seg fault while deteting the dynamically allocated memory

**livin** · 10-16-2012

Heres the piece of code I wrote to gather student details into a dynamically allocated array of structs. But when I try to delete the memory, it gives me a seg fault. I used print statements to make sure that it is reaching the delete[] part and crashing there.

Code:

#include <iostream>
#include <string>
#include "students.h"

using namespace std;

int main(){

        unsigned int number_of_students = 0;

        //Gather student details
        cin >> number_of_students;

        //read student information
        students *student_details = new students[number_of_students];
        read_students(number_of_students, student_details);

        delete(student_details);

        return 0;
}

the students.cpp is

Code:

#include <iostream>
#include <string>
#include "students.h"

using namespace std;

void read_students(const unsigned int number_of_students, students *student){

        for(int i = 0; i < number_of_students; i++){
                cin >> (student + i) -> student_id;
                cin >> (student + i) -> first_name
                    >> (student + i) -> last_name;
        }

        cout << "finished input" << endl;
}

and students.h is

Code:

#ifndef STUDENT_H
#define STUDENT_H

struct student_list{

        unsigned int student_id;
        std::string first_name;
        std::string last_name;
        };

typedef struct student_list students;

void read_students(const unsigned int number_of_students, students *student);

#endif

Thanks.

**rogster001** · 10-16-2012

worked fine for me - tho i did compile it in one file - can't see any reason why you should have a problem

**stahta01** · 10-16-2012

I am a C programer; I am working off and on at learning C++.

There is two different deletes in C++; one with arrays one without arrays.

Code:

students *student_details = new students[number_of_students];

Code:

delete(student_details);

I am guessing this is the correct way!

Code:

delete [] student_details;

Tim S.

**grumpy** · 10-16-2012

Originally Posted by stahta01

There is two different deletes in C++; one with arrays one without arrays.

There are actually more than two forms of operator delete in C++.

However, your conclusion is valid. The form of operator delete used to release an object (or set of objects) needs to match the form of operator new used to allocate it.

**livin** · 10-16-2012

Hmm interesting. So u cannot delete an array with delete() ? I tried delete [] student_details and it worked. I am also learning c++ after learning c. So I thought all free() translate to delete() irrespective of being an element or an array.

Thank you for your help.

Someone above mentioned it worked for him. Is this behaviour system dependent?

-livin

**Elysia** · 10-16-2012

Deleting something you allocated with new[] with delete invokes undefined behavior.
Meaning, it might work, it might not work, it might blow up your computer, blow out your monitor or just do nothing.
You may also want to check out std::vector that handles dynamic arrays with ease.

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