I have a vector of class objects. A function randomly choses two elements and return their addresses.
Now using these two elements, I want to generate two new objects of the same class and add them to the vector by using push_back.
Here is the address of the two parent elements:
No problem here. The first child object is then generated, and I use vector_pushback to add it to the end of the vector. The problem is, after the push_back command has been executed, it seems like the addresses of the parent objects change. Here is the state of debugger after push_back:
As you can see, the addresses obviously stay the same, but it seems like they point to garbage values after push_back. To my understanding, push_back adds an element at the end of the vector. Therefore I expect the address of the 2 elements to not change at all.
What's wrong?
TL;DR version:
Full explanation:
A std::vector has two useful metrics:
size, which is the number of elements stored.capacity, which is the number of elements it's currently capable of storing.capacity >= size at all times.
The capacity is the length of the internal dynamically-allocated array.* When you insert an element, the size increments by 1. But once it reaches capacity, a new, larger array must be allocated (hence increasing the capacity). This requires all the elements to be copied across, and the originals to be deleted. So all their addresses change.
std::vector.