CODEWITHSUNDEEP
c++memory-management
IanCZane
IanCZane

Reputation: 640

Does deallocating an instance of a class also deallocate any memory dynamically allocated by its objects/methods?

For example, as simplified as possible:

class thing{
    public:
        char* arr;
        thing();
}

thing::thing{
    arr = new char[1000];
}

If I create a dynamically allocated instance of thing, then deallocate it with delete, will the memory that was dynamically allocated by the constructor also be deallocated, or do I have to deallocate arr first?

Upvotes: 1

Views: 760

Answers (2)

Emil Laine
Emil Laine

Reputation: 42838

No, you will leak the allocated array. A char* doesn't know it's supposed to delete itself when it goes out of scope — it's simply pointing to that memory.

If you use the right tool for the right job though, i.e. change arr to be a unique_ptr then it will automatically know to free the memory you assigned to it once the thing is deallocated.

Upvotes: 1

Mats Petersson
Mats Petersson

Reputation: 129374

Not as that class is written. You will need to declare a destructor that does delete [] arr; - and you should follow the rule or three (or rule of five if you add move semantics).

Upvotes: 3

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