I got a function and i want to store some objects into a globally list. Both methods work fine. But do they both create a variable on the heap? What's the difference between them?
vector.push_back(* new object());
vector.push_back(object());
ty for help
DrTosh
This is wrong:
vector.push_back(* new object());
Don't do that. You're leaking memory, because every new must be matched with a delete and you don't call that. The best thing you can do is never call new at all.
This is OK:
vector.push_back(object());
But in C++11 you can more easily do this:
vector.emplace_back(/*any constructor args go here*/);
new object() creates an anonymous temporary variable with dynamic storage duration.
* new object() will give you one horrendous memory leak, since you don't store the pointer from new object(), you merely dereference it, and pass it to push_back.
So don't do it that way.
On the other hand, object() is an anonymous temporary with automatic storage duration.
Both store them in the vector, the vector itself is free in how it wants to store them but it usually uses the free store.
There is a big difference though :
vector.push_back(* new object());
This dynamically allocates an object object and then saves a copy of the object in the vector, the pointer pointing to the newly allocated object is then instantly destroyed.
This way causes a memory leak because you do not delete the object you have allocated with new nor do you save the address for later use.
vector.push_back(object());
This creates a temporary object which is copied and stored in the vector and then destroyed, which is the "correct" way of adding objects to your vector.
They are similar to the following code
object* temp = new object();
vector.push_back(*temp);
object temp;
vector.push_back(object);
It has nothing to do with vector, just no delete is called (and you can't)
