CODEWITHSUNDEEP
c++pointersstlstdvectorfunction-call
The Light Spark
The Light Spark

Reputation: 504

Does calling functions of an element of an `std::vector` which gets reallocated during the function call cause trouble?

I have a std::vector of GameObjects. I access these GameObjects using direct pointers to them. (Don't worry about the pointers getting invalidated, I update the pointers when the vector realocates itself). The GameObject class has a function called load().

So, in one case, I call the load() of an instance of GameObject which is stored within the vector. This function pushes another GameObject at the back of the vector. This causes the vector to run out of memory and reallocate.(or resize). Now, then that call to push_back returns, the load() is not able to access any of the GameObject instance's members any more. The instance still exists on the same vector though.

Why is the function not able to access the members? The members seen by the load contain junk/incorrect values. Any explanations?

Upvotes: 1

Views: 41

Answers (1)

MSalters
MSalters

Reputation: 179819

vector can't do magic. It has to move elements, either by using their move constructors (if possible) or copy constructors, and then destroy the old objects in the previous location.

So, in your case, GameObject::~GameObject will be called for the object on which you called GameObject::load. Sure, there's another logically identical object elsewhere, but your this pointer is invalid when load returns. There's no way that vector can update your this pointer while a call is in progress.

Upvotes: 2

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