Noob programmer(again) getting "double free or corruption (out)" error

So I'm back. I've made some good progress on the program and getting close to finishing.

So, now I'm trying to dynamically allocate some arrays to hold to test scores. I am assigning all values in these arrays to zero. After I get them then to function properly I will uncomment setScore and allow the user to input the test scores.

Here is my code:

Code:

#include<iostream>
#include<string>

using namespace std;

class Student
{
private:
    string name;
    int id;
    int * test;
    int num;
    void makeArray()
    {
        test = new int[num];

        for (int i = 0 ; i < num ; i++)
        {
            test[i] = 0;
            cout << test[i] << endl;
        }

        cout << "making array...\n";
    }

public:
    Student()
    {
        cout << "Calling set functions...\n";
        setName("None");
        setID(10);
        num = 3;
        makeArray();
        cout << "creating student...1\n";

    }

    Student(int n)
    {
        cout << "Calling set functions...\n";
        setName("None");
        setID(10);

        if (n > 0)
            num = n;
        else
            num = 3;

        makeArray();

        cout << "creating student...2\n";
    }

    Student(string nm, int i, int n)
    {
        cout << "Calling set functions...\n";
        setName(nm);
        setID(i);

        if (n > 0)
            num = n;
        else
            num = 3;

        makeArray();

        cout << "creating student...3\n";
    }

    void setName(string nm)
    {
        cout << "\nThe Name: ";
        cin >> nm;
        name = nm;

    }

    void setID(int i)
    {
        bool validInput;
        do
        {

            cout << "\nThe ID: ";
            cin >> i;
            cout << endl;
            if ( i >= 10 && i <= 99)
            {
                id = i;
                validInput = true;
            }
            else
                {
                    cout << " Invalid.   Can not set id to " << i << " for student " << getName();
                    cout << endl;
                    id = 10;
                    validInput = false;

                }
        } while(!validInput);

    }

//    void setScore(int i, int s)
//    {
//
//    }

    string getName() const
    {
        return name;
    }

    int getID() const
    {
        return id;
    }

    void showScore()
    {
        cout << "showing score";

    }

    void display()
    {
        cout << "showing display";

    }

    ~Student()
    {
        cout << "Freeing dynamicly allocated memory...\n";
        delete [] test;

    }

};

int main()
{
    cout << "In main\n";
    Student studentA,
            studentB(4),
            studentC("Joe",40,5);

    cout << "\nThe Name: ";
    cout << studentA.getName() << endl;
    cout << "The ID: ";
    cout << studentA.getID() << endl;

    cout << "\nThe Name: ";
    cout << studentB.getName() << endl;
    cout << "The ID: ";
    cout << studentB.getID() << endl;

    cout << "\nThe Name: ";
    cout << studentC.getName() << endl;
    cout << "The ID: ";
    cout << studentC.getID() << endl;

    studentA.~Student();
    studentB.~Student();
    studentC.~Student();
    return 0;

}

This is output so far:

Code:

In main
Calling set functions...

The Name: Tom 

The ID: 20

0
0
0
making array...
creating student...1
Calling set functions...

The Name: John

The ID: 30

0
0
0
0
making array...
creating student...2
Calling set functions...

