Segmentation fault c++ causing program to crash

Question

I am trying to run the following code but it crashes as soon as the object of inherited class is created.

The program works fine until the creation of the inherited class object but segmentation fault occurs after "Student *s" line is executed.

Here's the code:

#include <iostream>
#include <vector>

using namespace std;

class Person
{
protected:
    string firstName;
    string lastName;
    int id;
public:
    Person(string firstName, string lastName, int identification)
    {
        this->firstName = firstName;
        this->lastName = lastName;
        this->id = identification;
    }
    void printPerson()
    {
        cout << "Name: " << lastName << ", " << firstName << "\nID: " << id
                << "\n";
    }

};

class Student: public Person
{
private:
    vector<int> testScores;
public:
    Student(string f, string l, int i, vector<int>& scores) :
            Person(firstName, lastName, id)
    {
        this->firstName = f;
        this->lastName = l;
        this->id = i;
        this->testScores = scores;
    }

    char calculate()
    {
        vector<int>::iterator it;
        int sum = 0;
        for (it = testScores.begin(); it != testScores.end(); it++)
        {
            sum += *it;
        }
        int avg = sum / (testScores.size());
        if (avg >= 90 && avg <= 100)
            return 'O';
        else if (avg >= 80 && avg < 90)
            return 'E';
        else if (avg >= 70 && avg < 80)
            return 'A';
        else if (avg >= 55 && avg < 70)
            return 'P';
        else if (avg >= 40 && avg < 55)
            return 'D';
        else
            return 'T';

    }
};

int main()
{
    string firstName;
    string lastName;
    int id;
    int numScores;
    cin >> firstName >> lastName >> id >> numScores;
    vector<int> scores;
    for (int i = 0; i < numScores; i++)
    {
        int tmpScore;
        cin >> tmpScore;
        scores.push_back(tmpScore);
    }
    cout << "Calling\n";
    Student* s = new Student(firstName, lastName, id, scores);
    cout << "Done\n";
    s->printPerson();
    cout << "Grade: " << s->calculate() << "\n";
    return 0;
}

i don't get the Student(string f, string l, int i, vector<int>& scores) : Person(firstName, lastName, id) statement. What are you trying to achieve by sending the uninitialized data members to the base class constructor? — Biruk Abebe
– Biruk Abebe, Commented Jun 3, 2016 at 21:40
Student* s = new Student(firstName, lastName, id, scores); does not seem to require dynamic allocation and there is no matching delete to release the Student. — user4581301
– user4581301, Commented Jun 3, 2016 at 21:41

user4581301 · Accepted Answer · 2016-06-03 21:58:25Z

1

    Student(string f, string l, int i, vector<int>& scores) :
            Person(firstName, lastName, id)

uses Person's own firstName, lastName, and id members to construct Person. This may or may not segfault and go boom, but is definitely going into undefined behaviour.

OP wants something more like this where the passed parameters are used instead:

    Student(string f, string l, int i, vector<int>& scores) :
            Person(f, l, i)
    {
        // all of the members that were set here don't need to be set. 
        // Person did it already
        this->testScores = scores;
    }

One more improvement can be made. testScores can be initialized with the member initializer list. This allows scores to be stuffed into testScores immediately and the compiler can make all sorts of interesting optimizations.

    Student(string f, string l, int i, vector<int>& scores) :
            Person(f, l, i), testScores(scores)
    {
    }

Where possible initialize member variables in the initializer list. `Person can be improved as well:

    Person(string first, string last, int identification):
        firstName(first),
        lastName(last),
        id(identification)
    {
    }

Now the divide by zero bug spotted by Rakete1111's can be found and fixed.

answered Jun 3, 2016 at 21:58

user4581301

34.1k7 gold badges42 silver badges65 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Aditya Over a year ago

Still no progress... The program is still crashing

Biruk Abebe Over a year ago

@Aditya This should work. For what input did the program keeps crashing?

user4581301 Over a year ago

@Aditya In addition to the empty vector problem @Rakete1111 spotted, all of your IO is unchecked, so there is plenty of room for bad inputs. For example input of "a b c 1 1" puts cin into an error state because "c" is not a valid integer. This is not caught, so Student s will be created with undefined input. No one can say what will happen then.

Aditya Over a year ago

@bkVnet .For this input: Bob Smith 1482342\n 2\n 100 90\n

user4581301 Over a year ago

Unable to reproduce. input: "Bob Smith 1482342 2 100 90" Output: "Calling Done Name: Smith, Bob ID: 1482342 Grade: O"

Collectives™ on Stack Overflow

Segmentation fault c++ causing program to crash

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related