Recently I noticed that it is possible to associate a pointer with a data object without the target attribute through the use of a subroutine. I tested this with a 4×4 array arr by associating ptr_to_arr => arr and then by performing subtraction arr-ptr_to_arr, which yielded 0.0 everywhere.

Because only the dummy argument of subroutine assign_ptr and not the actual argument has the target attribute, I expected the pointer to become disassociated outside the subroutine’s scope. However it remains associated.

Can someone say whether this conforms to the Fortran standard or whether this is a bug? I am using GCC 11.4.0.

! ---------------------------
! MODULE CONTAINING PROCEDURE
! ---------------------------
module assign_ptr_mod

  implicit none
  
  contains

  subroutine assign_ptr (arr, ptr)

    implicit none

    real, dimension (:, :), target, intent (in) :: arr
    real, dimension (:, :), pointer, intent (out) :: ptr

    ptr => arr

  end subroutine assign_ptr

end module assign_ptr_mod



! -------------
! BEGIN PROGRAM
! -------------
program main

  use assign_ptr_mod, only : assign_ptr

  implicit none

  integer, parameter :: nx = 4, ny = 4
  integer :: j
  real, dimension (:, :), allocatable :: arr
  real, dimension (:, :), pointer :: ptr_to_arr

  ! Populate array with random numbers
  allocate (arr(nx, ny))
  call random_number (arr)
  call assign_ptr (arr, ptr_to_arr)

  print *, '-------------------------'
  print *, 'Is ptr_to_arr associated?'
  print *, '-------------------------'
  print *, 'Association status is ', associated (ptr_to_arr)
  print *

  print *, '------------------------------------------------'
  print *, 'INITIAL ARRAY VALUES BY RANDOM NUMBER GENERATOR'
  print *, '------------------------------------------------'
  call printer ()

  ! Repopulate array with random numbers
  call random_number (arr)

  print *, '------------------------------------------------'
  print *, 'UPDATED ARRAY VALUES BY RANDOM NUMBER GENERATOR'
  print *, '------------------------------------------------'
  call printer ()

  contains

  subroutine printer

    implicit none

    print *, 'array values are'
    print *
  
    do j = ny, 1, -1
      print *, arr(:, j)
    end do
    print *
  
    print *, 'ptr values are'
    print *
  
    do j = ny, 1, -1
      print *, ptr_to_arr(:, j)
    end do
    print *
  
    print *, 'substract ptr values from arr (should yield zero)'
    print *
  
    do j = ny, 1, -1
      print *, arr(:, j) - ptr_to_arr(:, j)
    end do
    print *

  end subroutine printer

end program main