The Name: Joe

The ID: 40

0
0
0
0
0
making array...
creating student...3

The Name: Tom
The ID: 20

The Name: John
The ID: 30

The Name: Joe
The ID: 40
Freeing dynamicly allocated memory...
Freeing dynamicly allocated memory...
Freeing dynamicly allocated memory...
Freeing dynamicly allocated memory...
*** glibc detected *** /home/john/bin/lab9/Lab9: double free or corruption (fasttop): 0x000000000098e140 ***
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x7eb96)[0x7fc267718b96]
/home/john/bin/lab9/Lab9[0x4016cf]
/home/john/bin/lab9/Lab9[0x401067]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xed)[0x7fc2676bb76d]
/home/john/bin/lab9/Lab9[0x400d29]
======= Memory map: ========
00400000-00402000 r-xp 00000000 00:15 43647168                           /home/john/bin/lab9/Lab9
00601000-00602000 r--p 00001000 00:15 43647168                           /home/john/bin/lab9/Lab9
00602000-00603000 rw-p 00002000 00:15 43647168                           /home/john/bin/lab9/Lab9
0098e000-009af000 rw-p 00000000 00:00 0                                  [heap]
7fc26739e000-7fc267499000 r-xp 00000000 08:01 56102364                   /lib/x86_64-linux-gnu/libm-2.15.so
7fc267499000-7fc267698000 ---p 000fb000 08:01 56102364                   /lib/x86_64-linux-gnu/libm-2.15.so
7fc267698000-7fc267699000 r--p 000fa000 08:01 56102364                   /lib/x86_64-linux-gnu/libm-2.15.so
7fc267699000-7fc26769a000 rw-p 000fb000 08:01 56102364                   /lib/x86_64-linux-gnu/libm-2.15.so
7fc26769a000-7fc26784f000 r-xp 00000000 08:01 56102322                   /lib/x86_64-linux-gnu/libc-2.15.so
7fc26784f000-7fc267a4e000 ---p 001b5000 08:01 56102322                   /lib/x86_64-linux-gnu/libc-2.15.so
7fc267a4e000-7fc267a52000 r--p 001b4000 08:01 56102322                   /lib/x86_64-linux-gnu/libc-2.15.so
7fc267a52000-7fc267a54000 rw-p 001b8000 08:01 56102322                   /lib/x86_64-linux-gnu/libc-2.15.so
7fc267a54000-7fc267a59000 rw-p 00000000 00:00 0 
7fc267a59000-7fc267a6e000 r-xp 00000000 08:01 56102347                   /lib/x86_64-linux-gnu/libgcc_s.so.1
7fc267a6e000-7fc267c6d000 ---p 00015000 08:01 56102347                   /lib/x86_64-linux-gnu/libgcc_s.so.1
7fc267c6d000-7fc267c6e000 r--p 00014000 08:01 56102347                   /lib/x86_64-linux-gnu/libgcc_s.so.1
7fc267c6e000-7fc267c6f000 rw-p 00015000 08:01 56102347                   /lib/x86_64-linux-gnu/libgcc_s.so.1
7fc267c6f000-7fc267d54000 r-xp 00000000 08:01 15998324                   /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.17
7fc267d54000-7fc267f53000 ---p 000e5000 08:01 15998324                   /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.17
7fc267f53000-7fc267f5b000 r--p 000e4000 08:01 15998324                   /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.17
7fc267f5b000-7fc267f5d000 rw-p 000ec000 08:01 15998324                   /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.17
7fc267f5d000-7fc267f72000 rw-p 00000000 00:00 0 
7fc267f72000-7fc267f94000 r-xp 00000000 08:01 56102300                   /lib/x86_64-linux-gnu/ld-2.15.so
7fc268171000-7fc268176000 rw-p 00000000 00:00 0 
7fc26818f000-7fc268194000 rw-p 00000000 00:00 0 
7fc268194000-7fc268195000 r--p 00022000 08:01 56102300                   /lib/x86_64-linux-gnu/ld-2.15.so
7fc268195000-7fc268197000 rw-p 00023000 08:01 56102300                   /lib/x86_64-linux-gnu/ld-2.15.so
7fff14746000-7fff14767000 rw-p 00000000 00:00 0                          [stack]
7fff147ff000-7fff14800000 r-xp 00000000 00:00 0                          [vdso]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]
Aborted (core dumped)

One thing I would like to point out: It appears to be freeing the dynamically allocated memory an extra time. I dont know if that is realted to the "double free or corruption (out)" error or not but it shoudn't be doing that.


Thanks for all the help.

Deleted idea was wrong.

New Idea/Question

I am a C programmer, just learning C++; I have never seen a destructor called except for inside another destructor. Is this valid thing to do in C++?

Code:

    studentA.~Student();
    studentB.~Student();
    studentC.~Student();

Tim S.

Line 19:

Code:

            test[i] = 0;

Originally Posted by goldfish

Line 19:

Code:

            test[i] = 0;

I would say this line instead.

test = new int[num];

Note: I edited my prior post.

Tim S.

Oh I lead you astray. In Line 19 I am asigning a value to the contents of test[].
I meant line 15:

Code:

        test = new int[num];

You know I think you might be right. I believe the destructors are called automatically when the program ends.

I'm going to try it and get back to you.

The problem is that you are invoking destructors by hand

Code:

    studentA.~Student();
    studentB.~Student();
    studentC.~Student();

and they will be automatically invoked again as main() returns.

Remove the three lines I've shown.

There is a place for manually calling constructors, but this isn't it.

Yuppers that was it! Thanks for the help. I shall trek on and FINISH my program!!! Almost done! Yay!!

Btw Cprogramming forums, you guys seem like a great community of programmers.
This will not be the last you see of me!!!

This thread needs to be marked as solved. I cant seem to edit my first post and mark it as such.

Btw, if you need a dynamic array, you can use std::vector instead. Avoid raw pointers in C++.