CODEWITHSUNDEEP
c++pointersreference
Ali1S232
Ali1S232

Reputation: 3411

is this a valid delete operation in c++?

I have a vector<some_struct&> array in my code, and whenever I want to add some object to my vector I use array.push_back(*new some_struct). now I'm wondering if I should delete every object in my array before clearing my array (using delete &array[i]) or not?

Upvotes: 2

Views: 172

Answers (5)

Razzupaltuff
Razzupaltuff

Reputation: 2311

The vector reference says that push_back copies the data to the container. In your example, not the pointer to, but the contents of each structure would be copied. So if you use *new my_struct, the reference to the memory allocated for the structs will be lost after having used them to pass the data to the container, meaning you need to store those pointers to each of the structs you allocated somewhere to be able to release them, or you will get memory leaks.

If you wanted to keep the pointers, the container should be a vector<some_struct*>, and you could pass new some_struct and should (e.g.) release them with delete array [i].

Upvotes: 2

James McNellis
James McNellis

Reputation: 355307

vector<some_struct&> array is invalid, period.

The type (or types) with which you instantiate a Standard Library container must be object types. A reference type (like some_struct&) is not an object type.

By definition, "containers are objects that store other objects" (from §23.1/1 in both C++03 and C++0x). References are not objects.

The behavior is undefined if you instantiate a container with a type that does not meet the requirements that the container imposes: your code may or may not compile and if it does compile, who knows what the result will be; anything could happen..

Upvotes: 9

MSN
MSN

Reputation: 54634

How does this even compile? That's not legal C++ code on any compiler I've used in the past 5 years.

Upvotes: 3

MGZero
MGZero

Reputation: 5973

You're going to lose the memory allocated every time you do this. You're essentially creating a copy of that data, but the original is lost in memory somewhere once this process completes. Either keep an external reference to it somewhere which you can delete after you copy it, or use a vector of pointers, not references.

Upvotes: 0

Daniel
Daniel

Reputation: 31609

If your vector is declared vector<some_struct&> array, array.push_back(new some_struct) shouldn't work. array.push_back(some_struct()) will work and in that case you don't need to call delete.

Upvotes: 0

Related Questions