[Bug fortran/57904] New: Bogus(?) "invokes undefined behavior" warning with Fortran's finalization wrapper (gfortran.dg/class_48.f90)

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

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57904

            Bug ID: 57904
           Summary: Bogus(?) "invokes undefined behavior" warning with
                    Fortran's finalization wrapper
                    (gfortran.dg/class_48.f90)
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: burnus at gcc dot gnu.org

The test case is based on gfortran.dg/class_48.f90 - and the issue is exposed
by r200954.

Compiling the following test case with "gfortran -m32 -O2"  (or "-m32 -Os")
gives the warning:

test.f90: In function '__final_test2_T.1838.constprop.0':
test.f90:21:0: warning: iteration 2147483648 invokes undefined behavior
[-Waggressive-loop-optimizations]
       class(t), allocatable :: a
 ^


Test case:

program test
  call test2 ()
contains
  subroutine test2 ()
    type t
      integer, allocatable :: x
    end type t

    type t2
      class(t), allocatable :: a
    end type t2

    type(t2) :: one, two

    allocate (two%a)
    one = two
  end subroutine test2
end program test