Behaviour of pointer to allocatable array with SAVE attribute

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The correct solution to this depends on the behavior you desire. Do you want the pointer to remember what it points to between calls, or should it begin each invocation anew? Beware, if you give it the save attribute (which => null() does implicitly), do not point at anything that does not also have the save attribute. For example, the following will crash

program bad_idea
  implicit none
  call bar()
  call bar()
contains
  subroutine foo(bad)
    integer, intent(in), target :: bad
    integer, pointer, save :: a => null()
    logical, save :: first = .true.
    if (first) then
      a => bad
    end
    print *, bad
  end subroutine
  subroutine bar
    integer, target :: x
    x = 42
    call foo(x)
  end subroutine
end program

because when x goes out of scope, it disappears and thus a will remain pointing at something that doesn’t exist. Note that the associated intrinsic will not save you in this case either, because the pointer is associated with something, it’s just random memory. A simpler example that suffers from the same problem

program bad_idea
  implicit none
  call foo()
  call foo()
contains
  subroutine foo()
    integer, target :: bad
    integer, pointer, save :: a => null()
    logical, save :: first = .true.
    bad = 42
    if (first) then
      a => bad
    end
    print *, bad
  end subroutine
end program