[Bug fortran/86328] New: Runtime segfault reading an allocatable class(*) object in allocate statements

[mscfd at gmx dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86328

            Bug ID: 86328
           Summary: Runtime segfault reading an allocatable class(*)
                    object in allocate statements
           Product: gcc
           Version: 8.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mscfd at gmx dot net
  Target Milestone: ---

The following code leads to a runtime segfault:

program ptr_alloc

   type :: t
      class(*), allocatable :: val
   end type t

   type :: list
      type(t), dimension(:), pointer :: ll
      integer :: cnt
   end type list

   integer :: i
   type(list) :: a

   allocate(a%ll(1:1))
   do i = 1,10
      print *,i
      a%cnt = i
      allocate(a%ll(i)%val, source=i)
      call rrr(a)
   end do

contains

   subroutine rrr(a)
      type(list) :: a

      integer :: s, i
      type(t), dimension(:), pointer :: mm

      s = ubound(a%ll,1) + 1
      allocate(mm(1:s))

      do i = 1, s-1
         if (allocated(a%ll(i)%val)) then
            allocate(mm(i)%val, source=a%ll(i)%val)
!            allocate(mm(i)%val, mold=a%ll(i)%val)
!            mm(i)%val = a%ll(i)%val

            deallocate(a%ll(i)%val)
         end if
      end do
      deallocate(a%ll)
      a%ll => mm
   end subroutine rrr

end program ptr_alloc


Using the commented mold and assignment version also leads to a segfault. Using
allocation on assignment (just the commented assignment) works, but then the
deallocation statement fails with a segfault.

valgrind reports an "Invalid read of size 8".