How a destructor removes a nested stack types?

Question

Example:

class A
{
   char * data;
   ...
   A(){data = new char[50];}
   ~A(){delete [] data;}
};

class B
{
   A a;

   B();
   // default destructor
}

void foo()
{
   B b;
}

int main()
{
   foo();

   // "A.data" still in the heap or no?
}

This program is correct and "A.data" will be removed after foo() in main, or will be still exist in the heap?

Sorry, fixed. Question still exist. – Qewo Setner Apr 21 '13 at 21:19 — Qewo Setner, Apr 21 '13 at 21:19

score 5 · Answer 1 · edited May 23 '17 at 12:12

5

Yes it will be removed, thru you need to use delete[] for arrays. Also you should keep in mind Rule of three

edited May 23 '17 at 12:12

Community

1
1

answered Apr 21 '13 at 21:17

alexrider

4,449
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Or use `std::vector` and dance to the [Rule of Zero](http://isocpp.org/blog/2012/11/rule-of-zero) – Captain Obvlious Apr 21 '13 at 21:51

taocp · Answer 2 · 2013-04-21T21:24:12.233

3

~A(){delete data;}

should be

~A()
{
    delete[] data;
 }
 //remove the dynamic array

In your current code, when main exits, it will call the destructor to release memory and will not exist in heap.

edited Apr 21 '13 at 21:24

answered Apr 21 '13 at 21:18

taocp

23,276
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Remy Lebeau · Answer 3 · 2013-04-21T22:07:37.147

2

When an object is destructed, the compiler automatically destructs all of the class's non-pointer data members. So when your B b variable goes out of scope, the compiler automatically destructs it, which in turn destructs the A a data member since it is not a pointer, which calls ~A() to free the array.

edited Apr 21 '13 at 22:07

answered Apr 21 '13 at 21:25

Remy Lebeau

555,201
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How a destructor removes a nested stack types?

3 Answers3