[Bug fortran/82064] [7/8 Regression] [OOP] multiple incompatible definitions of extended derived type via module use

[pault at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82064

--- Comment #4 from Paul Thomas <pault at gcc dot gnu.org> ---
(In reply to janus from comment #3)
> It appears that the regression has been introduced by r241450, which was the
> fix for PR 69834. Reverting it, in particular the changes to
> resolve_select_type, makes the error go away.

Strangely, my GNU Fortran (GCC) 8.0.0 20170830 gives me two "OK"s :-)

That said, this is a repeat of another recent bug (sorry, I am rushing off to
work - no time to find the number). I posted a work around, which translates in
this case to:

module mod_types
  type, abstract :: t
  end type t
  type, extends(t) :: t2
  end type t2
  class(t), allocatable :: dum1
  class(t2), allocatable :: dum2
end module mod_types

The permanent fix is to make sure that the vtables get produced unconditionally
for module derived types.

Cheers

Paul