module dummyproc
contains
subroutine callback(x)
real(8), dimension(0:) :: x
end subroutine

subroutine forward(cb,x)
interface
subroutine cb(x)
real(8), dimension(:) :: x
end subroutine
end interface
real(8), dimension(:) :: x

call cb(x)
end subroutine
end module

use dummyproc
real(8), dimension(5) :: x
x = (/1d0, 2d0, 3d0, 4d0, 5d0/)
call forward(callback, x)
end