gfortran: an allocatable array in host_data use_device is rejected ("ALLOCATABLE object ... in USE_DEVICE clause")

! # Finding (GCC 16.2): an allocatable array in use_device is rejected (Fortran); the reproducer is the catalog program
!   acc34-clause-use_device
!
! - toolchains: gcc_g90 (GCC 16.2.0, AMD Instinct MI250X gfx90a, Tioga) and gcc_sm80 (GCC 16.2.0,
!   NVIDIA A100 sm_80, wingtip); separate memory only; -O2; OMP_TARGET_OFFLOAD=mandatory
! - build: gfortran -fopenacc -foffload=amdgcn-amdhsa -foffload-options=amdgcn-amdhsa=-march=gfx90a -O2 (gcc_g90);
!   -foffload=nvptx-none -foffload-options=nvptx-none=-march=sm_80 -foffload-options=nvptx-none=-latomic -O2 (gcc_sm80)
! - failure: rejected: ALLOCATABLE object .* in USE_DEVICE clause
! - observed: `Error: ALLOCATABLE object 'a' in USE_DEVICE clause at (1)` on both GPUs (the host_data and deviceptr programs pass
!   their allocatable arrays the same way).
! - expected: compiles; `RESULT ran_on_host=0 check=pass`
! - spec: "A var in a use_device clause must be the name of a variable or array" (OpenACC 3.4 §2.8 l.2230); the restriction names no
!   attribute, and an allocatable array is an array.
! - GCC 16.2 documentation (libgomp.texi "Enabling OpenACC"): "A complete description of all OpenACC directives accepted may be
!   found in the OpenACC Application Programming Interface manual, version 2.6"; _OPENACC is 201711 (2.6). No list of OpenACC gaps
!   is documented.
! - other families: CCE 19/20/21 (MI300A, MI250X) and NVHPC 25.11/26.9 compile and run all three programs correctly.
! - gate and confirmer: 6 cells (3 gcc_g90, 3 gcc_sm80), each confirmed in the gate's four environments (a-d;
!   results/gcc/gate-tioga/ and gate-wingtip/ verdicts.jsonl); confirmer verdicts (results/gcc/confirm/batch.gcc_*.jsonl):
!   compiler_bug (R11-compile-rejection) 6
! - catalog programs (3): acc34-clause-deviceptr, acc34-clause-use_device, acc34-directive-host_data
! - legality: the catalog programs are legal by construction (offload.engine.gen, c_gen and acc_gen
!   check every program against the catalog rules and the offload scope as it is built; no
!   compiler). GCC is a compiler under test only: never a legality witness, here or for another
!   family's case (catalog/machines.yaml under_test_only).
! Generated by compliance.gen (OpenACC 3.4, free-form Fortran). Do not edit.
! id: acc34-clause-use_device
! primary atom: acc.clause.use_device
! legal: yes
! observable: yes
! ran_on_host: inside the compute region of interest (acc_on_device)
! evidence: copy_mode_only
! needs: none
! std: f2008
module gen_mod
  use openacc
  implicit none
  contains
    subroutine dev_twice(x, y, m, hf)
      integer, intent(in) :: m
      integer :: x(m), y(m), hf
      integer :: k
      !$acc parallel loop deviceptr(x, y) copy(hf)
      do k = 1, m
        if (k == 1) hf = merge(1, 0, acc_on_device(acc_device_host))
        y(k) = 2*x(k) + 1
      end do
    end subroutine dev_twice
end module gen_mod

program gen_prog
  use openacc, only: acc_device_host, acc_on_device
  use gen_mod
  implicit none
  integer, parameter :: n = 64
  integer, allocatable, target :: a(:), b(:)
  integer :: ref(n)
  integer :: i, host_flag
  logical :: ok
  logical :: pres, shared_mem
  integer :: zc(1)
  allocate(a(n), b(n))
  do i = 1, n
    a(i) = i
    b(i) = 0
    ref(i) = 2*i + 1
  end do
  host_flag = 1
  pres = .true.
  zc = 0
  !$acc serial copyin(zc)
    zc(1) = 1
  !$acc end serial
  shared_mem = zc(1) == 1
  !$acc data copyin(a) copyout(b)
    !$acc host_data use_device(a, b)
      call dev_twice(a, b, n, host_flag)
    !$acc end host_data
  !$acc end data
  ok = all(b == ref) .and. pres
  print '(a,i0,a,a)', 'RESULT ran_on_host=', host_flag, ' check=', merge('pass', 'fail', ok)
  deallocate(a, b)
end program gen_prog