C ++按值返回vs按引用返回

Question

If I have two functions like:

1.

vector<Student_Info> extract_failed(vector<Student_Info>& students) {
    return students;
}

2.

vector<Student_Info>& extract_failed(vector<Student_Info>& students) {
    return students;
}

Is it correct to say that function 1 is returning by value , which means a copy of students will be created and returned and function 2 is returning by reference ?

Answer 1

Is it correct to say that function 1 is returning by value, which means a copy of students will be created and returned and function 2 is returning by reference?

Yes, it is correct. Another way to phrase it, which I prefer, is to say that 1 returns a value, and 2 returns a reference.

Answer 2

YES

Although 2. in its current form would make sence if you plan to use the return value (something like print(extract_failed(students)); or for(const auto& s : extract_failed(students) ).

Meanwhile, some scenarios may be confusing, since you can do something like

auto& new_students = extract_failed(students);

and you'll have two names in the same scope for the same vector.