[Bug fortran/107501] New: Aliasing warning not working properly in certain situations

[Bug fortran/107501] New: Aliasing warning not working properly in certain situations

[mhbalsmeier at mail dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107501

            Bug ID: 107501
           Summary: Aliasing warning not working properly in certain
                    situations
           Product: gcc
           Version: og11 (devel/omp/gcc-11)
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mhbalsmeier at mail dot de
  Target Milestone: ---

Created attachment 53816
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=53816&action=edit
source file

Hi,

this is my first bug report. During developing a scientific code I found that
the -Waliasing warning is not thrown in certain situations where in fact it
should be thrown.

The following code shows three calls to a subroutine, but in one of them, the
alaising warning does not appear.

program test

  implicit none

  type t_state
    real(8) :: array_1(2,2)
    real(8) :: array_2(2,2)
    real(8) :: array_3(2,2)
  end type t_state

  type(t_state) :: state

  real(8) :: array_1(2,2)
  real(8) :: array_2(2,2)
  real(8) :: array_3(2,2)

  state%array_1 = .0
  state%array_2 = .0
  state%array_3 = .0
  array_1 = .0
  array_2 = .0
  array_3 = .0

  ! should trigger warning, but doesn't
  call
aliasing_routine_1(state%array_1,state%array_2,state%array_3,state%array_2,state%array_3)
  ! does trigger warning, as it should
  call aliasing_routine_1(array_1,array_2,array_3,array_2,array_3)
  ! does trigger warning, as it should
  call aliasing_routine_2(state%array_1,state%array_2,state%array_2)

  contains

  subroutine aliasing_routine_1(factor,in_1,in_2,out_1,out_2)

    real(8), intent(in)  :: factor(:,:)
    real(8), intent(in)  :: in_1(:,:)
    real(8), intent(in)  :: in_2(:,:)
    real(8), intent(out) :: out_1(:,:)
    real(8), intent(out) :: out_2(:,:)

    out_1 = factor*in_1
    out_2 = factor*in_2

  end subroutine aliasing_routine_1

  subroutine aliasing_routine_2(factor,in_1,out_1)

    real(8), intent(in)  :: factor(:,:)
    real(8), intent(in)  :: in_1(:,:)
    real(8), intent(out) :: out_1(:,:)

    out_1 = factor*in_1

  end subroutine aliasing_routine_2

end program test