[Bug libfortran/21333] New: in_pack / in_unpack alignment issues

["tkoenig at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>]

I don't have the machines to test this on, but I think
there is a chance of an alignment issue with in_pack / in_unpack.

Look at the following program:

program main
  complex a(5),b(5)
  equivalence(a(1),r(1)),(b(1),r(12))
  real r(100)
  a = (1.0, -1.0)
  b = (2.0, -2.0)
  call foo(a(5:1:-1),5)
  call foo(b(5:1:-1),5)
end program main

subroutine foo(arr,n)
  complex, dimension(n) :: a
end subroutine foo

The equivalence makes sure that a and b cannot both be
aligned on an 8-byte-boundary.

The array reference gets repacked for both calls to foo:

    parm.2.dtype = 545;
    parm.2.dim[0].lbound = 1;
    parm.2.dim[0].ubound = 5;
    parm.2.dim[0].stride = -1;
    parm.2.data = (complex4[0:] *) (complex4[0:] *) &equiv.0.a[4];
    parm.2.offset = 0;
    D.529 = _gfortran_internal_pack (&parm.2);
    foo (D.529, &C.530);
    if (D.529 != parm.2.data)
      {
        _gfortran_internal_unpack (&parm.2, D.529);
        _gfortran_internal_free (D.529);
      }

internal_pack_generic has the following code:

  size = GFC_DESCRIPTOR_SIZE (source);
  switch (size)
    {
    case 4:
      return internal_pack_4 ((gfc_array_i4 *)source);

    case 8:
      return internal_pack_8 ((gfc_array_i8 *)source);
    }

so internal_pack_8 is called.

This operates on a gfc_array_i8.

On machines where you can only align an i8 on an eight-byte-boundary,
this will fail.

I'd appreciate if somebody could run the test program on such a
machine, to see wehter I got this right :-)

Thomas

-- 
           Summary: in_pack / in_unpack alignment issues
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: libfortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: tkoenig at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21333