pointer dummy argument

Hi to everyone. I've found a problem illustrates as follows:

module mod

    type :: test
        integer :: i
    end type test

    contains

    subroutine equals(left, right)

        type(test) :: left
        type(test) :: right

        write(*,*) loc(p), loc(q)

    end subroutine equals
end module mod

program main
    use mod

    type(test), target  :: tar
    type(test), pointer :: p=>null(), q=>null()

    allocate(p, q)
    write(*,*) loc(p), loc(q) ! First
    p => tar
    q => tar
    write(*,*) loc(p), loc(q) ! Second
    call equals(p,q)          ! Third

end program main

The First and Second WRITE statements work fine and loc(p) and loc(q) equal to each other in the Second part. But in the Third time, the returned WRITE statement within the SUBROUTINE outputs a wired result which loc(p) and loc(q) were no longer identical. Is there anything wrong with the code? And if so, what are the returned values in the Third WRITE statement considering that they are not the location of pointer p and q which should be equal then?