[Bug fortran/78053] New: [OOP] SELECT TYPE on CLASS(*) component for deferred length char arrays ICEs for -O > 0

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78053

            Bug ID: 78053
           Summary: [OOP] SELECT TYPE on CLASS(*) component for deferred
                    length char arrays ICEs for -O > 0
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vehre at gcc dot gnu.org
  Target Milestone: ---

Created attachment 39852
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=39852&action=edit
Testprogram causing ICE with -On n>0

The test program:

program test_gimp

  type container
    class(*), allocatable :: items(:)
  end type

  type(container), allocatable :: a_list(:)

  select type (x=>a_list(1)%items)
    type is (character(len=:))
      if (any(x /= ["bla", "foo", "bar"])) call abort()
  end select
end

ICEs when compiled with any optimization level greater than 0. The ICE is
somewhere in the SSA_NAME resolution stage. But I assume the cause is way
earlier, because at the location of the error, the routine that contains the
SELECT TYPE is not in the dumps (-fdump-tree-all) anymore. I therefore assume,
that some information on the temporary representation of the char-array is not
set correctly leading to some optimization step terminating without giving a
proper message.