfCourses; i++)
			{
				spi[i] = subjSpi[i];
			}
		}
        
		void getSpi (float subjSpi[])
		{
			int i;
			for (i = 0; i < noOfCourses; i++)
			{
				subjSpi[i] = spi[i];
			}
		}

		void setCpi (float subjCpi)
		{
			cpi = subjCpi;
		}

		float getCpi ()
		{
			return cpi;
		}

		void setAttendance (float attend[])
		{
			int i;
			for (i = 0; i < noOfCourses; i++)
			{
				attendance[i] = attend[i];
			}
		}

		void getAttendance (float attend[])
		{
			int i;
			for (i = 0; i < noOfCourses; i++)
			{
				attend[i] = attendance[i];
			}
		}

		void setPassword (char pwd[])
		{
			strcpy (password, pwd);
		}

		void getPassword (char pwd[])
		{
			strcpy (pwd, password);
		}
		
		student ()
		{
			left = NULL;
			right = NULL;
		}
		student (char key[])
		{
			strcpy (name, key);
			left = NULL;
			right = NULL;
		}
};

Please help!!

[ModShop]

Check how you are accessing your arrays/pointers. Make sure you stay within the arrays size and don't use invalid pointers. I'm not gonna read through all that to check for those though, that's your job.

[Azagaros]

First question: Why aren't we using strings instead of c-style strings?

There are a lot of places I can see a segmentation fault generated looking over the code. Using c++ style string verses c-style strings would save a lot of headache, since you are misusing the c-style strings in your code to begin with.

The easiest way to find the segmentation faults is with a debugger or strategic code that outputs markers to standard out for where I am in the execution.

[ciphermagi]

The point of classes is so that you don't have to do all that crap that you did up there.

		void setCpi (float subjCpi)
		{
			cpi = subjCpi;
		}

		float getCpi ()
		{
			return cpi;
		}

This is VBA programming; you don't have to put all of this in there, there are much cleaner and easier ways to assign variables.

[ne555]

void treeInsert (student *& root, char key[])
{
	char item[50];
	strcpy (item, root -> getName ()); //deferencing the pointer
	if (root == NULL)  //checking if it is a valid point
	{
		root = new student (key);
	}
	else if (key < item) //comparing pointers
	{
		treeInsert (root -> left, key);
	}
	else if (key > item)
	{
		treeInsert (root -> right, key);
	}
}

The first thing you need to do is to check if the pointer is valid.
Later you've got a problem because you are comparing pointers, not their contents. Also the copy to 'item' is unnecessary.

You should encapsulate that behaviour in classes.

class bintree_node{
  friend class bintree;
private:
  student me;
  student *left, *right;
};

class bintree{
private:
  bintree_node root;
public:
  //all the functions to insert, delete, find students
  //you will be operating with nodes, but the user doesn't need to know that.
};

Then you will notice that your tree class shouldn't care if it is storing students, numbers, monsters, etc. so you will make it a template.

You really should review 'student' design.
There are a lot of things that shouldn't be in 'student' (like the credits of the courses) and others that could be encapsulated in other classes (like dates)
And ~260 LOC that don't do anything,

@ciphermagi: ¿could you expand your answer? ¿what ways are you talking about?

[ciphermagi]

http://www.cplusplus.com/doc/tutorial/classes/

If you look under constructors and destructors in this page, you'll see how to build a constructor and a destructor. It doesn't quite give the same functionality as being able to use each of the variables independently, but if you wanted to do that, then there isn't really a clear purpose to having the class in the first place (Note: I said clear purpose...there are cases where individually changing variables in a class is appropriate). Classes and structs are designed to be implemented as objects, and this looks like it's being used as a complicated global variable container instead.

[ybq5Djzh]

@ne555

Could you elaborate? I'm a novice and still learning. :)

@ciphermagi

I need to use each variable independently. If not the whole point of my project is lost.

[Moschops]

As Azagaros says, build with debug symbols and use a debugger. It will catch the segFault and tell you exactly which line the code segFaults on. A segFault happens when you try to read or write memory that the operating system hasn't given you.

[ne555]

¿elaborate on what?
This is basically what you are doing

student *s = NULL;
s->getName(); //crash 

And to compare

//if (key == item) //key and item are pointers
if( strcmp(key, item) == 0 )

It would be easier if you use std::string

[ybq5Djzh]

Thanks for the tip1!! And how to get a debugger?