Trouble using an array in a class (C++)

Question

I've looked through various forum posts from here and other sites however I have not seen anything referring to a similar problem. The problem I'm having is: the studentInfo array will not run properly besides when the array elements are 6 or below. I just want to be able to have an array with a size of 23, however the code returns:

bash: line 12: 51068 Segmentation fault      $file.o $args

The code I've provided below is a simplified version of my actual code. I have to use an array in my program (no vectors as some may want to suggest) because it is part of my assignment. I am still a little new to c++ so a good explanation for any answers would be awesome. Thanks for any help!

#include <iostream>
#include <string>

using namespace std;

class StudentGrades {
    private:
    string studentInfo[23];

    public:
    void setStudentInfo(string info) {
        for (int i = 0; i < 23; ++i) {
            studentInfo[i] = info;
        }
    }

    string getStudentInfo() {
        for (int i = 0; i < 23; ++i) {
            cout << studentInfo[i] << " ";
        }
    }
};

int main() {

    StudentGrades student1;

    student1.setStudentInfo("Bob");

    student1.getStudentInfo();
}

How simplified is it? One problem is that getStudentInfo doesn't return a string. — Bo Persson
– Bo Persson, Commented Nov 12, 2016 at 23:33

Vlad from Moscow · Accepted Answer · 2016-11-12 23:38:13Z

1

The code has undefined behavior because member function getStudentInfo returns nothing though it is declared with non-void return type.

Declare it like

void  getStudentInfo() const {
    for (int i = 0; i < 23; ++i) {
        cout << studentInfo[i] << " ";
    }
}

Also it would be better not to use magic numbers. You can add a static constant data member in the class like this

class StudentGrades {
    private:
    static const size_t N = 23;
    string studentInfo[N];
    ....

and use it everywhere where it is needed. For example

void  getStudentInfo() const {
    for (size_t i = 0; i < N; ++i) {
        cout << studentInfo[i] << " ";
    }
}

edited Nov 12, 2016 at 23:38

answered Nov 12, 2016 at 23:33

Vlad from Moscow

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