Pass C++ vector by reference and then do push_back()

Question

Consider this function to illustrate the case:

void appendAndPrint(std::vector<int> &v, int number)
{
    v.push_back(number);    // let there has been a reallocation
    std::cout << v.back();  // does the local reference v become invalid here?

    // is it safe, for example, to call here push_back() with v once again, like
    // v.push_back(number);
}

and then call it with some vector:

std::vector<int> vec;
appendAndPrint(vec, 5);

Is the reference passed into the function become invalid after the first vector reallocation?

EDIT:

This construction is used quite often, but where this kind of safety is referenced in the C++ Standard?

All what is mentioned is the lifetime of references/pointers/iterators to the container elements.

Answer 1

Iterators and references to elements are invalidated, but not container itself. It's normal code.