C++ Using delete[] on an Array of Class Pointers

Question

T** class_array
/* snip: malloc/creating classes */
delete[] class_array

Will the delete[] call correctly free class_array (an array of class pointers) and the requisite destructors?

It will not do what you hope it will. Also, don't mix `malloc/free` with `new/delete`. — StoryTeller - Unslander Monica, Oct 25 '16 at 21:13
Use `std::vector` instead. And don't mix `delete` and `malloc`. — Jarod42, Oct 25 '16 at 21:15
If you allocate it like this, `class_array = new T*[34]` you will get an array that you can delete using `delete []` — Jens Munk, Oct 25 '16 at 21:31
@JensMunk but that only deletes the array, it doesn't delete the pointers within the array or destroy the objects those pointers reference. — Mark Ransom, Oct 25 '16 at 22:13
[boost::ptr_vector](http://www.boost.org/doc/libs/1_62_0/libs/ptr_container/doc/ptr_vector.html) may interest you as well. — Aaron D. Marasco, Oct 25 '16 at 22:36
It deletes only the pointers. You need to delete whatever they are pointing to — Jens Munk, Oct 27 '16 at 14:44

WaltK · Accepted Answer · 2017-01-09T01:07:45.270

No, it will not.

The following is maybe an illustrative example along the lines of what I think you are trying to do. There is no need for an explicit delete, it's performed by arr_of_arr's destructor.

#include <iostream>
#include <memory>

using std::unique_ptr;
using std::cout;

class A
  {
  public:
    A() { my_cnt = cnt++; cout << "cons " << my_cnt << '\n'; }
    ~A() { cout << "kill " << my_cnt << '\n'; }

  private:
    unsigned my_cnt;
    static unsigned cnt;
  };

unsigned A::cnt;

int main()
  {
    unique_ptr<unique_ptr<A []> []> arr_of_arr(new unique_ptr<A []>[3]);

    arr_of_arr[0] = unique_ptr<A []>(new A[1]);
    arr_of_arr[1] = unique_ptr<A []>(new A[2]);
    arr_of_arr[2] = unique_ptr<A []>(new A[3]);

    return(0);
  }

C++ Using delete[] on an Array of Class Pointers

1 Answers1