CODEWITHSUNDEEP
c++memory
Derek
Derek

Reputation: 11915

Does memory that is allocated in a function get freed when function returns?

I have a function that allocates memory using the new keyword.

That array gets returned from the function, but I need to somehow free it. Is it ever freed after the function returns, or is it up to the receiving code to free the array after it is done with it?

Should I just make this array a member variable, and free it in the class destructor?

Upvotes: 0

Views: 809

Answers (4)

BЈовић
BЈовић

Reputation: 64203

Take a look at boost::shared_array. It does what you need. Either that, or use std::vector

Upvotes: 0

Walter Mundt
Walter Mundt

Reputation: 25271

If you allocate memory explicitly with new, you must free it explicitly with delete. Local variables will be freed upon return; classes like vector may do some allocation behind the scenes but they will clean that up for you.

In general, C++ largely lets you pick your memory management model. You can stick with locals and non-pointer class members and get scope-based allocation. You can play with pointers and malloc/free or new/delete (but never free() a new'd pointer and vice versa!). Or, you could grab Boost and get boost::shared_ptr for reference counting semantics.

Upvotes: 5

fredoverflow
fredoverflow

Reputation: 263078

Should I just make this array a member variable, and free it in the class deconstructor?

That's generally a very good idea, but why reinvent the wheel? Just use std::vector<T>.

Upvotes: 3

peoro
peoro

Reputation: 26060

It depends. You need to define who has got the ownership of such object.

You can allocate the array in your function, return it, and let the caller free it, or put a pointer to it in a class which will destroy the pointer in the destructor.

If the ownership for such object should be shared among many entities you should use something like a shared_ptr.

I'd also suggest to always use some kind of smart pointer to handle your raw pointers.

Upvotes: 2

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