[Bug fortran/31205] aliased operator assignment produces wrong result

[burnus at gcc dot gnu dot org]

------- Comment #3 from burnus at gcc dot gnu dot org  2007-04-15 18:39 -------
Minimal example:

program test
  implicit none
  type data_type
    integer :: i=2
  end type data_type
  type(data_type) :: d
  d%i = 4
  call set(d,d)
contains
  subroutine set(x1,x2)
    type(data_type),intent(out):: x1
    type(data_type),intent(in) :: x2
    x1%i = x2%i
  end subroutine set
end program test

Hereby,
  d%i = 4
  call set(d,d)
is translated into:
  d.i = 4;
  {
    struct data_type data_type.0;
    data_type.0.i = 2;
    d = data_type.0;
  }
  set (&d, &d);
If one removes the "intent(out)" for x1, data_type.0 is not created and
everything is fine. If one creates a temporary structure, shouldn't one have
something like the following? (Handcrafted)
  d.i = 4;
  {
    struct data_type data_type.0;
    data_type.0.i = 2;
    set (&data_type.0, &d);
    d = data_type.0;
  }

There is actually a difference how gfortran and how g95 and NAG f95 do the
default initialization. For the following Fortran code

program test
  implicit none
  type data_type
    integer :: i=2
  end type data_type
  type(data_type) :: d
  d%i = 4
  call set(d)
  print *, d%i
contains
  subroutine set(x1)
    type(data_type),intent(out):: x1
  end subroutine set
end program test

"2" is printed (by all compilers). gfortran does:
  d.i = 4;
  {
    struct data_type data_type.0;
    data_type.0.i = 2;
    d = data_type.0;
  }
  set (&d);
set (x1)
{
  (void) 0;

whereas g95 does:
  d.i = 4;
  set_ (&d);;
set_ (x1)
{
  int4 D.470;
  D.470 = 0;
  if (x1 != 0B)
      *x1 = {.i=2};
  return D.470;;

analogously does NAG f95:
 d_.i_ = 2;
 d_.i_ = 4;
 test_IP_set(&d_);

static void test_IP_set(x1_)
     struct test_DT_data_type *x1_;
{
  x1_->i_ = 2;

Though, I don't know which method is better.


-- 

burnus at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |burnus at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31205