[Bug fortran/64787] New: Invalid code on sourced allocation of class(*) character string

["antony at cosmologist dot info" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64787

            Bug ID: 64787
           Summary: Invalid code on sourced allocation of class(*)
                    character string
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: antony at cosmologist dot info

On trunk

 module X
 contains

    subroutine AddCopy(C)
    class(*), intent(in) :: C
    class(*), pointer :: P
    allocate(P, source=C)
    end subroutine

 end module X

 program test
 use X

 call AddCopy('test string')

 end program test


compiles, but when compiled with -O3 this always gives me a Seg Fault when run
(and probably invalid code more generally).

It may be related to
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64692
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=44672