Local variables defined inside for loops in C++

Question

In the following piece of C++ code:

    for (int i=0; i<10; i++)
    {
        int y = someFunctionCall();

        //Some statements
    }

is the variable (y) allocated each time the loop iterate and then de-allocated when the iteration is done, or it's allocated one time for all loop iterations?

Is the mentioned code equivalent to the following?:

    int y;
    for (int i=0;i<10;i++)
    {
        y = someFunctionCall();

        //Some statements
    }

Answer 1

It will be allocated on the stack once, when the function is called. Performance-wise, there is no difference between the two ways of doing it (but recall that with the last way, y will still be in scope after the loop). That the variable appears to be created and destroyed between each iteration (so that it "loses" its value between iterations) is a behavior that is created by the compiler; the actual memory location is the same all of the time.

Answer 2

It's not allocated each time, however it's assigned a new value in each iteration. The loop is within a method, which has its own stack frame. The variable y is allocated in that stack frame.